I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n
ITU-T X.509
TELECOMMUNICATION
STANDARDIZATION SECTOR
OF ITU
(08/2005)
SERIES X: DATA NETWORKS, OPEN SYSTEM
COMMUNICATIONS AND SECURITY
Directory
Information technology ­ Open Systems
Interconnection ­ The Directory: Public-key and
attribute certificate frameworks
ITU-T Recommendation X.509
ITU-T X-SERIES RECOMMENDATIONS
DATA NETWORKS, OPEN SYSTEM COMMUNICATIONS AND SECURITY
PUBLIC DATA NETWORKS
Services and facilities X.1­X.19
Interfaces X.20­X.49
Transmission, signalling and switching X.50­X.89
Network aspects X.90­X.149
Maintenance X.150­X.179
Administrative arrangements X.180­X.199
OPEN SYSTEMS INTERCONNECTION
Model and notation X.200­X.209
Service definitions X.210­X.219
Connection-mode protocol specifications X.220­X.229
Connectionless-mode protocol specifications X.230­X.239
PICS proformas X.240­X.259
Protocol Identification X.260­X.269
Security Protocols X.270­X.279
Layer Managed Objects X.280­X.289
Conformance testing X.290­X.299
INTERWORKING BETWEEN NETWORKS
General X.300­X.349
Satellite data transmission systems X.350­X.369
IP-based networks X.370­X.379
MESSAGE HANDLING SYSTEMS X.400­X.499
DIRECTORY X.500­X.599
OSI NETWORKING AND SYSTEM ASPECTS
Networking X.600­X.629
Efficiency X.630­X.639
Quality of service X.640­X.649
Naming, Addressing and Registration X.650­X.679
Abstract Syntax Notation One (ASN.1) X.680­X.699
OSI MANAGEMENT
Systems Management framework and architecture X.700­X.709
Management Communication Service and Protocol X.710­X.719
Structure of Management Information X.720­X.729
Management functions and ODMA functions X.730­X.799
SECURITY X.800­X.849
OSI APPLICATIONS
Commitment, Concurrency and Recovery X.850­X.859
Transaction processing X.860­X.879
Remote operations X.880­X.889
Generic applications of ASN.1 X.890­X.899
OPEN DISTRIBUTED PROCESSING X.900­X.999
TELECOMMUNICATION SECURITY X.1000For
further details, please refer to the list of ITU-T Recommendations.
ITU-T Rec. X.509 (08/2005) i
INTERNATIONAL STANDARD ISO/IEC 9594-8
ITU-T RECOMMENDATION X.509
Information technology ­ Open Systems Interconnection ­ The Directory:
Public-key and attribute certificate frameworks
Summary
This Recommendation | International Standard defines a framework for public-key certificates and attribute certificates.
These frameworks may be used by other standards bodies to profile their application to Public Key Infrastructures (PKI)
and Privilege Management Infrastructures (PMI). Also, this Recommendation | International Standard defines a
framework for the provision of authentication services by Directory to its users. It describes two levels of authentication:
simple authentication, using a password as a verification of claimed identity; and strong authentication, involving
credentials formed using cryptographic techniques. While simple authentication offers some limited protection against
unauthorized access, only strong authentication should be used as the basis for providing secure services
Source
ITU-T Recommendation X.509 was approved on 29 August 2005 by ITU-T Study Group 17 (2005-2008) under the
ITU-T Recommendation A.8 procedure. An identical text is also published as ISO/IEC 9594-8.
ii ITU-T Rec. X.509 (08/2005)
FOREWORD
The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of
telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of
ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing
Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
The World Telecommunication Standardization Assembly (WTSA), which meets every four years,
establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on
these topics.
The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
In some areas of information technology which fall within ITU-T's purview, the necessary standards are
prepared on a collaborative basis with ISO and IEC.
NOTE
In this Recommendation, the expression "Administration" is used for conciseness to indicate both a
telecommunication administration and a recognized operating agency.
Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain
mandatory provisions (to ensure e.g., interoperability or applicability) and compliance with the
Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some
other obligatory language such as "must" and the negative equivalents are used to express requirements. The
use of such words does not suggest that compliance with the Recommendation is required of any party.
INTELLECTUAL PROPERTY RIGHTS
ITU draws attention to the possibility that the practice or implementation of this Recommendation may
involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence,
validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others
outside of the Recommendation development process.
As of the date of approval of this Recommendation, ITU had received notice of intellectual property,
protected by patents, which may be required to implement this Recommendation. However, implementors
are cautioned that this may not represent the latest information and are therefore strongly urged to consult the
TSB patent database.
 ITU 2006
All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the
prior written permission of ITU.
ITU-T Rec. X.509 (08/2005) iii
CONTENTS
Page
SECTION 1 ­ GENERAL...................................................................................................................................... 1
1 Scope.............................................................................................................................................................. 1
2 Normative references ..................................................................................................................................... 2
2.1 Identical Recommendations | International Standards ........................................................................ 2
2.2 Paired Recommendations | International Standards equivalent in technical content........................... 3
3 Definitions...................................................................................................................................................... 3
3.1 OSI Reference Model security architecture definitions ...................................................................... 3
3.2 Directory model definitions ................................................................................................................ 3
3.3 Definitions........................................................................................................................................... 4
4 Abbreviations ................................................................................................................................................. 6
5 Conventions.................................................................................................................................................... 7
6 Frameworks overview .................................................................................................................................... 8
6.1 Digital signatures ................................................................................................................................ 9
SECTION 2 ­ PUBLIC-KEY CERTIFICATE FRAMEWORK.......................................................................... 11
7 Public-keys and public-key certificates.......................................................................................................... 11
7.1 Generation of key pairs ....................................................................................................................... 15
7.2 Public-key certificate creation............................................................................................................. 15
7.3 Certificate Validity.............................................................................................................................. 16
7.4 Repudiation of a digital signing .......................................................................................................... 18
8 Public-key certificate and CRL extensions..................................................................................................... 19
8.1 Policy handling.................................................................................................................................... 19
8.1.1 Certificate policy................................................................................................................... 19
8.1.2 Cross-certification................................................................................................................. 20
8.1.3 Policy mapping ..................................................................................................................... 21
8.1.4 Certification path processing................................................................................................. 21
8.1.5 Self-issued certificates .......................................................................................................... 22
8.2 Key and policy information extensions............................................................................................... 22
8.2.1 Requirements ........................................................................................................................ 22
8.2.2 Public-key certificate and CRL extension fields................................................................... 23
8.3 Subject and issuer information extensions .......................................................................................... 28
8.3.1 Requirements ........................................................................................................................ 28
8.3.2 Certificate and CRL extension fields .................................................................................... 28
8.4 Certification path constraint extensions .............................................................................................. 30
8.4.1 Requirements ........................................................................................................................ 30
8.4.2 Certificate extension fields.................................................................................................... 30
8.5 Basic CRL extensions ......................................................................................................................... 34
8.5.1 Requirements ........................................................................................................................ 34
8.5.2 CRL and CRL entry extension fields.................................................................................... 35
8.6 CRL distribution points and delta-CRL extensions............................................................................. 43
8.6.1 Requirements ........................................................................................................................ 43
8.6.2 CRL distribution point and delta-CRL extension fields........................................................ 44
9 Delta CRL relationship to base....................................................................................................................... 49
10 Certification path processing procedure......................................................................................................... 50
10.1 Path processing inputs......................................................................................................................... 50
10.2 Path processing outputs....................................................................................................................... 51
10.3 Path processing variables .................................................................................................................... 51
10.4 Initialization step................................................................................................................................. 51
10.5 Certificate processing.......................................................................................................................... 52
10.5.1 Basic certificate checks......................................................................................................... 52
10.5.2 Processing intermediate certificates...................................................................................... 52
10.5.3 Explicit policy indicator processing...................................................................................... 53
10.5.4 Final processing .................................................................................................................... 54
iv ITU-T Rec. X.509 (08/2005)
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11 PKI directory schema ..................................................................................................................................... 54
11.1 PKI directory object classes and name forms...................................................................................... 54
11.1.1 PKI user object class............................................................................................................. 54
11.1.2 PKI CA object class .............................................................................................................. 54
11.1.3 CRL distribution points object class and name form ............................................................ 54
11.1.4 Delta CRL object class.......................................................................................................... 55
11.1.5 Certificate Policy & CPS object class................................................................................... 55
11.1.6 PKI certificate path object class............................................................................................ 55
11.2 PKI directory attributes....................................................................................................................... 55
11.2.1 User certificate attribute........................................................................................................ 55
11.2.2 CA certificate attribute.......................................................................................................... 55
11.2.3 Cross-certificate pair attribute............................................................................................... 56
11.2.4 Certificate revocation list attribute........................................................................................ 56
11.2.5 Authority revocation list attribute ......................................................................................... 56
11.2.6 Delta revocation list attribute................................................................................................ 56
11.2.7 Supported algorithms attribute.............................................................................................. 56
11.2.8 Certification practice statement attribute .............................................................................. 57
11.2.9 Certificate policy attribute..................................................................................................... 57
11.2.10 PKI path attribute.................................................................................................................. 57
11.3 PKI directory matching rules .............................................................................................................. 58
11.3.1 Certificate exact match.......................................................................................................... 58
11.3.2 Certificate match................................................................................................................... 58
11.3.3 Certificate pair exact match .................................................................................................. 59
11.3.4 Certificate pair match............................................................................................................ 59
11.3.5 Certificate list exact match.................................................................................................... 60
11.3.6 Certificate list match ............................................................................................................. 60
11.3.7 Algorithm identifier match.................................................................................................... 61
11.3.8 Policy match.......................................................................................................................... 61
11.3.9 PKI path match...................................................................................................................... 61
11.3.10 Enhanced certificate match ................................................................................................... 61
SECTION 3 ­ ATTRIBUTE CERTIFICATE FRAMEWORK ........................................................................... 62
12 Attribute Certificates ...................................................................................................................................... 63
12.1 Attribute certificate structure .............................................................................................................. 63
12.2 Attribute certificate paths.................................................................................................................... 65
13 Attribute Authority, SOA and Certification Authority relationship ............................................................... 65
13.1 Privilege in attribute certificates ......................................................................................................... 66
13.2 Privilege in public-key certificates...................................................................................................... 67
14 PMI models .................................................................................................................................................... 67
14.1 General model..................................................................................................................................... 67
14.1.1 PMI in access control context ............................................................................................... 68
14.1.2 PMI in a non-repudiation context.......................................................................................... 69
14.2 Control model ..................................................................................................................................... 69
14.3 Delegation model ................................................................................................................................ 69
14.4 Roles model......................................................................................................................................... 70
14.4.1 Role attribute......................................................................................................................... 71
14.5 XML privilege information attribute................................................................................................... 71
15 Privilege management certificate extensions.................................................................................................. 73
15.1 Basic privilege management extensions.............................................................................................. 73
15.1.1 Requirements ........................................................................................................................ 73
15.1.2 Basic privilege management extension fields ....................................................................... 73
15.2 Privilege revocation extensions........................................................................................................... 76
15.2.1 Requirements ........................................................................................................................ 76
15.2.2 Privilege revocation extension fields .................................................................................... 76
15.3 Source of Authority extensions........................................................................................................... 76
15.3.1 Requirements ........................................................................................................................ 76
15.3.2 SOA extension fields ............................................................................................................ 77
ITU-T Rec. X.509 (08/2005) v
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15.4 Role extensions ................................................................................................................................... 78
15.4.1 Requirements ........................................................................................................................ 78
15.4.2 Role extension fields............................................................................................................. 78
15.5 Delegation extensions ......................................................................................................................... 80
15.5.1 Requirements ........................................................................................................................ 80
15.5.2 Delegation extension fields................................................................................................... 80
16 Privilege path processing procedure............................................................................................................... 84
16.1 Basic processing procedure................................................................................................................. 84
16.2 Role processing procedure .................................................................................................................. 85
16.3 Delegation processing procedure ........................................................................................................ 85
16.3.1 Verify integrity of domination rule....................................................................................... 85
16.3.2 Establish valid delegation path.............................................................................................. 86
16.3.3 Verify privilege delegation ................................................................................................... 86
16.3.4 Pass/fail determination.......................................................................................................... 86
17 PMI directory schema .................................................................................................................................... 86
17.1 PMI directory object classes ............................................................................................................... 86
17.1.1 PMI user object class ............................................................................................................ 86
17.1.2 PMI AA object class ............................................................................................................. 87
17.1.3 PMI SOA object class........................................................................................................... 87
17.1.4 Attribute certificate CRL distribution point object class....................................................... 87
17.1.5 PMI delegation path.............................................................................................................. 87
17.1.6 Privilege policy object class.................................................................................................. 87
17.1.7 Protected privilege policy object class.................................................................................. 87
17.2 PMI Directory attributes...................................................................................................................... 88
17.2.1 Attribute certificate attribute................................................................................................. 88
17.2.2 AA certificate attribute.......................................................................................................... 88
17.2.3 Attribute descriptor certificate attribute ................................................................................ 88
17.2.4 Attribute certificate revocation list attribute ......................................................................... 88
17.2.5 AA certificate revocation list attribute.................................................................................. 88
17.2.6 Delegation path attribute....................................................................................................... 88
17.2.7 Privilege policy attribute....................................................................................................... 89
17.2.8 Protected privilege policy attribute ....................................................................................... 89
17.2.9 XML Protected privilege policy attribute ............................................................................. 89
17.3 PMI general directory matching rules................................................................................................. 89
17.3.1 Attribute certificate exact match ........................................................................................... 89
17.3.2 Attribute certificate match..................................................................................................... 89
17.3.3 Holder issuer match .............................................................................................................. 90
17.3.4 Delegation path match........................................................................................................... 90
SECTION 4 ­ DIRECTORY USE OF PUBLIC-KEY & ATTRIBUTE CERTIFICATE FRAMEWORKS............ 90
18 Directory authentication................................................................................................................................. 90
18.1 Simple authentication procedure......................................................................................................... 91
18.1.1 Generation of protected identifying information................................................................... 91
18.1.2 Procedure for protected simple authentication...................................................................... 92
18.1.3 User Password attribute type................................................................................................. 93
18.2 Strong Authentication ......................................................................................................................... 93
18.2.1 Obtaining public-key certificates from the directory ............................................................ 93
18.2.2 Strong authentication procedures.......................................................................................... 96
19 Access control ................................................................................................................................................ 99
20 Protection of Directory operations ................................................................................................................. 99
Annex A ­ Public-Key and Attribute Certificate Frameworks.................................................................................. 100
-- A.1 Authentication framework module ...................................................................................................... 100
-- A.2 Certificate extensions module ............................................................................................................. 105
-- A.3 Attribute Certificate Framework module ............................................................................................ 114
Annex B ­ CRL generation and processing rules...................................................................................................... 122
B.1 Introduction......................................................................................................................................... 122
B.1.1 CRL types ............................................................................................................................. 122
B.1.2 CRL processing..................................................................................................................... 123
vi ITU-T Rec. X.509 (08/2005)
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B.2 Determine parameters for CRLs ......................................................................................................... 123
B.3 Determine CRLs required ................................................................................................................... 124
B.3.1 End-entity with critical CRL DP........................................................................................... 124
B.3.2 End-entity with no critical CRL DP...................................................................................... 124
B.3.3 CA with critical CRL DP...................................................................................................... 124
B.3.4 CA with no critical CRL DP ................................................................................................. 125
B.4 Obtain CRLs ....................................................................................................................................... 125
B.5 Process CRLs...................................................................................................................................... 125
B.5.1 Validate base CRL scope ...................................................................................................... 125
B.5.2 Validate delta CRL scope...................................................................................................... 127
B.5.3 Validity and currency checks on the base CRL..................................................................... 128
B.5.4 Validity and checks on the delta CRL................................................................................... 128
Annex C ­ Examples of delta CRL issuance............................................................................................................. 129
Annex D ­ Privilege policy and privilege attribute definition examples................................................................... 131
D.1 Introduction......................................................................................................................................... 131
D.2 Sample syntaxes.................................................................................................................................. 131
D.2.1 First example......................................................................................................................... 131
D.2.2 Second example .................................................................................................................... 133
D.3 Privilege attribute example.................................................................................................................. 134
Annex E ­ An introduction to public key cryptography............................................................................................ 136
Annex F ­ Reference definition of algorithm object identifiers ................................................................................ 138
Annex G ­ Examples of use of certification path constraints.................................................................................... 139
G.1 Example 1: Use of basic constraints.................................................................................................... 139
G.2 Example 2: Use of policy mapping and policy constraints ................................................................ 139
G.3 Use of Name Constraints Extension.................................................................................................... 139
G.3.1 Examples of Certificate Format with Name Constraints Extension...................................... 139
G.3.2 Examples of Certificate Handling with Name Constraint Extension.................................... 143
Annex H ­ Guidance on determining for which policies a certification path is valid ............................................... 156
H.1 Certification path valid for a user-specified policy required............................................................... 156
H.2 Certification path valid for any policy required .................................................................................. 157
H.3 Certification path valid regardless of policy ....................................................................................... 157
H.4 Certification path valid for a user-specific policy desired, but not required ....................................... 157
Annex I ­ Key usage certificate extension issues...................................................................................................... 158
Annex J ­ Alphabetical list of information item definitions...................................................................................... 159
Annex K ­ Amendments and corrigenda................................................................................................................... 162
ITU-T Rec. X.509 (08/2005) vii
Introduction
This Recommendation | International Standard, together with other Recommendations | International Standards, has
been produced to facilitate the interconnection of information processing systems to provide directory services. A set of
such systems, together with the directory information which they hold, can be viewed as an integrated whole, called the
Directory. The information held by the Directory, collectively known as the Directory Information Base (DIB), is
typically used to facilitate communication between, with or about objects such as application-entities, people, terminals
and distribution lists.
The Directory plays a significant role in Open Systems Interconnection, whose aim is to allow, with a minimum of
technical agreement outside of the interconnection standards themselves, the interconnection of information processing
systems:
­ from different manufacturers;
­ under different managements;
­ of different levels of complexity; and
­ of different ages.
Many applications have requirements for security to protect against threats to the communication of information.
Virtually all security services are dependent upon the identities of the communicating parties being reliably known, i.e.,
authentication.
This Recommendation | International Standard defines a framework for public-key certificates. That framework
includes specification of data objects used to represent the certificates themselves as well as revocation notices for
issued certificates that should no longer be trusted. The public-key certificate framework defined in this Specification,
while it defines some critical components of a Public-key Infrastructure (PKI), it does not define a PKI in its entirety.
However, this Specification provides the foundation upon which full PKIs and their specifications would be built.
Similarly, this Recommendation | International Standard defines a framework for attribute certificates. That framework
includes specification of data objects used to represent the certificates themselves as well as revocation notices for
issued certificates that should no longer be trusted. The attribute certificate framework defined in this Specification,
while it defines some critical components of a Privilege Management Infrastructure (PMI), does not define a PMI in its
entirety. However, this Specification provides the foundation upon which full PMIs and their specifications would be
built.
Information objects for holding PKI and PMI objects in the Directory and for comparing presented values with stored
values are also defined.
This Recommendation | International Standard also defines a framework for the provision of authentication services by
the Directory to its users.
This Recommendation | International Standard provides the foundation frameworks upon which industry profiles can be
defined by other standards groups and industry forums. Many of the features defined as optional in these frameworks
may be mandated for use in certain environments through profiles. This fifth edition technically revises and enhances,
but does not replace, the fourth edition of this Recommendation | International Standard. Implementations may still
claim conformance to the fourth edition. However, at some point, the fourth edition will not be supported (i.e., reported
defects will no longer be resolved). It is recommended that implementations conform to this fifth edition as soon as
possible.
This fifth edition specifies versions 1, 2 and 3 of public-key certificates and versions 1 and 2 of certificate revocation
lists. This edition also specifies version 2 of attribute certificates.
The extensibility function was added in an earlier edition with version 3 of the public-key certificate and with version 2
of the certificate revocation list and was incorporated into the attribute certificate from its initial inception. This
function is specified in clause 7. It is anticipated that any enhancements to this edition can be accommodated using this
function and avoid the need to create new versions
Annex A, which is an integral part of this Recommendation | International Standard, provides the ASN.1 modules
which contain all of the definitions associated with the frameworks.
Annex B, which is an integral part of this Recommendation | International Standard, provides rules for generating and
processing Certificate Revocation Lists.
Annex C, which is not an integral part of this Recommendation | International Standard, provides examples of deltaCRL
issuance.
Annex D, which is not an integral part of this Recommendation | International Standard, provides examples of privilege
policy syntaxes and privilege attributes.
viii ITU-T Rec. X.509 (08/2005)
Annex E, which is not an integral part of this Recommendation | International Standard, is an introduction to public-key
cryptography.
Annex F, which is an integral part of this Recommendation | International Standard, defines object identifiers assigned
to authentication and encryption algorithms, in the absence of a formal register.
Annex G, which is not an integral part of this Recommendation | International Standard, contains examples of the use of
certification path constraints.
Annex H, which is not an integral part of this Recommendation | International Standard, provides guidance for PKI
enabled applications on the processing of certificate policy while in the certificate path validation process.
Annex I, which is not an integral part of this Recommendation | International Standard, provides guidance on the use of
the contentCommitment bit in the keyUsage certificate extension.
Annex J, which is not an integral part of this Recommendation | International Standard, contains an alphabetical list of
information item definitions in this Specification.
Annex K, which is not an integral part of this Recommendation | International Standard, lists the amendments and
defect reports that have been incorporated to form this edition of this Recommendation | International Standard.
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 1
INTERNATIONAL STANDARD
ITU-T RECOMMENDATION
Information technology ­ Open Systems Interconnection ­ The Directory:
Public-key and attribute certificate frameworks
SECTION 1 ­ GENERAL
1 Scope
This Recommendation | International Standard addresses some of the security requirements in the areas of
authentication and other security services through the provision of a set of frameworks upon which full services can be
based. Specifically, this Recommendation | International Standard defines frameworks for:
­ Public-key certificates;
­ Attribute certificates;
­ Authentication services.
The public-key certificate framework defined in this Recommendation | International Standard includes definition of the
information objects for Public Key Infrastructure (PKI), including public-key certificates, and Certificate Revocation
List (CRL). The attribute certificate framework includes definition of the information objects for Privilege Management
Infrastructure (PMI), including attribute certificates, and Attribute Certificate Revocation List (ACRL). This
Specification also provides the framework for issuing, managing, using and revoking certificates. An extensibility
mechanism is included in the defined formats for both certificate types and for all revocation list schemes. This
Recommendation | International Standard also includes a set of standard extensions for each, which is expected to be
generally useful across a number of applications of PKI and PMI. The schema components, including object classes,
attribute types and matching rules for storing PKI and PMI objects in the Directory, are included in this
Recommendation | International Standard. Other elements of PKI and PMI, beyond these frameworks, such as key and
certificate management protocols, operational protocols, additional certificate and CRL extensions are expected to be
defined by other standards bodies (e.g., ISO TC 68, IETF, etc.).
The authentication scheme defined in this Recommendation | International Standard is generic and may be applied to a
variety of applications and environments.
The Directory makes use of public-key certificates and attribute certificates, and the framework for the Directory's use
of these facilities is also defined in this Recommendation | International Standard. Public-key technology, including
certificates, is used by the Directory to enable strong authentication, signed and/or encrypted operations, and for storage
of signed and/or encrypted data in the Directory. Attribute certificates can be used by the Directory to enable rule-based
access control. Although the framework for these is provided in this Specification, the full definition of the Directory's
use of these frameworks, and the associated services provided by the Directory and its components is supplied in the
complete set of Directory Specifications.
This Recommendation | International Standard, in the Authentication services framework, also:
­ specifies the form of authentication information held by the Directory;
­ describes how authentication information may be obtained from the Directory;
­ states the assumptions made about how authentication information is formed and placed in the Directory;
­ defines three ways in which applications may use this authentication information to perform
authentication and describes how other security services may be supported by authentication.
This Recommendation | International Standard describes two levels of authentication: simple authentication, using a
password as a verification of claimed identity; and strong authentication, involving credentials formed using
cryptographic techniques. While simple authentication offers some limited protection against unauthorized access, only
strong authentication should be used as the basis for providing secure services. It is not intended to establish this as a
general framework for authentication, but it can be of general use for applications which consider these techniques
adequate.
ISO/IEC 9594-8:2005 (E)
2 ITU-T Rec. X.509 (08/2005)
Authentication (and other security services) can only be provided within the context of a defined security policy. It is a
matter for users of an application to define their own security policy which may be constrained by the services provided
by a standard.
It is a matter for standards-defining applications which use the authentication framework to specify the protocol
exchanges which need to be performed in order to achieve authentication based upon the authentication information
obtained from the Directory. The protocol used by applications to obtain credentials from the Directory is the Directory
Access Protocol (DAP), specified in ITU-T Rec. X.519 | ISO/IEC 9594-5.
2 Normative references
The following Recommendations and International Standards contain provisions which, through reference in this text,
constitute provisions of this Recommendation | International Standard. At the time of publication, the editions indicated
were valid. All Recommendations and Standards are subject to revision, and parties to agreements based on this
Recommendation | International Standard are encouraged to investigate the possibility of applying the most recent
edition of the Recommendations and Standards listed below. Members of IEC and ISO maintain registers of currently
valid International Standards. The Telecommunication Standardization Bureau of the ITU maintains a list of currently
valid ITU-T Recommendations.
2.1 Identical Recommendations | International Standards
­ ITU-T Recommendation X.411 (1999) | ISO/IEC 10021-4:2003, Information technology ­ Message
Handling Systems (MHS) ­ Message transfer system: Abstract service definition and procedures.
­ ITU-T Recommendation X.500 (2005) | ISO/IEC 9594-1:2005, Information technology ­ Open Systems
Interconnection ­ The Directory: Overview of concepts, models and services.
­ ITU-T Recommendation X.501 (2005) | ISO/IEC 9594-2:2005, Information technology ­ Open Systems
Interconnection ­ The Directory: Models.
­ ITU-T Recommendation X.511 (2005) | ISO/IEC 9594-3:2005, Information technology ­ Open Systems
Interconnection ­ The Directory: Abstract service definition.
­ ITU-T Recommendation X.518 (2005) | ISO/IEC 9594-4:2005, Information technology ­ Open Systems
Interconnection ­ The Directory: Procedures for distributed operation.
­ ITU-T Recommendation X.519 (2005) | ISO/IEC 9594-5:2005, Information technology ­ Open Systems
Interconnection ­ The Directory: Protocol specifications.
­ ITU-T Recommendation X.520 (2005) | ISO/IEC 9594-6:2005, Information technology ­ Open Systems
Interconnection ­ The Directory: Selected attribute types.
­ ITU-T Recommendation X.521 (2005) | ISO/IEC 9594-7:2005, Information technology ­ Open Systems
Interconnection ­ The Directory: Selected object classes.
­ ITU-T Recommendation X.525 (2005) | ISO/IEC 9594-9:2005, Information technology ­ Open Systems
Interconnection ­ The Directory: Replication.
­ ITU-T Recommendation X.530 (2005) | ISO/IEC 9594-10:2005, Information technology ­ Open Systems
Interconnection ­ The Directory: Use of systems management for administration of the Directory.
­ ITU-T Recommendation X.660 (2004) | ISO/IEC 9834-1:2005, Information technology ­ Open Systems
Interconnection ­ Procedures for the operation of OSI Registration Authorities: General procedures,
and top arcs of the ASN.1 Object Identifier tree.
­ ITU-T Recommendation X.680 (2002) | ISO/IEC 8824-1:2002, Information technology ­ Abstract
Syntax Notation One (ASN.1): Specification of basic notation.
­ ITU-T Recommendation X.681 (2002) | ISO/IEC 8824-2:2002, Information technology ­ Abstract
Syntax Notation One (ASN.1): Information object specification.
­ ITU-T Recommendation X.682 (2002) | ISO/IEC 8824-3:2002, Information technology ­ Abstract
Syntax Notation One (ASN.1): Constraint specification.
­ ITU-T Recommendation X.683 (2002) | ISO/IEC 8824-4:2002, Information technology ­ Abstract
Syntax Notation One (ASN.1): Parameterization of ASN.1 specifications.
­ ITU-T Recommendation X.690 (2002) | ISO/IEC 8825-1:2002, Information technology ­ ASN.1
encoding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and
Distinguished Encoding Rules (DER).
­ ITU-T Recommendation X.691 (2002) | ISO/IEC 8825-2:2002, Information technology ­ ASN.1
encoding rules: Specification of Packed Encoding Rules (PER).
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ITU-T Rec. X.509 (08/2005) 3
­ ITU-T Recommendation X.812 (1995) | ISO/IEC 10181-3:1996, Information technology ­ Open Systems
Interconnection ­ Security frameworks for open systems: Access control framework.
­ ITU-T Recommendation X.813 (1996) | ISO/IEC 10181-4:1997, Information technology ­ Open Systems
Interconnection ­ Security frameworks for open systems: Non-repudiation framework.
­ ITU-T Recommendation X.880 (1994) | ISO/IEC 13712-1:1995, Information technology ­ Remote
Operations: Concepts, model and notation.
­ ITU-T Recommendation X.881 (1994) | ISO/IEC 13712-2:1995, Information technology ­ Remote
Operations: OSI realizations ­ Remote Operations Service Element (ROSE) service definition.
2.2 Paired Recommendations | International Standards equivalent in technical content
­ CCITT Recommendation X.800 (1991), Security Architecture for Open Systems Interconnection for
CCITT applications.
ISO 7498-2:1989, Information processing systems ­ Open Systems Interconnection ­ Basic Reference
Model ­ Part 2: Security Architecture.
3 Definitions
For the purposes of this Recommendation | International Standard, the following definitions apply.
3.1 OSI Reference Model security architecture definitions
The following terms are defined in CCITT Rec. X.800 | ISO 7498-2:
a) asymmetric (encipherment);
b) authentication exchange;
c) authentication information;
d) confidentiality;
e) credentials;
f) cryptography;
g) data origin authentication;
h) decipherment;
i) digital signature;
j) encipherment;
k) key;
l) password;
m) peer-entity authentication;
n) symmetric (encipherment).
3.2 Directory model definitions
The following terms are defined in ITU-T Rec. X.501 | ISO/IEC 9594-2:
a) attribute;
b) Directory Information Base;
c) Directory Information Tree;
d) Directory System Agent;
e) Directory User Agent;
f) distinguished name;
g) entry;
h) object;
i) root.
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3.3 Definitions
The following terms are defined in this Recommendation | International Standard:
3.3.1 attribute certificate (AC): A data structure, digitally signed by an Attribute Authority, that binds some
attribute values with identification information about its holder.
3.3.2 Attribute Authority (AA): An authority which assigns privileges by issuing attribute certificates.
3.3.3 attribute authority revocation list (AARL): A revocation list containing a list of references to attribute
certificates issued to AAs that are no longer considered valid by the issuing authority.
3.3.4 attribute certificate revocation list (ACRL): A revocation list containing a list of references to attribute
certificates that are no longer considered valid by the issuing authority.
3.3.5 authentication token; (token): Information conveyed during a strong authentication exchange, which can be
used to authenticate its sender.
3.3.6 authority: An entity, responsible for the issuance of certificates. Two types are defined in this Specification;
certification authority which issues public-key certificates and attribute authority which issues attribute certificates.
3.3.7 authority certificate: A certificate issued to an authority (e.g., either to a certification authority or to an
attribute authority).
3.3.8 base CRL: A CRL that is used as the foundation in the generation of a dCRL.
3.3.9 CA-certificate: A certificate for one CA issued by another CA.
3.3.10 certificate policy: A named set of rules that indicates the applicability of a certificate to a particular
community and/or class of application with common security requirements. For example, a particular certificate policy
might indicate applicability of a type of certificate to the authentication of electronic data interchange transactions for
the trading of goods within a given price range.
3.3.11 certification practice statement (CPS): A statement of the practices that a Certification Authority employs
in issuing certificates.
3.3.12 certificate revocation list (CRL): A signed list indicating a set of certificates that are no longer considered
valid by the certificate issuer. In addition to the generic term CRL, some specific CRL types are defined for CRLs that
cover particular scopes.
3.3.13 certificate user: An entity that needs to know, with certainty, the attributes and/or public key of another
entity.
3.3.14 certificate serial number: An integer value, unique within the issuing authority, which is unambiguously
associated with a certificate issued by that authority.
3.3.15 certificate-using system: An implementation of those functions defined in this Directory Specification that
are used by a certificate-user.
3.3.16 certificate validation: The process of ensuring that a certificate was valid at a given time, including possibly
the construction and processing of a certification path, and ensuring that all certificates in that path were valid (i.e., were
not expired or revoked) at that given time.
3.3.17 certification authority (CA): An authority trusted by one or more users to create and assign public-key
certificates. Optionally the certification authority may create the users' keys.
3.3.18 certification authority revocation list (CARL): A revocation list containing a list of public-key certificates
issued to certification authorities, that are no longer considered valid by the certificate issuer.
3.3.19 certification path: An ordered sequence of public key certificates of objects in the DIT which, together with
the public key of the initial object in the path, can be processed to obtain that of the final object in the path.
3.3.20 CRL distribution point: A directory entry or other distribution source for CRLs; a CRL distributed through a
CRL distribution point may contain revocation entries for only a subset of the full set of certificates issued by one CA
or may contain revocation entries for multiple CAs.
3.3.21 cross-certificate: A public-key or attribute certificate where the issuer and the subject/holder are different
CAs or AAs respectively. CAs and AAs issue cross-certificates to other CAs or AAs respectively as a mechanism to
authorize the subject CA's existence (e.g., in a strict hierarchy) or to recognize the existence of the subject CA or holder
AA (e.g., in a distributed trust model). The cross-certificate structure is used for both of these.
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3.3.22 cryptographic system, cryptosystem: A collection of transformations from plain text into ciphertext and
vice versa, the particular transformation(s) to be used being selected by keys. The transformations are normally defined
by a mathematical algorithm.
3.3.23 data confidentiality: This service can be used to provide for protection of data from unauthorized disclosure.
The data confidentiality service is supported by the authentication framework. It can be used to protect against data
interception.
3.3.24 delegation: Conveyance of privilege from one entity that holds such privilege, to another entity.
3.3.25 delegation path: An ordered sequence of certificates which, together with authentication of a privilege
asserter's identity can be processed to verify the authenticity of an asserter's privilege.
3.3.26 delta-CRL (dCRL): A partial revocation list that only contains entries for certificates that have had their
revocation status changed since the issuance of the referenced base CRL.
3.3.27 end entity: Either a public key certificate subject that uses its private key for purposes other than signing
certificates, or an attribute certificate holder that uses its attributes to gain access to a resource, or an entity that is a
relying party.
3.3.28 end-entity attribute certificate revocation list (EARL): A revocation list containing a list of attribute
certificates issued to holders, that are not also AAs, that are no longer considered valid by the certificate issuer.
3.3.29 end-entity public-key certificate revocation list (EPRL): A revocation list containing a list of public-key
certificates issued to subjects, that are not also CAs, that are no longer considered valid by the certificate issuer.
3.3.30 environmental variables: Those aspects of policy required for an authorization decision, that are not
contained within static structures, but are available through some local means to a privilege verifier (e.g., time of day or
current account balance).
3.3.31 full CRL: A complete revocation list that contains entries for all certificates that have been revoked for the
given scope.
3.3.32 hash function: A (mathematical) function which maps values from a large (possibly very large) domain into a
smaller range. A "good" hash function is such that the results of applying the function to a (large) set of values in the
domain will be evenly distributed (and apparently at random) over the range.
3.3.33 holder: An entity to whom some privilege has been delegated either directly from the Source of Authority or
indirectly through another Attribute Authority.
3.3.34 indirect CRL (iCRL): A revocation list that at least contains revocation information about certificates issued
by authorities other than that which issued this CRL.
3.3.35 key agreement: A method for negotiating a key value on-line without transferring the key, even in an
encrypted form, e.g., the Diffie-Hellman technique (see ISO/IEC 11770-1 for more information on key agreement
mechanisms).
3.3.36 object method: An action that can be invoked on a resource (e.g., a file system may have read, write and
execute object methods).
3.3.37 one-way function: A (mathematical) function f which is easy to compute, but which for a general value y in
the range, it is computationally difficult to find a value x in the domain such that f(x) = y. There may be a few values y
for which finding x is not computationally difficult.
3.3.38 policy mapping: Recognizing that, when a CA in one domain certifies a CA in another domain, a particular
certificate policy in the second domain may be considered by the authority of the first domain to be equivalent (but not
necessarily identical in all respects) to a particular certificate policy in the first domain.
3.3.39 private key; secret key (deprecated): (In a public key cryptosystem) that key of a user's key pair which is
known only by that user.
3.3.40 privilege: An attribute or property assigned to an entity by an authority.
3.3.41 privilege asserter: A privilege holder using their attribute certificate or public-key certificate to assert
privilege.
3.3.42 privilege management infrastructure (PMI): The infrastructure able to support the management of
privileges in support of a comprehensive authorization service and in relationship with a Public Key Infrastructure.
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3.3.43 privilege policy: The policy that outlines conditions for privilege verifiers to provide/perform sensitive
services to/for qualified privilege asserters. Privilege policy relates attributes associated with the service as well as
attributes associated with privilege asserters.
3.3.44 privilege verifier: An entity verifying certificates against a privilege policy.
3.3.45 public-key: (In a public key cryptosystem) that key of a user's key pair which is publicly known.
3.3.46 public-key certificate (PKC): The public key of a user, together with some other information, rendered
unforgeable by digital signature with the private key of the certification authority which issued it.
3.3.47 public key infrastructure (PKI): The infrastructure able to support the management of public keys able to
support authentication, encryption, integrity or non-repudiation services.
3.3.48 relying party: A user or agent that relies on the data in a certificate in making decisions.
3.3.49 role assignment certificate: A certificate that contains the role attribute, assigning one or more roles to the
certificate subject/holder.
3.3.50 role specification certificate: A certificate that contains the assignment of privileges to a role.
3.3.51 sensitivity: Characteristic of a resource that implies its value or importance.
3.3.52 simple authentication: Authentication by means of simple password arrangements.
3.3.53 security policy: The set of rules laid down by the security authority governing the use and provision of
security services and facilities.
3.3.54 self-issued AC: An attribute certificate where the issuer and the subject are the same Attribute Authority. An
Attribute Authority might use a self-issued AC, for example, to publish policy information.
3.3.55 self-issued certificate: A public-key certificate where the issuer and the subject are the same CA. A CA
might use self-issued certificates, for example, during a key rollover operation to provide trust from the old key to the
new key.
3.3.56 self-signed certificate: A special case of self-issued certificates where the private key used by the CA to sign
the certificate corresponds to the public key that is certified within the certificate. A CA might use a self-signed
certificate, for example, to advertise their public key or other information about their operations.
NOTE ­ Use of self-issued certificates and self-signed certificates issued by other than CAs are outside the scope of this
Recommendation | International Standard.
3.3.57 source of authority (SOA): An Attribute Authority that a privilege verifier for a particular resource trusts as
the ultimate authority to assign a set of privileges.
3.3.58 strong authentication: Authentication by means of cryptographically derived credentials.
3.3.59 trust: Generally, an entity can be said to "trust" a second entity when it (the first entity) makes the assumption
that the second entity will behave exactly as the first entity expects. This trust may apply only for some specific
function. The key role of trust in this framework is to describe the relationship between an authenticating entity and an
authority; an entity shall be certain that it can trust the authority to create only valid and reliable certificates.
3.3.60 trust anchor: A trust anchor is a set of the following information in addition to the public key: algorithm
identifier, public key parameters (if applicable), distinguished name of the holder of the associated private key (i.e., the
subject CA) and optionally a validity period. The trust anchor may be provided in the form of a self-signed certificate.
A trust anchor is trusted by a certificate using system and used for validating certificates in certification paths.
4 Abbreviations
For the purposes of this Recommendation | International Standard, the following abbreviations apply:
AA Attribute Authority
AARL Attribute Authority Revocation List
AC Attribute Certificate
ACRL Attribute Certificate Revocation List
CA Certification Authority
CARL Certification Authority Revocation List
CRL Certificate Revocation List
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dCRL Delta Certificate Revocation List
DIB Directory Information Base
DIT Directory Information Tree
DSA Directory System Agent
DUA Directory User Agent
EARL End-entity Attribute certificate Revocation List
EPRL End-entity Public-key certificate Revocation List
iCRL Indirect Certificate Revocation List
OCSP Online Certificate Status Protocol
PKC Public-Key Certificate
PKCS Public-Key Cryptosystem
PKI Public-Key Infrastructure
PMI Privilege Management Infrastructure
SOA Source of Authority
5 Conventions
With minor exceptions this Directory Specification has been prepared according to the Rules for presentation of
ITU-T | ISO/IEC common text, November 2001.
The term "Directory Specification" (as in "this Directory Specification") shall be taken to mean ITU-T Rec. X.509 |
ISO/IEC 9594-8. The term "Directory Specifications" shall be taken to mean the X.500-series Recommendations and all
parts of ISO/IEC 9594.
This Directory Specification uses the term first edition systems to refer to systems conforming to the first edition of the
Directory Specifications, i.e., the 1988 edition of the series of CCITT X.500 Recommendations and the
ISO/IEC 9594:1990 edition. This Directory Specification uses the term second edition systems to refer to systems
conforming to the second edition of the Directory Specifications, i.e., the 1993 edition of the series of ITU-T X.500
Recommendations and the ISO/IEC 9594:1995 edition. This Directory Specification uses the term third edition systems
to refer to systems conforming to the third edition of the Directory Specifications, i.e., the 1997 edition of the series of
ITU-T X.500 Recommendations and the ISO/IEC 9594:1998 edition. This Directory Specification uses the term fourth
edition systems to refer to systems conforming to the fourth edition of the Directory Specifications, i.e., the 2001
editions of ITU-T Recs X.500, X.501, X.511, X.518, X.519, X.520, X.521, X.525, and X.530, the 2000 edition of
ITU-T Rec. X.509, and parts 1-10 of the ISO/IEC 9594:2001 edition.
This Directory Specification uses the term fifth edition systems to refer to systems conforming to the fifth edition of the
Directory Specifications, i.e., the 2005 editions of ITU-T Rec. X.500, X.501, X.509, X.511, X.518, X.519, X.520,
X.521, X.525, and X.530 and parts 1-10 of the ISO/IEC 9594:2005 edition.
This Directory Specification presents ASN.1 notation in the bold Helvetica typeface. When ASN.1 types and values are
referenced in normal text, they are differentiated from normal text by presenting them in the bold Helvetica typeface.
The names of procedures, typically referenced when specifying the semantics of processing, are differentiated from
normal text by displaying them in bold Times. Access control permissions are presented in italicized Times.
If the items in a list are numbered (as opposed to using "­" or letters), then the items shall be considered steps in a
procedure.
The notation used in this Directory Specification is defined in Table 1 below.
Table 1 ­ Notation
Notation Meaning
Xp Public key of a user X.
Xs Private key of X.
Xp[I] Encipherment of some information, I, using the public key of X.
Xs[I] Encipherment of I using the private key of X.
X{I} The signing of I by user X. It consists of I with an enciphered summary appended.
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CA(X) A certification authority of user X.
CAn
(X) (Where n>1): CA(CA(...n times...(X)))
X1<<X2>> The certificate of user X2 issued by certification authority X1.
X1<<X2>>
X2<<X3>>
A chain of certificates (can be of arbitrary length), where each item is the certificate for the certification
authority which produced the next. It is functionally equivalent to the following certificate X1<<Xn+1>>.
For example, possession of A<<B>>B<<C>> provides the same capability as A<<C>>, namely the
ability to find out Cp given Ap.
X1p  X1<<X2>> The operation of unwrapping a certificate (or certificate chain) to extract a public key. It is an infix
operator, whose left operand is the public key of a certification authority, and whose right operand is a
certificate issued by that certification authority. The outcome is the public key of the user whose
certificate is the right operand. For example:
Ap  A<<B>> B<<C>>
denotes the operation of using the public key of A to obtain B's public key, Bp, from its certificate,
followed by using Bp to unwrap C's certificate. The outcome of the operation is the public key of C, Cp.
AB A certification path from A to B, formed of a chain of certificates, starting with CA(A)<<CA2
(A)>> and
ending with CA(B)<<B>>.
NOTE ­ In the table, the symbols X, X1, X2, etc. occur in place of the names of users, while the symbol I occurs in place of
arbitrary information.
6 Frameworks overview
This Specification defines a framework for obtaining and trusting a public key of an entity in order to encrypt
information to be decrypted by that entity, or in order to verify the digital signature of that entity. The framework
includes the issuance of a public-key certificate by a Certification Authority (CA) and the validation of that certificate
by the certificate user. The validation includes:
­ establishing a trusted path of certificates between the certificate user and the certificate subject;
­ verifying the digital signatures on each certificate in the path; and
­ validating all the certificates along that path (i.e., that they were not expired or not revoked at a given
time).
This Specification defines a framework for obtaining and trusting privilege attributes of an entity in order to determine
whether or not they are authorized to access a particular resource. The framework includes the issuance of a certificate
by an Attribute Authority (AA) and the validation of that certificate by a privilege verifier. The validation includes:
­ ensuring that the privileges in the certificate are sufficient when compared against the privilege policy;
­ establishing a trusted delegation path of certificates if necessary;
­ verifying the digital signature on each certificate in the path;
­ ensuring that each issuer was authorized to delegate privileges; and
­ validating that the certificates have not expired or been revoked by their issuers.
Although PKI and PMI are separate infrastructures and may be established independently from one another, they are
related. This Specification recommends that holders and issuers of attribute certificates be identified within attribute
certificates by pointers to their appropriate public-key certificates. Authentication of the attribute certificate issuers and
holders, to ensure that entities claiming privilege and issuing privilege are who they claim to be, is done using the
normal processes of the PKI to authenticate identities. This authentication process is not duplicated within the attribute
certificate framework.
6.1 Digital signatures
Digital signatures are used in both PKI and PMI as the mechanism by which the authority that issues a certificate
certifies the binding in the certificate. In PKI the digital signature of the issuing CA on a public-key certificate certifies
the binding between the public-key material and the subject of the certificate. In PMI the digital signature of the
issuing AA certifies the binding between the attributes (privileges) and the holder of the certificate. This subclause
describes digital signatures in general. Sections 2 and 3 of this Specification discuss the use of digital signatures within
PKI and PMI specifically.
This subclause is not intended to specify a standard for digital signatures in general, but to specify the means by which
the tokens are signed in PKI, PMI and in the Directory.
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Information (info) is signed by appending to it an enciphered summary of the information. The summary is produced by
means of a one-way hash function, while the enciphering is carried out using the private key of the signer (see
Figure 1). Thus:
X{Info} = Info, Xs[h (Info)]
Figure 1 ­ Digital signatures
NOTE 1 ­ The encipherment using the private key ensures that the signature cannot be forged. The one-way nature of the hash
function ensures that false information, generated so as to have the same hash result (and thus signature), cannot be substituted.
The recipient of signed information verifies the signature by:
­ applying the one-way hash function to the information;
­ comparing the result with that obtained by deciphering the signature using the public key of the signer.
This Specification does not mandate a single one-way hash function for use in signing. It is intended that the framework
shall be applicable to any suitable hash function, and shall thus support changes to the methods used as a result of future
advances in cryptography, mathematical techniques or computational capabilities. However, two users wishing to
authenticate shall support the same hash function for authentication to be performed correctly. Thus, within the context
of a set of related applications, the choice of a single function shall serve to maximize the community of users able to
authenticate and communicate securely.
The signed information includes indicators that identify the hashing algorithm and the encryption algorithm used to
compute the digital signature.
The encipherment of some data item may be described using the following ASN.1:
ENCRYPTED { ToBeEnciphered } ::= BIT STRING ( CONSTRAINED BY {
-- shall be the result of applying an encipherment procedure --
-- to the BER-encoded octets of a value of -- ToBeEnciphered } )
The value of the bit string is generated by taking the octets which form the complete encoding (using the ASN.1 Basic
Encoding Rules ­ ITU-T Rec. X.690 (2002) | ISO/IEC 8825-1:2002) of the value of the ToBeEnciphered type and
applying an encipherment procedure to those octets.
NOTE 2 ­ The encryption procedure requires agreement on the algorithm to be applied, including any parameters of the
algorithm such as any necessary keys, initialization values, and padding instructions. It is the responsibility of the encryption
procedures to specify the means by which synchronization of the sender and receiver of data is achieved, which may include
information in the bits to be transmitted.
NOTE 3 ­ The encryption procedure is required to take as input a string of octets and to generate a single string of bits as its
result.
NOTE 4 ­ Mechanisms for secure agreement on the encryption algorithm and its parameters by the sender and receiver of data
are outside the scope of this Directory Specification.
The signature of some data item is formed by encrypting a shortened or "hashed" transformation of the item, and may
be described by the following ASN.1:
HASH {ToBeHashed} ::= SEQUENCE {
algorithmIdentifier AlgorithmIdentifier,
hashValue BIT STRING ( CONSTRAINED BY {
-- shall be the result of applying a hashing procedure to the DER-encoded octets --
-- of a value of -- ToBeHashed } ) }
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ENCRYPTED-HASH { ToBeSigned } ::= BIT STRING ( CONSTRAINED BY {
-- shall be the result of applying a hashing procedure to the DER-encoded octets --
-- of a value of -- ToBeSigned -- and then applying an encipherment procedure to those octets -- })
SIGNATURE { ToBeSigned } ::= SEQUENCE {
algorithmIdentifier AlgorithmIdentifier,
encrypted ENCRYPTED-HASH { ToBeSigned }}
NOTE 5 ­ The encryption procedure requires the agreements listed in Note 2, and also agreement as to whether the hashed octets
are encrypted directly, or only after further encoding them as a BIT STRING using the ASN.1 Basic Encoding Rules.
In the case where a signature is appended to a data type, the following ASN.1 may be used to define the data type
resulting from applying a signature to the given data type.
SIGNED { ToBeSigned } ::= SEQUENCE {
toBeSigned ToBeSigned,
COMPONENTS OF SIGNATURE { ToBeSigned }}
In order to enable the validation of SIGNED and SIGNATURE types in a distributed environment, a distinguished
encoding is required. A distinguished encoding of a SIGNED or SIGNATURE data value shall be obtained by applying
the Basic Encoding Rules defined in ITU-T Rec. X.690 (2002) | ISO/IEC 8825-1:2002, with the following restrictions:
a) the definite form of length encoding shall be used, encoded in the minimum number of octets;
b) for string types, the constructed form of encoding shall not be used;
c) if the value of a type is its default value, it shall be absent;
d) the components of a Set type shall be encoded in ascending order of their tag value;
e) the components of a Set-of type shall be encoded in ascending order of their octet value;
f) if the value of a Boolean type is true, the encoding shall have its contents octet set to "FF"16;
g) each unused bit in the final octet of the encoding of a Bit String value, if there are any, shall be set to
zero;
h) the encoding of a Real type shall be such that bases 8, 10, and 16 shall not be used, and the binary scaling
factor shall be zero.
i) the encoding of a UTC time shall be as specified in ITU-T Rec. X.690 (2002) | ISO/IEC 8825-1:2002;
j) the encoding of a Generalized time shall be as specified in ITU-T Rec. X.690 (2002) |
ISO/IEC 8825-1:2002.
Generating a distinguished encoding requires the abstract syntax of the data to be encoded to be fully understood. The
Directory may be required to sign data or check the signature of data that contains unknown protocol extensions or
unknown attribute syntaxes. The Directory shall follow these rules:
­ It shall preserve the encoding of received information whose abstract syntax it does not fully know and
which it expects to subsequently sign;
­ When signing data for sending, it shall send data whose syntax it fully knows with a distinguished
encoding and any other data with its preserved encoding, and shall sign the actual encoding it sends;
­ When checking signatures in received data, it shall check the signature against the actual data received
rather than its conversion of the received data to a distinguished encoding.
SECTION 2 ­ PUBLIC-KEY CERTIFICATE FRAMEWORK
The public-key certificate framework defined here is for use by applications with requirements for authentication,
integrity, confidentiality and non-repudiation.
The binding of a public-key to an entity is provided by an authority through a digitally signed data structure called a
public-key certificate. The format of public-key certificates is defined here, including an extensibility mechanism and a
set of specific certificate extensions. If, for any reason, an authority revokes a previously issued public-key certificate,
users need to be able to learn that revocation has occurred so they do not use an untrustworthy certificate. Revocation
lists are one scheme that can be used to notify users of revocations. The format of revocation lists is defined here,
including an extensibility mechanism and a set of revocation list extensions. In both the certificate and revocation list
case, other bodies may also define additional extensions that are useful to their specific environments.
A public key certificate-using system needs to validate a certificate prior to using that certificate for an application.
Procedures for performing that validation are also defined here, including verifying the integrity of the certificate itself,
its revocation status, and its validity with respect to the intended use.
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The Directory uses public-key certificates in its provision of security services including:
­ strong authentication between and among directory components;
­ authentication, integrity and confidentiality of directory operations; as well as
­ integrity and authentication of stored data.
7 Public-keys and public-key certificates
In order for a user to be able to trust a public-key for another user, for instance to authenticate the identity of that user,
the public-key shall be obtained from a trusted source. Such a source, called a Certification Authority (CA), certifies a
public key by issuing a public-key certificate which binds the public-key to the entity which holds the corresponding
private-key. The procedures used by a CA to ensure that an entity is in fact in the possession of the private key and
other procedures related to the issuance of public-key certificates are outside the scope of this Specification. The
certificate, the form of which is specified later in this clause, has the following properties:
­ any user with access to the public key of the certification authority can recover the public key which was
certified;
­ no party other than the certification authority can modify the certificate without this being detected
(certificates are unforgeable).
Because certificates are unforgeable, they can be published by being placed in the Directory, without the need for the
latter to make special efforts to protect them.
NOTE 1 ­ Although the CAs are unambiguously defined by a distinguished name in the DIT, this does not imply that there is any
relationship between the organization of the CAs and the DIT.
A certification authority produces the certificate of a user by signing (see 6.1) a collection of information, including the
user's distinguished name and public key, as well as an optional unique identifier containing additional information
about the user. The exact form of the unique identifier contents is unspecified here and left to the certification authority
and might be, for example, an object identifier, a certificate, a date, or some other form of certification on the validity of
the distinguished name. Specifically, the certificate of a user with distinguished name A and unique identifier UA,
produced by the certification authority with name CA and unique identifier UCA, has the following form:
CA<<A>> = CA{V,SN,AI,CA,UCA,A,UA,Ap,TA}
where V is the version of the certificate, SN is the serial number of the certificate, AI is the identifier of the algorithm
used to sign the certificate, UCA is the optional unique identifier of the CA, UA is the optional unique identifier of the
user A, TA indicates the period of validity of the certificate, and consists of two dates, the first and last on which the
certificate is valid. The certificate validity period is the time interval during which the CA warrants that it will maintain
information about the status of the certificate, i.e., publish revocation data. Since TA is assumed to be changed in
periods not less than 24 hours, it is expected that systems would use Coordinated Universal Time as a reference time
base. The signature in the certificate can be checked for validity by any user with knowledge of CAp. The following
ASN.1 data type can be used to represent certificates:
Certificate ::= SIGNED { SEQUENCE {
version [0] Version DEFAULT v1,
serialNumber CertificateSerialNumber,
signature AlgorithmIdentifier,
issuer Name,
validity Validity,
subject Name,
subjectPublicKeyInfo SubjectPublicKeyInfo,
issuerUniqueIdentifier [1] IMPLICIT UniqueIdentifier OPTIONAL,
-- if present, version shall be v2 or v3
subjectUniqueIdentifier [2] IMPLICIT UniqueIdentifier OPTIONAL,
-- if present, version shall be v2 or v3
extensions [3] Extensions OPTIONAL
-- If present, version shall be v3 -- } }
Version ::= INTEGER { v1(0), v2(1), v3(2) }
CertificateSerialNumber ::= INTEGER
AlgorithmIdentifier ::= SEQUENCE {
algorithm ALGORITHM.&id ({SupportedAlgorithms}),
parameters ALGORITHM.&Type ({SupportedAlgorithms}{ @algorithm}) OPTIONAL }
ISO/IEC 9594-8:2005 (E)
12 ITU-T Rec. X.509 (08/2005)
-- Definition of the following information object set is deferred, perhaps to standardized
-- profiles or to protocol implementation conformance statements. The set is required to
-- specify a table constraint on the parameters component of AlgorithmIdentifier.
-- SupportedAlgorithms ALGORITHM ::= { ... }
Validity ::= SEQUENCE {
notBefore Time,
notAfter Time }
SubjectPublicKeyInfo ::= SEQUENCE {
algorithm AlgorithmIdentifier,
subjectPublicKey BIT STRING }
Time ::= CHOICE {
utcTime UTCTime,
generalizedTime GeneralizedTime }
Extensions ::= SEQUENCE OF Extension
Extension ::= SEQUENCE {
extnId EXTENSION.&id ({ExtensionSet}),
critical BOOLEAN DEFAULT FALSE,
extnValue OCTET STRING
-- contains a DER encoding of a value of type &ExtnType
-- for the extension object identified by extnId -- }
ExtensionSet EXTENSION ::= { ... }
Before a value of Time is used in any comparison operation, e.g., as part of a matching rule in a search, and if the
syntax of Time has been chosen as the UTCTime type, the value of the two digit year field shall be rationalized into a
four digit year value as follows:
­ If the 2-digit value is 00 through 49 inclusive, the value shall have 2000 added to it.
­ If the 2-digit value is 50 through 99 inclusive, the value shall have 1900 added to it.
NOTE 2 ­ The use of GeneralizedTime may prevent interworking with implementations unaware of the possibility of
choosing either UTCTime or GeneralizedTime. It is the responsibility of those specifying the domains in which certificates
defined in this Directory Specification will be used, e.g., profiling groups, as to when the GeneralizedTime may be used. In no
case shall UTCTime be used for representing dates beyond 2049.
version is the version of the encoded certificate. If the extensions component is present in the certificate, version shall
be v3. If the issuerUniqueIdentifier or subjectUniqueIdentifier component is present version shall be v2 or v3.
serialNumber is an integer assigned by the CA to each certificate. The value of serialNumber shall be unique for each
certificate issued by a given CA (i.e., the issuer name and serial number identify a unique certificate).
signature contains the algorithm identifier for the algorithm and hash function used by the CA in signing the certificate
(e.g., md5WithRSAEncryption, sha-1WithRSAEncryption, id-dsa-with-sha1, etc.)
issuer identifies the entity that has signed and issued the certificate.
validity is the time interval during which the CA warrants that it will maintain information about the status of the
certificate.
subject identifies the entity associated with the public-key found in the subject public key field.
subjectPublicKeyInfo is used to carry the public key being certified and to identify the algorithm which this public key
is an instance of (e.g., rsaEncryption, dhpublicnumber, id-dsa, etc.)
issuerUniqueIdentifier is used to uniquely identify an issuer in case of name re-use.
subjectUniqueIdentifier is used to uniquely identify a subject in case of name re-use.
NOTE 3 ­ In situations where a distinguished name might be reassigned to a different user by the Naming Authority, CAs can
use the unique identifier to distinguish between reused instances. However, if the same user is provided certificates by multiple
CAs, it is recommended that the CAs coordinate on the assignment of unique identifiers as part of their user registration
procedures.
The extensions field allows addition of new fields to the structure without modification to the ASN.1 definition. An
extension field consists of an extension identifier, a criticality flag, and an encoding of a data value of an ASN.1 type
associated with the identified extension. For those extensions where ordering of individual extensions within the
SEQUENCE is significant, the specification of those individual extensions shall include the rules for the significance of
the order therein. When an implementation processing a certificate does not recognize an extension, if the criticality flag
is FALSE, it may ignore that extension. If the criticality flag is TRUE, unrecognized extensions shall cause the structure
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 13
to be considered invalid, i.e., in a certificate, an unrecognized critical extension would cause validation of a signature
using that certificate to fail. When a certificate-using implementation recognizes and is able to process an extension,
then the certificate-using implementation shall process the extension regardless of the value of the criticality flag. Note
that any extension that is flagged non-critical will cause inconsistent behaviour between certificate-using systems that
will process the extension and certificate-using systems that do not recognize the extension and will ignore it.
If unknown elements appear within the extension, and the extension is not marked critical, those unknown elements
shall be ignored according to the rules of extensibility documented in 12.2.2 in ITU-T Rec. X.519 | ISO/IEC 9594-5.
A CA has three options with respect to an extension:
i) it can exclude the extension from the certificate;
ii) it can include the extension and flag it non-critical;
iii) it can include the extension and flag it critical.
A validation engine has two possible actions to take with respect to an extension:
i) it can ignore the extension and accept the certificate (all other things being equal);
ii) it can process the extension and accept or reject the certificate depending on the content of the extension
and the conditions under which processing is occurring (e.g., the current values of the path processing
variables).
Some extensions can only be marked critical. In these cases a validation engine that understands the extension processes
it; the acceptance/rejection of the certificate is dependent (at least in part) on the content of the extension. A validation
engine that does not understand the extension rejects the certificate.
Some extensions can only be marked non-critical. In these cases a validation engine that understands the extension
processes it and acceptance/rejection of the certificate is dependent (at least in part) on the content of the extension. A
validation engine that does not understand the extension accepts the certificate (unless factors other than this extension
cause it to be rejected).
Some extensions can be marked critical or non-critical. In these cases a validation engine that understands the extension
processes it: the acceptance/rejection of the certificate is dependent (at least in part) on the content of the extension,
regardless of the criticality flag. A validation engine that does not understand the extension accepts the certificate if the
extension is marked non-critical (unless factors other than this extension cause it to be rejected) and rejects the
certificate if the extension is marked critical.
When a CA considers including an extension in a certificate it does so with the expectation that its intent will be
adhered to wherever possible. If it is necessary that the content of the extension be considered prior to any reliance on
the certificate, a CA would flag the extension critical. This is done with the realization that any validation engine that
does not process the extension will reject the certificate (probably limiting the set of applications that can verify the
certificate). The CA may mark certain extension non-critical to achieve backward compatibility with validation
applications that cannot process the extensions. Where the need for backward compatibility and interoperability with
validation applications incapable of processing the extensions is more vital than the ability of the CA to rinforce the
extensions, then these optionally critical extensions would be marked non-critical. It is most likely that CAs would set
optionally critical extensions as non-critical during a transition period while the verifiers' certificate processing
applications are upgraded to ones that can process the extensions.
Specific extensions may be defined in ITU-T Recommendations | International Standards or by any organization which
has a need. The object identifier which identifies an extension shall be defined in accordance with ITU-T Rec. X.660 |
ISO/IEC 9834-1. Standard extensions for certificates are defined in clause 8 of this Directory Specification.
The following object class is used to define specific extensions.
EXTENSION ::= CLASS {
&id OBJECT IDENTIFIER UNIQUE,
&ExtnType }
WITH SYNTAX {
SYNTAX &ExtnType
IDENTIFIED BY &id }
There are two primary types of public-key certificates, end-entity certificates and CA-certificates.
An end-entity certificate is a certificate issued by a CA to a subject that is not an issuer of other public-key certificates.
ISO/IEC 9594-8:2005 (E)
14 ITU-T Rec. X.509 (08/2005)
A CA-certificate is a certificate issued by a CA to a subject that is itself a CA and therefore is capable of issuing
public-key certificates. CA-certificates can be themselves categorized by the following types:
­ Self-issued certificate ­ This is a certificate where the issuer and the subject are the same CA. A CA
might use self-issued certificates, for example, during a key rollover operation to provide trust from the
old key to the new key.
­ Self-signed certificate ­ This is a special case of self-issued certificates where the private key used by the
CA to sign the certificate corresponds to the public key that is certified within the certificate. A CA
might use a self-signed certificate, for example, to advertise their public key or other information about
their operations.
­ Cross-certificate ­ This is a certificate where the issuer and the subject are different CAs. CAs issue
certificates to other CAs either as a mechanism to authorize the subject CA's existence (e.g., in a strict
hierarchy) or to recognize the existence of the subject CA (e.g., in a distributed trust model). The
cross-certificate structure is used for both of these. In some situations, conflicting or overlapping
requirements for constraints, such as name constraints, may require a CA to issue more than one crosscertificate
to another CA.
The directory entry of each user, A, who is participating in strong authentication, contains the certificate(s) of A. Such a
certificate is generated by a Certification Authority of A, which is an entity in the DIT. A Certification Authority of A,
which may not be unique, is denoted CA(A), or simply CA if A is understood. The public key of A can thus be
discovered by any user knowing the public key of CA. Discovering public keys is thus recursive.
If user A, trying to obtain the public key of user B, has already obtained the public key of CA(B), then the process is
complete. In order to enable A to obtain the public key of CA(B), the directory entry of each Certification Authority, X,
contains a number of certificates. These certificates are of two types. First, there are forward certificates of X generated
by other Certification Authorities. Second, there are reverse certificates generated by X itself which are the certified
public keys of other certification authorities. The existence of these certificates enables users to construct certification
paths from one point to another.
A list of certificates needed to allow a particular user to obtain the public key of another, is known as a certification
path. Each item in the list is a certificate of the certification authority of the next item in the list. A certification path
from A to B (denoted AB):
­ starts with a certificate produced by CA(A), namely CA(A)<<X1>> for some entity X1;
­ continues with further certificates Xi<<Xi+1>>;
­ ends with the certificate of B.
The issuer and subject fields of each certificate are used, in part, to identify a valid path. For each pair of adjacent
certificates in a valid certification path, the value of the subject field in one certificate shall match the value of the
issuer field in the subsequent certificate. In addition, the value of the issuer field in the first certificate shall match
the DN of the trust anchor. Only the names in these fields are used when checking validity of a certification path.
Names in certificate extensions are not used for this purpose. A certification path logically forms an unbroken chain of
trusted points in the Directory Information Tree between two users wishing to authenticate. The precise method
employed by users A and B to obtain certification paths AB and BA may vary. One way to facilitate this is to
arrange a hierarchy of CAs, which may or may not coincide with all or part of the DIT hierarchy. The benefit of this is
that users who have CAs in the hierarchy may establish a certification path between them using the Directory without
any prior information. In order to allow for this each CA may store one certificate and one reverse certificate designated
as corresponding to its superior CA. The distinguishedNameMatch matching rule, defined in 13.5.2 of ITU-T
Rec. X.501 | ISO/IEC 9594-2, should be used to compare the Distinguished Name (DN) in the issuer field of one
certificate with the DN in the subject field of another.
A user may obtain one or more certificates from one or more Certification Authorities. Each certificate bears the name
of the Certification Authority which issued it. The following ASN.1 data types can be used to represent certificates and
a certification path:
Certificates ::= SEQUENCE {
userCertificate Certificate,
certificationPath CertPath OPTIONAL }
CertificationPath ::= SEQUENCE {
userCertificate Certificate,
theCACertificates SEQUENCE OF CertificatePair OPTIONAL }
In addition, the following ASN.1 data type can be used to represent the forward certification path. This component
contains the certification path which can point back to the originator.
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 15
CertPath ::= SEQUENCE OF CrossCertificates
CrossCertificates ::= SET OF Certificate
PkiPath ::= SEQUENCE OF Certificate
PkiPath is used to represent a certification path. Within the sequence, the order of certificates is such that the subject of
the first certificate is the issuer of the second certificate, etc.
Each certificate in a certification path shall be unique. No certificate may appear more than once in a value of the
theCACertificates component of CertificationPath or in a value of Certificate in the CrossCertificates component of
CertPath or a value of Certificate in PkiPath.
7.1 Generation of key pairs
The overall security management policy of an implementation shall define the lifecycle of key pairs, and is, thus,
outside the scope of this framework. However, it is vital to the overall security that all private keys remain known only
to the user to whom they belong.
Key data is not easy for a human user to remember, so a suitable method for storing it in a convenient transportable
manner shall be employed. One possible mechanism would be to use a "Smart Card". This would hold the private and
(optionally) public keys of the user, the user's certificate, and a copy of the certification authority's public key. The use
of this card shall additionally be secured by, e.g., at least use of a Personal Identification Number (PIN), increasing the
security of the system by requiring the user to possess the card and to know how to access it. The exact method chosen
for storing such data, however, is beyond the scope of this Directory Specification.
Three ways in which a user's key pair may be produced are:
a) The user generates its own key pair. This method has the advantage that a user's private key is never
released to another entity, but requires a certain level of competence by the user.
b) The key pair is generated by a third party. The third party shall release the private key to the user in a
physically secure manner, then actively destroy all information relating to the creation of the key pair
plus the keys themselves. Suitable physical security measures shall be employed to ensure that the third
party and the data operations are free from tampering.
c) The key pair is generated by the CA. This is a special case of b), and the considerations there apply.
NOTE ­ The certification authority already exhibits trusted functionality with respect to the user, and shall be subject to the
necessary physical security measures. This method has the advantage of not requiring secure data transfer to the CA for
certification.
The cryptosystem in use imposes particular (technical) constraints on key generation.
7.2 Public-key certificate creation
A public-key certificate associates the public key and unique distinguished name of the user it describes. Thus:
a) a certification authority shall be satisfied of the identity of a user before creating a certificate for it;
b) a certification authority shall not issue certificates for two users with the same name.
It is important that the transfer of information to the certification authority is not compromised, and suitable physical
security measures shall be taken. In this regard:
a) It would be a serious breach of security if the CA issued a certificate for a user with a public key that had
been tampered with.
b) If the means of generation of key pairs of 7.1 b) or of 7.1 c) is employed, the user's private key shall be
transferred to the user in a secure manner.
c) If the means of generation of key pairs of 7.1 a) or of 7.1 b) is employed, the user may use different
methods (on-line or off-line) to communicate its public key to the CA in a secure manner. On-line
methods may provide some additional flexibility for remote operations performed between the user and
the CA.
A public-key certificate is a publicly available piece of information, and no specific security measures need to be
employed with respect to its transportation to the Directory. As it is produced by an off-line certification authority on
behalf of a user who shall be given a copy of it, the user need only store this information in its directory entry on a
subsequent access to the Directory. Alternatively the CA could lodge the certificate for the user, in which case this
agent shall be given suitable access rights.
ISO/IEC 9594-8:2005 (E)
16 ITU-T Rec. X.509 (08/2005)
7.3 Certificate Validity
The authority that issues certificates (public-key or attribute) also has the responsibility to indicate the validity of
certificates it issues. Generally, certificates are subject to possible subsequent revocation. This revocation, and
notification of the revocation may be done directly by the same authority that issued the certificate, or indirectly by
another authority duly authorized by the authority that issued the certificate. An authority that issues certificates is
required to state, possibly through a published statement of their practices, through the certificates themselves, or
through some other identified means, whether:
­ the certificates cannot be revoked; or
­ the certificates may be revoked by the same certificate-issuing authority directly; or
­ the certificate-issuing authority authorizes a different entity to perform revocation.
Authorities that do revoke certificates are required to state, through some similar means, what mechanism(s) can be
used by relying parties to obtain revocation status information about certificates issued by that authority. This
Specification defines a Certificate Revocation List (CRL) mechanism but does not preclude the use of alternative
mechanisms. One such alternative mechanism is the Online Certificate Status Protocol (OCSP) specified in
IETF RFC 25601). Using this protocol, a relying party (client) requests the revocation status of a certificate from an
OCSP server. The server may use CRLs, or other mechanisms to check the status of the certificate and respond to the
client accordingly. If OCSP can be used by relying parties to check the status of a certificate, IETF RFC 32802) contains
a certificate extension (Authority Info Access) that would be included in such certificates and would provide sufficient
information to access an appropriate OCSP server. Relying parties check revocation status information, as appropriate,
for all certificates considered during path processing procedure described in clause 10 and the delegation path
processing procedure described in clause 16 to validate a certificate.
Only a CA that is authorized to issue CRLs, may choose to delegate that authority to another entity. If this delegation is
done, it shall be verifiable at the time of certificate/CRL verification. The cRLDistributionPoints extension can be
used for this purpose. The cRLIssuer field of this extension would be populated with the name(s) of any entities, other
than the certificate issuer itself, that have been authorized to issue CRLs concerning the revocation status of the
certificate in question.
Certificates, including public-key certificates as well as attribute certificates, shall have a lifetime associated with them,
at the end of which they expire. In order to provide continuity of service, the authority shall ensure timely availability of
replacement certificates to supersede expired/expiring certificates. Revocation notice date is the date/time that a
revocation notice for a certificate first appears on a CRL, regardless of whether it is a base or dCRL. In the CRL,
revocation notice date is the value contained in the thisUpdate field. Revocation date is the date/time the CA actually
revoked the certificate, which could be different from the first time it appears on a CRL. In the CRL, revocation date is
the value contained in the revocationDate component. Invalidity date is the date/time at which it is known or suspected
that the private key was compromised or that the certificate should otherwise be considered invalid. This date may be
earlier that the revocation date. In the CRL, invalidity date is the value contained in the invalidityDate entry extension.
Two related points are:
­ Validity of certificates may be designed so that each becomes valid at the time of expiry of its
predecessor, or an overlap may be allowed. The latter prevents the authority from having to install and
distribute a large number of certificates that may run out at the same expiration date.
­ Expired certificates will normally be removed from the Directory. It is a matter for the security policy
and responsibility of the authority to keep old certificates for a period of time if a non-repudiation of data
service is provided.
Certificates may be revoked prior to their expiration time, e.g., if the user's private key is assumed to be compromised,
or the user is no longer to be certified by the authority, or if the authority's certificate is assumed to be compromised.
The revocation of a user certificate or authority certificate shall be made known by the authority, and a new certificate
shall be made available, if appropriate. The authority may then inform the holder of the certificate about its revocation
by some off-line procedure.
An authority that issues and subsequently revokes certificates:
a) may be required to maintain an audit record of its revocation events for all certificate types issued by that
authority (e.g., public-key certificates, attribute certificates issued to end-entities as well as other
authorities);
_______________
1) IETF RFC 2560, X.509 Internet Public Key Infrastructure Online Certificate Status Protocol (OCSP), June 1999.
2) IETF RFC 3280, Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile, April 2002.
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 17
b) shall provide revocation status information to relying parties using CRLs, on-line certificate status
protocol or some other mechanism for the publication of revocation status information;
c) if using CRLs, shall maintain and publish CRLs even if the lists of revoked certificates are empty;
d) if using only partitioned CRLs, shall issue a full set of partitioned CRLs covering the complete set of
certificates whose revocation status will be reported using the CRL mechanism. Thus the complete set of
partitioned CRLs shall be equivalent to a full CRL for the same set of certificates, if the CRL issuer was
not using partitioned CRLs.
Relying parties may use a number of mechanisms to locate revocation status information provided by an authority. For
example, there may be a pointer in the certificate itself that directs the relying party to a location where revocation
information is provided. There may be a pointer in a revocation list that redirects the relying party to a different
location. The relying party may locate revocation information in a repository (e.g., a directory) or through other means
outside the scope of this Specification (e.g., locally configured).
The maintenance of Directory entries affected by the authority's revocation lists is the responsibility of the Directory
and its users, acting in accordance with the security policy. For example, the user may modify its object entry by
replacing the old certificate with a new one. The latter shall then be used to authenticate the user to the Directory.
If revocation lists are published in the Directory, they are held within entries as attributes of the following types:
­ Certificate revocation list;
­ Authority revocation list;
­ Delta revocation list;
­ Attribute certificate revocation list;
­ Attribute authority revocation list.
CertificateList ::= SIGNED { SEQUENCE {
version Version OPTIONAL,
-- if present, version shall be v2
signature AlgorithmIdentifier,
issuer Name,
thisUpdate Time,
nextUpdate Time OPTIONAL,
revokedCertificates SEQUENCE OF SEQUENCE {
serialNumber CertificateSerialNumber,
revocationDate Time,
crlEntryExtensions Extensions OPTIONAL } OPTIONAL,
crlExtensions [0] Extensions OPTIONAL }}
version is the version of the encoded revocation list. If the extensions component flagged as critical is present in the
revocation list, version shall be v2. If no extensions component flagged as critical is present in the revocation list,
version may either be absent or present as v2.
signature contains the algorithm identifier for the algorithm used by the authority to sign the revocation list.
issuer identifies the entity that has signed and issued the revocation list.
thisUpdate is the date/time at which this revocation list was issued.
nextUpdate, if present, indicates the date/time by which the next revocation list in this series will be issued. The next
revocation list could be issued before the indicated date, but it will not be issued any later than the indicated time.
revokedCertificates identifies certificates that have been revoked. The revoked certificates are identified by their serial
numbers. If none of the certificates covered by this CRL have been revoked, it is strongly recommended that
revokedCertificates parameter be omitted from the CRL, rather than being included with an empty SEQUENCE.
crlExtensions, if present, contains one or more CRL extensions.
NOTE 1 ­ The checking of the entire list of certificates is a local matter. The list shall not be assumed to be in any particular
order unless specific ordering rules have been specified by the issuing authority, e.g., in that authority's policy.
NOTE 2 ­ If a non-repudiation of data service is dependent on keys provided by the authority, the service should ensure that all
relevant keys of the authority (revoked or expired) and the timestamped revocation lists are archived and certified by a current
authority.
NOTE 3 ­ If any extensions included in a CertificateList are defined as critical, the version element of the CertificateList
shall be present. If no extensions defined as critical are included, the version element may be absent. If version is absent, this
may permit an implementation that only supports version 1 CRLs to still use the CRL if in its examination of the
revokedCertificates sequence in the CRL, it does not encounter an extension. An implementation that supports version 2 (or
greater) CRLs, in the absence of version, may also be able to optimize its processing if it can determine early in processing that
no critical extensions are present in the CRL.
ISO/IEC 9594-8:2005 (E)
18 ITU-T Rec. X.509 (08/2005)
NOTE 4 ­ When an implementation processing a certificate revocation list does not recognize a critical extension in the
crlEntryExtensions field, it shall assume that, at a minimum, the identified certificate has been revoked and is no longer valid
and perform additional actions concerning that revoked certificate as dictated by local policy. When an implementation does not
recognize a critical extension in the crlExtensions field, it shall assume that identified certificates have been revoked and are
no longer valid. However in the latter case, since the list may not be complete, certificates that have not been identified as being
revoked cannot be assumed to be valid. In this case local policy shall dictate the action to be taken. In any case local policy may
dictate actions in addition to and/or stronger than those stated in this Specification.
NOTE 5 ­ If an extension affects the treatment of the list (e.g., multiple CRLs need to be scanned to examine the entire list of
revoked certificates, or an entry may represent a range of certificates), then that extension shall be indicated as critical in the
crlExtensions field regardless of where the extension is placed in the CRL. An extension indicated in the
crlEntryExtensions field of an entry shall be placed in that entry and shall affect only the certificate(s) specified in that entry.
NOTE 6 ­ Standard extensions for CRLs are defined in clause 8 of this Directory Specification.
If unknown elements appear within the extension, and the extension is not marked criticial, those unknown elements
shall be ignored according to the rules of extensibility documented in 12.2.2 of ITU-T Rec. X.519 | ISO/IEC 9594-5.
7.4 Repudiation of a digital signing
Any participant in an event may subsequently decide to repudiate anything that participant digitally signed in that event.
For example, one can dispute one's participation in a key establishment or being the originator of a signed email
message as easily as one can dispute one's signing a document with the intent to be bound to the content of that
document. The repudiation may not be successful. The Non-repudiation Framework, ITU-T Rec. X.813 |
ISO/IEC 10181-4, describes a dispute resolution process as follows:
1) evidence generation;
2) evidence transfer, storage and retrieval;
3) evidence verification; and
4) dispute resolution.
The generated evidence may include, but is not limited to:
­ audit records pertinent to the event and assertion of intent;
­ statements made by third party notaries;
­ policy statements;
­ digitally signed information, including audit records and notary statements;
­ timestamps of the digitally signed information;
­ the certificates supporting the digital signature;
­ the appropriate revocation information published and available at the time of the disputed event; and,
­ any certificate revocations subsequent to the time of the event which indicate key compromise occurred
before the time of the event.
The integrity of stored data that might be presented as evidence may be maintained in a variety of ways, e.g., access
control, storage of hashes by trusted third party, digital signature. It may also be necessary to periodically strengthen the
protection of that stored data to counteract improvements in computer processing and/or crypto-analysis.
NOTE ­ Neither the type and amount of evidence generated nor the level of integrity is specified by this Directory Specification.
However it is expected that the level of effort will be commensurate with the risk involved.
Evidence verification may require the revalidation of the digital signatures of data, e.g., messages, documents,
certificates, CRLs, and timestamps that were used in the initial validation process. The fact that a certificate has expired
shall not preclude its use for revalidating signatures created during the validity period of that certificate. A certificate
that has been revoked may be used if it can be determined that the certificate was valid at the time of the disputed event.
Even if all the digital evidence described above is considered technically valid, other conditions, e.g., the intent,
understanding, or competence of the signer, may allow the signer to successfully repudiate it.
8 Public-key certificate and CRL extensions
The certificate extensions defined in this clause are for use with public-key certificates, unless otherwise stated.
Extensions for use with attribute certificates are defined in clause 15. CRL extensions defined in this clause may be
used in CRLs, CARLs and also for ACRLs and AARLs defined in clause 17.
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 19
This clause specifies extensions in the following areas:
a) Key and policy information: These certificate and CRL extensions convey additional information about
the keys involved, including key identifiers for subject and issuer keys, indicators of intended or
restricted key usage, and indicators of certificate policy.
b) Subject and issuer attributes: These certificate and CRL extensions support alternative names, of various
name forms, for a certificate subject, a certificate issuer, or a CRL issuer. These extensions can also
convey additional attribute information about the certificate subject, to assist a certificate user in being
confident that the certificate subject is a particular person or entity.
c) Certification path constraints: These certificate extensions allow constraint specifications to be included
in CA-certificates, i.e., certificates for CAs issued by other CAs, to facilitate the automated processing of
certification paths when multiple certificate policies are involved. Multiple certificate policies arise when
policies vary for different applications in an environment or when interoperation with external
environments occurs. The constraints may restrict the types of certificates that can be issued by the
subject CA or that may occur subsequently in a certification path.
d) Basic CRL extensions: These CRL extensions allow a CRL to include indications of revocation reason, to
provide for temporary suspension of a certificate, and to include CRL-issue sequence numbers to allow
certificate users to detect missing CRLs in a sequence from one CRL issuer.
e) CRL distribution points and delta-CRLs: These certificate and CRL extensions allow the complete set of
revocation information from one CA to be partitioned into separate CRLs and allow revocation
information from multiple CAs to be combined in one CRL. These extensions also support the use of
partial CRLs indicating only changes since an earlier CRL issue.
Inclusion of any extension in a certificate or CRL is at the option of the authority issuing that certificate or CRL.
In a certificate or CRL, an extension is flagged as being either critical or non-critical. If an extension is flagged critical
and a certificate-using system does not recognize the extension field type or does not implement the semantics of the
extension, then that system shall consider the certificate invalid. If an extension is flagged non-critical, a certificateusing
system that does not recognize or implement that extension type may process the remainder of the certificate
ignoring the extension. If an extension is flagged non-critical, a certificate-using system that does recognize the
extension, shall process the extension. Extension type definitions in this Directory Specification indicate if the extension
is always critical, always non-critical, or if criticality can be decided by the certificate or CRL issuer. The reason for
requiring some extensions to be always non-critical is to allow certificate-using implementations which do not need to
use such extensions to omit support for them without jeopardizing the ability to interoperate with all certification
authorities.
NOTE ­ A certificate-using system may require certain non-critical extensions to be present in a certificate in order for that
certificate to be considered acceptable. The need for inclusion of such extensions may be implied by local policy rules of the
certificate user or may be a CA policy rule indicated to the certificate-using system by inclusion of a particular certificate policy
identifier in the certificate policies extension with that extension being flagged critical.
For all certificate extensions, CRL extensions, and CRL entry extensions defined in this Directory Specification, there
shall be no more than one instance of each extension type in any certificate, CRL, or CRL entry, respectively.
8.1 Policy handling
8.1.1 Certificate policy
This framework contains three types of entity: the certificate user, the certification authority and the certificate subject
(or end-entity). Each entity operates under obligations to the other two entities and, in return, enjoys limited warranties
offered by them. These obligations and warranties are defined in a certificate policy. A certificate policy is a document
(usually in plain-language). It can be referenced by a unique identifier, which may be included in the certificate policies
extension of the certificate issued by the certification authority, to the end-entity and upon which the certificate user
relies. A certificate may be issued in accordance with one or more than one policy. Definition of the policy, and
assignment of the identifier, are performed by a policy authority. The set of policies administered by a policy authority
is called a policy domain. All certificates are issued in accordance with a policy, even if the policy is neither recorded
anywhere nor referenced in the certificate. This Specification does not prescribe the style or contents of the certificate
policy.
The certificate user may be bound to its obligations under the certificate policy by the act of importing an authority
public key and using it as a trust anchor, or by relying on a certificate that includes the associated policy identifier. The
certification authority may be bound to its obligations under the policy by the act of issuing a certificate that includes
the associated policy identifier. The end-entity may be bound to its obligations under the policy by the act of requesting
and accepting a certificate that includes the associated policy identifier and by using the corresponding private key.
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Implementations that do not use the certificate policies extension should achieve the required binding by some other
means.
For an entity to simply declare conformance to a policy does not generally satisfy the assurance requirements of the
other entities in the framework. They require some reason to believe that the other parties operate a reliable
implementation of the policy. However, if explicitly so stated in the policy, certificate users may accept the certification
authority's assurances that its end-entities agree to be bound by their obligations under the policy, without having to
confirm this directly with them. This aspect of certificate policy is outside the scope of this Specification.
A certification authority may place limitations on the use of its certificates, in order to control the risk that it assumes as
a result of issuing certificates. For instance, it may restrict the community of certificate users, the purposes for which
they may use its certificates and/or the type and extent of damages that it is prepared to make good in the event of a
failure on its part, or that of its end-entities. These matters should be defined in the certificate policy.
Additional information, to help affected entities understand the provisions of the policy, may be included in the
certificate policies extension in the form of policy qualifiers.
8.1.2 Cross-certification
A certification authority may be the subject of a certificate issued by another certification authority. In this case, the
certificate is called a cross-certificate, the certification authority that is the subject of the certificate is called the subject
certification authority and the certification authority that issues the cross-certificate is called an intermediate
certification authority (see Figure 2). Both the cross-certificate and the end-entity's certificate may contain a certificate
policies extension.
The warranties and obligations shared by the subject certification authority, the intermediate certification authority and
the certificate user are defined by the certificate policy identified in the cross-certificate, in accordance with which the
subject certification authority may act as, or on behalf of, an end-entity. And the warranties and obligations shared by
the certificate subject, the subject certification authority and the intermediate certification authority are defined by the
certificate policy identified in the end-entity's certificate, in accordance with which the intermediate certification
authority may act as, or on behalf of, a certificate user.
Figure 2 ­ Cross-certification
A certification path is said to be valid under the set of policies that are common to all certificates in the path.
An intermediate certification authority may, in turn, be the subject of a certificate issued by another certification
authority, thereby creating certification paths of length greater than two certificates. And, since trust suffers dilution as
certificate paths grow in length, controls are required to ensure that end-entity certificates with an unacceptably low
associated trust level will be rejected by the certificate user. This is part of the function of the certification path
processing procedure.
In addition to the situation described above, there are two special cases to be considered:
a) the certification authority does not use the certificate policies extension to convey its policy requirements to
certificate users; and
b) the certificate user or intermediate certification authority delegates the job of controlling policy to the next
authority in the path.
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In the first case, the certificate should not contain a certificate policies extension at all. As a result, the set of policies
under which the path is valid will be null. But, the path may be valid nonetheless. Certificate users shall still ensure that
they are using the certificate in conformance with the policies of the authorities in the path.
In the second case, the certificate user or intermediate certification authority should include the special value any-policy
in the initial-policy-set or cross-certificate. Where a certificate includes the special value any-policy, it should not
include any other certificate policy identifiers. The identifier any-policy should not have any associated policy
qualifiers.
The certificate user can ensure that all its obligations are conveyed in accordance with the standard by setting the initialexplicit-policy
indicator. In this way, only authorities that use the standard certificate policies extension as their way of
achieving binding are accepted in the path, and certificate users have no additional obligations. Because authorities also
attract obligations when they act as, or on behalf of, a certificate user, they can ensure that all their obligations are
conveyed in accordance with the standard by setting requireExplicitPolicy in the cross-certificate.
8.1.3 Policy mapping
Some certification paths may cross boundaries between policy domains. The warranties and obligations according to
which the cross-certificate is issued may be materially equivalent to some or all of the warranties and obligations
according to which the subject certification authority issues certificates to end-entities, even though the policy
authorities under which the two certification authorities operate may have selected different unique identifiers for these
materially equivalent policies. In this case, the intermediate certification authority may include a policy mappings
extension in the cross-certificate. In the policy mappings extension, the intermediate certification authority assures the
certificate user that it will continue to enjoy the familiar warranties, and that it should continue to fulfil its familiar
obligations, even though subsequent entities in the certification path operate in a different policy domain. The
intermediate certification authority should include one or more mappings for each of a subset of the policies under
which it issued the cross-certificate, and it should not include mappings for any other policies. If one or more of the
certificate policies according to which the subject certification authority operates is identical to those according to
which the intermediate certification authority operates (i.e., it has the same unique identifier), then these identifiers
should be excluded from the policy mapping extension, but included in the certificate policies extension.
Policy mapping has the effect of converting all policy identifiers in certificates further down the certification path to the
identifier of the equivalent policy, as recognized by the certificate user.
Policies shall not be mapped either to or from the special value any-policy.
Certificate users may determine that certificates issued in a policy domain other than its own should not be relied upon,
even though a trusted intermediate certification authority may determine its policy to be materially equivalent to its
own. It can do this by setting the initial-policy-mapping-inhibit input to the path validation procedure. Additionally, an
intermediate certification authority may make a similar determination on behalf of its certificate users. In order to
ensure that certificate users correctly enforce this requirement, it can set inhibitPolicyMapping in a policy constraints
extension.
8.1.4 Certification path processing
The certificate user faces a choice between two strategies:
a) it can require that the certification path be valid under at least one of a set of policies pre-determined by
the user; or
b) it can ask the path validation module to report the set of policies for which the certification path is valid.
The first strategy may be most appropriate when the certificate user knows, a priori, the set of policies that are
acceptable for its intended use.
The second strategy may be most appropriate when the certificate user does not know, a priori, the set of policies that
are acceptable for its intended use.
In the first instance, the certification path validation procedure will indicate the path to be valid only if it is valid under
one or more of the policies specified in the initial-policy-set, and it will return the sub-set of the initial-policy-set under
which the path is valid. In the second instance, the certification path validation procedure may indicate that the path is
invalid under the initial-policy-set, but valid under a disjoint set: the authorities-constrained-policy-set. Then the
certificate user shall determine whether its intended use of the certificate is consistent with one or more of the certificate
policies under which the path is valid. By setting the initial-policy-set to any-policy, the certificate user can cause the
procedure to return a valid result if the path is valid under any (unspecified) policy.
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8.1.5 Self-issued certificates
There are three circumstances under which a certification authority may issue a certificate to itself:
a) as a convenient way of encoding the public key associated with the private key used to sign the
certificate, so that it can be communicated to, and stored as trust anchors by, its certificate using
systems;
b) for certifying additional public keys of the CA used for purposes other than those covered by category a)
(such as OCSP and possibly CRL signing); and,
c) for replacing its own expired certificates.
These types of certificate are called self-issued certificates, and they can be recognized by the fact that the issuer and
subject names present in them are identical. For purposes of path validation, self-issued certificates of category a) are
self-signed certificates and are therefore verified with the public key contained in them, and if they are encountered in
the path, they shall be ignored.
Self-issued certificates of type b) may only appear as end certificates in a path, and shall be processed as end
certificates.
Self-issued certificates of type c) (also known as self-issued intermediate certificates) may appear as intermediate
certificates in a path. As a matter of good practice, when replacing a key that is on the point of expiration, a certification
authority should request the issuance of any in-bound cross-certificates that it requires for its replacement public key
before using the key. Nevertheless, if self-issued certificates of this category are encountered in the path, they shall be
processed as intermediate certificates, with the following exception: they do not contribute to the path length for
purposes of processing the pathLenConstraint component of the basicConstraints extension and the skip-certificates
values associated with the policy-mapping-inhibitpending and explicit-policy-pending indicators.
If an authority uses the same key to sign certificates and CRLs, a single self-issued certificate of category a) shall be
used. If an authority uses a different key to sign CRLs than that used to sign certificates, the authority may choose to
issue two self-issued certificates of category a), one for each of the keys. In this situation, certificate users would need
access to both self-issued certificates to establish separate trust anchors for certificates and CRLs signed by that
authority. Alternatively, an authority may issue one self-issued certificate of category a) for certificate signing and one
self-issued certificate of category b) for CRL signing. In this situation, certificate users use the key certified in the
certificate of category a) as their single trust anchor for both certificates and CRLs signed by that authority. In this case,
if the self-issued certificate of category b) were to be used to verify signatures on CRLs, there is no means defined in
this standard to check the validity of that certificate.
If self-issued certificates of category b) are encountered within a path, they shall be ignored.
NOTE ­ Other mechanisms for distributing CA public keys are outside the scope of this Directory Specification.
8.2 Key and policy information extensions
8.2.1 Requirements
The following requirements relate to key and policy information:
a) CA key pair updating can occur at regular intervals or in special circumstances. There is a need for a
certificate field to convey an identifier of the public key to be used to verify the certificate signature. A
certificate-using system can use such identifiers in finding the correct CA-certificate for validating the
certificate issuer's public key.
b) In general, a certificate subject has different public keys and, correspondingly, different certificates for
different purposes, e.g., digital signature and encipherment key agreement. A certificate field is needed to
assist a certificate user in selecting the correct certificate for a given subject for a particular purpose or to
allow a CA to stipulate that a certified key may only be used for a particular purpose.
c) Subject key pair updating can occur at regular intervals or in special circumstances. There is a need for a
certificate field to convey an identifier to distinguish between different public keys for the same subject
used at different points in time. A certificate-using system can use such identifiers in finding the correct
certificate.
d) The private key corresponding to a certified public key is typically used over a different period from the
validity of the public key. With digital signature keys, the usage period for the signing private key is
typically shorter than that for the verifying public key. The validity period of the certificate indicates a
period for which the public key may be used, which is not necessarily the same as the usage period of the
private key. In the event of a private key compromise, the period of exposure can be limited if the
signature verifier knows the legitimate use period for the private key. There is therefore a requirement to
be able to indicate the usage period of the private key in a certificate.
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e) Because certificates may be used in environments where multiple certificate policies apply, provision
needs to be made for including certificate policy information in certificates.
f) When cross-certifying from one organization to another, it can sometimes be agreed that certain of the
two organizations' policies can be considered equivalent. A CA-certificate needs to allow the certificate
issuer to indicate that one of its own certificate policies is equivalent to another certificate policy in the
subject CA's domain. This is known as policy mapping.
g) A user of an encipherment or digital signature system which uses certificates defined in this Directory
Specification needs to be able to determine in advance the algorithms supported by other users.
8.2.2 Public-key certificate and CRL extension fields
The following extension fields are defined:
a) Authority key identifier;
b) Subject key identifier;
c) Key usage;
d) Extended key usage;
e) Private key usage period;
f) Certificate policies;
g) Policy mappings.
These extension fields shall be used only as certificate extensions, except for authority key identifier which may also be
used as a CRL extension. Unless otherwise noted , these extensions may be used in both CA-certificates and end-entity
certificates.
8.2.2.1 Authority key identifier extension
This field, which may be used as either a certificate extension or CRL extension, identifies the public key to be used to
verify the signature on this certificate or CRL. It enables distinct keys used by the same CA to be distinguished (e.g., as
key updating occurs). This field is defined as follows:
authorityKeyIdentifier EXTENSION ::= {
SYNTAX AuthorityKeyIdentifier
IDENTIFIED BY id-ce-authorityKeyIdentifier }
AuthorityKeyIdentifier ::= SEQUENCE {
keyIdentifier [0] KeyIdentifier OPTIONAL,
authorityCertIssuer [1] GeneralNames OPTIONAL,
authorityCertSerialNumber [2] CertificateSerialNumber OPTIONAL }
( WITH COMPONENTS {..., authorityCertIssuer PRESENT,
authorityCertSerialNumber PRESENT} |
WITH COMPONENTS {..., authorityCertIssuer ABSENT,
authorityCertSerialNumber ABSENT} )
KeyIdentifier ::= OCTET STRING
The key may be identified by an explicit key identifier in the keyIdentifier component, by identification of a certificate
for the key (giving certificate issuer in the authorityCertIssuer component and certificate serial number in the
authorityCertSerialNumber component), or by both explicit key identifier and identification of a certificate for the key.
If both forms of identification are used then the certificate or CRL issuer shall ensure they are consistent. A key
identifier shall be unique with respect to all key identifiers for the issuing authority for the certificate or CRL containing
the extension. An implementation which supports this extension is not required to be able to process all name forms in
the authorityCertIssuer component. (See 8.3.2.1 for details of the GeneralNames type.)
Certification authorities shall assign certificate serial numbers such that every (issuer, certificate serial number) pair
uniquely identifies a single certificate. The keyIdentifier form can be used to select CA certificates during path
construction. The authorityCertIssuer, authoritySerialNumber pair can only be used to provide preference to one
certificate over others during path construction.
This extension is always non-critical.
8.2.2.2 Subject key identifier extension
This field identifies the public key being certified. It enables distinct keys used by the same subject to be differentiated
(e.g., as key updating occurs). This field is defined as follows:
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24 ITU-T Rec. X.509 (08/2005)
subjectKeyIdentifier EXTENSION ::= {
SYNTAX SubjectKeyIdentifier
IDENTIFIED BY id-ce-subjectKeyIdentifier }
SubjectKeyIdentifier ::= KeyIdentifier
A key identifier shall be unique with respect to all key identifiers for the subject with which it is used. This extension is
always non-critical.
8.2.2.3 Key usage extension
This field identifies the intended usage for which the certificate has been issued. The intended usage may be further
constrained by policy. This policy may be stated in a certificate policy definition, a contract, or other specification.
However, a policy shall not override the constraint indicated by a KeyUsage bit, e.g., a certificate policy could not
allow a certificate to be used for digital signature if KeyUsage indicated that it could only be used for key agreement.
Setting a specific value of KeyUsage in a certificate does not in itself signal for an instance of communication that the
communicating parties are acting in accordance with this setting, e.g., when signing a document. Definition of methods
by which parties may signal their intent for a specific instance of communication (e.g., commitment to content for that
specific instance) is outside the scope of this Directory Specification, but it is anticipated that multiple methods will
exist. Although not recommended, it is possible to use the content of the certificate, e.g., certificate policy, to signal the
intent of the signing. However, since that signal was made when the certificate was issued by the CA, such use may not
meet the requirement that declaring the intent is made at the time of signing by the signer.
More than one bit may be set in an instance of the keyUsage extension. The setting of multiple bits shall not change the
meaning of each individual bit but shall indicate that the certificate may be used for all of the purposes indicated by the
set bits. There may be risks incurred when setting multiple bits. A review of those risks is documented in Annex I.
This field is defined as follows:
keyUsage EXTENSION ::= {
SYNTAX KeyUsage
IDENTIFIED BY id-ce-keyUsage }
KeyUsage ::= BIT STRING {
digitalSignature (0),
contentCommitment (1),
keyEncipherment (2),
dataEncipherment (3),
keyAgreement (4),
keyCertSign (5),
cRLSign (6),
encipherOnly (7),
decipherOnly (8) }
Bits in the KeyUsage type are as follows:
a) digitalSignature: for verifying digital signatures that are used with an entity authentication service, a
data origin authentication service and/or an integrity service;
b) contentCommitment: for verifying digital signatures which are intended to signal that the signer is
committing to the content being signed. The type of commitment the certificate can be used to support
may be further constrained by the CA, e.g., through a certificate policy. The precise type of commitment
of the signer e.g., "reviewed and approved" or "with the intent to be bound", may be signalled by the
content being signed, e.g., the signed document itself or some additional signed information.
Since a content commitment signing is considered to be a digitally signed transaction, the
digitalSignature bit need not be set in the certificate. If it is set, it does not affect the level of
commitment the signer has endowed in the signed content.
Note that it is not incorrect to refer to this keyUsage bit using the identifier nonRepudiation. However,
the use of this identifier has been deprecated. Regardless of the identifier used, the semantics of this bit
are as specified in this Directory Specification;
c) keyEncipherment: for enciphering keys or other security information, e.g., for key transport;
d) dataEncipherment: for enciphering user data, but not keys or other security information as in c) above;
e) keyAgreement: for use as a public key agreement key;
f) keyCertSign: for verifying a CA's signature on certificates.
Since certificate signing is considered to be a commitment to the content of the certificate by the CA,
neither the digitalSignature bit nor the contentCommitment bit need be set in the certificate. If either
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(or both) is set, it does not affect the level of commitment the signer has endowed in the signed
certificate;
g) cRLSign: for verifying an authority's signature on CRLs.
Since CRL signing is considered to be commitment to the content of the CRL by the CRL issuer, neither
the digitalSignature bit nor the contentCommitment bit need be set in the certificate. If either (or both)
is set, it does not affect the level of commitment the signer has endowed in the signed CRL;
h) encipherOnly: public key agreement key for use only in enciphering data when used with
keyAgreement bit also set (meaning with other key usage bit set is undefined);
i) decipherOnly: public key agreement key for use only in deciphering data when used with
keyAgreement bit also set (meaning with other key usage bit set is undefined).
Application specifications should indicate which of the digitalSignature or contentCommitment bits are appropriate
for their use. If a signing application has no knowledge of the signer's intent regarding commitment to content, the
application shall sign and support that signing with a certificate that has the digitalSignature bit set in that certificate's
keyUsage extension.
Even though a digital signature was verified using a certificate that has only the digitalSignature bit set, other factors
external to the verification of the digital signature may also play a role in determining the intent of the signing.
Conversely, even though a digital signature was verified using a certificate that has only the contentCommitment bit
set, external factors may be used by the signer to disclaim commitment to the signed content.
The bit keyCertSign is for use in CA-certificates only. If KeyUsage is set to keyCertSign, the value of the cA
component of the basicConstraints extension shall be set to TRUE. CAs may also use other defined key usage bits in
KeyUsage, e.g., digitalSignature for providing authentication and integrity of on-line administration transactions.
This extension may, at the option of the certificate issuer, be either critical or non-critical.
If the extension is flagged critical or if the extension is flagged non-critical but the certificate-using system recognizes
it, then the certificate shall be used only for a purpose for which the corresponding key usage bit is set to one. If the
extension if flagged non-critical and the certificate-using system does not recognize it, then this extension shall be
ignored. A bit set to zero indicates that the key is not intended for that purpose. If the extension is present with all bits
set to zero, the key is intended for some purpose other than those listed above.
8.2.2.4 Extended key usage extension
This field indicates one or more purposes for which the certified public key may be used, in addition to or in place of
the basic purposes indicated in the key usage extension field. This field is defined as follows:
extKeyUsage EXTENSION ::= {
SYNTAX SEQUENCE SIZE (1..MAX) OF KeyPurposeId
IDENTIFIED BY id-ce-extKeyUsage }
KeyPurposeId ::= OBJECT IDENTIFIER
A CA may assert any-extended-key-usage by using the anyExtendedKeyUsage identifier. This enables a CA to issue a
certificate that contains OIDs for extended key usages that may be required by certificate-using applications, without
restricting the certificate to only those key usages. If extended key usage would restrict key usage, then the inclusion of
this OID removes that restriction.
anyExtendedKeyUsage OBJECT IDENTIFIER ::= { 2 5 29 37 0 }[S9]
Key purposes may be defined by any organization with a need. Object identifiers used to identify key purposes shall be
assigned in accordance with ITU-T Rec. X.660 | ISO/IEC 9834-1.
This extension may, at the option of the certificate issuer, be either critical or non-critical.
If the extension is flagged critical, then the certificate shall be used only for one of the purposes indicated.
If the extension is flagged non-critical, then it indicates the intended purpose or purposes of the key, and may be used in
finding the correct key/certificate of an entity that has multiple keys/certificates. If this extension is present, and the
certificate-using system recognizes and processes the extendedKeyUsage extension type, then the certificate-using
system shall ensure that the certificate shall be used only for one of the purposes indicated. (Using applications may
nevertheless require that a particular purpose be indicated in order for the certificate to be acceptable to that
application.)
If a certificate contains both a critical key usage field and a critical extended key usage field, then both fields shall be
processed independently and the certificate shall only be used for a purpose consistent with both fields. If there is no
purpose consistent with both fields, then the certificate shall not be used for any purpose.
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This specification defines the following key purpose that can be included in the extended key usage extension. Other
purposes that can also be included are defined in other specifications, such as IETF RFC 3280.
keyPurposes OBJECT IDENTIFIER ::= {ds 38 1}
8.2.2.5 Private key usage period extension
This field indicates the period of use of the private key corresponding to the certified public key. It is applicable only
for digital signature keys. This field is defined as follows:
privateKeyUsagePeriod EXTENSION ::= {
SYNTAX PrivateKeyUsagePeriod
IDENTIFIED BY id-ce-privateKeyUsagePeriod }
PrivateKeyUsagePeriod ::= SEQUENCE {
notBefore [0] GeneralizedTime OPTIONAL,
notAfter [1] GeneralizedTime OPTIONAL }
( WITH COMPONENTS {..., notBefore PRESENT} |
WITH COMPONENTS {..., notAfter PRESENT} )
The notBefore component indicates the earliest date and time at which the private key could be used for signing. If the
notBefore component is not present, then no information is provided as to when the period of valid use of the private
key commences. The notAfter component indicates the latest date and time at which the private key could be used for
signing. If the notAfter component is not present then no information is provided as to when the period of valid use of
the private key concludes.
This extension is always non-critical.
NOTE 1 ­ The period of valid use of the private key may be different from the certified validity of the public key as indicated by
the certificate validity period. With digital signature keys, the usage period for the signing private key is typically shorter than
that for the verifying public key.
NOTE 2 ­ If the verifier of a digital signature wants to check that the certificate has not been revoked, for example due to key
compromise, up to the time of verification, then a valid certificate will still exist for the public key at verification time. After the
certificate(s) for a public key have expired, a signature verifier cannot rely on compromises being notified via CRLs.
8.2.2.6 Certificate policies extension
This field lists certificate policies, recognized by the issuing CA, that apply to the certificate, together with optional
qualifier information pertaining to these certificate policies. The list of certificate policies is used in determining the
validity of a certification path, as described in clause 10. The optional qualifiers are not used in the certification path
processing procedure, but relevant qualifiers are provided as an output of that process to the certificate using application
to assist in determining whether a valid path is appropriate for the particular transaction. Typically, different certificate
policies will relate to different applications which may use the certified key. The presence of this extension in an endentity
certificate indicates the certificate policies for which this certificate is valid. The presence of this extension in a
certificate issued by one CA to another CA indicates the certificate policies for which certification paths containing this
certificate may be valid. This field is defined as follows:
certificatePolicies EXTENSION ::= {
SYNTAX CertificatePoliciesSyntax
IDENTIFIED BY id-ce-certificatePolicies }
CertificatePoliciesSyntax ::= SEQUENCE SIZE (1..MAX) OF PolicyInformation
PolicyInformation ::= SEQUENCE {
policyIdentifier CertPolicyId,
policyQualifiers SEQUENCE SIZE (1..MAX) OF
PolicyQualifierInfo OPTIONAL }
CertPolicyId ::= OBJECT IDENTIFIER
PolicyQualifierInfo ::= SEQUENCE {
policyQualifierId CERT-POLICY-QUALIFIER.&id
({SupportedPolicyQualifiers}),
qualifier CERT-POLICY-QUALIFIER.&Qualifier
({SupportedPolicyQualifiers}{@policyQualifierId})
OPTIONAL }
SupportedPolicyQualifiers CERT-POLICY-QUALIFIER ::= { ... }
A value of the PolicyInformation type identifies and conveys qualifier information for one certificate policy. The
component policyIdentifier contains an identifier of a certificate policy and the component policyQualifiers contains
policy qualifier values for that element.
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 27
This extension may, at the option of the certificate issuer, be either critical or non-critical.
If the extension is flagged critical, it indicates that the certificate shall only be used for the purpose, and in accordance
with the rules implied by one of the indicated certificate policies. The rules of a particular policy may require the
certificate-using system to process the qualifier value in a particular way.
If the extension is flagged non-critical, use of this extension does not necessarily constrain use of the certificate to the
policies listed. However, a certificate user may require a particular policy to be present in order to use the certificate
(see clause 10). Policy qualifiers may, at the option of the certificate user, be processed or ignored.
Certificate policies and certificate policy qualifier types may be defined by any organization with a need. Object
identifiers used to identify certificate policies and certificate policy qualifier types shall be assigned in accordance with
ITU-T Rec. X.660 | ISO/IEC 9834-1. A CA may assert any-policy by using the anyPolicy identifier in order to trust a
certificate for all possible policies. Because of the need for identification of this special value to apply regardless of the
application or environment, that object identifier is assigned in this Specification. No object identifiers will be assigned
in this Specification for specific certificate policies. That assignment is the responsibility of the entity that defines the
certificate policy.
anyPolicy OBJECT IDENTIFIER ::= { 2 5 29 32 0 }
The identifier anyPolicy should not have any associated policy qualifiers.
The following ASN.1 object class is used in defining certificate policy qualifier types:
CERT-POLICY-QUALIFIER ::= CLASS {
&id OBJECT IDENTIFIER UNIQUE,
&Qualifier OPTIONAL }
WITH SYNTAX {
POLICY-QUALIFIER-ID &id
[QUALIFIER-TYPE &Qualifier] }
A definition of a policy qualifier type shall include:
­ a statement of the semantics of the possible values; and
­ an indication of whether the qualifier identifier may appear in a certificate policies extension without an
accompanying value and, if so, the implied semantics in such a case.
NOTE ­ A qualifier may be specified as having any ASN.1 type. When the qualifier is anticipated to be used primarily with
applications that do not have ASN.1 decoding functions, it is recommended that the type OCTET STRING be specified. The
ASN.1 OCTET STRING value can then convey a qualifier value encoded according to any convention specified by the policy
element defining organization.
8.2.2.7 Policy mappings extension
This field, which shall be used in CA-certificates only, allows a certificate issuer to indicate that, for the purposes of the
user of a certification path containing this certificate, one of the issuer's certificate policies can be considered equivalent
to a different certificate policy used in the subject CA's domain. This field is defined as follows:
policyMappings EXTENSION ::= {
SYNTAX PolicyMappingsSyntax
IDENTIFIED BY id-ce-policyMappings }
PolicyMappingsSyntax ::= SEQUENCE SIZE (1..MAX) OF SEQUENCE {
issuerDomainPolicy CertPolicyId,
subjectDomainPolicy CertPolicyId }
The issuerDomainPolicy component indicates a certificate policy that is recognized in the issuing CA's domain and
that can be considered equivalent to the certificate policy indicated in the subjectDomainPolicy component that is
recognized in the subject CA's domain.
Policies shall not be mapped to or from the special value anyPolicy.
This extension may, at the option of the certificate issuer, be either critical or non-critical. It is recommended that it be
critical, otherwise a certificate user may not correctly interpret the stipulation of the issuing CA.
NOTE 1 ­ An example of policy mapping is as follows. The U.S. government domain may have a policy called Canadian Trade
and the Canadian government may have a policy called U.S. Trade. While the two policies are distinctly identified and defined,
there may be an agreement between the two governments to accept certification paths extending cross-border within the rules
implied by these policies for relevant purposes.
NOTE 2 ­ Policy mapping implies significant administrative overheads and the involvement of suitably diligent and authorized
personnel in related decision-making. In general, it is preferable to agree upon more global use of common policies than it is to
apply policy mapping. In the above example, it would be preferable for the U.S., Canada and Mexico to agree upon a common
policy for North American Trade.
ISO/IEC 9594-8:2005 (E)
28 ITU-T Rec. X.509 (08/2005)
NOTE 3 ­ It is anticipated that policy mapping will be practical only in limited environments in which policy statements are very
simple.
8.3 Subject and issuer information extensions
8.3.1 Requirements
The following requirements relate to certificate subject and certificate issuer attributes:
a) Certificates need to be usable by applications that employ a variety of name forms, including Internet
electronic mail names, Internet domain names, X.400 originator/recipient addresses, and EDI party
names. It is therefore necessary to be able to securely associate multiple names of a variety of name
forms with a certificate subject or a certificate or CRL issuer.
b) A certificate user may need to securely know certain identifying information about a subject in order to
have confidence that the subject is indeed the person or thing intended. For example, information such as
postal address, position in a corporation, or a picture image may be required. Such information may be
conveniently represented as directory attributes, but these attributes are not necessarily part of the
distinguished name. A certificate field is therefore needed for conveying additional directory attributes
beyond those in the distinguished name.
8.3.2 Certificate and CRL extension fields
The following extension fields are defined:
a) Subject alternative name;
b) Issuer alternative name;
c) Subject directory attributes.
These fields shall be used only as certificate extensions, except for issuer alternative name which may also be used as a
CRL extension. As certificate extensions, they may be present in CA-certificates or end-entity certificates.
8.3.2.1 Subject alternative name extension
This field contains one or more alternative names, using any of a variety of name forms, for the entity that is bound by
the CA to the certified public key. This field is defined as follows:
subjectAltName EXTENSION ::= {
SYNTAX GeneralNames
IDENTIFIED BY id-ce-subjectAltName }
GeneralNames ::= SEQUENCE SIZE (1..MAX) OF GeneralName
GeneralName ::= CHOICE {
otherName [0] INSTANCE OF OTHER-NAME,
rfc822Name [1] IA5String,
dNSName [2] IA5String,
x400Address [3] ORAddress,
directoryName [4] Name,
ediPartyName [5] EDIPartyName,
uniformResourceIdentifier [6] IA5String,
iPAddress [7] OCTET STRING,
registeredID [8] OBJECT IDENTIFIER }
OTHER-NAME ::= TYPE-IDENTIFIER
EDIPartyName ::= SEQUENCE {
nameAssigner [0] DirectoryString {ub-name} OPTIONAL,
partyName [1] DirectoryString {ub-name} }
The values in the alternatives of the GeneralName type are names of various forms as follows:
­ otherName is a name of any form defined as an instance of the OTHER-NAME information object class;
­ rfc822Name is an Internet electronic mail address defined in accordance with Internet RFC 822;
­ dNSName is an Internet domain name defined in accordance with Internet RFC 1035;
­ x400Address is an O/R address defined in accordance with ITU-T Rec. X.411 | ISO/IEC 10021-4;
­ directoryName is a directory name defined in accordance with ITU-T Rec. X.501 | ISO/IEC 9594-2;
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 29
­ ediPartyName is a name of a form agreed between communicating Electronic Data Interchange partners;
the nameAssigner component identifies an authority that assigns unique values of names in the
partyName component;
­ uniformResourceIdentifier is a Uniform Resource Identifier for the World Wide Web defined in
accordance with Internet RFC 1630;
­ iPAddress is an Internet Protocol address defined in accordance with Internet RFC 791, represented as a
binary string.
­ registeredID is an identifier of any registered object assigned in accordance with ITU-T Rec. X.660 |
ISO/IEC 9834-1.
For every name form used in the GeneralName type, there shall be a name registration system that ensures that any
name used unambiguously identifies one entity to both certificate issuer and certificate users.
This extension may, at the option of the certificate issuer, be either critical or non-critical. An implementation which
supports this extension is not required to be able to process all name forms. If the extension is flagged critical, at least
one of the name forms that is present shall be recognized and processed, otherwise the certificate shall be considered
invalid. Apart from the preceding restriction, a certificate-using system is permitted to ignore any name with an
unrecognized or unsupported name form. It is recommended that, provided the subject field of the certificate contains a
directory name that unambiguously identifies the subject, this field be flagged non-critical.
NOTE 1 ­ Use of the TYPE-IDENTIFIER class is described in Annexes A and C of ITU-T Rec. X.681 | ISO/IEC 8824-2.
NOTE 2 ­ If this extension field is present and is flagged critical, the subject field of the certificate may contain a null name
(e.g., a sequence of zero relative distinguished names) in which case the subject is identified only by the name or names in this
extension.
8.3.2.2 Issuer alternative name extension
This field contains one or more alternative names, using any of a variety of name forms, for the certificate or CRL
issuer. This field is defined as follows:
issuerAltName EXTENSION ::= {
SYNTAX GeneralNames
IDENTIFIED BY id-ce-issuerAltName }
This extension may, at the option of the certificate or CRL issuer, be either critical or non-critical. An implementation
which supports this extension is not required to be able to process all name forms. If the extension is flagged critical, at
least one of the name forms that is present shall be recognized and processed, otherwise the certificate or CRL shall be
considered invalid. Apart from the preceding restriction, a certificate-using system is permitted to ignore any name with
an unrecognized or unsupported name form. It is recommended that, provided the issuer field of the certificate or CRL
contains a directory name that unambiguously identifies the issuing authority, this field be flagged non-critical.
NOTE ­ If this extension field is present and is flagged critical, the issuer field of the certificate or CRL may contain a null
name (e.g., a sequence of zero relative distinguished names) in which case the issuer is identified only by the name or names in
this extension.
8.3.2.3 Subject directory attributes extension
This field conveys any desired Directory attribute values for the subject of the certificate. This field is defined as
follows:
subjectDirectoryAttributes EXTENSION ::= {
SYNTAX AttributesSyntax
IDENTIFIED BY id-ce-subjectDirectoryAttributes }
AttributesSyntax ::= SEQUENCE SIZE (1..MAX) OF Attribute
This extension may, at the option of the certificate issuer, be either critical or non-critical. A certificate using system
processing this extension is not required to understand all attribute types included in the extension. If the extension is
flagged critical, at least one of the attribute types contained in the extension shall be understood for the certificate to be
accepted. If the extension is flagged critical and none of the contained attribute types are understood, the certificate
shall be rejected.
If this extension is present in a public-key certificate, some of the extensions defined in clause 15 may also be present.
8.4 Certification path constraint extensions
8.4.1 Requirements
For certification path processing:
ISO/IEC 9594-8:2005 (E)
30 ITU-T Rec. X.509 (08/2005)
a) End-entity certificates need to be distinguishable from CA-certificates, to protect against end-entities
establishing themselves as CAs without authorization. It also needs to be possible for a CA to limit the
length of a subsequent chain resulting from a certified subject CA, e.g., to no more than one more
certificate or no more than two more certificates.
b) A CA needs to be able to specify constraints which allow a certificate user to check that less-trusted CAs
in a certification path (i.e., CAs further down the certification path from the CA with whose public key
the certificate user starts) are not violating their trust by issuing certificates to subjects in an
inappropriate name space. Adherence to these constraints needs to be automatically checkable by the
certificate user.
c) Certification path processing needs to be implementable in an automated, self-contained module. This is
necessary to permit trusted hardware or software modules to be implemented which perform the
certification path processing functions.
d) It should be possible to implement certification path processing without depending upon real-time
interactions with the local user.
e) It should be possible to implement certification path processing without depending upon the use of
trusted local databases of policy-description information. (Some trusted local information ­ an initial
public key, at least ­ is needed for certification path processing but the amount of such information
should be minimized.)
f) Certification paths need to operate in environments in which multiple certificate policies are recognized.
A CA needs to be able to stipulate which CAs in other domains it trusts and for which purposes.
Chaining through multiple policy domains needs to be supported.
g) Complete flexibility in trust models is required. A strict hierarchical model which is adequate for a single
organization is not adequate when considering the needs of multiple interconnected enterprises.
Flexibility is required in selection of the first trusted CA in a certification path. In particular, it should be
possible to require that the certification path start in the local security domain of the public-key user
system.
h) Naming structures should not be constrained by the need to use names in certificates, i.e., Directory
name structures considered natural for organizations or geographical areas shall not need adjustment in
order to accommodate certification authority requirements.
i) Certificate extension fields need to be backward-compatible with the unconstrained certification path
approach system as specified in earlier editions of ITU-T Rec. X.509 | ISO/IEC 9594-8.
j) A CA needs to be able to inhibit use of policy mapping and to require explicit certificate policy
identifiers to be present in subsequent certificates in a certification path.
NOTE ­ In any certificate-using system, processing of a certification path requires an appropriate level of
assurance. This Directory Specification defines functions that may be used in implementations that are required
to conform to specific assurance statements. For example, an assurance requirement could state that certification
path processing shall be protected from subversion of the process (such as software-tampering or data
modification). The level of assurance should be commensurate with business risk. For example:
­ processing internal to an appropriate cryptographic module may be required for public keys used to validate
high value funds transfer; whereas
­ processing in software may be appropriate for home banking balance inquiries.
Consequently, certification path processing functions should be suitable for implementation in hardware
cryptographic modules or cryptographic tokens as one option.
k) A CA needs to be able to prevent the special value any-policy from being considered a valid policy in
subsequent certificates in a certification path.
8.4.2 Certificate extension fields
The following extension fields are defined:
a) Basic constraints;
b) Name constraints;
c) Policy constraints;
d) Inhibit any policy.
These extension fields shall be used only as certificate extensions. Name constraints and policy constraints shall be used
only in CA-certificates; basic constraints may also be used in end-entity certificates. Examples of the use of these
extensions are given in Annex G.
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 31
8.4.2.1 Basic constraints extension
This field indicates if the subject may act as a CA, with the certified public key being used to verify certificate
signatures. If so, a certification path length constraint may also be specified. This field is defined as follows:
basicConstraints EXTENSION ::= {
SYNTAX BasicConstraintsSyntax
IDENTIFIED BY id-ce-basicConstraints }
BasicConstraintsSyntax ::= SEQUENCE {
cA BOOLEAN DEFAULT FALSE,
pathLenConstraint INTEGER (0..MAX) OPTIONAL }
The cA component indicates if the certified public key may be used to verify certificate signatures.
The pathLenConstraint component shall be present only if cA is set to true. It gives the maximum number of
CA-certificates that may follow this certificate in a certification path. Value 0 indicates that the subject of this certificate
may issue certificates only to end-entities and not to further CAs. If no pathLenConstraint field appears in any
certificate of a certification path, there is no limit to the allowed length of the certification path. The constraint takes
effect beginning with the next certificate in the path. The constraint restricts the length of the segment of the
certification path between the certificate containing this extension and the end-entity certificate. It has no impact on the
number of CA-certificates in the certification path between the trust anchor and the certificate containing this extension.
Therefore, the length of a complete certification path may exceed the maximum length of the segment constrained by
this extension. The constraint controls the number of non self-issued CA certificates between the CA certificate
containing the constraint and the end-entity certificate. Therefore the total length of this segment of the path, excluding
self-issued certificates, may exceed the value of the constraint by as many as two certificates. (This includes the
certificates at the two endpoints of the segment plus the CA certificates between the two endpoints that are constrained
by the value of this extension.)
This extension may, at the option of the certificate issuer, be either critical or non-critical. It is recommended that it be
flagged critical, otherwise an entity which is not authorized to be a CA may issue certificates and a certificate-using
system may unwittingly use such a certificate.
If this extension is present and is flagged critical, or is flagged non-critical but is recognized by the certificate-using
system, then:
­ if the value of cA is not set to true then the certified public key shall not be used to verify a certificate
signature;
­ if the value of cA is set to true and pathLenConstraint is present then the certificate-using system shall
check that the certification path being processed is consistent with the value of pathLenConstraint.
NOTE 1 ­ If this extension is not present, or is flagged non-critical and is not recognized by a certificate-using system, then the
certificate is to be considered an end-entity certificate and cannot be used to verify certificate signatures.
NOTE 2 ­ To constrain a certificate subject to being only an end entity, i.e., not a CA, the issuer can include this extension field
containing only an empty SEQUENCE value.
8.4.2.2 Name constraints extension
This field, which shall be used only in a CA-certificate, indicates a name space within which all subject names in
subsequent certificates in a certification path must be located. This field is defined as follows:
nameConstraints EXTENSION ::= {
SYNTAX NameConstraintsSyntax
IDENTIFIED BY id-ce-nameConstraint }
NameConstraintsSyntax ::= SEQUENCE {
permittedSubtrees [0] GeneralSubtrees OPTIONAL,
excludedSubtrees [1] GeneralSubtrees OPTIONAL,
requiredNameForms [2] NameForms OPTIONAL }
GeneralSubtrees ::= SEQUENCE SIZE (1..MAX) OF GeneralSubtree
GeneralSubtree ::= SEQUENCE {
base GeneralName,
minimum [0] BaseDistance DEFAULT 0,
maximum [1] BaseDistance OPTIONAL }
BaseDistance ::= INTEGER (0..MAX)
NameForms ::= SEQUENCE {
basicNameForms [0] BasicNameForms OPTIONAL,
ISO/IEC 9594-8:2005 (E)
32 ITU-T Rec. X.509 (08/2005)
otherNameForms [1] SEQUENCE SIZE (1..MAX) OF OBJECT IDENTIFIER OPTIONAL }
(ALL EXCEPT ({ -- none; i.e., at least one component shall be present -- }))
BasicNameForms ::= BIT STRING {
rfc822Name (0),
dNSName (1),
x400Address (2),
directoryName (3),
ediPartyName (4),
uniformResourceIdentifier (5),
iPAddress (6),
registeredID (7) } (SIZE (1..MAX))
If present, the permittedSubtrees and excludedSubtrees components each specify one or more naming subtrees, each
defined by the name of the root of the subtree and optionally, within that subtree, an area that is bounded by upper
and/or lower levels. If permittedSubtrees is present, subject names within these subtrees are acceptable. If
excludedSubtrees is present, any certificate issued by the subject CA or subsequent CAs in the certification path that
has a subject name within these subtrees is unacceptable. If both permittedSubtrees and excludedSubtrees are
present and the name spaces overlap, the exclusion statement takes precedence for names within that overlap. If neither
permitted nor excluded subtrees are specified for a name form, then any name within that name form is acceptable. If
requiredNameForms is present, all subsequent certificates in the certification path must include a name of at least one
of the required name forms.
If permittedSubtrees is present, the following applies to all subsequent certificates in the path. If any certificate
contains a subject name (in the subject field or subjectAltNames extension) of a name form for which permitted
subtrees are specified, the name must fall within at least one of the specified subtrees. If any certificate contains only
subject names of name forms other than those for which permitted subtrees are specified, the subject names are not
required to fall within any of the specified subtrees. For example, assume that two permitted subtrees are specified, one
for the DN name form and one for the rfc822 name form, no excluded subtrees are specified, but requiredNameForms
is specified with the directoryName bit and rfc822Name bit present. A certificate that contained only names other than
a directory name or rfc822 name would be unacceptable. If requiredNameForms were not specified, however, such a
certificate would be acceptable. For example, assume that two permitted subtrees are specified, one for the DN name
form and one for the rfc822 name form, no excluded subtrees are specified, and requiredNameForms is not present. A
certificate that only contained a DN and where the DN is within the specified permitted subtree, would be acceptable. A
certificate that contained both a DN and an rfc822 name and where only one of them is within its specified permitted
subtree, would be unacceptable. A certificate that contained only names other than a DN or rfc822 name would also be
acceptable.
NOTE ­ This example is for illustrative purposes only. How to handle names that are in the name forms of the GeneralName
type, except the directoryName name form, in their hierarchical structure, is not defined in this Recommendation |
International Standard.
If excludedSubtrees is present, any certificate issued by the subject CA or subsequent CAs in the certification path
that has a subject name (in the subject field or subjectAltNames extension) within these subtrees is unacceptable. For
example, assume that two excluded subtrees are specified, one for the DN name form and one for the rfc822 name form.
A certificate that only contained a DN and where the DN is within the specified excluded subtree, would be
unacceptable. A certificate that contained both a DN and an rfc822 name and where at least one of them is within its
specified excluded subtree, would be unacceptable.
When a certificate subject has multiple names of the same name form (including, in the case of the directoryName
name form, the name in the subject field of the certificate if non-null) then all such names shall be tested for consistency
with a name constraint of that name form.
If requiredNameForms is present, all subsequent certificates in the certification path must include a subject name of at
least one of the required name forms.
Of the name forms available through the GeneralName type, only those name forms that have a well-defined
hierarchical structure may be used in the permittedSubtrees and excludedSubtrees fields. The directoryName name
form satisfies this requirement; when using this name form a naming subtree corresponds to a DIT subtree.
The minimum field specifies the upper bound of the area within the subtree. All names whose final name component is
above the level specified are not contained within the area. A value of minimum equal to zero (the default) corresponds
to the base, i.e., the top node of the subtree. For example, if minimum is set to one, then the naming subtree excludes
the base node but includes subordinate nodes.
The maximum field specifies the lower bound of the area within the subtree. All names whose last component is below
the level specified are not contained within the area. A value of maximum of zero corresponds to the base, i.e., the top
of the subtree. An absent maximum component indicates that no lower limit should be imposed on the area within the
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 33
subtree. For example, if maximum is set to one, then the naming subtree excludes all nodes except the subtree base and
its immediate subordinates.
For the directoryName name form, a certificate is considered subordinate to the base (and therefore a candidate to be
within the subtree) if the SEQUENCE of RDNs, which forms the full DN in base, is identical to the initial SEQUENCE
of the same number of RDNs which forms the first part of the DN in the subject field of the certificate. The DN in the
subject field of the certificate may have additional trailing RDNs in its sequence that do not appear in the DN in base.
The distinguishedNameMatch matching rule is used to compare the value of base with the initial sequence of RDNs in
the DN in the subject field of the certificate.
This extension may, at the option of the certificate issuer, be either critical or non-critical. It is recommended that it be
flagged critical, otherwise a certificate user may not check that subsequent certificates in a certification path are located
in the name space intended by the issuing CA.
Conformant implementations are not required to recognize all possible name forms.
If the extension is present and is flagged critical, a certificate-using implementation must recognize and process all
name forms for which there is both a subtree specification (permitted or excluded) in the extension and a corresponding
value in the subject field or subjectAltNames extension of any subsequent certificate in the certification path. If an
unrecognized name form appears in both a subtree specification and a subsequent certificate, that certificate shall be
handled as if an unrecognized critical extension was encountered. If any subject name in the certificate falls within an
excluded subtree, the certificate is unacceptable. If a subtree is specified for a name form that is not contained in any
subsequent certificate, that subtree can be ignored. If the requiredNameForms component specifies only unrecognized
name forms, that certificate shall be handled as if an unrecognized critical extension was encountered. Otherwise, at
least one of the recognized name forms must appear in all subsequent certificates in the path.
If the extension is present and is flagged non-critical and a certificate-using implementation does not recognize a name
form used in any base component, then that subtree specification may be ignored. If the extension is flagged noncritical
and any of the name forms specified in the requiredNameForms component are not recognized by the
certificate-using implementation, then the certificate shall be treated as if the requiredNameForms component was
absent.
Note that in some cases it may be required that more than one certificate be issued from a CA to another CA in order to
achieve the desired results if some of the name constraints requirements conflict. For example, assume the Acme
Corporation has 20 branches in the U.S.
The Widget Corporation wants to cross-certify the central CA of Acme Corporation, but only wants the Widget
community to use Acme certificates for the subjects that meet the following criteria:
­ Branch1 to Branch19 of Acme Corporation, all sections are acceptable as subject;
­ Branch20 of Acme Corporation, all sections are unacceptable as subject except for subject in Purchasing
Section.
This could be achieved by issuing two certificates as follows; the first certificate would have a permittedSubtrees of
{base: C=US, O=Acme} and an excludedSubtrees of {base: C=US, O=Acme, OU=branch20}. The second certificate
would have a permittedSubtrees of {base: C=US, O=Acme, OU=branch20, OU=Purchasing}.
Annex G contains examples of use of the name constraints extension.
8.4.2.3 Policy constraints extension
This field specifies constraints which may require explicit certificate policy identification or inhibit policy mapping for
the remainder of the certification path. This field is defined as follows:
policyConstraints EXTENSION ::= {
SYNTAX PolicyConstraintsSyntax
IDENTIFIED BY id-ce-policyConstraints }
PolicyConstraintsSyntax ::= SEQUENCE {
requireExplicitPolicy [0] SkipCerts OPTIONAL,
inhibitPolicyMapping [1] SkipCerts OPTIONAL }
SkipCerts ::= INTEGER (0..MAX)
If the requireExplicitPolicy component is present, and the certification path includes a certificate issued by a nominated
CA, it is necessary for all certificates in the path to contain, in the certificate policies extension, an acceptable policy
identifier. An acceptable policy identifier is the identifier of a certificate policy required by the user of the certification
path, the identifier of a policy which has been declared equivalent to one of these policies through policy mapping, or
any-policy. The nominated CA is either the issuer CA of the certificate containing this extension (if the value of
ISO/IEC 9594-8:2005 (E)
34 ITU-T Rec. X.509 (08/2005)
requireExplicitPolicy is 0) or a CA which is the issuer of a subsequent certificate in the certification path (as indicated
by a non-zero value).
If the inhibitPolicyMapping component is present, it indicates that, in all certificates starting from a nominated CA in
the certification path until the end of the certification path, policy mapping is not permitted. The nominated CA is either
the subject CA of the certificate containing this extension (if the value of inhibitPolicyMapping is 0) or a CA which is
the subject of a subsequent certificate in the certification path (as indicated by a non-zero value).
A value of type SkipCerts indicates the number of certificates in the certification path to skip before a constraint
becomes effective.
This extension may, at the option of the certificate issuer, be either critical or non-critical. It is recommended that it be
flagged critical, otherwise a certificate user may not correctly interpret the stipulation of the issuing CA.
8.4.2.4 Inhibit any policy extension
This field specifies a constraint that indicates any-policy is not considered an explicit match for other certificate policies
for all non-self-issued certificates in the certification path starting with a nominated CA. The nominated CA is either the
subject CA of the certificate containing this extension (if the value of inhibitAnyPolicy is 0) or a CA which is the
subject of a subsequent certificate in the certification path (as indicated by a non-zero value).
inhibitAnyPolicy EXTENSION ::= {
SYNTAX SkipCerts
IDENTIFIED BY id-ce-inhibitAnyPolicy }
This extension may, at the option of the certificate issuer, be either critical or non-critical. It is recommended that it be
critical, otherwise a certificate user may not correctly interpret the stipulation of the issuing CA.
8.5 Basic CRL extensions
8.5.1 Requirements
The following requirements relate to CRLs:
a) Certificate users need to be able to track all CRLs issued from a CRL issuer or CRL distribution point
(see 8.6) and be able to detect a missing CRL in the sequence. CRL sequence numbers are therefore
required.
b) Some CRL users may wish to respond differently to a revocation, depending upon the reason for the
revocation. There is therefore a requirement for a CRL entry to indicate the reason for revocation.
c) There is a requirement for an authority to be able to temporarily suspend validity of a certificate and
subsequently either revoke or reinstate it. Possible reasons for such an action include:
­ desire to reduce liability for erroneous revocation when a revocation request is unauthenticated and
there is inadequate information to determine whether it is valid;
­ other business needs, such as temporarily disabling the certificate of an entity pending an audit or
investigation.
d) A CRL contains, for each revoked certificate, the date when the authority posted the revocation. Further
information may be known as to when an actual or suspected key compromise occurred, and this
information may be valuable to a certificate user. The revocation date is insufficient to solve some
disputes because, assuming the worst, all signatures issued during the validity period of the certificate
have to be considered invalid. However, it may be important for a user that a signed document be
recognized as valid even though the key used to sign the message was compromised after the signature
was produced. To assist in solving this problem, a CRL entry can include a second date which indicates
when it was known or suspected that the private key was compromised.
e) Certificate users need to be able to determine, from the CRL itself, additional information including the
scope of certificates covered by this list, the ordering of revocation notices, and which stream of CRLs
the CRL number is unique within.
f) Issuers need the ability to dynamically change the partitioning of CRLs and to refer certificate users to
the new location for relevant CRLs if the partitioning changes.
g) Delta CRLs may also be available that update a given base CRL. Certificate users need to be able to
determine, from a given CRL, whether delta CRLs are available, where they are located and when the
next delta CRL will be issued.
h) In addition to CRLs publishing notification that certificates have been revoked, there is a requirement to
publish notification that certificates will be revoked as of a specified date and time in the future.
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ITU-T Rec. X.509 (08/2005) 35
i) There is a requirement to provide more efficient ways to indicate in a CRL that a set of certificates has
been revoked.
8.5.2 CRL and CRL entry extension fields
The following extension fields are defined:
a) CRL number;
b) Reason code;
c) Hold instruction code;
d) Invalidity date;
e) CRL scope;
f) Status referral;
g) CRL stream identifier;
h) Ordered list;
i) Delta information.
The CRL number, CRL scope, status referral, CRL stream identifier, ordered list and delta information shall be used
only as a CRL extension field and the other fields shall be used only as CRL entry extension fields.
8.5.2.1 CRL number extension
This CRL extension field conveys a monotonically increasing sequence number for each CRL issued by a given CRL
issuer through a given authority directory attribute or CRL distribution point. It allows a CRL user to detect whether
CRLs issued prior to the one being processed were also seen and processed. This field is defined as follows:
cRLNumber EXTENSION ::= {
SYNTAX CRLNumber
IDENTIFIED BY id-ce-cRLNumber }
CRLNumber ::= INTEGER (0..MAX)
This extension is always non-critical.
8.5.2.2 Reason code extension
This CRL entry extension field identifies a reason for the certificate revocation. The reason code may be used by
applications to decide, based on local policy, how to react to posted revocations. This field is defined as follows:
reasonCode EXTENSION ::= {
SYNTAX CRLReason
IDENTIFIED BY id-ce-reasonCode }
CRLReason ::= ENUMERATED {
unspecified (0),
keyCompromise (1),
cACompromise (2),
affiliationChanged (3),
superseded (4),
cessationOfOperation (5),
certificateHold (6),
removeFromCRL (8),
privilegeWithdrawn (9),
aaCompromise (10) }
The following reason code values indicate why a certificate was revoked:
­ unspecified can be used to revoke certificates for reasons other than the specific codes;
­ keyCompromise is used in revoking an end-entity certificate; it indicates that it is known or suspected
that the subject's private key, or other aspects of the subject validated in the certificate, have been
compromised;
­ cACompromise is used in revoking a CA-certificate; it indicates that it is known or suspected that the
subject's private key, or other aspects of the subject validated in the certificate, have been compromised;
­ affiliationChanged indicates that the subject's name or other information in the certificate has been
modified but there is no cause to suspect that the private key has been compromised;
ISO/IEC 9594-8:2005 (E)
36 ITU-T Rec. X.509 (08/2005)
­ superseded indicates that the certificate has been superseded but there is no cause to suspect that the
private key has been compromised;
­ cessationOfOperation indicates that the certificate is no longer needed for the purpose for which it was
issued but there is no cause to suspect that the private key has been compromised;
­ privilegeWithdrawn indicates that a certificate (public-key or attribute certificate) was revoked because
a privilege contained within that certificate has been withdrawn;
­ aACompromise indicates that it is known or suspected that aspects of the AA validated in the attribute
certificate, have been compromised.
A certificate may be placed on hold by issuing a CRL entry with a reason code of certificateHold. The certificate hold
notice may include an optional hold instruction code to convey additional information to certificate users (see 8.5.2.3).
Once a hold has been issued, it may be handled in one of three ways:
a) it may remain on the CRL with no further action, causing users to reject transactions issued during the
hold period; or,
b) it may be replaced by a (final) revocation for the same certificate, in which case the reason shall be one
of the standard reasons for revocation, the revocation date shall be the date the certificate was placed on
hold, and the optional instruction code extension field shall not appear; or,
c) it may be explicitly released and the entry removed from the CRL.
The removeFromCRL reason code is for use with delta-CRLs (see 8.6) only and indicates that an existing CRL entry
should now be removed owing to certificate expiration or hold release. An entry with this reason code shall be used in
delta-CRLs for which the corresponding base CRL or any subsequent (delta or complete for scope) CRL contains an
entry for the same certificate with reason code certificateHold.
This extension is always non-critical.
8.5.2.3 Hold instruction code extension
This CRL entry extension field provides for inclusion of a registered instruction identifier to indicate the action to be
taken on encountering a held certificate. It is applicable only in an entry having a certificateHold reason code. This
field is defined as follows:
holdInstructionCode EXTENSION ::= {
SYNTAX HoldInstruction
IDENTIFIED BY id-ce-instructionCode }
HoldInstruction ::= OBJECT IDENTIFIER
This extension is always non-critical. No standard hold instruction codes are defined in this Directory Specification.
NOTE ­ Examples of hold instructions might be "please communicate with the CA" or "repossess the user's token".
8.5.2.4 Invalidity date extension
This CRL entry extension field indicates the date at which it is known or suspected that the private key was
compromised or that the certificate should otherwise be considered invalid. This date may be earlier than the revocation
date in the CRL entry, which is the date at which the authority processed the revocation. This field is defined as follows:
invalidityDate EXTENSION ::= {
SYNTAX GeneralizedTime
IDENTIFIED BY id-ce-invalidityDate }
This extension is always non-critical.
NOTE 1 ­ The date in this extension is not, by itself, sufficient for non-repudiation purposes. For example, this date may be a
date advised by the private key holder, and it is possible for such a person to fraudulently claim that a key was compromised
some time in the past, in order to repudiate a validly-generated signature.
NOTE 2 ­ When a revocation is first posted by an authority in a CRL, the invalidity date may precede the date of issue of earlier
CRLs. The revocation date should not precede the date of issue of earlier CRLs.
8.5.2.5 CRL scope extension
NOTE ­ Use of the CRL scope extension is deprecated.
The scope of a CRL is indicated within that CRL using the following CRL extension. In order to prevent a CRL
substitution attack against an application that does not support the scope extension, the scope extension, if present, shall
be marked critical.
This extension may be used to provide scope statements of various CRL types including:
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 37
­ simple CRLs that provide revocation information about certificates issued by a single authority;
­ indirect CRLs that provide revocation information about certificates issued by multiple authorities;
­ delta-CRLs that update previously issued revocation information;
­ indirect delta-CRLs that provide revocation information that updates multiple base CRLs issued by a
single authority or by multiple authorities.
crlScope EXTENSION ::= {
SYNTAX CRLScopeSyntax
IDENTIFIED BY id-ce-cRLScope }
CRLScopeSyntax ::= SEQUENCE SIZE (1..MAX) OF PerAuthorityScope
PerAuthorityScope ::= SEQUENCE {
authorityName [0] GeneralName OPTIONAL,
distributionPoint [1] DistributionPointName OPTIONAL,
onlyContains [2] OnlyCertificateTypes OPTIONAL,
onlySomeReasons [4] ReasonFlags OPTIONAL,
serialNumberRange [5] NumberRange OPTIONAL,
subjectKeyIdRange [6] NumberRange OPTIONAL,
nameSubtrees [7] GeneralNames OPTIONAL,
baseRevocationInfo [9] BaseRevocationInfo OPTIONAL
}
OnlyCertificateTypes ::= BIT STRING {
user (0),
authority (1),
attribute (2) }
NumberRange ::= SEQUENCE {
startingNumber [0] INTEGER OPTIONAL,
endingNumber [1] INTEGER OPTIONAL,
modulus INTEGER OPTIONAL }
BaseRevocationInfo ::= SEQUENCE {
cRLStreamIdentifier [0] CRLStreamIdentifier OPTIONAL,
cRLNumber [1] CRLNumber,
baseThisUpdate [2] GeneralizedTime }
If the CRL is an indirect CRL that provides revocation status information for multiple authorities, the extension will
include multiple PerAuthorityScope constructs, one or more for each of the authorities for which revocation
information is included. Each instance of PerAuthorityScope that relates to an authority other than that issuing this
CRL shall contain the authorityName component. If the CRL is a dCRL that provides delta revocation status
information for multiple base CRLs issued by a single authority, the extension will include multiple
PerAuthorityScope constructs, one for each of the base CRLs for which this dCRL provides updates. Even though
there would be multiple instances of the PerAuthorityScope construct, the value of the authorityName component, if
present, would be the same for all instances.
If the CRL is an indirect dCRL that provides delta revocation status information for multiple base CRLs issued by
multiple authorities, the extension will include multiple PerAuthorityScope constructs, one for each of the base CRLs
for which this dCRL provides updates. Each instance of PerAuthorityScope that relates to an authority other than that
issuing this indirect dCRL shall include the authorityName component.
For each instance of PerAuthorityScope present in the extension, the fields are used as follows. Note that in the case of
indirect CRLs and indirect dCRLs, each instance of PerAuthorityScope may contain different combinations of these
fields and different values.
The authorityName field, if present, identifies the authority that issued the certificates for which revocation information
is provided. If authorityName is omitted, it defaults to the CRL issuer name.
The distributionPoint field, if present, is used as described in the issuingDistributionPoint extension.
The onlyContains field, if present, indicates the type(s) of certificates for which the CRL contains revocation status
information. If this field is absent, the CRL contains information about all certificate types.
The onlySomeReasons field, if present, is used as described in the issuingDistributionPoint extension.
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The serialNumberRange element, if present, is used as follows. When a modulus value is present, the serial number is
reduced modulo the given value before checking for presence in the range. Then, a certificate with a (reduced) serial
number is considered to be within the scope of the CRL if it is:
­ equal to or greater than startingNumber, and less than endingNumber, where both are present; or
­ equal to or greater than startingNumber, when endingNumber is not present; or
­ less than endingNumber when startingNumber is not present.
The subjectKeyIdRange element, if present, is interpreted the same as serialNumberRange, except that the number
used is the value in the certificate's subjectKeyIdentifier extension. The DER encoding of the BIT STRING (omitting
the tag, length and unused bits octet) is to be regarded as the value of the DER encoding of an INTEGER. If bit 0 of the
BIT STRING is set, then an additional zero octet should be prepended so as to ensure the resulting encoding represents a
positive INTEGER. e.g.:
03 02 01 f7 (represents bits 0-6 set)
maps to
02 02 00 f7 (i.e. decimal 247)
The nameSubtrees field, if present, uses the same conventions for name forms as specified in the nameConstraints
extension.
The baseRevocationInfo field, if present, indicates that the CRL is a dCRL with respect to the certificates covered by
that PerAuthorityScope construct. Use of the crlScope extension to identify a CRL as a dCRL differs from use of the
deltaCRLIdentifier extension in the following way. In the crlScope case, the information in the baseRevocationInfo
component indicates the point in time from which the CRL containing this extension provides updates. Although this is
done by referencing a CRL, the referenced CRL may or may not be one that is complete for the applicable scope,
whereas the deltaCRLIdentifier extension references an issued CRL that is complete for the applicable scope. However,
the updated information provided in a dCRL containing the crlScope extension are updates to the revocation
information that is complete for the applicable scope regardless of whether or not the CRL referenced in
baseRevocationInfo was actually issued as one that is complete for that same scope. This mechanism provides more
flexibility than the deltaCRLIndicator extension since users can be constructing full CRLs locally and be constructing
based on time rather than issuance of base CRLs that are complete for the applicable scope. In both cases, a dCRL
always provides updates to revocation status for certificates within a given scope since a specific point in time.
However, in the deltaCRLIndicator case, that point in time shall be one for which a CRL that is complete for that scope
was issued and referenced. In the crlScope case, that point in time may be one for which the referenced CRL that was
issued may or may not be one that is complete for that scope.
Depending on the policy of the responsible authority, several dCRLs may be published before a new base CRL is
published. dCRLs containing the crlScope extension to reference their building point need not necessarily reference the
cRLNumber of the most recently issued base CRL in the BaseRevocationInfo field. However, the cRLNumber
referenced in the BaseRevocationInfo field of a dCRL shall be less than or equal to the cRLNumber of the most
recently issued CRL that is complete for the applicable scope.
Note that the issuingDistributionPoint extension and crlScope extension can conflict with each other and are not
intended to be used together. However, if the CRL contains both an issuingDistributionPoint extension and a
crlScope extension, then a public-key certificate falls within the scope of the CRL if and only if it meets the criteria of
both extensions. If the CRL contains an AAissuingDistributionPoint extension, but does not contain an
issuingDistributionPoint or crlScope extension, then the scope does not include public-key certificates. If the CRL
does not contain an issuingDistributionPoint, AAissuingDistributionPoint, or crlScope extension, then the scope is
the entire scope of the authority, and the CRL may be used for any certificate from that authority. Similarly, the
AAissuingDistributionPoint extension and crlScope extension can conflict with each other and are not intended to be
used together. However, if the CRL contains both an AAissuingDistributionPoint extension and a crlScope extension,
then an attribute certificate falls within the scope of the CRL if and only if it meets the criteria of both extensions. If the
CRL contains an issuingDistributionPoint extension, but does not contain an AAissuingDistributionPoint or
crlScope extension, then the scope does not include attribute certificates. If the CRL does not contain an
issuingDistributionPoint, AAissuingDistributionPoint, or crlScope extension, then the scope is the entire scope of
the authority, and the CRL may be used for any certificate from that authority.
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When a certificate-using system uses a CRL that contains a crlScope extension to check the status of a certificate, it
should check that the certificate and reason codes of interest fall within the scope of the CRL as defined by the
crlScope extension, as follows:
a) The certificate-using system shall check that the certificate falls within the scope indicated by the
intersection of the serialNumberRange, subjectKeyIdRange, and nameSubtrees scopes, and is
consistent with distributionPoint, and onlyContains if present, for the relevant PerAuthorityScope
construct.
b) If the CRL contains an onlySomeReasons component in the crlScope extension, then the certificateusing
system shall check that the reason codes covered by this CRL are adequate for purposes of the
application. If not, additional CRLs may be required. Note that if the CRL contains both a crlScope
extension and an issuingDistributionPoint extension, and both contain an onlySomeReasons
component, then only those reason codes included in the onlySomeReasons components of both
extensions are covered by this CRL.
8.5.2.6 Status referral extension
This CRL extension is for use within the CRL structure as a means to convey information about revocation notices to
certificate users. As such it would be present in a CRL structure that itself contains no certificate revocation notices. A
CRL structure containing this extension shall not be used by certificate users or relying parties as a source of revocation
notices, but rather as a tool to ensure that the appropriate revocation information is used. Any CRL containing this
extension shall not be used as the source for a relying party to check revocation status of any certificate. Rather, a CRL
containing this extension may be used by a relying party as an additional tool to locate the appropriate CRLs for
checking revocation status.
This extension serves two primary functions:
­ This extension provides a mechanism to publish a trusted "list of CRLs" including all the relevant
information to aid relying parties in determining whether or not they have sufficient revocation
information for their needs. For example, an authority may issue a new, authenticated CRL list
periodically, typically with a relatively high reissue frequency (in comparison with other CRL reissue
frequencies). The list might include a last-update time/date for every referenced CRL. A certificate user,
on obtaining this list, can quickly determine if cached copies of CRLs are still up-to-date. This may
eliminate much unnecessary retrieval of CRLs. Furthermore, by using this mechanism, certificate users
become aware of CRLs issued by the authority between its usual update cycle, thereby improving the
timeliness of the CRL system;
­ This extension also provides a mechanism to redirect a relying party from a preliminary location (e.g.,
one pointed to in a CRL distribution point extension, or the directory entry of the issuing authority) to a
different location for revocation information. This feature enables authorities to modify the CRL
partitioning scheme they use without impacting existing certificates or certificate users. To achieve this,
the authority would include each new location and the scope of the CRL that would be found at that
location. The relying party would compare the certificate of interest with the scope statements and follow
the pointer to the appropriate new location for revocation information relevant to that certificate they are
validating.
The extension is itself extensible and in future other non-CRL based revocation schemes may also be referred to, using
this extension.
statusReferrals EXTENSION ::= {
SYNTAX StatusReferrals
IDENTIFIED BY id-ce-statusReferrals }
StatusReferrals ::= SEQUENCE SIZE (1..MAX) OF StatusReferral
StatusReferral ::= CHOICE {
cRLReferral [0] CRLReferral,
otherReferral [1] INSTANCE OF OTHER-REFERRAL}
CRLReferral ::= SEQUENCE {
issuer [0] GeneralName OPTIONAL,
location [1] GeneralName OPTIONAL,
deltaRefInfo [2] DeltaRefInfo OPTIONAL,
cRLScope CRLScopeSyntax,
lastUpdate [3] GeneralizedTime OPTIONAL,
lastChangedCRL [4] GeneralizedTime OPTIONAL}
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40 ITU-T Rec. X.509 (08/2005)
DeltaRefInfo ::= SEQUENCE {
deltaLocation GeneralName,
lastDelta GeneralizedTime OPTIONAL }
OTHER-REFERRAL ::= TYPE-IDENTIFIER
The issuer field identifies the entity that signs the CRL; this defaults to the issuer name of the encompassing CRL.
The location field provides the location to which the referral is to be directed, and defaults to the same value as the
issuer name.
The deltaRefInfo field provides an optional alternative location from which a dCRL may be obtained and an optional
date of the previous delta.
The cRLScope field provides the scope of the CRL that will be found at the referenced location.
The lastUpdate field is the value of the thisUpdate field in the most recently issued referenced CRL.
The lastChangedCRL is the value of the thisUpdate field in the most recently issued CRL that has changed content.
The OTHER-REFERRAL provides extensibility to enable other non-CRL based revocation schemes to be
accommodated in future.
This extension, is always flagged critical, to ensure that the CRL containing this extension is not inadvertently relied on
by certificate using systems as the source of revocation status information about certificates.
If this extension is present and is recognized by a certificate using system, that system shall not use the CRL as a source
of revocation status information. The system should use either the information contained in this extension, or other
means outside the scope of this Specification, to locate appropriate revocation status information.
If this extension is present but is not recognized by a certificate-using system, that system shall not use the CRL as a
source of revocation status information. The system should use other means, outside the scope of this Specification, to
locate appropriate revocation information.
8.5.2.7 CRL stream identifier extension
The CRL stream identifier field is used to identify the context within which the CRL number is unique.
cRLStreamIdentifier EXTENSION ::= {
SYNTAX CRLStreamIdentifier
IDENTIFIED BY id-ce-cRLStreamIdentifier }
CRLStreamIdentifier ::= INTEGER (0..MAX)
This extension is always non-critical.
Each value of this extension, per authority, shall be unique. The CRL stream identifier combined with a CRL Number
serve as a unique identifier for each CRL issued by any given authority, regardless of the type of CRL.
8.5.2.8 Ordered list extension
The ordered list extension indicates that the sequence of revoked certificates in the revokedCertificates field of a CRL
is in ascending order by either certificate serial number or revocation date. This field is defined as follows:
orderedList EXTENSION ::= {
SYNTAX OrderedListSyntax
IDENTIFIED BY id-ce-orderedList }
OrderedListSyntax ::= ENUMERATED {
ascSerialNum (0),
ascRevDate (1) }
This extension is always non-critical.
­ ascSerialNum indicates that the sequence of revoked certificates in a CRL is in ascending order of
certificate serial number, based on the value of the serialNumber component of each entry in the list;
­ ascRevDate indicates that the sequence of revoked certificates in a CRL is in ascending order of
revocation date, based on the value of the revocationDate component of each entry in the list.
If orderedList is not present, no information is provided as to the ordering, if any, of the list of revoked certificates in
the CRL.
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8.5.2.9 Delta Information extension
This CRL extension is for use in CRLs that are not dCRLs and is used to indicate to relying parties that dCRLs are also
available for the CRL containing this extension. The extension provides the location at which the related dCRLs can be
found and optionally the time at which the next dCRL is to be issued.
deltaInfo EXTENSION ::= {
SYNTAX DeltaInformation
IDENTIFIED BY id-ce-deltaInfo }
DeltaInformation ::= SEQUENCE {
deltaLocation GeneralName,
nextDelta GeneralizedTime OPTIONAL }
This extension is always non-critical.
8.5.2.10 To be revoked extension
This CRL extension allows for notification that certificates will be revoked as of a specified date and time in the future.
The toBeRevoked extension is used to specify the reason for the certificate revocation, the date and time at which the
certificate will be revoked, and the group of certificates to be revoked. Each list can contain a single certificate serial
number, a range of certificate serial numbers or a named subtree. These certificates may be public-key certificates or
attribute certificates.
toBeRevoked EXTENSION ::= {
SYNTAX ToBeRevokedSyntax
IDENTIFIED BY id-ce-toBeRevoked }
ToBeRevokedSyntax::= SEQUENCE SIZE(1..MAX) OF ToBeRevokedGroup
ToBeRevokedGroup ::= SEQUENCE {
certificateIssuer [0] GeneralName OPTIONAL,
reasonInfo [1] ReasonInfo OPTIONAL,
revocationTime GeneralizedTime,
certificateGroup CertificateGroup }
ReasonInfo ::= SEQUENCE {
reasonCode CRLReason,
holdInstructionCode HoldInstruction OPTIONAL }
CertificateGroup ::= CHOICE {
serialNumbers [0] CertificateSerialNumbers,
serialNumberRange [1] CertificateGroupNumberRange,
nameSubtree [2] GeneralName }
CertificateGroupNumberRange ::= SEQUENCE {
startingNumber [0] INTEGER,
endingNumber [1] INTEGER }
CertificateSerialNumbers ::= SEQUENCE SIZE(1..MAX) OF CertificateSerialNumber
The certificateIssuer field, if present, identifies the authority (CA or AA) that issued all the certificates listed in this
ToBeRevokedGroup. If certificateIssuer is omitted, it defaults to the CRL issuer name.
The reasonInfo field, if present, identifies the reason for the certificate revocations. If present, this field indicates that
all certificates identified in ToBeRevokedGroup will be revoked for the reason indicated in this field. If reasonCode
contains the value certificateHold, the holdInstructionCode may also be present. If present, holdInstructionCode
indicates the action to be taken on encountering any of the certificates identified in RevokedGroup. This action should
only be taken, after the revocation time indicated in the revocationTime field has passed.
The revocationTime field indicates the date and time at which this group of certificates will be revoked and should
therefore be considered invalid. This date shall be later than the thisUpdate time of the CRL containing this extension.
If revocationTime is before the nextUpdate time of the CRL containing this extension, the certificates shall be
considered revoked between the revocationTime and the nextUpdate time by a relying party using a CRL containing
this extension. Otherwise this is a notice that at specified time in the future these certificates will be revoked. Once the
revocation time has passed either the CA has revoked the certificate or not. If it has revoked the certificate, future CRLs
shall include this on the list of revoked certificates, at least until the certificate expires. If the CA has not revoked the
certificate, but still intends to revoke it in the future, it may include the certificate in this extension on subsequent CRLs
with a revised revocationTime. If the CA no longer intends to revoke the certificate, it may be excluded from all
subsequent CRLs and the certificate shall not be considered revoked.
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The certificateGroup field lists the set of certificates to be revoked. This field identifies the certificates issued by the
authority identified in certificateIssuer to be revoked at the date/time identified in revocationTime. This set of
certificates is not further refined by any outside controls (e.g., issuingDistributionPoint).
If serialNumbers is present, the certificate(s) with serial numbers indicated in this field, and issued by the identified
certificate issuer, will be revoked at the specified time.
If serialNumberRange is present, all certificates in the range beginning with the starting serial number and ending with
the ending serial number and issued by the identified certificate issuer will be revoked at the specified time.
If nameSubtree is present, all certificates with a subject/holder name that is subordinate to the specified name and
issued by the identified certificate issuer will be revoked at the specified time. If the nameSubtree contains a DN then
all DNs associated with the subject of a public-key certificate (i.e., subject field and subjectAltNames extension) or
holder field of an attribute certificate need to be considered. For other name forms the subjectAltNames extension of
public-key certificates and the holder field of attribute certificates need to be considered. If at least one of the names
associated with the subject/holder, contained in the certificate, is within the subtree specified in nameSubtree, that
certificate will be revoked at the specified time. As with the nameConstraints extension, not all name forms are
appropriate for subtree specification. Only those that have recognized subordination rules should be used in this
extension.
This extension may, at the option of the CRL issuer, be flagged critical or non-critical. As the information provided in
this extension applies to revocations, which will occur in the future, it is recommended that it be flagged non-critical,
reducing the risk of problems with interoperability and backward compatibility.
8.5.2.11 Revoked group of certificates extension
A set of certificates that have been revoked can be published using the following CRL extension. Each list of
certificates to be revoked is associated with a specific certificate issuer and revocation time. Each list can contain a
range of certificate serial numbers or a named subtree. These certificates may be public-key certificates or attribute
certificates.
revokedGroups EXTENSION ::= {
SYNTAX RevokedGroupsSyntax
IDENTIFIED BY id-ce-RevokedGroups }
RevokedGroupsSyntax ::= SEQUENCE SIZE (1..MAX) OF RevokedGroup
RevokedGroup ::= SEQUENCE {
certificateIssuer [0] GeneralName OPTIONAL,
reasonInfo [1] ReasonInfo OPTIONAL,
invalidityDate [2] GeneralizedTime OPTIONAL,
revokedcertificateGroup [3] RevokedCertificateGroup }
RevokedCertificateGroup ::= CHOICE {
serialNumberRange NumberRange,
nameSubtree GeneralName }
The certificateIssuer field, if present, identifies the authority (CA or AA) that issued all the certificates listed in this
RevokedGroup. If certificateIssuer is omitted, it defaults to the CRL issuer name.
The reasonInfo field, if present, identifies the reason for the certificate revocations. If present, this field indicates that
all certificates identified in RevokedGroup were revoked for the reason indicated in this field. If reasonCode contains
the value certificateHold, the holdInstructionCode may also be present. If present, holdInstructionCode indicates the
action to be taken on encountering any of the certificates identified in RevokedGroup.
The invalidityDate field, if present, indicates the time from which all certificates identified in RevokedGroup should
be considered invalid. This date shall be earlier than the date contained in thisUpdate field of the CRL. If omitted, all
certificates identified in RevokedGroup should be considered invalid at least from the time indicated in the thisUpdate
field of the CRL. If the status of the certificate prior to the thisUpdate time is critical to a certificate using system (e.g.,
to determine whether a digital signature that was created prior to this CRL issuance occurred while the certificate was
still valid or after it had been revoked), additional revocation status checking techniques will be required to determine
the actual date/time from which a given certificate should be considered invalid.
The revokedCertificateGroup field lists the set of certificates that have been revoked. This field identifies the
certificates issued by the authority identified in certificateIssuer revoked under the specified conditions. This set of
certificates is not further refined by any outside controls (e.g., issuingDistributionPoint).
If serialNumberRange is present, all certificates containing certificate serial numbers within the specified range, issued
by the identified certificate issuer are applicable.
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If nameSubtree is present, all certificates with a subject/holder name that is subordinate to the specified name and
issued by the identified certificate issuer will be revoked at the specified time. If the nameSubtree contains a DN then
all DNs associated with the subject of a public-key certificate (i.e., subject field and subjectAltNames extension) or
holder field of an attribute certificate need to be considered. For other name forms the subjectAltNames extension of
public-key certificates and the holder field of attribute certificates need to be considered. If at least one of the names
associated with the subject/holder, contained in the certificate, is within the subtree specified in nameSubtree, that
certificate has been revoked. As with the nameConstraints extension, not all name forms are appropriate for subtree
specification. Only those that have recognized subordination rules should be used in this extension.
This extension is always flagged critical. Otherwise a certificate using system may incorrectly assume that certificates,
identified as revoked within this extension, are not revoked. When this extension is present it may be the only indication
of revoked certificates in a CRL (i.e., the revokedCertificates may be empty) or it may list revoked certificates that are
in addition to those indicated in the revokedCertificates field. A revoked certificate shall not be listed both in the
revokedCertificates field and in this extension.
8.5.2.12 Expired certificates on CRL extension
This CRL extension field indicates that the CRL includes revocation notices for expired certificates.
expiredCertsOnCRL EXTENSION ::= {
SYNTAX ExpiredCertsOnCRL
IDENTIFIED BY id-ce-expiredCertsOnCRL }
ExpiredCertsOnCRL ::= GeneralizedTime
This extension is always non-critical.
The scope of a CRL containing this extension is extended to include the revocation status of certificates that expired at
the exact time specified in the extension or after that time. If limitations in the CRL's scope are specified (by either
reason codes or by distribution points), that applies to expired certificates as well. The revocation status of a certificate
shall not be updated once the certificate has expired.
8.6 CRL distribution points and delta-CRL extensions
8.6.1 Requirements
As it is possible for revocation lists to become large and unwieldy, the ability to represent partial CRLs is required.
Different solutions are needed for two different types of implementations that process CRLs.
The first type of implementation is in individual workstations, possibly in an attached cryptographic token. These
implementations are likely to have limited, if any, trusted storage capacity. Therefore the entire CRL would need to be
examined to determine if it is valid, and then to see if the certificate is valid. This processing could be lengthy if the
CRL is long. Partitioning of CRLs is required to eliminate this problem for these implementations.
The second type of implementation is on high performance servers where a large volume of messages is processed, e.g.,
a transaction processing server. In this environment CRLs are typically processed as a background task where, after the
CRL is validated, the contents of the CRL are stored locally in a representation which expedites their examination, e.g.,
one bit for each certificate indicating if it has been revoked. This representation is held in trusted storage. This type of
server will typically require up-to-date CRLs for a large number of authorities. Since it already has a list of previously
revoked certificates, it only needs to retrieve a list of newly revoked certificates. This list, called a dCRL, will be
smaller and require fewer resources to retrieve and process than a complete CRL.
The following requirements therefore relate to CRL distribution points and dCRLs:
a) In order to control CRL sizes, it needs to be possible to assign subsets of the set of all certificates issued
by one authority to different CRLs. This can be achieved by associating every certificate with a CRL
distribution point which is either:
­ a Directory entry whose CRL attribute will contain a revocation entry for that certificate, if it has
been revoked; or
­ a location such as an electronic mail address or Internet Uniform Resource Identifier from which the
applicable CRL can be obtained.
b) For performance reasons, it is desirable to reduce the number of CRLs that need to be checked when
validating multiple certificates, e.g., a certification path. This can be achieved by having one CRL issuer
sign and issue CRLs containing revocations from multiple authorities.
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c) There is a requirement for separate CRLs covering revoked authority certificates and revoked end-entity
certificates. This facilitates processing of certification paths as the CRL for revoked authority certificates
can be expected to be very short (usually empty). The authorityRevocationList and
certificateRevocationList attributes have been specified for this purpose. However, for this separation
to be secure, it is necessary to have an indicator in a CRL identifying which list it is. Otherwise,
illegitimate substitution of one list for the other cannot be detected.
d) Provision is needed for a different CRL to exist for potential compromise situations (when there is a
significant risk of private key misuse) than that including all routine binding terminations (when there is
no significant risk of private key misuse).
e) Provision is also needed for partial CRLs (known as dCRLs) which only contain entries for certificates
that have been revoked since the issuance of a base CRL.
f) For delta CRLs, provision is needed to indicate the date/time after which this list contains updates.
g) There is a requirement to indicate within a certificate, where to find the freshest CRL (e.g., most recent
delta).
8.6.2 CRL distribution point and delta-CRL extension fields
The following extension fields are defined:
a) CRL distribution points;
b) Issuing distribution point;
c) AAissuingDistributionPoint;
d) Certificate issuer;
e) Delta CRL indicator;
f) Base update;
g) Freshest CRL.
CRL distribution points and freshest CRL shall be used only as a certificate extension. Issuing distribution point, AA
issuing distribution point, delta CRL indicator and base update shall be used only as CRL extensions. Certificate issuer
shall be used only as a CRL entry extension.
While the issuing distribution point extension and the AA issuing distribution point extension serve similar purposes,
they apply to different certificates. The issuing distribution point extension applies only to public-key certificates issued
to users and/or CAs. The AA issuing distribution point extension applies only to attribute certificates issued to users and
AAs as well as public-key certificates issued to SOAs. If a single CRL covers certificate types that span these, then that
CRL would need to include both extensions.
8.6.2.1 CRL distribution points extension
The CRL distribution points extension shall be used only as a certificate extension and may be used in authoritycertificates,
end-entity public-key certificates, and in attribute certificates. This field identifies the CRL distribution
point or points to which a certificate user should refer to ascertain if the certificate has been revoked. A certificate user
can obtain a CRL from an applicable distribution point or it may be able to obtain a current complete CRL from the
authority directory entry.
This field is defined as follows:
cRLDistributionPoints EXTENSION ::= {
SYNTAX CRLDistPointsSyntax
IDENTIFIED BY id-ce-cRLDistributionPoints }
CRLDistPointsSyntax ::= SEQUENCE SIZE (1..MAX) OF DistributionPoint
DistributionPoint ::= SEQUENCE {
distributionPoint [0] DistributionPointName OPTIONAL,
reasons [1] ReasonFlags OPTIONAL,
cRLIssuer [2] GeneralNames OPTIONAL }
DistributionPointName ::= CHOICE {
fullName [0] GeneralNames,
nameRelativeToCRLIssuer [1] RelativeDistinguishedName }
ReasonFlags ::= BIT STRING {
unused (0),
keyCompromise (1),
cACompromise (2),
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affiliationChanged (3),
superseded (4),
cessationOfOperation (5),
certificateHold (6),
privilegeWithdrawn (7),
aACompromise (8) }
The distributionPoint component identifies the location from which the CRL can be obtained. If this component is
absent, the distribution point name defaults to the CRL issuer name.
When the fullName alternative is used or when the default applies, the distribution point name may have multiple name
forms. The same name, in at least one of its name forms, shall be present in the distributionPoint field of the issuing
distribution point extension of the CRL. A certificate-using system is not required to be able to process all name forms.
It may use a distribution point provided at least one name form can be processed. If no name forms for a distribution
point can be processed, a certificate-using system can still use the certificate provided requisite revocation information
can be obtained from another source, e.g., another distribution point or the authority's directory entry.
The nameRelativeToCRLIssuer component can be used only if the CRL distribution point is assigned a directory name
that is directly subordinate to the directory name of the CRL issuer. In this case, the nameRelativeToCRLIssuer
component conveys the relative distinguished name with respect to the CRL issuer directory name.
The reasons component indicates the revocation reasons covered by this CRL. If the reasons component is absent, the
corresponding CRL distribution point distributes a CRL which will contain an entry for this certificate if this certificate
has been revoked, regardless of revocation reason. Otherwise, the reasons value indicates which revocation reasons are
covered by the corresponding CRL distribution point.
The cRLIssuer component identifies the authority that issues and signs the CRL. If this component is absent, the CRL
issuer name defaults to the certificate issuer name.
This extension may, at the option of the certificate issuer, be either critical or non-critical. In the interests of
interoperability, it is recommended that it be flagged non-critical.
If this extension is flagged critical then a certificate-using system shall not use the certificate without first retrieving and
checking a CRL from one of the nominated distribution points covering the reason codes of interest. Where the
distribution points are used to distribute CRL information for all revocation reason codes and all certificates issued by
the CA include the cRLDistributionPoints as a critical extension, the CA is not required to also publish a full CRL at
the CA entry.
If this extension is flagged non-critical and a certificate-using system does not recognize the extension field type, then
that system should only use the certificate if:
­ it can acquire and check a complete CRL from the authority (that the latter CRL is complete is indicated
by the absence of an issuing distribution point extension field in the CRL);
­ revocation checking is not required under local policy; or
­ revocation checking is accomplished by other means.
NOTE 1 ­ It is possible to have CRLs issued by more than one CRL issuer for the one certificate. Coordination of these CRL
issuers and the issuing authority is an aspect of authority policy.
NOTE 2 ­ The meaning of each reason code is as defined in the Reason Code field in 8.5.2.2 of this Specification.
8.6.2.2 Issuing distribution point extension
This CRL extension field identifies the CRL distribution point for public-key certificates for this particular CRL, and
indicates if the CRL is indirect, or if it is limited to covering only a subset of the revocation information. If using only
partitioned CRLs, the full set of partitioned CRLs shall cover the complete set of certificates whose revocation status
will be reported using the CRL mechanism. Thus the complete set of partitioned CRLs shall be equivalent to a full CRL
for the same set of certificates, if the CRL issuer was not using partitioned CRLs. The limitation may be based on a
subset of the certificate population or on a subset of revocation reasons. The CRL is signed by the CRL issuer's private
key ­ CRL distribution points do not have their own key pairs. However, for a CRL distributed via the Directory, the
CRL is stored in the entry of the CRL distribution point, which may not be the directory entry of the CRL issuer. If the
issuing distribution point field, the AA issuing distribution point field, and the CRL scope field are all absent, the CRL
shall contain entries for all revoked unexpired public-key certificates issued by the CRL issuer. If the issuing
distribution point field and the CRL scope field are both absent, but the AA issuing distribution point field is present,
the scope of the CRL does not include public-key certificates.
After a certificate appears on a CRL, it may be deleted from a subsequent CRL after the certificate's expiry. This field is
defined as follows:
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46 ITU-T Rec. X.509 (08/2005)
issuingDistributionPoint EXTENSION ::= {
SYNTAX IssuingDistPointSyntax
IDENTIFIED BY id-ce-issuingDistributionPoint }
IssuingDistPointSyntax ::= SEQUENCE {
-- If onlyContainsUserPublicKeyCerts and onlyContainsCACerts are both FALSE,
-- the CRL covers both certificate types
distributionPoint [0] DistributionPointName OPTIONAL,
onlyContainsUserPublicKeyCerts [1] BOOLEAN DEFAULT FALSE,
onlyContainsCACerts [2] BOOLEAN DEFAULT FALSE,
onlySomeReasons [3] ReasonFlags OPTIONAL,
indirectCRL [4] BOOLEAN DEFAULT FALSE }
The distributionPoint component contains the name of the distribution point in one or more name forms. If
onlyContainsUserPublicKeyCerts is true, the CRL contains revocations for end-entity public-key certificates. If
onlyContainsCACerts is true, the CRL contains revocations for CA certificates. If onlyContainsUserPublicKeyCerts
and onlyContainsCACerts are both false, the CRL contains revocations for both end-entity public-key certificates and
CA certificates. If onlySomeReasons is present, the CRL only contains revocations of public-key certificates for the
identified reason or reasons, otherwise the CRL contains revocations for all reasons. If indirectCRL is true, then the
CRL may contain revocation notifications for public-key certificates from authorities other than the issuer of the CRL.
The particular authority responsible for each entry is as indicated by the certificate issuer CRL entry extension in that
entry or in accordance with the defaulting rules described in 8.6.2.3. In such a CRL, it is the responsibility of the CRL
issuer to ensure that the CRL is complete in that it contains all revocation entries, consistent with
onlyContainsUserPublicKeyCerts, onlyContainsCACerts, and onlySomeReasons indicators, from all authorities
that identify this CRL issuer in their public-key certificates.
If CRLs are partitioned by reason code, and the reason code changes for a revoked certificate (causing the certificate to
move from one CRL stream to another), it is necessary to continue to include the certificate on the CRL stream for the
old revocation reason until the nextUpdate times of all CRLs, that do not list the certificate, on the CRL stream for the
new reason code have been reached.
If the CRL contains an issuingDistributionPoint extension with the distributionPoint field present, at least one name
for the distribution point in the certificate (e.g., cRLDistributionPoints, freshestCRL, issuer) shall match a name for
the distribution point in the CRL. Also, it may be the case that only the nameRelativeToCRLIssuer field is present. In
that case, a name comparison would be done on the full DN, constructed by appending the value of the
nameRelativeToCRLIssuer to the DN found in the issuer field of the CRL. If the names being compared are DNs (as
opposed to names of other forms within the GeneralNames construct), the distinguishedNameMatch matching rule is
used to compare the two DNs for equality.
For CRLs distributed via the Directory the following rules apply. If the CRL is a dCRL it shall be distributed via the
deltaRevocationList attribute of the associated distribution point or, if no distribution point is identified, via the
deltaRevocationList attribute of the CRL issuer entry, regardless of the settings for certificate types covered by the
CRL. Unless the CRL is a dCRL:
* a CRL which has onlyContainsCACerts set and does not contain an AAissuingDistributionPoint
extension shall be distributed via the authorityRevocationList attribute of the associated distribution
point or, if no distribution point is identified, via the authorityRevocationList attribute of the CRL
issuer entry;
* a CRL which has onlyContainsCACerts set and contains an AAissuingDistributionPoint extension
with containsUserAttributeCerts set to false shall be distributed via the authorityRevocationList
attribute of the associated distribution point or, if no distribution point is identified, via the
authorityRevocationList attribute of the CRL issuer entry;
* a CRL which has only onlyContainsCACerts set to false shall be distributed via the
certificateRevocationList attribute of the associated distribution point or, if no distribution point is
identified, via the certificateRevocationList attribute of the CRL issuer entry;
* a CRL which contains both an issuingDistributionPoint extension and an AAissuingDistributionPoint
extension with containsUserAttributeCerts set shall be distributed via the certificateRevocationList
attribute of the associated distribution point or, if no distribution point is identified, via the
certificateRevocationList attribute of the CRL issuer entry.
This extension is always critical. A certificate user that does not understand this extension cannot assume that the CRL
contains a complete list of revoked certificates of the identified authority. CRLs not containing critical extensions shall
contain all current CRL entries for the issuing authority, including entries for all revoked user certificates and authority
certificates.
NOTE 1 ­ The means by which revocation information is communicated by authorities to CRL issuers is beyond the scope of
this Directory Specification.
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NOTE 2 ­ If an authority publishes a CRL with onlyContainsUserPublicKeyCerts or onlyContainsCACerts set to true,
then the authority shall ensure that all CA certificates covered by this CRL contain the basicConstraints extension.
8.6.2.3 Certificate issuer extension
This CRL entry extension identifies the certificate issuer associated with an entry in an indirect CRL, i.e., a CRL that
has the indirectCRL indicator set in its issuing distribution point extension. If this extension is not present on the first
entry in an indirect CRL, the certificate issuer defaults to the CRL issuer. On subsequent entries in an indirect CRL, if
this extension is not present, the certificate issuer for the entry is the same as that for the preceding entry.
This field is defined as follows:
certificateIssuer EXTENSION ::= {
SYNTAX GeneralNames
IDENTIFIED BY id-ce-certificateIssuer }
This extension is always critical. If an implementation ignored this extension, it could not correctly attribute CRL
entries to certificates.
8.6.2.4 Delta CRL indicator extension
The delta CRL indicator field identifies a CRL as being a delta CRL (dCRL) that provides updates to a referenced base
CRL. The referenced base CRL is a CRL that was explicitly issued as a CRL that is complete for a given scope. The
CRL containing the delta CRL indicator extension contains updates to the certificate revocation status for that same
scope. This scope does not necessarily include all revocation reasons or all certificates issued by a CA, especially in the
case where the CRL is a CRL distribution point. However, the combination of a CRL containing the delta CRL
indicator extension plus the CRL referenced in the BaseCRLNumber component of this extension is equivalent to a full
CRL, for the applicable scope, at the time of publication of the dCRL.
This field is defined as follows:
deltaCRLIndicator EXTENSION ::= {
SYNTAX BaseCRLNumber
IDENTIFIED BY id-ce-deltaCRLIndicator }
BaseCRLNumber ::= CRLNumber
The value of type BaseCRLNumber identifies the CRL number of the base CRL that was used as the foundation in the
generation of this dCRL. The referenced CRL shall be a CRL that is complete for the applicable scope.
This extension is always critical. A certificate user that does not understand the use of dCRLs should not use a CRL
containing this extension, as the CRL may not be as complete as the user expects.
8.6.2.5 Base update extension
The base update field is for use in dCRLs and is used to identify the date/time after which this delta provides updates to
the revocation status. This extension should only be used in dCRLs that contain the deltaCRLIndicator extension. A
dCRL that instead contains the crlScope extension, does not require this extension as the baseThisUpdate field of the
crlScope extension can be used for the same purpose.
baseUpdateTime EXTENSION ::= {
SYNTAX GeneralizedTime
IDENTIFIED BY id-ce-baseUpdateTime }
This extension is always non-critical.
8.6.2.6 Freshest CRL extension
The freshest CRL extension may be used either as a certificate or CRL extension. Within certificates, this extension
may be used in certificates issued to authorities as well as certificates issued to users. This field identifies the CRL to
which a certificate user should refer to obtain the freshest revocation information (e.g., latest dCRL). This field is
defined as follows:
freshestCRL EXTENSION ::= {
SYNTAX CRLDistPointsSyntax
IDENTIFIED BY id-ce-freshestCRL }
The value of type CRLDistPointsSyntax is as defined in the CRL distribution points extension in 8.6.2.1.
This extension may, at the option of the certificate issuer, be either critical or non-critical. If the freshest CRL extension
is made critical, a certificate-using system shall not use the certificate without first retrieving and checking the freshest
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CRL. If the extension is flagged non-critical, the certificate using system may use local means to determine whether or
not the freshest CRL is required to be checked.
8.6.2.7 AA Issuing Distribution Point extension
This CRL extension field identifies the CRL distribution point for attribute certificates for this particular CRL, and
indicates if the CRL is indirect, or if it is limited to covering only a subset of the revocation information. The limitation
may be based on a subset of the certificate population or on a subset of revocation reasons. The CRL is signed by the
CRL issuer's private key ­ CRL distribution points do not have their own key pairs. However, for a CRL distributed via
the Directory, the CRL is stored in the entry of the CRL distribution point, which may not be the directory entry of the
CRL issuer. If the issuing distribution point extension, the AA issuing distribution point extension, and the CRL scope
field are all absent, the CRL shall contain entries for all revoked unexpired attribute certificates issued by the CRL
issuer. If the AA issuing distribution point field and the CRL scope field are both absent, but the issuing distribution
point field is present, the scope of the CRL does not include attribute certificates.
After a certificate appears on a CRL, it may be deleted from a subsequent CRL after the certificate's expiry.
This field is defined as follows:
AAissuingDistributionPoint EXTENSION ::= {
SYNTAX AAIssuingDistPointSyntax
IDENTIFIED BY id-ce-AAissuingDistributionPoint }
AAIssuingDistPointSyntax ::= SEQUENCE {
distributionPoint [ 0 ] DistributionPointName OPTIONAL,
onlySomeReasons [ 1 ] ReasonFlags OPTIONAL,
indirectCRL [ 2 ] BOOLEAN DEFAULT FALSE,
containsUserAttributeCerts [ 3 ] BOOLEAN DEFAULT TRUE,
containsAACerts [ 4 ] BOOLEAN DEFAULT TRUE,
containsSOAPublicKeyCerts [ 5 ] BOOLEAN DEFAULT TRUE }
The distributionPoint component contains the name of the distribution point in one or more name forms. If
onlySomeReasons is present, the CRL only contains revocations for attribute certificates for the identified reason or
reasons; otherwise, the CRL contains revocations for all reasons.
If indirectCRL is true, then the CRL may contain revocation notifications for attribute certificates from authorities other
than the issuer of the CRL. The particular authority responsible for each entry is as indicated by the certificate issuer
CRL entry extension in that entry or in accordance with the defaulting rules described in 8.6.2.3. In such a CRL, it is the
responsibility of the CRL issuer to ensure that the CRL is complete in that it contains all revocation entries, consistent
with containsUserAttributeCerts, containsAACerts, containsSOAPublicKeyCerts and onlySomeReasons
indicators, from all authorities that identify this CRL issuer in their attribute certificates.
If containsUserAttributeCerts is true, the CRL contains revocations for attribute certificates issued to end entities that
are not themselves AAs. If containsAACerts is true, the CRL contains revocations for attribute certificates issued to
subjects that are themselves AAs.
If containsSOAPublicKeyCerts is true, the CRL contains revocations for public-key certificates issued to an entity that
is an SOA for purposes of privilege management (i.e., certificates that contain the SOAIdentifier extension). For CRLs
distributed via the Directory, the following rules apply. If the CRL is a dCRL it shall be distributed via the
deltaRevocationList attribute of the associated distribution point or, if no distribution point is identified, via the
deltaRevocationList attribute of the CRL issuer entry, regardless of the settings for certificate types covered by the
CRL. Unless the CRL is a dCRL:
* a CRL that does not contain an issuingDistributionPoint extension which has only containsAACerts
and/or containsSOAPublicKeyCerts set shall be distributed via the attributeAuthorityRevocationList
attribute of the associated distribution point or, if no distribution point is identified, via the
attributeAuthorityRevocationList attribute of the CRL issuer entry;
* a CRL that does not contain an issuingDistributionPoint extension which has
containsUserAttributeCerts set (with or without containsAACerts and/or
containsSOAPublicKeyCerts also set) shall be distributed via the attributeCertificateRevocationList
attribute of the associated distribution point or, if no distribution point is identified, via the
attributeCertificateRevocationList attribute of the CRL issuer entry;
* a CRL which contains an issuingDistributionPoint extension shall be distributed as specified in 8.6.2.2.
This extension is always critical. A certificate user that does not understand this extension cannot assume that the CRL
contains a complete list of revoked certificates of the identified authority. CRLs not containing critical extensions shall
contain all current CRL entries for the issuing authority, including entries for all revoked user certificates and authority
certificates.
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NOTE 1 ­ The means by which revocation information is communicated by authorities to CRL issuers is beyond the scope of
this Directory Specification.
NOTE 2 ­ If an authority publishes a CRL with containsAACerts set to true and containsUserAttributeCerts not set to
true, then the authority shall ensure that all AA certificates covered by this CRL contain the basicAttConstraints extension.
NOTE 3 ­ If an authority publishes a CRL with containsSOAPublicKeyCerts set to true, then the authority shall ensure that
all SOA certificates covered by this CRL contain the SOAIdentifier extension.
9 Delta CRL relationship to base
A dCRL includes either a deltaCRLIndicator or a crlScope extension to indicate the base revocation information that is
being updated with this dCRL.
If the deltaCRLIndicator is present in a dCRL, the base revocation information that is being updated is the base CRL
referenced in that extension. The base CRL referenced by a deltaCRLIndicator extension shall be a CRL that is issued
as complete for its scope (i.e., it is not itself a dCRL).
If the crlScope extension is present and contains the baseRevocationInfo component to reference the base revocation
information that is being updated, this is a reference to a particular point in time from which this dCRL provides
updates. The baseRevocationInfo component references a CRL that may or may not have been issued as one that is
complete for that scope (i.e., the referenced CRL may only have been issued as a dCRL). However, the dCRL
containing the baseRevocationInfo component updates the revocation information that is complete for the scope of the
referenced CRL at the time that the referenced CRL was issued. The certificate user may apply the dCRL to a CRL that
is complete for the given scope and that was issued at the same time as or after the CRL referenced in the dCRL
containing the baseRevocationInfo component was issued.
Because of the potential for conflicting information, a CRL shall not contain both the deltaCRLIndicator extension and
a crlScope extension with the baseRevocationInfo component. A CRL may contain both the deltaCRLIndicator
extension and crlScope extension only if the baseRevocationInfo component is not present in the crlScope extension.
A dCRL may also be an indirect CRL in that it may contain updated revocation information related to base CRLs issued
by one or more than one authorities. The crlScope extension shall be used as the means of identifying a CRL as an
indirect dCRL. The crlScope extension shall contain one instance of the PerAuthorityScope component for each base
CRL for which the indirect dCRL provides updated information.
Application of a dCRL to the referenced base revocation information shall accurately reflect the current status of
revocation.
­ A certificate's revocation notice, with revocation reason certificateHold, may appear on either a dCRL or
a CRL that is complete for a given scope. This reason code is intended to indicate a temporary revocation
of the certificate pending a further decision on whether to permanently revoke the certificate or reinstate
it as one that is not revoked.
* If a certificate was listed as revoked with revocation reason certificateHold on a CRL (either a
dCRL or a CRL that is complete for a given scope), whose cRLNumber is n, and the hold is
subsequently released, the certificate shall be included in all dCRLs issued after the hold is released
where the cRLNumber of the referenced base CRL is less than or equal to n. Depending on the
extension used to indicate that this CRL is a dCRL, the CRL number of a referenced base CRL is
either the value of the BaseCRLNumber component of the deltaCRLIndicator extension or the
cRLNumber element of the BaseRevocationInfo component of the cRLScope extension. The
certificate shall be listed with revocation reason removeFromCRL unless the certificate is
subsequently revoked again for one of the revocation reasons covered by the dCRL, in which case
the certificate shall be listed with the revocation reason appropriate for the subsequent revocation.
* If the certificate was not removed from hold, but was permanently revoked, then it shall be listed on
all subsequent dCRLs where the cRLNumber of the referenced base CRL is less than the
cRLNumber of the CRL (either a dCRL or a CRL that is complete for the given scope) on which
the permanent revocation notice first appeared. Depending on the extension used to indicate that this
CRL is a dCRL, the CRL number of a referenced base CRL is either the value of the
BaseCRLNumber component of the deltaCRLIndicator extension or the cRLNumber element of
the BaseRevocationInfo component of the cRLScope extension.
­ A certificate's revocation notice may first appear on dCRL and it is possible that the certificate's validity
period might expire before the next CRL that is complete for the applicable scope is issued. In this
situation, that revocation notice shall be included in all subsequent dCRLs until that revocation notice is
included on at least one issued CRL that is complete for the scope of that certificate.
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A CRL that is complete for a given scope, at the current time, can be constructed locally in either of the following ways:
­ by retrieving the current dCRL for that scope, and combining it with an issued CRL that is complete for
that scope and that has a cRLNumber greater than or equal to the cRLNumber of the base CRL
referenced in the dCRL; or
­ by retrieving the current dCRL for that scope and combining it with a locally constructed CRL that is
complete for that scope and that was constructed with a dCRL that has a cRLNumber greater than or
equal to the cRLNumber of the base CRL referenced in the current dCRL.
10 Certification path processing procedure
Certification path processing is carried out in a system which needs to use the public key of a remote end entity, e.g., a
system which is verifying a digital signature generated by a remote entity. The certificate policies, basic constraints,
name constraints, and policy constraints extensions have been designed to facilitate automated, self-contained
implementation of certification path processing logic.
Following is an outline of a procedure for validating certification paths. An implementation shall be functionally
equivalent to the external behaviour resulting from this procedure. The algorithm used by a particular implementation to
derive the correct output(s) from the given inputs is not standardized.
10.1 Path processing inputs
The inputs to the certification path processing procedure are:
a) a set of certificates comprising a certification path;
NOTE ­ Each certificate in a certification path is unique. A path that contains the same certificate two or more times
is not a valid certification path.
b) a trusted public key value or key identifier (if the key is stored internally to the certification path
processing module), for use in verifying the first certificate in the certification path;
c) an initial-policy-set comprising one or more certificate policy identifiers, indicating that any one of these
policies would be acceptable to the certificate user for the purposes of certification path processing; this
input can also take the special value any-policy, but it cannot be null;
d) an initial-explicit-policy indicator value, which indicates if an acceptable policy identifier needs to
explicitly appear in the certificate policies extension field of all certificates in the path;
e) an initial-policy-mapping-inhibit indicator value, which indicates if policy mapping is forbidden in the
certification path;
f) an initial-inhibit-policy indicator value, which indicates if the special value anyPolicy, if present in a
certificate policies extension, is considered a match for any specific certificate policy value in a
constrained set;
g) the current date/time (if not available internally to the certification path processing module);
h) an initial-permitted-subtrees-set containing an initial set of subtree specifications defining subtrees
within which subject names (of the name form used to specify the subtrees) are permitted. In the
certificates in the certification path all subject names of a given name form, for which initial permitted
subtrees are defined, shall fall within the permitted subtrees set for that given name form. This input may
also contain the special value unbounded to indicate that initially all subject names are acceptable. For
clause 10, subject names are those name values appearing in the subject field or the subjectAltName
extension;
i) an initial-excluded-subtrees-set containing an initial set of subtree specifications defining subtrees within
which the subject names in the certificates in the certification path cannot fall. This input may also be an
empty set to indicate that initially no subtree exclusions are in effect;
j) an initial-required-name-forms containing an initial set of name forms indicating that all certificates in
the path must include a subject name of at least one of the specified name forms. This input may also be
an empty set to indicate that no specific name forms are required for subject names in the certificates.
The values of c), d), e) and f) will depend upon the policy requirements of the user-application combination that needs
to use the certified end-entity public key.
Note that because these are individual inputs to the path validation process, a certificate user may limit the trust it places
in any given trusted public key to a given set of certificate policies. This can be achieved by ensuring that a given public
key is the input to the process only when initial-policy-set input includes policies for which the certificate user trusts
ISO/IEC 9594-8:2005 (E)
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that public key. Since another input to the process is the certification path itself, this control could be exercised on a
transaction by transaction basis.
10.2 Path processing outputs
The outputs of the procedure are:
a) an indication of success or failure of certification path validation;
b) if validation failed, a diagnostic code indicating the reason for failure;
c) the set of authorities-constrained policies and their associated qualifiers in accordance with which the
certification path is valid, or the special value any-policy;
d) the set of user-constrained policies, formed from the intersection of the authorities-constrained-policyset
and the initial-policy-set;
e) explicit-policy-indicator, indicating whether the certificate user or an authority in the path requires that
an acceptable policy be identified in every certificate in the path; and
f) details of any policy mapping that occurred in processing the certification path.
NOTE ­ If validation is successful, the certificate-using system may still choose not to use the certificate as a result of values of
policy qualifiers or other information in the certificate.
10.3 Path processing variables
The procedure makes use of the following set of state variables:
a) authorities-constrained-policy-set: A table of policy identifiers and qualifiers from the certificates of the
certification path (rows represent policies, their qualifiers and mapping history, and columns represent
certificates in the certification path);
b) permitted-subtrees: A set of subtree specifications defining subtrees within which all subject names in
subsequent certificates in the certification path need to fall, or may take the special value unbounded;
c) excluded-subtrees: A (possibly empty) set of subtree specifications (each comprising a subtree base name
and maximum and minimum level indicators) defining subtrees within which no subject name in a
subsequent certificate in the certification path may fall;
d) required-name-forms: A (possibly empty) set of sets of name forms. For each set of name forms, every
subsequent certificate must contain a name of one of the name forms in the set;
e) explicit-policy-indicator: Indicates whether an acceptable policy needs to be explicitly identified in every
certificate in the path;
f) path depth: An integer equal to one more than the number of certificates in the certification path for
which processing has been completed;
g) policy-mapping-inhibit-indicator: Indicates whether policy mapping is inhibited;
h) inhibit-any-policy-indicator: Indicates whether the special value anyPolicy is considered a match for any
specific certificate policy;
i) pending-constraints: Details of explicit-policy inhibit-policy-mapping and/or inhibit-any-policy
constraints which have been stipulated but have yet to take effect. There are three one-bit indicators
called explicit-policy-pending, policy-mapping-inhibit-pending and inhibit-any-policy-pending together
with, for each, an integer called skip-certificates which gives the number of certificates yet to skip before
the constraint takes effect.
10.4 Initialization step
The procedure involves an initialization step, followed by a series of certificate-processing steps. The initialization step
comprises:
a) Write any-policy in the zeroth and first columns of the zeroth row of the authorities-constrained-policyset
table;
b) Initialize the permitted-subtrees variable to the initial-permitted-subtrees-set value;
c) Initialize the excluded-subtrees variable to the initial-excluded-subtrees-set value;
d) Initialize the required-name-forms variable to the initial-required-name-forms value;
e) Initialize the explicit-policy-indicator to the initial-explicit-policy value;
f) Initialize path-depth to one;
ISO/IEC 9594-8:2005 (E)
52 ITU-T Rec. X.509 (08/2005)
g) Initialize the policy-mapping-inhibit-indicator to the initial-policy-mapping-inhibit value;
h) Initialize the inhibit-any-policy-indicator to the initial-inhibit-policy value;
i) Initialize the three pending-constraints indicators to unset.
10.5 Certificate processing
Each certificate is then processed in turn, starting with the certificate signed using the input trusted public key. The last
certificate is considered to be the end certificate; any other certificates are considered to be intermediate certificates.
10.5.1 Basic certificate checks
The following checks are applied to a certificate. Self-signed certificates, if encountered in the path, are ignored.
a) Check that the signature verifies, that dates are valid, that the certificate subject and certificate issuer
names chain correctly, and that the certificate has not been revoked.
b) For an intermediate version 3 certificate, check that basicConstraints is present and that the cA
component in the basicConstraints extension is TRUE. If the pathLenConstraint component is present,
check that the current certification path does not violate that constraint (ignoring intermediate self-issued
certificates).
c) If the certificate policies extension is not present, then set the authorities-constrained-policy-set to null
by deleting all rows from the authorities-constrained-policy-set table.
d) If the certificate policies extension is present, then for each policy, P, in the extension other than
anyPolicy, attach the policy qualifiers associated with P to each row in the authorities-constrainedpolicy-set
table whose [path-depth] column entry contains the value P. If no row in the authoritiesconstrained-policy-set
table contains P in its [path-depth] column entry but the value in authoritiesconstrained-policy-set[0,
path-depth] is any-policy, then add a new row to the table by duplicating the
zeroth row and writing the policy identifier P along with its qualifiers in the [path-depth] column entry of
the new row.
e) If the certificate policies extension is present and does not include the value anyPolicy or if the inhibitany-policy-indicator
is set and the certificate is not a self-issued intermediate certificate, then delete any
row for which the [path-depth] column entry contains the value any-policy along with any row for which
the [path-depth] column entry does not contain one of the values in the certificate policies extension.
f) If the certificate policies extension is present and includes the value anyPolicy and the inhibit-anypolicy-indicator
is not set, then attach the policy qualifiers associated with anyPolicy to each row in the
authorities-constrained-policy-set table whose [path-depth] column entry contains the value any-policy
or contains a value that does not appear in the certificate policies extension.
g) If the certificate is not an intermediate self-issued certificate, check that the subject name is within the
name-space given by the value of permitted-subtrees and is not within the name-space given by the value
of excluded-subtrees.
h) If the certificate is not an intermediate self-issued certificate, and if required-name-forms is not an empty
set, for each set of name forms in required-name-forms check that there is a subject name in the
certificate of one of the name forms in the set.
10.5.2 Processing intermediate certificates
For an intermediate certificate, the following constraint recording actions are then performed, in order to correctly set
up the state variables for the processing of the next certificate. Self-signed certificates, if encountered in the path, are
ignored.
a) If the nameConstraints extension with a permittedSubtrees component is present in the certificate, set
the permitted-subtrees state variable to the intersection of its previous value and the value indicated in
the certificate extension.
b) If the nameConstraints extension with an excludedSubtrees component is present in the certificate, set
the excluded-subtrees state variable to the union of its previous value and the value indicated in the
certificate extension.
c) If the nameConstraints extension with a requiredNameForms component is present in the certificate,
set the required-name-forms variable to the union of its previous value and the set consisting of the set of
name forms specified in the certificate extension. If the requiredNameForms component contains more
than one name form, the required-name-forms variable shall signal that a name of at least one of the
indicated name forms in this extension shall be present in all subsequent certificates. The union of the
value of the required-name-forms variable with the value from the current certificate extension is a set of
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 53
sets signalling requirements for all subsequent certificates. For example if the current required-nameforms
is set to requiring that either a DN or an rfc822 name must be present in certificates and the current
extension in the certificate being processed indicates that either rfc822 names or DNS names are
required, the resulting union that is the new required-name-forms indicates that each of the subsequent
certificates must have either an rfc822 name or both a DN and a DNS name.
d) If policy-mapping-inhibit-indicator is set:
­ process any policy mappings extension by, for each mapping identified in the extension, locating all
rows in the authorities-constrained-policy-set table whose [path-depth] column entry is equal to the
issuer domain policy value in the extension and delete the row.
e) If policy-mapping-inhibit-indicator is not set:
­ process any policy mappings extension by, for each mapping identified in the extension, locating all
rows in the authorities-constrained-policy-set table whose [path-depth] column entry is equal to the
issuer domain policy value in the extension, and write the subject domain policy value from the
extension in the [path-depth+1] column entry of the same row. If the extension maps an issuer
domain policy to more than one subject domain policy, then the affected row is copied and the new
entry added to each row. If the value in authorities-constrained-policy-set[0, path-depth] is anypolicy,
then write each issuer domain policy identifier from the policy mappings extension in the
[path-depth] column, making duplicate rows as necessary and retaining qualifiers if they are
present, and write the subject domain policy value from the extension in the [path-depth+1] column
entry of the same row;
­ if the policy-mapping-inhibit-pending indicator is set and the certificate is not self-issued, decrement
the corresponding skip-certificates value and, if this value becomes zero, set the policy-mapping-
inhibit-indicator;
­ if the inhibitPolicyMapping constraint is present in the certificate, perform the following. For a
SkipCerts value of 0, set the policy-mapping-inhibit-indicator. For any other SkipCerts value, set
the policy-mapping-inhibit-pending indicator, and set the corresponding skip-certificates value to
the lesser of the SkipCerts value and the previous skip-certificates value (if the policy-mappinginhibit-pending
indicator was already set).
f) For any row not modified in either step c) or d), above (and every row in the case that there is no
mapping extension present in the certificate), write the policy identifier from [path-depth] column in the
[path-depth+1] column of the row.
g) If inhibit-any-policy-indicator is not set:
­ If the inhibit-any-policy-pending indicator is set and the certificate is not self-issued, decrement the
corresponding skip-certificates value and, if this value becomes zero, set the inhibit-any-policy-
indicator.
­ If the inhibitAnyPolicy constraint is present in the certificate, perform the following. For a
SkipCerts value of 0, set the inhibit-any-policy-indicator. For any other SkipCerts value, set the
inhibit-any-policy-pending indicator, and set the corresponding skip-certificates value to the lesser
of the SkipCerts value and the previous skip-certificates value (if the inhibit-any-policy-pending
indicator was already set).
h) Increment [path-depth].
10.5.3 Explicit policy indicator processing
For all certificates, the following actions are then performed:
a) If explicit-policy-indicator is not set:
­ if the explicit-policy-pending indicator is set and the certificate is not a self-issued intermediate
certificate, decrement the corresponding skip-certificates value and, if this value becomes zero, set
explicit-policy-indicator.
­ If the requireExplicitPolicy constraint is present in the certificate, perform the following. For a
SkipCerts value of 0, set the explicit-policy-indicator. For any other SkipCerts value, set the
explicit-policy-pending indicator, and set the corresponding skip-certificates value to the lesser of
the SkipCerts value and the previous skip-certificates value (if the explicit-policy-pending indicator
was already set).
­ If the requireExplicitPolicy component is present, and the certification path includes a certificate
issued by a nominated CA, it is necessary for all certificates in the path to contain, in the certificate
policies extension, an acceptable policy identifier. An acceptable policy identifier is the identifier of
the certificate policy required by the user of the certification path, the identifier of a policy which
ISO/IEC 9594-8:2005 (E)
54 ITU-T Rec. X.509 (08/2005)
has been declared equivalent to it through policy mapping, or any-policy. The nominated CA is
either the issuer CA of the certificate containing this extension (if the value of
requireExplicitPolicy is 0) or a CA which is the subject of a subsequent certificate in the
certification path (as indicated by a non-zero value).
10.5.4 Final processing
Once all certificates in the path have been processed, the following actions are then performed:
a) Determine the authorities-constrained-policy-set from the authorities-constrained-policy-set table. If the
table is empty, then the authorities-constrained-policy-set is the empty or null set. If the authoritiesconstrained-policy-set[0,
path-depth] is any-policy, then the authorities-constrained-policy-set is anypolicy.
Otherwise, the authorities-constrained-policy-set is, for each row in the table, the value in the
left-most cell which does not contain the identifier any-policy.
b) Calculate the user-constrained-policy-set by forming the intersection of the authorities-constrainedpolicy-set
and the initial-policy-set.
c) If the explicit-policy-indicator is set, check that neither the authorities-constrained-policy-set nor the
user-constrained-policy-set is empty.
If any of the above checks were to fail, then the procedure shall terminate, returning a failure indication, an appropriate
reason code, the explicit-policy-indicator, the authorities-constrained-policy-set and the user-constrained-policy-set. If
the failure is due to an empty user-constrained-policy-set, then the path is valid under the authority-constrained
policy(s), but none is acceptable to the user.
If none of the above checks were to fail on the end certificate, then the procedure shall terminate, returning a success
indication together with the explicit-policy-indicator, the authorities-constrained-policy-set and the user-constrained-
policy-set.
11 PKI directory schema
This clause defines the directory schema elements used to represent PKI information in the Directory. It includes
specification of relevant object classes, attributes and attribute value matching rules.
11.1 PKI directory object classes and name forms
This subclause includes the definition of object classes used to represent PKI objects in the Directory.
11.1.1 PKI user object class
The PKI user object class is used in defining entries for objects that may be the subject of public-key certificates.
pkiUser OBJECT-CLASS ::= {
SUBCLASS OF {top}
KIND auxiliary
MAY CONTAIN {userCertificate}
ID id-oc-pkiUser }
11.1.2 PKI CA object class
The PKI CA object class is used in defining entries for objects that act as certification authorities.
pkiCA OBJECT-CLASS ::= {
SUBCLASS OF {top}
KIND auxiliary
MAY CONTAIN {cACertificate |
certificateRevocationList |
authorityRevocationList |
crossCertificatePair }
ID id-oc-pkiCA }
11.1.3 CRL distribution points object class and name form
The CRL Distribution Point object class is used in defining entries for object which act as CRL Distribution Points.
cRLDistributionPoint OBJECT-CLASS ::= {
SUBCLASS OF { top }
KIND structural
MUST CONTAIN { commonName }
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 55
MAY CONTAIN { certificateRevocationList |
authorityRevocationList |
deltaRevocationList }
ID id-oc-cRLDistributionPoint }
The CRL Distribution Point name form specifies how entries of object class cRLDistributionPoint may be named.
cRLDistPtNameForm NAME-FORM ::= {
NAMES cRLDistributionPoint
WITH ATTRIBUTES { commonName}
ID id-nf-cRLDistPtNameForm }
11.1.4 Delta CRL object class
The delta CRL object class is used in defining entries for objects that hold delta revocation lists (e.g., CAs, AAs etc.).
deltaCRL OBJECT-CLASS ::= {
SUBCLASS OF {top}
KIND auxiliary
MAY CONTAIN {deltaRevocationList}
ID id-oc-deltaCRL }
11.1.5 Certificate Policy & CPS object class
The CP CPS object class is used in defining entries for objects that contain certificate policy and/or certification
practice information.
cpCps OBJECT-CLASS ::= {
SUBCLASS OF {top}
KIND auxiliary
MAY CONTAIN {certificatePolicy |
certificationPracticeStmt}
ID id-oc-cpCps }
11.1.6 PKI certificate path object class
The PKI cert path object class is used in defining entries for objects that contain PKI paths. It will generally be used in
conjunction with entries of structural pkiCA or pkiUser.
pkiCertPath OBJECT-CLASS ::= {
SUBCLASS OF {top}
KIND auxiliary
MAY CONTAIN { pkiPath }
ID id-oc-pkiCertPath }
11.2 PKI directory attributes
This subclause includes the definition of directory attributes to store PKI information elements in the Directory.
11.2.1 User certificate attribute
A user may obtain one or more public-key certificates from one or more CAs. The userCertificate attribute type
contains the public-key certificates a user has obtained from one or more CAs.
userCertificate ATTRIBUTE ::= {
WITH SYNTAX Certificate
EQUALITY MATCHING RULE certificateExactMatch
ID id-at-userCertificate}
11.2.2 CA certificate attribute
The cACertificate attribute of a CA's directory entry shall be used to store self-issued certificates (if any) and
certificates issued to this CA by CAs in the same realm as this CA. In the case of v3 certificates, these certificates shall
include a basicConstraints extension with the cA value set to TRUE. The definition of realm is purely a matter of local
policy.
cACertificate ATTRIBUTE ::= {
WITH SYNTAX Certificate
EQUALITY MATCHING RULE certificateExactMatch
ID id-at-cAcertificate }
ISO/IEC 9594-8:2005 (E)
56 ITU-T Rec. X.509 (08/2005)
11.2.3 Cross-certificate pair attribute
The issuedToThisCA elements of the crossCertificatePair attribute of a CA's directory entry shall be used to store all,
except self-issued certificates issued to this CA. Optionally, the issuedByThisCA elements of the crossCertificatePair
attribute, of a CA's directory entry may contain a subset of certificates issued by this CA to other CAs. If a CA issues a
certificate to another CA, and the subject CA is not a subordinate to the issuer CA in a hierarchy, then the issuer CA
shall place that certificate in the issuedByThisCA element of the crossCertificatePair attribute of its own directory
entry. When both the issuedToThisCA and the issuedByThisCA elements are present in a single attribute value, issuer
name in one certificate shall match the subject name in the other and vice versa, and the subject public key in one
certificate shall be capable of verifying the digital signature on the other certificate and vice versa. The term forward
was used in previous editions for issuedToThisCA and the term reverse was used in previous editions for
issuedByThisCA.
When an issuedByThisCA element is present, the issuedToThisCA element value and the issuedByThisCA element
value need not be stored in the same attribute value; in other words, they can be stored in either a single attribute value
or two attribute values.
In the case of v3 certificates, these shall include a basicConstraints extension with the cA value set to TRUE.
crossCertificatePair ATTRIBUTE ::= {
WITH SYNTAX CertificatePair
EQUALITY MATCHING RULE certificatePairExactMatch
ID id-at-crossCertificatePair }
CertificatePair ::= SEQUENCE {
issuedToThisCA [0] Certificate OPTIONAL,
issuedByThisCA [1] Certificate OPTIONAL
-- at least one of the pair shall be present -- }
(WITH COMPONENTS { ..., issuedToThisCA PRESENT} |
WITH COMPONENTS { ..., issuedByThisCA PRESENT})
11.2.4 Certificate revocation list attribute
The following attribute contains a list of revoked certificates.
certificateRevocationList ATTRIBUTE ::= {
WITH SYNTAX CertificateList
EQUALITY MATCHING RULE certificateListExactMatch
ID id-at-certificateRevocationList }
11.2.5 Authority revocation list attribute
The following attribute contains a list of revoked authority certificates.
authorityRevocationList ATTRIBUTE ::= {
WITH SYNTAX CertificateList
EQUALITY MATCHING RULE certificateListExactMatch
ID id-at-authorityRevocationList }
11.2.6 Delta revocation list attribute
The following attribute type is defined for holding a dCRL in a directory entry:
deltaRevocationList ATTRIBUTE ::= {
WITH SYNTAX CertificateList
EQUALITY MATCHING RULE certificateListExactMatch
ID id-at-deltaRevocationList }
11.2.7 Supported algorithms attribute
A Directory attribute is defined to support the selection of an algorithm for use when communicating with a remote end
entity using certificates as defined in this Directory Specification. The following ASN.1 defines this (multi-valued)
attribute:
supportedAlgorithms ATTRIBUTE ::= {
WITH SYNTAX SupportedAlgorithm
EQUALITY MATCHING RULE algorithmIdentifierMatch
ID id-at-supportedAlgorithms }
ISO/IEC 9594-8:2005 (E)
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SupportedAlgorithm ::= SEQUENCE {
algorithmIdentifier AlgorithmIdentifier,
intendedUsage [0] KeyUsage OPTIONAL,
intendedCertificatePolicies [1] CertificatePoliciesSyntax OPTIONAL }
Each value of the multi-valued attribute shall have a distinct algorithmIdentifier value. The value of the
intendedUsage component provides an indication of the intended usage of the algorithm (see 8.2.2.3 for recognized
uses). The value of the intendedCertificatePolicies component identifies the certificate policies and, optionally,
certificate policy qualifiers with which the identified algorithm may be used.
11.2.8 Certification practice statement attribute
The certificationPracticeStmt attribute is used to store information about an authority's certification practice statement.
certificationPracticeStmt ATTRIBUTE ::= {
WITH SYNTAX InfoSyntax
ID id-at-certificationPracticeStmt }
InfoSyntax ::= CHOICE {
content DirectoryString {ub-content},
pointer SEQUENCE {
name GeneralNames,
hash HASH { HashedPolicyInfo } OPTIONAL } }
POLICY ::= TYPE-IDENTIFIER
HashedPolicyInfo ::= POLICY.&Type( {Policies} )
Policies POLICY ::= {...} -- Defined by implementors --
If content is present, the complete content of the authority's certification practice statement is included.
If pointer is present, the name component references one or more locations where a copy of the authority's certification
practice statement can be located. If the hash component is present, it contains a HASH of the content of the
certification practice statement that should be found at a referenced location. This hash can be used to perform an
integrity check of the referenced document.
11.2.9 Certificate policy attribute
The certificatePolicy attribute is used to store information about a certificate policy.
certificatePolicy ATTRIBUTE ::= {
WITH SYNTAX PolicySyntax
ID id-at-certificatePolicy }
PolicySyntax ::= SEQUENCE {
policyIdentifier PolicyID,
policySyntax InfoSyntax
}
PolicyID ::= CertPolicyId
The policyIdentifier component includes the object identifier registered for the particular certificate policy.
If content is present, the complete content of the certificate policy is included.
If pointer is present, the name component references one or more locations where a copy of the certificate policy can
be located. If the hash component is present, it contains a HASH of the content of the certificate policy that should be
found at a referenced location. This hash can be used to perform an integrity check of the referenced document.
NOTE ­ The option to include a hash in this attribute is purely to perform an integrity check against data located from a source
other than the directory. The HASH stored in the Directory needs to be protected. Directory security services, including strong
authentication, access control and/or signed attributes could be used for this purpose. In addition, even if the HASH matches the
original CP/CPS document, there are additional security requirements to ensure that the original specification itself is the correct
document (e.g., the document is signed by an appropriate authority).
11.2.10 PKI path attribute
The PKI path attribute is used to store certification paths, each consisting of a sequence of certificates.
pkiPath ATTRIBUTE ::= {
WITH SYNTAX PkiPath
ID id-at-pkiPath }
This attribute can be stored in a directory entry of object class pkiCA or pkiUser.
ISO/IEC 9594-8:2005 (E)
58 ITU-T Rec. X.509 (08/2005)
When stored in pkiCA entries, values of this attribute contain certification paths excluding end-entity certificates. As
such, the attribute is used to store certification paths that are frequently used by relying parties associated with that CA.
A value of this attribute can be used in conjunction with any end-entity certificate issued by the last certificate subject in
the attribute value.
When stored in pkiUser entries, values of this attribute contain certification paths that include the end-entity certificate.
In this case, the end-entity is the user whose entry holds this attribute. The values of the attribute represent complete
certification paths for certificates issued to this user.
11.3 PKI directory matching rules
This Directory Specification defines matching rules for use with attributes of type Certificate, CertificatePair,
CertificateList, CertificatePolicy, and SupportedAlgorithm, respectively. This clause also defines matching rules to
facilitate the selection of certificates or CRLs with specific characteristics from multi-valued attributes holding multiple
certificates or CRLs. The enhanced certificate matching rule provides the ability to perform more sophisticated
matching against certificates held in directory entries.
11.3.1 Certificate exact match
The certificate exact match rule compares for equality a presented value with an attribute value of type Certificate. It
uniquely selects a single certificate.
certificateExactMatch MATCHING-RULE ::= {
SYNTAX CertificateExactAssertion
ID id-mr-certificateExactMatch }
CertificateExactAssertion ::= SEQUENCE {
serialNumber CertificateSerialNumber,
issuer Name }
This matching rule returns TRUE if the components in the attribute value match those in the presented value.
11.3.2 Certificate match
The certificate match rule compares a presented value with an attribute value of type Certificate. It selects one or more
certificates on the basis of various characteristics.
certificateMatch MATCHING-RULE ::= {
SYNTAX CertificateAssertion
ID id-mr-certificateMatch }
CertificateAssertion ::= SEQUENCE {
serialNumber [0] CertificateSerialNumber OPTIONAL,
issuer [1] Name OPTIONAL,
subjectKeyIdentifier [2] SubjectKeyIdentifier OPTIONAL,
authorityKeyIdentifier [3] AuthorityKeyIdentifier OPTIONAL,
certificateValid [4] Time OPTIONAL,
privateKeyValid [5] GeneralizedTime OPTIONAL,
subjectPublicKeyAlgID [6] OBJECT IDENTIFIER OPTIONAL,
keyUsage [7] KeyUsage OPTIONAL,
subjectAltName [8] AltNameType OPTIONAL,
policy [9] CertPolicySet OPTIONAL,
pathToName [10] Name OPTIONAL,
subject [11] Name OPTIONAL,
nameConstraints [12] NameConstraintsSyntax OPTIONAL
}
AltNameType ::= CHOICE {
builtinNameForm ENUMERATED {
rfc822Name (1),
dNSName (2),
x400Address (3),
directoryName (4),
ediPartyName (5),
uniformResourceIdentifier (6),
iPAddress (7),
registeredId (8) },
otherNameForm OBJECT IDENTIFIER }
CertPolicySet ::= SEQUENCE SIZE (1..MAX) OF CertPolicyId
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 59
This matching rule returns TRUE if all of the components that are present in the presented value match the
corresponding components of the attribute value, as follows:
serialNumber matches if the value of this component in the attribute value equals that in the presented value;
issuer matches if the value of this component in the attribute value equals that in the presented value;
subjectKeyIdentifier matches if the value of this component in the stored attribute value equals that in the presented
value; there is no match if the stored attribute value contains no subject key identifier extension;
authorityKeyIdentifier matches if the value of this component in the stored attribute value equals that in the presented
value; there is no match if the stored attribute value contains no authority key identifier extension or if not all
components in the presented value are present in the stored attribute value;
certificateValid matches if the presented value falls within the validity period of the stored attribute value;
privateKeyValid matches if the presented value falls within the period indicated by the private key usage period
extension of the stored attribute value or if there is no private key usage period extension in the stored attribute value;
subjectPublicKeyAlgID matches if it is equal to the algorithm component of the algorithmIdentifier of the
subjectPublicKeyInformation component of the stored attribute value;
keyUsage matches if all of the bits set in the presented value are also set in the key usage extension in the stored
attribute value, or if there is no key usage extension in the stored attribute value;
subjectAltName matches if the stored attribute value contains the subject alternative name extension with an AltNames
component of the same name type as indicated in the presented value;
policy matches if at least one member of the CertPolicySet presented appears in the certificate policies extension in the
stored attribute value or if either the presented or stored certificate contains the special value anyPolicy in the policy
component. There is no match if there is no certificate policies extension in the stored attribute value;
pathToName matches unless the certificate has a name constraints extension which inhibits the construction of a
certification path to the presented name value;
subject matches if the value of this component in the attribute value equals that in the presented value;
nameConstraints matches if the subject names in the stored attribute value are within the name space given by the
value of the permitted-subtrees component of the presented value and are not within the name space given by the value
of the excluded-subtrees component of the presented value.
11.3.3 Certificate pair exact match
The certificate pair exact match rule compares for equality a presented value with an attribute value of type
CertificatePair. It uniquely selects a single cross-certificate pair.
certificatePairExactMatch MATCHING-RULE ::= {
SYNTAX CertificatePairExactAssertion
ID id-mr-certificatePairExactMatch }
CertificatePairExactAssertion ::= SEQUENCE {
issuedToThisCAAssertion [0] CertificateExactAssertion OPTIONAL,
issuedByThisCAAssertion [1] CertificateExactAssertion OPTIONAL }
( WITH COMPONENTS {..., issuedToThisCAAssertion PRESENT} |
WITH COMPONENTS {..., issuedByThisCAAssertion PRESENT} )
This matching rule returns TRUE if the components that are present in the issuedToThisCAAssertion and
issuedByThisCAAssertion components of the presented value match the corresponding components of the
issuedToThisCA and issuedByThisCA components, respectively, in the stored attribute value.
11.3.4 Certificate pair match
The certificate pair match rule compares a presented value with an attribute value of type CertificatePair. It selects one
or more cross-certificate pairs on the basis of various characteristics of either the issuedToThisCA or issuedByThisCA
certificate of the pair.
certificatePairMatch MATCHING-RULE ::= {
SYNTAX CertificatePairAssertion
ID id-mr-certificatePairMatch }
CertificatePairAssertion ::= SEQUENCE {
issuedToThisCAAssertion [0] CertificateAssertion OPTIONAL,
issuedByThisCAAssertion [1] CertificateAssertion OPTIONAL }
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( WITH COMPONENTS {..., issuedToThisCAAssertion PRESENT} |
WITH COMPONENTS {..., issuedByThisCAAssertion PRESENT} )
This matching rule returns TRUE if all of the components that are present in the issuedToThisCAAssertion and
issuedByThisCAAssertion components of the presented value match the corresponding components of the
issuedToThisCA and issuedByThisCA components, respectively, in the stored attribute value.
11.3.5 Certificate list exact match
The certificate list exact match rule compares for equality a presented value with an attribute value of type
CertificateList. It uniquely selects a single CRL.
certificateListExactMatch MATCHING-RULE ::= {
SYNTAX CertificateListExactAssertion
ID id-mr-certificateListExactMatch }
CertificateListExactAssertion ::= SEQUENCE {
issuer Name,
thisUpdate Time,
distributionPoint DistributionPointName OPTIONAL }
The rule returns TRUE if the components in the stored attribute value match those in the presented value. If the
distributionPoint component is present, then it shall match in at least one name form.
11.3.6 Certificate list match
The certificate list match rule compares a presented value with an attribute value of type CertificateList. It selects one
or more CRLs on the basis of various characteristics.
certificateListMatch MATCHING-RULE ::= {
SYNTAX CertificateListAssertion
ID id-mr-certificateListMatch }
CertificateListAssertion ::= SEQUENCE {
issuer Name OPTIONAL,
minCRLNumber [0] CRLNumber OPTIONAL,
maxCRLNumber [1] CRLNumber OPTIONAL,
reasonFlags ReasonFlags OPTIONAL,
dateAndTime Time OPTIONAL,
distributionPoint [2] DistributionPointName OPTIONAL,
authorityKeyIdentifier [3] AuthorityKeyIdentifier OPTIONAL }
The matching rule returns TRUE if all of the components that are present in the presented value match the
corresponding components of the stored attribute value, as follows:
issuer matches if the value of this component in the attribute value equals that in the presented value;
minCRLNumber matches if its value is less than or equal to the value in the CRL number extension of the stored
attribute value; there is no match if the stored attribute value contains no CRL number extension;
maxCRLNumber matches if its value is greater than or equal to the value in the CRL number extension of the stored
attribute value; there is no match if the stored attribute value contains no CRL number extension;
reasonFlags matches if any of the bits that are set in the presented value are also set in the onlySomeReasons
components of the issuing distribution point extension of the stored attribute value; there is also a match if the stored
attribute value contains no reasonFlags in the issuing distribution point extension, or if the stored attribute value
contains no issuing distribution point extension;
NOTE ­ Even though a CRL matches on a particular value of reasonFlags, the CRL may not contain any revocation notices
with that reason code.
dateAndTime matches if the value is equal to or later than the value in the thisUpdate component of the stored
attribute value and is earlier than the value in the nextUpdate component of the stored attribute value; there is no match
if the stored attribute value contains no nextUpdate component;
distributionPoint matches if the stored attribute value contains an issuing distribution point extension and the value of
this component in the presented value equals the corresponding value, in at least one name form, in that extension;
authorityKeyIdentifier matches if the value of this component in the stored attribute value equals that in the presented
value; there is no match if the stored attribute value contains no authority key identifier extension or if not all
components in the presented value are present in the stored attribute value.
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11.3.7 Algorithm identifier match
The algorithm identifier match rule compares for equality a presented value with an attribute value of type
SupportedAlgorithms.
algorithmIdentifierMatch MATCHING-RULE::= {
SYNTAX AlgorithmIdentifier
ID id-mr-algorithmIdentifierMatch }
The rule returns TRUE if the presented value is equal to the algorithmIdentifier component of the stored attribute
value.
11.3.8 Policy match
The policy match rule compares for equality a presented value with an attribute value of type CertificatePolicy or an
attribute value of type privPolicy.
policyMatch MATCHING-RULE ::= {
SYNTAX PolicyID
ID id-mr-policyMatch }
The rule returns TRUE if the presented value is equal to the policyIdentifier component of the stored attribute value.
11.3.9 PKI path match
The pkiPathMatch match rule compares for equality a presented value with an attribute value of type pkiPath. A
certificate using system may use this matching rule to select a path beginning with a certificate issued by a CA which it
trusts and ending with a certificate issued to the specified subject.
pkiPathMatch MATCHING-RULE ::= {
SYNTAX PkiPathMatchSyntax
ID id-mr-pkiPathMatch }
PkiPathMatchSyntax ::= SEQUENCE {
firstIssuer Name,
lastSubject Name }
This matching rule returns TRUE if the presented value in the firstIssuer component matches the corresponding
elements of the issuer field of the first certificate in the SEQUENCE in the stored value and the presented value in the
lastSubject component matches the corresponding elements of the subject field of the last certificate in the
SEQUENCE in the stored value. This matching rule returns FALSE if either match fails.
11.3.10 Enhanced certificate match
The enhanced certificate match rule compares a presented value with an attribute value of type Certificate. It selects
one or more certificates on the basis of various characteristics.
enhancedCertificateMatch MATCHING-RULE ::= {
SYNTAX EnhancedCertificateAssertion
ID id-mr-enhancedCertificateMatch }
EnhancedCertificateAssertion ::= SEQUENCE {
serialNumber [0] CertificateSerialNumber OPTIONAL,
issuer [1] Name OPTIONAL,
subjectKeyIdentifier [2] SubjectKeyIdentifier OPTIONAL,
authorityKeyIdentifier [3] AuthorityKeyIdentifier OPTIONAL,
certificateValid [4] Time OPTIONAL,
privateKeyValid [5] GeneralizedTime OPTIONAL,
subjectPublicKeyAlgID [6] OBJECT IDENTIFIER OPTIONAL,
keyUsage [7] KeyUsage OPTIONAL,
subjectAltName [8] AltName OPTIONAL,
policy [9] CertPolicySet OPTIONAL,
pathToName [10] GeneralNames OPTIONAL,
subject [11] Name OPTIONAL,
nameConstraints [12] NameConstraintsSyntax OPTIONAL
}
(ALL EXCEPT ({ -- none; at least one component shall be present -- }))
AltName ::= SEQUENCE {
altnameType AltNameType,
altNameValue GeneralName OPTIONAL }
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The directory search operation allows for multiple values of EnhancedCertificateAssertion to be combined in filter
specifications, including and/or logic. This matching rule returns TRUE if all of the components that are present in the
presented value match the corresponding components of the attribute value, as follows:
Matching for serialNumber; issuer; subjectKeyIdentifier; authorityKeyIdentifier; certificateValid, privateKeyValid,
policy, subject, and nameConstraints components is as defined for the same components in the certificateMatch
matching rule.
subjectAltName component contains an altNameType and optional altNameValue fields. If altNameValue is present,
the value shall be of the same name form as indicated in altNameType.
subjectAltName matches if at least one of the following conditions is true:
­ The presented value contains only the altNameType component and the stored attribute value contains
the subject alternative name extension with an AltNames component of the same type as indicated in the
presented value;
­ The presented value contains both the altNameType and altNameValue components and the stored
attribute value contains the subject alternative name extension with an AltNames component of the same
type and value indicated in the presented value.
subjectAltName match fails if at least one of the following conditions is true:
­ The stored attribute value does not contain the subject alternative name extension;
­ The stored attribute value contains the subject alternative name extension but the AltNames component
does not include the same type as identified in the presented value;
­ The presented value contains both the altNameType and altNameValue components and the stored
attribute value contains the subject alternative name extension with an AltNames component of the same
type indicated in the presented value, but the stored value does not contain the same value of that type as
in the presented value.
subjectAltName match is undefined if the presented value contains both the altNameType and altNameValue
components and the stored attribute value contains the subject alternative name extension with an AltNames component
of the same type indicated in the presented value, but the type is one for which the directory is unable to compare values
for purposes of determining a match. This may be because the name form is not appropriate for matching or because the
directory is unable to perform the required comparisons.
pathToName matches unless the certificate has a name constraints extension which inhibits the construction of a
certification path to any of the presented name values. For example, if attempting to retrieve certificates that form a path
to a user certificate which has a subject value of "dc=com; dc=corporate; cn=john.smith", it may be useful to include an
assertion in the search operation containing this DN in the pathToName component. A stored certificate that contained
a name constraints extension that excluded the complete subtree below base "dc=com; dc=company A" would fail in
certification path validation to that user certificate and would therefore not be a matched value for this sample assertion.
SECTION 3 ­ ATTRIBUTE CERTIFICATE FRAMEWORK
The attribute certificate framework defined here provides a foundation upon which Privilege Management
Infrastructures (PMI) can be built. These infrastructures can support applications such as access control.
The binding of a privilege to an entity is provided by an authority through a digitally signed data structure called an
attribute certificate or through a public-key certificate containing an extension defined explicitly for this purpose. The
format of attribute certificates is defined here, including an extensibility mechanism and a set of specific certificate
extensions. Revocation of attribute certificates may or may not be needed. For example, in some environments, the
attribute certificate validity periods may be very short (e.g., minutes), negating the need for a revocation scheme. If, for
any reason, an authority revokes a previously issued attribute certificate, users need to be able to learn that revocation
has occurred so they do not use an untrustworthy certificate. Revocation lists are one scheme that can be used to notify
users of revocations. The format of revocation lists is defined in Section 2 of this Specification, including an
extensibility mechanism and a set of revocation list extensions. Additional extensions are defined here. In both the
certificate and revocation list case, other bodies may also define additional extensions that are useful to their specific
environments.
An attribute certificate using system needs to validate a certificate prior to using that certificate for an application.
Procedures for performing that validation are also defined here, including verifying the integrity of the certificate itself,
its revocation status, and its validity with respect to the intended use.
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This framework includes a number of optional elements that are appropriate only in some environments. Although the
models are defined as complete, this framework can be used in environments where not all components of the defined
models are used. For example there are environments where revocation of attribute certificates is not required. Privilege
delegation and the use of roles are also aspects of this framework that are not universally applicable. However, these are
included in this Specification so that those environments that do have requirements for them can also be supported.
The Directory uses attribute certificates to provide rule-based access control to Directory information.
12 Attribute Certificates
Public-key certificates are principally intended to provide an identity service upon which other security services, such as
data integrity, entity authentication, confidentiality and authorization, may be built. There are two distinct mechanisms
provided in this Specification for binding a privilege attribute to a holder.
Public-key certificates, used in combination with the entity authentication service, can provide an authorization service
directly, if privileges are associated with the subject through the practices of the issuing CA. Public-key certificates may
contain a subjectDirectoryAttributes extension that contains privileges associated with the subject of the public-key
certificate. This mechanism is appropriate in situations where the authority issuing the public-key certificate (CA) is
also the authority for delegating the privilege (AA) and the validity period of the privilege corresponds to the validity
period of the public-key certificate. End-entities cannot act as AAs. If any of the extensions defined in clause 15 are
included in a public-key certificate, those extensions apply equally to all privileges assigned in the
subjectDirectoryAttributes extension of that public-key certificate.
In the more general case, entity privileges will have lifetimes that do not match the validity period for a public-key
certificate. Privileges will often have a much shorter lifetime. The authority for assignment of privilege will frequently
be other than the authority issuing that same entity a public-key certificate and different privileges may be assigned by
different Attribute Authorities (AA). Privileges may also be assigned based on a temporal context and the 'turn on/turn
off' aspect of privileges may well be asynchronous with the lifetime of the public-key certificate and/or asynchronous
with entity privileges issued from a different AA . The use of attribute certificates issued by an AA provides a flexible
Privilege Management Infrastructure (PMI) which can be established and managed independently from a PKI. At the
same time, there is a relationship between the two whereby the PKI is used to authenticate identities of issuers and
holders in attribute certificates.
12.1 Attribute certificate structure
An attribute certificate is a separate structure from a subject's public key certificate. A subject may have multiple
attribute certificates associated with each of its public key certificates. There is no requirement that the same authority
create both the public key certificate and attribute certificate(s) for a user; in fact separation of duties will frequently
dictate otherwise. In environments where different authorities have responsibility for issuing public key and attribute
certificates, the public key certificate(s) issued by a Certification Authority (CA) and the attribute certificate(s) issued
by an Attribute Authority (AA) would be signed using different private signing keys. In environments where a single
entity is both the CA, issuing public key certificates, and the AA, issuing attribute certificates, it is strongly
recommended that a different key be used to sign attribute certificates than the key used to sign public-key certificates.
Exchanges between the issuing authority and the entity receiving a certificate are outside the scope of this Specification.
The attribute certificate is defined as follows.
AttributeCertificate ::= SIGNED {AttributeCertificateInfo}
AttributeCertificateInfo ::= SEQUENCE
{
version AttCertVersion, -- version is v2
holder Holder,
issuer AttCertIssuer,
signature AlgorithmIdentifier,
serialNumber CertificateSerialNumber,
attrCertValidityPeriod AttCertValidityPeriod,
attributes SEQUENCE OF Attribute,
issuerUniqueID UniqueIdentifier OPTIONAL,
extensions Extensions OPTIONAL
}
AttCertVersion ::= INTEGER { v2(1) }
Holder ::= SEQUENCE
{
baseCertificateID [0] IssuerSerial OPTIONAL,
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-- the issuer and serial number of the holder's Public Key Certificate
entityName [1] GeneralNames OPTIONAL,
-- the name of the entity or role
objectDigestInfo [2] ObjectDigestInfo OPTIONAL
-- used to directly authenticate the holder, e.g., an executable
-- at least one of baseCertificateID, entityName or objectDigestInfo shall be present --}
ObjectDigestInfo ::= SEQUENCE {
digestedObjectType ENUMERATED {
publicKey (0),
publicKeyCert (1),
otherObjectTypes (2) },
otherObjectTypeID OBJECT IDENTIFIER OPTIONAL,
digestAlgorithm AlgorithmIdentifier,
objectDigest BIT STRING }
AttCertIssuer ::= [0] SEQUENCE {
issuerName GeneralNames OPTIONAL,
baseCertificateID [0] IssuerSerial OPTIONAL,
objectDigestInfo [1] ObjectDigestInfo OPTIONAL }
-- At least one component shall be present
( WITH COMPONENTS { ..., issuerName PRESENT } |
WITH COMPONENTS { ..., baseCertificateID PRESENT } |
WITH COMPONENTS { ..., objectDigestInfo PRESENT } )
IssuerSerial ::= SEQUENCE {
issuer GeneralNames,
serial CertificateSerialNumber,
issuerUID UniqueIdentifier OPTIONAL }
AttCertValidityPeriod ::= SEQUENCE {
notBeforeTime GeneralizedTime,
notAfterTime GeneralizedTime }
The version differentiates between different versions of the attribute certificate. For attribute certificates issued in
accordance with the syntax in this Specification, version shall be v2.
The holder field conveys the identity of the attribute certificate's holder.
The baseCertificateID component, if present, identifies a particular public-key certificate that is to be used to
authenticate the identity of this holder when asserting privileges with this attribute certificate.
The entityName component, if present, identifies one or more names for the holder. If entityName is the only
component present in holder, any public-key certificate that has one of these names as its subject can be used to
authenticate the identity of this holder when asserting privileges with this attribute certificate. If baseCertificateID and
entityName are both present, only the certificate specified by baseCertificateID may be used. In this case entityName
is included only as a tool to help the privilege verifier locate the identified public-key certificate.
NOTE 1 ­ There is a risk with the sole use of GeneralNames to identify the holder in that this points only to a name for the
holder. This is generally insufficient to enable the authentication of a holder's identity for purposes of issuing privileges to that
holder. Use of the issuer name and serial number of a specific public-key certificate, however, enables the issuer of attribute
certificates to rely on the authentication process performed by the CA when issuing that particular public-key certificate. Also,
some of the options in GeneralNames (e.g., IPAddress) are inappropriate for use in naming an attribute certificate holder,
especially when the holder is a role and not an individual entity. Another problem with GeneralNames alone as an identifier
for a holder is that many name forms within that construct do not have strict registration authorities or processes for the
assignment of names.
The objectDigestInfo component, if present, is used directly to authenticate the identity of a holder, including an
executable holder (e.g., an applet). The holder is authenticated by comparing a digest of the corresponding information,
created by the privilege verifier with the same algorithm identified in objectDigestInfo with the content of
objectDigest. If the two are identical, the holder is authenticated for purposes of asserting privileges with this attribute
certificate.
­ publicKey shall be indicated when a hash of an entity's public-key is included. Hashing a public-key
may not uniquely identify one certificate (i.e., the identical key value may appear in multiple
certificates). In order to link an attribute certificate to a public-key, the hash is calculated over the
representation of that public-key which would be present in a public-key certificate. Specifically, the
input for the hash algorithm shall be the DER encoding of a SubjectPublicKeyInfo representation of the
key. Note that this includes the AlgorithmIdentifier as well as the BIT STRING. Note that if the publickey
value used as input to the hash function has been extracted from a public-key certificate, then it is
possible (e.g., if parameters for the Digital Signature Algorithm were inherited) then this may not be
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sufficient input for the HASH. The correct input for hashing in this context will include the value of the
inherited parameters and thus may differ from the SubjectPublicKeyInfo present in the public-key
certificate.
­ publicKeyCert shall be indicated when a public-key certificate is hashed; the hash is over the entire DER
encoding of the public-key certificate, including the signature bits.
­ otherObjectTypes shall be indicated when objects other than public-keys or public-key certificates are
hashed (e.g., software objects). The identity of the type of object may optionally be supplied. The portion
of the object to be hashed can be determined either by the explicitly stated identifier of the type or, if the
identifier is not supplied, by the context in which the object is used.
The issuer field conveys the identity of the AA that issued the certificate.
­ The issuerName component, if present, identifies one or more names for the issuer.
­ The baseCertificateID component, if present, identifies the issuer by reference to a specific public-key
certificate for which this issuer is the subject.
­ The objectDigestInfo component, if present, identifies the issuer by providing a hash of identifying
information for the issuer.
The signature identifies the cryptographic algorithm used to digitally sign the attribute certificate.
The serialNumber is the serial number that uniquely identifies the attribute certificate within the scope of its issuer.
The attrCertValidityPeriod field conveys the time period during which the attribute certificate is considered valid,
expressed in GeneralizedTime format.
The attributes field contains the attributes associated with the holder that are being certified (e.g., the privileges).
NOTE 2 ­ In the case of attribute descriptor attribute certificates, this sequence of attributes can be empty.
The issuerUniqueID may be used to identify the issuer of the attribute certificate in instances where the issuer
component is not sufficient.
The extensions field allows addition of new fields to the attribute certificate.
If unknown elements appear within the extension, and the extension is not marked criticial, those unknown elements
shall be ignored according to the rules of extensibility documented in 12.2.2 of ITU-T Rec. X.519 | ISO/IEC 9594-5.
The framework for attribute certificates described in this section is primarily focused on the model in which privilege is
placed within attribute certificates. However, as mentioned earlier, the certificate extensions defined in this section can
also be placed in a public-key certificate using the subjectDirectoryAttributes extension.
12.2 Attribute certificate paths
Just as with public-key certificates, there may be a requirement to convey an attribute certificate path (e.g., within an
application protocol to assert privileges). The following ASN.1 data type can be used to represent an attribute certificate
path:
AttributeCertificationPath ::= SEQUENCE {
attributeCertificate AttributeCertificate,
acPath SEQUENCE OF ACPathData OPTIONAL }
ACPathData ::= SEQUENCE {
certificate [0] Certificate OPTIONAL,
attributeCertificate [1] AttributeCertificate OPTIONAL }
13 Attribute Authority, SOA and Certification Authority relationship
The Attribute Authority (AA) and Certification Authority (CA) are logically (and, in many cases, physically)
completely independent. The creation and maintenance of "identity" can (and often should) be separated from the PMI.
Thus the entire PKI, including CAs, may be existing and operational prior to the establishment of the PMI. The CA,
although it is the source of authority for identity within its domain, is not automatically the source of authority for
privilege. The CA, therefore, will not necessarily itself be an AA and, by logical implication, will not necessarily be
responsible for the decision as to what other entities will be able to function as AAs (e.g., by including such a
designation in their identity certificates).
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The Source of Authority (SOA) is the entity that is trusted by a privilege verifier as the entity with ultimate
responsibility for assignment of a set of privileges. A resource may limit the SOA authority by trusting certain SOAs for
specific functions (e.g., one for read privileges and a different one for write privileges). An SOA is itself an AA as it
issues certificates to other entities in which privileges are assigned to those entities. An SOA is analogous to a 'root CA'
or 'trust anchor' in the PKI, in that a privilege verifier trusts certificates signed by the SOA. In some environments there
is a need for CAs to have tight control over the entities that can act as SOAs. This framework provides a mechanism for
supporting that requirement. In other environments, that control is not needed and mechanisms for determining the
entities that can act as SOAs in such environments may be outside the scope of this Specification.
This framework is flexible and can satisfy the requirements of many types of environments.
a) In many environments, all privileges will be assigned directly to individual entities by a single AA,
namely the SOA.
b) Other environments may require support for the optional roles feature, whereby individuals are issued
certificates that assign various roles to them. The privileges associated with the role are implicitly
assigned to such individuals. The role privileges may themselves be assigned in an attribute certificate
issued to the role itself or through some other means (e.g., locally configured).
c) Another optional feature of this framework is the support of privilege delegation. If delegation is done,
the SOA assigns privilege to an entity that is permitted to also act as an AA and further delegate the
privilege. Delegation may continue through several intermediary AAs until it is ultimately assigned to an
end-entity that cannot further delegate that privilege. The intermediary AAs may or may not also be able
to act as privilege asserters for the privileges they delegate.
d) In some environments, the same physical entity may be acting as both an AA and a CA. This dual logical
role for the same physical entity is always the case when privilege is conveyed within
subjectDirectoryAttributes extension of a public-key certificate. In other environments, separate
physical entities act as CAs and AAs. In the latter case, privilege is assigned using attribute certificates
instead of public-key certificates.
When attribute certificates point to public-key certificates for their issuers and holders, the PKI is used to authenticate
holders (privilege asserters) and verify the digital signatures of the issuers.
Two delegation models are described in this Specification. The first delegation model is one where the privilege
delegator is an AA that can issue certificates delegating that privilege to others. The second model allows for an
independent Delegation Service (DS) in which the entity issues certificates on behalf of another AA (that may or may
not be able to issue ACs itself). This DS cannot itself act as a claimant for that privilege. The DS model is particularly
relevant to environments that wish to maintain some central management over the set of privileges delegated within
their domain. For example, a set of one or more DS servers performing delegation, rather than individual privilege
holders, allows the total set of privileges delegated within an environment to be determined from a centralized facility
and enables policy and management decisions to be modified accordingly. Two distinct deployment models are possible
for DS servers. In one model, a privilege is assigned by an SOA to privilege holders and those holders are authorized to
delegate that privilege to others. However, rather than issue the attribute certificates that delegate the privilege
themselves, the privilege holder requests the DS to delegate that privilege on their behalf. The DS does not itself hold
that privilege and therefore cannot act as a claimant for that privilege; however, the DS is authorized by the SOA to
issue attribute certificates on behalf of other privilege holders. The second deployment model is similar to the first with
the following exception. The DS is actually a holder that is assigned the privilege to be delegated, but the DS is not
authorized to act as a claimant for the privilege, only as a delegator. In this case, the noAssertion extension must be set
in the AC issued to the DS by the SOA. The DS is termed an indirect issuer.
In both deployment models, the SOA issues attributes/privileges to subordinate AAs. The AAs then request the DS to
issue a subset of these privilege attributes to other holders. In the second deployment model, the DS can check that an
AA is delegating within the overall scope set by the SOA; in the first deployment model, the DS cannot check and the
relying party will have to check that delegation was performed correctly.
13.1 Privilege in attribute certificates
Entities may acquire privilege in two ways:
­ An AA may unilaterally assign privilege to an entity through the creation of an attribute certificate
(perhaps totally on its own initiative, or at the request of some third party). This certificate may be stored
in a publicly accessible repository and may subsequently be processed by one or more privilege verifiers
to make an authorization decision. All of this may occur without the entity's knowledge or explicit
action.
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­ Alternatively, an entity may request a privilege of some AA. Once created, this certificate may be
returned (only) to the requesting entity, which explicitly supplies it when requesting access to some
protected resource.
Note that in both procedures the AA needs to perform its due diligence to ensure that the entity should really be
assigned this privilege. This may involve some out-of-band mechanisms, analogous to the certification of an
identity/key-pair binding by a CA.
The attribute certificate based PMI is suitable in environments where any one of the following is true:
­ A different entity is responsible for assigning particular privilege to a holder than for issuing public-key
certificates to the same subject;
­ There are a number of privilege attributes to be assigned to a holder, from a variety of authorities;
­ The lifetime of a privilege differs from that of the holder's public key certificate validity (generally the
lifetime of privileges is much shorter); or
­ The privilege is valid only during certain intervals of time which are asynchronous with that user's
public-key validity or validity of other privileges.
13.2 Privilege in public-key certificates
In some environments, privileges are associated with the subject through the practices of a CA. Such privilege may be
put directly into public-key certificates (thereby re-using much of an already-established infrastructure), rather than
issuing attribute certificates. In such cases, the privilege is included in the subjectDirectoryAttributes extension of the
public-key certificate.
This mechanism is suitable in environments where one or more of the following are true:
­ The same physical entity is acting both as a CA and an AA;
­ The lifetime of the privilege is aligned with that of the public-key included in the certificate;
­ Delegation of privilege is not permitted; or
­ Delegation is permitted, but for any one delegation, all privileges in the certificate (in the
subjectDirectoryAttributes extension) have the same delegation parameters and all extensions relevant
to delegation apply equally to all privileges in the certificate.
14 PMI models
14.1 General model
The general privilege management model consists of three entities: the object, the privilege asserter and the privilege
verifier.
The object may be a resource being protected, for example in an access control application. The resource being
protected is referred to as the object. This type of object has methods which may be invoked (for example, the object
may be a firewall which has an "Allow Entry" object method, or the object may be a file in a file system which has
Read, Write, and Execute object methods). Another type of object in this model may be an object that was signed in a
non-repudiation application.
The privilege asserter is the entity that holds a particular privilege and asserts its privileges for a particular context of
use.
The privilege verifier is the entity that makes the determination as to whether or not asserted privileges are sufficient for
the given context of use.
The pass/fail determination made by the privilege verifier is dependent upon four things:
­ privilege of the privilege asserter;
­ privilege policy in place;
­ current environment variables, if relevant; and
­ sensitivity of the object method, if relevant.
The privilege of a privilege holder reflects the degree of trust placed in that holder, by the certificate issuer, that the
privilege holder will adhere to those aspects of policy which are not enforced by technical means. This privilege is
encapsulated in the privilege holder's attribute certificate(s) (or subjectDirectoryAttributes extension of its public-key
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certificate), which may be presented to the privilege verifier in the invocation request, or may be distributed by some
other means, such as via the Directory. Codifying privilege is done through the use of the Attribute construct,
containing an AttributeType and a SET OF AttributeValue. Some attribute types used to specify privilege may have
very simple syntax, such as a single INTEGER or an OCTET STRING. Others may have more complex syntaxes. An
example is provided in Annex D.
The privilege policy specifies the degree of privilege which is considered sufficient for a given object method's
sensitivity or context of use. The privilege policy needs to be protected for integrity and authenticity. A number of
possibilities exist for conveying policy. At one extreme is the idea that policy is not really conveyed at all, but is simply
defined and only ever kept locally in the privilege verifier's environment. At the other extreme is the idea that some
policies are "universal" and should be conveyed to, and known by, every entity in the system. Between these extremes
are many shades of variation. Schema components for storing privilege policy information in the Directory are defined
in this Specification.
Privilege policy specifies the threshold for acceptance for a given set of privileges. That is, it defines precisely when a
privilege verifier should conclude that a presented set of privileges is "sufficient" in order that it may grant access (to
the requested object, resource, application, etc.) to the privilege asserter.
Syntax for the definition of privilege policy is not standardized in this Specification. Annex D contains a couple of
examples of syntaxes that could be used for this purpose. However, these are examples only. Any syntax may be used
for this purpose, including clear text. Regardless of the syntax used to define the privilege policy, each instance of
privilege policy shall be uniquely identified. Object identifiers are used for this purpose.
PrivilegePolicy ::= OBJECT IDENTIFIER
The environment variables, if relevant, capture those aspects of policy required for the pass/fail determination
(e.g., time of day or current account balance) which are available through some local means to the privilege verifier.
Representation of environment variables is entirely a local matter.
The object method sensitivity, if relevant, may reflect attributes of the document or request to be processed, such as the
monetary value of a funds transfer that it purports to authorize, or the confidentiality of a document's content. The
object method's sensitivity may be explicitly encoded in an associated security label or in an attribute certificate held by
the object method, or it may be implicitly encapsulated in the structure and contents of the associated data object. It may
be encoded in one of a number of different ways. For instance, it may be encoded outside the scope of PMI in the X.411
label associated with a document, in the fields of an EDIFACT interchange, or hard-coded in the privilege verifier's
application. Alternatively, it may be done within the PMI, in an attribute certificate associated with the object method.
For some contexts of use, no object method sensitivity is used.
There is not necessarily any binding relationship between a privilege verifier and any particular AA. Just as privilege
holders may have attribute certificates issued to them by many different AAs, privilege verifiers may accept certificates
issued by numerous AAs, which need not be hierarchically related to one another, to grant access to a particular
resource.
The attribute certificate framework can be used to manage privileges of various types and for a number of purposes.
The terms used in this Specification, such as privilege asserter, privilege verifier, etc. are independent of the particular
application or use.
14.1.1 PMI in access control context
There is a standard framework for access control (ITU-T Rec. X.812 | ISO/IEC 10181-3) that defines a corresponding
set of terms that are specific to the access control application. A mapping of the generic terms used in this Specification
to those in the access control framework is provided here, to clarify the relationship between this model and that
Specification.
Privilege asserter in this Specification would be acting in the role of an 'initiator' in the access control framework.
Privilege verifier in this Specification would be acting in the role of an 'access control decision function (ADF)' in the
access control framework.
Object method for which privilege is being asserted in this Specification would correspond to the 'target' defined in the
access control framework.
Environmental variables in this Specification would correspond to the 'contextual information' in the access control
framework.
Privilege policy discussed in this Specification could include 'access control policy', and 'access control policy rules' as
defined in the access control framework.
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This model allows a PMI to be overlaid fairly seamlessly on an existing network of resources to be protected. In
particular, having the privilege verifier act as a gateway to a sensitive object method, granting or denying requests for
invocation of that object method, enables the object to be protected with little or no impact to the object itself. The
privilege verifier screens all requests and only those that are properly authorized are passed on to the appropriate object
methods.
14.1.2 PMI in a non-repudiation context
There is a standard framework for non-repudiation (ITU-T Rec. X.813 | ISO/IEC 10181-4) which defines a
corresponding set of terms that are specific to non-repudiation. A mapping of the generic terms used in this
Specification to those in the non-repudiation framework is provided here, to clarify the relationship between this model
and that Specification.
Privilege asserter in this Specification would be acting in the role of an 'evidence subject' or an 'originator' in the nonrepudiation
framework.
Privilege verifier in this Specification would be acting in the role of an 'evidence user' or a 'recipient' in the nonrepudiation
framework.
Object method for which privilege is being asserted in this Specification would correspond to the 'target' defined in the
non-repudiation framework.
Environmental variables in this Specification would correspond to the 'date and time the evidence was generated or
verified' in the non-repudiation framework.
Privilege policy discussed in this Specification could include 'non-repudiation security policy' in the non-repudiation
framework.
14.2 Control model
The control model illustrates how control is exerted over access to the sensitive object method. There are five
components of the model: the privilege asserter, the privilege verifier, the object method, the privilege policy, and
environmental variables (see Figure 3). The privilege asserter has privilege; the object method has sensitivity. The
techniques described here enable the privilege verifier to control access to the object method by the privilege asserter, in
accordance with the privilege policy. Both the privilege and the sensitivity may be multi-valued parameters.
Figure 3 ­ Control model
The privilege asserter may be an entity identified by a public-key certificate, or an executable object identified by the
digest of its disk image, etc.
14.3 Delegation model
In some environments there may be a need to delegate privilege; however, this is an optional aspect of the framework
and is not required in all environments. There are four components of the delegation model: the privilege verifier, the
SOA, other AAs and the privilege asserter (see Figure 4).
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Figure 4 ­ Delegation model
As with environments where delegation is not used, the SOA is the initial issuer of certificates that assign privilege to
privilege holders. However, in this case the SOA authorizes the privilege holder to act as AA and further delegate that
privilege to other entities through the issuance of certificates that contain the same privilege (or a subset thereof). The
SOA may impose constraints on the delegation that can be done (e.g., limit the path length, limit the name space within
delegation can be done). Each of these intermediary AAs may, in certificates that it issues to further privilege holders,
authorize further delegation to be done by those holders also acting as AAs. A universal restriction on delegation is that
no AA can delegate more privilege than it holds. A delegator may also further restrict the ability of downstream AAs.
When delegation is used, the privilege verifier trusts the SOA to delegate some or all of those privileges to holders,
some of which may further delegate some or all of those privileges to other holders.
The privilege verifier trusts the SOA as the authority for a given set of privileges for the resource. If the privilege
asserter's certificate is not issued by that SOA, then the privilege verifier shall locate a delegation path of certificates
from that of the privilege asserter to one issued by the SOA. The validation of that delegation path includes checking
that each AA had sufficient privileges and was duly authorized to delegate those privileges.
For the case in which privileges are conveyed by means of attribute certificates, the delegation path is distinct from the
certificate validation path used to validate the public key certificates of the entities involved in the delegation process.
However, the quality of authenticity offered by the public key certificate validation process shall be commensurate with
the sensitivity of the object method that is being protected.
A delegation path shall either consist completely of attribute certificates or completely of public-key certificates. A
delegator that obtains its privilege in an attribute certificate may only delegate, if authorized, by issuance of subsequent
attribute certificates. Similarly, a delegator that obtains its privilege in a public-key certificate, if authorized, may only
delegate by issuance of subsequent public-key certificates. Ony AAs may delegate privilege. End-entities cannot.
14.4 Roles model
Roles provide a means to indirectly assign privileges to individuals. Individuals are issued role assignment certificates
that assign one or more roles to them through the role attribute contained in the certificate. Specific privileges are
assigned to a role name through role specification certificates, rather than to individual privilege holders through
attribute certificates. This level of indirection enables, for example, the privileges assigned to a role to be updated,
without impacting the certificates that assign roles to individuals. Role assignment certificates may be attribute
certificates or public-key certificates. Role specification certificates may be attribute certificates, but not public-key
certificates. If role specification certificates are not used, the assignment of privileges to a role may be done through
other means (e.g., may be locally configured at a privilege verifier).
The following are all possible:
­ Any number of roles can be defined by any AA;
­ The role itself and the members of a role can be defined and administered separately, by different AAs;
­ Role membership, just as any other privilege, may be delegated; and
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­ Roles and membership may be assigned any suitable lifetime.
If the role assignment certificate is an attribute certificate, the role attribute is contained in the attributes component of
the attribute certificate. If the role assignment certificate is a public-key certificate, the role attribute is contained in the
subjectDirectoryAttributes extension. In the latter case, any additional privileges contained in the public-key
certificate are privileges that are directly assigned to the certificate subject, not privileges assigned to the role.
Thus, a privilege asserter may present a role assignment certificate to the privilege verifier demonstrating only that the
privilege asserter has a particular role (e.g., "manager", or "purchaser"). The privilege verifier may know a priori, or
may have to discover by some other means, the privileges associated with the asserted role in order to make a pass/fail
authorization decision. The role specification certificate can be used for this purpose.
A privilege verifier needs to have an understanding of the privileges specified for the role. The assignment of those
privileges to the role may be done within the PMI in a role specification certificate or outside the PMI (e.g., locally
configured). If the role privileges are asserted in a role specification certificate, mechanisms for linking that certificate
with the relevant role assignment certificate for the privilege asserter are provided in this Specification. A role
specification certificate cannot be delegated to any other entity. The issuer of the role assignment certificate may be
independent of the issuer of the role specification certificate and these may be administered (expired, revoked, and so
on) entirely separately. The same certificate (attribute certificate or public-key certificate) can be a role assignment
certificate as well as contain assignment of other privileges directly to the same individual. However, a role
specification certificate shall be a separate certificate.
NOTE ­ The use of roles within an authorization framework can increase the complexity of path processing, because such
functionality essentially defines another delegation path which needs to be followed. The delegation path for the role assignment
certificate may involve different AAs and may be independent of the AA that issued the role specification certificate.
14.4.1 Role attribute
The specification of privilege attribute types is generally an application-specific issue that is outside the scope of this
Specification. The single exception to this is an attribute defined here for the assignment of a holder to a role. The
specification of values for the role attribute is outside the scope of this Specification.
role ATTRIBUTE ::= {
WITH SYNTAX RoleSyntax
ID id-at-role }
RoleSyntax ::= SEQUENCE {
roleAuthority [0] GeneralNames OPTIONAL,
roleName [1] GeneralName }
This privilege attribute would be used to populate the attributes field of a role assignment certificate. If the role
assignment certificate is a public-key certificate, this attribute would be used to populate the
subjectDirectoryAttributes extension of that public-key certificate.
The roleAuthority, if present, identifies the recognized authority that is responsible for issuing the role specification
certificate.
If roleAuthority is present, and a privilege verifier uses a role specification certificate to determine the privileges
assigned to the role, at least one of the names in roleAuthority shall be present in the issuer field of that role
specification certificate. If the privilege verifier used means other than a role specification certificate to determine the
privileges assigned to the role, mechanisms to ensure that those privileges were assigned by an authority named in this
component are outside the scope of this Specification.
If roleAuthority is absent, the identity of the responsible authority shall be determined through other means. The
roleSpecCertIdentifier extension in a role assignment certificate is one way to achieve this binding, in the case where a
role specification certificate was used to assign privileges to the role.
The roleName component identifies the role to which the holder of a role assignment certificate containing this attribute
is assigned. If a privilege verifier uses a role specification certificate to determine the privileges assigned to that role,
this role name shall also appear in the holder field of the role specification certificate.
14.5 XML privilege information attribute
The specification of privileges is generally an application-specific issue that is outside the scope of this Specification.
While this attribute does not define any specific privilege information, it provides a container attribute in which XMLencoded
privileges can be conveyed in attribute certificates.
xmlPrivilegeInfo ATTRIBUTE ::= {
WITH SYNTAX UTF8String -- contains XML-encoded privilege information
ID id-at-xMLPrivilegeInfo }
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The XML schema for the role attribute type can be defined either with ASN.1 or with XSD.
The XML contained within the UTF8String needs to be self-identifying.
The following is an ASN.1 schema defining an XML role attribute type. It is followed by an XSD specification for the
same attribute type, and by an example XML instance. The example instance is a valid instance for both the ASN.1 and
the XSD schema instances, and can be validated by either ASN.1 or XSD tools.
The example schema defines a role attribute with an ID, an issuing authority and the name of the role.
CERTIFICATE-ATTRIBUTE DEFINITIONS ::=
BEGIN
Role ::= [UNCAPITALIZED] SEQUENCE {
id [ATTRIBUTE] XML-ID,
authorities SEQUENCE (1..MAX) OF
authority UTF8String,
name UTF8String }
XML-ID ::= UTF8String
END
The following XSD schema is an alternative (exactly equivalent) definition:
<schema xmlns="http://www.w3.org/2000/08/XMLSchema">
<element name="role">
<attribute name="id" type="ID"/>
<complexType>
<sequence>
<element name="authorities">
<complexType>
<sequence>
<element name="authority" type="string" minOccurs="1" maxOccurs="*"/>
</sequence>
</complexType>
</element>
<element name="name" type="string"/>
</sequence>
</complexType>
</element>
</schema>
An example of an instance conforming to the above schema definitions, that would be a value of the xMLPrivilegeInfo
attribute type would be:
<role id="123" xmlns="http://www.example.org/certificates/attribute">
<authorities>
<authority>Fictitious Organization</authority>
</authorities>
<name>manager</name>
</role>
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15 Privilege management certificate extensions
The following certificate extensions may be included in certificates for purposes of privilege management. Along with
the definition of the extensions themselves, the rules for certificate types in which the extension may be present are also
provided.
With the exception of the SOA identifier extension, any of the extensions that may be included in a public-key
certificate shall only be included if that public-key certificate is one that assigns privilege to its subject (i.e., the
subjectDirectoryAttributes extension shall be present). If any of these extensions is present in a public-key certificate,
that extension applies to ALL privileges present in the subjectDirectoryAttributes extension.
Revocation lists used to publish revocation notices for attribute certificates (ACRLs and AARLs) may contain any CRL
or CRL entry extensions as defined for use in CRLs and CARLs in Section 2 of this Specification.
This clause specifies extensions in the following areas:
a) Basic privilege management: These certificate extensions convey information relevant to the assertion of
a privilege.
b) Privilege revocation: These certificate extensions convey information regarding location of revocation
status information.
c) Source of Authority: These certificate extensions relate to the trusted source of privilege assignment by a
verifier for a given resource.
d) Roles: These certificate extensions convey information regarding location of related role specification
certificates.
e) Delegation: These certificate extensions allow constraints to be set on subsequent delegation of assigned
privileges.
15.1 Basic privilege management extensions
15.1.1 Requirements
The following requirements relate to basic privilege management:
a) Issuers need to be able to place constraints on the time during which a privilege can be asserted;
b) Issuers need to be able to target attribute certificates to specific servers/services;
c) It may be necessary for issuers to convey information intended for display to privilege asserters and/or
privilege verifiers using the certificate;
d) Issuers may need to be able to place constraints on the privilege policies with which the assigned
privilege can be used.
15.1.2 Basic privilege management extension fields
The following extension fields are defined:
a) Time specification;
b) Targeting information;
c) User notice;
d) Acceptable privilege policies;
e) Indirect issuer;
f) No assertion.
15.1.2.1 Time specification extension
The time specification extension can be used by an AA to restrict the specific periods of time during which the
privilege, assigned in the certificate containing this extension, can be asserted by the privilege holder. For example, an
AA may issue a certificate assigning privileges which can only be asserted between Monday and Friday and between
the hours of 9:00 a.m. and 5:00 p.m.. Another example, in the case of delegation, might be a manager delegating signing
authority to a subordinate for the time that the manager will be away on vacation.
This field is defined as follows:
timeSpecification EXTENSION ::= {
SYNTAX TimeSpecification
IDENTIFIED BY id-ce-timeSpecification }
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This extension may be present in attribute certificates or public-key certificates issued by AAs, including SOAs, to
entities that may act as privilege asserters, including other AAs and end-entities. This extension shall not be included in
certificates that contain the SOA identifier extension or in certificates issued to AAs that may not also act as privilege
asserters.
If this extension is present in a certificate issued to an entity that is an AA, it applies only to that entity's assertion of the
privileges contained in the certificate. It does not impact the time period during which the AA is able to issue
certificates.
Because this extension is effectively specifying a refinement on the validity period of the certificate that contains it, this
extension shall be marked critical (i.e., the issuer, by including this extension, is explicitly defining the privilege
assignment to be invalid outside the time specified).
If this extension is present, but not understood by the privilege verifier, the certificate shall be rejected.
15.1.2.1.1 Time specification match
The time specification matching rule compares for equality a presented value with an attribute value of type
AttributeCertificate.
timeSpecificationMatch MATCHING-RULE ::= {
SYNTAX TimeSpecification
ID id-mr-timeSpecMatch }
This matching rule returns TRUE if the stored value contains the timeSpecification extension and if components that
are present in the presented value match the corresponding components of the stored value.
15.1.2.2 Targeting information extension
The targeting information extension enables the targeting of an attribute certificate to a specific set of servers/services.
An attribute certificate that contains this extension should only be usable at the specified servers/services.
This field is defined as follows.
targetingInformation EXTENSION ::= {
SYNTAX SEQUENCE SIZE (1..MAX) OF Targets
IDENTIFIED BY id-ce-targetInformation }
Targets ::= SEQUENCE SIZE (1..MAX) OF Target
Target : := CHOICE {
targetName [0] GeneralName,
targetGroup [1] GeneralName,
targetCert [2] TargetCert }
TargetCert ::= SEQUENCE {
targetCertificate IssuerSerial,
targetName GeneralName OPTIONAL,
certDigestInfo ObjectDigestInfo OPTIONAL }
The targetName component, if present, provides the name of target servers/services for which the containing attribute
certificate is targeted.
The targetGroup component, if present, provides the name of a target group for which the containing attribute
certificate is targeted. How the membership of a target within a targetGroup is determined is outside the scope of this
Specification.
The targetCert component, if present, identifies target servers/services by reference to their certificate.
This extension may be present in attribute certificates issued by AAs, including SOAs, to entities that may act as
privilege asserters, including other AAs and end-entities. This extension shall not be included in public-key certificates
or in attribute certificates issued to AAs that may not also act as privilege asserters.
If this extension is present in an attribute certificate issued to an entity that is an AA, it applies only to that entity's
assertion of the privileges contained in the certificate. It does not impact the AA ability to issue certificates.
This extension is always critical.
If this extension is present, but the privilege verifier is not among those specified, the attribute certificate should be
rejected.
If this extension is not present, then the attribute certificate is not targeted and may be accepted by any server.
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15.1.2.3 User notice extension
The user notice extension enables an AA to include a notice that should be displayed to the holder, when asserting their
privilege, and/or to a privilege verifier when making use of the attribute certificate containing this extension.
This field is defined as follows:
userNotice EXTENSION ::= {
SYNTAX SEQUENCE SIZE (1..MAX) OF UserNotice
IDENTIFIED BY id-ce-userNotice }
This extension may be present in attribute certificates or public-key certificates issued by AAs, including SOAs, to
entities that may act as privilege asserters, including other AAs and end-entities. This extension shall not be included in
certificates that contain the SOA identifier extension or in certificates issued to AAs that may not also act as privilege
asserters.
If this extension is present in a certificate issued to an entity that is an AA, it applies only to that entity's assertion of the
privileges contained in the certificate. It does not impact the AA ability to issue certificates.
This extension may, at the option of the certificate issuer, be either critical or non-critical.
If this extension is flagged critical, the user notices shall be displayed to a privilege verifier each time a privilege is
asserted. If the privilege asserter supplies the attribute certificate to the privilege verifier (i.e., the privilege verifier does
not retrieve it directly from a repository), the user notices shall also be displayed to the privilege asserter.
If this extension is flagged non-critical, the privilege asserted in the certificate may be granted by a privilege verifier
regardless of whether or not the user notices were displayed to the privilege asserter and/or privilege verifier.
15.1.2.4 Acceptable privilege policies extension
The acceptable privilege policies field is used to constrain the assertion of the assigned privileges for use with a specific
set of privilege policies.
This field is defined as follows:
acceptablePrivilegePolicies EXTENSION ::= {
SYNTAX AcceptablePrivilegePoliciesSyntax
IDENTIFIED BY id-ce-acceptablePrivilegePolicies }
AcceptablePrivilegePoliciesSyntax ::= SEQUENCE SIZE (1..MAX) OF PrivilegePolicy
This extension may be present in attribute certificates or public-key certificates issued by AAs, including SOAs, to
other AAs or to end-entities. If this extension is contained in a public-key certificate it relates only to the subject's
ability to act as a privilege asserter for the privileges contained in the subjectDirectoryAttributes extension.
If present, this extension shall be flagged critical.
If this extension is present and the privilege verifier understands it, the verifier shall ensure that the privilege policy that
these privileges are being compared to is one of those identified in this extension.
If this extension is present, but not understood by the privilege verifier, the certificate shall be rejected.
15.1.2.5 Indirect issuer extension
In some environments, privilege may be delegated indirectly. In such cases, the delegator requests that an AA issue a
certificate delegating privilege on their behalf to another entity. The indirect issuer field is used in either an attribute
certificate or a public-key certificate issued to an AA by an SOA. Presence of this extension means that the subject AA
is authorized by that SOA to act as a proxy and issue certificates that delegate privilege, on behalf of other delegators.
indirectIssuer EXTENSION ::= {
SYNTAX BOOLEAN
IDENTIFIED BY id-ce-indirectIssuer }
This extension is always non-critical.
The indirect issuer matching rule compares for equality a presented value with an attribute value of type
AttributeCertificate.
indirectIssuerMatch MATCHING-RULE ::= {
SYNTAX BOOLEAN
ID id-mr-indirectIssuerMatch }
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This matching rule returns TRUE if the stored value contains the indirectIssuer extension and if the value that is
present in the presented value match the stored value.
15.1.2.6 No assertion extension
If present, this extension indicates that the AC holder cannot assert the privileges indicated in the attributes of the AC.
This field can only be inserted into AA ACs, and not into end entity ACs. If present, this extension shall always be
marked critical.
noAssertion EXTENSION ::= {
SYNTAX NULL
IDENTIFIED BY id-ce-noAssertion }
15.2 Privilege revocation extensions
15.2.1 Requirements
The following requirements relate to revocation of attribute certificates:
a) In order to control CRL sizes, it may be necessary to assign subsets of the set of all certificates issued by
one AA to different CRLs;
b) Attribute certificate issuers need to be able to indicate, in an attribute certificate, that no revocation
information is available for that certificate.
15.2.2 Privilege revocation extension fields
The following extension fields are defined:
a) CRL distribution points;
b) No revocation information.
15.2.2.1 CRL distribution points extension
The CRL distribution points extension is defined in Section 2 of this Specification, for use in public-key certificates.
This field may also be included in an attribute certificate. It may be present in certificates issued to AAs, including
SOAs, as well as certificates issued to end-entities.
If present in a certificate, a privilege verifier shall process this extension in exactly the same manner as described in
Section 2 for public-key certificates.
15.2.2.2 No revocation information extension
In some environments (e.g., where attribute certificates are issued with very short validity periods), there may not be a
need to revoke certificates. An AA may use this extension to indicate that revocation status information is not provided
for this attribute certificate. This field is defined as follows:
noRevAvail EXTENSION ::= {
SYNTAX NULL
IDENTIFIED BY id-ce-noRevAvail }
This extension may be present in attribute certificates issued by AAs, including SOAs, to end-entities. This extension
shall not be included in public-key certificates or in attribute certificates issued to AAs.
This extension is always non-critical.
If this extension is present in an attribute certificate, a privilege verifier need not seek revocation status information.
15.3 Source of Authority extensions
15.3.1 Requirements
The following requirements relate to Sources of Authority:
a) In some environments there is a need for tight control, by a CA, of the entities that can act as SOAs;
b) There is a need to make the valid syntax definitions and domination rules for privilege attributes
available by the responsible SOAs.
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15.3.2 SOA extension fields
The following extension fields are defined:
a) SOA identifier;
b) Attribute descriptor.
15.3.2.1 SOA identifier extension
The SOA identifier extension indicates that the certificate subject may act as an SOA for purposes of privilege
management. As such, the certificate subject may define attributes that assign privilege, issue attribute descriptor
certificates for those attributes and use the private-key corresponding to the certified public-key to issue certificates that
assign privilege to holders. Those subsequent certificates may be attribute certificates or public-key certificates with a
subjectDirectoryAttributes extension containing the privileges.
In some environments, this extension is not required and other mechanisms may be used to determine the entities that
may act as SOAs. This extension is required only in environments where tight centralized control by a CA is required to
manage the entities that act as SOAs.
This field is defined as follows:
sOAIdentifier EXTENSION ::= {
SYNTAX NULL
IDENTIFIED BY id-ce-sOAIdentifier }
If this extension is not present in a certificate, the subject/holder ability to act as an SOA shall be determined by other
means.
This field may only be present in a public-key certificate issued to an SOA. It shall not be included in attribute
certificates or public-key certificates issued to other AAs or to end-entity privilege holders.
Cross-certification applies only to public-key certificates and not to attribute certificates. Therefore, a cross-certificate
issued to the CA that is the issuer of a certificate containing the SOA identifier extension does not provide transitive
trust to the SOA identified in this extension.
This extension is always non-critical.
15.3.2.1.1 SOA identifier match
The SOA identifier matching rule compares a presented value with an attribute value of type Certificate.
sOAIdentifierMatch MATCHING-RULE ::= {
SYNTAX NULL
ID id-mr-sOAIdentifierMatch }
This matching rule returns TRUE if the stored value contains an SOA Identifier extension.
15.3.2.2 Attribute descriptor extension
The definition of a privilege attribute, and the domination rules governing subsequent delegation of that privilege, are
needed by privilege verifiers to ensure that authorization is done correctly. These definitions and rules may be provided
to privilege verifiers in a variety of ways outside the scope of this Specification (e.g., they may be locally configured at
the privilege verifier).
This extension provides one mechanism that can be used by an SOA to make privilege attribute definitions and
associated domination rules available to privilege verifiers. An attribute certificate that contains this extension is called
an attribute descriptor certificate and is a special type of attribute certificate. Although syntactically identical to an
AttributeCertificate, an attribute descriptor certificate:
­ contains an empty SEQUENCE in its attributes field;
­ is a self-issued certificate (i.e., the issuer and holder are the same entity); and
­ includes the attribute descriptor extension.
This field is defined as follows:
attributeDescriptor EXTENSION ::= {
SYNTAX AttributeDescriptorSyntax
IDENTIFIED BY {id-ce-attributeDescriptor } }
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AttributeDescriptorSyntax ::= SEQUENCE {
identifier AttributeIdentifier,
attributeSyntax OCTET STRING (SIZE(1..MAX)),
name [0] AttributeName OPTIONAL,
description [1] AttributeDescription OPTIONAL,
dominationRule PrivilegePolicyIdentifier}
AttributeIdentifier ::= ATTRIBUTE.&id({AttributeIDs})
AttributeIDs ATTRIBUTE ::= {...}
AttributeName ::= UTF8String(SIZE(1..MAX))
AttributeDescription ::= UTF8String(SIZE(1..MAX))
PrivilegePolicyIdentifier ::= SEQUENCE {
privilegePolicy PrivilegePolicy,
privPolSyntax InfoSyntax }
The identifier component of a value of the attributeDescriptor extension is the object identifier identifying the attribute
type.
The attributeSyntax component contains the ASN.1 definition of the attribute's syntax. Such an ASN.1 definition shall
be given as specified for the information component of the Matching Rules operational attribute defined in ITU-T
Rec. X.501 | ISO/IEC 9594-2.
The name component optionally contains a user-friendly name by which the attribute may be recognized.
The description component optionally contains a user-friendly description of the attribute.
The dominationRule component specifies, for the attribute, what it means for a delegated privilege to be "less than" the
corresponding privilege held by the delegator. The privilegePolicy component identifies the instance of privilege policy
that contains the rules, by its object identifier. The privPolSyntax component contains either the privilege policy itself
or a pointer to a location where it can be located. If a pointer is included, an optional hash of the privilege policy can
also be included to allow an integrity check on the referenced privilege policy.
This extension may only be present in attribute descriptor certificates. This extension shall not be present in public-key
certificates or in attribute certificates other than self-issued certificates of SOAs.
This extension shall always be non-critical.
The attribute descriptor certificate, created by the SOA at the time of creation/definition of the corresponding attribute
type, is a means by which the universal constraint of delegating "down" can be understood and enforced in the
infrastructure. In the Directory, attribute certificates that contain this extension would be stored in the
attributeDescriptorCertificate attribute of the SOA's directory entry.
15.3.2.2.1 Attribute descriptor match
The attribute descriptor matching rule compares for equality a presented value with an attribute value of type
AttributeCertificate.
attDescriptor MATCHING-RULE ::= {
SYNTAX AttributeDescriptorSyntax
ID id-mr-attDescriptorMatch }
This matching rule returns TRUE if the stored value contains the attributeDescriptor extension and if components that
are present in the presented value match the corresponding components of the stored value.
15.4 Role extensions
15.4.1 Requirements
The following requirement relates to roles:
­ If a certificate is a role assignment certificate, a privilege verifier needs to be able to locate the
corresponding role specification certificate that contains the specific privileges assigned to the role itself.
15.4.2 Role extension fields
The following extension field is defined:
­ Role specification certificate identifier.
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15.4.2.1 Role specification certificate identifier extension
This extension may be used by an AA as a pointer to a role specification certificate that contains the assignment of
privileges to a role. It may be present in a role assignment certificate (i.e., a certificate that contains the role attribute).
A privilege verifier, when dealing with a role assignment certificate, needs to obtain the set of privileges of that role in
order to determine whether to pass or fail the verification. If the privileges were assigned to the role in a role
specification certificate, this field may be used to locate that certificate.
This field is defined as follows:
roleSpecCertIdentifier EXTENSION ::=
{
SYNTAX RoleSpecCertIdentifierSyntax
IDENTIFIED BY { id-ce-roleSpecCertIdentifier }
}
RoleSpecCertIdentifierSyntax ::= SEQUENCE SIZE (1..MAX) OF RoleSpecCertIdentifier
RoleSpecCertIdentifier ::= SEQUENCE {
roleName [0] GeneralName,
roleCertIssuer [1] GeneralName,
roleCertSerialNumber [2] CertificateSerialNumber OPTIONAL,
roleCertLocator [3] GeneralNames OPTIONAL
}
The roleName identifies the role. This name would be the same as that in the holder component of the role
specification certificate being referenced by this extension.
The roleCertIssuer identifies the AA that issued the referenced role specification certificate.
The roleCertSerialNumber, if present, contains the serial number of the role specification certificate. Note that if the
privileges assigned to the role itself change, then a new role specification certificate would be issued to the role. Any
certificates that contain this extension, including the roleCertSerialNumber component, would then need to be replaced
by certificates that referenced the new serial number. Although this behaviour is required in some environments, it is
undesirable in many others. Typically, this component would be absent, enabling automatic updating of the privileges
assigned to the role itself, without impacting the role assignment certificates.
The roleCertLocator, if present, contains information that can be used to locate the role specification certificate.
This extension may be present in role assignment certificates that are attribute certificates or public-key certificates
issued by AAs, including SOAs, to other AAs or to end-entity privilege holders. This extension shall not be included in
certificates that contain the SOA identifier extension.
If present, this extension can be used by a privilege verifier to locate the role specification certificate.
If this extension is not present, either:
a) other means will be used to locate the role specification certificate; or
b) mechanisms other than a role specification certificate were used to assign privileges to the role (e.g., role
privileges may be locally configured at the privilege verifier).
This extension is always non-critical.
15.4.2.1.1 Role specification certificate ID match
The role specification certificate identifier matching rule compares for equality a presented value with an attribute value
of type AttributeCertificate.
roleSpecCertIdMatch MATCHING-RULE ::= {
SYNTAX RoleSpecCertIdentifierSyntax
ID id-mr-roleSpecCertIdMatch }
This matching rule returns TRUE if the stored value contains the roleSpecCertIdentifier extension and if components
that are present in the presented value match the corresponding components of the stored value.
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15.5 Delegation extensions
15.5.1 Requirements
The following requirements relate to delegation of privileges:
a) End-entity privilege certificates need to be distinguishable from AA certificates, to protect against endentities
establishing themselves as AAs without authorization. It also needs to be possible for an AA to
limit the length of a subsequent delegation path;
b) An AA needs to be able to specify the appropriate name space within which delegation of privilege can
occur. Adherence to these constraints needs to be checkable by the privilege verifier;
c) An AA needs to be able to specify the acceptable certificate policies that privilege asserters further down
a delegation path shall use to authenticate themselves when asserting a privilege delegation by this AA;
d) A privilege verifier needs to be able to locate the corresponding attribute certificate for an issuer to
ensure that the issuer had sufficient privilege to delegate the privilege in the current certificate;
e) There is a requirement for an independent Delegation Service (DS) to issue certificates that delegate
privileges, whilst the DS server cannot itself act as a claimant for those privileges.
15.5.2 Delegation extension fields
The following extension fields are defined:
a) Basic attribute constraints;
b) Delegated name constraints;
c) Acceptable certificate policies;
d) Authority attribute identifier;
e) Indirect Issuer;
f) Issued on behalf of.
15.5.2.1 Basic attribute constraints extension
This field indicates whether subsequent delegation of the privileges assigned in the certificate containing this extension
is permitted. If so, a delegation path length constraint may also be specified.
This field is defined as follows:
basicAttConstraints EXTENSION ::=
{
SYNTAX BasicAttConstraintsSyntax
IDENTIFIED BY { id-ce-basicAttConstraints }
}
BasicAttConstraintsSyntax ::= SEQUENCE
{
authority BOOLEAN DEFAULT FALSE,
pathLenConstraint INTEGER (0..MAX) OPTIONAL
}
The authority component indicates whether or not the holder is authorized to further delegate privilege. If authority is
TRUE the holder is also an AA and is authorized to further delegate privilege, dependent on relevant constraints. If
authority is FALSE, the holder is an end-entity and is not authorized to delegate the privilege.
The pathLenConstraint component is meaningful only if authority is set to TRUE. It gives the maximum number of
AA certificates that may follow this certificate in a delegation path. Value 0 indicates that the subject of this certificate
may issue certificates only to end-entities and not to AAs. If no pathLenConstraint field appears in any certificate of a
delegation path, there is no limit to the allowed length of the delegation path. Note that the constraint takes effect
beginning with the next certificate in the path. The constraint controls the number of AA certificates between the AA
certificate containing the constraint and end-entity certificate. The constraint restricts the length of the segment of the
delegation path between the certificate containing this extension and the end-entity certificate. It has no impact on the
number of AA certificates in the delegation path between the trust anchor and the certificate containing this extension.
Therefore, the length of a complete delegation path may exceed the maximum length of the segment constrained by this
extension. The constraint controls the number of AA certificates between the AA certificate containing the constraint
and the end-entity certificate. Therefore the total length of this segment of the path may exceed the value of the
constraint by as many as two certificates. (This includes the certificates at the two endpoints of the segment plus the AA
certificates between the two endpoints that are constrained by the value of this extension.)
ISO/IEC 9594-8:2005 (E)
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This extension may be present in attribute certificates or public-key certificates issued by AAs, including SOAs, to
other AAs or to end-entities. This extension shall not be included in certificates that contain the SOA identifier
extension.
If this extension is present in an attribute certificate, and authority is TRUE, the holder is authorized to issue subsequent
attribute certificates delegating the contained privileges to other entities, but not public-key certificates.
If this extension is present in a public-key certificate, and if the basicConstraints extension indicates that the subject is
also a CA, the subject is authorized to issue subsequent public-key certificates that delegate these privileges to other
entities, but not attribute certificates. If a path length constraint is included, the subject may only delegate within the
intersection of the constraint specified in this extension and any specified in the basicConstraints extension. If this
extension is present in a public-key certificate but the basicConstraints extension is absent, or indicates that the subject
is an end-entity, the subject is not authorized to delegate the privileges.
This extension may, at the option of the certificate issuer, be either critical or non-critical. It is recommended that it be
flagged critical, otherwise a holder that is not authorized to be an AA may issue certificates and the privilege verifier
may unwittingly use such a certificate.
If this extension is present and is flagged critical, then:
­ if the value of authority is not set to TRUE, then the delegated attribute shall not be used to further
delegate;
­ if the value of authority is set to TRUE and pathLenConstraint is present, then the privilege verifier
shall check that the delegation path being processed is consistent with the value of pathLenConstraint.
If this extension is present, flagged non-critical, and is not recognized by the privilege verifier, then that system should
use other means to determine if the delegated attribute may be used to further delegate.
If this extension is not present, or if the extension is present with an empty SEQUENCE value, the holder is constrained
to being only an end-entity and not an attribute authority and no delegation of the privileges contained in the attribute
certificate is permitted by the holder.
15.5.2.1.1 Basic attribute constraints match
The basic attribute constraints matching rule compares for equality a presented value with an attribute value of type
AttributeCertificate.
basicAttConstraintsMatch MATCHING-RULE ::= {
SYNTAX BasicAttConstraintsSyntax
ID id-mr-basicAttConstraintsMatch }
This matching rule returns TRUE if the stored value contains the basicAttConstraints extension and if components that
are present in the presented value match the corresponding components of the stored value.
15.5.2.2 Delegated name constraints extension
The delegated name constraints field indicates a name space within which all holder names in subsequent certificates in
a delegation path need to be located.
This field is defined as follows:
delegatedNameConstraints EXTENSION ::= {
SYNTAX NameConstraintsSyntax
IDENTIFIED BY id-ce-delegatedNameConstraints }
This extension is processed in the same manner as the nameConstraints extension for public-key certificates. If
permittedSubtrees is present, of all the attribute certificates issued by the holder AA and subsequent AAs in the
delegation path, only those attribute certificates with holder names within these subtrees are acceptable. If
excludedSubtrees is present, any attribute certificate issued by the holder AA or subsequent AAs in the delegation
path that has a holder name within these subtrees is unacceptable. If both permittedSubtrees and excludedSubtrees
are present and the name spaces overlap, the exclusion statement takes precedence.
This extension may be present in attribute certificates or public-key certificates issued by AAs, including SOAs, to
other AAs. This extension shall not be included in certificates issued to end-entities or certificates that contain the SOA
identifier extension.
If this extension is present in a public-key certificate, and if the nameConstraints extension is also present, the subject
may only delegate within the intersection of the constraint specified in this extension and that specified in the
nameConstraints extension.
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This extension may, at the option of the attribute certificate issuer, be either critical or non-critical. It is recommended
that it be flagged critical, otherwise an attribute certificate user may not check that subsequent attribute certificates in a
delegation path are located in the name space intended by the issuing AA.
15.5.2.2.1 Delegated name constraints match
The delegated name constraints matching rule compares for equality a presented value with an attribute value of type
AttributeCertificate.
delegatedNameConstraintsMatch MATCHING-RULE ::= {
SYNTAX NameConstraintsSyntax
ID id-mr-delegatedNameConstraintsMatch}
This matching rule returns TRUE if the stored value contains the attributeNameConstraints extension and if
components that are present in the presented value match the corresponding components of the stored value.
15.5.2.3 Acceptable certificate policies extension
The acceptable certificate policies field is used, in delegation with attribute certificates, to control the acceptable
certificate policies under which the public-key certificates for subsequent holders in a delegation path need to have been
issued. By enumerating a set of policies in this field, an AA is requiring that subsequent issuers in a delegation path
only delegate the contained privileges to holders that have public-key certificates issued under one or more of the
enumerated certificate policies. The policies listed here are not policies under which the attribute certificate was issued,
but policies under which acceptable public-key certificates for subsequent holders need to have been issued.
This field is defined as follows:
acceptableCertPolicies EXTENSION ::= {
SYNTAX AcceptableCertPoliciesSyntax
IDENTIFIED BY id-ce-acceptableCertPolicies }
AcceptableCertPoliciesSyntax ::= SEQUENCE SIZE (1..MAX) OF CertPolicyId
CertPolicyId ::= OBJECT IDENTIFIER
This extension may only be present in attribute certificates issued by AAs, including SOAs, to other AAs. This
extension shall not be included in end-entity attribute certificates or in any public-key certificates. In the case of
delegation using public-key certificates, this same functionality is provided by the certificatePolicies and other related
extensions.
If present, this extension shall be flagged critical.
If this extension is present and the privilege verifier understands it, the verifier shall ensure that all subsequent privilege
asserters in the delegation path are authenticated with a public-key certificate under one or more of the enumerated
certificate policies.
If this extension is present, but not understood by the privilege verifier, the certificate shall be rejected.
15.5.2.3.1 Acceptable certificate policies match
The acceptable certificate policies matching rule compares for equality a presented value with an attribute value of type
AttributeCertificate.
acceptableCertPoliciesMatch MATCHING-RULE ::= {
SYNTAX AcceptableCertPoliciesSyntax
ID id-mr-acceptableCertPoliciesMatch }
This matching rule returns TRUE if the stored value contains the acceptableCertPolicies extension and if components
that are present in the presented value match the corresponding components of the stored value.
15.5.2.4 Authority attribute identifier extension
In privilege delegation, an AA that delegates privileges shall itself have at least the same privilege and the authority to
delegate that privilege. An AA that is delegating privilege to another AA or to an end-entity may place this extension in
the AA or end-entity certificate that it issues. The extension is a back pointer to the certificate in which the issuer of the
certificate containing the extension was assigned its corresponding privilege. The extension can be used by a privilege
verifier to ensure that the issuing AA had sufficient privilege to be able to delegate to the holder of the certificate
containing this extension.
ISO/IEC 9594-8:2005 (E)
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This field is defined as follows:
authorityAttributeIdentifier EXTENSION ::=
{
SYNTAX AuthorityAttributeIdentifierSyntax
IDENTIFIED BY { id-ce-authorityAttributeIdentifier }
}
AuthorityAttributeIdentifierSyntax ::= SEQUENCE SIZE (1..MAX) OF AuthAttId
AuthAttId ::= IssuerSerial
A certificate that contains this extension may include delegation of multiple privileges to the certificate holder. If the
assignment of those privileges to the AA that issued this certificate was done in more than one certificate, then this
extension would include more than one pointer.
This extension may be present in attribute certificates or public-key certificates issued by AAs to other AAs or to endentity
privilege holders. This extension shall not be included in certificates issued by an SOA or in public-key
certificates that contain the SOA identifier extension.
This extension is always non-critical.
15.5.2.4.1 AA identifier match
The authority attribute identifier matching rule compares for equality a presented value with an attribute value of type
AttributeCertificate.
authAttIdMatch MATCHING-RULE ::= {
SYNTAX AuthorityAttirbuteIdentifierSyntax
ID id-mr-authAttIdMatch }
This matching rule returns TRUE if the stored value contains the authorityAttributeIdentifier extension and if
components that are present in the presented value match the corresponding components of the stored value.
15.5.2.5 Indirect issuer extension
In some environments, privilege may be delegated indirectly. In such cases, the delegator requests that a DS server issue
a certificate delegating privilege on their behalf to another entity. The indirect issuer field is used in either an attribute
certificate or a public-key certificate issued to a DS server by an SOA. Presence of this extension means that the subject
AA (the DS server) is authorized by that SOA to act as a proxy and issue certificates that delegate privilege, on behalf
of other delegators.
indirectIssuer EXTENSION ::= {
SYNTAX NULL
IDENTIFIED BY id-ce-indirectIssuer }
This extension is always non-critical.
The indirect issuer matching rule compares for equality a presented value with an attribute value of type
AttributeCertificate.
indirectIssuerMatch MATCHING-RULE ::= {
SYNTAX NULL
ID id-mr-indirectIssuerMatch }
This matching rule returns TRUE if the stored value contains the indirectIssuer extension and if the value that is
present in the presented value matches the stored value.
15.5.2.6 Issued on Behalf Of
This extension is inserted into an AC by an indirect issuer (DS server). It indicates the AA that has requested the DS
server to issue the AC, and allows the delegation chain to be constructed and validated.
issuedOnBehalfOf EXTENSION ::= {
SYNTAX GeneralName
ID id-ce-issuedOnBehalfOf }
The GeneralName is the name of the AA who has asked the indirect issuer (DS server) to issue this AC.
The issuer of this AC must have been granted the privilege to issue ACs on behalf of other AAs by an SOA, through the
IndirectIssuer extension in its AC.
This extension may be critical or non-critical as necessary to ensure delegation path validation.
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16 Privilege path processing procedure
Privilege path processing is carried out by a privilege verifier. The path processing rules for attribute certificates are
somewhat analogous to those for public-key certificates.
Other components of the path processing that are not addressed in this clause include verification of certificate
signatures, validation of certificate validity periods, etc.
For privilege paths consisting of a single certificate (i.e., the privileges were assigned directly to the privilege asserter
by the SOA), only the basic procedure, as described in 16.1 below is required, unless the privilege is assigned to a role.
In that case, if the privilege verifier is not configured with the specific privileges of the role, it may need to obtain the
role specification certificate that assigns the specific privileges to the role as described in 16.2 below. If the privilege
asserter was delegated its privilege by an intermediary AA, then the delegation path procedure in 16.3 is also required.
These procedures are not performed sequentially. The role processing procedure and delegation processing procedure
are done prior to the determination of whether or not the asserted privileges are sufficient for the context of use within
the basic procedure.
16.1 Basic processing procedure
The signature on every certificate in the path shall be verified. Procedures related to validating signatures and publickey
certificates are not repeated in this clause. The privilege verifier shall verify the identity of every entity in the path,
using the procedures of clause 10. Note that checking the signature on an attribute certificate necessarily involves
checking the referenced public-key certificate for its validity. Where privileges are assigned using attribute certificates,
path processing engines will need to consider elements of both the PMI and the PKI in the course of determining the
ultimate validity of a privilege asserter's attribute certificate. Once that validity has been confirmed, the privileges
contained in that certificate may be used depending on a comparison with the relevant privilege policy and other
information associated with the context in which the certificate is being used.
The context of use shall determine if the privilege holder actually intended to assert the contained privilege for use with
that context. The fact that a chain of certificates to a trusted SOA exists is not in itself enough upon which to make this
determination. The willingness of the privilege holder to use that certificate has to be clearly indicated and verified.
However, mechanisms to ensure that such a privilege assertion has been adequately demonstrated by the privilege
holder are outside the scope of this Specification. As an example, such a privilege assertion may be verifiable if the
privilege holder signed a reference to that certificate, thereby indicating their willingness to use that certificate for that
context.
For each attribute certificate in the path that does not contain the noRevAvail extension, the privilege verifier shall
ensure that the attribute certificate has not been revoked.
The privilege verifier shall ensure that the asserted privilege is valid for the time called "time of evaluation" which can
be done for any time, i.e., the current time of checking or any time in the past. In the context of an access control
service, the checking is always done for the present time. However, in the context of non-repudiation, the checking can
be done for a time in the past or the current time. When certificates are validated, the privilege verifier shall ensure that
the time of evaluation falls within all the validity periods of all the certificates used in the path. Also, if any of the
certificates in the path contain the timeSpecification extension, the constraints placed over the times the privilege can
be asserted need to also allow the privilege assertion to be valid at the time of evaluation.
If the targetingInformation extension is present in the certificate used to assert a privilege, the privilege verifier shall
check that the server/service for which it is verifying is included in the list of targets.
If the certificate is a role assignment certificate, the processing procedure described in 16.2 is needed to ensure that the
appropriate privileges are identified. If the privilege was delegated to the entity rather than assigned directly by the SOA
trusted by the privilege verifier, the processing procedure described in 16.3 is needed to ensure that delegation was done
properly.
The privilege verifier shall also determine whether or not the privileges being asserted are sufficient for the context of
use. The privilege policy establishes the rules for making this determination and includes specification of any
environmental variables that need to be considered. The privileges asserted, including those resulting from the role
procedure in 16.2 and the delegation procedure in 16.3 and any relevant environmental variables (e.g., time of day or
current account balance) are compared against the privilege policy to determine whether or not they are sufficient for
the context of use. If the acceptablePrivilegePolicies extension is present, the privilege assertion can only succeed if
the privilege policy the privilege verifier is comparing against is one of those contained in this extension.
If the comparison succeeds, any relevant user notices are provided to the privilege verifier.
ISO/IEC 9594-8:2005 (E)
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16.2 Role processing procedure
If the asserted certificate is a role assignment certificate, the privilege verifier shall obtain the specific privileges
assigned to that role. The name of the role to which the privilege asserter is assigned is contained in the role attribute of
the certificate. The privilege verifier, if not already configured with the privileges of the named role, may need to locate
the role specification certificate that assigns the privileges to that role. Information in the role attribute and in the
roleSpecCertIdentifier extension may be used to locate that certificate.
The privileges assigned to the role are implicitly assigned to the privilege asserter and are therefore included among the
asserted privileges that are compared against the privilege policy in the basic procedure in 16.1 to determine whether or
not the asserted privileges are sufficient for the context of use.
16.3 Delegation processing procedure
If the privileges asserted are delegated to the privilege asserter by an intermediary AA, the privilege verifier shall ensure
that the path is a valid delegation path, by ensuring that:
­ each AA that issued a certificate in the delegation path was authorized to do so;
­ each certificate in the delegation path is valid with respect to path and name constraints imposed on it;
­ each entity in the delegation path is authenticated with a public-key certificate that is valid according to
any imposed policy constraints;
­ no AA delegation privilege is greater than the privilege held by that AA.
Prior to commencing delegation path validation, the privilege verifier shall obtain the following. Any of these may be
provided by the privilege asserter, or obtained by the privilege verifier from some other source, such as the Directory.
The attributes of the service may be provided to the privilege verifier in a structured document or by some other means.
­ Established trust in the public verification key used to validate the trusted SOA's signature. This trust can
either be established through out-of-band means or through a public-key certificate issued to the SOA by
a CA in which the privilege verifier already has established trust. Such a certificate would contain the
sOAIdentifier extension.
­ The privilege asserter's privilege, encoded in their attribute certificate or subject directory attributes
extension of their public key certificate.
­ Delegation path of certificates from the privilege asserter to the trusted SOA.
­ Domination rule for the privilege being asserted; this may be obtained from the attribute descriptor
issued by the SOA responsible for the attribute in question or it may be obtained through out-of-band
means.
­ Privilege policy; this may be obtained from the Directory or from some out-of-band means.
­ Environmental variables, including for example current date/time, current account balance, etc.
An implementation shall be functionally equivalent to the external behaviour resulting from this procedure; however,
the algorithm used by a particular implementation to derive the correct output(s) from the given inputs is not
standardized.
In the case where attribute certificates are issued by an indirect issuer (DS), the relying party should fully validate the
delegation chain as follows:
i) Starting with the end entity AC, the RP extracts the issuer name and the issuedOnBehalfOf name.
ii) The RP retrieves the AC of the issuer and validates that the issuer is an indirect issuer of the SOA
(i.e., has the indirectIssuer extension).
iii) The RP retrieves the AC of the issuedOnBehalfOf AA and validates that the AA has a superset of the
privilege attributes issued to the end entity.
The RP recurses to step ii) using the AC of the AA, and thereby moves up the chain until it arrives at the AC of an AA
that is issued by the SOA.
16.3.1 Verify integrity of domination rule
The domination rule is associated with the privilege being delegated. The syntax and method for obtaining the
domination rule is not standardized. However, the integrity of the retrieved domination rule can be verified. The
attribute descriptor certificate issued by the SOA responsible for the attribute being delegated may contain a HASH of
the domination rule. The privilege verifier may reproduce the HASH function on the retrieved copy of the domination
rule and compare the two hashes. If they are identical, the privilege verifier has the accurate domination rule.
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16.3.2 Establish valid delegation path
The privilege verifier shall find the delegation path and obtain certificates for every entity in the path. The delegation
path extends from the direct privilege asserter to the SOA. Each intermediary certificate in the delegation path shall
contain the basicAttConstraints extension with the authority component set to TRUE. The issuer of each certificate
shall be the same as the holder/subject of the certificate which is adjacent to it in the delegation path. The
authorityAttributeIdentifier extension is used to locate the appropriate certificate of the adjacent entity in the
delegation path. The number of certificates in the path from each entity to the direct privilege asserter (inclusive) shall
not exceed the value of the pathLenConstraint value in the entity's basicAttConstraints extension by more than 2.
This is because the pathLenConstraint limits the number of intermediary certificates between the two endpoints
(i.e., the certificate containing the constraint and the end-entity certificate) so the maximum length is the value of that
constraint plus the certificates that are the endpoints.
If delegatedNameConstraints extension is present in any of the certificates in the delegation path, the constraints are
processed in the same way as the nameConstraints extension is processed in the certification path processing
procedure in clause 10.
If the acceptableCertPolicies extension is present in any of the certificates in the delegation path, the privilege verifier
shall ensure that the authentication of each subsequent entity in the delegation path is done with a public-key certificate
that contains at least one of the acceptable policies.
16.3.3 Verify privilege delegation
No delegator can delegate privilege that is greater than the privilege they own. The domination rule in the attribute
descriptor attribute provides the rules for when a given value is 'less than' another value for the attribute being
delegated.
For each certificate in the delegation path, including the direct privilege asserter's certificate, the privilege verifier shall
ensure that the delegator was authorized to delegate the privilege they own and that the privilege delegated was not
greater than the privilege owned.
For each of these certificates, the privilege verifier shall compare the delegated privilege with the privilege owned by
that delegator, in accordance with the domination rule for the privilege. The privilege owned by the delegator is
obtained from the adjacent certificate in the delegation path, as described in 16.2. The comparison of the two privileges
is done based on the domination rule discussed in 16.3.1.
16.3.4 Pass/fail determination
Assuming that a valid delegation path is established, the privileges of the direct privilege asserter are provided as input
for the comparison against the privilege policy as discussed in 16.1 to determine whether or not the direct privilege
asserter has sufficient privilege for the context of use.
17 PMI directory schema
This clause defines the directory schema elements used to represent PMI information in the Directory. It includes
specification of relevant object classes, attributes and attribute value matching rules.
17.1 PMI directory object classes
This subclause defines object class definitions for representing PMI objects in the Directory.
17.1.1 PMI user object class
The PMI user object class is used in defining entries for objects that may be the holder of attribute certificates.
pmiUser OBJECT-CLASS ::= {
-- a PMI user (i.e., a "holder")
SUBCLASS OF {top}
KIND auxiliary
MAY CONTAIN {attributeCertificateAttribute}
ID id-oc-pmiUser }
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17.1.2 PMI AA object class
The PMI AA object class is used in defining entries for objects that act as attribute authorities.
pmiAA OBJECT-CLASS ::= {
-- a PMI AA
SUBCLASS OF {top}
KIND auxiliary
MAY CONTAIN {aACertificate |
attributeCertificateRevocationList |
attributeAuthorityRevocationList}
ID id-oc-pmiAA }
17.1.3 PMI SOA object class
The PMI SOA object class is used in defining entries for objects that act as sources of authority. Note that if the object
was authorized to act as an SOA through issuance of a public-key certificate containing the sOAIdentifier extension, a
directory entry representing that object would also contain the pkiCA object class.
pmiSOA OBJECT-CLASS ::= { -- a PMI Source of Authority
SUBCLASS OF {top}
KIND auxiliary
MAY CONTAIN {attributeCertificateRevocationList |
attributeAuthorityRevocationList |
attributeDescriptorCertificate}
ID id-oc-pmiSOA }
17.1.4 Attribute certificate CRL distribution point object class
The attribute certificate CRL distribution point object class is used in defining entries for objects that contain attribute
certificate and/or attribute authority revocation list segments. This auxiliary class is intended to be combined with the
crlDistributionPoint structural object class when instantiating entries. Since the certificateRevocationList and
authorityRevocationList attributes are optional in that class, it is possible to create entries which contain, for example,
only an attribute authority revocation list or entries which contain revocation lists of multiple types, depending on the
requirements.
attCertCRLDistributionPt OBJECT-CLASS ::= {
SUBCLASS OF {top}
KIND auxiliary
MAY CONTAIN { attributeCertificateRevocationList |
attributeAuthorityRevocationList }
ID id-oc-attCertCRLDistributionPts }
17.1.5 PMI delegation path
The PMI delegation path object class is used in defining entries for objects that may contain delegation paths. It will
generally be used in conjunction with entries of structural object class pmiAA.
pmiDelegationPath OBJECT-CLASS ::= {
SUBCLASS OF {top}
KIND auxiliary
MAY CONTAIN { delegationPath }
ID id-oc-pmiDelegationPath }
17.1.6 Privilege policy object class
The privilege policy object class is used in defining entries for objects that contain privilege policy information.
privilegePolicy OBJECT-CLASS ::= {
SUBCLASS OF {top}
KIND auxiliary
MAY CONTAIN {privPolicy }
ID id-oc-privilegePolicy }
17.1.7 Protected privilege policy object class
The protected privilege policy object class is used in defining entries for objects that contain privilege policies protected
within attribute certificates.
protectedPrivilegePolicy OBJECT-CLASS ::= {
SUBCLASS OF {top}
KIND auxiliary
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MAY CONTAIN {protPrivPolicy }
ID id-oc-protectedPrivilegePolicy }
17.2 PMI Directory attributes
This subclause defines directory attributes used to store PMI data in directory entries.
17.2.1 Attribute certificate attribute
The following attribute contains attribute certificates issued to a specific holder and is stored in the directory entry of
that holder.
attributeCertificateAttribute ATTRIBUTE ::= {
WITH SYNTAX AttributeCertificate
EQUALITY MATCHING RULE attributeCertificateExactMatch
ID id-at-attributeCertificate }
17.2.2 AA certificate attribute
The following attribute contains attribute certificates issued to an AA and is stored in the directory entry of the
holder AA.
aACertificate ATTRIBUTE ::= {
WITH SYNTAX AttributeCertificate
EQUALITY MATCHING RULE attributeCertificateExactMatch
ID id-at-aACertificate }
17.2.3 Attribute descriptor certificate attribute
The following attribute contains attribute certificates issued by an SOA that contain the attributeDescriptor extension.
These attribute certificates contain the valid syntax and domination rule specification of privilege attributes and is
stored in the directory entry of the issuing SOA.
attributeDescriptorCertificate ATTRIBUTE ::= {
WITH SYNTAX AttributeCertificate
EQUALITY MATCHING RULE attributeCertificateExactMatch
ID id-at-attributeDescriptorCertificate }
17.2.4 Attribute certificate revocation list attribute
The following attribute contains a list of revoked attribute certificates. These lists may be stored in the directory entry of
the issuing authority, or other directory entry (e.g., a distribution point).
attributeCertificateRevocationList ATTRIBUTE ::= {
WITH SYNTAX CertificateList
EQUALITY MATCHING RULE certificateListExactMatch
ID id-at-attributeCertificateRevocationList}
17.2.5 AA certificate revocation list attribute
The following attribute contains a list of revoked attribute certificates issued to AAs. These lists may be stored in the
directory entry of the issuing authority or other directory entry (e.g., a distribution point).
attributeAuthorityRevocationList ATTRIBUTE ::= {
WITH SYNTAX CertificateList
EQUALITY MATCHING RULE certificateListExactMatch
ID id-at-attributeAuthorityRevocationList }
17.2.6 Delegation path attribute
The delegation path attribute contains delegation paths, each consisting of a sequence of attribute certificates.
delegationPath ATTRIBUTE ::= {
WITH SYNTAX AttCertPath
ID id-at-delegationPath }
AttCertPath ::= SEQUENCE OF AttributeCertificate
This attribute can be stored in the AA directory entry and would contain some delegation paths from that AA to other
AAs. This attribute, if used, enables more efficient retrieval of delegated attribute certificates that form frequently used
delegation paths. As such, there are no specific requirements for this attribute to be used and the set of values that are
stored in the attribute is unlikely to represent the complete set of delegation paths for any given AA.
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17.2.7 Privilege policy attribute
The privilege policy attribute contains information about privilege policies.
privPolicy ATTRIBUTE ::= {
WITH SYNTAX PolicySyntax
ID id-at-privPolicy }
The policyIdentifier component includes the object identifier registered for the particular privilege policy.
If content is present, the complete content of the privilege policy is included.
If pointer is present, the name component references one or more locations where a copy of the privilege policy can be
located. If the hash component is present, it contains a HASH of the content of the privilege policy that should be
found at a referenced location. This hash can be used to perform an integrity check of the referenced document.
17.2.8 Protected privilege policy attribute
The protected privilege policy attribute contains privilege policies, protected within attribute certificates.
protPrivPolicy ATTRIBUTE ::= {
WITH SYNTAX AttributeCertificate
EQUALITY MATCHING RULE attributeCertificateExactMatch
ID id-at-protPrivPolicy }
Note that unlike typical attribute certificates, those within the protPrivPolicy attribute contain privilege policies, not
privileges. The issuer and holder components of these attribute certificates identify the same entity. The attribute that is
included in the attribute certificate contained within the protPrivPolicy attribute is either the privPolicy attribute or the
xmlPrivPolicy attribute.
17.2.9 XML Protected privilege policy attribute
The XML protected privilege policy attribute contains XML encoded privilege policy information.
xmlPrivPolicy ATTRIBUTE ::= {
WITH SYNTAX UTF8String -- contains XML-encoded privilege policy information
ID id-at-xMLPprotPrivPolicy }
17.3 PMI general directory matching rules
This subclause defines matching rules for PMI directory attributes.
17.3.1 Attribute certificate exact match
The attribute certificate exact match rule compares for equality a presented value with an attribute value of type
AttributeCertificate.
attributeCertificateExactMatch MATCHING-RULE ::= {
SYNTAX AttributeCertificateExactAssertion
ID id-mr-attributeCertificateExactMatch }
AttributeCertificateExactAssertion ::= SEQUENCE {
serialNumber CertificateSerialNumber,
issuer AttCertIssuer }
This matching rule returns TRUE if the components in the attribute value match those in the presented value.
17.3.2 Attribute certificate match
The attribute certificate matching rule compares a presented value with an attribute value of type AttributeCertificate.
This matching rule allows more complex matching than the certificateExactMatch.
attributeCertificateMatch MATCHING-RULE ::= {
SYNTAX AttributeCertificateAssertion
ID id-mr-attributeCertificateMatch }
AttributeCertificateAssertion ::= SEQUENCE {
holder [0] CHOICE {
baseCertificateID [0] IssuerSerial,
holdertName [1] GeneralNames} OPTIONAL,
issuer [1] GeneralNames OPTIONAL,
attCertValidity [2] GeneralizedTime OPTIONAL,
attType [3] SET OF AttributeType OPTIONAL}
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-- At least one component of the sequence shall be present
The matching rule returns TRUE if all of the components that are present in the presented value match the
corresponding components of the attribute value, as follows:
­ baseCertificateID matches if it is equal to the IssuerSerial component of the stored attribute value;
­ holderName matches if the stored attribute value contains the name extension with the same name type
as indicated in the presented value;
­ issuer matches if the stored attribute value contains the name component of the same name type as
indicated in the presented value;
­ attCertValidity matches if it falls within the specified validity period of the stored attribute value; and
­ for each attType in the presented value, there is an attribute of that type present in the attributes
component of the stored value.
17.3.3 Holder issuer match
The attribute certificate holder issuer match rule compares for equality a presented value of the holder and/or issuer
components of a presented value with an attribute value of type AttributeCertificate.
holderIssuerMatch MATCHING-RULE ::= {
SYNTAX HolderIssuerAssertion
ID id-mr-holderIssuerMatch }
HolderIssuerAssertion ::= SEQUENCE {
holder [0] Holder OPTIONAL,
issuer [1] AttCertIssuer OPTIONAL }
This matching rule returns TRUE if all the components that are present in the presented value match the corresponding
components of the attribute value.
17.3.4 Delegation path match
The delegationPathMatch match rule compares for equality a presented value with an attribute value of type
delegationPath. A privilege verifier may use this matching rule to select a path beginning with a certificate issued by
its SOA and ending with a certificate issued to the AA that issued the end-entity holder certificate being validated.
delegationPathMatch MATCHING-RULE ::= {
SYNTAX DelMatchSyntax
ID id-mr-delegationPathMatch }
DelMatchSyntax ::= SEQUENCE {
firstIssuer AttCertIssuer,
lastHolder Holder }
This matching rule returns TRUE if the presented value in the firstIssuer component matches the corresponding
elements of the issuer field of the first certificate in the SEQUENCE in the stored value and the presented value in the
lastHolder component matches the corresponding elements of the holder field of the last certificate in the SEQUENCE
in the stored value. This matching rule returns FALSE if either match fails.
SECTION 4 ­ DIRECTORY USE OF PUBLIC-KEY & ATTRIBUTE CERTIFICATE
FRAMEWORKS
The Directory uses the public-key certificate framework as the foundation for a number of security services including
strong authentication and protection of Directory operations as well as protection of stored data. The Directory uses the
attribute certificate framework as the foundation for rule-based access control scheme. The relationship of the elements
of the public-key certificate framework and of the attribute certificate framework to the various Directory security
services is defined here. The specific security services provided by the Directory are fully specified over the complete
set of Directory Specifications.
18 Directory authentication
The Directory supports authentication of users accessing the Directory via DUAs and authentication of directory
systems (DSAs) to users and to other DSAs. Depending on the environment, either simple or strong authentication may
be used. The procedures to be used for simple and strong authentication in the Directory are described in the following
subclauses.
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18.1 Simple authentication procedure
Simple authentication is intended to provide local authorization based upon the distinguished name of a user, a
bilaterally agreed (optional) password, and a bilateral understanding of the means of using and handling this password
within a single domain. Utilization of simple authentication is primarily intended for local use only, i.e., for peer entity
authentication between one DUA and one DSA or between one DSA and one DSA. Simple authentication may be
achieved by several means:
a) the transfer of the user's distinguished name and (optional) password in the clear (non-protected) to the
recipient for evaluation;
b) the transfer of the user's distinguished name, password, and a random number and/or a timestamp, all of
which are protected by applying a one-way function;
c) the transfer of the protected information described in b) together with a random number and/or a
timestamp, all of which is protected by applying a one-way function.
NOTE 1 ­ There is no requirement that the one-way functions applied be different.
NOTE 2 ­ The signalling of procedures for protecting passwords may be a matter for extension to the document.
Where passwords are not protected, a minimal degree of security is provided for preventing unauthorized access. It
should not be considered a basis for secure services. Protecting the user's distinguished name and password provides
greater degrees of security. The algorithms to be used for the protection mechanism are typically non-enciphering oneway
functions that are very simple to implement.
The general procedure for achieving simple authentication is shown in Figure 5.
Figure 5 ­ The unprotected simple authentication procedure
The following steps are involved:
1) An originating user A sends its distinguished name and password to a recipient user B;
2) B sends the purported distinguished name and password of A to the Directory, where the password is
checked against that held as the UserPassword attribute within the directory entry for A (using the
Compare operation of the Directory);
3) The Directory confirms (or denies) to B that the credentials are valid;
4) The success (or failure) of authentication may be conveyed to A.
The most basic form of simple authentication involves only step 1) and after B has checked the distinguished name and
password, may include step 4).
18.1.1 Generation of protected identifying information
Figure 6 illustrates two approaches by which protected identifying information may be generated. f1 and f2 are one-way
functions (either identical or different) and the timestamps and random numbers are optional and subject to bilateral
agreements.
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Figure 6 ­ Protected simple authentication
18.1.2 Procedure for protected simple authentication
Figure 7 illustrates the procedure for protected simple authentication.
Figure 7 ­ The protected simple authentication procedure
The following steps are involved (initially using f1 only):
1) An originating user, user A, sends its protected identifying information (Authenticator1) to user B.
Protection is achieved by applying the one-way function (f1) of Figure 6, where the timestamp and/or
random number (when used) is used to minimize replay and to conceal the password.
The protection of A's password is of the form:
Protected1 = f1 (t1A, q1A, A, passwA)
The information conveyed to B is of the form:
Authenticator1 = t1A, q1A, A, Protected1
2) B verifies the protected identifying information offered by A by generating (using the distinguished
name and optional timestamp and/or random number provided by A, together with a local copy of A's
password) a local protected copy of A's password (of the form Protected1). B compares for equality the
purported identifying information (Protected1) with the locally generated value.
3) B confirms or denies to A the verification of the protected identifying information.
The procedure can be modified to afford greater protection using f1 and f2. The main differences are as follows:
1) A sends its additionally protected identifying information (Authenticator2) to B. Additional protection is
achieved by applying a further one-way function, f2, as illustrated in Figure 6. The further protection is
of the form:
Protected2 = f2 (t2A
, q2A
, Protected1)
The information conveyed to B is of the form:
Authenticator2 = t1A
, t2A
, q1A
, q2A
, A, Protected2
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For comparison, B generates a local value of A's additionally protected password and compares it for equality with that
of Protected2.
2) B confirms or denies to A the verification of the protected identifying information.
NOTE ­ The procedures defined in these clauses are specified in terms of A and B. As applied to the Directory (specified in
ITU-T Rec. X.511 | ISO/IEC 9594-3 and ITU-T Rec. X.518 | ISO/IEC 9594-4), A could be a DUA binding to a DSA, B;
alternatively, A could be a DSA binding to another DSA, B.
18.1.3 User Password attribute type
A User Password attribute type contains the password of an object. An attribute value for the user password is a string
specified by the object.
userPassword ATTRIBUTE ::= {
WITH SYNTAX OCTET STRING (SIZE (0..ub-user-password))
EQUALITY MATCHING RULE octetStringMatch
ID id-at-userPassword }
18.2 Strong Authentication
The procedures described in this subclause are for use in authentication between a DUA and a DSA as well as between
pairs of DSAs. The procedures make use of the public-key certificate framework defined in this Specification. In
addition, the procedures make use of the Directory itself as the repository for public-key information required to
perform the authentication. The inclusion of relevant parameters in Directory protocols is defined in the protocol
specifications themselves. The procedures defined here for strong authentication may also be used by applications other
than the Directory that also make use of such a repository. For the Directory use of these procedures, the term 'user' in
these procedures can refer to either a DUA or a DSA.
The approach to strong authentication taken in this Directory Specification makes use of the properties of a family of
cryptographic systems, known as public-key cryptosystems (PKCS). These cryptosystems, also described as
asymmetric, involve a pair of keys, one private and one public, rather than a single key as in conventional cryptographic
systems. Annex E gives a brief introduction to these cryptosystems and the properties which make them useful in
authentication. For a PKCS to be usable in this authentication framework at this present time, it shall have the property
that both keys in the key pair can be used for encipherment, with the private key being used to decipher if the public key
was used, and the public key being used to decipher if the private key was used. In other words, Xp ˇ Xs = Xs ˇ Xp,
where Xp/Xs are encipherment/decipherment functions using the public/private keys of user X.
NOTE ­ Alternative types of PKCS, i.e., ones which do not require the property of permutability and that can be supported
without great modification to this Directory Specification, are a possible future extension.
This authentication framework does not mandate a particular cryptosystem for use. It is intended that the framework
shall be applicable to any suitable public key cryptosystem, and shall thus support changes to the methods used as a
result of future advances in cryptography, mathematical techniques or computational capabilities. However, two users
wishing to authenticate shall support the same cryptographic algorithm for authentication to be performed correctly.
Thus, within the context of a set of related applications, the choice of a single algorithm shall serve to maximize the
community of users able to authenticate and communicate securely.
Authentication relies on each user possessing a unique distinguished name. The allocation of distinguished names is the
responsibility of the Naming Authorities. Each user shall therefore trust the Naming Authorities not to issue duplicate
distinguished names.
Each user is identified by its possession of its private key. A second user is able to determine if a communication
partner is in possession of the private key, and can use this to corroborate that the communication partner is in fact the
user. The validity of this corroboration depends on the private key remaining confidential to the user.
For a user to determine that a communication partner is in possession of another user's private key, it shall itself be in
possession of that user's public key. Whilst obtaining the value of this public key from the user's entry in the Directory
is straightforward, verifying its correctness is more problematic. There are many possible ways for doing this:
subclause 18.2.1 describes a process whereby a user's public key can be checked by reference to the Directory. This
process can only operate if there is an unbroken chain of trusted points in the Directory between the users requiring to
authenticate. Such a chain can be constructed by identifying a common point of trust. This common point of trust shall
be linked to each user by an unbroken chain of trusted points.
18.2.1 Obtaining public-key certificates from the directory
Certificates are held within directory entries as attributes of type UserCertificate, CACertificate and CrossCertificatePair.
These attribute types are known to the Directory. These attributes can be operated on using the same protocol operations
as other attributes. The definition of these types can be found in 3.3; the specification of these attribute types is defined
in 11.2.
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In the general case, before users can mutually authenticate, the Directory shall supply the complete certification and
return certification paths. However, in practice, the amount of information which shall be obtained from the Directory
can be reduced for a particular instance of authentication by:
a) if the two users that want to authenticate are served by the same certification authority, then the
certification path becomes trivial, and the users unwrap each other's certificates directly;
b) if the CAs of the users are arranged in a hierarchy, a user could store the public keys, certificates and
reverse certificates of all certification authorities between the user and the root of the DIT. Typically, this
would involve the user in knowing the public keys and certificates of only three or four certification
authorities. The user would then only require to obtain the certification paths from the common point of
trust;
c) if a user frequently communicates with users certified by a particular other CA, that user could learn the
certification path to that CA and the return certification path from that CA, making it necessary only to
obtain the certificate of the other user itself from the Directory;
d) certification authorities can cross-certify one another by bilateral agreement. The result is to shorten the
certification path;
e) if two users have communicated before and have learned one another's certificates, they are able to
authenticate without any recourse to the Directory.
In any case, having learned each other's certificates from the certification path, the users shall check the validity of the
received certificates.
18.2.1.1 Example
Figure 8 illustrates a hypothetical example of a DIT fragment, where the CAs form a hierarchy. Besides the information
shown at the CAs, we assume that each user knows the public key of its certification authority, and its own public and
private keys.
Figure 8 ­ CA hierarchy ­ A hypothetical example
If the CAs of the users are arranged in a hierarchy, A can acquire the following certificates from the Directory to
establish a certification path to B:
X<<W>>, W<<V>>, V<<Y>>, Y<<Z>>, Z<<B>>
When A has obtained these certificates, it can unwrap the certification path in sequence to yield the contents of the
certificate of B, including Bp:
Bp = Xp ˇ X<<W>> W<<V>> V<<Y>> Y<<Z>> Z<<B>>
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In general, A also has to acquire the following certificates from the Directory to establish the return certification path
from B to A:
Z<<Y>>, Y<<V>>, V<<W>>, W<<X>>, X<<A>>
When B receives these certificates from A, it can unwrap the return certification path in sequence to yield the contents
of the certificate of A, including Ap:
Ap = Zp ˇ Z<<Y>> Y<<V>> V<<W>> W<<X>> X<<A>>
Applying the optimizations of 18.2.1:
a) taking A and C, for example: both know Xp, so that A simply has to directly acquire the certificate of C.
Unwrapping the certification path reduces to:
Cp = Xp ˇ X<<C>>
and unwrapping the return certification Path reduces to:
Ap = Xp ˇ X<<A>>
b) assuming that A would thus know W<<X>>, Wp, V<<W>>, Vp, U<<V>>, Up, etc. reduces the
information which A has to obtain from the Directory to form the certification path to:
V<<Y>>, Y<<Z>>, Z<<B>>
and the information which A has to obtain from the Directory to form the return certification path to:
Z<<Y>>, Y<<V>>
c) assuming that A frequently communicates with users certified by Z, it can learn (in addition to the public
keys learned in b) above) V<<Y>>, Y<<V>>, Y<<Z>>, and Z<<Y>>. To communicate with B, it need
therefore only obtain Z<<B>> from the Directory.
d) assuming that users certified by X and Z frequently communicate, then X<<Z>> would be held in the
directory entry for X, and vice versa (this is shown in Figure 8). If A wants to authenticate to B, A need
only obtain:
X<<Z>>, Z<<B>>
to form the certification path, and:
Z<<X>>
to form the return certification path.
e) assuming users A and C have communicated before and have learned one another's certificates, they may
use each other's public key directly, i.e.,
Cp = Xp ˇ X<<C>>
and
Ap = Xp ˇ X<<A>>
In the more general case the Certification Authorities do not relate in a hierarchical manner. Referring to the
hypothetical example in Figure 9, suppose a user D, certified by U, wishes to authenticate to user E, certified by W. The
Directory entry of user D shall hold the certificate U<<D>> and the entry of user E shall hold the certificate W<<E>>.
Figure 9 ­ Non-hierarchical certification path ­ An example
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Let V be a CA with whom CAs U and W have at some previous time exchanged public keys in a trusted way. As a
result, certificates U<<V>>, V<<U>>, W<<V>> and V<<W>> have been generated and stored in the Directory.
Assume U<<V>> and W<<V>> are stored in the entry of V, V<<U>> is stored in U's entry, and V<<W>> is stored in
W's entry.
User D needs to find a certification path to E. Various strategies could be used. One such strategy would be to regard
the users and CAs as nodes, and the certificates as arcs in a directed graph. in these terms, D has to perform a search in
the graph to find a path from U to E, one such being U<<V>>, V<<W>>, W<<E>>. When this path has been
discovered, the reverse path W<<V>>, V<<U>>, U<<D>> can also be constructed.
18.2.2 Strong authentication procedures
The basic approach to authentication has been outlined above, namely the corroboration of identity by demonstrating
possession of a private key. However, many authentication procedures employing this approach are possible. In general
it is the business of a specific application to determine the appropriate procedures, so as to meet the security policy of
the application. This clause describes three particular authentication procedures, which may be found useful across a
range of applications.
NOTE ­ This Directory Specification does not specify the procedures to the detail required for implementation. However,
additional standards could be envisaged which would do so, either in an application-specific or in a general-purpose way.
The three procedures involve different numbers of exchanges of authentication information, and consequently provide
different types of assurance to their participants. Specifically:
a) one-way authentication, described in 18.2.2.1, involves a single transfer of information from one user (A)
intended for another (B), and establishes the following:
­ the identity of A, and that the authentication token actually was generated by A;
­ the identity of B, and that the authentication token actually was intended to be sent to B;
­ the integrity and "originality" (the property of not having been sent two or more times) of the
authentication token being transferred.
The latter properties can also be established for arbitrary additional data accompanying the transfer;
b) two-way authentication, described in 18.2.2.2, involves, in addition, a reply from B to A. It establishes,
in addition, the following:
­ that the authentication token generated in the reply actually was generated by B and was intended to
be sent to A;
­ the integrity and originality of the authentication token sent in the reply;
­ (optionally) the mutual secrecy of part of the tokens;
c) three-way authentication, described in 18.2.2.3, involves, in addition, a further transfer from A to B. It
establishes the same properties as the two-way authentication, but does so without the need for
association timestamp checking.
In each case where Strong Authentication is to take place, A shall obtain the public key of B, and the return certification
path from B to A, prior to any exchange of information. This may involve access to the Directory, as described in 18.2.
Any such access is not mentioned again in the description of the procedures below.
The checking of timestamps as mentioned in the following clauses only applies when either synchronized clocks are
used in a local environment, or if clocks are logically synchronized by bilateral agreements. In any case, it is
recommended that Coordinated Universal Time be used.
For each of the three authentication procedures described below, it is assumed that party A has checked the validity of
all of the certificates in the certification path.
18.2.2.1 One-way authentication
The following steps are involved, as depicted in Figure 10:
1) A generates rA
, a non-repeating number, which is used to detect replay attacks and to prevent forgery.
2) A sends the following message to B:
BA, A{tA
, rA
, B}
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where tA
is a timestamp. tA
consists of one or two dates: the generation time of the token (which is
optional) and the expiry date. Alternatively, if data origin authentication of "sgnData" is to be provided
by the digital signature:
BA, A{tA
, rA
, B, sgnData}
In cases where information is to be conveyed which will subsequently be used as a private key (this
information is referred to as "encData" ):
BA, A{tA
, rA
, B, sgnData, Bp[encData]}
The use of "encData" as a private key implies that it shall be chosen carefully, e.g., to be a strong key for
whatever cryptosystem is used as indicated in the "sgnData" field of the token.
3) B carries out the following actions:
a) obtains Ap from BA, checking that A's certificate has not expired;
b) verifies the signature, and thus the integrity of the signed information;
c) checks that B itself is the intended recipient;
d) checks that the timestamp is "current";
e) optionally, checks that rA
has not been replayed. This could, for example, be achieved by having rA
include a sequential part that is checked by a local implementation for its value uniqueness.
rA
is valid until the expiry date indicated by tA
. rA
is always accompanied by a sequential part, which
indicates that A shall not repeat the token during the timerange tA
and therefore that checking of the
value of rA
itself is not required.
In any case it is reasonable for party B to store the sequential part together with timestamp tA
in the
clear and together with the hashed part of the token during timerange tA
.
Figure 10 ­ One-way authentication
18.2.2.2 Two-way authentication
The following steps are involved, as depicted in Figure 11:
1) as for 18.2.2.1;
2) as for 18.2.2.1;
3) as for 18.2.2.1;
4) B generates rB
, a non-repeating number, used for similar purpose(s) to rA
;
5) B sends the following authentication token to A:
B{tB
, rB
, A, rA
}
where tB
is a timestamp defined in the same way as tA
.
Alternatively, if data origin authentication of "sgnData" is to be provided by the digital signature:
B{tB
, rB
, A, rA
, sgnData}
In cases where information is to be conveyed which will subsequently be used as a private key (this
information is referred to as "encData" ):
B{tB
, rB
, A, rA
, sgnData, Ap[encData]}
ISO/IEC 9594-8:2005 (E)
98 ITU-T Rec. X.509 (08/2005)
The use of "encData" as a private key implies that it shall be chosen carefully, e.g., to be a strong key for
whatever cryptosystem is used as indicated in the "sgnData" field of the token.
6) A carries out the following actions:
a) verifies the signature, and thus the integrity of the signed information;
b) checks that A is the intended recipient;
c) checks that the timestamp tB is "current";
d) optionally, checks that rB has not been replayed (see 18.2.2.1, step 3), d)).
Figure 11 ­ Two-way authentication
18.2.2.3 Three-way authentication
The following steps are involved, as depicted in Figure 12:
1) as for 18.2.2.2;
2) as for 18.2.2.2. Timestamp tA
may be zero;
3) as for 18.2.2.2, except that the timestamp need not be checked;
4) as for 18.2.2.2;
5) as for 18.2.2.2. Timestamp tB
may be zero;
6) as for 18.2.2.2, except that the timestamp need not be checked;
7) A checks that the received rA
is identical to the rA
which was sent;
8) A sends the following authentication token to B:
A{rB,B}
9) B carries out the following actions:
a) checks the signature and thus, the integrity of the signed information;
b) checks that the received rB is identical to the rB which was sent by B.
Figure 12 ­ Three-way authentication
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 99
19 Access control
The Directory exists in an environment where various administrative authorities control access to their portion of
the DIB. The definition of an access control scheme in the context of the Directory includes methods to:
­ specify access control information (ACI);
­ enforce access rights defined by that access control information;
­ maintain access control information.
The enforcement of access rights applies to controlling access to:
­ Directory information related to names;
­ Directory user information;
­ Directory operational information including access control information.
Administrative authorities may make use of all or parts of any standardized access control scheme in implementing their
security policies, or may freely define their own schemes at their discretion.
The Basic Access Control (BAC) scheme defined in ITU-T Rec. X.501 | ISO/IEC 9594-2 is an access control list based
scheme that enables Directory Administrators to tie permissions to the level of authentication performed to bind to the
Directory. The public-key certificate framework defined in this Specification is used to provide the strong
authentication scheme used for this binding.
The Rules Based Access Control (RBAC) scheme defined in ITU-T Rec. X.501 | ISO/IEC 9594-2 makes use of the
attribute certificate framework defined in this Specification to carry clearance attributes used in making access control
decisions. RBAC may also be used in conjunction with BAC.
20 Protection of Directory operations
The public-key certificate framework defined in this Specification is used in all Directory protocols defined in this
series of Recommendations to optionally protect the operations including requests, responses and errors. Integrity
protection is provided through the digital signature of the sender and the verification of that signature by the recipient
using the sender's corresponding public-key certificate. Privacy protection is provided through the use of public-key
encryption where the content is encrypted with the public-key obtained from the intended recipient's public-key
certificate and decrypted by the recipient using their corresponding private key.
The specific mechanisms and syntax for requesting and including the protection elements in protocol exchanges are
defined within each of the Directory protocols in this series of Specifications.
ISO/IEC 9594-8:2005 (E)
100 ITU-T Rec. X.509 (08/2005)
Annex A
Public-Key and Attribute Certificate Frameworks
(This annex forms an integral part of this Recommendation | International Standard)
This annex includes all of the ASN.1 type, value, and information object class definitions contained in this Directory
Specification in the form of three ASN.1 modules: AuthenticationFramework, CertificateExtensions, and
AttributeCertificateDefinitions.
-- A.1 Authentication framework module
AuthenticationFramework {joint-iso-itu-t ds(5) module(1) authenticationFramework(7) 5}
DEFINITIONS ::=
BEGIN
-- EXPORTS All --
-- The types and values defined in this module are exported for use in the other ASN.1 modules contained
-- within the Directory Specifications, and for the use of other applications which will use them to access
-- Directory services. Other applications may use them for their own purposes, but this will not constrain
-- extensions and modifications needed to maintain or improve the Directory service.
IMPORTS
id-at, id-nf, id-oc, informationFramework, upperBounds, selectedAttributeTypes, basicAccessControl,
certificateExtensions
FROM UsefulDefinitions {joint-iso-itu-t ds(5) module(1) usefulDefinitions(0) 5}
Name, ATTRIBUTE, OBJECT-CLASS, NAME-FORM, top
FROM InformationFramework informationFramework
ub-user-password, ub-content
FROM UpperBounds upperBounds
UniqueIdentifier, octetStringMatch, DirectoryString{}, commonName
FROM SelectedAttributeTypes selectedAttributeTypes
certificateExactMatch, certificatePairExactMatch, certificateListExactMatch, KeyUsage, GeneralNames,
CertificatePoliciesSyntax, algorithmIdentifierMatch, CertPolicyId
FROM CertificateExtensions certificateExtensions ;
-- public-key certificate definition --
Certificate ::= SIGNED { SEQUENCE {
version [0] Version DEFAULT v1,
serialNumber CertificateSerialNumber,
signature AlgorithmIdentifier,
issuer Name,
validity Validity,
subject Name,
subjectPublicKeyInfo SubjectPublicKeyInfo,
issuerUniqueIdentifier [1] IMPLICIT UniqueIdentifier OPTIONAL,
-- if present, version shall be v2 or v3
subjectUniqueIdentifier [2] IMPLICIT UniqueIdentifier OPTIONAL,
-- if present, version shall be v2 or v3
extensions [3] Extensions OPTIONAL
-- If present, version shall be v3 -- } }
Version ::= INTEGER { v1(0), v2(1), v3(2) }
CertificateSerialNumber ::= INTEGER
AlgorithmIdentifier ::= SEQUENCE {
algorithm ALGORITHM.&id ({SupportedAlgorithms}),
parameters ALGORITHM.&Type ({SupportedAlgorithms}{ @algorithm}) OPTIONAL }
-- Definition of the following information object set is deferred, perhaps to standardized
-- profiles or to protocol implementation conformance statements. The set is required to
-- specify a table constraint on the parameters component of AlgorithmIdentifier.
SupportedAlgorithms ALGORITHM ::= { ... }
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 101
Validity ::= SEQUENCE {
notBefore Time,
notAfter Time }
SubjectPublicKeyInfo ::= SEQUENCE {
algorithm AlgorithmIdentifier,
subjectPublicKey BIT STRING }
Time ::= CHOICE {
utcTime UTCTime,
generalizedTime GeneralizedTime }
Extensions ::= SEQUENCE OF Extension
-- For those extensions where ordering of individual extensions within the SEQUENCE is significant, the
-- specification of those individual extensions shall include the rules for the significance of the order therein
Extension ::= SEQUENCE {
extnId EXTENSION.&id ({ExtensionSet}),
critical BOOLEAN DEFAULT FALSE,
extnValue OCTET STRING
-- contains a DER encoding of a value of type &ExtnType
-- for the extension object identified by extnId -- }
ExtensionSet EXTENSION ::= { ... }
EXTENSION ::= CLASS {
&id OBJECT IDENTIFIER UNIQUE,
&ExtnType }
WITH SYNTAX {
SYNTAX &ExtnType
IDENTIFIED BY &id }
-- other PKI certificate constructs
Certificates ::= SEQUENCE {
userCertificate Certificate,
certificationPath ForwardCertificationPath OPTIONAL}
ForwardCertificationPath ::= SEQUENCE OF CrossCertificates
CrossCertificates ::= SET OF Certificate
CertificationPath ::= SEQUENCE {
userCertificate Certificate,
theCACertificates SEQUENCE OF CertificatePair OPTIONAL}
CertificatePair ::= SEQUENCE {
forward [0] Certificate OPTIONAL,
reverse [1] Certificate OPTIONAL
-- at least one of the pair shall be present -- }
(WITH COMPONENTS { ..., forward PRESENT} |
WITH COMPONENTS { ..., reverse PRESENT})
-- certificate revocation list (CRL)
CertificateList ::= SIGNED { SEQUENCE {
version Version OPTIONAL,
-- if present, version shall be v2
signature AlgorithmIdentifier,
issuer Name,
thisUpdate Time,
nextUpdate Time OPTIONAL,
revokedCertificates SEQUENCE OF SEQUENCE {
serialNumber CertificateSerialNumber,
revocationDate Time,
crlEntryExtensions Extensions OPTIONAL } OPTIONAL,
crlExtensions [0] Extensions OPTIONAL }}
-- information object classes --
ALGORITHM ::= TYPE-IDENTIFIER
-- parameterized types --
HASH {ToBeHashed} ::= SEQUENCE {
algorithmIdentifier AlgorithmIdentifier,
ISO/IEC 9594-8:2005 (E)
102 ITU-T Rec. X.509 (08/2005)
hashValue BIT STRING ( CONSTRAINED BY {
-- shall be the result of applying a hashing procedure to the DER-encoded octets --
-- of a value of --ToBeHashed } ) }
ENCRYPTED-HASH { ToBeSigned } ::= BIT STRING ( CONSTRAINED BY {
-- shall be the result of applying a hashing procedure to the DER-encoded (see 6.1) octets --
-- of a value of -- ToBeSigned -- and then applying an encipherment procedure to those octets -- })
ENCRYPTED { ToBeEnciphered } ::= BIT STRING ( CONSTRAINED BY {
-- shall be the result of applying an encipherment procedure --
-- to the BER-encoded octets of a value of -- ToBeEnciphered})
SIGNATURE { ToBeSigned } ::= SEQUENCE {
algorithmIdentifier AlgorithmIdentifier,
encrypted ENCRYPTED-HASH { ToBeSigned }}
SIGNED { ToBeSigned } ::= SEQUENCE {
toBeSigned ToBeSigned,
COMPONENTS OF SIGNATURE { ToBeSigned }}
-- PKI object classes --
pkiUser OBJECT-CLASS ::= {
SUBCLASS OF {top}
KIND auxiliary
MAY CONTAIN {userCertificate}
ID id-oc-pkiUser }
pkiCA OBJECT-CLASS ::= {
SUBCLASS OF {top}
KIND auxiliary
MAY CONTAIN {cACertificate |
certificateRevocationList |
authorityRevocationList |
crossCertificatePair }
ID id-oc-pkiCA }
cRLDistributionPoint OBJECT-CLASS ::= {
SUBCLASS OF { top }
KIND structural
MUST CONTAIN { commonName }
MAY CONTAIN { certificateRevocationList |
authorityRevocationList |
deltaRevocationList }
ID id-oc-cRLDistributionPoint }
cRLDistPtNameForm NAME-FORM ::= {
NAMES cRLDistributionPoint
WITH ATTRIBUTES { commonName}
ID id-nf-cRLDistPtNameForm }
deltaCRL OBJECT-CLASS ::= {
SUBCLASS OF {top}
KIND auxiliary
MAY CONTAIN {deltaRevocationList}
ID id-oc-deltaCRL }
cpCps OBJECT-CLASS ::= {
SUBCLASS OF {top}
KIND auxiliary
MAY CONTAIN {certificatePolicy |
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 103
certificationPracticeStmt}
ID id-oc-cpCps }
pkiCertPath OBJECT-CLASS ::= {
SUBCLASS OF {top}
KIND auxiliary
MAY CONTAIN { pkiPath }
ID id-oc-pkiCertPath }
-- PKI directory attributes --
userCertificate ATTRIBUTE ::= {
WITH SYNTAX Certificate
EQUALITY MATCHING RULE certificateExactMatch
ID id-at-userCertificate}
cACertificate ATTRIBUTE ::= {
WITH SYNTAX Certificate
EQUALITY MATCHING RULE certificateExactMatch
ID id-at-cAcertificate }
crossCertificatePair ATTRIBUTE ::= {
WITH SYNTAX CertificatePair
EQUALITY MATCHING RULE certificatePairExactMatch
ID id-at-crossCertificatePair }
certificateRevocationList ATTRIBUTE ::= {
WITH SYNTAX CertificateList
EQUALITY MATCHING RULE certificateListExactMatch
ID id-at-certificateRevocationList }
authorityRevocationList ATTRIBUTE ::= {
WITH SYNTAX CertificateList
EQUALITY MATCHING RULE certificateListExactMatch
ID id-at-authorityRevocationList }
deltaRevocationList ATTRIBUTE ::= {
WITH SYNTAX CertificateList
EQUALITY MATCHING RULE certificateListExactMatch
ID id-at-deltaRevocationList }
supportedAlgorithms ATTRIBUTE ::= {
WITH SYNTAX SupportedAlgorithm
EQUALITY MATCHING RULE algorithmIdentifierMatch
ID id-at-supportedAlgorithms }
SupportedAlgorithm ::= SEQUENCE {
algorithmIdentifier AlgorithmIdentifier,
intendedUsage [0] KeyUsage OPTIONAL,
intendedCertificatePolicies [1] CertificatePoliciesSyntax OPTIONAL }
certificationPracticeStmt ATTRIBUTE ::= {
WITH SYNTAX InfoSyntax
ID id-at-certificationPracticeStmt }
InfoSyntax ::= CHOICE {
content DirectoryString {ub-content},
pointer SEQUENCE {
ISO/IEC 9594-8:2005 (E)
104 ITU-T Rec. X.509 (08/2005)
name GeneralNames,
hash HASH { HashedPolicyInfo } OPTIONAL } }
POLICY ::= TYPE-IDENTIFIER
HashedPolicyInfo ::= POLICY.&Type( {Policies} )
Policies POLICY ::= {...} -- Defined by implementors --
certificatePolicy ATTRIBUTE ::= {
WITH SYNTAX PolicySyntax
ID id-at-certificatePolicy }
PolicySyntax ::= SEQUENCE {
policyIdentifier PolicyID,
policySyntax InfoSyntax
}
PolicyID ::= CertPolicyId
pkiPath ATTRIBUTE ::= {
WITH SYNTAX PkiPath
ID id-at-pkiPath }
PkiPath ::= SEQUENCE OF Certificate
userPassword ATTRIBUTE ::= {
WITH SYNTAX OCTET STRING (SIZE (0..ub-user-password))
EQUALITY MATCHING RULE octetStringMatch
ID id-at-userPassword }
-- object identifier assignments --
-- object classes --
id-oc-cRLDistributionPoint OBJECT IDENTIFIER ::= {id-oc 19}
id-oc-pkiUser OBJECT IDENTIFIER ::= {id-oc 21}
id-oc-pkiCA OBJECT IDENTIFIER ::= {id-oc 22}
id-oc-deltaCRL OBJECT IDENTIFIER ::= {id-oc 23}
id-oc-cpCps OBJECT IDENTIFIER ::= {id-oc 30}
id-oc-pkiCertPath OBJECT IDENTIFIER ::= {id-oc 31}
-- name forms--
id-nf-cRLDistPtNameForm OBJECT IDENTIFIER ::= {id-nf 14}
-- directory attributes--
id-at-userPassword OBJECT IDENTIFIER ::= {id-at 35}
id-at-userCertificate OBJECT IDENTIFIER ::= {id-at 36}
id-at-cAcertificate OBJECT IDENTIFIER ::= {id-at 37}
id-at-authorityRevocationList OBJECT IDENTIFIER ::= {id-at 38}
id-at-certificateRevocationList OBJECT IDENTIFIER ::= {id-at 39}
id-at-crossCertificatePair OBJECT IDENTIFIER ::= {id-at 40}
id-at-supportedAlgorithms OBJECT IDENTIFIER ::= {id-at 52}
id-at-deltaRevocationList OBJECT IDENTIFIER ::= {id-at 53}
id-at-certificationPracticeStmt OBJECT IDENTIFIER ::= {id-at 68}
id-at-certificatePolicy OBJECT IDENTIFIER ::= {id-at 69}
id-at-pkiPath OBJECT IDENTIFIER ::= {id-at 70}
END
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 105
-- A.2 Certificate extensions module
CertificateExtensions {joint-iso-itu-t ds(5) module(1) certificateExtensions(26) 5}
DEFINITIONS IMPLICIT TAGS ::=
BEGIN
-- EXPORTS ALL --
IMPORTS
id-at, id-ce, id-mr, informationFramework, authenticationFramework,
selectedAttributeTypes, upperBounds
FROM UsefulDefinitions {joint-iso-itu-t ds(5) module(1)
usefulDefinitions(0) 5}
Name, RelativeDistinguishedName, ATTRIBUTE, Attribute, MATCHING-RULE
FROM InformationFramework informationFramework
CertificateSerialNumber, CertificateList, AlgorithmIdentifier,
EXTENSION, Time, PolicyID
FROM AuthenticationFramework authenticationFramework
DirectoryString {}
FROM SelectedAttributeTypes selectedAttributeTypes
ub-name
FROM UpperBounds upperBounds
ORAddress
FROM MTSAbstractService {joint-iso-itu-t mhs(6) mts(3)
modules(0) mts-abstract-service(1) version-1999 (1) } ;
-- Unless explicitly noted otherwise, there is no significance to the ordering
-- of components of a SEQUENCE OF construct in this Specification.
-- public-key certificate and CRL extensions --
authorityKeyIdentifier EXTENSION ::= {
SYNTAX AuthorityKeyIdentifier
IDENTIFIED BY id-ce-authorityKeyIdentifier }
AuthorityKeyIdentifier ::= SEQUENCE {
keyIdentifier [0] KeyIdentifier OPTIONAL,
authorityCertIssuer [1] GeneralNames OPTIONAL,
authorityCertSerialNumber [2] CertificateSerialNumber OPTIONAL }
( WITH COMPONENTS {..., authorityCertIssuer PRESENT,
authorityCertSerialNumber PRESENT} |
WITH COMPONENTS {..., authorityCertIssuer ABSENT,
authorityCertSerialNumber ABSENT} )
KeyIdentifier ::= OCTET STRING
subjectKeyIdentifier EXTENSION ::= {
SYNTAX SubjectKeyIdentifier
IDENTIFIED BY id-ce-subjectKeyIdentifier }
SubjectKeyIdentifier ::= KeyIdentifier
keyUsage EXTENSION ::= {
SYNTAX KeyUsage
IDENTIFIED BY id-ce-keyUsage }
KeyUsage ::= BIT STRING {
digitalSignature (0),
contentCommitment (1),
keyEncipherment (2),
dataEncipherment (3),
keyAgreement (4),
keyCertSign (5),
cRLSign (6),
encipherOnly (7),
decipherOnly (8) }
ISO/IEC 9594-8:2005 (E)
106 ITU-T Rec. X.509 (08/2005)
extKeyUsage EXTENSION ::= {
SYNTAX SEQUENCE SIZE (1..MAX) OF KeyPurposeId
IDENTIFIED BY id-ce-extKeyUsage }
KeyPurposeId ::= OBJECT IDENTIFIER
privateKeyUsagePeriod EXTENSION ::= {
SYNTAX PrivateKeyUsagePeriod
IDENTIFIED BY id-ce-privateKeyUsagePeriod }
PrivateKeyUsagePeriod ::= SEQUENCE {
notBefore [0] GeneralizedTime OPTIONAL,
notAfter [1] GeneralizedTime OPTIONAL }
( WITH COMPONENTS {..., notBefore PRESENT} |
WITH COMPONENTS {..., notAfter PRESENT} )
certificatePolicies EXTENSION ::= {
SYNTAX CertificatePoliciesSyntax
IDENTIFIED BY id-ce-certificatePolicies }
CertificatePoliciesSyntax ::= SEQUENCE SIZE (1..MAX) OF PolicyInformation
PolicyInformation ::= SEQUENCE {
policyIdentifier CertPolicyId,
policyQualifiers SEQUENCE SIZE (1..MAX) OF
PolicyQualifierInfo OPTIONAL }
CertPolicyId ::= OBJECT IDENTIFIER
PolicyQualifierInfo ::= SEQUENCE {
policyQualifierId CERT-POLICY-QUALIFIER.&id
({SupportedPolicyQualifiers}),
qualifier CERT-POLICY-QUALIFIER.&Qualifier
({SupportedPolicyQualifiers}{@policyQualifierId})
OPTIONAL }
SupportedPolicyQualifiers CERT-POLICY-QUALIFIER ::= { ... }
anyPolicy OBJECT IDENTIFIER ::= { 2 5 29 32 0 }
CERT-POLICY-QUALIFIER ::= CLASS {
&id OBJECT IDENTIFIER UNIQUE,
&Qualifier OPTIONAL }
WITH SYNTAX {
POLICY-QUALIFIER-ID &id
[QUALIFIER-TYPE &Qualifier] }
policyMappings EXTENSION ::= {
SYNTAX PolicyMappingsSyntax
IDENTIFIED BY id-ce-policyMappings }
PolicyMappingsSyntax ::= SEQUENCE SIZE (1..MAX) OF SEQUENCE {
issuerDomainPolicy CertPolicyId,
subjectDomainPolicy CertPolicyId }
subjectAltName EXTENSION ::= {
SYNTAX GeneralNames
IDENTIFIED BY id-ce-subjectAltName }
GeneralNames ::= SEQUENCE SIZE (1..MAX) OF GeneralName
GeneralName ::= CHOICE {
otherName [0] INSTANCE OF OTHER-NAME,
rfc822Name [1] IA5String,
dNSName [2] IA5String,
x400Address [3] ORAddress,
directoryName [4] Name,
ediPartyName [5] EDIPartyName,
uniformResourceIdentifier [6] IA5String,
iPAddress [7] OCTET STRING,
registeredID [8] OBJECT IDENTIFIER }
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 107
OTHER-NAME ::= TYPE-IDENTIFIER
EDIPartyName ::= SEQUENCE {
nameAssigner [0] DirectoryString {ub-name} OPTIONAL,
partyName [1] DirectoryString {ub-name} }
issuerAltName EXTENSION ::= {
SYNTAX GeneralNames
IDENTIFIED BY id-ce-issuerAltName }
subjectDirectoryAttributes EXTENSION ::= {
SYNTAX AttributesSyntax
IDENTIFIED BY id-ce-subjectDirectoryAttributes }
AttributesSyntax ::= SEQUENCE SIZE (1..MAX) OF Attribute
basicConstraints EXTENSION ::= {
SYNTAX BasicConstraintsSyntax
IDENTIFIED BY id-ce-basicConstraints }
BasicConstraintsSyntax ::= SEQUENCE {
cA BOOLEAN DEFAULT FALSE,
pathLenConstraint INTEGER (0..MAX) OPTIONAL }
nameConstraints EXTENSION ::= {
SYNTAX NameConstraintsSyntax
IDENTIFIED BY id-ce-nameConstraint }
NameConstraintsSyntax ::= SEQUENCE {
permittedSubtrees [0] GeneralSubtrees OPTIONAL,
excludedSubtrees [1] GeneralSubtrees OPTIONAL,
requiredNameForms [2] NameForms OPTIONAL }
GeneralSubtrees ::= SEQUENCE SIZE (1..MAX) OF GeneralSubtree
GeneralSubtree ::= SEQUENCE {
base GeneralName,
minimum [0] BaseDistance DEFAULT 0,
maximum [1] BaseDistance OPTIONAL }
BaseDistance ::= INTEGER (0..MAX)
NameForms ::= SEQUENCE {
basicNameForms [0] BasicNameForms OPTIONAL,
otherNameForms [1] SEQUENCE SIZE (1..MAX) OF OBJECT IDENTIFIER OPTIONAL }
(ALL EXCEPT ({ -- none; i.e., at least one component shall be present -- }))
BasicNameForms ::= BIT STRING {
rfc822Name (0),
dNSName (1),
x400Address (2),
directoryName (3),
ediPartyName (4),
uniformResourceIdentifier (5),
iPAddress (6),
registeredID (7) } (SIZE (1..MAX))
policyConstraints EXTENSION ::= {
SYNTAX PolicyConstraintsSyntax
IDENTIFIED BY id-ce-policyConstraints }
PolicyConstraintsSyntax ::= SEQUENCE {
requireExplicitPolicy [0] SkipCerts OPTIONAL,
inhibitPolicyMapping [1] SkipCerts OPTIONAL }
ISO/IEC 9594-8:2005 (E)
108 ITU-T Rec. X.509 (08/2005)
SkipCerts ::= INTEGER (0..MAX)
cRLNumber EXTENSION ::= {
SYNTAX CRLNumber
IDENTIFIED BY id-ce-cRLNumber }
CRLNumber ::= INTEGER (0..MAX)
reasonCode EXTENSION ::= {
SYNTAX CRLReason
IDENTIFIED BY id-ce-reasonCode }
CRLReason ::= ENUMERATED {
unspecified (0),
keyCompromise (1),
cACompromise (2),
affiliationChanged (3),
superseded (4),
cessationOfOperation (5),
certificateHold (6),
removeFromCRL (8),
privilegeWithdrawn (9),
aaCompromise (10) }
holdInstructionCode EXTENSION ::= {
SYNTAX HoldInstruction
IDENTIFIED BY id-ce-instructionCode }
HoldInstruction ::= OBJECT IDENTIFIER
invalidityDate EXTENSION ::= {
SYNTAX GeneralizedTime
IDENTIFIED BY id-ce-invalidityDate }
crlScope EXTENSION ::= {
SYNTAX CRLScopeSyntax
IDENTIFIED BY id-ce-cRLScope }
CRLScopeSyntax ::= SEQUENCE SIZE (1..MAX) OF PerAuthorityScope
PerAuthorityScope ::= SEQUENCE {
authorityName [0] GeneralName OPTIONAL,
distributionPoint [1] DistributionPointName OPTIONAL,
onlyContains [2] OnlyCertificateTypes OPTIONAL,
onlySomeReasons [4] ReasonFlags OPTIONAL,
serialNumberRange [5] NumberRange OPTIONAL,
subjectKeyIdRange [6] NumberRange OPTIONAL,
nameSubtrees [7] GeneralNames OPTIONAL,
baseRevocationInfo [9] BaseRevocationInfo OPTIONAL
}
OnlyCertificateTypes ::= BIT STRING {
user (0),
authority (1),
attribute (2) }
NumberRange ::= SEQUENCE {
startingNumber [0] INTEGER OPTIONAL,
endingNumber [1] INTEGER OPTIONAL,
modulus INTEGER OPTIONAL }
BaseRevocationInfo ::= SEQUENCE {
cRLStreamIdentifier [0] CRLStreamIdentifier OPTIONAL,
cRLNumber [1] CRLNumber,
baseThisUpdate [2] GeneralizedTime }
statusReferrals EXTENSION ::= {
SYNTAX StatusReferrals
IDENTIFIED BY id-ce-statusReferrals }
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 109
StatusReferrals ::= SEQUENCE SIZE (1..MAX) OF StatusReferral
StatusReferral ::= CHOICE {
cRLReferral [0] CRLReferral,
otherReferral [1] INSTANCE OF OTHER-REFERRAL}
CRLReferral ::= SEQUENCE {
issuer [0] GeneralName OPTIONAL,
location [1] GeneralName OPTIONAL,
deltaRefInfo [2] DeltaRefInfo OPTIONAL,
cRLScope CRLScopeSyntax,
lastUpdate [3] GeneralizedTime OPTIONAL,
lastChangedCRL [4] GeneralizedTime OPTIONAL}
DeltaRefInfo ::= SEQUENCE {
deltaLocation GeneralName,
lastDelta GeneralizedTime OPTIONAL }
OTHER-REFERRAL ::= TYPE-IDENTIFIER
cRLStreamIdentifier EXTENSION ::= {
SYNTAX CRLStreamIdentifier
IDENTIFIED BY id-ce-cRLStreamIdentifier }
CRLStreamIdentifier ::= INTEGER (0..MAX)
orderedList EXTENSION ::= {
SYNTAX OrderedListSyntax
IDENTIFIED BY id-ce-orderedList }
OrderedListSyntax ::= ENUMERATED {
ascSerialNum (0),
ascRevDate (1) }
deltaInfo EXTENSION ::= {
SYNTAX DeltaInformation
IDENTIFIED BY id-ce-deltaInfo }
DeltaInformation ::= SEQUENCE {
deltaLocation GeneralName,
nextDelta GeneralizedTime OPTIONAL }
cRLDistributionPoints EXTENSION ::= {
SYNTAX CRLDistPointsSyntax
IDENTIFIED BY id-ce-cRLDistributionPoints }
CRLDistPointsSyntax ::= SEQUENCE SIZE (1..MAX) OF DistributionPoint
DistributionPoint ::= SEQUENCE {
distributionPoint [0] DistributionPointName OPTIONAL,
reasons [1] ReasonFlags OPTIONAL,
cRLIssuer [2] GeneralNames OPTIONAL }
DistributionPointName ::= CHOICE {
fullName [0] GeneralNames,
nameRelativeToCRLIssuer [1] RelativeDistinguishedName }
ReasonFlags ::= BIT STRING {
unused (0),
keyCompromise (1),
cACompromise (2),
affiliationChanged (3),
superseded (4),
cessationOfOperation (5),
certificateHold (6),
privilegeWithdrawn (7),
aACompromise (8) }
ISO/IEC 9594-8:2005 (E)
110 ITU-T Rec. X.509 (08/2005)
issuingDistributionPoint EXTENSION ::= {
SYNTAX IssuingDistPointSyntax
IDENTIFIED BY id-ce-issuingDistributionPoint }
IssuingDistPointSyntax ::= SEQUENCE {
-- If onlyContainsUserPublicKeyCerts and onlyContainsCACerts are both FALSE,
-- the CRL covers both certificate types
distributionPoint [0] DistributionPointName OPTIONAL,
onlyContainsUserPublicKeyCerts [1] BOOLEAN DEFAULT FALSE,
onlyContainsCACerts [2] BOOLEAN DEFAULT FALSE,
onlySomeReasons [3] ReasonFlags OPTIONAL,
indirectCRL [4] BOOLEAN DEFAULT FALSE }
certificateIssuer EXTENSION ::= {
SYNTAX GeneralNames
IDENTIFIED BY id-ce-certificateIssuer }
deltaCRLIndicator EXTENSION ::= {
SYNTAX BaseCRLNumber
IDENTIFIED BY id-ce-deltaCRLIndicator }
BaseCRLNumber ::= CRLNumber
toBeRevoked EXTENSION ::= {
SYNTAX ToBeRevokedSyntax
IDENTIFIED BYid-ce-toBeRevoked }
ToBeRevokedSyntax::= SEQUENCE SIZE(1..MAX) OF ToBeRevokedGroup
ToBeRevokedGroup ::= SEQUENCE {
certificateIssuer [0] GeneralName OPTIONAL,
reasonInfo [1] ReasonInfo OPTIONAL,
revocationTime GeneralizedTime,
certificateGroup CertificateGroup }
ReasonInfo ::= SEQUENCE {
reasonCode CRLReason,
holdInstructionCode HoldInstruction OPTIONAL }
CertificateGroup ::= CHOICE {
serialNumbers [0] CertificateSerialNumbers,
serialNumberRange [1] CertificateGroupNumberRange,
nameSubtree [2] GeneralName }
CertificateGroupNumberRange ::= SEQUENCE {
startingNumber [0] INTEGER,
endingNumber [1] INTEGER }
CertificateSerialNumbers ::= SEQUENCE SIZE(1..MAX) OF CertificateSerialNumber
revokedGroups EXTENSION ::= {
SYNTAX RevokedGroupsSyntax
IDENTIFIED BYid-ce-RevokedGroups }
RevokedGroupsSyntax ::= SEQUENCE SIZE (1..MAX) OF RevokedGroup
RevokedGroup ::=SEQUENCE {
certificateIssuer [0] GeneralName OPTIONAL,
reasonInfo [1] ReasonInfo OPTIONAL,
invalidityDate [2] GeneralizedTime OPTIONAL,
revokedcertificateGroup [3] RevokedCertificateGroup }
RevokedCertificateGroup ::= CHOICE {
serialNumberRange NumberRange,
nameSubtree GeneralName }
expiredCertsOnCRL EXTENSION ::= {
SYNTAXExpiredCertsOnCRL
IDENTIFIED BYid-ce-expiredCertsOnCRL }
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 111
ExpiredCertsOnCRL ::= GeneralizedTime
baseUpdateTime EXTENSION ::= {
SYNTAX GeneralizedTime
IDENTIFIED BY id-ce-baseUpdateTime }
freshestCRL EXTENSION ::= {
SYNTAX CRLDistPointsSyntax
IDENTIFIED BY id-ce-freshestCRL }
aAissuingDistributionPoint EXTENSION ::= {
SYNTAX AAIssuingDistPointSyntax
IDENTIFIED BY id-ce-aAissuingDistributionPoint }
AAIssuingDistPointSyntax ::= SEQUENCE {
distributionPoint [ 0 ] DistributionPointName OPTIONAL,
onlySomeReasons [ 1 ] ReasonFlags OPTIONAL,
indirectCRL [ 2 ] BOOLEAN DEFAULT FALSE,
containsUserAttributeCerts [ 3 ] BOOLEAN DEFAULT TRUE,
containsAACerts [ 4 ] BOOLEAN DEFAULT TRUE,
containsSOAPublicKeyCerts [ 5 ] BOOLEAN DEFAULT TRUE }
inhibitAnyPolicy EXTENSION ::= {
SYNTAX SkipCerts
IDENTIFIED BY id-ce-inhibitAnyPolicy }
-- PKI matching rules --
certificateExactMatch MATCHING-RULE ::= {
SYNTAX CertificateExactAssertion
ID id-mr-certificateExactMatch }
CertificateExactAssertion ::= SEQUENCE {
serialNumber CertificateSerialNumber,
issuer Name }
certificateMatch MATCHING-RULE ::= {
SYNTAX CertificateAssertion
ID id-mr-certificateMatch }
CertificateAssertion ::= SEQUENCE {
serialNumber [0] CertificateSerialNumber OPTIONAL,
issuer [1] Name OPTIONAL,
subjectKeyIdentifier [2] SubjectKeyIdentifier OPTIONAL,
authorityKeyIdentifier [3] AuthorityKeyIdentifier OPTIONAL,
certificateValid [4] Time OPTIONAL,
privateKeyValid [5] GeneralizedTime OPTIONAL,
subjectPublicKeyAlgID [6] OBJECT IDENTIFIER OPTIONAL,
keyUsage [7] KeyUsage OPTIONAL,
subjectAltName [8] AltNameType OPTIONAL,
policy [9] CertPolicySet OPTIONAL,
pathToName [10] Name OPTIONAL,
subject [11] Name OPTIONAL,
nameConstraints [12] NameConstraintsSyntax OPTIONAL }
AltNameType ::= CHOICE {
builtinNameForm ENUMERATED {
rfc822Name (1),
dNSName (2),
x400Address (3),
directoryName (4),
ediPartyName (5),
uniformResourceIdentifier (6),
iPAddress (7),
registeredId (8) },
otherNameForm OBJECT IDENTIFIER }
CertPolicySet ::= SEQUENCE SIZE (1..MAX) OF CertPolicyId
ISO/IEC 9594-8:2005 (E)
112 ITU-T Rec. X.509 (08/2005)
certificatePairExactMatch MATCHING-RULE ::= {
SYNTAX CertificatePairExactAssertion
ID id-mr-certificatePairExactMatch }
CertificatePairExactAssertion ::= SEQUENCE {
issuedToThisCAAssertion [0] CertificateExactAssertion OPTIONAL,
issuedByThisCAAssertion [1] CertificateExactAssertion OPTIONAL }
( WITH COMPONENTS {..., issuedToThisCAAssertion PRESENT} |
WITH COMPONENTS {..., issuedByThisCAAssertion PRESENT} )
certificatePairMatch MATCHING-RULE ::={
SYNTAX CertificatePairAssertion
ID id-mr-certificatePairMatch }
CertificatePairAssertion ::= SEQUENCE {
issuedToThisCAAssertion [0] CertificateAssertion OPTIONAL,
issuedByThisCAAssertion [1] CertificateAssertion OPTIONAL }
( WITH COMPONENTS {..., issuedToThisCAAssertion PRESENT} |
WITH COMPONENTS {..., issuedByThisCAAssertion PRESENT} )
certificateListExactMatch MATCHING-RULE ::= {
SYNTAX CertificateListExactAssertion
ID id-mr-certificateListExactMatch }
CertificateListExactAssertion ::= SEQUENCE {
issuer Name,
thisUpdate Time,
distributionPoint DistributionPointName OPTIONAL }
certificateListMatch MATCHING-RULE ::= {
SYNTAX CertificateListAssertion
ID id-mr-certificateListMatch }
CertificateListAssertion ::= SEQUENCE {
issuer Name OPTIONAL,
minCRLNumber [0] CRLNumber OPTIONAL,
maxCRLNumber [1] CRLNumber OPTIONAL,
reasonFlags ReasonFlags OPTIONAL,
dateAndTime Time OPTIONAL,
distributionPoint [2] DistributionPointName OPTIONAL,
authorityKeyIdentifier [3] AuthorityKeyIdentifier OPTIONAL}
algorithmIdentifierMatch MATCHING-RULE ::= {
SYNTAX AlgorithmIdentifier
ID id-mr-algorithmIdentifierMatch }
policyMatch MATCHING-RULE ::= {
SYNTAX PolicyID
ID id-mr-policyMatch }
pkiPathMatch MATCHING-RULE ::= {
SYNTAX PkiPathMatchSyntax
ID id-mr-pkiPathMatch }
PkiPathMatchSyntax ::= SEQUENCE {
firstIssuer Name,
lastSubject Name }
enhancedCertificateMatch MATCHING-RULE ::= {
SYNTAX EnhancedCertificateAssertion
ID id-mr-enhancedCertificateMatch }
EnhancedCertificateAssertion ::= SEQUENCE {
serialNumber [0] CertificateSerialNumber OPTIONAL,
issuer [1] Name OPTIONAL,
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 113
subjectKeyIdentifier [2] SubjectKeyIdentifier OPTIONAL,
authorityKeyIdentifier [3] AuthorityKeyIdentifier OPTIONAL,
certificateValid [4] Time OPTIONAL,
privateKeyValid [5] GeneralizedTime OPTIONAL,
subjectPublicKeyAlgID [6] OBJECT IDENTIFIER OPTIONAL,
keyUsage [7] KeyUsage OPTIONAL,
subjectAltName [8] AltName OPTIONAL,
policy [9] CertPolicySet OPTIONAL,
pathToName [10] GeneralNames OPTIONAL,
subject [11] Name OPTIONAL,
nameConstraints [12] NameConstraintsSyntax OPTIONAL
}
(ALL EXCEPT ({ -- none; at least one component shall be present -- }))
AltName ::= SEQUENCE {
altnameType AltNameType,
altNameValue GeneralName OPTIONAL }
-- Object identifier assignments --
id-ce-subjectDirectoryAttributes OBJECT IDENTIFIER ::= {id-ce 9}
id-ce-subjectKeyIdentifier OBJECT IDENTIFIER ::= {id-ce 14}
id-ce-keyUsage OBJECT IDENTIFIER ::= {id-ce 15}
id-ce-privateKeyUsagePeriod OBJECT IDENTIFIER ::= {id-ce 16}
id-ce-subjectAltName OBJECT IDENTIFIER ::= {id-ce 17}
id-ce-issuerAltName OBJECT IDENTIFIER ::= {id-ce 18}
id-ce-basicConstraints OBJECT IDENTIFIER ::= {id-ce 19}
id-ce-cRLNumber OBJECT IDENTIFIER ::= {id-ce 20}
id-ce-reasonCode OBJECT IDENTIFIER ::= {id-ce 21}
id-ce-instructionCode OBJECT IDENTIFIER ::= {id-ce 23}
id-ce-invalidityDate OBJECT IDENTIFIER ::= {id-ce 24}
id-ce-deltaCRLIndicator OBJECT IDENTIFIER ::= {id-ce 27}
id-ce-issuingDistributionPoint OBJECT IDENTIFIER ::= {id-ce 28}
id-ce-certificateIssuer OBJECT IDENTIFIER ::= {id-ce 29}
id-ce-nameConstraint OBJECT IDENTIFIER ::= {id-ce 30 1}
id-ce-cRLDistributionPoints OBJECT IDENTIFIER ::= {id-ce 31}
id-ce-certificatePolicies OBJECT IDENTIFIER ::= {id-ce 32}
id-ce-policyMappings OBJECT IDENTIFIER ::= {id-ce 33}
-- deprecated OBJECT IDENTIFIER ::= {id-ce 34}
id-ce-authorityKeyIdentifier OBJECT IDENTIFIER ::= {id-ce 35}
id-ce-policyConstraints OBJECT IDENTIFIER ::= {id-ce 36}
id-ce-extKeyUsage OBJECT IDENTIFIER ::= {id-ce 37}
id-ce-cRLStreamIdentifier OBJECT IDENTIFIER ::= {id-ce 40}
id-ce-cRLScope OBJECT IDENTIFIER ::= {id-ce 44}
id-ce-statusReferrals OBJECT IDENTIFIER ::= {id-ce 45}
id-ce-freshestCRL OBJECT IDENTIFIER ::= {id-ce 46}
id-ce-orderedList OBJECT IDENTIFIER ::= {id-ce 47}
id-ce-baseUpdateTime OBJECT IDENTIFIER ::= {id-ce 51}
id-ce-deltaInfo OBJECT IDENTIFIER ::= {id-ce 53}
id-ce-inhibitAnyPolicy OBJECT IDENTIFIER ::= {id-ce 54}
id-ce-toBeRevoked OBJECT IDENTIFIER ::= {id-ce 58}
id-ce-RevokedGroups OBJECT IDENTIFIER ::= {id-ce 59}
id-ce-expiredCertsOnCRL OBJECT IDENTIFIER ::= {id-ce 60}
id-ce-aAissuingDistributionPoint OBJECT IDENTIFIER ::= {id-ce 63}
-- matching rule OIDs --
id-mr-certificateExactMatch OBJECT IDENTIFIER ::= {id-mr 34}
id-mr-certificateMatch OBJECT IDENTIFIER ::= {id-mr 35}
id-mr-certificatePairExactMatch OBJECT IDENTIFIER ::= {id-mr 36}
id-mr-certificatePairMatch OBJECT IDENTIFIER ::= {id-mr 37}
id-mr-certificateListExactMatch OBJECT IDENTIFIER ::= {id-mr 38}
id-mr-certificateListMatch OBJECT IDENTIFIER ::= {id-mr 39}
id-mr-algorithmIdentifierMatch OBJECT IDENTIFIER ::= {id-mr 40}
id-mr-policyMatch OBJECT IDENTIFIER ::= {id-mr 60}
ISO/IEC 9594-8:2005 (E)
114 ITU-T Rec. X.509 (08/2005)
id-mr-pkiPathMatch OBJECT IDENTIFIER ::= {id-mr 62}
id-mr-enhancedCertificateMatch OBJECT IDENTIFIER ::= {id-mr 65}
-- The following OBJECT IDENTIFIERS are not used by this Specification:
-- {id-ce 2}, {id-ce 3}, {id-ce 4}, {id-ce 5}, {id-ce 6}, {id-ce 7},
-- {id-ce 8}, {id-ce 10}, {id-ce 11}, {id-ce 12}, {id-ce 13},
-- {id-ce 22}, {id-ce 25}, {id-ce 26}, {id-ce 30}
END
-- A.3 Attribute Certificate Framework module
AttributeCertificateDefinitions {joint-iso-itu-t ds(5) module(1) attributeCertificateDefinitions(32) 5}
DEFINITIONS IMPLICIT TAGS ::=
BEGIN
-- EXPORTS ALL --
IMPORTS
id-at, id-ce, id-mr, informationFramework, authenticationFramework,
selectedAttributeTypes, upperBounds, id-oc, certificateExtensions
FROM UsefulDefinitions {joint-iso-itu-t ds(5) module(1)
usefulDefinitions(0) 5}
Name, RelativeDistinguishedName, ATTRIBUTE, Attribute,
MATCHING-RULE, AttributeType, OBJECT-CLASS, top
FROM InformationFramework informationFramework
CertificateSerialNumber, CertificateList, AlgorithmIdentifier,
EXTENSION, SIGNED{}, InfoSyntax, PolicySyntax, Extensions, Certificate
FROM AuthenticationFramework authenticationFramework
DirectoryString{}, TimeSpecification, UniqueIdentifier
FROM SelectedAttributeTypes selectedAttributeTypes
GeneralName, GeneralNames, NameConstraintsSyntax, certificateListExactMatch
FROM CertificateExtensions certificateExtensions
ub-name
FROM UpperBounds upperBounds
UserNotice
FROM PKIX1Implicit93 {iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5)
pkix(7) id-mod(0) id-pkix1-implicit-93(4)}
ORAddress
FROM MTSAbstractService {joint-iso-itu-t mhs(6) mts(3)
modules(0) mts-abstract-service(1) version-1999 (1) } ;
-- Unless explicitly noted otherwise, there is no significance to the ordering
-- of components of a SEQUENCE OF construct in this Specification.
-- attribute certificate constructs --
AttributeCertificate ::= SIGNED {AttributeCertificateInfo}
AttributeCertificateInfo ::= SEQUENCE
{
version AttCertVersion, -- version is v2
holder Holder,
issuer AttCertIssuer,
signature AlgorithmIdentifier,
serialNumber CertificateSerialNumber,
attrCertValidityPeriod AttCertValidityPeriod,
attributes SEQUENCE OF Attribute,
issuerUniqueID UniqueIdentifier OPTIONAL,
extensions Extensions OPTIONAL
}
AttCertVersion ::= INTEGER { v2(1) }
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 115
Holder ::= SEQUENCE
{
baseCertificateID [0] IssuerSerial OPTIONAL,
-- the issuer and serial number of the holder's Public Key Certificate
entityName [1] GeneralNames OPTIONAL,
-- the name of the entity or role
objectDigestInfo [2] ObjectDigestInfo OPTIONAL
-- used to directly authenticate the holder, e.g., an executable
-- at least one of baseCertificateID, entityName or objectDigestInfo shall be present --}
ObjectDigestInfo ::= SEQUENCE {
digestedObjectType ENUMERATED {
publicKey (0),
publicKeyCert (1),
otherObjectTypes (2) },
otherObjectTypeID OBJECT IDENTIFIER OPTIONAL,
digestAlgorithm AlgorithmIdentifier,
objectDigest BIT STRING }
AttCertIssuer ::= [0] SEQUENCE {
issuerName GeneralNames OPTIONAL,
baseCertificateID [0] IssuerSerial OPTIONAL,
objectDigestInfo [1] ObjectDigestInfo OPTIONAL }
-- At least one component shall be present
( WITH COMPONENTS { ..., issuerName PRESENT } |
WITH COMPONENTS { ..., baseCertificateID PRESENT } |
WITH COMPONENTS { ..., objectDigestInfo PRESENT } )
IssuerSerial ::= SEQUENCE {
issuer GeneralNames,
serial CertificateSerialNumber,
issuerUID UniqueIdentifier OPTIONAL }
AttCertValidityPeriod ::= SEQUENCE {
notBeforeTime GeneralizedTime,
notAfterTime GeneralizedTime }
AttributeCertificationPath ::= SEQUENCE {
attributeCertificate AttributeCertificate,
acPath SEQUENCE OF ACPathData OPTIONAL }
ACPathData ::= SEQUENCE {
certificate [0] Certificate OPTIONAL,
attributeCertificate [1] AttributeCertificate OPTIONAL }
PrivilegePolicy ::= OBJECT IDENTIFIER
-- privilege attributes --
role ATTRIBUTE::= {
WITH SYNTAX RoleSyntax
ID id-at-role }
xmlPrivilegeInfo ATTRIBUTE ::= {
WITH SYNTAX UTF8String --contains XML-encoded privilege information
ID id-at-xMLPrivilegeInfo }
RoleSyntax ::= SEQUENCE {
roleAuthority [0] GeneralNames OPTIONAL,
roleName [1] GeneralName }
-- PMI object classes --
ISO/IEC 9594-8:2005 (E)
116 ITU-T Rec. X.509 (08/2005)
pmiUser OBJECT-CLASS ::= {
SUBCLASS OF {top}
KIND auxiliary
MAY CONTAIN {attributeCertificateAttribute}
ID id-oc-pmiUser
}
pmiAA OBJECT-CLASS ::= {
-- a PMI AA
SUBCLASS OF {top}
KIND auxiliary
MAY CONTAIN {aACertificate |
attributeCertificateRevocationList |
attributeAuthorityRevocationList}
ID id-oc-pmiAA
}
pmiSOA OBJECT-CLASS ::= { -- a PMI Source of Authority
SUBCLASS OF {top}
KIND auxiliary
MAY CONTAIN {attributeCertificateRevocationList |
attributeAuthorityRevocationList |
attributeDescriptorCertificate}
ID id-oc-pmiSOA
}
attCertCRLDistributionPt OBJECT-CLASS ::= {
SUBCLASS OF {top}
KIND auxiliary
MAY CONTAIN { attributeCertificateRevocationList |
attributeAuthorityRevocationList }
ID id-oc-attCertCRLDistributionPts
}
pmiDelegationPath OBJECT-CLASS ::= {
SUBCLASS OF {top}
KIND auxiliary
MAY CONTAIN { delegationPath }
ID id-oc-pmiDelegationPath }
privilegePolicy OBJECT-CLASS ::= {
SUBCLASS OF {top}
KIND auxiliary
MAY CONTAIN {privPolicy }
ID id-oc-privilegePolicy }
protectedPrivilegePolicy OBJECT-CLASS ::= {
SUBCLASS OF {top}
KIND auxiliary
MAY CONTAIN {protPrivPolicy }
ID id-oc-protectedPrivilegePolicy }
-- PMI directory attributes --
attributeCertificateAttribute ATTRIBUTE ::= {
WITH SYNTAX AttributeCertificate
EQUALITY MATCHING RULE attributeCertificateExactMatch
ID id-at-attributeCertificate }
aACertificate ATTRIBUTE ::= {
WITH SYNTAX AttributeCertificate
EQUALITY MATCHING RULE attributeCertificateExactMatch
ID id-at-aACertificate }
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 117
attributeDescriptorCertificate ATTRIBUTE ::= {
WITH SYNTAX AttributeCertificate
EQUALITY MATCHING RULE attributeCertificateExactMatch
ID id-at-attributeDescriptorCertificate }
attributeCertificateRevocationList ATTRIBUTE ::= {
WITH SYNTAX CertificateList
EQUALITY MATCHING RULE certificateListExactMatch
ID id-at-attributeCertificateRevocationList}
attributeAuthorityRevocationList ATTRIBUTE ::= {
WITH SYNTAX CertificateList
EQUALITY MATCHING RULE certificateListExactMatch
ID id-at-attributeAuthorityRevocationList }
delegationPath ATTRIBUTE ::= {
WITH SYNTAX AttCertPath
ID id-at-delegationPath }
AttCertPath ::= SEQUENCE OF AttributeCertificate
privPolicy ATTRIBUTE ::= {
WITH SYNTAX PolicySyntax
ID id-at-privPolicy }
protPrivPolicy ATTRIBUTE ::= {
WITH SYNTAX AttributeCertificate
EQUALITY MATCHING RULE attributeCertificateExactMatch
ID id-at-protPrivPolicy }
xmlPrivPolicyATTRIBUTE ::= {
WITH SYNTAX UTF8String --contains XML-encoded privilege policy information
ID id-at-xMLPprotPrivPolicy }
-- Attribute certificate extensions and matching rules --
attributeCertificateExactMatch MATCHING-RULE ::= {
SYNTAX AttributeCertificateExactAssertion
ID id-mr-attributeCertificateExactMatch }
AttributeCertificateExactAssertion ::= SEQUENCE {
serialNumber CertificateSerialNumber,
issuer AttCertIssuer
}
attributeCertificateMatch MATCHING-RULE ::= {
SYNTAX AttributeCertificateAssertion
ID id-mr-attributeCertificateMatch }
AttributeCertificateAssertion ::= SEQUENCE {
holder [0] CHOICE {
baseCertificateID [0] IssuerSerial,
holderName [1] GeneralNames} OPTIONAL,
issuer [1] GeneralNames OPTIONAL,
attCertValidity [2] GeneralizedTime OPTIONAL,
attType [3] SET OF AttributeType OPTIONAL}
-- At least one component of the sequence shall be present
holderIssuerMatch MATCHING-RULE ::= {
SYNTAX HolderIssuerAssertion
ID id-mr-holderIssuerMatch }
HolderIssuerAssertion ::= SEQUENCE {
holder [0] Holder OPTIONAL,
issuer [1] AttCertIssuer OPTIONAL
}
ISO/IEC 9594-8:2005 (E)
118 ITU-T Rec. X.509 (08/2005)
delegationPathMatch MATCHING-RULE ::= {
SYNTAX DelMatchSyntax
ID id-mr-delegationPathMatch }
DelMatchSyntax ::= SEQUENCE {
firstIssuer AttCertIssuer,
lastHolder Holder }
sOAIdentifier EXTENSION ::= {
SYNTAX NULL
IDENTIFIED BY id-ce-sOAIdentifier }
sOAIdentifierMatch MATCHING-RULE ::= {
SYNTAX NULL
ID id-mr-sOAIdentifierMatch }
authorityAttributeIdentifier EXTENSION ::=
{
SYNTAX AuthorityAttributeIdentifierSyntax
IDENTIFIED BY { id-ce-authorityAttributeIdentifier } }
AuthorityAttributeIdentifierSyntax ::= SEQUENCE SIZE (1..MAX) OF AuthAttId
AuthAttId ::= IssuerSerial
authAttIdMatch MATCHING-RULE ::= {
SYNTAX AuthorityAttributeIdentifierSyntax
ID id-mr-authAttIdMatch }
roleSpecCertIdentifier EXTENSION ::=
{
SYNTAX RoleSpecCertIdentifierSyntax
IDENTIFIED BY { id-ce-roleSpecCertIdentifier } }
RoleSpecCertIdentifierSyntax ::= SEQUENCE SIZE (1..MAX) OF RoleSpecCertIdentifier
RoleSpecCertIdentifier ::= SEQUENCE {
roleName [0] GeneralName,
roleCertIssuer [1] GeneralName,
roleCertSerialNumber [2] CertificateSerialNumber OPTIONAL,
roleCertLocator [3] GeneralNames OPTIONAL }
roleSpecCertIdMatch MATCHING-RULE ::= {
SYNTAX RoleSpecCertIdentifierSyntax
ID id-mr-roleSpecCertIdMatch }
basicAttConstraints EXTENSION ::=
{
SYNTAX BasicAttConstraintsSyntax
IDENTIFIED BY { id-ce-basicAttConstraints }
}
BasicAttConstraintsSyntax ::= SEQUENCE
{
authority BOOLEAN DEFAULT FALSE,
pathLenConstraint INTEGER (0..MAX) OPTIONAL
}
basicAttConstraintsMatch MATCHING-RULE ::= {
SYNTAX BasicAttConstraintsSyntax
ID id-mr-basicAttConstraintsMatch }
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 119
delegatedNameConstraints EXTENSION ::= {
SYNTAX NameConstraintsSyntax
IDENTIFIED BY id-ce-delegatedNameConstraints }
delegatedNameConstraintsMatch MATCHING-RULE ::= {
SYNTAX NameConstraintsSyntax
ID id-mr-delegatedNameConstraintsMatch}
timeSpecification EXTENSION ::= {
SYNTAX TimeSpecification
IDENTIFIED BY id-ce-timeSpecification }
timeSpecificationMatch MATCHING-RULE ::= {
SYNTAX TimeSpecification
ID id-mr-timeSpecMatch }
acceptableCertPolicies EXTENSION ::= {
SYNTAX AcceptableCertPoliciesSyntax
IDENTIFIED BY id-ce-acceptableCertPolicies }
AcceptableCertPoliciesSyntax ::= SEQUENCE SIZE (1..MAX) OF CertPolicyId
CertPolicyId ::= OBJECT IDENTIFIER
acceptableCertPoliciesMatch MATCHING-RULE ::= {
SYNTAX AcceptableCertPoliciesSyntax
ID id-mr-acceptableCertPoliciesMatch }
attributeDescriptor EXTENSION ::= {
SYNTAX AttributeDescriptorSyntax
IDENTIFIED BY {id-ce-attributeDescriptor } }
AttributeDescriptorSyntax ::= SEQUENCE {
identifier AttributeIdentifier,
attributeSyntax OCTET STRING (SIZE(1..MAX)),
name [0] AttributeName OPTIONAL,
description [1] AttributeDescription OPTIONAL,
dominationRule PrivilegePolicyIdentifier}
AttributeIdentifier ::= ATTRIBUTE.&id({AttributeIDs})
AttributeIDs ATTRIBUTE ::= {...}
AttributeName ::= UTF8String(SIZE(1..MAX))
AttributeDescription ::= UTF8String(SIZE(1..MAX))
PrivilegePolicyIdentifier ::= SEQUENCE {
privilegePolicy PrivilegePolicy,
privPolSyntax InfoSyntax }
attDescriptor MATCHING-RULE ::= {
SYNTAX AttributeDescriptorSyntax
ID id-mr-attDescriptorMatch }
userNotice EXTENSION ::= {
SYNTAX SEQUENCE SIZE (1..MAX) OF UserNotice
IDENTIFIED BY id-ce-userNotice }
targetingInformation EXTENSION ::= {
SYNTAX SEQUENCE SIZE (1..MAX) OF Targets
IDENTIFIED BY id-ce-targetInformation }
ISO/IEC 9594-8:2005 (E)
120 ITU-T Rec. X.509 (08/2005)
Targets ::= SEQUENCE SIZE (1..MAX) OF Target
Target::=CHOICE {
targetName [0] GeneralName,
targetGroup [1] GeneralName,
targetCert [2] TargetCert }
TargetCert ::= SEQUENCE {
targetCertificate IssuerSerial,
targetName GeneralName OPTIONAL,
certDigestInfo ObjectDigestInfo OPTIONAL }
noRevAvail EXTENSION ::= {
SYNTAX NULL
IDENTIFIED BY id-ce-noRevAvail }
acceptablePrivilegePolicies EXTENSION ::= {
SYNTAX AcceptablePrivilegePoliciesSyntax
IDENTIFIED BY id-ce-acceptablePrivilegePolicies }
AcceptablePrivilegePoliciesSyntax ::= SEQUENCE SIZE (1..MAX) OF PrivilegePolicy
indirectIssuer EXTENSION ::= {
SYNTAX BOOLEAN
IDENTIFIED BY id-ce-indirectIssuer }
indirectIssuerMatch MATCHING-RULE ::= {
SYNTAX BOOLEAN
ID id-mr-indirectIssuerMatch }
noAssertion EXTENSION ::= {
SYNTAX NULL
IDENTIFIED BY id-ce-noAssertion }
issuedOnBehalfOf EXTENSION ::= {
SYNTAX GeneralName
IDENTIFIED BY id-ce-issuedOnBehalfOf }
-- object identifier assignments --
-- object classes --
id-oc-pmiUser OBJECT IDENTIFIER ::= {id-oc 24}
id-oc-pmiAA OBJECT IDENTIFIER ::= {id-oc 25}
id-oc-pmiSOA OBJECT IDENTIFIER ::= {id-oc 26}
id-oc-attCertCRLDistributionPts OBJECT IDENTIFIER ::= {id-oc 27}
id-oc-privilegePolicy OBJECT IDENTIFIER ::= {id-oc 32}
id-oc-pmiDelegationPath OBJECT IDENTIFIER ::= {id-oc 33}
id-oc-protectedPrivilegePolicy OBJECT IDENTIFIER ::= {id-oc 34}
-- directory attributes --
id-at-attributeCertificate OBJECT IDENTIFIER ::= {id-at 58}
id-at-attributeCertificateRevocationList OBJECT IDENTIFIER ::= {id-at 59}
id-at-aACertificate OBJECT IDENTIFIER ::= {id-at 61}
id-at-attributeDescriptorCertificate OBJECT IDENTIFIER ::= {id-at 62}
id-at-attributeAuthorityRevocationList OBJECT IDENTIFIER ::= {id-at 63}
id-at-privPolicy OBJECT IDENTIFIER ::= {id-at 71}
id-at-role OBJECT IDENTIFIER ::= {id-at 72}
id-at-delegationPath OBJECT IDENTIFIER ::= {id-at 73}
id-at-protPrivPolicy OBJECT IDENTIFIER ::= {id-at 74}
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 121
id-at-xMLPrivilegeInfo OBJECT IDENTIFIER ::= {id-at 75}
id-at-xMLPprotPrivPolicy OBJECT IDENTIFIER ::= {id-at 76}
-- attribute certificate extensions --
id-ce-authorityAttributeIdentifier OBJECT IDENTIFIER ::= {id-ce 38}
id-ce-roleSpecCertIdentifier OBJECT IDENTIFIER ::= {id-ce 39}
id-ce-basicAttConstraints OBJECT IDENTIFIER ::= {id-ce 41}
id-ce-delegatedNameConstraints OBJECT IDENTIFIER ::= {id-ce 42}
id-ce-timeSpecification OBJECT IDENTIFIER ::= {id-ce 43}
id-ce-attributeDescriptor OBJECT IDENTIFIER ::= {id-ce 48}
id-ce-userNotice OBJECT IDENTIFIER ::= {id-ce 49}
id-ce-sOAIdentifier OBJECT IDENTIFIER ::= {id-ce 50}
id-ce-acceptableCertPolicies OBJECT IDENTIFIER ::= {id-ce 52}
id-ce-targetInformation OBJECT IDENTIFIER ::= {id-ce 55}
id-ce-noRevAvail OBJECT IDENTIFIER ::= {id-ce 56}
id-ce-acceptablePrivilegePolicies OBJECT IDENTIFIER ::= {id-ce 57}
id-ce-indirectIssuer OBJECT IDENTIFIER ::= {id-ce 61}
id-ce-noAssertion OBJECT IDENTIFIER ::= {id-ce 62}
id-ce-issuedOnBehalfOf OBJECT IDENTIFIER ::= {id-ce 64}
-- PMI matching rules --
id-mr-attributeCertificateMatch OBJECT IDENTIFIER ::= {id-mr 42}
id-mr-attributeCertificateExactMatch OBJECT IDENTIFIER ::= {id-mr 45}
id-mr-holderIssuerMatch OBJECT IDENTIFIER ::= {id-mr 46}
id-mr-authAttIdMatch OBJECT IDENTIFIER ::= {id-mr 53}
id-mr-roleSpecCertIdMatch OBJECT IDENTIFIER ::= {id-mr 54}
id-mr-basicAttConstraintsMatch OBJECT IDENTIFIER ::= {id-mr 55}
id-mr-delegatedNameConstraintsMatch OBJECT IDENTIFIER ::= {id-mr 56}
id-mr-timeSpecMatch OBJECT IDENTIFIER ::= {id-mr 57}
id-mr-attDescriptorMatch OBJECT IDENTIFIER ::= {id-mr 58}
id-mr-acceptableCertPoliciesMatch OBJECT IDENTIFIER ::= {id-mr 59}
id-mr-delegationPathMatch OBJECT IDENTIFIER ::= {id-mr 61}
id-mr-sOAIdentifierMatch OBJECT IDENTIFIER ::= {id-mr 66}
id-mr-indirectIssuerMatch OBJECT IDENTIFIER ::= {id-mr 67}
END
ISO/IEC 9594-8:2005 (E)
122 ITU-T Rec. X.509 (08/2005)
Annex B
CRL generation and processing rules
(This annex forms an integral part of this Recommendation | International Standard)
B.1 Introduction
A relying party (certificate user) needs the ability to check the revocation status of a certificate in order to determine
whether or not to trust that certificate. Certificate Revocation Lists (CRL) are one mechanism for relying parties to
obtain the revocation information. Other mechanisms may also be used, but are outside the scope of this Specification.
This annex addresses the use of CRLs for certificate revocation status checking by relying parties. Various authorities
may have different policies regarding their issuance of revocation lists. For instance, in some cases the certificate
issuing authority may authorize a different authority to issue a certificate revocation list for the certificates it issues.
Some authorities may combine revocation of end-entity and CA-certificates into a single list while other authorities may
split these into separate lists. Some authorities may partition their certificate population onto CRL fragments and some
authorities may issue delta updates to a revocation list between regular CRL intervals. As a result, relying parties need
to be able to determine the scope of the CRLs they retrieve to enable them to ensure they have the complete set of
revocation information covering the scope of the certificate in question for the revocation reasons of interest, given the
policy under which they are working. This annex provides a mechanism for the relying parties to determine the scope of
retrieved CRLs.
This annex is written for revocation status checking of public-key certificates using CRLs, Full and Complete EndEntity
CRLs (EPRLs) and Certification Authority Revocation Lists (CARLs). However, this description can also be
applied to revocation status checking of attribute certificates using Attribute Certificate Revocation Lists (ACRL) and
Attribute Authority Revocation Lists (AARL). For purposes of this annex, ACRL can be considered in place of CRL,
EPRL can be full and complete end-entity ACRL, and AARL in place of CARL. Similarly, the directory attributes
identified in B.4 shall be mapped to those for the AARL and ACRL and the fields identifying certificate types in the
Issuing Distribution Point extension can be mapped to those applicable to PMI.
B.1.1 CRL types
CRLs of one or more of the following types may be available to a relying party, based on the revocation aspects of the
policy of the certificate issuing authority:
­ Full and complete CRL;
­ Full and complete end-entity CRL (EPRL);
­ Full and complete Certification Authority Revocation List (CARL);
­ Distribution Point CRL, EPRL or CARL;
­ Indirect CRL, EPRL or CARL (ICRL);
­ Delta CRL, EPRL or CARL;
­ Indirect dCRL, EPRL or CARL.
A full and complete CRL is a list of all revoked end-entity and CA-certificates issued by an authority for any and all
reasons.
A full and complete EPRL is a list of all revoked end-entity certificates issued by an authority for any and all reasons.
A full and complete CARL is a list of revoked CA-certificates issued by an authority for any and all reasons.
A distribution point CRL, EPRL or CARL is one that covers all or a subset of certificates issued by an authority. The
subset could be based on a variety of criteria.
An indirect CRL, EPRL or CARL (ICRL) is a CRL that contains a list of revoked certificates, in which some or all of
those certificates were not issued by the authority signing and issuing the CRL.
A delta CRL, EPRL or CARL is a CRL that only contains changes to a CRL that is complete for the given scope at the
time of the CRL referenced in the dCRL. Note that the referenced CRL might be one that is complete for the given
scope or it might be a dCRL that is used to locally construct a CRL that is complete for the given scope.
All of the above CRL types (except for the dCRL) are CRL types that are complete for their given scope. A dCRL shall
be used in conjunction with an associated CRL that is complete for the same scope in order to form a complete picture
of the revocation status of certificates.
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 123
An indirect delta-CRL, EPRL or CARL is a CRL which only contains changes to a set of one or more CRLs, that are
complete for their given scopes and in which some or all of those certificates may not have been issued by the authority
signing and issuing this CRL.
Within this annex as well as this Specification, "Scope of a CRL" is defined by two independent dimensions. One
dimension is the set of certificates covered by the CRL. Another dimension is the set of reason codes covered by
the CRL. The scope of a CRL can be determined in one or more of the following ways:
­ Issuing Distribution Point (IDP) extension in the CRL; or
­ Other means, outside the scope of this Specification.
B.1.2 CRL processing
If a relying party is using CRLs as the mechanism to determine if a certificate is revoked, they shall use the appropriate
CRL(s) for that certificate. This annex describes a procedure for obtaining and processing appropriate CRLs by walking
through a number of specific steps. An implementation functionally equivalent to the external behaviour resulting from
this procedure shall also be considered compliant with this annex and the associated Specification. The algorithm used
by a particular implementation to derive the correct output (i.e., revocation status for a certificate) from the given inputs
(the certificate itself and input from local policy) is not standardized. For example, although this procedure is described
as a sequence of steps to be processed in order, an implementation may use CRLs which are in its local cache rather
than retrieving CRLs each time it processes a certificate, provided those CRLs are complete for the scope of the
certificate and do not violate any of the parameters of the certificate or policy.
The following general steps are described in B.2 through B.5 below:
1) Determine Parameters for CRLs;
2) Determine CRLs Required;
3) Obtain the CRLs;
4) Process the CRLs.
Step 1) identifies the parameters from the certificate and elsewhere that will be used to determine which types of CRLs
are required.
Step 2) applies the values of the parameters to make the determination.
Step 3) identifies the directory attributes from which the CRL types can be retrieved.
Step 4) describes the processing of appropriate CRLs.
B.2 Determine parameters for CRLs
Information located in the certificate itself, as well information from the policy under which the relying party is
operating, provide the parameters for determining the appropriateness of candidate CRLs. The following information is
required to determine which CRL types are appropriate:
­ Certificate type (i.e., end-entity or CA);
­ Critical CRL Distribution Point;
­ Critical Freshest CRL;
­ Reason codes of interest.
The certificate type can be determined from the basic constraints extension in the certificate. If the extension is present,
it indicates whether the certificate is a CA-certificate or an end-entity certificate. If the extension is absent, the
certificate type is considered to be end-entity. This information is required to determine if a CRL, EPRL or CARL can
be used to check the certificate for revocation.
If the certificate contains a critical CRL Distribution Point extension, the relying party certificate processing system
shall understand this extension and obtain and use the CRL(s) pointed to by the CRL Distribution Point extension for
the reason codes of interest in order to determine revocation status of the certificate. Reliance on a full CRL, for
instance, would not be sufficient.
If the certificate contains a critical Freshest CRL extension, the relying party cannot use the certificate without first
retrieving and checking the freshest CRL.
The reason codes of interest are determined by policy and are generally supplied by the application. It is recommended
that these should include all reason codes. This information is required to determine which CRLs are sufficient in terms
of reason codes.
ISO/IEC 9594-8:2005 (E)
124 ITU-T Rec. X.509 (08/2005)
Note that policy may also dictate whether or not a relying party is expected to check dCRLs for revocation status, when
the freshestCRL extension is flagged non-critical or is absent from the certificate. Though excluded from this step, the
processing of these optional dCRLs is described in step 4).
B.3 Determine CRLs required
The values of the parameters described in B.2 determine the criteria upon which the CRL types required to check
revocation status of a given certificate is determined. The determination of CRL types can be done based on the
following sets of criteria as described in B.3.1 through B.3.4 below.
­ End-entity certificate with critical CRL DP asserted;
­ End-entity certificate with no critical CRL DP asserted;
­ CA-certificate with critical CRL DP asserted;
­ CA-certificate with no critical CRL DP asserted.
Handling of the remaining parameters (critical freshest CRL extension and set of reason codes of interest) is done
within each of the subclauses.
Note that in each case, more than one CRL type can satisfy the requirements. Where there is a choice of CRL types, the
relying party may select any of the appropriate types to use.
B.3.1 End-entity with critical CRL DP
If the certificate is an end-entity certificate and cRLDistributionPoints extension is present in the certificate and
flagged critical, the following CRLs shall be obtained:
­ A CRL from one of the nominated distribution Point CRLs that covers one or more of the reason codes
of interest;
­ If all the reason codes of interest are not covered by that CRL, revocation status for the remaining reason
codes may be satisfied by any combination of the following CRLs:
* Additional distribution point CRLs;
* Additional complete CRLs;
* Additional complete EPRLs.
If the freshest CRL extension is also present in the certificate and if flagged critical, one or more CRLs shall also be
obtained from one or more of the nominated distribution points in that extension, ensuring that freshest revocation
information for all reason codes of interest is checked.
B.3.2 End-entity with no critical CRL DP
If the certificate is an end-entity certificate and the cRLDistributionPoints extension is absent from the certificate or
present and not flagged critical, revocation status for the reason codes of interest may be satisfied by any combination
of the following CRLs:
­ Distribution point CRLs (if present);
­ Complete CRLs;
­ Complete EPRLs.
If the freshest CRL extension is also present in the certificate and if flagged critical, one or more CRLs shall also be
obtained from one or more of the nominated distribution points in that extension, ensuring that freshest revocation
information for all reason codes of interest is checked.
B.3.3 CA with critical CRL DP
If the certificate is a CA and the cRLDistributionPoints extension is present in the certificate and flagged critical, the
following CRLs/CARLs shall be obtained:
­ A CRL or CARL from one of the nominated distribution points that covers one or more of the reason
codes of interest;
­ If all the reason codes of interest are not covered by that CRL/CARL, revocation status for the remaining
reason codes may be satisfied by any combination of the following CRLs/CARLs:
* Additional distribution point CRLs/CARLs;
* Additional complete CRLs;
* Additional complete CARLs.
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 125
If the freshest CRL extension is also present in the certificate and if flagged critical, one or more CRLs/CARLs shall
also be obtained from one or more of the nominated distribution points in that extension, ensuring that freshest
revocation information for all reason codes of interest is checked.
B.3.4 CA with no critical CRL DP
If the certificate is a CA certificate and the cRLDistributionPoints extension is absent from the certificate or present
and not flagged critical, revocation status for the reason codes of interest may be satisfied by any combination of the
following CRLs:
­ Distribution point CRLs/CARLs (if present);
­ Complete CRLs;
­ Complete CARLs.
If the freshest CRL extension is also present in the certificate and if flagged critical, one or more CRLs/CARLs shall
also be obtained from one or more of the nominated distribution points in that extension, ensuring that freshest
revocation information for all reason codes of interest is checked.
B.4 Obtain CRLs
If the relying party is retrieving appropriate CRLs from the Directory, these CRLs are obtained from the CRL DP or
certificate issuer directory entry by retrieving the appropriate attributes, i.e., one or more of the following attributes:
­ Certificate Revocation List;
­ Authority Revocation List;
­ Delta Revocation List.
B.5 Process CRLs
After considering the parameters discussed in B.2, identifying appropriate CRL types as described in B.3 and retrieving
an appropriate set of CRLs as described in B.4, a relying party is ready to process the CRLs. The set of CRLs will
contain at least one base CRL and may also contain one or more dCRLs. For each CRL being processed, the relying
party shall ensure that the CRL is accurate with respect to its scope. The relying party has already determined that the
CRL is appropriate for the scope of the certificate of interest, through the process of B.2 and B.3 above. In addition,
validity checks shall be conducted on the CRLs and they shall be checked to determine whether or not the certificate
has been revoked. These checks are described in B.5.1 through B.5.4 below.
B.5.1 Validate base CRL scope
As described in B.3, there can be more than one type of CRL that can be used as the base CRL for checking revocation
status of a certificate. Depending on the policy of issuing authority with respect to CRL issuance, the relying party may
have one or more of the following base CRL types available to them.
­ Complete CRL for all entities;
­ Complete EPRL;
­ Complete CARL;
­ Distribution Point Based CRL/EPRL/CARL.
Subclauses B.5.1.1 through B.5.1.4 provide the set of conditions which shall be true in order for a relying party to use a
CRL of each type as the base CRL for certificate revocation status checking for reason codes of interest.
Indirect base CRLs are addressed within each of the subclauses.
B.5.1.1 Complete CRL
In order to determine that a CRL is a complete CRL for end-entity and CA-certificates for which the CRL issuer is
responsible, for all reason codes of interest, the following shall be true:
­ Delta CRL indicator extension shall be absent; and
­ Issuing distribution point extension may be present; and
­ Either the issuing distribution point extension shall not contain distribution point field or one of the
names in the distribution point field shall match the issuer field in the CRL; and
ISO/IEC 9594-8:2005 (E)
126 ITU-T Rec. X.509 (08/2005)
­ Issuing distribution point extension shall either not contain any of the following fields or if it contains
any of the following fields, none of the fields present shall be set to TRUE: containsUserPublicKeyCerts,
containsCACerts, containsUserAttributeCerts, containsAACerts, and/or containsSOAPublicKeyCerts;
and
­ If the reasonCodes field is present in the issuing distribution point extension, the reasons code field
shall include all the reasons of interest to the application; and
­ Issuing distribution point extension may or may not contain indirectCRL field (hence, this field need not
be checked).
B.5.1.2 Complete EPRL
In order to determine that a CRL is a complete EPRL for reason codes of interest, all of the following shall be true:
­ Delta CRL indicator extension shall be absent; and
­ Issuing distribution point extension shall be present; and
­ Either the issuing distribution point extension shall not contain distribution point field or one of the
names in the distribution point field shall match the issuer field in the CRL; and
­ Issuing distribution point extension shall contain containsUserPublicKeyCerts field. This field shall be
set to TRUE; and
­ If the reasonCodes field is present in the issuing distribution point extension, the reasons code field
shall include all the reasons of interest to the application; and
­ Issuing distribution point extension may or may not contain indirectCRL field (hence, this field need not
be checked); and
This CRL may be only used if the relying party has determined the subject certificate to be an end entity certificate.
Thus, if the subject certificate contains the basicConstraints extension, its value shall be cA=FALSE.
B.5.1.3 Complete CARL
In order to determine that a CRL is a complete CARL for reason codes of interest, all of the following conditions shall
be true:
­ Delta CRL indicator extension shall be absent; and
­ Issuing point distribution shall be present; and
­ Either the issuing distribution point extension shall not contain distribution point field or one of the
names in the distribution point field shall match the issuer field in the CRL; and
­ Issuing distribution point shall contain containsCACerts field. This field shall be set to TRUE; and
­ If the reasonCodes field is present in the issuing distribution point extension, the reasons code field
shall include all the reasons of interest to the application; and
­ Issuing distribution point may or may not contain indirectCRL field (hence, this field need not be
checked); and
This CARL may be only used if the subject certificate is a CA-certificate. Thus, the subject certificate shall contain the
basicConstraints extension with the value cA=TRUE.
B.5.1.4 Distribution point based CRL/EPRL/CARL
In order to determine that a CRL is one of the CRLs indicated by a CRL distribution point extension or freshest CRL
Extension in the certificate, all of the following conditions shall be true:
­ Either the distribution point field in the CRL's issuing distribution point extension shall be absent (only
when not looking for a critical CRL DP), or one of the names in the distribution point field in the CRL
distribution point extension or freshest CRL extension of the certificate shall match one of the names in
the distribution point field in the issuing distribution point extension of the CRL. Alternatively, one of
the names in the cRLIssuer field of the certificate's CRL DP or freshest CRL extension can match one of
the names in DP of the IDP; and
­ Issuing distribution point extension shall either not contain any of the following fields, or if it contains
any of the following fields, none of the fields present shall be set to TRUE: containsUserPublicKeyCerts,
containsCACerts, containsUserAttributeCerts, containsAACerts, and/or containsSOAPublicKeyCerts, or
the field appropriate for the certificate type shall be set to TRUE (See Table B.1 for field type for each
certificate type); and
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 127
­ If the reasons code field is present in the CRL distribution point extension or freshest CRL extension of
the certificate, this field shall be either absent from the issuing distribution point extension of the CRL or
contain at least one of the reason codes asserted in the CRL distribution point extension of the certificate;
and
­ If the cRLIssuer field is absent from the CRL distribution point extension of the certificate, the CRL
shall be signed by the same CA that signed the certificate; and
­ If the cRLIssuer field is present in the relative extension (CRL distribution point or freshest CRL
extension) of the certificate, the CRL shall be signed by the CRL Issuer identified in the CRL
distribution point extension or freshest CRL extension of the certificate and the CRL shall contain the
indirectCRL field in the issuing distribution point extension.
NOTE ­ When testing the reasons and cRLIssuer field for presence, the test succeeds only if the field is present
in the same DistributionPoint of the CRL DP or freshest CRL extension for which there is a name match in the
distribution point field of the IDP extension in the corresponding CRL.
Table B.1 ­ Certificate Type and Issuing Distribution Point Field
Certificate Type Issuing Distribution Point Field
End Entity (public key) containsUserPublicKeyCerts
CA containsCACerts
End Entity (attribute) containsUserAttributeCerts
AA containsAACerts
SOA containsSOAPublicKeyCerts
B.5.2 Validate delta CRL scope
The relying party may also be checking dCRLs, either because required to through a critical freshestCRL extension in
the certificate or CRL, or because the policy under which the relying party is operating requires dCRL checking.
A relying party can always be sure that it has the appropriate CRL information for a certificate if all of the following
conditions are met:
­ The base CRL the relying party is using is appropriate for the certificate (in terms of the scope); and
­ The delta CRL the relying party is using is appropriate for the certificate (in terms of the scope); and
­ The base CRL was issued at the time or later than the base CRL referenced by the dCRL.
In order to determine that the dCRL is appropriate for the certificate, all of the following conditions shall be true:
­ Delta CRL indicator extension shall be present; and
­ The dCRL shall be issued after the base CRL. One way to ensure this is to check that the CRL number in
the crlNumber extension of the dCRL is greater than the CRL number in the crlNumber extension of the
base CRL the relying party is using and the cRLStreamIdentifier fields in the base and the dCRL match.
This approach may require additional logic to account for number wrapping. Another way is to compare
the thisUpdate fields in the base and dCRLs the relying party has; and
­ The base CRL the relying party is using shall be the one the dCRL is issued for or a later one. One way
to ensure this is to check that the CRL number in the deltaCRLIndicator extension of the dCRL is less
than or equal to the CRL number in the crlNumber extension of the base CRL the relying party is using
and the cRLStreamIdentifier fields in the base and the dCRL match. This approach may require
additional logic to account for number wrapping. Another way is to compare the thisUpdate fields of the
base CRL the relying party has and the base CRL pointed to by the dCRL. Yet another way is to
compare the thisUpdate field in the base CRL the relying party has and the baseUpdateTime extension
in the dCRL the relying party has; and
NOTE ­ A relying party can always construct a base CRL by applying a dCRL to a base CRL as long as the
above two rules are satisfied using the crlNumber and cRLStreamIdentifier checks. In that case, the new
base CRL's crlNumber extension and thisUpdate field are those of the dCRL. The relying party does not
know the nextUpdate field of the new base CRL and does not need to know for the purpose of associating it
with another dCRL.
­ If the dCRL contains an Issuing Distribution Point extension, then the scope of the issuing distribution
point shall be consistent with the certificate as described in B.5.1.4 above; and
­ If the dCRL does not contain any of the following extensions: streamIdentifier and
issuingDistributionPoint, it shall be used only in conjunction with a full and complete base CRL.
ISO/IEC 9594-8:2005 (E)
128 ITU-T Rec. X.509 (08/2005)
B.5.3 Validity and currency checks on the base CRL
In order to verify that a base CRL is accurate and has not been modified since its issuance, all of the following
conditions shall be satisfied:
­ The relying party shall be able to obtain the public key of the issuer identified in the CRL using
authenticated means; and
­ The signature on the base CRL shall be verified using this authenticated public key; and
­ If the nextUpdate field is present, the current time should be prior to the nextUpdate field; and
­ The issuer name in the CRL shall match the issuer name in the certificate that is being checked for
revocation, unless the CRL is retrieved from the CRL DP in the certificate and the CRL DP extension
contains the CRL issuer component. In that case, one of the names in CRL issuer component in the
CRL DP extension shall match issuer name in the CRL.
B.5.4 Validity and checks on the delta CRL
In order to verify that a dCRL is accurate and has not been modified since its issuance, all of the following conditions
shall be satisfied:
­ The relying party shall be able to obtain the public key of the issuer identified in the CRL using
authenticated means; and
­ The signature on the dCRL shall be verified using this authenticated public key; and
­ If the nextUpdate field is present, the current time should be prior to the nextUpdate field; and
­ The issuer name in the dCRL shall match the issuer name in the certificate which is being checked for
revocation, unless the Delta CRL is retrieved from the CRL DP in the certificate and the CRL DP
extension contains the CRL issuer component. In that case, one of the names in CRL issuer component
in the CRL DP extension shall match issuer name in the CRL.
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 129
Annex C
Examples of delta CRL issuance
(This annex does not form an integral part of this Recommendation | International Standard)
There are two models for issuing CRLs involving the use of dCRLs for a given set of certificates.
In the first model, each dCRL references the most recent CRL that is complete for the given scope. Several dCRLs may
be issued for that same scope before a new CRL that is complete for that scope is issued. The new CRL that is complete
for that scope is used as the foundation for the next sequence of dCRLs and is the CRL that is referenced in the relevant
extension in the dCRL. When the new CRL that is complete for the scope is issued, a final dCRL for the previous CRL
that is complete for the scope is also issued.
The second model, while very similar, differs in that the CRL referenced by a dCRL is not necessarily one that is
complete for given scope (i.e., the referenced CRL may only have been issued as a dCRL). If the referenced CRL is one
that is complete for the given scope, it may not necessarily be the most recent one that is complete for that scope.
A certificate using system that is processing a dCRL shall also have a CRL that is complete for the given scope and that
is at least as current as the CRL referenced in the dCRL. This CRL that is complete for the given scope may be one that
was issued as such by the responsible authority or it may be one constructed locally by the certificate using system.
Note that in some situations there may be duplicate information in the dCRL and CRL that is complete for the given
scope if, for example, the certificate using system has a CRL that was issued after the one referenced in the dCRL.
The following table illustrates three examples of the use of dCRLs. Example 1 is the traditional scheme described as the
first model above. Examples 2 and 3 are variants of the second model described above.
In example 2, the authority issues CRLs, that are complete for the given scope, every second day and the dCRLs
reference the second to last complete for scope CRL. This scheme may be useful in environments where there is a need
to reduce the number of users accessing a repository at the same time to retrieve a CRL that is complete for a given
scope. In example 2, users that have the most recent CRL that is complete for the scope as well as users who have the
second most recent complete for scope CRL can use the same dCRL. Both sets of users have complete revocation
information about the certificates for that given scope at the time of issuance of the dCRL being used.
In example 3, CRLs that are complete for the given scope are issued once a week as in example 1, but every dCRL
references a base of revocation information 7 days prior to that dCRL.
An example of the use of indirect CRLs is not provided here, but is a superset of those examples.
These are examples only and other variants are also possible, depending on local policy. Some factors which might be
considered when establishing that policy include: number of users and frequency accessing CRLs, replication of CRLs,
load balancing for directory systems holding CRLs, performance, latency requirements, etc.
ISO/IEC 9594-8:2005 (E)
130 ITU-T Rec. X.509 (08/2005)
Day
Example 1 ­ Delta references most recent
CRL that is complete for given scope
Example 2 ­ Delta references second most
recent CRL that is complete for given scope
Example 3 ­ Delta references
7-day-old revocation
information
CRL complete for
given scope
Delta-CRL CRL complete for
given scope
Delta-CRL CRL complete for
given scope
Delta-CRL
8 thisUpdate=day 8
nextUpdate=day 15
crlNumber=8
thisUpdate=day 8
nextUpdate=day 9
crlNumber=8
BaseCRLNumber=1
thisUpdate=day 8
nextUpdate=day 10
crlNumber=8
thisUpdate=day 8
nextUpdate=day 9
crlNumber=8
BaseCRLNumber=6
thisUpdate=day 8
nextUpdate=day 15
cRLNumber=8
thisUpdate=day 8
nextUpdate=day 9
cRLNumber=8
BaseCRLNumber= 1
9 not issued thisUpdate=day 9
nextUpdate=day 10
crlNumber=9
BaseCRLNumber=8
not issued thisUpdate=day 9
nextUpdate=day 10
crlNumber=9
BaseCRLNumber=6
not issued thisUpdate=day 9
nextUpdate=day 10
cRLNumber=9
BaseCRLNumber= 2
10 not issued thisUpdate=day 10
nextUpdate=day 11
crlNumber=10
BaseCRLNumber=8
thisUpdate=day 10
nextUpdate=day 12
crlNumber=10
thisUpdate=day 10
nextUpdate=day 11
crlNumber=10
BaseCRLNumber=8
not issued thisUpdate=day 10
nextUpdate=day 11
cRLNumber=10
BaseCRLNumber= 3
11-
14
Patterns continue as for previous days
15 thisUpdate=day 15
nextUpdate=day 22
crlNumber=15
thisUpdate=day 15
nextUpdate=day 16
crlNumber=15
BaseCRLNumber=8
not issued thisUpdate=day 15
nextUpdate=day 16
crlNumber=15
BaseCRLNumber=12
thisUpdate=day 15
nextUpdate=day 22
cRLNumber=15
thisUpdate=day 15
nextUpdate=day 16
cRLNumber=15
BaseCRLNumber= 8
16 not issued thisUpdate=day 16
nextUpdate=day 17
crlNumber=16
BaseCRLNumber=15
thisUpdate=day 16
nextUpdate=day 18
crlNumber=16
thisUpdate=day 16
nextUpdate=day 17
crlNumber=16
BaseCRLNumber=14
not issued thisUpdate=day 16
nextUpdate=day 17
cRLNumber=16
BaseCRLNumber= 9
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 131
Annex D
Privilege policy and privilege attribute definition examples
(This annex does not form an integral part of this Recommendation | International Standard)
D.1 Introduction
Privilege policy defines, for privilege management, precisely when a privilege verifier should conclude that a presented
set of privileges is sufficient in order that it may grant access (to the requested object, resource, application, etc.) to the
privilege asserter. Formal specification of privilege policy can aid a privilege verifier with automated assessment of a
privilege asserter's privileges against the sensitivity of the requested resource, since it includes the rules for determining
the pass/fail of a privilege asserter's request, given their privilege and the sensitivity of the resource.
Because there are requirements to ensure the integrity of the privilege policy being used in those determinations, an
identifier of the privilege policy, in the form of an object identifier, and a HASH of the entire privilege policy can be
carried in signed objects, stored in directory entries, etc. However, no specific syntax used to define an instance of
privilege policy is standardized in this Specification.
D.2 Sample syntaxes
Privilege policy may be defined using any syntax, including plain text. In order to assist those defining privilege
policies in understanding various options for the definitions, two sample syntaxes, which could be used for this purpose,
are provided in this annex. It needs to be stressed that these are examples only and implementation of privilege
management through the use of attribute certificates or the subjectDirectoryAttributes extension of public-key
certificates are NOT required to support these or any other specific syntaxes.
D.2.1 First example
The following ASN.1 syntax is one example of a comprehensive and flexible tool for the definition of privilege policy.
PrivilegePolicySyntax ::= SEQUENCE {
version Version,
ppe PrivPolicyExpression }
PrivPolicyExpression ::= CHOICE {
ppPredicate [0] PrivPolicyPredicate,
and [1] SET SIZE (2..MAX) OF PrivPolicyExpression,
or [2] SET SIZE (2..MAX) OF PrivPolicyExpression,
not [3] PrivPolicyExpression,
orderedPPE [4] SEQUENCE OF PrivPolicyExpression }
-- Note: "sequence" defines the temporal order in which the
-- privilege shall be examined
PrivPolicyPredicate ::= CHOICE {
present [0] PrivilegeIdentifier,
equality [1] PrivilegeComparison, -- single/set-valued priv.
greaterOrEqual [2] PrivilegeComparison, -- single-valued priv.
lessOrEqual [3] PrivilegeComparison, -- single-valued priv.
subordinate [4] PrivilegeComparison, -- single-valued priv.
substrings [5] SEQUENCE { -- single-valued priv.
type PrivilegeType,
initial [0] PrivilegeValue OPTIONAL,
any [1] SEQUENCE OF PrivilegeValue,
final [2] PrivilegeValue OPTIONAL },
subsetOf [6] PrivilegeComparison, -- set-valued priv.
supersetOf [7] PrivilegeComparison, -- set-valued priv.
nonNullSetInter [8] PrivilegeComparison, -- set-valued priv.
approxMatch [9] PrivilegeComparison,
-- single/set-valued priv. (approximation defined by application)
extensibleMatch [10] SEQUENCE {
matchingRule OBJECT IDENTIFIER,
inputs PrivilegeComparison } }
PrivilegeComparison ::= CHOICE {
explicit [0] Privilege,
ISO/IEC 9594-8:2005 (E)
132 ITU-T Rec. X.509 (08/2005)
-- the value(s) of an external privilege identified by
-- Privilege.privilegeId is(are) compared with the value(s)
-- explicitly provided in Privilege.privilegeValueSet
byReference [1] PrivilegeIdPair }
-- the value(s) of an external privilege identified by
-- PrivilegeIdPair.firstPrivilege is(are) compared with
-- the value(s) of a second external privilege identified by
-- PrivilegeIdPair.secondPrivilege
Privilege ::= SEQUENCE {
type PRIVILEGE.&id ({SupportedPrivileges}),
values SET SIZE (0..MAX) OF
PRIVILEGE.&Type ({SupportedPrivileges} {@type})
}
SupportedPrivileges PRIVILEGE::= { ... }
PRIVILEGE ::= ATTRIBUTE
-- Privilege is analogous to Attribute
PrivilegeIdPair ::= SEQUENCE {
firstPrivilege PrivilegeIdentifier,
secondPrivilege PrivilegeIdentifier }
PrivilegeIdentifier ::= CHOICE {
privilegeType [0] PRIVILEGE.&id ({SupportedPrivileges}),
xmlTag [1] OCTET STRING,
edifactField [2] OCTET STRING }
-- PrivilegeIdentifier extends the concept of AttributeType to other
-- (e.g., tagged) environments, such as XML and EDIFACT
Version ::= INTEGER { v1(0) }
A concrete example may help to clarify the creation and use of the above PrivilegePolicy construct.
Consider the privilege to approve a salary increase. For simplicity, assume that the policy to be enforced states that only
Senior Managers and above can approve increases, and that an approval can only be given for a position lower than
your own (e.g., a Director can approve an increase for a Senior Manager, but not for a Vice-President). For this
example, assume that there are six possible ranks ("TechnicalStaff" = 0, "Manager" = 1, "Senior Manager" = 2,
"Director" = 3, "Vice-President" = 4, "President" = 5).
Assume, furthermore, that the Attribute Type (the "privilege") identifying rank in an Attribute Certificate is OBJECT
ID OID-C and that the Attribute Type (the "sensitivity") identifying rank in the database record whose salary field is to
be modified is OBJECT ID OID-D (these would of course be replaced by real object identifiers in an actual
implementation). The following Boolean expression denotes the desired "salary approval" policy (codifying this in a
PrivilegePolicy expression is a relatively straightforward task):
AND ( NOT ( lessOrEqual ( value corresponding to OID-C, value corresponding to OID-D ) )
subsetOf ( value corresponding to OID-C, { 2, 3, 4, 5 } ) )
This policy encoding says that the rank of the approver shall be greater than (expressed as "NOT less-than-or-equal-to")
the rank of the approvee AND that the rank of the approver shall be one of {Senior Manager, ..., President} in order for
this Boolean expression to evaluate to TRUE. The first privilege comparison is "by reference", comparing the values
corresponding to the Attribute Type "rank" for both entities involved. The second privilege comparison is "explicit";
here the value corresponding to the privilege "rank" for the approver is compared with an explicitly-included list of
values. The privilege verifier in this situation, therefore, needs a construct codifying this policy along with two
Attributes, one associated with the approver and one associated with the approvee. The approver's Attribute (which
would be contained in an Attribute Certificate) may have the value {OID-C 3} and the approvee's Attribute (which may
be contained in a database record) may have the value {OID-D 3}. Comparing the AttributeValue corresponding to the
approver's Attribute Type (in this example, 3) with the Attribute Value corresponding to the approvee's Attribute Type
(in this example, also 3) results in a FALSE for the "NOT lessOrEqual" expression, and so the first Director is denied
the ability to approve a salary increase for the second Director. On the other hand, if the approvee's Attribute was
{OID-D 1}, the Director would be granted the ability to approve the Manager's increase.
It is not difficult to conceive of useful additions to the above expression. For example, a third component of the 'and'
could be added saying that the environment variable "currentTime", read from the local clock and then encoded as an
attribute of type OBJECT ID OID-E, shall be within a particular span specified explicitly in the expression as an
attribute of type OBJECT ID OID-F. Thus, for example, salary updates may be permitted only if the above conditions
are satisfied and the request takes place during business hours.
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 133
D.2.2 Second example
A security policy in its simplest form is a set of criteria for the provision of security services. With regard to access
control, security policy is a subset of a higher system-level security policy that defines the means for enforcing access
control policies between initiators and targets. The access control mechanisms need to permit communication where a
specific policy permits; deny communication where a specific policy does not explicitly permit.
A security policy is the basis for the decisions made by the access control mechanisms. Domain-specific security policy
information is conveyed via the Security Policy Information File (SPIF).
The SPIF is a signed object to protect it from unauthorized changes. The SPIF contains information used to interpret the
access control parameters contained in the security label and the clearance attribute. The security policy identifier that
appears in the clearance attribute needs to be associated with a specific implementation syntax and semantics as defined
by the security policy. This implementation syntax associated with a specific security policy is maintained in a SPIF.
The SPIF conveys equivalencies between authorizations and sensitivities across security policy domains as determined
by security policies, provides a printable representation of security labels, and maps displayable strings to security
levels and categories for presentation to end users when selecting a data object's security attributes. Equivalency
mappings are expressed such that a label generated under one security policy domain may be correctly interpreted by an
application operating in another security policy domain. The SPIF also maps the clearance attribute to the message
security label fields and the presentation labels that should be displayed to the user. This mapping, if successful, verifies
that the intended recipient has the proper authorizations to accept the data object.
A SPIF contains a sequence of the following:
­ versionInformation ­ indicates the version of the ASN.1 syntax.
­ updateInformation ­ indicates the version of the syntax and semantics of the SPIF specification.
­ securityPolicyIdData ­ identifies the security policy to which the SPIF applies.
­ privilegeId ­ indicates the OID that identifies the syntax that is included in the clearance attribute
security category.
­ rbacId ­ object identifier which identifies the syntax of the security category that is used in conjunction
with the SPIF.
­ securityClassifications ­ maps the classification of the security label to a classification in the clearance
attribute, and also provides equivalency mappings.
­ securityCategoryTagSets ­ maps the security categories of the security label to the security categories
in the clearance attribute, and also provides equivalency mappings.
­ equivalentPolicies ­ consolidates all equivalent policies in the SPIF.
­ defaultSecurityPolicyIdData ­ identifies the security policy which will apply if data is received without
a security label.
­ extensions ­ provides a mechanism to include additional capabilities as future requirements are
identified.
The Security Policy Information File is defined in the following syntax:
SecurityPolicyInformationFile ::= SIGNED {SPIF}
SPIF ::= SEQUENCE {
versionInformation VersionInformationData DEFAULT v1,
updateInformation UpdateInformationData,
securityPolicyIdData ObjectIdData,
privilegeId OBJECT IDENTIFIER,
rbacId OBJECT IDENTIFIER,
securityClassifications [0] SEQUENCE OF SecurityClassification OPTIONAL,
securityCategories [1] SEQUENCE OF SecurityCategory OPTIONAL,
equivalentPolicies [2] SEQUENCE OF EquivalentPolicy OPTIONAL,
defaultSecurityPolicyIdData [3] ObjectIdData OPTIONAL,
extensions [4] Extensions OPTIONAL }
VersionInformationData ::= INTEGER { v1(0) }
UpdateInformationData ::= SEQUENCE {
sPIFVersionNumber INTEGER,
creationDate GeneralizedTime,
originatorDistinguishedName Name,
keyIdentifier OCTET STRING OPTIONAL }
ISO/IEC 9594-8:2005 (E)
134 ITU-T Rec. X.509 (08/2005)
ObjectIdData ::= SEQUENCE {
objectId OBJECT IDENTIFIER,
objectIdName DirectoryString {ubObjectIdNameLength} }
SecurityClassification ::= SEQUENCE {
labelAndCertValue INTEGER,
classificationName DirectoryString {ubClassificationNameLength},
equivalentClassifications [0] SEQUENCE OF EquivalentClassification OPTIONAL,
hierarchyValue INTEGER,
markingData [1] SEQUENCE OF MarkingData OPTIONAL,
requiredCategory [2] SEQUENCE OF OptionalCategoryGroup OPTIONAL,
obsolete BOOLEAN DEFAULT FALSE }
EquivalentClassification ::= SEQUENCE {
securityPolicyId OBJECT IDENTIFIER,
labelAndCertValue INTEGER,
applied INTEGER {
encrypt (0),
decrypt (1),
both (2) } }
MarkingData ::= SEQUENCE {
markingPhrase DirectoryString {ubMarkingPhraseLength} OPTIONAL,
markingCodes SEQUENCE OF MarkingCode OPTIONAL }
MarkingCode ::= INTEGER {
pageTop (1),
pageBottom (2),
pageTopBottom (3),
documentEnd (4),
noNameDisplay (5),
noMarkingDisplay (6),
unused (7),
documentStart (8),
suppressClassName (9)}
OptionalCategoryGroup ::= SEQUENCE {
operation INTEGER {
onlyOne (1),
oneOrMore (2),
all (3)},
categoryGroup SEQUENCE OF OptionalCategoryData }
OptionalCategoryData ::= SEQUENCE {
optCatDataId OC-DATA.&id({CatData}),
categorydata OC-DATA.&Type({CatData}{@optCatDataId }) }
OC-DATA ::= TYPE-IDENTIFIER
CatData OC-DATA ::= { ... }
EquivalentPolicy ::= SEQUENCE {
securityPolicyId OBJECT IDENTIFIER,
securityPolicyName DirectoryString {ubObjectIDNameLength}
OPTIONAL}
Extensions ::= SEQUENCE OF Extension
Extension ::= SEQUENCE {
extensionId EXTENSION.&objId ({ExtensionSet}),
critical BOOLEAN DEFAULT FALSE,
extensionValue OCTET STRING }
Note that the SPIF example is an evolving syntax and full definition and description of each element can be found in
ITU-T Rec. X.841 | ISO/IEC 15816.
D.3 Privilege attribute example
The following example of an attribute to convey a particular privilege is provided purely as an illustration only. The
actual specification of this syntax and associated attribute is contained in ITU-T Rec. X.501 | ISO/IEC 9594-2
clause 19.5. This particular attribute conveys clearance that can be associated with a named entity, including a DUA for
purposes of communication with a DSA.
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 135
A clearance attribute associates a clearance with a named entity including DUAs.
clearance ATTRIBUTE ::= {
WITH SYNTAX Clearance
ID id-at-clearance }
Clearance ::= SEQUENCE {
policyId OBJECT IDENTIFIER,
classList ClassList DEFAULT {unclassified},
securityCategories SET SIZE (1MAX) OF SecurityCategory OPTIONAL}
ClassList ::= BIT STRING {
unmarked (0),
unclassified (1),
restricted (2),
confidential (3),
secret (4),
topSecret (5) }
The individual components are described with the actual specification of this privilege in the referenced document.
ISO/IEC 9594-8:2005 (E)
136 ITU-T Rec. X.509 (08/2005)
Annex E
An introduction to public key cryptography3)
(This annex does not form an integral part of this Recommendation | International Standard)
In conventional cryptographic systems, the key used to encipher information by the originator of a secret message is the
same as that used to decipher the message by the legitimate recipient.
In public key cryptosystems (PKCS), however, keys come in pairs, one key of which is used for enciphering and the
other for deciphering. Each key pair is associated with a particular user X. One of the keys, known as the public key
(Xp) is publicly known, and can be used by any user to encipher data. Only X, who possesses the complementary
private key (Xs) may decipher the data. (This is represented notationally by D = Xs[Xp[D]]). It is computationally
unfeasible to derive the private key from knowledge of the public key. Any user can thus communicate a piece of
information which only X can find out, by enciphering it under Xp. By extension, two users can communicate in secret,
by using each other's public key to encipher the data, as shown in Figure E.1.
Figure E.1 ­ Use of a PKCS to exchange secret information
User A has public key Ap and private key As, and user B has another set of keys, Bp and Bs. A and B both know the
public keys of each other, but are unaware of the private key of the other party. A and B may therefore exchange secret
information with one another using the following steps (illustrated in Figure E.1).
1) A wishes to send some secret information x to B. A therefore enciphers x under B's enciphering key and
sends the enciphered information e to B. This is represented by:
e = Bp[x]
2) B may now decipher this encipherment e to obtain the information x by using the secret decipherment
key Bs. Note that B is the only possessor of Bs, and because this key may never be disclosed or sent, it is
impossible for any other party to obtain the information x. The possession of Bs determines the identity
of B. The decipherment operation is represented by:
x = Bs[e], or x = Bs[Bp[x]]
3) B may now similarly send some secret information, x', to A, under A's enciphering key, Ap:
e' = Ap[x']
4) A obtains x' by deciphering e':
x' = As[e'], or x' = As[Ap[x']]
_______________
3) For further information, see:
DIFFIE (W.) and HELLMAN (M.E.): New Directions in Cryptography, IEEE Transactions on Information Theory, IT-22, No. 6,
November 1976.
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 137
By this means, A and B have exchanged secret information x and x'. This information may not be obtained by anyone
other than A and B, providing that their private keys are not revealed.
Such an exchange can, as well as transferring secret information between the parties, serve to verify their identities.
Specifically, A and B are identified by their possession of the secret deciphering keys, As and Bs respectively. A may
determine if B is in possession of the secret deciphering key, Bs, by having returned part of his information x in B's
message x'. This indicates to A that communication is taking place with the possessor of Bs. B may similarly test the
identity of A.
It is a property of some PKCS that the steps of decipherment and encipherment can be reversed, as in D = Xp[Xs[D]].
This allows a piece of information which could only have been originated by X, to be readable by any user (who has
possession of Xp). This can, therefore, be used in the certifying of the source of information, and is the basis for digital
signatures. Only PKCS which have this (permutability) property are suitable for use in this authentication framework.
One such algorithm is described in Annex D.
ISO/IEC 9594-8:2005 (E)
138 ITU-T Rec. X.509 (08/2005)
Annex F
Reference definition of algorithm object identifiers
(This annex forms an integral part of this Recommendation | International Standard)
This annex defines object identifiers assigned to authentication and encryption algorithms, in the absence of a formal
register. It is intended to make use of such a register as it becomes available. The definitions take the form of the ASN.1
module, "AlgorithmObjectIdentifiers".
AlgorithmObjectIdentifiers {joint-iso-itu-t ds(5) module(1) algorithmObjectIdentifiers(8) 5}
DEFINITIONS ::=
BEGIN
-- EXPORTS All --
-- The types and values defined in this module are exported for use in the other ASN.1 modules contained
-- within the Directory Specifications, and for the use of other applications which will use them to access
-- Directory services. Other applications may use them for their own purposes, but this will not constrain
-- extensions and modifications needed to maintain or improve the Directory service.
IMPORTS
algorithm, authenticationFramework
FROM UsefulDefinitions {joint-iso-itu-t ds(5) module(1) usefulDefinitions(0) 5}
ALGORITHM
FROM AuthenticationFramework authenticationFramework ;
-- categories of object identifier --
encryptionAlgorithm OBJECT IDENTIFIER ::= {algorithm 1}
hashAlgorithm OBJECT IDENTIFIER ::= {algorithm 2}
signatureAlgorithm OBJECT IDENTIFIER ::= {algorithm 3}
-- synonyms --
id-ea OBJECT IDENTIFIER ::= encryptionAlgorithm
id-ha OBJECT IDENTIFIER ::= hashAlgorithm
id-sa OBJECT IDENTIFIER ::= signatureAlgorithm
-- algorithms --
rsaALGORITHM ::= {
KeySize
IDENTIFIED BYid-ea-rsa }
KeySize ::= INTEGER
-- the following object identifier assignments reserve values assigned to deprecated functions
id-ea-rsa OBJECT IDENTIFIER ::= {id-ea 1}
id-ha-sqMod-n OBJECT IDENTIFIER ::= {id-ha 1}
id-sa-sqMod-nWithRSA OBJECT IDENTIFIER ::= {id-sa 1}
END
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 139
Annex G
Examples of use of certification path constraints
(This annex does not form an integral part of this Recommendation | International Standard)
G.1 Example 1: Use of basic constraints
Suppose the Widget Corporation wants to cross-certify the central CA of the Acme Corporate Group, but only wants the
Widget community to use end-entity certificates issued by that CA, not certificates issued by other CAs certified by
that CA.
The Widget Corporation could satisfy this requirement by issuing a certificate for Acme's central CA, including the
following extension field value:
Value of Basic Constraints Field:
{ cA TRUE, pathLenConstraint 0 }
G.2 Example 2: Use of policy mapping and policy constraints
Suppose the following cross-certification scenario is required between the Canadian and U.S. governments:
a) a Canadian government CA wishes to certify use of U.S. government signatures with respect to a
Canadian policy called Can/US-Trade;
b) the U.S. government has a policy called US/Can-Trade, which the Canadian government is prepared to
consider equivalent to its Can/US-Trade policy;
c) the Canadian government wants to apply safeguards which require all U.S. certificates to explicitly state
support for the policy and which inhibit mapping to other policies within the U.S. domain.
A Canadian government CA could issue a certificate for a U.S. government CA with the following extension field
values:
Value of Certificate Policies Field:
{{ policyIdentifier -- object identifier for Can/US-Trade -- }}
Value of Policy Mappings Field:
{{ issuerDomainPolicy -- object identifier for Can/US-Trade -- ,
subjectDomainPolicy -- object identifier for US/Can-Trade -- }}
Value of PolicyConstraints Field:
{{ policySet { -- object identifier for Can/US-Trade -- }, requireExplicitPolicy (0),
inhibitPolicyMapping (0)}}
G.3 Use of Name Constraints Extension
G.3.1 Examples of Certificate Format with Name Constraints Extension
The CAs can put various restrictions to the subject names (in the subject field or subjectAltName extension) of the
certificates that they issue and the subsequent certificates in the certification path, by inclusion of the Name Constraints
extension to their CA-certificates. This clause describes the examples of certificate format with Name Constraints
extension.
Making the examples simple, required name forms (requiredNameForms) of Name Constraints extension in these
examples indicates rfc822 name (rfc822Name) and DN (directoryName) only.
ISO/IEC 9594-8:2005 (E)
140 ITU-T Rec. X.509 (08/2005)
G.3.1.1 Examples of permittedSubtrees
(1-1) If the CA-certificate contains the following Name Constraints extension, for all subsequent certificates in the
certification path, each subject name (in the subject field or subjectAltName extension) in DN name form, if
it exists, shall be equal to or subordinate to the Acme Inc. in U.S. (i.e., {C=US, O=Acme Inc}).
nameConstraints extension
permittedSubtrees excludedSubtrees requiredNameForms
{{base(directoryName)
{C=US, O=Acme Inc}}}
(void) (void)
(1-2) If the CA-certificate contains the following Name Constraints extension, for all subsequent certificates in the
certification path, each subject name (in the subject field or subjectAltName extension) in DN name form, if
it exists, shall be equal to or immediately subordinate to the Acme Inc. in U.S. (i.e., {C=US, O=Acme Inc}).
nameConstraints extension
permittedSubtrees excludedSubtrees requiredNameForms
{{base(directoryName)
{C=US, O=Acme Inc},
maximum 1}}
(void) (void)
(1-3) If the CA-certificate contains the following Name Constraints extension, for all subsequent certificates in the
certification path, each subject name (in the subject field or subjectAltName extension) in DN name form, if
it exists, shall be subordinate to the Acme Inc. in U.S. (i.e., {C=US, O=Acme Inc}).
nameConstraints extension
permittedSubtrees excludedSubtrees requiredNameForms
{{base(directoryName)
{C=US, O=Acme Inc},
minimum 1}}
(void) (void)
(1-4) If the CA-certificate contains the following Name Constraints extension, for all subsequent certificates in the
certification path, each subject name (in the subject field or subjectAltName extension) in DN name form, if
it exists, shall be equal to or subordinate to the Acme Inc. in U.S. (i.e., {C=US, O=Acme Inc}), or equal to or
subordinate to the Acme Ltd. in U.K. (i.e., {C=UK, O=Acme Ltd}).
nameConstraints extension
permittedSubtrees excludedSubtrees requiredNameForms
{{base(directoryName)
{C=US, O=Acme Inc}},
{base(directoryName)
{C=UK, O=Acme Ltd}}}
(void) (void)
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 141
G.3.1.2 Examples of excludedSubtrees
(2-1) If the CA-certificate contains the following Name Constraints extension, for all subsequent certificates in the
certification path, each subject name (in the subject field or subjectAltName extension) in DN name form, if
it exists, shall not be equal to nor subordinate to the Acme Corp. in Canada. (i.e., {C=CA, O=Acme Corp}).
nameConstraints extension
permittedSubtrees excludedSubtrees requiredNameForms
(void)
{{base(directoryName)
{C=CA, O=Acme Corp}}}
(void)
(2-2) If the CA-certificate contains the following Name Constraints extension, for all subsequent certificates in the
certification path, each subject name (in the subject field or subjectAltName extension) in DN name form, if
it exists, shall not be subordinate to each immediately subordinate of the Acme Corp. in Canada (i.e., {C=CA,
O=Acme Corp}).
nameConstraints extension
permittedSubtrees excludedSubtrees requiredNameForms
(void)
{{base(directoryName)
{C=CA, O=Acme Corp},
minimum 2}}
(void)
(2-3) If the CA-certificate contains the following Name Constraints extension, for all subsequent certificates in the
certification path, each subject name (in the subject field or subjectAltName extension) in DN name form, if
it exists, shall not be equal to the Acme Corp. in Canada (i.e., {C=CA, O=Acme Corp}).
nameConstraints extension
permittedSubtrees excludedSubtrees requiredNameForms
(void)
{{base(directoryName)
{C=CA, O=Acme Corp},
maximum 0}}
(void)
(2-4) If the CA-certificate contains the following Name Constraints extension, for all subsequent certificates in the
certification path, each subject name (in the subject field or subjectAltName extension) in DN name form, if
it exists, shall not be equal to nor subordinate to the Acme Corp. in Canada (i.e., {C=CA, O=Acme Corp}),
nor equal to nor subordinate to the Asia Acme in Japan (i.e., {C=JP, O=Asia Acme}).
nameConstraints extension
permittedSubtrees excludedSubtrees requiredNameForms
(void)
{{base(directoryName)
{C=CA, O=Acme Corp}},
{base(directoryName)
{C=JP, O=Asia Acme}}}
(void)
ISO/IEC 9594-8:2005 (E)
142 ITU-T Rec. X.509 (08/2005)
G.3.1.3 Examples of permittedSubtrees and excludedSubtrees
(3-1) If the CA-certificate contains the following Name Constraints extension, for all subsequent certificates in the
certification path, each subject name (in the subject field or subjectAltName extension) in DN name form, if
it exists, shall be equal to or subordinate to the Acme Inc. in U.S. (i.e., {C=US, O=Acme Inc}) except the
R&D organization unit of Acme Inc. and the R&D organization's subordinates.
nameConstraints extension
permittedSubtrees excludedSubtrees requiredNameForms
{{base(directoryName)
{C=US, O=Acme Inc}}}
{{base(directoryName)
{C=US, O=Acme Inc,
OU=R&D}}}
(void)
(3-2) If the CA-certificate contains the following Name Constraints extension, for all subsequent certificates in the
certification path, each subject name (in the subject field or subjectAltName extension) in DN name form, if
it exists, shall be equal to one of immediately subordinates to the Acme Inc. in U.S. (i.e., {C=US, O=Acme
Inc}) except the Purchasing organization unit (i.e., {C=US, O=Acme Inc, OU=Purchasing}).
nameConstraints extension
permittedSubtrees excludedSubtrees requiredNameForms
{{base(directoryName)
{C=US, O=Acme Inc},
minimum 1,
maximum 1}}
{{base(directoryName)
{C=US, O=Acme Inc,
OU=Purchasing}}}
(void)
G.3.1.4 Examples of permittedSubtrees and excludedSubtrees with requiredNameForms
(4-1) If the CA-certificate contains the following Name Constraints extension, for all subsequent certificates in the
certification path, at least one of subject names (in the subject field or subjectAltName extension) of
certificate shall be in the DN name form. However, each subject name is not constrained by any name spaces.
nameConstraints extension
requiredNameForms
permittedSubtrees excludedSubtrees
rfc822 name DN
(void) (void) OFF ON
(4-2) If the CA-certificate contains the following Name Constraints extension, for all subsequent certificates in the
certification path, at least one of subject names (in the subject field or subjectAltName extension) shall be in
the DN name form. Moreover, each subject name in DN name form shall satisfy the name spaces constrained
by the permittedSubtrees and excludedSubtrees.
nameConstraints extension
requiredNameForms
permittedSubtrees excludedSubtrees
rfc822 name DN
{{base(directoryName)
{C=JP, O=Asia Acme}}}
{{base(directoryName)
{C=JP, O=Asia Acme,
OU=Marketing}}}
OFF ON
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 143
(4-3) If the CA-certificate contains the following Name Constraints extension, for all subsequent certificates in the
certification path, each subject name (in the subject field or subjectAltName extension) in DN name form, if
it exists, shall satisfy the name spaces constrained by the permittedSubtrees and excludedSubtrees.
nameConstraints extension
requiredNameForms
permittedSubtrees excludedSubtrees
rfc822 name DN
{{base(directoryName)
{C=JP, O=Asia Acme}}}
{{base(directoryName)
{C=JP, O=Asia Acme,
OU=Marketing}}}
OFF OFF
NOTE ­ The above example of CA-certificate is compatible with the following CA-certificate with Name Constraints extension
without requiredNameForms element.
nameConstraints extension
permittedSubtrees excludedSubtrees requiredNameForms
{{base(directoryName)
{C=JP, O=Asia Acme}}}
{{base(directoryName)
{C=JP, O=Asia Acme,
OU=Marketing}}}
(void)
(4-4) If the CA-certificate contains the following Name Constraints extension, for all subsequent certificates in the
certification path, each subject name (in the subject field or subjectAltName extension) in DN name form, if
it exists, shall satisfy the name spaces constrained by the permittedSubtrees and excludedSubtrees.
Moreover, at least one subjectAltName in rfc822Name name form shall be present, though its name is not
constrained by any name spaces.
nameConstraints extension
requiredNameForms
permittedSubtrees excludedSubtrees
rfc822 name DN
{{base(directoryName)
{C=JP, O=Asia Acme}}}
{{base(directoryName)
{C=JP, O=Asia Acme,
OU=Marketing}}}
ON OFF
(4-5) If the CA-certificate contains the following Name Constraints extension, for all subsequent certificates in the
certification path, at least one of subject names (in the subject field or subjectAltName extension) of
certificate shall be in the DN name form or in the rfc822 name form. Each subject name in DN name form, if
it exists, shall satisfy the name spaces constrained by the permittedSubtrees and excludedSubtrees. Each
subject name in rfc822Name name form is not constrained by any name spaces.
nameConstraints extension
requiredNameForms
permittedSubtrees ExcludedSubtrees
rfc822 name DN
{{base(directoryName)
{C=JP, O=Asia Acme}}}
{{base(directoryName)
{C=JP, O=Asia Acme,
OU=Marketing}}}
ON ON
G.3.2 Examples of Certificate Handling with Name Constraint Extension
This clause describes the examples of how subject name (in the subject field or subjectAltName extension) are
validated in the certificate processing with the path processing state variables, namely permitted-subtrees, excludedsubtrees
and required-name-forms.
Making the examples simple, the path processing state variable required-name-forms in these examples indicates rfc822
name (rfc822Name), DN (directoryName) and URI (uniformResourceIdentifier) only.
ISO/IEC 9594-8:2005 (E)
144 ITU-T Rec. X.509 (08/2005)
G.3.2.1 Name Spaces Constraints by permitted-subtrees in DN Name Form
In this case, each subject name (in the subject field or subjectAltName extension) in DN name form appeared in the
certificate in question shall satisfy the constraint by path processing state variable permitted-subtrees.
(1-1) One permitted subtree for DN is present and DN is required in required-name-forms.
Path Processing State Variables
required-name-forms
permitted-subtrees excluded-subtrees
rfc822 DN URI
{{base(directoryName)
{C=US, O=Acme Inc}}}
NONE OFF ON OFF
Acceptable Certificate Examples
1 subject = {C=US, O=Acme Inc, OU=Purchasing}
2
subject = {}
subjectAltName(directoryName) = {C=US, O=Acme Inc, OU=Purchasing}
3
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName (rfc822Name) = manager@purchasing.acme.com
4
subject = {}
subjectAltName (directoryName) = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName (rfc822Name) = manager@purchasing.acme.com
5
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName (directoryName) = {C=US, O=Acme Inc, OU=Accounting}
Unacceptable Certificate Examples
1 subject = {C=US, O=Acme Ltd,OU=Purchasing}
2
subject = {}
subjectAltName (rfc822Name) = manager@purchasing.acme.com
NOTE ­ DN missing
3
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName (directoryName) = {C=US, O=Acme Ltd, OU=Purchasing}
4
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName (directoryName) = {C=US, O=Acme Inc, OU=Purchasing}
5
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName (directoryName) = {C=US, O=Acme Ltd, OU=Accounting}
(1-2) Two permitted subtrees for DN are present and DN is required in required-name-forms
Path Processing State Variables
required-name-forms
permitted-subtrees excluded-subtrees
rfc822 DN URI
{{base(directoryName)
{C=US, O=Acme Inc}},
{base(directoryName)
{C=US, O=Acme Ltd}}}
NONE OFF ON OFF
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 145
Acceptable Certificate Examples
1 subject = {C=US, O=Acme Ltd, OU=Purchasing}
2
subject = {}
subjectAltName(directoryName) = {C=US, O=Acme Ltd, OU=Purchasing}
3
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme-ltd.com
4
subject = {}
subjectAltName(directoryName) = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(directoryName) = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
5
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(directoryName) = {C=US, O=Acme Ltd, OU= Accounting}
Unacceptable Certificate Examples
1 subject = {C=US, O=Acme International, OU=Accounting}
2
subject = {}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
NOTE ­ DN missing
3
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(directoryName) = {C=US, O=Acme International, OU=Accounting}
4
subject = {C=US, O=Acme International, OU=Accounting}
subjectAltName(directoryName) = {C=US, O=Acme Inc, OU=Purchasing}
5
subject = {C=US, O=Acme International, OU=Accounting}
subjectAltName(directoryName) = {C=US, O=Acme Corp, OU=Accounting}
6
subject = {}
subjectAltName(directoryName) = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(directoryName) = {C=US, O=Acme International, OU=Accounting}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
(1-3) One permitted subtree for DN is present and required-name-forms is empty.
Path Processing State Variables
required-name-forms
permitted-subtrees excluded-subtrees
rfc822 DN URI
{{base(directoryName)
{C=US, O=Acme Inc}}}
NONE Empty
ISO/IEC 9594-8:2005 (E)
146 ITU-T Rec. X.509 (08/2005)
Acceptable Certificate Examples
1 subject = {C=US, O=Acme Inc, OU=Purchasing}
2
subject = {}
subjectAltName(directoryName) = {C=US, O=Acme Inc, OU=Purchasing}
3
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
4
subject = {}
subjectAltName(directoryName) = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
5
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(directoryName) = {C=US, O=Acme Inc, OU=Accounting}
6
subject = {}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
Unacceptable Certificate Examples
1 subject = {C=US, O=Acme Ltd,OU=Purchasing}
2
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(directoryName) = {C=US, O=Acme Ltd, OU=Accounting}
3
subject = {C=US, O=Acme Ltd, OU=Accounting}
subjectAltName(directoryName) = {C=US, O=Acme Inc, OU=Purchasing}
4
subject = {C=US, O=Acme Ltd, OU=Accounting}
subjectAltName(directoryName) = {C=US, O=Acme Ltd, OU=Purchasing}
G.3.2.2 Name Spaces Constraints by excluded-subtrees in DN Name Form
In this case, each subject name (in the subject field or subjectAltName extension) in DN name form appeared in the
certificate in question shall satisfy the constraint by path processing state variable excluded-subtrees.
(2-1) One excluded subtree for DN is present and DN is required in required-name-forms.
Path Processing State Variables
required-name-forms
permitted-subtrees excluded-subtrees
rfc822 DN URI
NONE
{{base(directoryName)
{C=US, O=Acme Ltd}}}
OFF ON OFF
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 147
Acceptable Certificate Examples
1 subject = {C=US, O=Acme Inc, OU=Purchasing}
2
subject = {}
subjectAltName(directoryName) = {C=US, O=Acme Inc, OU=Purchasing}
3
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
4
subject = {}
subjectAltName(directoryName) = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
5
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(directoryName) = {C=US, O=Acme Inc, OU=Accounting}
Unacceptable Certificate Examples
1 subject = {C=US, O=Acme Ltd, OU=Purchasing}
2
subject = {}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
NOTE ­ DN missing
3
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(directoryName) = {C=US, O=Acme Ltd, OU=Accounting}
(2-2) Two excluded subtrees for DN are present and DN is required in required-name-forms.
Path Processing State Variables
required-name-forms
permitted-subtrees excluded-subtrees
rfc822 DN URI
NONE
{{base(directoryName)
{C=US, O=Acme Inc}},
{base(directoryName)
{C=US, O=Acme Ltd}}}
OFF ON OFF
Acceptable Certificate Examples
1 subject = {C=US, O=Acme International, OU=Purchasing}
2
subject = {}
subjectAltName(directoryName) = {C=US, O=Acme International, OU=Purchasing}
3
subject = {C=US, O=Acme International, OU=Purchasing}
subjectAltName(rfc822Name) = purchasing@acme-international.com
4
subject = {}
subjectAltName(directoryName) = {C=US, O=Acme International, OU=Purchasing}
subjectAltName(directoryName) = {C=US, O=Acme N.Y, OU=Purchasing}
subjectAltName(rfc822Name) = purchasing@acme-international.com
ISO/IEC 9594-8:2005 (E)
148 ITU-T Rec. X.509 (08/2005)
Unacceptable Certificate Examples
1 subject = {C=US, O=Acme Inc, OU=Purchasing}
2 subject = {C=US, O=Acme Ltd, OU=Purchasing}
3
subject = {}
subjectAltName(rfc822Name) = purchasing@acme-international.com
NOTE ­ DN missing
4
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(directoryName) = {C=US, O=Acme International, OU=Accounting}
5
subject = {}
subjectAltName(directoryName) = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(directoryName) = {C=US, O=Acme International, OU=Purchasing}
subjectAltName(rfc822Name) = purchasing@acme-international.com
(2-3) One excluded subtree for DN is present and required-name-forms is empty.
Path Processing State Variables
required-name-forms
permitted-subtrees excluded-subtrees
rfc822 DN URI
NONE
{{base(directoryName)
{C=US, O=Acme Inc}}}
empty
Acceptable Certificate Examples
1 subject = {C=US, O=Acme Ltd, OU=Purchasing}
2
subject = {}
subjectAltName(directoryName) = {C=US, O=Acme Ltd, OU=Purchasing}
3
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme-ltd.com
4
subject = {}
subjectAltName(directoryName) = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme-ltd.com
5
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(directoryName) = {C=US, O=Acme Ltd, OU=Accounting}
6
subject = {}
subjectAltName(rfc822Name) = manager@purchasing.acme-ltd.com
Unacceptable Certificate Examples
1 subject = {C=US, O=Acme Inc, OU=Purchasing}
2
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(directoryName) = {C=US, O=Acme Ltd, OU=Accounting}
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 149
G.3.2.3 Name Spaces Constraints only by required-name-forms
(3-1) DN is required in required-name-forms.
Path Processing State Variables
required-name-forms
permitted-subtrees excluded-subtrees
rfc822 DN URI
NONE NONE OFF ON OFF
Acceptable Certificate Examples
1 subject = {C=US, O=Acme Ltd, OU=Purchasing}
2
subject = {}
subjectAltName(directoryName) = {C=JP, O=Acme Inc, OU=Purchasing}
3
subject = {C=JP, O=Acme Ltd, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme-ltd.com
4
subject = {}
subjectAltName(directoryName) = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme-ltd.com
5
subject = {C=JP, O=Acme Ltd, OU=Purchasing}
subjectAltName(directoryName) = {C=US, O=Acme Ltd, OU=Accounting}
Unacceptable Certificate Examples
1
subject = {}
subjectAltName(rfc822Name) = manager@purchasing.acme-ltd.com
NOTE ­ DN missing
2
subject = {}
subjectAltName(uniformResourceIdentifier) = http://purchasing.www.acme-ltd.com
NOTE ­ DN missing
(3-2) DN or rfc822Name are required in required-name-forms.
Path Processing State Variables
required-name-forms
permitted-subtrees excluded-subtrees
rfc822 DN URI
NONE NONE ON ON OFF
ISO/IEC 9594-8:2005 (E)
150 ITU-T Rec. X.509 (08/2005)
Acceptable Certificate Examples
1 subject = {C=US, O=Acme Ltd, OU=Purchasing}
2
subject = {}
subjectAltName(directoryName) = {C=JP, O=Acme Inc, OU=Purchasing}
3
subject = {}
subjectAltName(rfc822Name) = manager@purchasing.acme-ltd.com
4
subject = {}
subjectAltName(directoryName) = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme-ltd.com
5
subject = {}
subjectAltName(rfc822Name) = manager@purchasing.acme-ltd.com
subjectAltName(rfc822Name) = purchasing@acme-ltd.com
Unacceptable Certificate Examples
1
subject = {}
subjectAltName(uniformResourceIdentifier) = http://purchasing.www.acme-ltd.com
NOTE ­ DN and rfc822 missing
2
subject = {}
subjectAltName(dNSName) = www.acme-ltd.com
NOTE ­ DN and rfc822 missing
G.3.2.4 Name Spaces Constraints by permitted-subtrees in Multiple Name Forms
In this case, each subject name (in the subject field or subjectAltName extension) in DN name form or rfc822 name
form appeared in the certificate in question shall satisfy the constraint by path processing state variable permitted-
subtrees.
(4-1) One permitted subtree for DN and another permitted subtree rfc822Name are present. In addition, DN is
required in required-name-forms.
Path Processing State Variables
required-name-forms
permitted-subtrees excluded-subtrees
rfc822 DN URI
{{base(directoryName)
{C=US, O=Acme Inc}},
{base(rfc822Name)
.acme.com}}
NONE OFF ON OFF
Acceptable Certificate Examples
1 subject = {C=US, O=Acme Inc, OU=Purchasing}
2
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
3
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(directoryName) = {C=US, O=Acme Inc, OU=Accounting}
4
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(uniformResourceIdentifier) = http://purchasing.www.acme-inc.com
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 151
Unacceptable Certificate Examples
1 subject = {C=US, O=Acme Ltd, OU=Purchasing}
2
subject = {}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
NOTE ­ DN missing
3
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
4
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme-inc.com
5
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme-ltd.com
6
subject = {}
subjectAltName(uniformResourceIdentifier) = http://purchasing.www.acme-inc.com
NOTE ­ DN missing
(4-2) One permitted subtree for DN and another permitted subtree rfc822Name are present. In addition, at least one
of DN or rfc822Name is required in required-name-forms.
Path Processing State Variables
required-name-forms
permitted-subtrees excluded-subtrees
rfc822 DN URI
{{base(directoryName)
{C=US, O=Acme Inc}},
{base(rfc822Name)
.acme.com}}
NONE ON ON OFF
Acceptable Certificate Examples
1 subject = {C=US, O=Acme Inc, OU=Purchasing}
2
subject = {}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
3
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
4
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(directoryName) = { C=US, O=Acme Inc, OU=Accounting}
5
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(uniformResourceIdentifier) = http://purchasing.www.acme-inc.com
ISO/IEC 9594-8:2005 (E)
152 ITU-T Rec. X.509 (08/2005)
Unacceptable Certificate Examples
1 subject = {C=US, O=Acme Ltd, OU=Purchasing}
2
subject = {}
subjectAltName(rfc822Name) = manager@purchasing.acme-inc.com
3
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
4
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme-inc.com
5
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme-ltd.com
6
subject = {}
subjectAltName(uniformResourceIdentifier) = http://purchasing.www.acme-inc.com
NOTE ­ DN and rfc822 missing
(4-3) One permitted subtree for DN and another permitted subtree rfc822Name are present. No name forms are
required in required-name-forms.
Path Processing State Variables
required-name-forms
permitted-subtrees excluded-subtrees
rfc822 DN URI
{{base(directoryName)
{C=US, O=Acme Inc}},
{base(rfc822Name)
.acme.com}}
NONE empty
Acceptable Certificate Examples
1 subject = {C=US, O=Acme Inc, OU=Purchasing}
2
subject = {}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
3
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
4
subject = {}
subjectAltName(uniformResourceIdentifier) = http://purchasing.www.acme.com
5
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(uniformResourceIdentifier) = http://purchasing.www.acme.com
Unacceptable Certificate Examples
1 subject = {C=US, O=Acme Ltd, OU=Purchasing}
2
subject = {}
subjectAltName(rfc822Name) = manager@purchasing.acme-inc.com
3
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
4
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme-inc.com
5
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme-inc.com
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 153
G.3.2.5 Name Spaces Constraints by excluded-subtrees in Multiple Name Forms
In this case, each subject name (in the subject field or subjectAltName extension) in DN name form or rfc822 name
form appeared in the certificate in question shall satisfy the constraint by path processing state variable excluded-
subtrees.
(5-1) One excluded subtree for DN and another excluded subtree rfc822Name are present. In addition, DN is
required in required-name-forms.
Path Processing State Variables
required-name-forms
permitted-subtrees excluded-subtrees
rfc822 DN URI
NONE
{{base(directoryName)
{C=US, O=Acme Inc}},
{base(rfc822Name)
.acme.com}}
OFF ON OFF
Acceptable Certificate Examples
1 subject = {C=US, O=Acme Ltd, OU=Purchasing}
2
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme-ltd.com
3
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(directoryName) = {C=US, O=Acme Ltd, OU=Accounting}
4
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(uniformResourceIdentifier) = http://purchasing.www.acme-ltd.com
Unacceptable Certificate Examples
1 subject = {C=US, O=Acme Inc, OU=Purchasing}
2
subject = {}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
NOTE ­ DN missing
3
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
4
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme-inc.com
5
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
6
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(directoryName) = {C=US, O=Acme Inc, OU=Accounting}
7
subject = {}
subjectAltName(uniformResourceIdentifier) = http://purchasing.www.acme-inc.com
NOTE ­ DN missing
ISO/IEC 9594-8:2005 (E)
154 ITU-T Rec. X.509 (08/2005)
(5-2) One excluded subtree for DN and another excluded subtree rfc822Name are present. In addition, at least one
of DN or rfc822Name is required in required-name-forms.
Path Processing State Variables
required-name-forms
permitted-subtrees excluded-subtrees
rfc822 DN URI
NONE
{{base(directoryName)
{C=US, O=Acme Inc}},
{base(rfc822Name)
.acme.com}}
ON ON OFF
Acceptable Certificate Examples
1 subject = {C=US, O=Acme Ltd, OU=Purchasing}
2
subject = {}
subjectAltName(rfc822Name) = manager@purchasing.acme.org
3
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme-ltd.com
4
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(directoryName) = {C=US, O=Acme Ltd, OU=Accounting}
5
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(uniformResourceIdentifier) = http://purchasing.www.acme-ltd.com
Unacceptable Certificate Examples
1 subject = {C=US, O=Acme Inc, OU=Purchasing}
2
subject = {}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
3
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
4
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme-inc.com
5
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
6
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(directoryName) = {C=US, O=Acme Inc, OU=Accounting}
7
subject = {}
subjectAltName(uniformResourceIdentifier) = http://purchasing.www.acme-inc.com
NOTE ­ DN and rfc822 missing
(5-3) One excluded subtree for DN and another excluded subtree rfc822Name are present. No name forms are
required in required-name-forms.
Path Processing State Variables
required-name-forms
permitted-subtrees excluded-subtrees
rfc822 DN URI
NONE
{{base(directoryName)
{C=US, O=Acme Inc}},
{base(rfc822Name)
.acme.com}}
Empty
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 155
Acceptable Certificate Examples
1 subject = {C=US, O=Acme Ltd, OU=Purchasing}
2
subject = {}
subjectAltName(rfc822Name) = manager@purchasing.acme-ltd.com
3
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme-ltd.com
4
subject = {}
subjectAltName(uniformResourceIdentifier) = http://purchasing.www.acme-inc.com
5
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(uniformResourceIdentifier) = http://purchasing.www.acme-ltd.com
Unacceptable Certificate Examples
1 subject = {C=US, O=Acme Inc, OU=Purchasing}
2
subject = {}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
3
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
4
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme-inc.com
5
subject = {C=US, O=Acme Inc, OU=Purchasing}
subjectAltName(rfc822Name) = manager@purchasing.acme.com
6
subject = {C=US, O=Acme Ltd, OU=Purchasing}
subjectAltName(directoryName) = {C=US, O=Acme Inc, OU=Accounting}
ISO/IEC 9594-8:2005 (E)
156 ITU-T Rec. X.509 (08/2005)
Annex H
Guidance on determining for which policies a certification path is valid
(This annex does not form an integral part of this Recommendation | International Standard)
The purpose of this annex is to provide guidance for PKI-enabled applications with respect to control of the certificate
policy-related processing of certificate path validation. Control of certificate policy-related processing by the PKI
through the contents of certificates is described in the Certificate Path Processing Procedure clause of this Specification.
This annex addresses initialization of two of the policy-related inputs in the path processing procedure: initial-policy-set
and initial-explicit-policy. In addition to these, the initial-policy-mapping-inhibit and initial-inhibit-any-policy inputs to
the procedure, which can also be initialized by the user, impact the processing of policy-related information during path
processing; however, these are outside the scope of this annex. Setting the initial-policy-mapping-inhibit to TRUE
prevents policy mappings from being used in successful path validations. Setting the initial-inhibit-any-policy to TRUE
prevents the special OID for anyPolicy, if present in a certificate, from being an acceptable match for a specific
policy OID.
The term "user" in this annex can be used to mean a "human user" or a PKI-enabled "application".
The following scenarios are envisioned:
1) The user requires that the certification path be valid for one of the policies of interest to the user.
2) The user requires that the certification path be valid for at least a policy, but the user does not care which
policy it is. This scenario should (can) be used when the user intends to do additional policy processing
using other contextual information and information content, to determine if one of the policies the
certification path is valid for is acceptable to the user for the particular transaction.
3) The user has no policy-related requirements on the certification path. In other words, the user is willing
to accept a certification path that is not valid for any policy, but is otherwise valid.
4) The user desires that the certification path be valid for one of the policies of interest to the user, but
failing that, wants the opportunity to reconsider paths that are not valid for the policies of interest to the
user. This scenario should (can) be used when the user generally requires the certification path to be
valid for a policy acceptable to the user, but based on other contextual information and information
content, the user may wish to override policy failure.
The following clauses describe how the user should go about obtaining the desired information from a compliant path
validation engine.
H.1 Certification path valid for a user-specified policy required
In this scenario, the user requires that the certification path be valid for one of the policies of interest to the user. In
order to obtain the desired information, the user should set the policy processing related certification path validation
inputs as follows:
initial-policy-set = {set of policies of interest to the user}
initial-explicit-policy = TRUE
If the path validation is successful, the certification path is valid for at least one of the policies of interest to the user.
The certification path is valid for the policies listed in the user-constrained-policy-set output variable.
Under this scenario, applications should not use a certification path if it is rejected by a path validation engine for
certificate policy-related failures4).
_______________
4) A path validation failure is a certificate policy-related failure when failure is caused by the certificate policy-related extension(s)
or certificate policy-related state variable(s). The certificate policy-related extensions are: certificatePolicies, policyMappings,
policyConstraints, and inhibitAnyPolicy. Certificate policy-related state variables are: authorities-constrained-policy-set,
explicit-policy-indicator, policy-mapping-inhibit-indicator, and inhibit-any-policy-indicator.
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 157
H.2 Certification path valid for any policy required
In this scenario, the user requires that the certification path be valid for at least a policy, but the user does not care
which policy it is. In order to obtain the desired information, the user should set the policy processing related
certification path validation inputs as follows:
initial-policy-set = {anyPolicy}
initial-explicit-policy = TRUE
If the path validation is successful, the certification path is valid for at least a policy. The certification path is valid for
the policies listed in the user-constrained-policy-set output variable.
Under this scenario, applications should not use a certification path if it is rejected by a path validation engine for
certificate policy-related failures.
H.3 Certification path valid regardless of policy
In this scenario, the user has no policy-related requirements on the certification path. In order to obtain the desired
information, the user should set the policy processing related certification path validation inputs as follows:
initial-policy-set = {anyPolicy}
initial-explicit-policy = FALSE
If the path validation is successful, the certification path is valid for the policies listed in the user-constrained-policy-set
output variable.
Under this scenario, applications should not use a certification path if it is rejected by a path validation engine for
certificate policy-related failures.
It should be noted that in this scenario, the certification path can have policy-related failure. An example is if the
infrastructure (i.e., a CA certificate in the certification path) causes the setting of explicit-policy-indicator. In this case,
if the path is not valid for any policy, i.e., authorities-constrained-policy-set is empty, a compliant path validation
engine will return a failure. Applications should reject the certification path for failure of this type.
H.4 Certification path valid for a user-specific policy desired, but not required
In this scenario, the user desires that the certification path be valid for one of the policies of interest to the user, but does
not want to reject paths that are not valid for any of the policies of interest to the user. In order to obtain the desired
information, the user should set the policy processing related certification path validation inputs as follows:
initial-policy-set = {set of policies of interest to the user}
initial-explicit-policy = FALSE
If the path validation is successful, the certification path is valid for the policies listed in the user-constrained-policy-set
output variable. The user-constrained-policy-set is a subset of the initial-policy-set. Please note that user-constrainedpolicy-set
could be NULL in this case when explicit-policy-indicator is not set. The application should examine the
returned user-constrained-policy-set to determine if the path is acceptable to the user.
Applications should reject the certification path for policy-related failure caused by the infrastructure in this scenario,
(i.e., when the authorities-constrained-policy-set is empty and the explicit-policy-indicator is set).
It should be noted that in this scenario, the certification path can have policy-related failure. An example is if the
infrastructure (i.e., a CA certificate in the certification path) causes the setting of explicit-policy-indicator. In this case,
if the path is not valid for any policy, i.e., authorities-constrained-policy-set is empty, a compliant path validation
engine will return a failure. Applications should reject the certification path for failure of this type.
Another example is the combination of the user input and infrastructure causes policy-related failure. This occurs when
a CA certificate in the certification path causes the setting of explicit-policy-indicator, authorities-constrained-policyset
is not empty, and user-constrained-policy-set is empty. Compliant path validation engine will return a failure. Under
these conditions, if the only reason for the path validation engine returning a failure is that the user-constrained-policyset
is empty, applications may choose to override that failure and accept the certification path. Authority imposed
constraints are still respected, by virtue of the authorities-constrained-policy-set not being empty. Acceptance of this
path by an application is equivalent to the application re-submitting the path to the validation engine with initial-policyset
equal to anyPolicy initial-explicit-policy equal to FALSE, and examining the returned user-constrained-policy-set
to determine if the path is acceptable.
ISO/IEC 9594-8:2005 (E)
158 ITU-T Rec. X.509 (08/2005)
Annex I
Key usage certificate extension issues
(This annex does not form an integral part of this Recommendation | International Standard)
Combining the contentCommitment bit in the keyUsage certificate extension with other keyUsage bits may have
security implications depending on the security environment in which the certificate is to be used. If the subject's
environment can be fully controlled and trusted, then there are no specific security implications. For example, in cases
where the subject is fully confident about exactly which data is signed or cases where the subject is fully confident
about the security characteristics of the authentication protocol being used. If the subject's environment is not fully
controlled or not fully trusted, then unintentional signing of commitments is possible. Examples include the use of badly
formed authentication exchanges and the use of a rogue software component. If untrusted environments are used by a
subject, these security implications can be limited through use of the following measures:
­ to not combine contentCommitment key usage setting in certificates with any other key usage setting and
to use the corresponding private key only with this certificate;
­ to limit the use of private keys associated with certificates that have the contentCommitment key usage
bit set, to environments which are considered adequately controlled and trustworthy.
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 159
Annex J
Alphabetical list of information item definitions
(This annex does not form an integral part of this Recommendation | International Standard)
This annex provides an alphabetical index to the definitions of certificate and CRL formats, certificate extensions,
object classes, name forms, attribute types and matching rules defined in this Directory Specification.
Item Clause
Certificate and CRL formats
Attribute certificate format 12.1
Certificate revocation list 7.3
Public-key certificate format 7
Certificate, CRL & CRL entry extensions
Acceptable certificate policies extension 15.5.2.3
Acceptable privilege policies extension 15.1.2.4
Attribute descriptor extension 15.3.2.2
Authority attribute identifier extension 15.5.2.4
Authority key identifier extension 8.2.2.1
Base update extension 8.6.2.5
Basic attribute constraints extension 15.5.2.1
Basic constraints extension 8.4.2.1
Certificate issuer extension 8.6.2.3
Certificate policies extension 8.2.2.6
CRL distribution points extension 8.6.2.1
CRL number extension 8.5.2.1
CRL scope extension 8.5.2.5
CRL stream identifier extension 8.5.2.7
Delegated name constraints extension 15.5.2.2
Delta CRL indicator extension 8.6.2.4
Delta information extension 8.5.2.9
Expired certificates on CRL extension 8.5.2.12
Extended key usage extension 8.2.2.4
Freshest CRL extension 8.6.2.6
Hold instruction code extension 8.5.2.3
Indirect issuer extension 15.1.2.5
Inhibit any policy extension 8.4.2.4
Invalidity date extension 8.5.2.4
Issued on Behalf Of extension 15.5.2.6
Issuer alternative name extension 8.3.2.2
Issuing distribution point extension 8.6.2.2
Key usage extension 8.2.2.3
Name constraints extension 8.4.2.2
No assertion extension 15.1.2.6
No revocation information extension 15.2.2.2
Ordered list extension 8.5.2.8
Policy constraints extension 8.4.2.3
Policy mappings extension 8.2.2.7
Private key usage period extension 8.2.2.5
Reason code extension 8.5.2.2
ISO/IEC 9594-8:2005 (E)
160 ITU-T Rec. X.509 (08/2005)
Item Clause
Revoked group of certificates extension 8.5.2.11
Role specification certificate identifier extension 15.4.2.1
SOA identifier extension 15.3.2.1
Status referral extension 8.5.2.6
Subject alternative name extension 8.3.2.1
Subject key identifier extension 8.2.2.2
Subject directory attributes extension 8.3.2.3
Targeting information extension 15.1.2.2
Time specification extension 15.1.2.1
To be revoked extension 8.5.2.10
User notice extension 15.1.2.3
Object classes and name forms
Attribute certificate CRL distribution point object class 17.1.4
Certificate policy and CPS object class 11.1.5
CRL distribution points object class and name form 11.1.3
Delta CRL object class 11.1.4
PKI CA object class 11.1.2
PKI certificate path object class 11.1.6
PKI user object class 11.1.1
PMI AA object class 17.1.2
PMI delegation path 17.1.5
PMI SOA object class 17.1.3
PMI user object class 17.1.1
Privilege policy object class 17.1.6
Protected privilege policy object class 17.1.7
Directory attributes
AA certificate attribute 17.2.2
AA certificate revocation list attribute 17.2.5
Attribute certificate attribute 17.2.1
Attribute certificate revocation list attribute 17.2.4
Attribute descriptor certificate attribute 17.2.3
Authority revocation list attribute 11.2.5
CA certificate attribute 11.2.2
Certification practice statement attribute 11.2.8
Certificate policy attribute 11.2.9
Certificate revocation list attribute 11.2.4
Cross-certificate pair attribute 11.2.3
Delegation path attribute 17.2.6
Delta revocation list attribute 11.2.6
PKI path attribute 11.2.10
Privilege policy attribute 17.2.7
Protected privilege policy attribute 17.2.8
Supported algorithms attribute 11.2.7
User certificate attribute 11.2.1
XML privilege information attribute 14.5
XML Protected privilege policy attribute 17.2.9
Matching rules
AA identifier match 15.5.2.4.1
Acceptable certificate policies match 15.5.2.3.1
Algorithm identifier match 11.3.7
ISO/IEC 9594-8:2005 (E)
ITU-T Rec. X.509 (08/2005) 161
Item Clause
Attribute certificate exact match 17.3.1
Attribute certificate match 17.3.2
Attribute descriptor match 15.3.2.2.1
Basic attribute constraints match 15.5.2.1.1
Certificate exact match 11.3.1
Certificate list exact match 11.3.5
Certificate list match 11.3.6
Certificate match 11.3.2
Certificate pair exact match 11.3.3
Certificate pair match 11.3.4
Delegated name constraints match 15.5.2.2.1
Delegation path match 17.3.4
Enhanced certificate match 11.3.10
Holder issuer match 17.3.3
Indirect issuer match 15.1.2.5
PKI Path match 11.3.9
Policy match 11.3.8
Role specification certificate ID match 15.4.2.1.1
SOA identifier match 15.3.2.1.1
Time specification match 15.1.2.1.1
ISO/IEC 9594-8:2005 (E)
162 ITU-T Rec. X.509 (08/2005)
Annex K
Amendments and corrigenda
(This annex does not form an integral part of this Recommendation | International Standard)
This edition of this Directory Specification includes the following draft amendments that were balloted and approved
by ISO/IEC:
­ Amendment 4 for Public-key and Attribute Certificate Extensions.
This edition of this Directory Specification includes the following technical corrigenda correcting the defects in the
following defect reports against the 4th edition of this Specification:
­ Technical Corrigendum 1 (covering Defect Reports 272, 273, 274, 275, 276, 277, 278, and 279);
­ Technical Corrigendum 2 (covering Defect Reports 284, 285, and 286); and
­ Technical Corrigendum 3 (covering Defect Reports 281, 282, 289, 291, 296, 298, 299, 300, 301, 304,
and 305).
Printed in Switzerland
Geneva, 2006
SERIES OF ITU-T RECOMMENDATIONS
Series A Organization of the work of ITU-T
Series D General tariff principles
Series E Overall network operation, telephone service, service operation and human factors
Series F Non-telephone telecommunication services
Series G Transmission systems and media, digital systems and networks
Series H Audiovisual and multimedia systems
Series I Integrated services digital network
Series J Cable networks and transmission of television, sound programme and other multimedia signals
Series K Protection against interference
Series L Construction, installation and protection of cables and other elements of outside plant
Series M Telecommunication management, including TMN and network maintenance
Series N Maintenance: international sound programme and television transmission circuits
Series O Specifications of measuring equipment
Series P Telephone transmission quality, telephone installations, local line networks
Series Q Switching and signalling
Series R Telegraph transmission
Series S Telegraph services terminal equipment
Series T Terminals for telematic services
Series U Telegraph switching
Series V Data communication over the telephone network
Series X Data networks, open system communications and security
Series Y Global information infrastructure, Internet protocol aspects and next-generation networks
Series Z Languages and general software aspects for telecommunication systems