Network Working Group S. Boeyen
Request for Comments: 2587 Entrust
Category: Standards Track T. Howes
Netscape
P. Richard
Xcert
June 1999
Internet X.509 Public Key Infrastructure
LDAPv2 Schema
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved.
1. Abstract
The schema defined in this document is a minimal schema to support
PKIX in an LDAPv2 environment, as defined in RFC 2559. Only PKIX-
specific components are specified here. LDAP servers, acting as PKIX
repositories should support the auxiliary object classes defined in
this specification and integrate this schema specification with the
generic and other application-specific schemas as appropriate,
depending on the services to be supplied by that server.
The key words 'MUST', 'SHALL', 'REQUIRED', 'SHOULD', 'RECOMMENDED',
and 'MAY' in this document are to be interpreted as described in RFC
2119.
2. Introduction
This specification is part of a multi-part standard for development
of a Public Key Infrastructure (PKI) for the Internet. LDAPv2 is one
mechanism defined for access to a PKI repository. Other mechanisms,
such as http, are also defined. If an LDAP server, accessed by LDAPv2
is used to provide a repository, the minimum requirement is that the
repository support the addition of X.509 certificates to directory
Boeyen, et al. Standards Track [Page 1]
RFC 2587 PKIX LDAPv2 Schema June 1999 entries. Certificate Revocation List (CRL)is one mechanism for publishing revocation information in a repository. Other mechanisms, such as http, are also defined. This specification defines the attributes and object classes to be used by LDAP servers acting as PKIX repositories and to be understood by LDAP clients communicating with such repositories to query, add, modify and delete PKI information. Some object classes and attributes defined in X.509 are duplicated here for completeness. For end entities and Certification Authorities (CA), the earlier X.509 defined object classes mandated inclusion of attributes which are optional for PKIX. Also, because of the mandatory attribute specification, this would have required dynamic modification of the object class attribute should the attributes not always be present in entries. For these reasons, alternative object classes are defined in this document for use by LDAP servers acting as PKIX repositories. 3. PKIX Repository Objects The primary PKIX objects to be represented in a repository are: - End Entities - Certification Authorities (CA) These objects are defined in RFC 2459. 3.1. End Entities For purposes of PKIX schema definition, the role of end entities as subjects of certificates is the major aspect relevant to this specification. End entities may be human users, or other types of entities to which certificates may be issued. In some cases, the entry for the end entity may already exist and the PKI-specific information is added to the existing entry. In other cases the entry may not exist prior to the issuance of a certificate, in which case the entity adding the certificate may also need to create the entry. Schema elements used to represent the non PKIX aspects of an entry, such as the structural object class used to represent organizational persons, may vary, depending on the particular environment and set of applications served and are outside the scope of this specification. The following auxiliary object class MAY be used to represent certificate subjects: Boeyen, et al. Standards Track [Page 2]
RFC 2587 PKIX LDAPv2 Schema June 1999 pkiUser OBJECT-CLASS ::= { SUBCLASS OF { top} KIND auxiliary MAY CONTAIN {userCertificate} ID joint-iso-ccitt(2) ds(5) objectClass(6) pkiUser(21)} userCertificate ATTRIBUTE ::= { WITH SYNTAX Certificate EQUALITY MATCHING RULE certificateExactMatch ID joint-iso-ccitt(2) ds(5) attributeType(4) userCertificate(36) } An end entity may obtain one or more certificates from one or more Certification Authorities. The userCertificate attribute MUST be used to represent these certificates in the directory entry representing that user. 3.2. Certification Authorities As with end entities, Certification Authorities are typically represented in directories as auxiliary components of entries representing a more generic object, such as organizations, organizational units etc. The non PKIX-specific schema elements for these entries, such as the structural object class of the object, are outside the scope of this specification. The following auxiliary object class MAY be used to represent Certification Authorities: pkiCA OBJECT-CLASS ::= { SUBCLASS OF { top} KIND auxiliary MAY CONTAIN {cACertificate | certificateRevocationList | authorityRevocationList | crossCertificatePair } ID joint-iso-ccitt(2) ds(5) objectClass(6) pkiCA(22)} cACertificate ATTRIBUTE ::= { WITH SYNTAX Certificate EQUALITY MATCHING RULE certificateExactMatch ID joint-iso-ccitt(2) ds(5) attributeType(4) cACertificate(37) } crossCertificatePairATTRIBUTE::={ WITH SYNTAX CertificatePair EQUALITY MATCHING RULE certificatePairExactMatch ID joint-iso-ccitt(2) ds(5) attributeType(4) crossCertificatePair(40)} Boeyen, et al. Standards Track [Page 3]
RFC 2587 PKIX LDAPv2 Schema June 1999 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. The forward 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 reverse elements of the crossCertificatePair attribute, of a CA's directory entry may contain a subset of certificates issued by this CA to other CAs. When both the forward and the reverse 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. When a reverse element is present, the forward element value and the reverse 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, none of the above CA certificates shall include a basicConstraints extension with the cA value set to FALSE. The definition of realm is purely a matter of local policy. certificateRevocationListATTRIBUTE::={ WITH SYNTAX CertificateList EQUALITY MATCHING RULE certificateListExactMatch ID joint-iso-ccitt(2) ds(5) attributeType(4) certificateRevocationList(39)} The certificateRevocationList attribute, if present in a particular CA's entry, contains CRL(s) as defined in RFC 2459. authorityRevocationListATTRIBUTE::={ WITH SYNTAX CertificateList EQUALITY MATCHING RULE certificateListExactMatch ID joint-iso-ccitt(2) ds(5) attributeType(4) authorityRevocationList(38)} The authorityRevocationList attribute, if present in a particular CA's entry, includes revocation information regarding certificates issued to other CAs. Boeyen, et al. Standards Track [Page 4]
RFC 2587 PKIX LDAPv2 Schema June 1999 3.2.1. CRL distribution points CRL distribution points are an optional mechanism, specified in RFC 2459, which MAY be used to distribute revocation information. A patent statement regarding CRL distribution points can be found at the end of this document. If a CA elects to use CRL distribution points, the following object class is used to represent these. cRLDistributionPoint OBJECT-CLASS::= { SUBCLASS OF { top } KIND structural MUST CONTAIN { commonName } MAY CONTAIN { certificateRevocationList | authorityRevocationList | deltaRevocationList } ID joint-iso-ccitt(2) ds(5) objectClass(6) cRLDistributionPoint(19) } The certificateRevocationList and authorityRevocationList attributes are as defined above. The commonName attribute and deltaRevocationList attributes, defined in X.509, are duplicated below. commonName ATTRIBUTE::={ SUBTYPE OF name WITH SYNTAX DirectoryString ID joint-iso-ccitt(2) ds(5) attributeType(4) commonName(3) } deltaRevocationList ATTRIBUTE ::= { WITH SYNTAX CertificateList EQUALITY MATCHING RULE certificateListExactMatch ID joint-iso-ccitt(2) ds(5) attributeType(4) deltaRevocationList(53) } 3.2.2. Delta CRLs Delta CRLs are an optional mechanism, specified in RFC 2459, which MAY be used to enhance the distribution of revocation information. If a CA elects to use delta CRLs, the following object class is used to represent these. Boeyen, et al. Standards Track [Page 5]
RFC 2587 PKIX LDAPv2 Schema June 1999 deltaCRL OBJECT-CLASS::= { SUBCLASS OF { top } KIND auxiliary MAY CONTAIN { deltaRevocationList } ID joint-iso-ccitt(2) ds(5) objectClass(6) deltaCRL(23) } 4. Security Considerations Since the elements of information which are key to the PKI service (certificates and CRLs) are both digitally signed pieces of information, no additional integrity service is REQUIRED. Security considerations with respect to retrieval, addition, deletion, and modification of the information supported by this schema definition are addressed in RFC 2559. 5. References [1] Yeong, Y., Howes, T. and S. Kille, "Lightweight Directory Access Protocol", RFC 1777, March 1995. [2] Bradner, S., "Key Words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 6 Intellectual Property Rights The IETF has been notified of intellectual property rights claimed in regard to some or all of the specification contained in this document. For more information consult the online list of claimed rights. The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. Copies of claims of rights made available for publication and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementors or users of this specification can be obtained from the IETF Secretariat. Boeyen, et al. Standards Track [Page 6]
RFC 2587 PKIX LDAPv2 Schema June 1999 7. Authors' Addresses Sharon Boeyen Entrust Technologies Limited 750 Heron Road Ottawa, Ontario Canada K1V 1A7 EMail: sharon.boeyen@entrust.com Tim Howes Netscape Communications Corp. 501 E. Middlefield Rd. Mountain View, CA 94043 USA EMail: howes@netscape.com Patrick Richard Xcert Software Inc. Suite 1001, 701 W. Georgia Street P.O. Box 10145 Pacific Centre Vancouver, B.C. Canada V7Y 1C6 EMail: patr@xcert.com Boeyen, et al. Standards Track [Page 7]
RFC 2587 PKIX LDAPv2 Schema June 1999
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Boeyen, et al. Standards Track [Page 8]
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