





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




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   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:








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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)}





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   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.







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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.







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      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.







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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






















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Full Copyright Statement

   Copyright (C) The Internet Society (1999).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
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   The limited permissions granted above are perpetual and will not be
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   This document and the information contained herein is provided on an
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   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
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   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.



















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