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Network Working Group                                      S. BoeyenRequest for Comments: 2559                                   EntrustUpdates:1778                                               T. HowesCategory: Standards Track                                   Netscape                                                          P. Richard                                                               Xcert                                                          April 1999Internet X.509 Public Key InfrastructureOperational Protocols - LDAPv2Status 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 protocol described in this document is designed to satisfy some   of the operational requirements within the Internet X.509 Public Key   Infrastructure (IPKI).  Specifically, this document addresses   requirements to provide access to Public Key Infrastructure (PKI)   repositories for the purposes of retrieving PKI information and   managing that same information.  The mechanism described in this   document is based on the Lightweight Directory Access Protocol (LDAP)   v2, defined inRFC 1777, defining a profile of that protocol for use   within the IPKI and updates encodings for certificates and revocation   lists fromRFC 1778. Additional mechanisms addressing PKIX   operational requirements are specified in separate documents.   The key words 'MUST', 'REQUIRED', 'SHOULD', 'RECOMMENDED', and 'MAY'   in this document are to be interpreted as described inRFC 2119.2.  Introduction   This specification is part of a multi-part standard for development   of a Public Key Infrastructure (PKI) for the Internet. This   specification addresses requirements to provide retrieval of X.509   PKI information, including certificates and CRLs from a repository.   This specification also addresses requirements to add, delete andBoeyen, et al.              Standards Track                     [Page 1]

RFC 2559          PKIX Operational Protocols - LDAPv2         April 1999   modify PKI information in a repository. A profile based on the LDAP   version 2 protocol is provided to satisfy these requirements.3.  Model   The PKI components, as defined in PKIX Part 1, which are involved in   PKIX operational protocol interactions include:      -  End Entities      -  Certification Authorities (CA)      -  Repository   End entities and CAs using LDAPv2, retrieve PKI information from the   repository using a subset of the LDAPv2 protocol.   CAs populate the repository with PKI information using a subset of   the LDAPv2 protocol.4.  Lightweight Directory Access Protocol (LDAP)   The following sections examine the retrieval of PKI information from   a repository and management of PKI information in a repository. A   profile of the LDAPv2 protocol is defined for providing these   services.Section 5 satisfies the requirement to retrieve PKI information (a   certificate, CRL, or other information of interest) from an entry in   the repository, where the retrieving entity (either an end entity or   a CA) has knowledge of the name of the entry. This is termed   "repository read".Section 6 satisfies the same requirement as 5 for the situation where   the name of the entry is not known, but some other related   information which may optionally be used as a filter against   candidate entries in the repository, is known.  This is termed   "repository search".Section 7 satisfies the requirement of CAs to add, delete and modify   PKI information information (a certificate, CRL, or other information   of interest)in the repository. This is termed "repository modify".   The subset of LDAPv2 needed to support each of these functions is   described below.  Note that the repository search service is a   superset of the repository read service in terms of the LDAPv2   functionality needed.   Note that all tags are implicit by default in the ASN.1 definitions   that follow.Boeyen, et al.              Standards Track                     [Page 2]

RFC 2559          PKIX Operational Protocols - LDAPv2         April 19995.  LDAP Repository Read   To retrieve information from an entry corresponding to the subject or   issuer name of a certificate, requires a subset of the following   three LDAP operations:     BindRequest (and BindResponse)     SearchRequest (and SearchResponse)     UnbindRequest   The subset of each REQUIRED operation is given below.5.1.  Bind5.1.1.  Bind Request   The full LDAP v2 Bind Request is defined inRFC 1777.   An application providing a LDAP repository read service MUST   implement the following subset of this operation:      BindRequest ::=        [APPLICATION 0] SEQUENCE {           version      INTEGER (2),           name         LDAPDN, -- MUST accept NULL LDAPDN           simpleauth [0] OCTET STRING  -- MUST accept NULL simple           }   An application providing a LDAP repository read service MAY implement   other aspects of the BindRequest as well.   Different services may have different security requirements.  Some   services may allow anonymous search, others may require   authentication. Those services allowing anonymous search may choose   only to allow search based on certain criteria and not others.   A LDAP repository read service SHOULD implement some level of   anonymous search access. A LDAP repository read service MAY implement   authenticated search access.5.1.2.  Bind Response   The full LDAPv2 BindResponse is described inRFC 1777.   An application providing a LDAP repository read service MUST   implement this entire protocol element, though only the following   error codes may be returned from a Bind operation:Boeyen, et al.              Standards Track                     [Page 3]

RFC 2559          PKIX Operational Protocols - LDAPv2         April 1999       success                      (0),       operationsError              (1),       protocolError                (2),       authMethodNotSupported       (7),       noSuchObject                 (32),       invalidDNSyntax              (34),       inappropriateAuthentication  (48),       invalidCredentials           (49),       busy                         (51),       unavailable                  (52),       unwillingToPerform           (53),       other                        (80)5.2.  Search5.2.1.  Search Request   The full LDAPv2 SearchRequest is defined inRFC 1777.   An application providing a LDAP repository read service MUST   implement the following subset of the SearchRequest.      SearchRequest ::=        [APPLICATION 3] SEQUENCE {           baseObject     LDAPDN,           scope             ENUMERATED {                             baseObject   (0),                                        },           derefAliases   ENUMERATED {                             neverDerefAliases   (0),                                     },           sizeLimit      INTEGER (0),           timeLimit      INTEGER (0),           attrsOnly      BOOLEAN, -- FALSE only           filter         Filter,           attributes     SEQUENCE OF AttributeType                               }      Filter ::=        CHOICE {          present        [7] AttributeType, -- "objectclass" only                 }   This subset of the LDAPv2 SearchRequest allows the LDAPv2 "read"   operation: a base object search with a filter testing for the   existence of the objectClass attribute.Boeyen, et al.              Standards Track                     [Page 4]

RFC 2559          PKIX Operational Protocols - LDAPv2         April 1999   An application providing a LDAP repository read service MAY implement   other aspects of the SearchRequest as well.5.2.2.   The full LDAPv2 SearchResponse is defined inRFC 1777.   An application providing a LDAP repository read service over LDAPv2   MUST implement the full SearchResponse.   Note that in the case of multivalued attributes such as   userCertificate a SearchResponse containing this attribute will   include all values, assuming the requester has sufficient access   permissions.  The application/relying party may need to select an   appropriate value to be used. Also note that retrieval of a   certificate from a named entry does not guarantee that the   certificate will include that same Distinguished Name (DN) and in   some cases the subject DN in the certificate may be NULL.5.3.  Unbind   The full LDAPv2 UnbindRequest is defined inRFC 1777.   An application providing a LDAP repository read service MUST   implement the full UnbindRequest.6.  LDAP Repository Search   To search, using arbitrary criteria, for an entry in a repository   containing a certificate, CRL, or other information of interest,   requires a subset of the following three LDAP operations:     BindRequest (and BindResponse)     SearchRequest (and SearchResponse)     UnbindRequest   The subset of each operation REQUIRED is given below.6.1.  Bind   The BindRequest and BindResponse subsets needed are the same as those   described inSection 5.1.   The full LDAP v2 Bind Request is defined inRFC 1777.Boeyen, et al.              Standards Track                     [Page 5]

RFC 2559          PKIX Operational Protocols - LDAPv2         April 19996.2.  Search6.2.1.  Search Request   The full LDAPv2 SearchRequest is defined inRFC 1777.   An application providing a LDAP repository search service MUST   implement the following subset of the SearchRequest protocol unit.      SearchRequest ::=        [APPLICATION 3] SEQUENCE {           baseObject     LDAPDN,           scope          ENUMERATED {                               baseObject     (0),                               singleLevel    (1),                               wholeSubtree   (2)                                     },           derefAliases   ENUMERATED {                               neverDerefAliases     (0),                                     },           sizeLimit      INTEGER (0 .. maxInt),           timeLimit      INTEGER (0 .. maxInt),           attrsOnly      BOOLEAN,  -- FALSE only           filter         Filter,           attributes     SEQUENCE OF AttributeType                                }   All aspects of the SearchRequest MUST be supported, except for the   following:   - Only the neverDerefAliases value of derefAliases needs to be     supported   - Only the FALSE value for attrsOnly needs to be supported   This subset provides a more general search capability.  It is a   superset of the SearchRequest subset defined inSection 5.2.1. The   elements added to this service are:   - singleLevel and wholeSubtree scope needs to be supported   - sizeLimit is included   - timeLimit is included   - Enhanced filter capabilityBoeyen, et al.              Standards Track                     [Page 6]

RFC 2559          PKIX Operational Protocols - LDAPv2         April 1999   An application providing a LDAP repository search service MAY   implement other aspects of the SearchRequest as well.6.2.2.  Search Response   The full LDAPv2 SearchResponse is defined inRFC 1777.   An application providing a LDAP repository search service over LDAPv2   MUST implement the full SearchResponse.6.3.  Unbind   An application providing a LDAP repository search service MUST   implement the full UnbindRequest.7.  LDAP Repository Modify   To add, delete and modify PKI information in a repository  requires a   subset of the following LDAP operations:     BindRequest (and BindResponse)     ModifyRequest (and ModifyResponse)     AddRequest (and AddResponse)     DelRequest (and DelResponse     UnbindRequest   The subset of each operation REQUIRED is given below.7.1.  Bind   The full LDAP v2 Bind Request is defined inRFC 1777.   An application providing a LDAP repository modify service MUST   implement the following subset of this operation:      BindRequest ::=        [APPLICATION 0] SEQUENCE {           version      INTEGER (2),           name         LDAPDN,           simpleauth [0] OCTET STRING           }   A LDAP repository modify service MUST implement authenticated access.   The BindResponse subsets needed are the same as those described inSection 5.1.2.Boeyen, et al.              Standards Track                     [Page 7]

RFC 2559          PKIX Operational Protocols - LDAPv2         April 19997.2.  Modify7.2.1.  Modify Request   The full LDAPv2 ModifyRequest is defined inRFC 1777.   An application providing a LDAP repository modify service MUST   implement the following subset of the ModifyRequest protocol unit.      ModifyRequest ::=        [APPLICATION 6] SEQUENCE {       object         LDAPDN,       modification   SEQUENCE OF SEQUENCE {                        operation     ENUMERATED {                                        add     (0),                                        delete  (1)                                      },                        modification  SEQUENCE {                                      type   AttributeType,                                      values SET OF                                             AttributeValue                                      }                      }        }   All aspects of the ModifyRequest MUST be supported, except for the   following:   - Only the add and delete values of operation need to be supported7.2.2.  Modify Response   The full LDAPv2 ModifyResponse is defined inRFC 1777.   An application providing a LDAP repository modify service MUST   implement the full ModifyResponse.7.3.  Add7.3.1.  Add Request   The full LDAPv2 AddRequest is defined inRFC 1777.   An application providing a LDAP repository modify service MUST   implement the full AddRequest.Boeyen, et al.              Standards Track                     [Page 8]

RFC 2559          PKIX Operational Protocols - LDAPv2         April 19997.3.2.  Add Response   The full LDAPv2 AddResponse is defined inRFC 1777.   An application providing a LDAP repository modify service MUST   implement the full AddResponse.7.4.  Delete7.4.1.  Delete Request   The full LDAPv2 DelRequest is defined inRFC 1777.   An application providing a LDAP repository modify service MUST   implement the full DelRequest.7.4.2.  Delete Response   The full LDAPv2 DelResponse is defined inRFC 1777.   An application providing a LDAP repository modify service MUST   implement the full DelResponse.7.5.  Unbind   An application providing a LDAP repository modify service MUST   implement the full UnbindRequest.8.  Non-standard attribute value encodings   When conveyed in LDAP requests and results, attributes defined in   X.500 are to be encoded using string representations defined inRFC1778, The String Representation of Standard Attribute Syntaxes.   These string encodings were based on the attribute definitions from   X.500(1988).  Thus, the string representations of the PKI information   elements are for version 1 certificates and version 1 revocation   lists.  Since this specification uses version 3 certificates and   version 2 revocation lists, as defined in X.509(1997), theRFC 1778   string encoding of these attributes is inappropriate.   For this reason, these attributes MUST be encoded using a syntax   similar to the syntax "Undefined" fromsection 2.1 of RFC 1778:   values of these attributes are encoded as if they were values of type   "OCTET STRING", with the string value of the encoding being the DER-   encoding of the value itself.  For example, when writing a   userCertificate to the repository, the CA generates a DER-encoding of   the certificate and uses that encoding as the value of the   userCertificate attribute in the LDAP Modify request.This encodingBoeyen, et al.              Standards Track                     [Page 9]

RFC 2559          PKIX Operational Protocols - LDAPv2         April 1999   style is consistent with the encoding scheme proposed for LDAPv3,   which is now being defined within the IETF.   Note that certificates and revocation lists will be transferred using   this mechanism rather than the string encodings inRFC 1778 and   client systems which do not understand this encoding may experience   problems with these attributes.9.  Transport   An application providing a LDAP repository read service, LDAP   repository search service, or LDAP repository modify service MUST   support LDAPv2 transport over TCP, as defined in Section 3.1 ofRFC1777.   An application providing a LDAP repository read service, LDAP   repository search service, or LDAP repository modify service MAY   support LDAPv2 transport over other reliable transports as well.10.  Security Considerations   Since the elements of information which are key to the PKI service   (certificates and CRLs) are both digitally signed pieces of   information, additional integrity service is NOT REQUIRED.  As   neither information element need be kept secret and anonymous access   to such information, for retrieval purposes is generally acceptable,   privacy service is NOT REQUIRED for information retrieval requests.   CAs have additional requirements, including modification of PKI   information.  Simple authentication alone is not sufficient for these   purposes. It is RECOMMENDED that some stronger means of   authentication and/or (if simple authentication is used) some means   of protecting the privacy of the password is used, (e.g.  accept   modifications only via physically secure networks, use IPsec, use SSH   or TLS or SSL tunnel). Without such authentication, it is possible   that a denial-of-service attack could occur where the attacker   replaces valid certificates with bogus ones.   For the LDAP repository modify service, profiled insection 7, there   are some specific security considerations with respect to access   control. These controls apply to a repository which is under the same   management control as the CA. Organizations operating directories are   NOT REQUIRED to provide external CAs access permission to their   directories.Boeyen, et al.              Standards Track                    [Page 10]

RFC 2559          PKIX Operational Protocols - LDAPv2         April 1999   The CA MUST have access control permissions allowing it to:      For CA entries:         - add, modify and delete all PKI attributes for its own           directory entry;         - add, modify and delete all values of these attributes.      For CRL distribution point entries (if used):         - create, modify and delete entries of object class           cRLDistributionPoint immediately subordinate to its own           entry;         - add, modify and delete all attributes, and all values of           these attributes for these entries.      For subscriber (end-entity) entries:         - add, modify and delete the attribute userCertificate and all           values of that attribute, issued by this CA to/from these           entries.   The CA is the ONLY entity with these permissions.   An application providing LDAP repository read, LDAP repository   search, or LDAP repository modify service as defined in this   specification is NOT REQUIRED to implement any additional security   features other than those described herein, however an implementation   SHOULD do so.11.  References   [1]  Yeong, Y., Howes, T. and S. Kille, "Lightweight Directory Access        Protocol",RFC 1777, March 1995.   [2]  Howes, T., Kille, S., Yeong, W. and C. Robbins, "The String        Representation of Standard Attribute Syntaxes",RFC 1778, March        1995.   [3]  Bradner, S., "Key Words for use in RFCs to Indicate Requirement        Levels",BCP 14,RFC 2119, March 1997.Boeyen, et al.              Standards Track                    [Page 11]

RFC 2559          PKIX Operational Protocols - LDAPv2         April 199912.  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.comBoeyen, et al.              Standards Track                    [Page 12]

RFC 2559          PKIX Operational Protocols - LDAPv2         April 199913.  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   Internet organizations, except as needed for the purpose of   developing Internet standards in which case the procedures for   copyrights defined in the Internet Standards process must be   followed, or as required to translate it into languages other than   English.   The limited permissions granted above are perpetual and will not be   revoked by the Internet Society or its successors or assigns.   This document and the information contained herein is provided on an   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Boeyen, et al.              Standards Track                    [Page 13]