Network Working Group
Request for Comments: 5020
Category: Standards Track

K. Zeilenga
Isode Limited
August 2007

The Lightweight Directory Access Protocol (LDAP) entryDN

Operational Attribute

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

Abstract

This document describes the Lightweight Directory Access Protocol (LDAP) / X.500 'entryDN' operational attribute. The attribute provides a copy of the entry's distinguished name for use in attribute value assertions.

1. Background and Intended Use

In X.500 Directory Services [X.501], such as those accessible using the Lightweight Directory Access Protocol (LDAP) [RFC4510], an entry is identified by its distinguished name (DN) [RFC4512]. However, as an entry's DN is not an attribute of the entry, it is not possible to perform attribute value assertions [RFC4511] against it.

This document describes the 'entryDN' operational attribute which holds a copy of the entry's distinguished name. This attribute may be used in search filters. For instance, searching the subtree <dc=example,dc=com> with the filter:

(entryDN:componentFilterMatch:=or:{

item:{ component "3", rule rdnMatch, value "ou=A" },

item:{ component "3", rule rdnMatch, value "ou=B" } })

would return entries in the subtree <ou=A,dc=example,dc=com> and entries in subtree <ou=B,dc=example,dc=com>, but would not return any other entries in the subtree <dc=example,dc=com>.

In the above paragraph, DNs are presented using the string representation defined in [RFC4514], and the example search filter is presented using the string representation defined in [RFC4515] with whitespace (line breaks and indentation) added to improve readability. The 'componentFilterMatch' and 'rdnMatch' rules are specified in [RFC3687].

Schema definitions are provided using LDAP description formats [RFC4512]. Definitions provided here are formatted (line wrapped) for readability.

2. 'entryDN' Operational Attribute

The 'entryDN' operational attribute provides a copy of the entry's current DN.

The following is an LDAP attribute type description suitable for publication in subschema subentries.

( 1.3.6.1.1.20 NAME 'entryDN'

          DESC 'DN of the entry'
          EQUALITY distinguishedNameMatch
          SYNTAX 1.3.6.1.4.1.1466.115.121.1.12
          SINGLE-VALUE
          NO-USER-MODIFICATION
          USAGE directoryOperation )

Note that the DN of the entry cannot be modified through this attribute.

3. Security Considerations

As this attribute only provides an additional mechanism to access an entry's DN, the introduction of this attribute is not believed to introduce new security considerations.

4. IANA Considerations

4.1. Object Identifier Registration

IANA has registered (upon Standards Action) an LDAP Object Identifier [RFC4520] for use in this document.

      Subject: Request for LDAP OID Registration
      Person & email address to contact for further information:
          Kurt Zeilenga <Kurt.Zeilenga@Isode.COM>
      Specification: RFC 5020
      Author/Change Controller: IESG
      Comments:
          Identifies the 'entryDN' attribute type

4.2. 'entryDN' Descriptor Registration

IANA has registered (upon Standards Action) the LDAP 'entryDN' descriptor [RFC4520].

      Subject: Request for LDAP Descriptor Registration
      Descriptor (short name): entryDN
      Object Identifier: 1.3.6.1.1.20
      Person & email address to contact for further information:
          Kurt Zeilenga <Kurt.Zeilenga@Isode.COM>
      Usage: Attribute Type
      Specification: RFC 5020
      Author/Change Controller: IESG

5. References

5.1. Normative References

   [RFC4510]   Zeilenga, K., Ed., "Lightweight Directory Access Protocol
               (LDAP): Technical Specification Road Map", RFC 4510, June
               2006.
   
   [RFC4512]   Zeilenga, K., Ed., "Lightweight Directory Access Protocol
               (LDAP): Directory Information Models", RFC 4512, June
               2006.
   
   [X.501]     International Telecommunication Union - Telecommunication
               Standardization Sector, "The Directory -- Models,"
               X.501(1993) (also ISO/IEC 9594-2:1994).

5.2. Informative References

   [RFC3687]   Legg, S., "Lightweight Directory Access Protocol (LDAP)
               and X.500 Component Matching Rules", RFC 3687, February
               2004.
   
   [RFC4511]   Sermersheim, J., Ed., "Lightweight Directory Access
               Protocol (LDAP): The Protocol", RFC 4511, June 2006.
   
   [RFC4514]   Zeilenga, K., Ed., "Lightweight Directory Access Protocol
               (LDAP): String Representation of Distinguished Names",
               RFC 4514, June 2006.
   
   [RFC4515]   Smith, M., Ed., and T. Howes, "Lightweight Directory
               Access Protocol (LDAP): String Representation of Search
               Filters", RFC 4515, June 2006.
   
   [RFC4520]   Zeilenga, K., "Internet Assigned Numbers Authority (IANA)
               Considerations for the Lightweight Directory Access
               Protocol (LDAP)", BCP 64, RFC 4520, June 2006.

Author's Address

Kurt D. Zeilenga
Isode Limited

   EMail: Kurt.Zeilenga@Isode.COM

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