Network Working Group                                        K. Zeilenga
Request for Comments: 4529                           OpenLDAP Foundation
Category: Informational                                        June 2006


              Requesting Attributes by Object Class in the
              Lightweight Directory Access Protocol (LDAP)

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   The Lightweight Directory Access Protocol (LDAP) search operation
   provides mechanisms for clients to request all user application
   attributes, all operational attributes, and/or attributes selected by
   their description.  This document extends LDAP to support a mechanism
   that LDAP clients may use to request the return of all attributes of
   an object class.

Table of Contents

   1. Background and Intended Use .....................................1
   2. Terminology .....................................................2
   3. Return of all Attributes of an Object Class .....................2
   4. Security Considerations .........................................3
   5. IANA Considerations .............................................3
   6. References ......................................................4
      6.1. Normative References .......................................4
      6.2. Informative References .....................................4

1.  Background and Intended Use

   In the Lightweight Directory Access Protocol (LDAP) [RFC4510], the
   search operation [RFC4511] supports requesting the return of a set of
   attributes.  This set is determined by a list of attribute
   descriptions.  Two special descriptors are defined to request all
   user attributes ("*") [RFC4511] and all operational attributes ("+")
   [RFC3673].  However, there is no convenient mechanism for requesting
   pre-defined sets of attributes such as the set of attributes used to
   represent a particular class of object.



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   This document extends LDAP to allow an object class identifier to be
   specified in attributes lists, such as in Search requests, to request
   the return of all attributes belonging to an object class.  The
   COMMERCIAL AT ("@", U+0040) character is used to distinguish an
   object class identifier from an attribute descriptions.

   For example, the attribute list of "@country" is equivalent to the
   attribute list of 'c', 'searchGuide', 'description', and
   'objectClass'.  This object class is described in [RFC4519].

   This extension is intended primarily to be used where the user is in
   direct control of the parameters of the LDAP search operation, for
   instance when entering an LDAP URL [RFC4516] into a web browser, such
   as <ldap:///dc=example,dc=com?@organization?base>.

2.  Terminology

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
   and "OPTIONAL" are to be interpreted as described in BCP 14
   [RFC2119].

   DSA stands for Directory System Agent (or server).
   DSE stands for DSA-specific Entry.

3.  Return of All Attributes of an Object Class

   This extension allows object class identifiers to be provided in the
   attributes field of the LDAP SearchRequest [RFC4511] or other request
   values of the AttributeSelection data type (e.g., attributes field in
   pre/post read controls [ReadEntry]) and/or <attributeSelector>
   production (e.g., attributes of an LDAP URL [RFC4516]).  For each
   object class identified in the attributes field, the request is to be
   treated as if each attribute allowed by that class (by "MUST" or
   "MAY", directly or by "SUP"erior) [RFC4512] were itself listed.

   This extension extends the <attributeSelector> [RFC4511] production
   as indicated by the following ABNF [RFC4234]:

        attributeSelector =/ objectclassdescription
        objectclassdescription = ATSIGN oid options
        ATSIGN = %x40 ; COMMERCIAL AT ("@" U+0040)

   where <oid> and <options> productions are as defined in [RFC4512].







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   The <oid> component of an <objectclassdescription> production
   identifies the object class by short name (descr) or object
   identifier (numericoid).  If the value of the <oid> component is
   unrecognized or does not refer to an object class, the object class
   description is to be treated as an unrecognized attribute
   description.

   The <options> production is included in the grammar for extensibility
   purposes.  An object class description with an unrecognized or
   inappropriate option is to be treated as unrecognized.

   Although object class description options and attribute description
   options share the same syntax, they are not semantically related.
   This document does not define any object description option.

   Servers supporting this feature SHOULD publish the object identifier
   (OID) 1.3.6.1.4.1.4203.1.5.2 as a value of the 'supportedFeatures'
   [RFC4512] attribute in the root DSE.  Clients supporting this feature
   SHOULD NOT use the feature unless they know that the server supports
   it.

4.  Security Considerations

   This extension provides a shorthand for requesting all attributes of
   an object class.  Because these attributes could have been listed
   individually, introduction of this shorthand is not believed to raise
   additional security considerations.

   Implementors of this LDAP extension should be familiar with security
   considerations applicable to the LDAP search operation [RFC4511], as
   well as with general LDAP security considerations [RFC4510].

5.  IANA Considerations

   Registration of the LDAP Protocol Mechanism [RFC4520] defined in this
   document has been completed.

       Subject: Request for LDAP Protocol Mechanism Registration
       Object Identifier: 1.3.6.1.4.1.4203.1.5.2
       Description: OC AD Lists
       Person & email address to contact for further information:
            Kurt Zeilenga <kurt@openldap.org>
       Usage: Feature
       Specification: RFC 4529
       Author/Change Controller: Kurt Zeilenga <kurt@openldap.org>
       Comments: none





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   This OID was assigned [ASSIGN] by OpenLDAP Foundation, under its
   IANA-assigned private enterprise allocation [PRIVATE], for use in
   this specification.

6.  References

6.1.  Normative References

   [RFC2119]     Bradner, S., "Key words for use in RFCs to Indicate
                 Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4234]     Crocker, D., Ed. and P. Overell, "Augmented BNF for
                 Syntax Specifications: ABNF", RFC 4234, October 2005.

   [RFC4510]     Zeilenga, K., Ed., "Lightweight Directory Access
                 Protocol (LDAP): Technical Specification Road Map", RFC
                 4510, June 2006.

   [RFC4511]     Sermersheim, J., Ed., "Lightweight Directory Access
                 Protocol (LDAP): The Protocol", RFC 4511, June 2006.

   [RFC4512]     Zeilenga, K., "Lightweight Directory Access Protocol
                 (LDAP): Directory Information Models", RFC 4512, June
                 2006.

   [RFC4516]     Smith, M., Ed. and T. Howes, "Lightweight Directory
                 Access Protocol (LDAP): Uniform Resource Locator", RFC
                 4516, June 2006.

   [X.680]       International Telecommunication Union -
                 Telecommunication Standardization Sector, "Abstract
                 Syntax Notation One (ASN.1) - Specification of Basic
                 Notation", X.680(2002) (also ISO/IEC 8824-1:2002).

6.2.  Informative References

   [RFC3673]     Zeilenga, K., "Lightweight Directory Access Protocol
                 version 3 (LDAPv3): All Operational Attributes", RFC
                 3673, December 2003.

   [RFC4519]     Sciberras, A., Ed., "Lightweight Directory Access
                 Protocol (LDAP): Schema for User Applications", RFC
                 4519, June 2006.

   [RFC4520]     Zeilenga, K., "Internet Assigned Numbers Authority
                 (IANA) Considerations for the Lightweight Directory
                 Access Protocol (LDAP)", BCP 64, RFC 4520, June 2006.




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   [ReadEntry]   Zeilenga, K., "Lightweight Directory Access Protocol
                 (LDAP) Read Entry Controls", RFC 4527, June 2006.

   [ASSIGN]      OpenLDAP Foundation, "OpenLDAP OID Delegations",
                 http://www.openldap.org/foundation/oid-delegate.txt.

   [PRIVATE]     IANA, "Private Enterprise Numbers",
                 http://www.iana.org/assignments/enterprise-numbers.

Author's Address

   Kurt D. Zeilenga
   OpenLDAP Foundation

   EMail: Kurt@OpenLDAP.org




































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