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rfc:rfc4529

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.

Zeilenga Informational [Page 1] RFC 4529 Requesting Attributes by Object Class June 2006

 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].

Zeilenga Informational [Page 2] RFC 4529 Requesting Attributes by Object Class June 2006

 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

Zeilenga Informational [Page 3] RFC 4529 Requesting Attributes by Object Class June 2006

 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.

Zeilenga Informational [Page 4] RFC 4529 Requesting Attributes by Object Class June 2006

 [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

Zeilenga Informational [Page 5] RFC 4529 Requesting Attributes by Object Class June 2006

Full Copyright Statement

 Copyright (C) The Internet Society (2006).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
 ENGINEERING TASK FORCE DISCLAIM 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.

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Acknowledgement

 Funding for the RFC Editor function is provided by the IETF
 Administrative Support Activity (IASA).

Zeilenga Informational [Page 6]

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