INTERNET-DRAFT Kurt D. Zeilenga Intended Category: Standard Track OpenLDAP Foundation Expires in six months 4 August 2002 Feature Discovery in LDAP Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. This document is intended to be, after appropriate review and revision, submitted to the RFC Editor as an Standard Track document. Distribution of this memo is unlimited. Technical discussion of this document will take place on the IETF LDAP Extension Working Group mailing list . Please send editorial comments directly to the author . Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as ``work in progress.'' The list of current Internet-Drafts can be accessed at . The list of Internet-Draft Shadow Directories can be accessed at . Copyright 2002, The Internet Society. All Rights Reserved. Please see the Copyright section near the end of this document for more information. Abstract The Lightweight Directory Access Protocol (LDAP) is an extensible protocol with numerous elective features. This document introduces a general mechanism for discovery of elective features and extensions which cannot be discovered using existing mechanisms. Zeilenga draft-zeilenga-ldap-features-04 [Page 1] INTERNET-DRAFT LDAP supportedFeatures 4 August 2002 1. Background and Intended Use LDAP [RFC2251] is an extensible protocol with numerous elective features. LDAP provides mechanisms for a client to discover supported protocol versions, controls, extended operations, SASL mechanisms, and subschema information. However, these mechanisms are not designed to support general feature discovery. This document describes a simple, general-purpose mechanism which clients may use to discover the set of elective features supported by a server. For example, this mechanism could be used by a client to discover whether or not the server supports request for all operational attributes, e.g. "+" [OPATTRS]. As another example, this mechanism could be used to discover absolete true, e.g. "(&)" and false, e.g. "(|)", search filters [T-F] support. This document extends the IANA LDAP Protocol Mechanism registry [LDAPIANA] to support registration of values of the supportedFeatures attribute. Schema definitions are provided using LDAPv3 description formats [RFC2252]. Definitions provided here are formatted (line wrapped) for readability. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119]. 2. Discovery of supported features Each elective feature whose support may be discovered SHALL be identified by an Object Identifier (OID). A server advertises its support for a given feature by providing the OID associated with the feature as a value of the 'supportedFeatures' attribute held in the root DSE. A client may examine the values of this attribute to determine if a particular feature is supported by the server. A client MUST ignore values it doesn't recognize as they refer to elective features it doesn't implement. Features associated with Standard Track protocol mechanisms MUST be registered. Features associated with other protocol mechanisms SHOULD be registered. Procedures for registering protocol mechanisms are are described in [LDAPIANA]. "Feature" should be placed in the usage field of the submitted LDAP Protocol Mechanism template. The 'supportedFeatures' attribute type is described as follows: Zeilenga draft-zeilenga-ldap-features-04 [Page 2] INTERNET-DRAFT LDAP supportedFeatures 4 August 2002 ( 1.3.6.1.4.1.4203.1.3.5 NAME 'supportedFeatures' DESC 'features supported by the server' EQUALITY objectIdentifierMatch SYNTAX 1.3.6.1.4.1.1466.115.121.1.38 USAGE dSAOperation ) Servers MUST be capable of recognizing this attribute type by the name 'supportedFeatures'. Servers MAY recognize the attribute type by other names. 4. Security Considerations As rogue clients can discover features of a server by other means (such as by trial and error), this feature discovery mechanism is not believed to introduce any new security risk to LDAP. 5. IANA Considerations 5.1. Registration of Features as Protocol Mechanisms Future specifications detail LDAP features are to be registered as LDAP Protocol Mechanisms per guidance provided in [LDAPIANA]. A usage of "Feature" in a Protocol Mechanism registration template indicates that the value to be registered is associated with an LDAP feature. 5.2. Registration of the supportedFeature descriptor It is requested that IANA register upon Standards Action the LDAP 'supportedFeatures' descriptor. The following registration template is suggested: Subject: Request for LDAP Descriptor Registration Descriptor (short name): supportedFeatures Object Identifier: 1.3.6.1.4.1.4203.1.3.5 Person & email address to contact for further information: Kurt Zeilenga Usage: Attribute Type Specification: RFCXXXX Author/Change Controller: IESG This OID was assigned [ASSIGN] by OpenLDAP Foundation under its IANA assigned private enterprise allocation [PRIVATE] for use in this specification. Zeilenga draft-zeilenga-ldap-features-04 [Page 3] INTERNET-DRAFT LDAP supportedFeatures 4 August 2002 6. Acknowledgment This document is based upon input from the IETF LDAPext working group. 7. Author's Address Kurt D. Zeilenga OpenLDAP Foundation 8. Normative References [RFC2119] S. Bradner, "Key words for use in RFCs to Indicate Requirement Levels", BCP 14 (also RFC 2119), March 1997. [RFC2251] M. Wahl, T. Howes, S. Kille, "Lightweight Directory Access Protocol (v3)", RFC 2251, December 1997. [RFC2252] M. Wahl, A. Coulbeck, T. Howes, S. Kille, "Lightweight Directory Access Protocol (v3): Attribute Syntax Definitions", RFC 2252, December 1997. 9. Informative References [LDAPIANA] K. Zeilenga, "IANA Considerations for LDAP", draft-ietf- ldapbis-iana-xx.txt, a work in progress. [OPATTRS] K. Zeilenga, "LDAPv3: All Operational Attributes", draft-zeilenga-ldap-opattrs-xx.txt (a work in progress). [T-F] K. Zeilenga, "LDAP True/False Filters", draft-zeilenga-ldap-t-f-xx.txt (a work in progress). Full Copyright Copyright 2002, The Internet Society. 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 Zeilenga draft-zeilenga-ldap-features-04 [Page 4] INTERNET-DRAFT LDAP supportedFeatures 4 August 2002 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 AUTHORS, 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. Zeilenga draft-zeilenga-ldap-features-04 [Page 5]