INTERNET-DRAFT Kurt D. Zeilenga Intended Category: Standard Track OpenLDAP Foundation Expires in six months 25 October 2003 LDAP Absolute True and False Filters 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 a Standard Track document. Distribution of this memo is unlimited. Technical discussion of this document will take place on the IETF LDAP Extensions 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 (C) The Internet Society (2003). All Rights Reserved. Please see the Full Copyright section near the end of this document for more information. Abstract This document extends the Lightweight Directory Access Protocol (LDAP) to support absolute True and False filters based upon similar capabilities found in X.500 directory systems. The document also extends the String Representation of LDAP Search Filters to support these filters. Zeilenga LDAP True & False Filters [Page 1] INTERNET-DRAFT draft-zeilenga-ldap-t-f-07.txt 25 October 2003 1. Background The X.500 Directory Access Protocol (DAP) [X.511] supports absolute True and False assertions. An 'and' filter with zero elements always evaluates to True. An 'or' filter with zero elements always evaluates to False. These filters are commonly used when requesting DSA- specific Entries (DSEs) which do not necessarily have 'objectClass' attributes. That is, where "(objectClass=*)" may evaluate to False. While LDAPv2 [RFC1777][RFC3494] placed no restriction on the number of elements in 'and' and 'or' filter sets, the LDAPv2 string representation [RFC1960] could not represent empty 'and' and 'or' filter sets. Due to this, absolute True or False filters were (unfortunately) eliminated from LDAPv3 [RFC3377]. This documents extends LDAPv3 to support absolute True and False matches by allowing empty 'and' and 'or' in Search filters [RFC2251] and extends the filter string representation [RFC2254] to allow empty filter lists. This feature is intended to allow a more direct mapping between DAP and LDAP (as needed to implement DAP-to-LDAP gateways). 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. Absolute True and False Filters Implementations of this extension SHALL allow 'and' and 'or' choices with zero filter elements. An 'and' filter consisting of an empty set of filters SHALL evaluate to True. This filter is represented by the string "(&)". An 'or' filter consisting of an empty set of filters SHALL evaluate to False. This filter is represented by the string "(|)". Servers supporting this feature SHOULD publish the Object Identifier (OID) 1.3.6.1.4.1.4203.1.5.3 as a value of the 'supportedFeatures' [FEATURES] attribute in the root DSE. Clients supporting this feature SHOULD NOT use the feature unless they have knowledge the server supports it. Zeilenga LDAP True & False Filters [Page 2] INTERNET-DRAFT draft-zeilenga-ldap-t-f-07.txt 25 October 2003 3. Security Considerations The (re)introduction of absolute True and False filters is not believed to raise any new security considerations. Implementors of this (or any) LDAPv3 extension should be familiar with general LDAPv3 security considerations [RFC3377]. 4. IANA Considerations The OID 1.3.6.1.4.1.4203.1.5.3 identifies the feature described above. This OID was assigned [ASSIGN] by OpenLDAP Foundation, under its IANA-assigned private enterprise allocation [PRIVATE], for use in this specification. Registration of this feature is requested [FEATURES][RFC3383]. Subject: Request for LDAP Protocol Mechanism Registration Object Identifier: 1.3.6.1.4.1.4203.1.5.3 Description: T/F Filters Person & email address to contact for further information: Kurt Zeilenga Usage: Feature Specification: RFC XXXX Author/Change Controller: IESG Comments: none 5. Author's Address Kurt D. Zeilenga OpenLDAP Foundation 6. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14 (also RFC 2119), March 1997. [RFC2251] Wahl, M., T. Howes and S. Kille, "Lightweight Directory Access Protocol (v3)", RFC 2251, December 1997. [RFC2254] Howes, T., "A String Representation of LDAP Search Filters", RFC 2254, December 1997. [RFC3377] Hodges, J. and R. Morgan, "Lightweight Directory Access Zeilenga LDAP True & False Filters [Page 3] INTERNET-DRAFT draft-zeilenga-ldap-t-f-07.txt 25 October 2003 Protocol (v3): Technical Specification", RFC 3377, September 2002. [FEATURES] Zeilenga, K., "Feature Discovery in LDAP", draft-zeilenga-ldap-features-xx.txt, a work in progress. 7. Informative References [RFC1777] Yeong, W., Howes, T., and S. Kille, "Lightweight Directory Access Protocol", RFC 1777, March 1995. [RFC1960] Howes, T., "A String Representation of LDAP Search Filters", RFC 1960, June 1996. [RFC3383] Zeilenga, K., "IANA Considerations for LDAP", BCP 64 (also RFC 3383), September 2002. [RFC3494] Zeilenga, K., "Lightweight Directory Access Protocol version 2 (LDAPv2) to Historic Status", RFC 3494, March 2003. [X.500] International Telecommunication Union - Telecommunication Standardization Sector, "The Directory -- Overview of concepts, models and services," X.500(1993) (also ISO/IEC 9594-1:1994). [X.501] International Telecommunication Union - Telecommunication Standardization Sector, "The Directory -- Models," X.501(1993) (also ISO/IEC 9594-2:1994). [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. 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