Lightweight Directory Access Protocol (LDAP) Absolute True and False Filters
draft-zeilenga-ldap-t-f-10

INTERNET-DRAFT                                      Kurt D. Zeilenga
Intended Category: Standard Track                OpenLDAP Foundation
Expires in six months                               10 February 2005

                   LDAP Absolute True and False Filters
                     <draft-zeilenga-ldap-t-f-10.txt>

Status of this Memo

  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
  <ldapext@ietf.org>.  Please send editorial comments directly to the
  author <Kurt@OpenLDAP.org>.

  By submitting this Internet-Draft, I accept the provisions of Section
  4 of RFC 3667.  By submitting this Internet-Draft, I certify that any
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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.

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][RFC3494] could not represent empty 'and' and
  'or' filter sets.  Due to this, absolute True or False filters were
  (unfortunately) eliminated from LDAPv3 [Roadmap].

  This documents extends LDAPv3 to support absolute True and False
  assertions by allowing empty 'and' and 'or' in Search filters
  [Protocol] and extends the filter string representation [Filters] to
  allow empty filter lists.

  It is noted that certain search operations, such as those used to
  retrieve subschema information [Models], require use of particular
  filters.  This document does not change these requirements.

  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 "(&)".

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  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
  1.3.6.1.4.1.4203.1.5.3 as a value of the 'supportedFeatures' [RFC3674]
  attribute in the root DSE.

  Clients supporting this feature SHOULD NOT use the feature unless they
  have knowledge the server supports it.

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 [Roadmap].

4.  IANA Considerations

  Registration of this feature is requested [BCP64bis].

  Subject: Request for LDAP Protocol Mechanism Registration
  Object Identifier: 1.3.6.1.4.1.4203.1.5.3
  Description: True/False filters
  Person & email address to contact for further information:
       Kurt Zeilenga <kurt@openldap.org>
  Usage: Feature
  Specification: RFC XXXX
  Author/Change Controller: IESG
  Comments: none

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

5.  Author's Address

  Kurt D. Zeilenga
  OpenLDAP Foundation
  <Kurt@OpenLDAP.org>

6. References

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  [[Note to the RFC Editor: please replace the citation tags used in
  referencing Internet-Drafts with tags of the form RFCnnnn where
  possible.]]

6.1. Normative References

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

  [Roadmap]     Zeilenga, K. (editor), "LDAP: Technical Specification
                Road Map", draft-ietf-ldapbis-roadmap-xx.txt, a work in
                progress.

  [Protocol]    Sermersheim, J. (editor), "LDAP: The Protocol",
                draft-ietf-ldapbis-protocol-xx.txt, a work in progress.

  [Models]      Zeilenga, K. (editor), "LDAP: Directory Information
                Models", draft-ietf-ldapbis-models-xx.txt, a work in
                progress.

  [Filters]     Smith, M. (editor), LDAPbis WG, "LDAP: String
                Representation of Search Filters",
                draft-ietf-ldapbis-filter-xx.txt, a work in progress.

  [Features]    Zeilenga, K., "Feature Discovery in LDAP", RFC 3674,
                December 2003.

6.2. 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.

  [BCP64bis]    Zeilenga, K., "IANA Considerations for LDAP",
                draft-ietf-ldapbis-bcp64-xx.txt, a work in progress.

  [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).

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  [X.501]       International Telecommunication Union -
                Telecommunication Standardization Sector, "The Directory
                -- Models," X.501(1993) (also ISO/IEC 9594-2:1994).

  [X.511]       International Telecommunication Union -
                Telecommunication Standardization Sector, "The
                Directory: Abstract Service Definition", X.511(1993)
                (also ISO/IEC 9594-3:1993).

  [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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Full Copyright

  Copyright (C) The Internet Society (2005).  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.

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