datatracker.ietf.org
Sign in
Version 5.13.0, 2015-03-25
Report a bug

Lightweight Directory Access Protocol (LDAP) Absolute True and False Filters
RFC 4526

Document type: RFC - Proposed Standard (June 2006; Errata)
Was draft-zeilenga-ldap-t-f (individual in app area)
Document stream: IETF
Last updated: 2013-03-02
Other versions: plain text, pdf, html

IETF State: (None)
Consensus: Unknown
Document shepherd: No shepherd assigned

IESG State: RFC 4526 (Proposed Standard)
Responsible AD: Ted Hardie
Send notices to: kurt@openLDAP.org

Network Working Group                                        K. Zeilenga
Request for Comments: 4526                           OpenLDAP Foundation
Category: Standards Track                                      June 2006

              Lightweight Directory Access Protocol (LDAP)
                    Absolute True and False Filters

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2006).

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.

Table of Contents

   1. Background ......................................................1
   2. Absolute True and False Filters .................................2
   3. Security Considerations .........................................2
   4. IANA Considerations .............................................3
   5. References ......................................................3
      5.1. Normative References .......................................3
      5.2. Informative References .....................................3

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) that do not necessarily have
   'objectClass' attributes; that is, where "(objectClass=*)" may
   evaluate to False.

Zeilenga                    Standards Track                     [Page 1]
RFC 4526          LDAP Absolute True and False Filters         June 2006

   Although 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 [RFC4510].

   This documents extends LDAPv3 to support absolute True and False
   assertions by allowing empty 'and' and 'or' in Search filters
   [RFC4511] and extends the filter string representation [RFC4515] to
   allow empty filter lists.

   It is noted that certain search operations, such as those used to
   retrieve subschema information [RFC4512], 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).

   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].

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
   1.3.6.1.4.1.4203.1.5.3 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.

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 [RFC4510].

Zeilenga                    Standards Track                     [Page 2]
RFC 4526          LDAP Absolute True and False Filters         June 2006

4.  IANA Considerations

[include full document text]