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Versions: 00 01 02 03 04 05 06 07 08 09 RFC 4515

Network Working Group                                 M. Smith, Editor
Request for Comments: DRAFT              Netscape Communications Corp.
Obsoletes: RFC 2254                                           T. Howes
Expires: 9 February 2003                               Loudcloud, Inc.
                                                         9 August 2002


             LDAP: String Representation of Search Filters
                   <draft-ietf-ldapbis-filter-03.txt>



1.  Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   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
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   Discussion of this document should take place on the LDAP (v3)
   Revision (ldapbis) Working Group mailing list <ietf-
   ldapbis@openldap.org>.

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

2.  Abstract

   LDAP search filters are transmitted in the LDAP protocol using a
   binary representation that is appropriate for use on the network.
   This document defines a human-readable string representation of LDAP
   search filters that is appropriate for use in LDAP URLs and in other
   applications.





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3.  Table of Contents

1.     Status of this Memo............................................1
2.     Abstract.......................................................1
3.     Table of Contents..............................................2
4.     Introduction...................................................2
5.     LDAP Search Filter Definition..................................2
6.     String Search Filter Definition................................3
7.     Examples.......................................................5
8.     Security Considerations........................................6
9.     Normative References...........................................7
10.    Acknowledgments................................................7
11.    Authors' Address...............................................7
12.    Full Copyright Statement.......................................8
13.    Appendix A: Changes Since RFC 2254.............................8
13.1.     Technical Changes...........................................8
13.2.     Editorial Changes...........................................9
14.    Appendix B: Changes Since Previous Document Revision...........10
14.1.     Technical Changes...........................................10
14.2.     Editorial Changes...........................................10

4.  Introduction

   The Lightweight Directory Access Protocol (LDAP) [Protocol] defines a
   network representation of a search filter transmitted to an LDAP
   server.  Some applications may find it useful to have a common way of
   representing these search filters in a human-readable form; LDAP URLs
   are an example of one such application.  This document defines a
   human-readable string format for representing the full range of
   possible LDAP version 3 search filters, including extended match
   filters.

    This document is an integral part of the LDAP Technical
   Specification [Roadmap].

   This document replaces RFC 2254.  Changes to RFC 2254 are summarized
   in Appendix A.

5.  LDAP Search Filter Definition

   An LDAPv3 search filter is defined in Section 4.5.1 of [Protocol] as
   follows:

        Filter ::= CHOICE {
                and                [0] SET SIZE (1..MAX) OF Filter,
                or                 [1] SET SIZE (1..MAX) OF Filter,
                not                [2] Filter,
                equalityMatch      [3] AttributeValueAssertion,



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                substrings         [4] SubstringFilter,
                greaterOrEqual     [5] AttributeValueAssertion,
                lessOrEqual        [6] AttributeValueAssertion,
                present            [7] AttributeDescription,
                approxMatch        [8] AttributeValueAssertion,
                extensibleMatch    [9] MatchingRuleAssertion }

        SubstringFilter ::= SEQUENCE {
                type    AttributeDescription,
                -- at least one must be present,
                -- initial and final can occur at most once
                substrings    SEQUENCE OF CHOICE {
                        initial        [0] AssertionValue,
                        any            [1] AssertionValue,
                        final          [2] AssertionValue } }

        AttributeValueAssertion ::= SEQUENCE {
                attributeDesc   AttributeDescription,
                assertionValue  AssertionValue }

        MatchingRuleAssertion ::= SEQUENCE {
                matchingRule    [1] MatchingRuleId OPTIONAL,
                type            [2] AttributeDescription OPTIONAL,
                matchValue      [3] AssertionValue,
                dnAttributes    [4] BOOLEAN DEFAULT FALSE }

        AttributeDescription ::= LDAPString

        AttributeValue ::= OCTET STRING

        MatchingRuleId ::= LDAPString

        AssertionValue ::= OCTET STRING

        LDAPString ::= OCTET STRING

   where the LDAPString above is limited to the UTF-8 encoding of the
   ISO 10646 character set [RFC2279].  The AttributeDescription is a
   string representation of the attribute description and is defined in
   [Protocol].  The AttributeValue and AssertionValue OCTET STRING have
   the form defined in [Syntaxes].  The Filter is encoded for
   transmission over a network using the Basic Encoding Rules defined in
   [ASN.1], with simplifications described in [Protocol].

6.  String Search Filter Definition

   The string representation of an LDAP search filter is defined by the
   following grammar, following the ABNF notation defined in [RFC2234].



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   The filter format uses a prefix notation.

      filter         = "(" filtercomp ")"
      filtercomp     = and / or / not / item
      and            = "&" filterlist
      or             = "|" filterlist
      not            = "!" filter
      filterlist     = 1*filter
      item           = simple / present / substring / extensible
      simple         = attr filtertype assertionvalue
      filtertype     = equal / approx / greater / less
      equal          = "="
      approx         = "~="
      greater        = ">="
      less           = "<="
      extensible     = attr [":dn"] [":" matchingrule] ":=" assertionvalue
                       / [":dn"] ":" matchingrule ":=" assertionvalue
                       / ":=" assertionvalue
      present        = attr "=*"
      substring      = attr "=" [initial] any [final]
      initial        = assertionvalue
      any            = "*" *(assertionvalue "*")
      final          = assertionvalue
      attr           = AttributeDescription
                         ; The <AttributeDescription> rule is defined in
                         ; Section 4.1.4 of [Protocol].
      matchingrule   = oid
                         ; The <oid> rule is defined in Section 2.1
                         ; of [Syntaxes] and is used to encode a
                         ; matching rule OBJECT IDENTIFIER.
      assertionvalue = valueencoding
                         ; The <valueencoding> rule is used to encode an
                         ; <AssertionValue> from Section 4.1.6 of [Protocol].
      valueencoding  = 0*(normal / escaped)
      normal         = %x01-27 / %x2b-5b / %x5d-7f
      escaped        = "\" hex hex
      hex            = %x30-39 / %x41-46 / %x61-66


   Note that although both the <substring> and <present> productions in
   the grammar above can produce the "attr=*" construct, this construct
   is used only to denote a presence filter.

   The <valueencoding> rule provides that the octets that represent the
   ASCII characters "*" (ASCII 0x2a), "(" (ASCII 0x28), ")" (ASCII
   0x29), "\" (ASCII 0x5c), NUL (ASCII 0x00), and all octets greater
   than 0x7f are represented as a backslash "\" (ASCII 0x5c) followed by
   the two hexadecimal digits representing the value of the encoded



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   octet.

   This simple escaping mechanism eliminates filter-parsing ambiguities
   and allows any filter that can be represented in LDAP to be
   represented as a NUL-terminated string. Other octets that are part of
   the <normal> set may be escaped using this mechanism, for example,
   non-printing ASCII characters.

   For AssertionValues that contain UTF-8 character data, each octet of
   the character to be escaped is replaced by a backslash and two hex
   digits, which form a single octet in the code of the character.

   For example, the filter checking whether the "cn" attribute contained
   a value with the character "*" anywhere in it would be represented as
   "(cn=*\2a*)".


7.  Examples

   This section gives a few examples of search filters written using
   this notation.

        (cn=Babs Jensen)
        (!(cn=Tim Howes))
        (&(objectClass=Person)(|(sn=Jensen)(cn=Babs J*)))
        (o=univ*of*mich*)
        (seeAlso=)

   The following examples illustrate the use of extensible matching.

        (cn:1.2.3.4.5:=Fred Flintstone)
        (cn:=Betty Rubble)
        (sn:dn:2.4.6.8.10:=Barney Rubble)
        (o:dn:=Ace Industry)
        (:1.2.3:=Wilma Flintstone)
        (:dn:2.4.6.8.10:=Dino)
        (:=Fred Flintstone)

   The first example shows use of the matching rule "1.2.3.4.5".

   The second example demonstrates use of a MatchingRuleAssertion form
   without a matchingRule.

   The third example illustrates the use of the ":dn" notation to
   indicate that matching rule "2.4.6.8.10" should be used when making
   comparisons, and that the attributes of an entry's distinguished name
   should be considered part of the entry when evaluating the match.




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   The fourth example denotes an equality match, except that DN
   components should be considered part of the entry when doing the
   match.

   The fifth example is a filter that should be applied to any attribute
   supporting the matching rule given (since the attr has been omitted).

   The sixth example is also a filter that should be applied to any
   attribute supporting the matching rule given.  Attributes supporting
   the matching rule contained in the DN should also be considered.

   The seventh and final example is a filter that should be applied to
   any attribute (since both the attr and matching rule have been
   omitted).

   The following examples illustrate the use of the escaping mechanism.

        (o=Parens R Us \28for all your parenthetical needs\29)
        (cn=*\2A*)
        (filename=C:\5cMyFile)
        (bin=\00\00\00\04)
        (sn=Lu\c4\8di\c4\87)
        (1.3.6.1.4.1.1466.0;binary=\04\02\48\69)

   The first example shows the use of the escaping mechanism to
   represent parenthesis characters. The second shows how to represent a
   "*" in an assertion value, preventing it from being interpreted as a
   substring indicator. The third illustrates the escaping of the
   backslash character.

   The fourth example shows a filter searching for the four-byte value
   0x00000004, illustrating the use of the escaping mechanism to
   represent arbitrary data, including NUL characters.

   The fifth example illustrates the use of the escaping mechanism to
   represent various non-ASCII UTF-8 characters.

   The sixth and final example demonstrates assertion of a BER encoded
   value.

8.  Security Considerations

   This memo describes a string representation of LDAP search filters.
   While the representation itself has no known security implications,
   LDAP search filters do. They are interpreted by LDAP servers to
   select entries from which data is retrieved.  LDAP servers should
   take care to protect the data they maintain from unauthorized access.




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   Please refer to the Security Considerations sections of [Protocol]
   and [AuthMeth] for more information.

9.  Normative References

   [ASN.1] Specification of ASN.1 encoding rules: Basic, Canonical, and
   Distinguished Encoding Rules, ITU-T Recommendation X.690, 1994.

   [AuthMeth] Harrison, R. (editor), "LDAP: Authentication Methods and
   Connection Level Security Mechanisms", draft-ietf-ldapbis-authmeth-
   xx.txt, a work in progress.

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

   [RFC2234] Crocker, D., Overell, P., "Augmented BNF for Syntax
   Specifications:  ABNF", RFC 2234, November 1997.

   [RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO 10646",
   RFC 2279, January 1998.

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

   [Syntaxes] Dally, K. (editor), "LDAP: Syntaxes", draft-ietf-ldapbis-
   syntaxes-xx.txt, a work in progress.


10.  Acknowledgments

   This document replaces RFC 2254 by Tim Howes.  Changes included in
   this revised specification are based upon discussions among the
   authors, discussions within the LDAP (v3) Revision Working Group
   (ldapbis), and discussions within other IETF Working Groups.  The
   contributions of individuals in these working groups is gratefully
   acknowledged.


11.  Authors' Address

   Mark Smith, Editor
   Netscape Communications Corp.
   360 W. Caribbean Drive
   Sunnyvale, CA 94089
   USA
   +1 650 937-3477
   mcs@netscape.com




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   Tim Howes
   Loudcloud, Inc.
   599 N. Mathilda Ave.
   Sunnyvale, CA 94086
   USA
   +1 408 744-7509
   howes@loudcloud.com

12.  Full Copyright Statement

   Copyright (C) The Internet Society (2002).  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
   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 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.


13.  Appendix A: Changes Since RFC 2254

13.1.  Technical Changes

   "String Search Filter Definition" section: replaced the "value" rule
   with a new "assertionvalue" rule within the "simple", "extensible",
   and "substring" ("initial", "any", and "final") rules.  This matches
   a change made in [Syntaxes].
   Revised the "attr", "matchingrule", and "assertionvalue" ABNF to more
   precisely reference productions from the [Protocol] and [Syntaxes]
   documents.



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   Introduced the "valueencoding" and associated "normal" and "escaped"
   rules to reduce the dependence on descriptive text.
   Added a third option to the "extensible" production to allow creation
   of a MatchingRuleAssertion that only has a matchValue.



13.2.  Editorial Changes

   Changed document title to include "LDAP:" prefix.

   IESG Note: removed note about lack of satisfactory mandatory
   authentication mechanisms.

   Header and "Authors' Addresses" sections: added Mark Smith as the
   document editor and updated affiliation and contact information.

   "Table of Contents" section: added.

   Copyright: updated the year.

   "Abstract" section: separated from introductory material.

   "Introduction" section: new section; separated from the Abstract.
   Updated second paragraph to indicate that RFC 2254 is replaced by
   this document (instead of RFC 1960). Added reference to the [Roadmap]
   document.

   "LDAP Search Filter Definition" section: made corrections to the
   LDAPv3 search filter ABNF so it matches that used in [Protocol].

   "String Search Filter Definition" section:  clarified the definition
   of 'value' (now 'assertionvalue') to take into account the fact that
   it is not precisely an AttributeAssertion from [Protocol] section
   4.1.6 (special handling is required for some characters).  Added a
   note that each octet of a character to be escaped is replaced by a
   backslash and two hex digits, which represent a single octet.

   "Examples" section: added five additional examples: (seeAlso=),
   (cn:=Betty Rubble), (:1.2.3:=Wilma Flintstone), (:=Fred Flintstone),
   and (1.3.6.1.4.1.1466.0;binary=\04\02\48\69). Replaced one occurrence
   of "a value" with "an assertion value".

   "Security Considerations" section: added references to [Protocol] and
   [AuthMeth].

   "Normative References" section: renamed from "References" per new RFC
   guidelines. Changed from [1] style to [Protocol] style throughout the



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   document.  Added entries for [AuthMeth] and [Roadmap] and updated
   UTF-8 reference to RFC 2279.  Replaced RFC 822 reference with a
   reference to RFC 2234.

   "Acknowledgments" section: added.

   "Appendix A: Changes Since RFC 2254" section: added.

   "Appendix B: Changes Since Previous Document Revision" section:
   added.


14.  Appendix B: Changes Since Previous Document Revision

   This appendix lists all changes relative to the last published
   revision, draft-ietf-ldapbis-filter-02.txt.  Note that these changes
   are also included in Appendix A, but are included here for those who
   have already reviewed draft-ietf-ldapbis-filter-02.txt.  This section
   will be removed before this document is published as an RFC.


14.1.  Technical Changes

   None.


14.2.  Editorial Changes

   "Abstract" section: separated from introductory material.

   "Table of Contents" section: moved to correct location (after
   Abstract).

   "Introduction" section: new section; separated from the Abstract.

   "LDAP Search Filter Definition " section: updated section references
   to match current LDAPBis drafts. Made minor changes to the ASN.1 so
   it exactly matches that used in the Protocol document.

   "Normative References" section: renamed from "References" per new RFC
   guidelines; changed author names to "Last, F." format for
   consistency.

   "Authors' Address" section: updated Mark Smith's postal address.


This Internet Draft expires on 9 February 2003.




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