GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc4515

Network Working Group M. Smith, Ed. Request for Comments: 4515 Pearl Crescent, LLC Obsoletes: 2254 T. Howes Category: Standards Track Opsware, Inc.

                                                             June 2006
           Lightweight Directory Access Protocol (LDAP):
              String Representation of Search 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

 Lightweight Directory Access Protocol (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 (RFC 4516) and in other
 applications.

Table of Contents

 1. Introduction ....................................................2
 2. LDAP Search Filter Definition ...................................2
 3. String Search Filter Definition .................................3
 4. Examples ........................................................5
 5. Security Considerations .........................................7
 6. Normative References ............................................7
 7. Informative References ..........................................8
 8. Acknowledgements ................................................8
 Appendix A: Changes Since RFC 2254 .................................9
    A.1. Technical Changes ..........................................9
    A.2. Editorial Changes ..........................................9

Smith and Howes Standards Track [Page 1] RFC 4515 LDAP: String Representation of Search Filters June 2006

1. Introduction

 The Lightweight Directory Access Protocol (LDAP) [RFC4510] 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
 [RFC4516] 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 a integral part of the LDAP technical specification
 [RFC4510], which obsoletes the previously defined LDAP technical
 specification, RFC 3377, in its entirety.
 This document replaces RFC 2254.  Changes to RFC 2254 are summarized
 in Appendix A.
 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. LDAP Search Filter Definition

 An LDAP search filter is defined in Section 4.5.1 of [RFC4511] as
 follows:
      Filter ::= CHOICE {
          and                [0] SET SIZE (1..MAX) OF filter Filter,
          or                 [1] SET SIZE (1..MAX) OF filter Filter,
          not                [2] Filter,
          equalityMatch      [3] AttributeValueAssertion,
          substrings         [4] SubstringFilter,
          greaterOrEqual     [5] AttributeValueAssertion,
          lessOrEqual        [6] AttributeValueAssertion,
          present            [7] AttributeDescription,
          approxMatch        [8] AttributeValueAssertion,
          extensibleMatch    [9] MatchingRuleAssertion }
      SubstringFilter ::= SEQUENCE {
          type    AttributeDescription,
          -- initial and final can occur at most once
          substrings    SEQUENCE SIZE (1..MAX) OF substring CHOICE {
           initial        [0] AssertionValue,
           any            [1] AssertionValue,
           final          [2] AssertionValue } }

Smith and Howes Standards Track [Page 2] RFC 4515 LDAP: String Representation of Search Filters June 2006

      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
                      -- Constrained to <attributedescription>
                      -- [RFC4512]
      AttributeValue ::= OCTET STRING
      MatchingRuleId ::= LDAPString
      AssertionValue ::= OCTET STRING
      LDAPString ::= OCTET STRING -- UTF-8 encoded,
                                  -- [Unicode] characters
 The AttributeDescription, as defined in [RFC4511], is a string
 representation of the attribute description that is discussed in
 [RFC4512].  The AttributeValue and AssertionValue OCTET STRING have
 the form defined in [RFC4517].  The Filter is encoded for
 transmission over a network using the Basic Encoding Rules (BER)
 defined in [X.690], with simplifications described in [RFC4511].

3. String Search Filter Definition

 The string representation of an LDAP search filter is a string of
 UTF-8 [RFC3629] encoded Unicode characters [Unicode] that is defined
 by the following grammar, following the ABNF notation defined in
 [RFC4234].  The productions used that are not defined here are
 defined in Section 1.4 (Common ABNF Productions) of [RFC4512] unless
 otherwise noted.  The filter format uses a prefix notation.
    filter         = LPAREN filtercomp RPAREN
    filtercomp     = and / or / not / item
    and            = AMPERSAND filterlist
    or             = VERTBAR filterlist
    not            = EXCLAMATION filter
    filterlist     = 1*filter
    item           = simple / present / substring / extensible
    simple         = attr filtertype assertionvalue
    filtertype     = equal / approx / greaterorequal / lessorequal

Smith and Howes Standards Track [Page 3] RFC 4515 LDAP: String Representation of Search Filters June 2006

    equal          = EQUALS
    approx         = TILDE EQUALS
    greaterorequal = RANGLE EQUALS
    lessorequal    = LANGLE EQUALS
    extensible     = ( attr [dnattrs]
                         [matchingrule] COLON EQUALS assertionvalue )
                     / ( [dnattrs]
                          matchingrule COLON EQUALS assertionvalue )
    present        = attr EQUALS ASTERISK
    substring      = attr EQUALS [initial] any [final]
    initial        = assertionvalue
    any            = ASTERISK *(assertionvalue ASTERISK)
    final          = assertionvalue
    attr           = attributedescription
                       ; The attributedescription rule is defined in
                       ; Section 2.5 of [RFC4512].
    dnattrs        = COLON "dn"
    matchingrule   = COLON oid
    assertionvalue = valueencoding
    ; The <valueencoding> rule is used to encode an <AssertionValue>
    ; from Section 4.1.6 of [RFC4511].
    valueencoding  = 0*(normal / escaped)
    normal         = UTF1SUBSET / UTFMB
    escaped        = ESC HEX HEX
    UTF1SUBSET     = %x01-27 / %x2B-5B / %x5D-7F
                        ; UTF1SUBSET excludes 0x00 (NUL), LPAREN,
                        ; RPAREN, ASTERISK, and ESC.
    EXCLAMATION    = %x21 ; exclamation mark ("!")
    AMPERSAND      = %x26 ; ampersand (or AND symbol) ("&")
    ASTERISK       = %x2A ; asterisk ("*")
    COLON          = %x3A ; colon (":")
    VERTBAR        = %x7C ; vertical bar (or pipe) ("|")
    TILDE          = %x7E ; tilde ("~")
 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 ensures that the entire filter string is a
 valid UTF-8 string and provides that the octets that represent the
 ASCII characters "*" (ASCII 0x2a), "(" (ASCII 0x28), ")" (ASCII
 0x29), "\" (ASCII 0x5c), and NUL (ASCII 0x00) are represented as a
 backslash "\" (ASCII 0x5c) followed by the two hexadecimal digits
 representing the value of the encoded octet.

Smith and Howes Standards Track [Page 4] RFC 4515 LDAP: String Representation of Search Filters June 2006

 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*)".
 As indicated by the <valueencoding> rule, implementations MUST escape
 all octets greater than 0x7F that are not part of a valid UTF-8
 encoding sequence when they generate a string representation of a
 search filter.  Implementations SHOULD accept as input strings that
 are not valid UTF-8 strings.  This is necessary because RFC 2254 did
 not clearly define the term "string representation" (and in
 particular did not mention that the string representation of an LDAP
 search filter is a string of UTF-8-encoded Unicode characters).

4. 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:caseExactMatch:=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)
 The first example shows use of the matching rule "caseExactMatch."
 The second example demonstrates use of a MatchingRuleAssertion form
 without a matchingRule.

Smith and Howes Standards Track [Page 5] RFC 4515 LDAP: String Representation of Search Filters June 2006

 The third example illustrates the use of the ":oid" notation to
 indicate that the matching rule identified by the OID "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 (indicated by the use of ":dn").
 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 and final 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 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=\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-octet value
 00 00 00 04 (hex), 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.  Specifically, there
 are 5 characters in the <assertionvalue> portion of this example:
 LATIN CAPITAL LETTER L (U+004C), LATIN SMALL LETTER U (U+0075), LATIN
 SMALL LETTER C WITH CARON (U+010D), LATIN SMALL LETTER I (U+0069),
 and LATIN SMALL LETTER C WITH ACUTE (U+0107).
 The sixth and final example demonstrates assertion of a BER-encoded
 value.

Smith and Howes Standards Track [Page 6] RFC 4515 LDAP: String Representation of Search Filters June 2006

5. 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.
 Please refer to the Security Considerations sections of [RFC4511] and
 [RFC4513] for more information.

6. Normative References

 [RFC2119]   Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC3629]   Yergeau, F., "UTF-8, a transformation format of ISO
             10646", STD 63, RFC 3629, November 2003.
 [RFC4234]   Crocker, D. and P. Overell, "Augmented BNF for Syntax
             Specifications: ABNF", RFC 4234, October 2005.
 [RFC4510]   Zeilenga, K., Ed., "Lightweight Directory Access Protocol
             (LDAP): Technical Specification Road Map", RFC 4510, June
             2006.
 [RFC4511]   Sermersheim, J., Ed., "Lightweight Directory Access
             Protocol (LDAP): The Protocol", RFC 4511, June 2006.
 [RFC4512]   Zeilenga, K., "Lightweight Directory Access Protocol
             (LDAP): Directory Information Models", RFC 4512, June
             2006.
 [RFC4513]   Harrison, R., Ed., "Lightweight Directory Access Protocol
             (LDAP): Authentication Methods and Security Mechanisms",
             RFC 4513, June 2006.
 [RFC4517]   Legg, S., Ed., "Lightweight Directory Access Protocol
             (LDAP): Syntaxes and Matching Rules", RFC 4517, June
             2006.
 [Unicode]   The Unicode Consortium, "The Unicode Standard, Version
             3.2.0" is defined by "The Unicode Standard, Version 3.0"
             (Reading, MA, Addison-Wesley, 2000. ISBN 0-201-61633-5),
             as amended by the "Unicode Standard Annex #27: Unicode
             3.1" (http://www.unicode.org/reports/tr27/) and by the
             "Unicode Standard Annex #28: Unicode 3.2."

Smith and Howes Standards Track [Page 7] RFC 4515 LDAP: String Representation of Search Filters June 2006

7. Informative References

 [RFC4516]   Smith, M., Ed. and T. Howes, "Lightweight Directory
             Access Protocol (LDAP): Uniform Resource Locator", RFC
             4516, June 2006.
 [X.690]     Specification of ASN.1 encoding rules: Basic, Canonical,
             and Distinguished Encoding Rules, ITU-T Recommendation
             X.690, 1994.

8. Acknowledgements

 This document replaces RFC 2254 by Tim Howes.  RFC 2254 was a product
 of the IETF ASID Working Group.
 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.

Smith and Howes Standards Track [Page 8] RFC 4515 LDAP: String Representation of Search Filters June 2006

Appendix A: Changes Since RFC 2254

A.1. Technical Changes

 Replaced [ISO 10646] reference with [Unicode].
 The following technical changes were made to the contents of the
 "String Search Filter Definition" section:
 Added statement that the string representation is a string of UTF-8-
 encoded Unicode characters.
 Revised all of the ABNF to use common productions from [RFC4512].
 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 [RFC4517].
 Added "(" and ")" around the components of the <extensible>
 subproductions for clarity.
 Revised the "attr", "matchingrule", and "assertionvalue" ABNF to more
 precisely reference productions from the [RFC4512] and [RFC4511]
 documents.
 "String Search Filter Definition" section: replaced "greater" and
 "less" with "greaterorequal" and "lessorequal" to avoid confusion.
 Introduced the "valueencoding" and associated "normal" and "escaped"
 rules to reduce the dependence on descriptive text.  The "normal"
 production restricts filter strings to valid UTF-8 sequences.
 Added a statement about expected behavior in light of RFC 2254's lack
 of a clear definition of "string representation."

A.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" and "Intellectual Property" sections: added.
 Copyright: updated per latest IETF guidelines.

Smith and Howes Standards Track [Page 9] RFC 4515 LDAP: String Representation of Search Filters June 2006

 "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
 [RFC4510] document.
 "LDAP Search Filter Definition" section: made corrections to the LDAP
 search filter ABNF so it matches that used in [RFC4511].
 Clarified the definition of 'value' (now 'assertionvalue') to take
 into account the fact that it is not precisely an AttributeAssertion
 from [RFC4511] 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 four additional examples: (seeAlso=),
 (cn:=Betty Rubble), (:1.2.3:=Wilma Flintstone), and
 (1.3.6.1.4.1.1466.0=\04\02\48\69).  Replaced one occurrence of "a
 value" with "an assertion value".  Corrected the description of this
 example: (sn:dn:2.4.6.8.10:=Barney Rubble).  Replaced the numeric OID
 in the first extensible match example with "caseExactMatch" to
 demonstrate use of the descriptive form.  Used "DN" (uppercase) in
 the last extensible match example to remind the reader to treat the
 <dnattrs> production as case insensitive.  Reworded the description
 of the fourth escaping mechanism example to avoid making assumptions
 about byte order.  Added text to the fifth escaping mechanism example
 to spell out what the non-ASCII characters are in Unicode terms.
 "Security Considerations" section: added references to [RFC4511] and
 [RFC4513].
 "Normative References" section: renamed from "References" per new RFC
 guidelines.  Changed from [1] style to [RFC4511] style throughout the
 document.  Added entries for [Unicode], [RFC2119], [RFC4513],
 [RFC4512], and [RFC4510] and updated the UTF-8 reference.  Replaced
 RFC 822 reference with a reference to RFC 4234.
 "Informative References" section: (new section) moved [X.690] to this
 section.  Added a reference to [RFC4516].
 "Acknowledgements" section: added.
 "Appendix A: Changes Since RFC 2254" section: added.
 Surrounded the names of all ABNF productions with "<" and ">" where
 they are used in descriptive text.

Smith and Howes Standards Track [Page 10] RFC 4515 LDAP: String Representation of Search Filters June 2006

 Replaced all occurrences of "LDAPv3" with "LDAP."

Authors' Addresses

 Mark Smith, Editor
 Pearl Crescent, LLC
 447 Marlpool Dr.
 Saline, MI 48176
 USA
 Phone: +1 734 944-2856
 EMail: mcs@pearlcrescent.com
 Tim Howes
 Opsware, Inc.
 599 N. Mathilda Ave.
 Sunnyvale, CA 94085
 USA
 Phone: +1 408 744-7509
 EMail: howes@opsware.com

Smith and Howes Standards Track [Page 11] RFC 4515 LDAP: String Representation of Search Filters June 2006

Full Copyright Statement

 Copyright (C) The Internet Society (2006).
 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.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
 ENGINEERING TASK FORCE DISCLAIM 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.

Intellectual Property

 The IETF takes no position regarding the validity or scope of any
 Intellectual Property Rights or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; nor does it represent that it has
 made any independent effort to identify any such rights.  Information
 on the procedures with respect to rights in RFC documents can be
 found in BCP 78 and BCP 79.
 Copies of IPR disclosures made to the IETF Secretariat and any
 assurances of licenses to be made available, or the result of an
 attempt made to obtain a general license or permission for the use of
 such proprietary rights by implementers or users of this
 specification can be obtained from the IETF on-line IPR repository at
 http://www.ietf.org/ipr.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights that may cover technology that may be required to implement
 this standard.  Please address the information to the IETF at
 ietf-ipr@ietf.org.

Acknowledgement

 Funding for the RFC Editor function is provided by the IETF
 Administrative Support Activity (IASA).

Smith and Howes Standards Track [Page 12]

/data/webs/external/dokuwiki/data/pages/rfc/rfc4515.txt · Last modified: 2006/06/06 22:57 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki