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Network Working Group M. Smith, Editor
Request for Comments: DRAFT Pearl Crescent, LLC
Obsoletes: RFC 2254 T. Howes
Expires: 13 August 2004 Opsware, Inc.
13 February 2004
LDAP: String Representation of Search Filters
<draft-ietf-ldapbis-filter-06.txt>
1. Status of this Memo
This document is an Internet-Draft and is subject to 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/1id-abstracts.html
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 (2004). 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.
Smith & Howes Intended Category: Standards Track [Page 1]
INTERNET-DRAFT LDAP: String Repres. of Search Filters 13 February 2004
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................................4
7. Examples.......................................................5
8. Security Considerations........................................7
9. Normative References...........................................7
10. Informative References.........................................8
11. Intellectual Property Rights...................................8
12. Acknowledgments................................................8
13. Authors' Addresses.............................................9
14. Full Copyright Statement.......................................9
15. Appendix A: Changes Since RFC 2254.............................10
15.1. Technical Changes...........................................10
15.2. Editorial Changes...........................................10
16. Appendix B: Changes Since Previous Document Revision...........11
16.1. Technical Changes...........................................12
16.2. Editorial Changes...........................................12
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.
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].
5. LDAP Search Filter Definition
An LDAPv3 search filter is defined in Section 4.5.1 of [Protocol] as
follows:
Smith & Howes Intended Category: Standards Track [Page 2]
INTERNET-DRAFT LDAP: String Repres. of Search Filters 13 February 2004
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 } }
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>
-- [Models]
AttributeValue ::= OCTET STRING
MatchingRuleId ::= LDAPString
AssertionValue ::= OCTET STRING
LDAPString ::= OCTET STRING -- UTF-8 encoded,
-- [ISO10646] characters
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 [X.690], with simplifications described in
Smith & Howes Intended Category: Standards Track [Page 3]
INTERNET-DRAFT LDAP: String Repres. of Search Filters 13 February 2004
[Protocol].
6. String Search Filter Definition
The string representation of an LDAP search filter is a string of
UTF-8[RFC3629] encoded ISO 10646-1 characters that is defined by the
following grammar, following the ABNF notation defined in [RFC2234].
The productions used that are not defined here are defined in section
1.4 (Common ABNF Productions) of [Models] 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 / greater / less
equal = EQUALS
approx = TILDE EQUALS
greater = RANGLE EQUALS
less = LANGLE EQUALS
extensible = attr [dnattrs] [matchingrule] COLON EQUALS assertionvalue
/ [dnattrs] matchingrule COLON EQUALS assertionvalue
/ 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 [Models].
dnattrs = COLON "dn"
matchingrule = COLON oid
assertionvalue = valueencoding
; The <valueencoding> rule is used to encode an
; <AssertionValue> from Section 4.1.6 of [Protocol].
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) ("&")
Smith & Howes Intended Category: Standards Track [Page 4]
INTERNET-DRAFT LDAP: String Repres. of Search Filters 13 February 2004
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.
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 ISO 10646-1 characters).
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*)))
Smith & Howes Intended Category: Standards Track [Page 5]
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(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)
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 ":oid" 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
(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
Smith & Howes Intended Category: Standards Track [Page 6]
INTERNET-DRAFT LDAP: String Repres. of Search Filters 13 February 2004
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.
Please refer to the Security Considerations sections of [Protocol]
and [AuthMeth] for more information.
9. Normative References
[AuthMeth] Harrison, R. (editor), "LDAP: Authentication Methods and
Connection Level Security Mechanisms", draft-ietf-ldapbis-
authmeth-xx.txt, a work in progress.
[ISO10646] Universal Multiple-Octet Coded Character Set (UCS) -
Architecture and Basic Multilingual Plane, ISO/IEC 10646-1,
1993.
[Models] Zeilenga, K. (editor), "LDAP: Directory Information Models",
draft-ietf-ldapbis-models-xx.txt, a work in progress.
[Protocol] draft-ietf-ldapbis-protocol-xx.txt, a work in progress.
[RFC2119] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14 (also RFC 2119), March 1997.
[RFC2234] Crocker, D., Overell, P., "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 10646",
RFC 3629, November 2003.
Smith & Howes Intended Category: Standards Track [Page 7]
INTERNET-DRAFT LDAP: String Repres. of Search Filters 13 February 2004
[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.
[X.690] Specification of ASN.1 encoding rules: Basic, Canonical, and
Distinguished Encoding Rules, ITU-T Recommendation X.690,
1994.
10. Informative References
None.
11. Intellectual Property Rights
The IETF takes no position regarding the validity or scope of any
intellectual property 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; neither does it represent that it
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication 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 implementors or users of this specification can
be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive
Director.
12. 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.
Smith & Howes Intended Category: Standards Track [Page 8]
INTERNET-DRAFT LDAP: String Repres. of Search Filters 13 February 2004
13. Authors' Addresses
Mark Smith, Editor
Pearl Crescent, LLC
447 Marlpool Dr.
Saline, MI 48176
USA
+1 734 944-2856
mcs@pearlcrescent.com
Tim Howes
Opsware, Inc.
599 N. Mathilda Ave.
Sunnyvale, CA 94085
USA
+1 408 744-7509
howes@opsware.com
14. Full Copyright Statement
Copyright (C) The Internet Society (2004). 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.
Smith & Howes Intended Category: Standards Track [Page 9]
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15. Appendix A: Changes Since RFC 2254
15.1. Technical Changes
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 ISO 10646-1 characters.
Revised all of the ABNF to use common productions from [Models].
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 [Models] and [Protocol]
documents.
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 third option to the "extensible" production to allow creation
of a MatchingRuleAssertion that only has a matchValue.
Added a statement about expected behavior in light of RFC 2254's lack
of a clear definition of "string representation."
15.2. 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 Rights" sections:
added.
Copyright: updated per latest IETF guidelines.
"Abstract" section: separated from introductory material.
Smith & Howes Intended Category: Standards Track [Page 10]
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"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].
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 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).
"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
document. Added entries for [ISO10646], [RFC2119], [AuthMeth],
[Models], and [Roadmap] and updated the UTF-8 reference. Replaced
RFC 822 reference with a reference to RFC 2234.
"Informative References" section: added for clarity.
"Acknowledgments" section: added.
"Appendix A: Changes Since RFC 2254" section: added.
"Appendix B: Changes Since Previous Document Revision" section:
added.
16. Appendix B: Changes Since Previous Document Revision
This appendix lists all changes relative to the previously published
revision, draft-ietf-ldapbis-filter-05.txt. Note that when
appropriate these changes are also included in Appendix A, but are
also included here for the benefit of the people who have already
reviewed draft-ietf-ldapbis-filter-05.txt. This section will be
removed before this document is published as an RFC.
Smith & Howes Intended Category: Standards Track [Page 11]
INTERNET-DRAFT LDAP: String Repres. of Search Filters 13 February 2004
16.1. Technical Changes
None.
16.2. Editorial Changes
"LDAP Search Filter Definition" section: changed the LDAPv3 search
filter ABNF so it matches that used in the latest revision of
[Protocol] and removed the following redundant descriptive text:
"where the LDAPString above is limited to the UTF-8 encoding [UTF-8]
of the ISO 10646 character set [ISO10646]."
"String Search Filter Definition" section: Corrected section
reference to [Models] and replaced this sentence: "Implementations
SHOULD accept as input a string that includes invalid UTF-8 octet
sequences." with the following: "Implementations SHOULD accept as
input strings that are not valid UTF-8 strings."
"Examples" section: Corrected the description of this example:
(sn:dn:2.4.6.8.10:=Barney Rubble).
"Normative References" section: changed UTF-8 reference to point to
RFC 3629, replaced [ASN.1] with [X.690] for consistency, and indented
the reference descriptions to enhance readability.
Authors' Addresses section: New contact information for Mark Smith.
Updated the copyright year to 2004.
This Internet Draft expires on 13 August 2004.
Smith & Howes Intended Category: Standards Track [Page 12]
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