Network Working Group M. Smith, Editor Request for Comments: DRAFT Pearl Crescent, LLC Obsoletes: RFC 2254 T. Howes Expires: 13 January 2005 Opsware, Inc. 13 July 2004 LDAP: String Representation of Search Filters <draft-ietf-ldapbis-filter-07.txt> Status of this Memo This document is intended to be published as a Standard Track RFC, replacing RFC 2254. Distribution of this memo is unlimited. Technical discussion of this document will take place on the IETF LDAP (v3) Revision (ldapbis) Working Group mailing list <ietf-ldapbis@openldap.org>. Please send editorial comments directly to the editor <mcs@pearlcrescent.com>. By submitting this Internet-Draft, I accept the provisions of Section 4 of RFC 3667. By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. 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 a "work in progress." Copyright (C) The Internet Society (2004). All Rights Reserved. Please see the Full Copyright section near the end of this document for more information. 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 July 2004 Table of Contents Status of this Memo............................................1 Abstract.......................................................1 Table of Contents..............................................2 1. Introduction...................................................2 2. LDAP Search Filter Definition..................................3 3. String Search Filter Definition................................4 4. Examples.......................................................6 5. Security Considerations........................................7 6. IANA Considerations............................................7 7. Normative References...........................................7 8. Informative References.........................................8 9. Acknowledgments................................................8 10. Authors' Addresses.............................................8 11. Appendix A: Changes Since RFC 2254.............................9 11.1. Technical Changes...........................................9 11.2. Editorial Changes...........................................10 12. Appendix B: Changes Since Previous Document Revision...........11 12.1. Technical Changes...........................................11 12.2. Editorial Changes...........................................11 13. Intellectual Property Rights...................................12 14. Full Copyright.................................................12 1. 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]. Smith & Howes Intended Category: Standards Track [Page 2]
INTERNET-DRAFT LDAP: String Repres. of Search Filters 13 July 2004 2. 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 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, -- [Unicode] characters Smith & Howes Intended Category: Standards Track [Page 3]
INTERNET-DRAFT LDAP: String Repres. of Search Filters 13 July 2004 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 (BER) defined in [X.690], with simplifications described in [Protocol]. 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 [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 / greaterorequal / lessorequal equal = EQUALS approx = TILDE EQUALS greaterorequal = RANGLE EQUALS lessorequal = 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) Smith & Howes Intended Category: Standards Track [Page 4]
INTERNET-DRAFT LDAP: String Repres. of Search Filters 13 July 2004 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. 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). Smith & Howes Intended Category: Standards Track [Page 5]
INTERNET-DRAFT LDAP: String Repres. of Search Filters 13 July 2004 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: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) Smith & Howes Intended Category: Standards Track [Page 6]
INTERNET-DRAFT LDAP: String Repres. of Search Filters 13 July 2004 (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-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. 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 [Protocol] and [AuthMeth] for more information. 6. IANA Considerations This document has no actions for IANA. 7. Normative References [AuthMeth] Harrison, R. (editor), "LDAP: Authentication Methods and Connection Level Security Mechanisms", draft-ietf-ldapbis-authmeth-xx.txt, a work in progress. [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. Smith & Howes Intended Category: Standards Track [Page 7]
INTERNET-DRAFT LDAP: String Repres. of Search Filters 13 July 2004 [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. [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. [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." [X.690] Specification of ASN.1 encoding rules: Basic, Canonical, and Distinguished Encoding Rules, ITU-T Recommendation X.690, 1994. 8. Informative References None. 9. 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. 10. Authors' Addresses Mark Smith, Editor Pearl Crescent, LLC 447 Marlpool Dr. Saline, MI 48176 USA +1 734 944-2856 mcs@pearlcrescent.com Smith & Howes Intended Category: Standards Track [Page 8]
INTERNET-DRAFT LDAP: String Repres. of Search Filters 13 July 2004 Tim Howes Opsware, Inc. 599 N. Mathilda Ave. Sunnyvale, CA 94085 USA +1 408 744-7509 howes@opsware.com 11. Appendix A: Changes Since RFC 2254 11.1. 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 [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. "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 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." Smith & Howes Intended Category: Standards Track [Page 9]
INTERNET-DRAFT LDAP: String Repres. of Search Filters 13 July 2004 11.2. 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", "IANA Considerations", and "Intellectual Property Rights" sections: added. Copyright: updated per latest IETF guidelines. "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]. 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 [Unicode], [RFC2119], [AuthMeth], [Models], and [Roadmap] and updated the UTF-8 reference. Replaced RFC 822 reference with a reference to RFC 2234. Smith & Howes Intended Category: Standards Track [Page 10]
INTERNET-DRAFT LDAP: String Repres. of Search Filters 13 July 2004 "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. 12. Appendix B: Changes Since Previous Document Revision This appendix lists all changes relative to the previously published revision, draft-ietf-ldapbis-filter-06.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-06.txt. This section will be removed before this document is published as an RFC. 12.1. Technical Changes Replaced [ISO 10646] reference with [Unicode]. "String Search Filter Definition" section: replaced "greater" and "less" with "greaterorequal" and "lessorequal" to avoid confusion. Also, broke some long lines into two lines to avoid exceeding the 72 column limit. 12.2. Editorial Changes "Status of this Memo", "Intellectual Property Rights", and "Full Copyright" sections: updated to use boilerplate from RFC 3667 and RFC 3668. "Status of this Memo", "Abstract" and "Table of Contents" sections: removed section numbers. "LDAP Search Filter Definition" section: added (BER) to the last sentence. "IANA Considerations" section: added. Smith & Howes Intended Category: Standards Track [Page 11]
INTERNET-DRAFT LDAP: String Repres. of Search Filters 13 July 2004 13. Intellectual Property Rights 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. 14. Full Copyright Copyright (C) The Internet Society (2004). 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. This Internet Draft expires on 13 January 2005. Smith & Howes Intended Category: Standards Track [Page 12]
