Network Working Group M. Smith, Editor Request for Comments: DRAFT Netscape Communications Corp. Obsoletes: RFC 2254 T. Howes Expires: 20 August 2001 Loudcloud, Inc. 20 February 2001 The String Representation of LDAP Search Filters <draft-ietf-ldapbis-filter-00.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) Revison (ldapbis) Working Group mailing list <ietf- ldapbis@openldap.org>. After appropriate review and discussion, this document will be submitted as a Standards Track replacement for RFC 2254. Copyright Notice Copyright (C) The Internet Society (2001). All Rights Reserved. 2. Abstract The Lightweight Directory Access Protocol (LDAP) [RFC2251] 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. This document defines a human-readable string format for representing the Smith & Howes Intended Category: Standards Track [Page 1]
INTERNET-DRAFT String Representation of LDAP Filters 22 November 2000 full range of possible LDAP version 3 search filters, including extended match filters. This document replaces RFC 2254. See Appendix A for a list of changes relative to RFC 2254. 3. LDAP Search Filter Definition An LDAPv3 search filter is defined in Sections 4.5.1 of [RFC2251] as follows: Filter ::= CHOICE { and [0] SET OF Filter, or [1] SET OF 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, -- at least one must be present substrings SEQUENCE OF CHOICE { initial [0] LDAPString, any [1] LDAPString, final [2] LDAPString } } 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 Smith & Howes Intended Category: Standards Track [Page 2]
INTERNET-DRAFT String Representation of LDAP Filters 22 November 2000 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 [RFC2251]. The AttributeValue and AssertionValue OCTET STRING have the form defined in [RFC2252]. The Filter is encoded for transmission over a network using the Basic Encoding Rules defined in [ASN.1], with simplifications described in [RFC2251]. 4. 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]. 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 present = attr "=*" substring = attr "=" [initial] any [final] initial = value any = "*" *(value "*") final = value attr = <AttributeDescription from Section 4.1.5 of [RFC2251]> matchingrule = <MatchingRuleId from Section 4.1.9 of [RFC2251]> value = <AttributeValue from Section 4.1.6 of [RFC2251] encoded using the valueencoding rule> assertionvalue = <AssertionValue from Section 4.1.7 of [RFC2251] encoded using the valueencoding rule> Smith & Howes Intended Category: Standards Track [Page 3]
INTERNET-DRAFT String Representation of LDAP Filters 22 November 2000 valueencoding = 0*(normal / escaped) normal = %x01-27 / %x2b-5b / %x5d-7f escaped = " 0" / "2" ( "8" / "9" / "a" ) / "5c" The attr and matchingrule constructs are as described in the corresponding section of [RFC2251] given above. Smith & Howes Intended Category: Standards Track [Page 4]
INTERNET-DRAFT String Representation of LDAP Filters 22 November 2000 The valueencoding rule provides that the characters "*" (ASCII 0x2a), "(" (ASCII 0x28), ")" (ASCII 0x29), " 0x00) are represented as the backslash " followed by the two hexadecimal digits representing the ASCII value of the encoded character. 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 characters besides the ones listed above may be escaped using this mechanism, for example, non-printing characters. For example, the filter checking whether the "cn" attribute contained a value with the character "*" anywhere in it would be represented as "(cn=*\2a*)". 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. 5. 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 ":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. Smith & Howes Intended Category: Standards Track [Page 5]
INTERNET-DRAFT String Representation of LDAP Filters 22 November 2000 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;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 a 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. 6. 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 RFC 2251 [RFC2251], RFC 2829 [RFC2829], and RFC 2830 [RFC2830] for more information. Smith & Howes Intended Category: Standards Track [Page 6]
INTERNET-DRAFT String Representation of LDAP Filters 22 November 2000 7. References [ASN.1] Specification of ASN.1 encoding rules: Basic, Canonical, and Distinguished Encoding Rules, ITU-T Recommendation X.690, 1994. [RFC2234] Crocker, D., Overell, P., "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, November 1997. [RFC2251] Wahl, M., Howes, T., and S. Kille, "Lightweight Directory Access Protocol (v3)", RFC 2251, December 1997. [RFC2252] Wahl, M., Coulbeck, A., Howes, T., and S. Kille, "Lightweight Directory Access Protocol (v3): Attribute Syntax Definitions", RFC 2252, December 1997. [RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO 10646", RFC 2279, January 1998. [RFC2829] Wahl, M., Alvestrand, H., Hodges, J. and R. Morgan, "Authentication Methods for LDAP", RFC 2829, May 2000. [RFC2830] Hodges, J., Morgan, R., Wahl, M., "Lightweight Directory Access Protocol (v3): Extension for Transport Layer Security", RFC 2830, May 2000. 8. Acknowledgments This document is an update to 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. 9. Authors' Address Mark Smith (document editor) Netscape Communications Corp. Mailstop USCA17-201 4170 Network Circle Santa Clara, CA 95054 USA +1 650 937-3477 mcs@netscape.com Tim Howes Smith & Howes Intended Category: Standards Track [Page 7]
INTERNET-DRAFT String Representation of LDAP Filters 22 November 2000 Loudcloud, Inc. 599 N. Mathilda Ave. Sunnyvale, CA 94086 USA +1 408 744-7509 howes@loudcloud.com 10. Full Copyright Statement Copyright (C) The Internet Society (2001). 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. 11. Appendix A: Changes Since RFC 2254 11.1. Technical Changes "String Search Filter Definition" section: replaced the "value" rule with a new "assertionvalue" rule within the "simple" and "extensible" rules. Added angle brackets around free-form prose in the "attr", "matchingrule", and "value" rules. Introduced the "valueencoding" and associated "normal" and "escaped" rules to reduce the dependence on descriptive text. Smith & Howes Intended Category: Standards Track [Page 8]
INTERNET-DRAFT String Representation of LDAP Filters 22 November 2000 11.2. Editorial Changes 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 Tim's affiliation and contact information. Copyright: changed the year to 2001. "Abstract" section: updated second paragraph to indicate that RFC 2254 is replaced by this document (instead of RFC 1960). "LDAP Search Filter Definition" section: made corrections to the LDAPv3 search filter ABNF so it matches RFC 2251. In particular, the "at least one must be present" comment and the "substrings" label were added to the SubstringFilter initial/any/final sequence and the second element of the AttributeValueAssertion was changed from "attributeValue AttributeValue" to "assertionValue AssertionValue." "Search Filter Definition" section: clarified the definition of AttributeValue from RFC 2251 section 4.1.6 (special handling is required for some characters). "Examples" section: added four additional examples: (seeAlso=), (cn:=Betty Rubble), (:1.2.3:=Wilma Flintstone), and (1.3.6.1.4.1.1466.0;binary=\04\02\48\69). "Security Considerations" section: added references to RFC 2251, RFC 2829, and RFC 2830. "References" section: changed from [1] style to [RFC2251] style throughout the document. Added entries for RFC 2829 and RFC 2830 and updated UTF-8 reference to RFC 2279. Replaced RFC 822 reference with a RFC 2234. "Acknowledgments" section: added. "Appendix A: Changes Since RFC 2254" section: added. "Appendix B: Changes Since Previous Document Revision" section: added. "Appendix C: Loose Ends" section: added. "Table of Contents" section: added. Smith & Howes Intended Category: Standards Track [Page 9]
INTERNET-DRAFT String Representation of LDAP Filters 22 November 2000 12. Appendix B: Changes Since Previous Document Revision This appendix lists all changes relative to the last published revision, draft-smith-ldapv3-filter-update-01.txt. Note that these changes are also included in Appendix A, but are included here for those who have already reviewed draft-smith-ldapv3-filter-update-01.txt. 12.1. Technical Changes "String Search Filter Definition" section: replaced the "value" rule with a new "assertionvalue" rule within the "simple" and "extensible" rules. Added angle brackets around free-form prose in the "attr", "matchingrule", and "value" rules. Introduced the "valueencoding" and associated "normal" and "escaped" rules to reduce the dependence on descriptive text. 12.2. Editorial Changes Header: changed document from an individual submission to an ldapbis working group submission. Discussion referred to the ietf- ldapbis@openldap.org mailing list. Header and "Authors' Addresses" sections: added "editor" next to Mark Smith's name. Copyright: changed the year to 2001. "LDAP Search Filter Definition" section: made corrections to the LDAPv3 search filter ABNF so it matches RFC 2251. In particular, the "at least one must be present" comment and the "substrings" label were added to the SubstringFilter initial/any/final sequence and the second element of the AttributeValueAssertion was changed from "attributeValue AttributeValue" to "assertionValue AssertionValue." "Examples" section: added the "(seeAlso=)" example to demonstrate assertion of a zero-length value. References: changed from [1] style to [RFC2251] style throughout the document. Replaced reference to RFC 822 with a reference to RFC 2234. "Acknowledgments" section: added. "Appendix C: Loose Ends": removed RFC 2234 ABNF item and added a new item about possible changes to the LDAPv3 protocol document that may result in changes to this document. Smith & Howes Intended Category: Standards Track [Page 10]
INTERNET-DRAFT String Representation of LDAP Filters 22 November 2000 13. Appendix C: Loose Ends There has been some discussion on the LDAPBIS working group discussion list about how to modify the LDAPv3 protocol specification to support use of substring filters within an extensible match filter, which led to further discussion about whether the definition of the SubstringFilter should be changed from LDAPString to AssertionValue. Once that issue is resolved, this filter specification will likely need to be revised to accommodate the group's decision. This Internet Draft expires on 20 August 2001. Smith & Howes Intended Category: Standards Track [Page 11]
1. Status of this Memo............................................1 2. Abstract.......................................................1 3. LDAP Search Filter Definition..................................2 4. String Search Filter Definition................................3 5. Examples.......................................................5 6. Security Considerations........................................6 7. References.....................................................7 8. Acknowledgments................................................7 9. Authors' Address...............................................7 10. Full Copyright Statement.......................................8 11. Appendix A: Changes Since RFC 2254.............................8 11.1. Technical Changes...........................................8 11.2. Editorial Changes...........................................9 12. Appendix B: Changes Since Previous Document Revision...........10 12.1. Technical Changes...........................................10 12.2. Editorial Changes...........................................10 13. Appendix C: Loose Ends.........................................11
