Network Working Group T. Howes Request for Comments: DRAFT Loudcloud, Inc. Obsoletes: RFC 2254 M. Smith Expires: May 2001 Netscape Communications Corp. 22 November 2000 The String Representation of LDAP Search Filters <draft-smith-ldapv3-filter-update-01.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 Extensions Working Group mailing list <ietf-ldapext@netscape.com>. 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 (2000). All Rights Reserved. 2. Abstract The Lightweight Directory Access Protocol (LDAP) [1] 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 full range of possible LDAP version 3 search filters, including Howes & Smith Intended Category: Standards Track [Page 1]
INTERNET-DRAFT String Representation of LDAP Filters 22 November 2000 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 Section 4.5.1 of [1] 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, SEQUENCE OF CHOICE { initial [0] LDAPString, any [1] LDAPString, final [2] LDAPString } } AttributeValueAssertion ::= SEQUENCE { attributeDesc AttributeDescription, attributeValue AttributeValue } MatchingRuleAssertion ::= SEQUENCE { matchingRule [1] MatchingRuleID OPTIONAL, type [2] AttributeDescription OPTIONAL, matchValue [3] AssertionValue, dnAttributes [4] BOOLEAN DEFAULT FALSE } AttributeDescription ::= LDAPString AttributeValue ::= OCTET STRING Howes & Smith Intended Category: Standards Track [Page 2]
INTERNET-DRAFT String Representation of LDAP Filters 22 November 2000 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 [4]. The AttributeDescription is a string representation of the attribute description and is defined in [1]. The AttributeValue and AssertionValue OCTET STRING have the form defined in [2]. The Filter is encoded for transmission over a network using the Basic Encoding Rules defined in [3], with simplifications described in [1]. 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 [5]. 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 value filtertype = equal / approx / greater / less equal = "=" approx = "~=" greater = ">=" less = "<=" extensible = attr [":dn"] [":" matchingrule] ":=" value / [":dn"] ":" matchingrule ":=" value present = attr "=*" substring = attr "=" [initial] any [final] initial = value any = "*" *(value "*") final = value attr = AttributeDescription from Section 4.1.5 of [1] matchingrule = MatchingRuleId from Section 4.1.9 of [1] value = AttributeValue from Section 4.1.6 of [1] with some characters escaped (see below). The attr and matchingrule constructs are as described in the corresponding section of [1] given above. Howes & Smith Intended Category: Standards Track [Page 3]
INTERNET-DRAFT String Representation of LDAP Filters 22 November 2000 The value construct is as described in the corresponding section of [1] given above, except that if an AttributeValue contains any of the following characters Character ASCII value --------------------------- * 0x2a ( 0x28 ) 0x29 \ 0x5c NUL 0x00 the character must be encoded as the backslash '\' character (ASCII 0x5c) followed by the two hexadecimal digits representing the ASCII value of the encoded character. The case of the two hexadecimal digits is not significant. 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*) 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) Howes & Smith Intended Category: Standards Track [Page 4]
INTERNET-DRAFT String Representation of LDAP Filters 22 November 2000 (: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. 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. Howes & Smith Intended Category: Standards Track [Page 5]
INTERNET-DRAFT String Representation of LDAP Filters 22 November 2000 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 [1], RFC 2829 [6], and RFC 2830 [7] for more information. 7. References [1] Wahl, M., Howes, T., and S. Kille, "Lightweight Directory Access Protocol (v3)", RFC 2251, December 1997. [2] Wahl, M., Coulbeck, A., Howes, T., and S. Kille, "Lightweight Directory Access Protocol (v3): Attribute Syntax Definitions", RFC 2252, December 1997. [3] Specification of ASN.1 encoding rules: Basic, Canonical, and Distinguished Encoding Rules, ITU-T Recommendation X.690, 1994. [4] Yergeau, F., "UTF-8, a transformation format of ISO 10646", RFC 2279, January 1998. [5] Crocker, D., "Standard for the Format of ARPA Internet Text Messages", STD 11, RFC 822, August 1982. [6] Wahl, M., Alvestrand, H., Hodges, J. and R. Morgan, "Authentication Methods for LDAP", RFC 2829, May 2000. [7] Hodges, J., Morgan, R., Wahl, M., "Lightweight Directory Access Protocol (v3): Extension for Transport Layer Security", RFC 2830, May 2000. 8. Authors' Address Tim Howes Loudcloud, Inc. 599 N. Mathilda Ave. Sunnyvale, CA 94086 USA +1 408 744-7509 howes@loudcloud.com Mark Smith Netscape Communications Corp. Howes & Smith Intended Category: Standards Track [Page 6]
INTERNET-DRAFT String Representation of LDAP Filters 22 November 2000 Mailstop USCA17-201 4170 Network Circle Santa Clara, CA 95054 USA +1 650 937-3477 mcs@netscape.com 9. Full Copyright Statement Copyright (C) The Internet Society (2000). 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. 10. Appendix A: Changes Since RFC 2254 10.1. Technical Changes None. 10.2. Editorial Changes IESG Note: removed note about lack of satisfactory mandatory authentication mechanisms. Howes & Smith Intended Category: Standards Track [Page 7]
INTERNET-DRAFT String Representation of LDAP Filters 22 November 2000 "Abstract" section: updated second paragraph to indicate that RFC 2254 is replaced by this document (instead of RFC 1960). "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 three examples: (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: added entries for RFC 2829 and RFC 2830 and updated UTF-8 reference to RFC 2279. Authors: added Mark Smith as an author and updated Tim's affiliation and contact information. "Appendix C: Loose Ends" section: added. "Table of Contents" section: added. 11. Appendix B: Changes since draft-smith-ldapv3-filter-update-00.txt Note that these changes are also listed in Appendix A, but are included here for those who have already reviewed draft-smith-ldapv3-filter- update-00.txt. 11.1. Technical Changes "Search Filter Definition" section: removed the change made in -00 that changed the ABNF definition of 'filterlist' from 1*filter to 0*filter. RFC 2251 in fact DOES NOT allow an empty filter set. Section 4.5.1 of 2251 says in part: "At least one filter element MUST be present in an 11.2. Editorial Changes "Examples" section: added three examples: (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 and Howes & Smith Intended Category: Standards Track [Page 8]
INTERNET-DRAFT String Representation of LDAP Filters 22 November 2000 RFC 2830. "References" section: added an entry for RFC 2830. "Appendix C: Loose Ends" section: added. "Table of Contents" section: added. 12. Appendix C: Loose Ends The BNF needs to be updated to use the ABNF specified in RFC 2234, and a reference to 2234 needs to be added. This Internet Draft expires in May 2001. Howes & Smith Intended Category: Standards Track [Page 9]
1. Status of this Memo............................................1 2. Abstract.......................................................1 3. LDAP Search Filter Definition..................................2 4. String Search Filter Definition................................3 5. Examples.......................................................4 6. Security Considerations........................................6 7. References.....................................................6 8. Authors' Address...............................................6 9. Full Copyright Statement.......................................7 10. Appendix A: Changes Since RFC 2254.............................7 10.1. Technical Changes...........................................7 10.2. Editorial Changes...........................................7 11. Appendix B: Changes since draft-smith-ldapv3-filter-update-00.txt8 11.1. Technical Changes...........................................8 11.2. Editorial Changes...........................................8 12. Appendix C: Loose Ends.........................................9