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Date: Tue, 09 Apr 2002 00:52:45 GMT Server: Apache/1.3.20 (Unix) Last-Modified: Mon, 05 May 1997 18:55:00 GMT ETag: "2e9d36-2847-336e2d04" Accept-Ranges: bytes Content-Length: 10311 Connection: close Content-Type: text/plain Network Working GroupTimT. HowesINTERNET DRAFTRequest for Comments: 2254 Netscape Communications Corp.OBSOLETES: RFC 1960 MayCategory: Standards Track December 1997 The String Representation of LDAP Search Filters<draft-ietf-asid-ldapv3-filter-02.txt>1. Status of this Memo This documentisspecifies anInternet-Draft. Internet-Drafts are working docu- ments ofInternet standards track protocol for the InternetEngineering Task Force (IETF), its areas,community, andits working groups.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 (1997). All Rights Reserved. IESG Note This document describes a directory access protocol thatother groups may also distribute working documentsprovides both read and update access. Update access requires secure authentication, but this document does not mandate implementation of any satisfactory authentication mechanisms. In accordance with RFC 2026, section 4.4.1, this specification is being approved by IESG asInternet-Drafts. Internet-Drafts are draft documents valid foramaximum of six monthsProposed Standard despite this limitation, for the following reasons: a. to encourage implementation andmay be updated, replaced,interoperability testing of these protocols (with orobsoleted by other documents at any time. It is inappropriatewithout update access) before they are deployed, and b. to encourage deployment and useInternet- Draftsof these protocols in read-only applications. (e.g. applications where LDAPv3 is used asreference material or to cite thema query language for directories which are updated by some secure mechanism other thanas ``work in progress.'' To learnLDAP), and c. to avoid delaying thecurrent statusadvancement and deployment ofany Internet-Draft, please check the ``1id-abstracts.txt'' listing contained inother Internet standards-track protocols which require theInternet- Drafts Shadow Directories on ds.internic.net (US East Coast), nic.nordu.net (Europe), ftp.isi.edu (US West Coast),ability to query, but not update, LDAPv3 directory servers. Howes Standards Track [Page 1] RFC 2254 String Representation of LDAP December 1997 Readers are hereby warned that until mandatory authentication mechanisms are standardized, clients and servers written according to this specification which make use of update functionality are UNLIKELY TO INTEROPERATE, ormunnari.oz.au (Pacific Rim).MAY INTEROPERATE ONLY IF AUTHENTICATION IS REDUCED TO AN UNACCEPTABLY WEAK LEVEL. Implementors are hereby discouraged from deploying LDAPv3 clients or servers which implement the update functionality, until a Proposed Standard for mandatory authentication in LDAPv3 has been approved and published as an RFC. 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 LDAP search filters. This document replaces RFC 1960, extending the string LDAP filterdefin- itiondefinition to include support for LDAP version 3 extended match filters, and including support for representing the full range of possible LDAP search filters. Howes Standards Track [Page1]2] RFCDRAFT May2254 String Representation of LDAP December 1997 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 MatchingRuleID ::= LDAPString AssertionValue ::= OCTET STRING LDAPString ::= OCTET STRING Howes Standards Track [Page2]3] RFCDRAFT May2254 String Representation of LDAP December 1997 where the LDAPString above is limited to the UTF-8 encoding of the ISO 10646 character set [4]. The AttributeDescription is a stringrepresen- tationrepresentation of the attribute description and is defined in [1]. TheAttribu- teValueAttributeValue 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] The attr, matchingrule, and value constructs are as described in the corresponding section of [1] given above. Howes Standards Track [Page3]4] RFCDRAFT May2254 String Representation of LDAP December 1997 If a value should contain 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-printingcharac- ters.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) (sn:dn:2.4.6.8.10:=Barney Rubble) (o:dn:=Ace Industry) (:dn:2.4.6.8.10:=Dino) Howes Standards Track [Page 5] RFC 2254 String Representation of LDAP December 1997 The second example illustrates the use of the ":dn" notation to indicate that matching rule "2.4.6.8.10" should be used when making comparisons,Howes [Page 4] RFC DRAFT May 1997and that the attributes of an entry's distinguished name should becon- sideredconsidered part of the entry when evaluating the match. The third example denotes an equality match, except that DN components should be considered part of the entry when doing the match. The fourth example is a filter that should be applied to any attribute supporting the matching rule given (since the attr has been left off). 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\c7)(sn=Lu\c4\8di\c4\87) 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 final example illustrates the use of the escaping mechanism to represent various non-ASCII UTF-8 characters. 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. Howes Standards Track [Page 6] RFC 2254 String Representation of LDAP December 1997 7. References [1]LightweightWahl, M., Howes, T., and S. Kille, "Lightweight Directory Access Protocol(v3), M.(v3)", RFC 2251, December 1997. [2] Wahl,T.M., Coulbeck, A., Howes, T., and S. Kille,Internet Draft draft-ietf-asid-ldapv3-protocol-04.txt, March, 1997. [2] Lightweight"Lightweight Directory Access Protocol (v3): Attribute SyntaxDefin- itions, M. Wahl, A. Coulbeck, T. Howes, S. Kille, Internet Draft draft-ietf-asid-ldapv3-attributes-04.txt, March, 1997. Howes [Page 5]Definitions", RFCDRAFT May 19972252, December 1997. [3] Specification of ASN.1 encoding rules: Basic, Canonical, andDis- tinguishedDistinguished Encoding Rules, ITU-T Recommendation X.690, 1994. [4]UTF-8,Yergeau, F., "UTF-8, a transformation format of Unicode and ISO10646, F. Yer- geau, draft-yergeau-utf8-rev-00.txt, April, 1997.10646", RFC 2044, October 1996. [5]StandardCrocker, D., "Standard for the Format of ARPA Internet TextMessages, D. Crocker,Messages", STD 11, RFC 822,August,August 1982. 8. Author's Address Tim Howes Netscape Communications Corp. 501 E. Middlefield Road Mountain View, CA 94043 USA Phone: +1 415 937-3419 EMail: howes@netscape.com Howes Standards Track [Page6]7] RFC 2254 String Representation of LDAP December 1997 9. Full Copyright Statement Copyright (C) The Internet Society (1997). 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. Howes Standards Track [Page 8] ----