INTERNET-DRAFT Kurt D. Zeilenga Intended Category: Standard Track OpenLDAP Foundation Expires: 4 January 2001 4 July 2000 LDAPv3bis Suggestions: The String Representation of LDAP Search Filters Status of Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. This document is intended to be, after appropriate review and revision, submitted to the RFC Editor as a Standard Track document. Distribution of this memo is unlimited. Technical discussion of this document will take place on the IETF LDAP Extension Working Group mailing list . Please send editorial comments directly to the author . 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. Copyright 2000, The Internet Society. All Rights Reserved. Please see the Copyright section near the end of this document for more information. Forward This Internet Draft suggests a number of updates to "The String Representation of LDAP Search Filters" [RFC 2254]. This document is not intended to be published as an RFC but used to identify LDAPv3bis work items. The remainer of this documents incorporates the substantive portion of RFC 2254 text (less status of memo, appendices, etc). Comments and Zeilenga [Page 1] INTERNET-DRAFT draft-zeilenga-ldapv3bis-rfc2254-00 4 July 2000 suggested updates to this text are inserted as inline notes prefixed with '//'. // Start of RFC 2254 text 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 filter definition to include support for LDAP version 3 extended match filters, and including support for representing the full range of possible LDAP search filters. 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 Zeilenga [Page 2] INTERNET-DRAFT draft-zeilenga-ldapv3bis-rfc2254-00 4 July 2000 } 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 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 // replace (to support empty SET OF) with: // filterlist = 0*filter item = simple / present / substring / extensible simple = attr filtertype value filtertype = equal / approx / greater / less equal = "=" approx = "~=" Zeilenga [Page 3] INTERNET-DRAFT draft-zeilenga-ldapv3bis-rfc2254-00 4 July 2000 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. 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-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 Zeilenga [Page 4] INTERNET-DRAFT draft-zeilenga-ldapv3bis-rfc2254-00 4 July 2000 notation. (cn=Babs Jensen) (!(cn=Tim Howes)) (&(objectClass=Person)(|(sn=Jensen)(cn=Babs J*))) (o=univ*of*mich*) // Add (for empty SET OF): // The following filters evaluate to true or false, // respectively. // (&) // (|) 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) 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, and that the attributes of an entry's distinguished name should be considered 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\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 Zeilenga [Page 5] INTERNET-DRAFT draft-zeilenga-ldapv3bis-rfc2254-00 4 July 2000 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 // Add consideration requiring the use of strong authentication // to update the directory. 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. 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 Unicode and ISO 10646", RFC 2044, October 1996. [5] Crocker, D., "Standard for the Format of ARPA Internet Text Messages", STD 11, RFC 822, August 1982. // Remainder trimmed // End of RFC 2254 text Additional Information Discussions regarding these suggestions may directed to the author: Kurt D. Zeilenga OpenLDAP Foundation or the LDAPext Working Group mailing list: Zeilenga [Page 6] INTERNET-DRAFT draft-zeilenga-ldapv3bis-rfc2254-00 4 July 2000 Copyright 2000, The Internet Society. 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 AUTHORS, 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. Zeilenga [Page 7]