Network Working Group Mark Smith, Editor Request for Comments: DRAFT
Netscape Communications Corp.Pearl Crescent, LLC Obsoletes: RFC 2255 Tim Howes Expires: 25 April13 August 2004 Opsware, Inc. 25 October 200313 February 2004 LDAP: Uniform Resource Locator <draft-ietf-ldapbis-url-04.txt><draft-ietf-ldapbis-url-05.txt> 1. Status of this Memo This document is an Internet-Draft and is subject to 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/1id-abstracts.html 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) Revision (ldapbis) Working Group mailing list <ietf- email@example.com>. Copyright (C) The Internet Society (2003).(2004). All Rights Reserved. 2. Abstract This document describes a format for an LDAP Uniform Resource Locator (URL). An LDAP URL describes an LDAP search operation that is used to retrieve information from an LDAP directory, or, in the context of an LDAPv3 referral or reference, an LDAP URL describes a service where an LDAP operation may be progressed. 3. Table of Contents 1. Status of this Memo............................................1 2. Abstract.......................................................1 3. Table of Contents..............................................2 4. Introduction...................................................2 5. URL Definition.................................................2Definition.................................................3 5.1. Escaping Using the % Method.................................4 6. Defaults for Fields of the LDAP URL............................5 7. Examples.......................................................6Examples.......................................................5 8. Security Considerations........................................8Considerations........................................7 9. Normative References...........................................8 10. Informative References.........................................9 11. Intellectual Property Rights...................................9 12. Acknowledgements...............................................10 13. Authors' Address...............................................10Addresses.............................................10 14. Full Copyright Statement.......................................11 15. Appendix A: Changes Since RFC 2255.............................11 15.1. Technical Changes...........................................11 15.2. Editorial Changes...........................................12 16. Appendix B: Changes Since Previous Document Revision...........13 16.1. Technical Changes...........................................14 16.2. Editorial Changes...........................................14 4. Introduction LDAP is the Lightweight Directory Access Protocol, defined in [Protocol]. This document specifies the LDAP URL format for version 3 of LDAP and clarifies how LDAP URLs are resolved. This document also defines an extension mechanism for LDAP URLs, so that future documents can extend their functionality, for example, to provide access to new LDAPv3 extensions as they are defined. Note: not all of the parameters of the LDAP search operation described in [Protocol] can be expressed using the format defined in this document. This document is an integral part of the LDAP Technical Specification [Roadmap]. This document replaces RFC 2255. See Appendix A for a list of changes relative to RFC 2255. The key words "MUST", "MAY", and "SHOULD" used in this document are to be interpreted as described in [RFC2119]. 5. URL Definition An LDAP URL begins with the protocol prefix "ldap" and is defined by the following grammar, following the ABNF notation defined in [RFC2234]. ldapurl = scheme COLON SLASH SLASH [hostport] [SLASH dn [QUESTION [attributes] [QUESTION [scope] [QUESTION [filter] [QUESTION extensions]]]]] scheme = "ldap" hostport = <hostport from Section 3.2.2 of [RFC2396]> ; as updated by [RFC2732] to allow IPv6 literal addresses dn = <distinguishedName from Section 3 of [LDAPDN]> ; see the "Escaping Using the % Method" section below. attributes = attrdesc *(COMMA attrdesc) attrdesc = <AttributeDescription from Section 4.1.4 of [Protocol]> / ASTERISK ; see the "Escaping Using the % Method" section below. scope = "base" / "one" / "sub" filter = <filter from Section 4 of [Filters]> ; see the "Escaping Using the % Method" section below. extensions = extension *(COMMA extension) extension = [EXCLAMATION] extype [EQUALS exvalue] extype = oid / oiddescr exvalue = <LDAPString from section 4.1.2 of [Protocol]> ; see the "Escaping Using the % Method" section below. oid = <LDAPOID from section 4.1.2 of [Protocol]> oiddescr = <name from section 3.3 of [RFC3383]>[LDAPIANA]> EXCLAMATION = %x21 ; exclamation mark ("!") ASTERISK = %x2A ; asterisk ("*") COLON = %x3A ; colon (":") QUESTION = %x3F ; question mark ("?") SLASH = %x5C; forward slash ("/") The "ldap" prefix indicates an entry or entries residing in the LDAP server running on the given hostname at the given portnumber. Note that the hostport may contain literal IPv6 addresses as specified in [RFC2732]. The dn is an LDAP Distinguished Name using the string format described in [LDAPDN]. It identifies the base object of the LDAP search or the target of a non-search operation. The attributes construct is used to indicate which attributes should be returned from the entry or entries. Individual attrdesc names are as defined for AttributeDescription in [Protocol]. The scope construct is used to specify the scope of the search to perform in the given LDAP server. The allowable scopes are "base" for a base object search, "one" for a one-level search, or "sub" for a subtree search. The filter is used to specify the search filter to apply to entries within the specified scope during the search. It has the format specified in [Filters]. The extensions construct provides the LDAP URL with an extensibility mechanism, allowing the capabilities of the URL to be extended in the future. Extensions are a simple comma-separated list of type=value pairs, where the =value portion MAY be omitted for options not requiring it. Each type=value pair is a separate extension. These LDAP URL extensions are not necessarily related to any of the LDAPv3 extension mechanisms. Extensions may be supported or unsupported by the client resolving the URL. An extension prefixed with a '!' character (ASCII 33) is critical. An extension not prefixed with a '!' character is non-critical. If an LDAP URL extension is supportedrecognized by an implementation, the client, the clientimplementation MUST obey the extension if the extension is critical. The client SHOULD obey supported extensions that are non-critical.make use of it. If an extension is unsupported by the client,not recognized and is marked critical, the clientimplementation MUST NOT process the URL if the extension is critical.URL. If an unsupportedextension is non-critical, the client MUST ignore the extension. If a critical extension cannot be processed successfully by the client,not recognized and it not marked critical, the clientimplementation MUST NOT process the URL. If a non-critical extension cannot be processed successfully by the client, the client SHOULDignore the extension. The extension type (extype) MAY be specified using the oid form (e.g., 126.96.36.199) or the oiddesc form (e.g., myLDAPURLExtension). Use of the oiddesc form SHOULD be restricted to registered object identifier descriptive names. See [RFC3383][LDAPIANA] for registration details and usage guidelines for descriptive names. No LDAP URL extensions are defined in this document. Other documents or a future version of this document MAY define one or more extensions. 5.1. Escaping Using the % Method A generated LDAP URL MUST consist only of the restricted set of characters included in the uric production that is defined in section 2 of [RFC2396]. Implementations SHOULD accept other valid UTF-8 strings [UTF-8][RFC3629] as input. An octet MUST be escaped using the % method described in section 2.4 of [RFC2396] in any of these situations: The octet is not in the reserved set defined in section 2.2 of [RFC2396] or in the unreserved set defined in section 2.3 of [RFC2396]. It is the single Reserved character '?' and occurs inside a dn, filter, or other element of an LDAP URL. It is a comma character ',' that occurs inside an extension value. 6. Defaults for Fields of the LDAP URL Some fields of the LDAP URL are optional, as described above. In the absence of any other specification, the following general defaults SHOULD be used when a field is absent. Note: other documents MAY specify different defaulting rules; for example, section 188.8.131.52.10 of [Protocol] specifies a different rule for determining the correct DN to use when it is absent in an LDAP URL that is returned as a referral. hostport The default LDAP port is TCP port 389. If no hostport is given, the client must have some apriori knowledge of an appropriate LDAP server to contact. dn If no dn is given, the default is the zero-length DN, "". attributes If the attributes part is omitted, all user attributes of the entry or entries should be requested (e.g., by setting the attributes field AttributeDescriptionList in the LDAP search request to a NULL list, or (in LDAPv3) by requesting the special attribute name "*"). scope If scope is omitted, a scope of "base" is assumed. filter If filter is omitted, a filter of "(objectClass=*)" is assumed. extensions If extensions is omitted, no extensions are assumed. 7. Examples The following are some example LDAP URLs using the format defined above. The first example is an LDAP URL referring to the University of Michigan entry, available from an LDAP server of the client's choosing: ldap:///o=University%20of%20Michigan,c=US The next example is an LDAP URL referring to the University of Michigan entry in a particular ldap server: ldap://ldap1.example.net/o=University%20of%20Michigan,c=US Both of these URLs correspond to a base object search of the "o=University of Michigan,c=US" entry using a filter of "(objectclass=*)", requesting all attributes. The next example is an LDAP URL referring to only the postalAddress attribute of the University of Michigan entry: ldap://ldap1.example.net/o=University%20of%20Michigan, c=US?postalAddress The corresponding LDAP search operation is the same as in the previous example, except that only the postalAddress attribute is requested. The next example is an LDAP URL referring to the set of entries found by querying the given LDAP server on port 6666 and doing a subtree search of the University of Michigan for any entry with a common name of "Babs Jensen", retrieving all attributes: ldap://ldap1.example.net:6666/o=University%20of%20Michigan, c=US??sub?(cn=Babs%20Jensen) The next example is an LDAP URL referring to all children of the c=GB entry: ldap://ldap1.example.com/c=GB?objectClass?one The objectClass attribute is requested to be returned along with the entries, and the default filter of "(objectclass=*)" is used. The next example is an LDAP URL to retrieve the mail attribute for the LDAP entry named "o=Question?,c=US" is given below, illustrating the use of the escaping mechanism on the reserved character '?'. ldap://ldap2.example.com/o=Question%3f,c=US?mail The next example (which is broken into two lines for readability) illustrates the interaction between the LDAP string representation of filters quoting mechanism and URL quoting mechanisms. ldap://ldap3.example.com/o=Babsco,c=US???(four-octet=%5c00%5c00%5c00%5c04) IPldap://ldap3.example.com/o=Babsco,c=US ???(four-octet=%5c00%5c00%5c00%5c04) The filter in this example uses the LDAP escaping mechanism of \ to encode three zero or null bytes in the value. In LDAP, the filter would be written as (four-octet=\00\00\00\04). Because the \ character must be escaped in a URL, the \'s are escaped as %5c in the URL encoding. The next example illustrates the interaction between the LDAP string representation of DNs quoting mechanism and URL quoting mechanisms. ldap://ldap.example.com/o=An%20Example%5c2c%20Inc.,c=US The DN encoded in the above URL is: o=An Example\2c Inc.,c=US That is, the left-most RDN value is: An Example, Inc. The following three URLs that are equivalent, assuming that the defaulting rules specified in section 4 of this document are used: ldap://ldap.example.net ldap://ldap.example.net/ ldap://ldap.example.net/? These three URLs all point to the root DSE on the ldap.example.net server. The final two examples show use of a hypothetical, experimental bind name extension (the value associated with the extension is an LDAP DN). ldap:///??sub??e-bindname=cn=Manager%2cdc=example%2cdc=com ldap:///??sub??!e-bindname=cn=Manager%2cdc=example%2cdc=com The two URLs are the same, except that the second one marks the e- bindname extension as critical. Notice the use of the % encoding method to encode the commas within the distinguished name value in the e-bindname extension. 8. Security Considerations General URL security considerations discussed in [RFC2396] are relevant for LDAP URLs. The use of security mechanisms when processing LDAP URLs requires particular care, since clients may encounter many different servers via URLs, and since URLs are likely to be processed automatically, without user intervention. A client SHOULD have a user-configurable policy about which servers to connect to using which security mechanisms, and SHOULD NOT make connections that are inconsistent with this policy. If a client chooses to reuse an existing connection when resolving one or more LDAP URL, it MUST ensure that the connection is compatible with the URL and that no security policies are violated. Sending authentication information, no matter the mechanism, may violate a user's privacy requirements. In the absence of specific policy permitting authentication information to be sent to a server, a client should use an anonymous connection. (Note that clients conforming to previous LDAP URL specifications, where all connections are anonymous and unprotected, are consistent with this specification; they simply have the default security policy.) Simply opening a connection to another server may violate some users' privacy requirements, so clients should provide the user with a way to control URL processing. Some authentication methods, in particular reusable passwords sent to the server, may reveal easily-abused information to the remote server or to eavesdroppers in transit, and should not be used in URL processing unless explicitly permitted by policy. Confirmation by the human user of the use of authentication information is appropriate in many circumstances. Use of strong authentication methods that do not reveal sensitive information is much preferred. If the URL represents a referral for an update operation, strong authentication methods SHOULD be used. Please refer to the Security Considerations section of [AuthMeth] for more information. The LDAP URL format allows the specification of an arbitrary LDAP search operation to be performed when evaluating the LDAP URL. Following an LDAP URL may cause unexpected results, for example, the retrieval of large amounts of data, the initiation of a long-lived search, etc. The security implications of resolving an LDAP URL are the same as those of resolving an LDAP search query. 9. Normative References [AuthMeth] Harrison, R. (editor), "LDAP: Authentication Methods", draft-ietf-ldapbis-authmeth-xx.txt, a work in progress. a work in progress. [LDAPDN] Zeilenga, K. (editor), "LDAP: String Representation of Distinguished Names", draft-ietf-ldapbis-dn-xx.txt, a work in progress. [Filters] Smith, M. and Howes, T., "LDAP: String Representation of Search Filters", draft-ietf-ldapbis-filter-xx.txt, a work in progress. [LDAPIANA] Zeilenga, K., "IANA Considerations for LDAP", draft-ietf- ldapbis-bcp64-xx.txt, a work in progress. [RFC2119] Bradner, S., "Key Words for use in RFCs to Indicate Requirement Levels," RFC 2119, BCP 14, March 1997. [Protocol] Sermersheim, J. (editor), "LDAP: The Protocol", draft- ietf-ldapbis-protocol-xx.txt,draft-ietf- ldapbis-protocol-xx.txt, a work in progress. [RFC2234] Crocker, D., Overell, P., "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, November 1997. [RFC2396] Berners-Lee, T., Fielding, R., and Masinter, L., "Uniform Resource Identifiers (URI): Generic Syntax", RFC 2396, August 1998. [RFC2732] Hinden, R., Carpenter, B., Masinter, L., "Format for Literal IPv6 Addresses in URL's", RFC 2732, December 1999. [RFC3383] Zeilenga, K., "Internet Assigned Numbers Authority (IANA) Considerations for the Lightweight Directory Access Protocol (LDAP)", RFC 3383, September 2002. [AuthMeth] Harrison, R. (editor), "LDAP: Authentication Methods", draft-ietf-ldapbis-authmeth-xx.txt, a work in progress. a work in progress.[Roadmap] K. Zeilenga (editor), "LDAP: Technical Specification Road Map", draft-ietf-ldapbis-roadmap-xx.txt, a work in progress. [UTF-8][RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 10646", draft-yergeau-rfc2279bis-xx.txt, a work in progress.RFC 3629, November 2003. 10. Informative References None. 11. Intellectual Property Rights The IETF takes no position regarding the validity or scope of any intellectual property 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; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. Copies of claims of rights made available for publication 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 implementors or users of this specification can be obtained from the IETF Secretariat. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights which may cover technology that may be required to practice this standard. Please address the information to the IETF Executive Director. 12. Acknowledgements The LDAP URL format was originally defined at the University of Michigan. This material is based upon work supported by the National Science Foundation under Grant No. NCR-9416667. The support of both the University of Michigan and the National Science Foundation is gratefully acknowledged. This document is an update to RFC 2255 by Tim Howes and Mark Smith. 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. Several people in particular have made valuable comments on this document; RL "Bob" Morgan, Mark Wahl, Kurt Zeilenga, Jim Sermersheim, and Hallvard Furuseth deserve special thanks for their contributions. 13. Authors' AddressAddresses Mark Smith, Editor Netscape Communications Corp. 360 W. Caribbean Drive Sunnyvale, CA 94089Pearl Crescent, LLC 447 Marlpool Dr. Saline, MI 48176 USA +1 650 937-3477 MarkCSmithWork@aol.com734 944-2856 firstname.lastname@example.org Tim Howes Opsware, Inc. 599 N. Mathilda Ave. Sunnyvale, CA 94085 USA +1 408 744-7509 email@example.com 14. Full Copyright Statement Copyright (C) The Internet Society (2003).(2004). 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. 15. Appendix A: Changes Since RFC 2255 15.1. Technical Changes The following technical changes were made to the contents of the "URL Definition" section: Revised all of the ABNF to use common productions from [Models]. Added note and references to [RFC2732] to allow literal IPv6 addresses inside the hostport portion of the URL. Added missing ASTERISK as an alternative for the attrdesc part of the URL. It is believed that existing implementations of RFC 2255 already support this. Added angle brackets around free-form prose in the "dn", "hostport", "attrdesc", "filter", and "exvalue" rules. Changed the ABNF for ldapurl to group the dn component with the preceding slash. Changed the extype rule to be an LDAPOID from [Protocol] or an OID description from [RFC3383].[LDAPIANA]. Changed the text about extension types so it references [RFC3383].[LDAPIANA]. Reordered rules to more closely follow the order the elements appear in the URL. "Bindname Extension": removed due to lack of known implementations. 15.2. Editorial Changes Changed document title to include "LDAP:" prefix. IESG Note: removed note about lack of satisfactory mandatory authentication mechanisms. "Status of this Memo" section: updated boilerplate to match current I-D guidelines. "Abstract" section: separated from introductory material. "Table of Contents" section: added. "Introduction" section: new section; separated from the Abstract. Changed the text indicate that RFC 2255 is replaced by this document (instead of RFC 1959). Added text to indicate that LDAP URLs are used for references and referrals. Fixed typo (replaced the nonsense phrase "to perform to retrieve" with "used to retrieve"). Added a note to let the reader know that not all of the parameters of the LDAP search operation described in [Protocol] can be expressed using this format. "URL Definition" section: removed second copy of ldapurl grammar and following two paragraphs (editorial error in RFC 2255). Fixed line break within '!' sequence. Reworded last paragraph to clarify which characters must be URL escaped. Added text to indicate that LDAP URLs are used for references and referrals. Added text that refers to the ABNF from RFC 2234. Clarified and strengthened the requirements with respect to processing of URLs that contain recognized and unrecognized extensions (the approach now matches that specified in [Protocol] for LDAP controls). "Defaults for Fields of the LDAP URL" section: added; formed by moving text about defaults out of the "URL Definition" section. "URL Processing" section: clarified that connections MAY be reused only if the open connection is compatible with the URL. Added text to indicate that use of security services is encouraged and that they SHOULD be used when updates are involved. Removed "dn" from discussion of authentication methods. Added note that the client MAY interrogate the server to determine the most appropriate method. "Examples" section: Modified examples to use example.com and example.net hostnames. Added missing '?' to the LDAP URL example whose filter contains three null bytes. Removed space after one comma within a DN. Revised the bindname example to use e-bindname. Changed the name of an attribute used in one example from "int" to "four-octet" to avoid potential confusion. Added an example that demonstrates the interaction between DN escaping and URL escaping. Added some examples to show URL equivalence with respect to the dn portion of the URL. "Security Considerations" section: Added a note about connection reuse. Added a note about using strong authentication methods for updates. Added a reference to RFC 2829.[AuthMeth]. Added note that simply opening a connection may violate some users' privacy requirements. "Acknowledgements" section: added statement about this being an update to RFC 2255. Added Kurt Zeilenga, Jim Sermersheim, and Hallvard Furuseth. "Normative References" section: renamed from "References" per new RFC guidelines. Changed from  style to [Protocol] style throughout the document. Added references to RFCsRFC 2234, 2829,RFC 2732, and 3383.RFC 3629. Updated all RFC 1738 references to point to the appropriate sections within RFC 2396. Updated the LDAP references to refer to LDAPBis WG documents. Removed the reference to the LDAP Attribute Syntaxes document and added a referencereferences to the Roadmap document.[AuthMeth], [LDAPIANA], and [Roadmap] documents. "Informative References" section: added for clarity. Header and "Authors' Address"Addresses" sections: added "editor" next to Mark Smith's name. Updated affiliation and contact information. Copyright: updated the year. 16. Appendix B: Changes Since Previous Document Revision This appendix lists all changes relative to the previously published revision, draft-ietf-ldapbis-url-03.txt.draft-ietf-ldapbis-url-04.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-url-03.txt.ietf-ldapbis-url-04.txt. This section will be removed before this document is published as an RFC. 16.1. Technical Changes None.Clarified and strengthened the requirements with respect to processing of URLs that contain recognized and unrecognized extensions (the approach now matches that specified in [Protocol] for LDAP controls). 16.2. Editorial Changes "URL Definition" section: added comments in the ABNF to point the reader to the "Escaping Using the % Method" section, which was changed intocorrected a section of its ownreference to highlight the importance of escaping the URL components correctly.[Protocol]. "Examples" section: changed the name of an attribute usedimproved formatting and fixed a typographic error (removed extraneous "IP") in one example from "int" to "four-octet" to avoid potential confusion. Replaced all occurrences of "asterix" withthe correctly spelled "asterisk.""four-octet" example. "Normative References" section: changed the UTF-8 reference to point to RFC 3629, changed the RFC 3383 reference to point to the UTF-8 Internet Draft; replace [LDAPIANA]LDAP IANA Internet Draft reference with aDraft, and indented the reference descriptions to RFC 3383. "Intellectual Property Rights" section: added. Author'senhance readability. Authors' Addresses section: New email addresscontact information for Mark Smith. "Full Copyright Statement" section: updated textUpdated the copyright year to match latest IETF guidelines.2004. This Internet Draft expires on 25 April13 August 2004.