INTERNET-DRAFT S. Legg draft-legg-ldap-transfer-00.txt Adacel Technologies Intended Category: Standard Track 19 June 2003 Updates: RFC 2252bis LDAP: Transfer Encoding Options Copyright (C) The Internet Society (2003). All Rights Reserved. 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. This document is intended to be, after appropriate review and revision, submitted to the RFC Editor as a Standard Track document. Distribution of this document is unlimited. Technical discussion of this document should take place on the IETF LDAP Revision Working Group (LDAPbis) mailing list <ietf-ldapbis@openldap.org>. Please send editorial comments directly to the editor <steven.legg@adacel.com.au>. This Internet-Draft expires on 19 December 2003. Abstract Each attribute stored in a Lightweight Directory Access Protocol (LDAP) directory has a defined syntax (i.e. data type). A syntax definition specifies how attribute values conforming to the syntax Legg Expires 19 December 2003 [Page 1]
INTERNET-DRAFT LDAP: Transfer Encoding Options June 19, 2003 are normally represented when transferred in LDAP operations. This representation is referred to as the LDAP-specific encoding to distinguish it from other methods of encoding attribute values. This document introduces a new category of attribute options, called transfer encoding options, which can be used to specify that the associated attribute values are encoded according to one of these other methods. Legg Expires 19 December 2003 [Page 2]
INTERNET-DRAFT LDAP: Transfer Encoding Options June 19, 2003 1. Table of Contents 1. Table of Contents ............................................. 3 2. Introduction .................................................. 3 3. Conventions ................................................... 3 4. Transfer Encoding Options ..................................... 4 5. Defined Transfer Encoding Options ............................. 5 6. Attributes Returned in a Search ............................... 5 7. Syntaxes Requiring Binary Transfer ............................ 7 8. Security Considerations ....................................... 7 9. IANA Considerations ........................................... 7 10. Normative References ......................................... 8 11. Informative References ....................................... 9 12. Intellectual Property Notice ................................. 9 13. Copyright Notice ............................................. 10 14. Author's Address ............................................. 10 2. Introduction Each attribute stored in a Lightweight Directory Access Protocol (LDAP) directory [ROADMAP] has a defined syntax (i.e. data type) which constrains the structure and format of its values. The description of each syntax [SYNTAX] specifies how attribute or assertion values [MODELS] conforming to the syntax are normally represented when transferred in LDAP operations [PROT]. This representation is referred to as the LDAP-specific encoding to distinguish it from other methods of encoding attribute values. This document introduces a new category of attribute options [MODELS], called transfer encoding options, that allow attribute and assertion values to be transferred using an alternative method of encoding. This document defines several transfer encoding options which can be used in an attribute description [MODELS] in an LDAP operation to specify that the associated attribute values or assertion value are, or are requested to be, encoded according to specific Abstract Syntax Notation One (ASN.1) [X680] encoding rules, instead of the usual LDAP-specific encoding. 3. Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [KEYWORD]. Legg Expires 19 December 2003 [Page 3]
INTERNET-DRAFT LDAP: Transfer Encoding Options June 19, 2003 4. Transfer Encoding Options Transfer encoding options enable attribute and assertion values to be transferred using an alternative method of encoding to the default LDAP-specific encoding. In fact, some attribute and assertion syntaxes do not have a defined LDAP-specific encoding in which case the only way values of those syntaxes can be transferred is by using an alternative encoding. The binary option [BINARY] is not formally regarded as a transfer encoding option, though it has much in common with transfer encoding options. The requirements governing the use of transfer encoding options do not apply to the binary option. The requirements governing the use of the binary option are described elsewhere [BINARY]. In terms of the protocol [PROT], a transfer encoding option specifies that the contents octets of an associated AttributeValue or AssertionValue OCTET STRING are a complete encoding of the relevant value according to the encoding method specified by the option. Where a transfer encoding option is present in an attribute description the associated attribute values or assertion value MUST be encoded according to the encoding method corresponding to the option. Note that it is possible for a syntax to be defined such that its LDAP-specific encoding is exactly the same as its encoding according to some transfer encoding option (e.g. the LDAP-specific encoding might be defined to be the same as the BER encoding). Transfer encoding options are mutually exclusive. An attribute description SHALL NOT contain more than one transfer encoding option, and SHALL NOT contain both a transfer encoding option and the binary option. Transfer encoding options are not tagging options [MODELS] so the presence of a transfer encoding option does not specify an attribute subtype. An attribute description containing a transfer encoding option references exactly the same attribute as the same attribute description without the transfer encoding option. The supertype/subtype relationships of attributes with tagging options are not altered in any way by the presence or absence of transfer encoding options. An attribute description SHALL be treated as unrecognized if it contains a transfer encoding option and the syntax of the attribute does not have an associated ASN.1 type [SYNTAX], or if the nominated encoding is not supported for that type. Legg Expires 19 December 2003 [Page 4]
INTERNET-DRAFT LDAP: Transfer Encoding Options June 19, 2003 The presence or absence of a transfer encoding option only affects the transfer of attribute and assertion values in protocol; servers store any particular attribute value in a single format of their choosing. 5. Defined Transfer Encoding Options The attribute option string "transfer-ber" specifies that the associated attribute values or assertion value are (to be) encoded according to the Basic Encoding Rules [X690] of ASN.1. This option is similar to the binary option [BINARY], however servers are more restricted in when they can use "transfer-ber" which leads to more predictability in the results returned to clients who request "transfer-ber". The attribute option string "transfer-der" specifies that the associated attribute values or assertion value are (to be) encoded according to the Distinguished Encoding Rules [X690] of ASN.1. The attribute option string "transfer-gser" specifies that the associated attribute values or assertion value are (to be) encoded according to the Generic String Encoding Rules [GSER]. Note that, like all attribute options, the strings representing transfer encoding options are case insensitive. All future registrations of option strings for transfer encoding options should use the "transfer-" prefix so that LDAP clients and servers can recognize that an option is a transfer encoding option even though the particular encoding rules may be unrecognized. 6. Attributes Returned in a Search An LDAP search request [PROT] contains a list of the attributes (the requested attributes list) to be returned from each entry matching the search filter. An attribute description in the requested attributes list also implicitly requests all subtypes of the attribute type in the attribute description, whether through attribute subtyping or attribute tagging option subtyping [MODELS]. The requested attributes list MAY contain attribute descriptions with a transfer encoding option, but MUST NOT contain two attribute descriptions with the same attribute type and the same tagging options (even if only one of them has a transfer encoding option). A transfer encoding option in an attribute description in the requested attributes list implicitly applies to the subtypes of the attribute Legg Expires 19 December 2003 [Page 5]
INTERNET-DRAFT LDAP: Transfer Encoding Options June 19, 2003 type in the attribute description. If the list of attributes in a search request is empty, or contains the special attribute description string "*", then all user attributes are requested to be returned. This specification defines an open-ended set of special attribute description strings that consist of the asterisk character followed by any defined transfer encoding option, e.g. "*;transfer-ber", "*;transfer-gser". These special attribute description strings request that all user attributes be returned in the encoding specified by the option. The requested attributes list MUST NOT contain more than one of the special attribute description strings beginning with "*". In general, it is possible for a particular attribute to be explicitly requested by an attribute description and/or implicitly requested by the attribute descriptions of one or more of its supertypes, or by one of the special attribute description strings beginning with "*". In such cases the effective transfer encoding being requested for a particular attribute is determined by the transfer encoding option (or lack therof) in the most specific attribute description in the requested attributes list that applies to the attribute. An applicable attribute description with an actual attribute type is more specific than one of the special attribute description strings beginning with "*". If the attribute type of one applicable attribute description is a direct or indirect subtype of the attribute type in another applicable attribute description then the first attribute description is more specific than the second attribute description. If two applicable attribute descriptions have the same attribute type and the tagging options of the first attribute description are a superset of the tagging options of the second attribute description then the first attribute description is more specific than the second attribute description. Attributes MUST either be returned in the effective transfer encoding requested, be returned with no attribute values, or be omitted from the results. An attribute SHALL NOT be returned using an encoding other than the effective transfer encoding requested. Regardless of the encoding chosen, a particular attribute value is returned at most once. Legg Expires 19 December 2003 [Page 6]
INTERNET-DRAFT LDAP: Transfer Encoding Options June 19, 2003 7. Syntaxes Requiring Binary Transfer Certain syntaxes are required to be transferred in the BER encoded form. These syntaxes are said to have a binary transfer requirement. The Certificate, Certificate List, Certificate Pair and Supported Algorithm syntaxes [PKI] are examples of syntaxes with a binary transfer requirement. These syntaxes also have an additional requirement that the exact BER encoding must be preserved. Note that this is a property of the syntaxes themselves, and not a property of the binary option or any of the transfer encoding options. Transfer encoding options SHALL take precedence over the requirement for binary transfer. For example, if the effective transfer encoding requested is say "transfer-gser", then attribute values of a syntax with a binary transfer requirement will be GSER encoded. In the absence of a transfer encoding option the normal rules on binary transfer and the use of the binary option SHALL apply. 8. Security Considerations There is a requirement on some attribute syntaxes that the exact BER encoding of values of that syntax be preserved. In general, a transformation from the BER encoding into some other encoding (e.g. GSER) and back into the BER encoding will not necessarily reproduce exactly the octets of the original BER encoding. Applications needing the original BER encoding to be preserved, e.g. for the verification of digital signatures, MUST NOT request attributes with such a requirement using a transfer encoding option. These attributes MUST be requested explicitly or implicitly with the binary option, or implicitly without the binary option (or any transfer encoding option). When interpreting security-sensitive fields, and in particular fields used to grant or deny access, implementations MUST ensure that any matching rule comparisons are done on the underlying abstract value, regardless of the particular encoding used. 9. IANA Considerations The Internet Assigned Numbers Authority (IANA) is requested to update the LDAP attribute description option registry [BCP64] as indicated by the following templates: Subject: Request for LDAP Attribute Description Option Registration Legg Expires 19 December 2003 [Page 7]
INTERNET-DRAFT LDAP: Transfer Encoding Options June 19, 2003 Option Name: transfer-ber Family of Options: NO Person & email address to contact for further information: Steven Legg <steven.legg@adacel.com.au> Specification: RFC XXXX Author/Change Controller: IESG Comments: Subject: Request for LDAP Attribute Description Option Registration Option Name: transfer-der Family of Options: NO Person & email address to contact for further information: Steven Legg <steven.legg@adacel.com.au> Specification: RFC XXXX Author/Change Controller: IESG Comments: Subject: Request for LDAP Attribute Description Option Registration Option Name: transfer-gser Family of Options: NO Person & email address to contact for further information: Steven Legg <steven.legg@adacel.com.au> Specification: RFC XXXX Author/Change Controller: IESG Comments: 10. Normative References [KEYWORD] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [BCP64] Zeilenga, K., "Internet Assigned Numbers Authority (IANA) Considerations for the Lightweight Directory Access Protcol (LDAP)", BCP 64, RFC 3383, September 2002. [ROADMAP] Zeilenga, K., "LDAP: Technical Specification Road Map", draft-ietf-ldapbis-roadmap-xx.txt, a work in progress, March 2003. [MODELS] Zeilenga, K., "LDAP: Directory Information Models", draft-ietf-ldapbis-models-xx.txt, a work in progress, March 2003. [PROT] Sermersheim, J., "LDAP: The Protocol", draft-ietf-ldapbis-protocol-xx.txt, a work in progress, Legg Expires 19 December 2003 [Page 8]
INTERNET-DRAFT LDAP: Transfer Encoding Options June 19, 2003 June 2003. [SYNTAX] Legg, S. and K. Dally, "LDAP: Syntaxes and Matching Rules", draft-ietf-ldapbis-syntaxes-xx.txt, a work in progress, June 2003. [GSER] Legg, S., "Generic String Encoding Rules for ASN.1 Types", draft-legg-ldap-gser-xx.txt, a work in progress, June 2003. [BINARY] Legg, S., "LDAP: The Binary Encoding Option", draft-legg-ldap-binary-xx.txt, a work in progress, June 2003. [X680] ITU-T Recommendation X.680 (07/02) | ISO/IEC 8824-1, Information technology - Abstract Syntax Notation One (ASN.1): Specification of basic notation. [X690] ITU-T Recommendation X.690 (07/02) | ISO/IEC 8825-1, Information Technology - ASN.1 encoding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER). 11. Informative References [BCP11] Hovey, R. and S. Bradner, "The Organizations Involved in the IETF Standards Process", BCP 11, RFC 2028, October 1996. 12. Intellectual Property Notice 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. [BCP11] 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. Legg Expires 19 December 2003 [Page 9]
INTERNET-DRAFT LDAP: Transfer Encoding Options June 19, 2003 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. 13. Copyright Notice Copyright (C) The Internet Society (2003). 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. 14. Author's Address Steven Legg Adacel Technologies Ltd. 250 Bay Street Brighton, Victoria 3186 AUSTRALIA Phone: +61 3 8530 7710 Fax: +61 3 8530 7888 Email: steven.legg@adacel.com.au Legg Expires 19 December 2003 [Page 10]