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INTERNET-DRAFT S. Legg draft-legg-ldap-transfer-03.txt Adacel Technologies Intended Category: Standards Track 16 June 2004 Updates: RFC 2252bis Lightweight Directory Access Protocol (LDAP): Transfer Encoding Options Copyright (C) The Internet Society (2004). 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 16 December 2004. Abstract Each attribute stored in a Lightweight Directory Access Protocol (LDAP) directory has a defined syntax (i.e., data type). A syntax Legg Expires 16 December 2004 [Page 1]  INTERNET-DRAFT LDAP: Transfer Encoding Options June 16, 2004 definition specifies how attribute values conforming to the syntax 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 16 December 2004 [Page 2]  INTERNET-DRAFT LDAP: Transfer Encoding Options June 16, 2004 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions. . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Transfer Encoding Options. . . . . . . . . . . . . . . . . . . 4 4. Defined Transfer Encoding Options. . . . . . . . . . . . . . . 5 5. Attributes Returned in a Search. . . . . . . . . . . . . . . . 6 6. Syntaxes Requiring Binary Transfer . . . . . . . . . . . . . . 7 7. Security Considerations. . . . . . . . . . . . . . . . . . . . 7 8. IANA Considerations. . . . . . . . . . . . . . . . . . . . . . 8 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 9.1. Normative References . . . . . . . . . . . . . . . . . . 9 9.2. Informative References . . . . . . . . . . . . . . . . . 10 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10 Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 10 1. 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. One option in particular allows Extensible Markup Language (XML) [XML] encodings. 2. 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 BCP 14, RFC 2119 [KEYWORD]. This specification makes use of definitions from the XML Information Set (Infoset) [ISET]. In particular, information item property names Legg Expires 16 December 2004 [Page 3]  INTERNET-DRAFT LDAP: Transfer Encoding Options June 16, 2004 are presented per the Infoset, e.g., [local name]. 3. 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 Legg Expires 16 December 2004 [Page 4]  INTERNET-DRAFT LDAP: Transfer Encoding Options June 16, 2004 encoding is not supported for that type. 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. 4. 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) [RFC3641]. The attribute option string "transfer-rxer" specifies that the associated attribute values or assertion value are (to be) encoded as an XML document [XML]. The [local name] of the [document element] of the document information item representing the associated value SHALL be the identifier of the NamedType [X680] in the LDAP ASN.1 specification [PROT] defining the associated attribute value or assertion value, or "item" if the associated value isn't in a NamedType. This means: - for an AttributeValue the identifier is "value" in every case, - for an AssertionValue in an AttributeValueAssertion the identifier is "assertionValue", - for an AssertionValue in a SubstringFilter the identifier is "initial", "any" or "final", as appropriate, - for an AssertionValue in a MatchingRuleAssertion the identifier is "matchValue". The [namespace name] of the [document element] SHALL have no value. The content of the [document element] is the Robust XML Encoding Rules (RXER) [RXER] encoding of the associated attribute or assertion Legg Expires 16 December 2004 [Page 5]  INTERNET-DRAFT LDAP: Transfer Encoding Options June 16, 2004 value. Note that the enclosing element for the RXER encoding has the form it would take in an XLDAP operation [XLDAP]. 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. 5. 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 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. 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. In such cases the effective transfer encoding being requested for a particular attribute is determined by the transfer encoding option (or lack thereof) 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 the special attribute description string "*". 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 former attribute description is more specific than the latter attribute description. Legg Expires 16 December 2004 [Page 6]  INTERNET-DRAFT LDAP: Transfer Encoding Options June 16, 2004 If two applicable attribute descriptions have the same attribute type and the tagging options of one attribute description are a superset of the tagging options of the other attribute description then the former attribute description is more specific than the latter 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. 6. 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. 7. 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 Legg Expires 16 December 2004 [Page 7]  INTERNET-DRAFT LDAP: Transfer Encoding Options June 16, 2004 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. 8. 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 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: Subject: Request for LDAP Attribute Description Option Registration Option Name: transfer-rxer 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 Legg Expires 16 December 2004 [Page 8]  INTERNET-DRAFT LDAP: Transfer Encoding Options June 16, 2004 Comments: 9. References 9.1. 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., "Lightweight Directory Access Protocol (LDAP): Technical Specification Road Map", draft-ietf-ldapbis-roadmap-xx.txt, a work in progress, June 2004. [MODELS] Zeilenga, K., "LDAP: Directory Information Models", draft-ietf-ldapbis-models-xx.txt, a work in progress, June 2004. [PROT] Sermersheim, J., "LDAP: The Protocol", draft-ietf-ldapbis-protocol-xx.txt, a work in progress, May 2004. [SYNTAX] Legg, S. and K. Dally, "Lightweight Directory Access Protocol (LDAP): Syntaxes and Matching Rules", draft-ietf-ldapbis-syntaxes-xx.txt, a work in progress, May 2004. [RFC3641] Legg, S., "Generic String Encoding Rules (GSER) for ASN.1 Types", RFC 3641, October 2003. [BINARY] Legg, S., "Lightweight Directory Access Protocol (LDAP): The Binary Encoding Option", draft-legg-ldap-binary-xx.txt, a work in progress, June 2004. [RXER] Legg, S. and D. Prager, "Robust XML Encoding Rules for ASN.1 Types", draft-legg-xed-rxer-00.txt, a work in progress, June 2004. [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, Legg Expires 16 December 2004 [Page 9]  INTERNET-DRAFT LDAP: Transfer Encoding Options June 16, 2004 Information Technology - ASN.1 encoding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER). [XML] Bray, T., Paoli, J., Sperberg-McQueen, C., Maler, E. and F. Yergeau, "Extensible Markup Language (XML) 1.0 (Third Edition)", W3C Recommendation, http://www.w3.org/TR/2004/REC-xml-20040204, February 2004. [ISET] Cowan, J. and R. Tobin, "XML Information Set", http://www.w3.org/TR/2001/REC-xml-infoset-20011024, October 2001. 9.2. Informative References [XLDAP] Legg, S. and D. Prager, "The XML Enabled Directory: Protocols", draft-legg-xed-protocols-xx.txt, a work in progress, May 2004. 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 Full Copyright Statement Copyright (C) The Internet Society (2004). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM 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. Intellectual Property Legg Expires 16 December 2004 [Page 10]  INTERNET-DRAFT LDAP: Transfer Encoding Options June 16, 2004 The IETF takes no position regarding the validity or scope of any Intellectual Property Rights 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; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat 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 implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Changes in Draft 01 A transfer encoding option for RXER has been added. Changes in Draft 02 The local name of the root element of the XML document representing an attribute value encoded according to the transfer-rxer encoding option has been changed from "item" to "value" to align with revisions to the LDAP protocol specification [PROT]. The Directory XML Encoding Rules (DXER) have been renamed to the Robust XML Encoding Rules (RXER). Changes in Draft 03 The special attribute description strings that consist of the asterisk character followed by a transfer encoding option, e.g., "*;transfer-ber", "*;transfer-gser", have been removed from this specification. An LDAP control will be defined in a separate document to provide equivalent functionality. Legg Expires 16 December 2004 [Page 11]