Network Working Group T. Howes Request for Comments: 1778 University of Michigan Obsoletes: 1488 S. Kille Category: Standards Track ISODE Consortium W. Yeong Performance Systems International C. Robbins NeXor Ltd. March 1995
The String Representation of Standard Attribute Syntaxes
Status of this Memo
This document specifies an Internet standards track protocol for the Internet community, and 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.
Abstract
The Lightweight Directory Access Protocol (LDAP) [9] requires that the contents of AttributeValue fields in protocol elements be octet strings. This document defines the requirements that must be satisfied by encoding rules used to render X.500 Directory attribute syntaxes into a form suitable for use in the LDAP, then goes on to define the encoding rules for the standard set of attribute syntaxes defined in [1,2] and [3].
1. Attribute Syntax Encoding Requirements.
This section defines general requirements for lightweight directory protocol attribute syntax encodings. All documents defining attribute syntax encodings for use by the lightweight directory protocols are expected to conform to these requirements.
The encoding rules defined for a given attribute syntax must produce octet strings. To the greatest extent possible, encoded octet strings should be usable in their native encoded form for display purposes. In particular, encoding rules for attribute syntaxes defining non-binary values should produce strings that can be displayed with little or no translation by clients implementing the lightweight directory protocols.
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2. Standard Attribute Syntax Encodings
For the purposes of defining the encoding rules for the standard attribute syntaxes, the following auxiliary BNF definitions will be used:
<caseexactstring> ::= a string encoded according to the rules for Case Exact String as above.
2.12. Distinguished Name
Values of type distinguishedNameSyntax are encoded to have the representation defined in [5].
2.13. Boolean
Values of type booleanSyntax are encoded according to the following BNF:
<boolean> ::= "TRUE" | "FALSE"
Boolean values have an encoding of "TRUE" if they are logically true, and have an encoding of "FALSE" otherwise.
2.14. Integer
Values of type integerSyntax are encoded as the decimal representation of their values, with each decimal digit represented by the its character equivalent. So the digit 1 is represented by the character
2.15. Object Identifier
Values of type objectIdentifierSyntax are encoded according to the following BNF:
In the above BNF, <descr> is the syntactic representation of an object descriptor. When encoding values of type objectIdentifierSyntax, the first encoding option should be used in preference to the second, which should be used in preference to the
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third wherever possible. That is, in encoding object identifiers, object descriptors (where assigned and known by the implementation) should be used in preference to numeric oids to the greatest extent possible. For example, in encoding the object identifier representing an organizationName, the descriptor "organizationName" is preferable to "ds.4.10", which is in turn preferable to the string "2.5.4.10".
2.16. Telephone Number
Values of type telephoneNumberSyntax are encoded as if they were Printable String types.
2.17. Telex Number
Values of type telexNumberSyntax are encoded according to the following BNF:
In the above, <actual-number> is the syntactic representation of the number portion of the TELEX number being encoded, <country> is the TELEX country code, and <answerback> is the answerback code of a TELEX terminal.
2.18. Teletex Terminal Identifier
Values of type teletexTerminalIdentifier are encoded according to the following BNF:
In the above, the first <printablestring> is the encoding of the first portion of the teletex terminal identifier to be encoded, and the subsequent 0 or more <printablestrings> are subsequent portions of the teletex terminal identifier.
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2.19. Facsimile Telephone Number
Values of type FacsimileTelephoneNumber are encoded according to the following BNF:
The syntactic components <signature-algorithm-id>, <issuer>, <encrypted-sign-value>, <utc-time>, <subject> and <serial> have the same definitions as in the BNF for the userCertificate attribute syntax.
2.28. Certificate Revocation List
Values of type certificateRevocationList are encoded as if the values were of type authorityRevocationList.
2.29. Cross Certificate Pair
Values of type crossCertificatePair are encoded according to the following BNF:
Values of the type otherMailboxSyntax are encoded according to the following BNF:
<otherMailbox> ::= <mailbox-type> '$' <mailbox>
<mailbox-type> ::= an encoded Printable String
<mailbox> ::= an encoded IA5 String
In the above, <mailbox-type> represents the type of mail system in which the mailbox resides, for example "Internet" or "MCIMail"; and <mailbox> is the actual mailbox in the mail system defined by <mailbox-type>.
2.32. Mail Preference
Values of type mailPreferenceOption are encoded according to the following BNF:
Values of type Photo are encoded as if they were octet strings containing JPEG images in the JPEG File Interchange Format (JFIF), as described in [8].
2.36. Fax
Values of type Fax are encoded as if they were octet strings containing Group 3 Fax images as defined in [7].
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3. Security Considerations
Security issues are not discussed in this memo.
4. Acknowledgements
Many of the attribute syntax encodings defined in this document are adapted from those used in the QUIPU X.500 implementation. The contributions of the authors of the QUIPU implementation in the specification of the QUIPU syntaxes [4] are gratefully acknowledged.
5. Bibliography
[1] The Directory: Selected Attribute Syntaxes. CCITT, Recommendation X.520.
[2] Information Processing Systems -- Open Systems Interconnection -- The Directory: Selected Attribute Syntaxes.
[3] Barker, P., and S. Kille, "The COSINE and Internet X.500 Schema", RFC 1274, University College London, November 1991.
[4] The ISO Development Environment: User's Manual -- Volume 5: QUIPU. Colin Robbins, Stephen E. Kille.
[5] Kille, S., "A String Representation of Distinguished Names", RFC 1779, ISODE Consortium, March 1995.
[6] Kille, S., "A String Representation for Presentation Addresses", RFC 1278, University College London, November 1991.
[7] Terminal Equipment and Protocols for Telematic Services - Standardization of Group 3 facsimile apparatus for document transmission. CCITT, Recommendation T.4.
[8] JPEG File Interchange Format (Version 1.02). Eric Hamilton, C- Cube Microsystems, Milpitas, CA, September 1, 1992.
[9] Yeong, W., Howes, T., and S. Kille, "Lightweight Directory Access Protocol", RFC 1777, Performance Systems International, University of Michigan, ISODE Consortium, March 1995.
[10] Alvestrand, H., Kille, S., Miles, R., Rose, M., and S. Thompson, "Mapping between X.400 and RFC-822 Message Bodies", RFC 1495, SINTEF DELAB, ISODE Consortium, Soft*Switch, Inc., Dover Beach Consulting, Inc., Soft*Switch, Inc., August 1993.
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6. Authors' Addresses
Tim Howes University of Michigan ITD Research Systems 535 W William St. Ann Arbor, MI 48103-4943 USA
Phone: +1 313 747-4454 EMail: tim@umich.edu
Steve Kille ISODE Consortium PO Box 505 London SW11 1DX UK
Phone: +44-71-223-4062 EMail: S.Kille@isode.com
Wengyik Yeong PSI Inc. 510 Huntmar Park Drive Herndon, VA 22070 USA
Phone: +1 703-450-8001 EMail: yeongw@psilink.com
Colin Robbins NeXor Ltd University Park Nottingham NG7 2RD UK
