RFC1778 - The String Representation of Standard Attribute Syntaxes

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.

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:

<a> ::= 'a' 'b' 'c' 'd' 'e' 'f' 'g' 'h' 'i'

'j' 'k' 'l' 'm' 'n' 'o' 'p' 'q' 'r'

's' 't' 'u' 'v' 'w' 'x' 'y' 'z' 'A'

'B' 'C' 'D' 'E' 'F' 'G' 'H' 'I' 'J'

'K' 'L' 'M' 'N' 'O' 'P' 'Q' 'R' 'S'

'T' 'U' 'V' 'W' 'X' 'Y' 'Z'

<d> ::= '0' '1' '2' '3' '4' '5' '6' '7' '8' '9'

<hex-digit> ::= <d> 'a' 'b' 'c' 'd' 'e' 'f'

'A' 'B' 'C' 'D' 'E' 'F'

<k> ::= <a> <d> '-'

<p> ::= <a> <d> ''' '(' ')' '+' ',' '-' '.'

'/' ':' '?' ' '

<CRLF> ::= The ASCII newline character with hexadecimal value 0x0A

2.1. Undefined

Values of type Undefined are encoded as if they were values of type

Octet String, with the string value being the BER-encoded version of

the value.

2.2. Case Ignore String

A string of type caseIgnoreStringSyntax is encoded as the string

value itself.

2.3. Case Exact String

The encoding of a string of type caseExactStringSyntax is the string

value itself.

2.4. Printable String

The encoding of a string of type printableStringSyntax is the string

value itself.

2.5. Numeric String

The encoding of a string of type numericStringSyntax is the string

value itself.

2.6. Octet String

The encoding of a string of type octetStringSyntax is the string

value itself.

2.7. Case Ignore IA5 String

The encoding of a string of type caseIgnoreIA5String is the string

value itself.

2.8. IA5 String

The encoding of a string of type iA5StringSyntax is the string value

itself.

2.9. T61 String

The encoding of a string of type t61StringSyntax is the string value

itself.

2.10. Case Ignore List

Values of type caseIgnoreListSyntax are encoded according to the

following BNF:

<caseignorestring> ::= a string encoded according to the rules for Case

Ignore String as above.

2.11. Case Exact List

Values of type caseExactListSyntax are encoded according to the

following BNF:

<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

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:

<telex-number> ::= <actual-number> '$' <country> '$' <answerback>

<actual-number> ::= <printablestring>

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:

<teletex-id> ::= <printablestring> 0*('$' <ttx-parm>)

<ttx-param> ::= <ttx-key> ':' <ttx-value>

<ttx-key> ::= 'graphic' 'control' 'misc' 'page' 'private'

<ttx-value> ::= <octetstring>

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.

2.19. Facsimile Telephone Number

Values of type FacsimileTelephoneNumber are encoded according to the

following BNF:

<fax-number> ::= <printablestring> [ '$' <faxparameters> ]

<faxparm> ::= 'twoDimensional' 'fineResolution' 'unlimitedLength'

'b4Length' 'a3Width' 'b4Width' 'uncompressed'

In the above, the first <printablestring> is the actual fax number,

and the <faxparm> tokens represent fax parameters.

2.20. Presentation Address

Values of type PresentationAddress are encoded to have the

representation described in [6].

2.21. UTC Time

Values of type uTCTimeSyntax are encoded as if they were Printable

Strings with the strings containing a UTCTime value.

2.22. Guide (search guide)

Values of type Guide, such as values of the searchGuide attribute,

are encoded according to the following BNF:

<guide-value> ::= [ <object-class> '#' ] <criteria>

<criteria-set> ::= [ '(' ] <criteria> '&' <criteria-set> [ ')' ]

[ '(' ] <criteria> '' <criteria-set> [ ')' ]

<criteria-item> ::= [ '(' ] <attributetype> '$' <match-type> [ ')' ]

<match-type> ::= "EQ" "SUBSTR" "GE" "LE" "APPROX"

2.23. Postal Address

Values of type PostalAddress are encoded according to the following

BNF:

<postal-address> ::= <t61string> <t61string> '$' <postal-address>

In the above, each <t61string> component of a postal address value is

encoded as a value of type t61StringSyntax.

2.24. User PassWord

Values of type userPasswordSyntax are encoded as if they were of type

octetStringSyntax.

2.25. User Certificate

Values of type userCertificate are encoded according to the following

BNF:

'#' <issuer> '#' <validity> '#' <subject>

'#' <public-key-info> '#' <encrypted-sign-value>

<signature-algorithm-id> ::= <algorithm-id>

<issuer> ::= an encoded Distinguished Name

<not-before-time> ::= <utc-time>

<not-after-time> ::= <utc-time>

<algorithm-parameters> ::= <null> <integervalue>

'{ASN}' <hex-string>

<subject> ::= an encoded Distinguished Name

<public-key-info> ::= <algorithm-id> '#' <encrypted-sign-value>

<encrypted-sign-value> ::= <hex-string> <hex-string> '-' <d>

<algorithm-id> ::= <oid> '#' <algorithm-parameters>

<utc-time> ::= an encoded UTCTime value

<hex-string> ::= <hex-digit> <hex-digit> <hex-string>

2.26. CA Certificate

Values of type cACertificate are encoded as if the values were of

type userCertificate.

2.27. Authority Revocation List

Values of type authorityRevocationList are encoded according to the

following BNF:

<certificate-list> ::= <signature-algorithm-id> '#' <issuer> '#' <utc-time>

[ '#' <revoked-certificates> ]

'#' <signature-algorithm-id>

'#' <encrypted-sign-value>

<revoked-certificates> ::= 1*( '#' <revoked-certificate> )

<signature-algorithm-id> '#' <encrypted-sign-value>

<revoked-certificate> ::= <signature-algorithm-id> '#' <issuer> '#'

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:

<certificate-pair> ::= <forward> '#' <reverse>

<forward> ::= 'forward:' <certificate>

<reverse> ::= 'reverse:' <certificate>

The syntactic component <certificate> has the same definition as in

the BNF for the userCertificate attribute syntax.

2.30. Delivery Method

Values of type deliveryMethod are encoded according to the following

BNF:

<delivery-value> ::= <pdm> <pdm> '$' <delivery-value>

<pdm> ::= 'any' 'mhs' 'physical' 'telex' 'teletex'

'g3fax' 'g4fax' 'ia5' 'videotex' 'telephone'

2.31. Other Mailbox

Values of the type otherMailboxSyntax are encoded according to the

following BNF:

<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:

<mail-preference> ::= "NO-LISTS" "ANY-LIST" "PROFESSIONAL-LISTS"

2.33. MHS OR Address

Values of type MHS OR Address are encoded as strings, according to

the format defined in [10].

2.34. Distribution List Submit Permission

Values of type DLSubmitPermission are encoded as strings, according

to the following BNF:

<dlsubmit-perm> ::= <dlgroup_label> ':' <dlgroup-value>

<dl-label> ':' <dl-value>

<dlgroup-label> ::= 'group_member'

<dlgroup-value> ::= <name>

<name> ::= an encoded Distinguished Name

<dl-label> ::= 'individual' 'dl_member' 'pattern'

<dl-value> ::= <orname>

<add-label> = 'X400'

<dn-label> = 'X500'

where <oraddress> is as defined in RFC1327.

2.35. Photo

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].

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",

RFC1274, 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",

RFC1278, 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", RFC1777, 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", RFC1495,

SINTEF DELAB, ISODE Consortium, Soft*Switch, Inc., Dover Beach

Consulting, Inc., Soft*Switch, Inc., August 1993.

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

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