RFC 1488

The X.500 String Representation of Standard Attribute Syntaxes

📅 published July 1993, from ietf

RFC 1488 🎀 The X.500 String Representation of Standard Attribute Syntaxes

Bestie, this one is a whole vibe 💅 Here's the title block tea ☕

  • Number: RFC 1488 ✨
  • Authors: T. Howes (University of Michigan), S. Kille (ISODE Consortium), W. Yeong (Performance Systems International), and C. Robbins (NeXor Ltd.) 🧚
  • Date: July 1993 📅
  • Category: an IAB standards track protocol 🔥

Status of this Memo 🌸

Okay so this RFC is an IAB standards track protocol for the Internet community, and it's asking for discussion and suggestions for improvements 🫶 For the standardization state and status of this protocol, check the current edition of the "IAB Official Protocol Standards" 📚 Distribution of this memo is unlimited 🦋

Abstract 🦋

The Lightweight Directory Access Protocol (LDAP) [9] is giving strict energy here: the contents of AttributeValue fields in protocol elements have to be octet strings 💜 This document lays out the requirements that encoding rules MUST be satisfied by when they're rendering Directory attribute syntaxes into a form suitable for use in LDAP ✨ Then it 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 is where the general requirements live 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 😭 Like, to the greatest extent possible, encoded octet strings SHOULD be usable in their native encoded form for display purposes 🌈 Especially for attribute syntaxes defining non-binary values: their encoding rules SHOULD produce strings that can be displayed with little or no translation by clients implementing the lightweight directory protocols 🔥

2. Standard Attribute Syntax Encodings 🧚

Okay, so for defining the encoding rules for the standard attribute syntaxes, these auxiliary BNF definitions are going to 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

<letterstring> ::= <a> | <a> <letterstring>

<numericstring> ::= <d> | <d> <numericstring>

<keystring> ::= <a> | <a> <anhstring>

<anhstring> ::= <k> | <k> <anhstring>

<printablestring> ::= <p> | <p> <printablestring>

<space> ::= ' ' | ' ' <space>

2.1. Undefined 🫧

Values of type Undefined are encoded as if they were values of type Octet String 🌸

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, and it's giving very structured 💅

<caseignorelist> ::= <caseignorestring> |
                     <caseignorestring> '$' <caseignorelist>

<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 🫶

<caseexactlist> ::= <caseexactstring> |
                    <caseexactstring> '$' <caseexactlist>

<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, and it's a simple one 🙈

<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, and this part is so iconic 🔥

<oid> ::= <descr> | <descr> '.' <numericoid> | <numericoid>

<descr> ::= <keystring>

<numericoid> ::= <numericstring> | <numericstring> '.' <numericoid>

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, and it's a whole multi-part situation 🎀

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

<actual-number> ::= <printablestring>

<country> ::= <printablestring>

<answerback> ::= <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*( '$' <printablestring>)

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, and the parameters are lowkey the best part 🦋

<fax-number> ::= <printablestring> [ '$' <faxparameters> ]
<faxparameters> ::= <faxparm> | <faxparm> '$' <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, and it's giving logic puzzle 🧩

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

<object-class> ::= an encoded value of type objectIdentifierSyntax

<criteria> ::= <criteria-item> | <criteria-set> | '!' <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, and there are a lot of hash marks here 🙈

<certificate> ::= <signature> '#' <issuer> '#' <validity> '#' <subject>
                  '#' <public-key-info>

<signature> ::= <algorithm-id>

<issuer> ::= an encoded Distinguished Name

<validity> ::= <not-before-time> '#' <not-after-time>

<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-value>

<encrypted-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, and yes there are two <revoked-certificates> lines, it's not a typo 💀

<certificate-list> ::= <signature> '#' <issuer> '#'
                       <utc-time> [ '#' <revoked-certificates> ]

<revoked-certificates> ::= <algorithm> '#' <encrypted-value>
                           [ '#' 0*(<revoked-certificate>) '#']

<revoked-certificates> ::= <subject> '#' <algorithm> '#'
                           <serial> '#' <utc-time>

The syntactic components <algorithm>, <issuer>, <encrypted-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, and the pipe is doing a lot of work here 🫶

<certificate-pair> ::= <certificate> '|' <certificate>

The syntactic component <certificate> has the same definition as in the BNF for the userCertificate attribute syntax 🌈

2.30. Delivery Method 📬

Okay so values of type deliveryMethod get encoded using this BNF, and it's giving pure grammar energy 💅

<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 get encoded using this BNF 🎀

<otherMailbox> ::= <mailbox-type> '$' <mailbox>

<mailbox-type> ::= an encoded Printable String

<mailbox> ::= an encoded IA5 String

So the <mailbox-type> is the kind of mail system where the mailbox lives, like "Internet" or "MCIMail" 🌸 And the <mailbox> is the actual mailbox inside that mail system, the one defined by <mailbox-type>. Iconic pairing, honestly 🦋

2.32. Mail Preference 💌

Values of type mailPreferenceOption are encoded using this BNF ✨

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

2.33. MHS OR Address 📮

Values of type MHS OR Address are encoded as strings, following the format defined in [10]. No notes, just vibes 🫶

2.34. Photo 📸

Values of type Photo are encoded as if they were octet strings holding JPEG images in the JPEG File Interchange Format (JFIF), as described in [8]. Main character photo energy 👑

2.35. Fax 📠

Values of type Fax are encoded as if they were octet strings holding Group 3 Fax images, as defined in [7]. Old-school but iconic 🧚

3. Acknowledgements 🫶

Lowkey, a lot of the attribute syntax encodings in this document are adapted from the ones used in the QUIPU X.500 implementation. The authors of the QUIPU implementation get all the love for their work on the QUIPU syntaxes [4] 💜

4. 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 1485, July 1993.
  • [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 1487, Performance Systems International, University of Michigan, ISODE Consortium, July 1993.
  • [10] Kille, S., "Mapping between X.400(1988)/ISO 10021 and RFC 822", RFC 1327, University College London, May 1992.

5. Security Considerations 😱

Okay, prepare yourself 💀 Security issues are not discussed in this memo. The whole doc is silent on security, so don't go looking for it in here 🙈

6. Authors' Addresses 🦋

Tim Howes

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

Steve Kille
ISODE Consortium
PO Box 505
London
SW11 1DX
UK

Phone: +44-71-223-4062
EMail: S.Kille@isode.com

Wengyik Yeong

Wengyik Yeong
PSI, Inc.
510 Huntmar Park Drive
Herndon, VA 22070
USA

Phone: +1 703-450-8001
EMail: yeongw@psilink.com

Colin Robbins

Colin Robbins
NeXor Ltd
University Park
Nottingham
NG7 2RD
UK
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