

INTERNET-DRAFT                                                   S. Legg
draft-legg-ldap-binary-01.txt                        Adacel Technologies
Intended Category: Standards Track                          16 June 2004
Updates: RFC 2251bis


             Lightweight Directory Access Protocol (LDAP):
                       The Binary Encoding Option

    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.

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   This document is intended to be, after appropriate review and
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   Distribution of this document is unlimited.  Technical discussion of
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   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



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   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 defines an attribute option, the binary option, which can be
   used to specify that the associated attribute values are instead
   encoded according to the Basic Encoding Rules (BER) used by X.500
   directories.











































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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions. . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  The binary Option. . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Syntaxes Requiring Binary Transfer . . . . . . . . . . . . . .  4
   5.  Attributes Returned in a Search. . . . . . . . . . . . . . . .  5
   6.  All User Attributes. . . . . . . . . . . . . . . . . . . . . .  5
   7.  Conflicting Requests . . . . . . . . . . . . . . . . . . . . .  6
   8.  Security Considerations. . . . . . . . . . . . . . . . . . . .  6
   9.  IANA Considerations. . . . . . . . . . . . . . . . . . . . . .  6
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . .  6
       10.1.  Normative References. . . . . . . . . . . . . . . . . .  6
       10.2.  Informative References. . . . . . . . . . . . . . . . .  7
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . .  7
   Full Copyright Statement . . . . . . . . . . . . . . . . . . . . .  8

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 defines an attribute option, the binary option, 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 the Basic Encoding
   Rules (BER) [BER] as used by X.500 [X500] directories, instead of the
   usual LDAP-specific encoding.

   The binary option was originally defined in RFC 2251 [RFC2251].  The
   LDAP technical specification [ROADMAP] has obsoleted the previously
   defined LDAP technical specification [RFC3377], which included RFC
   2251.  However the binary option was not included in the newer LDAP
   technical specification due to a lack of consistency in its
   implementation.  This document reintroduces the binary option.
   However, except for the case of certain attribute syntaxes whose
   values are required to BER encoded, no attempt is made here to
   eliminate the known consistency problems.  Rather the focus is on
   capturing current behaviours.  A more thorough solution is left for a
   future specification.




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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].

3.  The binary Option

   The binary option is indicated with the attribute option string
   "binary" in an attribute description.  Note that, like all attribute
   options, the string representing the binary option is case
   insensitive.

   In terms of the protocol [PROT], the binary option specifies that the
   contents octets of the associated AttributeValue or AssertionValue
   OCTET STRING are a complete BER encoding of the relevant value.

   Where the binary option is present in an attribute description the
   associated attribute values or assertion value MUST be BER encoded.
   Note that it is possible for a syntax to be defined such that its
   LDAP-specific encoding is exactly the same as its BER encoding.

   The binary option is not a tagging option [MODELS] so the presence of
   the binary option does not specify an attribute subtype.  An
   attribute description containing the binary option references exactly
   the same attribute as the same attribute description without the
   binary option.  The supertype/subtype relationships of attributes
   with tagging options are not altered in any way by the presence or
   absence of the binary option.

   An attribute description SHALL be treated as unrecognized if it
   contains the binary option and the syntax of the attribute does not
   have an associated ASN.1 type [SYNTAX], or the BER encoding of that
   type is not supported.

   The presence or absence of the binary 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.  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



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   this is a property of the syntaxes themselves, and not a property of
   the binary option.

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
   the binary 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 the binary option).  The binary option in an
   attribute description in the requested attributes list implicitly
   applies to all the subtypes of the attribute type in the attribute
   description (however, see Section 7).

   Attributes of a syntax with the binary transfer requirement SHALL be
   returned in the binary form, i.e., with the binary option in the
   attribute description and the associated attribute values BER
   encoded, regardless of whether the binary option was present in the
   request (for the attribute or for one of its supertypes).

   Attributes of a syntax without the binary transfer requirement SHOULD
   be returned in the form explicitly requested.  That is, if the
   attribute description in the requested attributes list contains the
   binary option then the corresponding attribute in the result SHOULD
   be in the binary form.  If the attribute description in the request
   does not contain the binary option then the corresponding attribute
   in the result SHOULD NOT be in the binary form.  A server MAY omit an
   attribute from the result if it does not support the requested
   encoding.

   Regardless of the encoding chosen, a particular attribute value is
   returned at most once.

6.  All User Attributes

   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.

   Attributes of a syntax with the binary transfer requirement SHALL be
   returned in the binary form.




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   Attributes of a syntax without the binary transfer requirement and
   having a defined LDAP-specific encoding SHOULD NOT be returned in the
   binary form.

   Attributes of a syntax without the binary transfer requirement and
   without a defined LDAP-specific encoding may be returned in the
   binary form or omitted from the result.

7.  Conflicting Requests

   A particular attribute could be explicitly requested by an attribute
   description and/or implicitly requested by the attribute descriptions
   of one or more of its supertypes, or by the special attribute
   description string "*".  If the binary option is not present in all
   these attribute descriptions, nor absent in all these attribute
   descriptions, then the server is free to choose whether to return the
   attribute in the binary form.

8.  Security Considerations

   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 template:

      Subject: Request for
        LDAP Attribute Description Option Registration
      Option Name: binary
      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: The existing registration for "binary"
                should be updated to refer to RFC XXXX.

10.  References

10.1.  Normative References

   [KEYWORD]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.



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   [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.

   [PKI]      Chadwick, D. and S. Legg, "Internet X.509 Public Key
              Infrastructure Additional LDAP Schema for PKIs and PMIs",
              draft-pkix-ldap-schema-xx.txt, a work in progress, April
              2002.

   [BER]      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).

10.2.  Informative References

   [RFC2251]  Wahl, M., Howes, T. and S. Kille, "Lightweight Directory
              Access Protocol (v3)", RFC 2251, December 1997.

   [RFC3377]  Hodges, J. and R. Morgan, "Lightweight Directory Access
              Protocol (v3): Technical Specification", RFC 3377,
              September 2002.

   [X500]     ITU-T Recommendation X.500 (1993) | ISO/IEC 9594-1:1994,
              "Information Technology - Open Systems Interconnection -
              The Directory: Overview of concepts, models and services".

Author's Address




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   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

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