The Lightweight Directory Access Protocol (LDAP) Don't Use Copy Control
draft-zeilenga-ldap-dontusecopy-09

INTERNET-DRAFT                                   Kurt D. Zeilenga
Intended Category: Standard Track                Isode Limited
Expires in six months                            6 January 2011

                     The LDAP Don't Use Copy Control
                 <draft-zeilenga-ldap-dontusecopy-09.txt>

Status of this Memo

  This document is intended to be, after appropriate review and
  revision, submitted to the IESG for consideration as a Standard Track
  document.  Distribution of this memo is unlimited.  Technical
  discussion of this document will take place on the IETF LDAP
  Extensions mailing list <ldapext@ietf.org>.  Please send editorial
  comments directly to the author <Kurt.Zeilenga@Isode.COM>.

  This Internet-Draft is submitted to IETF in full conformance with the
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  Copyright (c) 2011 IETF Trust and the persons identified as the
  document authors.  All rights reserved.

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Abstract

  This document defines the Lightweight Directory Access Protocol (LDAP)
  Don't Use Copy control extension which allows a client to specify that
  copied information should not be used in providing service.  This
  control is based upon the X.511 dontUseCopy service control option.

1.  Background and Intended Usage

  This document defines the Lightweight Directory Access Protocol (LDAP)
  [RFC4510] Don't Use Copy control extension.  The control may be
  attached to request messages to indicate that copied (replicated or
  cached) information [X.500] is not be used in providing service.  This
  control is based upon the X.511 [X.511] dontUseCopy service control
  option.

  The Don't Use Copy control is intended to be used where the client
  requires the service be provided using original (master) information
  [X.500].  In absence of this control, the server is free to make use
  of copied information in providing the requested service.

  For instance, a client might desire to have an authoritative answer to
  a question of whether or not a particular user is a member of a group.
  To ask this question of a server, the client might issue a compare
  request [RFC4511], with the Don't Use Copy control, where the entry
  parameter is the Distinguished Name (DN) of the group, the
  ava.attributeDesc is 'member', and the ava.assertionValue is the DN of
  the user the client desires to know is or isn't a member of the group.
  If the server has access to the original (master) information directly
  or through chaining, it performs the operation against the original
  (master) information and return compareTrue or compareFalse (or an
  error).  If the server does not have access to the orignal
  information, the server is obligated to either return a referral or an
  error.

  It is noted that a referral, if returned, is not necessarily to the
  server holding the original (master) information.  It is also noted
  that an authoritative answer to the question might not be available to
  the client for any number of reasons.

  Where the client chases a referral to a server as referenced by an
  LDAP URL in the server response in order to obtain an authorative
  response , the client MUST provide the dontUseCopy control with the
  interrogation request it makes to the referred to server.  While LDAP
  allows return of other kinds of URIs, the syntax and semantics of
  other kinds of URIs, as well the particulars of acting upon such other
  kinds of URIs, to future specifications.  This document also leaves

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  the particulars of how to act upon other kinds of URIs to future
  specifications.  It is noted that in absence of some assurance that
  only authoratitive information is used in producing an answer, the
  client ought to assume non-authorative information is used.

  It is not intended that this control be used generally (e.g., for all
  LDAP interrogation operations) but only as required to ensure proper
  directory application behavior.  In general, directory applications
  ought to designed to well use copied information.

2. Terminology

  DSA stands for Directory System Agent (or server).
  DSE stands for DSA-specific Entry.

  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 RFC 2119 [RFC2119].

3.  The Don't Use Copy Control

  The Don't Use Copy control is an LDAP Control [RFC4511] whose
  controlType is IANA-ASSIGNED-OID and controlValue is absent.  The
  criticality MUST be TRUE.  There is no corresponding response control.

  The control is appropriate for LDAP interrogation operations,
  including Compare and Search operations [RFC4511].  It is
  inappropriate for all other operations, including Abandon, Bind,
  Delete, Modify, ModifyDN, StartTLS, and Unbind operations [RFC4511].

  When the control is attached to an LDAP request, the requested
  operation MUST NOT be performed on copied information.  That is, the
  requested operation MUST be performed on original information.

  If original (master) information for the target or base object of the
  operation is not available (either locally or through chaining), the
  server MUST either return a referral directing the client to a server
  believed to be better able to service the request or return an
  appropriate result code (e.g., unwillingToPerform).

  Servers implementing this technical specification SHOULD publish the
  object identifier IANA-ASSIGNED-OID as a value of the
  'supportedControl' attribute [RFC4512] in their root DSE.  A server
  MAY choose to advertise this extension only when the client is
  authorized to use it.

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4.  Security Considerations

  This control is intended to be provided where providing service using
  copied information might lead to unexpected application behavior.

  Use of the Don't Use Copy control may permit an attacker to perform or
  amplify a Denial of Service attack by causing additional server
  resources to be employed, such as when the server chooses to chain the
  request instead of returning a referral.  Server capable of such
  chaining can mitigate this threat by limiting chaining to a particular
  group of authenticated entities.

  LDAP is frequently used for storage and distribution of security
  sensitive information, including access control and security policy
  information. Failure to use the Don't Use Copy control may thus permit
  an attacker to gain unauthorized access by allowing reliance on stale
  data.

5.  IANA Considerations

5.1.  Object Identifier

  It is requested that IANA assign upon Standards Action an LDAP Object
  Identifier [RFC4520] to identify the LDAP Don't Use Copy Control
  defined in this document.

      Subject: Request for LDAP Object Identifier Registration
      Person & email address to contact for further information:
          Kurt Zeilenga <Kurt.Zeilenga@Isode.COM>
      Specification: RFC XXXX
      Author/Change Controller: IESG
      Comments:
          Identifies the LDAP Don't Use Copy Control

5.2  LDAP Protocol Mechanism

  Registration of this protocol mechanism [RFC4520] is requested.

      Subject: Request for LDAP Protocol Mechanism Registration
      Object Identifier: IANA-ASSIGNED-OID
      Description: Don't Use Copy Control
      Person & email address to contact for further information:
          Kurt Zeilenga <Kurt.Zeilenga@Isode.COM>
      Usage: Control
      Specification: RFC XXXX
      Author/Change Controller: IESG
      Comments: none

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6.  Acknowledgements

  The author thanks Ben Campbell, Phillip Hallam-Baker, and Ted Hardie
  for providing review and specific suggestions.

7.  Author's Address

  Kurt D. Zeilenga
  Isode Limited

  Email: Kurt.Zeilenga@Isode.COM

8. References

  [[Note to the RFC Editor: please replace the citation tags used in
  referencing Internet-Drafts with tags of the form RFCnnnn where
  possible.]]

8.1. Normative References

  [RFC2119]     Bradner, S., "Key words for use in RFCs to Indicate
                Requirement Levels", BCP 14 (also RFC 2119), March 1997.

  [RFC4510]     Zeilenga, K. (editor), "LDAP: Technical Specification
                Road Map", RFC 4510, June 2006.

  [RFC4511]     Sermersheim, J. (editor), "LDAP: The Protocol", RFC
                4511, June 2006.

  [RFC4512]     Zeilenga, K. (editor), "LDAP: Directory Information
                Models", RFC 4512, June 2006.

8.2. Informative References

  [X.500]       International Telecommunication Union -
                Telecommunication Standardization Sector, "The Directory
                -- Overview of concepts, models and services,"
                X.500(1993) (also ISO/IEC 9594-1:1994).

  [X.511]       International Telecommunication Union -
                Telecommunication Standardization Sector, "The
                Directory: Abstract Service Definition", X.511(1993)
                (also ISO/IEC 9594-3:1993).

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  [RFC4520]     Zeilenga, K., "Internet Assigned Numbers Authority
                (IANA) Considerations for the Lightweight Directory
                Access Protocol (LDAP)", RFC 4520, BCP 64, June 2006.

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