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Versions: 00 01 02 03 RFC 4531

INTERNET-DRAFT                                   Kurt D. Zeilenga
Intended Category: Experimental                  OpenLDAP Foundation
Expires in six months                            10 February 2005



                           LDAP Turn Operation
                    <draft-zeilenga-ldap-turn-02.txt>


1.      Status of this Memo

  This document is intended to be, after appropriate review and
  revision, submitted to the RFC Editor for publication as an
  Experimental 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@OpenLDAP.org>.

  By submitting this Internet-Draft, I accept the provisions of Section
  4 of RFC 3667.  By submitting this Internet-Draft, I certify that any
  applicable patent or other IPR claims of which I am aware have been
  disclosed, or will be disclosed, and any of which I become aware will
  be disclosed, in accordance with RFC 3668.

  Internet-Drafts are working documents of the Internet Engineering Task
  Force (IETF), its areas, and its working groups. Note that other
  groups may also distribute working documents as Internet-Drafts.

  Internet-Drafts are draft documents valid for a maximum of six months
  and may be updated, replaced, or obsoleted by other documents at any
  time. It is inappropriate to use Internet-Drafts as reference material
  or to cite them other than as "work in progress."

  The list of current Internet-Drafts can be accessed at
  http://www.ietf.org/1id-abstracts.html

  The list of Internet-Draft Shadow Directories can be accessed at
  http://www.ietf.org/shadow.html


  Copyright (C) The Internet Society (2005).  All Rights Reserved.

  Please see the Full Copyright section near the end of this document
  for more information.


Abstract



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  This specification describes a Lightweight Directory Access Protocol
  (LDAP) extended operation to reverse (or "turn") the roles of client
  and server for subsequent protocol exchanges in the session, or to
  enable each peer to act as both client and server with respect to the
  other.


1. Background and Intent of Use

  The Lightweight Directory Access Protocol (LDAP) [Roadmap][Protocol]
  is a client-server protocol which typically operates over reliable
  octet-stream transports such as the Transport Control Protocol (TCP).
  Generally, the client initiates the stream by connecting to the
  server's listener at some well-known address.

  There are cases where it is desirable for the server to initiate the
  stream.  While it certainly is possible to write a technical
  specification detailing how to implement server-initiated LDAP
  sessions, this would require the design of new authentication and
  other security mechanisms to support server-initiated LDAP sessions.

  Instead, this document introduces an operation, the Turn operation,
  which may be used to reverse the client-servers roles of the protocol
  peers.  This allows the initiating protocol peer to become server
  (after the reversal).

  As an additional feature, the Turn operation may be used to allow both
  peers to act in both roles.  This is useful where both peers are
  directory servers that desire to request, as LDAP clients, operations
  be performed by the other.  This may be useful in replicated and/or
  distributed environments.

  This operation is intended to be used between protocol peers which
  have established a mutual agreement, by means outside of the protocol,
  which requires reversal of client-server roles, or allows both peers
  to act both as client and server.


1.1 Terminology

  Protocol elements are described using ASN.1 [X.680] with implicit
  tags.  The term "BER-encoded" means the element is to be encoded using
  the Basic Encoding Rules [X.690] under the restrictions detailed in
  Section 5.2 of [Protocol].

  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 [RFC2119].



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2. Turn Operation

  The Turn operation is defined as a LDAP Extended Operation [Protocol,
  Section 4.12] identified by the IANA-ASSIGNED-OID.  The function of
  the Turn Operation is to request that the client-server roles be
  reversed, or, optionally to request that both protocol peers to be
  able to act both as client and server in respect to the other.


2.1. Turn Request

  The Turn request is an ExtendedRequest with the requestName field
  containing the IANA-ASSIGNED-OID and a requestValue field is a
  BER-encoded turnValue:

       turnValue ::= SEQUENCE {
            mutual         BOOLEAN DEFAULT FALSE,
            identifier     LDAPString,
       }

  A TRUE mutual field value indicates a request to allow both peers to
  act both as client and server.  A FALSE mutual field value indicates a
  request to reserve the client and server roles.

  The value of the identifier field is a locally-defined policy
  identifier (typically associated with a mutual agreement for which
  this turn is be executed as part of).


2.2. Turn Response

  A Turn response is an ExtendedResponse where the responseName and
  responseValue fields are absent.  A resultCode of success is returned
  if and only if the responder is willing and able to turn the session
  as requested.  Otherwise, a different resultCode is returned.


3. Security Considerations

  It is generally recommended that before issuing the Turn operation the
  protocol peers:

    - establish each other's identities through appropriate
      authentication mechanism,
    - establish appropriate data integrity, data confidentiality, and
      other protections,
    - establish an LDAP association between the initiating peer and the
      responding peer.



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  And upon successful completion of turn:
    - establish an LDAP association in the reverse.

  That is, for peer A connecting to the listening peer B and where TLS
  and SASL/EXTERNAL were to be used, the sequence of LDAP messages could
  be:

      A->B: StartTLS Request
      B->A: StartTLS(success) Response
      A->B: Bind(SASL(EXTERNAL)) Request
      B->A: Bind(success) Response
      A->B: Turn(TRUE,"XXYYZ") Request
      B->A: Turn(success) Response
      B->A: Bind(SASL(EXTERNAL)) Request
      A->B: Bind(success) Response


4.  IANA Considerations

  Registration of the following values [BCP64bis] is requested.


4.1.  Object Identifier

  It is requested that IANA assign an LDAP Object Identifier to identify
  the LDAP Turn Operation as defined in this document.

      Subject: Request for LDAP Object Identifier Registration
      Person & email address to contact for further information:
           Kurt Zeilenga <kurt@OpenLDAP.org>
      Specification: RFC XXXX
      Author/Change Controller: Author
      Comments:
           Identifies the LDAP Turn Operation


4.2.  LDAP Protocol Mechanism

  It is requested that IANA register the LDAP Protocol Mechanism
  described in this document.

      Subject: Request for LDAP Protocol Mechanism Registration
      Object Identifier: IANA-ASSIGNED-OID
      Description: LDAP Turn Operation
      Person & email address to contact for further information:
           Kurt Zeilenga <kurt@openldap.org>
      Usage: Extended Operation
      Specification: RFC XXXX



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      Author/Change Controller: Author
      Comments: none


5. Author's Address

  Kurt D. Zeilenga
  OpenLDAP Foundation

  Email: Kurt@OpenLDAP.org


6. References

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


6.1. Normative References

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

  [Roadmap]     Zeilenga, K. (editor), "LDAP: Technical Specification
                Road Map", draft-ietf-ldapbis-roadmap-xx.txt, a work in
                progress.

  [Protocol]    Sermersheim, J. (editor), "LDAP: The Protocol",
                draft-ietf-ldapbis-protocol-xx.txt, a work in progress.

  [X.680]       International Telecommunication Union -
                Telecommunication Standardization Sector, "Abstract
                Syntax Notation One (ASN.1) - Specification of Basic
                Notation", X.680(1997) (also ISO/IEC 8824-1:1998).

  [X.690]       International Telecommunication Union -
                Telecommunication Standardization Sector, "Specification
                of ASN.1 encoding rules: Basic Encoding Rules (BER),
                Canonical Encoding Rules (CER), and Distinguished
                Encoding Rules (DER)", X.690(1997) (also ISO/IEC
                8825-1:1998).


6.2. Informative References

  [BCP64bis]    Zeilenga, K., "IANA Considerations for LDAP",
                draft-ietf-ldapbis-bcp64-xx.txt, a work in progress.



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Full Copyright

  Copyright (C) The Internet Society (2005).  This document is subject
  to the rights, licenses and restrictions contained in BCP 78, and
  except as set forth therein, the authors retain all their rights.

  This document and the information contained herein are provided on an
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