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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                                8 February 2004

                           LDAP Turn Operation

1.      Status of this Memo

  This document is an Internet-Draft and is in full conformance with all
  provisions of Section 10 of RFC2026.

  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>.

  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/ietf/1id-abstracts.txt>. The list of
  Internet-Draft Shadow Directories can be accessed at

  Copyright (C) The Internet Society (2004).  All Rights Reserved.

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


  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.

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1. Background and Intent of Use

  The Lightweight Directory Access Protocol (LDAP) [RFC3377] 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 requiring designing new authentication and other
  security features to support server-initiated LDAP sessions.

  This document instead introduces an operation, the Turn operation,
  which may be used to reverse the client / server roles of the
  protocol peers.  This allows the initiating protocol peer to be server
  (after 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 which desire to issue, as LDAP clients, operations
  against the other.  This may be useful in replicated environments.

  This operation is intended to used between protocol peers which have
  established a mutual agreement, by means outside of the protocol,
  which requires reversal of client / server roles or 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 5.1 of [RFC2251].

  The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
  document are to be interpreted as described in BCP 14 [RFC2119].

2. Turn Operation

  The Turn operation is defined as a LDAP Extended Operation [RFC2251,
  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

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  able to act both as client and server.

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

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

2.2. Turn Response

  A Turn response is an ExtendedResponse where the responseName and
  response 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 identities through appropriate authentication
    - establish appropriate data integrity, data confidentiality, and
      other protections,
    - establish an LDAP association between the initiating peer and the
      responding peer.

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

  That is, for peer A connecting to peer B listening and where TLS and

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  SASL/EXTERNAL were to be used, the sequence of operations would be:

      A->B: StartTLS
      A->B: Bind(SASL,EXTERNAL)
      A->B: Turn
      B->A: Bind(SASL,EXTERNAL)

4.  IANA Considerations

  Registration of the following values [RFC3383] 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
           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
      Author/Change Controller: Author
      Comments: none

5. Normative References

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

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  [RFC2251]     Wahl, M., T. Howes 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.

  [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

6. Informative References

  [RFC3383]     Zeilenga, K., "IANA Considerations for LDAP", BCP 64
                (also RFC 3383), September 2002.

7. Author's Address

  Kurt D. Zeilenga
  OpenLDAP Foundation

  Email: Kurt@OpenLDAP.org

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  rights by implementors or users of this specification can be obtained
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Full Copyright

  Copyright (C) The Internet Society (2004). All Rights Reserved.

  This document and translations of it may be copied and furnished to
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  or assist in its implementation may be prepared, copied, published and
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  or as required to translate it into languages other than English.

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