Lightweight Directory Access Protocol (LDAP) "Who am I?" Operation
draft-zeilenga-ldap-authzid-10

INTERNET-DRAFT                                      Kurt D. Zeilenga
Intended Category: Standard Track                OpenLDAP Foundation
Expires in six months                               19 November 2004

                        LDAP "Who am I?" Operation
                   <draft-zeilenga-ldap-authzid-10.txt>

Status of this Memo

  This document is intended to be, after appropriate review and
  revision, submitted to the RFC Editor 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@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.

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

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

Abstract

  This specification provides a mechanism for Lightweight Directory

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  Access Protocol (LDAP) clients to obtain the authorization identity
  which the server has associated with the user or application entity.
  This mechanism is specified as an LDAP extended operation called the
  LDAP "Who am I?" operation.

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 [RFC2119].

1. Background and Intent of Use

  This specification describes a Lightweight Directory Access Protocol
  (LDAP) [RFC3377] operation which clients can use to obtain the primary
  authorization identity in its primary form which the server has
  associated with the user or application entity.  The operation is
  called the "Who am I?" operation.

  This specification is intended to replace the existing [AUTHRESP]
  mechanism which uses Bind request and response controls to request and
  return the authorization identity.  Bind controls are not protected by
  the security layers established by the Bind operation which includes
  them.  While it is possible to establish security layers using Start
  TLS [RFC2830] prior to the Bind operation, it is often desirable to
  use security layers established by the Bind operation.  An extended
  operation sent after a Bind operation is protected by the security
  layers established by the Bind operation.

  There are other cases where it is desirable to request the
  authorization identity which the server associated with the client
  separately from the Bind operation.  For example, the "Who am I?"
  operation can be augmented with a Proxied Authorization Control
  [PROXYAUTH] to determine the authorization identity which the server
  associates with the identity asserted in the Proxied Authorization
  Control.  The "Who am I?" operation can also be used prior to the Bind
  operation.

  Servers often associate multiple authorization identities with the
  client and each authorization identity may be represented by multiple
  authzId [RFC2829] strings.  This operation requests and returns the
  authzId the server considers to be primary.  In the specification, the
  term "the authorization identity" and "the authzId" are generally to
  be read as "the primary authorization identity" and the "the primary
  authzId", respectively.

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2. The "Who am I?" Operation

  The "Who am I?" operation is defined as an LDAP Extended Operation
  [RFC2251, Section 4.12] identified by the whoamiOID Object Identifier
  (OID).  This section details the syntax of the operation's whoami
  request and response messages.

      whoamiOID ::= "1.3.6.1.4.1.4203.1.11.3"

2.1. The whoami Request

  The whoami request is an ExtendedRequest with the requestName field
  containing the whoamiOID OID and an absent requestValue field.  For
  example, a whoami request could be encoded as the sequence of octets
  (in hex):

      30 1e 02 01 02 77 19 80  17 31 2e 33 2e 36 2e 31
      2e 34 2e 31 2e 34 32 30  33 2e 31 2e 31 31 2e 33

2.2. The whoami Response

  The whoami response is an ExtendedResponse where the responseName
  field is absent and the response field, if present, is empty or an
  authzId [RFC2829].   For example, a whoami response returning the
  authzId "u:xxyyz@EXAMPLE.NET" (in response to the example request)
  would be encoded as the sequence of octets (in hex):

      30 21 02 01 02 78 1c 0a  01 00 04 00 04 00 8b 13
      75 3a 78 78 79 79 7a 40  45 58 41 4d 50 4c 45 2e
      4e 45 54

3. Operational Semantics

  The "Who am I?" operation provides a mechanism, a whoami Request, for
  the client to request that the server returns the authorization
  identity it currently associates with the client and provides a
  mechanism, a whoami Response, for the server to respond to that
  request.

  Servers indicate their support for this extended operation by
  providing whoamiOID object identifier as a value of the
  'supportedExtension' attribute type in their root DSE.  Server SHOULD
  advertise this extension only when the client is willing and able to
  perform this operation.

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  If the server is willing and able to provide the authorization
  identity it associates with the client, the server SHALL return a
  whoami Response with a success resultCode.  If the server is treating
  the client as an anonymous entity, the response field is present but
  empty.  Otherwise the server provides the authzId [RFC2829]
  representing the authorization identity it currently associates with
  the client in the response field.

  If the server is unwilling or unable to provide the authorization
  identity it associates with the client, the server SHALL return a
  whoami Response with an appropriate non-success resultCode (such as
  operationsError, protocolError, confidentialityRequired,
  insufficientAccessRights, busy, unavailable, unwillingToPerform, or
  other) and an absent response field.

  As described in [RFC2251] and [RFC2829], an LDAP session has an
  "anonymous" association until the client has been successfully
  authenticated using the Bind operation.  Clients MUST NOT invoke the
  "Who Am I?" operation while any Bind operation is in progress,
  including between two Bind requests made as part of a multi-stage Bind
  operation.  Where a whoami Request is received in violation of this
  absolute prohibition, the server should return a whoami Response with
  an operationsError resultCode.

4. Extending the "Who am I?" operation with controls

  Future specifications may extend the "Who am I?" operation using the
  control mechanism [RFC2251].  When extended by controls, the "Who am
  I?" operation requests and returns the authorization identity the
  server associates with the client in a particular context indicated by
  the controls.

4.1. Proxied Authorization Control

  The Proxied Authorization Control [PROXYAUTH] is used by clients to
  request that the operation it is attached to operates under the
  authorization of an assumed identity.  The client provides the
  identity to assume in the Proxied Authorization request control.  If
  the client is authorized to assume the requested identity, the server
  executes the operation as if the requested identity had issued the
  operation.

  As servers often map the asserted authzId to another identity
  [RFC2829], it is desirable to request the server provide the authzId
  it associates with the assumed identity.

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  When a Proxied Authorization Control is be attached to the "Who Am I?"
  operation, the operation requests the return of the authzId the server
  associates with the identity asserted in the Proxied Authorization
  Control.  The TBD result code is used to indicate that the server does
  not allow the client to assume the asserted identity.  [[Note to RFC
  Editor: TBD is to be replaced with the name/code assigned by IANA for
  [PROXYAUTH] use.]]

5. Security Considerations

  Identities associated with users may be sensitive information.  When
  so, security layers [RFC2829][RFC2830] should be established to
  protect this information.  This mechanism is specifically designed to
  allow security layers established by a Bind operation to protect the
  integrity and/or confidentiality of the authorization identity.

  Servers may place access control or other restrictions upon the use of
  this operation.  As stated in Section 3, the server SHOULD advertise
  this extension when it is willing and able to perform the operation.

  As with any other extended operations, general LDAP security
  considerations [RFC3377] apply.

6. IANA Considerations

  The OID 1.3.6.1.4.1.4203.1.11.3 is used to identify the LDAP "Who Am
  I?" extended operation.  This OID was assigned [ASSIGN] by OpenLDAP
  Foundation, under its IANA-assigned private enterprise allocation
  [PRIVATE], for use in this specification.

  Registration of this protocol mechanism [RFC3383] is requested.

  Subject: Request for LDAP Protocol Mechanism Registration
  Object Identifier: 1.3.6.1.4.1.4203.1.11.3
  Description: Who am I?
  Person & email address to contact for further information:
       Kurt Zeilenga <kurt@openldap.org>
  Usage: Extended Operation
  Specification: RFC XXXX
  Author/Change Controller: IESG
  Comments: none

7. Acknowledgment

  This document borrows from prior work in this area including

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  "Authentication Response Control" [AUTHRESP] by Rob Weltman, Mark
  Smith and Mark Wahl.

  The LDAP "Who am I?" operation takes it name from the UNIX whoami(1)
  command.  The whoami(1) command displays the effective user id.

8. Author's Address

  Kurt D. Zeilenga
  OpenLDAP Foundation

  Email: Kurt@OpenLDAP.org

9. References

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

9.1. Normative References

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

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

  [RFC2829]     Wahl, M., H. Alvestrand, and J. Hodges, RL "Bob" Morgan,
                "Authentication Methods for LDAP", RFC 2829, June 2000.

  [RFC2830]     Hodges, J., R. Morgan, and M. Wahl, "Lightweight
                Directory Access Protocol (v3): Extension for Transport
                Layer Security", RFC 2830, May 2000.

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

  [PROXYAUTH]   Weltman, R., "LDAP Proxy Authentication Control",
                draft-weltman-ldapv3-proxy-xx.txt, a work in progress.

9.2. Informative References

  [RFC3383]     Zeilenga, K., "IANA Considerations for LDAP", BCP 64

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                (also RFC 3383), September 2002.

  [AUTHRESP]    Weltman, R., M. Smith and M. Wahl, "LDAP Authorization
                Identity Response and Request Controls",
                draft-weltman-ldapv3-auth-response-xx.txt, a work in
                progress.

  [ASSIGN]      OpenLDAP Foundation, "OpenLDAP OID Delegations",
                http://www.openldap.org/foundation/oid-delegate.txt.

  [PRIVATE]     IANA, "Private Enterprise Numbers",
                http://www.iana.org/assignments/enterprise-numbers.

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  Copyright (C) The Internet Society (2004).  This document is subject
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