Network Working Group                                         R. Weltman
Request for Comments: 3829                                America Online
Category: Informational                                         M. Smith
                                                     Pearl Crescent, LLC
                                                                 M. Wahl
                                                               July 2004

             Lightweight Directory Access Protocol (LDAP)
         Authorization Identity Request and Response Controls

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2004).

Abstract

   This document extends the Lightweight Directory Access Protocol
   (LDAP) bind operation with a mechanism for requesting and returning
   the authorization identity it establishes.  Specifically, this
   document defines the Authorization Identity Request and Response
   controls for use with the Bind operation.

1.  Introduction

   This document defines support for the Authorization Identity Request
   Control and the Authorization Identity Response Control for
   requesting and returning the authorization established in a bind
   operation.  The Authorization Identity Request Control may be
   submitted by a client in a bind request if authenticating with
   version 3 of the Lightweight Directory Access Protocol (LDAP)
   protocol [LDAPv3].  In the LDAP server's bind response, it may then
   include an Authorization Identity Response Control.  The response
   control contains the identity assumed by the client.  This is useful
   when there is a mapping step or other indirection during the bind, so
   that the client can be told what LDAP identity was granted.  Client
   authentication with certificates is the primary situation where this
   applies.  Also, some Simple Authentication and Security Layer [SASL]
   authentication mechanisms may not involve the client explicitly
   providing a DN, or may result in an authorization identity which is
   different from the authentication identity provided by the client
   [AUTH].




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   The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
   used in this document are to be interpreted as described in
   [RFCKeyWords].

2.  Publishing support for the Authorization Identity Request Control
    and the Authorization Identity Response Control

   Support for the Authorization Identity Request Control and the
   Authorization Identity Response Control is indicated by the presence
   of the Object Identifiers (OIDs) 2.16.840.1.113730.3.4.16 and
   2.16.840.1.113730.3.4.15, respectively, in the supportedControl
   attribute [LDAPATTRS] of a server's root DSA-specific Entry (DSE).

3.  Authorization Identity Request Control

   This control MAY be included in any bind request which specifies
   protocol version 3, as part of the controls field of the LDAPMessage
   as defined in [LDAPPROT].  In a multi-step bind operation, the client
   MUST provide the control with each bind request.

   The controlType is "2.16.840.1.113730.3.4.16" and the controlValue is
   absent.

4.  Authorization Identity Response Control

   This control MAY be included in any final bind response where the
   first bind request of the bind operation included an Authorization
   Identity Request Control as part of the controls field of the
   LDAPMessage as defined in [LDAPPROT].

   The controlType is "2.16.840.1.113730.3.4.15".  If the bind request
   succeeded and resulted in an identity (not anonymous), the
   controlValue contains the authorization identity (authzId), as
   defined in [AUTH] section 9, granted to the requestor.  If the bind
   request resulted in an anonymous association, the controlValue field
   is a string of zero length.  If the bind request resulted in more
   than one authzId, the primary authzId is returned in the controlValue
   field.

   The control is only included in a bind response if the resultCode for
   the bind operation is success.

   If the server requires confidentiality protections to be in place
   prior to use of this control (see Security Considerations), the
   server reports failure to have adequate confidentiality protections
   in place by returning the confidentialityRequired result code.





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   If the client has insufficient access rights to the requested
   authorization information, the server reports this by returning the
   insufficientAccessRights result code.

   Identities presented by a client as part of the authentication
   process may be mapped by the server to one or more authorization
   identities.  The bind response control can be used to retrieve the
   primary authzId.

   For example, during client authentication with certificates [AUTH], a
   client may possess more than one certificate and may not be able to
   determine which one was ultimately selected for authentication to the
   server.  The subject DN field in the selected certificate may not
   correspond exactly to a DN in the directory, but rather have gone
   through a mapping process controlled by the server.  Upon completing
   the certificate-based authentication, the client may issue a SASL
   [SASL] bind request, specifying the EXTERNAL mechanism and including
   an Authorization Identity Request Control.  The bind response MAY
   include an Authorization Identity Response Control indicating the DN
   in the server's Directory Information Tree (DIT) which the
   certificate was mapped to.

5.  Alternative Approach with Extended Operation

   The LDAP "Who am I?" [AUTHZID] extended operation provides a
   mechanism to query the authorization identity associated with a bound
   connection.  Using an extended operation, as opposed to a bind
   response control, allows a client to learn the authorization identity
   after the bind has established integrity and data confidentiality
   protections.  The disadvantages of the extended operation approach
   are coordination issues between "Who am I?" requests, bind requests,
   and other requests, and that an extra operation is required to learn
   the authorization identity.  For multithreaded or high bandwidth
   server application environments, the bind response approach may be
   preferable.

6.  Security Considerations

   The Authorization Identity Request and Response Controls are subject
   to standard LDAP security considerations.  The controls may be passed
   over a secure as well as over an insecure channel.  They are not
   protected by security layers negotiated by the bind operation.

   The response control allows for an additional authorization identity
   to be passed.  In some deployments, these identities may contain
   confidential information which require privacy protection.  In such
   deployments, a security layer should be established prior to issuing
   a bind request with an Authorization Identity Request Control.



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7.  IANA Considerations

   The OIDs 2.16.840.1.113730.3.4.16 and 2.16.840.1.113730.3.4.15 are
   reserved for the Authorization Identity Request and Response
   Controls, respectively.  The Authorization Identity Request Control
   has been registered as an LDAP Protocol Mechanism [IANALDAP].

8.  References

8.1.  Normative References

   [LDAPv3]      Hodges, J. and R. Morgan, "Lightweight Directory Access
                 Protocol (v3): Technical Specification", RFC 3377,
                 September 2002.

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

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

   [AUTH]        Wahl, M., Alvestrand, H., Hodges, J. and R. Morgan,
                 "Authentication Methods for LDAP", RFC 2829, May 2000.

   [SASL]        Myers, J., "Simple Authentication and Security Layer
                 (SASL)", RFC 2222, October 1997.

   [LDAPATTRS]   Wahl, M., Coulbeck, A., Howes, T. and S. Kille,
                 "Lightweight Directory Access Protocol (v3): Attribute
                 Syntax Definitions", RFC 2252, December 1997.

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

8.2.  Informative References

   [AUTHZID]     Zeilenga, K., "LDAP 'Who am I?' Operation", Work in
                 Progress, April 2002.











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9.  Author's Addresses

   Rob Weltman
   America Online
   360 W. Caribbean Drive
   Sunnyvale, CA 94089
   USA

   Phone: +1 650 937-3194
   EMail: robw@worldspot.com


   Mark Smith
   Pearl Crescent, LLC
   447 Marlpool Drive
   Saline, MI 48176
   USA

   Phone: +1 734 944-2856
   EMail: mcs@pearlcrescent.com


   Mark Wahl
   PO Box 90626
   Austin, TX 78709-0626
   USA

























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10.  Full Copyright Statement

   Copyright (C) The Internet Society (2004).  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
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.









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