Network Working Group R. Weltman
Request for Comments: 3829 America Online
Category: Informational M. Smith
Pearl Crescent, LLC
M. WahlJuly 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 (C) The Internet Society (2004).
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.
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
The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
used in this document are to be interpreted as described in
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) 2.16.840.1.1137184.108.40.206 and
2.16.840.1.1137220.127.116.11, 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 "2.16.840.1.113718.104.22.168" and the controlValue is
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 "2.16.840.1.113722.214.171.124". 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
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.
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
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
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.
7. IANA Considerations
The OIDs 2.16.840.1.1137126.96.36.199 and 2.16.840.1.1137188.8.131.52 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].
8.1. Normative References
[LDAPv3] Hodges, J. and R. Morgan, "Lightweight Directory Access
Protocol (v3): Technical Specification", RFC 3377,
[LDAPPROT] Wahl, M., Howes, T. and S. Kille, "Lightweight
Directory Access Protocol (v3)", RFC 2251, December
[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,
8.2. Informative References
[AUTHZID] Zeilenga, K., "LDAP 'Who am I?' Operation", Work in
Progress, April 2002.
9. Author's Addresses
360 W. Caribbean Drive
Sunnyvale, CA 94089
Phone: +1 650 937-3194
Pearl Crescent, LLC
447 Marlpool Drive
Saline, MI 48176
Phone: +1 734 944-2856
PO Box 90626
Austin, TX 78709-0626
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