INTERNET-DRAFT Rob Weltman
Intended Category: Informational Mark Smith
Netscape Communications Corp.
Mark Wahl
Sun Microsystems, Inc.
April 2002
LDAP Authorization Identity Bind Control
draft-weltman-ldapv3-auth-response-07.txt
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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Abstract
This document defines a way for an LDAP [LDAPv3] server to return the
identity assumed by a client on binding using the LDAP Control
mechanism .
1. Introduction
This document defines support for the Authentication Request Control
and the Authorization Identity Bind Control. The Authentication
Request Control may be submitted by a client in a bind request if
authenticating with version 3 of the LDAP protocol [LDAPv3]. In the
LDAP server's bind response, it may then include an Authorization
Identity Bind 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
SASL authentication mechanisms may not involve the client explicitly
providing a DN, or may result in an authorization identity which is
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different from the authentication identity provided by the client
[AUTH].
The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", "MAY", and
"MAY NOT" used in this document are to be interpreted as described
in [RFCKeyWords].
2. Publishing support for the Authentication Request Control and the
Authorization Identity Bind Control
Support for the Authentication Request Control and the Authorization
Identity Bind Control is indicated by the presence of the OIDs
2.16.840.1.113730.3.4.16 and 2.16.840.1.113730.3.4.15, respectively,
in the supportedControl attribute of a server's root DSE.
3. Authorization Identity Bind 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 [LDAPv3]. 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 Authentication
Request Control as part of the controls field of the LDAPMessage as
defined in [LDAPv3].
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 anonymous authentication, 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 request control is marked critical and the client is not
authorized for it, the server MUST return a resultCode of
insufficientAccessRights. If the request control is not marked
critical and the client is not authorized for it, the server MUST NOT
include a response control with the bind response.
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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 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. On completing the
certificate-based authentication, the client may issue a SASL [SASL]
bind request, specifying the EXTERNAL mechanism and including an
Authorization Identity Bind Control. The bind response MAY include an
Authorization Identity Response Control indicating the DN in the
server's 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 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 Response Control is subject to standard
LDAP security considerations. The control may be passed over a secure
as well as over an insecure channel. It is not protected by security
layers negotiated by the bind operation.
The 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 Bind Control.
7. Copyright
Copyright (C) The Internet Society (2000). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
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or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS 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.
8. Bibliography
[LDAPv3] M. Wahl, T. Howes, S. Kille, "Lightweight Directory Access
Protocol (v3)", RFC 2251, December 1997.
[RFCKeyWords] Bradner, Scott, "Key Words for use in RFCs to Indicate
Requirement Levels", draft-bradner-key-words-03.txt, January
1997.
[AUTH] M. Wahl, H. Alvestrand, J. Hodges, RL "Bob" Morgan,
"Authentication Methods for LDAP", RFC 2829, May 2000.
[SASL] J. Myers, "Simple Authentication and Security Layer (SASL",
RFC 2222, October 1997.
[ASN.1] X.680 : ITU-T Recommendation X.680 (1997) | ISO/IEC 8824-
1:1998, Information Technology - Abstract Syntax Notation One
(ASN.1): Specification of Basic Notation
[AUTHZID] K. Zeilenga, "LDAP 'Who am I?' Operation", draft-zeilenga-
ldap-authzid-02.txt, March 2002
9. Author's Addresses
Rob Weltman
Netscape Communications Corp.
466 Ellis Street
Mountain View, CA 94043
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USA
+1 650 937-3194
rweltman@netscape.com
Mark Smith
Netscape Communications Corp.
466 Ellis Street
Mountain View, CA 94043
USA
+1 650 937-3477
mcs@netscape.com
Mark Wahl
Sun Microsystems, Inc.
911 Capital of Texas Hwy, Suite 4140
Austin, TX 78759
USA
+1 512 231 7224
Mark.Wahl@sun.com
10. Revision history
10.1 Changes from draft-weltman-ldapv3-auth-response-06.txt
General
Changed Intended Category from Standards Track to Informational.
Swapped the Abstract and Introduction sections
Added section "Alternative Approach with Extended Operation"
10.2 Changes from draft-weltman-ldapv3-auth-response-05.txt
General
Change name of control from "Authentication Response Control" to
"Authorization Identity Bind Control".
Authorization Identity Bind Control
Control must be provided with each bind request in a multi-step bind.
Replaced "failure" with "resultCode other than success".
Authorization Identity Response Control
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There may be more than one authzId.
10.3 Changes from draft-weltman-ldapv3-auth-response-04.txt
Authentication Request Control
Removed clause saying that the control may not be marked critical.
Added sentence stating that the server should ignore authentication
request controls other than on the first bind request in a multi-step
bind operation.
Authorization Identity Bind Control
Added "(authzId)" to "authorization identity".
Security Considerations
Added a sentence recommending that a security layer be negotiated
before issuing a bind request with the authentication request control
in deployments where the authorization identity requires privacy
protection.
10.4 No Changes from draft-weltman-ldapv3-auth-response-03.txt
No changes
10.5 Changes from draft-weltman-ldapv3-auth-response-02.txt
Publishing support
The controls are published in supportedControl, not
supportedExtension.
Authorization Identity Bind Control
The value of an Authorization Identity Bind Control is an
authorization identity, not necessarily a DN.
Security Considerations
Added a short discussion of the fact that an identity is exposed in
the response control.
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Miscellaneous
Eliminated BNF for control contents.
10.6 Changes from draft-weltman-ldapv3-auth-response-01.txt
Authentication Request Control
An Authorization Identity Bind Control is now only returned if the
client requested one by submitting an Authentication Request Control.
Contents of Authorization Identity Bind Control
Rather than returning both the authentication DN and the
authentication mechanism, the control only returns the authentication
DN.
10.7 Changes from draft-weltman-ldapv3-auth-response-00.txt
Capitalization of ASN.1 macros
AuthResponseControl and AuthResponseValue are capitalized.
Clarifications
Added sentence on behavior for anonymous binds.
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