Network Working Group R. Weltman
Request for Comments: 4370 Yahoo!, Inc.
Category: Standards Track February 2006
Lightweight Directory Access Protocol (LDAP)
Proxied Authorization Control
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
This document defines the Lightweight Directory Access Protocol
(LDAP) Proxy Authorization Control. The Proxy Authorization Control
allows a client to request that an operation be processed under a
provided authorization identity instead of under the current
authorization identity associated with the connection.
1. Introduction
Proxy authorization allows a client to request that an operation be
processed under a provided authorization identity instead of under
the current authorization identity associated with the connection.
This document defines support for proxy authorization using the
Control mechanism [RFC2251]. The Lightweight Directory Access
Protocol [LDAPV3] supports the use of the Simple Authentication and
Security Layer [SASL] for authentication and for supplying an
authorization identity distinct from the authentication identity,
where the authorization identity applies to the whole LDAP session.
The Proxy Authorization Control provides a mechanism for specifying
an authorization identity on a per-operation basis, benefiting
clients that need to perform operations efficiently on behalf of
multiple users.
The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
used in this document are to be interpreted as described in
[KEYWORDS].
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RFC 4370 LDAP Proxied Authorization Control February 2006
2. Publishing Support for the Proxy Authorization Control
Support for the Proxy Authorization Control is indicated by the
presence of the Object Identifier (OID) "2.16.840.1.113730.3.4.18" in
the supportedControl attribute [RFC2252] of a server's root
DSA-specific Entry (DSE).
3. Proxy Authorization Control
A single Proxy Authorization Control may be included in any search,
compare, modify, add, delete, or modify Distinguished Name (DN) or
extended operation request message. The exception is any extension
that causes a change in authentication, authorization, or data
confidentiality [RFC2829], such as Start TLS [LDAPTLS] as part of the
controls field of the LDAPMessage, as defined in [RFC2251].
The controlType of the proxy authorization control is
"2.16.840.1.113730.3.4.18".
The criticality MUST be present and MUST be TRUE. This requirement
protects clients from submitting a request that is executed with an
unintended authorization identity.
Clients MUST include the criticality flag and MUST set it to TRUE.
Servers MUST reject any request containing a Proxy Authorization
Control without a criticality flag or with the flag set to FALSE with
a protocolError error. These requirements protect clients from
submitting a request that is executed with an unintended
authorization identity.
The controlValue SHALL be present and SHALL either contain an authzId
[AUTH] representing the authorization identity for the request or be
empty if an anonymous association is to be used.
The mechanism for determining proxy access rights is specific to the
server's proxy authorization policy.
If the requested authorization identity is recognized by the server,
and the client is authorized to adopt the requested authorization
identity, the request will be executed as if submitted by the proxy
authorization identity; otherwise, the result code 123 is returned.
4. Implementation Considerations
One possible interaction of proxy authorization and normal access
control is illustrated here. During evaluation of a search request,
an entry that would have been returned for the search (if submitted
by the proxy authorization identity directly) may not be returned if
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RFC 4370 LDAP Proxied Authorization Control February 2006
the server finds that the requester does not have the right to assume
the requested identity for searching the entry, even if the entry is
within the scope of a search request under a base DN that does imply
such rights. This means that fewer results, or no results, may be
returned than would be if the proxy authorization identity issued the
request directly. An example of such a case may be a system with
fine-grained access control, where the proxy right requester has
proxy rights at the top of a search tree, but not at or below a point
or points within the tree.
5. Security Considerations
The Proxy Authorization Control method is subject to general LDAP
security considerations [RFC2251] [AUTH] [LDAPTLS]. The control may
be passed over a secure channel as well as over an insecure channel.
The control allows for an additional authorization identity to be
passed. In some deployments, these identities may contain
confidential information that requires privacy protection.
Note that the server is responsible for determining if a proxy
authorization request is to be honored. "Anonymous" users SHOULD NOT
be allowed to assume the identity of others.
6. IANA Considerations
The OID "2.16.840.1.113730.3.4.18" is reserved for the Proxy
Authorization Control. It has been registered as an LDAP Protocol
Mechanism [RFC3383].
A result code (123) has been assigned by the IANA for the case where
the server does not execute a request using the proxy authorization
identity.
7. Acknowledgements
Mark Smith, formerly of Netscape Communications Corp., Mark Wahl,
formerly of Sun Microsystems, Inc., Kurt Zeilenga of OpenLDAP
Foundation, Jim Sermersheim of Novell, and Steven Legg of Adacel have
contributed with reviews of this document.
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RFC 4370 LDAP Proxied Authorization Control February 2006
8. Normative References
[KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[LDAPV3] Hodges, J. and R. Morgan, "Lightweight Directory Access
Protocol (v3): Technical Specification", RFC 3377,
September 2002.
[SASL] Myers, J., "Simple Authentication and Security Layer
(SASL)", RFC 2222, October 1997.
[AUTH] Wahl, M., Alvestrand, H., Hodges, J., and R. Morgan,
"Authentication Methods for LDAP", RFC 2829, May 2000.
[LDAPTLS] Hodges, J., Morgan, R., and M. Wahl, "Lightweight
Directory Access Protocol (v3): Extension for Transport
Layer Security", RFC 2830, May 2000.
[RFC2251] Wahl, M., Howes, T., and S. Kille, "Lightweight Directory
Access Protocol (v3)", RFC 2251, December 1997.
[RFC2252] Wahl, M., Coulbeck, A., Howes, T., and S. Kille,
"Lightweight Directory Access Protocol (v3): Attribute
Syntax Definitions", RFC 2252, December 1997.
[RFC2829] Wahl, M., Alvestrand, H., Hodges, J., and R. Morgan,
"Authentication Methods for LDAP", RFC 2829, May 2000.
[RFC3383] Zeilenga, K., "Internet Assigned Numbers Authority (IANA)
Considerations for the Lightweight Directory Access
Protocol (LDAP)", BCP 64, RFC 3383, September 2002.
Author's Address
Rob Weltman
Yahoo!, Inc.
701 First Avenue
Sunnyvale, CA 94089
USA
Phone: +1 408 349-5504
EMail: robw@worldspot.com
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RFC 4370 LDAP Proxied Authorization Control February 2006
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