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
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Copyright (C) The Internet Society (2004). All Rights Reserved.
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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:[email protected]" (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 <[email protected]>
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: [email protected]
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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Full Copyright
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
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