INTERNET-DRAFT Kurt D. Zeilenga
Intended Category: Standard Track OpenLDAP Foundation
Expires in six months 17 May 2002
LDAP Cancel Extended Operation
<draft-zeilenga-ldap-cancel-05.txt>
1. Status of this Memo
This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026.
This document is intended to be, after appropriate review and
revision, submitted to the RFC Editor as a Standard Track document.
Distribution of this memo is unlimited. Technical discussion of this
document will take place on the IETF LDAP Extension Working Group
mailing list <ietf-ldapext@netscape.com>. Please send editorial
comments directly to the author <Kurt@OpenLDAP.org>.
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Copyright 2002, The Internet Society. All Rights Reserved.
Please see the Copyright section near the end of this document for
more information.
Abstract
This specification describes an LDAP (Lightweight Directory Access
Protocol) extended operation to cancel (or abandon) an outstanding
operation. Unlike the LDAP Abandon operation but like the X.511 DAP
Abandon operation, this operation has a response which provides an
indication of its outcome.
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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].
Protocol elements are described using ASN.1 [X.680]. The term
"BER-encoded" means the element is to be encoded using the Basic
Encoding Rules [X.690] under the restrictions detailed in Section 5.1
of [RFC2251].
1. Background and Intent of Use
LDAP [RFC2251] provides an Abandon operation which clients may use to
cancel other operations. The Abandon operation does not have a
response and also calls for there to be no response of the abandoned
operation. These semantics provide the client with no clear
indication of the outcome of the Abandon operation.
X.511 DAP [X.511] provides an Abandon operation which does have a
response and also requires the abandoned operation to return a
response with indicating it was canceled. The Cancel operation is
modeled after the DAP Abandon operation.
The Cancel operation SHOULD be used instead of the LDAP Abandon
operation when the client needs an indication of the outcome. This
operation may be used to cancel both interrogation and update
operations.
4. Cancel Operation
The Cancel operation is defined as a LDAPv3 Extended Operation
[RFC2251, Section 4.12] identified by the OBJECT IDENTIFIER cancelOID.
This section details the syntax of the Cancel request and response
messages and defines additional LDAP resultCodes.
cancelOID OBJECT IDENTIFIER ::= IANA-ASSIGNED
cancelRequestValue ::= SEQUENCE {
cancelID MessageID
}
4.1. Cancel Request
The Cancel request is an ExtendedRequest with the requestName field
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containing cancelOID OID and a requestValue field which contains a
cancelRequestValue value encoded per [RFC2251, Section 5.1]. The
cancelID field contains the message id associated with the operation
to be canceled.
4.2. Cancel Response
A Cancel response is an ExtendedResponse where the responseName and
response fields are absent.
4.3. Additional Result Codes
Implementations of this specification SHALL recognize the following
additional resultCode values:
canceled (IANA-ASSIGNED-1)
noSuchOperation (IANA-ASSIGNED-2)
tooLate (IANA-ASSIGNED-3)
cannotCancel (IANA-ASSIGNED-4)
5. Operational Semantics
The function of the Cancel Operation is to request that the server
cancel an outstanding operation issued within the same session.
The client requests the cancelation of an outstanding operation by
issuing a Cancel Response with a cancelID with the message id
identifying the outstanding operation. The Cancel Request itself has
a distinct message id. Clients SHOULD NOT request cancelation of an
operation multiple times.
If the server is unable to parse the requestValue or the requestValue
is absent, the server shall return protocolError.
If the server is willing and able to cancel the outstanding operation
identified by the cancelId, the server SHALL return a Cancel Response
with a success resultCode and the canceled operation SHALL fail with
canceled resultCode. Otherwise the Cancel Response SHALL have a
non-success resultCode and SHALL NOT have impact upon the outstanding
operation (if it exists).
The server SHALL return noSuchOperation if it has no knowledge of the
operation requested to be canceled.
The server SHALL return cannotCancel if the identified operation does
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not support cancelation or the cancel operation could not be
performed. The following classes of operations are not cancelable:
- operations which have no response,
- operations which associate or disassociate authentication and/or
authorization associations,
- operations which establish or tear-down security services, and
- operations which abandon or cancel other operations.
Specifically, Abandon, Bind, Start TLS [RFC2830], Unbind and Cancel
operations are not cancelable.
If the result of the outstanding operation has been determined by the
server, the outstanding operation SHALL NOT be canceled and the cancel
operation SHALL result in tooLate.
Servers SHOULD indicate their support for this extended operation by
providing cancelOID as a value of the supportedExtension attribute
type in their root DSE. A server MAY choose to advertise this
extension only when the client is authorized and/or has established
the necessary security protections to use this operation. Clients
SHOULD verify the server implements this extended operation prior to
attempting the operation by asserting the supportedExtension attribute
contains a value of cancelOID.
6. Security Considerations
This operation is intended to allow a user to cancel operations they
previously issued. No user should be allowed to cancel an operation
issued by another user (within the same session or not). However, as
this operation may only be used to cancel within the same session and
LDAP requires operations to be abandoned upon bind requests, this is a
non-issue.
Some operations should not be cancelable for security reasons. This
specification disallows cancelation of Bind operation and Start TLS
extended operation so as to avoid adding complexity to authentication,
authorization, and security layer semantics. Designers of future
extended operations and/or controls SHOULD disallow abandonment and
cancelation when appropriate.
7. IANA Considerations
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7.1. Object Identifiers
It is requested that IANA register a Directory Number OID for use in
this document upon Standards Action by the IESG. This OID will be
used to identify the LDAP Cancel extended operation as indicated
above. The following registration template is suggested:
Subject: Request for LDAP OID Registration
Person & email address to contact for further information:
Kurt Zeilenga <kurt@OpenLDAP.org>
Specification: RFCXXX
Author/Change Controller: IESG
7.2. LDAP Result Codes
It is requested that IANA register the LDAP result codes:
canceled (IANA-ASSIGNED-1)
noSuchOperation (IANA-ASSIGNED-2)
tooLate (IANA-ASSIGNED-3)
cannotCancel (IANA-ASSIGNED-4)
upon Standards Action by the IESG. The following registration
template is suggested:
Subject: LDAP Result Code Registration
Person & email address to contact for further information:
Kurt Zeilenga <kurt@OpenLDAP.org>
Result Code Name: canceled
Result Code Name: noSuchOperation
Result Code Name: tooLate
Result Code Name: cannotCancel
Specification: RFCXXXX
Author/Change Controller: IESG
Comments: request four consecutive result codes be assigned
8. Acknowledgment
This document is based upon input from the IETF LDAPext working group.
9. Normative References
[RFC2119] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14 (also RFC 2119), March 1997.
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[RFC2251] M. Wahl, T. Howes, S. Kille, "Lightweight Directory Access
Protocol (v3)", RFC 2251, December 1997.
[RFC2830] J. Hodges, R. Morgan, and M. Wahl, "Lightweight Directory
Access Protocol (v3): Extension for Transport Layer
Security", RFC 2830, May 2000.
[X.680] ITU-T, "Abstract Syntax Notation One (ASN.1) - Specification
of Basic Notation", X.680, 1994.
[X.690] ITU-T, "Specification of ASN.1 encoding rules: Basic,
Canonical, and Distinguished Encoding Rules", X.690, 1994.
9. Informative References
[X.511] ITU-T Rec. X.511, "The Directory: Abstract Service
Definition", 1993.
11. Author's Address
Kurt D. Zeilenga
OpenLDAP Foundation
<Kurt@OpenLDAP.org>
Copyright 2002, The Internet Society. All Rights Reserved.
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