Network Working Group K. Zeilenga
Request for Comments: 4528 OpenLDAP Foundation
Category: Standards Track June 2006
Lightweight Directory Access Protocol (LDAP)
Assertion 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) Assertion Control, which allows a client to specify that a
directory operation should only be processed if an assertion applied
to the target entry of the operation is true. It can be used to
construct "test and set", "test and clear", and other conditional
operations.
Table of Contents
1. Overview ........................................................2
2. Terminology .....................................................2
3. The Assertion Control ...........................................2
4. Security Considerations .........................................3
5. IANA Considerations .............................................4
5.1. Object Identifier ..........................................4
5.2. LDAP Protocol Mechanism ....................................4
5.3. LDAP Result Code ...........................................4
6. Acknowledgements ................................................5
7. References ......................................................5
7.1. Normative References .......................................5
7.2. Informative References .....................................5
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RFC 4528 LDAP Assertion Control June 2006
1. Overview
This document defines the Lightweight Directory Access Protocol
(LDAP) [RFC4510] assertion control. The assertion control allows the
client to specify a condition that must be true for the operation to
be processed normally. Otherwise, the operation is not performed.
For instance, the control can be used with the Modify operation
[RFC4511] to perform atomic "test and set" and "test and clear"
operations.
The control may be attached to any update operation to support
conditional addition, deletion, modification, and renaming of the
target object. The asserted condition is evaluated as an integral
part the operation.
The control may also be used with the search operation. Here, the
assertion is applied to the base object of the search before
searching for objects that match the search scope and filter.
The control may also be used with the compare operation. Here, it
extends the compare operation to allow a more complex assertion.
2. Terminology
Protocol elements are described using ASN.1 [X.680] with implicit
tags. 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 [RFC4511].
DSA stands for Directory System Agent (or server).
DSE stands for DSA-specific Entry.
In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" are to be interpreted as described in BCP 14
[RFC2119].
3. The Assertion Control
The assertion control is an LDAP Control [RFC4511] whose controlType
is 1.3.6.1.1.12 and whose controlValue is a BER-encoded Filter
[Protocol, Section 4.5.1]. The criticality may be TRUE or FALSE.
There is no corresponding response control.
The control is appropriate for both LDAP interrogation and update
operations [RFC4511], including Add, Compare, Delete, Modify,
ModifyDN (rename), and Search. It is inappropriate for Abandon,
Bind, Unbind, and StartTLS operations.
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RFC 4528 LDAP Assertion Control June 2006
When the control is attached to an LDAP request, the processing of
the request is conditional on the evaluation of the Filter as applied
against the target of the operation. If the Filter evaluates to
TRUE, then the request is processed normally. If the Filter
evaluates to FALSE or Undefined, then assertionFailed (122)
resultCode is returned, and no further processing is performed.
For Add, Compare, and ModifyDN operations, the target is indicated by
the entry field in the request. For Modify operations, the target is
indicated by the object field. For Delete operations, the target is
indicated by the DelRequest type. For Compare operations and all
update operations, the evaluation of the assertion MUST be performed
as an integral part of the operation. That is, the evaluation of the
assertion and the normal processing of the operation SHALL be done as
one atomic action.
For Search operations, the target is indicated by the baseObject
field, and the evaluation is done after "finding" but before
"searching" [RFC4511]. Hence, no entries or continuations references
are returned if the assertion fails.
Servers implementing this technical specification SHOULD publish the
object identifier 1.3.6.1.1.12 as a value of the 'supportedControl'
attribute [RFC4512] in their root DSE. A server MAY choose to
advertise this extension only when the client is authorized to use
it.
Other documents may specify how this control applies to other LDAP
operations. In doing so, they must state how the target entry is
determined.
4. Security Considerations
The filter may, like other components of the request, contain
sensitive information. When it does, this information should be
appropriately protected.
As with any general assertion mechanism, the mechanism can be used to
determine directory content. Hence, this mechanism SHOULD be subject
to appropriate access controls.
Some assertions may be very complex, requiring significant time and
resources to evaluate. Hence, this mechanism SHOULD be subject to
appropriate administrative controls.
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RFC 4528 LDAP Assertion Control June 2006
Security considerations for the base operations [RFC4511] extended by
this control, as well as general LDAP security considerations
[RFC4510], generally apply to implementation and use of this
extension.
5. IANA Considerations
5.1. Object Identifier
The IANA has assigned an LDAP Object Identifier [RFC4520] to identify
the LDAP Assertion Control defined in this document.
Subject: Request for LDAP Object Identifier Registration
Person & email address to contact for further information:
Kurt Zeilenga
Specification: RFC 4528
Author/Change Controller: IESG
Comments:
Identifies the LDAP Assertion Control
5.2. LDAP Protocol Mechanism
Registration of this protocol mechanism [RFC4520] is requested.
Subject: Request for LDAP Protocol Mechanism Registration
Object Identifier: 1.3.6.1.1.12
Description: Assertion Control
Person & email address to contact for further information:
Kurt Zeilenga
Usage: Control
Specification: RFC 4528
Author/Change Controller: IESG
Comments: none
5.3. LDAP Result Code
The IANA has assigned an LDAP Result Code [RFC4520] called
'assertionFailed' (122).
Subject: LDAP Result Code Registration
Person & email address to contact for further information:
Kurt Zeilenga
Result Code Name: assertionFailed
Specification: RFC 4528
Author/Change Controller: IESG
Comments: none
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RFC 4528 LDAP Assertion Control June 2006
6. Acknowledgements
The assertion control concept is attributed to Morteza Ansari.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4510] Zeilenga, K., Ed., "Lightweight Directory Access
Protocol (LDAP): Technical Specification Road Map", RFC
4510, June 2006.
[RFC4511] Sermersheim, J., Ed., "Lightweight Directory Access
Protocol (LDAP): The Protocol", RFC 4511, June 2006.
[RFC4512] Zeilenga, K., "Lightweight Directory Access Protocol
(LDAP): Directory Information Models", RFC 4512, June
2006.
[X.680] International Telecommunication Union -
Telecommunication Standardization Sector, "Abstract
Syntax Notation One (ASN.1) - Specification of Basic
Notation", X.680(2002) (also ISO/IEC 8824-1:2002).
[X.690] International Telecommunication Union -
Telecommunication Standardization Sector,
"Specification of ASN.1 encoding rules: Basic Encoding
Rules (BER), Canonical Encoding Rules (CER), and
Distinguished Encoding Rules (DER)", X.690(2002) (also
ISO/IEC 8825-1:2002).
7.2. Informative References
[RFC4520] Zeilenga, K., "Internet Assigned Numbers Authority
(IANA) Considerations for the Lightweight Directory
Access Protocol (LDAP)", BCP 64, RFC 4520, June 2006.
Author's Address
Kurt D. Zeilenga
OpenLDAP Foundation
EMail: Kurt@OpenLDAP.org
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RFC 4528 LDAP Assertion Control June 2006
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