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rfc:rfc4528

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

Zeilenga Standards Track [Page 1] 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.

Zeilenga Standards Track [Page 2] 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.

Zeilenga Standards Track [Page 3] 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 <kurt@OpenLDAP.org>
     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 <kurt@openldap.org>
     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 <kurt@OpenLDAP.org>
     Result Code Name: assertionFailed
     Specification: RFC 4528
     Author/Change Controller: IESG
     Comments:  none

Zeilenga Standards Track [Page 4] 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

Zeilenga Standards Track [Page 5] RFC 4528 LDAP Assertion Control June 2006

Full Copyright Statement

 Copyright (C) The Internet Society (2006).
 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
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
 ENGINEERING TASK FORCE DISCLAIM 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.

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Acknowledgement

 Funding for the RFC Editor function is provided by the IETF
 Administrative Support Activity (IASA).

Zeilenga Standards Track [Page 6]

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