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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 <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





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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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