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Internet Engineering Task Force (IETF)                       K. ZeilengaRequest for Comments: 6171                                 Isode LimitedCategory: Standards Track                                     March 2011ISSN: 2070-1721The Lightweight Directory Access Protocol (LDAP) Don't Use Copy ControlAbstract   This document defines the Lightweight Directory Access Protocol   (LDAP) Don't Use Copy control extension, which allows a client to   specify that copied information should not be used in providing   service.  This control is based upon the X.511 dontUseCopy service   control option.Status of This Memo   This is an Internet Standards Track document.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Further information on   Internet Standards is available inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc6171.Copyright Notice   Copyright (c) 2011 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   include Simplified BSD License text as described in Section 4.e of   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.Zeilenga                     Standards Track                    [Page 1]

RFC 6171               LDAP Don't Use Copy Control            March 2011   This document may contain material from IETF Documents or IETF   Contributions published or made publicly available before November   10, 2008.  The person(s) controlling the copyright in some of this   material may not have granted the IETF Trust the right to allow   modifications of such material outside the IETF Standards Process.   Without obtaining an adequate license from the person(s) controlling   the copyright in such materials, this document may not be modified   outside the IETF Standards Process, and derivative works of it may   not be created outside the IETF Standards Process, except to format   it for publication as an RFC or to translate it into languages other   than English.1.  Background and Intended Usage   This document defines the Lightweight Directory Access Protocol   (LDAP) [RFC4510] Don't Use Copy control extension.  The control may   be attached to request messages to indicate that copied (replicated   or cached) information [X.500] is not be used in providing service.   This control is based upon the X.511 [X.511] dontUseCopy service   control option.   The Don't Use Copy control is intended to be used where the client   requires the service be provided using original (master) information   [X.500].  In absence of this control, the server is free to make use   of copied (i.e., non-authoritative) information in providing the   requested service.   For instance, a client might desire to have an authoritative answer   to a question of whether or not a particular user is a member of a   group.  To ask this question of a server, the client might issue a   compare request [RFC4511], with the Don't Use Copy control, where the   entry parameter is the Distinguished Name (DN) of the group, the   ava.attributeDesc is 'member', and the ava.assertionValue is the DN   of the user in question.  If the server has access to the original   (master) information directly or through chaining, it performs the   operation against the original (master) information and returns   compareTrue or compareFalse (or an error).  If the server does not   have access to the original information, the server is obligated to   either return a referral or an error.   It is not intended that this control be used generally (e.g., for all   LDAP interrogation operations) but only as required to ensure proper   directory application behavior.  In general, directory applications   ought to designed to use copied information well.Zeilenga                     Standards Track                    [Page 2]

RFC 6171               LDAP Don't Use Copy Control            March 20112.  Terminology   DSA stands for Directory System Agent (or server).   DSE stands for DSA-Specific Entry.   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 inRFC 2119 [RFC2119].3.  The Don't Use Copy Control   The Don't Use Copy control is an LDAP Control [RFC4511] whose   controlType is 1.3.6.1.1.22 and controlValue is absent.  The   criticality MUST be TRUE.  There is no corresponding response   control.   The control is appropriate for LDAP interrogation operations,   including Compare and Search operations [RFC4511].  It is   inappropriate for all other operations, including Abandon, Bind,   Delete, Modify, ModifyDN, StartTLS, and Unbind operations [RFC4511].   When the control is attached to an LDAP request, the requested   operation MUST NOT be performed on copied information.  That is, the   requested operation MUST be performed on original information.   If original (master) information for the target or base object of the   operation is not available (either locally or through chaining), the   server MUST either return a referral directing the client to a server   believed to be better able to service the request or return an   appropriate result code (e.g., unwillingToPerform).   It is noted that a referral, if returned, is not necessarily to the   server holding the original (master) information.  It is also noted   that an authoritative answer to the question might not be available   to the client for any number of reasons.   Where the client chases a referral to a server (as referenced by an   LDAP URL) in the server response in order to obtain an authoritative   response, the client MUST provide the dontUseCopy control with the   interrogation request it makes to the referred to server.  While LDAP   allows return of other kinds of URIs, the syntax and semantics of   other kinds of URIs are left to future specifications.  The    particulars of how to act upon other kinds of URIs are also left to   future specifications.Zeilenga                     Standards Track                    [Page 3]

RFC 6171               LDAP Don't Use Copy Control            March 2011   Servers implementing this technical specification SHOULD publish the   object identifier 1.3.6.1.1.22 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.4.  Security Considerations   This control is intended to be provided where providing service using   copied information might lead to unexpected application behavior.   Use of the Don't Use Copy control may permit an attacker to perform   or amplify a denial-of-service attack by causing additional server   resources to be employed, such as when the server chooses to chain   the request instead of returning a referral.  Servers capable of such   chaining can mitigate this threat by limiting chaining to a   particular group of authenticated entities.   LDAP is frequently used for storage and distribution of security-   sensitive information, including access control and security policy   information.  Failure to use the Don't Use Copy control may thus   permit an attacker to gain unauthorized access by allowing reliance   on stale data.5.  IANA Considerations5.1.  Object Identifier   IANA has assigned an LDAP Object Identifier [RFC4520] to identify the   LDAP Don't Use Copy Control defined in this document.      Subject: Request for LDAP Object Identifier Registration      Person & email address to contact for further information:          Kurt Zeilenga <Kurt.Zeilenga@Isode.COM>      Specification:RFC 6171      Author/Change Controller: IESG      Comments:          Identifies the LDAP Don't Use Copy ControlZeilenga                     Standards Track                    [Page 4]

RFC 6171               LDAP Don't Use Copy Control            March 20115.2.  LDAP Protocol Mechanism   IANA has registered this protocol mechanism [RFC4520] as follows.      Subject: Request for LDAP Protocol Mechanism Registration      Object Identifier: 1.3.6.1.1.22      Description: Don't Use Copy Control      Person & email address to contact for further information:          Kurt Zeilenga <Kurt.Zeilenga@Isode.COM>      Usage: Control      Specification:RFC 6171      Author/Change Controller: IESG      Comments: none6.  Acknowledgements   The author thanks Ben Campbell, Phillip Hallam-Baker, and Ted Hardie   for providing review and specific suggestions.7.  References7.1.  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., Ed., "Lightweight Directory Access Protocol              (LDAP): Directory Information Models",RFC 4512, June              2006.7.2.  Informative References   [X.500]    International Telecommunication Union - Telecommunication              Standardization Sector, "The Directory -- Overview of              concepts, models and services," X.500(1993) (also ISO/IEC              9594-1:1994).   [X.511]    International Telecommunication Union - Telecommunication              Standardization Sector, "The Directory: Abstract Service              Definition", X.511(1993) (also ISO/IEC 9594-3:1993).Zeilenga                     Standards Track                    [Page 5]

RFC 6171               LDAP Don't Use Copy Control            March 2011   [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   Isode Limited   EMail: Kurt.Zeilenga@Isode.COMZeilenga                     Standards Track                    [Page 6]