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Network Working Group P. Masarati Internet-Draft Politecnico di Milano Intended status: Standards Track H. Chu Expires: May 23, 2009 Symas Corp. November 19, 2008 LDAP Dereference Control draft-masarati-ldap-deref-00.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on May 23, 2009. Masarati & Chu Expires May 23, 2009 [Page 1]  Internet-Draft LDAP Deref November 2008 Abstract This document describes the Dereference Control for LDAP. This control is intended to provide a concise means to collect extra information related to cross-links present in entries returned as part of search responses. Table of Contents 1. Background and Intended Use . . . . . . . . . . . . . . . . . 3 2. The LDAP Dereference Control . . . . . . . . . . . . . . . . . 4 2.1. Control Semantics . . . . . . . . . . . . . . . . . . . . 4 2.2. Control Request . . . . . . . . . . . . . . . . . . . . . 5 2.3. Control Response . . . . . . . . . . . . . . . . . . . . . 5 3. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4. Implementation Notes . . . . . . . . . . . . . . . . . . . . . 7 5. Security Considerations . . . . . . . . . . . . . . . . . . . 8 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 6.1. Object Identifier Registration . . . . . . . . . . . . . . 9 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10 8. Normative References . . . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12 Intellectual Property and Copyright Statements . . . . . . . . . . 13 Masarati & Chu Expires May 23, 2009 [Page 2]  Internet-Draft LDAP Deref November 2008 1. Background and Intended Use Cross-links between entries are often used to describe relationships between entries. To exploit the uniqueness of entries naming, these links are usually represented by the distinguished name (DN) of the linked entries. In many cases, DUAs need to collect information about linked entries. This requires to explicitly dereference each linked entry in order to collect the desired attributes, resulting in the need to perform a specific sequence of search operations, using the links as search base, with a SearchRequest.scope of baseObject [RFC4511]. This document describes a LDAP Control [RFC4511] that allows a DUA to request the DSA to return specific attributes of linked entries along with the link, under the assumption that this operation can be performed by the DSA in a more efficient manner than the DUA would itself by performing the complete sequence of required search operations. 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 [RFC2119]. Masarati & Chu Expires May 23, 2009 [Page 3]  Internet-Draft LDAP Deref November 2008 2. The LDAP Dereference Control 2.1. Control Semantics This control allows specifying a dereference attribute and a set of attributes to be dereferenced, as illustrated in Section 2.2. The dereference attribute's syntax MUST be 1.3.6.1.4.1.1466.115.121.1.12 (DN) [RFC4517]. Each value of the dereference attribute in a SearchResultEntry SHOULD result in dereferencing the corresponding entry, collecting the values of the attributes to be dereferenced, and returning them as part of the control value in the SearchResultEntry response, in the format detailed in Section 2.3. The control value may contain dereference attribute values without any dereferenced attribute values, as detailed in Section 2.3. The control semantics does not specify whether this is a consequence of a dangling link or of the application of access restrictions on the values of the attributes to be dereferenced. Attribute description hierarchy [RFC4512] SHALL NOT be exploited when collecting the values of the attributes to be dereferenced. On the contrary, all of the attribute descriptions in an attribute hierarchy SHOULD be treated as distinct and unrelated descriptions. This control is only appropriate for the search operation [RFC4511]. The semantics of the criticality field are specified in [RFC4511]. In detail, the criticality of the control determines whether the control will or will not be used, and if it will not be used, whether the operation will continue without returning the control in the response, or fail, returning unavailableCriticalExtension. If the control is appropriate for an operation and, for any reason, it cannot be applied in its entirety to a single SearchResultEntry response, it MUST NOT be applied to that specific SearchResultEntry response, without affecting its application to any subsequent SearchResultEntry response. Servers implementing this technical specification SHOULD publish the object identifier deref-oid (IANA assigned; see Section 6) as a value of the 'supportedControl' attribute [RFC4512] in their root DSE. This control is totally unrelated to alias dereferencing [RFC4511]. Masarati & Chu Expires May 23, 2009 [Page 4]  Internet-Draft LDAP Deref November 2008 2.2. Control Request The control type is deref-oid (IANA assigned; see Section 6). The specification of the Dereference Control request is: controlValue ::= SEQUENCE OF derefSpec DerefSpec DerefSpec ::= SEQUENCE { derefAttr attributeDescription, ; with DN syntax attributes AttributeList } AttributeList ::= SEQUENCE OF attr AttributeDescription Each derefSpec.derefAttr MUST be unique within controlValue. 2.3. Control Response The control type is deref-oid (IANA assigned; see Section 6). The specification of the Dereference Control response is: controlValue ::= SEQUENCE OF derefRes DerefRes DerefRes ::= SEQUENCE { derefAttr AttributeDescription, derefVal LDAPDN, attrVals [0] PartialAttributeList OPTIONAL } PartialAttributeList ::= SEQUENCE OF partialAttribute PartialAttribute PartialAttribute is defined in [RFC4511]; the definition is reported here for clarity: PartialAttribute ::= SEQUENCE { type AttributeDescription, vals SET OF value AttributeValue } If partialAttribute.vals is empty, the corresponding partialAttribute is omitted. If all partialAttribute.vals in attrVals are empty, that derefRes.attrVals is omitted. Masarati & Chu Expires May 23, 2009 [Page 5]  Internet-Draft LDAP Deref November 2008 3. Examples Given these entries: dn: cn=Howard Chu,ou=people,dc=example,dc=org objectClass: inetOrgPerson cn: Howard Chu sn: Chu uid: hyc dn: cn=Pierangelo Masarati,ou=people,dc=example,dc=org objectClass: inetOrgPerson cn: Pierangelo Masarati sn: Masarati uid: ando dn: cn=Test Group,ou=groups,dc=example,dc=org objectClass: groupOfNames cn: Test Group member: cn=Howard Chu,ou=people,dc=example,dc=org member: cn=Pierangelo Masarati,ou=people,dc=example,dc=org A search could be performed with a Dereference request control value specified as { member, uid } and the "cn=Test Group" entry would be returned with the response control value { { member, cn=Howard Chu,ou=people,dc=example,dc=org, { { uid, [hyc] } } }, { member, cn=Pierangelo Masarati,ou=people,dc=example,dc=org, { { uid, [ando] } } } } Masarati & Chu Expires May 23, 2009 [Page 6]  Internet-Draft LDAP Deref November 2008 4. Implementation Notes This LDAP extension is currently implemented in OpenLDAP software using the temporary OID 1.3.6.1.4.1.4203.666.5.16 under OpenLDAP's experimental OID arc. Masarati & Chu Expires May 23, 2009 [Page 7]  Internet-Draft LDAP Deref November 2008 5. Security Considerations The control result MUST NOT disclose information the client's identity could not have accessed by performing the related search operations. The presence of a derefRes.derefVal in the response control, with no derefRes.attrVals, does not imply neither the existence of nor any access privilege to the corresponding entry. It is merely a consequence of the read access the client's identity has on the corresponding value of the derefRes.derefAttr that would be returned as part of the attributes of a SearchResultEntry response [RFC4511]. Security considerations described in documents listed in [RFC4510] apply. Masarati & Chu Expires May 23, 2009 [Page 8]  Internet-Draft LDAP Deref November 2008 6. IANA Considerations 6.1. Object Identifier Registration It is requested that IANA register upon Standards Action an LDAP Object Identifier for use in this technical specification. Subject: Request for LDAP OID Registration Person & email address to contact for further information: Pierangelo Masarati <ando@OpenLDAP.org> Specification: (I-D) Author/Change Controller: IESG Comments: Identifies the LDAP Dereference Control request and response Masarati & Chu Expires May 23, 2009 [Page 9]  Internet-Draft LDAP Deref November 2008 7. Acknowledgments TBD Masarati & Chu Expires May 23, 2009 [Page 10]  Internet-Draft LDAP Deref November 2008 8. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4510] Zeilenga, K., "Lightweight Directory Access Protocol (LDAP): Technical Specification Road Map", RFC 4510, June 2006. [RFC4511] Sermersheim, J., "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. [RFC4517] Legg, S., "Lightweight Directory Access Protocol (LDAP): Syntaxes and Matching Rules", RFC 4517, June 2006. Masarati & Chu Expires May 23, 2009 [Page 11]  Internet-Draft LDAP Deref November 2008 Authors' Addresses Pierangelo Masarati Politecnico di Milano Dipartimento di Ingegneria Aerospaziale via La Masa 34 Milano 20156 IT Phone: +39 02 2399 8309 Fax: +39 02 2399 8334 Email: ando@OpenLDAP.org URI: http://www.aero.polimi.it/masarati/ Howard Y. Chu Symas Corporation 18740 Oxnard St., Suite 313A Tarzana, California 91356 USA Phone: +1 818 757-7087 Email: hyc@symas.com URI: http://www.symas.com/ Masarati & Chu Expires May 23, 2009 [Page 12]  Internet-Draft LDAP Deref November 2008 Full Copyright Statement Copyright (C) The IETF Trust (2008). 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