Network Working Group K. Zeilenga
Request for Comments: 4527 OpenLDAP Foundation
Category: Standards Track June 2006
Lightweight Directory Access Protocol (LDAP)
Read Entry Controls
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 specifies an extension to the Lightweight Directory
Access Protocol (LDAP) to allow the client to read the target entry
of an update operation. The client may request to read the entry
before and/or after the modifications are applied. These reads are
done as an atomic part of the update operation.
Table of Contents
1. Background and Intent of Use ....................................2
2. Terminology .....................................................2
3. Read Entry Controls .............................................3
3.1. The Pre-Read Controls ......................................3
3.2. The Post-Read Controls .....................................3
4. Interaction with Other Controls .................................4
5. Security Considerations .........................................4
6. IANA Considerations .............................................5
6.1. Object Identifier ..........................................5
6.2. LDAP Protocol Mechanisms ...................................5
7. Acknowledgement .................................................5
8. References ......................................................6
8.1. Normative References .......................................6
8.2. Informative References .....................................7
Zeilenga Standards Track [Page 1]RFC 4527 LDAP Read Entry Controls June 2006
1. Background and Intent of Use
This document specifies an extension to the Lightweight Directory
Access Protocol (LDAP) [RFC4510] to allow the client to read the
target entry of an update operation (e.g., Add, Delete, Modify,
ModifyDN). The extension utilizes controls [RFC4511] attached to
update requests to request and return copies of the target entry.
One request control, called the Pre-Read request control, indicates
that a copy of the entry before application of update is to be
returned. Another control, called the Post-Read request control,
indicates that a copy of the entry after application of the update is
to be returned. Each request control has a corresponding response
control used to return the entry.
To ensure proper isolation, the controls are processed as an atomic
part of the update operation.
The functionality offered by these controls is based upon similar
functionality in the X.500 Directory Access Protocol (DAP) [X.511].
The Pre-Read controls may be used to obtain replaced or deleted
values of modified attributes or a copy of the entry being deleted.
The Post-Read controls may be used to obtain values of operational
attributes, such as the 'entryUUID' [RFC4530] and 'modifyTimestamp'
[RFC4512] attributes, updated by the server as part of the update
operation.
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].
DN stands for Distinguished Name.
DSA stands for Directory System Agent (i.e., a directory 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].
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RFC 4527 LDAP Read Entry Controls June 2006
3. Read Entry Controls
3.1. The Pre-Read Controls
The Pre-Read request and response controls are identified by the
1.3.6.1.1.13.1 object identifier. Servers implementing these
controls SHOULD publish 1.3.6.1.1.13.1 as a value of the
'supportedControl' [RFC4512] in their root DSE.
The Pre-Read request control is a LDAP Control [RFC4511] whose
controlType is 1.3.6.1.1.13.1 and whose controlValue is a BER-encoded
AttributeSelection [RFC4511], as extended by [RFC3673]. The
criticality may be TRUE or FALSE. This control is appropriate for
the modifyRequest, delRequest, and modDNRequest LDAP messages.
The corresponding response control is a LDAP Control whose
controlType is 1.3.6.1.1.13.1 and whose the controlValue, an OCTET
STRING, contains a BER-encoded SearchResultEntry. The criticality
may be TRUE or FALSE. This control is appropriate for the
modifyResponse, delResponse, and modDNResponse LDAP messages with a
resultCode of success (0).
When the request control is attached to an appropriate update LDAP
request, the control requests the return of a copy of the target
entry prior to the application of the update. The AttributeSelection
indicates, as discussed in [RFC4511][RFC3673], which attributes are
requested to appear in the copy. The server is to return a
SearchResultEntry containing, subject to access controls and other
constraints, values of the requested attributes.
The normal processing of the update operation and the processing of
this control MUST be performed as one atomic action isolated from
other update operations.
If the update operation fails (in either normal or control
processing), no Pre-Read response control is provided.
3.2. The Post-Read Controls
The Post-Read request and response controls are identified by the
1.3.6.1.1.13.2 object identifier. Servers implementing these
controls SHOULD publish 1.3.6.1.1.13.2 as a value of the
'supportedControl' [RFC4512] in their root DSE.
The Post-Read request control is a LDAP Control [RFC4511] whose
controlType is 1.3.6.1.1.13.2 and whose controlValue, an OCTET
STRING, contains a BER-encoded AttributeSelection [RFC4511], as
extended by [RFC3673]. The criticality may be TRUE or FALSE. This
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RFC 4527 LDAP Read Entry Controls June 2006
control is appropriate for the addRequest, modifyRequest, and
modDNRequest LDAP messages.
The corresponding response control is a LDAP Control whose
controlType is 1.3.6.1.1.13.2 and whose controlValue is a BER-encoded
SearchResultEntry. The criticality may be TRUE or FALSE. This
control is appropriate for the addResponse, modifyResponse, and
modDNResponse LDAP messages with a resultCode of success (0).
When the request control is attached to an appropriate update LDAP
request, the control requests the return of a copy of the target
entry after the application of the update. The AttributeSelection
indicates, as discussed in [RFC4511][RFC3673], which attributes are
requested to appear in the copy. The server is to return a
SearchResultEntry containing, subject to access controls and other
constraints, values of the requested attributes.
The normal processing of the update operation and the processing of
this control MUST be performed as one atomic action isolated from
other update operations.
If the update operation fails (in either normal or control
processing), no Post-Read response control is provided.
4. Interaction with Other Controls
The Pre-Read and Post-Read controls may be combined with each other
and/or with a variety of other controls. When combined with the
assertion control [RFC4528] and/or the manageDsaIT control [RFC3296],
the semantics of each control included in the combination applies.
The Pre-Read and Post-Read controls may be combined with other
controls as detailed in other technical specifications.
5. Security Considerations
The controls defined in this document extend update operations to
support read capabilities. Servers MUST ensure that the client is
authorized for reading of the information provided in this control
and that the client is authorized to perform the requested directory
update.
Security considerations for the update operations [RFC4511] extended
by this control, as well as general LDAP security considerations
[RFC4510], generally apply to implementation and use of this
extension
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RFC 4527 LDAP Read Entry Controls June 2006
6. IANA Considerations
Registration of the following protocol values [RFC4520] have been
completed by the IANA.
6.1. Object Identifier
The IANA has registered an LDAP Object Identifier to identify LDAP
protocol elements 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 4527
Author/Change Controller: IESG
Comments: Identifies the LDAP Read Entry Controls
6.2. LDAP Protocol Mechanisms
The IANA has registered the LDAP Protocol Mechanism described in this
document.
Subject: Request for LDAP Protocol Mechanism Registration
Object Identifier: 1.3.6.1.1.13.1
Description: LDAP Pre-read Control
Person & email address to contact for further information:
Kurt Zeilenga <kurt@openldap.org>
Usage: Control
Specification: RFC 4527
Author/Change Controller: IESG
Comments: none
Subject: Request for LDAP Protocol Mechanism Registration
Object Identifier: 1.3.6.1.1.13.2
Description: LDAP Post-read Control
Person & email address to contact for further information:
Kurt Zeilenga <kurt@openldap.org>
Usage: Control
Specification: RFC 4527
Author/Change Controller: IESG
Comments: none
7. Acknowledgement
The LDAP Pre-Read and Post-Read controls are modeled after similar
capabilities offered in the DAP [X.511].
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8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3296] Zeilenga, K., "Named Subordinate References in
Lightweight Directory Access Protocol (LDAP)
Directories", RFC 3296, July 2002.
[RFC3673] Zeilenga, K., "Lightweight Directory Access Protocol
version 3 (LDAPv3): All Operational Attributes", RFC
3673, December 2003.
[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.
[RFC4528] Zeilenga, K., "Lightweight Directory Access Protocol
(LDAP) Assertion Control", RFC 4528, June 2006.
[X.680] International Telecommunication Union -
Telecommunication Standardization Sector, "Abstract
Syntax Notation One (ASN.1) - Specification of Basic
Notation", X.680(1997) (also ISO/IEC 8824-1:1998).
[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(1997) (also
ISO/IEC 8825-1:1998).
Zeilenga Standards Track [Page 6]RFC 4527 LDAP Read Entry Controls June 2006
8.2. Informative References
[RFC4520] Zeilenga, K., "Internet Assigned Numbers Authority
(IANA) Considerations for the Lightweight Directory
Access Protocol (LDAP)", BCP 64, RFC 4520, June 2006.
[RFC4530] Zeilenga, K., "Lightweight Directory Access Protocol
(LDAP) EntryUUID Operational Attribute", RFC 4530, June
2006.
[X.511] International Telecommunication Union -
Telecommunication Standardization Sector, "The
Directory: Abstract Service Definition", X.511(1993)
(also ISO/IEC 9594-3:1993).
Author's Address
Kurt D. Zeilenga
OpenLDAP Foundation
EMail: Kurt@OpenLDAP.org
Zeilenga Standards Track [Page 7]RFC 4527 LDAP Read Entry Controls June 2006
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Zeilenga Standards Track [Page 8]
