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INTERNET-DRAFT                                         Kurt D. Zeilenga
Intended Category: Standard Track                         Isode Limited
Expires in six months                                      13 July 2008



                            LDAP Transactions
                     <draft-zeilenga-ldap-txn-12.txt>


Status of Memo

  This document is intended to be, after appropriate review and
  revision, submitted to the IESG for consideration as a Proposed
  Standard.  Distribution of this memo is unlimited.  Technical
  discussion of this document will take place on the IETF LDAP
  Extensions mailing list <ldapext@ietf.org>.  Please send editorial
  comments directly to the author <Kurt.Zeilenga@Isode.COM>.

  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
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  Copyright (C) The IETF Trust (2008).

  Please see the Full Copyright section near the end of this document
  for more information.







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Abstract

  Lightweight Directory Access Protocol (LDAP) update operations, such
  as Add, Delete, and Modify operations, have atomic, consistency,
  isolation, durability (ACID) properties.  Each of these update
  operations act upon an entry.  It is often desirable to update two or
  more entries in a single unit of interaction, a transaction.
  Transactions are necessary to support a number of applications
  including resource provisioning.  This document extends LDAP to
  support transactions.


1. Overview

  This document extends the Lightweight Directory Access Protocol (LDAP)
  [RFC4510] to allow clients to relate a number of update operations
  [RFC4511] and have them performed as one unit of interaction, a
  transaction.  As with distinct update operations, each transaction has
  atomic, consistency, isolation, and durability (ACID) properties
  [ACID].

  This extension consists of two extended operations, one control, and
  one unsolicited notification message.  The Start Transaction operation
  is used to obtain a transaction identifier.  This identifier is then
  attached to multiple update operations to indicate that they belong to
  the transaction using the Transaction Specification control.  The End
  Transaction is used to settle (commit or abort) the transaction.  The
  Aborted Transaction Notice is provided by the server to notify the
  client that the server is no longer willing or able to process an
  outstanding transaction.


1.1. Conventions and Terminology

  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 RFC 2119 [RFC2119].

  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" (a server).  DSE stands for
  "DSA-specific entry".


2.  Elements of an LDAP Transaction



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2.1.  Start Transaction Request and Response

  A Start Transaction Request is an LDAPMessage of CHOICE extendedReq
  where the requestName is IANA-ASSIGNED-OID.1 and the requestValue is
  absent.

  A Start Transaction Response is an LDAPMessage of CHOICE extendedRes
  sent in response to a Start Transaction Request.  Its responseName is
  absent.  When the resultCode is success (0), responseValue is present
  and contains a transaction identifier.  Otherwise, the responseValue
  is absent.


2.2.  Transaction Specification Control

  A Transaction Specification control is an LDAPControl where the
  controlType is IANA-ASSIGNED-OID.2, the criticality is TRUE, and the
  controlValue is a transaction identifier.  The control is appropriate
  for update requests including Add, Delete, Modify, and ModifyDN
  (Rename) requests [RFC4511], as well as the Password Modify requests
  [RFC3062].

  As discussed in Section 4, the Transaction Specification control can
  be used in conjunction with request controls appropriate for the
  update request.


2.3.  End Transactions Request and Response

  An End Transaction Request is an LDAPMessage of CHOICE extendedReq
  where the requestName is IANA-ASSIGNED-OID.3 and the requestValue is
  present and contains a BER-encoded txnEndReq.

       txnEndReq ::= SEQUENCE {
            commit         BOOLEAN DEFAULT TRUE,
            identifier     OCTET STRING }

  A commit value of TRUE indicates a request to commit the transaction
  identified by the identifier.  A commit value of FALSE indicates a
  request to abort the identified transaction.

  An End Transaction Response is an LDAPMessage sent in response to a
  End Transaction Request.  Its response name is absent.  The
  responseValue when present contains a BER-encoded txnEndRes.

       txnEndRes ::= SEQUENCE {
            messageID MessageID OPTIONAL,
                 -- msgid associated with non-success resultCode



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            updatesControls SEQUENCE OF updateControls SEQUENCE {
                 messageID MessageID,
                      -- msgid associated with controls
                 controls  Controls
            } OPTIONAL
       }
       -- where MessageID and Controls are as specified in RFC 4511

  The txnEndRes.messageID provides the message id of the update request
  associated with a non-success response.  txnEndRes.messageID is absent
  when resultCode of the End Transaction Response is success (0).

  The txnEndRes.updatesControls provides a facility for returning
  response controls that normally (i.e., in absence of transactions)
  would be returned in an update response.  The updateControls.messageID
  provides the message id of the update request associated with the
  response controls provided in updateControls.controls.

  The txnEndRes.updatesControls is absent when there are no update
  response controls to return.

  If both txnEndRes.messageID and txnEndRes.updatesControl are absent,
  the responseValue of the End Transaction Response is absent.


2.4. Aborted Transaction Notice

  The Aborted Transaction Notice is an Unsolicited Notification message
  where the responseName is IANA-ASSIGNED-OID.4 and responseValue is
  present and contains a transaction identifier.


3. An LDAP Transaction

3.1. Extension Discovery

  To allow clients to discover support for this extension, servers
  implementing this specification SHOULD publish IANA-ASSIGNED-OID.1 and
  IANA-ASSIGNED-OID.3 as values of the 'supportedExtension' attribute
  [RFC4512] within the Root DSE, and publish the IANA-ASSIGNED-OID.2 as
  a value of the 'supportedControl' attribute [RFC4512] of the Root DSE.

  A server MAY choose to advertise this extension only when the client
  is authorized to use it.


3.2. Starting a Transaction




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  A client wishing to perform a sequence of directory updates as an
  transaction issues a Start Transaction Request.  A server which is
  willing and able to support transactions responds to this request with
  a Start Transaction Response providing a transaction identifier and
  with a resultCode of success (0).  Otherwise, the server responds with
  a Start Transaction Response with a result code other than success
  indicating the nature of the failure.

  The transaction identifier provided upon successful start of a
  transaction is used in subsequent protocol messages to identify this
  transaction.


3.3. Specification of a Transaction

  The client then can issue one or more update requests, each with a
  Transaction Specification control containing the transaction
  identifier indicating the updates are to processed as part of the
  transaction.  Each of these update request MUST have a different
  MessageID value.  If the server is unwilling or unable to attempt to
  process the requested update operation as part of the transaction, the
  server immediately returns the appropriate response to the request
  with a resultCode indicating the nature of the failure.  Otherwise,
  the server immediately returns success (0) and the defers further
  processing of the operation is then deferred until settlement.

  If the server becomes unwilling or unable to continue the
  specification of a transaction, the server issues an Aborted
  Transaction Notice with a non-success resultCode indicating the nature
  of the failure.  All operations that were to be processed as part of
  the transaction are implicitly abandoned.  Upon receipt of an Aborted
  Transaction Notice, the client is to discontinue all use of the
  transaction identifier as the transaction is null and void.  Any
  future use of identifier by the client will result in a response
  containing a non-success resultCode.


3.4. Transaction Settlement

  A client requests settlement of transaction by issuing an End
  Transaction request for the transaction indicating whether it desires
  the transaction to be committed or aborted.

  Upon receipt of a request to abort the transaction, the server is to
  abort the identified transaction (abandoning all operations which are
  part of the transaction) and indicate that it has done so by returning
  an End Transaction Response with a resultCode of success (0).




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  Upon receipt of a request to commit the transaction, the server
  processes all update operations of the transaction as one atomic,
  durable, isolated, and consistent action with each requested update
  being processed in turn.  Either all of the requested updates are to
  be successfully applied or none of the requested are to be applied.
  The server returns an End Transaction Response with a resultCode of
  success (0) and no responseValue to indicate all the requested updates
  were applied.  Otherwise, the server returns an End Transaction with
  an non-success resultCode indicating the nature of the failure.  If
  the failure is associated with a particular update request, the
  txnEndRes.messageID in the responseValue is the messageID of this
  update request.  If the failure was not associated with any particular
  update request, no txnEnd.messageID is provided.

  There is no requirement that a server serialize transactions, or
  updates requested outside of a transaction.  That is, a server MAY
  process multiple commit requests (from one or more clients) acting
  upon different sets of entries concurrently.   A server MUST avoid
  deadlock.


3.5. Miscellaneous Issues

  Transactions cannot be nested.

  Each LDAP transaction should be initiated, specified, and settled
  within a stable security context.   Between the Start request and the
  End response, the peers SHOULD avoid negotiating new security
  associations and/or layers.

  Upon receipt of a Bind or Unbind request, the server SHALL abort any
  and all outstanding transactions without notice and nullify their
  identifiers.


4. Interaction with Other Extensions

  The LDAP Transaction extension may be used with many but not all LDAP
  control extensions designed to extend Update (and possibly other)
  operations.  The remainder of this subsection discusses interaction
  with a number of control extensions.  Interaction with other control
  extensions may be discussed in other documents, in particular in
  control extension specifications.


4.1. Assertion Control

  The Assertion [RFC4528] control is appropriate for use with update



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  requests specified as part of a transaction.  The evaluation of the
  assertion is performed as part of the transaction.

  The Assertion control is inappropriate for use with either the
  Transaction Start or End extended operations.


4.2. ManageDsaIT Control

  The ManageDsaIT [RFC3296] control is appropriate for use with update
  requests specified as part of a transaction.

  The ManageDsaIT control is inappropriate for use with either the
  Transaction Start or End extended operations.


4.3. No-Op Control

  The No-Op [NO-OP] control is appropriate for use with the Transaction
  Start or End extended operations.

  The No-Op control is not appropriate for update requests specified as
  part of a transaction.  A server supporting both the No-Op control
  extension and this extension SHALL regard a request containing both
  controls as a protocol violation.  As both of the No-Op and
  Transaction Specification request controls are required to be marked
  as critical, a server implementing one of these request controls, or
  neither, is expected to return unavailableCriticalExtension as
  prescribed by [RFC4511].


4.4. Proxied Authorization Control

  The Proxied Authorization [RFC4370] control is appropriate for use
  with the Transaction Start extended operation, but not the Transaction
  End extended operation or any update request specified as part of a
  transaction.

  To request that a transaction be performed under a different
  authorization, the client provides a Proxied Authorization control
  with the Transaction Start request.  If the client is not authorized
  to assume the requested authorization identity, the server is to
  return the authorizationDenied (123) resultCode in its response.
  Otherwise, further processing of the request and transaction is
  performed under the requested authorization identity.

  Any proxied authorization request attached to an update request
  specified as part of a transaction, or attached to a Transaction end



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  request, is to be regarded as a protocol error.


4.5. Read Entry Controls

  The Pre- and Post-Read Entry [RFC4527] request control are appropriate
  for use with update requests specified as part of a transaction.

  The response control produced in response to a Pre- or Post-Read Entry
  request control is returned in the txnEndRes.updatesControls field of
  responseValue of the End Transaction Response.

  The Pre- and Post-Read Entry controls are inappropriate for use in the
  LDAPMessage.controls field of the Transaction Start and End request
  and response messages.


4.6. Relax Rules Control

  The Relax Rules [RELAX] control is appropriate for use with update
  requests specified as part of a transaction.

  The Relax Rules control is inappropriate for use with either the
  Transaction Start or End extended operations.


5. Distributed Directory Considerations

  The LDAP/X.500 models provide for distributed directory operations,
  including server-side chaining and client-side chasing of referrals.

  This document does not preclude servers from chaining operations which
  are part of a transaction.  However, if a server does attempt such
  chaining, it MUST ensure that transaction semantics are provided.

  This mechanism defined by this document does not support client-side
  chasing.  Grouping cookies used to identify the transaction are
  specific to a particular client/server session.

  The LDAP/X.500 models provide for a single-master/multiple-shadow
  replication architecture.  There is no requirement that changes made
  to the directory based upon processing a transaction be replicated as
  one atomic action.  Hence, clients SHOULD NOT assume tight data
  consistency nor fast data convergence of shadow copies unless they
  have prior knowledge that these properties are provided.  Note that
  DontUseCopy control [DONTUSECOPY] control may be used in conjunction
  with the LDAP search request to ask for the return of the
  authoritative copy of the entry.



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6. Security Considerations

  Transactions mechanisms may be the target of denial-of-service
  attacks, especially where implementation lock shared resources for the
  duration of a transaction.

  General security considerations [RFC4510], especially those associated
  with update operations [RFC4511], apply to this extension.


7. IANA Considerations

  It is requested that Internet Assigned Numbers Authority (IANA) make
  the following assignments.


7.1.  Object Identifier

  Assignment of an LDAP Object Identifier [RFC4520] to identify the
  protocol elements specified in this document this document is
  requested.

      Subject: Request for LDAP Object Identifier Registration
      Person & email address to contact for further information:
          Kurt Zeilenga <Kurt.Zeilenga@Isode.COM>
      Specification: RFC XXXX
      Author/Change Controller: IESG
      Comments: Identifies protocol elements for LDAP Transactions


7.2.  LDAP Protocol Mechanism

  Registration of the protocol mechanisms [RFC4520] specified in this
  document is requested.

      Subject: Request for LDAP Protocol Mechanism Registration
      Object Identifier: see table
      Description: see table
      Person & email address to contact for further information:
          Kurt Zeilenga <Kurt.Zeilenga@Isode.COM>
      Specification: RFC XXXX
      Author/Change Controller: IESG
      Comments:

      Object Identifier   Type  Description
      ------------------- ----  ----------------------------------
      IANA-ASSIGNED-OID.1 E     Start Transaction Extended Request
      IANA-ASSIGNED-OID.2 C     Transaction Specification Control



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      IANA-ASSIGNED-OID.3 E     End Transaction Extended Request
      IANA-ASSIGNED-OID.4 N     Aborted Transaction Notice

      Legend
      ------------------------
      C => supportedControl
      E => supportedExtension
      N => Unsolicited Notice


8. Acknowledgments

  The author gratefully acknowledges the contributions made by Internet
  Engineering Task Force participants.


9. Author's Address

  Kurt D. Zeilenga
  Isode Limited

  Email: Kurt.Zeilenga@Isode.COM


10. References

  [[Note to the RFC Editor: please replace the citation tags used in
  referencing Internet-Drafts with tags of the form RFCnnnn where
  possible.]]


10.1. Normative References

  [RFC2119]     Bradner, S., "Key words for use in RFCs to Indicate
                Requirement Levels", BCP 14 (also RFC 2119), March 1997.

  [RFC3062]     Zeilenga, K., "LDAP Password Modify Extended Operation",
                RFC 3062, February 2001.

  [RFC3296]     Zeilenga, K., "Named Subordinate References in
                Lightweight Directory Access Protocol (LDAP)
                Directories", RFC 3296, July 2002.

  [RFC4370]     Weltman, R., "LDAP Proxied Authentication Control", RFC
                4370, Feb. 2006.

  [RFC4510]     Zeilenga, K. (editor), "LDAP: Technical Specification
                Road Map", RFC 4510, June 2006.



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  [RFC4511]     Sermersheim, J. (editor), "LDAP: The Protocol", RFC
                4511, June 2006.

  [RFC4512]     Zeilenga, K. (editor), "LDAP: Directory Information
                Models", RFC 4512, June 2006.

  [RFC4527]     Zeilenga, K., "LDAP Read Entry Controls", RFC 4527, June
                2006.

  [RFC4528]     Zeilenga, K., "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(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).

  [NO-OP]       Zeilenga, K., "LDAP No-Operation Control", draft-
                zeilenga-ldap-noop-xx.txt, a work in progress.

  [RELAX]       Zeilenga, K., "LDAP Relax Rules Control", draft-
                zeilenga-ldap-relax-xx.txt, a work in progress.


10.2. Informative References

  [RFC4520]     Zeilenga, K., "Internet Assigned Numbers Authority
                (IANA) Considerations for the Lightweight Directory
                Access Protocol (LDAP)", RFC 4520, BCP 64, June 2006.

  [ACID]        Section 4 of ISO/IEC 10026-1:1992.

  [DONTUSECOPY] Zeilenga, K., "LDAP Don't Use Copy Control", draft-
                zeilenga-ldap-dontusecopy-xx.txt, a work in progress.



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  pertain to the implementation or use of the technology described in
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Full Copyright

  Copyright (C) The IETF Trust (2008).

  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, THE IETF TRUST AND
  THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
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  WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.














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