One document matched: draft-sermersheim-ldap-chaining-03.txt
Differences from draft-sermersheim-ldap-chaining-02.txt
Network Working Group J. Sermersheim
Internet-Draft Novell, Inc
Expires: August 24, 2005 February 20, 2005
LDAP Control to Specify Chaining Behavior
draft-sermersheim-ldap-chaining-03.txt
Status of this Memo
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document describes a Lightweight Directory Access Protocol
(LDAP) request control that allows specification of chaining behavior
for LDAP operations. By using the control with various LDAP
operations, a directory client (DUA), or directory server (DSA)
specifies whether or not a DSA or secondary DSA chains operations to
other DSAs or returns referrals and/or search result references to
the client.
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Discussion Forum
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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Chaining Behavior Control . . . . . . . . . . . . . . . . . . 5
4. Chaining Behavior Result Codes . . . . . . . . . . . . . . . . 7
5. Application to LDAP operations . . . . . . . . . . . . . . . . 8
5.1 Unbind and Abandon . . . . . . . . . . . . . . . . . . . . . . 8
5.2 StartTLS . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6. Relationship with other Extensions . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. Normative References . . . . . . . . . . . . . . . . . . . . . 10
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 10
A. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
A.1 LDAP Object Identifier Registrations . . . . . . . . . . . . . 11
A.2 LDAP Protocol Mechanism Registrations . . . . . . . . . . . . 11
A.3 LDAP Result Code Registrations . . . . . . . . . . . . . . . . 11
Intellectual Property and Copyright Statements . . . . . . . . 13
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1. Introduction
Many directory servers have the ability through the use of various
mechanisms to participate in a distributed directory model. A
distributed directory is one where the DIT is distributed over
multiple DSAs. One operation completion mechanism used by DSAs in a
distributed directory is chaining. Chaining is defined in [X518],
and is the act of one DSA communicating a directory operation that
originated from a DUA to another DSA in a distributed directory.
Contrast this with the act of passing referrals (4.1.11 of [RFC2251])
and SearchResultReferences (4.5.2 of [RFC2251]) back to the client.
Chaining may happen during the name resolution part of an operation
or during other parts of operations like search which apply to a
number of entries in a subtree.
This document does not attempt to define the distributed directory
model, nor does it attempt to define the manner in which DSAs chain
requests. This document defines a request control that the client
can use to specify whether parts of an operation should or should not
be chained.
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2. Conventions
Imperative keywords defined in [RFC2119] are used in this document,
and carry the meanings described there.
All Basic Encoding Rules (BER) [X690] encodings follow the
conventions found in Section 5.1 of [RFC2251].
The term chaining may apply to uni-chaining as well as multi-chaining
(see [X518]) depending on the capabilities and configuration of the
DSAs.
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3. Chaining Behavior Control
This control MAY be included in any LDAP request operation except
abandon, unbind, and StartTLS as part of the controls field of the
LDAPMessage, as defined in Section 4.1.12 of [RFC2251].
The controlType is set to <IANA-ASSIGNED-OID.1>. The criticality MAY
be set to either TRUE or FALSE. The controlValue is an OCTET STRING,
whose value is the following ChainingBehavior type:
ChainingBehavior ::= SEQUENCE {
resolveBehavior Behavior OPTIONAL,
evaluationBehavior Behavior OPTIONAL }
Behavior :: = ENUMERATED {
chainingPreferred (0),
chainingRequired (1),
referralsPreferred (2),
referralsRequired (3) }
The intent is that at least resolveBehavior or evaluationBehavior
(and possibly both) be specified.
resolveBehavior instructs the DSA what to do when distributed
knowledge data is encountered during the local name resolution part
of an operation. If this field is not specified, other policy
dictates the DSA's behavior.
evaluationBehavior instructs the DSA what to do when distributed
knowledge data is encountered after the name resolution part of an
operation has completed. This scenario occurs during search
operations, and may occur in other operations which are capable of
returning intermediate referrals. Any specification of this field is
ignored for operations which are incapable of returning intermediate
referrals. If this field is not specified, other policy dictates the
DSA's behavior.
Behavior specifies whether the DSA should chain the operation or
return referrals when a target object is held by a remote service.
chainingPreferred indicates that the preference is that chaining,
rather than referrals, be used to progress the operation. When
this value is set, the server attempts to chain the request but if
it is unable or unwilling, it may referrals.
chainingRequired indicates that chaining is to be used rather than
referrals to progress the operation. When this value is set, the
server MUST NOT return referrals. It either chains the request or
fails.
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referralsPreferred indicates that the client wishes to receive
referrals rather than allow the server to chain the operation.
When this value is set, the server return referrals when possible,
but may chain the operation when returning a referral is not
possible or not allowed (i.e. due to local policy).
referralsRequired indicates that chaining is prohibited. When
this value is set, the server MUST NOT chain the request to other
DSAs. Instead it returns referrals as necessary, or fails.
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4. Chaining Behavior Result Codes
In some cases, the chaining behavior control imposes behavioral
restrictions on operations which cannot be met. In order to indicate
such problems, two result codes are added:
o noReferralsFound (<IANA-ASSIGNED-1>) Could not produce a referral.
o cannotChain (<IANA-ASSIGNED-2>) Unable to chain the request.
noReferralsFound indicates that the ChainingBehavior.resolveBehavior
or ChainingBehavior.continuationBehavior was set to
referralsRequired, the server located (during name resolution or
operation evaluation) distributed knowledge information but could not
locate or fabricate a valid referral.
cannotChain indicates that the ChainingBehavior.resolveBehavior or
ChainingBehavior.continuationBehavior was set to chainingRequired,
the server located (during name resolution or operation evaluation)
distributed knowledge information but could not chain.
Note that either result code may be returned during the operation
evaluation phase of an operation, and thus, the operation may have
already returned a number of intermediate responses. For example, a
search operation may return a number of search entries prior to
returning a chaining behavior result code.
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5. Application to LDAP operations
5.1 Unbind and Abandon
Clients MUST NOT include the ChainingBehavior control with an Abandon
operation or an Unbind operation. Servers MUST ignore any chaining
control on the abandon and unbind requests. Servers that chain
operation are responsible to keep track of where an operation was
chained to for the purposes of unbind and abandon.
5.2 StartTLS
This operation cannot be chained because the TLS handshake protocol
does not allow man-in-the-middle attacks.
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6. Relationship with other Extensions
This control MAY be used with other controls or with extended
operations. When it is used with other controls or with extended
operations not listed here, server behavior is undefined unless
otherwise specified.
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7. Security Considerations
Because this control directs a DSA to chain requests to other DSAs,
it may be used in a denial of service attack. Implementers should be
cognizant of this possibility.
This control may be used to allow access to hosts and portions of the
DIT not normally available to clients. Servers supporting this
control should provide sufficient policy to prevent unwanted
occurrences of this.
8. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2251] Wahl, M., Howes, T. and S. Kille, "Lightweight Directory
Access Protocol (v3)", RFC 2251, December 1997.
[RFC3383] Zeilenga, K., "Internet Assigned Numbers Authority (IANA)
Considerations for the Lightweight Directory Access
Protocol (LDAP)", BCP 64, RFC 3383, September 2002.
[X518] International Telephone and Telegraph Consultative
Committee, "The Directory - The Directory: Procedures for
distributed operation", ITU-T Recommendation X.518,
November 1993.
[X690] International Telecommunications Union, "Information
Technology - ASN.1 encoding rules: Specification of Basic
Encoding Rules (BER), Canonical Encoding Rules (CER) and
Distinguished Encoding Rules (DER)", ITU-T Recommendation
X.690, July 2002.
Author's Address
Jim Sermersheim
Novell, Inc
1800 South Novell Place
Provo, Utah 84606
USA
Phone: +1 801 861-3088
Email: jimse@novell.com
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Appendix A. IANA Considerations
Registration of the following values is requested [RFC3383].
A.1 LDAP Object Identifier Registrations
It is requested that IANA register upon Standards Action an LDAP
Object Identifier in identifying the protocol elements defined in
this technical specification. The following registration template is
provided:
Subject: Request for LDAP OID Registration
Person & email address to contact for further information:
Jim Sermersheim
jimse@novell.com
Specification: RFCXXXX
Author/Change Controller: IESG
Comments:
One delegations will be made under the assigned OID:
IANA-ASSIGNED-OID.1 Chaining Behavior Request Control
A.2 LDAP Protocol Mechanism Registrations
It is requested that IANA register upon Standards Action the LDAP
protocol mechanism described in this document. The following
registration templates are given:
Subject: Request for LDAP Protocol Mechanism Registration
Object Identifier: IANA-ASSIGNED-OID.1
Description: Chaining Behavior Request Control
Person & email address to contact for further information:
Jim Sermersheim
jimse@novell.com
Usage: Control
Specification: RFCXXXX
Author/Change Controller: IESG
Comments: none
A.3 LDAP Result Code Registrations
It is requested that IANA register upon Standards Action the LDAP
result codes described in this document. The following registration
templates are given:
Subject: Request for LDAP Result Code Registration
Result Code Name: chainingRequired
Result Code Name: cannotChain
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Person & email address to contact for further information:
Jim Sermersheim
jimse@novell.com
Specification: RFCXXXX
Author/Change Controller: IESG
Comments: none
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Acknowledgment
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Internet Society.
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