INTERNET-DRAFT Kurt D. Zeilenga
Intended Category: Experimental OpenLDAP Foundation
Expires in six months 24 October 2004
LDAP Turn Operation
<draft-zeilenga-ldap-turn-01.txt>
1. Status of this Memo
This document is intended to be, after appropriate review and
revision, submitted to the RFC Editor for publication as an
Experimental document. Distribution of this memo is unlimited.
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comments directly to the author <Kurt@OpenLDAP.org>.
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Copyright (C) The Internet Society (2004). All Rights Reserved.
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Abstract
This specification describes a Lightweight Directory Access Protocol
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(LDAP) extended operation to reverse (or "turn") the roles of client
and server for subsequent protocol exchanges in the session, or to
enable each peer to act as both client and server with respect to the
other.
1. Background and Intent of Use
The Lightweight Directory Access Protocol (LDAP) [Roadmap][Protocol]
is a client-server protocol which typically operates over reliable
octet-stream transports such as the Transport Control Protocol (TCP).
Generally, the client initiates the stream by connecting to the
server's listener at some well-known address.
There are cases where it is desirable for the server to initiate the
stream. While it certainly is possible to write a technical
specification detailing how to implement server-initiated LDAP
sessions, this would require the design of new authentication and
other security mechanisms to support server-initiated LDAP sessions.
Instead, this document introduces an operation, the Turn operation,
which may be used to reverse the client-servers roles of the protocol
peers. This allows the initiating protocol peer to become server
(after the reversal).
As an additional feature, the Turn operation may be used to allow both
peers to act in both roles. This is useful where both peers are
directory servers that desire to request, as LDAP clients, operations
for the other to perform. This may be useful in replicated and/or
distributed environments.
This operation is intended to be used between protocol peers which
have established a mutual agreement, by means outside of the protocol,
which requires reversal of client-server roles, or allows both peers
to act both as client and server.
1.1 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 5.2 of [Protocol].
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 BCP 14 [RFC2119].
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2. Turn Operation
The Turn operation is defined as a LDAP Extended Operation [Protocol,
Section 4.12] identified by the IANA-ASSIGNED-OID. The function of
the Turn Operation is to request that the client-server roles be
reversed, or, optionally to request that both protocol peers to be
able to act both as client and server in respect to the other.
2.1. Turn Request
The Turn request is an ExtendedRequest with the requestName field
containing the IANA-ASSIGNED-OID and a requestValue field is a
BER-encoded turnValue:
turnValue ::= SEQUENCE {
mutual BOOLEAN DEFAULT FALSE,
identifier LDAPString,
}
A TRUE mutual field value indicates a request to allow both peers to
act both as client and server. A FALSE mutual field value indicates a
request to reserve the client and server roles.
The value of the identifier field is a locally-defined policy
identifier (typically associated with a mutual agreement for which
this turn is be executed as part of).
2.2. Turn Response
A Turn response is an ExtendedResponse where the responseName and
responseValue fields are absent. A resultCode of success is returned
if and only if the responder is willing and able to turn the session
as requested. Otherwise, a different resultCode is returned.
3. Security Considerations
It is generally recommended that before issuing the Turn operation the
protocol peers:
- establish each other's identities through appropriate
authentication mechanism,
- establish appropriate data integrity, data confidentiality, and
other protections,
- establish an LDAP association between the initiating peer and the
responding peer.
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And upon successful completion of turn:
- establish an LDAP association in the reverse.
That is, for peer A connecting to the listening peer B and where TLS
and SASL/EXTERNAL were to be used, the sequence of LDAP messages could
be:
A->B: StartTLS Request
B->A: StartTLS(success) Response
A->B: Bind(SASL(EXTERNAL)) Request
B->A: Bind(success) Response
A->B: Turn(TRUE,"XXYYZ") Request
B->A: Turn(success) Response
B->A: Bind(SASL(EXTERNAL)) Request
A->B: Bind(success) Response
4. IANA Considerations
Registration of the following values [BCP64bis] is requested.
4.1. Object Identifier
It is requested that IANA assign an LDAP Object Identifier to identify
the LDAP Turn Operation as 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 XXXX
Author/Change Controller: Author
Comments:
Identifies the LDAP Turn Operation
4.2. LDAP Protocol Mechanism
It is requested that IANA register the LDAP Protocol Mechanism
described in this document.
Subject: Request for LDAP Protocol Mechanism Registration
Object Identifier: IANA-ASSIGNED-OID
Description: LDAP Turn Operation
Person & email address to contact for further information:
Kurt Zeilenga <kurt@openldap.org>
Usage: Extended Operation
Specification: RFC XXXX
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Author/Change Controller: Author
Comments: none
5. Author's Address
Kurt D. Zeilenga
OpenLDAP Foundation
Email: Kurt@OpenLDAP.org
6. References
[[Note to the RFC Editor: please replace the citation tags used in
referencing Internet-Drafts with tags of the form RFCnnnn where
possible.]]
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14 (also RFC 2119), March 1997.
[Roadmap] Zeilenga, K. (editor), "LDAP: Technical Specification
Road Map", draft-ietf-ldapbis-roadmap-xx.txt, a work in
progress.
[Protocol] Sermersheim, J. (editor), "LDAP: The Protocol",
draft-ietf-ldapbis-protocol-xx.txt, a work in progress.
[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).
6.2. Informative References
[BCP64bis] Zeilenga, K., "IANA Considerations for LDAP",
draft-ietf-ldapbis-bcp64-xx.txt, a work in progress.
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