As per Relevance of the word establish, we have this rfc below:
Network Working Group J.
Request for Comments: 2830 Oblix Inc
Category: Standards Track R.
Univ of
M.
Sun Microsystems, Inc
May 2000
Lightweight Directory Access Protocol (v3):
Extension for Transport Layer
Status of this
This document specifies an Internet standards track protocol for
Internet community, and requests discussion and suggestions
improvements. Please refer to the current edition of the "
Official Protocol Standards" (STD 1) for the standardization
and status of this protocol. Distribution of this memo is unlimited
Copyright
Copyright (C) The Internet Society (2000). All Rights Reserved
This document defines the "Start Transport Layer Security (TLS
Operation" for LDAP [LDAPv3, TLS]. This operation provides for
establishment in an LDAP association and is defined in terms of
LDAP extended request
1. Conventions Used in this
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
document are to be interpreted as described in [ReqsKeywords].
2. The Start TLS
This section describes the Start TLS extended request and
response themselves: how to form the request, the form of
response, and enumerates the various result codes the client MUST
prepared to handle
The section following this one then describes how to sequence
overall Start TLS Operation
Hodges, et al. Standards Track [Page 1]
RFC 2830 LDAPv3: Extension for Transport Layer Security May 2000
2.1. Requesting TLS
A client may perform a Start TLS operation by transmitting an
PDU containing an ExtendedRequest [LDAPv3] specifying the OID for
Start TLS operation
1.3.6.1.4.1.1466.20037
An LDAP ExtendedRequest is defined as follows
ExtendedRequest ::= [APPLICATION 23] SEQUENCE {
requestName [0] LDAPOID
requestValue [1] OCTET STRING OPTIONAL }
A Start TLS extended request is formed by setting the
field to the OID string given above. The requestValue field
absent. The client MUST NOT send any PDUs on this
following this request until it receives a Start TLS
response
When a Start TLS extended request is made, the server MUST return
LDAP PDU containing a Start TLS extended response. An
ExtendedResponse is defined as follows
ExtendedResponse ::= [APPLICATION 24] SEQUENCE {
COMPONENTS OF LDAPResult
responseName [10] LDAPOID OPTIONAL
response [11] OCTET STRING OPTIONAL }
A Start TLS extended response MUST contain a responseName field
MUST be set to the same string as that in the responseName
present in the Start TLS extended request. The response field
absent. The server MUST set the resultCode field to either success
one of the other values outlined in section 2.3.
2.2. "Success"
If the ExtendedResponse contains a resultCode of success,
indicates that the server is willing and able to negotiate TLS.
to section 3, below, for details
2.3. Response other than "success
If the ExtendedResponse contains a resultCode other than success
this indicates that the server is unwilling or unable to
TLS
Hodges, et al. Standards Track [Page 2]
RFC 2830 LDAPv3: Extension for Transport Layer Security May 2000
If the Start TLS extended request was not successful, the
will be one of
operationsError (operations sequencing incorrect; e.g. TLS
established
protocolError (TLS not supported or incorrect PDU structure
referral (this server doesn't do TLS, try this one
unavailable (e.g. some major problem with TLS, or server
shutting down
The server MUST return operationsError if the client violates any
the Start TLS extended operation sequencing requirements described
section 3, below
If the server does not support TLS (whether by design or by
configuration), it MUST set the resultCode to protocolError (
section 4.1.1 of [LDAPv3]), or to referral. The server MUST
an actual referral value in the LDAP Result if it returns
resultCode of referral. The client's current session is unaffected
the server does not support TLS. The client MAY proceed with any
operation, or it MAY close the connection
The server MUST return unavailable if it supports TLS but
establish a TLS connection for some reason, e.g. the
server not responding, it cannot contact its TLS implementation,
if the server is in process of shutting down. The client MAY
the StartTLS operation, or it MAY proceed with any other
operation, or it MAY close the connection
3. Sequencing of the Start TLS
This section describes the overall procedures clients and
MUST follow for TLS establishment. These procedures take
consideration various aspects of the overall security of the
association including discovery of resultant security level
assertion of the client's authorization identity
Note that the precise effects, on a client's authorization identity
of establishing TLS on an LDAP association are described in detail
section 5.
Hodges, et al. Standards Track [Page 3]
RFC 2830 LDAPv3: Extension for Transport Layer Security May 2000
3.1. Requesting to Start TLS on an LDAP
The client MAY send the Start TLS extended request at any time
establishing an LDAP association, except that in the following
the client MUST NOT send a Start TLS extended request
- if TLS is currently established on the connection,
- during a multi-stage SASL negotiation,
- if there are any LDAP operations outstanding on the connection
The result of violating any of these requirements is a resultCode
operationsError, as described above in section 2.3.
The client MAY have already performed a Bind operation when it
a Start TLS request, or the client might have not yet bound
If the client did not establish a TLS connection before sending
other requests, and the server requires the client to establish a
connection before performing a particular request, the server
reject that request with a confidentialityRequired
strongAuthRequired result. The client MAY send a Start TLS
request, or it MAY choose to close the connection
3.2. Starting
The server will return an extended response with the resultCode
success if it is willing and able to negotiate TLS. It will
other resultCodes, documented above, if it is unable
In the successful case, the client, which has ceased to transfer
requests on the connection, MUST either begin a TLS negotiation
close the connection. The client will send PDUs in the TLS
Protocol directly over the underlying transport connection to
server to initiate TLS negotiation [TLS].
3.3. TLS Version
Negotiating the version of TLS or SSL to be used is a part of the
Handshake Protocol, as documented in [TLS]. Please refer to
document for details
3.4. Discovery of Resultant Security
After a TLS connection is established on an LDAP association,
parties MUST individually decide whether or not to continue based
the privacy level achieved. Ascertaining the TLS connection's
level is implementation dependent, and accomplished by
with one's respective local TLS implementation
Hodges, et al. Standards Track [Page 4]
RFC 2830 LDAPv3: Extension for Transport Layer Security May 2000
If the client or server decides that the level of authentication
privacy is not high enough for it to continue, it SHOULD
close the TLS connection immediately after the TLS negotiation
completed (see sections 4.1 and 5.2, below).
The client MAY attempt to Start TLS again, or MAY send an
request, or send any other LDAP request
3.5. Assertion of Client's Authorization
The client MAY, upon receipt of a Start TLS extended
indicating success, assert that a specific authorization identity
utilized in determining the client's authorization status. The
accomplishes this via an LDAP Bind request specifying a
mechanism of "EXTERNAL" [SASL]. See section 5.1.2, below
3.6. Server Identity
The client MUST check its understanding of the server's
against the server's identity as presented in the server'
Certificate message, in order to prevent man-in-the-middle attacks
Matching is performed according to these rules
- The client MUST use the server hostname it used to open the
connection as the value to compare against the server name
expressed in the server's certificate. The client MUST NOT use
server's canonical DNS name or any other derived form of name
- If a subjectAltName extension of type dNSName is present in
certificate, it SHOULD be used as the source of the server'
identity
- Matching is case-insensitive
- The "*" wildcard character is allowed. If present, it applies
to the left-most name component
E.g. *.bar.com would match a.bar.com, b.bar.com, etc. but
bar.com. If more than one identity of a given type is present in
certificate (e.g. more than one dNSName name), a match in any one
the set is considered acceptable
If the hostname does not match the dNSName-based identity in
certificate per the above check, user-oriented clients SHOULD
notify the user (clients MAY give the user the opportunity
Hodges, et al. Standards Track [Page 5]
RFC 2830 LDAPv3: Extension for Transport Layer Security May 2000
continue with the connection in any case) or terminate the
and indicate that the server's identity is suspect. Automated
SHOULD close the connection, returning and/or logging an
indicating that the server's identity is suspect
Beyond the server identity checks described in this section,
SHOULD be prepared to do further checking to ensure that the
is authorized to provide the service it is observed to provide.
client MAY need to make use of local policy information
3.7. Refresh of Server Capabilities
The client MUST refresh any cached server capabilities
(e.g. from the server's root DSE; see section 3.4 of [LDAPv3])
TLS session establishment. This is necessary to protect
active-intermediary attacks which may have altered any
capabilities information retrieved prior to TLS establishment.
server MAY advertise different capabilities after TLS establishment
4. Closing a TLS
4.1. Graceful
Either the client or server MAY terminate the TLS connection on
LDAP association by sending a TLS closure alert. This will leave
LDAP association intact
Before closing a TLS connection, the client MUST either wait for
outstanding LDAP operations to complete, or explicitly abandon
[LDAPv3].
After the initiator of a close has sent a closure alert, it
discard any TLS messages until it has received an alert from
other party. It will cease to send TLS Record Protocol PDUs,
following the receipt of the alert, MAY send and receive LDAP PDUs
The other party, if it receives a closure alert, MUST
transmit a TLS closure alert. It will subsequently cease to send
Record Protocol PDUs, and MAY send and receive LDAP PDUs
4.2. Abrupt
Either the client or server MAY abruptly close the entire
association and any TLS connection established on it by dropping
underlying TCP connection. A server MAY beforehand send the client
Notice of Disconnection [LDAPv3] in this case
Hodges, et al. Standards Track [Page 6]
RFC 2830 LDAPv3: Extension for Transport Layer Security May 2000
5. Effects of TLS on a Client's Authorization
This section describes the effects on a client's
identity brought about by establishing TLS on an LDAP association
The default effects are described first, and next the facilities
client assertion of authorization identity are discussed
error conditions. Lastly, the effects of closing the TLS
are described
Authorization identities and related concepts are defined
[AuthMeth].
5.1. TLS Connection Establishment
5.1.1. Default
Upon establishment of the TLS connection onto the LDAP association
any previously established authentication and
identities MUST remain in force, including anonymous state.
holds even in the case where the server requests
authentication via TLS -- e.g. requests the client to supply
certificate during TLS negotiation (see [TLS]).
5.1.2. Client Assertion of Authorization
A client MAY either implicitly request that its LDAP
identity be derived from its authenticated TLS credentials or it
explicitly provide an authorization identity and assert that it
used in combination with its authenticated TLS credentials.
former is known as an implicit assertion, and the latter as
explicit assertion
5.1.2.1. Implicit
An implicit authorization identity assertion is accomplished
TLS establishment by invoking a Bind request of the SASL form
the "EXTERNAL" mechanism name [SASL, LDAPv3] that SHALL NOT
the optional credentials octet string (found within
SaslCredentials sequence in the Bind Request). The server will
the client's authorization identity from the authentication
supplied in the client's TLS credentials (typically a public
certificate) according to local policy. The underlying mechanics
how this is accomplished are implementation specific
Hodges, et al. Standards Track [Page 7]
RFC 2830 LDAPv3: Extension for Transport Layer Security May 2000
5.1.2.2. Explicit
An explicit authorization identity assertion is accomplished
TLS establishment by invoking a Bind request of the SASL form
the "EXTERNAL" mechanism name [SASL, LDAPv3] that SHALL include
credentials octet string. This string MUST be constructed
documented in section 9 of [AuthMeth].
5.1.2.3. Error
For either form of assertion, the server MUST verify that
client's authentication identity as supplied in its TLS
is permitted to be mapped to the asserted authorization identity.
server MUST reject the Bind operation with an
resultCode in the Bind response if the client is not so authorized
Additionally, with either form of assertion, if a TLS session has
been established between the client and server prior to making
SASL EXTERNAL Bind request and there is no other external source
authentication credentials (e.g. IP-level security [IPSEC]), or if
during the process of establishing the TLS session, the server
not request the client's authentication credentials, the
EXTERNAL bind MUST fail with a result code
inappropriateAuthentication
After the above Bind operation failures, any client
and authorization state of the LDAP association is lost, so the
association is in an anonymous state after the failure.
connection state is unaffected, though a server MAY end the
connection, via a TLS close_notify message, based on the Bind
(as it MAY at any time).
5.2. TLS Connection Closure
Closure of the TLS connection MUST cause the LDAP association to
to an anonymous authentication and authorization state regardless
the state established over TLS and regardless of the
and authorization state prior to TLS connection establishment
6. Security
The goals of using the TLS protocol with LDAP are to
connection confidentiality and integrity, and to optionally
for authentication. TLS expressly provides these capabilities,
described in [TLS].
Hodges, et al. Standards Track [Page 8]
RFC 2830 LDAPv3: Extension for Transport Layer Security May 2000
All security gained via use of the Start TLS operation is gained
the use of TLS itself. The Start TLS operation, on its own, does
provide any additional security
The use of TLS does not provide or ensure for confidentiality and/
non-repudiation of the data housed by an LDAP-based directory server
Nor does it secure the data from inspection by the
administrators. Once established, TLS only provides for and
confidentiality and integrity of the operations and data in
over the LDAP association, and only if the implementations on
client and server support and negotiate it
The level of security provided though the use of TLS depends
on both the quality of the TLS implementation used and the style
usage of that implementation. Additionally, an active-
attacker can remove the Start TLS extended operation from
supportedExtension attribute of the root DSE. Therefore, both
SHOULD independently ascertain and consent to the security
achieved once TLS is established and before beginning use of the
connection. For example, the security level of the TLS
might have been negotiated down to plaintext
Clients SHOULD either warn the user when the security level
does not provide confidentiality and/or integrity protection, or
configurable to refuse to proceed without an acceptable level
security
Client and server implementors SHOULD take measures to ensure
protection of credentials and other confidential data where
measures are not otherwise provided by the TLS implementation
Server implementors SHOULD allow for server administrators to
whether and when connection confidentiality and/or integrity
required, as well as elect whether and when client authentication
TLS is required
7.
The authors thank Tim Howes, Paul Hoffman, John Kristian,
Rai, Jonathan Trostle, Harald Alvestrand, and Marcus Leech for
contributions to this document
Hodges, et al. Standards Track [Page 9]
RFC 2830 LDAPv3: Extension for Transport Layer Security May 2000
8.
[AuthMeth] Wahl, M., Alvestrand, H., Hodges, J. and R. Morgan
"Authentication Methods for LDAP", RFC 2829, May 2000.
[IPSEC] Kent, S. and R. Atkinson, "Security Architecture
the Internet Protocol", RFC 2401, November 1998.
[LDAPv3] Wahl, M., Kille S. and T. Howes, "
Directory Access Protocol (v3)", RFC 2251,
1997.
[ReqsKeywords] Bradner, S., "Key Words for use in RFCs to
Requirement Levels", BCP 14, RFC 2119, March 1997.
[SASL] Myers, J., "Simple Authentication and Security
(SASL)", RFC 2222, October 1997.
[TLS] Dierks, T. and C. Allen. "The TLS Protocol
1.0", RFC 2246, January 1999.
9. Authors'
Jeff
Oblix, Inc
18922 Forge
Cupertino, CA 95014
Phone: +1-408-861-6656
EMail: JHodges@oblix.
RL "Bob"
Computing and
University of
Seattle,
Phone: +1-206-221-3307
EMail: rlmorgan@washington.
Mark
Sun Microsystems, Inc
8911 Capital of Texas Hwy #4140
Austin TX 78759
EMail: M.Wahl@innosoft.
Hodges, et al. Standards Track [Page 10]
RFC 2830 LDAPv3: Extension for Transport Layer Security May 2000
10. Intellectual Property Rights
The IETF takes no position regarding the validity or scope of
intellectual property or other rights that might be claimed
pertain to the implementation or use of the technology described
this document or the extent to which any license under such
might or might not be available; neither does it represent that
has made any effort to identify any such rights. Information on
IETF's procedures with respect to rights in standards-track
standards-related documentation can be found in BCP-11. Copies
claims of rights made available for publication and any assurances
licenses to be made available, or the result of an attempt made
obtain a general license or permission for the use of
proprietary rights by implementors or users of this specification
be obtained from the IETF Secretariat
The IETF invites any interested party to bring to its attention
copyrights, patents or patent applications, or other
rights which may cover technology that may be required to
this standard. Please address the information to the IETF
Director
Hodges, et al. Standards Track [Page 11]
RFC 2830 LDAPv3: Extension for Transport Layer Security May 2000
11. Full Copyright
Copyright (C) The Internet Society (2000). All Rights Reserved
This document and translations of it may be copied and furnished
others, and derivative works that comment on or otherwise explain
or assist in its implementation may be prepared, copied,
and distributed, in whole or in part, without restriction of
kind, provided that the above copyright notice and this paragraph
included on all such copies and derivative works. However,
document itself may not be modified in any way, such as by
the copyright notice or references to the Internet Society or
Internet organizations, except as needed for the purpose
developing Internet standards in which case the procedures
copyrights defined in the Internet Standards process must
followed, or as required to translate it into languages other
English
The limited permissions granted above are perpetual and will not
revoked by the Internet Society or its successors or assigns
This document and the information contained herein is provided on
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED,
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE
Funding for the RFC Editor function is currently provided by
Internet Society
Hodges, et al. Standards Track [Page 12]
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