NETWORK WORKING GROUP J. Altman
Internet-Draft Secure Endpoints
Expires: June 16, 2007 N. Williams
Sun Microsystems
December 13, 2006
On the Use of Channel Bindings to Secure Channels
draft-altman-tls-channel-bindings-01
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Abstract
This document defines a form of channel bindings for TLS (Transport
Layer Security), namely the concatenation of the initial client and
server "finished" messages for a TLS connection.
Table of Contents
1. Conventions used in this document . . . . . . . . . . . . . . 3
2. Naming TLS Connections . . . . . . . . . . . . . . . . . . . . 4
3. Recommended Application Programming Interfaces . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. Normative References . . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
Intellectual Property and Copyright Statements . . . . . . . . . . 10
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1. Conventions used in this document
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 [RFC2119].
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2. Naming TLS Connections
Whenever a "name" is needed for a TLS connection such that the "name"
is cryptographically bound to the said TLS [RFC4346]connection (its
pre-master secret, negotiation, messages, etc...) such a name may be
constructed as described below; we term this a "channel binding."
The channel bindings for TLS connections consist of the concatenation
of the initial client and server "finished" TLS messages section
7.4.9 [RFC4346] (note: the unencrypted messages). The initial TLS
finished messages are the first pair of TLS finished messages
exchanged after TLS channel establishment. It is irrelevant whether
the TLS channel was established with a previous SessionID section
7.4.1.2 [RFC4346] or not.
Application protocols MAY specify which of the two initial finished
messages, or combination of both of them, to use. If this is not
specified, the concatenation of the client and the server finished
TLS messages are used. (client finished message first.)
The process by which applications perform "channel binding," that is,
the process by which applications establish that the channel bindings
for a given TLS connection are observed to be the same at both
application ends of the TLS connection is not described here.
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3. Recommended Application Programming Interfaces
TLS implementations supporting the use of initial TLS finished
messages as channel bindings should provide application programming
interfaces to enable higher level protocol implementations to obtain
the initial TLS finished messages for both the client and server
endpoints.
It is acceptable for the API to provide access to the most recent
finished messages although doing so will require that the application
be aware of TLS renegotiations in order to ensure that the correct
set of TLS finished messages are used.
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4. IANA Considerations
There are no IANA considerations for this document.
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5. Security Considerations
The TLS finished messages section7.4.9 [RFC4346] are known to both
TLS endpoints and can therefore be safely used as a channel binding
provided that the higher level protocol binding to the TLS channel
provides integrity protection for the TLS finished messages and only
communicates the TLS finished messages across the TLS channel that it
is binding to.
If there is an active man-in-the-middle attack, the attacker will
already possess knowledge of the TLS finished messages for both
inbound and outbound TLS channels. Therefore, there is no additional
information obtained by the attacker via the use of the TLS finished
messages as a channel binding
The Security Considerations section of
"draft-williams-on-channel-binding" applies to this document.
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6. Normative References
[I-D.williams-on-channel-binding]
Williams, N., "On the Use of Channel Bindings to Secure
Channels", draft-williams-on-channel-binding-00 (work in
progress), August 2006.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.1", RFC 4346, April 2006.
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Authors' Addresses
Jeffrey Altman
Secure Endpoints Inc.
255 W 94TH ST PHB
NEW YORK, NY 10025
US
Email: jaltman@secure-endpoints.com
Nicolas Williams
Sun Microsystems Inc.
5300 Riata Trace Ct
Austin, TX 78727
US
Email: Nicolas.Williams@sun.com
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