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 Status of this Memo 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 Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on June 16, 2007. Copyright Notice Copyright (C) The IETF Trust (2006). Altman & Williams Expires June 16, 2007 [Page 1] Internet-Draft On Channel Bindings December 2006 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 Altman & Williams Expires June 16, 2007 [Page 2] Internet-Draft On Channel Bindings December 2006 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]. Altman & Williams Expires June 16, 2007 [Page 3] Internet-Draft On Channel Bindings December 2006 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. Altman & Williams Expires June 16, 2007 [Page 4] Internet-Draft On Channel Bindings December 2006 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. Altman & Williams Expires June 16, 2007 [Page 5] Internet-Draft On Channel Bindings December 2006 4. IANA Considerations There are no IANA considerations for this document. Altman & Williams Expires June 16, 2007 [Page 6] Internet-Draft On Channel Bindings December 2006 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. Altman & Williams Expires June 16, 2007 [Page 7] Internet-Draft On Channel Bindings December 2006 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. Altman & Williams Expires June 16, 2007 [Page 8] Internet-Draft On Channel Bindings December 2006 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 Altman & Williams Expires June 16, 2007 [Page 9] Internet-Draft On Channel Bindings December 2006 Full Copyright Statement Copyright (C) The IETF Trust (2006). 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