INTERNET-DRAFT S. Santesson (Microsoft) Updates: 2246, 4346 Intended Category: Standards track Expires September 2006 March 2006 TLS Handshake Message for Supplemental Data <draft-santesson-tls-supp-00.txt> 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 a "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html Abstract This specification specifies a TLS handshake message for exchange of supplemental application data. TLS hello message extensions are used to determine which supplemental data types are supported by both the TLS client and the TLS server. Then, the supplemental data handshake message is used to exchange the data. Other documents will define the syntax of these extensions and the syntax of the associated supplemental data types. Santesson [Page 1]
INTERNET DRAFT TLS Handshake Message for Supplemental Data March 2006 1. Introduction Recent standards activities have proposed different mechanisms for transmitting supplemental application data in the TLS handshake message. For example, recent proposals transfer data that is not processed by the TLS protocol itself, but assist the TLS-protected application in the authentication and authorization decisions. One proposal transfers user name hints for locating credentials, and another proposal transfers attribute certificates and SAML assertions for authorization checks. In order to avoid definition of multiple handshake messages, one for each new type of application specific supplemental data, this specification defines a new handshake message type that bundles all such data objects together and sends them in a single handshake message. 1.1 Terminology 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 RFC 2119 [STDWORDS]. The syntax for the supplemental_data handshake message is defined using the TLS Presentation Language, which is specified in Section 4 of [N2]. 2 Supplemental Data Handshake Message The new supplemental_data handshake message type is defined to accommodate communication of supplemental data objects as agreed during the exchange of extensions in the client and server hello messages. See RFC 2246 (TLS 1.0) [N2] and RFC 4346 (TLS 1.1) [N3] for other handshake message types. enum { supplemental_data(TBD), (255) } HandshakeType; struct { HandshakeType msg_type; /* handshake type */ uint24 length; /* octets in message */ select (HandshakeType) { case supplemental_data: SupplementalData; } body; } Handshake; Santesson [Page 2]
INTERNET DRAFT TLS Handshake Message for Supplemental Data March 2006 struct { SupplementalDataEntry supp_data<1..2^24-1>; } SupplementalData; struct { SupplementalDataType supp_data_type; select(SupplementalDataType) { } } SupplementalDataEntry; enum { (65535) } SupplementalDataType; If present, the SupplementalData handshake message MUST contain a non empty SupplementalDataEntry structure carrying data associated with at least one defined SupplementalDataType. An explicit agreement that governs presence of any associated data MUST be concluded between client and server for each SupplementalDataType. This agreement MUST be concluded through the use of TLS extensions in the client and server hello messages. Other documents will specify specific SupplementalDataType and their associated data syntax and processing. These same specifications must also specify the client and server hello message extensions that are used to negotiate the support for the specified supplemental data type. This document simply specifies the TLS Handshake Protocol message that will carry the supplemental data objects. Different situations require the transfer of supplemental data from the client to the server, require the transfer of supplemental data from server to the client, or require the transfer of supplemental data from the client to the server as well as the transfer from the server to the client. All three situations are fully supported. Santesson [Page 3]
INTERNET DRAFT TLS Handshake Message for Supplemental Data March 2006 4 Message flow The SupplementalData handshake message, if exchanged, MUST be sent as the first handshake message as illustrated in Figure 1 below. Client Server ClientHello (with extensions) --------> ServerHello(with extensions) SupplementalData* Certificate* ServerKeyExchange* CertificateRequest* <-------- ServerHelloDone SupplementalData* Certificate* ClientKeyExchange CertificateVerify* [ChangeCipherSpec] Finished --------> [ChangeCipherSpec] <-------- Finished Application Data <-------> Application Data * Indicates optional or situation-dependent messages. Figure 1. Message flow with SupplementalData Santesson [Page 4]
INTERNET DRAFT TLS Handshake Message for Supplemental Data March 2006 5 Security Considerations Each SupplementalDataType included in the handshake message defined in this specification introduces its own unique set of security properties and related considerations. Security considerations must therefore be defined in each document that defines a supplemetal data type. Santesson [Page 5]
INTERNET DRAFT TLS Handshake Message for Supplemental Data March 2006 6 Normative References [N1] S. Bradner, "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [N2] T. Dierks, C. Allen, "The TLS Protocol Version 1.0", RFC 2246, January 1999. [N3] T. Dierks, E. Rescorla, "The TLS Protocol Version 1.1", RFC 4346, January 2006. [N4] S. Blake-Wilson, M. Nystrom, D. Hopwood, J. Mikkelsen, T. Wright, "Transport Layer Security (TLS) Extensions", RFC 4366, February 2006. 7 IANA Considerations IANA needs to establish a registry for TLS Supplemental Data Formats. TLS Authorization Data Format identifiers with values in the inclusive range 0-16385 (decimal) are assigned via RFC 2434 [IANA] Standards Action. Values from the inclusive range 16385-65279 (decimal) are assigned via RFC 2434 Specification Required. Values from the inclusive range 65280-65535 (decimal) are reserved for RFC 2434 Private Use. Santesson [Page 6]
INTERNET DRAFT TLS Handshake Message for Supplemental Data March 2006 Author's Address Stefan Santesson Microsoft Finlandsgatan 30 164 93 KISTA Sweden EMail: stefans(at)microsoft.com Acknowledgements The fundamental architectural idea for the supplemental data handshake message was provided by Russ Housley and Eric Rescorla. Santesson [Page 7]
INTERNET DRAFT TLS Handshake Message for Supplemental Data March 2006 Disclaimer This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2006). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Expires September 2006 Santesson [Page 8]
