Transport Layer Security (TLS) Renegotiation Indication Extension
RFC 5746

Internet Engineering Task Force (IETF)                       E. Rescorla
Request for Comments: 5746                                    RTFM, Inc.
Updates: 5246, 4366, 4347, 4346, 2246                             M. Ray
Category: Standards Track                                    S. Dispensa
ISSN: 2070-1721                                              PhoneFactor
                                                                N. Oskov
                                                               Microsoft
                                                           February 2010

   Transport Layer Security (TLS) Renegotiation Indication Extension

Abstract

   Secure Socket Layer (SSL) and Transport Layer Security (TLS)
   renegotiation are vulnerable to an attack in which the attacker forms
   a TLS connection with the target server, injects content of his
   choice, and then splices in a new TLS connection from a client.  The
   server treats the client's initial TLS handshake as a renegotiation
   and thus believes that the initial data transmitted by the attacker
   is from the same entity as the subsequent client data.  This
   specification defines a TLS extension to cryptographically tie
   renegotiations to the TLS connections they are being performed over,
   thus preventing this attack.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc5746.

Rescorla, et al.             Standards Track                    [Page 1]
RFC 5746               TLS Renegotiation Extension         February 2010

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1. Introduction ....................................................3
   2. Conventions Used in This Document ...............................4
   3. Secure Renegotiation Definition .................................4
      3.1. Additional Connection State ................................4
      3.2. Extension Definition .......................................5
      3.3. Renegotiation Protection Request Signaling Cipher
           Suite Value ................................................6
      3.4. Client Behavior: Initial Handshake .........................6
      3.5. Client Behavior: Secure Renegotiation ......................7
      3.6. Server Behavior: Initial Handshake .........................7
      3.7. Server Behavior: Secure Renegotiation ......................8
   4. Backward Compatibility ..........................................9
      4.1. Client Considerations ......................................9
      4.2. Client Behavior: Legacy (Insecure) Renegotiation ..........10
      4.3. Server Considerations .....................................10
      4.4. Server Behavior: Legacy (Insecure) Renegotiation ..........11
      4.5. SSLv3 .....................................................11
   5. Security Considerations ........................................12
   6. IANA Considerations ............................................13
   7. Acknowledgements ...............................................13
   8. References .....................................................13
      8.1. Normative References ......................................13
      8.2. Informative References ....................................13

Rescorla, et al.             Standards Track                    [Page 2]
RFC 5746               TLS Renegotiation Extension         February 2010

1.  Introduction

   TLS [RFC5246] allows either the client or the server to initiate
   renegotiation -- a new handshake that establishes new cryptographic
   parameters.  Unfortunately, although the new handshake is carried out