Token Binding for 0-RTT TLS 1.3 Connections
draft-ietf-tokbind-tls13-0rtt-01

Document Type Active Internet-Draft (tokbind WG)
Last updated 2017-03-13
Replaces draft-nharper-0-rtt-token-binding
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Token Binding Working Group                                    N. Harper
Internet-Draft                                               Google Inc.
Intended status: Standards Track                          March 13, 2017
Expires: September 14, 2017

              Token Binding for 0-RTT TLS 1.3 Connections
                    draft-ietf-tokbind-tls13-0rtt-01

Abstract

   This document describes how Token Binding can be used in the 0-RTT
   data of a TLS 1.3 connection.  This involves updating how Token
   Binding negotiation works and adding a mechanism for indicating
   whether a server prevents replay.  A TokenBindingMessage sent in
   0-RTT data has different security properties than one sent after the
   TLS handshake has finished, which this document also describes.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on September 14, 2017.

Copyright Notice

   Copyright (c) 2017 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
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of

Harper                 Expires September 14, 2017               [Page 1]
Internet-Draft             0-RTT Token Binding                March 2017

   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   2.  Proposed Design . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  TokenBinding Signature Definition . . . . . . . . . . . .   3
       2.1.1.  Selecting Which Exporter Secret to Use  . . . . . . .   3
     2.2.  Negotiating Token Binding . . . . . . . . . . . . . . . .   4
       2.2.1.  Negotiation TLS Extension . . . . . . . . . . . . . .   4
       2.2.2.  Replay Protection Indication Extension  . . . . . . .   4
   3.  Implementation Challenges . . . . . . . . . . . . . . . . . .   5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
     5.1.  Proof of Possession of Token Binding Key  . . . . . . . .   6
     5.2.  Attacks on PSK-only Key Exchange and Token Binding  . . .   6
     5.3.  Exporter Replayability  . . . . . . . . . . . . . . . . .   7
     5.4.  Replay Mitigations  . . . . . . . . . . . . . . . . . . .   7
       5.4.1.  Server Mitigations  . . . . . . . . . . . . . . . . .   8
       5.4.2.  Client Mitigations  . . . . . . . . . . . . . . . . .   8
     5.5.  Early Data Ticket Age Window  . . . . . . . . . . . . . .   8
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   9
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   9
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   Token Binding ([I-D.ietf-tokbind-protocol]) cryptographically binds
   security tokens (e.g.  HTTP cookies, OAuth tokens) to the TLS layer
   on which they are presented.  It does so by signing an [RFC5705]
   exporter value from the TLS connection.  TLS 1.3 introduces a new
   mode that allows a client to send application data on its first
   flight.  If this 0-RTT data contains a security token, then a client
   using Token Binding would want to prove possession of its Token
   Binding private key so that the server can verify the binding.  The
   [RFC5705]-style exporter provided by TLS 1.3 cannot be run until the
   handshake has finished.  TLS 1.3 also provides an exporter that can
   be used with 0-RTT data, but it requires that the application
   explicitly specify that use.  This document specifies how to use the
   early_exporter_secret with Token Binding in TLS 1.3 0-RTT data.
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