Attested TLS Token Binding
draft-mandyam-tokbind-attest-01

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Last updated 2017-03-07
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Token Binding Working Group                                   G. Mandyam
Internet-Draft                                              L. Lundblade
Intended status: Standards Track                                 J. Azen
Expires: September 8, 2017                    Qualcomm Technologies Inc.
                                                           March 7, 2017

                       Attested TLS Token Binding
                    draft-mandyam-tokbind-attest-01

Abstract

   Token binding allows HTTP servers to bind bearer tokens to TLS
   connections.  In order to do this, clients or user agents must prove
   possession of a private key.  However, proof-of-possession of a
   private key becomes truly meaningful to a server when accompanied by
   an attestation statement.  This specification describes extensions to
   the existing token binding protocol to allow for attestation
   statements to be sent along with the related token binding messages.

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   This Internet-Draft will expire on September 8, 2017.

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Mandyam, et al.         Expires September 8, 2017               [Page 1]
Internet-Draft                TokBindAttest                   March 2017

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Attestation Enhancement to TLS Token Binding Message  . . . .   3
   3.  Example - Platform Attestation for Anomaly Detection  . . . .   3
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     5.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   [I-D.ietf-tokbind-protocol] and [I-D.ietf-tokbind-negotiation]
   describe a framework whereby servers can leverage cryptographically-
   bound authentication tokens to verify TLS connections.  This is
   useful for prevention of man-in-the-middle attacks on TLS sessions,
   and provides a mechanism by which identity federation systems can be
   leveraged by a relying party to verify a client based on proof-of-
   possession of a private key.

   Once the use of token binding is negotiated as part of the TLS
   handshake, an application layer message (the Token Binding message)
   may be sent from the client to the relying party whose primary
   purpose is to encapsulate a signature over a value associated with
   the current TLS session (Exported Key Material, i.e. EKM - see
   [I-D.ietf-tokbind-protocol]).

   Proof-of-possession of a private key is useful to a relying party,
   but the associated signature in the Token Binding message does not
   provide an indication as to how the private key is stored and in what
   kind of environment the associated cryptographic operation takes
   place.  This information may be required by a relying party in order
   to satisfy requirements regarding client platform integrity.
   Therefore, attestations are sometimes required by relying parties in
   order for them to accept signatures from clients.  As per the
   definition in [I-D.birkholz-tuda], "remote attestation describes the
   attempt to determine the integrity and trustworthiness of an endpoint
   -- the attestee -- over a network to another endpoint -- the verifier
   -- without direct access."  Attestation statements are therefore
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