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Versions: 00

Internet Engineering Task Force                                C. Paasch
Internet-Draft                                               Apple, Inc.
Intended status: Experimental                                    A. Ford
Expires: November 28, 2016                                         Pexip
                                                            May 27, 2016


                      TLS Authentication for MPTCP
                draft-paasch-mptcp-tls-authentication-00

Abstract

   Multipath TCP (MPTCP), described in [4], is an extension to TCP to
   provide the ability to simultaneously use multiple paths between
   peers.

   draft-paasch-mptcp-application-authentication specifies "application
   layer authentication" for Multipath TCP, an alternatively negotiated
   keying mechanism for MPTCP.  This allows keying material to be
   sourced from an application layer protocol in order to secure MP_JOIN
   handshakes.

   This document explains how to use the proposed application-layer
   authentication extension with TLS [6], in order to leverage securely
   exchanged keys for MPTCP security, whilst simultaneously freeing the
   MPTCP token to be used as a channel for additional information.

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on November 28, 2016.








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Copyright Notice

   Copyright (c) 2016 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
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Technical Implementation  . . . . . . . . . . . . . . . . . .   3
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     5.2.  Informative References  . . . . . . . . . . . . . . . . .   4

1.  Introduction

   As described in draft-paasch-mptcp-application-authentication, the
   use of "application-layer authentication" allows the Key used in
   MPTCP authentication to be provided by the application layer, thus
   permitting the use of existing secure communication channels for
   exchanging keying material.  Furthermore, this decouples the key from
   the token and thus allows the token to be used for conveying
   additional semantics, such as helping front-end proxies route traffic
   to appropriate back-end servers.

   TLS [6] provides a secure authentication channel between end hosts,
   where keys are not transmitted in the clear.  The protocol generates
   a master secret for a connection, and a method is described in [3]
   for exporting a key generated from this and other properties which
   can then be used by the application layer.  This document shows how
   to use this exported key, along with the method in draft-paasch-
   mptcp-application-authentication, for providing alternative keying
   mechanisms for MPTCP.







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2.  Technical Implementation

   As described in draft-paasch-mptcp-application-authentication, the
   initial MP_CAPABLE handshake will exchange an arbitrary token for
   identifying an MPTCP connection.  Whilst it is RECOMMENDED that the
   token is hard to guess, it can be used to carry any data, such as
   arbitrary routing information, and the security provided by the
   application-layer security will mitigate any risks of an attacker
   guessing tokens.

   When an MPTCP end host wishes to open a new subflow, it will follow
   the same exchange as described in [4], however the keying material
   (Key-A and Key-B) will be derived from the TLS handshake, as
   described in [3].  The "label" field MUST be "EXPORTER-MPTCP".  The
   length used in the key-derivation, following [3] is 16.  Key-A are
   the 64 most-significant bits, while Key-B are the 64 remaining bits.
   This requires the key exchange to have completed before subflows can
   be created.  Other than the source of the keys, the exchange remains
   the same.  The MP_CAPABLE and MP_JOIN exchange therefore looks like
   this:

              Host A                                  Host B
     ------------------------                       ----------
     Address A1    Address A2                       Address B1
     ----------    ----------                       ----------
         |             |                                |
         |             |  SYN + MP_CAPABLE              |
         |--------------------------------------------->|
         |<---------------------------------------------|
         |         SYN/ACK + MP_CAPABLE(Token-B)        |
         |             |                                |
         |      ACK + MP_CAPABLE(Token-A, Token-B)      |
         |--------------------------------------------->|
         |             |                                |
         |             |   SYN + MP_JOIN(Token-B, R-A)  |
         |             |------------------------------->|
         |             |<-------------------------------|
         |             | SYN/ACK + MP_JOIN(HMAC-B, R-B) |
         |             |                                |
         |             |     ACK + MP_JOIN(HMAC-A)      |
         |             |------------------------------->|
         |             |<-------------------------------|
         |             |             ACK                |

   HMAC-A = HMAC(Key=(Key-A+Key-B), Msg=(R-A+R-B))
   HMAC-B = HMAC(Key=(Key-B+Key-A), Msg=(R-B+R-A))

               Figure 1: Example Use of MPTCP Authentication



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3.  Security Considerations

   This draft relies on the security provided by TLS [6] and the key
   export mechanism of [3] to provide additional security for the MPTCP
   handshake mechanism.  These changes remove lingering risks,
   originally identified in [7], where an intercept of the initial MPTCP
   handshake could allow session hijack.

4.  IANA Considerations

   IANA would be requested to add a value to the TLS Exporter Label
   registry as described in [3].  The label is "EXPORTER-MPTCP".

5.  References

5.1.  Normative References

   [1]        Postel, J., "Transmission Control Protocol", STD 7, RFC
              793, September 1981.

   [2]        Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [3]        Rescorla, E., "Keying Material Exporters for Transport
              Layer Security (TLS)", RFC 5705, DOI 10.17487/RFC5705,
              March 2010, <http://www.rfc-editor.org/info/rfc5705>.

   [4]        Ford, A., Raiciu, C., Handley, M., Bonaventure, O., and C.
              Paasch, "TCP Extensions for Multipath Operation with
              Multiple Addresses", draft-ietf-mptcp-rfc6824bis-05 (work
              in progress), January 2016.

   [5]        National Institute of Science and Technology, "Secure Hash
              Standard", Federal Information Processing Standard (FIPS)
              180-3, October 2008,
              <http://csrc.nist.gov/publications/fips/fips180-3/
              fips180-3_final.pdf>.

5.2.  Informative References

   [6]        Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/
              RFC5246, August 2008,
              <http://www.rfc-editor.org/info/rfc5246>.

   [7]        Ford, A., Raiciu, C., Handley, M., and O. Bonaventure,
              "TCP Extensions for Multipath Operation with Multiple
              Addresses", RFC 6824, January 2013.



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Authors' Addresses

   Christoph Paasch
   Apple, Inc.
   Cupertino
   US

   EMail: cpaasch@apple.com


   Alan Ford
   Pexip

   EMail: alan.ford@gmail.com





































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