Realm Crossover for SASL via Diameter
draft-vanrein-diameter-sasl-01

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Network Working Group                                        R. Van Rein
Internet-Draft                                                 ARPA2.net
Intended status: Standards Track                          April 10, 2019
Expires: October 12, 2019

                 Realm Crossover for SASL via Diameter
                     draft-vanrein-diameter-sasl-01

Abstract

   SASL is used for authentication in many application protocols.  This
   specification extends it to allow credentials from a home realm to be
   used against external services.  To this end, it introduces a secure
   end-to-end wrapper for SASL traffic and a link back from to the home
   realm based on Diameter.

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Van Rein                Expires October 12, 2019                [Page 1]
Internet-Draft                Diameter SASL                   April 2019

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  The SASL crossover mechanism SXOVER . . . . . . . . . . . . .   3
     2.1.  SXOVER initial response . . . . . . . . . . . . . . . . .   4
     2.2.  SXOVER initial challenge  . . . . . . . . . . . . . . . .   5
     2.3.  SXOVER responses  . . . . . . . . . . . . . . . . . . . .   5
     2.4.  SXOVER challenges . . . . . . . . . . . . . . . . . . . .   6
   3.  Embedding SASL in Diameter  . . . . . . . . . . . . . . . . .   6
     3.1.  AVP Definitions for SASL  . . . . . . . . . . . . . . . .   6
       3.1.1.  SASL-Mechanism  . . . . . . . . . . . . . . . . . . .   6
       3.1.2.  SASL-Token  . . . . . . . . . . . . . . . . . . . . .   7
       3.1.3.  SASL-Channel-Binding  . . . . . . . . . . . . . . . .   7
   4.  Running Diameter as a SASL Backend  . . . . . . . . . . . . .   7
     4.1.  Diameter is an SCTP service . . . . . . . . . . . . . . .   8
     4.2.  Reliance on DANE and DNSSEC . . . . . . . . . . . . . . .   8
     4.3.  Foreign Service SASL Mechanisms . . . . . . . . . . . . .   9
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .  11
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   It is common for Internet users to combine services from a varierity
   of providers.  Along with this, an ad hoc practice has arisen of
   using the local identity schemes of these providers.  These are not
   integrated, and the practice tends to reduce the control of users
   over their online identity.  A solution to this is generic support
   for realm crossover, where an externally acquired service can make a
   callback to a home realm to authenticate a user's identity and use
   that for service-specific authorisation.

   SASL [RFC4422] is instrumental in authentication across a wide range
   of application protocols; it allows those protocols to abstract from
   the actual authentication mechanisms, and at the same time it allows
   authentication mechanisms to not be concerned about the application
   protocol.  SASL can easily be funneled from one protocol into
   another, modulo a number of security concerns.

   Diameter and its Network Access application are instrumental in
   authenticating a user under a realm, while not providing the
   resources that an application protocol would imply.  Moreover,