Realm Crossover for SASL and GSS-API via Diameter
draft-vanrein-diameter-sasl-03

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Network Working Group                                        R. Van Rein
Internet-Draft                                                 ARPA2.net
Intended status: Informational                          January 21, 2020
Expires: July 24, 2020

           Realm Crossover for SASL and GSS-API via Diameter
                     draft-vanrein-diameter-sasl-03

Abstract

   SASL and GSS-API are used for authentication in many application
   protocols.  This specification extends them to allow credentials of a
   home realm to be used against external services.  To this end, it
   introduces end-to-end encryption for SASL that is safe to relay to
   the client's home realm.

Status of This Memo

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   This Internet-Draft will expire on July 24, 2020.

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Van Rein                  Expires July 24, 2020                 [Page 1]
Internet-Draft                Diameter SASL                 January 2020

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Messages of GS2-SXOVER-PLUS . . . . . . . . . . . . . . . . .   3
     2.1.  Initial Client-to-Server Message  . . . . . . . . . . . .   4
     2.2.  Initial Server-to-Client Message  . . . . . . . . . . . .   5
     2.3.  Continued Client-to-Server Messages . . . . . . . . . . .   6
     2.4.  Continued Server-to-Client Messages . . . . . . . . . . .   6
   3.  GS2-SXOVER-PLUS as a GS2 Mechanism  . . . . . . . . . . . . .   7
     3.1.  Encrypting GS2-SXOVER-PLUS Messages . . . . . . . . . . .   7
     3.2.  Initial Round-trip Optimisation . . . . . . . . . . . . .   8
     3.3.  Initial Header for GSS-API  . . . . . . . . . . . . . . .   8
     3.4.  Initial Header for SASL . . . . . . . . . . . . . . . . .   9
   4.  AVP Definitions for SASL in Diameter  . . . . . . . . . . . .  10
     4.1.  SASL-Mechanism  . . . . . . . . . . . . . . . . . . . . .  10
     4.2.  SASL-Token  . . . . . . . . . . . . . . . . . . . . . . .  11
     4.3.  SASL-Channel-Binding  . . . . . . . . . . . . . . . . . .  11
   5.  Diameter Message Requirements for GS2-SXOVER-PLUS . . . . . .  11
     5.1.  C2S-Init Requests over Diameter . . . . . . . . . . . . .  12
     5.2.  S2C-Init Responses over Diameter  . . . . . . . . . . . .  12
     5.3.  C2S-Cont Requests over Diameter . . . . . . . . . . . . .  13
     5.4.  S2C-Cont Responses over Diameter  . . . . . . . . . . . .  14
   6.  Running Diameter as a SASL Backend  . . . . . . . . . . . . .  14
     6.1.  Diameter is an SCTP service . . . . . . . . . . . . . . .  14
     6.2.  Reliance on DANE and DNSSEC . . . . . . . . . . . . . . .  14
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .  16
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .  17
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  17

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 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