Reciprocal OAuth

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Last updated 2019-09-06 (latest revision 2019-08-01)
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OAuth Working Group                                             D. Hardt
Internet-Draft                                           August 01, 2019
Intended status: Standards Track
Expires: February 2, 2020

                            Reciprocal OAuth


   There are times when a user has a pair of protected resources that
   would like to request access to each other.  While OAuth flows
   typically enable the user to grant a client access to a protected
   resource, granting the inverse access requires an additional flow.
   Reciprocal OAuth enables a more seamless experience for the user to
   grant access to a pair of protected resources.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on February 2, 2020.

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   Copyright (c) 2019 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
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   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of

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

1.  Introduction

   In the usual three legged, authorization code grant, the OAuth flow
   enables a resource owner (user) to enable a client (party A) to be
   granted authorization to access a protected resource (party B).  If
   party A also has a protected resource that the user would like to let
   party B access, then a second complete OAuth flow, but in the reverse
   direction, must be performed.  In practice, this is a complicated
   user experience as the user is at Party A, but the OAuth flow needs
   to start from Party B.  This requires the second flow to send the
   user back to party B, which then sends the user to Party A as the
   first step in the flow.  At the end, the user is at Party B, even
   though the original flow started at Party A.

   Reciprocal OAuth simplifies the user experience by eliminating the
   redirections in the second OAuth flow.  After the intial OAuth flow,
   party A obtains consent from the user to grant party B access to a
   protected resource at party A, and then passes an authorization code
   to party B using the access token party A obtained from party B to
   provide party B the context of the user.  Party B then exchanges the
   authorization code for an access token per the usual OAuth flow.

   For example, a user would like their voice assistant (party A) and
   music service (party B) to work together.  The voice assistant wants
   to call the music service to play music, and the music service wants
   to call the voice assistant with music information to present to the
   user.  The user starts the OAuth flow at the voice assistant, and is
   redirected to the music service.  The music services obtains consent
   from the user and the redirects back to the voice assistant.  At this
   point the voice assistant is able to obtain an access token for the
   music service.  The voice assistant can the get consent from the user
   to authorize the music service to access the voice assistant, and
   then the voice assistant can create an authorization code and send it
   to the music service, which then exchanges the authorization code for
   an access token, all without further user interaction.  Note that
   either the voice assistant or the music service can initiate the
   flow, so that either can prompt the user for the two parties to work

1.1.  Terminology

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   and "OPTIONAL" are to be interpreted as described in BCP 14, RFC 2119

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