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Network Working Group                                      D. Hardt, Ed.
Internet-Draft                                                SignIn.Org
Intended status: Standards Track                             6 June 2020
Expires: 8 December 2020


            The Grant Negotiation and Authorization Protocol
                     draft-hardt-xauth-protocol-07

Abstract

   Client software often desires resources or identity claims that are
   independent of the client.  This protocol allows a user and/or
   resource owner to delegate resource authorization and/or release of
   identity claims to a server.  Client software can then request access
   to resources and/or identity claims by calling the server.  The
   server acquires consent and authorization from the user and/or
   resource owner if required, and then returns to the client software
   the authorization and identity claims that were approved.  This
   protocol can be extended to support alternative authorizations,
   claims, interactions, and client authentication mechanisms.

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
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   Drafts is at https://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
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 8 December 2020.

Copyright Notice

   Copyright (c) 2020 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 (https://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



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   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  . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.1.  Parties . . . . . . . . . . . . . . . . . . . . . . . . .   5
     1.2.  Reused Terms  . . . . . . . . . . . . . . . . . . . . . .   6
     1.3.  New Terms . . . . . . . . . . . . . . . . . . . . . . . .   6
     1.4.  Notational Conventions  . . . . . . . . . . . . . . . . .   7
   2.  Sequences . . . . . . . . . . . . . . . . . . . . . . . . . .   8
     2.1.  Create and Verify Grant . . . . . . . . . . . . . . . . .   8
     2.2.  Create and Read Grant - Redirect  . . . . . . . . . . . .   9
     2.3.  Create and Read Grant - Indirect  . . . . . . . . . . . .  10
     2.4.  Reciprocal Grant  . . . . . . . . . . . . . . . . . . . .  11
     2.5.  GS Initiated Grant  . . . . . . . . . . . . . . . . . . .  12
     2.6.  Create and Update . . . . . . . . . . . . . . . . . . . .  12
     2.7.  Create and Delete . . . . . . . . . . . . . . . . . . . .  14
     2.8.  Create, Discover, and Delete  . . . . . . . . . . . . . .  16
     2.9.  Create and Wait . . . . . . . . . . . . . . . . . . . . .  16
     2.10. Read Grant  . . . . . . . . . . . . . . . . . . . . . . .  17
     2.11. Resource Server Access  . . . . . . . . . . . . . . . . .  18
     2.12. GS API Table  . . . . . . . . . . . . . . . . . . . . . .  19
   3.  Grant and AuthZ Life Cycle  . . . . . . . . . . . . . . . . .  19
   4.  GS APIs . . . . . . . . . . . . . . . . . . . . . . . . . . .  20
     4.1.  Create Grant  . . . . . . . . . . . . . . . . . . . . . .  20
     4.2.  Verify Grant  . . . . . . . . . . . . . . . . . . . . . .  23
     4.3.  Read Grant  . . . . . . . . . . . . . . . . . . . . . . .  24
     4.4.  Update Grant  . . . . . . . . . . . . . . . . . . . . . .  24
     4.5.  Delete Grant  . . . . . . . . . . . . . . . . . . . . . .  25
     4.6.  Request JSON  . . . . . . . . . . . . . . . . . . . . . .  25
       4.6.1.  "client" Object . . . . . . . . . . . . . . . . . . .  25
       4.6.2.  "interaction" Object  . . . . . . . . . . . . . . . .  26
       4.6.3.  "user" Object . . . . . . . . . . . . . . . . . . . .  26
       4.6.4.  "authorization" Object  . . . . . . . . . . . . . . .  27
       4.6.5.  "authorizations" Object . . . . . . . . . . . . . . .  27
       4.6.6.  "claims" Object . . . . . . . . . . . . . . . . . . .  27
       4.6.7.  "verification" Object . . . . . . . . . . . . . . . .  28
     4.7.  Read Authorization  . . . . . . . . . . . . . . . . . . .  28
     4.8.  Update Authorization  . . . . . . . . . . . . . . . . . .  28
     4.9.  Delete Authorization  . . . . . . . . . . . . . . . . . .  29
     4.10. GS Options  . . . . . . . . . . . . . . . . . . . . . . .  29
     4.11. Grant Options . . . . . . . . . . . . . . . . . . . . . .  30
     4.12. AuthZ Options . . . . . . . . . . . . . . . . . . . . . .  30
     4.13. Request Verification  . . . . . . . . . . . . . . . . . .  30
   5.  GS Initiated Grant  . . . . . . . . . . . . . . . . . . . . .  31



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   6.  GS Responses  . . . . . . . . . . . . . . . . . . . . . . . .  31
     6.1.  Grant Response  . . . . . . . . . . . . . . . . . . . . .  31
     6.2.  Interaction Response  . . . . . . . . . . . . . . . . . .  32
     6.3.  Wait Response . . . . . . . . . . . . . . . . . . . . . .  33
     6.4.  Response JSON . . . . . . . . . . . . . . . . . . . . . .  34
       6.4.1.  "client" Object . . . . . . . . . . . . . . . . . . .  34
       6.4.2.  "interaction" Object  . . . . . . . . . . . . . . . .  34
       6.4.3.  "user" Object . . . . . . . . . . . . . . . . . . . .  34
       6.4.4.  "authorization" Object  . . . . . . . . . . . . . . .  34
       6.4.5.  "authorizations" Object . . . . . . . . . . . . . . .  34
       6.4.6.  "claims" Object . . . . . . . . . . . . . . . . . . .  35
     6.5.  Authorization JSON  . . . . . . . . . . . . . . . . . . .  35
       6.5.1.  Signing and Encryption  . . . . . . . . . . . . . . .  36
     6.6.  Response Verification . . . . . . . . . . . . . . . . . .  36
   7.  interaction mode Objects  . . . . . . . . . . . . . . . . . .  36
     7.1.  "redirect" mode . . . . . . . . . . . . . . . . . . . . .  37
       7.1.1.  request "interaction" object contains:  . . . . . . .  37
       7.1.2.  response "interaction" object contains: . . . . . . .  37
     7.2.  "indirect" mode . . . . . . . . . . . . . . . . . . . . .  37
       7.2.1.  request "interaction" object contains:  . . . . . . .  37
       7.2.2.  response "interaction" object contains: . . . . . . .  37
     7.3.  "user_code" mode  . . . . . . . . . . . . . . . . . . . .  37
       7.3.1.  request "interaction" object contains:  . . . . . . .  38
       7.3.2.  response "interaction" object contains: . . . . . . .  38
   8.  RS Access . . . . . . . . . . . . . . . . . . . . . . . . . .  38
     8.1.  Bearer Token  . . . . . . . . . . . . . . . . . . . . . .  38
   9.  Error Responses . . . . . . . . . . . . . . . . . . . . . . .  38
   10. JOSE Authentication . . . . . . . . . . . . . . . . . . . . .  38
     10.1.  GS Access  . . . . . . . . . . . . . . . . . . . . . . .  39
       10.1.1.  Authorization Header . . . . . . . . . . . . . . . .  40
       10.1.2.  Signed Body  . . . . . . . . . . . . . . . . . . . .  41
       10.1.3.  Public Key Resolution  . . . . . . . . . . . . . . .  42
     10.2.  RS Access  . . . . . . . . . . . . . . . . . . . . . . .  42
       10.2.1.  JOSE header  . . . . . . . . . . . . . . . . . . . .  43
       10.2.2.  "jose" Mechanism . . . . . . . . . . . . . . . . . .  43
       10.2.3.  "jose+body" Mechanism  . . . . . . . . . . . . . . .  44
       10.2.4.  Public Key Resolution  . . . . . . . . . . . . . . .  45
     10.3.  Request Encryption . . . . . . . . . . . . . . . . . . .  45
     10.4.  Response Signing . . . . . . . . . . . . . . . . . . . .  45
     10.5.  Response Encryption  . . . . . . . . . . . . . . . . . .  46
   11. Extensibility . . . . . . . . . . . . . . . . . . . . . . . .  46
   12. Rational  . . . . . . . . . . . . . . . . . . . . . . . . . .  47
   13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  51
   14. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  51
   15. Security Considerations . . . . . . . . . . . . . . . . . . .  51
   16. References  . . . . . . . . . . . . . . . . . . . . . . . . .  51
     16.1.  Normative References . . . . . . . . . . . . . . . . . .  51
     16.2.  Informative References . . . . . . . . . . . . . . . . .  53



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   Appendix A.  Document History . . . . . . . . . . . . . . . . . .  54
     A.1.  draft-hardt-xauth-protocol-00 . . . . . . . . . . . . . .  54
     A.2.  draft-hardt-xauth-protocol-01 . . . . . . . . . . . . . .  54
     A.3.  draft-hardt-xauth-protocol-02 . . . . . . . . . . . . . .  55
     A.4.  draft-hardt-xauth-protocol-03 . . . . . . . . . . . . . .  55
     A.5.  draft-hardt-xauth-protocol-04 . . . . . . . . . . . . . .  55
     A.6.  draft-hardt-xauth-protocol-05 . . . . . . . . . . . . . .  55
     A.7.  draft-hardt-xauth-protocol-06 . . . . . . . . . . . . . .  55
     A.8.  draft-hardt-xauth-protocol-07 . . . . . . . . . . . . . .  56
   Appendix B.  Comparison with OAuth 2.0 and OpenID Connect . . . .  56
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  57

1.  Introduction

   This protocol supports the widely deployed use cases supported by
   OAuth 2.0 [RFC6749] & [RFC6750], and OpenID Connect [OIDC], an
   extension of OAuth 2.0, as well as other extensions, and other use
   cases that are not supported, such as acquiring multiple access
   tokens at the same time, and updating the request during user
   interaction.  This protocol also addresses many of the security
   issues in OAuth 2.0 by having parameters securely sent directly
   between parties, rather than via a browser redirection.

   The technology landscape has changed since OAuth 2.0 was initially
   drafted.  More interactions happen on mobile devices than PCs.
   Modern browsers now directly support asymetric cryptographic
   functions.  Standards have emerged for signing and encrypting tokens
   with rich payloads (JOSE) that are widely deployed.

   Additional use cases are now being served with extensions to OAuth
   2.0: OpenID Connect added support for authentication and releasing
   identity claims; [RFC8252] added support for native apps; [RFC8628]
   added support for smart devices; and support for [browser_based_apps]
   is being worked on.  There are numerous efforts on adding proof-of-
   possession to resource access.

   This protocol simplifies the overall architectural model, takes
   advantage of today's technology landscape, provides support for all
   the widely deployed use cases, and offers numerous extension points.

   While this protocol is not backwards compatible with OAuth 2.0, it
   strives to minimize the migration effort.

   This protocol centers around a Grant, a representation of the
   collection of user identity claims and/or resource authorizations the
   Client is requesting, and the resulting identity claims and/or
   resource authorizations granted by the Grant Server.




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   [Editor: suggestions on how to improve this are welcome!]

   [Editor: suggestions for other names than XAuth are welcome!]

1.1.  Parties

   The parties and their relationships to each other:

   +--------+                           +------------+
   |  User  |                           |  Resource  |
   |        |                           | Owner (RO) |
   +--------+                           +------------+
       |      \                       /      |
       |       \                     /       |
       |        \                   /        |
       |         \                 /         |
   +--------+     +---------------+     +------------+
   | Client |---->|     Grant     | _ _ |  Resource  |
   |        |<----|  Server (GS)  |     |   Server   |
   |        |     +---------------+     |    (RS)    |
   |        |-------------------------->|            |
   |        |<--------------------------|            |
   +--------+                           +------------+

   *  *User* - the person interacting with the Client who has delegated
      access to identity claims about themselves to the Grant Server
      (GS), and can authenticate at the GS.

   *  *Client* - requests a Grant from the GS to access one or more
      Resource Servers (RSs), and/or identity claims about the User.
      The Client can create, verify, retrieve, update, and delete a
      Grant.  When a Grant is created, the Client receives from the GS
      the granted access token(s) for the RS(s), and identity claims
      about the User.  The Client uses an access token to access the RS.
      There are two types of Clients: Registered Clients and Dynamic
      Clients.  All Clients have a key to authenticate with the Grant
      Server.

   *  *Registered Client* - a Client that has registered with the GS and
      has a Client ID to identify itself, and can prove it possesses a
      key that is linked to the Client ID.  The GS may have different
      policies for what different Registered Clients can request.  A
      Registered Client MAY be interacting with a User.

   *  *Dynamic Client* - a Client that has not been registered with the
      GS, and each instance will generate it's own key pair so it can
      prove it is the same instance of the Client on subsequent
      requests, and to requests of a Resource Server that require proof-



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      of-possession access.  A single-page application with no active
      server component is an example of a Dynamic Client.  A Dynamic
      Client MUST be interacting with a User.

   *  *Grant Server* (GS) - manages Grants for access to APIs at RSs and
      release of identity claims about the User.  The GS may require
      explicit consent from the RO or User to provide these to the
      Client.  A GS may support Registered Clients and/or Dynamic
      Clients.  The GS is a combination of the Authorization Server (AS)
      in OAuth 2.0, and the OpenID Provider (OP) in OpenID Connect.

   *  *Resource Server* (RS) - has API resources that require an access
      token from the GS.  Some, or all of the resources are owned by the
      Resource Owner.

   *  *Resource Owner* (RO) - owns resources at the RS, and has
      delegated RS access management to the GS.  The RO may be the same
      entity as the User, or may be a different entity that the GS
      interacts with independently.  GS and RO interactions are out of
      scope of this document.

1.2.  Reused Terms

   *  *access token* - an access token as defined in [RFC6749]
      Section 1.4.

   *  *Claim* - a Claim as defined in [OIDC] Section 5.  Claims may be
      issued by the GS, or by other issuers.

   *  *Client ID* - a GS unique identifier for a Registered Client as
      defined in [RFC6749] Section 2.2.

   *  *ID Token* - an ID Token as defined in [OIDC] Section 2.

   *  *NumericDate* - a NumericDate as defined in [RFC7519] Section 2.

   *  *authN* - short for authentication.

   *  *authZ* - short for authorization.

1.3.  New Terms

   *  *GS URI* - the endpoint at the GS the Client calls to create a
      Grant, and is the unique identifier for the GS.

   *  *Grant* - the user identity claims and/or RS authorizations the GS
      has granted to the Client.




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   *  *Grant URI* - the URI that represents the Grant.  The Grant URI
      MUST start with the GS URI.

   *  *Authorization* - the access granted by the RO to the Client.
      Contains an access token.

   *  *Authorization URI* (AZ URI) - the URI that represents the
      Authorization the Client was granted by the RO.  The AZ URI MUST
      start with the GS URI.  The AZ URI is used to read, update, and
      delete an access token.

   *  *Interaction* - how the Client directs the User to interact with
      the GS.  This document defines the interaction modes redirect,
      indirect, and user_code in Section 7

   *  *Client Handle* - a GS unique identifier for a Dynamic Client for
      the Dynamic Client to refer to itself in subsequent requests.

1.4.  Notational Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   specification are to be interpreted as described in [RFC2119].

   Certain security-related terms are to be understood in the sense
   defined in [RFC4949].  These terms include, but are not limited to,
   "attack", "authentication", "authorization", "certificate",
   "confidentiality", "credential", "encryption", "identity", "sign",
   "signature", "trust", "validate", and "verify".

   Unless otherwise noted, all the protocol parameter names and values
   are case sensitive.

   Some protocol parameters are parts of a JSON document, and are
   referred to in JavaScript notation.  For example, foo.bar refers to
   the "bar" boolean attribute in the "foo" object in the following
   example JSON document:

   {
       "foo" : {
           "bar": true
       }
   }








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2.  Sequences

   Before any sequence, the Client needs to be manually or
   programmatically configured for the GS.  See GS Options Section 4.10
   for details on acquiring GS metadata.

   [Editor: a plethora of sequences are included to illustrate all the
   different use cases that are supported.  Many sequences are similar,
   and show a slightly different sequence that can support different use
   cases.  These could potentially be moved to a use case document in
   the future.]

2.1.  Create and Verify Grant

   A Dynamic Client wants a Grant from the User using a Redirect
   Interaction:

   +--------+                                  +-------+
   | Client |                                  |  GS   |
   |        |--(1)--- Create Grant ----------->|       |
   |        |                                  |       |
   |        |<--- Interaction Response ---(2)--|       |         +------+
   |        |                                  |       |         | User |
   |        |--(3)--- Interaction Transfer --- | - - - | ------->|      |
   |        |                                  |       |         |      |
   |        |                                  |       |<--(4)-->|      |
   |        |                                  |       |  authN  |      |
   |        |                                  |       |<--(5)-->|      |
   |        |                                  |       |  authZ  |      |
   |        |<--- Interaction Transfer ---(6)- | - - - | --------|      |
   |        |                                  |       |         |      |
   |        |--(7)--- Verify Grant ----------->|       |         +------+
   |        |                                  |       |
   |        |<--------- Grant Response ---(8)--|       |
   |        |                                  |       |
   +--------+                                  +-------+

   1.  *Create Grant* The Client creates a Request JSON document
       Section 4.6 and makes a Create Grant request (Section 4.1) by
       sending the JSON with an HTTP POST to the GS URI.

   2.  *Interaction Response* The GS determines that interaction with
       the User is required and sends an Interaction Response
       (Section 6.2) containing the Grant URI and an interaction object.

   3.  *Interaction Transfer* The Client redirects the User to the
       Redirect URI at the GS.




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   4.  *User Authentication* The GS authenticates the User.

   5.  *User Authorization* If required, the GS interacts with the User
       to determine which identity claims and/or authorizations in the
       Grant Request are to be granted.

   6.  *Interaction Transfer* The GS redirects the User to the
       Completion URI at the Client, passing an Interaction Nonce.

   7.  *Read Grant* The Client creates a JSON document containing a
       verification object Section 4.6.7 and does a Verify Grant
       Section 4.2 request by HTTP PATCH with the document to the Grant
       URI.

   8.  *Grant Response* The GS responds with a Grant Response
       (Section 6.1).

2.2.  Create and Read Grant - Redirect

   A Registered Client wants a Grant from the User using a Redirect
   Interaction:

   +--------+                                  +-------+
   | Client |                                  |  GS   |
   |        |--(1)--- Create Grant ----------->|       |
   |        |                                  |       |
   |        |<--- Interaction Response ---(2)--|       |
   |        |                                  |       |
   |        |--(3)--- Read Grant ------------->|       |         +------+
   |        |                                  |       |         | User |
   |        |--(4)--- Interaction Transfer --- | - - - | ------->|      |
   |        |                                  |       |         |      |
   |        |                                  |       |<--(5)-->|      |
   |        |                                  |       |  authN  |      |
   |        |                                  |       |<--(6)-->|      |
   |        |                                  |       |  authZ  |      |
   |        |<--------- Grant Response ---(7)--|       |         |      |
   |        |                                  |       |         |      |
   |        |<--- Interaction Transfer ---(8)- | - - - | --------|      |
   |        |                                  |       |         |      |
   +--------+                                  +-------+         +------+

   1.  *Create Grant* The Client makes a Create Grant request
       (Section 4.1) to the GS URI.

   2.  *Interaction Response* The GS determines that interaction with
       the User is required and sends an Interaction Response
       (Section 6.2) containing the Grant URI and an interaction object.



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   3.  *Read Grant* The Client does an HTTP GET of the Grant URI
       (Section 4.3).

   4.  *Interaction Transfer* The Client transfers User interaction to
       the GS.

   5.  *User Authentication* The GS authenticates the User.

   6.  *User Authorization* If required, the GS interacts with the User
       to determine which identity claims and/or authorizations in the
       Grant Request are to be granted.

   7.  *Grant Response* The GS responds with a Grant Response
       (Section 6.1).

   8.  *Interaction Transfer* The GS redirects the User to the
       Completion URI of the Client.  The Client verifies it is the same
       User that it transferred to the GS.

2.3.  Create and Read Grant - Indirect

   A Registered Client wants a Grant from the User using an Indirect
   Interaction:

   +--------+                                  +-------+
   | Client |                                  |  GS   |
   |        |--(1)--- Create Grant ----------->|       |
   |        |                                  |       |
   |        |<--- Interaction Response ---(2)--|       |
   |        |                                  |       |
   |        |--(3)--- Read Grant ------------->|       |         +------+
   |        |                                  |       |         | User |
   |        |--(4)--- Interaction Transfer --- | - - - | ------->|      |
   |        |                                  |       |         |      |
   |        |                                  |       |<--(5)-->|      |
   |        |                                  |       |  authN  |      |
   |        |                                  |       |<--(6)-->|      |
   |        |                                  |       |  authZ  |      |
   |        |<--------- Grant Response ---(7)--|       |         |      |
   +--------+                                  |       |         |      |
                                               |       |         |      |
   +--------+                                  |       |         |      |
   |  Info  |<--- Interaction Transfer ---(8)- | - - - | --------|      |
   | Server |                                  |       |         |      |
   +--------+                                  +-------+         +------+

   The sequence is the same except:




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   *  In step (4) the User either scans a bar code or uses a separate
      device to navigate to the Code URI and enters the User Code.

   *  In step (8) the GS redirects the User to the Information URI
      provided by the Client.

2.4.  Reciprocal Grant

   Party A and Party B are both a Client and a GS, and each Client would
   like a Grant for the other GS.  The sequence starts off the same as
   in Section 2.2, but Party B makes a Create Grant Request before
   sending a Grant Response:

                   Party A                                    Party B
                  +--------+                                 +--------+
                  | Client |                                 |   GS   |
                  ~ ~ ~ ~ ~ ~     Same as steps 1 - 6 of    ~ ~ ~ ~ ~ ~
   +------+       |        |   Create and Read Grant above   |        |
   | User |       |        |                                 |        |
   |      |       |   GS   |<--------- Create Grant ---(1)---| Client |
   |      |       |        |                                 |        |
   |      |       |        |<------- Grant Response ---(2)---|        |
   |      |       |        |                                 |        |
   |      |<----- | - - -  | -- Interaction Transfer --(3)---|        |
   |      |       |        |                                 |        |
   |      |<-(4)->|        |                                 |        |
   |      | AuthZ |        |                                 |        |
   +------+       |   GS   |--(5)--- Grant Response -------->| Client |
                  |        |                                 |        |
                  +--------+                                 +--------+

   1.  *Create Grant* Party B creates a Grant Request (Section 4.1) with
       user.reciprocal set to the Party B Grant URI that will be in the
       step (2) Grant Response, and sends it with an HTTP POST to the
       Party A GS URI.  This enables Party A to link the reciprocal
       Grants.

   2.  *Grant Response* Party B responds to Party A's Create Grant
       Request with a Grant Response that includes the Party B Grant
       URI.

   3.  *Interaction Transfer* Party B redirects the User to the
       Completion URI at Party A.

   4.  *User Authorization* If required, Party A interacts with the User
       to determine which identity claims and/or authorizations in Party
       B's Create Grant Request are to be granted.




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   5.  *Grant Response* Party A responds with a Grant Response
       (Section 6.1).

2.5.  GS Initiated Grant

   The User is at the GS, and wants to interact with a Registered
   Client.  The GS can redirect the User to the Client:

   +--------+                                  +-------+         +------+
   | Client |                                  |  GS   |         | User |
   |        |                                  |       |<--(1)-->|      |
   |        |                                  |       |         |      |
   |        |<----- GS Initiation Redirect --- | - - - | --(2)---|      |
   |   (3)  |                                  |       |         |      |
   | verify |--(4)--- Read Grant ------------->|       |         +------+
   |        |                                  |       |
   |        |<--------- Grant Response --(5)---|       |
   |        |                                  |       |
   +--------+                                  +-------+

   1.  *User Interaction* The GS interacts with the User to determine
       the Client and what identity claims and authorizations to
       provide.  The GS creates a Grant and corresponding Grant URI.

   2.  *GS Initiated Redirect* The GS redirects the User to the Client's
       interaction_uri, adding a query parameter with the name "Grant
       URI" and the value being the URL encoded Grant URI.

   3.  *Client Verification* The Client verifies the Grant URI is from
       an GS the Client trusts, and starts with the GS GS URI.

   4.  *Read Grant* The Client does an HTTP GET of the Grant URI
       (Section 4.3).

   5.  *Grant Response* The GS responds with a Grant Response
       (Section 6.1).

   See Section 5 for more details.

2.6.  Create and Update

   The Client requests an identity claim to determine who the User is.
   Once the Client learns who the User is, and the Client updates the
   Grant for additional identity claims which the GS prompts the User
   for and returns to the Client.  Once those are received, the Client
   updates the Grant with the remaining identity claims required.





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   +--------+                                  +-------+
   | Client |                                  |  GS   |
   |        |--(1)--- Create Grant ----------->|       |
   |        |      interaction.keep:true       |       |
   |        |                                  |       |
   |        |<--- Interaction Response ---(2)--|       |
   |        |                                  |       |
   |        |--(3)--- Read Grant ------------->|       |         +------+
   |        |                                  |       |         | User |
   |        |--(4)--- Interaction Transfer --- | - - - | ------->|      |
   |        |                                  |       |         |      |
   |        |                                  |       |<--(5)-->|      |
   |        |                                  |       |  authN  |      |
   |        |<--------- Grant Response ---(6)--|       |         |      |
   |  (7)   |                                  |       |         |      |
   |  eval  |--(8)--- Update Grant ----------->|       |         |      |
   |        |      interaction.keep:true       |       |<--(9)-->|      |
   |        |                                  |       |  authZ  |      |
   |        |<--------- Grant Response --(10)--|       |         |      |
   |  (11)  |                                  |       |         |      |
   |  eval  |--(12)-- Update Grant ----------->|       |         |      |
   |        |  interaction.keep:false          |       |<--(13)->|      |
   |        |                                  |       |  authZ  |      |
   |        |                                  |       |         |      |
   |        |<--- Interaction Transfer --(14)- | - - - | --------|      |
   |        |                                  |       |         |      |
   |        |<--------- Grant Response --(15)--|       |         +------+
   |        |                                  |       |
   +--------+                                  +-------+

   1.   *Create Grant* The Client creates a Grant Request (Section 4.1)
        including an identity claim and interaction.keep:true, and sends
        it with an HTTP POST to the GS GS URI.

   2.   *Interaction Response* The GS sends an Interaction Response
        (Section 6.2) containing the Grant URI, an interaction object,
        and interaction.keep:true.

   3.   *Read Grant* The Client does an HTTP GET of the Grant URI
        (Section 4.3).

   4.   *Interaction Transfer* The Client transfers User interaction to
        the GS.

   5.   *User Authentication* The GS authenticates the User.






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   6.   *Grant Response* The GS responds with a Grant Response
        (Section 6.1) including the identity claim from User
        authentication and interaction.keep:true.

   7.   *Grant Evaluation* The Client queries its User database and does
        not find a User record matching the identity claim.

   8.   *Update Grant* The Client creates an Update Grant Request
        (Section 4.4) including the initial identity claims required and
        interaction.keep:true, and sends it with an HTTP PUT to the
        Grant URI.

   9.   *User AuthN* The GS interacts with the User to determine which
        identity claims in the Update Grant Request are to be granted.

   10.  *Grant Response* The GS responds with a Grant Response
        (Section 6.1) including the identity claims released by the User
        and interaction.keep:true.

   11.  *Grant Evaluation* The Client evaluates the identity claims in
        the Grant Response and determines the remaining User identity
        claim required.

   12.  *Update Grant* The Client creates an Update Grant Request
        (Section 4.4) including the remaining required identity claims
        and interaction.keep:false, and sends it with an HTTP PUT to the
        Grant URI.

   13.  *User AuthZ* The GS interacts with the User to determine which
        identity claims in the Update Grant Request are to be granted.

   14.  *Interaction Transfer* The GS transfers User interaction to the
        Client.

   15.  *Grant Response* The GS responds with a Grant Response
        (Section 6.1) including the identity claims released by the
        User.

2.7.  Create and Delete

   The Client requests an identity claim to determine who the User is.
   Once the Client learns who the User is, and the Client knows it
   already has all the identity claims and authorizations needed for the
   User, the Client deletes the Grant which prompts the GS to transfer
   the interaction back to the Client.  (If the Client did not already
   have what was needed, the Client would follow the Create and Update
   sequence Section 2.6 )




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   +--------+                                  +-------+
   | Client |                                  |  GS   |
   |        |--(1)--- Create Grant ----------->|       |
   |        |      interaction.keep:true       |       |
   |        |                                  |       |
   |        |<--- Interaction Response ---(2)--|       |
   |        |                                  |       |
   |        |--(3)--- Read Grant ------------->|       |         +------+
   |        |                                  |       |         | User |
   |        |--(4)--- Interaction Transfer --- | - - - | ------->|      |
   |        |                                  |       |         |      |
   |        |                                  |       |<--(5)-->|      |
   |        |                                  |       |  authN  |      |
   |        |<--------- Grant Response ---(6)--|       |         |      |
   |  (7)   |                                  |       |         |      |
   |  eval  |--(8)--- Delete Grant ----------->|       |         |      |
   |        |<------- Delete Response ---------|       |         |      |
   |        |                                  |       |         |      |
   |        |<--- Interaction Transfer ---(9)- | - - - | --------|      |
   |        |                                  |       |         |      |
   +--------+                                  +-------+         +------+

   1.  *Create Grant* The Client creates a Grant Request (Section 4.1)
       including an identity claim and interaction.keep:true, and sends
       it with an HTTP POST to the GS GS URI.

   2.  *Interaction Response* The GS sends an Interaction Response
       (Section 6.2) containing the Grant URI, an interaction object,
       and interaction.keep:true.

   3.  *Read Grant* The Client does an HTTP GET of the Grant URI
       (Section 4.3).

   4.  *Interaction Transfer* The Client transfers User interaction to
       the GS.

   5.  *User Authentication* The GS authenticates the User.

   6.  *Grant Response* The GS responds with a Grant Response
       (Section 6.1) including the identity claim from User
       authentication and interaction.keep:true.

   7.  *Grant Evaluation* The Client queries its User database and finds
       the User record matching the identity claim, and that no
       additional claims or authorizations are required.






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   8.  *Delete Grant* The Client no longer needs the Grant and decides
       to Delete Grant (Section 4.5) by sending an HTTP DELETE to the
       Grant URI.  If the GS responds with success the Grant no longer
       exists.

2.8.  Create, Discover, and Delete

   The Client wants to discover if the GS has a User with a given
   identifier.  If not, it will abort the request and not transfer
   interaction to the GS.

   +--------+                                  +-------+
   | Client |                                  |  GS   |
   |        |--(1)--- Create Grant ----------->|       |
   |        |      user.exists:true            |       |
   |        |                                  |       |
   |        |<--- Interaction Response ---(2)--|       |
   |        |         user.exists:false        |       |
   |        |                                  |       |
   |        |--(3)--- Delete Grant ----------->|       |
   |        |<------- Delete Response ---------|       |
   |        |                                  |       |
   +--------+                                  +-------+

   1.  *Create Grant* The Client creates a Grant Request (Section 4.1)
       including an identity claim request, a User identifier, and
       user.exists:true.  The Client sends it with an HTTP POST to the
       GS GS URI.

   2.  *Interaction Response* The GS sends an Interaction Response
       (Section 6.2) containing the Grant URI, an interaction object,
       and user.exists:false.

   3.  *Delete Grant* The Client determines the GS cannot fulfil its
       Grant Request, and decides to Delete Grant (Section 4.5) by
       sending an HTTP DELETE to the Grant URI.  If the GS responds with
       success the Grant no longer exists.

2.9.  Create and Wait

   The Client wants access to resources that require the GS to interact
   with the RO, which may not happen immediately, so the GS instructs
   the Client to wait and check back later.








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   +--------+                                  +-------+
   | Client |                                  |  GS   |
   |        |--(1)--- Create Grant ----------->|       |
   |        |                                  |       |
   |        |<---------- Wait Response ---(2)--|       |         +------+
   |  (3)   |                                  |       |         |  RO  |
   |  Wait  |                                  |       |<--(4)-->|      |
   |        |                                  |       |  AuthZ  |      |
   |        |--(5)--- Read Grant ------------->|       |         +------+
   |        |                                  |       |
   |        |<--------- Grant Response --(6)---|       |
   |        |                                  |       |
   +--------+                                  +-------+

   1.  *Create Grant* The Client creates a Grant Request (Section 4.1)
       and sends it with an HTTP POST to the GS GS URI.

   2.  *Wait Response* The GS sends an Interaction Response
       (Section 6.3) containing the Grant URI and wait time.

   3.  *Client Waits* The Client waits the wait time.

   4.  *RO AuthZ* The GS interacts with the RO to determine which
       identity claims in the Grant Request are to be granted.

   5.  *Read Grant* The Client does an HTTP GET of the Grant URI
       (Section 4.3).

   6.  *Grant Response* The GS responds with a Grant Response
       (Section 6.1).

2.10.  Read Grant

   The Client wants to re-acquire the identity claims and authorizations
   in the Grant.  No User or RO interaction is required as no new
   consent or authorization is required.

   +--------+                                  +-------+
   | Client |                                  |  GS   |
   |        |--(1)--- Read Grant ------------->|       |
   |        |                                  |       |
   |        |<--------- Grant Response --(2)---|       |
   |        |                                  |       |
   +--------+                                  +-------+

   1.  *Read Grant* The Client does an HTTP GET of the Grant URI
       (Section 4.3).




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   2.  *Grant Response* The GS responds with a Grant Response
       (Section 6.1) containing updated identity claims and
       authorizations.

2.11.  Resource Server Access

   The Client received an AZ URI from the GS.  The Client acquires an
   access token, calls the RS, and later the access token expires.  The
   Client then gets a fresh access token.

   +--------+                                           +-------+
   | Client |                                           |  GS   |
   |        |--(1)--- Read AuthZ ---------------------->|       |
   |        |<------- AuthZ Response -------------------|       |
   |        |                                           |       |
   |        |                             +----------+  |       |
   |        |                             | Resource |  |       |
   |        |--(2)--- Access Resource --->|  Server  |  |       |
   |        |<------- Resource Response --|   (RS)   |  |       |
   |        |                             |          |  |       |
   |        |--(3)--- Access Resource --->|          |  |       |
   |        |<------- Error Response -----|          |  |       |
   |        |                             |          |  |       |
   |        |                             +----------+  |       |
   |        |                                           |       |
   |        |--(4)--- Read AuthZ ---------------------->|       |
   |        |<------- AuthZ Response -------------------|       |
   |        |                                           |       |
   +--------+                                           +-------+

   1.  *Read AuthZ* The Client makes a Read AuthZ (Section 4.7) with an
       HTTP GET to the AZ URI and receives an Response JSON
       "authorization" object (Section 6.4.4) with a fresh access token.

   2.  *Resource Request* The Client accesses the RS with the access
       token per Section 8 and receives a response from the RS.

   3.  *Resource Request* The Client attempts to access the RS, but
       receives an error indicating the access token has expired.

   4.  *Read AuthZ* The Client makes another Read AuthZ (Section 4.7)
       with an HTTP GET to the AZ URI and receives an Response JSON
       "authorization" object (Section 6.4.4) with a fresh access token.








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2.12.  GS API Table

    +--------------+-----------+--------+-----------------------------+
    | request      | http verb | uri    | response                    |
    +==============+===========+========+=============================+
    | Create Grant | POST      | GS URI | interaction, wait, or grant |
    +--------------+-----------+--------+-----------------------------+
    | Verify Grant | PATCH     | Grant  | grant                       |
    |              |           | URI    |                             |
    +--------------+-----------+--------+-----------------------------+
    | Read Grant   | GET       | Grant  | wait, or grant              |
    |              |           | URI    |                             |
    +--------------+-----------+--------+-----------------------------+
    | Update Grant | PUT       | Grant  | interaction, wait, or grant |
    |              |           | URI    |                             |
    +--------------+-----------+--------+-----------------------------+
    | Delete Grant | DELETE    | Grant  | success                     |
    |              |           | URI    |                             |
    +--------------+-----------+--------+-----------------------------+
    | Read AuthZ   | GET       | AZ URI | authorization               |
    +--------------+-----------+--------+-----------------------------+
    | Update AuthZ | PUT       | AZ URI | authorization               |
    +--------------+-----------+--------+-----------------------------+
    | Delete AuthZ | DELETE    | AZ URI | success                     |
    +--------------+-----------+--------+-----------------------------+
    | GS Options   | OPTIONS   | GS URI | metadata                    |
    +--------------+-----------+--------+-----------------------------+
    | Grant        | OPTIONS   | Grant  | metadata                    |
    | Options      |           | URI    |                             |
    +--------------+-----------+--------+-----------------------------+
    | AuthZ        | OPTIONS   | AZ URI | metadata                    |
    | Options      |           |        |                             |
    +--------------+-----------+--------+-----------------------------+

                                  Table 1

   [ Editor: is there value in an API for listing a Client's Grants?
   eg:]

   List Grants     GET     GS URI    JSON array of Grant URIs

3.  Grant and AuthZ Life Cycle

   [Editor: straw man for life cycles.]

   *Grant life Cycle*





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   The Client MAY create, read, update, and delete Grants.  A Grant
   persists until it has expired, is deleted, or another Grant is
   created for the same GS, Client, and User tuple.

   At any point in time, there can only be one Grant for the GS, Client,
   and User tuple.  When a Client creates a Grant at the same GS for the
   same User, the GS MUST invalidate a previous Grant for the Client at
   that GS for that User.

   *Authorization Life Cycle*

   An Authorization are represented by an AZ URI and are MAY be included
   in a Grant Response "authorization" Object (Section 6.4.4) or as a
   member of the Grant Response "authorizations" list.  If a Client
   receives an Authorization, the Client MUST be able to do a Read AuthZ
   request Section 4.7, and MAY be able to update Section 4.8 and delete
   Section 4.9 depending on GS policy.

   An Authorization will persist independent of the Grant, and persist
   until invalidated by the GS per GS policy, or deleted by the Client.

4.  GS APIs

   *Client Authentication*

   All APIs except for GS Options require the Client to authenticate.

   This document defines the JOSE Authentication mechanism in
   Section 10.  Other mechanisms include [TBD].

4.1.  Create Grant

   The Client creates a Grant by doing an HTTP POST of a JSON [RFC8259]
   document to the GS URI.

   The JSON document MUST include the following from the Request JSON
   Section 4.6:

   *  iat

   *  nonce

   *  uri set to the GS URI

   *  client

   and MAY include the following from Request JSON Section 4.6




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   *  user

   *  interaction

   *  authorization or authorizations

   *  claims

   The GS MUST respond with one of Grant Response Section 6.1,
   Interaction Response Section 6.2, Wait Response Section 6.3, or one
   of the following errors:

   *  TBD

   from Error Responses Section 9.

   Following is a non-normative example where the Client is requesting
   identity claims about the User and read access to the User's
   contacts:
































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   Example 1

   {
       "iat"       : 15790460234,
       "uri"       : "https://as.example/endpoint",
       "nonce"     : "f6a60810-3d07-41ac-81e7-b958c0dd21e4",
       "client": {
           "display": {
               "name"  : "SPA Display Name",
               "uri"   : "https://spa.example/about"
           }
       },
       "interaction": {
           "redirect": {
               "redirect_uri"    : "https://web.example/return"
           },
           "global" : {
               "ui_locals" : "de"
           }
       },
       "authorization": {
           "type"      : "oauth_scope",
           "scope"     : "read_contacts"
       },
       "claims": {
           "oidc": {
               "id_token" : {
                   "email"          : { "essential" : true },
                   "email_verified" : { "essential" : true }
               },
               "userinfo" : {
                   "name"           : { "essential" : true },
                   "picture"        : null
               }
           }
       }
   }

   Following is a non-normative example where the Client is requesting
   the GS to keep the interaction with the User after returning the ID
   Token so the Client can update the Grant, and is also asking if the
   user exists:









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   Example 2

   {
       "iat"       : 15790460234,
       "uri"       : "https://as.example/endpoint",
       "nonce"     : "5c9360a5-9065-4f7b-a330-5713909e06c6",
       "client": {
           "id"        : "di3872h34dkJW"
       },
       "interaction": {
           "indirect": {
               "completion_uri": "https://device.example/completion"
           },
           "user_code": {
               "completion_uri": "https://device.example/completion"
            }
       },
       "user": {
           "identifiers": {
               "email" : "jane.doe@example.com"
           },
           "exists"    : true
       },
       "claims"    : { "oidc": { "id_token" : {} } }
   }

4.2.  Verify Grant

   The Client verifies a Grant by doing an HTTP PATCH of a JSON document
   to the corresponding Grant URI.

   The JSON document MUST contain verification.nonce per Section 4.6.7.
   Following is a non-normative example:

   {
       "verification": { "nonce":"55e8a90f-a563-426d-8c35-d6d8ed54afeb" }
   }

   The GS MUST respond with one of Grant Response Section 6.1 or one of
   the following errors:

   *  TBD

   from Error Responses Section 9.







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4.3.  Read Grant

   The Client reads a Grant by doing an HTTP GET of the corresponding
   Grant URI.

   The GS MUST respond with one of Grant Response Section 6.1, Wait
   Response Section 6.3, or one of the following errors:

   *  TBD

   from Error Responses Section 9.

4.4.  Update Grant

   The Client updates a Grant by doing an HTTP PUT of a JSON document to
   the corresponding Grant URI.

   The JSON document MUST include the following from the Request JSON
   Section 4.6

   *  iat

   *  uri set to the Grant URI

   and MAY include the following from Request JSON Section 4.6

   *  user

   *  interaction

   *  authorization or authorizations

   *  claims

   The GS MUST respond with one of Grant Response Section 6.1,
   Interaction Response Section 6.2, Wait Response Section 6.3, or one
   of the following errors:

   *  TBD

   from Error Responses Section 9.

   Following is a non-normative example where the Client made an
   interaction.keep:true request, and now wants to update the request
   with additional claims:






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   Example 3

   {
       "iat"       : 15790460234,
       "uri"       : "https://as.example/endpoint/grant/example3",
       "claims": {
           "oidc": {
               "userinfo" : {
                   "email"          : { "essential" : true },
                   "name"           : { "essential" : true },
                   "picture"        : null
               }
           }
       }
   }

4.5.  Delete Grant

   The Client deletes a Grant by doing an HTTP DELETE of the
   corresponding Grant URI.

   The GS MUST respond with OK 200, or one of the following errors:

   *  TBD

   from Error Responses Section 9.

4.6.  Request JSON

   [Editor: do we want to reuse the JWT claims "iat", "jti", etc.? ]

   *  *iat* - the time of the request as a NumericDate.

   *  *nonce* - a unique identifier for this request.  Note the Grant
      Response MUST contain a matching nonce attribute value.

   *  *uri* - the GS URI if in a Create Grant Section 4.1, or the Grant
      URI if in an Update Grant Section 4.4.

4.6.1.  "client" Object

   The client object MUST contain one of: the "id" attribute for a
   Registered Client, the "handle" attribute for a Dynamic Client, or
   the "display" object for Dynamic Clients.

   *  *id* - the Client ID the GS has for a Registered Client.





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   *  *handle* = the Client Handle the GS previously provided a Dynamic
      Client

   *  *display* - the display object contains the following attributes:

      -  *name* - a string that represents the Dynamic Client

      -  *uri* - a URI representing the Dynamic Client

   The name and uri will be displayed by the GS when prompting for
   authorization.

   [Editor: a max length for the name and URI so a GS can reserve
   appropriate space?]

4.6.2.  "interaction" Object

   The interaction object contains one or more interaction mode objects
   per Section 7 representing the interactions the Client is willing to
   provide the User.  In addition to the interaction mode objects, the
   interaction object may contain the "global" object;

   *  *global* - and optional object containing parameters that are
      applicable for all types of interactions.  Only one attribute is
      defined in this document:

      -  *ui_locales* - End-User's preferred languages and scripts for
         the user interface, represented as a space-separated list of
         [RFC5646] language tag values, ordered by preference.  This
         attribute is OPTIONAL.

   [Editor: why is this not a JSON array?  Why space-separated?]

4.6.3.  "user" Object

   *  *exists* - if present, MUST contain the JSON true value.
      Indicates the Client requests the GS to return a user.exists value
      in an Interaction Response Section 6.2.  This attribute is
      OPTIONAL, and MAY be ignored by the GS.

   *  *identifiers* - REQUIRED if the exists attribute is present.  The
      values MAY be used by the GS to improve the User experience.
      Contains one or more of the following identifiers for the User:

      -  *phone_number* - contains a phone number per Section 5 of
         [RFC3966].

      -  *email* - contains an email address per [RFC5322].



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      -  *oidc* - is an object containing both the "iss" and "sub"
         attributes from an OpenID Connect ID Token [OIDC] Section 2.

   *  *claims* - an optional object containing one or more assertions
      the Client has about the User.

      -  *oidc_id_token* - an OpenID Connect ID Token per [OIDC]
         Section 2.

   *  *reciprocal* - indicates this Grant Request or Update is the
      reciprocal of another Grant.  Contains the Grant URI of the
      reciprocal Grant.

4.6.4.  "authorization" Object

   *  *type* - one of the following values: "oauth_scope" or
      "oauth_rich".  This attribute is REQUIRED.

   *  *scope* - a string containing the OAuth 2.0 scope per [RFC6749]
      section 3.3.  MUST be included if type is "oauth_scope" or
      "oauth_rich".

   *  *authorization_details* - an authorization_details object per
      [RAR].  MUST be included if type is "oauth_rich".

   [Editor: details may change as the [RAR] document evolves]

4.6.5.  "authorizations" Object

   One or more key / value pairs, where each unique key is created by
   the client, and the value is an authorization object.

4.6.6.  "claims" Object

   Includes one or more of the following:

   *  *oidc* - an object that contains one or both of the following
      objects:

      -  *userinfo* - Claims that will be returned as a JSON object

      -  *id_token* - Claims that will be included in the returned ID
         Token.  If the null value, an ID Token will be returned
         containing no additional Claims.

   The contents of the userinfo and id_token objects are Claims as
   defined in [OIDC] Section 5.




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   *  *oidc4ia* - OpenID Connect for Identity Assurance claims request
      per [OIDC4IA].

   *  *vc* - [Editor: define how W3C Verifiable Credentials [W3C_VC] can
      be requested.]

4.6.7.  "verification" Object

   The verification Object is used with the Verify Grant Section 4.2.

   *  *nonce* the Interaction Nonce received from the GS via the
      Completion URI.  This attribute MUST only be used in the Verify
      Grant Section 4.2.

   [Editor: parameters for the Client to request it wants the Grant
   Response signed and/or encrypted?]

4.7.  Read Authorization

   The Client acquires an Authorization by doing an HTTP GET to the
   corresponding AZ URI.

   The GS MUST respond with a Authorization JSON document Section 6.5,
   or one of the following errors:

   *  TBD

   from Error Responses Section 9.

4.8.  Update Authorization

   The Client updates an Authorization by doing an HTTP PUT to the
   corresponding AZ URI of the following JSON.  All of the following
   MUST be included.

   *  *iat* - the time of the response as a NumericDate.

   *  *uri* - the AZ URI.

   *  *authorization* - the new authorization requested per the Request
      JSON "authorization" object Section 4.6.4.

   The GS MUST respond with a Authorization JSON document Section 6.5,
   or one of the following errors:

   *  TBD

   from Error Responses Section 9.



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4.9.  Delete Authorization

   The Client deletes an Authorization by doing an HTTP DELETE to the
   corresponding AZ URI.

   The GS MUST respond with OK 200, or one of the following errors:

   *  TBD

   from Error Responses Section 9.

4.10.  GS Options

   The Client can get the metadata for the GS by doing an HTTP OPTIONS
   of the corresponding GS URI.  This is the only API where the GS MAY
   respond to an unauthenticated request.

   The GS MUST respond with the the following JSON document:

   [Editor: this section is a work in progress]

   *  *uri* - the GS URI.

   *  *client_authentication* - an array of the Client Authentication
      mechanisms supported by the GS

   *  *interactions* - an array of the interaction modes supported by
      the GS.

   *  *authorization* - an object containing the authorizations the
      Client may request from the GS, if any.

      -  Details TBD

   *  *claims* - an object containing the identity claims the Client may
      request from the GS, if any, and what public keys the claims will
      be signed with.

      -  Details TBD

   *  *algorithms* - a list of the cryptographic algorithms supported by
      the GS.

   *  *features* - an object containing feature support

      -  *user_exists* - boolean indicating if user.exists is supported.





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      -  *authorizations* - boolean indicating if a request for more
         than one authorization in a request is supported.

   [Editor: keys used by Client to encrypt requests, or verify signed
   responses?]

   [Editor: namespace metadata for extensions?]

   or one of the following errors:

   *  TBD

   from Error Responses Section 9.

4.11.  Grant Options

   The Client can get the metadata for the Grant by doing an HTTP
   OPTIONS of the corresponding Grant URI.

   The GS MUST respond with the the following JSON document:

   *  *verbs* - an array of the HTTP verbs supported at the GS URI.

   or one of the following errors:

   *  TBD

   from Error Responses Section 9.

4.12.  AuthZ Options

   The Client can get the metadata for the AuthZ by doing an HTTP
   OPTIONS of the corresponding AZ URI.

   The GS MUST respond with the the following JSON document:

   *  *verbs* - an array of the HTTP verbs supported at the GS URI.

   or one of the following errors:

   *  TBD

   from Error Responses Section 9.

4.13.  Request Verification

   On receipt of a request, the GS MUST verify the following:




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   *  TBD

5.  GS Initiated Grant

   [Editor: In OAuth 2.0, all flows are initiated at the Client.  If the
   AS wanted to initiate a flow, it redirected to the Client, that
   redirected back to the AS to initiate a flow.

   Here is a proposal to support GS initiated: authentication; just-in-
   time (JIT) provisioning; and authorization]

   *initiation_uri* A URI at the Client that contains no query or
   fragment.  How the GS learns the Client initiation_uri is out of
   scope.

   The GS creates a Grant and Grant URI, and redirects the User to the
   initiation_uri with the query parameter "grant" and the value of
   Grant URI.

   See Section 2.5 for the sequence diagram.

6.  GS Responses

   There are three successful responses to a grant request: Grant
   Response, Interaction Response, or Wait Response.

6.1.  Grant Response

   The Grant Response MUST include the following from the Response JSON
   Section 6.4

   *  iat

   *  nonce

   *  uri

   and MAY include the following from the Response JSON Section 6.4

   *  client.handle

   *  authorization or authorizations

   *  claims

   *  expires_in





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   Example non-normative Grant Response JSON document for Example 1 in
   Section 4.1:

   {
       "iat"           : 15790460234,
       "nonce"         : "f6a60810-3d07-41ac-81e7-b958c0dd21e4",
       "uri"           : "https://as.example/endpoint/grant/example1",
       "expires_in"    : 300
       "authorization": {
           "type"          : "oauth_scope",
           "scope"         : "read_contacts",
           "expires_in"    : 3600,
           "mechanism"     : "bearer",
           "token"         : "eyJJ2D6.example.access.token.mZf9p"
       },
       "claims": {
           "oidc": {
               "id_token"      : "eyJhbUzI1N.example.id.token.YRw5DFdbW",
               "userinfo" : {
                   "name"      : "John Doe",
                   "picture"   : "https://photos.example/p/eyJzdkiO"
               }
           }
       }
   }

   Example non-normative Grant Response JSON document for Example 2 in
   Section 4.1:

   {
       "iat"   : 15790460234,
       "nonce" : "5c9360a5-9065-4f7b-a330-5713909e06c6",
       "uri"   : "https://as.example/endpoint/grant/example2",
       "authorization": {
           "uri"   : "https://as.example/endpoint/authz/example2"
       }
   }

6.2.  Interaction Response

   The Interaction Response MUST include the following from the Response
   JSON Section 6.4

   *  iat

   *  nonce

   *  uri



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   *  interaction

   and MAY include the following from the Response JSON Section 6.4

   *  user

   *  wait

   A non-normative example of an Interaction Response follows:

   {
       "iat"       : 15790460234,
       "nonce"     : "0d1998d8-fbfa-4879-b942-85a88bff1f3b",
       "uri"       : "https://as.example/endpoint/grant/example4",
       "interaction" : {
           ""redirect" : {
               "authorization_uri"     : "https://as.example/i/example4"
           }
       },
       "user": {
           "exists" : true
       }
   }

6.3.  Wait Response

   The Wait Response MUST include the following from the Response JSON
   Section 6.4

   *  iat

   *  nonce

   *  uri

   *  wait

   A non-normative example of Wait Response follows:

   {
       "iat"       : 15790460234,
       "nonce"     : "0d1998d8-fbfa-4879-b942-85a88bff1f3b",
       "uri"       : "https://as.example/endpoint/grant/example5",
       "wait"      : 300
   }






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6.4.  Response JSON

   Details of the JSON document:

   *  *iat* - the time of the response as a NumericDate.

   *  *nonce* - the nonce that was included in the Request JSON
      Section 4.6.

   *  *uri* - the Grant URI.

   *  *wait* - a numeric value representing the number of seconds the
      Client should want before making a Read Grant request to the Grant
      URI.

   *  *expires_in* - a numeric value specifying how many seconds until
      the Grant expires.  This attribute is OPTIONAL.

6.4.1.  "client" Object

   The GS may

6.4.2.  "interaction" Object

   If the GS wants the Client to start the interaction, the GS MUST
   return an interaction object containing one or more interaction mode
   responses per Section 7 to one or more of the interaction mode
   requests provided by the Client.

6.4.3.  "user" Object

   *  *exists* - a boolean value indicating if the GS has a user with
      one or more of the provided identifiers in the Request
      user.identifiers object Section 4.6.3

6.4.4.  "authorization" Object

   The authorization object contains Authorization JSON Section 6.5.
   See Grant Response Section 6.1 for non-normative examples.

6.4.5.  "authorizations" Object

   A key / value pair for each key in the client's request
   authorizations object, and the value is Authorization JSON
   Section 6.5.






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6.4.6.  "claims" Object

   The claims object is a response to the Request "claims" object
   Section 4.6.4.

   *  *oidc*

      -  *id_token* - an OpenID Connect ID Token containing the Claims
         the User consented to be released.

      -  *userinfo* - the Claims the User consented to be released.

      Claims are defined in [OIDC] Section 5.

   *  *oidc4ia* - OpenID Connect for Identity Assurance claims response
      per [OIDC4IA].

   *  *vc*

      The verified claims the user consented to be released.  [Editor:
      details TBD]

6.5.  Authorization JSON

   The Authorization JSON is a response to a Read AuthZ request by the
   Client Section 4.7.  A subset of the Authorization JSON is included
   in the "authorization" object Section 4.6.4 and "authorizations" list
   members Section 6.4.5.

   *  *type* - the type of claim request: "oauth_scope" or "oauth_rich".
      See the "type" object in Section 4.6.4 for details.  This
      attribute is REQUIRED.

   *  *scope* - the scopes the Client was granted authorization for.
      This will be all, or a subset, of what was requested.  This
      attribute is OPTIONAL.

   *  *authorization_details* - the authorization details granted per
      [RAR].  Included if type is "oauth_rich".

   *  *mechanism* - one of the access mechanisms: "bearer", "jose", or
      "jose+body".  See Section 8 for details.  This attribute is
      REQUIRED.

   *  *token* - the access token for accessing an RS.  This attribute is
      REQUIRED.





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   *  *expires_in* - a numeric value specifying how many seconds until
      the access token expires.  This attribute is OPTIONAL.

   *  *certificate* - MUST be included if the mechanism is "jose" or
      "jose+body".  Contains the jwk header values for the Client to
      include in the JWS header when calling the RS using the "jose" or
      "jose+body" mechanisms.  See Section 10.2.1.

   *  *uri* - the AZ URI.  Used to refresh an authorization.  This
      attribute is OPTIONAL.

   [Editor: would an optional expiry for the Authorization be useful?]

   The following is a non-normative example of an Authorization JSON
   document:

   {
       "type"          : "oauth_scope",
       "scope"         : "read_calendar write_calendar",
       "mechanism"     : "jose",
       "token"         : "eyJJ2D6.example.access.token.mZf9p"
       "expires_in"    : 3600,
       "certificate": {
           "x5u"   : "https://as.example/cert/example2"
       },
       "uri"       : "https://as.example/endpoint/authz/example2"
   }

6.5.1.  Signing and Encryption

   [Editor: TBD - how response is signed and/or encrypted by the GS.  Is
   there a generalized description, or is it mechanism specific?]

6.6.  Response Verification

   On receipt of a response, the Client MUST verify the following:

   *  TBD

7.  interaction mode Objects

   This document defines three interaction modes: "redirect",
   "indirect", and "user_code".  Extensions may define additional
   interaction modes.

   The "global" attribute is reserved in the interaction object for
   attributes that apply to all interaction modes.




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7.1.  "redirect" mode

   A Redirect Interaction is characterized by the Client redirecting the
   User's browser to the GS, the GS interacting with the User, and then
   GS redirecting the User's browser back to the Client.  The GS
   correlates the Grant Request with the unique authorization_uri, and
   the Client correlates the Grant Request with the unique redirect_uri.

7.1.1.  request "interaction" object contains:

   *redirect_uri* a grant request request unique URI at the Client that
   the GS will return the User to.  This attribute is REQUIRED.

7.1.2.  response "interaction" object contains:

   *authorization_uri* a grant request request unique URI at the GS that
   the Client will redirect the User to.  This attribute is REQUIRED.

7.2.  "indirect" mode

   An Indirect Interaction is characterized by the Client causing the
   User's browser to load the short_uri at GS, the GS interacting with
   the User, and then the GS MAY optionally redirecting the User's
   Browser to a completion_uri.  There is no mechanism for the GS to
   redirect the User's browser back to the Client.  Examples of how the
   Client may initiate the interaction are encoding the short_uri as a
   code scannable by the User's mobile device, or launching a system
   browser from a command line interface (CLI) application.

   The "indirect" mode is susceptible to session fixation attacks.  See
   TBD in the Security Considerations for details.

7.2.1.  request "interaction" object contains:

   *completion_uri* an OPTIONAL URI that the GS will redirect the User's
   browser to after GS interaction.

7.2.2.  response "interaction" object contains:

   *short_uri* the URI the Client will cause to load in the User's
   browser.  The URI SHOULD be short enough to be easily encoded in a
   scannable code.  [Editor: recommend a length?]

7.3.  "user_code" mode

   An Indirect Interaction is characterized by the Client displaying a
   code and a URI for the User to load in a browser and then enter the
   code.



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7.3.1.  request "interaction" object contains:

   *completion_uri* an OPTIONAL URI that the GS will redirect the User's
   browser to after GS interaction.

7.3.2.  response "interaction" object contains:

   *code* the code the Client displays to the User to enter at the
   display_uri.  This attribute is REQUIRED.

   *display_uri* the URI the Client displays to the User to load in a
   browser to enter the code.

8.  RS Access

   This document specifies three different mechanisms for the Client to
   access an RS ("bearer", "jose", and "jose+body").  The "bearer"
   mechanism is defined in {BearerToken}. The "jose" and "jose+body"
   mechanisms are proof-of-possession mechanisms and are defined in
   Section 10.2.2 and Section 10.2.3 respectively.  Additional proof-of-
   possession mechanisms may be defined in other documents.  The
   mechanism the Client is to use with an RS is the Response JSON
   authorization.mechanism attribute Section 6.4.4.

8.1.  Bearer Token

   If the access mechanism is "bearer", then the Client accesses the RS
   per Section 2.1 of [RFC6750]

   A non-normative example of the HTTP request headers follows:

   GET /calendar HTTP/2
   Host: calendar.example
   Authorization: bearer eyJJ2D6.example.access.token.mZf9pTSpA

9.  Error Responses

   *  TBD

10.  JOSE Authentication

   How the Client authenticates to the GS and RS are independent of each
   other.  One mechanism can be used to authenticate to the GS, and a
   different mechanism to authenticate to the RS.

   Other documents that specify other Client authentication mechanisms
   will replace this section.




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   In the JOSE Authentication Mechanism, the Client authenticates by
   using its private key to sign a JSON document with JWS per [RFC7515]
   which results in a token using JOSE compact serialization.

   [Editor: are there advantages to using JSON serialization in the
   body?]

   Different instances of a Registered Client MAY have different private
   keys, but each instance has a certificate to bind its private key to
   to a public key the GS has for the Client ID.  An instance of a
   Client will use the same private key for all signing operations.

   The Client and the GS MUST both use HTTP/2 ([RFC7540]) or later, and
   TLS 1.3 ([RFC8446]) or later, when communicating with each other.

   [Editor: too aggressive to mandate HTTP/2 and TLS 1.3?]

   The token may be included in an HTTP header, or as the HTTP message
   body.

   The following sections specify how the Client uses JOSE to
   authenticate to the GS and RS.

10.1.  GS Access

   The Client authenticates to the GS by passing either a signed header
   parameter, or a signed message body.  The following table shows the
   verb, uri and token location for each Client request to the GS:























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           +---------------+-----------+-----------+----------+
           | request       | http verb | uri       | token in |
           +===============+===========+===========+==========+
           | Create Grant  | POST      | GS URI    | body     |
           +---------------+-----------+-----------+----------+
           | Verify Grant  | PATCH     | Grant URI | body     |
           +---------------+-----------+-----------+----------+
           | Read Grant    | GET       | Grant URI | header   |
           +---------------+-----------+-----------+----------+
           | Update Grant  | PUT       | Grant URI | body     |
           +---------------+-----------+-----------+----------+
           | Delete Grant  | DELETE    | Grant URI | header   |
           +---------------+-----------+-----------+----------+
           | Read AuthZ    | GET       | AZ URI    | header   |
           +---------------+-----------+-----------+----------+
           | Update AuthZ  | PUT       | AZ URI    | body     |
           +---------------+-----------+-----------+----------+
           | Delete AuthZ  | DELETE    | AZ URI    | header   |
           +---------------+-----------+-----------+----------+
           | GS Options    | OPTIONS   | GS URI    | header   |
           +---------------+-----------+-----------+----------+
           | Grant Options | OPTIONS   | Grant URI | header   |
           +---------------+-----------+-----------+----------+
           | AuthZ Options | OPTIONS   | AZ URI    | header   |
           +---------------+-----------+-----------+----------+

                                 Table 2

10.1.1.  Authorization Header

   For requests with the token in the header, the JWS payload MUST
   contain the following attributes:

   *iat* - the time the token was created as a NumericDate.

   *jti* - a unique identifier for the token per [RFC7519] section
   4.1.7.

   *uri* - the value of the URI being called (GS URI, Grant URI, or AZ
   URI).

   *verb* - the HTTP verb being used in the call ("GET", "DELETE",
   "OPTIONS")

   The HTTP authorization header is set to the "jose" parameter followed
   by one or more white space characters, followed by the resulting
   token.




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   A non-normative example of a JWS payload and the HTTP request
   follows:

   {
       "iat"   : 15790460234,
       "jti"   : "f6d72254-4f23-417f-b55e-14ad323b1dc1",
       "uri"   : "https://as.example/endpoint/grant/example6",
       "verb"  : "GET"
   }

   GET /endpoint/example.grant HTTP/2
   Host: as.example
   Authorization: jose eyJhbGciOiJIUzI1NiIsIn ...

   [Editor: make a real example token]

   *GS Verification*

   The GS MUST verify the token by:

   *  TBD

10.1.2.  Signed Body

   For requests with the token in the body, the Client uses the Request
   JSON as the payload in a JWS.  The resulting token is sent with the
   content-type set to "application/jose".

   A non-normative example (line breaks added to the body for
   readability):

   POST /endpoint HTTP/2
   Host: as.example
   Content-Type: application/jose
   Content-Length: 155

   eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyzdWIiOiIxMjM0NTY3ODkwIiwibmF
   tZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMe
   Jf36POk6yJV_adQssw5c

   [Editor: make a real example token]

   *GS Verification*

   The GS MUST verify the token by:

   *  TBD




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10.1.3.  Public Key Resolution

   *  *Registered Clients* can use any of the JWS header values to
      direct the GS to resolve the public key matching the private key
      used to the Client ID.  The GS MAY restrict with JWS headers a
      Client can use.

   [Editor: would examples help here so that implementors understand the
   full range of options, and how an instance can have its own asymetric
   key pair]

   A non-normative example of a JOSE header for a Registered Client with
   a key identifier of "12":

   {
       "alg"   : "ES256",
       "typ"   : "JOSE",
       "kid"   : "12"
   }

   *  *Dynamic Clients* include their public key in the "jwk" JWS
      header.

   A non-normative example of a JOSE header for a Dynamic Client:

   {
       "alg"   : "ES256",
       "typ"   : "JOSE",
       "jwk"   : {
           "kty"   : "EC",
           "crv"   : "P-256",
           "x"     : "Kgl5DJSgLyV-G32osmLhFKxJ97FoMW0dZVEqDG-Cwo4",
           "y"     : "GsL4mOM4x2e6iON8BHvRDQ6AgXAPnw0m0SfdlREV7i4"
       }
   }

10.2.  RS Access

   In the "jose" mechanism Section 10.2.2, all Client requests to the RS
   include a proof-of-possession token in the HTTP authorization header.
   In the "jose+body" mechanism Section 10.2.3, the Client signs the
   JSON document in the request if the POST or PUT verbs are used,
   otherwise it is the same as the "jose" mechanism.








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10.2.1.  JOSE header

   The GS provides the Client one or more JWS header parameters and
   values for a a certificate, or a reference to a certificate or
   certificate chain, that the RS can use to resolve the public key
   matching the private key being used by the Client.

   A non-normative examples JOSE header:

   {
       "alg"   : "ES256",
       "typ"   : "JOSE",
       "x5u"   : "https://as.example/cert/example2"
   }

   [Editor: this enables Dynamic Clients to make proof-of-possession API
   calls the same as Registered Clients.]

10.2.2.  "jose" Mechanism

   The JWS payload MUST contain the following attributes:

   *iat* - the time the token was created as a NumericDate.

   *jti* - a unique identifier for the token per [RFC7519] section
   4.1.7.

   *uri* - the value of the RS URI being called.

   *verb* - the HTTP verb being used in the call

   *token* - the access token provided by the GS to the Client

   The HTTP authorization header is set to the "jose" parameter followed
   by one or more white space characters, followed by the resulting
   token.

   A non-normative example of a JWS payload and the HTTP request
   follows:












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   {
       "iat"   : 15790460234,
       "jti"   : "f6d72254-4f23-417f-b55e-14ad323b1dc1",
       "uri"   : "https://calendar.example/calendar",
       "verb"  : "GET",
       "token" : "eyJJ2D6.example.access.token.mZf9pTSpA"
   }

   GET /calendar HTTP/2
   Host: calendar.example
   Authorization: jose eyJhbG.example.jose.token.adks

   [Editor: make a real example token]

   *RS Verification*

   The RS MUST verify the token by:

   *  verify access token is bound to the public key - include key
      fingerprint in access token?

   *  TBD

10.2.3.  "jose+body" Mechanism

   The "jose+body" mechanism can only be used if the content being sent
   to the RS is a JSON document.

   Any requests not sending a message body will use the "jose" mechanism
   Section 10.2.2.

   Requests sending a message body MUST have the following JWS payload:

   *iat* - the time the token was created as a NumericDate.

   *jti* - a unique identifier for the token per [RFC7519] section
   4.1.7.

   *uri* - the value of the RS URI being called.

   *verb* - the HTTP verb being used in the call

   *token* - the access token provided by the GS to the Client

   *body* - the message body being sent to the RS

   A non-normative example of a JWS payload and the HTTP request
   follows:



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   {
       "iat"   : 15790460234,
       "jti"   : "f6d72254-4f23-417f-b55e-14ad323b1dc1",
       "uri"   : "https://calendar.example/calendar",
       "verb"  : "POST",
       "token" : "eyJJ2D6.example.access.token.mZf9pTSpA",
       "payload" : {
           "event" : {
               "title"             : "meeting with joe",
               "start_date_utc"    : "2020-02-21 11:00:00",
               "end_date_utc"      : "2020-02-21 11:00:00"
           }
       }
   }

   POST /calendar HTTP/2
   Host: calendar.example
   Content-Type: application/jose
   Content-Length: 155

   eyJhbGciOi.example.jose+body.adasdQssw5c

   [Editor: make a real example token]

   *RS Verification*

   The RS MUST verify the token by:

   *  TBD

10.2.4.  Public Key Resolution

   The RS has a public key for the GS that it uses to verify the
   certificate or certificate chain the Client includes in the JWS
   header.

10.3.  Request Encryption

   [Editor: to be fleshed out]

   The Client encrypts a request when ??? using the GS public key
   returned as the ??? attribute in GS Options Section 4.10.

10.4.  Response Signing

   [Editor: to be fleshed out]





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   The Client verifies a signed response ??? using the GS public key
   returned as the ??? attribute in GS Options Section 4.10.

10.5.  Response Encryption

   [Editor: to be fleshed out]

   The Client decrypts a response when ??? using the private key
   matching the public key included in the request as the ??? attribute
   in Section 4.6.

11.  Extensibility

   This standard can be extended in a number of areas:

   *  *Client Authentication Mechanisms*

      -  An extension could define other mechanisms for the Client to
         authenticate to the GS and/or RS such as Mutual TLS or HTTP
         Signing.  Constrained environments could use CBOR [RFC7049]
         instead of JSON, and COSE [RFC8152] instead of JOSE, and CoAP
         [RFC8323] instead of HTTP/2.

   *  *Grant*

      -  An extension can define new objects in the Grant Request and
         Grant Response JSON.

   *  *Top Level*

      -  Top level objects SHOULD only be defined to represent
         functionality other the existing top level objects and
         attributes.

   *  *"client" Object*

      -  Additional information about the Client that the GS would
         require related to an extension.

   *  *"user" Object*

      -  Additional information about the User that the GS would require
         related to an extension.

   *  *"authorization" Object*

      -  Additional authorization schemas in addition to OAuth 2.0
         scopes and RAR.



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   *  *"claims" Object*

      -  Additional claim schemas in addition to OpenID Connect claims
         and Verified Credentials.

   *  *interaction modes*

      -  Additional types of interactions a Client can start with the
         User.

   *  *Continuous Authentication*

      -  An extension could define a mechanism for the Client to
         regularly provide continuous authentication signals and receive
         responses.

   [Editor: do we specify access token / handle introspection in this
   document, or leave that to an extension?]

   [Editor: do we specify access token / handle revocation in this
   document, or leave that to an extension?]

12.  Rational

   1.   *Why is there only one mechanism for the Client to authenticate
        with the GS?  Why not support other mechanisms?*

        Having choices requires implementers to understand which choice
        is preferable for them.  Having one default mechanism in the
        document for the Client to authenticate simplifies most
        implementations.  Deployments that have unique characteristics
        can select other mechanisms that are preferable in specific
        environments.

   2.   *Why is the default Client authentication JOSE rather than
        MTLS?*

        MTLS cannot be used today by a Dynamic Client.  MTLS requires
        the application to have access below what is typically the
        application layer, that is often not available on some
        platforms.  JOSE is done at the application layer.  Many GS
        deployments will be an application behind a proxy performing
        TLS, and there are risks in the proxy passing on the results of
        MTLS.

   3.   *Why is the default Client authentication JOSE rather than HTTP
        signing?*




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        There is currently no widely deployed open standard for HTTP
        signing.  Additionally, HTTP signing requires passing all the
        relevant parts of the HTTP request to downstream services within
        an GS that may need to independently verify the Client identity.

   4.   *What are the advantages of using JOSE for the Client to
        authenticate to the GS and a resource?*

        Both Registered Clients and Dynamic Clients can have a private
        key, eliminating the public Client issues in OAuth 2.0, as a
        Dynamic Client can create an ephemeral key pair.  Using
        asymetric cryptography also allows each instance of a Registered
        Client to have its own private key if it can obtain a
        certificate binding its public key to the public key the GS has
        for the Client.  Signed tokens can be passed to downstream
        components in a GS or RS to enable independent verification of
        the Client and its request.  The GS Initiated Sequence Section 5
        requires a URL safe parameter, and JOSE is URL safe.

   5.   *Why does the GS not return parameters to the Client in the
        redirect url?*

        Passing parameters via a browser redirection is the source of
        many of the security risks in OAuth 2.0.  It also presents a
        challenge for smart devices.  In this protocol, the redirection
        from the Client to the GS is to enable the GS to interact with
        the User, and the redirection back to the Client is to hand back
        interaction control to the Client if the redirection was a full
        browser redirect.  Unlike OAuth 2.0, the identity of the Client
        is independent of the URI the GS redirects to.

   6.   *Why is there not a UserInfo endpoint as there is with OpenID
        Connect?*

        Since the Client can Read Grant at any time, it get the same
        functionality as the UserInfo endpoint, without the Client
        having to manage a separate access token and refresh token.  If
        the Client would like additional claims, it can Update Grant,
        and the GS will let the Client know if an interaction is
        required to get any of the additional claims, which the Client
        can then start.

        [Editor: is there some other reason to have the UserInfo
        endpoint?]

   7.   *Why is there still a Client ID?*





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        The GS needs an identifier to fetch the meta data associated
        with a Client such as the name and image to display to the User,
        and the policies on what a Client is allowed to do.  The Client
        ID was used in OAuth 2.0 for the same purpose, which simplifies
        migration.  Dynamic Clients do not have a Client ID.

   8.   *Why have both claims and authorizations?*

        There are use cases for each that are independent:
        authenticating a user and providing claims vs granting access to
        a resource.  A request for an authorization returns an access
        token which may have full CRUD capabilities, while a request for
        a claim returns the claim about the User - with no create,
        update or delete capabilities.  While the UserInfo endpoint in
        OIDC may be thought of as a resource, separating the concepts
        and how they are requested keeps each of them simpler in the
        Editor's opinion. :)

   9.   *Why specify HTTP/2 or later and TLS 1.3 or later for Client and
        GS communication in ?*Section 10

        Knowing the GS supports HTTP/2 enables a Client to set up a
        connection faster.  HTTP/2 will be more efficient when Clients
        have large numbers of access tokens and are frequently
        refreshing them at the GS as there will be less network traffic.
        Mandating TLS 1.3 similarly improves the performance and
        security of Clients and GS when setting up a TLS connection.

   10.  *Why do some of the JSON objects only have one child, such as
        the identifiers object in the user object in the Grant Request?*

        It is difficult to forecast future use cases.  Having more
        resolution may mean the difference between a simple extension,
        and a convoluted extension.

   11.  *Why is the "iss" included in the "oidc" identifier object?
        Would the "sub" not be enough for the GS to identify the User?*

        This decouples the GS from the OpenID Provider (OP).  The GS
        identifier is the GS URI, which is the endpoint at the GS.  The
        OP issuer identifier will likely not be the same as the GS URI.
        The GS may also provide claims from multiple OPs.

   12.  *Why complicate things with interaction.keep?*

        The common sequence has a back and forth between the Client and
        the GS, and the Client can update the Grant and have a new
        interaction.  Keeping the interaction provides a more seamless



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        user experience where the results from the first request
        determine subsequent requests.  For example, a common pattern is
        to use a GS to authenticate the User at the Client, and to
        register the User at the Client using additional claims from the
        GS.  The Client does not know a priori if the User is a new
        User, or a returning User.  Asking a returning User to consent
        releasing claims they have already provided is a poor User
        experience, as is sending the User back to the GS.  The Client
        requesting identity first enables the Client to get a response
        from the GS while the GS is still interacting with the User, so
        that the Client can request additional claims only if needed.
        Additionally, the claims a Client may want about a User may be
        dependent on some initial Claims.  For example, if a User is in
        a particular country, additional or different Claims my be
        required by the Client.

        There are also benefits for the GS.  Today, a GS usually keeps
        track of which claims a Client has requested for a User.
        Storing this information for all Clients a User uses may be
        undesirable for a GS that does not want to have that information
        about the User.  Keeping the interaction allows the Client to
        track what information it has about the User, and the GS can
        remain stateless.

   13.  *Why is there a "jose+body" RS access mechanism method for the
        Client?*Section 10.2.3

        There are numerous use cases where the RS wants non-repudiation
        and providence of the contents of an API call.  For example, the
        UGS Service Supplier Framework for Authentication and
        Authorization [UTM].

   14.  *Why use URIs to instead of handles for the Grant and
        Authorization?*

        A URI is an identifier just like a handle that can contain GS
        information that is opaque to the Client - so it has all the
        features of a handle, plus it can be the URL that is resolved to
        manipulate a Grant or an Authorization.  As the Grant URI and AZ
        URI are defined to start with the GS URI, the Client (and GS)
        can easily determine which GS a Grant or Authorization belong
        to.  URIs also enable a RESTful interface to the GS
        functionality.

   15.  *Why use the OPTIONS verb on the GS URI?  Why not use a .well-
        known mechanism?*





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        Having the GS URI endpoint respond to the metadata allows the GS
        to provide Client specific results using the same Client
        authentication used for other requests to the GS.  It also
        reduces the risk of a mismatch between what the advertised
        metadata, and the actual metadata.  A .well-known discovery
        mechanism may be defined to resolve from a hostname to the GS
        URI.

   16.  *Why support UPDATE, DELETE, and OPTIONS verbs on the AZ URI?*

        Maybe there are no use cases for them [that the editor knows
        of], but the GS can not implement, and they are available if use
        cases come up.

   17.  *Why have both Client ID and Client Handle?*

        While they both refer to a Client in the protocol, the Client ID
        refers to a pre-registered client,and the Client Handle is
        specific to an instance of a Dynamic Client.  Using separate
        terms clearly differentiates which identifier is being presented
        to the GS.

13.  Acknowledgments

   This draft derives many of its concepts from Justin Richer's
   Transactional Authorization draft [TxAuth].

   Additional thanks to Justin Richer and Annabelle Richard Backman for
   their strong critique of earlier drafts.

14.  IANA Considerations

   [ JOSE parameter for Authorization HTTP header ]

   TBD

15.  Security Considerations

   TBD

16.  References

16.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.



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   [RFC3966]  Schulzrinne, H., "The tel URI for Telephone Numbers",
              RFC 3966, DOI 10.17487/RFC3966, December 2004,
              <https://www.rfc-editor.org/info/rfc3966>.

   [RFC5322]  Resnick, P., Ed., "Internet Message Format", RFC 5322,
              DOI 10.17487/RFC5322, October 2008,
              <https://www.rfc-editor.org/info/rfc5322>.

   [RFC4949]  Shirey, R., "Internet Security Glossary, Version 2",
              FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
              <https://www.rfc-editor.org/info/rfc4949>.

   [RFC5646]  Phillips, A., Ed. and M. Davis, Ed., "Tags for Identifying
              Languages", BCP 47, RFC 5646, DOI 10.17487/RFC5646,
              September 2009, <https://www.rfc-editor.org/info/rfc5646>.

   [RFC6749]  Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
              RFC 6749, DOI 10.17487/RFC6749, October 2012,
              <https://www.rfc-editor.org/info/rfc6749>.

   [RFC6750]  Jones, M. and D. Hardt, "The OAuth 2.0 Authorization
              Framework: Bearer Token Usage", RFC 6750,
              DOI 10.17487/RFC6750, October 2012,
              <https://www.rfc-editor.org/info/rfc6750>.

   [RFC7515]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web
              Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
              2015, <https://www.rfc-editor.org/info/rfc7515>.

   [RFC7516]  Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
              RFC 7516, DOI 10.17487/RFC7516, May 2015,
              <https://www.rfc-editor.org/info/rfc7516>.

   [RFC7519]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
              (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
              <https://www.rfc-editor.org/info/rfc7519>.

   [RFC7540]  Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
              Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
              DOI 10.17487/RFC7540, May 2015,
              <https://www.rfc-editor.org/info/rfc7540>.

   [RFC8259]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", STD 90, RFC 8259,
              DOI 10.17487/RFC8259, December 2017,
              <https://www.rfc-editor.org/info/rfc8259>.





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   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [OIDC]     Sakimora, N., Bradley, J., Jones, M., de Medeiros, B., and
              C. Mortimore, "OpenID Connect Core 1.0", November 2014,
              <https://openiD.net/specs/openiD-connect-core-1_0.html>.

   [OIDC4IA]  Lodderstedt, T. and D. Fett, "OpenID Connect for Identity
              Assurance 1.0", October 2019, <https://openid.net/specs/
              openid-connect-4-identity-assurance-1_0.html>.

16.2.  Informative References

   [RFC7049]  Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
              October 2013, <https://www.rfc-editor.org/info/rfc7049>.

   [RFC8252]  Denniss, W. and J. Bradley, "OAuth 2.0 for Native Apps",
              BCP 212, RFC 8252, DOI 10.17487/RFC8252, October 2017,
              <https://www.rfc-editor.org/info/rfc8252>.

   [RFC8152]  Schaad, J., "CBOR Object Signing and Encryption (COSE)",
              RFC 8152, DOI 10.17487/RFC8152, July 2017,
              <https://www.rfc-editor.org/info/rfc8152>.

   [RFC8323]  Bormann, C., Lemay, S., Tschofenig, H., Hartke, K.,
              Silverajan, B., and B. Raymor, Ed., "CoAP (Constrained
              Application Protocol) over TCP, TLS, and WebSockets",
              RFC 8323, DOI 10.17487/RFC8323, February 2018,
              <https://www.rfc-editor.org/info/rfc8323>.

   [RFC8628]  Denniss, W., Bradley, J., Jones, M., and H. Tschofenig,
              "OAuth 2.0 Device Authorization Grant", RFC 8628,
              DOI 10.17487/RFC8628, August 2019,
              <https://www.rfc-editor.org/info/rfc8628>.

   [browser_based_apps]
              Parecki, A. and D. Waite, "OAuth 2.0 for Browser-Based
              Apps", September 2019, <https://tools.ietf.org/html/draft-
              ietf-oauth-browser-based-apps-04>.

   [RAR]      Lodderstedt, T., Richer, J., and B. Campbell, "OAuth 2.0
              Rich Authorization Requests", January 2020,
              <https://tools.ietf.org/html/draft-ietf-oauth-rar-00>.






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   [W3C_VC]   Sporny, M., Noble, G., and D. Chadwick, "Verifiable
              Credentials Data Model 1.0", November 2019,
              <https://w3c.github.io/vc-data-model/>.

   [QR_Code]  "ISO/IEC 18004:2015 - Information technology - Automatic
              identification and data capture techniques - QR Code bar
              code symbology specification", February 2015,
              <https://www.iso.org/standard/62021.html>.

   [TxAuth]   Richer, J., "Transactional AuthN", December 2019,
              <https://tools.ietf.org/html/draft-richer-transactional-
              authz-04>.

   [UTM]      Rios, J., Smith, I., and P. Venkatesen, "UGS Service
              Supplier Framework for Authentication and AuthN",
              September 2019, <https://utm.arc.nasa.gov/docs/2019-
              UTM_Framework-NGSA-TM220364.pdf>.

Appendix A.  Document History

A.1.  draft-hardt-xauth-protocol-00

   *  Initial version

A.2.  draft-hardt-xauth-protocol-01

   *  text clean up

   *  added OIDC4IA claims

   *  added "jws" method for accessing a resource.

   *  renamed Initiation Request -> Grant Request

   *  renamed Initiation Response -> Interaction Response

   *  renamed Completion Request -> Authorization Request

   *  renamed Completion Response -> Grant Request

   *  renamed completion handle -> authorization handle

   *  added Authentication Request, Authentication Response,
      authentication handle







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A.3.  draft-hardt-xauth-protocol-02

   *  major rewrite

   *  handles are now URIs

   *  the collection of claims and authorizations are a Grant

   *  an Authorization is its own type

   *  lots of sequences added

A.4.  draft-hardt-xauth-protocol-03

   *  fixed RO definition

   *  improved language in Rationals

   *  added user code interaction method, and aligned qrcode interaction
      method

   *  added completion_uri for code flows

A.5.  draft-hardt-xauth-protocol-04

   *  renamed interaction uris to have purpose specific names

A.6.  draft-hardt-xauth-protocol-05

   *  separated claims from identifiers in request user object

   *  simplified reciprocal grant flow

   *  reduced interactions to redirect and indirect

   *  simplified interaction parameters

   *  added in language for Client to verify interaction completion

   *  added Verify Grant API and Interaction Nonce

   *  replaced Refresh AuthZ with Read AuthZ.  Read and refresh are same
      operation.

A.7.  draft-hardt-xauth-protocol-06

   *  fixup examples to match specification




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A.8.  draft-hardt-xauth-protocol-07

   *  refactored interaction request and response syntax, and enabled
      interaction mode negotiation

   *  generation of client handle by GS for dynamic clients

   *  renamed title to Grant Negotiation and Authorization Protocol.
      Preserved draft-hardt-xauth-protocol filename to ease tracking
      changes.

   *  changed Authorizations to be key / value pairs (aka dictionary)
      instead of a JSON array

Appendix B.  Comparison with OAuth 2.0 and OpenID Connect

   *Changed Features*

   The major changes between this protocol and OAuth 2.0 and OpenID
   Connect are:

   *  The Client allows uses a private key to authenticate in this
      protocol instead of the client secret in OAuth 2.0 and OpenID
      Connect.

   *  The Client initiates the protocol by making a signed request
      directly to the GS instead of redirecting the User to the GS.

   *  The Client does not pass any parameters in redirecting the User to
      the GS, and optionally only receives an interaction nonce in the
      redirection back from the GS.

   *  The refresh_token has been replaced with a AZ URI that both
      represents the authorization, and is the URI for obtaining a fresh
      access token.

   *  The Client can request identity claims to be returned independent
      of the ID Token.  There is no UserInfo endpoint to query claims as
      there is in OpenID Connect.

   *  The GS URI is the token endpoint.

   *Preserved Features*

   *  This protocol reuses the OAuth 2.0 scopes, Client IDs, and access
      tokens of OAuth 2.0.





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   *  This protocol reuses the Client IDs, Claims and ID Token of OpenID
      Connect.

   *  No change is required by the Client or the RS for accessing
      existing bearer token protected APIs.

   *New Features*

   *  A Grant represents both the user identity claims and RS access
      granted to the Client.

   *  The Client can verify, update, retrieve, and delete a Grant.

   *  The GS can initiate a flow by creating a Grant and redirecting the
      User to the Client with the Grant URI.

   *  The Client can discovery if a GS has a User with an identifier
      before the GS interacts with the User.

   *  The Client can request the GS to first authenticate the User and
      return User identity claims, and then the Client can update Grant
      request based on the User identity.

   *  Support for scannable code initiated interactions.

   *  Each Client instance can have its own private / public key pair.

   *  Highly extensible per Section 11.

Author's Address

   Dick Hardt (editor)
   SignIn.Org
   United States

   Email: dick.hardt@gmail.com















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