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Network Working Group                                      D. Hardt, Ed.
Internet-Draft                                                SignIn.Org
Intended status: Standards Track                         8 February 2020
Expires: 11 August 2020


                           The XAuth Protocol
                     draft-hardt-xauth-protocol-02

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.

Note to Readers

   Source for this draft and an issue tracker can be found at
   https://github.com/dickhardt/hardt-xauth-protocol
   (https://github.com/dickhardt/hardt-xauth-protocol).

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
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 11 August 2020.







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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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   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Parties . . . . . . . . . . . . . . . . . . . . . . . . .   5
     2.2.  Reused Terms  . . . . . . . . . . . . . . . . . . . . . .   6
     2.3.  New Terms . . . . . . . . . . . . . . . . . . . . . . . .   6
   3.  Sequences . . . . . . . . . . . . . . . . . . . . . . . . . .   7
     3.1.  Create Grant  . . . . . . . . . . . . . . . . . . . . . .   7
     3.2.  Reciprocal Grant  . . . . . . . . . . . . . . . . . . . .   8
     3.3.  GS Initiated Grant  . . . . . . . . . . . . . . . . . . .  10
     3.4.  Create and Update . . . . . . . . . . . . . . . . . . . .  10
     3.5.  Create and Delete . . . . . . . . . . . . . . . . . . . .  12
     3.6.  Create, Discover, and Delete  . . . . . . . . . . . . . .  14
     3.7.  Create and Wait . . . . . . . . . . . . . . . . . . . . .  14
     3.8.  Read Grant  . . . . . . . . . . . . . . . . . . . . . . .  15
     3.9.  Access Token Refresh  . . . . . . . . . . . . . . . . . .  16
     3.10. GS API Table  . . . . . . . . . . . . . . . . . . . . . .  16
   4.  Grant and AuthZ Life Cycle  . . . . . . . . . . . . . . . . .  17
   5.  GS APIs . . . . . . . . . . . . . . . . . . . . . . . . . . .  18
     5.1.  Create Grant  . . . . . . . . . . . . . . . . . . . . . .  18
     5.2.  Read Grant  . . . . . . . . . . . . . . . . . . . . . . .  20
     5.3.  Update Grant  . . . . . . . . . . . . . . . . . . . . . .  20
     5.4.  Delete Grant  . . . . . . . . . . . . . . . . . . . . . .  21
     5.5.  Request JSON  . . . . . . . . . . . . . . . . . . . . . .  22
       5.5.1.  "client" Object . . . . . . . . . . . . . . . . . . .  22
       5.5.2.  "interaction" Object  . . . . . . . . . . . . . . . .  22
       5.5.3.  "user" Object . . . . . . . . . . . . . . . . . . . .  23
       5.5.4.  "authorization" Object  . . . . . . . . . . . . . . .  23
       5.5.5.  "authorizations" Object . . . . . . . . . . . . . . .  24
       5.5.6.  "claims" Object . . . . . . . . . . . . . . . . . . .  24
       5.5.7.  "reciprocal" Object . . . . . . . . . . . . . . . . .  24
     5.6.  Refresh Authorization . . . . . . . . . . . . . . . . . .  25
     5.7.  Update Authorization  . . . . . . . . . . . . . . . . . .  25



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     5.8.  Delete Authorization  . . . . . . . . . . . . . . . . . .  25
     5.9.  GS Options  . . . . . . . . . . . . . . . . . . . . . . .  26
     5.10. Grant Options . . . . . . . . . . . . . . . . . . . . . .  27
     5.11. AuthZ Options . . . . . . . . . . . . . . . . . . . . . .  27
     5.12. Request Verification  . . . . . . . . . . . . . . . . . .  27
   6.  GS Initiated Grant  . . . . . . . . . . . . . . . . . . . . .  28
   7.  GS API Responses  . . . . . . . . . . . . . . . . . . . . . .  28
     7.1.  Grant Response  . . . . . . . . . . . . . . . . . . . . .  28
     7.2.  Interaction Response  . . . . . . . . . . . . . . . . . .  29
     7.3.  Wait Response . . . . . . . . . . . . . . . . . . . . . .  30
     7.4.  Response JSON . . . . . . . . . . . . . . . . . . . . . .  31
       7.4.1.  "interaction" Object  . . . . . . . . . . . . . . . .  31
       7.4.2.  "user" Object . . . . . . . . . . . . . . . . . . . .  31
       7.4.3.  "authorization" Object  . . . . . . . . . . . . . . .  32
       7.4.4.  "authorizations" Object . . . . . . . . . . . . . . .  32
       7.4.5.  "claims" Object . . . . . . . . . . . . . . . . . . .  32
       7.4.6.  "reciprocal" Object . . . . . . . . . . . . . . . . .  33
       7.4.7.  Interaction Types . . . . . . . . . . . . . . . . . .  33
       7.4.8.  Signing and Encryption  . . . . . . . . . . . . . . .  34
     7.5.  Response Verification . . . . . . . . . . . . . . . . . .  34
   8.  RS Access . . . . . . . . . . . . . . . . . . . . . . . . . .  34
     8.1.  Bearer Token  . . . . . . . . . . . . . . . . . . . . . .  34
   9.  Error Responses . . . . . . . . . . . . . . . . . . . . . . .  35
   10. JOSE Authentication . . . . . . . . . . . . . . . . . . . . .  35
     10.1.  GS Access  . . . . . . . . . . . . . . . . . . . . . . .  35
       10.1.1.  Authorization Header . . . . . . . . . . . . . . . .  36
       10.1.2.  Signed Body  . . . . . . . . . . . . . . . . . . . .  37
       10.1.3.  Public Key Resolution  . . . . . . . . . . . . . . .  37
     10.2.  RS Access  . . . . . . . . . . . . . . . . . . . . . . .  38
       10.2.1.  JOSE header  . . . . . . . . . . . . . . . . . . . .  38
       10.2.2.  "jose" Mechanism . . . . . . . . . . . . . . . . . .  39
       10.2.3.  "jose+body" Mechanism  . . . . . . . . . . . . . . .  40
       10.2.4.  Public Key Resolution  . . . . . . . . . . . . . . .  41
     10.3.  Request Encryption . . . . . . . . . . . . . . . . . . .  41
     10.4.  Response Signing . . . . . . . . . . . . . . . . . . . .  41
     10.5.  Response Encryption  . . . . . . . . . . . . . . . . . .  42
   11. Extensibility . . . . . . . . . . . . . . . . . . . . . . . .  42
   12. Rational  . . . . . . . . . . . . . . . . . . . . . . . . . .  43
   13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  47
   14. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  47
   15. Security Considerations . . . . . . . . . . . . . . . . . . .  47
   16. References  . . . . . . . . . . . . . . . . . . . . . . . . .  47
     16.1.  Normative References . . . . . . . . . . . . . . . . . .  47
     16.2.  Informative References . . . . . . . . . . . . . . . . .  48
   Appendix A.  Document History . . . . . . . . . . . . . . . . . .  49
     A.1.  draft-hardt-xauth-protocol-00 . . . . . . . . . . . . . .  49
     A.2.  draft-hardt-xauth-protocol-01 . . . . . . . . . . . . . .  50
     A.3.  draft-hardt-xauth-protocol-02 . . . . . . . . . . . . . .  50



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   Appendix B.  Comparison with OAuth 2.0 and OpenID Connect . . . .  50
   Appendix C.  Open Questions . . . . . . . . . . . . . . . . . . .  51
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  51

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.

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

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

2.  Terminology






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2.1.  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, 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.  A single-page
      application with no server 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



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      explicit consent from the RO or User to provide these to the
      Client.  An 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.  Owned by the Resource Owner.

   *  *Resource Owner* (RO) - owns 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.

2.2.  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.

2.3.  New Terms

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

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

   *  *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.





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

   *  *interaction* - [Editor: what do we really mean by this term?]

3.  Sequences

   Before any sequence, the Client needs to be manually or
   programmatically configured for the GS.  See GS Options Section 5.9
   for details on acquiring GS metadata.

   [Editor: a plethora of sequences are included to illustrate all the
   different actions.  Many of these could potentially be moved to a use
   case document in the future.]

3.1.  Create Grant

   The Client requests a Grant from the GS that requires User
   interaction:

   +--------+                                  +-------+
   | Client |                                  |  GS   |
   |        |--(1)--- Create Grant ----------->|       |
   |        |                                  |  (2)  |
   |        |<--- Interaction Response ---(3)--|  eval |
   |        |                                  |       |
   |        |--(4)--- Read Grant ------------->|       |         +------+
   |        |                                  |       |         | User |
   |        |--(5)--- Interaction Transfer --- | - - - | ------->|      |
   |        |                                  |       |<--(6)-->|      |
   |        |                                  |       |  authN  |      |
   |        |                                  |       |<--(7)-->|      |
   |        |                                  |       |  authZ  |      |
   |        |<--- Interaction Transfer ---(8)- | - - - | --------|      |
   |        |                                  |       |         |      |
   |        |<--------- Grant Response ---(9)--|       |         +------+
   |        |                                  |       |
   +--------+                                  +-------+

   1.  *Create Grant* The Client creates a Grant Request (Section 5.1)
       and sends it with an HTTP POST to the GS GS URI.

   2.  *Grant Request Evaluation* The GS processes the request to
       determine if it will send a Interaction Response, Wait Response,
       or a Grant Response.  The GS determines that interaction with the
       User is required and sends an Interaction Response.  (For



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       readability, this step is not described in the following
       sequences)

   3.  *Interaction Response* The GS sends an Interaction Response
       (Section 7.2) containing the Grant URI and an interaction object.

   4.  *Read Grant* The Client does an HTTP GET of the Grant URI
       (Section 5.2).

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

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

   7.  *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.

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

   9.  *Grant Response* The GS responds with a Grant Response
       (Section 7.1).

3.2.  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.  Party A starts off being the Client
   per Create Grant Section 3.1.  Party B then includes a Reciprocal
   Request in its Grant Response.  Party A then gets authorization from
   the User and returns a Grant URI to Party B.  Party A and B swap
   roles, and Party B's Client obtains the Grant from Party A's GS.



















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                   Party A                                    Party B
                  +--------+                                 +--------+
                  | Client |                                 |   GS   |
                  ~ ~ ~ ~ ~ ~     Same as steps 1 - 8 of    ~ ~ ~ ~ ~ ~
   +------+       |        |        Create Grant above       |        |
   | User |       |        |                                 |        |
   |      |<----- | - - -  | -- Interaction Transfer ------- |        |
   |      |       |        |                                 |        |
   |      |       |        |<------- Grant Response ---(1)---|        |
   |      |       |        |      Reciprocal Grant Request   |        |
   |      |<-(2)->|        |                                 |        |
   |      | AuthZ |        |---(3)--- Update Grant --------->|        |
   +------+       |        |   Reciprocal Grant Response     |        |
                  |        |                                 |        |
                  |        |<-- Empty Grant Response ---(4)--|        |
                  |        |                                 |        |
                  +--------+       (5) Swap Roles            +--------+
                  |   GS   |                                 | Client |
                  |        |<------------ Read Grant ---(6)--|        |
                  |        |                                 |        |
                  |        |--(7)--- Grant Response -------->|        |
                  |        |                                 |        |
                  +--------+                                 +--------+

   1.  *Grant Response* Party B responds with a Grant Response including
       a Reciprocal Object Section 7.4.6 requesting its own Grant.

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

   3.  *Update Grant* Party A sends an Update Grant request containing
       the Grant URI in the Reciprocal object Section 5.5.7.

   4.  *Grant Response* Party B responds with an Empty Grant Response as
       there were no other requests in the Update Grant.

   5.  *Swap Roles* Party A now acts as a GS, Party B as a Client.

   6.  *Read Grant* Party B does an HTTP GET of the Grant URI
       (Section 5.2).

   7.  *Grant Response* Party A responds with a Grant Response
       (Section 7.1).







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3.3.  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 5.2).

   5.  *Grant Response* The GS responds with a Grant Response
       (Section 7.1).

   See Section 6 for more details.

3.4.  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 5.1)
        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 7.2) 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 5.2).

   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




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        (Section 7.1) 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 5.3) 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 7.1) 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 5.3) 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 7.1) including the identity claims released by the
        User.

3.5.  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 has
   all the identity claims and authorizations needed, the Client deletes
   the Grant which prompts the GS to transfer the interaction back to
   the Client.







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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 5.1)
       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 7.2) 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 5.2).

   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 7.1) 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.

   8.  *Delete Grant* The Client no longer needs the Grant and decides
       to Delete Grant (Section 5.4) by sending an HTTP DELETE to the



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       Grant URI.  If the GS responds with success the Grant no longer
       exists.

3.6.  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 5.1)
       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 7.2) 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 5.4) by
       sending an HTTP DELETE to the Grant URI.  If the GS responds with
       success the Grant no longer exists.

3.7.  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 5.1)
       and sends it with an HTTP POST to the GS GS URI.

   2.  *Wait Response* The GS sends an Interaction Response
       (Section 7.3) 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 5.2).

   6.  *Grant Response* The GS responds with a Grant Response
       (Section 7.1).

3.8.  Read Grant

   The Client wants to acquire fresh 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 5.2).




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   2.  *Grant Response* The GS responds with a Grant Response
       (Section 7.1) containing updated identity claims and
       authorizations.

3.9.  Access Token Refresh

   The Client has an access token and uses it to access resources at an
   RS.  The access token expires, and the Client acquires a fresh access
   token from the GS.

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

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

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

   3.  *Refresh AuthZ* If the Client received an AuthZ URI in the
       Response JSON "authorization" object (Section 7.4.3), the Client
       can Refresh AuthZ (Section 5.6) with an HTTP GET to the AuthZ URI
       and receive an Response JSON "authorization" object"
       (Section 7.4.3) with a fresh access token.

3.10.  GS API Table

    +--------------+-----------+--------+-----------------------------+
    | request      | http verb | uri    | response                    |
    +==============+===========+========+=============================+
    | Create Grant | POST      | GS URI | interaction, wait, or grant |
    +--------------+-----------+--------+-----------------------------+
    | Read Grant   | GET       | Grant  | wait, or grant              |
    |              |           | URI    |                             |
    +--------------+-----------+--------+-----------------------------+
    | Update Grant | PUT       | Grant  | interaction, wait, or grant |



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    |              |           | URI    |                             |
    +--------------+-----------+--------+-----------------------------+
    | Delete Grant | DELETE    | Grant  | success                     |
    |              |           | URI    |                             |
    +--------------+-----------+--------+-----------------------------+
    | Refresh      | GET       | AuthZ  | authorization               |
    | AuthZ        |           | URI    |                             |
    +--------------+-----------+--------+-----------------------------+
    | Update AuthZ | PUT       | AuthZ  | authorization               |
    |              |           | URI    |                             |
    +--------------+-----------+--------+-----------------------------+
    | Delete AuthZ | DELETE    | AuthZ  | success                     |
    |              |           | URI    |                             |
    +--------------+-----------+--------+-----------------------------+
    | GS Options   | OPTIONS   | GS URI | metadata                    |
    +--------------+-----------+--------+-----------------------------+
    | Grant        | OPTIONS   | Grant  | metadata                    |
    | Options      |           | URI    |                             |
    +--------------+-----------+--------+-----------------------------+
    | AuthZ        | OPTIONS   | AuthZ  | metadata                    |
    | Options      |           | URI    |                             |
    +--------------+-----------+--------+-----------------------------+

                                  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

4.  Grant and AuthZ Life Cycle

   [Editor: straw man for life cycles.]

   *Grant life Cycle*

   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*





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   Authorizations are OPTIONALLY included in a Grant Response
   "authorization" Object (Section 7.4.3), and are represented by an
   AuthZ URI.  If an AuthZ URI is included, the Client MAY refresh,
   update, and delete Authorizations.

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

5.  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].

5.1.  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 5.5:

   *  iat

   *  nonce

   *  uri set to the GS URI

   *  client

   and MAY include the following from Request JSON Section 5.5

   *  user

   *  interaction

   *  authorization or authorizations

   *  claims

   *  reciprocal

   The GS MUST respond with one of Grant Response Section 7.1,
   Interaction Response Section 7.2, Wait Response Section 7.3, or one
   of the following errors:



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   *  TBD

   from Error Responses Section 9.

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

   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": {
           "type"      : "popup"
       },
       "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": {
           "keep"      : true,
           "type"      : "redirect",
           "uri"       : "https://web.example/return"
       },
       "user": {
           "identifiers": {
               "email" : "jane.doe@example.com"
           },
           "exists"    : true
       },
       "claims"    : { "oidc": { "id_token" : {} } }
   }

5.2.  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 7.1,
   Interaction Response Section 7.2, Wait Response Section 7.3, or one
   of the following errors:

   *  TBD

   from Error Responses Section 9.

5.3.  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 5.5

   *  iat

   *  uri set to the Grant URI




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   and MAY include the following from Request JSON Section 5.5

   *  user

   *  interaction

   *  authorization or authorizations

   *  claims

   *  reciprocal

   The GS MUST respond with one of Grant Response Section 7.1,
   Interaction Response Section 7.2, Wait Response Section 7.3, 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:

   Example 3

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

5.4.  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



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   from Error Responses Section 9.

5.5.  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 5.1, or the Grant
      URI if in an Update Grant Section 5.3.

5.5.1.  "client" Object

   The client object MUST contain either the id attribute for Registered
   Clients, or the display object for Dynamic Clients.

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

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

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

      -  *uri* - a URI representing the Dynamic Client

   [Editor: a max length for the name?]  [Editor: a max length for the
   URI?]

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

5.5.2.  "interaction" Object

   The interaction object contains the type of interaction the Client
   will provide the User.  Other attributes

   *  *keep* - a JSON boolean.  If set to the JSON value true, the GS
      will not transfer the User interaction back to the Client after
      processing the Grant request.  The JSON value false is equivalent
      to the attribute not being present, and the GS will transfer the
      User interaction back to the Client after processing the request.
      This attribute is OPTIONAL

      -  *type* - contains one of the following values: "popup",
         "redirect", or "qrcode".  Details in Section 7.4.7.  This
         attribute is REQUIRED.



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      -  *redirect_uri* - this attribute is REQUIRED if the type is
         "redirect".  It is the URI that the Client requests the GS to
         redirect the User to after the GS has completed interacting
         with the User.  If the Client manages session state in URIs,
         then the redirect_uri SHOULD contain that state.

      -  *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: do we need max pixels or max chars for qrcode interaction?
   Either passed to GS, or max specified values here?]

   [Editor: other possible interaction models could be a "webview",
   where the Client can display a web page, or just a "message", where
   the client can only display a text message]

   [Editor: we may need to include interaction types for iOS and Android
   as the mobile OS APIs evolve.]

5.5.3.  "user" Object

   *  *exists* - MUST contain the JSON true value.  Indicates the Client
      requests the GS to return a "user"."exists" value in an
      Interaction Response Section 7.2.  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].

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

5.5.4.  "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]




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      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]

5.5.5.  "authorizations" Object

   A JSON array of "authorization" objects.  Only one of "authorization"
   or "authorizations" may be in the Request JSON.

   [Editor: instead of an array, we could have a Client defined
   dictionary of "authorization" objects]

5.5.6.  "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.

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

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

5.5.7.  "reciprocal" Object

   *  *uri* - the Grant URI for the Reciprocal Grant.  This attribute is
      REQUIRED.

   *  *client* - the client object must contain the "id" attribute with
      the Client ID the Grant was issued to.  This attribute is
      REQUIRED.





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   *  *authorization* - an authorization object per Section 7.4.3 in the
      Response JSON.

   *  *authorizations* - an authorizations object per Section 7.4.4 in
      the Response JSON.

   *  *claims* - a claims object per Section 7.4.5 in the Response JSON.

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

5.6.  Refresh Authorization

   The Client updates an Authorization by doing an HTTP GET to the
   corresponding AuthZ URI.

   The GS MUST respond with an Response JSON "authorization" object
   Section 7.4.3, or one of the following errors:

   *  TBD

   from Error Responses Section 9.

5.7.  Update Authorization

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

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

   *  *uri* - the AuthZ URI.

   *  *authorization* - the new authorization requested per the Request
      JSON "authorization" object Section 5.5.4.

   The GS MUST respond with an Response JSON "authorization" object
   Section 7.4.3, or one of the following errors:

   *  TBD

   from Error Responses Section 9.

5.8.  Delete Authorization

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




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

   *  TBD

   from Error Responses Section 9.

5.9.  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 types 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.

      -  *authorizations* - boolean indicating if a request for multiple
         authorizations is supported.

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



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   [Editor: namespace metadata for extensions?]

   or one of the following errors:

   *  TBD

   from Error Responses Section 9.

5.10.  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.

5.11.  AuthZ Options

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

5.12.  Request Verification

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

   *  TBD








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6.  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 3.3 for the sequence diagram.

7.  GS API Responses

7.1.  Grant Response

   The Grant Response MUST include the following from the Response JSON
   Section 7.4

   *  iat

   *  nonce

   *  uri

   *  expires_in

   and MAY include the following from the Response JSON Section 7.4

   *  authorization or authorizations

   *  claims

   *  reciprocal

   Example non-normative Grant Response JSON document for Example 1 in
   Section 3.1:







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   {
       "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 3.1:

   {
       "iat"   : 15790460234,
       "nonce" : "5c9360a5-9065-4f7b-a330-5713909e06c6",
       "uri"   : "https://as.example/endpoint/grant/example2",
       "authorization": {
           "type"          : "oauth_scope",
           "scope"         : "read_calendar write_calendar",
           "expires_in"    : 3600,
           "mechanism"     : "jose",
           "token"         : "eyJJ2D6.example.access.token.mZf9p"
           "certificate": {
               "x5u"   : "https://as.example/cert/example2"
           },
           "uri"       : "https://as.example/endpoint/authz/example2"
       }
   }

7.2.  Interaction Response

   The Interaction Response MUST include the following from the Response
   JSON Section 7.4




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   *  iat

   *  nonce

   *  uri

   *  interaction

   and MAY include the following from the Response JSON Section 7.4

   *  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" : {
           "type"      : "popup",
           "uri"       : "https://as.example/popup/example4"
       },
       "user": {
           "exists" : true
       }
   }

7.3.  Wait Response

   The Wait Response MUST include the following from the Response JSON
   Section 7.4

   *  iat

   *  nonce

   *  uri

   *  wait

   A non-normative example of an Wait Response follows:








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

7.4.  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 5.5.

   *  *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.

7.4.1.  "interaction" Object

   If the GS wants the Client to start the interaction, the GS MUST
   select one of the interaction mechanisms provided by the Client in
   the Grant Request, and include the matching attribute in the
   interaction object:

   *  *type* - this MUST match the type provided by the Client in the
      Grant Request client.interaction object.

   *  *uri* - the URI to interact with the User per the type.  This may
      be a temporary short URL if the type is qrcode so that it is easy
      to scan.

   *  *message* - a text string to display to the User if type is
      qrcode.

   [Editor: do we specify a maximum length for the uri and message so
   that a device knows the maximum it needs to support?  A smart device
   may have limited screen real estate.]

7.4.2.  "user" Object




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   *  *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 5.5.3

7.4.3.  "authorization" Object

   The "authorization" object is a response to the Request
   "authorization" object Section 5.5.4, the Refresh Authorization
   Section 5.6, or the Update Authorization Section 5.7.

   *  *type* - the type of claim request: "oauth_scope" or "oauth_rich".
      See the "type" object in Section 5.5.4 for details.

   *  *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.

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

   *  *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 AuthZ URI.  Used to refresh, update, and delete the
      authorization.  This attribute is OPTIONAL.

   [Editor: any value in an expiry for the Authorization?]

7.4.4.  "authorizations" Object

   A JSON array of authorization objects.  Support for the
   authorizations object is OPTIONAL.

7.4.5.  "claims" Object

   The claims object is a response to the Request "claims" object
   Section 5.5.4.



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   *  *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]

7.4.6.  "reciprocal" Object

   The following MUST be included

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

   *  *client*

      -  *id* - the Client ID making the request

   One or more of the following objects from the Request JSON
   Section 5.5 are included:

   *  *authorization* Section 7.4.3

   *  *authorizations* Section 7.4.4

   *  *claims* Section 7.4.5

7.4.7.  Interaction Types

   If the GS wants the Client to initiate the interaction with the User,
   then the GS will return an Interaction Response.  The Client will
   initiate the interaction with the User in one of the following ways:

   *  *popup* The Client will create a new popup child browser window
      containing the "interaction"."uri" attribute.  [Editor: more
      details on how to do this]





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   The GS will close the popup window when the interactions with the
   User are complete.  [Editor: confirm GS can do this still on all
   browsers, or does Client need to close]

   *  *redirect* The Client will redirect the User to the
      "interaction"."uri" attribute.  When the GS interactions with the
      User are complete, the GS will redirect the User to the
      "interaction"."redirect_uri" attribute the Client provided in the
      Grant Request.

   *  *qrcode* The Client will create a [QR_Code] of the
      "interaction"."uri" attribute and display the resulting graphic
      and the "interaction"."message" attribute as a character string.

   An GS MUST support the "popup", "redirect", and "qrcode" interaction
   types.

7.4.8.  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?]

7.5.  Response Verification

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

   *  TBD

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 7.4.3.

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:






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   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.

   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 Clients MAY have different
   private keys, but certificates bind them 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.

   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     |
           +---------------+-----------+-----------+----------+
           | Read Grant    | GET       | Grant URI | header   |
           +---------------+-----------+-----------+----------+
           | Update Grant  | PUT       | Grant URI | body     |
           +---------------+-----------+-----------+----------+
           | Delete Grant  | DELETE    | Grant URI | success  |
           +---------------+-----------+-----------+----------+
           | Refresh AuthZ | GET       | AuthZ URI | body     |
           +---------------+-----------+-----------+----------+
           | Update AuthZ  | PUT       | AuthZ URI | body     |
           +---------------+-----------+-----------+----------+
           | Delete AuthZ  | DELETE    | AuthZ URI | header   |
           +---------------+-----------+-----------+----------+
           | GS Options    | OPTIONS   | GS URI    | header   |
           +---------------+-----------+-----------+----------+
           | Grant Options | OPTIONS   | Grant URI | header   |
           +---------------+-----------+-----------+----------+
           | AuthZ Options | OPTIONS   | AuthZ 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
   AuthZ 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.

   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://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

10.1.3.  Public Key Resolution





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   *  *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.

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.



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   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:

   {
       "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*



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   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 5.9.

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 5.9.

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 5.5.

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 types of authorizations in addition to OAuth 2.0
         scopes and RAR.



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   *  *"claims" Object*

      -  Additional types of identity claims in addition to OpenID
         Connect claims and Verified Credentials.

   *  *Interaction types*

      -  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 6
        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 vs granting access to a resource.  A
        request for an authorization returns an access token or handle,
        while a request for a claim returns the claim.

   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 the sequence with "interaction"."keep"?*

        A common pattern is to use an GS to authenticate the User at the
        Client.  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 identity claims and/or authorizations 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



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        any identity claims/or authorizations required or desired.
        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

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

        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 have an UPDATE, DELETE, and OPTIONS verbs on the AuthZ
        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 list explicit interactions, instead of the Client and GS
        negotiating interaction capabilities?*





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        The Client knows what interactions it is capable of, and
        prefers.  Telling the GS the interaction allows the GS to know
        what interaction the User will have.  Knowing how the Client
        will transition the interaction will enable the GS to provider a
        better User experience.  For example, the GS may want to provide
        a short URL if it knows the Client will be showing a QR code vs
        a redirect, or have a different layout if it is a popup vs a
        redirect.

13.  Acknowledgments

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

   Additional thanks to Justin Richer for his 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

   [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>.

   [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>.





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   [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>.

   [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>.



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   [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>.

   [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




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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

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

   *  handles are now URIs

   *  the

   *  the collection of claims and authorizations are a Grant


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 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, nor receive any parameters in the redirection back from
      the GS.





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   *  The refresh_token has been replaced with a AuthZ URI that both
      represents the access, and is the URI to call to refresh access.

   *  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.  CHECK!!!s

   *Preserved Features*

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

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

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

   *New Features*

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

   *  The Client can 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 an 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 QR Code initiated interactions.

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

   *  More Extensibility dimensions.

Appendix C.  Open Questions


Author's Address




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   Dick Hardt (editor)
   SignIn.Org
   United States

   Email: dick.hardt@gmail.com














































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