[Docs] [txt|pdf|xml|html] [Tracker] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03

Web Authorization Protocol                                T. Lodderstedt
Internet-Draft                                                   yes.com
Intended status: Standards Track                               J. Richer
Expires: May 6, 2020                                 Bespoke Engineering
                                                             B. Campbell
                                                           Ping Identity
                                                        November 3, 2019


                 OAuth 2.0 Rich Authorization Requests
                     draft-lodderstedt-oauth-rar-03

Abstract

   This document specifies a new parameter "authorization_details" that
   is used to carry fine grained authorization data in the OAuth
   authorization request.

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
   working documents as Internet-Drafts.  The list of current Internet-
   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 May 6, 2020.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   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 and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of




Lodderstedt, et al.        Expires May 6, 2020                  [Page 1]


Internet-Draft                  oauth-rar                  November 2019


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

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Conventions and Terminology . . . . . . . . . . . . . . .   4
   2.  Request parameter "authorization_details" . . . . . . . . . .   4
     2.1.  Authorization data elements types . . . . . . . . . . . .   5
     2.2.  Relationship to "scope" parameter . . . . . . . . . . . .   8
       2.2.1.  Scope value "openid" and "claims" parameter . . . . .   8
     2.3.  Relationship to "resource" parameter  . . . . . . . . . .   9
   3.  Using "authorization_details" . . . . . . . . . . . . . . . .  11
     3.1.  Authorization Request . . . . . . . . . . . . . . . . . .  11
     3.2.  Authorization Request Processing  . . . . . . . . . . . .  14
     3.3.  Token Request . . . . . . . . . . . . . . . . . . . . . .  15
     3.4.  Token Response  . . . . . . . . . . . . . . . . . . . . .  15
       3.4.1.  Token Content . . . . . . . . . . . . . . . . . . . .  16
     3.5.  Token Introspection Request . . . . . . . . . . . . . . .  18
     3.6.  Token Introspection Response  . . . . . . . . . . . . . .  18
   4.  Metadata  . . . . . . . . . . . . . . . . . . . . . . . . . .  19
   5.  Implementation Considerations . . . . . . . . . . . . . . . .  20
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  20
   7.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .  20
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  21
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  21
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  21
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  21
     10.2.  Informative References . . . . . . . . . . . . . . . . .  22
   Appendix A.  Additional Examples  . . . . . . . . . . . . . . . .  23
     A.1.  OpenID Connect  . . . . . . . . . . . . . . . . . . . . .  23
     A.2.  Remote Electronic Signing . . . . . . . . . . . . . . . .  25
     A.3.  Access to Tax Data  . . . . . . . . . . . . . . . . . . .  26
     A.4.  eHealth . . . . . . . . . . . . . . . . . . . . . . . . .  27
   Appendix B.  Document History . . . . . . . . . . . . . . . . . .  29
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  30

1.  Introduction

   The OAuth 2.0 authorization framework [RFC6749] defines the parameter
   "scope" that allows OAuth clients to specify the requested scope,
   i.e., the permission, of an access token.  This mechanism is
   sufficient to implement static scenarios and coarse-grained
   authorization requests, such as "give me read access to the resource
   owner's profile" but it is not sufficient to specify fine-grained
   authorization requirements, such as "please let me make a payment
   with the amount of 45 Euros" or "please give me read access to folder
   A and write access to file X".



Lodderstedt, et al.        Expires May 6, 2020                  [Page 2]


Internet-Draft                  oauth-rar                  November 2019


   This draft introduces a new parameter "authorization_details" that
   allows clients to specify their fine-grained authorization
   requirements using the expressiveness of JSON data structures.

   For example, a request for payment authorization can be represented
   using a JSON object like this:

   {
      "type": "payment_initiation",
      "locations": [
         "https://example.com/payments"
      ],
      "instructedAmount": {
         "currency": "EUR",
         "amount": "123.50"
      },
      "creditorName": "Merchant123",
      "creditorAccount": {
         "iban": "DE02100100109307118603"
      },
      "remittanceInformationUnstructured": "Ref Number Merchant"
   }

   This object contains detailed information about the intended payment,
   such as amount, currency, and creditor, that are required to inform
   the user and obtain her consent.  The AS and the respective RS
   (providing the payment initation API) will together enforce this
   consent.

   For a comprehensive discussion of the challenges arising from new use
   cases in the open banking and electronic signing spaces see
   [transaction-authorization].

   In addition to facilitating custom authorization requests, this draft
   also introduces a set of common data type fields for use across
   different APIs.

   Most notably, the field "locations" allows a client to specify where
   it intends to use a certain authorization, i.e., it is now possible
   to unambiguously assign permissions to resource servers.  In
   situations with multiple resource servers, this prevents unintended
   client authorizations (e.g. a "read" scope value potentially
   applicable for an email as well as a cloud service).  In combination
   with the "resource" token request parameter as specified in
   [I-D.ietf-oauth-resource-indicators] it enables the AS to mint RS-
   specific structured access tokens that only contain the permissions
   applicable to the respective RS.




Lodderstedt, et al.        Expires May 6, 2020                  [Page 3]


Internet-Draft                  oauth-rar                  November 2019


1.1.  Conventions and Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   This specification uses the terms "access token", "refresh token",
   "authorization server", "resource server", "authorization endpoint",
   "authorization request", "authorization response", "token endpoint",
   "grant type", "access token request", "access token response", and
   "client" defined by The OAuth 2.0 Authorization Framework [RFC6749].

2.  Request parameter "authorization_details"

   The request parameter "authorization_details" contains, in JSON
   notation, an array of objects.  Each JSON object contains the data to
   specify the authorization requirements for a certain type of
   resource.  The type of resource or access requirement is determined
   by the "type" field.

   This example shows the specification of authorization details using
   the payment authorization object shown above:

   [
      {
         "type": "payment_initiation",
         "actions": [
            "initiate",
            "status",
            "cancel"
         ],
         "locations": [
            "https://example.com/payments"
         ],
         "instructedAmount": {
            "currency": "EUR",
            "amount": "123.50"
         },
         "creditorName": "Merchant123",
         "creditorAccount": {
            "iban": "DE02100100109307118603"
         },
         "remittanceInformationUnstructured": "Ref Number Merchant"
      }
   ]




Lodderstedt, et al.        Expires May 6, 2020                  [Page 4]


Internet-Draft                  oauth-rar                  November 2019


   This example shows a combined request asking for access to account
   information and permission to initiate a payment:

   [
      {
         "type": "account_information",
         "actions": [
            "list_accounts",
            "read_balances",
            "read_transactions"
         ],
         "locations": [
            "https://example.com/accounts"
         ]
      },
      {
         "type": "payment_initiation",
         "actions": [
            "initiate",
            "status",
            "cancel"
         ],
         "locations": [
            "https://example.com/payments"
         ],
         "instructedAmount": {
            "currency": "EUR",
            "amount": "123.50"
         },
         "creditorName": "Merchant123",
         "creditorAccount": {
            "iban": "DE02100100109307118603"
         },
         "remittanceInformationUnstructured": "Ref Number Merchant"
      }
   ]

   The JSON objects with "type" fields of "account_information" and
   "payment_initiation" represent the different authorization data to be
   used by the AS to ask for consent and MUST subsequently also be made
   available to the respective resource servers.  The array MAY contain
   several elements of the same "type".

2.1.  Authorization data elements types

   This draft defines a set of common data elements that are designed to
   be usable across different types of APIs.  These data elements MAY be




Lodderstedt, et al.        Expires May 6, 2020                  [Page 5]


Internet-Draft                  oauth-rar                  November 2019


   combined in different ways depending on the needs of the API.  Unless
   otherwise noted, all data elements are OPTIONAL.

   type:
      The type of resource request as a string.  This field MAY define
      which other elements are allowed in the request.  This element is
      REQUIRED.

   locations:
      An array of strings representing the location of the resource or
      resource server.  This is typically composed of URIs.

   actions:
      An array of strings representing the kinds of actions to be taken
      at the resource.  The values of the strings are determined by the
      API being protected.

   datatypes:
      An array of strings representing the kinds of data being requested
      from the resource.

   identifier:
      A string identifier indicating a specific resource available at
      the API.


   When different element types are used in combination, the permissions
   the client requests is the cartesian product of the values.  In the
   following example

   [
      {
         "type": "customer_information",
         "locations": [
            "https://example.com/customers",
         ]
         "actions": [
            "read",
            "write"
         ],
         "datatypes": [
            "contacts",
            "photos"
         ]
      }
   ]





Lodderstedt, et al.        Expires May 6, 2020                  [Page 6]


Internet-Draft                  oauth-rar                  November 2019


   the client is requesting read and write access to both the contacts
   and photos belonging to customers in a customer information API.  If
   the client wishes to have finer control over its access, it can send
   multiple objects.  For example:

   [
      {
         "type": "customer_information",
         "locations": [
            "https://example.com/customers"
         ],
         "actions": [
            "read"
         ],
         "datatypes": [
            "contacts"
         ]
      },
      {
         "type": "customer_information",
         "locations": [
            "https://example.com/customers"
         ],
         "actions": [
            "write"
         ],
         "datatypes": [
            "photos"
         ]
      }
   ]

   The client is asking for read access to the contacts and write access
   to the photos in the same API endpoint.

   An API MAY define its own extensions, subject to the "type" of the
   respective authorization object.  It is assumed that the full
   structure of each of the authorization objects is tailored to the
   needs of a certain application, API, or resource type.  The example
   structures shown above are based on certain kinds of APIs that can be
   found in the Open Banking space.

   Note: Applications MUST ensure that their authorization data types do
   not collide.  This is either achieved by using a namespace under the
   control of the entity defining the type name or by registering the
   type with the new "OAuth Authorization Data Type Registry" (see
   Section 9).




Lodderstedt, et al.        Expires May 6, 2020                  [Page 7]


Internet-Draft                  oauth-rar                  November 2019


   The following example shows how an implementation could utilize the
   namespace "https://scheme.example.org/" to ensure collision resistant
   element names.

   {
      "type": "https://scheme.example.org/files",
      "locations": [
         "https://example.com/files"
      ],
      "permissions": [
         {
            "path": "/myfiles/A",
            "access": [
               "read"
            ]
         },
         {
            "path": "/myfiles/A/X",
            "access": [
               "read",
               "write"
            ]
         }
      ]
   }

2.2.  Relationship to "scope" parameter

   "authorization_details" and "scope" can be used in the same
   authorization request for carrying independent authorization
   requirements.

   The AS MUST consider both sets of requirements in combination with
   each other for the given authorization request.  The details of how
   the AS combines these parameters are specific to the APIs being
   protected and outside the scope of this specification.

   It is RECOMMENDED that a given API use only one form of requirement
   specification.

   When gathering user consent, the AS MUST present the merged set of
   requirements represented by the authorization request.

2.2.1.  Scope value "openid" and "claims" parameter

   OpenID Connect [OIDC] specifies the JSON-based "claims" request
   parameter that can be used to specify the claims a client (acting as
   OpenID Connect Relying Party) wishes to receive in a fine-grained and



Lodderstedt, et al.        Expires May 6, 2020                  [Page 8]


Internet-Draft                  oauth-rar                  November 2019


   privacy preserving way as well as assign those claims to a certain
   delivery mechanisms, i.e. ID Token or userinfo response.

   The combination of the scope value "openid" and the additional
   parameter "claims" can be used beside "authorization_details" in the
   same way as every non-OIDC scope value.

   Alternatively, there could be an authorization data type for OpenID
   Connect.  Appendix A.1 gives an example of how such an authorization
   data type could look like.

2.3.  Relationship to "resource" parameter

   The request parameter "resource" as defined in
   [I-D.ietf-oauth-resource-indicators] indicates to the AS the
   resource(s) where the client intends to use the access tokens issued
   based on a certain grant.  This mechanism is a way to audience-
   restrict access tokens and to allow the AS to create resource server
   specific access tokens.

   If a client uses "authorization_details" with "locations" elements
   and the "resource" parameter in the same authorization request, the
   "locations" data take precedence over the data conveyed in the
   "resource" parameter for that particular authorization details
   object.

   If such a client uses the "resource" parameter in a subsequent token
   requests, the AS MUST utilize the data provided in the "locations"
   elements to filter the authorization data objects applicable to the
   respective resource server.  The AS will select all authorization
   details object where the "resource" string matches as prefix of one
   of the URLs provided in the respective "locations" element.

   This shall be illustrated using an example.

   The client has sent an authorization request using the following
   example authorization details.














Lodderstedt, et al.        Expires May 6, 2020                  [Page 9]


Internet-Draft                  oauth-rar                  November 2019


   [
      {
         "type": "account_information",
         "actions": [
            "list_accounts",
            "read_balances",
            "read_transactions"
         ],
         "locations": [
            "https://example.com/accounts"
         ]
      },
      {
         "type": "payment_initiation",
         "actions": [
            "initiate",
            "status",
            "cancel"
         ],
         "locations": [
            "https://example.com/payments"
         ],
         "instructedAmount": {
            "currency": "EUR",
            "amount": "123.50"
         },
         "creditorName": "Merchant123",
         "creditorAccount": {
            "iban": "DE02100100109307118603"
         },
         "remittanceInformationUnstructured": "Ref Number Merchant"
      }
   ]

   If this client then sends the following token request to the AS,

   POST /token HTTP/1.1
   Host: as.example.com
   Authorization: Basic czZCaGRSa3F0MzpnWDFmQmF0M2JW
   Content-Type: application/x-www-form-urlencoded

   grant_type=authorization_code&code=SplxlOBeZQQYbYS6WxSbIA
   &redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb
   &resource=https%3A%2F%2Fexample%2Ecom%2Fpayments

   that contains a resource parameter with the value of
   "https://example.com/payments", this value will be matched against
   the locations elements ("https://example.com/accounts" and



Lodderstedt, et al.        Expires May 6, 2020                 [Page 10]


Internet-Draft                  oauth-rar                  November 2019


   "https://example.com/payments") and will select the element of type
   "payment_initiation" for inclusion in the access token as illustrated
   by the following example JWT content.

   {
      "iss": "https://as.example.com",
      "sub": "24400320",
      "aud": "a7AfcPcsl2",
      "exp": 1311281970,
      ...
      "authorization_details": [
         {
            "type": "https://www.someorg.com/payment_initiation",
            "actions": [
               "initiate",
               "status",
               "cancel"
            ],
            "locations": [
               "https://example.com/payments"
            ],
            "instructedAmount": {
               "currency": "EUR",
               "amount": "123.50"
            },
            "creditorName": "Merchant123",
            "creditorAccount": {
               "iban": "DE02100100109307118603"
            },
            "remittanceInformationUnstructured": "Ref Number Merchant"
         }
      ],
      ...
   }

3.  Using "authorization_details"

3.1.  Authorization Request

   The request parameter can be used to specify authorization
   requirements in all places where the "scope" parameter is used for
   the same purpose, examples include:

   o  Authorization requests as specified in [RFC6749],

   o  Access token requests as specified in [RFC6749], if also used as
      authorization requests, e.g. in the case of assertion grant types
      [RFC7521],



Lodderstedt, et al.        Expires May 6, 2020                 [Page 11]


Internet-Draft                  oauth-rar                  November 2019


   o  Request objects as specified in [I-D.ietf-oauth-jwsreq],

   o  Device Authorization Request as specified in [RFC8628],

   o  Backchannel Authentication Requests as defined in [OpenID.CIBA].

   Parameter encoding is determined by the respective context.

   In the context of an authorization request according to [RFC6749],
   the parameter is encoded using the "application/x-www-form-
   urlencoded" format of the serialized JSON as shown in the following
   example:

   GET /authorize?response_type=code
      &client_id=s6BhdRkqt3
      &state=af0ifjsldkj
      &redirect_uri=https%3A%2F%2Fclient.example.org%2Fcb
      &code_challenge_method=S256
      &code_challenge=K2-ltc83acc4h0c9w6ESC_rEMTJ3bww-uCHaoeK1t8U
      &authorization_details=%5B%7B%22type%22%3A%22account%5Finformati
      on%22%2C%22actions%22%3A%5B%22list%5Faccounts%22%2C%22read%5Fbal
      ances%22%2C%22read%5Ftransactions%22%5D%2C%22locations%22%3A%5B%
      22https%3A%2F%2Fexample%2Ecom%2Faccounts%22%5D%7D%5D HTTP/1.1
   Host: server.example.com

   Implementors MUST ensure to protect personal identifiable information
   in transit.  One way is to utilize encrypted request objects as
   defined in [I-D.ietf-oauth-jwsreq].  In the context of a request
   object, "authorization_details" is added as another top level JSON
   element.





















Lodderstedt, et al.        Expires May 6, 2020                 [Page 12]


Internet-Draft                  oauth-rar                  November 2019


   {
      "iss": "s6BhdRkqt3",
      "aud": "https://server.example.com",
      "response_type": "code",
      "client_id": "s6BhdRkqt3",
      "redirect_uri": "https://client.example.com/cb",
      "state": "af0ifjsldkj",
      "code_challenge_method": "S256",
      "code_challenge": "K2-ltc83acc4h0c9w6ESC_rEMTJ3bww-uCHaoeK1t8U",
      "authorization_details": [
         {
            "type": "account_information",
            "actions": [
               "list_accounts",
               "read_balances",
               "read_transactions"
            ],
            "locations": [
               "https://example.com/accounts"
            ]
         },
         {
            "type": "payment_initiation",
            "actions": [
               "initiate",
               "status",
               "cancel"
            ],
            "locations": [
               "https://example.com/payments"
            ],
            "instructedAmount": {
               "currency": "EUR",
               "amount": "123.50"
            },
            "creditorName": "Merchant123",
            "creditorAccount": {
               "iban": "DE02100100109307118603"
            },
            "remittanceInformationUnstructured": "Ref Number Merchant"
         }
      ]
   }

   Authorization request URIs containing authorization details in a
   request parameter or a request object can become very long.
   Implementers SHOULD therefore consider using the "request_uri"
   parameter as defined in [I-D.ietf-oauth-jwsreq] in combination with



Lodderstedt, et al.        Expires May 6, 2020                 [Page 13]


Internet-Draft                  oauth-rar                  November 2019


   the pushed request object mechanism as defined in
   [I-D.lodderstedt-oauth-par] to pass authorization details in a
   reliable and secure manner.  Here is an example of such a pushed
   authorization request that sends the authorization request data
   directly to the AS via a HTTPS-protected connection:

     POST /as/par HTTP/1.1
     Host: as.example.com
     Content-Type: application/x-www-form-urlencoded
     Authorization: Basic czZCaGRSa3F0Mzo3RmpmcDBaQnIxS3REUmJuZlZkbUl3

     response_type=code&
     client_id=s6BhdRkqt3
     &state=af0ifjsldkj
     &redirect_uri=https%3A%2F%2Fclient.example.org%2Fcb
     &code_challenge_method=S256
     &code_challenge=K2-ltc83acc4h0c9w6ESC_rEMTJ3bww-uCHaoeK1t8U
     &authorization_details=%7B%22iss%22%3A%22s6BhdRkqt3%22%2C%22aud%22%
     3A%22https%3A%2F%2Fserver%2Eexample%2Ecom%22%2C%22response%5Ftype%2
     2%3A%22code%22%2C%22client%5Fid%22%3A%22s6BhdRkqt3%22%2C%22redirect
     %5Furi%22%3A%22https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb%22%2C%22st
     ate%22%3A%22af0ifjsldkj%22%2C%22code%5Fchallenge%5Fmethod%22%3A%22S
     256%22%2C%22code%5Fchallenge%22%3A%22K2%2Dltc83acc4h0c9w6ESC%5FrEMT
     J3bww%2DuCHaoeK1t8U%22%2C%22authorization%5Fdetails%22%3A%5B%7B%22t
     ype%22%3A%22account%5Finformation%22%2C%22actions%22%3A%5B%22list%5
     Faccounts%22%2C%22read%5Fbalances%22%2C%22read%5Ftransactions%22%5D
     %2C%22locations%22%3A%5B%22https%3A%2F%2Fexample%2Ecom%2Faccounts%2
     2%5D%7D%2C%7B%22type%22%3A%22payment%5Finitiation%22%2C%22actions%2
     2%3A%5B%22initiate%22%2C%22status%22%2C%22cancel%22%5D%2C%22locatio
     ns%22%3A%5B%22https%3A%2F%2Fexample%2Ecom%2Fpayments%22%5D%2C%22ins
     tructedAmount%22%3A%7B%22currency%22%3A%22EUR%22%2C%22amount%22%3A%
     22123%2E50%22%7D%2C%22creditorName%22%3A%22Merchant123%22%2C%22cred
     itorAccount%22%3A%7B%22iban%22%3A%22DE02100100109307118603%22%7D%2C
     %22remittanceInformationUnstructured%22%3A%22Ref%20Number%20Merchan
     t%22%7D%5D%7D

3.2.  Authorization Request Processing

   Based on the data provided in the "authorization_details" parameter
   the AS will ask the user for consent to the requested access
   permissions.

   The AS MUST refuse to process any unknown authorization data type.
   If the "authorization_details" contain any unknown authorization data
   type, the AS MUST abort processing and respond with an error
   "invalid_authorization_details" to the client.





Lodderstedt, et al.        Expires May 6, 2020                 [Page 14]


Internet-Draft                  oauth-rar                  November 2019


   Note: If the authorization request also contained the "scope"
   parameter, the AS MUST present the merged set of requirements
   represented by the authorization request in the user consent.

   If the resource owner grants the client the requested access, the AS
   will issue tokens to the client that are associated with the
   respective "authorization_details" (and scope values, if applicable).

   Note: The AS MUST make the "authorization_details" available to the
   respective resource servers.  The AS MAY add the
   "authorization_details" element to access tokens in JWT format and to
   Token Introspection responses (see below).

3.3.  Token Request

   Clients utilizing authorization details are RECOMMENDED to use the
   "resource" token request parameter to allow the AS to issue audience
   restricted access tokens as recommended in
   [I-D.ietf-oauth-security-topics].

   For example the following token request selects authorization details
   applicable for the resource server represented by the URI
   "https://example.com/payments".

   POST /token HTTP/1.1
   Host: as.example.com
   Authorization: Basic czZCaGRSa3F0MzpnWDFmQmF0M2JW
   Content-Type: application/x-www-form-urlencoded

   grant_type=authorization_code&code=SplxlOBeZQQYbYS6WxSbIA
   &redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb
   &resource=https%3A%2F%2Fexample%2Ecom%2Fpayments

3.4.  Token Response

   In addition to the token response parameters as defined in [RFC6749],
   the authorization server MUST also return the authorization details
   as granted by the resource owner and assigned to the respective
   access token.

   This is shown in the following example:










Lodderstedt, et al.        Expires May 6, 2020                 [Page 15]


Internet-Draft                  oauth-rar                  November 2019


   HTTP/1.1 200 OK
   Content-Type: application/json
   Cache-Control: no-cache, no-store

   {
      "access_token": "2YotnFZFEjr1zCsicMWpAA",
      "token_type": "example",
      "expires_in": 3600,
      "refresh_token": "tGzv3JOkF0XG5Qx2TlKWIA",
      "authorization_details": [
         {
            "type": "https://www.someorg.com/payment_initiation",
            "actions": [
               "initiate",
               "status",
               "cancel"
            ],
            "locations": [
               "https://example.com/payments"
            ],
            "instructedAmount": {
               "currency": "EUR",
               "amount": "123.50"
            },
            "creditorName": "Merchant123",
            "creditorAccount": {
               "iban": "DE02100100109307118603"
            },
            "remittanceInformationUnstructured": "Ref Number Merchant"
         }
      ]
   }

3.4.1.  Token Content

   In order to enable the RS to enforce the authorization details as
   approved in the authorization process, the AS MUST make this data
   available to the RS.

   If the access token is a JWT [RFC7519], the AS is RECOMMENDED to add
   the "authorization_details" object, filtered to the specific
   audience, as top-level claim.

   The AS will typically also add further claims to the JWT the RS
   requires for request processing, e.g., user id, roles, and
   transaction specific data.  What claims the particular RS requires is
   defined by the RS-specific policy with the AS.




Lodderstedt, et al.        Expires May 6, 2020                 [Page 16]


Internet-Draft                  oauth-rar                  November 2019


   The following shows the contents of an example JWT for the payment
   initation example above:

   {
      "iss": "https://as.example.com",
      "sub": "24400320",
      "aud": "a7AfcPcsl2",
      "exp": 1311281970,
      "acr": "psd2_sca",
      "txn": "8b4729cc-32e4-4370-8cf0-5796154d1296",
      "authorization_details": [
         {
            "type": "https://www.someorg.com/payment_initiation",
            "actions": [
               "initiate",
               "status",
               "cancel"
            ],
            "locations": [
               "https://example.com/payments"
            ],
            "instructedAmount": {
               "currency": "EUR",
               "amount": "123.50"
            },
            "creditorName": "Merchant123",
            "creditorAccount": {
               "iban": "DE02100100109307118603"
            },
            "remittanceInformationUnstructured": "Ref Number Merchant"
         }
      ],
      "debtorAccount": {
         "iban": "DE40100100103307118608",
         "user_role": "owner"
      }
   ]

   In this case, the AS added the following example claims:

   o  "sub": conveys the user on which behalf the client is asking for
      payment initation

   o  "txn": transaction id used to trace the transaction across the
      services of provider "example.com"

   o  "debtorAccount": API-specific element containing the debtor
      account.  In the example, this account was not passed in the



Lodderstedt, et al.        Expires May 6, 2020                 [Page 17]


Internet-Draft                  oauth-rar                  November 2019


      authorization details but selected by the user during the
      authorization process.  The field "user_role" conveys the role the
      user has with respect to this particuar account.  In this case,
      she is the owner.  This data is used for access control at the
      payment API (the RS).

3.5.  Token Introspection Request

   In case of opaque access tokens, the data provided to a certain RS is
   determined using the RS's identifier with the AS (see
   [I-D.ietf-oauth-jwt-introspection-response], section 3).

3.6.  Token Introspection Response

   The token endpoint response provides the RS with the authorization
   details applicable to it as a top-level JSON element along with the
   claims the RS requires for request processing.

   Here is an example for the payment initation example RS:
































Lodderstedt, et al.        Expires May 6, 2020                 [Page 18]


Internet-Draft                  oauth-rar                  November 2019


   {
      "active": true,
      "sub": "24400320",
      "aud": "s6BhdRkqt3",
      "exp": 1311281970,
      "acr": "psd2_sca",
      "txn": "8b4729cc-32e4-4370-8cf0-5796154d1296",
      "authorization_details": [
         {
            "type": "https://www.someorg.com/payment_initiation",
            "actions": [
               "initiate",
               "status",
               "cancel"
            ],
            "locations": [
               "https://example.com/payments"
            ],
            "instructedAmount": {
               "currency": "EUR",
               "amount": "123.50"
            },
            "creditorName": "Merchant123",
            "creditorAccount": {
               "iban": "DE02100100109307118603"
            },
            "remittanceInformationUnstructured": "Ref Number Merchant"
         }
      ],
      "debtorAccount": {
         "iban": "DE40100100103307118608",
         "user_role": "owner"
      }
   }

4.  Metadata

   The AS advertises support for "authorization_details" using the
   metadata parameter "authorization_details_supported" of type boolean.

   The authorization data types supported can be determined using the
   metadata parameter "authorization_data_types_supported", which is an
   JSON array.

   Clients announce the authorization data types they use in the new
   dynamic client registration parameter "authorization_data_types".





Lodderstedt, et al.        Expires May 6, 2020                 [Page 19]


Internet-Draft                  oauth-rar                  November 2019


   The registration of new authorization data types with the AS is out
   of scope of this draft.

5.  Implementation Considerations

   The scheme and processing will vary significantly among different
   authorization data types.  Any implementation of this draft is
   therefore supposed to allow the customization of the user consent and
   the handling of access token data.

   One option would be to have a mechanism allowing the registration of
   extension modules, each of them responsible for rendering the
   respective user consent and any transformation needed to provide the
   data needed to the resource server by way of structured access tokens
   or token introspection responses.

6.  Security Considerations

   Authorization details are sent through the user agent in case of an
   OAuth authorization request, which makes them vulnerable to
   modifications by the user.  In order to ensure their integrity, the
   client SHOULD send authorization details in a signed request object
   as defined in [I-D.ietf-oauth-jwsreq] or use the "request_uri"
   authorization request parameter as defined in [I-D.ietf-oauth-jwsreq]
   to pass the URI of the request object to the authorization server.

   All strings MUST be compared using the exact byte representation of
   the characters as defined by [RFC8259].  This is especially true for
   the "type" field, which dictates which other fields and functions are
   allowed in the request.  The server MUST NOT perform any form of
   collation, transformation, or equivalence on the string values.

7.  Privacy Considerations

   Implementers MUST design and use authorization details in a privacy
   preserving manner.

   Any sensitive personal data included in authorization details MUST be
   prevented from leaking, e.g., through referrer headers.
   Implementation options include encrypted request objects as defined
   in [I-D.ietf-oauth-jwsreq] or transmission of authorization details
   via end-to-end encrypted connections between client and authorization
   server by utilizing the "request_uri" authorization request parameter
   as defined in [I-D.ietf-oauth-jwsreq].

   Even if the request data are encrypted, an attacker could use the
   authorization server to learn the user data by injecting the
   encrypted request data into an authorization request on a device



Lodderstedt, et al.        Expires May 6, 2020                 [Page 20]


Internet-Draft                  oauth-rar                  November 2019


   under his control and use the authorization server's user consent
   screens to show the (decrypted) user data in the clear.
   Implementations MUST consider this attacker vector and implement
   appropriate counter measures, e.g. by only showing portions of the
   data or, if possible, determing whether the assumed user context is
   still the same (after user authentication).

   The AS MUST take into consideration the privacy implications when
   sharing authorization details with the resource servers.  The AS
   SHOULD share this data with the resource servers on a "need to know"
   basis.

8.  Acknowledgements

   We would would like to thank Daniel Fett, Sebastian Ebling, Dave
   Tonge, Mike Jones, Nat Sakimura, and Rob Otto for their valuable
   feedback during the preparation of this draft.

   We would also like to thank Daniel Fett, Dave Tonge, Travis Spencer,
   Joergen Binningsboe, Aamund Bremer, Steinar Noem, and Aaron Parecki
   for their valuable feedback to this draft.

9.  IANA Considerations

   TBD

   o  "authorization_details" as JWT claim

   o  "authorization_details_supported" and
      "authorization_data_types_supported" as metadata parameters

   o  "authorization_data_types" as dynamic client registration
      parameter

   o  establish authorization data type registry

   o  register type "openid_claims"

10.  References

10.1.  Normative References

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





Lodderstedt, et al.        Expires May 6, 2020                 [Page 21]


Internet-Draft                  oauth-rar                  November 2019


   [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>.

   [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>.

   [RFC7521]  Campbell, B., Mortimore, C., Jones, M., and Y. Goland,
              "Assertion Framework for OAuth 2.0 Client Authentication
              and Authorization Grants", RFC 7521, DOI 10.17487/RFC7521,
              May 2015, <https://www.rfc-editor.org/info/rfc7521>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [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>.

10.2.  Informative References

   [CSC]      Consortium, C. S., "Architectures and protocols for remote
              signature applications", Jun 2019,
              <https://cloudsignatureconsortium.org/wp-
              content/uploads/2019/07/CSC_API_V1_1.0.4.0.pdf>.

   [ETSI]     ETSI, "ETSI TS 119 432, Electronic Signatures and
              Infrastructures (ESI); Protocols for remote digital
              signature creation", Mar 2019,
              <https://www.etsi.org/deliver/
              etsi_ts/119400_119499/119432/01.01.01_60/
              ts_119432v010101p.pdf>.

   [I-D.ietf-oauth-jwsreq]
              Sakimura, N. and J. Bradley, "The OAuth 2.0 Authorization
              Framework: JWT Secured Authorization Request (JAR)",
              draft-ietf-oauth-jwsreq-20 (work in progress), October
              2019.

   [I-D.ietf-oauth-jwt-introspection-response]
              Lodderstedt, T. and V. Dzhuvinov, "JWT Response for OAuth
              Token Introspection", draft-ietf-oauth-jwt-introspection-
              response-08 (work in progress), September 2019.





Lodderstedt, et al.        Expires May 6, 2020                 [Page 22]


Internet-Draft                  oauth-rar                  November 2019


   [I-D.ietf-oauth-resource-indicators]
              Campbell, B., Bradley, J., and H. Tschofenig, "Resource
              Indicators for OAuth 2.0", draft-ietf-oauth-resource-
              indicators-08 (work in progress), September 2019.

   [I-D.ietf-oauth-security-topics]
              Lodderstedt, T., Bradley, J., Labunets, A., and D. Fett,
              "OAuth 2.0 Security Best Current Practice", draft-ietf-
              oauth-security-topics-13 (work in progress), July 2019.

   [I-D.lodderstedt-oauth-par]
              Lodderstedt, T., Campbell, B., Sakimura, N., Tonge, D.,
              and F. Skokan, "OAuth 2.0 Pushed Authorization Requests",
              draft-lodderstedt-oauth-par-00 (work in progress),
              September 2019.

   [OIDC]     Sakimura, N., Bradley, J., Jones, M., de Medeiros, B., and
              C. Mortimore, "OpenID Connect Core 1.0 incorporating
              errata set 1", Nov 2014,
              <http://openid.net/specs/openid-connect-core-1_0.html>.

   [OpenID.CIBA]
              Fernandez, G., Walter, F., Nennker, A., Tonge, D., and B.
              Campbell, "OpenID Connect Client Initiated Backchannel
              Authentication Flow - Core 1.0", January 2019,
              <https://openid.net/specs/openid-client-initiated-
              backchannel-authentication-core-1_0.html>.

   [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>.

   [transaction-authorization]
              Lodderstedt, T., "Transaction Authorization or why we need
              to re-think OAuth scopes", Apr 2019, <https://medium.com/
              oauth-2/transaction-authorization-or-why-we-need-to-re-
              think-oauth-scopes-2326e2038948>.

Appendix A.  Additional Examples

A.1.  OpenID Connect

   These hypothetical examples try to encapsulate all details specific
   to the OpenID Connect part of an authorization process into an
   authorization JSON object.

   The top-level elements are based on the definitions given in [OIDC]:



Lodderstedt, et al.        Expires May 6, 2020                 [Page 23]


Internet-Draft                  oauth-rar                  November 2019


   o  "claim_sets": names of predefined claim sets, replacement for
      respective scope values, such as "profile"

   o  "max_age": Maximum Authentication Age

   o  "acr_values": array of ACR values

   o  "claims": the "claims" JSON structure as defined in [OIDC]

   This is a simple request for some claim sets.

   [
      {
         "type": "openid",
         "locations": [
            "https://op.example.com/userinfo"
         ],
         "claim_sets": [
            "email",
            "profile"
         ]
      }
   ]

   Note: "locations" specifies the location of the userinfo endpoint
   since this is the only place where an access token is used by a
   client (RP) in OpenID Connect to obtain claims.

   A more sophisticated example is shown in the following






















Lodderstedt, et al.        Expires May 6, 2020                 [Page 24]


Internet-Draft                  oauth-rar                  November 2019


   [
      {
         "type": "openid",
         "locations": [
            "https://op.example.com/userinfo"
         ],
         "max_age": 86400,
         "acr_values": "urn:mace:incommon:iap:silver",
         "claims": {
            "userinfo": {
               "given_name": {
                  "essential": true
               },
               "nickname": null,
               "email": {
                  "essential": true
               },
               "email_verified": {
                  "essential": true
               },
               "picture": null,
               "http://example.info/claims/groups": null
            },
            "id_token": {
               "auth_time": {
                  "essential": true
               }
            }
         }
      }
   ]

A.2.  Remote Electronic Signing

   The following example is based on the concept layed out for remote
   electronic signing in ETSI TS 119 432 [ETSI] and the CSC API for
   remote signature creation [CSC].














Lodderstedt, et al.        Expires May 6, 2020                 [Page 25]


Internet-Draft                  oauth-rar                  November 2019


   [
      {
         "type": "sign",
         "locations": [
            "https://signing.example.com/signdoc"
         ],
         "credentialID": "60916d31-932e-4820-ba82-1fcead1c9ea3",
         "documentDigests": [
            {
               "hash": "sTOgwOm+474gFj0q0x1iSNspKqbcse4IeiqlDg/HWuI=",
               "label": "Credit Contract"
            },
            {
               "hash": "HZQzZmMAIWekfGH0/ZKW1nsdt0xg3H6bZYztgsMTLw0=",
               "label": "Contract Payment Protection Insurance"
            }
         ],
         "hashAlgorithmOID": "2.16.840.1.101.3.4.2.1"
      }
   ]

   The top-level elements have the following meaning:

   o  "credentialID": identifier of the certificate to be used for
      signing

   o  "documentDigests": array containing the hash of every document to
      be signed ("hash" elements).  Additionally, the corresponding
      "label" element identifies the respective document to the user,
      e.g. to be used in user consent.

   o  "hashAlgorithm": algomrithm that was used to calculate the hash
      values.

   The AS is supposed to ask the user for consent for the creation of
   signatues for the documents listed in the structure.  The client uses
   the access token issued as result of the process to call the sign doc
   endpoint at the respective signing service to actually create the
   signature.  This access token is bound to the client, the user id and
   the hashes (and signature algorithm) as consented by the user.

A.3.  Access to Tax Data

   This example is inspired by an API allowing third parties to access
   citizen's tax declarations and income statements, for example to
   determine their credit worthiness.





Lodderstedt, et al.        Expires May 6, 2020                 [Page 26]


Internet-Draft                  oauth-rar                  November 2019


   [
       {
           "type": "tax_data",
           "locations": [
               "https://taxservice.govehub.no"
           ],
           "actions":"read_tax_declaration",
           "periods": ["2018"],
           "duration_of_access": 30,
           "tax_payer_id": "23674185438934"
       }
   ]

   The top-level elements have the following meaning:

   o  "periods": determines the periods the client wants to access

   o  "duration_of_access": how long does the client intend to access
      the data in days

   o  "tax_payer_id": identifier of the tax payer (if known to the
      client)

A.4.  eHealth

   This example is inspired by an API used in the Norwegian eHealth
   system.

   In this use case the physical therapist sits in front of her computer
   using a local Electronic Health Records (EHR) system.  She wants to
   look at the electronic patient records of a certain patient and she
   also wants to fetch the patients journal entries in another system,
   perhaps at another institution or a national service.  Access to this
   data is provided by an API.

   The information necessary to authorize the request at the API is only
   known by the EHR system, and must be presented to the API.

   Here is an example authorization details object:

   [
      {
         "type": "patient_record",
         "location": "https://fhir.example.com/patient",
         "actions": [
            "read"
         ],
         "patient_identifier": [



Lodderstedt, et al.        Expires May 6, 2020                 [Page 27]


Internet-Draft                  oauth-rar                  November 2019


            {
               "system": "urn:oid:2.16.578.1.12.4.1.4.1",
               "value": "12345678901"
            }
         ],
         "reason_for_request": "Clinical treatment",
         "requesting_entity": {
            "type": "Practitioner",
            "practicioner_identifier": [
               {
                  "system": " urn:oid:2.16.578.1.12.4.1.4.4",
                  "value": "1234567"
               }
            ],
            "practitioner_role": {
               "organization": {
                  "organization_identifier": [
                     {
                        "system": "urn:oid:2.16.578.1.12.4.1.2.101",
                        "value": "<organizational number>"
                     }
                  ],
                  "organization_type": {
                     "coding": [
                        {
                           "system":
                              "http://hl7.org/fhir/organization-type",
                           "code": "dept",
                           "display": "Hospital Department"
                        }
                     ]
                  },
                  "name": "Akuttmottak"
               },
               "role": {
                  "coding": [
                     {
                        "system": "http://snomed.info/sct",
                        "code": "36682004",
                        "display": "Physical therapist"
                     }
                  ]
               }
            }
         }
      }
   ]




Lodderstedt, et al.        Expires May 6, 2020                 [Page 28]


Internet-Draft                  oauth-rar                  November 2019


   Description of the elements:

   o  "patient_identifier": the identifier of the patient composed of a
      system identifier in OID format (namespace) and the acutal value
      within this namespace.

   o  "reason_for_request": the reason why the user wants to access a
      certain API

   o  "requesting_entity": specification of the requester by means of
      identity, role and organizational context.  This data is provided
      to facilitate authorization and for auditing purposes.

   In this use case, the AS authenticates the requester, who is not the
   patient, and approves access based on policies.

Appendix B.  Document History

   [[ To be removed from the final specification ]]

   -03

   o  Reworked examples to illustrate privacy preserving use of
      "authorization_details"

   o  Added text on audience restriction

   o  Added description of relationship between "scope" and
      "authorization_details"

   o  Added text on token request & response and "authorization_details"

   o  Added text on how authorization details are conveyed to RSs by
      JWTs or token endpoint response

   o  Added description of relationship between "claims" and
      "authorization_details"

   o  Added more example from different sectors

   o  Clarified string comparison to be byte-exact without collation

   -02

   o  Added Security Considerations

   o  Added Privacy Considerations




Lodderstedt, et al.        Expires May 6, 2020                 [Page 29]


Internet-Draft                  oauth-rar                  November 2019


   o  Added notes on URI size and authorization details

   o  Added requirement to return the effective authorization details
      granted by the resource owner in the token response

   o  changed "authorization_details" structure from object to array

   o  added Justin Richer & Brian Campbell as Co-Authors

   -00 / -01

   o  first draft

Authors' Addresses

   Torsten Lodderstedt
   yes.com

   Email: torsten@lodderstedt.net


   Justin Richer
   Bespoke Engineering

   Email: ietf@justin.richer.org


   Brian Campbell
   Ping Identity

   Email: bcampbell@pingidentity.com




















Lodderstedt, et al.        Expires May 6, 2020                 [Page 30]


Html markup produced by rfcmarkup 1.129d, available from https://tools.ietf.org/tools/rfcmarkup/