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Network Working Group                                   T. Hardjono, Ed.
Internet-Draft                                                       MIT
Intended status: Standards Track                        October 16, 2011
Expires: April 18, 2012


                User-Managed Access (UMA) Core Protocol
                    draft-hardjono-oauth-umacore-01

Abstract

   This specification defines the User-Managed Access (UMA) core
   protocol.  This protocol provides a method for users to control
   access to their protected resources, residing on any number of host
   sites, through an authorization manager that governs access decisions
   based on user policy.

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 http://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 April 18, 2012.

Copyright Notice

   Copyright (c) 2011 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
   (http://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
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.



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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Notational Conventions . . . . . . . . . . . . . . . . . .  6
     1.2.  Basic Terminology  . . . . . . . . . . . . . . . . . . . .  6
     1.3.  Endpoints, Endpoint Protection, and Tokens . . . . . . . .  8
     1.4.  Scopes, Resource Sets, Permissions, and Authorization  . . 10
     1.5.  AM Metadata  . . . . . . . . . . . . . . . . . . . . . . . 10
   2.  Protecting a Resource  . . . . . . . . . . . . . . . . . . . . 13
     2.1.  Host Looks Up AM Metadata  . . . . . . . . . . . . . . . . 13
     2.2.  Host Registers with AM . . . . . . . . . . . . . . . . . . 14
     2.3.  Host Obtains Host Access Token . . . . . . . . . . . . . . 14
     2.4.  Host Registers Sets of Resources to Be Protected . . . . . 14
       2.4.1.  Scope Descriptions . . . . . . . . . . . . . . . . . . 15
       2.4.2.  Resource Set Descriptions  . . . . . . . . . . . . . . 16
       2.4.3.  Resource Set Registration API  . . . . . . . . . . . . 17
   3.  Getting Authorization and Accessing a Resource . . . . . . . . 24
     3.1.  Requester-Host: Attempt Access at Protected Resource . . . 26
       3.1.1.  Requester's Request Is Ambiguous . . . . . . . . . . . 26
       3.1.2.  Requester Presents No Access Token . . . . . . . . . . 27
       3.1.3.  Requester Presents an Invalid Access Token . . . . . . 27
       3.1.4.  Requester's Token Has Insufficient Permission  . . . . 28
       3.1.5.  Requester's Token Has Sufficient Permission  . . . . . 28
     3.2.  Requester-AM: Requester Obtains Access Token . . . . . . . 29
     3.3.  Host-AM: Ask for Requester's Presented Access Token
           Status . . . . . . . . . . . . . . . . . . . . . . . . . . 29
       3.3.1.  AM Returns a Token Status Description  . . . . . . . . 30
       3.3.2.  AM Returns a Token Invalid Response  . . . . . . . . . 31
     3.4.  Host-AM: Register a Permission . . . . . . . . . . . . . . 32
       3.4.1.  AM Returns a Permission Registration Success
               Response . . . . . . . . . . . . . . . . . . . . . . . 33
       3.4.2.  AM Returns a Permission Registration Error Response  . 33
     3.5.  Requester-AM: Request Authorization to Add Permission  . . 34
       3.5.1.  AM Returns an Add Permission Success Response  . . . . 35
       3.5.2.  AM Returns an Add Permission Error Response  . . . . . 35
     3.6.  AM-Requester Authorization Flows . . . . . . . . . . . . . 36
       3.6.1.  Authorization Flow for Requester Apps Operated by
               End-Users  . . . . . . . . . . . . . . . . . . . . . . 37
   4.  Error Messages . . . . . . . . . . . . . . . . . . . . . . . . 38
     4.1.  OAuth Error Responses  . . . . . . . . . . . . . . . . . . 38
     4.2.  UMA Error Responses  . . . . . . . . . . . . . . . . . . . 38
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 39
   6.  Privacy Considerations . . . . . . . . . . . . . . . . . . . . 40
   7.  Conformance  . . . . . . . . . . . . . . . . . . . . . . . . . 40
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 41
   9.  AM Metadata Example  . . . . . . . . . . . . . . . . . . . . . 41
   10. Example of Registering Resource Sets . . . . . . . . . . . . . 43
   11. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 46



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   12. Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
   13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 46
     13.1. Normative References . . . . . . . . . . . . . . . . . . . 46
     13.2. Informative References . . . . . . . . . . . . . . . . . . 47
   Appendix A.  Document History  . . . . . . . . . . . . . . . . . . 48
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 48













































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1.  Introduction

   The User-Managed Access (UMA) core protocol provides a method based
   on [OAuth2] (currently draft 16) for users to control access to their
   protected resources, residing on any number of host sites, through a
   single authorization manager (AM) that governs access decisions based
   on user policy.

   There are numerous use cases for UMA, where a resource owner
   nominates a third party to control access to these resources
   potentially without the real-time presence of the resource owner.  A
   typical example is the following.  A web user (authorizing user) can
   authorize a web app (requester) to gain one-time or ongoing access to
   a resource containing his home address stored at a "personal data
   store" service (host), by telling the host to act on access decisions
   made by his authorization decision-making service (authorization
   manager or AM).  The requesting party might be an e-commerce company
   whose site is acting on behalf of the user himself to assist him/her
   in arranging for shipping a purchased item, or it might be his friend
   who is using an online address book service to collect addresses, or
   it might be a survey company that uses an online service to compile
   population demographics.  Other scenarios and use cases for UMA usage
   can be found in [UMA-usecases] and [UMA-userstories].

   In enterprise settings, application access management often involves
   letting back-office applications serve only as policy enforcement
   points (PEPs), depending entirely on access decisions coming from a
   central policy decision point (PDP) to govern the access they give to
   requesters.  This separation eases auditing and allows policy
   administration to scale in several dimensions.  UMA makes use of a
   separation similar to this, letting the authorizing user serve as a
   policy administrator crafting authorization strategies on his or her
   own behalf.

   The UMA protocol profiles, extends, and embeds [OAuth2] in various
   ways.  An AM can be thought of as an enhanced OAuth authorization
   server; a host as an enhanced resource server; and a requester as an
   enhanced client, acquiring an access token and the requisite
   authorization to access a protected resource at the host.

   The UMA protocol has three broad phases, as shown in Figure 1.










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                   The Three Phases of the UMA Protocol
                                      +-----+----------------+
                                      | UA  |  authorizing   |
                  +-------Manage (A)--|     |      user      |
                  |                   +-----+----------------+
                  |   Phase 1:              |       UA       |
                  |   protect a             +----------------+
                  |   resource                      |
                  |                            Control (B)
                  |                                 |
                  v                                 v
           +-----------+              +-----+----------------+
           |   host    |<-Protect-(C)-|prot | authorization  |
           |           |              | API |  manager (AM)  |
           +-----------+              +-----+----------------+
           | protected |                    | authorization  |
           | resource  |                    |      API       |
           +-----------+                    +----------------+
                  ^                                 |
                  |   Phases 2 and 3:         Authorize (D)
                  |   get authz and                 |
                  |   access a resource             v
                  |                         +----------------+
                  +-------Access (E)--------|   requester    |
                                            +----------------+
                                            (requesting party)

                                 Figure 1

   In broad strokes, the phases are as follows:

   1.  Protect a resource (described in Section 2).

   2.  Get authorization (described in Section 3).

   3.  Access a resource (described along with Phase 2 in Section 3).

   In more detail, the phases work as follows:

   1.  _Protect a resource:_ The authorizing user has chosen to use a
       host for managing online resources ("A"), and introduces this
       host to an AM using an OAuth-mediated interaction that results in
       the AM giving the host an access token.  The host uses AM's
       protection API to tell the AM what sets of resources to protect
       ("C").  Out of band of the UMA protocol, the authorizing user
       instructs the AM what policies to attach to the registered
       resource sets ("B").  Requesters are not yet in the picture.




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   2.  _Get authorization:_ This phase involves the requester, host, and
       AM.  It may also involve synchronous action by the authorizing
       user if this person is the same person as the requesting party.
       This phase is dominated by a loop of activity in which the
       requester approaches the host seeking access to a protected
       resource ("E"), is sent to obtain an access token from the AM if
       it does not have one, and then must demonstrate to the AM that it
       satisfies the user's authorization policy governing the sought-
       for resource and scope of access if it does not already have the
       required access permission ("D").

   3.  _Access a resource:_ This phase involves the requester
       successfully presenting an access token that has sufficient
       permission associated with it to the host in order to gain access
       to the desired resource ("E").  In this sense, it is the "happy
       path" within phase 2.

1.1.  Notational Conventions

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

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

   The assignment in this document of URI labels is temporary, awaiting
   final standardization in the eventual standards body within which
   this specification is taken up as a work item.

1.2.  Basic Terminology

   UMA introduces the following terms, utilizing OAuth and other
   identity and access management concepts.

   authorizing user
         An UMA-defined variant of an OAuth end-user resource owner; a
         web user who configures an authorization manager with policies
         that control how it assigns access permissions to requesters
         for a protected resource.

   authorization manager (AM)
         An UMA-defined variant of an OAuth authorization server that
         carries out an authorizing user's policies governing access to
         a protected resource.






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   protected resource
         An access-restricted resource at a host, which is being policy-
         protected by an AM.

   host
         An UMA-defined variant of an OAuth resource server that
         enforces access to the protected resources it hosts, as
         governed by an authorization manager.

   host access token
         An access token representing the authorizing user's consent for
         a host to trust a particular authorization manager for control
         over authorizations to access protected resources hosted there.

   claim
         A statement of the value or values of one or more identity
         attributes of a requesting party.  A requesting party may need
         to provide claims to an authorization manager in order to
         satisfy policy and gain permission for access to a protected
         resource.

   requester
         An UMA-defined variant of an OAuth client that seeks access to
         a protected resource.

   requester access token
         An access token that can be associated with permissions to
         access particular resources at a host on behalf of a particular
         requesting party.

   requesting party
         A web user, or a corporation or other legal person, that uses a
         requester to seek access to a protected resource.  If the
         requesting party is a natural person, it may or may not be the
         same person as the authorizing user.

   resource set description
         A JSON-formatted document that represents a set of one or more
         resources to be AM-protected and maps available scopes to them.
         The host registers a resource set by providing this document to
         the AM.

   scope description  A JSON-formatted document that represents a
         bounded scope (extent) of access on a particular resource set.
         The host refers to this type of document from within its
         registered resource set descriptions and permissions.





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   token status description  A JSON-formatted document that represents
         the currently valid permissions for access associated with a
         requester access token.

   permission  A scope of access over a particular resource set at a
         particular host that is being asked for by a requester (a
         requested permission) or that has been granted by an AM (a
         granted permission).

1.3.  Endpoints, Endpoint Protection, and Tokens

   As indicated in Section 1, various UMA entities present APIs for
   other UMA entities to use.  These APIs are as follows:

   o  The AM presents a _protection API_ to the host, as standardized by
      this specification.  This API is OAuth-protected, requiring a host
      access token (issued by the AM) for successful access (see
      Section 2.3 for this issuance process).

   o  The AM presents an _authorization API_ to the requester, as
      standardized by this specification.  This API is OAuth-protected,
      requiring a requester access token (issued by the AM) for
      successful access (see Section 3.2 for this issuance process).

   o  The host presents a _protected resource_ to the requester, which
      can be considered -- and may in fact be -- an application-specific
      or proprietary API.  This API is UMA-protected, requiring a
      requester access token (issued by the AM) and sufficient
      permissions (also issued by the AM) for successful access (see
      Section 3.5 for this latter issuance process).

   The AM presents the following endpoints to the host as part of its
   protection API:

   host access token endpoint  Part of standard OAuth, as profiled by
         UMA.  The endpoint at which the host asks for a host access
         token on the authorizing user's behalf.  (The AM may also
         choose to issue a refresh token.)  It will use this token to
         gain access to the other protection API endpoints.

   host user authorization endpoint  Part of standard OAuth, as profiled
         by UMA.  The endpoint to which the host redirects the
         authorizing user to authorize the host to use this AM for
         protecting resources, if the OAuth authorization code grant
         type is being used.






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   resource set registration endpoint  The endpoint at which the host
         registers resource sets it wants the AM to protect.

   permission registration endpoint  The endpoint at which the host
         registers permissions that it anticipates a requester will
         shortly be asking for from the AM.

   token status endpoint  The endpoint at which the host submits
         requester access tokens that have accompanied an access
         request, to learn what currently valid permissions are
         associated with them.

   The AM presents the following endpoints to the requester as part of
   its authorization API:

   requester access token endpoint  Part of standard OAuth, as profiled
         by UMA.  The endpoint at which the requester asks for a
         requester access token.  (The AM may also choose to issue a
         refresh token.)  It will use this token to gain access to the
         other authorization API endpoint.

   permission endpoint  The endpoint at which the requester asks for
         authorization to have a new permission associated with its
         requester access token.

   Finally, the host presents one or more protected resource endpoints
   to the requester:

   protected resource endpoint  An endpoint at which a requester
         attempts to access resources.  This can be a singular API
         endpoint, one of a set of API endpoints, a URI corresponding to
         an HTML document, or any other URI.  The requester needs to
         present a requester access token associated with sufficient
         permissions in order to gain access.

   Similarly to OAuth authorization servers, an UMA AM has the
   opportunity to manage the validity periods of the access tokens, the
   corresponding refresh tokens, and even the client credentials that it
   issues.  Different lifetime strategies may be suitable for different
   resources and scopes of access, and the AM has the opportunity to
   give the authorizing user control through policy.

   Access tokens are currently assumed to be merely opaque strings (as
   discussed in Section 1.5 and Section 7).  Thus, when an AM associates
   a permission with a requester access token, a host cannot
   subsequently inspect such a token locally to assess whether a needed
   permission has been granted.  It must instead ask the AM to provide
   the token's status.



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1.4.  Scopes, Resource Sets, Permissions, and Authorization

   UMA extends the OAuth concept of a "scope" by defining scopes as
   applying to particular labeled resource sets, rather than leaving the
   relevant resources (such as API endpoints or URIs) implicit.  A
   resource set can have any number of scopes, which together describe
   the universe of actions that _can be_ taken on this protected
   resource set.  For example, a resource set representing a status
   update API might have scopes that include adding an update or reading
   updates.  A resource set representing a photo album might have scopes
   that include viewing a slideshow or printing the album.  Hosts
   register resource sets and their scopes without there being a
   requester in the picture.

   Resource sets and scopes have meaning only to hosts and their users,
   in the same way that application-specific host APIs have meaning only
   to these entities.  The AM is merely a conveyor of labels and
   descriptions for these constructs, to help the authorizing user set
   policies that guide eventual authorization processes.

   In contrast to an UMA scope, an UMA permission reflects an _actual_
   authorization process for a requester to access a particular resource
   set in a scoped (bounded) manner.  Hosts register permission requests
   on behalf of requesters that have attempted access.  Requesters
   subsequently ask AMs for permissions to be associated with their
   tokens.  AMs grant (or deny) permissions to requesters.

   In order to represent meaningful, auditable, and potentially legally
   enforceable authorization (see [UMA-trustmodel]), a permission is
   bound to a particular set of UMA entities and parties.  This includes
   the requesting party, the requester (so that the same requesting
   party would have to go through the authorization process for each
   client application they use), the host, the resource set on which
   access is being attempted, and therefore also the AM protecting it
   and the authorizing user who is controlling access.

   Unlike scopes (but similarly to tokens themselves; see Section 1.3),
   permissions have a validity period.

1.5.  AM Metadata

   The AM MUST provide an XRD 1.0-formatted document at the hostmeta
   location (see hostmeta [hostmeta]), documenting the following:

   o  Major conformance options supported by the AM (described further
      in Section 7)





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   o  Protection and authorization API endpoints (as described in
      Section 1.3)

   See Section 9 for a full example of AM metadata.

   XRD property type values for conformance options:

   http://docs.kantarainitiative.org/uma/1.0/client_reg
         OPTIONAL (zero or one).  Whether dynamic client registration,
         such as through [OCDynClientReg], is supported for both hosts
         and requesters.  The only options currently available are "yes"
         (dynamic registration is supported, using an unspecified
         method) and "no" (it is not supported; hosts and requesters are
         required to pre-register).  The default is currently AM-
         specific.  (This conformance option is largely a placeholder
         for now.)

   http://docs.kantarainitiative.org/uma/1.0/token_formats
         REQUIRED (one or more).  Access token format produced by this
         AM.  Currently the only option defined by this specification is
         "artifact", meaning an opaque token string as supported
         natively by the UMA protocol, and the AM is REQUIRED to support
         this option (and supply this value).  The AM MAY provide
         support for additional access token formats, indicated by
         extension values that MUST begin with "X-" or "x-".

   http://docs.kantarainitiative.org/uma/1.0/claim_formats
         OPTIONAL (zero or more).  Claim formats and associated claims-
         gathering sub-protocols supported by this AM.  Currently the
         only option defined by this specification is "openid", for
         which details are supplied in Section 3.6.1.1.  The AM MAY
         provide support for additional claim formats, indicated by
         extension values that MUST begin with "X-" or "x-".  If the AM
         is capable of requesting and accepting any claim formats at
         all, it MUST declare them.

   XRD link relationship rel values for protection API endpoints:

   http://docs.kantarainitiative.org/uma/1.0/host_token_uri
         REQUIRED.  The host access token endpoint.  Available HTTP
         methods are as defined by [OAuth2] for a token endpoint.
         Supplies the endpoint the host uses to ask for a host access
         token.

   http://docs.kantarainitiative.org/uma/1.0/host_user_uri
         REQUIRED.  The host user authorization endpoint.  AAvailable
         HTTP methods are as defined by [OAuth2] for an end-user
         authorization endpoint.  Supplies the endpoint the host uses to



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         gather the consent of the authorizing user for a host-AM
         relationship if it is using the authorization code grant type.
         The AM MUST support the authorization code grant type method of
         obtaining the authorizing user's consent.

   http://docs.kantarainitiative.org/uma/1.0/host_resource_reg_uri
         REQUIRED.  The resource set registration endpoint.  Requests to
         this endpoint require a host access token to be present.
         Supplies the endpoint the host uses for registering resource
         sets with the AM to be protected (see Section 2.4.3).  This
         endpoint SHOULD require the use of a transport-layer security
         mechanism such as TLS.

   http://docs.kantarainitiative.org/uma/1.0/host_token_status_uri
         REQUIRED.  The token status endpoint.  Requests to this
         endpoint require a host access token to be present.  Supplies
         the endpoint the host uses to request the status of access
         tokens presented to them by requesters with respect to
         currently valid permissions.  This endpoint SHOULD require the
         use of a transport-layer security mechanism such as TLS.

   http://docs.kantarainitiative.org/uma/1.0/host_perm_reg_uri
         REQUIRED.  The permission registration endpoint.  Requests to
         this endpoint require a host access token to be present.
         Supplies the endpoint the host uses for registering permissions
         with the AM for which a requester will be seeking authorization
         (see Section 3.4).  This endpoint SHOULD require the use of a
         transport-layer security mechanism such as TLS.

   XRD link relationship rel values for authorization API endpoints:

   http://docs.kantarainitiative.org/uma/1.0/req_token_uri
         REQUIRED.  The requester access token endpoint.  Available HTTP
         methods are as defined by [OAuth2] for a token issuance
         endpoint.  Supplies the endpoint the requester uses to ask for
         an access token.  This endpoint SHOULD require the use of a
         transport-layer security mechanism such as TLS.

   http://docs.kantarainitiative.org/uma/1.0/req_perm_uri
         REQUIRED.  The permission endpoint.  Supplies the endpoint the
         requester uses to ask for authorization to have a new
         permission associated with its existing requester access token,
         which MUST accompany the request.  This endpoint SHOULD require
         the use of a transport-layer security mechanism such as TLS.







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2.  Protecting a Resource

   Phase 1 of UMA is protecting a resource.  For a host to be able to
   delegate authorization of protected-resource access to an AM, the
   authorizing user must first introduce the host to the AM.  This phase
   is concluded successfuly when:

   o  The host has received metadata about the AM, such as endpoints it
      needs to use in interacting with the AM.

   o  The host has received an OAuth host access token that represents
      the authorizing user's approval for the host to work with the AM
      in protecting resources.  This host access token is later used
      when the host makes other requests at the AM's protection API.

   o  The AM has acquired information about resource sets on the host it
      is supposed to protect on behalf of the authorizing user.

   The user, host, and AM perform the following steps in order to
   successfully complete Phase 1:

   1.  The host looks up the AM's metadata and learns about its
       protection API endpoints and supported formats.

   2.  If the host has not yet obtained a unique OAuth client identifier
       and optional secret from the AM, it registers with the AM as
       required.  It MAY do this using [OCDynClientReg], if the AM
       supports it.

   3.  The host obtains a host access token from the AM with the
       authorizing user's consent, using either the authorization code
       grant type or the SAML bearer assertion grant type.

   4.  The host registers any resource sets with the AM that are
       intended to be protected.

2.1.  Host Looks Up AM Metadata

   The host needs to learn the AM's protection API endpoints before they
   can begin interacting.  The authorizing user might provide the AM's
   location to get the host started in this process, for example by
   typing a URL into a web form field or clicking a button.
   Alternatively, the host might already be configured to work with a
   single AM without requiring any user input.  The exact process is
   beyond the scope of this specification, and it is up to the host to
   choose a method to learn the AM's location.

   From the data provided, discovered, or configured, the host MUST use



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   the process described in Section 2 of hostmeta [hostmeta] to retrieve
   the AM hostmeta document.  For example, if the user supplied
   "am.example.com" as the Authorization Manager's domain, the host
   creates the URL "https://am.example.com/.well-known/host-meta" and
   performs a GET request on it.  The AM MUST return content that
   includes UMA protection API endpoints as defined in Section 1.5 (see
   Section 9 for an example).

2.2.  Host Registers with AM

   If the host has not already obtained a unique client identifier and
   optional secret from this AM, in this step it MUST do so in order to
   engage in OAuth-based interactions with the AM.  It MAY do this using
   [OCDynClientReg], if the AM supports it (see Section 1.5 for how the
   AM MAY indicate support).  The AM MUST issue a unique client
   identifier to every host.  This is to ensure that individual hosts
   can be unambiguously identified in resource set registration, where
   the client identifier is used as a URI component.

2.3.  Host Obtains Host Access Token

   In this step, the host acquires a host access token from the AM that
   represents the approval of the authorizing user for the host to trust
   the AM for protecting resources belonging to the user.

   The host MUST use the OAuth2 [OAuth2] authorization code grant type
   or the SAML bearer token grant type [OAuth-SAML], utilizing the end-
   user authorization and token endpoints as appropriate.  Here the host
   acts in the role of an OAuth client; the authorizing user acts in the
   role of an OAuth end-user resource owner; and the AM acts in the role
   of an OAuth authorization server.  (Once the host has obtained an
   access token, it presents it to the AM at various protection API
   endpoints, at which point the AM acts in the role of a resource
   server.)

   The host has completed this step successfully when it possesses a
   host access token it can use at the AM's protection API.

2.4.  Host Registers Sets of Resources to Be Protected

   Once the host has received a host access token, for any of the user's
   sets of resources that are to be protected by this AM, it MUST
   register these resource sets at the AM's registration endpoint.

   Note that the host is free to offer the option to protect any subset
   of the user's resources using different AMs or other means entirely,
   or to protect some resources and not others.  Additionally, the
   choice of protection regimes can be made explicitly by the user or



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   implicitly by the host.  Any such partitioning by the host or user is
   outside the scope of this specification.

   See Section 10 for an extended example of registering resource sets.

2.4.1.  Scope Descriptions

   The host defines a scope of access that is available for use with
   resources it manages in a document accessible to the AM that contains
   a scope description.  The scopes available for use at any one host
   MUST have unique URI references so that the host's scope descriptions
   are distinguishable by URI reference; the URI reference MAY include a
   fragment identifier.  Scope descriptions MAY reside anywhere; the
   host is not required to self-host scope descriptions and may wish to
   point to standardized scope descriptions residing elsewhere.  (See
   Section 1.4 for further discussion of scope-related concepts, and
   Section 10 for a long-form example of scopes used in resource set
   registration.)

   A scope description is a JSON [RFC4627] object with the name "scope"
   and with the following parameters:

   _id  REQUIRED.  A string that uniquely identifies the scope across
      all scopes available at this host.

   name  REQUIRED.  A human-readable string describing the scope of
      access.  The AM SHOULD use the name in its user interface to
      assist the user in setting policies for protected resource sets
      that have this available scope.

   icon_uri  OPTIONAL.  A URI for a graphic icon representing the scope.
      If this is provided, the AM SHOULD use the referenced icon in its
      user interface to assist the user in setting policies for
      protected resource sets that have this available scope.

   For example, this description characterizes a scope that involves
   reading or viewing resources (vs. creating them or editing them in
   some fashion):
  {
          "scope":
              {
              "_id": "view"
              "name": "Read-only",
              "icon_uri": "http://www.example.com/icons/reading-glasses"
          }
  }

   Scope descriptions MAY contain extension parameters that are not



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   defined in this specification.  The names of extension parameters
   MUST begin with "x-" or "X-".

2.4.2.  Resource Set Descriptions

   The host defines a resource set that needs protection by registering
   a resource set description at the AM.  The host registers the
   description and manages its lifecycle at the AM's host resource set
   registration endpoint by using the resource set registration API, as
   defined in Section 2.4.3.

   The resource set description is a JSON [RFC4627] object with the name
   "resource_set" and with the following parameters:

   _id  REQUIRED.  A string that uniquely identifies the resource set.
      The resource set identifier has meaning only to the host.  The AM
      merely maps this resource set description to a particular user by
      reference to the host access token that was used to access the
      resource set registration API.  The host MAY use any identifier
      scheme to represent resource sets, for example, making its
      identifiers unique across all users of this host or allowing for
      the sharing of resource set identifiers among users.  However, for
      privacy reasons, it is RECOMMENDED that the host assign an
      identifier that is obscured with respect to any human-readable
      resource set label used at this host.  Further, this identifier
      MUST match the resource set identifier path component of the URI
      used to manage this description in the resource set registration
      API; see Section 2.4.3 for more information.  (Typically this
      matching is achieved through automatically populating the
      parameter value on initial registration of the description.)

   name  REQUIRED.  A human-readable string describing a set of one or
      more resources.  The AM SHOULD use the name in its user interface
      to assist the user in setting policing for protecting this
      resource set.

   icon_uri  OPTIONAL.  A URI for a graphic icon representing the
      resource set.  If provided, the AM SHOULD use the referenced icon
      in its user interface to assist the user in setting policies for
      protecting this resource set.

   scopes  REQUIRED.  An array referencing one or more URI references of
      scope descriptions that are available for this resource set.








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   For example, this description characterizes a resource set (a photo
   album) that can potentially be only viewed, or alternatively to which
   full access can be granted; the URIs point to scopes descriptions as
   defined in Section 2.4.1:
   {
           "resource_set":
               {
               "_id":  "112210f47de98100",
               "name": "Photo album",
               "icon_uri": "http://www.example.com/icons/flower.png",
               "scopes":
                           ["http://photoz.example.com/dev/scopes/view",
                           "http://photoz.example.com/dev/scopes/all"]
           }
   }

   Resource set descriptions MAY contain extension parameters that are
   not defined in this specification.  The names of extension parameters
   MUST begin with "x-" or "X-".

   When a host creates or updates a resource set description (see
   Section 2.4.3), the AM MUST attempt to retrieve the referenced scope
   descriptions.  It MAY cache such descriptions as long as indicated in
   the HTTP cache-control header for the scope description resource
   unless the resource set description is subsequently updated within
   the validity period.  At the beginning of an authorizing user's login
   session at the AM, the AM MUST attempt to re-retrieve scope
   descriptions applying to that user whose cached versions have
   expired.

2.4.3.  Resource Set Registration API

   The host uses a RESTful API at the AM's resource set registration
   endpoint to create, read, update, and delete resource set
   descriptions, along with listing groups of such descriptions.  The
   host MUST use its valid host access token obtained previously to gain
   access to this endpoint.

   (Note carefully the similar but distinct senses in which the word
   "resource" is used in this section.  UMA resource set descriptions
   are themselves managed as web resources at the AM through this API.)

   The AM MUST present an API for registering resource set descriptions
   at a set of URIs with this structure: "{rsreguri}/host/{hostid}/
   resource_set/{rsid}"

   The components of these URIs are defined as follows:




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   {rsreguri}  The AM's resource set registration endpoint as advertised
      in its metadata (see Section 1.5).

   {hostid}  A registration area at the AM that is specific to this
      host.  The host MUST use the unique OAuth client identifier it was
      assigned by this AM as its host identifier.  If the host
      identifier does not match the host access token used at the host
      registration endpoint, the AM MUST report an HTTP 403 Forbidden
      error and fail to act on the request.

   {rsid}  An identifier for a resource set description.  The identifier
      MUST match the "_id" parameter value in the description itself.

   Without a specific resource set identifier path component, the URI
   applies to the set of resource set descriptions already registered.

   Following is a summary of the five registration operations the AM is
   REQUIRED to support.  Each is defined in its own section below.  All
   other methods are unsupported.

   o  Create resource set description: PUT /host/{hostid}/resource_set/
      {rsid}

   o  Read resource set description: GET /host/{hostid}/resource_set/
      {rsid}

   o  Update resource set description: PUT /host/{hostid}/resource_set/
      {rsid}

   o  Delete resource set description: DELETE /host/{hostid}/
      resource_set/{rsid}

   o  List resource set descriptions: GET /host/{hostid}/resource_set/

   If the request to the resource set registration endpoint is
   incorrect, then the AM responds with an error message (see
   Section 4.2) by including one of the following error codes with the
   response:

   unsupported_method_type  The host request used an unsupported HTTP
      method.  The AM MUST respond with the HTTP 403 (Forbidden) status
      code and MUST fail to act on the request.

   hostid_access_token_mismatch  The hostid does not match the presented
      host access token.  The AM MUST respond with the HTTP 403
      (Forbidden) status code.





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   ambiguous_resource_set_id  The resourcesetid provided in the resource
      set description does not match the one provided in the URI.  The
      AM MUST respond with the HTTP 400 (Bad Request) status code and
      MUST fail to act on the request.

   resource_set_not_found  The resource set requested from the AM cannot
      be found.  The AM MUST respond with HTTP 404 (Not Found) status
      code.

   resource_set_mismatch  The resource set that was requested to be
      deleted or updated at the AM did not match the ETag value present
      in the request.  The AM MUST respond with HTTP 412 (Precondition
      Failed) status code and MUST fail to act on the request.

   For example:

   HTTP/1.1 403 Forbidden
   Content-Type: application/json
   Cache-Control: no-store
   {
      "error":"unsupported_method_type"
   }

2.4.3.1.  Create Resource Set Description

   Adds a new resource set description using the PUT method, thereby
   putting it under the AM's protection.  The host is free to use its
   own methods of identifying and describing resource sets; the AM MUST
   treat them as opaque for the purpose of authorizing access, other
   than associating them with the authorizing user represented by the
   host access token used to access the API.  On successfully
   registering a resource set, the host MUST use UMA mechanisms to limit
   access to any resources corresponding to this resource set, relying
   on the AM to supply currently valid permissions for authorized
   access.

   HTTP request:
PUT /host/{hostid}/resource_set/{rsid} HTTP/1.1
Content-Type: application/json
...

(Body contains JSON representation of resource set description to be created)









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   Example of an HTTP request that creates a resource set description at
   the AM:
   PUT /host/photoz.example.com/resource_set/112210f47de98100 HTTP/1.1
   Content-Type: application/json
   Host: am.example.com

   {
           "resource_set":
               {
               "_id":  "112210f47de98100",
               "name": "Photo album",
               "icon_uri": "http://www.example.com/icons/flower.png",
               "scopes":
                           ["http://photoz.example.com/dev/scopes/view",
                           "http://photoz.example.com/dev/scopes/all"]
           }
   }

   HTTP response (success):
 HTTP/1.1 201 Created
 Content-Type: application/json
 Location: (URL of created resource, same as in the PUT request)
 ETag: (entity tag of resource artifact)
 ...

 (Body contains JSON representation of created resource set description)

   Example of an HTTP response confirming the created resource set
   description:
HTTP/1.1 201 Created
Content-Type: application/json
Location: https://am.example.com/rsreg_uri/host/photoz.example.com/resource_set/112210f47de98100
ETag: "1234sdbdDX"
...

{
        "resource_set":
            {
            "_id":  "112210f47de98100",
            "name": "Photo album",
            "icon_uri": "http://www.example.com/icons/flower.png",
            "scopes":
                        ["http://photoz.example.com/dev/scopes/view",
                        "http://photoz.example.com/dev/scopes/all"]
        }
}





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2.4.3.2.  Read Resource Set Description

   Reads a previously registered resource set description using the GET
   method.

   HTTP request:
   GET /host/{hostid}/resource_set/{rsid} HTTP/1.1
   ...

   Example of an HTTP request that reads a resource set description from
   the AM:
   GET /host/photoz.example.com/resource_set/112210f47de98100 HTTP/1.1
   Host: am.example.com
   ...

   HTTP response (success):
   HTTP/1.1 200 OK
   Content-Type: application/json
   ETag: (entity tag of resource artifact)
   ...

   (Body contains JSON representation of resource set description)

   Example of an HTTP response message containing a resource set
   description from the AM:
   HTTP/1.1 200 OK
   Content-Type: application/json
   ETag: "1234sdbdDX"
   ...

                 {
           "resource_set":
               {
               "_id":  "112210f47de98100",
               "name": "Photo album",
               "icon_uri": "http://www.example.com/icons/flower.png",
               "scopes":
                           ["http://photoz.example.com/dev/scopes/view",
                           "http://photoz.example.com/dev/scopes/all"]
           }











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   HTTP response (not found):
   HTTP/1.1 404 Not Found
   Content-Type: application/json
   ...

   {
      "error":"resource_set_not_found"
   }

2.4.3.3.  Update Resource Set Description

   Updates a previously registered resource set description using the
   PUT method, thereby changing the resource set's protection
   characteristics.

   This operation is different from the operation to create a new
   resource set description (Section 2.4.3.1) because it assumes that
   prior registration of the resource set in question has occurred.

   HTTP request:
PUT /host/{hostid}/resource_set/{rsid} HTTP/1.1
Content-Type: application/json
If-Match: (entity tag of resource if operation is to be idempotent)
...

(Body contains JSON representation of resource set description to be updated)

   Example of an HTTP request that updates a resource set description at
   AM:
   PUT /host/photoz.example.com/resource_set/112210f47de98100 HTTP/1.1
   Content-Type: application/json
   Host: am.example.com
   If-Match: "1234sdbdDX"

   {
           "resource_set":
               {
               "_id":  "112210f47de98100",
               "name": "Updated Photo album",
               "icon_uri": "http://www.example.com/icons/sun.png",
               "scopes":
                           ["http://photoz.example.com/dev/scopes/view",
                           "http://photoz.example.com/dev/scopes/all"]
           }
   }






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   HTTP response (success):
   HTTP/1.1 204 No Content
                 ETag: "54223dfda"
   ...

   HTTP response (entity tag does not match):
   HTTP/1.1 412 Precondition failed
   Content-Type: application/json
   ...

   {
      "error":"resource_set_mismatch"
   }

2.4.3.4.  Delete Resource Set Description

   Deletes a previously registered resource set description using the
   DELETE method, thereby removing it from the AM's protection regime.

   HTTP request:
   DELETE /host/{hostid}/resource_set/{rsid}
   If-Match: (entity tag of resource if operation is to be idempotent)
   ...

   Example of an HTTP request that deletes a resource set description
   from the AM:
  DELETE /host/photoz.example.com/resource_set/112210f47de98100 HTTP/1.1
  Host: am.example.com
  If-Match: "1234sdbdDX"

   HTTP response (success):
   HTTP/1.1 204 No content
   ...

   HTTP response (not found):
   HTTP/1.1 404 Not Found
   Content-Type: application/json
   ...

   {
      "error":"resource_set_not_found"
   }









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   HTTP response (entity tag does not match):
   HTTP/1.1 412 Precondition failed
   Content-Type: application/json
   ...

   {
      "error":"resource_set_mismatch"
   }

2.4.3.5.  List Resource Set Descriptions

   Lists all previously registered resource set identifiers for this
   user using the GET method.  The list is in the form of a JSON array
   of {rsid} values.

   HTTP request:
   GET /host/{hostid}/resource_set HTTP/1.1
   ...

   Example of an HTTP request that lists registered resource set
   descriptions at the AM:
   GET /host/photoz.example.com/resource_set HTTP/1.1
   Host: am.example.com
   ...

   HTTP response:
   HTTP/1.1 200 OK
   Content-Type: application/json
   ...

   (Body contains JSON array of {rsid} values)

   Example of an HTTP response with the list of registered resource set
   identifiers:
   HTTP/1.1 200 OK
   Content-Type: application/json
   ...

   {
     "resource_set_id_list": [ "112210f47de98100", "34234df47eL95300" ]
   }


3.  Getting Authorization and Accessing a Resource

   Phase 2 of UMA is getting authorization, and Phase 3 is accessing a
   resource.  In these phases, an AM orchestrates and controls
   requesting parties' access to a user's protected resources at a host,



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   under conditions dictated by that user.

   Phase 3 is merely the successful completion of a requester's access
   attempt (see Section 3.1.5) that initially involved several embedded
   interactions among the requester, AM, and host in Phase 2.  Phase 2
   always begins with the requester attempting access at a protected
   resource endpoint at the host.  How the requester came to learn about
   this endpoint is out of scope for UMA; the authorizing user might,
   for example, have advertised its availability publicly on a blog or
   other website, listed it in a discovery service, or emailed a link to
   a particular intended requesting party.

   The host responds to the requester's access request in one of several
   ways depending on the circumstances of the request, either
   immediately or having first performed one or more embedded
   interactions with the AM.  Depending on the nature of the host's
   response to an failed access attempt, the requester itself engages in
   embedded interactions with the AM before re-attempting access.

   The interactions are as follows.  The interaction summarized in each
   top-level list item MAY be the last interaction engaged in, if the
   requester chooses not to continue pursuing access to the resource.

   o  The requester attempts access at a particular protected resource
      at a host (see Section 3.1).

      *  If the user corresponding to the protected resource URI is
         ambiguous: host responds immediately with an error (see
         Section 3.1.1).

      *  If the user is unambiguous but the access attempt is
         unaccompanied by a requester access token: host responds
         immediately with instructions on where to go to obtain one (see
         Section 3.1.2).

   o  If the access attempt was accompanied by a requester access token,
      the host checks the token's status at the AM (see Section 3.3).

      *  If the AM reports that the requester access token is invalid
         (see Section 3.3.2), the host responds to the requester with
         instructions on where to go to obtain a token (see
         Section 3.1.2).

   o  If the AM supplies a token status description for a valid
      requester access token (see Section 3.3.1) but none of the
      permissions associated with the token match the scope of attempted
      access, the host registers a suitable permission on the
      requester's behalf at the AM (see Section 3.4) and then responds



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      to the requester with instructions on where to go to request
      authorization to associate that permission with its token (see
      Section 3.1.4).

   o  If the requester received instructions on where to get a token, it
      requests a token from the appropriate AM (see Section 3.2).

   o  If the requester received instructions on where to get
      authorization for access permission, it requests permission from
      the appropriate AM (see Section 3.5).

   o  If the AM gave status back on a valid requester access token, and
      at least one of the permissions associated with the token match
      the scope of attempted access, the host responds to the
      requester's access attempt with success (see Section 3.1.5).

   The interactions are described in detail in the following sections.

3.1.  Requester-Host: Attempt Access at Protected Resource

   This interaction assumes that the host has previously registered with
   an AM one or more resource sets that correspond to the resource to
   which access is being attempted, such that the host considers this
   resource to be protected by a particular AM.

   The requester typically attempts to access the desired resource at
   the host directly (for example, when a human operator of the
   requester software clicks on a thumbnail representation of the
   resource).  The requester is expected to discover, or be provisioned
   with, knowledge of the protected resource and its location out of
   band.  Further, the requester is expected to acquire its own
   knowledge about the methods made available by the host for operating
   on this resource (such as viewing it with a GET method, or
   transforming it with some complex API call) and the possible scopes
   of access.

   The host responds in one of five ways.

3.1.1.  Requester's Request Is Ambiguous

   By the nature of the requester's request for access (for example,
   through a URI parameter specifying a username or other identifier),
   the host needs to be able to detect uniquely which one of its users
   has the operative control over access to this resource.  Without
   this, the host will be unable to interact with the correct AM using
   the correct host access token in protecting the resource.

   If the requester's request is ambiguous with respect to the specific



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   user at the host, the host immediately responds with an "ambiguous-
   user" error message (see Section 4.2).

   For example:
   HTTP/1.1 403 Forbidden
   Content-Type: application/json
   Cache-Control: no-store

   {
      "error":"ambiguous-user"
   }

3.1.2.  Requester Presents No Access Token

   If the host is able to detect uniquely which one of its users has the
   operative control over access to the resource (see Section 3.1.1),
   but the requester does not present any access token with the request,
   the host MUST return an HTTP 400 (Bad Request) status code indicating
   it is an "invalid_request" (see Section 2.4.1 of [OAuth-bearer]),
   along with providing the AM's URI.  This error indicates to the
   requester that the request is missing a required parameter, includes
   an unsupported parameter or parameter value, repeats the same
   parameter, uses more than one method for including an access token,
   or is otherwise malformed.

   For example:
   HTTP/1.1 400 Bad Request
   WWW-Authenticate: UMA realm="example"
                        host_id="photoz.example.com",
                        am_uri="http://am.example.com"

3.1.3.  Requester Presents an Invalid Access Token

   If the requester presents an access token with its request, the host
   asks the AM to give it the requester access token's status (see
   Section 3.3).  If the AM reports that the token is invalid, the Host
   MUST return an HTTP 401 (Unauthorized) status code indicating it is
   an "invalid_token" (see Section 2.4.1 of [OAuth-bearer]), along with
   providing the AM's URI.

   For example:
   HTTP/1.1 401 Unauthorized
   WWW-Authenticate: UMA realm="example"
                        host_id="photoz.example.com",
                        am_uri="http://am.example.com"






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3.1.4.  Requester's Token Has Insufficient Permission

   If the requester presents an access token with its request, the host
   SHOULD ask the AM to give it the requester access token's status (see
   Section 3.3).  If the AM supplies a token status description for a
   valid requester access token, the host examines the token status
   description.  If the token status is not associated with any
   currently valid permission that applies to the scope of access
   attempted by the requester, the Host SHOULD register the desired
   permission with the AM (see Section 3.4) and then respond to the
   requester with the HTTP 403 (Forbidden) status code indicating that
   the token has "insufficient_scope" (see Section 2.4.1 of
   [OAuth-bearer]), along with providing the AM's URI and the permission
   ticket it just received from the AM.

   For example:
   HTTP/1.1 403 Forbidden
   WWW-Authenticate: UMA realm="example"
                        host_id="photoz.example.com"
                        am_uri="http://am.example.com",
                        ticket="5454345rdsaa4543"

3.1.5.  Requester's Token Has Sufficient Permission

   If the requester presents an access token with its request, the host
   SHOULD ask the AM to give it the requester access token's status (see
   Section 3.3) If the AM supplies a token status description for a
   valid requester access token, the host examines the token status
   description.  If the token status is associated with at least one
   currently valid permission that applies to the scope of access
   attempted by the requester, the host SHOULD give access to the
   desired resource.

   For example:
   HTTP/1.1 200 OK
   Content-Type: image/jpeg
   ...

   /9j/4AAQSkZJRgABAgAAZABkAAD/7AARRHVja
   3kAAQAEAAAAPAAA/+4ADkFkb2JlAGTAAAAAAf
   /bAIQABgQEBAUEBgUFBgkGBQYJCwgGBggLDAo
   KCwoKDBAMDAwMDAwQDA4PEA8ODBMTFBQTExwb

   This response constitutes the conclusion of Phase 3 of UMA.







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3.2.  Requester-AM: Requester Obtains Access Token

   When a requester does not possess a valid access token to access
   resources of a particular user at a particular host, it requests one
   from the AM's requester token endpoint.

   The requester learns about this endpoint by retrieving the AM's
   hostmeta document (see Section 1.5) based on the "am_uri" information
   that was provided by the host in its previous response, as described
   in Section 2 of hostmeta [hostmeta].  For example, if the "am_uri" is
   "am.example.com", the requester creates the URI
   "https://am.example.com/.well-known/host-meta" and performs a GET
   request on it.

   Each such token represents the set of permissions for that requesting
   party to access potentially many different resource sets (all
   controlled by a single authorizing user), with a variety of scopes,
   at that same host, on behalf of the same requesting party.

   The requester SHOULD use the OAuth 2.0 client credentials
   authorization grant type (see Section 4.4 of [OAuth2]).

   In UMA, unlike in plain OAuth, obtaining an access token does not
   automatically convey permission for access to any protected resource.
   The token must first be associated with at least one suitable
   permission for scoped access in order for the requester to succeed in
   accessing the resource.

   If the requester does not yet have a client identifier and optional
   client secret, it MAY request these using [OCDynClientReg], if the AM
   supports it (see Section 1.5 for how the AM MAY indicate support).

3.3.  Host-AM: Ask for Requester's Presented Access Token Status

   On receiving a requester access token in an access attempt, the host
   asks the AM for the token's status.  If it has a cached token status
   description available that has not expired yet, it MAY use it
   instead.

   The host makes the request to the AM with a POST to the AM's token
   status endpoint.  The body of the HTTP request message contains a
   JSON [RFC4627] document providing the requester access token and the
   IP address of the requester's request.  The host MAY, at its
   discretion, instead supply the originating IP address indicated in
   the requester's X-Forwarded-For: header value.  The IP address or
   originating IP address is advisory only; the AM MAY ignore it for
   purposes of its own token validation process.




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   The host gains access to the token status endpoint by presenting its
   own host access token in the request.  The host access token also
   allows the host and AM to uniquely identify the user they have in
   common, and therefore allows the AM to look up the correct
   authorizing user's policies and settings.

   Example of a request to the token validation endpoint that provides
   the host access token in the header:
   POST /token_status HTTP/1.1
   Host: am.example.com
   Authorization: Bearer vF9dft4qmT
   Content-Type: application/json

   {
      "token":"sbjsbhs(/SSJHBSUSSJHVhjsgvhsgvshgsv"
      "resource_set_id":"112210f47de98100"
      "host_id":"photoz.example.com"
      "ipaddr":"192.168.1.1"
   }

3.3.1.  AM Returns a Token Status Description

   If the the AM finds the requester's access token to be valid, it
   returns the token's status in an HTTP response using the 200 OK
   status code, containing a JSON [RFC4627] document supplying the token
   status description.  The token status description contains all of the
   permissions that are currently valid for this requester access token
   (and thus for the requesting party on whose behalf it is acting).
   The AM MAY set a cache period for the returned token status
   description that allows the host to reuse it over some period of time
   when it later sees the same requester access token.

   The token status description is a JSON object with the name
   "token_status" containing an array of zero or more permission
   objects, each with the following parameters:

   resource_set_id  REQUIRED.  A string that uniquely identifies the
      resource set, access to which has been granted to this requester
      on behalf of this requesting party.  The identifier MUST
      correspond to a resource set that was previously registered as
      protected.

   scopes  REQUIRED.  An array referencing one or more URIs of scopes to
      which access was granted for this resource set.  Each scope MUST
      correspond to a scope that was registered by this host for the
      referenced resource set.





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   exp  REQUIRED.  An integer representing the expiration time on or
      after which the permission MUST NOT be accepted for authorized
      access.  The processing of the exp parameter requires that the
      current date/time MUST be before the expiration date/time listed
      in the exp claim.  Host implementers MAY provide for some small
      leeway, usually no more than a few minutes, to account for clock
      skew.

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

   {
           "token_status":
              [
                 {
                         "resource_set_id": "112210f47de98100",
                         "scopes":
                         ["http://photoz.example.com/dev/actions/view",
                           "http://photoz.example.com/dev/actions/all"],
                         "exp": 1300819380
                 }
              ]
   }

3.3.2.  AM Returns a Token Invalid Response

   If the the AM finds the requester's access token to be invalid, it
   returns an UMA error message.

   The AM includes one of the following error codes in the error
   response: (see Section 4.2) and responds with the HTTP 400 status
   code:

   invalid_requester_token  AM determined that the requester access
      token was not valid.

   expired_requester_token  AM determined that the requester access
      token has expired.











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   For example:
   HTTP/1.1 400 Bad Request
   Content-Type: application/json
   Cache-Control: no-store
   {
      "error":"invalid_requester_token"
   }

3.4.  Host-AM: Register a Permission

   If the permissions returned by the AM from a token status request are
   insufficient to allow this requester's access attempt, the host
   registers a permission with the AM that it believes would be
   sufficient for the type of access sought.  As a result of the host
   registering a permission to the AM, the AM returns a permission
   ticket for the host to give to the requester in its response (see
   Section 3.1.4).

   The permissions ticket is a short-lived opaque structure whose
   contents is determined by the AM.  Later when the requester asks the
   AM to add permissions to the requester's token (see Section 3.5 it
   will submit this ticket to the AM.  It is therefore the task of the
   AM to perform binding of this ticket to the requester and its token.

   The host registers the permission using the POST method at the AM's
   permission registration endpoint, providing its host access token to
   get authorized access to this endpoint.  The body of the HTTP request
   message contains a JSON [RFC4627] document providing the requester's
   access token and the requested permission.

   The requested scope is an object with the name "requested_permission"
   and the following parameters:

   resource_set_id  REQUIRED.  A string that uniquely identifies a
      resource set, access to which this requester is seeking access.
      The identifier MUST correspond to a resource set that was
      previously registered as protected.

   scopes  REQUIRED.  An array referencing one or more identifiers of
      scopes to which access is needed for this resource set.  Each
      scope identifier MUST correspond to a scope that was registered by
      this host for the referenced resource set.









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   Example of an HTTP request that registers a permission at the AM's
   permission registration endpoint:
   POST /host/scope_reg_uri/photoz.example.com HTTP/1.1
   Content-Type: application/json
   Host: am.example.com

   {
           "requested_permission":
               {
               "resource_set_id":  "112210f47de98100",
               "scopes": ["http://photoz.example.com/dev/actions/view",
                           "http://photoz.example.com/dev/actions/all"]
           }
   }

   On receiving the scope registration request from the Host, the AM
   issues a response message that has one of the possible following
   outputs:

   o  A permission ticket and its expiration time (typically very
      short).

   o  Error message indicating a malformed scope registration request.

3.4.1.  AM Returns a Permission Registration Success Response

   The AM responds with an HTTP 201 (Created) status code and includes
   the Location header in its response as well as the "ticket" parameter
   in the JSON-formatted body:

   For example:
HTTP/1.1 201 Created
Content-Type: application/json
Location: https://am.example.com/permreg/host/photoz.example.com/5454345rdsaa4543

   {
      "ticket":"5454345rdsaa4543"
   }

3.4.2.  AM Returns a Permission Registration Error Response

   The AM responds with an HTTP 400 (Bad Request) status code and
   includes one of the following error codes with the error response
   (see Section 4.2):







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   invalid_resource_set_id  The provided resource set identifier was not
      found at the AM.

   invalid_scope  At least one of the scopes included in the request was
      not registered previously by this host.

   invalid_requester_token  The requester access token was not
      recognized by the AM.

   expired_requester_token  The requester access token has expired.

   For example:
   HTTP/1.1 400 Bad Request
   Content-Type: application/json
   Cache-Control: no-store
   ...

   {
      "error":"invalid_resource_set_id"
   }

3.5.  Requester-AM: Request Authorization to Add Permission

   In this interaction, the requester asks the AM to grant it permission
   for access.  It does this at the AM's permission endpoint by
   supplying the permission ticket it got from the host, along with its
   requester access token and other pertinent information.  The AM uses
   the ticket to look up the previously registered permission, uses the
   token to confirm that the correct requester is asking for it, maps
   the requested permission to operative user policies, and ultimately
   responds to the request positively or negatively.

   The requester learns about this endpoint by retrieving the AM's
   hostmeta document (see Section 1.5) based on the "am_uri" information
   that was provided by the host in its previous response, as described
   in Section 2 of hostmeta [hostmeta].  For example, if the "am_uri" is
   "am.example.com", the requester creates the URI
   "https://am.example.com/.well-known/host-meta" and performs a GET
   request on it.

   The requester performs a GET or POST on the permission endpoint,
   supplying:

   o  The permission ticket it received from the host

   o  Its own requester access token





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   o  A state parameter (to help avoid replay attacks)

   o  A redirect URL

   o  A callback URL

   The AM MUST support GET requests to this endpoint and MAY support
   POST requests; if it supports POST, the endpoint MUST use SSL/TLS.
   (Requesters will tend to prefer POST when they want to sign the
   request message and preserve certain URL information; however, GET
   typically provides a smoother user experience.)

   The AM responds with a successful or unsuccessful permission
   response.

3.5.1.  AM Returns an Add Permission Success Response

   If the AM determines that the requesting party meets the
   authorization criteria set out by the authorizing user's policy (see
   Section 3.6), it responds with an HTTP 201 (Created) status code and
   provides an updated token:

   For example:
   HTTP/1.1 201 Created
   Content-Type: application/json

      {
         "token":"sbjsbhs(/SSJHBSUSSJHVhjsgvhsgvshgsv"
      }

3.5.2.  AM Returns an Add Permission Error Response

   If the content-type of the request is not recognized by the AM, the
   AM MUST produce an HTTP error.

   If the request fails due to missing or invalid parameters, or is
   otherwise malformed, the AM SHOULD inform the requester of the error
   by sending an HTTP error response.

3.5.2.1.  AM Returns an Add Permission OAuth Error Response

   If the request fails due to an invalid, missing, or expired requester
   access token or requires higher privileges at this endpoint than
   provided by the access token, the AM responds with an OAuth error
   (see Section 4.1).






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   For example:
   HTTP/1.1 401 Unauthorized
      WWW-Authenticate: Bearer realm="example",
                        error="invalid_token",
                        error_description="The access token expired"

3.5.2.2.  AM Returns an Add Permission UMA Error Response

   The AM responds responds using the appropriate HTTP status code
   (typically 400 or 403), and includes one of the following error codes
   in the response: (see Section 4.2):

   invalid_requester_ticket  The provided ticket was not found at the
      AM.  The AM SHOULD respond with the HTTP 400 (Bad Request) status
      code.

   expired_requester_ticket  The provided ticket has expired.  The AM
      SHOULD respond with the HTTP 400 (Bad Request) status code.

   not_authorized_permission  The requester is definitively not
      authorized for this permission according to user policy.  The AM
      SHOULD respond with the HTTP 403 (Forbidden) status code.

   For example:
   HTTP/1.1 400 Bad Request
   Content-Type: application/json
   Cache-Control: no-store
   ...

   {
      "error":"expired_requester_ticket"
   }

3.6.  AM-Requester Authorization Flows

   The AM MUST base its decisions to add permissions to requester access
   tokens on user policies.  The nature of these policies is outside the
   scope of UMA, but generally speaking, they can be thought of as
   either independent of requesting-party features (for example, time of
   day) or dependent on requesting-party features (for example, whether
   they are over 18).  This latter case requires the requesting party to
   transmit identity claims to the AM in some fashion.

   The process for requesting and providing claims is extensible and may
   have a variety of dependencies on the type of requesting party (for
   example, natural person or legal person) and the type of requester
   application (for example, browser, native app, or autonomously
   running web service).  UMA currently provides a framework for



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   handling human-driven requester apps and an optional solution for
   gathering standardized claims from that end-user, and allows for
   extensions to support other solutions for this use case and other use
   cases.  The AM SHOULD document its claims-handling ability in its XRD
   metadata through the claim_formats parameter (see Section 1.5).  For
   the business-level and legal implications of different technical
   authorization flows, see [UMA-trustmodel].

3.6.1.  Authorization Flow for Requester Apps Operated by End-Users

   A natural person might be operating a requester app (whether a
   browser or a native app) in one of two typical situations:

   o  The requesting party is a natural person (for example, a friend of
      the authorizing user); the requesting party may even be the
      authorizing user herself.

   o  The requesting party is a legal person such as a corporation, and
      the human being operating the requester app is acting as an agent
      of that legal person (for example, a customer support specialist
      representing a credit card company).

   The AM has a variety of options at this point for satisfying the
   authorizing user's policy; this specification does not dictate a
   single answer.  For example, the AM could require the end-user
   requesting party to register for or log in to a local AM account, or
   fill in a questionnaire, or complete a purchase.

   An end-user-driven requester app MUST redirect the end-user
   requesting party to the AM to complete the process of authorization.
   If the AM succeeds in adding the requested permission, it MUST
   redirect the end-user requesting party back to the requester app when
   reporting success.

3.6.1.1.  Gathering Claims from End-Users with OpenID Connect

   An AM MAY use OpenID Connect as one means of gathering claims from an
   end-user requesting party, leveraging OpenID Connect mechanisms to
   transmit claims from distributed sources.  If it supports this
   option, the AM MUST supply the "openid" value for one of its
   "claim_formats" parameters in its AM metadata (see Section 1.5 for
   how to formulate this metadata).

   To conform to this option, the AM MUST do the following:

   o  Serve as a conforming OpenID Relying Party and Claims Client
      according to [OCStandard]




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   o  Be able to utilize at least all of the reserved claims defined in
      [OCMessages] in assessing policy and granting permissions

   The AM can then use any conforming OpenID Connect mechanisms and
   typical user interfaces for engaging with the UserInfo endpoints of
   OpenID Providers and Claims Providers, potentially allowing for the
   delivery of "trusted claims" (such as a verified email address or a
   date or birth) on which authorization policy may depend.


4.  Error Messages

   Ultimately the host is responsible for either granting the access the
   requester attempted, or returning an error response to the requester
   with a reason for the failure.  [OAuth2] defines several error
   responses for a resource server to return.  UMA makes use of these
   error responses, but requires the host to "outsource" the
   determination of some error conditions to the AM.  UMA defines its
   own additional error responses that the AM may give to the host and
   requester as they interact with it, and that the host may give to the
   requester.

4.1.  OAuth Error Responses

   When a client (host or requester) attempts to access one of the AM
   endpoints Section 1.5 or a client (requester) attempts to access a
   protected resource at the host, it has to make an authenticated
   request by including an OAuth access token in the HTTP request as
   described in [OAuth2] Section 7.

   If the client's request failed authentication, the AM or the host
   responds with an OAuth error message as described throughout
   Section 2 and Section 3.

4.2.  UMA Error Responses

   When a client (host or requester) attempts to access one of the AM
   endpoints Section 1.5 or a client (requester) attempts to access a
   protected resource at the host, if the client request is successfully
   authenticated by OAuth means, but is invalid for another reason, the
   AM or host responds with an UMA error response by adding the
   following parameters to the entity body of the HTTP response using
   the "application/json" media type:

   error  REQUIRED.  A single error code.  Value for this parameter is
      defined in the specific AM endpoint description.





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   error_description  OPTIONAL.  A human-readable text providing
      additional information, used to assist in the understanding and
      resolution of the error occurred.

   error_uri  OPTIONAL.  A URI identifying a human-readable web page
      with information about the error, used to provide the end-user
      with additional information about the error.

   Common error codes:

   invalid_request  The request is missing a required parameter or is
      otherwise malformed.  The AM MUST respond with the HTTP 400 (Bad
      Request) status code.

   For example:
HTTP/1.1 400 Bad Request
Content-Type: application/json
Cache-Control: no-store
...

{
   "error":"invalid_request",
   "error_description":"There is already a resource with this identifier.",
   "error_uri":"http://am.example.com/errors/resource_exists"
}


5.  Security Considerations

   This specification relies mainly on OAuth security mechanisms for
   protecting the host registration endpoint at the AM so that only a
   properly authorized host can access it on behalf of the intended
   user.  For example, the host needs to use a valid host access token
   issued through a user authorization process at the endpoint, and the
   interaction SHOULD take place over TLS.  It is expected that the host
   will protect its client secret (if it was issued one) and its host
   access token, particularly if used in "bearer token" fashion.

   In addition, this specification dictates a binding between the host
   access token and the host-specific registration area on the AM to
   prevent a host from interacting with a registration area not its own.

   For information about the technical, operational, and legal elements
   of trust establishment between UMA entities and parties, which
   affects security considerations, see [UMA-trustmodel].






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6.  Privacy Considerations

   The AM comes to be in possession of resource set information (such as
   names and icons) that may reveal information about the user, which
   the AM's trust relationship with the host is assumed to accommodate.
   However, the requester is a less-trusted party (in fact, entirely
   untrustworthy until it acquires permissions for a requester access
   token in UMA protocol step 2).  This specification recommends
   obscuring resource set identifiers in order to avoid leaking
   personally identifiable information to requesters through the "scope"
   mechanism.

   For information about the technical, operational, and legal elements
   of trust establishment between UMA entities and parties, which
   affects privacy considerations, see [UMA-trustmodel].


7.  Conformance

   This section outlines conformance requirements for various entities
   implementing UMA endpoints.

   This specification has dependencies on other specifications, as
   follows:

   o  OAuth 2.0: AMs, hosts, and requesters MUST support [OAuth2]
      features named in this specification for conformance.  For
      example, AMs MUST support the authorization code grant type for
      being introduced to hosts by authorizing users.

   o  hostmeta: AMs, hosts, and requesters MUST support the [hostmeta]
      features named in this specification.

   o  OpenID Connect: AMs MAY support [OCDynClientReg], and MAY choose
      to conform to the "openid" claim format option corresponding to
      the OpenID Connect RP role and support for OpenID Connect reserved
      claims.

   The AM's XRD metadata provides a machine-readable method for an AM to
   indicate certain of the conformance options it has chosen.  Several
   of the metadata fields allow for extensibility.  It is RECOMMENDED
   that UMA developers and deployers document any profiled or extended
   features formally and use XRD metadata to indicate their usage.  See
   Section 1.5 for information about providing and extending AM
   metadata.






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8.  IANA Considerations

   BD


9.  AM Metadata Example

   For example:











































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<!-- Applies to both hosts and requesters -->

<Property
  type="http://docs.kantarainitiative.org/uma/1.0/token_formats">artifact
</Property>
<Property
  type="http://docs.kantarainitiative.org/uma/1.0/claim_formats">openid
</Property>

<!-- Host protection API -->

<!-- AM as authorization server to host-as-client -->
<Link
  rel="http://docs.kantarainitiative.org/uma/1.0/host_token_uri"
  href="https://am.example.com/host/token_uri">
</Link>
<Link
  rel="http://docs.kantarainitiative.org/uma/1.0/host_user_uri"
  href="https://am.example.com/host/user_uri">
</Link>

<!-- AM as resource server to host-as-client -->
<Link
  rel="http://docs.kantarainitiative.org/uma/1.0/host_resource_reg_uri"
  href="https://am.example.com/host/resource_details_uri">
</Link>
<Link
  rel="http://docs.kantarainitiative.org/uma/1.0/host_token_status_uri"
  href="https://am.example.com/host/token_validation_uri">
</Link>
<Link
  rel="http://docs.kantarainitiative.org/uma/1.0/host_perm_reg_uri"
  href="https://am.example.com/host/scope_reg_uri">
</Link>

<!-- Requester authorization API -->

<!-- AM as authorization server to requester-as-client -->
<Link
  rel="http://docs.kantarainitiative.org/uma/1.0/req_token_uri"
  href="https://am.example.com/requester/token_uri">
</Link>

<!-- AM as resource server to requester-as-client -->
<Link
  rel="http://docs.kantarainitiative.org/uma/1.0/req_perm_uri"
  href="https://am.example.com/requester/perm_uri">
</Link>



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10.  Example of Registering Resource Sets

   The following example illustrates the intent and usage of resource
   set registration.

   This example contains some steps that are exclusively in the realm of
   user experience rather than web protocol, to achieve realistic
   illustration; these steps are labeled "User experience only".  Some
   other steps are exclusively internal to the operation of the entity
   being discussed; these are labeled "Internal only".

   An authorizing user, Alice Adams, has just uploaded a photo of her
   new puppy to a host, Photoz.example.com, and wants to ensure that
   this specific photo is not publicly accessible.

   Alice has already introduced this host to her AM,
   CopMonkey.example.com, and thus Photoz has already obtained a host
   access token from CopMonkey.  However, Alice has not previously
   instructed Photoz to use CopMonkey to protect any other photos of
   hers.

   Alice has previously visited CopMonkey to map a default "do not share
   with anyone" policy to any resource sets registered by Photoz, until
   such time as she maps some other less-draconian policies to those
   resources.  (User experience only.  This may have been done at the
   time Alice introduced the host to the AM, and/or it could have been a
   global or host-specific preference setting.  A different constraint
   or no constraint at all might be associated with newly protected
   resources.)  Other kinds of policies she may eventually map to
   particular photos or albums might be "Share only with
   husband@email.example.net" or "Share only with people in my 'family'
   group".

   Photoz itself has a publicly documented API that offers two dozen
   different methods that apply to single photos, such as "addTags" and
   "getSizes", but rolls them up into two photo-related scopes of
   access: "viewing" (consisting of various read-only operations) and
   "all" (consisting of various reading, editing, and printing
   operations).  It defines two Web-accessible JSON-encoded documents
   called scope descriptions that represent these scopes, which it is
   able to reuse for all of its users (not just Alice).

   The "name" parameter values are intended to be seen by Alice when she
   maps authorization constraints to specific resource sets and actions
   while visiting CopMonkey, such that Alice would see the strings "View
   Photo and Related Info" and "All Actions", likely accompanied by the
   referenced icons, in the CopMonkey interface.  (Other users of Photoz
   might similarly see the same labels at CopMonkey or whatever other AM



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   they use.  Photoz could distinguish natural-language labels per user
   if it wishes, by pointing to scopes with differently translated
   names.)

   Example of the "view" scope ,which description is a Web-accessible
   resource at http://photoz.example.com/dev/scopes/view:
{
        "scope":
            {
            "_id": "view"
            "name": "View Photo and Related Info",
            "icon_uri": "http://www.example.com/icons/reading-glasses.png"
        }
}

   Example of the "all" scope, which description is a Web-accessible
   resource at http://photoz.example.com/dev/scopes/all:
   {
           "scope":
               {
               "_id": "all"
               "name": "All Actions",
               "icon_uri": "http://www.example.com/icons/galaxy.png"
           }
   }

   While visiting Photoz, Alice selects a link or button that instructs
   the site to "Protect" or "Share" this single photo (user experience
   only; Photoz could have made this a default or preference setting).

   As a result, Photoz defines for itself a resource set that represents
   this photo (internal only; Photoz is the only application that knows
   how to map a particular photo to a particular resource set).  Photoz
   also prepares the following resource set description, which is
   specific to Alice and her photo.  The "name" parameter value is
   intended to be seen by Alice in mapping authorization constraints to
   specific resource sets and actions when she visits CopMonkey, such
   that Alice would see the string "Steve the puppy!", likely
   accompanied by the referenced icon, in the CopMonkey interface.  The
   possible scopes of access on this resource set are indicated with URI
   references to the scope descriptions, as defined just above.










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   {
           "resource_set":
               {
               "_id": "112210f47de98100"
               "name": "Steve the puppy!",
               "icon_uri": "http://www.example.com/icons/flower",
               "scopes":
                           ["http://photoz.example.com/dev/scopes/view",
                           "http://photoz.example.com/dev/scopes/all"]
           }
   }

   Photoz uses the "create resource set description" method of
   CopMonkey's standard UMA resource set registration API, presenting
   its Alice-specific host access token there, to register and assign an
   identifier to the resource set description.  The resource set
   identifier path component of the URL matches the "_id" parameter
   value in the description.
   PUT /host/photoz.example.com/resource_set/112210f47de98100 HTTP/1.1
   Content-Type: application/json
   ...

   {
           "resource_set":
              {
              "_id": "112210f47de98100"
              "name": "Steve the puppy!",
              "icon_uri": "http://www.example.com/icons/flower.png",
              "scopes":
                           ["http://photoz.example.com/dev/scopes/view",
                           "http://photoz.example.com/dev/scopes/all"]
            }
   }

   Once this description has been successfully registered, Photoz is
   responsible for responding to requesters' attempts to access this
   photo in a way that is consistent with the authorizing user's
   policies, achieving protection of the resource by "outsourcing" this
   task to CopMonkey.

   At the time Alice indicates she would like this photo protected,
   Photoz can choose to redirect Alice to CopMonkey for further policy
   setting, access auditing, and other AM-related tasks (user experience
   only).

   Over time, as Alice uploads other photos and creates and organizes
   photo albums, and as Photoz makes new action functionality available,
   Photoz can use additional methods of the resource set registration



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   API to ensure that CopMonkey's understanding of Alice's protected
   resources matches its own.


11.  Acknowledgments

   The current editor of this specification is Thomas Hardjono of MIT.
   The following people have additionally served as co-authors:

   o  Paul Bryan, ForgeRock (former editor)

   o  Domenico Catalano, Oracle Corp.

   o  Maciej Machulak, Newcastle University

   o  Eve Maler, XMLgrrl.com

   o  Lukasz Moren, Newcastle University

   o  Christian Scholz, COMlounge GmbH (former editor)

   Contributors to this specification include the Kantara UMA Work Group
   participants, a list of whom can be found at [UMAnitarians].


12.  Issues

   All issues are now captured at the project's GitHub site
   (<https://github.com/xmlgrrl/UMA-Specifications/issues>).


13.  References

13.1.  Normative References

   [OAuth-SAML]
              Campbell, B., "SAML 2.0 Bearer Assertion Grant Type
              Profile for OAuth 2.0", February 2011, <http://
              tools.ietf.org/html/draft-ietf-oauth-saml2-bearer-03>.

   [OAuth-bearer]
              Jones, M., "The OAuth 2.0 Protocol: Bearer Tokens",
              June 2011,
              <http://tools.ietf.org/html/
              draft-ietf-oauth-v2-bearer-06>.

   [OAuth2]   Hammer-Lahav, E., "The OAuth 2.0 Protocol", 2010,
              <http://tools.ietf.org/html/draft-ietf-oauth-v2-16>.



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   [OCDynClientReg]
              Sakimura, N., "OpenID Connect Dynamic Client Registration
              1.0", September 2011, <http://openid.net/specs/
              openid-connect-registration-1_0.html>.

   [OCMessages]
              Sakimura, N., "OpenID Connect Messages 1.0",
              September 2011,
              <http://openid.net/specs/
              openid-connect-messages-1_0.html>.

   [OCStandard]
              Sakimura, N., "OpenID Connect Standard 1.0",
              September 2011,
              <http://openid.net/specs/
              openid-connect-standard-1_0.html>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4627]  Crockford, D., "The application/json Media Type for
              JavaScript Object Notation (JSON)", RFC 4627, July 2006.

   [hostmeta]
              Hammer-Lahav, E., "Web Host Metadata", May 2011,
              <http://tools.ietf.org/html/draft-hammer-hostmeta-16>.

13.2.  Informative References

   [UMA-trustmodel]
              Maler, E., "UMA Trust Model", February 2011, <http://
              kantarainitiative.org/confluence/display/uma/
              UMA+Trust+Model>.

   [UMA-usecases]
              Maler, E., "UMA Scenarios and Use Cases", October 2010, <h
              ttp://kantarainitiative.org/confluence/display/uma/
              UMA+Scenarios+and+Use+Cases>.

   [UMA-userstories]
              Maler, E., "UMA User Stories", November 2010, <http://
              kantarainitiative.org/confluence/display/uma/
              User+Stories>.

   [UMAnitarians]
              Maler, E., "UMA Participant Roster", 2011, <http://
              kantarainitiative.org/confluence/display/uma/
              Participant+Roster>.



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Appendix A.  Document History

   NOTE: To be removed by RFC editor before publication as an RFC.


Author's Address

   Thomas Hardjono (editor)
   MIT

   Email: hardjono@mit.edu








































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