Step 1: User registers host at AM

In order for a host to be able to delegate authorization to an authorization manager the authorizing user must introduce the host to the AM. The result of this step is the following:

1. The host received metadata of the AM like OAuth 2.0 endpoints
2. The host received an OAuth access token in order to verify requester access tokens in step 3 and as a representation of the user's decision to
3. The AM received a list of protected resources on the host it is supposed to authorize on behalf of the user.

The following sub steps are performed in order to fulfill these requirements:

1. The host looks up the authorization manager metadata and learns about API endpoints and formats supported by the AM
2. The host obtains OAuth client credentials and a the location of the resource registration API from the authorization manager.
3. The host obtains an access token from the authorization manager by following the OAuth 2.0 web server flow.
4. The host registers the authorization user's resources with the AM by using the resource registration API.

host looks up the authorization manager metadata

The very first step for the host is to lookup the metadata of the authorization manager. There are many possible ways for the authorizing user to provide the location of the authorization manager or it might be discovered by the host. The exact process is beyond the scope of this specification and it is up to the host to choose a method. For example it could simply ask for the URL of the AM or it could be contained on a physical magnetic-stripe card.

From the data provided or discovered the host then has to retrieve the hostmeta document as described in section 2 of [hostmeta.

For example if the user gave "am.example.com" as the authorization manager's domain then the host would create the URL "https://am.example.com/.well-known/host-meta" and perform a GET request on it.

The authorization manager MUST provide a XRD 1.0 formatted document at the hostmeta location where it has to document the the following:

• One set of OAuth 2.0 URI endpoints for the host to use
• One set of OAuth 2.0 URI endpoints for any requester to use
• The location of the token verification API for the host to verify access tokens received from a requester in step 3.
• (The format of the access tokens to use)
• (The format of the claims formats the AM can generate)

The Property elements SHOULD be present in the hostmeta document:

Link relationships for the OAuth 2.0 endpoints for the host:

Link relationships for the OAuth 2.0 endpoints for the requester:

Example XRD document

<!-- Applies to both hosts and requesters -->
<Property 
    type="http://kantarainitiative.org/confluence/display/uma/token_formats">
       saml
</Property>
<Property 
    type="http://kantarainitiative.org/confluence/display/uma/claim_formats">
       json
</Property>

<!-- Host "authorization API" -->
<Link rel="http://kantarainitiative.org/confluence/display/uma/host_token_uri"
      href="https://am.example.com/host/token_uri"></Link>
<Link rel="http://kantarainitiative.org/confluence/display/uma/host_user_uri"
      href="https://am.example.com/host/user_uri"></Link>
<Link rel="http://kantarainitiative.org/confluence/display/uma/host_token_validation_uri"
      href="https://am.example.com/host/token_validation_uri"></Link>

<!-- Requester token-getting endpoints -->
<Link rel="http://kantarainitiative.org/confluence/display/uma/req_token_uri"
      href="https://am.example.com/requester/token_uri"></Link>
<Link rel="http://kantarainitiative.org/confluence/display/uma/req_user_uri"
      href="https://am.example.com/requester/user_uri"></Link>

The host obtains OAuth client credentials and the location of the resource registration API from the authorization manager

In order for the host to initiate an OAuth flow to retrieve an access token for the resource registration API and the token verification API, it needs to have a client identifier and optionally a client secret. How this is transferred is beyond the scope of the OAuth specification and usually a manual process of preregistration and transferring this information is used.

In this step the host is the OAuth client and the authorization manager is the OAuth authorization server. For User Managed access the authorization server MUST provide the client identifier, an OPTIONAL client secret and the URI of the resource registration API which can be individual for each client.

In order to also allow for dynamic binding of a host and authorization manager, this specification also defines a protocol for dynamic and automatic client registration for OAuth.

Dynamic binding of OAuth clients

Terminology

Dynamic binding will be explained in OAuth terminology, using client and authorization server as the parties involved in the process.

Moreover the following terminology is used:

client registration endpoint: This is the URI defining the location of the client registration API. This is used by the client to send the required data for obtaining a client identifier and additional information

Discovery of client registration endpoint

In order for the client to obtain the URI of the client registration endpoint the authorization server MUST provide a hostmeta document containing a Link element with rel-value http://kantarainitiative.org/uma/client_registration_uri.

Overview

The dynamic client registration process works as follows:

1. The client send it's name and description as well as an optional image to the client registration endpoint
2. the authorization server checks the data and returns a JSON formatted document containing a client identifier, optional client secret and optionally additional information

The client registration flow

The client sends a client descriptor to the authorization server

The client creates a JSON document with the following keys/value pairs:

• the name of the client in the key name
• the URL to the service in the key name
• a short description of the client in the key description
• OPTIONAL: the URI to an icon representing the client in the key icon

An example client descriptor might look like follows:

{
    name : 'A wonderful image hoster',
    url: 'http://wonderfulimagehoster.com',
    description : 'as the name implies',
    icon: 'http://wonderfulimagehoster.com/logo.png'
}

The client then performs a POST request to the client registration endpoint using application/json as content type and sending the client descriptor in the body of the message.

The authorization server sends a response containing the client credentials

The authorization server can check the client descriptor as it requires and will then send either a success or an error response.

The success response is a JSON document consisting of a REQUIRED client identifier in the field client_id and an optional matching secret in the field client_secret.

An example response might look like this:

{
client_id : 'AGSD)=bjchdb