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This is the description of the protocol flow I use in my prototype at http://host.clproject.net/

General notes

  • Instead of XRD I use a slightly modified variant of JRD as it is simpler to parse.
  • The Host contains three resources of Bob: a basic, a medium and a detailed profile.
  • The only access conditition right now is a check on the username the requesting party provides at the AM. This could be an OpenID login in a real world scenario.
  • many things are just inventions of my own where I thought it might work that way. These need discussion and proper specification.

Step 1: Introduction of Host to the AM

Step 1 starts when the user enters the location of the AM to be used for.

1.1: Obtaining the AM metadata

In order to start the process the Host needs to know various URI endpoints of the AM. These are retrieved by a hostmeta lookup by the Host (here is the live AM hostmeta). Technically it's a GET on the hostmeta URL and this is what it returns:

GET http://am.clprojects.net/.well-known/hostmeta
{
    "property": [
        {
            "http://uma/am/title": "Cop Monkey"
        }
    ], 
    "expires": "2011-01-30T09:30:00Z", 
    "link": {
        "http://uma/host/token_uri": [
            {
                "href": "http://am.clprojects.net/host/token"
            }
        ], 
        "http://uma/host/user_uri": [
            {
                "href": "http://am.clprojects.net/host/authorize"
            }
        ], 
        "http://uma/host/resources": [
            {
                "href": "http://am.clprojects.net/host/resources"
            }
        ], 
        "http://uma/requester/user_uri": [
            {
                "href": "http://am.clprojects.net/requester/authorize"
            }
        ], 
        "http://uma/requester/token_uri": [
            {
                "href": "http://am.clprojects.net/requester/token"
            }
        ]
    }, 
    "subject": "http://am.clprojects.net/"
}

We see various endpoints here:

The Host stores all these endpoints for later usage.

1.2: Host registers Bob's resources at the AM and obtains client_id

In order for the AM to be able to manage Bob's resources it needs to know what these resources are. Instead of entering the URIs of them manually I invented some registration step to do so automatically.

For this the Host crafts a JRD document containing the resources identified by their resource URI and a title. The example in the prototype looks as follows:

Resource Document Example
    {
        "subject" : "http://host.clprojects.net/profiles/bob",
        
        # we copied this from the hostmeta JRD so we can skip one lookup here
        "property":
        [
          { "http://uma/host/title" : "UMA Example Host" },
        ],
        "link" : {
            # our namespace defining a protected resource 
            "http://uma/am/resource" : [
                # we have three protected resources as links
                {
                    'href' : 'http://host.clprojects.net/profiles/bob.basic', 
                    'title' : 'Basic Profile',
                },
                {
                    'href' : 'http://host.clprojects.net/profiles/bob.medium', 
                    'title' : 'Medium Profile',
                },
                {
                    'href' : 'http://host.clprojects.net/profiles/bob.detail', 
                    'title' : 'Detailed Profile',
                },

            ]
        }
    }

This document is sent to the http://uma/host/resources endpoint of the AM which we retrieved via the hostmeta lookup. This is done via a POST request.

The AM then stores this information and assigns it a client_id which then is returned to the Host. This is done in the response of the POST request. The document is JSON formatted and looks liks this:

    {
        'client_id' : '622f5656-7211-4315-a69f-24fde3d65732',
    }

Now the AM knows about the resources of the Host and the Host has a client_id

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