[OAUTH-WG] 'Scope' parameter proposal

[Eran Hammer-Lahav <[e-mail]>]

Proposal:

'scope' is defined as a comma-separated list of resource URIs or resource
groups (e.g. contacts, photos). The server can provide a list of values for
the client to use in its documentation, or the client can use the URIs or
scope identifier of the protected resources it is trying to access (before
or after getting a 401 response).

For example:

1. Client requests resource

    GET /resource HTTP/1.1
    Host: example.com

2. Server requires authentication

    HTTP/1.1 401 Unauthorized
    WWW-Authenticate: Token realm='Example', scope='x2'

3. Client requests an access token by including scope=x2 in the request

Alternatively, the client can ask for an access token with
scope=http://example.com/resource.

If the client needs access to two resource with different scopes, it
requests an access token for scope=x2,x1.

That's it!

It allows the client to figure out what value to put in the scope parameter
and how to encode multiple scopes without any server-specific documentation.
Servers that wish to rely exclusively on paperwork can just omit the scope
parameter from the WWW-Authenticate header.

We can pick a different separator (space, semicolon, etc.) or different
parameter name (resource(s)).

EHL