Thanks for the comments,

On 01/03/12 17:00, Richer, Justin P. wrote:
If there's a fully trusted relationship between the client and the server, then 
the client may in fact be accessing data on behalf of another resource owner. 
It's a useful pattern when a three-legged flow like the Auth Code is not 
available. But it's kind of splitting hairs because the client has been granted 
a blanket access to the resource ahead of time, by virtue of its registration. 
Showing up to get a token is a method of limiting exposure and power of the 
client credentials, and making it easier to support both direct-client access 
and delegated-client access simultaneously with most of the same tooling.

It does make sense. What I'm still missing is how an access token returned as part of the client_credentials flow can 'link' to more than a single resource owner. The authorization server can establish the fact that a specific end user pre-authorized the client, but how to manage the case where many end users have pre-authorized the same client ? The returned access token won't uniquely identify the end user which have pre-authorized this client...


To your second question, no -- scopes do not have to be ignored in this case. In fact, a 
well-designed client and server can make use of scopes to let the client request an 
access token that's only good for whatever the current transaction is, as opposed to 
something that's representative of all of the client's capabilities. This is a method 
known as "downscoping" and it's a very powerful pattern that OAuth enables. Of 
course, if you want, you are fully allowed to leave the scope out entirely, then it's up 
to the Authorization Server alone to figure out what the token is really good for.

Sure - I can see why it is very useful for an authorization code flow.
Still a bit unclear why the scope can be needed in case where a client is accessing its own resources, but do see it can be useful when the access to the end user's resources is also thought...

many thanks
Sergey

Hope this clears things up,

  -- Justin



On Mar 1, 2012, at 11:39 AM, Sergey Beryozkin wrote:

Hi,

I have few questions about the client_credentials grant type.
Section 4.4 [1] says: "...client is requesting access to the protected resources 
under its control, or those of another resource owner..."

What I do not understand is the latter part of the above statement, how to 
establish a link between the client authentication (which is an actual grant in 
this case) and different resource owners given that the only thing we have is 
the client authentication. As far as I can see it is only possible to get a one 
to one link with the end user in this case.

Can someone please clarify what is meant by "those of another resource owner" 
phrase ?

The other question is about an optional scope parameter. It has to be ignored 
in case of the client requesting a token for accessing its own resources, right 
?

Thanks, Sergey



[1] http://tools.ietf.org/html/draft-ietf-oauth-v2-23#section-4.4
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