Re: [OAUTH-WG] Simpilfying use of assertions when requesting an access token

[David Waite <[e-mail]>]

I think combining the grant_type and assertion_type together is a great idea. However, I have recently been wondering if it would be a good idea to unify all the access grants to use the same parameters. 

For instance, you could have the parameters:

	grant_type - the type of access grant (of course)
	grant_qualifier - an identifier or URI associated with the grant
	grant_value - the data (such as an opaque or secret value) used for a particular type of access grant

So for the grant types mentioned below, you would have:

	password:
		a grant_qualifier of the user identifier, and a grant_value of their password

	client_credentials:
		a grant_qualifier of the client identifier, and a grant_value of the shared secret

	refresh_token:
		no grant_qualifier, a grant_value of the refresh token

	authorization_code:
		a grant_qualifier of the callback URI used to return the authorization code to the client, and a grant_value of the actual code

	<SAML assertion extension URI>:
		no grant_qualifier, a grant_value of the assertion as a string

This would seem to have the following benefits:
	- A number of query parameters defined to be used only in cases of a particular grant_type value would be eliminated
	- The qualifier/value would provide a guideline for structuring new grant types
	- The "grant_" prefix for the parameters could provide a logical grouping for any additional parameters, if a new grant type required more than the qualifier/value pair above.

I must admit however, I had difficulty figuring out how to phrase 'qualifier' so that it would apply to a callback URI. I think it makes sense in that an authorization code is issued against and only valid for a specific callback URI, but would understand if this came off feeling like overloading that parameter.

-David Waite

On Sep 2, 2010, at 3:11 PM, Eran Hammer-Lahav wrote:

> I would like to make this change in -11:
>  
> Instead of the current user of the ‘assertion’ grant type –
>  
>   POST /token HTTP/1.1
>   Host: server.example.com
>   Content-Type: application/x-www-form-urlencoded
>  
>   grant_type=assertion&
>   assertion_type=urn%3Aoasis%3Anames%3Atc%3ASAML%3A2.0%3Aassertion&
>   assertion=PHNhbWxwOl[...omitted for brevity...]ZT4%3D
>  
> Drop the ‘assertion’ grant type and put the assertion type directly in the grant_type parameter:
>  
>   POST /token HTTP/1.1
>   Host: server.example.com
>   Content-Type: application/x-www-form-urlencoded
>  
>   grant_type=urn%3Aoasis%3Anames%3Atc%3ASAML%3A2.0%3Aassertion&
>   assertion=PHNhbWxwOl[...omitted for brevity...]ZT4%3D
>  
> In other words, the grant_type parameter value will be defined as:
>  
> -          authorization_code
> -          password
> -          client_credentials
> -          refresh_token
> -          an abolute URI (extensions)
>  
> I considered turning all the values into URIs but found it to be counter-intuitive. The practice of using “official” short names and extension URIs is well established and is already the general architecture used here. This just makes it cleaner.
>  
> I ran this idea by Brian Campbell and Chuck Mortimore who are generally supportive of the idea.
>  
> Any objections?
>  
> EHL
>  
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