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Re: [OAUTH-WG] Reevaluating Assumptions (Important!)

This is possible but it gets complicated. If server A (the one issuing the long encrypted opaque token) is separate (meaning not from the same company) from server B (the server receiving and validating the token) then both server A and Server B have to agree on the format of the token and the mechanism for "encrypting" or "signing" it.
Since OAuth provides a way to secure requests via signing, this becomes a very easy way to support servers A and B being from multiple companies (or whatever). For sure, the partners could agree to take the string that would be the value of the Authorization header, base64 it and add it to the URL.
Maybe this could be the simplifying mechanism for adding OAuth to URLs. Just define an oauth_authz parameter that is optional and contains the base64 encoded version of the Authorization header. Simple to process and easy to implement. 

Thanks,
George

Eran Hammer-Lahav wrote:

Actually, I am going to take this back.

This is not really a valid reason to support authentication parameters in the query. In this scenario, the resource owner is able to make an authenticated request using the auth headers. That request produces a special URI which can be shared, bypassing the access controls. Why does this needs to be covered by OAuth? What prevents any server from issuing a time-limited/restricted/single-use/etc URI using long token such as:

http://example.com/resource/share/1k2j3h1oi823h123hk1j23ho182h31j2h3o182h3o12hi3o182h3o182h3

I just don't see any reason why this is lesser than producing a URI that uses OAuth parameters. Whatever the server needs can be either encoded into this long token or maintained in a database.

So back to no real use case for query parameters support.

EHL


-----Original Message-----
From: George Fletcher [mailto:gffletch at aol.com]
Sent: Friday, October 02, 2009 9:16 AM
To: oauth at ietf.org
Cc: Eran Hammer-Lahav
Subject: Re: [OAUTH-WG] Reevaluating Assumptions (Important!)

I would expect that in the Amazon case being able to reuse the URL
would
be beneficial, but I'm not really familiar with that use case.

For the SSO use cases, the desire is to prevent replay and make the URL
one time use only. We do set cookies during the redirect process so a
cache replaying those cookies could be problematic. There are a number
of cache control directives that can be used for correctly implemented
proxies.

A couple reasonable links on the topic

[1] http://blog.isc2.org/isc2_blog/2008/09/proxy-caches-ar.html
[2] http://www.oucs.ox.ac.uk/cache/faq.xml?splitLevel=-1
[3] http://code.google.com/speed/page-speed/docs/caching.html

However, I think this issue is bigger than just requests with URL
parameters. If I access a rest resource
http://photos.example.com/alice/album/vacation along with it's
Authorization header, if this request goes through a proxy, the proxy
will mostly likely ignore the Authorization header. Hence the next time
that static URL is requested, the contents is returned. The same cache
control headers the server needs to send for these specific use cases
will apply to the general case as well. I'm a little behind in the
lists
servs. Has this issue already been solved for the general case using
the
Authorization header?

Thanks,
George



Eran Hammer-Lahav wrote:

Thanks James, George.

If we are going to support sending authentication credentials in the

URI query, what are the requirements to make sure it works well with
proxies and caches? What headers do we need to require the server to
return to make sure it doesn't get cached? Do we need to require a
nonce value for all signature methods to ensure making the request more
unique and less likely to repeat?

In these two use cases, is there a reason for the URI to be used more

than once? Can we simplify the credentials passed via the URI query to
provide adequate security but without the need for a long and ugly URI
with multiple oauth_ prefixed parameters?


These are valid use cases and something we need to worry about to get

this new protocol deployed where other proprietary ones are deployed.
But I am not that concerned about the use case mentioned earlier of
'just making it easier to send requests'. So if we support query
parameters but after some processing of the parameters to make the URI
simpler, that would be acceptable to me.

EHL



-----Original Message-----
From: George Fletcher [mailto:gffletch at aol.com]
Sent: Friday, October 02, 2009 5:04 AM
To: oauth at ietf.org
Cc: Eran Hammer-Lahav; Brian Eaton
Subject: Re: [OAUTH-WG] Reevaluating Assumptions (Important!)

In addition to the use case James described, we use this to enable
single sign on from a client/desktop app into a browser session. The
client signs the URL and then opens the browser with that URL. The
backend validates the signature and access token and then

establishes

an
authentication session for the user.

A variant of this case is where a partner uses a back-channel
federation
call to authenticate their user to the AOL authentication service. A
successful response includes an access token and secret (the

equivalent

of) which the partner can then user to sign an URL when their user
invokes an AOL service (again providing SSO).

Thanks,
George

P.S. Documentation on this signed API call can be found here:
http://dev.aol.com/authentication_for_clients#client2web

P.P.S. While these APIs are not OAuth specifically, the patterns are
needed for OAuth compliant APIs to be developed

Eran Hammer-Lahav wrote:


Can you describe the actual use case?

EHL




-----Original Message-----
From: oauth-bounces at ietf.org [mailto:oauth-bounces at ietf.org] On


Behalf


Of Brian Eaton
Sent: Thursday, October 01, 2009 9:01 PM
To: George Fletcher
Cc: oauth at ietf.org
Subject: Re: [OAUTH-WG] Reevaluating Assumptions (Important!)

On Thu, Oct 1, 2009 at 7:52 PM, George Fletcher <gffletch at aol.com>
wrote:



One use case (I think I saw it mentioned somewhere else on the


list)


where



we've used the URI parameters is when we want the server to sign

a

URL and



then pass that signed value to the browser to load. This can be


done


with a



simple 302 and the signed URL. Switching to just supporting the
Authorization header will make this more difficult but probably

not

impossible.



Yep.  I've seen that done multiple places.

One more unexpected use of OAuth...
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