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

Eran Hammer-Lahav wrote:

I can live with something like that. The problem will be that it will require normalizing the request URI to remove the OAuth parameter before validating the signature. But this is completely on the server so I don't mind it.

I'll include something like this in the upcoming revision (pending more feedback).

As for sending form-encoded auth parameters, no one has argued to keep that so I think it is save to drop it completely.
I actually had a use case for this (as an idea) but it didn't go anywhere. Basically it was leveraging the signing mechanism as a binding for SAML messages. Logically it would be similar to SAML Simple Sign but for server-to-server calls.
However, if we add the body-hash support then I think that covers POST'd content and it can be in any format. 

Thanks,
George

EHL




-----Original Message-----
From: George Fletcher [mailto:gffletch at aol.com]
Sent: Friday, October 02, 2009 10:31 AM
To: oauth at ietf.org
Cc: Eran Hammer-Lahav
Subject: 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/1k2j3h1oi823h123hk1j23ho182h31j2h3o18
2h3o12hi3o182h3o182h3

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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