Brian,

it would probably help to clarify that you are proposing this as a additional or follow-on step to SSO implemented via the SAML web browser profiles (right?).

Maybe some text could be added to the draft to make that explicit. This is in contrast to more general token exchange scenarios - here are bunch of SAML /XYZ tokens, now give me an OAuth token for for a certain purpose. I agree with you that the latter would require quite a bit of additional work.

Here is my understanding of the current use-case -

The user delivers a SAML bearer token (issued at an IdP) via a browser profile to an SP. The SP, performs some business service for the user and at some point requires access to user resources at the IdP or at some third-party site. Switching to OAuth terminology, the Client (SP) exchanges the said SAML bearer token to the Authorization server (could be at the IdP - this would be a common case I think) for an OAuth token. This is the exchange you are describing in your draft.

Once the client obtains the OAuth token, it can bind it to a request for the user resource.

I have some mild SAMology concerns about this - historically the SAML bearer token has been constrained to have a short life-time and the general advice is not to forward it beyond the SP. I am aware that in practice this isnt the case - often the token is bound to some subsequent flows - somewhat along the lines you are proposing. I will follow up with these concerns on the SAML list.

- prateek
Seems like a much more complicated scenario.  Allowing more than one
assertion, off the top of my head, would necessitate some major
changes to this profile:

* Define how multiple assertions are encoded into the single
"assertion" form control (samlp:Response, concatenated, something
else?)
* Deal with subject equality across the assertions
* Define the processing rules for multiple assertion (from different
issuers) and the expected behavior when some but not all are valid.

That seems like it would add significant complexity to the existing
draft (that I'm trying to keep simple) for a particular scenario that
I'm not sure is very common.  But maybe I'm wrong.  Is this something
that others anticipate needing?   If so, does it belong here?


On Mon, Aug 2, 2010 at 4:26 PM, Anthony Nadalin <tony...@microsoft.com> wrote:
So the scenario we have is where there are multiple tokens from attribute and 
identity providers need to be delivered to an OAuth authorization server to 
satisfy the resource owner's policy of required claims. So this is a case where 
a single SAML token/assertion is not enough to satisfy the claim, we still 
expect that the signature verification is out of scope.

-----Original Message-----
From: oauth-boun...@ietf.org [mailto:oauth-boun...@ietf.org] On Behalf Of Brian 
Campbell
Sent: Monday, August 02, 2010 2:53 PM
To: oauth
Subject: Re: [OAUTH-WG] SAML 2.0 Bearer Assertion Profile for OAuth 2.0 draft

I guess I'd need to understand the scenario better before I'd have an
opinion one way or the other.   However, I will say that In this
profile I was specifically looking to avoid the complexity that exists in SAML 
Web SSO by allowing for multiple assertions and multiple subject confirmations.

On Mon, Aug 2, 2010 at 3:20 PM, Anthony Nadalin <tony...@microsoft.com> wrote:
There are many cases where we need to have more than 1 SAML assertion be used 
to represent the authorization token, so would want a provision for multiple 
SAML tokens and not sure it makes sense to have a separate profile for that or 
add it as an option here.

-----Original Message-----
From: oauth-boun...@ietf.org [mailto:oauth-boun...@ietf.org] On Behalf
Of Brian Campbell
Sent: Thursday, July 15, 2010 1:50 PM
To: oauth
Subject: [OAUTH-WG] SAML 2.0 Bearer Assertion Profile for OAuth 2.0
draft

I'm gong to join the growing list of people attaching a potential I-D
to an email due to he cut off time for the I-D submissions.  Attached
is a draft that aims to tightly define the particular format of a SAML
2.0 bearer assertion in requesting an access token using the assertion
grant_type.   I've been working with Chuck at Salesforce.com on this
and the primary goal is to have some documentation or specification
that is sufficient to facilitate interoperability between
independently developed implementations or products.    This, of course, 
wouldn't preclude using SAML in other ways - it would only provide one concrete 
definition to implement against.

I intend to submit this as an I-D when the submission process reopens.
 Any feedback from this group would be appreciated as well as thoughts about 
this eventually becoming a working group draft.

Thanks,
Brian Campbell

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