Things have gotten so muddled not sure where to begin, the original goal of 
this draft was to provide the function that we use in daily high volume 
production of WS-Trust as we transition to Oauth.  WS-Trust provided many 
options, one was ActAs and the other was OnBehalfOf, these were 2 distinct 
functions but could be combined (and thus the results are of a composite 
nature). There were also other options like delegateTo, Forwardable and 
Delegatable. So we have use cases for all these.

So we have straight forward scenarios for (1) a token request to be on behalf 
of a given/specified token, we also have a straight forward scenario for (2) 
requesting a token based upon a specific token. We also have complex scenarios 
for combining the semantics of both  (1) and (2) where the token request is on 
behalf of a specific token and the request is based upon a specific token, this 
happened a lot in our server to server scenarios for access to backend 
documents and services. Where we have chained services this is where the 
delegateTo, Forwardable and Delegatable options come into the scenario.

The way that this current specification is structured and written the Subject 
is always required which is a not a good thing since there may not be a 
subject, as basic token requests don’t have to have subjects (just 
authentication credentials), thus you can’t get the semantics of (2) without 
(1). Now the semantics of combing (1) and (2) seem to be not understood and 
wanting to be removed.


From: OAuth [mailto:oauth-boun...@ietf.org] On Behalf Of Justin Richer
Sent: Saturday, August 27, 2016 3:26 PM
To: Brian Campbell <bcampb...@pingidentity.com>
Cc: <oauth@ietf.org> <oauth@ietf.org>
Subject: Re: [OAUTH-WG] Following up on token exchange use case

No objections. Simplification is better, and this spec is already fairly 
convoluted with all the options turned on.

 — Justin

On Aug 26, 2016, at 1:30 PM, Brian Campbell 
<bcampb...@pingidentity.com<mailto:bcampb...@pingidentity.com>> wrote:

Looking for two things here:
1) Any objections to removing the want_composite request parameter? Please 
explain, if so. I plan to remove it in the next draft barring an outpouring of 
support to keep it.
2) Tony to explain his use case and describe what changes would be needed to 
accommodate it.

On Mon, Aug 1, 2016 at 2:00 PM, Brian Campbell 
<bcampb...@pingidentity.com<mailto:bcampb...@pingidentity.com>> wrote:
During the meeting in Berlin Tony voiced concern about a use case he had for 
token exchange. Honestly, it's still not entirely clear to me what that use 
case is or what would need to change in support of it. I'd like to better 
understand the use case and see if it's something that can reasonably be 
accommodated with Token Exchange. During the meeting Tony referred back to an 
earlier email where he said, "want_composite is not really the effect we are 
looking for since it provides for a single token, the use case we have is where 
you want the ability to use the subject_token and the actor_token in 
combination and not as a composite of only the claims."
The want_composite parameter came about during some iterative work on the 
document (between I-D publications) last year. At first the client could 
express that it wanted a composite token, one containing delegation semantics, 
with the inclusion of the actor_token parameter. One of the other editors 
suggested, however, that the actor_token token might be necessary for 
authorization in cases even when the client wasn't asking for a composite token 
and that placing the desire for delegation semantics on it was overloading the 
parameter too much. I introduced the want_composite parameter to give the 
client such a signal independent of the actor_token parameter. My (admittedly 
incomplete) understanding of WS-Trust is that the client/requester can make 
such an indication and I was trying to follow that model. However, I'm not sure 
it's needed or even makes much much sense. Ultimately it's the server's 
decision about how to construct the issued token and what to include in it. It 
is the server's policy, not a client signal, which makes the determination. So 
the want_composite parameter is really just noise that makes the spec longer. 
And, from the quote above, seems might also lead some readers to incorrect 
conclusions about what can and cannot be returned in a token exchange.
I'd propose then that the want_composite parameter be dropped from the document.


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