[Openid-specs-ab] Securing token requests when discovery service is used

Preibisch, Sascha H Sascha.Preibisch at ca.com
Fri Oct 30 18:27:36 UTC 2015


Hi!

Now that IIW is over I would like to bring up my thoughts regarding the
session we had with John regarding the discovery service issue.

If I am the 'bad' discovery service provider I can fake all values within
the discovery response. Except for the /token endpoint. That has to point
to my system in order for me to receive the authorization_code and client
credentials.

Therefore I believe there are two solutions:

* the discovery response to the client has to include a secret which has to be included
in the initial /authorize request. The authorization server validates the
value and fails the request if it is invalid. This of course has the
drawback that the authorization server has to keep state. As a server guy
I would not like to support this flow

* The better solution I see, and as I mentioned during the discussion, is
that the client should include the target /token endpoint as an additional
request parameter for the initial /authorize request. The authorization
server does a simple string comparison and fails if the /token endpoint is
not the one as expected

Regards,
Sascha
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