[keycloak-dev] direct exchanges

[Bill Burke]

I 100% agree that direct/custom grant is not the best way to do it.
The question is, is it something we should provide as an *additional*
exchange feature?  I think yes.  The way I plan to secure it is as
follows:

* client must be confidential and be secured by a secret or some other
mechanism configured for that client
* client must have permission to exchange tokens for target client
* client must have permission to impersonate users
* user must be impersonateable.


On Thu, Sep 14, 2017 at 3:04 AM, Schuster Sebastian (INST/ESY1)
<Sebastian.Schuster at bosch-si.com> wrote:
> While I do understand the reasons for introducing this feature. I am not convinced a custom grant is the best way to do it. Wouldn't it be better to expect that any external mechanism has some way of proving a user has been authenticated and only being able to get an access token in exchange for that proof (e.g. ID Token, Assertion, whatever). That's more in line with the current standardization efforts on token exchange...
>
> Best regards,
> Sebastian
>
> Mit freundlichen Grüßen / Best regards
>
> Dr.-Ing.  Sebastian Schuster
>
> Engineering and Support (INST/ESY1)
> Bosch Software Innovations GmbH | Schöneberger Ufer 89-91 | 10785 Berlin | GERMANY | www.bosch-si.com
> Tel. +49 30 726112-485 | Fax +49 30 726112-100 | Sebastian.Schuster at bosch-si.com
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>
> -----Original Message-----
> From: keycloak-dev-bounces at lists.jboss.org [mailto:keycloak-dev-bounces at lists.jboss.org] On Behalf Of Bill Burke
> Sent: Mittwoch, 13. September 2017 16:52
> To: keycloak-dev <keycloak-dev at lists.jboss.org>
> Subject: [keycloak-dev] direct exchanges
>
> We have direct grants where client passes username and creds to obtain a token for that user.  We have client credentials grant to get a token for the client itself.
>
> What if we had a direct exchange where the client provides  user id or username and gets a token for that user?  The client does not have to provide user credentials.
>
> What is the use case for this?  Consider an application that is authenticated via an external mechanism.  Consider that this external mechanism does not provide any type of token, it just authenticates a username.  This application needs to talk to services secured by Keycloak.  So, with this new direct exchange mechanism, the application only needs to have a client account on the Keycloak server
> to obtain a token for a keycloak user.   Another benefit of this is
> that Keycloak does not need to understand external token formats in order to provide a token to a client that authenticates users by an external mechanism.
>
> There's some big security risks for this.  If the client's secret is
> stolen the attacker would be able to mint token for any user.   This
> is somewhat mitigated in two ways:
>
> a) If the token is minted for the client, the scope of the token can be limited, i.e. role mappings limited
>
> b) if the client is asking for a different audience (a different
> client) the client can be limited on the audience it can ask for.  (we already do this check for client to client token exchange).
>
>
>
> --
> Bill Burke
> Red Hat
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-- 
Bill Burke
Red Hat