Re: [OAUTH-WG] OAUTB for Access Token in Implicit Grant

Typically when an access token is issued via the implicit grant directly
from the authorization endpoint, it is for a client that is running as
script in the user-agent. The AS binds the access token to the referred
token binding, which would be the token binding between the user-agent
(where the client is) and the protected resource.

It does mean that a hybrid style client couldn't pass the access token from
its script front-end in the user-agent to its server backed (well, it could
pass it but the server side couldn't use it because of the binding).

On Mon, May 14, 2018 at 6:46 AM, <pedram.h@gmx.de> wrote:

> Dear all,
>
> We are currently modeling part 1 and part 2 of the OpenID Financial API in
> the FKS Web Model and have a few questions regarding the OAuth 2.0 Token
> Binding.
>
> In section 3.1. of draft-ietf-oauth-token-binding-06, it is not very
> clear how an Access Token issued from the Authorization Endpoint is Token
> Bound. Is this intended to be the same as an AC issued for a web server
> client? It seems that the user-agent sends both the Provided and Referred
> Token Bindings to the AS, which means that the AS can bind the Access Token
> to the Referred Token Binding, which is the Token Binding between the
> user-agent and the client.
> However, the Access Token is not used by the user-agent, which means that
> the client can only send the Token Binding ID used by the user-agent (which
> essentially is the public key) to the Resource Server.
>
> Is this the intended flow of the Token Binding? Because the first
> paragraph of 3.1 says that the "Token Binding ID of the client's TLS
> channel to the protected resource is sent with the authorization request as
> the Referred Token Binding ID", but we assume that the user-agent reveals
> the TB-ID of its own channel to the client.
>
> Best regards,
> Pedram Hosseyni
>
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>

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