Re: [GNAP] Support of FIDO

OAuth 2.0 goal was not to get rid of usernames and passwords. It was to
stop site A from asking for the user's username and password at site B so
that site A could access resources at site B.

How the AS authenticates the User is out of scope, and I think should be
out of scope. There are a plethora of authentication mechanisms, and
standardizing how the user authenticates is not required for interop.
Sharing the "quality" of the authentication is an area of standardization
that has been done in OpenID Connect, and I think should be included in
GNAP.

Having said that, the Client could optionally use FIDO to authenticate the
User and somehow transmit that to the AS.

ᐧ

On Thu, Aug 13, 2020 at 10:31 AM Denis <denis.ietf@free.fr> wrote:

> This topic has already been tackled on the list, but I open a new thread
> for it.
>
> In OAuth 2.0, one of the goals was to get rid of IDs and passwords. Since
> the solution in OAuth 2.0 was to use access tokens,
> there have been used everywhere, even when they were not strictly needed.
>
> It is also possible to get rid of IDs and passwords using FIDO. FIDO
> discloses no private information at all about the user
> and no trust relationships need to be defined since there is no AS.
>
> FIDO should be one allowed possibility for the user authentication. In the
> case of FIDO, the user is authenticated under a pseudonym
> specific to the RS. It may observed that there is no equivalent in OAuth
> because of the two different semantics of the subject claim.
>
> RFC 7519 states:
>
> The "sub" (subject) claim identifies the principal that is the subject of
> the JWT.  The claims in a JWT are normally statements about the subject.
> The subject value MUST either be scoped to be locally unique in the
> context of the issuer or be globally unique.
>
> In one case, it is possible to link the subject claim of two users between
> two RSs (i.e. using a locally unique identifier in the context of the
> issuer)
> while in the other case (i.e. using a globally unique identifier) it is
> possible, in addition, to link the subject claim between one RS and any
> other server
> (i.e. not supporting OAuth) that is using the same globally unique
> identifier.
>
> None of these two semantics fit with the FIDO use case where the subject
> value is scoped to be locally unique in the context of one RS.
> Hence, the linkage of users between two RSs (or between one RS and any
> other server) becomes impossible.
>
> There are cases where a user would like to enjoy the unlinkeability
> properties of FIDO which cannot be met using the claims currently defined
> in OAuth.
>
> Denis
>
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