I'd like to observe the outcome of the Authentication feature and set a header accordingly so that t...

# ktor

[mp]

I'd like to observe the outcome of the Authentication feature and set a header accordingly so that the front-end can keep track of whether or not the back-end thinks that there is an authenticated user. (I can't just rely on 401, etc, because some endpoints work with and without an authenticated user.) I can set response headers inside a `SessionAuthenticationProvider`'s validate, but that only applies when a session is present, so it won't get hit on a request with no session or an invalid session cookie. What would be a better place to apply the header that can access call.authentication.principal() or equivalent, yet will also get called on requests without sessions, etc?

[Deactivated User]

Not sure if I understand the question. I recently had to implement a route using JWT that should produce a meaningful output with and without authentication (instead of a 401 if no authentication is provided). I have proposed this:
https://github.com/ktorio/ktor/compare/authenticate.optional
Maybe not the final design, but at least a proposal.
For session-based I think that you can already decide if the session is null or not.

[mp]

the validator only gets called if the session is non-null for the applicable type:

val session = call.sessions.get<T>()
        val principal = session?.let { provider.validator(call, it) }

[mp]

I have optional authn working ok with sessions as it is -- the problem is that the authn code doesn't get called at all if there is no session.

[mp]

To rephrase, I'd like to do something like set X-authn-state = true if you have a cookie that maps to a valid session that maps to a valid user, and X-authn-state = false in all other cases

[mp]

for context, optional stuff works fine with session like so:

session<ApiSessionData>("name of optional auth") {
    validate(closureThatReturnsNullablePrincipal)    
    challenge = SessionAuthChallenge.Ignore
}

[Deactivated User]

I would open an issue for that

[mp]

ok