Getting ID token from google sign-in - kotlin

Question

I am trying to use http4k's built in oauth module to implement Google sign-in in my backend app.
Here is what I have so far:
val googleClientId = "<GoogleClientID>"
val googleClientSecret = "<GoogleClientSecret>"
// this is a test implementation of the OAuthPersistence interface, which should be
// implemented by application developers
val oAuthPersistence = InsecureCookieBasedOAuthPersistence("Google")
// pre-defined configuration exist for common OAuth providers
val oauthProvider = OAuthProvider.google(
JavaHttpClient(),
Credentials(googleClientId, googleClientSecret),
Uri.of("http://localhost:9000/oauth/callback"),
oAuthPersistence
)
val app: HttpHandler = routes(
"/oauth" bind routes(
"/" bind GET to oauthProvider.authFilter.then {
val user = contextFn(it)
Response(OK).body("authenticated!")
},
"/callback" bind GET to oauthProvider.callback
)
app.asServer(SunHttp(9000)).start()
This lets me go to http://localhost:9000/oauth and I can sign-in to my google account. Cool!
However, after the redirect, I go to the following function contextFn, which looks like this atm:
val transport = NetHttpTransport()
val jsonFactory = GsonFactory.getDefaultInstance()
val verifier = GoogleIdTokenVerifier.Builder(transport, jsonFactory)
.setAudience(listOf(googleClientId))
.build()
fun contextFn(request: Request): Principal {
// TODO: get the id token somehow, but the request header only contains the following in cookie:
// - GoogleCsrf
// - GoogleAccessToken
// - GoogleOriginalUri
val idTokenString = ""
val idToken: GoogleIdToken = verifier.verify(idTokenString)
val payload: GoogleIdToken.Payload = idToken.payload
// Print user identifier
val userId: String = payload.subject
println("User ID: $userId")
// Get profile information from payload
val email: String = payload.email
val emailVerified: Boolean = payload.emailVerified
val name = payload["name"]
return GoogleUser(email)
}
How can i get the id token? Currently I am getting the access token from google.

Answer 1

Can you try to add this scope(openid)?
I am not sure listOf or addScope support in http4k
But it missed openid scope.
val oauthProvider = OAuthProvider.google(
JavaHttpClient(),
Credentials(googleClientId, googleClientSecret),
Uri.of("http://localhost:9000/oauth/callback"),
listOf("openidScope"),
oAuthPersistence
)
oauthProvider.addScope('openid');