What is the first parameter for Firebase.Auth.GoogleAuthProvider.GetCredential?

Question

The new Firebase for Unity support has just been released into Beta and I am trying to implement Auth with it. I already have a Google sign-in that implements the oauth2 flow using an auth code from GooglePlayGames.PlayGamesPlatform.Instance.GetServerAuthCode and sending it to a server that exchanges it for an access token using the https://www.googleapis.com/oauth2/v4/token endpoint.

I assume this access token is the second parameter of the Firebase.Auth.GoogleAuthProvider.GetCredential method, but what is the ID Token that the first parameter is asking for? Is that the token obtained from GooglePlayGames.PlayGamesPlatform.Instance.GetIdToken (same as GoogleAuthUtil.GetToken, if my reading of the docs/code is correct)?

If this is the case, why are both required? I thought the access token was all that was needed to authenticate a user with google cloud services and that the ID Token was being phased out.

Edit: After some testing, I found that passing the ID Token obtained from GooglePlayGames.PlayGamesPlatform.Instance.GetIdToken does allow Firebase to authenticate. Problem is, it asks for the user's email address every time. I'd like to avoid this if possible.

What is the difference between GetToken, GetAccessToken and GetIdToken, aside from the fact that GetIdToken requires a callback?

Answer 1

I managed to "hack" this in order to get it working... But still i think the correct method should only be using GetServerAuthCode but I cannot make it work with that.

Do your normal process of getting idToken and AccessToken the first time, when you log in to firebase get the user's email and store it in playerprefs. Then the second time if you already have the email you do this:

  AndroidJavaClass authUtil = new AndroidJavaClass("com.google.android.gms.auth.GoogleAuthUtil");
    AndroidJavaClass unity = new AndroidJavaClass("com.unity3d.player.UnityPlayer");
    AndroidJavaObject currentActivity = unity.GetStatic<AndroidJavaObject>("currentActivity");
    string idToken = authUtil.CallStatic<string>("getToken", currentActivity, PlayerData.Email, "audience:server:client_id:XXXXXXXXXX-xxxxxxxxxxxxxx.apps.googleusercontent.com"); // your client id, should be a number a dash and then a bunch of numbers and letters
    string accessToken = authUtil.CallStatic<string>("getToken", currentActivity, PlayerData.Email, "oauth2:https://www.googleapis.com/auth/plus.me");

Hope it helps although it would be greatif someone posts a solution with GetServerAuthCode cause that is the correct way