Unity/Firebase How to authenticate using Google?

Question

I'm trying to implement Firebase Authentication system in my Unity Game Project. Everything is setup properly on the console panel on the website. I've read the docs and can't find a way to login into Google using any api within Firebase within Unity. So I bought Prime31's Play GameServices Plugin for Unity.

Here are my questions:

1. How to authenticate using Google right within Firebase? Do I need to manage the google sign in myself?

2. In the Firebase docs I did find:

"After a user successfully signs in, exchange the access token for a Firebase credential, and authenticate with Firebase using the Firebase credential:"

Firebase.Auth.Credential credential = Firebase.Auth.GoogleAuthProvider.GetCredential(googleIdToken, googleAccessToken); auth.SignInWithCredentialAsync(credential).ContinueWith(task => { //......// });

How can I get the googleIdToken, googleAccessToken which are being passed as parameters above?

Please help (with code). I really like Firebase and would like to make it work without any third party plugins like PRIME31.

Answer 1

Here is the entirety of my Google SignIn code w/ Firebase Authentication and GoogleSignIn libraries:

private void SignInWithGoogle(bool linkWithCurrentAnonUser)
   {
      GoogleSignIn.Configuration = new GoogleSignInConfiguration
      {
         RequestIdToken = true,
         // Copy this value from the google-service.json file.
         // oauth_client with type == 3
         WebClientId = "[YOUR API CLIENT ID HERE].apps.googleusercontent.com"
      };

      Task<GoogleSignInUser> signIn = GoogleSignIn.DefaultInstance.SignIn();

      TaskCompletionSource<FirebaseUser> signInCompleted = new TaskCompletionSource<FirebaseUser>();
      signIn.ContinueWith(task =>
      {
         if (task.IsCanceled)
         {
            signInCompleted.SetCanceled();
         }
         else if (task.IsFaulted)
         {
            signInCompleted.SetException(task.Exception);
         }
         else
         {
            Credential credential = Firebase.Auth.GoogleAuthProvider.GetCredential(((Task<GoogleSignInUser>)task).Result.IdToken, null);
            if (linkWithCurrentAnonUser)
            {
               mAuth.CurrentUser.LinkWithCredentialAsync(credential).ContinueWith(HandleLoginResult);
            }
            else
            {
               SignInWithCredential(credential);
            }
         }
      });
   }

The parameter is for signing in with intentions of linking the new google account with an anonymous user that is currently logged on. You can ignore those parts of the method if desired. Also note all of this is called after proper initialization of the Firebase Auth libraries.

I used the following libraries for GoogleSignIn: https://github.com/googlesamples/google-signin-unity

The readme page from that link will take you through step-by-step instructions for getting this setup for your environment. After following those and using the code above, I have this working on both android and iOS.

Here is the SignInWithCredential method used in the code above:

private void SignInWithCredential(Credential credential)
   {
      if (mAuth != null)
      {
         mAuth.SignInWithCredentialAsync(credential).ContinueWith(HandleLoginResult);
      }
   }

mAuth is a reference to FirebaseAuth:

mAuth = Firebase.Auth.FirebaseAuth.DefaultInstance;