How to know if user is authenticated with Google auth using Firebase on Nodejs?

Question

I've used Google auth using Firebase on Android app before. But this time I want my backend server to know if user is authenticated or not. User will authenticate using Firebase auth from Flutter app. Right now I've done simple email and password auth. Flutter will send username and password to the server and server is authenticating using Firebase. But I don't know how to do in case with Google or Facebook auth.

Answer 1

Using Google or Facebook login the first thing is to login via plugging that does the authentification for you and will give you back some information about the login. Next step is to send the token to your server and the server will need to check with Google or Facebook if it's valid (With these verification we can verify that the user has done the sign in with the third party correctly).

I have used for Flutter the next dependency:

• Google: https://pub.dev/packages/google_sign_in that is created by the Flutter team.
• Facebook: https://pub.dev/packages/flutter_facebook_login.

For NodeJs verification in the Back-end:

• Google: https://www.npmjs.com/package/google-auth-library
• Facebook you need to check there documentation I know there is a API Rest that can give you back the information of the user with the token in the next url: https://graph.facebook.com/me?fields=id,name,email&access_token=

You need to follow the steps in the documentation to install the dependencies and you will need firebase.