[FIXED] How do I debug authentication in Firebase?

Issue

Currently, when I set authentication signinflow to redirect, the login process doesn't complete, although it does go to the Google or Facebook login screen. However, when I set the signinflow to popup, the authentication process works as intended. What I'm curious about is how do I go about debugging the authentication in Firebase? The console only shows front-end javascript related code obviously, and the DebugView in the firebase console doesn't show anything when I login or logout whether it's via popup or redirect. What are the steps involved in finding out where the authentication error is in relation to the redirect signinflow mode?

My app.js code is as follows:

firebaseUI.start('#firebaseui-auth-container', {
    signInFlow: 'redirect',
    signInSuccessUrl: 'http://www.bing.com',
    signInOptions: [
      firebaseDB.firebase_.auth.EmailAuthProvider.PROVIDER_ID,
      firebaseDB.firebase_.auth.GoogleAuthProvider.PROVIDER_ID,
      firebaseDB.firebase_.auth.FacebookAuthProvider.PROVIDER_ID
    ],
  });

  firebase.auth().onAuthStateChanged(user => {
    if (user) {
      console.log(user.displayName);
    } else {
      console.log('no user signed in');
    }
  });

Solution

Several tips come to mind:

(1) Look carefully at the JavaScript console logs on your browser. JavaScript is rather notorious for "spit out an error-message (in a place where you'd ordinarily never see it ...) and keep going."

(2) Look carefully at the server-side logs, both for Firebase and for the web server. The sequence of interest probably involves one or more "round trips" between several different pieces of software, and you need to methodically, systematically reconstruct exactly what took place and in what sequence. "The whole time-line."

(3) "Don't assume!" "Trust, but verify," as they say. Don't act on any "assumption" as to what the actual problem is – e.g. here you probably "assume" that it's a problem in "Firebase authentication." Assumptions can send you "chasing after white rabbits" for a distressingly long time, only to come up empty-handed. (Trust me on this one ...)

You probably won't get too much useful information from a "TCP/IP dumper" (such as tcpdump ...) because the communications is probably encrypted.

Answered By - Mike Robinson

Answer Checked By - Clifford M. (PHPFixing Volunteer)