Prevent Firebase auth from remembering Google account? - firebase

Question

So I'm using Firebase-UI to authenticate and sign in users, I need to use the account chooser in order for them to sign in to a different Google account (not using the account chooser results in it auto-signing them in), however, I want to either prevent it from displaying + saving accounts, or remove them on sign out.
And this is the Firebase-UI web I'm using: Firebase UI web
This isn't a huge issue when the application is running on a user's machine, however, it will also be running on a public machine with many users signing in an out, and we can't have them saved as an easy one-click sign in. The biggest security issue is the fact that I can also log into their emails once they've authenticated with Google. We want it to forget them once they sign out.
My sign-in flow:
<script type="text/javascript">
// FirebaseUI config.
var uiConfig = {
callbacks: {
signInSuccess: function (user, credential, redirectUrl) {
var userSignIn = {
displayName: user.displayName,
email: user.email,
emailVerified: user.emailVerified,
photoURL: user.photoURL,
uid: user.uid,
phoneNumber: user.phoneNumber
};
/* POST signed in user to Login Controller*/
var csrfToken = $('input[name="csrfToken"]').attr('value');
$.ajaxSetup({
beforeSend: function(xhr) {
xhr.setRequestHeader('Csrf-Token', csrfToken);
}
});
$.ajax({
url: '/signedIn',
type: 'POST',
data: JSON.stringify(userSignIn),
contentType: 'application/json',
error: function(err) {
console.log(err);
}
});
return true;
}
},
signInSuccessUrl: '/Dashboard',
signInOptions: [{
provider: firebase.auth.GoogleAuthProvider.PROVIDER_ID,
scopes: ['https://www.googleapis.com/auth/calendar']
}],
// Terms of service url.
tosUrl: '/Terms'
};
// Initialize the FirebaseUI Widget using FirestoreDB.
var ui = new firebaseui.auth.AuthUI(firebase.auth());
// The start method will wait until the DOM is loaded.
ui.start('#firebaseui-auth-container', uiConfig);
</script>
Sign-out flow:
initApp = function () {
firebase.auth().onAuthStateChanged(function (user) {
if (user) {
// User is signed in.
if (window.location.pathname === "/Login" || window.location.pathname === "/") {
window.location.href = '/Dashboard';
}
$('#sign-out').show();
} else {
// User is signed out.
$('#sign-out').hide();
disableLinks();
switch(window.location.pathname){
case "/Login":
case "/Terms":
case "/Help":
break;
default:
window.location.href = '/Login';
}
}
}, function (error) {
console.log(error);
});
};
window.addEventListener('load', function () {
initApp();
document.getElementById('sign-out').addEventListener('click', function () {
firebase.auth().signOut().then(function() {
sessionStorage.clear();
localStorage.clear();
window.location = "/Logout";
}).catch(function(error) {
console.log(error);
});
});
});

Answer 1

On sign out from Firebase Auth, redirect to Google single sign out URL:
firebase.auth().signOut()
.then(function() {
window.location.assign('https://accounts.google.com/Logout');
})
.catch(function(error) {
console.log(error);
});