Firebase auth: update lost phone number

Question

When a user has lost their phone number, and they want to update their account with a new phone number, what would be the best path to follow? We already have their email.

The problem is Firebase needs to send an SMS to the old phone number before updating it, which the user has lost.

My best idea so far is to authenticate them with their email, then send a request to our backend with the new phone number they entered, and then use the Firebase Admin SDK to update the user's phone number. There's just one problem here: How would I verify this new phone number, to make sure the user didn't just add some random one?

NSAlemu NSAlemu · Accepted Answer · 2020-11-23T10:31:04

Firebase has a method for phone authentication

For Android: https://firebase.google.com/docs/auth/android/phone-auth?authuser=0#send-a-verification-code-to-the-users-phone

For Web: https://firebase.google.com/docs/auth/web/phone-auth#send-a-verification-code-to-the-users-phone

For IOS: https://firebase.google.com/docs/auth/ios/phone-auth?authuser=0#send-a-verification-code-to-the-users-phone

Edit

The way to change a user's phone number is through the method below

PhoneAuthCredential credential = PhoneAuthProvider.getCredential(verificationId, code);
FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
    user.updatePhoneNumber(credentials)
            .addOnCompleteListener(new OnCompleteListener<Void>() {
                @Override
                public void onComplete(@NonNull Task<Void> task) {
                    if (task.isSuccessful()) {

                    }
                }
            });

The problem is you need to send a verification code to the user's old phone number (Links above) to create a PhoneAuthCredential (reference).

I do not know a way around that using firebase

Firebase auth: update lost phone number

1 Answers