How to create "credential" object needed by Firebase web user.reauthenticateWithCredential() method?

The (unclear) example in the new docs:

var user = firebase.auth().currentUser;
var credential;
// Prompt the user to re-provide their sign-in credentials
user.reauthenticateWithCredential(credential).then(function() {

How should I create this credential object?

I tried:

• reauthenticateWithCredential(email, password) (like the login method)
• reauthenticateWithCredential({ email, password }) (the docs mention one argument only)

No luck :(

PS: I don't count the hours wasted searching for relevant info in the new docs... I miss so much the fabulous firebase.com docs, but wanted to switch to v3 or superior for firebase.storage...

I managed to make it work, docs should be updated to include this for who does not want to spend too much time in the exhaustive-but-hard-to-read API reference.

Firebase 8.x

The credential object is created like so:

const user = firebase.auth().currentUser;
const credential = firebase.auth.EmailAuthProvider.credential(
    user.email, 
    userProvidedPassword
);
// Now you can use that to reauthenticate
user.reauthenticateWithCredential(credential);

Firebase 9.x

(Thanks @Dako Junior for his answer that I'm adding here for exhaustivity)

import {
    EmailAuthProvider,
    getAuth,
    reauthenticateWithCredential,
} from 'firebase/auth'

const auth = getAuth()
const credential = EmailAuthProvider.credential(
    auth.currentUser.email,
    userProvidedPassword
)
const result = await reauthenticateWithCredential(
    auth.currentUser, 
    credential
)
// User successfully reauthenticated. New ID tokens should be valid.

Note

Some people asked about userProvidedPassword, if it was some sort of stored variable from the first login. It is not, you should open a new dialog/page with a password input, and the user will enter their password again.

I insist that you must not try to workaround it by storing user password in cleartext. This is a normal feature for an app. In GMail for example, sometimes your session expires, or there is a suspicion of hack, you change location, etc. GMail asks for your password again. This is reauthentication.

It won't happen often but an app using Firebase should support it or the user will be stuck at some point.

Complete answer - you can use the following:

var user = firebase.auth().currentUser;
var credentials = firebase.auth.EmailAuthProvider.credential(
  user.email,
  'yourpassword'
);
user.reauthenticateWithCredential(credentials);

Please note that reauthenticateWithCredential is the updated version of reauthenticate()

There are multiple methods to re-authenticat. See the refs: https://firebase.google.com/docs/reference/js/firebase.User

firebase
.auth()
.currentUser.reauthenticateWithPopup(new firebase.auth.GoogleAuthProvider())
.then((UserCredential) => {
    console.log("re-outh", UserCredential);
});

In case your app allows multiple authentication methods you might want to first find out what privider was used. You can do this by looking at the firebase.auth().currentUser.providerData array.

With the new firebase version 9.*

import {
  EmailAuthProvider,
  getAuth,
  reauthenticateWithCredential,
} from "firebase/auth";

const auth = getAuth();


let credential = EmailAuthProvider.credential(
                  auth.currentUser.email,
                  password
                );

reauthenticateWithCredential(auth.currentUser, credential)
.then(result => {
      // User successfully reauthenticated. New ID tokens should be valid.
    })

I agree that the documentation is not pretty clear on this. But looking a little deeper on the API reference I found firebase.auth.AuthCredential and this and I guess you should be looking to pass it to reauthenticate().

I'm guessing here but I would start trying to log the firebase.auth() to see if there is any credential object there.

I suppose it will look something like the following:

user.reauthenticate(firebase.auth().credential).then(function() {

Now there's a small change in the method since both posted answers are deprecated,

    val user = auth.currentUser
    user?.let { _user ->
        val credentials = EmailAuthProvider.getCredential(
            _user.email!!,
            "userPassword"
        )
        _user.reauthenticate(credentials).addOnCompleteListener { _reauthenticateTask ->
  }

final FirebaseUser fireBaseUser = FirebaseAuth.getInstance().getCurrentUser();
AuthCredential credential = EmailAuthProvider.getCredential(fireBaseUser.getEmail(), storedPassword);
fireBaseUser.reauthenticate(credential).addOnCompleteListener(new OnCompleteListener<Void>() {
     @Override
     public void onComplete(@NonNull Task<Void> reAuthenticateTask) {
          if (!reAuthenticateTask.isSuccessful())
               ...
     }
});