signInWithCustomToken() with Firebase's own tokens

Question

I want to authenticate users on multiple websites via sharing the JWT token. The token was generated originally by firebase, so I assume it is a good and valid token (tested on jwt.io and seems to be fine). I get it by user.getToken().

As I call signInWithCustomToken(token) I always get an error auth/invalid-custom-token with a message "The custom token format is incorrect. Please check the documentation.".

What is strange, it does a HTTP POST request to https://www.googleapis.com/identitytoolkit/v3/relyingparty/verifyCustomToken... which returns HTTP 400. I have tried on both localhost and also on the https live website... but same result. I'm using Firebase 3.3.

Any ideas, what could be wrong? I was using this feature with the old Firebase.

Answer 1

You don't provide any code snippets so i am gonna speculate here.

I am assuming you are using node.js to generate the custom token. Try this in your node script:

var firebase = require("firebase");
var adminConfig = {
    serviceAccount: "serviceAccountCredentials.json"
};
var adminApp = firebase.initializeApp(adminConfig, 'admin');
var token = adminApp.auth().createCustomToken('12345678', {
    customField: 'customValue'
});

Then on the client try to signInWithCustomToken(token) Make sure the client is using the same api key that belongs to the same project where the service account was generated.