Setting custom claims for Firebase auth from flutter

Question

I'm using Firebase auth for an app, but as part of user creation I need to set some custom claims.

I've written a cloud function to set the claims when a user is created:

    const functions = require('firebase-functions');
    const admin = require('firebase-admin');
    admin.initializeApp(functions.config().firebase);

    // On sign up.
    exports.processSignUp = functions.auth.user().onCreate(user => {

    let customClaims;

    // Set custom user claims on this newly created user.
    return admin.auth().setCustomUserClaims(user.uid, {
            'https://hasura.io/jwt/claims': {
                'x-hasura-default-role': 'user',
                'x-hasura-allowed-roles': ['user'],
                'x-hasura-user-id': user.uid
            }
        })
        .then(() => {
            // Update real-time database to notify client to force refresh.
            const metadataRef = admin.database().ref("metadata/" + user.uid);
            // Set the refresh time to the current UTC timestamp.
            // This will be captured on the client to force a token refresh.
            return metadataRef.set({
                refreshTime: new Date().getTime()
            });
        })
        .then(() => {
            return admin.auth().getUser(user.uid);
        })
        .then(userRecord => {
            console.log(userRecord);
            return userRecord.toJSON();

        })
        .catch(error => {
            console.log(error);
        });
});

When I print out to the console the userRecord I can see the custom claims are set correctly.

Then in flutter I get the token from the created user, but it then doesn't seem to have the custom claims attached.

I'm using this code to create the user and print the claims in flutter

    Future<FirebaseUser> signUp({String email, String password}) async {
    final FirebaseUser user = (await auth.createUserWithEmailAndPassword(
      email: email,
      password: password,
    )).user;

    IdTokenResult result = await (user.getIdToken(refresh: true));
    print('claims : ${result.claims}');

    return user;
  }

If I inspect the token itself in a jwt debugger I can see its not got the custom claims on it. Is it that I need some additional steps to try and get an updated token once the claims have been set? I've tried user.reload() and user.getIdToken(refresh: true) but they don't seem to help.

Any ideas on how to get the token that has the custom claims?

I've found since posting that by calling AuthResult result = await auth.signInWithEmailAndPassword(email: email, password: password); before getting the claims means that I do get the custom claims. This is fine when logging in with email and password, but I don't know how I'd do the same when logging in with other auth providers such as google/facebook. — Andrew

Andrew Andrew · Accepted Answer · 2020-03-18T15:10:39

For future reference, I managed to get this working with Doug's suggestions.

Here's my firebase sdk admin function.

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp();

const firestore = admin.firestore();
const settings = {timestampsInSnapshots: true};
firestore.settings(settings);


// On sign up.
exports.processSignUp = functions.auth.user().onCreate(async user => {

// Check if user meets role criteria:
// Your custom logic here: to decide what roles and other `x-hasura-*` should the user get
let customClaims;
// Set custom user claims on this newly created user.

return admin.auth().setCustomUserClaims(user.uid, {
    'https://hasura.io/jwt/claims': {
    'x-hasura-default-role': 'user',
    'x-hasura-allowed-roles': ['user'],
    'x-hasura-user-id': user.uid
}
  })
.then(async () => {
    await firestore.collection('users').doc(user.uid).set({
        createdAt: admin.firestore.FieldValue.serverTimestamp()
    });
 })
 .catch(error => {
    console.log(error);
 });
});

Then on the flutter side of things

Future<FirebaseUser> signUp({String email, String password}) async {
    final FirebaseUser user = (await auth.createUserWithEmailAndPassword(
      email: email,
      password: password,
    )).user;
    currentUser = user;

    await waitForCustomClaims();
    return user;
}

Future waitForCustomClaims() async {
    DocumentReference userDocRef = 
    Firestore.instance.collection('users').document(currentUser.uid);
    Stream<DocumentSnapshot> docs = userDocRef.snapshots(includeMetadataChanges: false);

    DocumentSnapshot data = await docs.firstWhere((DocumentSnapshot snapshot) => snapshot?.data !=null && snapshot.data.containsKey('createdAt'));  
    print('data ${data.toString()}');

    IdTokenResult idTokenResult = await (currentUser.getIdToken(refresh: true));
    print('claims : ${idTokenResult.claims}');
}

Hopefully this will help somebody else looking to do similar.

Setting custom claims for Firebase auth from flutter

2 Answers