Is it possible to modify the authenticated user ID right before its creation in Firebase, especially when the user is being created via the Facebook provider?

Question

Is it possible to modify the authenticated user ID right before its creation in Firebase, especially when the user is being created via the Facebook provider?

As we transition our MongoDB database to Firebase with Firestore, we are facing the challenge of integrating Firebase authentication for our users. Currently, we store user data in Firestore and want to utilize Firebase authentication for user logins. Each user within our Firestore has a Facebook ID stored in their document, which we aim to use to create an Auth account.

Creating a Facebook user programmatically using cloud functions is not feasible. Our proposed solution involves implementing a cloud function that checks if a new Facebook user's ID already exists in our Firestore when they sign up. However, this approach is hindered by the fact that the authentication UID is set upon creation and cannot be modified. Ideally, we would like the authentication ID to match the user's document name.

Potential Solutions

Introducing a Redirect Collection for New Users

Initially, we considered creating a new collection of documents where Facebook user UIDs would be mapped to their corresponding documents with their original UIDs. However, this would significantly increase read operations and inflate our Firestore bill.

Changing User Document Names

Alternatively, we could rename user documents to align with the authentication UID. This would streamline the process and minimize changes required to handle authenticated users. Yet, updating all references to the user poses a substantial challenge, especially with a large user base.

We are actively searching for solutions to address this issue. Any feedback or suggestions to help guide us in the right direction would be greatly appreciated. Feel free to ask any questions for clarification. Thank you for your interest!

typescript google-cloud-firestore firebase-authentication facebook-login

Answer 1

Answer №1

To successfully resolve this issue, you can utilize a firebase auth trigger in conjunction with custom claims.

Implementing the Auth Trigger

Begin by creating a firebase auth trigger function that will be triggered after the user account is created.

import { auth } from 'firebase-functions';

export const onUserCreate = auth.user().onCreate((user) => { ... })

Within the trigger function, retrieve the necessary document and incorporate its value into a custom user claim using the admin SDK.

Setting a Custom Claim

import * as admin from 'firebase-admin';

...
const claims = user.customClaims || {};
admin.auth().setCustomUserClaims(user.uid, { ...claims, oldFacebookId: "value here"  });
...

Accessing Custom Claims

Although custom claims must be set through the admin SDK, they can easily be accessed client-side without any complications when the user logs in.

firebase.auth().onAuthStateChanged((user) => {
      if (user) {
        user?.getIdTokenResult().then((token) => {
          const oldFacebookId: token.claims.oldFacebookId;
          ... implement necessary actions
         });

       return;
      }
});

By utilizing the onAuthStateChanged listener along with getIdTokenResult, you can conveniently retrieve the claim whenever the user is logged in or their state is automatically updated by the firebase SDK within your application.

Answer 2

To successfully resolve this issue, you can utilize a firebase auth trigger in conjunction with custom claims.

Implementing the Auth Trigger

Begin by creating a firebase auth trigger function that will be triggered after the user account is created.

import { auth } from 'firebase-functions';

export const onUserCreate = auth.user().onCreate((user) => { ... })

Within the trigger function, retrieve the necessary document and incorporate its value into a custom user claim using the admin SDK.

Setting a Custom Claim

import * as admin from 'firebase-admin';

...
const claims = user.customClaims || {};
admin.auth().setCustomUserClaims(user.uid, { ...claims, oldFacebookId: "value here"  });
...

Accessing Custom Claims

Although custom claims must be set through the admin SDK, they can easily be accessed client-side without any complications when the user logs in.

firebase.auth().onAuthStateChanged((user) => {
      if (user) {
        user?.getIdTokenResult().then((token) => {
          const oldFacebookId: token.claims.oldFacebookId;
          ... implement necessary actions
         });

       return;
      }
});

By utilizing the onAuthStateChanged listener along with getIdTokenResult, you can conveniently retrieve the claim whenever the user is logged in or their state is automatically updated by the firebase SDK within your application.

Answer 3

Answer №2

To have control over the UID in Firebase Authentication, one can utilize a custom provider. Through this method, it is possible to generate personalized tokens containing any desired UID within Cloud Functions or other secure environments.

Answer 4

To have control over the UID in Firebase Authentication, one can utilize a custom provider. Through this method, it is possible to generate personalized tokens containing any desired UID within Cloud Functions or other secure environments.

Is it possible to modify the authenticated user ID right before its creation in Firebase, especially when the user is being created via the Facebook provider?

Potential Solutions

Introducing a Redirect Collection for New Users

Changing User Document Names

Answer №1

Answer №2

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