Custom authentication tokens in Firebase - Mini Project: Build & Apply

Custom Authentication Tokens with Firebase

📖 Scenario: You are building a secure app that needs to verify users with custom authentication tokens. These tokens allow your app to trust users who sign in through your own system.

🎯 Goal: Create a Firebase Cloud Function that generates a custom authentication token for a user with a specific user ID and a role claim.

📋 What You'll Learn

Create a variable with the user ID

Create a configuration object with custom claims

Generate a custom token using Firebase Admin SDK

Return the generated token

💡 Why This Matters

🌍 Real World

Custom authentication tokens let your app securely identify users with roles or permissions you define. This is useful when you have your own user system outside Firebase.

💼 Career

Many cloud jobs require integrating custom authentication with Firebase or other identity providers to control user access securely.

1

Set up the user ID variable

Create a variable called uid and set it to the string 'user123'.

Firebase

// Your code here

Need a hint?

Use const to declare the user ID variable.

2

Create custom claims configuration

Create a constant called customClaims and set it to an object with a key role and value 'admin'.

Firebase

const uid = 'user123';
// Your code here

Need a hint?

Use an object literal to set the role claim.

3

Generate the custom authentication token

Use admin.auth().createCustomToken(uid, customClaims) to generate a custom token and assign it to a constant called customToken. Use await since this returns a promise.

Firebase

const uid = 'user123';
const customClaims = { role: 'admin' };
// Your code here

Need a hint?

Remember to use await because createCustomToken returns a promise.

4

Return the generated token

Return the customToken from the function.

Firebase

const uid = 'user123';
const customClaims = { role: 'admin' };
const customToken = await admin.auth().createCustomToken(uid, customClaims);
// Your code here

Need a hint?

Use the return keyword to send back the token.