Signing in users with a custom authentication system

This document shows you how to use Identity Platform to sign in users with a custom authentication system. In custom authentication, you use an authentication server to produce custom signed tokens when a user successfully signs in. Your app receives this token and uses it to authenticate with Identity Platform.

Before you begin

• Install the client SDK.

• Configure your server to accept user credentials and mint custom tokens.

Signing in users

1. Collect sign-in credentials from the user.

2. Send the credentials to your server. Your server validates the request, and returns a custom JWT.

3. Pass the JWT to signInWithCustomToken() to authenticate the user with Identity Platform:

   Web version 9

   import{getAuth,signInWithCustomToken}from"firebase/auth";
   constauth=getAuth();
   signInWithCustomToken(auth,token)
   .then((userCredential)=>{
   // Signed in
   constuser=userCredential.user;
   // ...
   })
   .catch((error)=>{
   consterrorCode=error.code;
   consterrorMessage=error.message;
   // ...
   });
   auth_sign_in_custom.js 

   Web version 8

   firebase.auth().signInWithCustomToken(token)
   .then((userCredential)=>{
   // Signed in
   varuser=userCredential.user;
   // ...
   })
   .catch((error)=>{
   varerrorCode=error.code;
   varerrorMessage=error.message;
   // ...
   });
   custom.js 

What's next

• Configure custom claims on users.
• Use the REST API to integrate Identity Platform with other parts of your custom authentication system.