Authenticate with Firebase on iOS Using a Custom Authentication System

You can integrate Firebase Authentication with a custom authentication system by modifying your authentication server to produce custom signed tokens when a user successfully signs in. Your app receives this token and uses it to authenticate with Firebase.

Before you begin

  1. Add Firebase to your iOS project.
  2. Include the following pods in your Podfile:
    pod 'Firebase/Auth'
    
  3. Get your project's server keys:
    1. Go to the Service Accounts page in your project's settings.
    2. Click Generate New Private Key at the bottom of the Firebase Admin SDK section of the Service Accounts page.
    3. The new service account's public/private key pair is automatically saved on your computer. Copy this file to your authentication server.

Authenticate with Firebase

  1. Import the Firebase module in your UIApplicationDelegate subclass:

    Swift

    import Firebase
    

    Objective-C

    @import Firebase;
    
  2. Configure a FIRApp shared instance, typically in your application's application:didFinishLaunchingWithOptions: method:

    Swift

    // Use Firebase library to configure APIs
    FIRApp.configure()
    

    Objective-C

    // Use Firebase library to configure APIs
    [FIRApp configure];
    
  3. When users sign in to your app, send their sign-in credentials (for example, their username and password) to your authentication server. Your server checks the credentials and returns a custom token if they are valid.
  4. After you receive the custom token from your authentication server, pass it to signInWithCustomToken to sign in the user:

    Swift

    FIRAuth.auth()?.signIn(withCustomToken: customToken ?? "") { (user, error) in
      // ...
    }

    Objective-C

    [[FIRAuth auth] signInWithCustomToken:customToken
                               completion:^(FIRUser *_Nullable user,
                                            NSError *_Nullable error) {
                                 // ...
                               }];

Next steps

After a user signs in for the first time, a new user account is created and linked to the credentials—that is, the user name and password, or auth provider information—the user signed in with. This new account is stored as part of your Firebase project, and can be used to identify a user across every app in your project, regardless of how the user signs in.

  • In your apps, you can get the user's basic profile information from the FIRUser object. See Manage Users.

  • In your Firebase Realtime Database and Cloud Storage Security Rules, you can get the signed-in user's unique user ID from the auth variable, and use it to control what data a user can access.

You can allow users to sign in to your app using multiple authentication providers by linking auth provider credentials to an existing user account.

To sign out a user, call signOut:.

Swift

    let firebaseAuth = FIRAuth.auth()
do {
  try firebaseAuth?.signOut()
} catch let signOutError as NSError {
  print ("Error signing out: %@", signOutError)
}
  

Objective-C

    NSError *signOutError;
BOOL status = [[FIRAuth auth] signOut:&signOutError];
if (!status) {
  NSLog(@"Error signing out: %@", signOutError);
  return;
}

You may also want to add error handling code for the full range of authentication errors. See Handle Errors.

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