Masamune Auth Apple for Firebase

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Masamune Auth Apple for Firebase

Usage

masamune_auth_apple_firebase bridges Apple Sign In credentials to Firebase Authentication within the Masamune/Katana auth stack. It complements:

• katana_auth – core authentication abstractions
• katana_auth_firebase – Firebase Authentication integration
• masamune_auth_apple – native Apple Sign In flow

Installation

Install the base packages first:

flutter pub add katana_auth
flutter pub add katana_auth_firebase

Then add the Apple packages:

flutter pub add masamune_auth_apple
flutter pub add masamune_auth_apple_firebase

Register Adapters

Place the adapters near the root of your application so that Apple credentials can be exchanged for Firebase tokens.

// lib/adapter.dart

/// Masamune adapters used in the application.
final masamuneAdapters = <MasamuneAdapter>[
  const UniversalMasamuneAdapter(),

  const AppleAuthMasamuneAdapter(),
  FirebaseAppleAuthMasamuneAdapter(
    functionsAdapter: const FunctionsMasamuneAdapter(),
  ),
];

Note: This package requires katana_auth and katana_auth_firebase to be installed separately. Those packages provide the core authentication infrastructure.

FirebaseAppleAuthMasamuneAdapter expects a Cloud Functions endpoint (or direct Firebase SDK) capable of validating Apple ID tokens and minting Firebase credentials.

Authenticate Users

Use Authentication from katana_auth to trigger Apple Sign In and automatically sign the user into Firebase.

class SignInPage extends PageScopedWidget {
  @override
  Widget build(BuildContext context, PageRef ref) {
    final auth = ref.app.controller(Authentication.query());

    // Initialize on page load
    ref.page.on(
      initOrUpdate: () {
        auth.initialize();
      },
    );

    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            if (auth.isSignedIn)
              Column(
                children: [
                  Text("Signed in with Apple"),
                  Text("User ID: ${auth.userId}"),
                  Text("Email: ${auth.userEmail ?? 'N/A'}"),
                  TextButton(
                    onPressed: () => auth.signOut(),
                    child: const Text("Sign Out"),
                  ),
                ],
              )
            else
              ElevatedButton.icon(
                icon: Icon(Icons.apple),
                label: const Text("Sign in with Apple"),
                onPressed: () async {
                  try {
                    await auth.signIn(AppleAuthQuery.signIn());
                  } catch (e) {
                    print("Sign in failed: $e");
                  }
                },
              ),
          ],
        ),
      ),
    );
  }
}

Upon success, auth.isSignedIn becomes true and Firebase Authentication will contain the linked user record.

Cloud Functions Validation

Implement the provided FirebaseAppleAuthFunctionsAction on your server to verify Apple credentials. A high-level outline:

1. Receive the identity token and authorization code from the client.
2. Validate the token using Apple’s public keys.
3. Exchange the authorization code (if provided) for user information.
4. Mint a Firebase custom token or sign in via signInWithCredential.
5. Return the Firebase ID token back to the app.

Linking and Anonymous Upgrade

• Use auth.link(AppleAuthQuery.link()) to attach Apple Sign In to an existing account.
• Anonymous users can upgrade to Apple Sign In while preserving data.

iOS-Specific Setup

• Enable Sign In with Apple in the Apple Developer portal.
• Configure your services ID, redirect URI, and keys.
• Update Info.plist with the required entitlements and URL schemes.

Tips

• Test on real devices; the simulator does not fully support Apple Sign In token flows.
• Use AuthLoggerAdapter to record sign-in attempts and error states.
• Provide fallbacks for users who cannot use Apple Sign In (e.g., additional provider or email/password).
• Keep your Cloud Functions secure and monitor token exchange errors for debugging.

GitHub Sponsors

Sponsors are always welcome. Thank you for your support!

https://github.com/sponsors/mathrunet