Authentication Flow Security

In this lesson, you will learn how to orchestrate OAuth and biometric authentication flows so that user credentials never touch your application’s memory in plain text.

When integrating authentication in a React Native app, the biggest security risk isn't just the server connection—it's how the app handles the "handshake" between the native hardware (like FaceID) and your remote identity provider (like Google or Auth0).

The Secure Handshake

For OAuth, you should never implement a custom login form that captures usernames and passwords inside your JS bundle. Instead, use an "In-App Browser" approach (via WebBrowser modules). This ensures the user enters credentials on the provider’s own site, preventing your app from ever having access to the raw password. Once the authentication succeeds, the provider returns an access token, which must be immediately moved to Secure Storage (like iOS Keychain or Android Keystore) rather than kept in a global state variable.

For Biometric Authentication, the flow is different. You aren’t storing the user’s fingerprint; you are generating a cryptographic key pair managed by the device's Secure Enclave. Your app asks the device to "unlock" the private key via biometric verification. If the user passes, the device signs a challenge string, which you send to your server to prove identity.

Conceptual Implementation

Think of your authentication state as a gatekeeper. You should isolate the auth logic so that if the authentication fails or is interrupted, the app automatically transitions to a locked state:

// A conceptual flow for securing biometrics
const authenticateUser = async () => {
  const result = await LocalAuthentication.authenticateAsync();
  if (result.success) {
    const token = await SecureStore.getItemAsync('user_token');
    // Proceed to sensitive dashboard
  } else {
    // Force app to lock state/clear cache immediately
    AppState.removeChangeListener();
  }
};

By decoupling the authentication UI from your business logic and utilizing hardware-backed security, you ensure that even if an attacker intercepts the network traffic or inspects the app bundle, they cannot extract sensitive credentials.

Key Takeaway: Never handle raw passwords in your JS layer; use system-managed web sessions for OAuth and hardware-backed cryptographic keys for biometrics.