How to Build a Secure iOS App with MFA

Summary

This tutorial shows how to add secure authentication and backend authorization to an iOS app using Okta’s BrowserSignIn module from the Okta Swift SDK. It registers a native OIDC client with Authorization Code Flow and PKCE, configures redirect URIs and authorization-server policies, and recommends phishing-resistant MFA factors such as Okta Verify with biometrics and FIDO2 with WebAuthn. The implementation uses Swift Package Manager, an Okta.plist configuration file, a testable AuthService protocol, and SwiftUI views for login, token handling, user information, and authenticated state. It then demonstrates authorized API requests by attaching an access token to a URLRequest, calling a backend endpoint, decoding its response, and displaying a returned message, concluding that OAuth 2.0 and JWT validation provide integrated authorization verification.

Takeaways

1. 1

   The guide registers the iOS app as a native OIDC client and uses Authorization Code Flow with PKCE to help prevent authorization code interception attacks.

2. 2

   It recommends phishing-resistant MFA factors, including Okta Verify with biometrics and FIDO2 with WebAuthn, with policies tailored to risk, environment, and user behavior.

3. 3

   The Okta iOS SDK can automatically add an access token as an Authorization header, enabling the app to call a backend endpoint and display its response.