OAuth PKCE Flow for Kotlin Multiplatform (Android/iOS)

A Kotlin Multiplatform library for Android and iOS that provides an OAuth PKCE flow implementation.

Installation

⚠️ This is a work-in-progress library that was recently extracted from a reference project. The API is subject to change. Detailed installation instructions need to be written.

In general, the key steps for using this library are:

• Configure your iOS and Android apps to have a custom url app scheme (e.g. exampleapp://)
• Create an iOS and Android OAuth client on your server (we use Doorkeeper) for the PKCE flow and Redirect URI. Configure your iOS and Android apps with the proper client_id values.
• In your shared view model, create/inject a PKCEFlow.
• Collect the authState to be notified when the sign in process completes.
• Call startSignIn
  • On Android, in your main activity, override onNewIntent and handle the auth callback. Something like:

  override fun onNewIntent(intent: Intent) {
      // Ensure the callbackUrl is for OAuth before processing it as such.
      if (intent.data?.toString()?.startsWith(PKCE_REDIRECT_URL) == true) {
          pkceFlow.continueSignInWithCallbackOrError(dataUrl, null)
      }
  }

  • On iOS, nothing else is needed. The callback is automatically invoked by AuthenticationServices.
• When the authState.state is FINISHED, either extract/save the tokens and proceed with sign-in, or present the user with an error message. See, e.g. https://github.com/collectiveidea/oauth-kmp/blob/main/oauth-core/src/commonTest/kotlin/com/collectiveidea/oauth/PKCEFlowTest.kt#L186