KMPAuth - Kotlin Multiplatform Authentication Library

Simple and easy to use Kotlin Multiplatform Authentication library targeting iOS, Android, Desktop and Web (kmpauth-firebase module doesn't have web support yet). Supporting Google, Apple, Github, Facebook authentication integrations using Firebase.
Because I am using KMPAuth in FindTravelNow production KMP project, I'll support development of this library :).
Related blog post: Integrating Google Sign-In into Kotlin Multiplatform
You can check out Documentation for full library api information.

Sample App and Code

@Composable
fun AuthUiHelperButtonsAndFirebaseAuth(
    modifier: Modifier = Modifier,
    onFirebaseResult: (Result<FirebaseUser?>) -> Unit,
) {
    Column(modifier = modifier,verticalArrangement = Arrangement.spacedBy(10.dp)) {

        //Google Sign-In Button and authentication with Firebase
        GoogleButtonUiContainerFirebase(onResult = onFirebaseResult) {
            GoogleSignInButton(modifier = Modifier.fillMaxWidth()) { this.onClick() }
        }

        //Apple Sign-In Button and authentication with Firebase
        AppleButtonUiContainer(onResult = onFirebaseResult) {
            AppleSignInButton(modifier = Modifier.fillMaxWidth()) { this.onClick() }
        }

        //Facebook Sign-In Button and authentication with Firebase
        FacebookButtonUiContainer(
            onResult = { result -> /* handle FirebaseUser result or error */ },
            linkAccount = false
        ) {
            FacebookSignInButton(onClick = { this.onClick() })
        }

        //Github Sign-In with Custom Button and authentication with Firebase
        GithubButtonUiContainer(onResult = onFirebaseResult) {
            Button(onClick = { this.onClick() }) { Text("Github Sign-In (Custom Design)") }
        }

    }
}

You can check out more sample codes here.

Features

• ✅ Google One Tap Sign-In (without Firebase)
• ✅ Google Sign-In with Firebase
• ✅ Apple Sign-In with Firebase
• ✅ Github Sign-In with Firebase
• ✅ Facebook Sign-In (android and ios) with Firebase
• ✅ Apple, Google, Facebook "Sign in with " UiHelper buttons (according to each brand's guideline)
• 📱 Multiplatform (android, iOS, jvm and web (js,wasm))

Installation

KMPAuth is available on Maven Central. In your root project build.gradle.kts file (or settings.gradle file) add mavenCentral() to repositories.

repositories { 
  mavenCentral()
}

Then in your shared module add desired dependencies in commonMain. Latest version: .

sourceSets {
  commonMain.dependencies {
    implementation("io.github.mirzemehdi:kmpauth-google:<version>") //Google One Tap Sign-In 
    implementation("io.github.mirzemehdi:kmpauth-firebase:<version>") //Integrated Authentications with Firebase
    implementation("io.github.mirzemehdi:kmpauth-uihelper:<version>") //UiHelper SignIn buttons (AppleSignIn, GoogleSignInButton)

  }
}

You will also need to include Google Sign-In and/or FirebaseAuth library to your ios app using Swift Package Manager or Cocoapods.

Note: If in iOS you get MissingResourceException, I wrote solution in this issue's comment section.

---

Google Sign-In

For Google Sign-In you can either use only one-tap sign in functionality, or also implementing firebase google authentication integration to that. You need to set up OAuth 2.0 in Google Cloud Platform Console. For steps you can follow this link. Pro Easy Tip: If you use Firebase and enable Google Sign-In authentication in Firebase it will automatically generate OAuth client IDs for each platform, and one will be Web Client ID which will be needed for identifying signed-in users in backend server.

Platform Setup

Create GoogleAuthProvider instance by providing Web Client Id as a serverID on Application start.

GoogleAuthProvider.create(credentials = GoogleAuthCredentials(serverId = WebClientId))

Android

Android Setup

There is not any platform specific setup in Android side.

iOS

iOS Setup

Add clientID, and serverId to your Info.plist file as below:

<key>GIDServerClientID</key>
<string>YOUR_SERVER_CLIENT_ID</string>

<key>GIDClientID</key>
<string>YOUR_IOS_CLIENT_ID</string>
<key>CFBundleURLTypes</key>
<array>
  <dict>
    <key>CFBundleURLSchemes</key>
    <array>
      <string>YOUR_DOT_REVERSED_IOS_CLIENT_ID</string>
    </array>
  </dict>
</array>

And finally, you need the code below to implement application delegate function calls on the Swift side.

import SwiftUI
import shared
import GoogleSignIn

class AppDelegate: NSObject, UIApplicationDelegate {

    func application(
      _ app: UIApplication,
      open url: URL, options: [UIApplication.OpenURLOptionsKey : Any] = [:]
    ) -> Bool {
      var handled: Bool

      handled = GIDSignIn.sharedInstance.handle(url)
      if handled {
        return true
      }

      // Handle other custom URL types.

      // If not handled by this app, return false.
      return false
    }


}

@main
struct iOSApp: App {
    @UIApplicationDelegateAdaptor(AppDelegate.self) var delegate
    
   var body: some Scene {
      WindowGroup {
            ContentView().onOpenURL(perform: { url in
                GIDSignIn.sharedInstance.handle(url)
            })
      }
   }
}

Usage

After configuring above steps this is how you can use:

//Google Sign-In with Custom Button (only one tap sign-in functionality)
GoogleButtonUiContainer(onGoogleSignInResult = { googleUser ->
  val idToken = googleUser?.idToken // Send this idToken to your backend to verify
}) {
  Button(onClick = { this.onClick() }) { Text("Google Sign-In(Custom Design)") }
}

Google Sign-In Button and authentication with Firebase. You need to implement kmpauth-uihelper dependency

GoogleButtonUiContainerFirebase(onResult = onFirebaseResult) {
  GoogleSignInButton(modifier = Modifier.fillMaxWidth()) { this.onClick() }
}

Google Sign-In IconOnly Button and authentication with Firebase. You need to implement kmpauth-uihelper dependency

GoogleButtonUiContainerFirebase(onResult = onFirebaseResult) {
  GoogleSignInButtonIconOnly(onClick = { this.onClick() })
}

Apple Sign-In

After enabling and configuring Apple Sign-In in Firebase, make sure you added "Sign In with Apple" capability in XCode. Then, you can use it as below in your @Composable function:

//Apple Sign-In with Custom Button and authentication with Firebase
AppleButtonUiContainer(onResult = onFirebaseResult) {
  //Any View, you just need to delegate child view's click to this UI Container's click method
  Button(onClick = { this.onClick() }) { Text("Apple Sign-In (Custom Design)") }
}

Apple Sign-In with AppleSignInButton. You need to implement kmpauth-uihelper dependency

AppleButtonUiContainer(onResult = onFirebaseResult) {
  AppleSignInButton(modifier = Modifier.fillMaxWidth()) { this.onClick() }
}

Apple Sign-In IconOnly Button. You need to implement kmpauth-uihelper dependency

AppleButtonUiContainer(onResult = onFirebaseResult) {
  AppleSignInButtonIconOnly(onClick = { this.onClick() })
}

Github Sign-In

After enabling and configuring Github Sign-In in Firebase, you can use it as below in your @Composable function:

//Github Sign-In with Custom Button and authentication with Firebase
GithubButtonUiContainer(onResult = onFirebaseResult) {
  //Any View, you just need to delegate child view's click to this UI Container's click method
  Button(onClick = { this.onClick() }) { Text("Github Sign-In (Custom Design)") }
}

Facebook Sign-In

Usage Example

//Facebook button with icon
FacebookButtonUiContainer(
    onResult = { result -> /* handle FirebaseUser result or error */ },
    linkAccount = false
) {
    FacebookSignInButtonIconOnly(onClick = { this.onClick() })
}

//Icon Only Button
FacebookButtonUiContainer(
    modifier = Modifier.fillMaxWidth().height(44.dp),
    onResult = { result -> /* handle result */ },
    linkAccount = false
) {
    FacebookSignInButton(fontSize = 19.sp) { this.onClick() }
}

//Custom Button
FacebookButtonUiContainer(
    modifier = Modifier.fillMaxWidth().height(44.dp),
    onResult = { result -> /* handle result */ },
    linkAccount = false
) {
    //Your custom Button here
    YourCustomButton(fontSize = 19.sp) { this.onClick() }
}

Android Setup

Add these to your res/values/strings.xml:

<string name="facebook_app_id">YOUR_FACEBOOK_APP_ID</string>
<string name="fb_login_protocol_scheme">fbYOUR_FACEBOOK_APP_ID</string>
<string name="facebook_client_token">YOUR_FACEBOOK_CLIENT_TOKEN</string>

Add these metadata tags and Facebook Activity to your AndroidManifest.xml inside the <application> tag:

<meta-data
    android:name="com.facebook.sdk.ApplicationId"
    android:value="@string/facebook_app_id" />

<meta-data
    android:name="com.facebook.sdk.ClientToken"
    android:value="@string/facebook_client_token" />

<activity
    android:name="com.facebook.FacebookActivity"
    android:configChanges="keyboard|keyboardHidden|screenLayout|screenSize|orientation"
    android:label="@string/app_name" />

For Facebook Login, on Your Main Activity's activity result call KMPAuth.handleFacebookActivityResult function:

override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
    KMPAuth.handleFacebookActivityResult(requestCode, resultCode, data)
    super.onActivityResult(requestCode, resultCode, data)
}

IOS Setup

Add Facebook Login SDK Swift Package, and add below to your Info.plist:

<key>CFBundleURLTypes</key>
<array>
  <dict>
    <key>CFBundleURLSchemes</key>
    <array>
      <string>fbFACEBOOK_APP_ID</string> <!-- Your Facebook App ID with 'fb' prefix -->
    </array>
  </dict>
</array>

<key>FacebookAppID</key>
<string>FACEBOOK_APP_ID</string>

<key>FacebookClientToken</key>
<string>YOUR_FACEBOOK_CLIENT_TOKEN</string>

<key>FacebookDisplayName</key>
<string>YourAppDisplayName</string>

<key>LSApplicationQueriesSchemes</key>
<array>
  <string>fbapi</string>
  <string>fb-messenger-api</string>
  <string>fbauth2</string>
  <string>fbshareextension</string>
</array>

Initialize Facebook SDK on Ios Swift side

func application(_ application: UIApplication,
                     didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]? = nil) -> Bool {
        FirebaseApp.configure()
        // Initialize Facebook SDK. 
        FBSDKCoreKit.ApplicationDelegate.shared.application(
            application,
            didFinishLaunchingWithOptions: launchOptions
        )
        return true
    }

func application(
    _ app: UIApplication,
    open url: URL,
    options: [UIApplication.OpenURLOptionsKey : Any] = [:]
) -> Bool {
    
    var handled: Bool
    handled = FBSDKCoreKit.ApplicationDelegate.shared.application(
        app,
        open: url,
        options: options
    )

    if handled {
        return true
    }
    
    return false
}

Notes

• You must configure your Facebook App in Facebook Developers Console properly and enable Firebase Facebook provider.
• Facebook Sign in is supported in Android and iOS only.
• Facebook Login for iOS - https://developers.facebook.com/docs/facebook-login/android
• Facebook Login for Android - https://developers.facebook.com/docs/facebook-login/ios
• Firebase Authentication with Facebook - https://firebase.google.com/docs/auth/android/facebook-login
• Firebase Authentication with Facebook iOS - https://firebase.google.com/docs/auth/ios/facebook-login