feat(apple_login): Implement firebase Apple Auth

examples/flutter_firebase_login/README.md

@@ -7,6 +7,7 @@ Example Flutter app built with `flutter_bloc` to implement login using Firebase.
 ## Features
 
 - Sign in with Google
+- Sign in with Apple
 - Sign up with email and password
 - Sign in with email and password
 

examples/flutter_firebase_login/lib/login/cubit/login_cubit.dart

@@ -52,4 +52,16 @@ class LoginCubit extends Cubit<LoginState> {
       emit(state.copyWith(status: FormzStatus.pure));
     }
   }
+
+  Future<void> logInWithApple() async {
+    emit(state.copyWith(status: FormzStatus.submissionInProgress));
+    try {
+      await _authenticationRepository.logInWithApple();
+      emit(state.copyWith(status: FormzStatus.submissionSuccess));
+    } on Exception {
+      emit(state.copyWith(status: FormzStatus.submissionFailure));
+    } on NoSuchMethodError {
+      emit(state.copyWith(status: FormzStatus.pure));
+    }
+  }
 }

examples/flutter_firebase_login/lib/login/view/login_form.dart

@@ -38,6 +38,8 @@ class LoginForm extends StatelessWidget {
               _LoginButton(),
               const SizedBox(height: 8.0),
               _GoogleLoginButton(),
+              const SizedBox(height: 8.0),
+              _AppleLoginButton(),
               const SizedBox(height: 4.0),
               _SignUpButton(),
             ],
@@ -139,6 +141,28 @@ class _GoogleLoginButton extends StatelessWidget {
   }
 }
 
+class _AppleLoginButton extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    return ElevatedButton.icon(
+      key: const Key('loginForm_appleLogin_raisedButton'),
+      label: const Text(
+        'SIGN IN WITH Apple',
+        style: TextStyle(color: Colors.white),
+      ),
+      style: ElevatedButton.styleFrom(
+        shape: RoundedRectangleBorder(
+          borderRadius: BorderRadius.circular(0.0),
+        ),
+        primary: Colors.black,
+      ),
+      icon: const Icon(FontAwesomeIcons.apple, color: Colors.white),
+      onPressed: () => context.read<LoginCubit>().logInWithApple(),
+    );
+  }
+}
+
 class _SignUpButton extends StatelessWidget {
   @override
   Widget build(BuildContext context) {

examples/flutter_firebase_login/packages/authentication_repository/lib/src/authentication_repository.dart

@@ -1,10 +1,14 @@
 import 'dart:async';
+import 'dart:convert';
+import 'dart:math';
 
 import 'package:authentication_repository/authentication_repository.dart';
 import 'package:cache/cache.dart';
 import 'package:firebase_auth/firebase_auth.dart' as firebase_auth;
 import 'package:google_sign_in/google_sign_in.dart';
+import 'package:sign_in_with_apple/sign_in_with_apple.dart';
 import 'package:meta/meta.dart';
+import 'package:crypto/crypto.dart';
 
 /// Thrown if during the sign up process if a failure occurs.
 class SignUpFailure implements Exception {}
@@ -15,6 +19,9 @@ class LogInWithEmailAndPasswordFailure implements Exception {}
 /// Thrown during the sign in with google process if a failure occurs.
 class LogInWithGoogleFailure implements Exception {}
 
+/// Thrown during the sign in with apple process if a failure occurs.
+class LogInWithAppleFailure implements Exception {}
+
 /// Thrown during the logout process if a failure occurs.
 class LogOutFailure implements Exception {}
 
@@ -27,13 +34,16 @@ class AuthenticationRepository {
     CacheClient? cache,
     firebase_auth.FirebaseAuth? firebaseAuth,
     GoogleSignIn? googleSignIn,
+    SignInWithApple? appleSignIn,
   })  : _cache = cache ?? CacheClient(),
         _firebaseAuth = firebaseAuth ?? firebase_auth.FirebaseAuth.instance,
-        _googleSignIn = googleSignIn ?? GoogleSignIn.standard();
+        _googleSignIn = googleSignIn ?? GoogleSignIn.standard(),
+        _appleSignIn = appleSignIn ?? SignInWithApple();
 
   final CacheClient _cache;
   final firebase_auth.FirebaseAuth _firebaseAuth;
   final GoogleSignIn _googleSignIn;
+  final SignInWithApple _appleSignIn;
 
   /// User cache key.
   /// Should only be used for testing purposes.
@@ -89,6 +99,56 @@ class AuthenticationRepository {
     }
   }
 
+  /// Starts the Sign In with Apple Flow.
+  ///
+  /// Throws a [logInWithApple] if an exception occurs.
+  Future<void> logInWithApple() async {
+    // To prevent replay attacks with the credential returned from Apple, we
+    // include a nonce in the credential request. When signing in with
+    // Firebase, the nonce in the id token returned by Apple, is expected to
+    // match the sha256 hash of `rawNonce`.
+    final rawNonce = generateNonce();
+    final nonce = sha256ofString(rawNonce);
+
+    try {
+      final appleCredential = await SignInWithApple.getAppleIDCredential(
+        scopes: [
+          AppleIDAuthorizationScopes.email,
+          AppleIDAuthorizationScopes.fullName,
+        ],
+        nonce: nonce,
+      );
+
+      // Create an `OAuthCredential` from the credential returned by Apple.
+      final credential = firebase_auth.OAuthProvider('apple.com').credential(
+        idToken: appleCredential.identityToken,
+        rawNonce: rawNonce,
+      );
+      print(credential);
+
+      await _firebaseAuth.signInWithCredential(credential);
+    } on Exception {
+      throw LogInWithAppleFailure();
+    }
+  }
+
+  /// Generates a cryptographically secure random nonce, to be included in a
+  /// credential request.
+  String generateNonce([int length = 32]) {
+    final charset =
+        '0123456789ABCDEFGHIJKLMNOPQRSTUVXYZabcdefghijklmnopqrstuvwxyz-._';
+    final random = Random.secure();
+    return List.generate(length, (_) => charset[random.nextInt(charset.length)])
+        .join();
+  }
+
+  /// Returns the sha256 hash of [input] in hex notation.
+  String sha256ofString(String input) {
+    final bytes = utf8.encode(input);
+    final digest = sha256.convert(bytes);
+    return digest.toString();
+  }
+
   /// Signs in with the provided [email] and [password].
   ///
   /// Throws a [LogInWithEmailAndPasswordFailure] if an exception occurs.

examples/flutter_firebase_login/packages/authentication_repository/pubspec.yaml

@@ -17,6 +17,8 @@ dependencies:
   google_sign_in: ^5.0.0
   meta: ^1.3.0
   very_good_analysis: ^2.1.0
+  sign_in_with_apple: ^3.0.0
+  crypto: ^3.0.0
 
 dev_dependencies:
   flutter_test: