Add stickyAuth option which is off by default (flutter#216)

* Add stickyAuth option which is off by default

* Review comments

packages/local_auth/CHANGELOG.md

@@ -1,3 +1,7 @@
+## [0.0.2]
+
+* Support stickyAuth mode.
+
 ## [0.0.1] - 6/21/2017
 
 * Initial release of local authentication plugin.

packages/local_auth/README.md

@@ -96,6 +96,15 @@ Update your project's `AndroidManifest.xml` file to include the
 <manifest>
 ```
 
+## Sticky Auth
+
+You can set the `stickyAuth` option on the plugin to true so that plugin does not
+return failure if the app is put to background by the system. This might happen
+if the user receives a phone call before they get a chance to authenticate. With
+`stickyAuth` set to false, this would result in plugin returning failure result
+to the Dart app. If set to true, the plugin will retry authenticating when the
+app resumes.
+
 ## Getting Started
 
 For help getting started with Flutter, view our online

packages/local_auth/android/src/main/java/io/flutter/plugins/localauth/AuthenticationHelper.java

@@ -73,7 +73,6 @@ interface AuthCompletionHandler {
   private final AuthCompletionHandler completionHandler;
   private final KeyguardManager keyguardManager;
   private final FingerprintManagerCompat fingerprintManager;
-  private final CancellationSignal cancellationSignal;
   private final MethodCall call;
 
   /**
@@ -82,12 +81,13 @@ interface AuthCompletionHandler {
    */
   private AlertDialog fingerprintDialog;
 
+  private CancellationSignal cancellationSignal;
+
   AuthenticationHelper(
       Activity activity, MethodCall call, AuthCompletionHandler completionHandler) {
     this.activity = activity;
     this.completionHandler = completionHandler;
     this.call = call;
-    this.cancellationSignal = new CancellationSignal();
     this.keyguardManager = (KeyguardManager) activity.getSystemService(Context.KEYGUARD_SERVICE);
     this.fingerprintManager = FingerprintManagerCompat.from(activity);
   }
@@ -112,23 +112,31 @@ void authenticate() {
     }
   }
 
-  /** Starts the fingerprint listener and shows the fingerprint dialog. */
   private void start() {
     activity.getApplication().registerActivityLifecycleCallbacks(this);
+    resume();
+  }
+
+  private void resume() {
+    cancellationSignal = new CancellationSignal();
     showFingerprintDialog();
     fingerprintManager.authenticate(null, 0, cancellationSignal, this, null);
   }
 
+  private void pause() {
+    cancellationSignal.cancel();
+    if (fingerprintDialog != null && fingerprintDialog.isShowing()) {
+      fingerprintDialog.dismiss();
+    }
+  }
+
   /**
    * Stops the fingerprint listener and dismisses the fingerprint dialog.
    *
    * @param success If the authentication was successful.
    */
   private void stop(boolean success) {
-    cancellationSignal.cancel();
-    if (fingerprintDialog != null && fingerprintDialog.isShowing()) {
-      fingerprintDialog.dismiss();
-    }
+    pause();
     activity.getApplication().unregisterActivityLifecycleCallbacks(this);
     if (success) {
       completionHandler.onSuccess();
@@ -143,7 +151,18 @@ private void stop(boolean success) {
    */
   @Override
   public void onActivityPaused(Activity activity) {
-    stop(false);
+    if (call.argument("stickyAuth")) {
+      pause();
+    } else {
+      stop(false);
+    }
+  }
+
+  @Override
+  public void onActivityResumed(Activity activity) {
+    if (call.argument("stickyAuth")) {
+      resume();
+    }
   }
 
   @Override
@@ -261,9 +280,6 @@ public void onActivityCreated(Activity activity, Bundle bundle) {}
   @Override
   public void onActivityStarted(Activity activity) {}
 
-  @Override
-  public void onActivityResumed(Activity activity) {}
-
   @Override
   public void onActivityStopped(Activity activity) {}
 

packages/local_auth/example/lib/main.dart

@@ -25,7 +25,8 @@ class _MyAppState extends State<MyApp> {
     try {
       authenticated = await auth.authenticateWithBiometrics(
           localizedReason: 'Scan your fingerprint to authenticate',
-          useErrorDialogs: true);
+          useErrorDialogs: true,
+          stickyAuth: false);
     } on PlatformException catch (e) {
       print(e);
     }

packages/local_auth/ios/Classes/LocalAuthPlugin.m

@@ -5,13 +5,17 @@
 
 #import "LocalAuthPlugin.h"
 
-@implementation LocalAuthPlugin
+@implementation LocalAuthPlugin {
+  NSDictionary *lastCallArgs;
+  FlutterResult lastResult;
+}
 + (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar> *)registrar {
   FlutterMethodChannel *channel =
       [FlutterMethodChannel methodChannelWithName:@"plugins.flutter.io/local_auth"
                                   binaryMessenger:[registrar messenger]];
   LocalAuthPlugin *instance = [[LocalAuthPlugin alloc] init];
   [registrar addMethodCallDelegate:instance channel:channel];
+  [registrar addApplicationDelegate:instance];
 }
 
 - (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result {
@@ -45,7 +49,7 @@ - (void)alertMessage:(NSString *)message
         actionWithTitle:secondButton
                   style:UIAlertActionStyleDefault
                 handler:^(UIAlertAction *action) {
-                  if (&UIApplicationOpenSettingsURLString != NULL) {
+                  if (UIApplicationOpenSettingsURLString != NULL) {
                     NSURL *url = [NSURL URLWithString:UIApplicationOpenSettingsURLString];
                     [[UIApplication sharedApplication] openURL:url];
                     result(@NO);
@@ -62,6 +66,8 @@ - (void)authenticateWithBiometrics:(NSDictionary *)arguments
                  withFlutterResult:(FlutterResult)result {
   LAContext *context = [[LAContext alloc] init];
   NSError *authError = nil;
+  lastCallArgs = nil;
+  lastResult = nil;
   context.localizedFallbackTitle = @"";
 
   if ([context canEvaluatePolicy:LAPolicyDeviceOwnerAuthenticationWithBiometrics
@@ -81,6 +87,12 @@ - (void)authenticateWithBiometrics:(NSDictionary *)arguments
                                    flutterArguments:arguments
                                   withFlutterResult:result];
                               return;
+                            case LAErrorSystemCancel:
+                              if ([arguments[@"stickyAuth"] boolValue]) {
+                                lastCallArgs = arguments;
+                                lastResult = result;
+                                return;
+                              }
                           }
                           result(@NO);
                         }
@@ -97,7 +109,7 @@ - (void)handleErrors:(NSError *)authError
   switch (authError.code) {
     case LAErrorPasscodeNotSet:
     case LAErrorTouchIDNotEnrolled:
-      if (arguments[@"useErrorDialogs"]) {
+      if ([arguments[@"useErrorDialogs"] boolValue]) {
         [self alertMessage:arguments[@"goToSettingDescriptionIOS"]
                  firstButton:arguments[@"okButton"]
                flutterResult:result
@@ -118,4 +130,12 @@ - (void)handleErrors:(NSError *)authError
                              details:authError.domain]);
 }
 
+#pragma mark - AppDelegate
+
+- (void)applicationDidBecomeActive:(UIApplication *)application {
+  if (lastCallArgs != nil && lastResult != nil) {
+    [self authenticateWithBiometrics:lastCallArgs withFlutterResult:lastResult];
+  }
+}
+
 @end

packages/local_auth/lib/local_auth.dart

@@ -25,13 +25,21 @@ class LocalAuthentication {
   /// for authentication. This is typically along the lines of: 'Please scan
   /// your finger to access MyApp.'
   ///
-  /// useErrorDialogs = true means the system will attempt to handle user
+  /// [useErrorDialogs] = true means the system will attempt to handle user
   /// fixable issues encountered while authenticating. For instance, if
   /// fingerprint reader exists on the phone but there's no fingerprint
   /// registered, the plugin will attempt to take the user to settings to add
   /// one. Anything that is not user fixable, such as no biometric sensor on
   /// device, will be returned as a [PlatformException].
   ///
+  /// [stickyAuth] is used when the application goes into background for any
+  /// reason while the authentication is in progress. Due to security reasons,
+  /// the authentication has to be stopped at that time. If stickyAuth is set
+  /// to true, authentication resumes when the app is resumed. If it is set to
+  /// false (default), then as soon as app is paused a failure message is sent
+  /// back to Dart and it is up to the client app to restart authentication or
+  /// do something else.
+  ///
   /// Construct [AndroidAuthStrings] and [IOSAuthStrings] if you want to
   /// customize messages in the dialogs.
   ///
@@ -42,13 +50,15 @@ class LocalAuthentication {
   Future<bool> authenticateWithBiometrics({
     @required String localizedReason,
     bool useErrorDialogs: true,
+    bool stickyAuth: false,
     AndroidAuthMessages androidAuthStrings: const AndroidAuthMessages(),
     IOSAuthMessages iOSAuthStrings: const IOSAuthMessages(),
   }) {
     assert(localizedReason != null);
     final Map<String, Object> args = <String, Object>{
       'localizedReason': localizedReason,
       'useErrorDialogs': useErrorDialogs,
+      'stickyAuth': stickyAuth,
     };
     if (Platform.isIOS) {
       args.addAll(iOSAuthStrings.args);

packages/local_auth/pubspec.yaml

@@ -1,6 +1,6 @@
 name: local_auth
 description: A plugin that uses local sensors to authenticate users (such as Fingerprint Reader/Touch ID).
-version: 0.0.1
+version: 0.0.2
 author: Flutter Team <[email protected]>
 homepage: https://github.com/flutter/plugins/tree/master/packages/local_auth