Local authentication plugin (flutter#151)

* Initial commit of local_auth

* Make it work with example app.

* Analyzer and formatter fixes

* Fix review comments

packages/local_auth/.gitignore

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+.DS_Store
+.atom/
+.idea
+.packages
+.pub/
+build/
+ios/.generated/
+packages
+pubspec.lock

packages/local_auth/CHANGELOG.md

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+## [0.0.1] - 6/21/2017
+
+* Initial release of local authentication plugin.

packages/local_auth/LICENSE

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+// Copyright 2017 The Chromium Authors. All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//    * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

packages/local_auth/README.md

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+# local_auth
+
+This Flutter plugin provides means to perform local, on-device authentication of
+the user.
+
+This means referring to biometric authentication on iOS (Touch ID or lock code)
+and the fingerprint APIs on Android (introduced in Android 6.0).
+
+## Usage in Dart
+
+Import the relevant file:
+
+```dart
+import 'package:local_auth/local_auth.dart';
+```
+
+We have default dialogs with an 'OK' button to show authentication error
+messages for the following 2 cases:
+
+1.  Passcode/PIN/Pattern Not Set. The user has not yet configured a passcode on
+    iOS or PIN/pattern on Android.
+2.  Touch ID/Fingerprint Not Enrolled. The user has not enrolled any
+    fingerprints on the device.
+
+Which means, if there's no fingerprint on the user's device, a dialog with
+instructions will pop up to let the user set up fingerprint. If the user clicks
+'OK' button, it will return 'false'.
+
+Use the exported APIs to trigger local authentication with default dialogs:
+
+```dart
+LocalAuthentication localAuth = new LocalAuthentication();
+bool didAuthenticate =
+    await localAuth.authenticateWithBiometrics(
+    localizedReason: 'Please authenticate to show account balance');
+```
+
+If you don't want to use the default dialogs, call this API with
+'useErrorDialogs = false'. In this case, it will throw the error message back
+and you need to handle them in your dart code:
+
+```dart
+bool didAuthenticate =
+    await localAuth.authenticateWithBiometrics(
+        localizedReason: 'Please authenticate to show account balance',
+        useErrorDialogs: false);
+```
+
+You can use our default dialog messages, or you can use your own messages by
+passing in IOSAuthMessages and AndroidAuthMessages:
+
+```dart
+import 'package:local_auth/auth_strings.dart';
+
+const iosStrings = const IOSAuthMessages(
+    cancelButton: 'cancel',
+    goToSettingsButton: 'settings',
+    goToSettingsDescription: 'Please set up your Touch ID.',
+    lockOut: 'Please reenable your Touch ID');
+await localAuth.authenticateWithBiometrics(
+    localizedReason: 'Please authenticate to show account balance',
+    useErrorDialogs: false,
+    iOSAuthStrings: iosStrings);
+
+```
+
+### Exceptions
+
+There are 4 types of exceptions: PasscodeNotSet, NotEnrolled, NotAvailable and
+OtherOperatingSystem. They are wrapped in LocalAuthenticationError class. You can
+catch the exception and handle them by different types. For example:
+
+```dart
+import 'package:flutter/services.dart';
+import 'package:local_auth/error_codes.dart' as auth_error;
+
+try {
+  bool didAuthenticate = await local_auth.authenticateWithBiometrics(
+      localizedReason: 'Please authenticate to show account balance');
+} on PlatformException catch (e) {
+  if (e.code == auth_error.notAvailable) {
+    // Handle this exception here.
+  }
+}
+```
+
+## Android integration
+
+Update your project's `AndroidManifest.xml` file to include the
+`USE_FINGERPRINT` permissions:
+
+```
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+          package="com.example.app">
+  <uses-permission android:name="android.permission.USE_FINGERPRINT"/>
+<manifest>
+```
+
+## Getting Started
+
+For help getting started with Flutter, view our online
+[documentation](http://flutter.io/).
+
+For help on editing plugin code, view the [documentation](https://flutter.io/platform-plugins/#edit-code).

packages/local_auth/android/.gitignore

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+*.iml
+.gradle
+/local.properties
+/.idea/workspace.xml
+/.idea/libraries
+.DS_Store
+/build
+/captures
+
+/gradle
+/gradlew
+/gradlew.bat

packages/local_auth/android/build.gradle

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+group 'io.flutter.plugins.localauth'
+version '1.0-SNAPSHOT'
+
+buildscript {
+    repositories {
+        jcenter()
+    }
+
+    dependencies {
+        classpath 'com.android.tools.build:gradle:2.3.0'
+    }
+}
+
+allprojects {
+    repositories {
+        jcenter()
+        maven {
+            url "https://maven.google.com"
+        }
+    }
+}
+
+apply plugin: 'com.android.library'
+
+android {
+    compileSdkVersion 25
+    buildToolsVersion '25.0.3'
+
+    defaultConfig {
+        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
+    }
+    lintOptions {
+        disable 'InvalidPackage'
+    }
+}
+
+dependencies {
+    compile "com.android.support:support-v4:25.0.0"
+}

packages/local_auth/android/gradle.properties

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+org.gradle.jvmargs=-Xmx1536M

packages/local_auth/android/settings.gradle

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+rootProject.name = 'local_auth'

packages/local_auth/android/src/main/AndroidManifest.xml

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+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+  package="io.flutter.plugins.localauth"
+  android:versionCode="1"
+  android:versionName="0.0.1">
+
+  <uses-sdk android:minSdkVersion="16" android:targetSdkVersion="25" />
+</manifest>