biometric_storage

Encrypted file store, optionally secured by biometric lock for Android, iOS, MacOS and partial support for Linux, Windows and Web.

Meant as a way to store small data in a hardware encrypted fashion. E.g. to store passwords, secret keys, etc. but not massive amounts of data.

Android: Uses androidx with KeyStore.
iOS and MacOS: LocalAuthentication with KeyChain.
Linux: Stores values in Keyring using libsecret. (No biometric authentication support).
Windows: Uses wincreds.h to store into read/write into credential store.
Web: Warning Uses unauthenticated, unencrypted storage in localStorage. If you have a better idea for secure storage on web platform, please open an Issue.

Check out AuthPass Password Manager for a app which makes heavy use of this plugin.

Getting Started

Installation

Android

Requirements:

Android: API Level >= 23 (android/app/build.gradle minSdkVersion 23)
Make sure to use the latest kotlin version:
android/build.gradle: ext.kotlin_version = '1.4.31'
MainActivity must extend FlutterFragmentActivity
Theme for the main activity must use Theme.AppCompat thme. (Otherwise there will be crashes on Android < 29) For example:

android/app/src/main/AndroidManifest.xml:

<activity
    android:name=".MainActivity"
    android:launchMode="singleTop"
    android:theme="@style/LaunchTheme">
    [...]
    <meta-data
          android:name="io.flutter.embedding.android.NormalTheme"
          android:resource="@style/NormalTheme"
          />
</activity>

android/app/src/main/res/values/styles.xml:

<resources>
  <style name="LaunchTheme" parent="Theme.AppCompat.NoActionBar">
    ...
  </style>
  <style name="NormalTheme" parent="Theme.AppCompat.NoActionBar">
    ...
  </style>
</resources>

Resources

iOS

https://developer.apple.com/documentation/localauthentication/logging_a_user_into_your_app_with_face_id_or_touch_id

include the NSFaceIDUsageDescription key in your app’s Info.plist file
Supports all iOS versions supported by Flutter. (ie. iOS 12)

Known Issue: since iOS 15 the simulator seem to no longer support local authentication: https://developer.apple.com/forums/thread/685773

Mac OS

include the NSFaceIDUsageDescription key in your app’s Info.plist file
enable keychain sharing and signing. (not sure why this is required. but without it You will probably see an error like:

SecurityError, Error while writing data: -34018: A required entitlement isn't present.
Supports all MacOS Versions supported by Flutter (ie. >= MacOS 10.14)

Usage

You basically only need 4 methods.

Check whether biometric authentication is supported by the device

  final response = await BiometricStorage().canAuthenticate()
  if (response != CanAuthenticateResponse.success) {
    // panic..
  }

Create the access object

  final store = BiometricStorage().getStorage('mystorage');

Read data

  final data = await storageFile.read();

Write data

  final myNewData = 'Hello World';
  await storageFile.write(myNewData);

authpass / biometric_storage

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