Local Authentication

A flutter plugin that allows access to Local Authentication / Biometrics on iOS, macOS, Linux and Android (Windows Hello is a work in progress).

1. Features
2. Changelog
3. Usage 3.1. Initialization 3.2. Localization 3.3. Querying support and performing Local Authentication
4. Considerations 4.1. canAuthenticate 4.2. Supported Platforms
5. Next Steps
6. Contribution
7. License
8. Code of Conduct

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Features

• Detects if biometric authentication can be done in the current platform (canAuthenticate).

• Triggers platform's native authentication for the current user (authenticate).

• Read/Write macOS/iOS touchIDAuthenticationAllowableReuseDuration value

• Localized messages for iOS, macOS and Android

Usage

Initialization

Initialize an instance of the plugin, which requires no input parameters.

  final _flutterLocalAuthenticationPlugin = FlutterLocalAuthentication();

Localization

At any time a localization model can be applied. The latests applied is used by the plugin when the local authentication is performed.

    final localization = LocalizationModel(
        promptDialogTitle: "title for dialog",
        promptDialogReason: "reason for prompting biometric",
        cancelButtonTitle: "cancel"
    );
    _flutterLocalAuthenticationPlugin.setLocalizationModel(localization);

Querying support and performing Local Authentication

Two functions are available for the core feature of this library:

• canAuthenticate
• authenticate

Depending on each platform the behaviour of canAuthenticate can differ.

    bool canAuthenticate;
    try {
      // Query suppor for Local Authentication
      canAuthenticate = await _flutterLocalAuthenticationPlugin.canAuthenticate();

      // Setup TouchID Allowable Reuse duration
      // It works only in iOS and macOS, but it's safe to call it even on other platforms.
      await _flutterLocalAuthenticationPlugin.setTouchIDAuthenticationAllowableReuseDuration(30);
    } on Exception catch (error) {
      debugPrint("Exception checking support. $error");
      canAuthenticate = false;
    }

    if (canAuthenticate) {
      // Perform Local Authentication

      _flutterLocalAuthenticationPlugin.authenticate().then((authenticated) {
        String result = 'Authenticated: $authenticated';
        // handle result
      }).catchError((error) {
        String result = 'Exception: $error';
        // handle error
      });
    }

Considerations

canAuthenticate

The function canAuthenticate will return true in the following scenarios.

• Android: true if BiometricManager returns that it can authenticate with one of the following allowed authenticators:

  • BiometricManager.Authenticators.BIOMETRIC_STRONG
  • BiometricManager.Authenticators.BIOMETRIC_WEAK
  • BiometricManager.Authenticators.DEVICE_CREDENTIAL

• iOS: true if LAContext.supportsLocalAuthentication returns true for device policy:

  • deviceOwnerAuthenticationWithBiometrics

• macOS: true if LAContext.supportsLocalAuthentication returns true for device policy:

  • deviceOwnerAuthentication

• linux: true if fprintd-verify is installed and user can execute it.

Supported platforms

• iOS 12 or newer
• macOS 10.12.2 or newer
• Linux (requires libfprint)
• Android 6.0 or newer

Next Steps

• Add support to Windows Hello