local_biometric 0.0.2

A robust, efficient, and performant local biometric identity plugin for Flutter.

local_biometric

A robust, efficient, and performant local biometric identity plugin for Flutter. This plugin provides secure biometric authentication with support for cryptographic signatures (RSA/ECDSA) using the Secure Enclave (iOS) and Keystore (Android).

Features

• Simple Authentication: Quick biometric presence verification.
• Encrypted Authentication: Enroll secure identities and sign payloads without exposing private keys.
• Smart Lockout Recovery: Proactively detects biometric lockout states and provides a unified flow to re-enable biometrics using the device passcode.
• Consistent Behavior: Unified authentication experience across iOS and Android, specifically handling fallback and lockout behaviors consistently.
• Platform Specifics: Leverages native security hardware (Secure Enclave/StrongBox).

Installation

Add local_biometric to your pubspec.yaml:

dependencies:
  local_biometric: ^0.0.2

iOS Configuration

Add NSFaceIDUsageDescription to your Info.plist:

<key>NSFaceIDUsageDescription</key>
<string>This app uses Face ID to secure your identities and sign data.</string>

Android Configuration

Ensure your AndroidManifest.xml includes the biometric permission:

<uses-permission android:name="android.permission.USE_BIOMETRIC" />

Usage

1. Initialize the Plugin

final _plugin = LocalBiometric();

2. Check Availability

Before performing biometric actions, check if the device supports it and if biometrics are enrolled.

final availability = await _plugin.checkAvailability();
if (availability.canAuthenticate) {
  print("Biometrics are ready!");
} else {
  print("Biometrics unavailable: ${availability.reason}");
}

3. Simple Authentication (Presence Verification)

Verify the user's presence without using cryptographic keys.

final result = await _plugin.verifyPresence(
  promptMessage: 'Please confirm your identity',
  config: PresencePromptConfig(
    allowDeviceCredentials: true, // Allow fallback to passcode
  ),
);

if (result.success) {
  print("Authenticated!");
}

4. Encrypted Authentication (Signing)

Enrollment

Create a secure key pair protected by biometrics.

final result = await _plugin.enrollIdentity(
  keyAlias: 'my_secure_key',
  config: IdentityEnrollmentConfig(
    signatureType: IdentitySignatureType.rsa,
    enforceBiometric: true,
  ),
);

Signing

Sign data using the enrolled key. This requires biometric authentication by default.

final result = await _plugin.signPayload(
  payload: 'Data to sign',
  keyAlias: 'my_secure_key',
  config: IdentitySignatureConfig(
    allowDeviceCredentials: false, // Force biometric-only for signing
  ),
);

if (result.code == IdentityError.success) {
  print("Signature: ${result.signature}");
}

5. Handling Lockouts

If a user fails biometric authentication too many times, the system will lock biometrics. local_biometric helps you identify this state.

if (result.code == IdentityError.lockedOut) {
  // Show a dialog to the user
  // On iOS, verifying the passcode via verifyPresence(allowDeviceCredentials: true)
  // will reset the biometric lockout state.
}

Error Codes

The plugin uses standardized error codes across platforms:

• success: Operation completed successfully.
• userCanceled: The user dismissed the biometric prompt.
• lockedOut: Too many failed attempts. Passcode verification required.
• notAvailable: Biometrics are not supported on this device.
• notEnrolled: No biometrics are enrolled on the device.
• keyNotFound: The requested cryptographic key does not exist.

Limitations & Important Notes

• Simulator Limitations: Biometric authentication and secure hardware (Secure Enclave/StrongBox) cannot be fully tested on simulators. A physical device with biometrics is required for testing.
• Passcode Requirement: Biometrics cannot be enabled or used unless a device passcode/lock is set. If the user removes their device passcode, all enrolled identities will be permanently invalidated.
• Biometric Enrollment Changes: On iOS, if new biometrics (FaceID/TouchID) are enrolled or existing ones are significantly changed, identities enrolled with enforceBiometric: true may be invalidated depending on system policy.
• Lockout Reset: A biometric lockout can ONLY be reset by the user successfully entering their device passcode. There is no way to reset this programmatically without user interaction.
• Hardware Variation: While the plugin attempts to use the most secure hardware available (StrongBox on Android, Secure Enclave on iOS), it will fall back to standard TEE/Keystore if specialized hardware is not available on the device.

Developer Contact

For support, feature requests, or business inquiries, please visit our Web Portal.

License

This project is licensed under the MIT License - see the LICENSE file for details.