DEV Community

Cover image for LogGuard
Cahyanudien Aziz Saputra
Cahyanudien Aziz Saputra

Posted on

LogGuard

#flutter #security

A high-performance Flutter plugin that automatically sanitizes sensitive data in logs using Rust FFI with regex-based pattern matching.

Why LogGuard?

Accidentally logging sensitive information is one of the most common security vulnerabilities in mobile apps. LogGuard provides automatic protection by intercepting and sanitizing all log output before it reaches the console, crash reporters, or analytics systems.

Key Benefits

  • 🛡️ Automatic Protection: No code changes needed - wrap your app and you're protected
  • ⚡ High Performance: Rust FFI implementation processes logs 10x faster than pure Dart
  • 🌍 UTF-8 Safe: Properly handles international characters and emoji
  • 🔄 Zero Config: Works out of the box with sensible defaults
  • 📊 Production Ready: Efficiently handles large logs with automatic chunking

Quick Start

1. Add Dependency 

dependencies:
  logguard: ^0.1.0
Enter fullscreen mode Exit fullscreen mode

2. Protect Your App 

import 'package:flutter/material.dart';
import 'package:logguard/logguard.dart';

void main() {
  LogGuard.runApp(
    MaterialApp(
      home: MyHomePage(),
    ),
  );
}
Enter fullscreen mode Exit fullscreen mode

That's it! All print() and debugPrint() calls are now automatically sanitized.

What Gets Sanitized?

LogGuard automatically detects and masks:

Pattern Example Result
Passwords password=secret password=********
Tokens Bearer abc123 Bearer [MASKED]
API Keys AKIAIOSFODNN7 [MASKED]
Emails user@example.com [MASKED]
Credit Cards 4532-1234-5678-9010 [MASKED]
Phone Numbers +1-555-123-4567 [MASKED]
UUIDs 550e8400-e29b... [MASKED]
JWT Tokens eyJhbGc... [MASKED]
Hex Hashes a94a8fe5ccb1... [MASKED]

Usage Examples

Automatic Mode (Recommended)

Protects your entire application:

void main() {
  LogGuard.runApp(MyApp());
}

// Anywhere in your app
print('User email: user@example.com'); 
// Output: User email: [MASKED]

debugPrint('Auth token: Bearer abc123xyz');
// Output: Auth token: Bearer [MASKED]
Enter fullscreen mode Exit fullscreen mode

Selective Protection

Protect specific code blocks:

void main() async {
  await LogGuard.runGuarded(() {
    // Only logs inside this scope are sanitized
    print('password=secret123'); // Sanitized
    runApp(MyApp());
  });
}
Enter fullscreen mode Exit fullscreen mode

Manual Sanitization

For explicit control:

import 'package:logguard/logguard.dart';

// Direct sanitization
final safeText = LogGuard.sanitize('My email is user@example.com');
print(safeText); // Output: My email is [MASKED]

// Extension method
final userInput = 'password=test123';
print(userInput.sanitized); // Output: password=********

// Custom logging with levels
LogGuard.log(
  'User logged in with token: abc123',
  level: LogLevel.info,
  name: 'AuthService',
  toConsole: true,
  toDeveloper: true,
);
Enter fullscreen mode Exit fullscreen mode

Advanced Usage 

// Safe print helpers
LogGuard.safePrint('This will be sanitized automatically');
LogGuard.safeDebug('Debug message', wrapWidth: 80);

// Check FFI availability
if (LogGuard.isFFIAvailable) {
  print('Using high-performance Rust sanitizer');
} else {
  print('Using Dart fallback sanitizer');
}

// Hook management
LogGuard.setupHooks();   // Enable protection
LogGuard.removeHooks();  // Disable protection
Enter fullscreen mode Exit fullscreen mode

Platform Support

Platform Status Version
Android ✅ Supported v0.1.0+
Linux 🚧 Coming Soon v0.2.0
Windows 🚧 Coming Soon v0.3.0
iOS ⏳ Planned Future
macOS ⏳ Planned Future
Web ⏳ Planned Future

Performance

LogGuard is optimized for production use:

Log Size Processing Time
1 KB ~0.1ms
10 KB ~0.5ms
100 KB ~3ms (chunked)

*Benchmarked on Pixel 6 with Rust FFI enabled

Performance Features

  • Lazy Pattern Compilation: Regex patterns compiled once at startup
  • Automatic Chunking: Large logs processed in 10KB chunks
  • UTF-8 Optimized: Character-aware iteration prevents corruption
  • Memory Capped: Result buffer limited to 2MB max
  • Fast Path Optimization: Common patterns use prefix matching instead of regex

Architecture 

Flutter App (print/debugPrint)
         ↓
LogGuard Dart Layer (Zone interception)
         ↓
FFI Bridge
         ↓
Rust Core (Optimized regex + UTF-8 scanning)
Enter fullscreen mode Exit fullscreen mode

The plugin uses Dart Zones to intercept all log output, then passes it through a Rust FFI bridge for high-performance pattern matching.

How It Works

  1. Zone Interception: LogGuard creates a custom Zone that wraps your app
  2. Automatic Capture: All print() calls are intercepted before reaching the console
  3. FFI Processing: Log messages are passed to Rust for sanitization
  4. Pattern Matching: Rust applies optimized regex and prefix matching
  5. Safe Output: Sanitized logs are printed to the console

Security Notice

⚠️ Important: LogGuard significantly reduces the risk of sensitive data exposure, but should be used as part of a comprehensive security strategy. Always follow these best practices:

  • Never intentionally log sensitive information
  • Use LogGuard as a safety net, not a replacement for good coding practices
  • Test with your specific data patterns
  • Review logs regularly for new patterns
  • Use proper authentication and encryption for data transmission

Configuration

LogGuard works with zero configuration, but provides flexibility when needed:

// Enable/disable hooks manually
LogGuard.setupHooks();
LogGuard.removeHooks();

// Custom log levels
LogGuard.log(
  'Custom message',
  level: LogLevel.error,
  error: exception,
  stackTrace: stack,
);
Enter fullscreen mode Exit fullscreen mode

Testing 

import 'package:flutter_test/flutter_test.dart';
import 'package:logguard/logguard.dart';

void main() {
  test('sanitizes passwords', () {
    final input = 'password=secret123';
    final output = LogGuard.sanitize(input);
    expect(output, 'password=********');
  });

  test('sanitizes emails', () {
    final input = 'Contact: user@example.com';
    final output = LogGuard.sanitize(input);
    expect(output, 'Contact: [MASKED]');
  });
}
Enter fullscreen mode Exit fullscreen mode

Contributing

Contributions are welcome! Please check out our GitHub repository for:

  • 🐛 Bug reports
  • 💡 Feature requests
  • 🔧 Pull requests
  • 📖 Documentation improvements

Development Roadmap

  • [x] Android FFI support
  • [x] Automatic log interception
  • [x] Common pattern detection
  • [ ] Linux support (v0.2.0)
  • [ ] Windows support (v0.3.0)
  • [ ] Custom pattern configuration
  • [ ] Log encryption option
  • [ ] iOS/macOS support
  • [ ] Web support (WASM)

License

MIT License - see LICENSE file for details.

Support

Built with ❤️ using Rust + Flutter

If LogGuard helps secure your app, please consider:

  • ⭐ Starring the repo on GitHub
  • 👍 Liking on pub.dev
  • 📢 Sharing with other Flutter developers

Top comments (0)