With the rise of mobile apps, ensuring their security is more critical than ever. Mastering the 10 essential steps to perform penetration testing on a Flutter application is crucial, as Flutter, Google’s open-source framework for building cross-platform apps, continues to gain popularity. This blog provides a detailed step-by-step guide on how to perform penetration testing on Flutter applications, from static analysis to reporting vulnerabilities.
10 Essential Srpteps to Master Penetration Testing on a Flutter Application:-
1. Pre-Engagement Preparation
Before diving into the technicalities, ensure you have the proper setup:
- Understand the Application: Identify the app’s core functionality, its backend services, and how data flows through the app.
- Obtain Legal Permission: Ensure you have legal authorization to conduct penetration testing on the app.
- Set Up Testing Environment: Install the app on an emulator or real device, and configure proxy tools (like BurpSuite) to intercept traffic.
2. Static Analysis
Static analysis involves inspecting the app’s code for vulnerabilities:
- Decompile the APK: Tools like apktool or jadx can be used to decompile the APK file, allowing you to review the source code.
- Analyze Flutter/Dart Code: Check for insecure coding practices such as hardcoded credentials, weak encryption methods, or improper data handling.
- MobSF (Mobile Security Framework) is a tool for mobile app security testing that offers static and dynamic analysis. It helps explore app internals, like Smali code, endpoints, and servers, to identify vulnerabilities.
- Review Manifest File: Pay close attention to AndroidManifest.xml to identify misconfigurations, such as unnecessary permissions or missing security attributes like android:debuggable.
3. Dynamic Analysis
Dynamic analysis focuses on testing the app while it’s running:
- Intercept Network Traffic: Use tools like Burp Suite or OWASP ZAP to capture and inspect the app’s network requests. Ensure it uses HTTPS and look for data leakage (such as tokens or passwords being sent in plaintext).
- API Testing: Test backend APIs for common vulnerabilities like broken authentication, insecure direct object references (IDOR), or SQL injection, We can use Postman or Burp Suite.
- Authentication Flaws: Review login, registration, password reset, and other flows for security weaknesses such as MFA bypass or insecure session management. We can use Burp Suite’s Intruder to acomplish the same.
4. Local Storage Security
One of the key areas of concern is how apps handle local storage:
- Inspect Local Storage: Review how sensitive information is stored, such as in SharedPreferences, SQLite, or local files. Look for any insecure storage of credentials or tokens.
- Use Secure Storage: Ensure sensitive data is stored securely, leveraging Android Keystore or iOS Keychain where applicable, we can use adb tool.
5. Reverse Engineering and Code Obfuscation
Reverse engineering allows you to check for the app’s resilience against tampering:
- Test for Tampering: Try to modify the app (e.g., by changing values or injecting code) and observe if it can detect the tampering attempts.
- Check for Obfuscation: Ensure the app has implemented code obfuscation techniques (such as ProGuard or Dart obfuscation) to protect it from reverse engineering.
- Frida, Objection or Reflutter(To inspect n/w traffic To remove default certification pinning, To establish connection between given application and BurpSuite so that we can inspect n/w traffic and json) can be used.
6. Business Logic and Client-Side Security
Beyond technical vulnerabilities, the app’s business logic may also be vulnerable:
- Business Logic Testing: Test for flaws in business logic, such as weak authentication flow, incorrect validation, or insecure payment mechanisms. Tools like Burp Suite can assist in intercepting requests.
- In-App Security Mechanisms: Check if the app uses security controls like jailbreak/root detection, anti-debugging techniques, or integrity checks. Use Magisk(Root Bypass framework – Inspect Internals whicherver database is present) or RootCloak.
7. SSL Pinning Bypass
SSL Pinning is a security technique that ensures an app only communicates with trusted servers:
- Check for SSL Pinning: SSL Pinning is a security technique that ensures an app only communicates with trusted servers, So determine if the app uses SSL pinning, and attempt to bypass it using tools like Frida or Objection.
8. API Security Testing
APIs are a critical attack surface in mobile apps:
- API Vulnerability Testing: Perform security tests on the APIs, focusing on vulnerabilities like broken object-level authorization (BOLA), weak authentication, and insecure data handling. Use Postman or Burp Suite
9. Cryptographic Implementation
Proper cryptographic implementation is key to protecting sensitive data:
- Weak Encryption: Identify if the app uses weak encryption algorithms (e.g., MD5 or SHA-1) or improperly handles cryptographic keys.
- Token Security: Ensure security tokens (such as JWT or OAuth tokens) are securely generated, transmitted, and stored. Use tools like JWT.io or Burp Suite & GHIDRA (Machine code to high language code) can be used for binary file exploitation.
10. Reporting and Recommendations
Finally, the most important part of penetration testing is communicating the findings effectively:
- Document Your Findings: Provide a detailed report outlining the vulnerabilities, their risk levels, and how they can be mitigated using Notion.
- Security Best Practices: Include recommendations for secure coding practices, proper API security, and secure data storage techniques. Utilizing tools like OWASP Mobile Security Testing Guide (MSTG) as references.
Conclusion
Flutter apps are becoming increasingly popular, and with this comes the need for thorough security testing. By following these steps, you can ensure a comprehensive penetration test of a Flutter app, addressing potential vulnerabilities from static analysis to API testing. As security becomes a central concern in app development, penetration testing remains a critical component in safeguarding user data and ensuring app reliability.
