Tamper Detection Mechanism in React Native & Expo Apps

Your app is finally live. You celebrate the release 🎉.
Meanwhile, attackers are already pulling it apart by reverse engineering your app, modifying the code, and redistributing a compromised version to users.

Mobile app tampering is a real security risk and Tamper Detection is your app's is like a immune system. it detects when someone has modified your app and takes action.

Let me walk you through how to protect your React Native and Expo apps from tampering, reverse engineering, and unauthorized modifications.

A. Understanding why tamper detection matters and what its Protects Against:

Tamper Detection is a mechanism that detect when your app's code, resources, or runtime environment has been modified from its original state. some examples are:

Code modification for piracy, assets replacement, memory manipulation, debugger attachment, repackaging and redistribution, root/jailbreak exploitation, and API key extraction.

Here are some Real-World Impacts as regards to tampering of mobile applications

• Financial Apps: Modified app bypasses authentication, Fake transactions shown, Credentials stolen

• Gaming Apps: In-app purchases bypassed, Unlimited coins/lives, Leaderboard manipulation

• Streaming Apps: DRM bypassed, Content downloaded, Subscription checks removed

• Enterprise Apps: Corporate data exposed, Security policies bypassed, Unauthorized access

• as well as other critical Industries…

  

  Example of mobile apps can be attacked

B. Understanding the Threat Landscape

1. Attacker decompiles apk/ipa with tools like jadx/apktool, modify JavaScript bundle, remove important checks then repackage and sign distribute on third-party store

2. Using Rooted Devices or emulators which gives the attacker elevated privileges allowing deep system access here(your app sandbox can be bypassed, code injection, read secure storage, SSL pinning bypass and sometimes Hook any function

3.Attackers attach debuggers to inspect/modify runtime behavior of your app using tools like lldb(IOS), gdb(android), http-toolkit, charles proxy... here(they Inspect API calls, extract tokens/keys, modify variables and bypass checks)

4. Your app memory can be modified at runtime using tools like Frida or GameGuardian...

So yea.... we have understood how apps are been tampered but what measures can be taken to detect the tampering of your apps...

I tend to group them into 5 levels.

• Device level (for Root/JailBreak)

• Code level (Bundle Integrity)

• Runtime level (Debugging detection)

• Build-level (Signatures/certificates)

• Network/ Server level (Remote Verification)

C. Here are some Tamper Detection Strategies

- Using expo-device, react-native-root-detection, jail-monkey can be used in detecting if a device / emulator is been rooted... But, it may not be sufficient on their own due to advance tools like Frida or exposed framework which makes simple checks unreliable... but studies has shown custom native modules or using Talsec freeRASP Capacitor to detect Frida and other Xposed alike framework that does reverse engineering are more effective

- Certificate and signature pining verification / iOS Provisioning Profile Check

-Runtime Protection with JSI

-Using Expo Specific Protection such as EAS build with environment variables and secure store

- Server-Side Verification, Remote reporting, Runtime monitoring checking to avoid MITM attacks

- Logging and monitoring all security events for analysis..

- Code Obfuscation, removing all dev logs at production, Forced logout, clearing sensitive data and alerting users...

Example of some strategies used for tamper

Lastly, Test your defence 😅 Jail break your app to check your vulnerabilities.... Stay secure!