Certificate Pinning Bypass (Android)

Bypassing certificate pinning using three different methods: Frida, Xposed Framework with JustTrustMe, and Modifying APK.

Method 1: Using Frida

Frida is a powerful tool for dynamic instrumentation, allowing you to hook into an app's runtime and modify its behavior.

Steps to Implement Certificate Pinning Bypass with Frida:

1. Set Up Your Environment:

• Install Frida on your testing device and your computer.

  • On your computer:

    bash

    pip install frida-tools

  • On your Android device:

    bash

    adb push frida-server /data/local/tmp/
    adb shell "chmod 755 /data/local/tmp/frida-server"
    adb shell "/data/local/tmp/frida-server &"

  Reference to the Frida installation guide for details.

1. Create a Bypass Script:

• Write a Frida script to bypass SSL pinning. Save the script as bypass_script.js.

  // Frida script to bypass SSL pinning
  Java.perform(function () {
      var X509TrustManager = Java.use('javax.net.ssl.X509TrustManager');
      var SSLContext = Java.use('javax.net.ssl.SSLContext');
  
      // Custom TrustManager that does not validate certificates
      var TrustManager = Java.registerClass({
          name: 'com.example.TrustManager',
          implements: [X509TrustManager],
          methods: {
              checkClientTrusted: function (chain, authType) {},
              checkServerTrusted: function (chain, authType) {},
              getAcceptedIssuers: function () { return []; }
          }
      });
  
      // Hook SSLContext to use our custom TrustManager
      SSLContext.init.overload(
          '[Ljavax.net.ssl.KeyManager;',
          '[Ljavax.net.ssl.TrustManager;',
          'java.security.SecureRandom'
      ).implementation = function (keyManager, trustManager, secureRandom) {
          var customTrustManager = [TrustManager.$new()];
          this.init(keyManager, customTrustManager, secureRandom);
      };
  });

1. Run the Script:

• Use Frida to run the script on your Android device. Ensure your device is connected and Frida server is running:

  frida -U -f com.yourapp.package -l bypass_script.js --no-pause

1. Test the App:

• Set Up Proxy Tool - Burp Suite
• Interact with the app and monitor network traffic using tools like Burp Suite to ensure the certificate pinning is bypassed.

Method 2: Using Xposed Framework and JustTrustMe

Prerequisites

• Rooted Android Device: Ensure your device is rooted to install the Xposed Framework.

• Xposed Framework Installed: The Xposed Framework should be installed on your rooted device.

Steps:

1. Root Your Android Device:

   • Ensure your Android device is rooted. You can find specific guides for rooting your device based on its model and Android version. Popular tools for rooting include Magisk and Azerokit.
   • Follow the Root a Android Device for details
2. Install Xposed Framework:

   • Download the Xposed Installer APK from the official Xposed website.
   • Install the Xposed Installer APK on your device.

   • Open the Xposed Installer and install the framework by selecting "Framework" and then "Install/Update."

   • Reboot your device to apply the changes.

3. Install JustTrustMe Module:

   • Open the Xposed Installer app.

   • Go to the "Downloads" section and search for the "JustTrustMe" module.

   • Download and install the JustTrustMe module.

   • After installation, go to the "Modules" section in the Xposed Installer and check the box next to JustTrustMe to activate it.

4. Reboot Your Device:

   • Reboot your device to apply the changes and ensure the module is active.

5. Set Up Proxy Tool - Burp Suite
6. Test the App:

   • Open your app and perform actions that require network communication.

   • With JustTrustMe activated, the app should bypass certificate pinning, allowing Burp Suite to intercept and analyze the traffic.

7. Monitor Network Traffic:

   • Use Burp Suite to monitor and analyze the intercepted traffic. You should now be able to see and manipulate the encrypted data that the app sends and receives.

Method 3: Modifying APK

Prerequisites

• APKTool installed on your computer.

• Java Development Kit (JDK) installed.

• Android Debug Bridge (ADB) installed and set up.

• Rooted Android Device (optional for some steps).

Steps:

1. Set Up Your Environment:

   • Ensure you have APKTool, JDK, and ADB installed.

   • Set up the environment variables for JDK and ADB for easy access.

2. Decompile the APK:

   • Use APKTool to decompile the APK. This will convert the APK into a set of readable files and folders.

     apktool d yourapp.apk -o yourapp

   • The yourapp directory will contain the decompiled files.

3. Locate Certificate Pinning Logic:

   • Navigate through the decompiled files to find the network-related code. This is usually located in classes related to SSL/TLS connections.

   • Use a text editor or IDE to search for keywords like TrustManager, HostnameVerifier, checkServerTrusted, or SSLContext.

4. Modify the Code:

   • Modify the pinning logic to bypass the certificate checks. You can either comment out the pinning logic or modify it to accept all certificates. Example:

     // Original pinning logic
     public void checkServerTrusted(X509Certificate[] chain, String authType) throws CertificateException {
         // Validate the server certificate
     }
     
     // Modified pinning logic
     public void checkServerTrusted(X509Certificate[] chain, String authType) throws CertificateException {
         // Accept all certificates
     }

   • Ensure all necessary changes are made to bypass the pinning.

5. Recompile the APK:

   • Use APKTool to recompile the modified APK.

     apktool b yourapp -o yourapp-modified.apk

   • The recompiled APK (yourapp-modified.apk) will be generated in the specified output directory.

6. Sign the APK:

   • The recompiled APK needs to be signed before it can be installed on your device. Use the JDK's jarsigner tool to sign the APK with a debug certificate.

     jarsigner -verbose -sigalg SHA1withRSA -digestalg SHA1 -keystore ~/.android/debug.keystore yourapp-modified.apk androiddebugkey

   • When prompted, use the default keystore password (android).

7. Install the Modified APK:

   • Use ADB to install the modified APK on your Android device.

     bash

     adb install yourapp-modified.apk

   • If the app is already installed, you may need to uninstall the existing version first:

     bash

     adb uninstall com.yourapp.package
     adb install yourapp-modified.apk

8. Test the App:

   • Open the modified app on your Android device and perform actions that require network communication.

   • Use tools like Burp Suite to intercept and analyze the traffic. The certificate pinning should be bypassed, allowing you to intercept the SSL/TLS traffic.