Modifying runtime behavior of Android apps using HBCTool

In this technical deep dive, we will explore the powerful tool called HBCTool and its applications in hacking Android apps. HBCTool is a dynamic analysis tool that allows us to intercept and modify the behavior of Android apps at runtime. By leveraging HBCTool’s capabilities, we can uncover vulnerabilities, analyze the app’s behavior, and manipulate its functionality for security testing purposes. Let’s dive in!

Understanding HBCTool Link to heading

HBCTool is based on the Android framework’s built-in instrumentation capabilities. It leverages the framework’s ability to dynamically load and execute code within an app’s process. HBCTool injects code into the target app’s process and hooks specific methods to intercept their execution.

HBCTool utilizes function hooking to intercept method calls. It modifies the target method’s code to redirect the control flow to a custom function before or after the original method executes. This allows us to monitor, modify, or even block the method’s behavior.

Setting Up HBCTool Link to heading

Before we start using HBCTool, we need to set it up. Follow these steps:

Step 1: Download and Install HBCTool Link to heading

Visit the HBCTool GitHub repository and download the latest release. Extract the downloaded package to a directory of your choice.

Step 2: Install Android SDK and NDK Link to heading

To build and run HBCTool, we need to install the Android SDK and NDK. Follow the official Android documentation to set up the SDK and NDK on your system.

Step 3: Build HBCTool Link to heading

Navigate to the HBCTool directory and run the build command:

./build.sh

This will compile the HBCTool source code and generate the necessary binaries.

Using HBCTool Link to heading

Now that we have HBCTool set up, let’s explore its usage and capabilities.

Hooking a Method Link to heading

HBCTool allows us to hook any method within the target app. By hooking a method, we can intercept its execution and execute custom code before or after its original implementation. Here’s an example of hooking the onClick method of the MainActivity class in the com.example.app package:

public void hook_onClick() {
    HBCToolUtils.hookMethod(
        "com.example.app.MainActivity",
        "onClick",
        new XC_MethodHook() {
            @Override
            protected void beforeHookedMethod(MethodHookParam param) throws Throwable {
                // Custom code to be executed before the original onClick method
            }

            @Override
            protected void afterHookedMethod(MethodHookParam param) throws Throwable {
                // Custom code to be executed after the original onClick method
            }
        }
    );
}

In the above code snippet, we use HBCTool’s hookMethod function to hook the onClick method of the MainActivity class. We provide a custom XC_MethodHook implementation with beforeHookedMethod and afterHookedMethod callbacks to execute our custom code.

Modifying Variables Link to heading

HBCTool allows us to modify variables within the hooked method. This gives us the ability to manipulate the app’s behavior at runtime. Here’s an example of modifying the isLoginSuccessful variable within the onLogin method of the LoginActivity class:

public void modify_isLoginSuccessful() {
    HBCToolUtils.modifyVariable(
        "com.example.app.LoginActivity",
        "onLogin",
        "isLoginSuccessful",
        false
    );
}

In the above code snippet, we use HBCTool’s modifyVariable function to modify the isLoginSuccessful variable within the onLogin method of the LoginActivity class. We specify the new value (false) for the variable.

Examining Network Requests Link to heading

HBCTool can intercept network requests made by the target app, allowing us to analyze and manipulate the app’s communication with servers. Here’s an example of intercepting a network request using the OkHttp library:

public void interceptNetworkRequest() {
    HBCToolUtils.hookMethod(
        "okhttp3.OkHttpClient",
        "newCall",
        new XC_MethodHook() {
            @Override
            protected void beforeHookedMethod(MethodHookParam param) throws Throwable {
                Request request = (Request) param.args[0];
                // Custom code to examine or modify the network request
            }
        }
    );
}

In the above code snippet, we hook the newCall method of the OkHttpClient class from the OkHttp library. We extract the Request object from the method arguments and perform our custom analysis or modification on the network request.

It’s important to note that hacking apps without proper authorization is illegal and unethical. HBCTool should only be used for security research and penetration testing with the appropriate permissions and in controlled environments. HBCTool opens up a wide range of possibilities for security professionals to analyze and manipulate Android apps, providing valuable insights into their security vulnerabilities and behavior.