Api_Hooking

API Hooking using Trampoline

Explanation

The System API Interceptor is a Rust-based utility for intercepting and monitoring Windows API calls, specifically targeting the MessageBoxA function in user32.dll. It employs inline function hooking via a trampoline to redirect calls to a custom handler, log parameters, and invoke MessageBoxW with modified text. d

How It Works [Step-By-Step]

1. Interceptor Structure (ApiInterceptor):

   • Stores the target function address (MessageBoxA), replacement function address, original code bytes, and original memory protection state.
   • Uses a fixed-size array (INTERCEPTOR_SIZE) for storing original bytes (14 bytes for 64-bit, 5 bytes for 32-bit).

2. Setup (setup_interceptor):

   • Resolves MessageBoxA address using GetModuleHandleA and GetProcAddress.
   • Copies the first INTERCEPTOR_SIZE bytes of MessageBoxA to preserve the original code.
   • Changes memory protection to PAGE_EXECUTE_READWRITE using VirtualProtect to allow code modification.

3. Activation (activate_interceptor):

   • Constructs a trampoline to redirect execution:
     • 64-bit: Uses jmp [rip+0] (6 bytes) followed by an 8-byte absolute address of the custom handler.
     • 32-bit: Uses jmp <relative> (5 bytes) with a relative offset to the custom handler.
   • Writes the trampoline to the MessageBoxA entry point, ensuring minimal instruction overwriting.

4. Custom Handler (custom_dialog):

   • Logs input parameters (lpText, lpCaption) using CStr::to_string_lossy.
   • Converts new text to UTF-16 using WideCString for MessageBoxW.
   • Calls MessageBoxW with modified text ("Smukx Is Good") and caption ("System Dialog").

5. Deactivation (deactivate_interceptor):

   • Restores the original MessageBoxA bytes from the stored copy.
   • Reverts memory protection to its original state using VirtualProtect.
   • Clears the interceptor structure to prevent reuse.

6. Safety Considerations:

   • Uses unsafe blocks for WinAPI calls and pointer operations, ensuring controlled access.
   • Validates pointers and handles errors from WinAPI functions (e.g., GetLastError).
   • Maintains thread safety by avoiding shared mutable state.

Key Features

• Cross-Architecture: Adapts trampoline construction for 32-bit and 64-bit systems.
• Non-Invasive: Preserves original function behavior during deactivation.
• Error Handling: Checks for null pointers and failed WinAPI calls.
• Logging: Outputs parameter details for debugging and monitoring.

How to Compile and Use It

1. Compilation:

   • Build: cargo build --release.
   • Output: target/release/Api_Hooking.exe.

2. Execution:

   • Run: target/release/Api_Hooking.exe.
   • Behavior:
     • Displays an initial MessageBoxA dialog.
     • Activates interceptor, showing a modified MessageBoxW dialog.
     • Deactivates interceptor and shows a final MessageBoxA dialog.
     • Exits on Enter key press.
   • Run as administrator if memory protection changes fail.

3. Download the Snippet: Download

Credits

• https://github.com/ZeroMemoryEx/TrampHook
• https://www.ired.team/offensive-security/code-injection-process-injection/how-to-hook-windows-api-using-c++
• https://www.packtpub.com/en-us/product/mastering-malware-analysis-9781789610789/chapter/inspecting-process-injection-and-api-hooking-6/section/inline-api-hooking-with-trampoline-ch06lvl1sec86

Author

@5mukx