Memory patch using OpenProcess function [C++]

// patch.cpp

#include <iostream>
#include <windows.h>

// The patched function with modified behavior
int Patched_Add(int a, int b) {
    // Let's return the product of the two numbers instead of the sum
    return a * b;
}

int main() {
    // Target process information
    const char* targetProcessName = "victim.exe";

    // Find the target process
    HWND hWnd = FindWindowA(NULL, targetProcessName);
    if (hWnd == NULL) {
        std::cout << "Failed to find the target process." << std::endl;
        return 1;
    }

    // Get the process ID of the target process
    DWORD pid;
    GetWindowThreadProcessId(hWnd, &pid);

    // Open the target process with PROCESS_ALL_ACCESS permission
    HANDLE hProcess = OpenProcess(PROCESS_ALL_ACCESS, FALSE, pid);
    if (hProcess == NULL) {
        std::cout << "Failed to open the target process." << std::endl;
        return 1;
    }

    // Get the address of the function to be patched
    // In reality, this step can be more complex depending on the target function's location.
    // For demonstration purposes, let's assume the address of the "Add" function is known.
    DWORD addressToPatch = reinterpret_cast<DWORD>(Add);

    // Write the patched function into the target process
    DWORD oldProtect;
    VirtualProtectEx(hProcess, reinterpret_cast<LPVOID>(addressToPatch), sizeof(int), PAGE_EXECUTE_READWRITE, &oldProtect);
    WriteProcessMemory(hProcess, reinterpret_cast<LPVOID>(addressToPatch), Patched_Add, sizeof(int), NULL);
    VirtualProtectEx(hProcess, reinterpret_cast<LPVOID>(addressToPatch), sizeof(int), oldProtect, &oldProtect);

    // Close the process handle
    CloseHandle(hProcess);

    std::cout << "Patching complete." << std::endl;

    return 0;
}