#include <iostream>
#include <cstdlib>

#include <Windows.h>
#include <Psapi.h>

void __stdcall NewSleep(DWORD milliseconds)
{
    std::cout << "Sleep." << std::endl;

    std::cin.get();
}

void __stdcall NewExitProcess(UINT exitCode)
{
    std::cout << "ExitProcess." << std::endl;

    std::cin.get();
}

FARPROC f1 = NULL;
FARPROC f2 = NULL;

int main()
{
    HMODULE kernel32Module = GetModuleHandle("KERNEL32.dll");
    f1 = GetProcAddress(kernel32Module, "Sleep");
    f2 = GetProcAddress(kernel32Module, "ExitProcess");

    std::cout << f1 << std::endl;

    unsigned char* baseAddress = (unsigned char*)GetModuleHandle(NULL);

    IMAGE_DOS_HEADER* idh = (IMAGE_DOS_HEADER*)baseAddress;
    IMAGE_NT_HEADERS* inh = (IMAGE_NT_HEADERS*)(baseAddress + idh->e_lfanew);
    IMAGE_IMPORT_DESCRIPTOR* iid = (IMAGE_IMPORT_DESCRIPTOR*)(baseAddress + inh->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].VirtualAddress);

    for (IMAGE_IMPORT_DESCRIPTOR* i = iid; i->Name != 0; ++i)
    {
        std::string moduleName = (char*)(baseAddress + i->Name);

        if (moduleName == "KERNEL32.dll")
        {
            IMAGE_THUNK_DATA* itd = (IMAGE_THUNK_DATA*)(baseAddress + i->FirstThunk);

            for (IMAGE_THUNK_DATA* j = itd; j->u1.Function != 0; ++j)
            {
                if ((FARPROC)j->u1.Function == f1)
                {
                    DWORD oldProtect = 0;
                    VirtualProtect(&j->u1.Function, sizeof(DWORD), PAGE_READWRITE, &oldProtect);
                    j->u1.Function = (DWORD)&NewSleep;
                    VirtualProtect(&j->u1.Function, sizeof(DWORD), oldProtect, &oldProtect);
                }

                if ((FARPROC)j->u1.Function == f2)
                {
                    DWORD oldProtect = 0;
                    VirtualProtect(&j->u1.Function, sizeof(DWORD), PAGE_READWRITE, &oldProtect);
                    j->u1.Function = (DWORD)&NewExitProcess;
                    VirtualProtect(&j->u1.Function, sizeof(DWORD), oldProtect, &oldProtect);
                }
            }

            break;
        }
    }

    Sleep(0);
    Sleep(0);

    ExitProcess(0);
    //Crash.

    std::cin.sync();
    std::cin.get();
    return EXIT_SUCCESS;
}