Перехват API - C++ WinAPI - Ответ 5269919

DWORD dwProtect = PAGE_READWRITE;
 
BYTE old[5];
 
BYTE * fPtr;
 
#pragma pack(push, 1)
struct jump_near
{
    BYTE opcode;
    DWORD relativeAddress;
};
#pragma pack(pop)
 
 
#pragma pack(push, 1)
struct org
{
    char old[5];
    struct jump_near jump;
};
#pragma pack(pop)
 
 
struct org oPtr;
 
size_t _CalculateDispacement(void* lpFirst, void* lpSecond)
{
    return reinterpret_cast<char*>(lpSecond) - (reinterpret_cast<char*>(lpFirst) + 5);
}
 
void splice()
{
    MessageBox(0, "Hello from splice", "OK", MB_OK);
 
    VirtualProtect(&oPtr, sizeof(oPtr), dwProtect, &dwProtect);
 
    BYTE * go = (BYTE*)&oPtr;
 
    __asm
    {
        jmp go
    }
}
 
 
 
void WINAPI start()
{
    
    MessageBox(0, "Ready!?", "", MB_OK);
    
    struct jump_near jump;
 
    fPtr = (BYTE * )GetProcAddress(GetModuleHandle(TEXT("*******")), "*******");
 
    jump.relativeAddress = _CalculateDispacement(fPtr, splice);
 
    jump.opcode = 0xE9;
 
    memcpy(old, fPtr, 5);
    
    VirtualProtect(fPtr, sizeof(jump_near), dwProtect, &dwProtect);
    
    WriteProcessMemory(GetCurrentProcess(), (void*)fPtr, (void*)&jump, 5, 0);
    
    memcpy(oPtr.old, old, 5);
 
    oPtr.jump.opcode = 0x9E;
    oPtr.jump.relativeAddress = (unsigned long)(fPtr + 6);
    
    MessageBox(0, "Finish", "OK", MB_OK);
}
 
 
 
 
BOOL APIENTRY DllMain( HANDLE hModule, 
                       DWORD  ul_reason_for_call, 
                       LPVOID lpReserved
                     )
{
 
 
switch (ul_reason_for_call) 
{ 
    case DLL_PROCESS_ATTACH: 
    {
        CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)start, NULL, NULL, NULL); 
    }
    break; 
 
    case DLL_THREAD_ATTACH: break; 
    case DLL_THREAD_DETACH: break;
    case DLL_PROCESS_DETACH: break; 
} 
 
    return TRUE;
}

MessageBox(0, "Hello from splice", "OK", MB_OK);

oPtr.jump.opcode = 0x9E;

oPtr.jump.opcode = 0xEA;