本文实例讲述了C++实现修改函数代码HOOK的封装方法，分享给大家供大家参考。具体实现方法如下：

一、对外的接口如下：

1. 类初始化时对函数HOOK
2. 取消挂钩：
void UnHook();
3. 重新挂钩：
void ReHook();

在初始化时HOOK的代码：

复制代码 代码如下:*(DWORD*)(m_btNewBytes+1) = (DWORD)pfnHook;

8个字节的代码地址 0xB8, 0x00, 0x00,0x40,0x00,0xFF,0xE0,0x00 只要把第二位和第三位的数据改成函数的地址，调用原先的函数时就会调到自定义的函数执行.

二、实现方法：

.h头文件如下：

复制代码 代码如下:#ifndef _ULHOOK_H__
#define _ULHOOK_H__

#include <Windows.h>
#pragma once
class CULHook
{
public:
CULHook(LPSTR lpszModName, LPSTR lpszFuncNme, PROC pfnHook);
~CULHook(void);

//取消挂钩
void UnHook();
//重新挂钩
void ReHook();
protected:
PROC m_pfnOrig;
BYTE m_btNewBytes[8];
BYTE m_btOldBytes[8];
HMODULE m_hModule;
};

#endif

.cpp源文件如下：

复制代码 代码如下:#include "ULHook.h"

CULHook::CULHook(LPSTR lpszModName, LPSTR lpszFuncNme, PROC pfnHook)
{
BYTE btNewBytes[] = {0xB8, 0x00, 0x00,0x40,0x00,0xFF,0xE0,0x00};
memcpy(m_btNewBytes, btNewBytes, 8);
*(DWORD*)(m_btNewBytes+1) = (DWORD)pfnHook;

m_hModule = ::LoadLibraryA(lpszModName);
if (NULL == m_hModule)
{
m_pfnOrig = NULL;
return;
}
m_pfnOrig = (PROC)::GetProcAddress(m_hModule, lpszFuncNme);
if (NULL != m_pfnOrig)
{
MEMORY_BASIC_INFORMATION mbi = {0};
DWORD dwOldProtect;
::VirtualQuery(m_pfnOrig, &mbi, sizeof(mbi));
::VirtualProtect(m_pfnOrig, 8, PAGE_READWRITE, &dwOldProtect);
memcpy(m_btOldBytes, m_pfnOrig, 8);
::WriteProcessMemory(GetCurrentProcess(), (VOID*)m_pfnOrig, m_btNewBytes, 8, NULL);
::VirtualProtect(m_pfnOrig, 8, dwOldProtect, NULL);
}
}

CULHook::~CULHook(void)
{
UnHook();
if (m_hModule!=NULL)
{
::FreeLibrary(m_hModule);
}
}
void CULHook::UnHook()
{
if (m_pfnOrig != NULL)
{
MEMORY_BASIC_INFORMATION mbi = {0};
DWORD dwOldProtect;
::VirtualQuery(m_pfnOrig, &mbi, sizeof(mbi));
::VirtualProtect(m_pfnOrig, 8, PAGE_READWRITE, &dwOldProtect);
::WriteProcessMemory(GetCurrentProcess(), (VOID*)m_pfnOrig, m_btOldBytes, 8, NULL);
::VirtualProtect(m_pfnOrig, 8, dwOldProtect, NULL);
}
}

void CULHook::ReHook()
{
if (m_pfnOrig != NULL)
{
MEMORY_BASIC_INFORMATION mbi = {0};
DWORD dwOldProtect;
::VirtualQuery(m_pfnOrig, &mbi, sizeof(mbi));
::VirtualProtect(m_pfnOrig, 8, PAGE_READWRITE, &dwOldProtect);
::WriteProcessMemory(GetCurrentProcess(), (VOID*)m_pfnOrig, m_btNewBytes, 8, NULL);
::VirtualProtect(m_pfnOrig, 8, dwOldProtect, NULL);
}
}

希望本文所述对大家的C++程序设计有所帮助。