IAT HOOK RING3

#include "stdafx.h"#include <windows.h>#include <stdio.h>// 挂钩指定模块hMod对MessageBoxA的调用BOOL SetHookApi(HMODULE hMod);// 定义MessageBoxA函数原型typedef int (WINAPI *PFNMESSAGEBOX)(HWND, LPCSTR, LPCSTR, UINT uType);// 保存MessageBoxA函数的真实地址PROC g_orgProc = (PROC)MessageBoxA;void main(){// 调用原API函数::MessageBox(NULL, "原函数", "HookDemo", 0);// 挂钩后再调用SetHookApi(::GetModuleHandle(NULL));::MessageBox(NULL, "新函数", "HookDemo", 0);}// 用于替换MessageBoxA的自定义函数int WINAPI MyMessageBoxA(HWND hWnd, LPCSTR lpText, LPCSTR lpCaption, UINT uType){return ((PFNMESSAGEBOX)g_orgProc)(hWnd, "新函数", "HookDemo", uType);}BOOL SetHookApi(HMODULE hMod){IMAGE_DOS_HEADER* pDosHeader = (IMAGE_DOS_HEADER*)hMod;IMAGE_OPTIONAL_HEADER * pOptHeader =(IMAGE_OPTIONAL_HEADER *)((BYTE*)hMod + pDosHeader->e_lfanew + 24);IMAGE_IMPORT_DESCRIPTOR* pImportDesc = (IMAGE_IMPORT_DESCRIPTOR*)((BYTE*)hMod + pOptHeader->DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].VirtualAddress);// 在导入表中查找user32.dll模块。因为MessageBoxA函数从user32.dll模块导出while(pImportDesc->FirstThunk){char* pszDllName = (char*)((BYTE*)hMod + pImportDesc->Name);if(lstrcmpiA(pszDllName, "user32.dll") == 0){break;}pImportDesc++;}if(pImportDesc->FirstThunk){// 一个IMAGE_THUNK_DATA就是一个双字，它指定了一个导入函数// 调入地址表其实是IMAGE_THUNK_DATA结构的数组，也就是DWORD数组IMAGE_THUNK_DATA* pThunk = (IMAGE_THUNK_DATA*)((BYTE*)hMod + pImportDesc->FirstThunk);while(pThunk->u1.Function){// lpAddr指向的内存保存了函数的地址DWORD* lpAddr = (DWORD*)&(pThunk->u1.Function);if(*lpAddr == (DWORD)g_orgProc){ DWORD dwOldProtect;MEMORY_BASIC_INFORMATION mb;VirtualQuery(lpAddr, &mb, sizeof(mb));VirtualProtect(lpAddr, sizeof(DWORD), PAGE_READWRITE, &dwOldProtect);// 修改IAT表项，使其指向我们自定义的函数，相当于“*lpAddr = (DWORD)MyMessageBoxA;”DWORD* lpNewProc = (DWORD*)MyMessageBoxA;::WriteProcessMemory(::GetCurrentProcess(), lpAddr, &lpNewProc, sizeof(DWORD), NULL);VirtualProtect(lpAddr, sizeof(DWORD), dwOldProtect, 0);return TRUE;}pThunk++;}}return FALSE;}