挂接API

// hook.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include <windows.h>
PVOID HookAPI(LPBYTE pbModule,PCSTR pszName,PVOID pvOrg,PVOID pvNew)
{
	PIMAGE_THUNK_DATA r;
	PIMAGE_NT_HEADERS p;
	PIMAGE_IMPORT_DESCRIPTOR q;
	p=(PIMAGE_NT_HEADERS)(pbModule+(((IMAGE_DOS_HEADER*)(pbModule))->e_lfanew));
	q=(PIMAGE_IMPORT_DESCRIPTOR)(pbModule+p->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].VirtualAddress);
	for (;q->Name;q++)
	{
		if (lstrcmpi(pszName,(LPCSTR)(pbModule+q->Name))==0)
		{
			for (r=(PIMAGE_THUNK_DATA)(pbModule+q->FirstThunk);r->u1.Function;++r)
			{
				if ((PVOID)r->u1.Function==pvOrg)
				{
					WriteProcessMemory(GetCurrentProcess(),&r->u1.Function,&pvNew,sizeof(PVOID),NULL);
					return pvOrg;
				}
			}
		}
	}
	return NULL;
}
typedef int (WINAPI *PFMessageBox)(HWND,LPCSTR,LPCSTR,UINT);
PFMessageBox g_addr=MessageBox;
int WINAPI MyMessageBox(HWND hwnd,LPCSTR lpText,LPCSTR lpCaption,UINT uType)
{
	return g_addr(hwnd,"123","",uType);
}
int main(int argc, char* argv[])
{
	MessageBox(0,0,0,0);
	HookAPI((LPBYTE)GetModuleHandle(NULL),"user32.dll",MessageBox,MyMessageBox);
	MessageBox(0,0,0,0);
	return 0;
}