#include "hookiat.h"
 
void HookIAT(char *tohooklibrary, char *tohookfunc, void *newfunc)
{
	DWORD image_base=GetModuleHandleA(0);
	PIMAGE_DOS_HEADER DOS;
	PIMAGE_NT_HEADERS NT;
	PIMAGE_IMPORT_DESCRIPTOR IT;
	PIMAGE_IMPORT_BY_NAME *IMPORTED_FUNCTIONS;
	PIMAGE_THUNK_DATA Funcion;
	DWORD *IMPORTED_DLL_NAME;
	DWORD *IMPORTED_FUNCTION_NAME;
	unsigned int i=0;
 
	DOS=(PIMAGE_DOS_HEADER)image_base;
	NT=(PIMAGE_NT_HEADERS)(DOS->e_lfanew + image_base);
	IT=(PIMAGE_IMPORT_DESCRIPTOR)(NT->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].VirtualAddress + image_base);
	IMPORTED_DLL_NAME=(DWORD *)(IT->Name + image_base);
 
	while( (IT->Name) != 0 )
	{
		IMPORTED_DLL_NAME=(DWORD *)(IT->Name + image_base);
		if(!strcmp((char *)IMPORTED_DLL_NAME, tohooklibrary))
		{
			break;
		}
		IT++;
	}
 
	IMPORTED_FUNCTIONS=(PIMAGE_IMPORT_BY_NAME *)(IT->Characteristics + image_base);
 
	for(i=0;;i++)
	{
		IMPORTED_FUNCTION_NAME=(DWORD *)((*IMPORTED_FUNCTIONS)->Name + image_base);
		if(((*IMPORTED_FUNCTIONS)!=0) && (!strcmp((char *)IMPORTED_FUNCTION_NAME, tohookfunc)))
		{
			break;
		}
		IMPORTED_FUNCTIONS++;
	}
 
	Funcion=(PIMAGE_THUNK_DATA)(IT->FirstThunk + image_base);
	Funcion+=i;
	ORIGINAL_FUNCTION=(void *)Funcion->u1.Function;
	Funcion->u1.Function=(DWORD)newfunc;
}
 

#include <string.h>
#include <windows.h>
 
void *ORIGINAL_FUNCTION;
 
void HookIAT(char *tohooklibrary, char *tohookfunc, void *newfunc);