ring3下的IAT HOOK

标 题: 【原创】ring3下的IAT HOOK
作 者: hostzhen
时 间: 2013-03-28,11:30:53
链 接: http://bbs.pediy.com/showthread.php?t=166993


IAT hooking
当应用程序使用另一个动态库的函数时,PE装载器会找到每个IAMGE_IMPORT_BY_NAME结构所指向的输入函数的地址,然后把这些地址存储在一个叫做IAT的表。当函数CALL一个输入函数的时候,会先在IAT找到对应的函数地址,紧接着再进入该函数空间。熟悉PE结构的朋友应该清楚,IAT是一个IMAGE_THUNK_DATAj结构的数组。只要程序装载进内存中,就只与IAT查询信息,所以可见IAT表是一个非常重要的位置。
如果在IAT表中把某个函数的地址修改为钩子函数的地址,当调用到函数的时候,就会执行到该钩子函数中去。示例代码如下:
钩子函数,这里只是简单的弹出个窗口:

代码:
int

WINAPI

MyMessageBoxW(

/* __in_opt HWND hWnd,

__in_opt LPCWSTR lpText,

__in_opt LPCWSTR lpCaption,

__in UINT uType*/)

{

//todo yourself

return MessageBox(NULL, "hello world", "caption", MB_OK);

}

ROOKIT函数,获取目标函数的地址,然后调用IAT HOOK函数ImportAddressTableHook,修改IAT表的值。

代码:
BOOL Rookits

(

IN HMODULE hModule,

IN LPCTSTR pImageName,

IN LPCTSTR pTargetFuncName

)

{

LPDWORD pTargetFuncAddr = NULL;

HMODULE hLib = LoadLibrary(pImageName);

if (NULL != hLib)

{

pTargetFuncAddr = (LPDWORD)GetProcAddress(hLib, pTargetFuncName);

return ImportAddressTableHook(hModule, pImageName, pTargetFuncAddr, MyMessageBoxW);

}

 

return FALSE;

}

修改IAT表的函数,通过所在模块的基地址hModule找到输入表的数据目录项,获取IAT的首指针,查询目标函数地址所在的位置,然后修改为钩子函数的地址。

代码:
BOOL ImportAddressTableHook

(

 IN HMODULE hModule,

 IN LPCTSTR pImageName,

 IN LPCVOID pTargetFuncAddr,

 IN LPCVOID pReplaceFuncAddr

 )

{

    IMAGE_DOS_HEADER* pImageDosHearder = (IMAGE_DOS_HEADER*)hModule;

    IMAGE_OPTIONAL_HEADER* pImageOptionalHeader = (IMAGE_OPTIONAL_HEADER*)((DWORD)hModule+pImageDosHearder->e_lfanew+24);    

    IMAGE_IMPORT_DESCRIPTOR* pImageImportDescriptor = (IMAGE_IMPORT_DESCRIPTOR*)

        ((DWORD)hModule+

        pImageOptionalHeader->DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].VirtualAddress);

    IMAGE_THUNK_DATA* pImageThunkData = NULL;

    string TargetLibraryName;

    DWORD Value = 0, OldProtect = 0, NewProtect = 0;

    LPDWORD FunctionAddress = NULL;

    MEMORY_BASIC_INFORMATION InforMation;

 

 

    while(pImageImportDescriptor->Characteristics  != 0)   

    {   

        TargetLibraryName=(LPCTSTR)((DWORD)hModule+pImageImportDescriptor->Name);

        if(TargetLibraryName.compare(pImageName) == 0)

        {   

            pImageThunkData = (IMAGE_THUNK_DATA*)((DWORD)hModule + pImageImportDescriptor->FirstThunk);

            break; 

        } 

        pImageImportDescriptor++;   

    }  

    if (pImageThunkData == NULL)

    {

        return FALSE;

    } 

    while(pImageThunkData->u1.Function)   

    {   

        //循环查找目标函数地址所在的位置

        FunctionAddress = (LPDWORD)&(pImageThunkData->u1.Function);

        if(*FunctionAddress == (DWORD)pTargetFuncAddr)

        {    

            //找到目标函数的地址,然后修改为钩子函数的地址

            VirtualProtect(FunctionAddress, sizeof(DWORD), PAGE_READWRITE, &OldProtect);

            if(!WriteProcessMemory((HANDLE)-1, FunctionAddress, &pReplaceFuncAddr, 4, NULL))

            {

                return FALSE;

            }

            VirtualProtect(FunctionAddress, sizeof(DWORD), OldProtect, NewProtect );   

            return TRUE; 

        }  

        pImageThunkData++;   

    }

    return FALSE;

} 

也许你会注意到,如果使用了延迟装入数据,那么示例代码是无效的,因为程序会使用___delayLoadHelper2来加载,具体代码可在delayhlp.cpp查看,里面直接GetProcAddress获取该函数地址,对于这种情况只能再HOOK多一个函数,即GetProcAddress。
___delayLoadHelper2代码片段:

代码:
// Go for the procedure now.

//

dli.hmodCur = hmod;

if (__pfnDliNotifyHook2) {

pfnRet = (*__pfnDliNotifyHook2)(dliNotePreGetProcAddress, &dli);

}

if (pfnRet == 0) {

if (pidd->rvaBoundIAT && pidd->dwTimeStamp) {

// bound imports exist...check the timestamp from the target image

//

PIMAGE_NT_HEADERS pinh(PinhFromImageBase(hmod));

 

if (pinh->Signature == IMAGE_NT_SIGNATURE &&

TimeStampOfImage(pinh) == idd.dwTimeStamp &&

FLoadedAtPreferredAddress(pinh, hmod)) {

 

// Everything is good to go, if we have a decent address

// in the bound IAT!

//

pfnRet = FARPROC(UINT_PTR(idd.pBoundIAT[iIAT].u1.Function));

if (pfnRet != 0) {

goto SetEntryHookBypass;

}

}

}

 

pfnRet = ::GetProcAddress(hmod, dli.dlp.szProcName);

}

 

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