Defining Function Pointers

Question

I am trying to call the internal Windows NT API function NtOpenProcess. I know calling internal APIs can be a bad idea, but for this particular tool I need the low-level access this API provides.

My problem is that to use such an internal API, I need to use Runtime Dynamic Linking, as specified in this article

To do that, I need to define a function pointer to NtOpenProcess. Here's my declaration:

typedef NTSTATUS (NTAPI *_NtOpenProcess) (
OUT PHANDLE,
IN ACCESS_MASK,
IN POBJECT_ATTRIBUTES,
IN PCLIENT_ID OPTIONAL);

class procManager
{
    HINSTANCE hNTDLL;
public:
    procManager()
    {
        hNTDLL = LoadLibrary(L"ntdll.dll");
        if (!hNTDLL)
            throw std::runtime_error("NTDLL.DLL failure.");
        _NtOpenProcess NtOpenProcess;
        NtOpenProcess = reinterpret_cast <_NtOpenProcess> (GetProcAddress(hNTDLL, L"NtOpenProcess"));
        if (!NtOpenProcess)
            throw std::runtime_error("NtOpenProcess not found.");
        //Use NTOpenProcess for stuff here
    };
    ~procManager()
    {
        FreeLibrary(hNTDLL);
    };
};

Problem is, apparently there is an error in my typedef above. The compiler returns:

error C2059: syntax error : '__stdcall'

I used the handy dandy "Go To Definition" feature of my IDE (Visual Studio 2008) and found that NTAPI in the declaration is defined as __stdcall.

Unfortunately, removing NTAPI from my declaration, making it this:

typedef NTSTATUS (*_NtOpenProcess) (
OUT PHANDLE,
IN ACCESS_MASK,
IN POBJECT_ATTRIBUTES,
IN PCLIENT_ID OPTIONAL);

results in another error:

error C2065: '_NtOpenProcess' : undeclared identifier

At this point I'm saying "Of course it's undefined, that's why it's a typedef!"

Does anyone see my error in the declaration?

Answer 1

Did you include "ntdef.h" and "ntstatus.h" ? The compiler probably cant understand NTSTATUS.

Answer 2

View this good ref. How can I write a generic C function for calling a Win32 function?