2 Questions Interact/Select Target C++

[jockel]

Heya,

I have two questions I'm not able to figure out since hours , can't count my Wow crashes...

I'm injecting a C++ libary which communicates via named pipes with my main application.


1) My main application sends the "BaseAddress" of an object to the library

From the BaseAddress I'm figuring out the function pointer to the interact function, which looks like this:

typedef void (__thiscall *tInteract) (void);
tInteract oInteract;

void Interact(DWORD baseAddress)
{
	DWORD_PTR unitInteractVMT = *reinterpret_cast<DWORD_PTR*>(*reinterpret_cast<DWORD_PTR*>(baseAddress) + (38 *4));
	oInteract= reinterpret_cast<tInteract>(unitInteractVMT );
	oInteract();
}

But it seems to crash my Wow with a read error.

2) Targeting:
My main application sends a string containing the guid to my library, now how do I convert std::string to __int64 or _WowGuid?

Tried to search the internet, but I can't find a solution for this problem.


Would be really great to receive some hints.

[Shynd]

Maybe you shouldn't be sending the GUID in string format. Just write the individual bytes (or two, hi- and lo-word, DWORDs) to the stream and read them off in the same way you are reading the baseaddress, then combine them into an int64. Not too difficult.

And, by the way, __thiscall means it's called as a part of a class; more specifically, it's called as a part of the object class (or a derivative), which means you have to assign the baseaddress of the object with which you interact to the ecx register. I believe, actually, changing your typedef to typedef void (__thiscall * tInteract)(void * BaseAddress); and calling it with baseAddress as the first parameter will work, but I'm not sure. Cypher or someone else will correct me.

I always used a dummy CObject class and cast the baseAddress to CObject, then called obj->Interact() (much, much better way of doing it).

[jockel]

Thanks for clearing this up Shynd, slowly I'm going to understand how the things are working.

Now regarding to my SelectTarget problem, instead of passing a low and high word through the named pipe I decided to send the baseAddress and read the guid from the baseaddress of an object.

But now my SelectTarget function is also going to crash wow, but I'm nearly sure my code is correct.

FUNCTION_AT_ADDRESS( bool __fastcall _SelectTarget(_WoWGuid guid), _ptrSetTarget);

void SelectTarget(DWORD baseAddress)
{
_WoWGuid * pguid = (_WoWGuid *)(baseAddress + 0x30);
_WoWGuid guid = *pguid;

_SelectTarget(guid);
}

This application has encountered a critical error:

ERROR #132 (0x85100084) Fatal Exception
Program: Wow.exe
Exception: 0x80000003 (BREAKPOINT) at 001B:7C91120E

[ggg898]

Well I dont know what your definition of FUNCTION_AT_ADDRESS does, but if it types SelectTarget as a fastcall routine, i guess the stack gets messed up. If i remember right fastcall passes two parameters in eax and ebx and the rest on the stack.

this is how i type it, and it works fine

typedef void (__cdecl * tSelectUnit)(__int64 guid);

[jockel]

I feel like an idiot, working now...
Thanks for all helping me out.