Anti DC Hack solution

[juajua123]

Hi everyone, i guess some of you know about the DC Hack, its a hack that disconnects all the players around the character, sending some packets to the server. My question is, is there a way to prevent it?, i mean a way to ignore/block the packets sent by the "hacker". And i dont mean a clientside anticheat like anticheats who detect running procceses or injection into the main, i mean server-side protection. Has anybody done it already?.

[MentaL]

[MuIsBest]

I will leave this thread open even though you're seeking help. It might help out the Mu community in a good way.

Regards,
MuIsBest

[Bakuya]

what season are you playing?

[mauka]

Mirraseq allready posted OS one of several solution of this trouble.
Use search!

[KarLi]

There's .dll that blocks wpe pro xD
Posted via Mobile Device

[1Word]

By encrypting packets this can be achieved.

[[RCZ]ShadowKing]

limit animations per second in gameserver function CGActionRecv

[juajua123]

From Mirraseq source, here is what i've done, is .18 GS

Main.cpp

FunctionHook((DWORD)&CGActionRecv,0x040641A); // CGActionRecv hook offset {JMP 0044A760}

Player.h

struct PMSG_ACTION
{
	PBMSG_HEAD h;
	BYTE Dir;	// 3
	BYTE ActionNumber;	// 4
	BYTE iTargetIndexH;	// 5
	BYTE iTargetIndexL;	// 6
};

struct AddObj
{
	int AnimTick;
	int AnimCnt;
};

#define off_LogAddTD 0x0635992C
#define off_objtable 0x0660F078
#define off_CGActionRecv 0x0044A760

#define OBJ_MAX 4000
void CGActionRecv(PMSG_ACTION * lpMsg, int aIndex);

Player.cpp

void CGActionRecv(PMSG_ACTION * lpMsg, int aIndex)
{
	DWORD dwObj = off_objtable;
        AddObj *AddTab;
	AddTab = (AddObj*)malloc(OBJ_MAX * sizeof(AddObj));
	if (aIndex > OBJ_MAX)
		return;
		
	>>>>if (AddTab[aIndex].AnimTick == 0)<<<< Unhandled exception error if i comment out "if (aIndex > OBJ_MAX)
		return;"
	{
		AddTab[aIndex].AnimTick = GetTickCount();
		AddTab[aIndex].AnimCnt = 0;
		CloseClient(aIndex);
	}
	else
	{
		int tick = GetTickCount();
		if (tick - AddTab[aIndex].AnimTick >= 1000)
		{
			AddTab[aIndex].AnimTick = tick;
			AddTab[aIndex].AnimCnt = 0;
			CloseClient(aIndex);
		}
		else
		{
			AddTab[aIndex].AnimCnt += 1;
			if (AddTab[aIndex].AnimCnt >= 10)
			{
				Log.Add("[ANTI-HACK][MoveProto][%s][%s] Too many actions (DC Hack).", (LPVOID)(dwObj + 0x68), (LPVOID)(dwObj + 0x73));
				AddTab[aIndex].AnimTick = 0;
				AddTab[aIndex].AnimCnt = 0;
				CloseClient(aIndex);
				return;
			}
		}
	}
	
	CGActionRecvFunc(lpMsg, aIndex); // pCGActionRecvFunc CGActionRecvFunc = (pCGActionRecvFunc) 0x044A760;
}

IT compiles just fine, thing is, when i get in the game the function is well hooked, but, if i comment out "if (aIndex > OBJ_MAX)" so that it goes to "(AddTab[aIndex].AnimTick == 0", GS crashes in the marked line, under "unhandled exception error". I think AddTab is not working properly, any ideas?

[[RCZ]ShadowKing]

Its obvious why it crash, it reach invalid pointer because aIndex goes over the limit of AddTab. If you define AddTab like

short AddTab[255];

you will not be able to access AddTab[256] because its not allocated in declaration. By the way I have no idea why would you delete the line you marked. And this line

AddTab = (AddObj*)malloc(OBJ_MAX * sizeof(AddObj));

you need to free the memory used for allocating AddTab once you're done with it else there will be what's called memory leak. A global preallocated instance of AddTab would be better.

.h

struct PMSG_ACTION
{
     PBMSG_HEAD h;
     BYTE Dir;    // 3
     BYTE ActionNumber;    // 4
     BYTE iTargetIndexH;    // 5
     BYTE iTargetIndexL;    // 6 
};  

struct AddObj 
{
     int AnimTick;
     int AnimCnt; 
};

#define off_LogAddTD 0x0635992C 
#define off_objtable 0x0660F078 
#define off_CGActionRecv 0x0044A760  
#define OBJ_MAX 4000


void CGActionRecv(PMSG_ACTION * lpMsg, int aIndex);

.cpp

AddObj AddTab[OBJ_MAX];

void CGActionRecv(PMSG_ACTION * lpMsg, int aIndex) 
{
     DWORD dwObj = off_objtable;
     if (aIndex > OBJ_MAX)         return;
     if (AddTab[aIndex].AnimTick == 0)
     {
         AddTab[aIndex].AnimTick = GetTickCount();
         AddTab[aIndex].AnimCnt = 0;
         CloseClient(aIndex);
     }
     else
     {
         int tick = GetTickCount();
         if (tick - AddTab[aIndex].AnimTick >= 1000)
         {
             AddTab[aIndex].AnimTick = tick;
             AddTab[aIndex].AnimCnt = 0;
             CloseClient(aIndex);
         }
         else
         {
             AddTab[aIndex].AnimCnt += 1;
             if (AddTab[aIndex].AnimCnt >= 10)
             {
                 Log.Add("[ANTI-HACK][MoveProto][%s][%s] Too many actions (DC Hack).", (LPVOID)(dwObj + 0x68), (LPVOID)(dwObj + 0x73));
                 AddTab[aIndex].AnimTick = 0;
                 AddTab[aIndex].AnimCnt = 0;
                 CloseClient(aIndex);
                 return;
             }
         }
     }
          CGActionRecvFunc(lpMsg, aIndex); // pCGActionRecvFunc CGActionRecvFunc = (pCGActionRecvFunc) 0x044A760; 
}

Somewhere before starting using the AddTab clean it like

memset(&AddTab, 0x00, sizeof(AddTab));

[juajua123]

Ok, i done it, but why is it always returning in this part of the code?

if (aIndex > OBJ_MAX) 
		 Log.Add("[DBG] return > aIndex > OBJ_MAX");
			 >return;

Why is that happening, if im a valid player inside of the game?

Is this okay?, i mean the memset location.

void CGActionRecv(PMSG_ACTION * lpMsg, int aIndex) 
{
     memset(&AddTab, 0x00, sizeof(AddTab)); 
     DWORD dwObj = off_objtable;
     if (aIndex > OBJ_MAX) 
	Log.Add("[DBG] return > aIndex > OBJ_MAX");
	return;
     ...........
}

If i comment the "return;" there it shows "unhandled exception error" under this line
" AddTab[aIndex].AnimCnt += 1;"

Thanks for answering this noob questions.

[[RCZ]ShadowKing]

You need to set OBJ_MAX value for your gameserver, if you don't know to search it with olly then set OBJ_MAX to something like 10000 or bigger just to be sure.

Memset is not good located, put it before you do the hook like
memset(...);
Hook(...);

[juajua123]

I have OBJ_MAX already set to 7400 wich is MAX in GS .18, but its still returning in the "if (aIndex > OBJ_MAX) return;", if i comment out that line it works perfectly.

[[RCZ]ShadowKing]

Make this

Log.Add("[DBG] return > aIndex > OBJ_MAX");

to

Log.Add("[DBG] return > aIndex > OBJ_MAX %d", aIndex);

And tell me what value return.

[juajua123]

I get 6400 as index, im the only player in the server.

[[RCZ]ShadowKing]

You're sure you defined like

#define OBJ_MAX 7400

?
I see no other reason why it return at that line.
If you delete the line it may happen to crash if player index is bigger than AddTab size.