Access Violation
- by Justin
I've been learning how to NOP functions in C++ or even C but there are very few tutorials online about it. I've been googling for the past few hours now and I'm just stuck. Here is my code.
#include <iostream>
#include <windows.h>
#include <tlhelp32.h>
using namespace std;
//#define NOP 0x90
byte NOP[] = {0x90};
void enableDebugPrivileges() {
HANDLE hcurrent=GetCurrentProcess();
HANDLE hToken;
BOOL bret=OpenProcessToken(hcurrent,40,&hToken);
LUID luid;
bret=LookupPrivilegeValue(NULL,"SeDebugPrivilege",&luid);
TOKEN_PRIVILEGES NewState,PreviousState;
DWORD ReturnLength;
NewState.PrivilegeCount =1;
NewState.Privileges[0].Luid =luid;
NewState.Privileges[0].Attributes=2;
AdjustTokenPrivileges(hToken,FALSE,&NewState,28,&PreviousState,&ReturnLength);
}
DWORD GetProcId(char* ProcName)
{
PROCESSENTRY32 pe32;
HANDLE hSnapshot = NULL;
pe32.dwSize = sizeof( PROCESSENTRY32 );
hSnapshot = CreateToolhelp32Snapshot( TH32CS_SNAPPROCESS, 0 );
if( Process32First( hSnapshot, &pe32 ) )
{
do{
if( strcmp( pe32.szExeFile, ProcName ) == 0 )
break;
}while( Process32Next( hSnapshot, &pe32 ) );
}
if( hSnapshot != INVALID_HANDLE_VALUE )
CloseHandle( hSnapshot );
return pe32.th32ProcessID;
}
void WriteMem(DWORD Address, void* Value, size_t Size) {
DWORD Protect = NULL;
VirtualProtect((LPVOID)Address, 3, PAGE_READWRITE, &Protect);
memcpy((void*)Address, Value, 3);
VirtualProtect((LPVOID)Address, 3, Protect, &Protect);
}
void nop_(PVOID address, int bytes){
DWORD d, ds;
VirtualProtect(address, bytes, PAGE_EXECUTE_READWRITE, &d);
memset(address, 144, bytes);
VirtualProtect(address,bytes,d,&ds);
}
void MemCopy(HANDLE pHandle, void* Dest, const void* Src, int Len)
{
DWORD OldProtect;
DWORD OldProtect2;
VirtualProtect(Dest, Len, PAGE_EXECUTE_READWRITE, &OldProtect);
memcpy(Dest, Src, Len);
VirtualProtect(Dest, Len, OldProtect, &OldProtect2);
FlushInstructionCache(pHandle, Dest, Len);
}
int main()
{
enableDebugPrivileges();
DWORD pid;
HANDLE phandle;
// Obtain the process ID
pid = GetProcId("gr.exe");
if(GetLastError())
{
cout << "Error_PID_: " << GetLastError() << endl;
system("pause");
return -1;
}
// Obtain the process handle
phandle = OpenProcess(PROCESS_ALL_ACCESS,0,pid);
if(GetLastError())
{
cout << "Error_HANDLE_: " << GetLastError() << endl;
system("pause");
return -1;
}
// Debug info, 0 = bad
cout <<"pid : " << pid << endl;
cout <<"HANDLE: " << phandle << endl << endl;
system("pause");
// Change value to
short iValue = -1;
int choice = 0;
BYTE * bGodMode = (BYTE *) (0x409A7E); // Lives Address
bool hack = true;
while(hack)
{
system("cls");
cout << "What hack?\n0. Exit\n1. Lives\n\n!> ";
cin >> choice;
switch(choice)
{
case 0:
{
hack=false;
break;
}
case 1:
// Modify Time
cout << "God Mode On\n!> ";
// cin >> iValue;
// nop_((PVOID)(0x409A7E), 3);
// MemCopy(phandle, (PVOID)0x409A7E, &NOP, 1);
WriteMem((DWORD)(0x00409A7E), (void*)NOP, sizeof NOP);
if(GetLastError())
{
cout << "Error: " << GetLastError() << endl;
system("pause");
}
break;
default:
cout << "ERROR!\n";
break;
}
Sleep(100);
}
system("pause");
return 0;
}
This is suppose to NOP the DEC function that is 3 bytes long preventing me from losing lives. However each time I try it, it crashes the hack and says I had a access violation. I tried to look up the reasons and most of them dealt with with the size of the location I'm writing to and what I'm copying from. Otherwise, I have absolutely no idea. Any help would be nice. The game is GunRoar and the base address "0x409A7E" is where the DEC function is.
