Thread: What is wrong with my function?

im making a small anti-cheat, and i want to check if functions are patched.

Code:

bool cAntiCheat::IsFuncValid( DWORD dwAddress, char* szMemMatch, int iSize )
{
	BYTE* szMemOrig;
	DWORD dwOldProtection, dwDummy;
	VirtualProtect( ( PVOID )dwAddress, iSize, PAGE_EXECUTE_READWRITE, &dwOldProtection );
	memcpy( ( BYTE* )szMemOrig, ( BYTE* )dwAddress, iSize );
	VirtualProtect( ( PVOID )dwAddress, iSize, dwOldProtection, &dwDummy );
	if( !memcmp( ( BYTE* )szMemOrig, ( BYTE* )szMemMatch , iSize ))return true;
	return false;
}

you use it like this:

Code:

			if( !cAC.IsFuncValid( 0x7428E6, "\xFF\x4E\x0C\x8B\x46\x08", 6 ) )
				KICKTYPE = KICK_AMMO;

but it always crashes (also by this point i should mention im making an anti-cheat without source code access ( hacky ) )

thanks.

Originally Posted by s0beit

Code:

	BYTE* szMemOrig;
	memcpy( ( BYTE* )szMemOrig, ( BYTE* )dwAddress, iSize );

szMemOrig is an uninitialized pointer, and then you try to copy something to the place it points to

Code:

bool cAntiCheat::IsFuncValid( PVOID dwAddress, char* szMemMatch, int iSize )
{
	char* szMemOrig = 0;
	DWORD dwOldProtection, dwDummy;
	VirtualProtect( dwAddress, iSize, PAGE_EXECUTE_READWRITE, &dwOldProtection );
	memcpy( ( char* )szMemOrig, ( char* )dwAddress, iSize );
	VirtualProtect( dwAddress, iSize, dwOldProtection, &dwDummy );
	if( !memcmp( ( char* )szMemOrig, ( char* )szMemMatch , iSize ))return true;
	return false;
}

still crashes, ive done stuff like this before and its never been a problem.

Originally Posted by s0beit

Code:

bool cAntiCheat::IsFuncValid( PVOID dwAddress, char* szMemMatch, int iSize )
{
	char* szMemOrig = 0;
	DWORD dwOldProtection, dwDummy;
	VirtualProtect( dwAddress, iSize, PAGE_EXECUTE_READWRITE, &dwOldProtection );
	memcpy( ( char* )szMemOrig, ( char* )dwAddress, iSize );
	VirtualProtect( dwAddress, iSize, dwOldProtection, &dwDummy );
	if( !memcmp( ( char* )szMemOrig, ( char* )szMemMatch , iSize ))return true;
	return false;
}

still crashes, ive done stuff like this before and its never been a problem.

you did not fix the problem: you need to allocate memory before you can copy things into it

Code:

bool cAntiCheat::IsFuncValid( PVOID dwAddress, char* szMemMatch, int iSize )
{
	char* szMemOrig = ( char* )malloc( iSize );
	DWORD dwOldProtection, dwDummy = 0x0;
	VirtualProtect( dwAddress, iSize, PAGE_EXECUTE_READWRITE, &dwOldProtection );
	memcpy( szMemOrig, dwAddress, iSize );
	VirtualProtect( dwAddress, iSize, dwOldProtection, &dwDummy );
	//if( !memcmp( ( char* )szMemOrig, ( char* )szMemMatch , iSize ))return true;
	return true;
}

i still need to do the compare code, but it doesnt crash.

thanks for the hints.