munge.cpp

/*
*
*    This program is free software; you can redistribute it and/or modify it
*    under the terms of the GNU General Public License as published by the
*    Free Software Foundation; either version 2 of the License, or (at
*    your option) any later version.
*
*    This program is distributed in the hope that it will be useful, but
*    WITHOUT ANY WARRANTY; without even the implied warranty of
*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
*    General Public License for more details.
*
*    You should have received a copy of the GNU General Public License
*    along with this program; if not, write to the Free Software Foundation,
*    Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*
*    In addition, as a special exception, the author gives permission to
*    link the code of this program with the Half-Life Game Engine ("HL
*    Engine") and Modified Game Libraries ("MODs") developed by Valve,
*    L.L.C ("Valve").  You must obey the GNU General Public License in all
*    respects for all of the code used other than the HL Engine and MODs
*    from Valve.  If you modify this file, you may extend this exception
*    to your version of the file, but you are not obligated to do so.  If
*    you do not wish to do so, delete this exception statement from your
*    version.
*
*/

#include "precompiled.h"

const unsigned char mungify_table[] =
{
	0x7A, 0x64, 0x05, 0xF1,
	0x1B, 0x9B, 0xA0, 0xB5,
	0xCA, 0xED, 0x61, 0x0D,
	0x4A, 0xDF, 0x8E, 0xC7
};

const unsigned char mungify_table2[] =
{
	0x05, 0x61, 0x7A, 0xED,
	0x1B, 0xCA, 0x0D, 0x9B,
	0x4A, 0xF1, 0x64, 0xC7,
	0xB5, 0x8E, 0xDF, 0xA0
};

unsigned char mungify_table3[] =
{
	0x20, 0x07, 0x13, 0x61,
	0x03, 0x45, 0x17, 0x72,
	0x0A, 0x2D, 0x48, 0x0C,
	0x4A, 0x12, 0xA9, 0xB5
};

// Anti-proxy/aimbot obfuscation code
// COM_UnMunge should reversably fixup the data
void COM_Munge(unsigned char *data, int len, int seq)
{
	int i;
	int mungelen;
	int c;
	int *pc;
	unsigned char *p;
	int j;

	mungelen = len & ~3;
	mungelen /= 4;

	for (i = 0; i < mungelen; i++)
	{
		pc = (int *)&data[i * 4];
		c = *pc;
		c ^= ~seq;
		c = _LongSwap(c);

		p = (unsigned char *)&c;
		for (j = 0; j < 4; j++)
		{
			*p++ ^= (0xa5 | (j << j) | j | mungify_table[(i + j) & 0x0f]);
		}

		c ^= seq;
		*pc = c;
	}
}

void COM_UnMunge(unsigned char *data, int len, int seq)
{
	int i;
	int mungelen;
	int c;
	int *pc;
	unsigned char *p;
	int j;

	mungelen = len & ~3;
	mungelen /= 4;

	for (i = 0; i < mungelen; i++)
	{
		pc = (int *)&data[i * 4];
		c = *pc;
		c ^= seq;

		p = (unsigned char *)&c;
		for (j = 0; j < 4; j++)
		{
			*p++ ^= (0xa5 | (j << j) | j | mungify_table[(i + j) & 0x0f]);
		}

		c = _LongSwap(c);
		c ^= ~seq;
		*pc = c;
	}
}

void COM_Munge2(unsigned char *data, int len, int seq)
{
	int i;
	int mungelen;
	int c;
	int *pc;
	unsigned char *p;
	int j;

	mungelen = len & ~3;
	mungelen /= 4;

	for (i = 0; i < mungelen; i++)
	{
		pc = (int *)&data[i * 4];
		c = *pc;
		c ^= ~seq;
		c = _LongSwap(c);

		p = (unsigned char *)&c;
		for (j = 0; j < 4; j++)
		{
			*p++ ^= (0xa5 | (j << j) | j | mungify_table2[(i + j) & 0x0f]);
		}

		c ^= seq;
		*pc = c;
	}
}

void COM_UnMunge2(unsigned char *data, int len, int seq)
{
	int i;
	int mungelen;
	int c;
	int *pc;
	unsigned char *p;
	int j;

	mungelen = len & ~3;
	mungelen /= 4;

	for (i = 0; i < mungelen; i++)
	{
		pc = (int *)&data[i * 4];
		c = *pc;
		c ^= seq;

		p = (unsigned char *)&c;
		for (j = 0; j < 4; j++)
		{
			*p++ ^= (0xa5 | (j << j) | j | mungify_table2[(i + j) & 0x0f]);
		}

		c = _LongSwap(c);
		c ^= ~seq;
		*pc = c;
	}
}

void COM_Munge3(unsigned char *data, int len, int seq)
{
	int i;
	int mungelen;
	int c;
	int *pc;
	unsigned char *p;
	int j;

	mungelen = len & ~3;
	mungelen /= 4;

	for (i = 0; i < mungelen; i++)
	{
		pc = (int *)&data[i * 4];
		c = *pc;
		c ^= ~seq;
		c = _LongSwap(c);

		p = (unsigned char *)&c;
		for (j = 0; j < 4; j++)
		{
			*p++ ^= (0xa5 | (j << j) | j | mungify_table3[(i + j) & 0x0f]);
		}

		c ^= seq;
		*pc = c;
	}
}

void COM_UnMunge3(unsigned char *data, int len, int seq)
{
	int i;
	int mungelen;
	int c;
	int *pc;
	unsigned char *p;
	int j;

	mungelen = len & ~3;
	mungelen /= 4;

	for (i = 0; i < mungelen; i++)
	{
		pc = (int *)&data[i * 4];
		c = *pc;
		c ^= seq;

		p = (unsigned char *)&c;
		for (j = 0; j < 4; j++)
		{
			*p++ ^= (0xa5 | (j << j) | j | mungify_table3[(i + j) & 0x0f]);
		}

		c = _LongSwap(c);
		c ^= ~seq;
		*pc = c;
	}
}