syster-ca.c

/* Nagravision Syster encoder for hacktv                                 */
/*=======================================================================*/
/* Copyright 2020 Alex L. James                                          */
/* Copyright 2018 Philip Heron <phil@sanslogic.co.uk>                    */
/*                                                                       */
/* 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 3 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, see <http://www.gnu.org/licenses/>. */

#include <stdio.h>
#include <string.h>
#include <stdint.h>
#include <stdlib.h>

#define NG_ENCRYPT 1
#define NG_DECRYPT 0

/* Key left shift table */
unsigned char const LS[] = { 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1, 0 };

/* The S-boxes */
unsigned char const S[] = {
	0x1F, 0xB0, 0x28, 0xEB, 0xD1, 0x0D, 0x42, 0x7E,	0xC5, 0x59, 0x93, 0x34, 0xA6, 0x6A, 0xFC, 0x87,
	0xB0, 0xE3, 0x17, 0x7D, 0x2B, 0x96, 0xDE, 0x48,	0x0A, 0x34, 0x6C, 0x81, 0xC5, 0x5F, 0xA9, 0xF2,
	0x2E, 0xD0, 0x72, 0xB7, 0x95, 0x0C, 0x48, 0xEB,	0x53, 0x6A, 0xC9, 0x14, 0xAF, 0xF1, 0x36, 0x8D,
	0x8D, 0x4E, 0xB1, 0xE8, 0x6B, 0x35, 0x17, 0xD2,	0xF0, 0x93, 0x56, 0x2F, 0x0C, 0xCA, 0xA9, 0x74,
	0xB2, 0x4F, 0xD4, 0x18, 0x0B, 0xF6, 0x7E, 0x25,	0xC1, 0x3C, 0x6A, 0x83, 0xAD, 0x50, 0x97, 0xE9,
	0xE9, 0xB4, 0x42, 0x27, 0x3E, 0xCB, 0x85, 0x18,	0x56, 0x0A, 0x9F, 0x70, 0xF1, 0xAD, 0x6C, 0xD3,
	0x35, 0xE0, 0x5B, 0x0D, 0x68, 0xD3, 0x96, 0x7A,	0xF9, 0x2E, 0xC2, 0xB1, 0x1F, 0x84, 0xAC, 0x47,
	0x6B, 0x1C, 0x0D, 0xA3, 0xD6, 0x7A, 0x30, 0xC5,	0x84, 0xF1, 0xBE, 0x58, 0xE9, 0x2F, 0x47, 0x92,
	0xD1, 0x34, 0xBD, 0xE3, 0x8B, 0x58, 0x42, 0x9E,	0x7A, 0xAF, 0xC0, 0x05, 0x2C, 0xF6, 0x17, 0x69,
	0xB4, 0xD7, 0xE3, 0x48, 0x5E, 0x21, 0x8D, 0x72,	0x09, 0x60, 0x3F, 0xA6, 0x95, 0xCB, 0xFA, 0x1C,
	0x82, 0x27, 0x14, 0xCA, 0xF9, 0x90, 0x6F, 0x5C,	0xEB, 0xD8, 0x7D, 0xA3, 0x4E, 0x35, 0xB1, 0x06,
	0x5C, 0x90, 0x6F, 0xF9, 0x35, 0x4E, 0x82, 0x27,	0x06, 0xEB, 0xCA, 0x14, 0xA3, 0xD8, 0x7D, 0xB1,
	0x52, 0xF8, 0x6F, 0x16, 0x9C, 0xCB, 0x09, 0xA5,	0xED, 0x27, 0x3A, 0x81, 0x43, 0xB4, 0xD0, 0x7E,
	0x2E, 0x95, 0xB2, 0x6F, 0x79, 0x06, 0xC7, 0xF8,	0x4B, 0xE0, 0xD1, 0x3C, 0xA4, 0x5A, 0x1D, 0x83,
	0x0C, 0xE2, 0x7B, 0x18, 0x90, 0x4D, 0xC7, 0xB1,	0x63, 0x8F, 0xDE, 0x25, 0x39, 0xF6, 0xA4, 0x5A,
	0xF2, 0x17, 0x85, 0x4E, 0x5C, 0xB0, 0x2B, 0xED,	0xA4, 0x79, 0x38, 0x93, 0x6F, 0xCA, 0xD1, 0x06
 };

/* Key expansion table */
unsigned char const C[] = {	
	28, 31, 24, 10, 18, 14,  7, 26,
	 4, 21, 11, 16, 12, 27, 15,  9,
	20, 30,  5, 13, 23, 29,  8, 19,
	62, 51, 44, 37, 57, 48, 56, 38,
	60, 52, 45, 41, 54, 43, 58, 49,
	36, 61, 59, 63, 40, 53, 47, 50
};

/* CW expansion table */
unsigned char const E[] = {
	31,  0,  1,  2,  3,  4,  3,  4,
	 5,  6,  7,  8,  7,  8,  9, 10,
	11, 12, 11, 12, 13, 14, 15, 16,
	15, 16, 17, 18, 19, 20, 19, 20,
	21, 22, 23, 24, 23, 24, 25, 26,
	27, 28, 27, 28, 29, 30, 31,  0
 };
 
 /* Permuation table */
unsigned char const P[] = {
	0x31, 0x12, 0x50, 0x33, 0x13, 0x21, 0x42, 0x00,
	0x51, 0x52, 0x30, 0x43, 0x53, 0x70, 0x22, 0x03,
	0x73, 0x62, 0x41, 0x60, 0x23, 0x20, 0x02, 0x01,
	0x61, 0x63, 0x40, 0x32, 0x10, 0x11, 0x71, 0x72
};

/* Initial key permutation */
int kp[] = { 0, 3, 2, 1, 4, 5, 6, 7 };

/* Initial CW permutation */
int ip[] = { 4, 0, 5, 1, 6, 2, 7, 3 };

/* Final CW permutation */
int fp[] = { 7, 3, 6, 2, 5, 1, 4, 0 };

/* Permutation */
void _permute(unsigned char *in, unsigned char *buffer1, int *p)
{
	int i, j;
	unsigned char T[8];

	memcpy(T, in, 8);

	for(j = 7; j >= 0; j-- ) 
	{
		for(i = 0; i < 8; i++ ) 
		{
			if(p[0] & 3)
			/* Final permutation */
			{
				buffer1[j] = (buffer1[j] << 1) | (T[p[i]] & 1);
				T[p[i]] >>= 1;
			}
			else
			/* Initial CW and key permutation */
			{
				buffer1[p[i]] = (buffer1[p[i]] >> 1) | (T[j] & 1 ? 0x80 : 0);
				T[j] >>= 1;
			}
		}
	}
}

/* Expansion */
void _expand_des(unsigned char const *e, unsigned char *data, unsigned char *result)
{	
	unsigned char d, i, j;

	memset(result, 0 , 8);

	for(j = 0; j < 8; j++) 
	{
		for( i = 6; i > 0; i-- ) {
			result[j] <<= 1;
			d = e[((7 - j) * 6) + (i - 1)] & (e[0] == 0x1F ? 0x1F : 0xFF);
			if(data[d >> 3] & (1 << (d & 7))) result[j] |= 1;
		}
	}
}

/* Key rotation */
void _key_rotate(int rounds, unsigned char *k)
{	
	int i, j;

	/* Rotate each half of key separately */
	for(i = 0; i < LS[rounds]; i++)
	{
		for(j = 0; j < 3; j++)
		{
			k[j + 0] = k[j + 0] >> 1 | (k[j + 1] & 1) << 7;
			k[j + 4] = k[j + 4] >> 1 | (k[j + 5] & 1) << 7;
		}
		k[3] = k[3] >> 1 | ((k[0] >> 3) & 1) << 7;
		k[7] = k[7] >> 1 | ((k[4] >> 3) & 1) << 7;
	}
}

/* Main DES function */
void _syster_des_f(unsigned char *k, unsigned char *cw, int m)
{
	int i;

	/* Expanded key and control word */
	unsigned char ecw[8], ek[8];
	
	/* Array for rotated keys */
	unsigned char *kr[16];
	
	/* Create key rotation array */
	for(i = 0; i < 16 ; i++)
	{
		kr[i] = malloc(8);
		memcpy(kr[i], k, 8);
		
		/* Rotate key */
		_key_rotate(i, k);				
	}


	for(i = 0; i < 16; i++) 
	{
		int c, j;

		/* Right half of decoded 8-bit CW */
		unsigned char r[4];
		
		/* 
		   Key expansion 
		   m: 0 = decrypt
		   m: 1 = encrypt
		*/
		_expand_des(C, kr[(m ? 15 - i : i)], ek);

		/* Plain text expansion */
		_expand_des(E, cw, ecw);

		/* Main */
		for(j = 31, c = 0; c < 8; c++)
		{
			unsigned char x, sb, m;
			int b, l;

			/* XOR key with CW */
			x = (ek[c] ^ ecw[c]) & 0x3F;

			/* S-box selection */
			sb = S[x >> 1 | (0x20 * (8 - c) & 0xFF)];
			if(x & 1) sb = sb << 4 & 0xF0;

			/* Permutation */
			for(l = 0; l < 4; l++, j--)
			{
				b = P[j] & 0x03;
				m = 1 << ((P[j] >> 4) & 0x07);
				r[b] = sb & 0x80 ? r[b] & (m ^ 0xFF) : r[b] | m;
				sb <<=1;
			}
		}

		/* XOR to create r then rotate left/right halves of CW */
		for(int l = 0; l < 4; l++)
		{				
			 r[l + 0] ^= cw[l + 4];
			cw[l + 4]  = cw[l + 0];
			cw[l + 0]  =  r[l + 0];				
		}
	}
}

uint64_t _get_syster_cw(unsigned char *ecm, unsigned char k64[8], int m)
{
	int round, i;

	unsigned char buffer1[8], cw[8], pcw[8];
    uint64_t d, controlword;

    /* Run twice - one for each half of the 16-byte encrypted control word */
	for(round = 0; round < 2; round++)
	{
		unsigned char k56[8], buffer2[8];

		/* Convert 64-bit key to 56-bit key */
		_permute(k64, k56, kp);
		k56[0] = k56[4] << 4;
		
		/* Initial CW permutation */
		_permute(ecm + round * 8, pcw, ip);

		/* Call main DES function */
		_syster_des_f(k56, pcw, m);

		/* Final permutation of CW */
		_permute(pcw, buffer2, fp);
		
		if(m == NG_ENCRYPT)
		{
			/* Copy plain CW into buffer */
			memcpy(buffer1 + (round * 4), ecm + (round * 12), 4);

			/* Copy encrypted CW back into input */
			memcpy(ecm + (round * 8), buffer2, 8);
		}
		else
		{
			/* Copy decrypted CW into buffer */
			memcpy(buffer1 + (round * 4), buffer2 + (round * 4), 4);
		}
	}

	/* Create final decoded control word */
	for(i = 0; i < 4; i++)
	{
		cw[i] = buffer1[i + 4] & (i == 3 ? 0x7F : 0xFF);
		cw[i + 4] = (buffer1[i] << 1 & (i == 3 ? 0x1F : 0xFF)) | (buffer1[(i == 0 ? 7 : i - 1)] >> 7 & 1);
	}

    for(i = controlword = 0; i < 8; i++) 
    {
        	d = cw[i];
			controlword = d << (i * 8) | controlword;
    }
	return controlword;
}