proxmark3/client/loclass/cipherutils.c

/*****************************************************************************
 * This file is part of iClassCipher. It is a reconstructon of the cipher engine
 * used in iClass, and RFID techology.
 *
 * The implementation is based on the work performed by
 * Flavio D. Garcia, Gerhard de Koning Gans, Roel Verdult and
 * Milosch Meriac in the paper "Dismantling IClass".
 *
 * Copyright (C) 2014 Martin Holst Swende
 *
 * This is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation.
 *
 * This file 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 IClassCipher.  If not, see <http://www.gnu.org/licenses/>.
 ****************************************************************************/

#include "cipherutils.h"
#include "../util.h"
#include <stdint.h>
#include <stdio.h>
#include <string.h>

/**
 *
 * @brief Return and remove the first bit (x0) in the stream : <x0 x1 x2 x3 ... xn >
 * @param stream
 * @return
 */
bool headBit( BitstreamIn *stream)
{
	int bytepos = stream->position >> 3; // divide by 8
	int bitpos = (stream->position++) & 7; // mask out 00000111
	return (*(stream->buffer + bytepos) >> (7-bitpos)) & 1;
}
/**
 * @brief Return and remove the last bit (xn) in the stream: <x0 x1 x2 ... xn>
 * @param stream
 * @return
 */
bool tailBit( BitstreamIn *stream)
{
	int bitpos = stream->numbits -1 - (stream->position++);

	int bytepos= bitpos >> 3;
	bitpos &= 7;
	return (*(stream->buffer + bytepos) >> (7-bitpos)) & 1;
}
/**
 * @brief Pushes bit onto the stream
 * @param stream
 * @param bit
 */
void pushBit( BitstreamOut* stream, bool bit)
{
	int bytepos = stream->position >> 3; // divide by 8
	int bitpos = stream->position & 7;
	*(stream->buffer+bytepos) |= (bit & 1) <<  (7 - bitpos);
	stream->position++;
	stream->numbits++;
}

/**
 * @brief Pushes the lower six bits onto the stream
 * as b0 b1 b2 b3 b4 b5 b6
 * @param stream
 * @param bits
 */
void push6bits( BitstreamOut* stream, uint8_t bits)
{
	pushBit(stream, bits & 0x20);
	pushBit(stream, bits & 0x10);
	pushBit(stream, bits & 0x08);
	pushBit(stream, bits & 0x04);
	pushBit(stream, bits & 0x02);
	pushBit(stream, bits & 0x01);
}

/**
 * @brief bitsLeft
 * @param stream
 * @return number of bits left in stream
 */
int bitsLeft( BitstreamIn *stream)
{
	return stream->numbits - stream->position;
}
/**
 * @brief numBits
 * @param stream
 * @return Number of bits stored in stream
 */
int numBits(BitstreamOut *stream)
{
	return stream->numbits;
}

uint8_t reversebytes(uint8_t b) {
	b = (b & 0xF0) >> 4 | (b & 0x0F) << 4;
	b = (b & 0xCC) >> 2 | (b & 0x33) << 2;
	b = (b & 0xAA) >> 1 | (b & 0x55) << 1;
   return b;
}
void reverse_arraybytes(uint8_t* arr, size_t len)
{
	uint8_t i;
	for( i =0; i< len ; i++)
	{
		arr[i] = reversebytes(arr[i]);
	}
}


//-----------------------------
// Code for testing below
//-----------------------------


int testBitStream()
{
	uint8_t input [] = {0xDE,0xAD,0xBE,0xEF,0xDE,0xAD,0xBE,0xEF};
	uint8_t output [] = {0,0,0,0,0,0,0,0};
	BitstreamIn in = { input, sizeof(input) * 8,0};
	BitstreamOut out ={ output, 0,0}
					  ;
	while(bitsLeft(&in) > 0)
	{
		pushBit(&out, headBit(&in));
		//printf("Bits left: %d\n", bitsLeft(&in));
		//printf("Bits out: %d\n", numBits(&out));
	}
	if(memcmp(input, output, sizeof(input)) == 0)
	{
		printf("Bitstream test 1 ok\n");
	}else
	{
		printf("Bitstream test 1 failed\n");
		uint8_t i;
		for(i = 0 ; i < sizeof(input) ; i++)
		{
			printf("IN %02x, OUT %02x\n", input[i], output[i]);
		}
		return 1;
	}
	return 0;
}

int testReversedBitstream()
{
	uint8_t input [] = {0xDE,0xAD,0xBE,0xEF,0xDE,0xAD,0xBE,0xEF};
	uint8_t reverse [] = {0,0,0,0,0,0,0,0};
	uint8_t output [] = {0,0,0,0,0,0,0,0};
	BitstreamIn in = { input, sizeof(input) * 8,0};
	BitstreamOut out ={ output, 0,0};
	BitstreamIn reversed_in ={ reverse, sizeof(input)*8,0};
	BitstreamOut reversed_out ={ reverse,0 ,0};

	while(bitsLeft(&in) > 0)
	{
		pushBit(&reversed_out, tailBit(&in));
	}
	while(bitsLeft(&reversed_in) > 0)
	{
		pushBit(&out, tailBit(&reversed_in));
	}
	if(memcmp(input, output, sizeof(input)) == 0)
	{
		printf("Bitstream test 2 ok\n");
	}else
	{
		printf("Bitstream test 2 failed\n");
		uint8_t i;
		for(i = 0 ; i < sizeof(input) ; i++)
		{
			printf("IN %02x, MIDDLE: %02x, OUT %02x\n", input[i],reverse[i], output[i]);
		}
		return 1;
	}
	return 0;
}


int testCipherUtils(void)
{
	int retval = 0;
	retval |= testBitStream();
	retval |= testReversedBitstream();
	return retval;
}