/**********************************************************************
  my_crypt.c
 **********************************************************************

  my_crypt - Clone of the UNIX crypt (1) utility.

  The latest version of this program should be available at:
  http://saa.dyndns.org/stewart

  Copyright ©2001, 2003, 2009, Stewart Adcock <stewart--AT--linux-domain.com>
  All rights reserved.

  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions
  are met:
 
     * Redistributions of source code must retain the above copyright
       notice, this list of conditions and the following disclaimer.
     * Redistributions in binary form must reproduce the above
       copyright notice, this list of conditions and the following
       disclaimer in the documentation and/or other materials provided
       with the distribution.
 
  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
  OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
  WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  POSSIBILITY OF SUCH DAMAGE.

 **********************************************************************

  synopsis:	Dodgy clone of the dodgy UNIX crypt utility.

  compilation:	try typing something like this with the GNU compiler:
		gcc my_crypt.c -o crypt -lcrypt -Wall -O2

  usage:	crypt [-s] passkey < file > encrypted_file
		crypt [-s] passkey < encrypted_file > file

		Warning: This _IS_ _NOT_ designed to be
		cryptographically secure.  It was solely written as
		a means to decrypt files which were encrypted using
		the legacy UNIX crypt utility.

  Last Updated: 01 June 2009 SAA	Re-released under the terms of the 2-clause BSD license.
            28 May 2003 SAA	Fixed a bug - thanks to Dr A J Bartlett for pointing this out.
		11/06/01 SAA    Clone of UNIX crypt utility.

 **********************************************************************/

#define _XOPEN_SOURCE	/* For crypt() */
#define _ISO99_SOURCE	/* For int32_t */

#include <stdio.h>
#include <stdint.h>	/* Comment out this line for MIPSpro compiler on IRIX, and possibly others. */
#include <stdlib.h>
#include <unistd.h>

#define NUM_ROTORS	256
#define MASK		0377

char	t1[NUM_ROTORS];
char	t2[NUM_ROTORS];
char	t3[NUM_ROTORS];
char	deck[NUM_ROTORS];

char *init(char *key)
  {
  int		ic, i, j, temp;
  unsigned int	random;
  int32_t	seed=123;
  char		*password;

  password = (char *)crypt(key, key);

  for (i=0; i<13; i++) seed = seed*password[i] + i;

  for(i=0;i<NUM_ROTORS;i++)
    {
    t1[i] = i;
    deck[i] = i;
    t2[i] = 0;
    t3[i] = 0;
    }

  for(i=0;i<NUM_ROTORS;i++)
    {
    seed = 5*seed + password[i%13];
    random = seed % 65521;
    j = NUM_ROTORS - i;
    ic = (random&MASK) % j;
    j--;
    random >>= 8;
    temp = t1[ic];
    t1[ic] = t1[j];
    t1[j] = temp;
    if (t3[j]==0)
      {
      ic = (random&MASK) % j;
      while (t3[ic]!=0) ic = (ic+1) % j;
      t3[ic] = j;
      t3[j] = ic;
      }
    }

  for(i=0;i<NUM_ROTORS;i++) t2[t1[i]&MASK] = i;

  return password;
  }


void shuffle(char *deck, char *password)
  {
  int			ic, i, j, temp;
  static int32_t	seed = 123;

  for(i=0;i<NUM_ROTORS;i++)
    {
    seed = 5*seed + password[i%13];
    j = NUM_ROTORS - i;
    ic = ((seed%65521)&MASK)%j;
    j--;
    temp = deck[j];
    deck[j] = deck[ic];
    deck[ic] = temp;
    }

  return;
  }


int main(int argc, char **argv)
  {
  int	i;
  int	n1=0, n2=0, nr1=0, nr2=0;
  int	soption = 0;
  char	*password;

/* Check for the '-s' switch, the only supported option. */
  if (argc > 1 && argv[1][0] == '-' && argv[1][1] == 's')
    {
    argc--;
    argv++;
    soption = 1;
    }

  password = init(argv[1]);

  if (soption)
    {
    while((i=getchar())>=0)
      {
      nr1 = deck[n1]&MASK;
      nr2 = deck[nr1]&MASK;

      i = t2[(t3[(t1[(i+nr1)&MASK]+nr2)&MASK]-nr2)&MASK]-nr1;
      putchar(i);
      n1++;
      if (n1==NUM_ROTORS)
        {
        n1 = 0;
        n2++;
        if(n2==NUM_ROTORS) n2 = 0;

        shuffle(deck, password);
        }
      }
    }
  else
    {
    while((i=getchar())>=0)
      {
      nr1 = n1;

      i = t2[(t3[(t1[(i+nr1)&MASK]+nr2)&MASK]-nr2)&MASK]-nr1;
      putchar(i);
      n1++;
      if (n1==NUM_ROTORS)
        {
        n1 = 0;
        n2++;
        if(n2==NUM_ROTORS) n2 = 0;

        nr2 = n2;
        }
      }
    }

  exit(0);
  }