UNIX Crypt (1) Replacement Source-Code
/**********************************************************************
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 June 2001 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);
}