manual/examples/genpass.c

   1 /* Encrypting Passwords
   2    Copyright (C) 1991-2017 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU General Public License
   6    as published by the Free Software Foundation; either version 2
   7    of the License, or (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, if not, see <http://www.gnu.org/licenses/>.
  16 */
  17
  18 #include <stdio.h>
  19 #include <time.h>
  20 #include <unistd.h>
  21 #include <crypt.h>
  22
  23 int
  24 main(void)
  25 {
  26   unsigned long seed[2];
  27   char salt[] = "$1$........";
  28   const char *const seedchars =
  29     "./0123456789ABCDEFGHIJKLMNOPQRST"
  30     "UVWXYZabcdefghijklmnopqrstuvwxyz";
  31   char *password;
  32   int i;
  33
  34   /* Generate a (not very) random seed.
  35      You should do it better than this...  */
  36   seed[0] = time(NULL);
  37   seed[1] = getpid() ^ (seed[0] >> 14 & 0x30000);
  38
  39   /* Turn it into printable characters from `seedchars'.  */
  40   for (i = 0; i < 8; i++)
  41     salt[3+i] = seedchars[(seed[i/5] >> (i%5)*6) & 0x3f];
  42
  43   /* Read in the user's password and encrypt it.  */
  44   password = crypt(getpass("Password:"), salt);
  45
  46   /* Print the results.  */
  47   puts(password);
  48   return 0;
  49 }