/* Encrypting Passwords

   Copyright (C) 1991-2018 Free Software Foundation, Inc.

   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 2

   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, if not, see <http://www.gnu.org/licenses/>.

*/

#include <stdio.h>

#include <unistd.h>

#include <crypt.h>

int

main(void)

{

  unsigned char ubytes[16];

  char salt[20];

  const char *const saltchars =

    "./0123456789ABCDEFGHIJKLMNOPQRST"

    "UVWXYZabcdefghijklmnopqrstuvwxyz";

  char *hash;

  int i;

  /* Retrieve 16 unpredictable bytes from the operating system.  */

  if (getentropy (ubytes, sizeof ubytes))

    {

      perror ("getentropy");

      return 1;

    }

  /* Use them to fill in the salt string.  */

  salt[0] = '$';

  salt[1] = '5'; /* SHA-256 */

  salt[2] = '$';

  for (i = 0; i < 16; i++)

    salt[3+i] = saltchars[ubytes[i] & 0x3f];

  salt[3+i] = '\0';

  /* Read in the user's passphrase and hash it.  */

  hash = crypt (getpass ("Enter new passphrase: "), salt);

  if (!hash || hash[0] == '*')

    {

      perror ("crypt");

      return 1;

    }

  /* Print the results.  */

  puts (hash);

  return 0;

}