src/auth-shadow.c

   1 /* auth-shadow.c -- shadow authentification routine for vlock,
   2  *                  the VT locking program for linux
   3  *
   4  * This program is copyright (C) 2007 Frank Benkstein, and is free
   5  * software which is freely distributable under the terms of the
   6  * GNU General Public License version 2, included as the file COPYING in this
   7  * distribution.  It is NOT public domain software, and any
   8  * redistribution not permitted by the GNU General Public License is
   9  * expressly forbidden without prior written permission from
  10  * the author.
  11  *
  12  */
  13
  14 /* for crypt() */
  15 #define _XOPEN_SOURCE
  16
  17 #ifndef __FreeBSD__
  18 /* for asprintf() */
  19 #define _GNU_SOURCE
  20 #endif
  21
  22 #include <stdbool.h>
  23 #include <unistd.h>
  24 #include <stdio.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27
  28 #include <sys/mman.h>
  29
  30 #include <shadow.h>
  31
  32 #include "auth.h"
  33 #include "prompt.h"
  34
  35 bool auth(const char *user, struct timespec *timeout)
  36 {
  37   char *pwd;
  38   char *cryptpw;
  39   char *msg;
  40   struct spwd *spw;
  41   int result = false;
  42
  43   /* format the prompt */
  44   if (asprintf(&msg, "%s's Password: ", user) < 0)
  45     return false;
  46
  47   if ((pwd = prompt_echo_off(msg, timeout)) == NULL)
  48     goto out_pwd;
  49
  50   /* get the shadow password */
  51   if ((spw = getspnam(user)) == NULL)
  52     goto out_shadow;
  53
  54   /* hash the password */
  55   if ((cryptpw = crypt(pwd, spw->sp_pwdp)) == NULL) {
  56     perror("vlock-auth: crypt()");
  57     goto out_shadow;
  58   }
  59
  60   result = (strcmp(cryptpw, spw->sp_pwdp) == 0);
  61
  62   if (!result) {
  63     sleep(1);
  64     fprintf(stderr, "vlock-auth: Authentication error\n");
  65   }
  66
  67 out_shadow:
  68   /* deallocate shadow resources */
  69   endspent();
  70
  71   /* free the password */
  72   free(pwd);
  73
  74 out_pwd:
  75   /* free the prompt */
  76   free(msg);
  77
  78   return result;
  79 }