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 #include <unistd.h>
  17 #include <stdio.h>
  18 #include <string.h>
  19
  20 #include <sys/mman.h>
  21
  22 #include <shadow.h>
  23
  24 #define PWD_BUFFER_SIZE 256
  25
  26 int auth(const char *user) {
  27   char buffer[PWD_BUFFER_SIZE];
  28   size_t pwlen;
  29   char *cryptpw;
  30   struct spwd *spw;
  31   int result = 0;
  32
  33   /* lock the password buffer */
  34   (void) mlock(buffer, sizeof buffer);
  35
  36   /* write out the prompt */
  37   fprintf(stderr, "%s's Password: ", user); fflush(stderr);
  38
  39   /* read the password, echo was switched of by vlock-current */
  40   if (fgets(buffer, sizeof buffer, stdin) == NULL)
  41     goto out;
  42
  43   /* put newline */
  44   fputc('\n', stderr);
  45
  46   pwlen = strlen(buffer);
  47
  48   /* strip the newline */
  49   if (buffer[pwlen-1] == '\n')
  50     buffer[pwlen-1] = '\0';
  51
  52   /* get the shadow password */
  53   if ((spw = getspnam(user)) == NULL)
  54     goto out_shadow;
  55
  56   /* hash the password */
  57   if ((cryptpw = crypt(buffer, spw->sp_pwdp)) == NULL) {
  58     perror("vlock-auth: crypt()");
  59     goto out_shadow;
  60   }
  61
  62   /* XXX: sp_lstchg, sp_min, sp_inact, sp_expire should also be checked here */
  63
  64   result = strcmp(cryptpw, spw->sp_pwdp) == 0;
  65
  66 out_shadow:
  67   /* deallocate shadow resources */
  68   endspent();
  69
  70 out:
  71   /* clear the buffer */
  72   memset(buffer, 0, sizeof buffer);
  73
  74   /* unlock the password buffer */
  75   (void) munlock(buffer, sizeof buffer);
  76
  77   return result;
  78 }