auth-pam.c

   1 /* auth-pam.c -- PAM 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 #include <stdio.h>
  15
  16 #include <security/pam_appl.h>
  17 #include <security/pam_misc.h>
  18
  19 /* Try to authenticate the user.  When the user is successfully authenticated
  20  * this function returns 1.  When the authentication fails for whatever reason
  21  * the function returns 0.
  22  */
  23 int auth(const char *user) {
  24   pam_handle_t *pamh;
  25   int pam_status;
  26   int pam_end_status;
  27   struct pam_conv pamc = {
  28     &misc_conv,
  29     NULL
  30   };
  31
  32   /* initialize pam */
  33   pam_status = pam_start("vlock", user, &pamc, &pamh);
  34
  35   if (pam_status != PAM_SUCCESS) {
  36     fprintf(stderr, "vlock-auth: %s\n", pam_strerror(pamh, pam_status));
  37     goto end;
  38   }
  39
  40   /* put the username before the password prompt */
  41   fprintf(stderr, "%s's ", user); fflush(stderr);
  42   /* authenticate the user */
  43   pam_status = pam_authenticate(pamh, 0);
  44
  45   if (pam_status != PAM_SUCCESS) {
  46     fprintf(stderr, "vlock-auth: %s\n", pam_strerror(pamh, pam_status));
  47   }
  48
  49 end:
  50   /* finish pam */
  51   pam_end_status = pam_end(pamh, pam_status);
  52
  53   if (pam_end_status != PAM_SUCCESS) {
  54     fprintf(stderr, "vlock-auth: %s\n", pam_strerror(pamh, pam_end_status));
  55   }
  56
  57   return (pam_status == PAM_SUCCESS);
  58 }