File: polkitagenthelper-shadow.c

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policykit-1 0.105-15~deb8u2
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/*
 * Copyright (C) 2008 Red Hat, Inc.
 * Copyright (C) 2009-2010 Andrew Psaltis <ampsaltis@gmail.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General
 * Public License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 * Authors: Andrew Psaltis <ampsaltis@gmail.com>, based on
 *            polkitagenthelper.c which was written by
 *          David Zeuthen <davidz@redhat.com>
 */

#include "config.h"
#include "polkitagenthelperprivate.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <syslog.h>
#include <shadow.h>
#include <grp.h>
#include <pwd.h>
#include <time.h>

#include <polkit/polkit.h>

static gboolean shadow_authenticate (struct spwd *shadow);

int
main (int argc, char *argv[])
{
  struct spwd *shadow;
  const char *user_to_auth;
  char *cookie = NULL;
  time_t now;

  /* clear the entire environment to avoid attacks with
     libraries honoring environment variables */
  if (_polkit_clearenv () != 0)
    goto error;

  /* set a minimal environment */
  setenv ("PATH", "/usr/sbin:/usr/bin:/sbin:/bin", 1);

  /* check that we are setuid root */
  if (geteuid () != 0)
    {
      fprintf (stderr, "polkit-agent-helper-1: needs to be setuid root\n");
      goto error;
    }

  openlog ("polkit-agent-helper-1", LOG_CONS | LOG_PID, LOG_AUTHPRIV);

  /* check for correct invocation */
  if (!(argc == 2 || argc == 3))
    {
      syslog (LOG_NOTICE, "inappropriate use of helper, wrong number of arguments [uid=%d]", getuid ());
      fprintf (stderr, "polkit-agent-helper-1: wrong number of arguments. This incident has been logged.\n");
      goto error;
    }

  if (getuid () != 0)
    {
    /* check we're running with a non-tty stdin */
    if (isatty (STDIN_FILENO) != 0)
      {
        syslog (LOG_NOTICE, "inappropriate use of helper, stdin is a tty [uid=%d]", getuid ());
        fprintf (stderr, "polkit-agent-helper-1: inappropriate use of helper, stdin is a tty. This incident has been logged.\n");
        goto error;
      }
    }

  user_to_auth = argv[1];

  cookie = read_cookie (argc, argv);
  if (!cookie)
    goto error;

#ifdef PAH_DEBUG
  fprintf (stderr, "polkit-agent-helper-1: user to auth is '%s'.\n", user_to_auth);
#endif /* PAH_DEBUG */


  /* Ask shadow about the user requesting authentication */
  shadow = getspnam (user_to_auth);

  if (shadow == NULL)
    {
      syslog (LOG_NOTICE, "shadow file data information request for user '%s' [uid=%d] failed", user_to_auth, getuid ());
      fprintf(stderr, "polkit-agent-helper-1: could not get shadow information for '%s'", user_to_auth);
      goto error;
    }

  /* Check the user's identity */
  if (shadow_authenticate (shadow) == FALSE)
    {
      syslog (LOG_NOTICE, "authentication failure [uid=%d] trying to authenticate '%s'", getuid (), user_to_auth);
      fprintf (stderr, "polkit-agent-helper-1: authentication failure. This incident has been logged.\n");
      goto error;
    }

  /* Check whether the user's password has expired */
  now = time (NULL);
  if (shadow->sp_max >= 0 && (shadow->sp_lstchg + shadow->sp_max) * 60 * 60 * 24 <= now)
    {
      syslog (LOG_NOTICE, "password expired for user '%s' [uid=%d] trying to authenticate", user_to_auth, getuid ());
      fprintf (stderr, "polkit-agent-helper-1: authorization failure. This incident has been logged.\n");
      goto error;
    }

  /* Check whether the user's password has aged (and account expired along
   * with it)
   */
  if (shadow->sp_inact >= 0 && (shadow->sp_lstchg + shadow->sp_max + shadow->sp_inact) * 60 * 60 * 24 <= now)
    {
      syslog (LOG_NOTICE, "password aged for user '%s' [uid=%d] trying to authenticate", user_to_auth, getuid ());
      fprintf (stderr, "polkit-agent-helper-1: authorization failure. This incident has been logged.\n");
      goto error;
    }

  /* Check whether the user's account has expired */
  if (shadow->sp_expire >= 0 && shadow->sp_expire * 60 * 60 * 24 <= now)
    {
      syslog (LOG_NOTICE, "account expired for user '%s' [uid=%d] trying to authenticate", user_to_auth, getuid ());
      fprintf (stderr, "polkit-agent-helper-1: authorization failure. This incident has been logged.\n");
      goto error;
    }

#ifdef PAH_DEBUG
  fprintf (stderr, "polkit-agent-helper-1: sending D-Bus message to PolicyKit daemon\n");
#endif /* PAH_DEBUG */

  /* now send a D-Bus message to the PolicyKit daemon that
   * includes a) the cookie; and b) the user we authenticated
   */
  if (!send_dbus_message (cookie, user_to_auth))
    {
#ifdef PAH_DEBUG
      fprintf (stderr, "polkit-agent-helper-1: error sending D-Bus message to PolicyKit daemon\n");
#endif /* PAH_DEBUG */
      goto error;
    }

  free (cookie);

#ifdef PAH_DEBUG
  fprintf (stderr, "polkit-agent-helper-1: successfully sent D-Bus message to PolicyKit daemon\n");
#endif /* PAH_DEBUG */

  fprintf (stdout, "SUCCESS\n");
  flush_and_wait ();
  return 0;

error:
  free (cookie);
  fprintf (stdout, "FAILURE\n");
  flush_and_wait ();
  return 1;
}

static gboolean
shadow_authenticate (struct spwd *shadow)
{
  char passwd[512], *crypt_pass;

  fprintf (stdout, "PAM_PROMPT_ECHO_OFF password:\n");
  fflush (stdout);
  usleep (10 * 1000); /* since fflush(3) seems buggy */

  if (fgets (passwd, sizeof (passwd), stdin) == NULL)
    goto error;

  if (strlen (passwd) > 0 && passwd[strlen (passwd) - 1] == '\n')
    passwd[strlen (passwd) - 1] = '\0';

  /* Use the encrypted password as the salt, according to the crypt(3) man page,
   * it will perform whatever encryption method is specified in /etc/shadow
   */
  crypt_pass = crypt (passwd, shadow->sp_pwdp);

  if (crypt_pass == NULL)
    goto error;

  if (strcmp (shadow->sp_pwdp, crypt (passwd, shadow->sp_pwdp)) != 0)
    goto error;
  return 1;
error:
  return 0;
}