File: nscd.c

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/* Copyright (c) 1998-2014 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Thorsten Kukuk <kukuk@suse.de>, 1998.

   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; 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, see <http://www.gnu.org/licenses/>.  */

/* nscd - Name Service Cache Daemon. Caches passwd, group, and hosts.  */

#include <argp.h>
#include <assert.h>
#include <dirent.h>
#include <errno.h>
#include <error.h>
#include <fcntl.h>
#include <libintl.h>
#include <locale.h>
#include <paths.h>
#include <pthread.h>
#include <signal.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/uio.h>
#include <sys/un.h>

#include "dbg_log.h"
#include "nscd.h"
#include "selinux.h"
#include "../nss/nsswitch.h"
#include <device-nrs.h>
#ifdef HAVE_INOTIFY
# include <sys/inotify.h>
#endif

/* Get libc version number.  */
#include <version.h>

#define PACKAGE _libc_intl_domainname

/* Structure used by main() thread to keep track of the number of
   active threads.  Used to limit how many threads it will create
   and under a shutdown condition to wait till all in-progress
   requests have finished before "turning off the lights".  */

typedef struct
{
  int             num_active;
  pthread_cond_t  thread_exit_cv;
  pthread_mutex_t mutex;
} thread_info_t;

thread_info_t thread_info;

int do_shutdown;
int disabled_passwd;
int disabled_group;

typedef enum
{
  /* Running in background as daemon.  */
  RUN_DAEMONIZE,
  /* Running in foreground but otherwise behave like a daemon,
     i.e., detach from terminal and use syslog.  This allows
     better integration with services like systemd.  */
  RUN_FOREGROUND,
  /* Run in foreground in debug mode.  */
  RUN_DEBUG
} run_modes;

static run_modes run_mode = RUN_DAEMONIZE;

static const char *conffile = _PATH_NSCDCONF;

time_t start_time;

uintptr_t pagesize_m1;

int paranoia;
time_t restart_time;
time_t restart_interval = RESTART_INTERVAL;
const char *oldcwd;
uid_t old_uid;
gid_t old_gid;

static int check_pid (const char *file);
static int write_pid (const char *file);

/* Name and version of program.  */
static void print_version (FILE *stream, struct argp_state *state);
void (*argp_program_version_hook) (FILE *, struct argp_state *) = print_version;

/* Function to print some extra text in the help message.  */
static char *more_help (int key, const char *text, void *input);

/* Definitions of arguments for argp functions.  */
static const struct argp_option options[] =
{
  { "config-file", 'f', N_("NAME"), 0,
    N_("Read configuration data from NAME") },
  { "debug", 'd', NULL, 0,
    N_("Do not fork and display messages on the current tty") },
  { "foreground", 'F', NULL, 0,
    N_("Do not fork, but otherwise behave like a daemon") },
  { "nthreads", 't', N_("NUMBER"), 0, N_("Start NUMBER threads") },
  { "shutdown", 'K', NULL, 0, N_("Shut the server down") },
  { "statistics", 'g', NULL, 0, N_("Print current configuration statistics") },
  { "invalidate", 'i', N_("TABLE"), 0,
    N_("Invalidate the specified cache") },
  { "secure", 'S', N_("TABLE,yes"), OPTION_HIDDEN,
    N_("Use separate cache for each user")},
  { NULL, 0, NULL, 0, NULL }
};

/* Short description of program.  */
static const char doc[] = N_("Name Service Cache Daemon.");

/* Prototype for option handler.  */
static error_t parse_opt (int key, char *arg, struct argp_state *state);

/* Data structure to communicate with argp functions.  */
static struct argp argp =
{
  options, parse_opt, NULL, doc, NULL, more_help
};

/* True if only statistics are requested.  */
static bool get_stats;

int
main (int argc, char **argv)
{
  int remaining;

  /* Set locale via LC_ALL.  */
  setlocale (LC_ALL, "");
  /* Set the text message domain.  */
  textdomain (PACKAGE);

  /* Determine if the kernel has SELinux support.  */
  nscd_selinux_enabled (&selinux_enabled);

  /* Parse and process arguments.  */
  argp_parse (&argp, argc, argv, 0, &remaining, NULL);

  if (remaining != argc)
    {
      error (0, 0, gettext ("wrong number of arguments"));
      argp_help (&argp, stdout, ARGP_HELP_SEE, program_invocation_short_name);
      exit (1);
    }

  /* Read the configuration file.  */
  if (nscd_parse_file (conffile, dbs) != 0)
    /* We couldn't read the configuration file.  We don't start the
       server.  */
    error (EXIT_FAILURE, 0,
	   _("failure while reading configuration file; this is fatal"));

  /* Do we only get statistics?  */
  if (get_stats)
    /* Does not return.  */
    receive_print_stats ();

  /* Check if we are already running. */
  if (check_pid (_PATH_NSCDPID))
    error (EXIT_FAILURE, 0, _("already running"));

  /* Remember when we started.  */
  start_time = time (NULL);

  /* Determine page size.  */
  pagesize_m1 = getpagesize () - 1;

  if (run_mode == RUN_DAEMONIZE || run_mode == RUN_FOREGROUND)
    {
      int i;
      pid_t pid;

      /* Behave like a daemon.  */
      if (run_mode == RUN_DAEMONIZE)
	{
	  pid = fork ();
	  if (pid == -1)
	    error (EXIT_FAILURE, errno, _("cannot fork"));
	  if (pid != 0)
	    exit (0);
	}

      int nullfd = open (_PATH_DEVNULL, O_RDWR);
      if (nullfd != -1)
	{
	  struct stat64 st;

	  if (fstat64 (nullfd, &st) == 0 && S_ISCHR (st.st_mode) != 0
#if defined DEV_NULL_MAJOR && defined DEV_NULL_MINOR
	      && st.st_rdev == makedev (DEV_NULL_MAJOR, DEV_NULL_MINOR)
#endif
	      )
	    {
	      /* It is the /dev/null special device alright.  */
	      (void) dup2 (nullfd, STDIN_FILENO);
	      (void) dup2 (nullfd, STDOUT_FILENO);
	      (void) dup2 (nullfd, STDERR_FILENO);

	      if (nullfd > 2)
		close (nullfd);
	    }
	  else
	    {
	      /* Ugh, somebody is trying to play a trick on us.  */
	      close (nullfd);
	      nullfd = -1;
	    }
	}
      int min_close_fd = nullfd == -1 ? 0 : STDERR_FILENO + 1;

      DIR *d = opendir ("/proc/self/fd");
      if (d != NULL)
	{
	  struct dirent64 *dirent;
	  int dfdn = dirfd (d);

	  while ((dirent = readdir64 (d)) != NULL)
	    {
	      char *endp;
	      long int fdn = strtol (dirent->d_name, &endp, 10);

	      if (*endp == '\0' && fdn != dfdn && fdn >= min_close_fd)
		close ((int) fdn);
	    }

	  closedir (d);
	}
      else
	for (i = min_close_fd; i < getdtablesize (); i++)
	  close (i);

      setsid ();

      if (chdir ("/") != 0)
	error (EXIT_FAILURE, errno,
	       _("cannot change current working directory to \"/\""));

      openlog ("nscd", LOG_CONS | LOG_ODELAY, LOG_DAEMON);

      if (write_pid (_PATH_NSCDPID) < 0)
	dbg_log ("%s: %s", _PATH_NSCDPID, strerror (errno));

      if (!init_logfile ())
	dbg_log (_("Could not create log file"));

      /* Ignore job control signals.  */
      signal (SIGTTOU, SIG_IGN);
      signal (SIGTTIN, SIG_IGN);
      signal (SIGTSTP, SIG_IGN);
    }
  else
    /* In debug mode we are not paranoid.  */
    paranoia = 0;

  signal (SIGINT, termination_handler);
  signal (SIGQUIT, termination_handler);
  signal (SIGTERM, termination_handler);
  signal (SIGPIPE, SIG_IGN);

  /* Cleanup files created by a previous 'bind'.  */
  unlink (_PATH_NSCDSOCKET);

#ifdef HAVE_INOTIFY
  /* Use inotify to recognize changed files.  */
  inotify_fd = inotify_init1 (IN_NONBLOCK);
# ifndef __ASSUME_IN_NONBLOCK
  if (inotify_fd == -1 && errno == ENOSYS)
    {
      inotify_fd = inotify_init ();
      if (inotify_fd != -1)
	fcntl (inotify_fd, F_SETFL, O_RDONLY | O_NONBLOCK);
    }
# endif
#endif

#ifdef USE_NSCD
  /* Make sure we do not get recursive calls.  */
  __nss_disable_nscd (register_traced_file);
#endif

  /* Init databases.  */
  nscd_init ();

  /* Start the SELinux AVC.  */
  if (selinux_enabled)
    nscd_avc_init ();

  /* Handle incoming requests */
  start_threads ();

  return 0;
}


/* Handle program arguments.  */
static error_t
parse_opt (int key, char *arg, struct argp_state *state)
{
  switch (key)
    {
    case 'd':
      ++debug_level;
      run_mode = RUN_DEBUG;
      break;

    case 'F':
      run_mode = RUN_FOREGROUND;
      break;

    case 'f':
      conffile = arg;
      break;

    case 'K':
      if (getuid () != 0)
	error (4, 0, _("Only root is allowed to use this option!"));
      {
	int sock = nscd_open_socket ();

	if (sock == -1)
	  exit (EXIT_FAILURE);

	request_header req;
	req.version = NSCD_VERSION;
	req.type = SHUTDOWN;
	req.key_len = 0;

	ssize_t nbytes = TEMP_FAILURE_RETRY (send (sock, &req,
						   sizeof (request_header),
						   MSG_NOSIGNAL));
	close (sock);
	exit (nbytes != sizeof (request_header) ? EXIT_FAILURE : EXIT_SUCCESS);
      }

    case 'g':
      get_stats = true;
      break;

    case 'i':
      if (getuid () != 0)
	error (4, 0, _("Only root is allowed to use this option!"));
      else
	{
	  int sock = nscd_open_socket ();

	  if (sock == -1)
	    exit (EXIT_FAILURE);

	  dbtype cnt;
	  for (cnt = pwddb; cnt < lastdb; ++cnt)
	    if (strcmp (arg, dbnames[cnt]) == 0)
	      break;

	  if (cnt == lastdb)
	    {
	      argp_error (state, _("'%s' is not a known database"), arg);
	      return EINVAL;
	    }

	  size_t arg_len = strlen (arg) + 1;
	  struct
	  {
	    request_header req;
	    char arg[arg_len];
	  } reqdata;

	  reqdata.req.key_len = strlen (arg) + 1;
	  reqdata.req.version = NSCD_VERSION;
	  reqdata.req.type = INVALIDATE;
	  memcpy (reqdata.arg, arg, arg_len);

	  ssize_t nbytes = TEMP_FAILURE_RETRY (send (sock, &reqdata,
						     sizeof (request_header)
						     + arg_len,
						     MSG_NOSIGNAL));

	  if (nbytes != sizeof (request_header) + arg_len)
	    {
	      int err = errno;
	      close (sock);
	      error (EXIT_FAILURE, err, _("write incomplete"));
	    }

	  /* Wait for ack.  Older nscd just closed the socket when
	     prune_cache finished, silently ignore that.  */
	  int32_t resp = 0;
	  nbytes = TEMP_FAILURE_RETRY (read (sock, &resp, sizeof (resp)));
	  if (nbytes != 0 && nbytes != sizeof (resp))
	    {
	      int err = errno;
	      close (sock);
	      error (EXIT_FAILURE, err, _("cannot read invalidate ACK"));
	    }

	  close (sock);

	  if (resp != 0)
	    error (EXIT_FAILURE, resp, _("invalidation failed"));

	  exit (0);
	}

    case 't':
      nthreads = atol (arg);
      break;

    case 'S':
      error (0, 0, _("secure services not implemented anymore"));
      break;

    default:
      return ARGP_ERR_UNKNOWN;
    }

  return 0;
}

/* Print bug-reporting information in the help message.  */
static char *
more_help (int key, const char *text, void *input)
{
  char *tables, *tp = NULL;

  switch (key)
    {
    case ARGP_KEY_HELP_EXTRA:
      {
	dbtype cnt;

	tables = xmalloc (sizeof (dbnames) + 1);
	for (cnt = 0; cnt < lastdb; cnt++)
	  {
	    strcat (tables, dbnames[cnt]);
	    strcat (tables, " ");
	  }
      }

      /* We print some extra information.  */
      if (asprintf (&tp, gettext ("\
Supported tables:\n\
%s\n\
\n\
For bug reporting instructions, please see:\n\
%s.\n\
"), tables, REPORT_BUGS_TO) < 0)
	tp = NULL;
      free (tables);
      return tp;

    default:
      break;
    }

  return (char *) text;
}

/* Print the version information.  */
static void
print_version (FILE *stream, struct argp_state *state)
{
  fprintf (stream, "nscd %s%s\n", PKGVERSION, VERSION);
  fprintf (stream, gettext ("\
Copyright (C) %s Free Software Foundation, Inc.\n\
This is free software; see the source for copying conditions.  There is NO\n\
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n\
"), "2014");
  fprintf (stream, gettext ("Written by %s.\n"),
	   "Thorsten Kukuk and Ulrich Drepper");
}


/* Create a socket connected to a name.  */
int
nscd_open_socket (void)
{
  struct sockaddr_un addr;
  int sock;

  sock = socket (PF_UNIX, SOCK_STREAM, 0);
  if (sock < 0)
    return -1;

  addr.sun_family = AF_UNIX;
  assert (sizeof (addr.sun_path) >= sizeof (_PATH_NSCDSOCKET));
  strcpy (addr.sun_path, _PATH_NSCDSOCKET);
  if (connect (sock, (struct sockaddr *) &addr, sizeof (addr)) < 0)
    {
      close (sock);
      return -1;
    }

  return sock;
}


/* Cleanup.  */
void
termination_handler (int signum)
{
  close_sockets ();

  /* Clean up the file created by 'bind'.  */
  unlink (_PATH_NSCDSOCKET);

  /* Clean up pid file.  */
  unlink (_PATH_NSCDPID);

  // XXX Terminate threads.

  /* Synchronize memory.  */
  for (int cnt = 0; cnt < lastdb; ++cnt)
    {
      if (!dbs[cnt].enabled || dbs[cnt].head == NULL)
	continue;

      /* Make sure nobody keeps using the database.  */
      dbs[cnt].head->timestamp = 0;

      if (dbs[cnt].persistent)
	// XXX async OK?
	msync (dbs[cnt].head, dbs[cnt].memsize, MS_ASYNC);
    }

  _exit (EXIT_SUCCESS);
}

/* Returns 1 if the process in pid file FILE is running, 0 if not.  */
static int
check_pid (const char *file)
{
  FILE *fp;

  fp = fopen (file, "r");
  if (fp)
    {
      pid_t pid;
      int n;

      n = fscanf (fp, "%d", &pid);
      fclose (fp);

      /* If we cannot parse the file default to assuming nscd runs.
	 If the PID is alive, assume it is running.  That all unless
	 the PID is the same as the current process' since tha latter
	 can mean we re-exec.  */
      if ((n != 1 || kill (pid, 0) == 0) && pid != getpid ())
	return 1;
    }

  return 0;
}

/* Write the current process id to the file FILE.
   Returns 0 if successful, -1 if not.  */
static int
write_pid (const char *file)
{
  FILE *fp;

  fp = fopen (file, "w");
  if (fp == NULL)
    return -1;

  fprintf (fp, "%d\n", getpid ());

  int result = fflush (fp) || ferror (fp) ? -1 : 0;

  fclose (fp);

  return result;
}