dbus/bus/main.c

/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
/* main.c  main() for message bus
 *
 * Copyright (C) 2003 Red Hat, Inc.
 *
 * SPDX-License-Identifier: AFL-2.1 OR GPL-2.0-or-later
 *
 * Licensed under the Academic Free License version 2.1
 *
 * 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; either 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, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 */

#include <config.h>
#include "bus.h"
#include "driver.h"
#include <dbus/dbus-internals.h>
#include <dbus/dbus-watch.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifdef HAVE_SIGNAL_H
#include <signal.h>
#endif
#ifdef HAVE_ERRNO_H
#include <errno.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>     /* for write() and STDERR_FILENO */
#endif
#include "selinux.h"
#include "apparmor.h"
#include "audit.h"

#ifdef DBUS_UNIX
#include <dbus/dbus-sysdeps-unix.h>
#endif

static BusContext *context;

#ifdef DBUS_WIN
#include <dbus/dbus-sysdeps-win.h>
#endif

#ifdef DBUS_UNIX

/* Despite its name and its unidirectional nature, this is actually
 * a socket pair. */
static DBusSocket reload_pipe[2];
#define RELOAD_READ_END 0
#define RELOAD_WRITE_END 1

static void close_reload_pipe (DBusWatch **);

typedef enum
 {
   ACTION_RELOAD = 'r',
   ACTION_QUIT = 'q'
 } SignalAction;

static void
signal_handler (int sig)
{
  /* Signal handlers that might set errno must save and restore the errno
   * that the interrupted function might have been relying on. */
  int saved_errno = errno;

  switch (sig)
    {
    case SIGHUP:
      {
        DBusString str;
        char action[2] = { ACTION_RELOAD, '\0' };

        _dbus_string_init_const (&str, action);
        if ((reload_pipe[RELOAD_WRITE_END].fd > 0) &&
            !_dbus_write_socket (reload_pipe[RELOAD_WRITE_END], &str, 0, 1))
          {
            /* If we receive SIGHUP often enough to fill the pipe buffer (4096
             * times on old Linux, 65536 on modern Linux) before it can be
             * drained, let's just warn and ignore. The configuration will be
             * reloaded while draining the pipe buffer, which is what we
             * wanted. It's harmless that it will be reloaded fewer times than
             * we asked for, since the reload is delayed anyway, so new changes
             * will be picked up.
             *
             * We use write() because _dbus_warn uses vfprintf, which isn't
             * async-signal-safe.
             *
             * This is necessarily Unix-specific, but so are POSIX signals,
             * so... */
            static const char message[] =
              "Unable to write to reload pipe - buffer full?\n";

            if (write (STDERR_FILENO, message, strlen (message)) !=
                (ssize_t) strlen (message))
              {
                /* ignore failure to write out a warning */
              }
          }
      }
      break;

    case SIGTERM:
      {
        DBusString str;
        char action[2] = { ACTION_QUIT, '\0' };
        _dbus_string_init_const (&str, action);
        if ((reload_pipe[RELOAD_WRITE_END].fd < 0) ||
            !_dbus_write_socket (reload_pipe[RELOAD_WRITE_END], &str, 0, 1))
          {
            /* If we can't write to the socket, dying seems a more
             * important response to SIGTERM than cleaning up sockets,
             * so we exit. We'd use exit(), but that's not async-signal-safe,
             * so we'll have to resort to _exit(). */
            static const char message[] =
              "Unable to write termination signal to pipe - buffer full?\n"
              "Will exit instead.\n";

            if (write (STDERR_FILENO, message, strlen (message)) !=
                (ssize_t) strlen (message))
              {
                /* ignore failure to write out a warning */
              }
            _exit (1);
          }
      }
      break;

    default:
      /* can't happen unless this signal handler gets used for a wrong
       * signal, but keep -Wswitch-default happy */
      break;
    }

  errno = saved_errno;
}
#endif /* DBUS_UNIX */

static void usage (void) _DBUS_GNUC_NORETURN;

static void
usage (void)
{
  fprintf (stderr,
      DBUS_DAEMON_NAME
      " [--version]"
      " [--session]"
      " [--system]"
      " [--config-file=FILE]"
      " [--print-address[=DESCRIPTOR]]"
      " [--print-pid[=DESCRIPTOR]]"
      " [--introspect]"
      " [--address=ADDRESS]"
      " [--nopidfile]"
      " [--nosyslog]"
      " [--syslog]"
      " [--syslog-only]"
      " [--nofork]"
#ifdef DBUS_WIN
      " [--ready-event-handle=value]"
#endif
#ifdef DBUS_UNIX
      " [--fork]"
      " [--systemd-activation]"
#endif
      "\n");
  exit (1);
}

static void version (void) _DBUS_GNUC_NORETURN;

static void
version (void)
{
  printf ("D-Bus Message Bus Daemon %s\n"
          "Copyright (C) 2002, 2003 Red Hat, Inc., CodeFactory AB, and others\n"
          "This is free software; see the source for copying conditions.\n"
          "There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n",
          DBUS_VERSION_STRING);
  exit (0);
}

static void introspect (void) _DBUS_GNUC_NORETURN;

static void
introspect (void)
{
  DBusString xml;
  const char *v_STRING;

  if (!_dbus_string_init (&xml))
    goto oom;

  if (!bus_driver_generate_introspect_string (&xml, TRUE, NULL))
    {
      _dbus_string_free (&xml);
      goto oom;
    }

  v_STRING = _dbus_string_get_const_data (&xml);
  printf ("%s\n", v_STRING);

  exit (0);

 oom:
  _dbus_warn ("Can not introspect - Out of memory");
  exit (1);
}

static void
check_two_config_files (const DBusString *config_file,
                        const char       *extra_arg)
{
  if (_dbus_string_get_length (config_file) > 0)
    {
      fprintf (stderr, "--%s specified but configuration file %s already requested\n",
               extra_arg, _dbus_string_get_const_data (config_file));
      exit (1);
    }
}

static void
check_two_addresses (const DBusString *address,
                     const char       *extra_arg)
{
  if (_dbus_string_get_length (address) > 0)
    {
      fprintf (stderr, "--%s specified but address %s already requested\n",
               extra_arg, _dbus_string_get_const_data (address));
      exit (1);
    }
}

static void
check_two_addr_descriptors (const DBusString *addr_fd,
                            const char       *extra_arg)
{
  if (_dbus_string_get_length (addr_fd) > 0)
    {
      fprintf (stderr, "--%s specified but printing address to %s already requested\n",
               extra_arg, _dbus_string_get_const_data (addr_fd));
      exit (1);
    }
}

static void
check_two_pid_descriptors (const DBusString *pid_fd,
                           const char       *extra_arg)
{
  if (_dbus_string_get_length (pid_fd) > 0)
    {
      fprintf (stderr, "--%s specified but printing pid to %s already requested\n",
               extra_arg, _dbus_string_get_const_data (pid_fd));
      exit (1);
    }
}

#ifdef DBUS_UNIX
static dbus_bool_t
handle_reload_watch (DBusWatch    *watch,
		     unsigned int  flags,
		     void         *data)
{
  DBusError error;
  DBusString str;
  char *action_str;
  char action = '\0';

  while (!_dbus_string_init (&str))
    _dbus_wait_for_memory ();

  if ((reload_pipe[RELOAD_READ_END].fd > 0) &&
      _dbus_read_socket (reload_pipe[RELOAD_READ_END], &str, 1) != 1)
    {
      _dbus_warn ("Couldn't read from reload pipe.");
      close_reload_pipe (&watch);
      return TRUE;
    }

  action_str = _dbus_string_get_data (&str);
  if (action_str != NULL)
    {
      action = action_str[0];
    }
  _dbus_string_free (&str);

  /* this can only fail if we don't understand the config file
   * or OOM.  Either way we should just stick with the currently
   * loaded config.
   */
  dbus_error_init (&error);

  switch (action)
    {
    case ACTION_RELOAD:
      if (! bus_context_reload_config (context, &error))
        {
          _DBUS_ASSERT_ERROR_IS_SET (&error);
          _dbus_assert (dbus_error_has_name (&error, DBUS_ERROR_FAILED) ||
                        dbus_error_has_name (&error, DBUS_ERROR_NO_MEMORY));
          _dbus_warn ("Unable to reload configuration: %s",
                      error.message);
          dbus_error_free (&error);
        }
      break;

    case ACTION_QUIT:
      {
        DBusLoop *loop;
        /*
         * On OSs without abstract sockets, we want to quit
         * gracefully rather than being killed by SIGTERM,
         * so that DBusServer gets a chance to clean up the
         * sockets from the filesystem. fd.o #38656
         */
        loop = bus_context_get_loop (context);
        if (loop != NULL)
          {
            _dbus_daemon_report_stopping ();
            _dbus_loop_quit (loop);
          }
      }
      break;

    default:
      break;
    }

  return TRUE;
}

static void
setup_reload_pipe (DBusLoop *loop)
{
  DBusError error;
  DBusWatch *watch;

  dbus_error_init (&error);

  if (!_dbus_socketpair (&reload_pipe[0], &reload_pipe[1],
                         TRUE, &error))
    {
      _dbus_warn ("Unable to create reload pipe: %s",
		  error.message);
      dbus_error_free (&error);
      exit (1);
    }

  watch = _dbus_watch_new (_dbus_socket_get_pollable (reload_pipe[RELOAD_READ_END]),
                           DBUS_WATCH_READABLE, TRUE,
                           handle_reload_watch, NULL, NULL);

  if (watch == NULL)
    {
      _dbus_warn ("Unable to create reload watch: %s",
		  error.message);
      dbus_error_free (&error);
      exit (1);
    }

  if (!_dbus_loop_add_watch (loop, watch))
    {
      _dbus_warn ("Unable to add reload watch to main loop: %s",
		  error.message);
      dbus_error_free (&error);
      exit (1);
    }

}

static void
close_reload_pipe (DBusWatch **watch)
{
    _dbus_loop_remove_watch (bus_context_get_loop (context), *watch);
    _dbus_watch_invalidate (*watch);
    _dbus_watch_unref (*watch);
    *watch = NULL;

    _dbus_close_socket (&reload_pipe[RELOAD_READ_END], NULL);
    _dbus_close_socket (&reload_pipe[RELOAD_WRITE_END], NULL);
}
#endif /* DBUS_UNIX */

int
main (int argc, char **argv)
{
  DBusError error;
  DBusString config_file;
  DBusString address;
  DBusString addr_fd;
  DBusString pid_fd;
  const char *prev_arg;
  DBusPipe print_addr_pipe;
  DBusPipe print_pid_pipe;
  int i;
  dbus_bool_t print_address;
  dbus_bool_t print_pid;
  BusContextFlags flags;
  void *ready_event_handle;

#ifdef DBUS_UNIX
  const char *error_str;

  /* Redirect stdin from /dev/null since we will never need it, and
   * redirect stdout and stderr to /dev/null if not already open.
   *
   * We should do this as the very first thing, to ensure that when we
   * create other file descriptors (for example for epoll, inotify or
   * a socket), they never get assigned as fd 0, 1 or 2. If they were,
   * which could happen if our caller had (incorrectly) closed those
   * standard fds, they'd get closed when we daemonize - for example,
   * closing our listening socket would stop us listening, and closing
   * a Linux epoll socket would cause the main loop to fail. */
  if (!_dbus_ensure_standard_fds (DBUS_FORCE_STDIN_NULL, &error_str))
    {
      fprintf (stderr,
               "dbus-daemon: fatal error setting up standard fds: %s: %s\n",
               error_str, _dbus_strerror (errno));
      return 1;
    }

  /* Set all fds >= 3 close-on-execute. We don't want activated services
   * to inherit fds we might have inherited from our caller. */
  _dbus_fd_set_all_close_on_exec ();
#endif
  ready_event_handle = NULL;

  if (!_dbus_string_init (&config_file))
    return 1;

  if (!_dbus_string_init (&address))
    return 1;

  if (!_dbus_string_init (&addr_fd))
    return 1;

  if (!_dbus_string_init (&pid_fd))
    return 1;

  print_address = FALSE;
  print_pid = FALSE;

  flags = BUS_CONTEXT_FLAG_WRITE_PID_FILE;

  prev_arg = NULL;
  i = 1;
  while (i < argc)
    {
      const char *arg = argv[i];

      if (strcmp (arg, "--help") == 0 ||
          strcmp (arg, "-h") == 0 ||
          strcmp (arg, "-?") == 0)
        {
          usage ();
        }
      else if (strcmp (arg, "--version") == 0)
        {
          version ();
        }
      else if (strcmp (arg, "--introspect") == 0)
        {
          introspect ();
        }
      else if (strcmp (arg, "--nosyslog") == 0)
        {
          flags &= ~BUS_CONTEXT_FLAG_SYSLOG_ALWAYS;
          flags |= BUS_CONTEXT_FLAG_SYSLOG_NEVER;
        }
      else if (strcmp (arg, "--syslog") == 0)
        {
          flags &= ~BUS_CONTEXT_FLAG_SYSLOG_NEVER;
          flags |= BUS_CONTEXT_FLAG_SYSLOG_ALWAYS;
        }
      else if (strcmp (arg, "--syslog-only") == 0)
        {
          flags &= ~BUS_CONTEXT_FLAG_SYSLOG_NEVER;
          flags |= (BUS_CONTEXT_FLAG_SYSLOG_ALWAYS|BUS_CONTEXT_FLAG_SYSLOG_ONLY);
        }
      else if (strcmp (arg, "--nofork") == 0)
        {
          flags &= ~BUS_CONTEXT_FLAG_FORK_ALWAYS;
          flags |= BUS_CONTEXT_FLAG_FORK_NEVER;
        }
#ifdef DBUS_UNIX
      else if (strcmp (arg, "--fork") == 0)
        {
          flags &= ~BUS_CONTEXT_FLAG_FORK_NEVER;
          flags |= BUS_CONTEXT_FLAG_FORK_ALWAYS;
        }
      else if (strcmp (arg, "--systemd-activation") == 0)
        {
          flags |= BUS_CONTEXT_FLAG_SYSTEMD_ACTIVATION;
        }
#endif
      else if (strcmp (arg, "--nopidfile") == 0)
        {
          flags &= ~BUS_CONTEXT_FLAG_WRITE_PID_FILE;
        }
      else if (strcmp (arg, "--system") == 0)
        {
          check_two_config_files (&config_file, "system");

          if (!_dbus_get_system_config_file (&config_file))
            exit (1);
        }
      else if (strcmp (arg, "--session") == 0)
        {
          check_two_config_files (&config_file, "session");

          if (!_dbus_get_session_config_file (&config_file))
            exit (1);
        }
      else if (strstr (arg, "--config-file=") == arg)
        {
          const char *file;

          check_two_config_files (&config_file, "config-file");

          file = strchr (arg, '=');
          ++file;

          if (!_dbus_string_append (&config_file, file))
            exit (1);
        }
      else if (prev_arg &&
               strcmp (prev_arg, "--config-file") == 0)
        {
          check_two_config_files (&config_file, "config-file");

          if (!_dbus_string_append (&config_file, arg))
            exit (1);
        }
      else if (strcmp (arg, "--config-file") == 0)
        {
          /* wait for next arg */
        }
      else if (strstr (arg, "--address=") == arg)
        {
          const char *file;

          check_two_addresses (&address, "address");

          file = strchr (arg, '=');
          ++file;

          if (!_dbus_string_append (&address, file))
            exit (1);
        }
      else if (prev_arg &&
               strcmp (prev_arg, "--address") == 0)
        {
          check_two_addresses (&address, "address");

          if (!_dbus_string_append (&address, arg))
            exit (1);
        }
      else if (strcmp (arg, "--address") == 0)
        {
          /* wait for next arg */
        }
      else if (strstr (arg, "--print-address=") == arg)
        {
          const char *desc;

          check_two_addr_descriptors (&addr_fd, "print-address");

          desc = strchr (arg, '=');
          ++desc;

          if (!_dbus_string_append (&addr_fd, desc))
            exit (1);

          print_address = TRUE;
        }
      else if (strcmp (arg, "--print-address") == 0)
        {
          print_address = TRUE; /* and we'll get the next arg if appropriate */
        }
      else if (strstr (arg, "--print-pid=") == arg)
        {
          const char *desc;

          check_two_pid_descriptors (&pid_fd, "print-pid");

          desc = strchr (arg, '=');
          ++desc;

          if (!_dbus_string_append (&pid_fd, desc))
            exit (1);

          print_pid = TRUE;
        }
      else if (strcmp (arg, "--print-pid") == 0)
        {
          print_pid = TRUE; /* and we'll get the next arg if appropriate */
        }
#ifdef DBUS_WIN
      else if (strstr (arg, "--ready-event-handle=") == arg)
        {
          const char *desc;
          desc = strchr (arg, '=');
          _dbus_assert (desc != NULL);
          ++desc;
          if (sscanf (desc, "%p", &ready_event_handle) != 1)
            {
              fprintf (stderr, "%s specified, but invalid handle provided\n", arg);
              exit (1);
            }
        }
#endif
      else if (prev_arg &&
               strcmp (prev_arg, "--print-address") == 0)
        {
          check_two_addr_descriptors (&addr_fd, "print-address");

          if (!_dbus_string_append (&addr_fd, arg))
            exit (1);

          print_address = TRUE;
        }
      else if (prev_arg &&
               strcmp (prev_arg, "--print-pid") == 0)
        {
          check_two_pid_descriptors (&pid_fd, "print-pid");

          if (!_dbus_string_append (&pid_fd, arg))
            exit (1);

          print_pid = TRUE;
        }
      else
        {
          usage ();
        }

      prev_arg = arg;

      ++i;
    }

  if (_dbus_string_get_length (&config_file) == 0)
    {
      fprintf (stderr, "No configuration file specified.\n");
      usage ();
    }

  _dbus_pipe_invalidate (&print_addr_pipe);
  if (print_address)
    {
      _dbus_pipe_init_stdout (&print_addr_pipe);
      if (_dbus_string_get_length (&addr_fd) > 0)
        {
          long val;
          int end;
          if (!_dbus_string_parse_int (&addr_fd, 0, &val, &end) ||
              end != _dbus_string_get_length (&addr_fd) ||
              val < 0 || val > _DBUS_INT_MAX)
            {
              fprintf (stderr, "Invalid file descriptor: \"%s\"\n",
                       _dbus_string_get_const_data (&addr_fd));
              exit (1);
            }

          _dbus_pipe_init (&print_addr_pipe, val);
        }
    }
  _dbus_string_free (&addr_fd);

  _dbus_pipe_invalidate (&print_pid_pipe);
  if (print_pid)
    {
      _dbus_pipe_init_stdout (&print_pid_pipe);
      if (_dbus_string_get_length (&pid_fd) > 0)
        {
          long val;
          int end;
          if (!_dbus_string_parse_int (&pid_fd, 0, &val, &end) ||
              end != _dbus_string_get_length (&pid_fd) ||
              val < 0 || val > _DBUS_INT_MAX)
            {
              fprintf (stderr, "Invalid file descriptor: \"%s\"\n",
                       _dbus_string_get_const_data (&pid_fd));
              exit (1);
            }

          _dbus_pipe_init (&print_pid_pipe, val);
        }
    }
  _dbus_string_free (&pid_fd);

  if (!bus_selinux_pre_init ())
    {
      _dbus_warn ("SELinux pre-initialization failed");
      exit (1);
    }

  if (!bus_apparmor_pre_init ())
    {
      _dbus_warn ("AppArmor pre-initialization failed: out of memory");
      exit (1);
    }

  dbus_error_init (&error);
  context = bus_context_new (&config_file, flags,
                             &print_addr_pipe, &print_pid_pipe, ready_event_handle,
                             _dbus_string_get_length(&address) > 0 ? &address : NULL,
                             &error);
  _dbus_string_free (&config_file);
  _dbus_string_free (&address);
  if (context == NULL)
    {
      _dbus_warn ("Failed to start message bus: %s",
                  error.message);
      dbus_error_free (&error);
      exit (1);
    }

  /* bus_context_new() closes the print_addr_pipe and
   * print_pid_pipe
   */

#ifdef DBUS_UNIX
  setup_reload_pipe (bus_context_get_loop (context));

  /* POSIX signals are Unix-specific, and _dbus_set_signal_handler is
   * unimplemented (and probably unimplementable) on Windows, so there's
   * no point in trying to make the handler portable to non-Unix. */

  _dbus_set_signal_handler (SIGTERM, signal_handler);
  _dbus_set_signal_handler (SIGHUP, signal_handler);
#endif /* DBUS_UNIX */

  _dbus_verbose ("We are on D-Bus...\n");
  _dbus_daemon_report_ready ();
  _dbus_loop_run (bus_context_get_loop (context));

  bus_context_shutdown (context);
  bus_context_unref (context);
  bus_selinux_shutdown ();
  bus_apparmor_shutdown ();
  bus_audit_shutdown ();

  return 0;
}