login/programs/utmpd.c

   1 /* Copyright (C) 1997, 1998 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Mark Kettenis <kettenis@phys.uva.nl>, 1997.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <errno.h>
  21 #include <fcntl.h>
  22 #include <getopt.h>
  23 #include <libintl.h>
  24 #include <locale.h>
  25 #include <pwd.h>
  26 #include <stddef.h>
  27 #include <stdio.h>
  28 #include <stdlib.h>
  29 #include <signal.h>
  30 #include <string.h>
  31 #include <sys/param.h>
  32 #include <sys/select.h>
  33 #include <sys/socket.h>
  34 #include <sys/stat.h>
  35 #include <sys/types.h>
  36 #include <sys/un.h>
  37 #include <syslog.h>
  38 #include <unistd.h>
  39
  40 #include "utmpd.h"
  41 #include "utmpd-private.h"
  42
  43 #ifndef DEFAULT_USER
  44 #define DEFAULT_USER    "daemon"
  45 #endif
  46
  47 /* Get libc version number.  */
  48 #include <version.h>
  49
  50 #define PACKAGE _libc_intl_domainname
  51
  52 /* Long options.  */
  53 static const struct option long_options[] =
  54 {
  55   { "debug", no_argument, NULL, 'd' },
  56   { "help", no_argument, NULL, 'h' },
  57   { "version", no_argument, NULL, 'V' },
  58   { NULL, 0, NULL, 0}
  59 };
  60
  61 /* The UTMP database.  */
  62 utmp_database *utmp_db;
  63
  64 /* The socket for read only requests.  */
  65 int ro_sock = -1;
  66
  67 /* The socket for read/write requests.  */
  68 int rw_sock = -1;
  69
  70
  71 /* Prototypes for the local functions.  */
  72 static void usage (int status) __attribute__ ((noreturn));
  73 static void drop_priviliges (void);
  74 static int make_socket (const char *name);
  75 static void handle_requests (void) __attribute__ ((noreturn));
  76 static void termination_handler (int signum);
  77 static int check_pid (const char *file);
  78 static int write_pid (const char *file);
  79
  80
  81 int
  82 main (int argc, char *argv[])
  83 {
  84   mode_t mask;
  85   int debug;
  86   int do_help;
  87   int do_version;
  88   int opt;
  89
  90   /* Set locale via LC_ALL.  */
  91   setlocale (LC_ALL, "");
  92
  93   /* Set the text message domain.  */
  94   textdomain (PACKAGE);
  95
  96   /* Initialize local variables.  */
  97   debug = 0;
  98   do_help = 0;
  99   do_version = 0;
 100
 101   while ((opt = getopt_long (argc, argv, "dhV", long_options, NULL)) != -1)
 102     switch (opt)
 103       {
 104       case '\0':                /* Long option.  */
 105         break;
 106       case 'h':
 107         do_help = 1;
 108         break;
 109       case 'd':
 110         debug = 1;
 111         break;
 112       case 'V':
 113         do_version = 1;
 114         break;
 115       default:
 116         usage (EXIT_FAILURE);
 117       }
 118
 119   /* Version information is reequested.  */
 120   if (do_version)
 121     {
 122       printf ("utmpd (GNU %s) %s\n", PACKAGE, VERSION);
 123       printf (_("\
 124 Copyright (C) %s Free Software Foundation, Inc.\n\
 125 This is free software; see the source for copying conditions.  There is NO\n\
 126 warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n\
 127 "), "1997");
 128       printf (_("Written by %s.\n"), "Mark Kettenis");
 129
 130       exit (EXIT_SUCCESS);
 131     }
 132
 133   /* Help is requested.  */
 134   if (do_help)
 135     usage (EXIT_SUCCESS);
 136
 137   signal (SIGINT, termination_handler);
 138   signal (SIGQUIT, termination_handler);
 139   signal (SIGTERM, termination_handler);
 140
 141   /* Check if we are already running.  */
 142   if (check_pid (_PATH_UTMPDPID))
 143     error (EXIT_FAILURE, 0, _("already running"));
 144
 145   /* Cleanup files created by a previous `bind'.  */
 146   unlink (_PATH_UTMPD_RO);
 147   unlink (_PATH_UTMPD_RW);
 148
 149   /* Open UTMP database.  */
 150   utmp_db = open_database (_PATH_UTMP "x", _PATH_UTMP);
 151   if (utmp_db == NULL)
 152     exit (EXIT_FAILURE);
 153
 154   /* Create sockets, with the right permissions.  */
 155   mask = umask (S_IXUSR | S_IXGRP | S_IXOTH);
 156   ro_sock = make_socket (_PATH_UTMPD_RO);
 157   umask (S_IXUSR | S_IRWXG | S_IRWXO);
 158   rw_sock = make_socket (_PATH_UTMPD_RW);
 159   umask (mask);
 160
 161   /* Set the sockets up to accept connections.  */
 162   if (listen (ro_sock, MAX_CONNECTIONS) < 0
 163       || listen (rw_sock, MAX_CONNECTIONS) < 0)
 164     error (EXIT_FAILURE, errno,
 165            _("cannot enable socket to accept connections"));
 166
 167   /* Behave like a daemon.  */
 168   if (!debug)
 169     {
 170       openlog ("utmpd", LOG_CONS | LOG_ODELAY, LOG_DAEMON);
 171
 172       if (daemon (0, 0) < 0)
 173         error (EXIT_FAILURE, errno, _("cannot auto-background"));
 174       forked = 1;
 175
 176       if (write_pid (_PATH_UTMPDPID) < 0)
 177         warning (errno, "%s", _PATH_UTMPDPID);
 178
 179       /* Ignore job control signals.  */
 180       signal (SIGTTOU, SIG_IGN);
 181       signal (SIGTTIN, SIG_IGN);
 182       signal (SIGTSTP, SIG_IGN);
 183     }
 184
 185   /* Drop priviliges.  */
 186   drop_priviliges ();
 187
 188   /* Handle incoming requests.  */
 189   handle_requests ();
 190 }
 191
 192
 193 /* Display usage information and exit.  */
 194 static void
 195 usage (int status)
 196 {
 197   if (status != EXIT_SUCCESS)
 198     fprintf (stderr, _("Try `%s --help' for more information.\n"),
 199              program_invocation_name);
 200   else
 201     {
 202       printf (_("\
 203 Usage: %s [OPTION]...\n\
 204   -d, --debug           do not fork and display messages on the current tty\n\
 205   -h, --help            display this help and exit\n\
 206   -V, --version         output version information and exit\n"),
 207               program_invocation_name);
 208       fputs (_("\
 209 Report bugs using the `glibcbug' script to <bugs@gnu.org>.\n"),
 210              stdout);
 211     }
 212
 213   exit (status);
 214 }
 215
 216
 217 /* Drop priviliges.  */
 218 static void
 219 drop_priviliges (void)
 220 {
 221   struct passwd *pw;
 222
 223   pw = getpwnam (DEFAULT_USER);
 224   if (pw)
 225     {
 226       seteuid (pw->pw_uid);
 227       setegid (pw->pw_gid);
 228     }
 229 }
 230
 231
 232 /* Make a socket in the file namespace using the filename NAME as the
 233    socket's address.  */
 234 static int
 235 make_socket (const char *name)
 236 {
 237   struct sockaddr_un addr;
 238   size_t size;
 239   int sock;
 240
 241   /* Create the socket.  */
 242   sock = socket (PF_UNIX, SOCK_STREAM, 0);
 243   if (sock < 0)
 244     error (EXIT_FAILURE, errno, _("cannot create socket"));
 245
 246   /* Bind a name to the socket.  */
 247   addr.sun_family = AF_UNIX;
 248   strcpy (addr.sun_path, name);
 249
 250   /* The size of the address is the offset of the start
 251      of the filename, plus its length, plus one for the
 252      terminating null byte. */
 253   size = (offsetof (struct sockaddr_un, sun_path)
 254           + strlen (addr.sun_path));
 255
 256
 257   if (bind (sock, (struct sockaddr *) &addr, size) < 0)
 258     error (EXIT_FAILURE, errno, "%s", name);
 259
 260   return sock;
 261 }
 262
 263
 264 /* Hanlde incoming requests.  */
 265 static
 266 void handle_requests (void)
 267 {
 268   client_connection *connection;
 269   fd_set active_read_fd_set;
 270   fd_set active_write_fd_set;
 271   fd_set read_fd_set;
 272   fd_set write_fd_set;
 273   int fd;
 274   int maxfd;  /* Highest used fd to optimize select/loop.  */
 275
 276   /* Initialize the set of active sockets.  */
 277   FD_ZERO (&active_read_fd_set);
 278   FD_ZERO (&active_write_fd_set);
 279   FD_SET (rw_sock, &active_read_fd_set);
 280   FD_SET (ro_sock, &active_read_fd_set);
 281
 282   maxfd = MAX (rw_sock, ro_sock);
 283
 284   while (1)
 285     {
 286       /* Block until input arrives on one or more active sockets.  */
 287       read_fd_set = active_read_fd_set;
 288       write_fd_set = active_write_fd_set;
 289       if (select (maxfd + 1, &read_fd_set, &write_fd_set, NULL, NULL) < 0)
 290         error (EXIT_FAILURE, errno, _("cannot get input on sockets"));
 291
 292       /* Service all the sockets with input pending.  */
 293       for (fd = 0; fd <= maxfd; ++fd)
 294         {
 295           if (FD_ISSET (fd, &read_fd_set))
 296             {
 297               if (fd == ro_sock || fd == rw_sock)
 298                 {
 299                   int access = ((fd == rw_sock) ? (R_OK | W_OK) : R_OK);
 300
 301                   connection = accept_connection (fd, access);
 302                   if (connection == NULL)
 303                     error (0, errno, _("cannot accept connection"));
 304
 305                   FD_SET (connection->sock, &active_read_fd_set);
 306                   maxfd = MAX (maxfd, connection->sock);
 307                 }
 308               else
 309                 {
 310                   connection = find_connection (fd);
 311                   if (connection == NULL)
 312                     error (EXIT_FAILURE, 0, _("cannot find connection"));
 313
 314                   if (read_data (connection) < 0)
 315                     {
 316                       close_connection (connection);
 317                       FD_CLR (fd, &active_read_fd_set);
 318                       FD_CLR (fd, &active_write_fd_set);
 319                     }
 320
 321                   if (connection->write_ptr > connection->write_base)
 322                       FD_SET (fd, &active_write_fd_set);
 323                 }
 324             }
 325           if (FD_ISSET (fd, &write_fd_set) &&
 326               fd != rw_sock && fd != ro_sock)
 327             {
 328               connection = find_connection (fd);
 329               if (connection == NULL)
 330                 error (EXIT_FAILURE, 0, _("cannot find connection"));
 331
 332               if (write_data (connection) < 0)
 333                 {
 334                   close_connection (connection);
 335                   FD_CLR (fd, &active_read_fd_set);
 336                   FD_CLR (fd, &active_write_fd_set);
 337                 }
 338
 339               if (connection->write_ptr == connection->write_base)
 340                 FD_CLR (fd, &active_write_fd_set);
 341             }
 342         }
 343
 344       /* Check if maxfd can be lowered.  */
 345       for (; maxfd >= 0; --maxfd)
 346         {
 347           if (FD_ISSET (maxfd, &active_read_fd_set)
 348               || FD_ISSET (maxfd, &active_write_fd_set))
 349             break;
 350         }
 351     }
 352 }
 353
 354
 355 /* Cleanup.  */
 356 static void
 357 termination_handler (int signum)
 358 {
 359   /* Close sockets.  */
 360   close (ro_sock);
 361   close (rw_sock);
 362
 363   /* Restore user id.  */
 364   seteuid (getuid ());
 365
 366   /* Clean up the files created by `bind'.  */
 367   unlink (_PATH_UTMPD_RO);
 368   unlink (_PATH_UTMPD_RW);
 369
 370   if (utmp_db)
 371     close_database (utmp_db);
 372
 373   /* Clean up pid file.  */
 374   unlink (_PATH_UTMPDPID);
 375
 376   exit (EXIT_SUCCESS);
 377 }
 378
 379
 380 /* Returns 1 if the process in pid file FILE is running, 0 if not.  */
 381 static int
 382 check_pid (const char *file)
 383 {
 384   FILE *fp;
 385
 386   fp = fopen (_PATH_UTMPDPID, "r");
 387   if (fp)
 388     {
 389       pid_t pid;
 390
 391       fscanf (fp, "%d", &pid);
 392       fclose (fp);
 393
 394       if (kill (pid, 0) == 0)
 395         return 1;
 396     }
 397
 398   return 0;
 399 }
 400
 401 /* Write the current process id to the file FILE.  Returns 0 if
 402    successful, -1 if not.  */
 403 static int
 404 write_pid (const char *file)
 405 {
 406   FILE *fp;
 407
 408   fp = fopen (_PATH_UTMPDPID, "w");
 409   if (fp == NULL)
 410     return -1;
 411
 412   fprintf (fp, "%d\n", getpid ());
 413   if (ferror (fp))
 414     return -1;
 415
 416   fclose (fp);
 417
 418   return 0;
 419 }