login/utmp_file.c

   1 /* Copyright (C) 1996-2002, 2003, 2004 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@cygnus.com>
   4    and Paul Janzen <pcj@primenet.com>, 1996.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <assert.h>
  22 #include <errno.h>
  23 #include <fcntl.h>
  24 #include <signal.h>
  25 #include <stdio.h>
  26 #include <string.h>
  27 #include <unistd.h>
  28 #include <utmp.h>
  29 #include <not-cancel.h>
  30
  31 #include "utmp-private.h"
  32 #include "utmp-equal.h"
  33
  34
  35 /* Descriptor for the file and position.  */
  36 static int file_fd = -1;
  37 static off64_t file_offset;
  38
  39 /* Cache for the last read entry.  */
  40 static struct utmp last_entry;
  41
  42
  43 /* Locking timeout.  */
  44 #ifndef TIMEOUT
  45 # define TIMEOUT 1
  46 #endif
  47
  48 /* Do-nothing handler for locking timeout.  */
  49 static void timeout_handler (int signum) {};
  50
  51 /* LOCK_FILE(fd, type) failure_statement
  52      attempts to get a lock on the utmp file referenced by FD.  If it fails,
  53      the failure_statement is executed, otherwise it is skipped.
  54    LOCKING_FAILED()
  55      jumps into the UNLOCK_FILE macro and ensures cleanup of LOCK_FILE.
  56    UNLOCK_FILE(fd)
  57      unlocks the utmp file referenced by FD and performs the cleanup of
  58      LOCK_FILE.
  59  */
  60 #define LOCK_FILE(fd, type) \
  61 {                                                                             \
  62   struct flock fl;                                                            \
  63   struct sigaction action, old_action;                                        \
  64   unsigned int old_timeout;                                                   \
  65                                                                               \
  66   /* Cancel any existing alarm.  */                                           \
  67   old_timeout = alarm (0);                                                    \
  68                                                                               \
  69   /* Establish signal handler.  */                                            \
  70   action.sa_handler = timeout_handler;                                        \
  71   __sigemptyset (&action.sa_mask);                                            \
  72   action.sa_flags = 0;                                                        \
  73   __sigaction (SIGALRM, &action, &old_action);                                \
  74                                                                               \
  75   alarm (TIMEOUT);                                                            \
  76                                                                               \
  77   /* Try to get the lock.  */                                                 \
  78   memset (&fl, '\0', sizeof (struct flock));                                  \
  79   fl.l_type = (type);                                                         \
  80   fl.l_whence = SEEK_SET;                                                     \
  81   if (fcntl_not_cancel ((fd), F_SETLKW, &fl) < 0)
  82
  83 #define LOCKING_FAILED() \
  84   goto unalarm_return
  85
  86 #define UNLOCK_FILE(fd) \
  87   /* Unlock the file.  */                                                     \
  88   fl.l_type = F_UNLCK;                                                        \
  89   fcntl_not_cancel ((fd), F_SETLKW, &fl);                                     \
  90                                                                               \
  91  unalarm_return:                                                              \
  92   /* Reset the signal handler and alarm.  We must reset the alarm             \
  93      before resetting the handler so our alarm does not generate a            \
  94      spurious SIGALRM seen by the user.  However, we cannot just set          \
  95      the user's old alarm before restoring the handler, because then          \
  96      it's possible our handler could catch the user alarm's SIGARLM           \
  97      and then the user would never see the signal he expected.  */            \
  98   alarm (0);                                                                  \
  99   __sigaction (SIGALRM, &old_action, NULL);                                   \
 100   if (old_timeout != 0)                                                       \
 101     alarm (old_timeout);                                                      \
 102 } while (0)
 103
 104
 105 /* Functions defined here.  */
 106 static int setutent_file (void);
 107 static int getutent_r_file (struct utmp *buffer, struct utmp **result);
 108 static int getutid_r_file (const struct utmp *key, struct utmp *buffer,
 109                            struct utmp **result);
 110 static int getutline_r_file (const struct utmp *key, struct utmp *buffer,
 111                              struct utmp **result);
 112 static struct utmp *pututline_file (const struct utmp *data);
 113 static void endutent_file (void);
 114 static int updwtmp_file (const char *file, const struct utmp *utmp);
 115
 116 /* Jump table for file functions.  */
 117 const struct utfuncs __libc_utmp_file_functions =
 118 {
 119   setutent_file,
 120   getutent_r_file,
 121   getutid_r_file,
 122   getutline_r_file,
 123   pututline_file,
 124   endutent_file,
 125   updwtmp_file
 126 };
 127
 128
 129 #ifndef TRANSFORM_UTMP_FILE_NAME
 130 # define TRANSFORM_UTMP_FILE_NAME(file_name) (file_name)
 131 #endif
 132
 133 static int
 134 setutent_file (void)
 135 {
 136   if (file_fd < 0)
 137     {
 138       const char *file_name;
 139       int result;
 140
 141       file_name = TRANSFORM_UTMP_FILE_NAME (__libc_utmp_file_name);
 142
 143       file_fd = open_not_cancel_2 (file_name, O_RDWR);
 144       if (file_fd == -1)
 145         {
 146           /* Hhm, read-write access did not work.  Try read-only.  */
 147           file_fd = open_not_cancel_2 (file_name, O_RDONLY);
 148           if (file_fd == -1)
 149             return 0;
 150         }
 151
 152       /* We have to make sure the file is `closed on exec'.  */
 153       result = fcntl_not_cancel (file_fd, F_GETFD, 0);
 154       if (result >= 0)
 155         result = fcntl_not_cancel (file_fd, F_SETFD, result | FD_CLOEXEC);
 156       if (result == -1)
 157         {
 158           close_not_cancel_no_status (file_fd);
 159           return 0;
 160         }
 161     }
 162
 163   __lseek64 (file_fd, 0, SEEK_SET);
 164   file_offset = 0;
 165
 166   /* Make sure the entry won't match.  */
 167 #if _HAVE_UT_TYPE - 0
 168   last_entry.ut_type = -1;
 169 #else
 170   last_entry.ut_line[0] = '\177';
 171 # if _HAVE_UT_ID - 0
 172   last_entry.ut_id[0] = '\0';
 173 # endif
 174 #endif
 175
 176   return 1;
 177 }
 178
 179
 180 static int
 181 getutent_r_file (struct utmp *buffer, struct utmp **result)
 182 {
 183   ssize_t nbytes;
 184
 185   assert (file_fd >= 0);
 186
 187   if (file_offset == -1l)
 188     {
 189       /* Not available.  */
 190       *result = NULL;
 191       return -1;
 192     }
 193
 194   LOCK_FILE (file_fd, F_RDLCK)
 195     {
 196       nbytes = 0;
 197       LOCKING_FAILED ();
 198     }
 199
 200   /* Read the next entry.  */
 201   nbytes = read_not_cancel (file_fd, &last_entry, sizeof (struct utmp));
 202
 203   UNLOCK_FILE (file_fd);
 204
 205   if (nbytes != sizeof (struct utmp))
 206     {
 207       if (nbytes != 0)
 208         file_offset = -1l;
 209       *result = NULL;
 210       return -1;
 211     }
 212
 213   /* Update position pointer.  */
 214   file_offset += sizeof (struct utmp);
 215
 216   memcpy (buffer, &last_entry, sizeof (struct utmp));
 217   *result = buffer;
 218
 219   return 0;
 220 }
 221
 222
 223 static int
 224 internal_getut_r (const struct utmp *id, struct utmp *buffer)
 225 {
 226   int result = -1;
 227
 228   LOCK_FILE (file_fd, F_RDLCK)
 229     LOCKING_FAILED ();
 230
 231 #if _HAVE_UT_TYPE - 0
 232   if (id->ut_type == RUN_LVL || id->ut_type == BOOT_TIME
 233       || id->ut_type == OLD_TIME || id->ut_type == NEW_TIME)
 234     {
 235       /* Search for next entry with type RUN_LVL, BOOT_TIME,
 236          OLD_TIME, or NEW_TIME.  */
 237
 238       while (1)
 239         {
 240           /* Read the next entry.  */
 241           if (read_not_cancel (file_fd, buffer, sizeof (struct utmp))
 242               != sizeof (struct utmp))
 243             {
 244               __set_errno (ESRCH);
 245               file_offset = -1l;
 246               goto unlock_return;
 247             }
 248           file_offset += sizeof (struct utmp);
 249
 250           if (id->ut_type == buffer->ut_type)
 251             break;
 252         }
 253     }
 254   else
 255 #endif /* _HAVE_UT_TYPE */
 256     {
 257       /* Search for the next entry with the specified ID and with type
 258          INIT_PROCESS, LOGIN_PROCESS, USER_PROCESS, or DEAD_PROCESS.  */
 259
 260       while (1)
 261         {
 262           /* Read the next entry.  */
 263           if (read_not_cancel (file_fd, buffer, sizeof (struct utmp))
 264               != sizeof (struct utmp))
 265             {
 266               __set_errno (ESRCH);
 267               file_offset = -1l;
 268               goto unlock_return;
 269             }
 270           file_offset += sizeof (struct utmp);
 271
 272           if (__utmp_equal (buffer, id))
 273             break;
 274         }
 275     }
 276
 277   result = 0;
 278
 279 unlock_return:
 280   UNLOCK_FILE (file_fd);
 281
 282   return result;
 283 }
 284
 285
 286 /* For implementing this function we don't use the getutent_r function
 287    because we can avoid the reposition on every new entry this way.  */
 288 static int
 289 getutid_r_file (const struct utmp *id, struct utmp *buffer,
 290                 struct utmp **result)
 291 {
 292   assert (file_fd >= 0);
 293
 294   if (file_offset == -1l)
 295     {
 296       *result = NULL;
 297       return -1;
 298     }
 299
 300   if (internal_getut_r (id, &last_entry) < 0)
 301     {
 302       *result = NULL;
 303       return -1;
 304     }
 305
 306   memcpy (buffer, &last_entry, sizeof (struct utmp));
 307   *result = buffer;
 308
 309   return 0;
 310 }
 311
 312
 313 /* For implementing this function we don't use the getutent_r function
 314    because we can avoid the reposition on every new entry this way.  */
 315 static int
 316 getutline_r_file (const struct utmp *line, struct utmp *buffer,
 317                   struct utmp **result)
 318 {
 319   assert (file_fd >= 0);
 320
 321   if (file_offset == -1l)
 322     {
 323       *result = NULL;
 324       return -1;
 325     }
 326
 327   LOCK_FILE (file_fd, F_RDLCK)
 328     {
 329       *result = NULL;
 330       LOCKING_FAILED ();
 331     }
 332
 333   while (1)
 334     {
 335       /* Read the next entry.  */
 336       if (read_not_cancel (file_fd, &last_entry, sizeof (struct utmp))
 337           != sizeof (struct utmp))
 338         {
 339           __set_errno (ESRCH);
 340           file_offset = -1l;
 341           *result = NULL;
 342           goto unlock_return;
 343         }
 344       file_offset += sizeof (struct utmp);
 345
 346       /* Stop if we found a user or login entry.  */
 347       if (
 348 #if _HAVE_UT_TYPE - 0
 349           (last_entry.ut_type == USER_PROCESS
 350            || last_entry.ut_type == LOGIN_PROCESS)
 351           &&
 352 #endif
 353           !strncmp (line->ut_line, last_entry.ut_line, sizeof line->ut_line))
 354         break;
 355     }
 356
 357   memcpy (buffer, &last_entry, sizeof (struct utmp));
 358   *result = buffer;
 359
 360 unlock_return:
 361   UNLOCK_FILE (file_fd);
 362
 363   return ((*result == NULL) ? -1 : 0);
 364 }
 365
 366
 367 static struct utmp *
 368 pututline_file (const struct utmp *data)
 369 {
 370   struct utmp buffer;
 371   struct utmp *pbuf;
 372   int found;
 373
 374   assert (file_fd >= 0);
 375
 376   /* Find the correct place to insert the data.  */
 377   if (file_offset > 0
 378       && (
 379 #if _HAVE_UT_TYPE - 0
 380           (last_entry.ut_type == data->ut_type
 381            && (last_entry.ut_type == RUN_LVL
 382                || last_entry.ut_type == BOOT_TIME
 383                || last_entry.ut_type == OLD_TIME
 384                || last_entry.ut_type == NEW_TIME))
 385           ||
 386 #endif
 387           __utmp_equal (&last_entry, data)))
 388     found = 1;
 389   else
 390     found = internal_getut_r (data, &buffer);
 391
 392   LOCK_FILE (file_fd, F_WRLCK)
 393     {
 394       pbuf = NULL;
 395       LOCKING_FAILED ();
 396     }
 397
 398   if (found < 0)
 399     {
 400       /* We append the next entry.  */
 401       file_offset = __lseek64 (file_fd, 0, SEEK_END);
 402       if (file_offset % sizeof (struct utmp) != 0)
 403         {
 404           file_offset -= file_offset % sizeof (struct utmp);
 405           __ftruncate64 (file_fd, file_offset);
 406
 407           if (__lseek64 (file_fd, 0, SEEK_END) < 0)
 408             {
 409               pbuf = NULL;
 410               goto unlock_return;
 411             }
 412         }
 413     }
 414   else
 415     {
 416       /* We replace the just read entry.  */
 417       file_offset -= sizeof (struct utmp);
 418       __lseek64 (file_fd, file_offset, SEEK_SET);
 419     }
 420
 421   /* Write the new data.  */
 422   if (write_not_cancel (file_fd, data, sizeof (struct utmp))
 423       != sizeof (struct utmp))
 424     {
 425       /* If we appended a new record this is only partially written.
 426          Remove it.  */
 427       if (found < 0)
 428         (void) __ftruncate64 (file_fd, file_offset);
 429       pbuf = NULL;
 430     }
 431   else
 432     {
 433       file_offset += sizeof (struct utmp);
 434       pbuf = (struct utmp *) data;
 435     }
 436
 437  unlock_return:
 438   UNLOCK_FILE (file_fd);
 439
 440   return pbuf;
 441 }
 442
 443
 444 static void
 445 endutent_file (void)
 446 {
 447   assert (file_fd >= 0);
 448
 449   close_not_cancel_no_status (file_fd);
 450   file_fd = -1;
 451 }
 452
 453
 454 static int
 455 updwtmp_file (const char *file, const struct utmp *utmp)
 456 {
 457   int result = -1;
 458   off64_t offset;
 459   int fd;
 460
 461   /* Open WTMP file.  */
 462   fd = open_not_cancel_2 (file, O_WRONLY);
 463   if (fd < 0)
 464     return -1;
 465
 466   LOCK_FILE (fd, F_WRLCK)
 467     LOCKING_FAILED ();
 468
 469   /* Remember original size of log file.  */
 470   offset = __lseek64 (fd, 0, SEEK_END);
 471   if (offset % sizeof (struct utmp) != 0)
 472     {
 473       offset -= offset % sizeof (struct utmp);
 474       __ftruncate64 (fd, offset);
 475
 476       if (__lseek64 (fd, 0, SEEK_END) < 0)
 477         goto unlock_return;
 478     }
 479
 480   /* Write the entry.  If we can't write all the bytes, reset the file
 481      size back to the original size.  That way, no partial entries
 482      will remain.  */
 483   if (write_not_cancel (fd, utmp, sizeof (struct utmp))
 484       != sizeof (struct utmp))
 485     {
 486       __ftruncate64 (fd, offset);
 487       goto unlock_return;
 488     }
 489
 490   result = 0;
 491
 492 unlock_return:
 493   UNLOCK_FILE (fd);
 494
 495   /* Close WTMP file.  */
 496   close_not_cancel_no_status (fd);
 497
 498   return result;
 499 }