login/utmp_file.c

   1 /* Copyright (C) 1996-2002, 2003, 2004, 2007 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 #include <kernel-features.h>
  31
  32 #include "utmp-private.h"
  33 #include "utmp-equal.h"
  34
  35
  36 /* Descriptor for the file and position.  */
  37 static int file_fd = -1;
  38 static off64_t file_offset;
  39
  40 /* Cache for the last read entry.  */
  41 static struct utmp last_entry;
  42
  43
  44 /* Locking timeout.  */
  45 #ifndef TIMEOUT
  46 # define TIMEOUT 1
  47 #endif
  48
  49 /* Do-nothing handler for locking timeout.  */
  50 static void timeout_handler (int signum) {};
  51
  52 /* LOCK_FILE(fd, type) failure_statement
  53      attempts to get a lock on the utmp file referenced by FD.  If it fails,
  54      the failure_statement is executed, otherwise it is skipped.
  55    LOCKING_FAILED()
  56      jumps into the UNLOCK_FILE macro and ensures cleanup of LOCK_FILE.
  57    UNLOCK_FILE(fd)
  58      unlocks the utmp file referenced by FD and performs the cleanup of
  59      LOCK_FILE.
  60  */
  61 #define LOCK_FILE(fd, type) \
  62 {                                                                             \
  63   struct flock fl;                                                            \
  64   struct sigaction action, old_action;                                        \
  65   unsigned int old_timeout;                                                   \
  66                                                                               \
  67   /* Cancel any existing alarm.  */                                           \
  68   old_timeout = alarm (0);                                                    \
  69                                                                               \
  70   /* Establish signal handler.  */                                            \
  71   action.sa_handler = timeout_handler;                                        \
  72   __sigemptyset (&action.sa_mask);                                            \
  73   action.sa_flags = 0;                                                        \
  74   __sigaction (SIGALRM, &action, &old_action);                                \
  75                                                                               \
  76   alarm (TIMEOUT);                                                            \
  77                                                                               \
  78   /* Try to get the lock.  */                                                 \
  79   memset (&fl, '\0', sizeof (struct flock));                                  \
  80   fl.l_type = (type);                                                         \
  81   fl.l_whence = SEEK_SET;                                                     \
  82   if (fcntl_not_cancel ((fd), F_SETLKW, &fl) < 0)
  83
  84 #define LOCKING_FAILED() \
  85   goto unalarm_return
  86
  87 #define UNLOCK_FILE(fd) \
  88   /* Unlock the file.  */                                                     \
  89   fl.l_type = F_UNLCK;                                                        \
  90   fcntl_not_cancel ((fd), F_SETLKW, &fl);                                     \
  91                                                                               \
  92  unalarm_return:                                                              \
  93   /* Reset the signal handler and alarm.  We must reset the alarm             \
  94      before resetting the handler so our alarm does not generate a            \
  95      spurious SIGALRM seen by the user.  However, we cannot just set          \
  96      the user's old alarm before restoring the handler, because then          \
  97      it's possible our handler could catch the user alarm's SIGARLM           \
  98      and then the user would never see the signal he expected.  */            \
  99   alarm (0);                                                                  \
 100   __sigaction (SIGALRM, &old_action, NULL);                                   \
 101   if (old_timeout != 0)                                                       \
 102     alarm (old_timeout);                                                      \
 103 } while (0)
 104
 105
 106 /* Functions defined here.  */
 107 static int setutent_file (void);
 108 static int getutent_r_file (struct utmp *buffer, struct utmp **result);
 109 static int getutid_r_file (const struct utmp *key, struct utmp *buffer,
 110                            struct utmp **result);
 111 static int getutline_r_file (const struct utmp *key, struct utmp *buffer,
 112                              struct utmp **result);
 113 static struct utmp *pututline_file (const struct utmp *data);
 114 static void endutent_file (void);
 115 static int updwtmp_file (const char *file, const struct utmp *utmp);
 116
 117 /* Jump table for file functions.  */
 118 const struct utfuncs __libc_utmp_file_functions =
 119 {
 120   setutent_file,
 121   getutent_r_file,
 122   getutid_r_file,
 123   getutline_r_file,
 124   pututline_file,
 125   endutent_file,
 126   updwtmp_file
 127 };
 128
 129
 130 #ifndef TRANSFORM_UTMP_FILE_NAME
 131 # define TRANSFORM_UTMP_FILE_NAME(file_name) (file_name)
 132 #endif
 133
 134 static int
 135 setutent_file (void)
 136 {
 137   if (file_fd < 0)
 138     {
 139       const char *file_name;
 140       int result;
 141
 142       file_name = TRANSFORM_UTMP_FILE_NAME (__libc_utmp_file_name);
 143
 144 #ifdef O_CLOEXEC
 145 # define O_flags O_LARGEFILE | O_CLOEXEC
 146 #else
 147 # define O_flags O_LARGEFILE
 148 #endif
 149       file_fd = open_not_cancel_2 (file_name, O_RDWR | O_flags);
 150       if (file_fd == -1)
 151         {
 152           /* Hhm, read-write access did not work.  Try read-only.  */
 153           file_fd = open_not_cancel_2 (file_name, O_RDONLY | O_flags);
 154           if (file_fd == -1)
 155             return 0;
 156         }
 157
 158 #ifndef __ASSUME_O_CLOEXEC
 159 # ifdef O_CLOEXEC
 160       static int have_o_cloexec;
 161
 162       if (have_o_cloexec <= 0)
 163 # endif
 164         {
 165           /* We have to make sure the file is `closed on exec'.  */
 166           result = fcntl_not_cancel (file_fd, F_GETFD, 0);
 167           if (result >= 0)
 168             {
 169 # ifdef O_CLOEXEC
 170               if (have_o_cloexec == 0)
 171                 have_o_cloexec = (result & FD_CLOEXEC) ? 1 : -1;
 172 # endif
 173
 174               result = fcntl_not_cancel (file_fd, F_SETFD,
 175                                          result | FD_CLOEXEC);
 176             }
 177
 178           if (result == -1)
 179             {
 180               close_not_cancel_no_status (file_fd);
 181               return 0;
 182             }
 183         }
 184 #endif
 185     }
 186
 187   __lseek64 (file_fd, 0, SEEK_SET);
 188   file_offset = 0;
 189
 190   /* Make sure the entry won't match.  */
 191 #if _HAVE_UT_TYPE - 0
 192   last_entry.ut_type = -1;
 193 #else
 194   last_entry.ut_line[0] = '\177';
 195 # if _HAVE_UT_ID - 0
 196   last_entry.ut_id[0] = '\0';
 197 # endif
 198 #endif
 199
 200   return 1;
 201 }
 202
 203
 204 static int
 205 getutent_r_file (struct utmp *buffer, struct utmp **result)
 206 {
 207   ssize_t nbytes;
 208
 209   assert (file_fd >= 0);
 210
 211   if (file_offset == -1l)
 212     {
 213       /* Not available.  */
 214       *result = NULL;
 215       return -1;
 216     }
 217
 218   LOCK_FILE (file_fd, F_RDLCK)
 219     {
 220       nbytes = 0;
 221       LOCKING_FAILED ();
 222     }
 223
 224   /* Read the next entry.  */
 225   nbytes = read_not_cancel (file_fd, &last_entry, sizeof (struct utmp));
 226
 227   UNLOCK_FILE (file_fd);
 228
 229   if (nbytes != sizeof (struct utmp))
 230     {
 231       if (nbytes != 0)
 232         file_offset = -1l;
 233       *result = NULL;
 234       return -1;
 235     }
 236
 237   /* Update position pointer.  */
 238   file_offset += sizeof (struct utmp);
 239
 240   memcpy (buffer, &last_entry, sizeof (struct utmp));
 241   *result = buffer;
 242
 243   return 0;
 244 }
 245
 246
 247 static int
 248 internal_getut_r (const struct utmp *id, struct utmp *buffer)
 249 {
 250   int result = -1;
 251
 252   LOCK_FILE (file_fd, F_RDLCK)
 253     LOCKING_FAILED ();
 254
 255 #if _HAVE_UT_TYPE - 0
 256   if (id->ut_type == RUN_LVL || id->ut_type == BOOT_TIME
 257       || id->ut_type == OLD_TIME || id->ut_type == NEW_TIME)
 258     {
 259       /* Search for next entry with type RUN_LVL, BOOT_TIME,
 260          OLD_TIME, or NEW_TIME.  */
 261
 262       while (1)
 263         {
 264           /* Read the next entry.  */
 265           if (read_not_cancel (file_fd, buffer, sizeof (struct utmp))
 266               != sizeof (struct utmp))
 267             {
 268               __set_errno (ESRCH);
 269               file_offset = -1l;
 270               goto unlock_return;
 271             }
 272           file_offset += sizeof (struct utmp);
 273
 274           if (id->ut_type == buffer->ut_type)
 275             break;
 276         }
 277     }
 278   else
 279 #endif /* _HAVE_UT_TYPE */
 280     {
 281       /* Search for the next entry with the specified ID and with type
 282          INIT_PROCESS, LOGIN_PROCESS, USER_PROCESS, or DEAD_PROCESS.  */
 283
 284       while (1)
 285         {
 286           /* Read the next entry.  */
 287           if (read_not_cancel (file_fd, buffer, sizeof (struct utmp))
 288               != sizeof (struct utmp))
 289             {
 290               __set_errno (ESRCH);
 291               file_offset = -1l;
 292               goto unlock_return;
 293             }
 294           file_offset += sizeof (struct utmp);
 295
 296           if (__utmp_equal (buffer, id))
 297             break;
 298         }
 299     }
 300
 301   result = 0;
 302
 303 unlock_return:
 304   UNLOCK_FILE (file_fd);
 305
 306   return result;
 307 }
 308
 309
 310 /* For implementing this function we don't use the getutent_r function
 311    because we can avoid the reposition on every new entry this way.  */
 312 static int
 313 getutid_r_file (const struct utmp *id, struct utmp *buffer,
 314                 struct utmp **result)
 315 {
 316   assert (file_fd >= 0);
 317
 318   if (file_offset == -1l)
 319     {
 320       *result = NULL;
 321       return -1;
 322     }
 323
 324   if (internal_getut_r (id, &last_entry) < 0)
 325     {
 326       *result = NULL;
 327       return -1;
 328     }
 329
 330   memcpy (buffer, &last_entry, sizeof (struct utmp));
 331   *result = buffer;
 332
 333   return 0;
 334 }
 335
 336
 337 /* For implementing this function we don't use the getutent_r function
 338    because we can avoid the reposition on every new entry this way.  */
 339 static int
 340 getutline_r_file (const struct utmp *line, struct utmp *buffer,
 341                   struct utmp **result)
 342 {
 343   assert (file_fd >= 0);
 344
 345   if (file_offset == -1l)
 346     {
 347       *result = NULL;
 348       return -1;
 349     }
 350
 351   LOCK_FILE (file_fd, F_RDLCK)
 352     {
 353       *result = NULL;
 354       LOCKING_FAILED ();
 355     }
 356
 357   while (1)
 358     {
 359       /* Read the next entry.  */
 360       if (read_not_cancel (file_fd, &last_entry, sizeof (struct utmp))
 361           != sizeof (struct utmp))
 362         {
 363           __set_errno (ESRCH);
 364           file_offset = -1l;
 365           *result = NULL;
 366           goto unlock_return;
 367         }
 368       file_offset += sizeof (struct utmp);
 369
 370       /* Stop if we found a user or login entry.  */
 371       if (
 372 #if _HAVE_UT_TYPE - 0
 373           (last_entry.ut_type == USER_PROCESS
 374            || last_entry.ut_type == LOGIN_PROCESS)
 375           &&
 376 #endif
 377           !strncmp (line->ut_line, last_entry.ut_line, sizeof line->ut_line))
 378         break;
 379     }
 380
 381   memcpy (buffer, &last_entry, sizeof (struct utmp));
 382   *result = buffer;
 383
 384 unlock_return:
 385   UNLOCK_FILE (file_fd);
 386
 387   return ((*result == NULL) ? -1 : 0);
 388 }
 389
 390
 391 static struct utmp *
 392 pututline_file (const struct utmp *data)
 393 {
 394   struct utmp buffer;
 395   struct utmp *pbuf;
 396   int found;
 397
 398   assert (file_fd >= 0);
 399
 400   /* Find the correct place to insert the data.  */
 401   if (file_offset > 0
 402       && (
 403 #if _HAVE_UT_TYPE - 0
 404           (last_entry.ut_type == data->ut_type
 405            && (last_entry.ut_type == RUN_LVL
 406                || last_entry.ut_type == BOOT_TIME
 407                || last_entry.ut_type == OLD_TIME
 408                || last_entry.ut_type == NEW_TIME))
 409           ||
 410 #endif
 411           __utmp_equal (&last_entry, data)))
 412     found = 1;
 413   else
 414     found = internal_getut_r (data, &buffer);
 415
 416   LOCK_FILE (file_fd, F_WRLCK)
 417     {
 418       pbuf = NULL;
 419       LOCKING_FAILED ();
 420     }
 421
 422   if (found < 0)
 423     {
 424       /* We append the next entry.  */
 425       file_offset = __lseek64 (file_fd, 0, SEEK_END);
 426       if (file_offset % sizeof (struct utmp) != 0)
 427         {
 428           file_offset -= file_offset % sizeof (struct utmp);
 429           __ftruncate64 (file_fd, file_offset);
 430
 431           if (__lseek64 (file_fd, 0, SEEK_END) < 0)
 432             {
 433               pbuf = NULL;
 434               goto unlock_return;
 435             }
 436         }
 437     }
 438   else
 439     {
 440       /* We replace the just read entry.  */
 441       file_offset -= sizeof (struct utmp);
 442       __lseek64 (file_fd, file_offset, SEEK_SET);
 443     }
 444
 445   /* Write the new data.  */
 446   if (write_not_cancel (file_fd, data, sizeof (struct utmp))
 447       != sizeof (struct utmp))
 448     {
 449       /* If we appended a new record this is only partially written.
 450          Remove it.  */
 451       if (found < 0)
 452         (void) __ftruncate64 (file_fd, file_offset);
 453       pbuf = NULL;
 454     }
 455   else
 456     {
 457       file_offset += sizeof (struct utmp);
 458       pbuf = (struct utmp *) data;
 459     }
 460
 461  unlock_return:
 462   UNLOCK_FILE (file_fd);
 463
 464   return pbuf;
 465 }
 466
 467
 468 static void
 469 endutent_file (void)
 470 {
 471   assert (file_fd >= 0);
 472
 473   close_not_cancel_no_status (file_fd);
 474   file_fd = -1;
 475 }
 476
 477
 478 static int
 479 updwtmp_file (const char *file, const struct utmp *utmp)
 480 {
 481   int result = -1;
 482   off64_t offset;
 483   int fd;
 484
 485   /* Open WTMP file.  */
 486   fd = open_not_cancel_2 (file, O_WRONLY | O_LARGEFILE);
 487   if (fd < 0)
 488     return -1;
 489
 490   LOCK_FILE (fd, F_WRLCK)
 491     LOCKING_FAILED ();
 492
 493   /* Remember original size of log file.  */
 494   offset = __lseek64 (fd, 0, SEEK_END);
 495   if (offset % sizeof (struct utmp) != 0)
 496     {
 497       offset -= offset % sizeof (struct utmp);
 498       __ftruncate64 (fd, offset);
 499
 500       if (__lseek64 (fd, 0, SEEK_END) < 0)
 501         goto unlock_return;
 502     }
 503
 504   /* Write the entry.  If we can't write all the bytes, reset the file
 505      size back to the original size.  That way, no partial entries
 506      will remain.  */
 507   if (write_not_cancel (fd, utmp, sizeof (struct utmp))
 508       != sizeof (struct utmp))
 509     {
 510       __ftruncate64 (fd, offset);
 511       goto unlock_return;
 512     }
 513
 514   result = 0;
 515
 516 unlock_return:
 517   UNLOCK_FILE (fd);
 518
 519   /* Close WTMP file.  */
 520   close_not_cancel_no_status (fd);
 521
 522   return result;
 523 }