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1 /* Copyright (C) 1996-2015 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.
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.
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.
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <http://www.gnu.org/licenses/>. */
20 #include <assert.h>
21 #include <errno.h>
22 #include <fcntl.h>
23 #include <signal.h>
24 #include <stdbool.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>
32 #include "utmp-private.h"
33 #include "utmp-equal.h"
36 /* Descriptor for the file and position. */
37 static int file_fd = -1;
38 static bool file_writable;
39 static off64_t file_offset;
41 /* Cache for the last read entry. */
42 static struct utmp last_entry;
45 /* Locking timeout. */
46 #ifndef TIMEOUT
47 # define TIMEOUT 10
48 #endif
50 /* Do-nothing handler for locking timeout. */
51 static void timeout_handler (int signum) {};
53 /* LOCK_FILE(fd, type) failure_statement
54 attempts to get a lock on the utmp file referenced by FD. If it fails,
55 the failure_statement is executed, otherwise it is skipped.
56 LOCKING_FAILED()
57 jumps into the UNLOCK_FILE macro and ensures cleanup of LOCK_FILE.
58 UNLOCK_FILE(fd)
59 unlocks the utmp file referenced by FD and performs the cleanup of
60 LOCK_FILE.
62 #define LOCK_FILE(fd, type) \
63 { \
64 struct flock fl; \
65 struct sigaction action, old_action; \
66 unsigned int old_timeout; \
68 /* Cancel any existing alarm. */ \
69 old_timeout = alarm (0); \
71 /* Establish signal handler. */ \
72 action.sa_handler = timeout_handler; \
73 __sigemptyset (&action.sa_mask); \
74 action.sa_flags = 0; \
75 __sigaction (SIGALRM, &action, &old_action); \
77 alarm (TIMEOUT); \
79 /* Try to get the lock. */ \
80 memset (&fl, '\0', sizeof (struct flock)); \
81 fl.l_type = (type); \
82 fl.l_whence = SEEK_SET; \
83 if (fcntl_not_cancel ((fd), F_SETLKW, &fl) < 0)
85 #define LOCKING_FAILED() \
86 goto unalarm_return
88 #define UNLOCK_FILE(fd) \
89 /* Unlock the file. */ \
90 fl.l_type = F_UNLCK; \
91 fcntl_not_cancel ((fd), F_SETLKW, &fl); \
93 unalarm_return: \
94 /* Reset the signal handler and alarm. We must reset the alarm \
95 before resetting the handler so our alarm does not generate a \
96 spurious SIGALRM seen by the user. However, we cannot just set \
97 the user's old alarm before restoring the handler, because then \
98 it's possible our handler could catch the user alarm's SIGARLM \
99 and then the user would never see the signal he expected. */ \
100 alarm (0); \
101 __sigaction (SIGALRM, &old_action, NULL); \
102 if (old_timeout != 0) \
103 alarm (old_timeout); \
104 } while (0)
107 /* Functions defined here. */
108 static int setutent_file (void);
109 static int getutent_r_file (struct utmp *buffer, struct utmp **result);
110 static int getutid_r_file (const struct utmp *key, struct utmp *buffer,
111 struct utmp **result);
112 static int getutline_r_file (const struct utmp *key, struct utmp *buffer,
113 struct utmp **result);
114 static struct utmp *pututline_file (const struct utmp *data);
115 static void endutent_file (void);
116 static int updwtmp_file (const char *file, const struct utmp *utmp);
118 /* Jump table for file functions. */
119 const struct utfuncs __libc_utmp_file_functions =
121 setutent_file,
122 getutent_r_file,
123 getutid_r_file,
124 getutline_r_file,
125 pututline_file,
126 endutent_file,
127 updwtmp_file
131 #ifndef TRANSFORM_UTMP_FILE_NAME
132 # define TRANSFORM_UTMP_FILE_NAME(file_name) (file_name)
133 #endif
135 static int
136 setutent_file (void)
138 if (file_fd < 0)
140 const char *file_name;
142 file_name = TRANSFORM_UTMP_FILE_NAME (__libc_utmp_file_name);
144 #ifdef O_CLOEXEC
145 # define O_flags O_LARGEFILE | O_CLOEXEC
146 #else
147 # define O_flags O_LARGEFILE
148 #endif
149 file_writable = false;
150 file_fd = open_not_cancel_2 (file_name, O_RDONLY | O_flags);
151 if (file_fd == -1)
152 return 0;
154 #ifndef __ASSUME_O_CLOEXEC
155 # ifdef O_CLOEXEC
156 if (__have_o_cloexec <= 0)
157 # endif
159 /* We have to make sure the file is `closed on exec'. */
160 int result = fcntl_not_cancel (file_fd, F_GETFD, 0);
161 if (result >= 0)
163 # ifdef O_CLOEXEC
164 if (__have_o_cloexec == 0)
165 __have_o_cloexec = (result & FD_CLOEXEC) ? 1 : -1;
167 if (__have_o_cloexec < 0)
168 # endif
169 result = fcntl_not_cancel (file_fd, F_SETFD,
170 result | FD_CLOEXEC);
173 if (result == -1)
175 close_not_cancel_no_status (file_fd);
176 return 0;
179 #endif
182 __lseek64 (file_fd, 0, SEEK_SET);
183 file_offset = 0;
185 /* Make sure the entry won't match. */
186 #if _HAVE_UT_TYPE - 0
187 last_entry.ut_type = -1;
188 #else
189 last_entry.ut_line[0] = '\177';
190 # if _HAVE_UT_ID - 0
191 last_entry.ut_id[0] = '\0';
192 # endif
193 #endif
195 return 1;
199 static int
200 getutent_r_file (struct utmp *buffer, struct utmp **result)
202 ssize_t nbytes;
204 assert (file_fd >= 0);
206 if (file_offset == -1l)
208 /* Not available. */
209 *result = NULL;
210 return -1;
213 LOCK_FILE (file_fd, F_RDLCK)
215 nbytes = 0;
216 LOCKING_FAILED ();
219 /* Read the next entry. */
220 nbytes = read_not_cancel (file_fd, &last_entry, sizeof (struct utmp));
222 UNLOCK_FILE (file_fd);
224 if (nbytes != sizeof (struct utmp))
226 if (nbytes != 0)
227 file_offset = -1l;
228 *result = NULL;
229 return -1;
232 /* Update position pointer. */
233 file_offset += sizeof (struct utmp);
235 memcpy (buffer, &last_entry, sizeof (struct utmp));
236 *result = buffer;
238 return 0;
242 static int
243 internal_getut_r (const struct utmp *id, struct utmp *buffer,
244 bool *lock_failed)
246 int result = -1;
248 LOCK_FILE (file_fd, F_RDLCK)
250 *lock_failed = true;
251 LOCKING_FAILED ();
254 #if _HAVE_UT_TYPE - 0
255 if (id->ut_type == RUN_LVL || id->ut_type == BOOT_TIME
256 || id->ut_type == OLD_TIME || id->ut_type == NEW_TIME)
258 /* Search for next entry with type RUN_LVL, BOOT_TIME,
259 OLD_TIME, or NEW_TIME. */
261 while (1)
263 /* Read the next entry. */
264 if (read_not_cancel (file_fd, buffer, sizeof (struct utmp))
265 != sizeof (struct utmp))
267 __set_errno (ESRCH);
268 file_offset = -1l;
269 goto unlock_return;
271 file_offset += sizeof (struct utmp);
273 if (id->ut_type == buffer->ut_type)
274 break;
277 else
278 #endif /* _HAVE_UT_TYPE */
280 /* Search for the next entry with the specified ID and with type
281 INIT_PROCESS, LOGIN_PROCESS, USER_PROCESS, or DEAD_PROCESS. */
283 while (1)
285 /* Read the next entry. */
286 if (read_not_cancel (file_fd, buffer, sizeof (struct utmp))
287 != sizeof (struct utmp))
289 __set_errno (ESRCH);
290 file_offset = -1l;
291 goto unlock_return;
293 file_offset += sizeof (struct utmp);
295 if (__utmp_equal (buffer, id))
296 break;
300 result = 0;
302 unlock_return:
303 UNLOCK_FILE (file_fd);
305 return result;
309 /* For implementing this function we don't use the getutent_r function
310 because we can avoid the reposition on every new entry this way. */
311 static int
312 getutid_r_file (const struct utmp *id, struct utmp *buffer,
313 struct utmp **result)
315 assert (file_fd >= 0);
317 if (file_offset == -1l)
319 *result = NULL;
320 return -1;
323 /* We don't have to distinguish whether we can lock the file or
324 whether there is no entry. */
325 bool lock_failed = false;
326 if (internal_getut_r (id, &last_entry, &lock_failed) < 0)
328 *result = NULL;
329 return -1;
332 memcpy (buffer, &last_entry, sizeof (struct utmp));
333 *result = buffer;
335 return 0;
339 /* For implementing this function we don't use the getutent_r function
340 because we can avoid the reposition on every new entry this way. */
341 static int
342 getutline_r_file (const struct utmp *line, struct utmp *buffer,
343 struct utmp **result)
345 assert (file_fd >= 0);
347 if (file_offset == -1l)
349 *result = NULL;
350 return -1;
353 LOCK_FILE (file_fd, F_RDLCK)
355 *result = NULL;
356 LOCKING_FAILED ();
359 while (1)
361 /* Read the next entry. */
362 if (read_not_cancel (file_fd, &last_entry, sizeof (struct utmp))
363 != sizeof (struct utmp))
365 __set_errno (ESRCH);
366 file_offset = -1l;
367 *result = NULL;
368 goto unlock_return;
370 file_offset += sizeof (struct utmp);
372 /* Stop if we found a user or login entry. */
373 if (
374 #if _HAVE_UT_TYPE - 0
375 (last_entry.ut_type == USER_PROCESS
376 || last_entry.ut_type == LOGIN_PROCESS)
378 #endif
379 !strncmp (line->ut_line, last_entry.ut_line, sizeof line->ut_line))
380 break;
383 memcpy (buffer, &last_entry, sizeof (struct utmp));
384 *result = buffer;
386 unlock_return:
387 UNLOCK_FILE (file_fd);
389 return ((*result == NULL) ? -1 : 0);
393 static struct utmp *
394 pututline_file (const struct utmp *data)
396 struct utmp buffer;
397 struct utmp *pbuf;
398 int found;
400 assert (file_fd >= 0);
402 if (! file_writable)
404 /* We must make the file descriptor writable before going on. */
405 const char *file_name = TRANSFORM_UTMP_FILE_NAME (__libc_utmp_file_name);
407 int new_fd = open_not_cancel_2 (file_name, O_RDWR | O_flags);
408 if (new_fd == -1)
409 return NULL;
411 #ifndef __ASSUME_O_CLOEXEC
412 # ifdef O_CLOEXEC
413 if (__have_o_cloexec <= 0)
414 # endif
416 /* We have to make sure the file is `closed on exec'. */
417 int result = fcntl_not_cancel (file_fd, F_GETFD, 0);
418 if (result >= 0)
420 # ifdef O_CLOEXEC
421 if (__have_o_cloexec == 0)
422 __have_o_cloexec = (result & FD_CLOEXEC) ? 1 : -1;
424 if (__have_o_cloexec < 0)
425 # endif
426 result = fcntl_not_cancel (file_fd, F_SETFD,
427 result | FD_CLOEXEC);
430 if (result == -1)
432 close_not_cancel_no_status (file_fd);
433 return NULL;
436 #endif
438 if (__lseek64 (new_fd, __lseek64 (file_fd, 0, SEEK_CUR), SEEK_SET) == -1
439 || __dup2 (new_fd, file_fd) < 0)
441 close_not_cancel_no_status (new_fd);
442 return NULL;
444 close_not_cancel_no_status (new_fd);
445 file_writable = true;
448 /* Find the correct place to insert the data. */
449 if (file_offset > 0
450 && (
451 #if _HAVE_UT_TYPE - 0
452 (last_entry.ut_type == data->ut_type
453 && (last_entry.ut_type == RUN_LVL
454 || last_entry.ut_type == BOOT_TIME
455 || last_entry.ut_type == OLD_TIME
456 || last_entry.ut_type == NEW_TIME))
458 #endif
459 __utmp_equal (&last_entry, data)))
460 found = 1;
461 else
463 bool lock_failed = false;
464 found = internal_getut_r (data, &buffer, &lock_failed);
466 if (__builtin_expect (lock_failed, false))
468 __set_errno (EAGAIN);
469 return NULL;
473 LOCK_FILE (file_fd, F_WRLCK)
475 pbuf = NULL;
476 LOCKING_FAILED ();
479 if (found < 0)
481 /* We append the next entry. */
482 file_offset = __lseek64 (file_fd, 0, SEEK_END);
483 if (file_offset % sizeof (struct utmp) != 0)
485 file_offset -= file_offset % sizeof (struct utmp);
486 __ftruncate64 (file_fd, file_offset);
488 if (__lseek64 (file_fd, 0, SEEK_END) < 0)
490 pbuf = NULL;
491 goto unlock_return;
495 else
497 /* We replace the just read entry. */
498 file_offset -= sizeof (struct utmp);
499 __lseek64 (file_fd, file_offset, SEEK_SET);
502 /* Write the new data. */
503 if (write_not_cancel (file_fd, data, sizeof (struct utmp))
504 != sizeof (struct utmp))
506 /* If we appended a new record this is only partially written.
507 Remove it. */
508 if (found < 0)
509 (void) __ftruncate64 (file_fd, file_offset);
510 pbuf = NULL;
512 else
514 file_offset += sizeof (struct utmp);
515 pbuf = (struct utmp *) data;
518 unlock_return:
519 UNLOCK_FILE (file_fd);
521 return pbuf;
525 static void
526 endutent_file (void)
528 assert (file_fd >= 0);
530 close_not_cancel_no_status (file_fd);
531 file_fd = -1;
535 static int
536 updwtmp_file (const char *file, const struct utmp *utmp)
538 int result = -1;
539 off64_t offset;
540 int fd;
542 /* Open WTMP file. */
543 fd = open_not_cancel_2 (file, O_WRONLY | O_LARGEFILE);
544 if (fd < 0)
545 return -1;
547 LOCK_FILE (fd, F_WRLCK)
548 LOCKING_FAILED ();
550 /* Remember original size of log file. */
551 offset = __lseek64 (fd, 0, SEEK_END);
552 if (offset % sizeof (struct utmp) != 0)
554 offset -= offset % sizeof (struct utmp);
555 __ftruncate64 (fd, offset);
557 if (__lseek64 (fd, 0, SEEK_END) < 0)
558 goto unlock_return;
561 /* Write the entry. If we can't write all the bytes, reset the file
562 size back to the original size. That way, no partial entries
563 will remain. */
564 if (write_not_cancel (fd, utmp, sizeof (struct utmp))
565 != sizeof (struct utmp))
567 __ftruncate64 (fd, offset);
568 goto unlock_return;
571 result = 0;
573 unlock_return:
574 UNLOCK_FILE (fd);
576 /* Close WTMP file. */
577 close_not_cancel_no_status (fd);
579 return result;