1 | /* Copyright (C) 1996-2016 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, see |
18 | <http://www.gnu.org/licenses/>. */ |
19 | |
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> |
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 bool file_writable; |
39 | static off64_t file_offset; |
40 | |
41 | /* Cache for the last read entry. */ |
42 | static struct utmp last_entry; |
43 | |
44 | |
45 | /* Locking timeout. */ |
46 | #ifndef TIMEOUT |
47 | # define TIMEOUT 10 |
48 | #endif |
49 | |
50 | /* Do-nothing handler for locking timeout. */ |
51 | static void timeout_handler (int signum) {}; |
52 | |
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. |
61 | */ |
62 | #define LOCK_FILE(fd, type) \ |
63 | { \ |
64 | struct flock fl; \ |
65 | struct sigaction action, old_action; \ |
66 | unsigned int old_timeout; \ |
67 | \ |
68 | /* Cancel any existing alarm. */ \ |
69 | old_timeout = alarm (0); \ |
70 | \ |
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); \ |
76 | \ |
77 | alarm (TIMEOUT); \ |
78 | \ |
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) |
84 | |
85 | #define LOCKING_FAILED() \ |
86 | goto unalarm_return |
87 | |
88 | #define UNLOCK_FILE(fd) \ |
89 | /* Unlock the file. */ \ |
90 | fl.l_type = F_UNLCK; \ |
91 | fcntl_not_cancel ((fd), F_SETLKW, &fl); \ |
92 | \ |
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) |
105 | |
106 | |
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); |
117 | |
118 | /* Jump table for file functions. */ |
119 | const struct utfuncs __libc_utmp_file_functions = |
120 | { |
121 | setutent_file, |
122 | getutent_r_file, |
123 | getutid_r_file, |
124 | getutline_r_file, |
125 | pututline_file, |
126 | endutent_file, |
127 | updwtmp_file |
128 | }; |
129 | |
130 | |
131 | #ifndef TRANSFORM_UTMP_FILE_NAME |
132 | # define TRANSFORM_UTMP_FILE_NAME(file_name) (file_name) |
133 | #endif |
134 | |
135 | static int |
136 | setutent_file (void) |
137 | { |
138 | if (file_fd < 0) |
139 | { |
140 | const char *file_name; |
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_writable = false; |
150 | file_fd = open_not_cancel_2 (file_name, O_RDONLY | O_flags); |
151 | if (file_fd == -1) |
152 | return 0; |
153 | |
154 | #ifndef __ASSUME_O_CLOEXEC |
155 | # ifdef O_CLOEXEC |
156 | if (__have_o_cloexec <= 0) |
157 | # endif |
158 | { |
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) |
162 | { |
163 | # ifdef O_CLOEXEC |
164 | if (__have_o_cloexec == 0) |
165 | __have_o_cloexec = (result & FD_CLOEXEC) ? 1 : -1; |
166 | |
167 | if (__have_o_cloexec < 0) |
168 | # endif |
169 | result = fcntl_not_cancel (file_fd, F_SETFD, |
170 | result | FD_CLOEXEC); |
171 | } |
172 | |
173 | if (result == -1) |
174 | { |
175 | close_not_cancel_no_status (file_fd); |
176 | return 0; |
177 | } |
178 | } |
179 | #endif |
180 | } |
181 | |
182 | __lseek64 (file_fd, 0, SEEK_SET); |
183 | file_offset = 0; |
184 | |
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 |
194 | |
195 | return 1; |
196 | } |
197 | |
198 | |
199 | static int |
200 | getutent_r_file (struct utmp *buffer, struct utmp **result) |
201 | { |
202 | ssize_t nbytes; |
203 | |
204 | assert (file_fd >= 0); |
205 | |
206 | if (file_offset == -1l) |
207 | { |
208 | /* Not available. */ |
209 | *result = NULL; |
210 | return -1; |
211 | } |
212 | |
213 | LOCK_FILE (file_fd, F_RDLCK) |
214 | { |
215 | nbytes = 0; |
216 | LOCKING_FAILED (); |
217 | } |
218 | |
219 | /* Read the next entry. */ |
220 | nbytes = read_not_cancel (file_fd, &last_entry, sizeof (struct utmp)); |
221 | |
222 | UNLOCK_FILE (file_fd); |
223 | |
224 | if (nbytes != sizeof (struct utmp)) |
225 | { |
226 | if (nbytes != 0) |
227 | file_offset = -1l; |
228 | *result = NULL; |
229 | return -1; |
230 | } |
231 | |
232 | /* Update position pointer. */ |
233 | file_offset += sizeof (struct utmp); |
234 | |
235 | memcpy (buffer, &last_entry, sizeof (struct utmp)); |
236 | *result = buffer; |
237 | |
238 | return 0; |
239 | } |
240 | |
241 | |
242 | static int |
243 | internal_getut_r (const struct utmp *id, struct utmp *buffer, |
244 | bool *lock_failed) |
245 | { |
246 | int result = -1; |
247 | |
248 | LOCK_FILE (file_fd, F_RDLCK) |
249 | { |
250 | *lock_failed = true; |
251 | LOCKING_FAILED (); |
252 | } |
253 | |
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) |
257 | { |
258 | /* Search for next entry with type RUN_LVL, BOOT_TIME, |
259 | OLD_TIME, or NEW_TIME. */ |
260 | |
261 | while (1) |
262 | { |
263 | /* Read the next entry. */ |
264 | if (read_not_cancel (file_fd, buffer, sizeof (struct utmp)) |
265 | != sizeof (struct utmp)) |
266 | { |
267 | __set_errno (ESRCH); |
268 | file_offset = -1l; |
269 | goto unlock_return; |
270 | } |
271 | file_offset += sizeof (struct utmp); |
272 | |
273 | if (id->ut_type == buffer->ut_type) |
274 | break; |
275 | } |
276 | } |
277 | else |
278 | #endif /* _HAVE_UT_TYPE */ |
279 | { |
280 | /* Search for the next entry with the specified ID and with type |
281 | INIT_PROCESS, LOGIN_PROCESS, USER_PROCESS, or DEAD_PROCESS. */ |
282 | |
283 | while (1) |
284 | { |
285 | /* Read the next entry. */ |
286 | if (read_not_cancel (file_fd, buffer, sizeof (struct utmp)) |
287 | != sizeof (struct utmp)) |
288 | { |
289 | __set_errno (ESRCH); |
290 | file_offset = -1l; |
291 | goto unlock_return; |
292 | } |
293 | file_offset += sizeof (struct utmp); |
294 | |
295 | if (__utmp_equal (buffer, id)) |
296 | break; |
297 | } |
298 | } |
299 | |
300 | result = 0; |
301 | |
302 | unlock_return: |
303 | UNLOCK_FILE (file_fd); |
304 | |
305 | return result; |
306 | } |
307 | |
308 | |
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) |
314 | { |
315 | assert (file_fd >= 0); |
316 | |
317 | if (file_offset == -1l) |
318 | { |
319 | *result = NULL; |
320 | return -1; |
321 | } |
322 | |
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) |
327 | { |
328 | *result = NULL; |
329 | return -1; |
330 | } |
331 | |
332 | memcpy (buffer, &last_entry, sizeof (struct utmp)); |
333 | *result = buffer; |
334 | |
335 | return 0; |
336 | } |
337 | |
338 | |
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) |
344 | { |
345 | assert (file_fd >= 0); |
346 | |
347 | if (file_offset == -1l) |
348 | { |
349 | *result = NULL; |
350 | return -1; |
351 | } |
352 | |
353 | LOCK_FILE (file_fd, F_RDLCK) |
354 | { |
355 | *result = NULL; |
356 | LOCKING_FAILED (); |
357 | } |
358 | |
359 | while (1) |
360 | { |
361 | /* Read the next entry. */ |
362 | if (read_not_cancel (file_fd, &last_entry, sizeof (struct utmp)) |
363 | != sizeof (struct utmp)) |
364 | { |
365 | __set_errno (ESRCH); |
366 | file_offset = -1l; |
367 | *result = NULL; |
368 | goto unlock_return; |
369 | } |
370 | file_offset += sizeof (struct utmp); |
371 | |
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) |
377 | && |
378 | #endif |
379 | !strncmp (line->ut_line, last_entry.ut_line, sizeof line->ut_line)) |
380 | break; |
381 | } |
382 | |
383 | memcpy (buffer, &last_entry, sizeof (struct utmp)); |
384 | *result = buffer; |
385 | |
386 | unlock_return: |
387 | UNLOCK_FILE (file_fd); |
388 | |
389 | return ((*result == NULL) ? -1 : 0); |
390 | } |
391 | |
392 | |
393 | static struct utmp * |
394 | pututline_file (const struct utmp *data) |
395 | { |
396 | struct utmp buffer; |
397 | struct utmp *pbuf; |
398 | int found; |
399 | |
400 | assert (file_fd >= 0); |
401 | |
402 | if (! file_writable) |
403 | { |
404 | /* We must make the file descriptor writable before going on. */ |
405 | const char *file_name = TRANSFORM_UTMP_FILE_NAME (__libc_utmp_file_name); |
406 | |
407 | int new_fd = open_not_cancel_2 (file_name, O_RDWR | O_flags); |
408 | if (new_fd == -1) |
409 | return NULL; |
410 | |
411 | #ifndef __ASSUME_O_CLOEXEC |
412 | # ifdef O_CLOEXEC |
413 | if (__have_o_cloexec <= 0) |
414 | # endif |
415 | { |
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) |
419 | { |
420 | # ifdef O_CLOEXEC |
421 | if (__have_o_cloexec == 0) |
422 | __have_o_cloexec = (result & FD_CLOEXEC) ? 1 : -1; |
423 | |
424 | if (__have_o_cloexec < 0) |
425 | # endif |
426 | result = fcntl_not_cancel (file_fd, F_SETFD, |
427 | result | FD_CLOEXEC); |
428 | } |
429 | |
430 | if (result == -1) |
431 | { |
432 | close_not_cancel_no_status (file_fd); |
433 | return NULL; |
434 | } |
435 | } |
436 | #endif |
437 | |
438 | if (__lseek64 (new_fd, __lseek64 (file_fd, 0, SEEK_CUR), SEEK_SET) == -1 |
439 | || __dup2 (new_fd, file_fd) < 0) |
440 | { |
441 | close_not_cancel_no_status (new_fd); |
442 | return NULL; |
443 | } |
444 | close_not_cancel_no_status (new_fd); |
445 | file_writable = true; |
446 | } |
447 | |
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)) |
457 | || |
458 | #endif |
459 | __utmp_equal (&last_entry, data))) |
460 | found = 1; |
461 | else |
462 | { |
463 | bool lock_failed = false; |
464 | found = internal_getut_r (data, &buffer, &lock_failed); |
465 | |
466 | if (__builtin_expect (lock_failed, false)) |
467 | { |
468 | __set_errno (EAGAIN); |
469 | return NULL; |
470 | } |
471 | } |
472 | |
473 | LOCK_FILE (file_fd, F_WRLCK) |
474 | { |
475 | pbuf = NULL; |
476 | LOCKING_FAILED (); |
477 | } |
478 | |
479 | if (found < 0) |
480 | { |
481 | /* We append the next entry. */ |
482 | file_offset = __lseek64 (file_fd, 0, SEEK_END); |
483 | if (file_offset % sizeof (struct utmp) != 0) |
484 | { |
485 | file_offset -= file_offset % sizeof (struct utmp); |
486 | __ftruncate64 (file_fd, file_offset); |
487 | |
488 | if (__lseek64 (file_fd, 0, SEEK_END) < 0) |
489 | { |
490 | pbuf = NULL; |
491 | goto unlock_return; |
492 | } |
493 | } |
494 | } |
495 | else |
496 | { |
497 | /* We replace the just read entry. */ |
498 | file_offset -= sizeof (struct utmp); |
499 | __lseek64 (file_fd, file_offset, SEEK_SET); |
500 | } |
501 | |
502 | /* Write the new data. */ |
503 | if (write_not_cancel (file_fd, data, sizeof (struct utmp)) |
504 | != sizeof (struct utmp)) |
505 | { |
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; |
511 | } |
512 | else |
513 | { |
514 | file_offset += sizeof (struct utmp); |
515 | pbuf = (struct utmp *) data; |
516 | } |
517 | |
518 | unlock_return: |
519 | UNLOCK_FILE (file_fd); |
520 | |
521 | return pbuf; |
522 | } |
523 | |
524 | |
525 | static void |
526 | endutent_file (void) |
527 | { |
528 | assert (file_fd >= 0); |
529 | |
530 | close_not_cancel_no_status (file_fd); |
531 | file_fd = -1; |
532 | } |
533 | |
534 | |
535 | static int |
536 | updwtmp_file (const char *file, const struct utmp *utmp) |
537 | { |
538 | int result = -1; |
539 | off64_t offset; |
540 | int fd; |
541 | |
542 | /* Open WTMP file. */ |
543 | fd = open_not_cancel_2 (file, O_WRONLY | O_LARGEFILE); |
544 | if (fd < 0) |
545 | return -1; |
546 | |
547 | LOCK_FILE (fd, F_WRLCK) |
548 | LOCKING_FAILED (); |
549 | |
550 | /* Remember original size of log file. */ |
551 | offset = __lseek64 (fd, 0, SEEK_END); |
552 | if (offset % sizeof (struct utmp) != 0) |
553 | { |
554 | offset -= offset % sizeof (struct utmp); |
555 | __ftruncate64 (fd, offset); |
556 | |
557 | if (__lseek64 (fd, 0, SEEK_END) < 0) |
558 | goto unlock_return; |
559 | } |
560 | |
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)) |
566 | { |
567 | __ftruncate64 (fd, offset); |
568 | goto unlock_return; |
569 | } |
570 | |
571 | result = 0; |
572 | |
573 | unlock_return: |
574 | UNLOCK_FILE (fd); |
575 | |
576 | /* Close WTMP file. */ |
577 | close_not_cancel_no_status (fd); |
578 | |
579 | return result; |
580 | } |
581 | |