1 | /* Copyright (C) 1996-2017 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 | #include <sigsetops.h> |
32 | |
33 | #include "utmp-private.h" |
34 | #include "utmp-equal.h" |
35 | |
36 | |
37 | /* Descriptor for the file and position. */ |
38 | static int file_fd = -1; |
39 | static bool file_writable; |
40 | static off64_t file_offset; |
41 | |
42 | /* Cache for the last read entry. */ |
43 | static struct utmp last_entry; |
44 | |
45 | |
46 | /* Locking timeout. */ |
47 | #ifndef TIMEOUT |
48 | # define TIMEOUT 10 |
49 | #endif |
50 | |
51 | /* Do-nothing handler for locking timeout. */ |
52 | static void timeout_handler (int signum) {}; |
53 | |
54 | /* LOCK_FILE(fd, type) failure_statement |
55 | attempts to get a lock on the utmp file referenced by FD. If it fails, |
56 | the failure_statement is executed, otherwise it is skipped. |
57 | LOCKING_FAILED() |
58 | jumps into the UNLOCK_FILE macro and ensures cleanup of LOCK_FILE. |
59 | UNLOCK_FILE(fd) |
60 | unlocks the utmp file referenced by FD and performs the cleanup of |
61 | LOCK_FILE. |
62 | */ |
63 | #define LOCK_FILE(fd, type) \ |
64 | { \ |
65 | struct flock fl; \ |
66 | struct sigaction action, old_action; \ |
67 | unsigned int old_timeout; \ |
68 | \ |
69 | /* Cancel any existing alarm. */ \ |
70 | old_timeout = alarm (0); \ |
71 | \ |
72 | /* Establish signal handler. */ \ |
73 | action.sa_handler = timeout_handler; \ |
74 | __sigemptyset (&action.sa_mask); \ |
75 | action.sa_flags = 0; \ |
76 | __sigaction (SIGALRM, &action, &old_action); \ |
77 | \ |
78 | alarm (TIMEOUT); \ |
79 | \ |
80 | /* Try to get the lock. */ \ |
81 | memset (&fl, '\0', sizeof (struct flock)); \ |
82 | fl.l_type = (type); \ |
83 | fl.l_whence = SEEK_SET; \ |
84 | if (fcntl_not_cancel ((fd), F_SETLKW, &fl) < 0) |
85 | |
86 | #define LOCKING_FAILED() \ |
87 | goto unalarm_return |
88 | |
89 | #define UNLOCK_FILE(fd) \ |
90 | /* Unlock the file. */ \ |
91 | fl.l_type = F_UNLCK; \ |
92 | fcntl_not_cancel ((fd), F_SETLKW, &fl); \ |
93 | \ |
94 | unalarm_return: \ |
95 | /* Reset the signal handler and alarm. We must reset the alarm \ |
96 | before resetting the handler so our alarm does not generate a \ |
97 | spurious SIGALRM seen by the user. However, we cannot just set \ |
98 | the user's old alarm before restoring the handler, because then \ |
99 | it's possible our handler could catch the user alarm's SIGARLM \ |
100 | and then the user would never see the signal he expected. */ \ |
101 | alarm (0); \ |
102 | __sigaction (SIGALRM, &old_action, NULL); \ |
103 | if (old_timeout != 0) \ |
104 | alarm (old_timeout); \ |
105 | } while (0) |
106 | |
107 | |
108 | /* Functions defined here. */ |
109 | static int setutent_file (void); |
110 | static int getutent_r_file (struct utmp *buffer, struct utmp **result); |
111 | static int getutid_r_file (const struct utmp *key, struct utmp *buffer, |
112 | struct utmp **result); |
113 | static int getutline_r_file (const struct utmp *key, struct utmp *buffer, |
114 | struct utmp **result); |
115 | static struct utmp *pututline_file (const struct utmp *data); |
116 | static void endutent_file (void); |
117 | static int updwtmp_file (const char *file, const struct utmp *utmp); |
118 | |
119 | /* Jump table for file functions. */ |
120 | const struct utfuncs __libc_utmp_file_functions = |
121 | { |
122 | setutent_file, |
123 | getutent_r_file, |
124 | getutid_r_file, |
125 | getutline_r_file, |
126 | pututline_file, |
127 | endutent_file, |
128 | updwtmp_file |
129 | }; |
130 | |
131 | |
132 | #ifndef TRANSFORM_UTMP_FILE_NAME |
133 | # define TRANSFORM_UTMP_FILE_NAME(file_name) (file_name) |
134 | #endif |
135 | |
136 | static int |
137 | setutent_file (void) |
138 | { |
139 | if (file_fd < 0) |
140 | { |
141 | const char *file_name; |
142 | |
143 | file_name = TRANSFORM_UTMP_FILE_NAME (__libc_utmp_file_name); |
144 | |
145 | file_writable = false; |
146 | file_fd = open_not_cancel_2 |
147 | (file_name, O_RDONLY | O_LARGEFILE | O_CLOEXEC); |
148 | if (file_fd == -1) |
149 | return 0; |
150 | } |
151 | |
152 | __lseek64 (file_fd, 0, SEEK_SET); |
153 | file_offset = 0; |
154 | |
155 | /* Make sure the entry won't match. */ |
156 | #if _HAVE_UT_TYPE - 0 |
157 | last_entry.ut_type = -1; |
158 | #else |
159 | last_entry.ut_line[0] = '\177'; |
160 | # if _HAVE_UT_ID - 0 |
161 | last_entry.ut_id[0] = '\0'; |
162 | # endif |
163 | #endif |
164 | |
165 | return 1; |
166 | } |
167 | |
168 | |
169 | static int |
170 | getutent_r_file (struct utmp *buffer, struct utmp **result) |
171 | { |
172 | ssize_t nbytes; |
173 | |
174 | assert (file_fd >= 0); |
175 | |
176 | if (file_offset == -1l) |
177 | { |
178 | /* Not available. */ |
179 | *result = NULL; |
180 | return -1; |
181 | } |
182 | |
183 | LOCK_FILE (file_fd, F_RDLCK) |
184 | { |
185 | nbytes = 0; |
186 | LOCKING_FAILED (); |
187 | } |
188 | |
189 | /* Read the next entry. */ |
190 | nbytes = read_not_cancel (file_fd, &last_entry, sizeof (struct utmp)); |
191 | |
192 | UNLOCK_FILE (file_fd); |
193 | |
194 | if (nbytes != sizeof (struct utmp)) |
195 | { |
196 | if (nbytes != 0) |
197 | file_offset = -1l; |
198 | *result = NULL; |
199 | return -1; |
200 | } |
201 | |
202 | /* Update position pointer. */ |
203 | file_offset += sizeof (struct utmp); |
204 | |
205 | memcpy (buffer, &last_entry, sizeof (struct utmp)); |
206 | *result = buffer; |
207 | |
208 | return 0; |
209 | } |
210 | |
211 | |
212 | static int |
213 | internal_getut_r (const struct utmp *id, struct utmp *buffer, |
214 | bool *lock_failed) |
215 | { |
216 | int result = -1; |
217 | |
218 | LOCK_FILE (file_fd, F_RDLCK) |
219 | { |
220 | *lock_failed = true; |
221 | LOCKING_FAILED (); |
222 | } |
223 | |
224 | #if _HAVE_UT_TYPE - 0 |
225 | if (id->ut_type == RUN_LVL || id->ut_type == BOOT_TIME |
226 | || id->ut_type == OLD_TIME || id->ut_type == NEW_TIME) |
227 | { |
228 | /* Search for next entry with type RUN_LVL, BOOT_TIME, |
229 | OLD_TIME, or NEW_TIME. */ |
230 | |
231 | while (1) |
232 | { |
233 | /* Read the next entry. */ |
234 | if (read_not_cancel (file_fd, buffer, sizeof (struct utmp)) |
235 | != sizeof (struct utmp)) |
236 | { |
237 | __set_errno (ESRCH); |
238 | file_offset = -1l; |
239 | goto unlock_return; |
240 | } |
241 | file_offset += sizeof (struct utmp); |
242 | |
243 | if (id->ut_type == buffer->ut_type) |
244 | break; |
245 | } |
246 | } |
247 | else |
248 | #endif /* _HAVE_UT_TYPE */ |
249 | { |
250 | /* Search for the next entry with the specified ID and with type |
251 | INIT_PROCESS, LOGIN_PROCESS, USER_PROCESS, or DEAD_PROCESS. */ |
252 | |
253 | while (1) |
254 | { |
255 | /* Read the next entry. */ |
256 | if (read_not_cancel (file_fd, buffer, sizeof (struct utmp)) |
257 | != sizeof (struct utmp)) |
258 | { |
259 | __set_errno (ESRCH); |
260 | file_offset = -1l; |
261 | goto unlock_return; |
262 | } |
263 | file_offset += sizeof (struct utmp); |
264 | |
265 | if (__utmp_equal (buffer, id)) |
266 | break; |
267 | } |
268 | } |
269 | |
270 | result = 0; |
271 | |
272 | unlock_return: |
273 | UNLOCK_FILE (file_fd); |
274 | |
275 | return result; |
276 | } |
277 | |
278 | |
279 | /* For implementing this function we don't use the getutent_r function |
280 | because we can avoid the reposition on every new entry this way. */ |
281 | static int |
282 | getutid_r_file (const struct utmp *id, struct utmp *buffer, |
283 | struct utmp **result) |
284 | { |
285 | assert (file_fd >= 0); |
286 | |
287 | if (file_offset == -1l) |
288 | { |
289 | *result = NULL; |
290 | return -1; |
291 | } |
292 | |
293 | /* We don't have to distinguish whether we can lock the file or |
294 | whether there is no entry. */ |
295 | bool lock_failed = false; |
296 | if (internal_getut_r (id, &last_entry, &lock_failed) < 0) |
297 | { |
298 | *result = NULL; |
299 | return -1; |
300 | } |
301 | |
302 | memcpy (buffer, &last_entry, sizeof (struct utmp)); |
303 | *result = buffer; |
304 | |
305 | return 0; |
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 | getutline_r_file (const struct utmp *line, 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 | LOCK_FILE (file_fd, F_RDLCK) |
324 | { |
325 | *result = NULL; |
326 | LOCKING_FAILED (); |
327 | } |
328 | |
329 | while (1) |
330 | { |
331 | /* Read the next entry. */ |
332 | if (read_not_cancel (file_fd, &last_entry, sizeof (struct utmp)) |
333 | != sizeof (struct utmp)) |
334 | { |
335 | __set_errno (ESRCH); |
336 | file_offset = -1l; |
337 | *result = NULL; |
338 | goto unlock_return; |
339 | } |
340 | file_offset += sizeof (struct utmp); |
341 | |
342 | /* Stop if we found a user or login entry. */ |
343 | if ( |
344 | #if _HAVE_UT_TYPE - 0 |
345 | (last_entry.ut_type == USER_PROCESS |
346 | || last_entry.ut_type == LOGIN_PROCESS) |
347 | && |
348 | #endif |
349 | !strncmp (line->ut_line, last_entry.ut_line, sizeof line->ut_line)) |
350 | break; |
351 | } |
352 | |
353 | memcpy (buffer, &last_entry, sizeof (struct utmp)); |
354 | *result = buffer; |
355 | |
356 | unlock_return: |
357 | UNLOCK_FILE (file_fd); |
358 | |
359 | return ((*result == NULL) ? -1 : 0); |
360 | } |
361 | |
362 | |
363 | static struct utmp * |
364 | pututline_file (const struct utmp *data) |
365 | { |
366 | struct utmp buffer; |
367 | struct utmp *pbuf; |
368 | int found; |
369 | |
370 | assert (file_fd >= 0); |
371 | |
372 | if (! file_writable) |
373 | { |
374 | /* We must make the file descriptor writable before going on. */ |
375 | const char *file_name = TRANSFORM_UTMP_FILE_NAME (__libc_utmp_file_name); |
376 | |
377 | int new_fd = open_not_cancel_2 |
378 | (file_name, O_RDWR | O_LARGEFILE | O_CLOEXEC); |
379 | if (new_fd == -1) |
380 | return NULL; |
381 | |
382 | if (__lseek64 (new_fd, __lseek64 (file_fd, 0, SEEK_CUR), SEEK_SET) == -1 |
383 | || __dup2 (new_fd, file_fd) < 0) |
384 | { |
385 | close_not_cancel_no_status (new_fd); |
386 | return NULL; |
387 | } |
388 | close_not_cancel_no_status (new_fd); |
389 | file_writable = true; |
390 | } |
391 | |
392 | /* Find the correct place to insert the data. */ |
393 | if (file_offset > 0 |
394 | && ( |
395 | #if _HAVE_UT_TYPE - 0 |
396 | (last_entry.ut_type == data->ut_type |
397 | && (last_entry.ut_type == RUN_LVL |
398 | || last_entry.ut_type == BOOT_TIME |
399 | || last_entry.ut_type == OLD_TIME |
400 | || last_entry.ut_type == NEW_TIME)) |
401 | || |
402 | #endif |
403 | __utmp_equal (&last_entry, data))) |
404 | found = 1; |
405 | else |
406 | { |
407 | bool lock_failed = false; |
408 | found = internal_getut_r (data, &buffer, &lock_failed); |
409 | |
410 | if (__builtin_expect (lock_failed, false)) |
411 | { |
412 | __set_errno (EAGAIN); |
413 | return NULL; |
414 | } |
415 | } |
416 | |
417 | LOCK_FILE (file_fd, F_WRLCK) |
418 | { |
419 | pbuf = NULL; |
420 | LOCKING_FAILED (); |
421 | } |
422 | |
423 | if (found < 0) |
424 | { |
425 | /* We append the next entry. */ |
426 | file_offset = __lseek64 (file_fd, 0, SEEK_END); |
427 | if (file_offset % sizeof (struct utmp) != 0) |
428 | { |
429 | file_offset -= file_offset % sizeof (struct utmp); |
430 | __ftruncate64 (file_fd, file_offset); |
431 | |
432 | if (__lseek64 (file_fd, 0, SEEK_END) < 0) |
433 | { |
434 | pbuf = NULL; |
435 | goto unlock_return; |
436 | } |
437 | } |
438 | } |
439 | else |
440 | { |
441 | /* We replace the just read entry. */ |
442 | file_offset -= sizeof (struct utmp); |
443 | __lseek64 (file_fd, file_offset, SEEK_SET); |
444 | } |
445 | |
446 | /* Write the new data. */ |
447 | if (write_not_cancel (file_fd, data, sizeof (struct utmp)) |
448 | != sizeof (struct utmp)) |
449 | { |
450 | /* If we appended a new record this is only partially written. |
451 | Remove it. */ |
452 | if (found < 0) |
453 | (void) __ftruncate64 (file_fd, file_offset); |
454 | pbuf = NULL; |
455 | } |
456 | else |
457 | { |
458 | file_offset += sizeof (struct utmp); |
459 | pbuf = (struct utmp *) data; |
460 | } |
461 | |
462 | unlock_return: |
463 | UNLOCK_FILE (file_fd); |
464 | |
465 | return pbuf; |
466 | } |
467 | |
468 | |
469 | static void |
470 | endutent_file (void) |
471 | { |
472 | assert (file_fd >= 0); |
473 | |
474 | close_not_cancel_no_status (file_fd); |
475 | file_fd = -1; |
476 | } |
477 | |
478 | |
479 | static int |
480 | updwtmp_file (const char *file, const struct utmp *utmp) |
481 | { |
482 | int result = -1; |
483 | off64_t offset; |
484 | int fd; |
485 | |
486 | /* Open WTMP file. */ |
487 | fd = open_not_cancel_2 (file, O_WRONLY | O_LARGEFILE); |
488 | if (fd < 0) |
489 | return -1; |
490 | |
491 | LOCK_FILE (fd, F_WRLCK) |
492 | LOCKING_FAILED (); |
493 | |
494 | /* Remember original size of log file. */ |
495 | offset = __lseek64 (fd, 0, SEEK_END); |
496 | if (offset % sizeof (struct utmp) != 0) |
497 | { |
498 | offset -= offset % sizeof (struct utmp); |
499 | __ftruncate64 (fd, offset); |
500 | |
501 | if (__lseek64 (fd, 0, SEEK_END) < 0) |
502 | goto unlock_return; |
503 | } |
504 | |
505 | /* Write the entry. If we can't write all the bytes, reset the file |
506 | size back to the original size. That way, no partial entries |
507 | will remain. */ |
508 | if (write_not_cancel (fd, utmp, sizeof (struct utmp)) |
509 | != sizeof (struct utmp)) |
510 | { |
511 | __ftruncate64 (fd, offset); |
512 | goto unlock_return; |
513 | } |
514 | |
515 | result = 0; |
516 | |
517 | unlock_return: |
518 | UNLOCK_FILE (fd); |
519 | |
520 | /* Close WTMP file. */ |
521 | close_not_cancel_no_status (fd); |
522 | |
523 | return result; |
524 | } |
525 | |