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Commit | Line | Data |
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f4f15635 LP |
1 | /*** |
2 | This file is part of systemd. | |
3 | ||
4 | Copyright 2010 Lennart Poettering | |
5 | ||
6 | systemd is free software; you can redistribute it and/or modify it | |
7 | under the terms of the GNU Lesser General Public License as published by | |
8 | the Free Software Foundation; either version 2.1 of the License, or | |
9 | (at your option) any later version. | |
10 | ||
11 | systemd is distributed in the hope that it will be useful, but | |
12 | 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 License | |
17 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
18 | ***/ | |
19 | ||
11c3a366 TA |
20 | #include <errno.h> |
21 | #include <stddef.h> | |
22 | #include <stdio.h> | |
23 | #include <stdlib.h> | |
24 | #include <string.h> | |
25 | #include <sys/stat.h> | |
655f2da0 | 26 | #include <linux/magic.h> |
11c3a366 TA |
27 | #include <time.h> |
28 | #include <unistd.h> | |
29 | ||
b5efdb8a | 30 | #include "alloc-util.h" |
f4f15635 LP |
31 | #include "dirent-util.h" |
32 | #include "fd-util.h" | |
33 | #include "fileio.h" | |
34 | #include "fs-util.h" | |
11c3a366 TA |
35 | #include "log.h" |
36 | #include "macro.h" | |
37 | #include "missing.h" | |
93cc7779 TA |
38 | #include "mkdir.h" |
39 | #include "parse-util.h" | |
40 | #include "path-util.h" | |
34a8f081 | 41 | #include "stat-util.h" |
430fbf8e | 42 | #include "stdio-util.h" |
f4f15635 LP |
43 | #include "string-util.h" |
44 | #include "strv.h" | |
93cc7779 | 45 | #include "time-util.h" |
ee104e11 | 46 | #include "user-util.h" |
f4f15635 LP |
47 | #include "util.h" |
48 | ||
49 | int unlink_noerrno(const char *path) { | |
50 | PROTECT_ERRNO; | |
51 | int r; | |
52 | ||
53 | r = unlink(path); | |
54 | if (r < 0) | |
55 | return -errno; | |
56 | ||
57 | return 0; | |
58 | } | |
59 | ||
60 | int rmdir_parents(const char *path, const char *stop) { | |
61 | size_t l; | |
62 | int r = 0; | |
63 | ||
64 | assert(path); | |
65 | assert(stop); | |
66 | ||
67 | l = strlen(path); | |
68 | ||
69 | /* Skip trailing slashes */ | |
70 | while (l > 0 && path[l-1] == '/') | |
71 | l--; | |
72 | ||
73 | while (l > 0) { | |
74 | char *t; | |
75 | ||
76 | /* Skip last component */ | |
77 | while (l > 0 && path[l-1] != '/') | |
78 | l--; | |
79 | ||
80 | /* Skip trailing slashes */ | |
81 | while (l > 0 && path[l-1] == '/') | |
82 | l--; | |
83 | ||
84 | if (l <= 0) | |
85 | break; | |
86 | ||
87 | t = strndup(path, l); | |
88 | if (!t) | |
89 | return -ENOMEM; | |
90 | ||
91 | if (path_startswith(stop, t)) { | |
92 | free(t); | |
93 | return 0; | |
94 | } | |
95 | ||
96 | r = rmdir(t); | |
97 | free(t); | |
98 | ||
99 | if (r < 0) | |
100 | if (errno != ENOENT) | |
101 | return -errno; | |
102 | } | |
103 | ||
104 | return 0; | |
105 | } | |
106 | ||
107 | ||
108 | int rename_noreplace(int olddirfd, const char *oldpath, int newdirfd, const char *newpath) { | |
109 | struct stat buf; | |
110 | int ret; | |
111 | ||
112 | ret = renameat2(olddirfd, oldpath, newdirfd, newpath, RENAME_NOREPLACE); | |
113 | if (ret >= 0) | |
114 | return 0; | |
115 | ||
116 | /* renameat2() exists since Linux 3.15, btrfs added support for it later. | |
117 | * If it is not implemented, fallback to another method. */ | |
118 | if (!IN_SET(errno, EINVAL, ENOSYS)) | |
119 | return -errno; | |
120 | ||
121 | /* The link()/unlink() fallback does not work on directories. But | |
122 | * renameat() without RENAME_NOREPLACE gives the same semantics on | |
123 | * directories, except when newpath is an *empty* directory. This is | |
124 | * good enough. */ | |
125 | ret = fstatat(olddirfd, oldpath, &buf, AT_SYMLINK_NOFOLLOW); | |
126 | if (ret >= 0 && S_ISDIR(buf.st_mode)) { | |
127 | ret = renameat(olddirfd, oldpath, newdirfd, newpath); | |
128 | return ret >= 0 ? 0 : -errno; | |
129 | } | |
130 | ||
131 | /* If it is not a directory, use the link()/unlink() fallback. */ | |
132 | ret = linkat(olddirfd, oldpath, newdirfd, newpath, 0); | |
133 | if (ret < 0) | |
134 | return -errno; | |
135 | ||
136 | ret = unlinkat(olddirfd, oldpath, 0); | |
137 | if (ret < 0) { | |
138 | /* backup errno before the following unlinkat() alters it */ | |
139 | ret = errno; | |
140 | (void) unlinkat(newdirfd, newpath, 0); | |
141 | errno = ret; | |
142 | return -errno; | |
143 | } | |
144 | ||
145 | return 0; | |
146 | } | |
147 | ||
148 | int readlinkat_malloc(int fd, const char *p, char **ret) { | |
149 | size_t l = 100; | |
150 | int r; | |
151 | ||
152 | assert(p); | |
153 | assert(ret); | |
154 | ||
155 | for (;;) { | |
156 | char *c; | |
157 | ssize_t n; | |
158 | ||
159 | c = new(char, l); | |
160 | if (!c) | |
161 | return -ENOMEM; | |
162 | ||
163 | n = readlinkat(fd, p, c, l-1); | |
164 | if (n < 0) { | |
165 | r = -errno; | |
166 | free(c); | |
167 | return r; | |
168 | } | |
169 | ||
170 | if ((size_t) n < l-1) { | |
171 | c[n] = 0; | |
172 | *ret = c; | |
173 | return 0; | |
174 | } | |
175 | ||
176 | free(c); | |
177 | l *= 2; | |
178 | } | |
179 | } | |
180 | ||
181 | int readlink_malloc(const char *p, char **ret) { | |
182 | return readlinkat_malloc(AT_FDCWD, p, ret); | |
183 | } | |
184 | ||
185 | int readlink_value(const char *p, char **ret) { | |
186 | _cleanup_free_ char *link = NULL; | |
187 | char *value; | |
188 | int r; | |
189 | ||
190 | r = readlink_malloc(p, &link); | |
191 | if (r < 0) | |
192 | return r; | |
193 | ||
194 | value = basename(link); | |
195 | if (!value) | |
196 | return -ENOENT; | |
197 | ||
198 | value = strdup(value); | |
199 | if (!value) | |
200 | return -ENOMEM; | |
201 | ||
202 | *ret = value; | |
203 | ||
204 | return 0; | |
205 | } | |
206 | ||
207 | int readlink_and_make_absolute(const char *p, char **r) { | |
208 | _cleanup_free_ char *target = NULL; | |
209 | char *k; | |
210 | int j; | |
211 | ||
212 | assert(p); | |
213 | assert(r); | |
214 | ||
215 | j = readlink_malloc(p, &target); | |
216 | if (j < 0) | |
217 | return j; | |
218 | ||
219 | k = file_in_same_dir(p, target); | |
220 | if (!k) | |
221 | return -ENOMEM; | |
222 | ||
223 | *r = k; | |
224 | return 0; | |
225 | } | |
226 | ||
e1873695 | 227 | int readlink_and_canonicalize(const char *p, const char *root, char **ret) { |
f4f15635 | 228 | char *t, *s; |
e1873695 | 229 | int r; |
f4f15635 LP |
230 | |
231 | assert(p); | |
e1873695 | 232 | assert(ret); |
f4f15635 | 233 | |
e1873695 LP |
234 | r = readlink_and_make_absolute(p, &t); |
235 | if (r < 0) | |
236 | return r; | |
f4f15635 | 237 | |
c4f4fce7 | 238 | r = chase_symlinks(t, root, 0, &s); |
e1873695 LP |
239 | if (r < 0) |
240 | /* If we can't follow up, then let's return the original string, slightly cleaned up. */ | |
241 | *ret = path_kill_slashes(t); | |
242 | else { | |
243 | *ret = s; | |
f4f15635 | 244 | free(t); |
e1873695 | 245 | } |
f4f15635 LP |
246 | |
247 | return 0; | |
248 | } | |
249 | ||
0ec0deaa LP |
250 | int readlink_and_make_absolute_root(const char *root, const char *path, char **ret) { |
251 | _cleanup_free_ char *target = NULL, *t = NULL; | |
252 | const char *full; | |
253 | int r; | |
254 | ||
255 | full = prefix_roota(root, path); | |
256 | r = readlink_malloc(full, &target); | |
257 | if (r < 0) | |
258 | return r; | |
259 | ||
260 | t = file_in_same_dir(path, target); | |
261 | if (!t) | |
262 | return -ENOMEM; | |
263 | ||
264 | *ret = t; | |
265 | t = NULL; | |
266 | ||
267 | return 0; | |
268 | } | |
269 | ||
f4f15635 LP |
270 | int chmod_and_chown(const char *path, mode_t mode, uid_t uid, gid_t gid) { |
271 | assert(path); | |
272 | ||
273 | /* Under the assumption that we are running privileged we | |
274 | * first change the access mode and only then hand out | |
275 | * ownership to avoid a window where access is too open. */ | |
276 | ||
277 | if (mode != MODE_INVALID) | |
278 | if (chmod(path, mode) < 0) | |
279 | return -errno; | |
280 | ||
281 | if (uid != UID_INVALID || gid != GID_INVALID) | |
282 | if (chown(path, uid, gid) < 0) | |
283 | return -errno; | |
284 | ||
285 | return 0; | |
286 | } | |
287 | ||
f4f15635 LP |
288 | int fchmod_umask(int fd, mode_t m) { |
289 | mode_t u; | |
290 | int r; | |
291 | ||
292 | u = umask(0777); | |
293 | r = fchmod(fd, m & (~u)) < 0 ? -errno : 0; | |
294 | umask(u); | |
295 | ||
296 | return r; | |
297 | } | |
298 | ||
299 | int fd_warn_permissions(const char *path, int fd) { | |
300 | struct stat st; | |
301 | ||
302 | if (fstat(fd, &st) < 0) | |
303 | return -errno; | |
304 | ||
305 | if (st.st_mode & 0111) | |
306 | log_warning("Configuration file %s is marked executable. Please remove executable permission bits. Proceeding anyway.", path); | |
307 | ||
308 | if (st.st_mode & 0002) | |
309 | log_warning("Configuration file %s is marked world-writable. Please remove world writability permission bits. Proceeding anyway.", path); | |
310 | ||
df0ff127 | 311 | if (getpid_cached() == 1 && (st.st_mode & 0044) != 0044) |
f4f15635 LP |
312 | log_warning("Configuration file %s is marked world-inaccessible. This has no effect as configuration data is accessible via APIs without restrictions. Proceeding anyway.", path); |
313 | ||
314 | return 0; | |
315 | } | |
316 | ||
317 | int touch_file(const char *path, bool parents, usec_t stamp, uid_t uid, gid_t gid, mode_t mode) { | |
318 | _cleanup_close_ int fd; | |
319 | int r; | |
320 | ||
321 | assert(path); | |
322 | ||
323 | if (parents) | |
324 | mkdir_parents(path, 0755); | |
325 | ||
06eeacb6 MM |
326 | fd = open(path, O_WRONLY|O_CREAT|O_CLOEXEC|O_NOCTTY, |
327 | (mode == 0 || mode == MODE_INVALID) ? 0644 : mode); | |
f4f15635 LP |
328 | if (fd < 0) |
329 | return -errno; | |
330 | ||
ee735086 | 331 | if (mode != MODE_INVALID) { |
f4f15635 LP |
332 | r = fchmod(fd, mode); |
333 | if (r < 0) | |
334 | return -errno; | |
335 | } | |
336 | ||
337 | if (uid != UID_INVALID || gid != GID_INVALID) { | |
338 | r = fchown(fd, uid, gid); | |
339 | if (r < 0) | |
340 | return -errno; | |
341 | } | |
342 | ||
343 | if (stamp != USEC_INFINITY) { | |
344 | struct timespec ts[2]; | |
345 | ||
346 | timespec_store(&ts[0], stamp); | |
347 | ts[1] = ts[0]; | |
348 | r = futimens(fd, ts); | |
349 | } else | |
350 | r = futimens(fd, NULL); | |
351 | if (r < 0) | |
352 | return -errno; | |
353 | ||
354 | return 0; | |
355 | } | |
356 | ||
357 | int touch(const char *path) { | |
ee735086 | 358 | return touch_file(path, false, USEC_INFINITY, UID_INVALID, GID_INVALID, MODE_INVALID); |
f4f15635 LP |
359 | } |
360 | ||
361 | int symlink_idempotent(const char *from, const char *to) { | |
362 | _cleanup_free_ char *p = NULL; | |
363 | int r; | |
364 | ||
365 | assert(from); | |
366 | assert(to); | |
367 | ||
368 | if (symlink(from, to) < 0) { | |
369 | if (errno != EEXIST) | |
370 | return -errno; | |
371 | ||
372 | r = readlink_malloc(to, &p); | |
373 | if (r < 0) | |
374 | return r; | |
375 | ||
376 | if (!streq(p, from)) | |
377 | return -EINVAL; | |
378 | } | |
379 | ||
380 | return 0; | |
381 | } | |
382 | ||
383 | int symlink_atomic(const char *from, const char *to) { | |
384 | _cleanup_free_ char *t = NULL; | |
385 | int r; | |
386 | ||
387 | assert(from); | |
388 | assert(to); | |
389 | ||
390 | r = tempfn_random(to, NULL, &t); | |
391 | if (r < 0) | |
392 | return r; | |
393 | ||
394 | if (symlink(from, t) < 0) | |
395 | return -errno; | |
396 | ||
397 | if (rename(t, to) < 0) { | |
398 | unlink_noerrno(t); | |
399 | return -errno; | |
400 | } | |
401 | ||
402 | return 0; | |
403 | } | |
404 | ||
405 | int mknod_atomic(const char *path, mode_t mode, dev_t dev) { | |
406 | _cleanup_free_ char *t = NULL; | |
407 | int r; | |
408 | ||
409 | assert(path); | |
410 | ||
411 | r = tempfn_random(path, NULL, &t); | |
412 | if (r < 0) | |
413 | return r; | |
414 | ||
415 | if (mknod(t, mode, dev) < 0) | |
416 | return -errno; | |
417 | ||
418 | if (rename(t, path) < 0) { | |
419 | unlink_noerrno(t); | |
420 | return -errno; | |
421 | } | |
422 | ||
423 | return 0; | |
424 | } | |
425 | ||
426 | int mkfifo_atomic(const char *path, mode_t mode) { | |
427 | _cleanup_free_ char *t = NULL; | |
428 | int r; | |
429 | ||
430 | assert(path); | |
431 | ||
432 | r = tempfn_random(path, NULL, &t); | |
433 | if (r < 0) | |
434 | return r; | |
435 | ||
436 | if (mkfifo(t, mode) < 0) | |
437 | return -errno; | |
438 | ||
439 | if (rename(t, path) < 0) { | |
440 | unlink_noerrno(t); | |
441 | return -errno; | |
442 | } | |
443 | ||
444 | return 0; | |
445 | } | |
446 | ||
447 | int get_files_in_directory(const char *path, char ***list) { | |
448 | _cleanup_closedir_ DIR *d = NULL; | |
8fb3f009 | 449 | struct dirent *de; |
f4f15635 LP |
450 | size_t bufsize = 0, n = 0; |
451 | _cleanup_strv_free_ char **l = NULL; | |
452 | ||
453 | assert(path); | |
454 | ||
455 | /* Returns all files in a directory in *list, and the number | |
456 | * of files as return value. If list is NULL returns only the | |
457 | * number. */ | |
458 | ||
459 | d = opendir(path); | |
460 | if (!d) | |
461 | return -errno; | |
462 | ||
8fb3f009 | 463 | FOREACH_DIRENT_ALL(de, d, return -errno) { |
f4f15635 LP |
464 | dirent_ensure_type(d, de); |
465 | ||
466 | if (!dirent_is_file(de)) | |
467 | continue; | |
468 | ||
469 | if (list) { | |
470 | /* one extra slot is needed for the terminating NULL */ | |
471 | if (!GREEDY_REALLOC(l, bufsize, n + 2)) | |
472 | return -ENOMEM; | |
473 | ||
474 | l[n] = strdup(de->d_name); | |
475 | if (!l[n]) | |
476 | return -ENOMEM; | |
477 | ||
478 | l[++n] = NULL; | |
479 | } else | |
480 | n++; | |
481 | } | |
482 | ||
483 | if (list) { | |
484 | *list = l; | |
485 | l = NULL; /* avoid freeing */ | |
486 | } | |
487 | ||
488 | return n; | |
489 | } | |
430fbf8e | 490 | |
992e8f22 LP |
491 | static int getenv_tmp_dir(const char **ret_path) { |
492 | const char *n; | |
493 | int r, ret = 0; | |
34a8f081 | 494 | |
992e8f22 | 495 | assert(ret_path); |
34a8f081 | 496 | |
992e8f22 LP |
497 | /* We use the same order of environment variables python uses in tempfile.gettempdir(): |
498 | * https://docs.python.org/3/library/tempfile.html#tempfile.gettempdir */ | |
499 | FOREACH_STRING(n, "TMPDIR", "TEMP", "TMP") { | |
500 | const char *e; | |
501 | ||
502 | e = secure_getenv(n); | |
503 | if (!e) | |
504 | continue; | |
505 | if (!path_is_absolute(e)) { | |
506 | r = -ENOTDIR; | |
507 | goto next; | |
508 | } | |
509 | if (!path_is_safe(e)) { | |
510 | r = -EPERM; | |
511 | goto next; | |
512 | } | |
513 | ||
514 | r = is_dir(e, true); | |
515 | if (r < 0) | |
516 | goto next; | |
517 | if (r == 0) { | |
518 | r = -ENOTDIR; | |
519 | goto next; | |
520 | } | |
521 | ||
522 | *ret_path = e; | |
523 | return 1; | |
524 | ||
525 | next: | |
526 | /* Remember first error, to make this more debuggable */ | |
527 | if (ret >= 0) | |
528 | ret = r; | |
34a8f081 OW |
529 | } |
530 | ||
992e8f22 LP |
531 | if (ret < 0) |
532 | return ret; | |
34a8f081 | 533 | |
992e8f22 LP |
534 | *ret_path = NULL; |
535 | return ret; | |
536 | } | |
34a8f081 | 537 | |
992e8f22 LP |
538 | static int tmp_dir_internal(const char *def, const char **ret) { |
539 | const char *e; | |
540 | int r, k; | |
541 | ||
542 | assert(def); | |
543 | assert(ret); | |
544 | ||
545 | r = getenv_tmp_dir(&e); | |
546 | if (r > 0) { | |
547 | *ret = e; | |
548 | return 0; | |
549 | } | |
550 | ||
551 | k = is_dir(def, true); | |
552 | if (k == 0) | |
553 | k = -ENOTDIR; | |
554 | if (k < 0) | |
555 | return r < 0 ? r : k; | |
556 | ||
557 | *ret = def; | |
34a8f081 OW |
558 | return 0; |
559 | } | |
560 | ||
992e8f22 LP |
561 | int var_tmp_dir(const char **ret) { |
562 | ||
563 | /* Returns the location for "larger" temporary files, that is backed by physical storage if available, and thus | |
564 | * even might survive a boot: /var/tmp. If $TMPDIR (or related environment variables) are set, its value is | |
565 | * returned preferably however. Note that both this function and tmp_dir() below are affected by $TMPDIR, | |
566 | * making it a variable that overrides all temporary file storage locations. */ | |
567 | ||
568 | return tmp_dir_internal("/var/tmp", ret); | |
569 | } | |
570 | ||
571 | int tmp_dir(const char **ret) { | |
572 | ||
573 | /* Similar to var_tmp_dir() above, but returns the location for "smaller" temporary files, which is usually | |
574 | * backed by an in-memory file system: /tmp. */ | |
575 | ||
576 | return tmp_dir_internal("/tmp", ret); | |
577 | } | |
578 | ||
430fbf8e LP |
579 | int inotify_add_watch_fd(int fd, int what, uint32_t mask) { |
580 | char path[strlen("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1]; | |
581 | int r; | |
582 | ||
583 | /* This is like inotify_add_watch(), except that the file to watch is not referenced by a path, but by an fd */ | |
584 | xsprintf(path, "/proc/self/fd/%i", what); | |
585 | ||
586 | r = inotify_add_watch(fd, path, mask); | |
587 | if (r < 0) | |
588 | return -errno; | |
589 | ||
590 | return r; | |
591 | } | |
d944dc95 | 592 | |
c4f4fce7 | 593 | int chase_symlinks(const char *path, const char *original_root, unsigned flags, char **ret) { |
d944dc95 LP |
594 | _cleanup_free_ char *buffer = NULL, *done = NULL, *root = NULL; |
595 | _cleanup_close_ int fd = -1; | |
596 | unsigned max_follow = 32; /* how many symlinks to follow before giving up and returning ELOOP */ | |
a9fb0867 | 597 | bool exists = true; |
d944dc95 LP |
598 | char *todo; |
599 | int r; | |
600 | ||
601 | assert(path); | |
602 | ||
603 | /* This is a lot like canonicalize_file_name(), but takes an additional "root" parameter, that allows following | |
604 | * symlinks relative to a root directory, instead of the root of the host. | |
605 | * | |
fc4b68e5 | 606 | * Note that "root" primarily matters if we encounter an absolute symlink. It is also used when following |
c4f4fce7 LP |
607 | * relative symlinks to ensure they cannot be used to "escape" the root directory. The path parameter passed is |
608 | * assumed to be already prefixed by it, except if the CHASE_PREFIX_ROOT flag is set, in which case it is first | |
609 | * prefixed accordingly. | |
d944dc95 LP |
610 | * |
611 | * Algorithmically this operates on two path buffers: "done" are the components of the path we already | |
612 | * processed and resolved symlinks, "." and ".." of. "todo" are the components of the path we still need to | |
613 | * process. On each iteration, we move one component from "todo" to "done", processing it's special meaning | |
614 | * each time. The "todo" path always starts with at least one slash, the "done" path always ends in no | |
615 | * slash. We always keep an O_PATH fd to the component we are currently processing, thus keeping lookup races | |
fc4b68e5 LP |
616 | * at a minimum. |
617 | * | |
618 | * Suggested usage: whenever you want to canonicalize a path, use this function. Pass the absolute path you got | |
619 | * as-is: fully qualified and relative to your host's root. Optionally, specify the root parameter to tell this | |
620 | * function what to do when encountering a symlink with an absolute path as directory: prefix it by the | |
621 | * specified path. | |
622 | * | |
623 | * Note: there's also chase_symlinks_prefix() (see below), which as first step prefixes the passed path by the | |
624 | * passed root. */ | |
d944dc95 | 625 | |
c4f4fce7 LP |
626 | if (original_root) { |
627 | r = path_make_absolute_cwd(original_root, &root); | |
d944dc95 LP |
628 | if (r < 0) |
629 | return r; | |
c4f4fce7 LP |
630 | |
631 | if (flags & CHASE_PREFIX_ROOT) | |
632 | path = prefix_roota(root, path); | |
d944dc95 LP |
633 | } |
634 | ||
c4f4fce7 LP |
635 | r = path_make_absolute_cwd(path, &buffer); |
636 | if (r < 0) | |
637 | return r; | |
638 | ||
d944dc95 LP |
639 | fd = open("/", O_CLOEXEC|O_NOFOLLOW|O_PATH); |
640 | if (fd < 0) | |
641 | return -errno; | |
642 | ||
643 | todo = buffer; | |
644 | for (;;) { | |
645 | _cleanup_free_ char *first = NULL; | |
646 | _cleanup_close_ int child = -1; | |
647 | struct stat st; | |
648 | size_t n, m; | |
649 | ||
650 | /* Determine length of first component in the path */ | |
651 | n = strspn(todo, "/"); /* The slashes */ | |
652 | m = n + strcspn(todo + n, "/"); /* The entire length of the component */ | |
653 | ||
654 | /* Extract the first component. */ | |
655 | first = strndup(todo, m); | |
656 | if (!first) | |
657 | return -ENOMEM; | |
658 | ||
659 | todo += m; | |
660 | ||
661 | /* Just a single slash? Then we reached the end. */ | |
662 | if (isempty(first) || path_equal(first, "/")) | |
663 | break; | |
664 | ||
665 | /* Just a dot? Then let's eat this up. */ | |
666 | if (path_equal(first, "/.")) | |
667 | continue; | |
668 | ||
669 | /* Two dots? Then chop off the last bit of what we already found out. */ | |
670 | if (path_equal(first, "/..")) { | |
671 | _cleanup_free_ char *parent = NULL; | |
672 | int fd_parent = -1; | |
673 | ||
a4eaf3cf LP |
674 | /* If we already are at the top, then going up will not change anything. This is in-line with |
675 | * how the kernel handles this. */ | |
d944dc95 | 676 | if (isempty(done) || path_equal(done, "/")) |
a4eaf3cf | 677 | continue; |
d944dc95 LP |
678 | |
679 | parent = dirname_malloc(done); | |
680 | if (!parent) | |
681 | return -ENOMEM; | |
682 | ||
a4eaf3cf | 683 | /* Don't allow this to leave the root dir. */ |
d944dc95 LP |
684 | if (root && |
685 | path_startswith(done, root) && | |
686 | !path_startswith(parent, root)) | |
a4eaf3cf | 687 | continue; |
d944dc95 | 688 | |
3b319885 | 689 | free_and_replace(done, parent); |
d944dc95 LP |
690 | |
691 | fd_parent = openat(fd, "..", O_CLOEXEC|O_NOFOLLOW|O_PATH); | |
692 | if (fd_parent < 0) | |
693 | return -errno; | |
694 | ||
695 | safe_close(fd); | |
696 | fd = fd_parent; | |
697 | ||
698 | continue; | |
699 | } | |
700 | ||
701 | /* Otherwise let's see what this is. */ | |
702 | child = openat(fd, first + n, O_CLOEXEC|O_NOFOLLOW|O_PATH); | |
a9fb0867 LP |
703 | if (child < 0) { |
704 | ||
705 | if (errno == ENOENT && | |
cb638b5e | 706 | (flags & CHASE_NONEXISTENT) && |
a9fb0867 LP |
707 | (isempty(todo) || path_is_safe(todo))) { |
708 | ||
cb638b5e | 709 | /* If CHASE_NONEXISTENT is set, and the path does not exist, then that's OK, return |
a9fb0867 LP |
710 | * what we got so far. But don't allow this if the remaining path contains "../ or "./" |
711 | * or something else weird. */ | |
712 | ||
713 | if (!strextend(&done, first, todo, NULL)) | |
714 | return -ENOMEM; | |
715 | ||
716 | exists = false; | |
717 | break; | |
718 | } | |
719 | ||
d944dc95 | 720 | return -errno; |
a9fb0867 | 721 | } |
d944dc95 LP |
722 | |
723 | if (fstat(child, &st) < 0) | |
724 | return -errno; | |
655f2da0 N |
725 | if ((flags & CHASE_NO_AUTOFS) && |
726 | fd_check_fstype(child, AUTOFS_SUPER_MAGIC) > 0) | |
727 | return -EREMOTE; | |
d944dc95 LP |
728 | |
729 | if (S_ISLNK(st.st_mode)) { | |
877777d7 CCW |
730 | char *joined; |
731 | ||
d944dc95 LP |
732 | _cleanup_free_ char *destination = NULL; |
733 | ||
734 | /* This is a symlink, in this case read the destination. But let's make sure we don't follow | |
735 | * symlinks without bounds. */ | |
736 | if (--max_follow <= 0) | |
737 | return -ELOOP; | |
738 | ||
739 | r = readlinkat_malloc(fd, first + n, &destination); | |
740 | if (r < 0) | |
741 | return r; | |
742 | if (isempty(destination)) | |
743 | return -EINVAL; | |
744 | ||
745 | if (path_is_absolute(destination)) { | |
746 | ||
747 | /* An absolute destination. Start the loop from the beginning, but use the root | |
748 | * directory as base. */ | |
749 | ||
750 | safe_close(fd); | |
751 | fd = open(root ?: "/", O_CLOEXEC|O_NOFOLLOW|O_PATH); | |
752 | if (fd < 0) | |
753 | return -errno; | |
754 | ||
d944dc95 LP |
755 | free(done); |
756 | ||
757 | /* Note that we do not revalidate the root, we take it as is. */ | |
758 | if (isempty(root)) | |
759 | done = NULL; | |
760 | else { | |
761 | done = strdup(root); | |
762 | if (!done) | |
763 | return -ENOMEM; | |
764 | } | |
765 | ||
877777d7 | 766 | } |
d944dc95 | 767 | |
877777d7 CCW |
768 | /* Prefix what's left to do with what we just read, and start the loop again, |
769 | * but remain in the current directory. */ | |
d944dc95 | 770 | |
877777d7 CCW |
771 | joined = strjoin("/", destination, todo); |
772 | if (!joined) | |
773 | return -ENOMEM; | |
d944dc95 | 774 | |
877777d7 CCW |
775 | free(buffer); |
776 | todo = buffer = joined; | |
d944dc95 LP |
777 | |
778 | continue; | |
779 | } | |
780 | ||
781 | /* If this is not a symlink, then let's just add the name we read to what we already verified. */ | |
782 | if (!done) { | |
783 | done = first; | |
784 | first = NULL; | |
785 | } else { | |
786 | if (!strextend(&done, first, NULL)) | |
787 | return -ENOMEM; | |
788 | } | |
789 | ||
790 | /* And iterate again, but go one directory further down. */ | |
791 | safe_close(fd); | |
792 | fd = child; | |
793 | child = -1; | |
794 | } | |
795 | ||
796 | if (!done) { | |
797 | /* Special case, turn the empty string into "/", to indicate the root directory. */ | |
798 | done = strdup("/"); | |
799 | if (!done) | |
800 | return -ENOMEM; | |
801 | } | |
802 | ||
245f1d24 LP |
803 | if (ret) { |
804 | *ret = done; | |
805 | done = NULL; | |
806 | } | |
d944dc95 | 807 | |
a9fb0867 | 808 | return exists; |
d944dc95 | 809 | } |