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