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Commit | Line | Data |
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7336138e LP |
1 | /*** |
2 | This file is part of systemd. | |
3 | ||
4 | Copyright 2016 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 | ||
20 | #include <fcntl.h> | |
88cd066e | 21 | #include <linux/magic.h> |
349cc4a5 | 22 | #if HAVE_ACL |
7336138e LP |
23 | #include <sys/acl.h> |
24 | #endif | |
25 | #include <sys/stat.h> | |
88cd066e | 26 | #include <sys/vfs.h> |
7336138e LP |
27 | #include <unistd.h> |
28 | ||
29 | #include "acl-util.h" | |
30 | #include "dirent-util.h" | |
31 | #include "fd-util.h" | |
88cd066e | 32 | #include "missing.h" |
7336138e | 33 | #include "nspawn-patch-uid.h" |
88cd066e | 34 | #include "stat-util.h" |
7336138e LP |
35 | #include "stdio-util.h" |
36 | #include "string-util.h" | |
37 | #include "strv.h" | |
38 | #include "user-util.h" | |
39 | ||
349cc4a5 | 40 | #if HAVE_ACL |
7336138e LP |
41 | |
42 | static int get_acl(int fd, const char *name, acl_type_t type, acl_t *ret) { | |
43 | char procfs_path[strlen("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1]; | |
44 | acl_t acl; | |
45 | ||
46 | assert(fd >= 0); | |
47 | assert(ret); | |
48 | ||
49 | if (name) { | |
50 | _cleanup_close_ int child_fd = -1; | |
51 | ||
52 | child_fd = openat(fd, name, O_PATH|O_CLOEXEC|O_NOFOLLOW); | |
53 | if (child_fd < 0) | |
54 | return -errno; | |
55 | ||
56 | xsprintf(procfs_path, "/proc/self/fd/%i", child_fd); | |
57 | acl = acl_get_file(procfs_path, type); | |
58 | } else if (type == ACL_TYPE_ACCESS) | |
59 | acl = acl_get_fd(fd); | |
60 | else { | |
61 | xsprintf(procfs_path, "/proc/self/fd/%i", fd); | |
62 | acl = acl_get_file(procfs_path, type); | |
63 | } | |
64 | if (!acl) | |
65 | return -errno; | |
66 | ||
67 | *ret = acl; | |
68 | return 0; | |
69 | } | |
70 | ||
71 | static int set_acl(int fd, const char *name, acl_type_t type, acl_t acl) { | |
72 | char procfs_path[strlen("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1]; | |
73 | int r; | |
74 | ||
75 | assert(fd >= 0); | |
76 | assert(acl); | |
77 | ||
78 | if (name) { | |
79 | _cleanup_close_ int child_fd = -1; | |
80 | ||
81 | child_fd = openat(fd, name, O_PATH|O_CLOEXEC|O_NOFOLLOW); | |
82 | if (child_fd < 0) | |
83 | return -errno; | |
84 | ||
85 | xsprintf(procfs_path, "/proc/self/fd/%i", child_fd); | |
86 | r = acl_set_file(procfs_path, type, acl); | |
87 | } else if (type == ACL_TYPE_ACCESS) | |
88 | r = acl_set_fd(fd, acl); | |
89 | else { | |
90 | xsprintf(procfs_path, "/proc/self/fd/%i", fd); | |
91 | r = acl_set_file(procfs_path, type, acl); | |
92 | } | |
93 | if (r < 0) | |
94 | return -errno; | |
95 | ||
96 | return 0; | |
97 | } | |
98 | ||
99 | static int shift_acl(acl_t acl, uid_t shift, acl_t *ret) { | |
100 | _cleanup_(acl_freep) acl_t copy = NULL; | |
101 | acl_entry_t i; | |
102 | int r; | |
103 | ||
104 | assert(acl); | |
105 | assert(ret); | |
106 | ||
107 | r = acl_get_entry(acl, ACL_FIRST_ENTRY, &i); | |
108 | if (r < 0) | |
109 | return -errno; | |
110 | while (r > 0) { | |
111 | uid_t *old_uid, new_uid; | |
112 | bool modify = false; | |
113 | acl_tag_t tag; | |
114 | ||
115 | if (acl_get_tag_type(i, &tag) < 0) | |
116 | return -errno; | |
117 | ||
118 | if (IN_SET(tag, ACL_USER, ACL_GROUP)) { | |
119 | ||
120 | /* We don't distuingish here between uid_t and gid_t, let's make sure the compiler checks that | |
121 | * this is actually OK */ | |
122 | assert_cc(sizeof(uid_t) == sizeof(gid_t)); | |
123 | ||
124 | old_uid = acl_get_qualifier(i); | |
125 | if (!old_uid) | |
126 | return -errno; | |
127 | ||
128 | new_uid = shift | (*old_uid & UINT32_C(0xFFFF)); | |
129 | if (!uid_is_valid(new_uid)) | |
130 | return -EINVAL; | |
131 | ||
132 | modify = new_uid != *old_uid; | |
133 | if (modify && !copy) { | |
134 | int n; | |
135 | ||
136 | /* There's no copy of the ACL yet? if so, let's create one, and start the loop from the | |
137 | * beginning, so that we copy all entries, starting from the first, this time. */ | |
138 | ||
139 | n = acl_entries(acl); | |
140 | if (n < 0) | |
141 | return -errno; | |
142 | ||
143 | copy = acl_init(n); | |
144 | if (!copy) | |
145 | return -errno; | |
146 | ||
147 | /* Seek back to the beginning */ | |
148 | r = acl_get_entry(acl, ACL_FIRST_ENTRY, &i); | |
149 | if (r < 0) | |
150 | return -errno; | |
151 | continue; | |
152 | } | |
153 | } | |
154 | ||
155 | if (copy) { | |
156 | acl_entry_t new_entry; | |
157 | ||
158 | if (acl_create_entry(©, &new_entry) < 0) | |
159 | return -errno; | |
160 | ||
161 | if (acl_copy_entry(new_entry, i) < 0) | |
162 | return -errno; | |
163 | ||
164 | if (modify) | |
165 | if (acl_set_qualifier(new_entry, &new_uid) < 0) | |
166 | return -errno; | |
167 | } | |
168 | ||
169 | r = acl_get_entry(acl, ACL_NEXT_ENTRY, &i); | |
170 | if (r < 0) | |
171 | return -errno; | |
172 | } | |
173 | ||
174 | *ret = copy; | |
175 | copy = NULL; | |
176 | ||
177 | return !!*ret; | |
178 | } | |
179 | ||
180 | static int patch_acls(int fd, const char *name, const struct stat *st, uid_t shift) { | |
181 | _cleanup_(acl_freep) acl_t acl = NULL, shifted = NULL; | |
182 | bool changed = false; | |
183 | int r; | |
184 | ||
185 | assert(fd >= 0); | |
186 | assert(st); | |
187 | ||
188 | /* ACLs are not supported on symlinks, there's no point in trying */ | |
189 | if (S_ISLNK(st->st_mode)) | |
190 | return 0; | |
191 | ||
192 | r = get_acl(fd, name, ACL_TYPE_ACCESS, &acl); | |
193 | if (r == -EOPNOTSUPP) | |
194 | return 0; | |
195 | if (r < 0) | |
196 | return r; | |
197 | ||
198 | r = shift_acl(acl, shift, &shifted); | |
199 | if (r < 0) | |
200 | return r; | |
201 | if (r > 0) { | |
202 | r = set_acl(fd, name, ACL_TYPE_ACCESS, shifted); | |
203 | if (r < 0) | |
204 | return r; | |
205 | ||
206 | changed = true; | |
207 | } | |
208 | ||
209 | if (S_ISDIR(st->st_mode)) { | |
210 | acl_free(acl); | |
211 | acl_free(shifted); | |
212 | ||
213 | acl = shifted = NULL; | |
214 | ||
215 | r = get_acl(fd, name, ACL_TYPE_DEFAULT, &acl); | |
216 | if (r < 0) | |
217 | return r; | |
218 | ||
219 | r = shift_acl(acl, shift, &shifted); | |
220 | if (r < 0) | |
221 | return r; | |
222 | if (r > 0) { | |
223 | r = set_acl(fd, name, ACL_TYPE_DEFAULT, shifted); | |
224 | if (r < 0) | |
225 | return r; | |
226 | ||
227 | changed = true; | |
228 | } | |
229 | } | |
230 | ||
231 | return changed; | |
232 | } | |
233 | ||
234 | #else | |
235 | ||
236 | static int patch_acls(int fd, const char *name, const struct stat *st, uid_t shift) { | |
237 | return 0; | |
238 | } | |
239 | ||
240 | #endif | |
241 | ||
242 | static int patch_fd(int fd, const char *name, const struct stat *st, uid_t shift) { | |
243 | uid_t new_uid; | |
244 | gid_t new_gid; | |
245 | bool changed = false; | |
246 | int r; | |
247 | ||
248 | assert(fd >= 0); | |
249 | assert(st); | |
250 | ||
251 | new_uid = shift | (st->st_uid & UINT32_C(0xFFFF)); | |
252 | new_gid = (gid_t) shift | (st->st_gid & UINT32_C(0xFFFF)); | |
253 | ||
254 | if (!uid_is_valid(new_uid) || !gid_is_valid(new_gid)) | |
255 | return -EINVAL; | |
256 | ||
257 | if (st->st_uid != new_uid || st->st_gid != new_gid) { | |
258 | if (name) | |
259 | r = fchownat(fd, name, new_uid, new_gid, AT_SYMLINK_NOFOLLOW); | |
260 | else | |
261 | r = fchown(fd, new_uid, new_gid); | |
262 | if (r < 0) | |
263 | return -errno; | |
264 | ||
265 | /* The Linux kernel alters the mode in some cases of chown(). Let's undo this. */ | |
0c6aeb46 LP |
266 | if (name) { |
267 | if (!S_ISLNK(st->st_mode)) | |
268 | r = fchmodat(fd, name, st->st_mode, 0); | |
269 | else /* AT_SYMLINK_NOFOLLOW is not available for fchmodat() */ | |
270 | r = 0; | |
271 | } else | |
7336138e LP |
272 | r = fchmod(fd, st->st_mode); |
273 | if (r < 0) | |
274 | return -errno; | |
275 | ||
276 | changed = true; | |
277 | } | |
278 | ||
279 | r = patch_acls(fd, name, st, shift); | |
280 | if (r < 0) | |
281 | return r; | |
282 | ||
283 | return r > 0 || changed; | |
284 | } | |
285 | ||
231bfb1b DH |
286 | /* |
287 | * Check if the filesystem is fully compatible with user namespaces or | |
288 | * UID/GID patching. Some filesystems in this list can be fully mounted inside | |
289 | * user namespaces, however their inodes may relate to host resources or only | |
290 | * valid in the global user namespace, therefore no patching should be applied. | |
291 | */ | |
292 | static int is_fs_fully_userns_compatible(int fd) { | |
88cd066e LP |
293 | struct statfs sfs; |
294 | ||
295 | assert(fd >= 0); | |
296 | ||
297 | if (fstatfs(fd, &sfs) < 0) | |
298 | return -errno; | |
299 | ||
300 | return F_TYPE_EQUAL(sfs.f_type, BINFMTFS_MAGIC) || | |
301 | F_TYPE_EQUAL(sfs.f_type, CGROUP_SUPER_MAGIC) || | |
302 | F_TYPE_EQUAL(sfs.f_type, CGROUP2_SUPER_MAGIC) || | |
303 | F_TYPE_EQUAL(sfs.f_type, DEBUGFS_MAGIC) || | |
304 | F_TYPE_EQUAL(sfs.f_type, DEVPTS_SUPER_MAGIC) || | |
305 | F_TYPE_EQUAL(sfs.f_type, EFIVARFS_MAGIC) || | |
306 | F_TYPE_EQUAL(sfs.f_type, HUGETLBFS_MAGIC) || | |
307 | F_TYPE_EQUAL(sfs.f_type, MQUEUE_MAGIC) || | |
308 | F_TYPE_EQUAL(sfs.f_type, PROC_SUPER_MAGIC) || | |
309 | F_TYPE_EQUAL(sfs.f_type, PSTOREFS_MAGIC) || | |
310 | F_TYPE_EQUAL(sfs.f_type, SELINUX_MAGIC) || | |
311 | F_TYPE_EQUAL(sfs.f_type, SMACK_MAGIC) || | |
87c05f36 DH |
312 | F_TYPE_EQUAL(sfs.f_type, SECURITYFS_MAGIC) || |
313 | F_TYPE_EQUAL(sfs.f_type, BPF_FS_MAGIC) || | |
314 | F_TYPE_EQUAL(sfs.f_type, TRACEFS_MAGIC) || | |
88cd066e LP |
315 | F_TYPE_EQUAL(sfs.f_type, SYSFS_MAGIC); |
316 | } | |
317 | ||
4aeb20f5 | 318 | static int recurse_fd(int fd, bool donate_fd, const struct stat *st, uid_t shift, bool is_toplevel) { |
7336138e LP |
319 | bool changed = false; |
320 | int r; | |
321 | ||
322 | assert(fd >= 0); | |
323 | ||
88cd066e LP |
324 | /* We generally want to permit crossing of mount boundaries when patching the UIDs/GIDs. However, we |
325 | * probably shouldn't do this for /proc and /sys if that is already mounted into place. Hence, let's | |
231bfb1b DH |
326 | * stop the recursion when we hit procfs, sysfs or some other special file systems. */ |
327 | r = is_fs_fully_userns_compatible(fd); | |
88cd066e LP |
328 | if (r < 0) |
329 | goto finish; | |
330 | if (r > 0) { | |
331 | r = 0; /* don't recurse */ | |
332 | goto finish; | |
333 | } | |
334 | ||
7336138e | 335 | r = patch_fd(fd, NULL, st, shift); |
4aeb20f5 LP |
336 | if (r == -EROFS) { |
337 | _cleanup_free_ char *name = NULL; | |
338 | ||
339 | if (!is_toplevel) { | |
340 | /* When we hit a ready-only subtree we simply skip it, but log about it. */ | |
341 | (void) fd_get_path(fd, &name); | |
342 | log_debug("Skippping read-only file or directory %s.", strna(name)); | |
343 | r = 0; | |
344 | } | |
345 | ||
346 | goto finish; | |
347 | } | |
7336138e LP |
348 | if (r < 0) |
349 | goto finish; | |
64fbdc0f LP |
350 | if (r > 0) |
351 | changed = true; | |
7336138e LP |
352 | |
353 | if (S_ISDIR(st->st_mode)) { | |
354 | _cleanup_closedir_ DIR *d = NULL; | |
355 | struct dirent *de; | |
356 | ||
357 | if (!donate_fd) { | |
358 | int copy; | |
359 | ||
360 | copy = fcntl(fd, F_DUPFD_CLOEXEC, 3); | |
88cd066e LP |
361 | if (copy < 0) { |
362 | r = -errno; | |
363 | goto finish; | |
364 | } | |
7336138e LP |
365 | |
366 | fd = copy; | |
367 | donate_fd = true; | |
368 | } | |
369 | ||
370 | d = fdopendir(fd); | |
371 | if (!d) { | |
372 | r = -errno; | |
373 | goto finish; | |
374 | } | |
375 | fd = -1; | |
376 | ||
377 | FOREACH_DIRENT_ALL(de, d, r = -errno; goto finish) { | |
378 | struct stat fst; | |
379 | ||
49bfc877 | 380 | if (dot_or_dot_dot(de->d_name)) |
7336138e LP |
381 | continue; |
382 | ||
383 | if (fstatat(dirfd(d), de->d_name, &fst, AT_SYMLINK_NOFOLLOW) < 0) { | |
384 | r = -errno; | |
385 | goto finish; | |
386 | } | |
387 | ||
388 | if (S_ISDIR(fst.st_mode)) { | |
389 | int subdir_fd; | |
390 | ||
391 | subdir_fd = openat(dirfd(d), de->d_name, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW|O_NOATIME); | |
392 | if (subdir_fd < 0) { | |
393 | r = -errno; | |
394 | goto finish; | |
395 | ||
396 | } | |
397 | ||
4aeb20f5 | 398 | r = recurse_fd(subdir_fd, true, &fst, shift, false); |
7336138e LP |
399 | if (r < 0) |
400 | goto finish; | |
401 | if (r > 0) | |
402 | changed = true; | |
403 | ||
404 | } else { | |
405 | r = patch_fd(dirfd(d), de->d_name, &fst, shift); | |
406 | if (r < 0) | |
407 | goto finish; | |
408 | if (r > 0) | |
409 | changed = true; | |
410 | } | |
411 | } | |
412 | } | |
413 | ||
414 | r = changed; | |
415 | ||
416 | finish: | |
417 | if (donate_fd) | |
418 | safe_close(fd); | |
419 | ||
420 | return r; | |
421 | } | |
422 | ||
423 | static int fd_patch_uid_internal(int fd, bool donate_fd, uid_t shift, uid_t range) { | |
424 | struct stat st; | |
425 | int r; | |
426 | ||
427 | assert(fd >= 0); | |
428 | ||
429 | /* Recursively adjusts the UID/GIDs of all files of a directory tree. This is used to automatically fix up an | |
430 | * OS tree to the used user namespace UID range. Note that this automatic adjustment only works for UID ranges | |
431 | * following the concept that the upper 16bit of a UID identify the container, and the lower 16bit are the actual | |
432 | * UID within the container. */ | |
433 | ||
434 | if ((shift & 0xFFFF) != 0) { | |
435 | /* We only support containers where the shift starts at a 2^16 boundary */ | |
436 | r = -EOPNOTSUPP; | |
437 | goto finish; | |
438 | } | |
439 | ||
440 | if (range != 0x10000) { | |
441 | /* We only support containers with 16bit UID ranges for the patching logic */ | |
442 | r = -EOPNOTSUPP; | |
443 | goto finish; | |
444 | } | |
445 | ||
446 | if (fstat(fd, &st) < 0) { | |
447 | r = -errno; | |
448 | goto finish; | |
449 | } | |
450 | ||
451 | if ((uint32_t) st.st_uid >> 16 != (uint32_t) st.st_gid >> 16) { | |
452 | /* We only support containers where the uid/gid container ID match */ | |
453 | r = -EBADE; | |
454 | goto finish; | |
455 | } | |
456 | ||
457 | /* Try to detect if the range is already right. Of course, this a pretty drastic optimization, as we assume | |
458 | * that if the top-level dir has the right upper 16bit assigned, then everything below will have too... */ | |
459 | if (((uint32_t) (st.st_uid ^ shift) >> 16) == 0) | |
460 | return 0; | |
461 | ||
4aeb20f5 | 462 | return recurse_fd(fd, donate_fd, &st, shift, true); |
7336138e LP |
463 | |
464 | finish: | |
465 | if (donate_fd) | |
466 | safe_close(fd); | |
467 | ||
468 | return r; | |
469 | } | |
470 | ||
471 | int fd_patch_uid(int fd, uid_t shift, uid_t range) { | |
472 | return fd_patch_uid_internal(fd, false, shift, range); | |
473 | } | |
474 | ||
475 | int path_patch_uid(const char *path, uid_t shift, uid_t range) { | |
476 | int fd; | |
477 | ||
478 | fd = open(path, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW|O_NOATIME); | |
479 | if (fd < 0) | |
480 | return -errno; | |
481 | ||
482 | return fd_patch_uid_internal(fd, true, shift, range); | |
483 | } |