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Commit | Line | Data |
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53e1b683 | 1 | /* SPDX-License-Identifier: LGPL-2.1+ */ |
7336138e LP |
2 | |
3 | #include <fcntl.h> | |
88cd066e | 4 | #include <linux/magic.h> |
349cc4a5 | 5 | #if HAVE_ACL |
7336138e LP |
6 | #include <sys/acl.h> |
7 | #endif | |
8 | #include <sys/stat.h> | |
3603efde | 9 | #include <sys/statvfs.h> |
88cd066e | 10 | #include <sys/vfs.h> |
7336138e LP |
11 | #include <unistd.h> |
12 | ||
13 | #include "acl-util.h" | |
14 | #include "dirent-util.h" | |
15 | #include "fd-util.h" | |
3603efde | 16 | #include "fs-util.h" |
88cd066e | 17 | #include "missing.h" |
3603efde | 18 | #include "nspawn-def.h" |
7336138e | 19 | #include "nspawn-patch-uid.h" |
88cd066e | 20 | #include "stat-util.h" |
7336138e LP |
21 | #include "stdio-util.h" |
22 | #include "string-util.h" | |
23 | #include "strv.h" | |
24 | #include "user-util.h" | |
25 | ||
349cc4a5 | 26 | #if HAVE_ACL |
7336138e LP |
27 | |
28 | static int get_acl(int fd, const char *name, acl_type_t type, acl_t *ret) { | |
fbd0b64f | 29 | char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1]; |
7336138e LP |
30 | acl_t acl; |
31 | ||
32 | assert(fd >= 0); | |
33 | assert(ret); | |
34 | ||
35 | if (name) { | |
36 | _cleanup_close_ int child_fd = -1; | |
37 | ||
38 | child_fd = openat(fd, name, O_PATH|O_CLOEXEC|O_NOFOLLOW); | |
39 | if (child_fd < 0) | |
40 | return -errno; | |
41 | ||
42 | xsprintf(procfs_path, "/proc/self/fd/%i", child_fd); | |
43 | acl = acl_get_file(procfs_path, type); | |
44 | } else if (type == ACL_TYPE_ACCESS) | |
45 | acl = acl_get_fd(fd); | |
46 | else { | |
47 | xsprintf(procfs_path, "/proc/self/fd/%i", fd); | |
48 | acl = acl_get_file(procfs_path, type); | |
49 | } | |
50 | if (!acl) | |
51 | return -errno; | |
52 | ||
53 | *ret = acl; | |
54 | return 0; | |
55 | } | |
56 | ||
57 | static int set_acl(int fd, const char *name, acl_type_t type, acl_t acl) { | |
fbd0b64f | 58 | char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1]; |
7336138e LP |
59 | int r; |
60 | ||
61 | assert(fd >= 0); | |
62 | assert(acl); | |
63 | ||
64 | if (name) { | |
65 | _cleanup_close_ int child_fd = -1; | |
66 | ||
67 | child_fd = openat(fd, name, O_PATH|O_CLOEXEC|O_NOFOLLOW); | |
68 | if (child_fd < 0) | |
69 | return -errno; | |
70 | ||
71 | xsprintf(procfs_path, "/proc/self/fd/%i", child_fd); | |
72 | r = acl_set_file(procfs_path, type, acl); | |
73 | } else if (type == ACL_TYPE_ACCESS) | |
74 | r = acl_set_fd(fd, acl); | |
75 | else { | |
76 | xsprintf(procfs_path, "/proc/self/fd/%i", fd); | |
77 | r = acl_set_file(procfs_path, type, acl); | |
78 | } | |
79 | if (r < 0) | |
80 | return -errno; | |
81 | ||
82 | return 0; | |
83 | } | |
84 | ||
85 | static int shift_acl(acl_t acl, uid_t shift, acl_t *ret) { | |
86 | _cleanup_(acl_freep) acl_t copy = NULL; | |
87 | acl_entry_t i; | |
88 | int r; | |
89 | ||
90 | assert(acl); | |
91 | assert(ret); | |
92 | ||
93 | r = acl_get_entry(acl, ACL_FIRST_ENTRY, &i); | |
94 | if (r < 0) | |
95 | return -errno; | |
96 | while (r > 0) { | |
97 | uid_t *old_uid, new_uid; | |
98 | bool modify = false; | |
99 | acl_tag_t tag; | |
100 | ||
101 | if (acl_get_tag_type(i, &tag) < 0) | |
102 | return -errno; | |
103 | ||
104 | if (IN_SET(tag, ACL_USER, ACL_GROUP)) { | |
105 | ||
106 | /* We don't distuingish here between uid_t and gid_t, let's make sure the compiler checks that | |
107 | * this is actually OK */ | |
108 | assert_cc(sizeof(uid_t) == sizeof(gid_t)); | |
109 | ||
110 | old_uid = acl_get_qualifier(i); | |
111 | if (!old_uid) | |
112 | return -errno; | |
113 | ||
114 | new_uid = shift | (*old_uid & UINT32_C(0xFFFF)); | |
115 | if (!uid_is_valid(new_uid)) | |
116 | return -EINVAL; | |
117 | ||
118 | modify = new_uid != *old_uid; | |
119 | if (modify && !copy) { | |
120 | int n; | |
121 | ||
122 | /* There's no copy of the ACL yet? if so, let's create one, and start the loop from the | |
123 | * beginning, so that we copy all entries, starting from the first, this time. */ | |
124 | ||
125 | n = acl_entries(acl); | |
126 | if (n < 0) | |
127 | return -errno; | |
128 | ||
129 | copy = acl_init(n); | |
130 | if (!copy) | |
131 | return -errno; | |
132 | ||
133 | /* Seek back to the beginning */ | |
134 | r = acl_get_entry(acl, ACL_FIRST_ENTRY, &i); | |
135 | if (r < 0) | |
136 | return -errno; | |
137 | continue; | |
138 | } | |
139 | } | |
140 | ||
141 | if (copy) { | |
142 | acl_entry_t new_entry; | |
143 | ||
144 | if (acl_create_entry(©, &new_entry) < 0) | |
145 | return -errno; | |
146 | ||
147 | if (acl_copy_entry(new_entry, i) < 0) | |
148 | return -errno; | |
149 | ||
150 | if (modify) | |
151 | if (acl_set_qualifier(new_entry, &new_uid) < 0) | |
152 | return -errno; | |
153 | } | |
154 | ||
155 | r = acl_get_entry(acl, ACL_NEXT_ENTRY, &i); | |
156 | if (r < 0) | |
157 | return -errno; | |
158 | } | |
159 | ||
1cc6c93a | 160 | *ret = TAKE_PTR(copy); |
7336138e LP |
161 | |
162 | return !!*ret; | |
163 | } | |
164 | ||
165 | static int patch_acls(int fd, const char *name, const struct stat *st, uid_t shift) { | |
166 | _cleanup_(acl_freep) acl_t acl = NULL, shifted = NULL; | |
167 | bool changed = false; | |
168 | int r; | |
169 | ||
170 | assert(fd >= 0); | |
171 | assert(st); | |
172 | ||
173 | /* ACLs are not supported on symlinks, there's no point in trying */ | |
174 | if (S_ISLNK(st->st_mode)) | |
175 | return 0; | |
176 | ||
177 | r = get_acl(fd, name, ACL_TYPE_ACCESS, &acl); | |
178 | if (r == -EOPNOTSUPP) | |
179 | return 0; | |
180 | if (r < 0) | |
181 | return r; | |
182 | ||
183 | r = shift_acl(acl, shift, &shifted); | |
184 | if (r < 0) | |
185 | return r; | |
186 | if (r > 0) { | |
187 | r = set_acl(fd, name, ACL_TYPE_ACCESS, shifted); | |
188 | if (r < 0) | |
189 | return r; | |
190 | ||
191 | changed = true; | |
192 | } | |
193 | ||
194 | if (S_ISDIR(st->st_mode)) { | |
195 | acl_free(acl); | |
196 | acl_free(shifted); | |
197 | ||
198 | acl = shifted = NULL; | |
199 | ||
200 | r = get_acl(fd, name, ACL_TYPE_DEFAULT, &acl); | |
201 | if (r < 0) | |
202 | return r; | |
203 | ||
204 | r = shift_acl(acl, shift, &shifted); | |
205 | if (r < 0) | |
206 | return r; | |
207 | if (r > 0) { | |
208 | r = set_acl(fd, name, ACL_TYPE_DEFAULT, shifted); | |
209 | if (r < 0) | |
210 | return r; | |
211 | ||
212 | changed = true; | |
213 | } | |
214 | } | |
215 | ||
216 | return changed; | |
217 | } | |
218 | ||
219 | #else | |
220 | ||
221 | static int patch_acls(int fd, const char *name, const struct stat *st, uid_t shift) { | |
222 | return 0; | |
223 | } | |
224 | ||
225 | #endif | |
226 | ||
227 | static int patch_fd(int fd, const char *name, const struct stat *st, uid_t shift) { | |
228 | uid_t new_uid; | |
229 | gid_t new_gid; | |
230 | bool changed = false; | |
231 | int r; | |
232 | ||
233 | assert(fd >= 0); | |
234 | assert(st); | |
235 | ||
236 | new_uid = shift | (st->st_uid & UINT32_C(0xFFFF)); | |
237 | new_gid = (gid_t) shift | (st->st_gid & UINT32_C(0xFFFF)); | |
238 | ||
239 | if (!uid_is_valid(new_uid) || !gid_is_valid(new_gid)) | |
240 | return -EINVAL; | |
241 | ||
242 | if (st->st_uid != new_uid || st->st_gid != new_gid) { | |
243 | if (name) | |
244 | r = fchownat(fd, name, new_uid, new_gid, AT_SYMLINK_NOFOLLOW); | |
245 | else | |
246 | r = fchown(fd, new_uid, new_gid); | |
247 | if (r < 0) | |
248 | return -errno; | |
249 | ||
250 | /* The Linux kernel alters the mode in some cases of chown(). Let's undo this. */ | |
0c6aeb46 LP |
251 | if (name) { |
252 | if (!S_ISLNK(st->st_mode)) | |
253 | r = fchmodat(fd, name, st->st_mode, 0); | |
254 | else /* AT_SYMLINK_NOFOLLOW is not available for fchmodat() */ | |
255 | r = 0; | |
256 | } else | |
7336138e LP |
257 | r = fchmod(fd, st->st_mode); |
258 | if (r < 0) | |
259 | return -errno; | |
260 | ||
261 | changed = true; | |
262 | } | |
263 | ||
264 | r = patch_acls(fd, name, st, shift); | |
265 | if (r < 0) | |
266 | return r; | |
267 | ||
268 | return r > 0 || changed; | |
269 | } | |
270 | ||
231bfb1b DH |
271 | /* |
272 | * Check if the filesystem is fully compatible with user namespaces or | |
273 | * UID/GID patching. Some filesystems in this list can be fully mounted inside | |
274 | * user namespaces, however their inodes may relate to host resources or only | |
275 | * valid in the global user namespace, therefore no patching should be applied. | |
276 | */ | |
3603efde LP |
277 | static int is_fs_fully_userns_compatible(const struct statfs *sfs) { |
278 | ||
279 | assert(sfs); | |
280 | ||
281 | return F_TYPE_EQUAL(sfs->f_type, BINFMTFS_MAGIC) || | |
282 | F_TYPE_EQUAL(sfs->f_type, CGROUP_SUPER_MAGIC) || | |
283 | F_TYPE_EQUAL(sfs->f_type, CGROUP2_SUPER_MAGIC) || | |
284 | F_TYPE_EQUAL(sfs->f_type, DEBUGFS_MAGIC) || | |
285 | F_TYPE_EQUAL(sfs->f_type, DEVPTS_SUPER_MAGIC) || | |
286 | F_TYPE_EQUAL(sfs->f_type, EFIVARFS_MAGIC) || | |
287 | F_TYPE_EQUAL(sfs->f_type, HUGETLBFS_MAGIC) || | |
288 | F_TYPE_EQUAL(sfs->f_type, MQUEUE_MAGIC) || | |
289 | F_TYPE_EQUAL(sfs->f_type, PROC_SUPER_MAGIC) || | |
290 | F_TYPE_EQUAL(sfs->f_type, PSTOREFS_MAGIC) || | |
291 | F_TYPE_EQUAL(sfs->f_type, SELINUX_MAGIC) || | |
292 | F_TYPE_EQUAL(sfs->f_type, SMACK_MAGIC) || | |
293 | F_TYPE_EQUAL(sfs->f_type, SECURITYFS_MAGIC) || | |
294 | F_TYPE_EQUAL(sfs->f_type, BPF_FS_MAGIC) || | |
295 | F_TYPE_EQUAL(sfs->f_type, TRACEFS_MAGIC) || | |
296 | F_TYPE_EQUAL(sfs->f_type, SYSFS_MAGIC); | |
88cd066e LP |
297 | } |
298 | ||
4aeb20f5 | 299 | static int recurse_fd(int fd, bool donate_fd, const struct stat *st, uid_t shift, bool is_toplevel) { |
3603efde | 300 | _cleanup_closedir_ DIR *d = NULL; |
7336138e | 301 | bool changed = false; |
3603efde | 302 | struct statfs sfs; |
7336138e LP |
303 | int r; |
304 | ||
305 | assert(fd >= 0); | |
306 | ||
3603efde LP |
307 | if (fstatfs(fd, &sfs) < 0) |
308 | return -errno; | |
309 | ||
310 | /* We generally want to permit crossing of mount boundaries when patching the UIDs/GIDs. However, we probably | |
311 | * shouldn't do this for /proc and /sys if that is already mounted into place. Hence, let's stop the recursion | |
312 | * when we hit procfs, sysfs or some other special file systems. */ | |
313 | ||
314 | r = is_fs_fully_userns_compatible(&sfs); | |
88cd066e LP |
315 | if (r < 0) |
316 | goto finish; | |
317 | if (r > 0) { | |
318 | r = 0; /* don't recurse */ | |
319 | goto finish; | |
320 | } | |
321 | ||
3603efde LP |
322 | /* Also, if we hit a read-only file system, then don't bother, skip the whole subtree */ |
323 | if ((sfs.f_flags & ST_RDONLY) || | |
324 | access_fd(fd, W_OK) == -EROFS) | |
325 | goto read_only; | |
7336138e LP |
326 | |
327 | if (S_ISDIR(st->st_mode)) { | |
7336138e LP |
328 | struct dirent *de; |
329 | ||
330 | if (!donate_fd) { | |
331 | int copy; | |
332 | ||
333 | copy = fcntl(fd, F_DUPFD_CLOEXEC, 3); | |
88cd066e LP |
334 | if (copy < 0) { |
335 | r = -errno; | |
336 | goto finish; | |
337 | } | |
7336138e LP |
338 | |
339 | fd = copy; | |
340 | donate_fd = true; | |
341 | } | |
342 | ||
343 | d = fdopendir(fd); | |
344 | if (!d) { | |
345 | r = -errno; | |
346 | goto finish; | |
347 | } | |
348 | fd = -1; | |
349 | ||
350 | FOREACH_DIRENT_ALL(de, d, r = -errno; goto finish) { | |
351 | struct stat fst; | |
352 | ||
49bfc877 | 353 | if (dot_or_dot_dot(de->d_name)) |
7336138e LP |
354 | continue; |
355 | ||
356 | if (fstatat(dirfd(d), de->d_name, &fst, AT_SYMLINK_NOFOLLOW) < 0) { | |
357 | r = -errno; | |
358 | goto finish; | |
359 | } | |
360 | ||
361 | if (S_ISDIR(fst.st_mode)) { | |
362 | int subdir_fd; | |
363 | ||
364 | subdir_fd = openat(dirfd(d), de->d_name, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW|O_NOATIME); | |
365 | if (subdir_fd < 0) { | |
366 | r = -errno; | |
367 | goto finish; | |
368 | ||
369 | } | |
370 | ||
4aeb20f5 | 371 | r = recurse_fd(subdir_fd, true, &fst, shift, false); |
7336138e LP |
372 | if (r < 0) |
373 | goto finish; | |
374 | if (r > 0) | |
375 | changed = true; | |
376 | ||
377 | } else { | |
378 | r = patch_fd(dirfd(d), de->d_name, &fst, shift); | |
379 | if (r < 0) | |
380 | goto finish; | |
381 | if (r > 0) | |
382 | changed = true; | |
383 | } | |
384 | } | |
385 | } | |
386 | ||
3603efde LP |
387 | /* After we descended, also patch the directory itself. It's key to do this in this order so that the top-level |
388 | * directory is patched as very last object in the tree, so that we can use it as quick indicator whether the | |
389 | * tree is properly chown()ed already. */ | |
390 | r = patch_fd(d ? dirfd(d) : fd, NULL, st, shift); | |
391 | if (r == -EROFS) | |
392 | goto read_only; | |
393 | if (r > 0) | |
394 | changed = true; | |
395 | ||
7336138e | 396 | r = changed; |
3603efde LP |
397 | goto finish; |
398 | ||
399 | read_only: | |
400 | if (!is_toplevel) { | |
401 | _cleanup_free_ char *name = NULL; | |
402 | ||
403 | /* When we hit a ready-only subtree we simply skip it, but log about it. */ | |
404 | (void) fd_get_path(fd, &name); | |
405 | log_debug("Skippping read-only file or directory %s.", strna(name)); | |
406 | r = changed; | |
407 | } | |
7336138e LP |
408 | |
409 | finish: | |
410 | if (donate_fd) | |
411 | safe_close(fd); | |
412 | ||
413 | return r; | |
414 | } | |
415 | ||
416 | static int fd_patch_uid_internal(int fd, bool donate_fd, uid_t shift, uid_t range) { | |
417 | struct stat st; | |
418 | int r; | |
419 | ||
420 | assert(fd >= 0); | |
421 | ||
422 | /* Recursively adjusts the UID/GIDs of all files of a directory tree. This is used to automatically fix up an | |
423 | * OS tree to the used user namespace UID range. Note that this automatic adjustment only works for UID ranges | |
424 | * following the concept that the upper 16bit of a UID identify the container, and the lower 16bit are the actual | |
425 | * UID within the container. */ | |
426 | ||
427 | if ((shift & 0xFFFF) != 0) { | |
428 | /* We only support containers where the shift starts at a 2^16 boundary */ | |
429 | r = -EOPNOTSUPP; | |
430 | goto finish; | |
431 | } | |
432 | ||
3603efde LP |
433 | if (shift == UID_BUSY_BASE) { |
434 | r = -EINVAL; | |
435 | goto finish; | |
436 | } | |
437 | ||
7336138e LP |
438 | if (range != 0x10000) { |
439 | /* We only support containers with 16bit UID ranges for the patching logic */ | |
440 | r = -EOPNOTSUPP; | |
441 | goto finish; | |
442 | } | |
443 | ||
444 | if (fstat(fd, &st) < 0) { | |
445 | r = -errno; | |
446 | goto finish; | |
447 | } | |
448 | ||
449 | if ((uint32_t) st.st_uid >> 16 != (uint32_t) st.st_gid >> 16) { | |
450 | /* We only support containers where the uid/gid container ID match */ | |
451 | r = -EBADE; | |
452 | goto finish; | |
453 | } | |
454 | ||
455 | /* Try to detect if the range is already right. Of course, this a pretty drastic optimization, as we assume | |
456 | * that if the top-level dir has the right upper 16bit assigned, then everything below will have too... */ | |
457 | if (((uint32_t) (st.st_uid ^ shift) >> 16) == 0) | |
458 | return 0; | |
459 | ||
3603efde LP |
460 | /* Before we start recursively chowning, mark the top-level dir as "busy" by chowning it to the "busy" |
461 | * range. Should we be interrupted in the middle of our work, we'll see it owned by this user and will start | |
462 | * chown()ing it again, unconditionally, as the busy UID is not a valid UID we'd everpick for ourselves. */ | |
463 | ||
464 | if ((st.st_uid & UID_BUSY_MASK) != UID_BUSY_BASE) { | |
465 | if (fchown(fd, | |
466 | UID_BUSY_BASE | (st.st_uid & ~UID_BUSY_MASK), | |
467 | (gid_t) UID_BUSY_BASE | (st.st_gid & ~(gid_t) UID_BUSY_MASK)) < 0) { | |
468 | r = -errno; | |
469 | goto finish; | |
470 | } | |
471 | } | |
472 | ||
4aeb20f5 | 473 | return recurse_fd(fd, donate_fd, &st, shift, true); |
7336138e LP |
474 | |
475 | finish: | |
476 | if (donate_fd) | |
477 | safe_close(fd); | |
478 | ||
479 | return r; | |
480 | } | |
481 | ||
482 | int fd_patch_uid(int fd, uid_t shift, uid_t range) { | |
483 | return fd_patch_uid_internal(fd, false, shift, range); | |
484 | } | |
485 | ||
486 | int path_patch_uid(const char *path, uid_t shift, uid_t range) { | |
487 | int fd; | |
488 | ||
489 | fd = open(path, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW|O_NOATIME); | |
490 | if (fd < 0) | |
491 | return -errno; | |
492 | ||
493 | return fd_patch_uid_internal(fd, true, shift, range); | |
494 | } |