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53e1b683 | 1 | /* SPDX-License-Identifier: LGPL-2.1+ */ |
29206d46 LP |
2 | /*** |
3 | This file is part of systemd. | |
4 | ||
5 | Copyright 2016 Lennart Poettering | |
6 | ||
7 | systemd is free software; you can redistribute it and/or modify it | |
8 | under the terms of the GNU Lesser General Public License as published by | |
9 | the Free Software Foundation; either version 2.1 of the License, or | |
10 | (at your option) any later version. | |
11 | ||
12 | systemd is distributed in the hope that it will be useful, but | |
13 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
15 | Lesser General Public License for more details. | |
16 | ||
17 | You should have received a copy of the GNU Lesser General Public License | |
18 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
19 | ***/ | |
20 | ||
21 | #include <grp.h> | |
22 | #include <pwd.h> | |
23 | #include <sys/file.h> | |
24 | ||
98e4fcec | 25 | #include "clean-ipc.h" |
29206d46 LP |
26 | #include "dynamic-user.h" |
27 | #include "fd-util.h" | |
e6a7ec4b | 28 | #include "fileio.h" |
29206d46 | 29 | #include "fs-util.h" |
e6a7ec4b | 30 | #include "io-util.h" |
29206d46 LP |
31 | #include "parse-util.h" |
32 | #include "random-util.h" | |
33 | #include "stdio-util.h" | |
34 | #include "string-util.h" | |
35 | #include "user-util.h" | |
29206d46 | 36 | |
29206d46 | 37 | /* Takes a value generated randomly or by hashing and turns it into a UID in the right range */ |
61755fda | 38 | #define UID_CLAMP_INTO_RANGE(rnd) (((uid_t) (rnd) % (DYNAMIC_UID_MAX - DYNAMIC_UID_MIN + 1)) + DYNAMIC_UID_MIN) |
29206d46 LP |
39 | |
40 | static DynamicUser* dynamic_user_free(DynamicUser *d) { | |
41 | if (!d) | |
42 | return NULL; | |
43 | ||
44 | if (d->manager) | |
45 | (void) hashmap_remove(d->manager->dynamic_users, d->name); | |
46 | ||
47 | safe_close_pair(d->storage_socket); | |
6b430fdb | 48 | return mfree(d); |
29206d46 LP |
49 | } |
50 | ||
51 | static int dynamic_user_add(Manager *m, const char *name, int storage_socket[2], DynamicUser **ret) { | |
52 | DynamicUser *d = NULL; | |
53 | int r; | |
54 | ||
55 | assert(m); | |
56 | assert(name); | |
57 | assert(storage_socket); | |
58 | ||
59 | r = hashmap_ensure_allocated(&m->dynamic_users, &string_hash_ops); | |
60 | if (r < 0) | |
61 | return r; | |
62 | ||
63 | d = malloc0(offsetof(DynamicUser, name) + strlen(name) + 1); | |
64 | if (!d) | |
65 | return -ENOMEM; | |
66 | ||
67 | strcpy(d->name, name); | |
68 | ||
69 | d->storage_socket[0] = storage_socket[0]; | |
70 | d->storage_socket[1] = storage_socket[1]; | |
71 | ||
72 | r = hashmap_put(m->dynamic_users, d->name, d); | |
73 | if (r < 0) { | |
74 | free(d); | |
75 | return r; | |
76 | } | |
77 | ||
78 | d->manager = m; | |
79 | ||
80 | if (ret) | |
81 | *ret = d; | |
82 | ||
83 | return 0; | |
84 | } | |
85 | ||
9da440b1 | 86 | static int dynamic_user_acquire(Manager *m, const char *name, DynamicUser** ret) { |
29206d46 LP |
87 | _cleanup_close_pair_ int storage_socket[2] = { -1, -1 }; |
88 | DynamicUser *d; | |
89 | int r; | |
90 | ||
91 | assert(m); | |
92 | assert(name); | |
93 | ||
94 | /* Return the DynamicUser structure for a specific user name. Note that this won't actually allocate a UID for | |
95 | * it, but just prepare the data structure for it. The UID is allocated only on demand, when it's really | |
96 | * needed, and in the child process we fork off, since allocation involves NSS checks which are not OK to do | |
97 | * from PID 1. To allow the children and PID 1 share information about allocated UIDs we use an anonymous | |
98 | * AF_UNIX/SOCK_DGRAM socket (called the "storage socket") that contains at most one datagram with the | |
99 | * allocated UID number, plus an fd referencing the lock file for the UID | |
100 | * (i.e. /run/systemd/dynamic-uid/$UID). Why involve the socket pair? So that PID 1 and all its children can | |
101 | * share the same storage for the UID and lock fd, simply by inheriting the storage socket fds. The socket pair | |
102 | * may exist in three different states: | |
103 | * | |
104 | * a) no datagram stored. This is the initial state. In this case the dynamic user was never realized. | |
105 | * | |
106 | * b) a datagram containing a UID stored, but no lock fd attached to it. In this case there was already a | |
107 | * statically assigned UID by the same name, which we are reusing. | |
108 | * | |
109 | * c) a datagram containing a UID stored, and a lock fd is attached to it. In this case we allocated a dynamic | |
110 | * UID and locked it in the file system, using the lock fd. | |
111 | * | |
112 | * As PID 1 and various children might access the socket pair simultaneously, and pop the datagram or push it | |
113 | * back in any time, we also maintain a lock on the socket pair. Note one peculiarity regarding locking here: | |
114 | * the UID lock on disk is protected via a BSD file lock (i.e. an fd-bound lock), so that the lock is kept in | |
115 | * place as long as there's a reference to the fd open. The lock on the storage socket pair however is a POSIX | |
116 | * file lock (i.e. a process-bound lock), as all users share the same fd of this (after all it is anonymous, | |
117 | * nobody else could get any access to it except via our own fd) and we want to synchronize access between all | |
118 | * processes that have access to it. */ | |
119 | ||
120 | d = hashmap_get(m->dynamic_users, name); | |
121 | if (d) { | |
122 | /* We already have a structure for the dynamic user, let's increase the ref count and reuse it */ | |
123 | d->n_ref++; | |
124 | *ret = d; | |
125 | return 0; | |
126 | } | |
127 | ||
128 | if (!valid_user_group_name_or_id(name)) | |
129 | return -EINVAL; | |
130 | ||
131 | if (socketpair(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC, 0, storage_socket) < 0) | |
132 | return -errno; | |
133 | ||
134 | r = dynamic_user_add(m, name, storage_socket, &d); | |
135 | if (r < 0) | |
136 | return r; | |
137 | ||
138 | storage_socket[0] = storage_socket[1] = -1; | |
139 | ||
140 | if (ret) { | |
141 | d->n_ref++; | |
142 | *ret = d; | |
143 | } | |
144 | ||
145 | return 1; | |
146 | } | |
147 | ||
fd63e712 LP |
148 | static int make_uid_symlinks(uid_t uid, const char *name, bool b) { |
149 | ||
fbd0b64f | 150 | char path1[STRLEN("/run/systemd/dynamic-uid/direct:") + DECIMAL_STR_MAX(uid_t) + 1]; |
fd63e712 | 151 | const char *path2; |
986a34a6 | 152 | int r = 0, k; |
fd63e712 LP |
153 | |
154 | /* Add direct additional symlinks for direct lookups of dynamic UIDs and their names by userspace code. The | |
155 | * only reason we have this is because dbus-daemon cannot use D-Bus for resolving users and groups (since it | |
156 | * would be its own client then). We hence keep these world-readable symlinks in place, so that the | |
157 | * unprivileged dbus user can read the mappings when it needs them via these symlinks instead of having to go | |
158 | * via the bus. Ideally, we'd use the lock files we keep for this anyway, but we can't since we use BSD locks | |
159 | * on them and as those may be taken by any user with read access we can't make them world-readable. */ | |
160 | ||
161 | xsprintf(path1, "/run/systemd/dynamic-uid/direct:" UID_FMT, uid); | |
986a34a6 ZJS |
162 | if (unlink(path1) < 0 && errno != ENOENT) |
163 | r = -errno; | |
164 | ||
165 | if (b && symlink(name, path1) < 0) { | |
166 | k = log_warning_errno(errno, "Failed to symlink \"%s\": %m", path1); | |
167 | if (r == 0) | |
168 | r = k; | |
fd63e712 LP |
169 | } |
170 | ||
171 | path2 = strjoina("/run/systemd/dynamic-uid/direct:", name); | |
986a34a6 ZJS |
172 | if (unlink(path2) < 0 && errno != ENOENT) { |
173 | k = -errno; | |
174 | if (r == 0) | |
175 | r = k; | |
fd63e712 | 176 | } |
986a34a6 | 177 | |
fbd0b64f | 178 | if (b && symlink(path1 + STRLEN("/run/systemd/dynamic-uid/direct:"), path2) < 0) { |
986a34a6 ZJS |
179 | k = log_warning_errno(errno, "Failed to symlink \"%s\": %m", path2); |
180 | if (r == 0) | |
181 | r = k; | |
fd63e712 LP |
182 | } |
183 | ||
184 | return r; | |
185 | } | |
186 | ||
da50b85a LP |
187 | static int pick_uid(char **suggested_paths, const char *name, uid_t *ret_uid) { |
188 | ||
189 | /* Find a suitable free UID. We use the following strategy to find a suitable UID: | |
190 | * | |
191 | * 1. Initially, we try to read the UID of a number of specified paths. If any of these UIDs works, we use | |
192 | * them. We use in order to increase the chance of UID reuse, if StateDirectory=, CacheDirectory= or | |
193 | * LogDirectory= are used, as reusing the UID these directories are owned by saves us from having to | |
194 | * recursively chown() them to new users. | |
195 | * | |
196 | * 2. If that didn't yield a currently unused UID, we hash the user name, and try to use that. This should be | |
197 | * pretty good, as the use ris by default derived from the unit name, and hence the same service and same | |
198 | * user should usually get the same UID as long as our hashing doesn't clash. | |
199 | * | |
200 | * 3. Finally, if that didn't work, we randomly pick UIDs, until we find one that is empty. | |
201 | * | |
202 | * Since the dynamic UID space is relatively small we'll stop trying after 100 iterations, giving up. */ | |
203 | ||
204 | enum { | |
205 | PHASE_SUGGESTED, /* the first phase, reusing directory ownership UIDs */ | |
206 | PHASE_HASHED, /* the second phase, deriving a UID from the username by hashing */ | |
207 | PHASE_RANDOM, /* the last phase, randomly picking UIDs */ | |
208 | } phase = PHASE_SUGGESTED; | |
29206d46 LP |
209 | |
210 | static const uint8_t hash_key[] = { | |
211 | 0x37, 0x53, 0x7e, 0x31, 0xcf, 0xce, 0x48, 0xf5, | |
212 | 0x8a, 0xbb, 0x39, 0x57, 0x8d, 0xd9, 0xec, 0x59 | |
213 | }; | |
214 | ||
da50b85a | 215 | unsigned n_tries = 100, current_suggested = 0; |
29206d46 LP |
216 | int r; |
217 | ||
29206d46 LP |
218 | (void) mkdir("/run/systemd/dynamic-uid", 0755); |
219 | ||
220 | for (;;) { | |
fbd0b64f | 221 | char lock_path[STRLEN("/run/systemd/dynamic-uid/") + DECIMAL_STR_MAX(uid_t) + 1]; |
29206d46 | 222 | _cleanup_close_ int lock_fd = -1; |
da50b85a | 223 | uid_t candidate; |
29206d46 LP |
224 | ssize_t l; |
225 | ||
226 | if (--n_tries <= 0) /* Give up retrying eventually */ | |
227 | return -EBUSY; | |
228 | ||
da50b85a LP |
229 | switch (phase) { |
230 | ||
231 | case PHASE_SUGGESTED: { | |
232 | struct stat st; | |
233 | ||
234 | if (!suggested_paths || !suggested_paths[current_suggested]) { | |
235 | /* We reached the end of the suggested paths list, let's try by hashing the name */ | |
236 | phase = PHASE_HASHED; | |
237 | continue; | |
238 | } | |
239 | ||
240 | if (stat(suggested_paths[current_suggested++], &st) < 0) | |
241 | continue; /* We can't read the UID of this path, but that doesn't matter, just try the next */ | |
242 | ||
243 | candidate = st.st_uid; | |
244 | break; | |
245 | } | |
246 | ||
247 | case PHASE_HASHED: | |
248 | /* A static user by this name does not exist yet. Let's find a free ID then, and use that. We | |
249 | * start with a UID generated as hash from the user name. */ | |
250 | candidate = UID_CLAMP_INTO_RANGE(siphash24(name, strlen(name), hash_key)); | |
251 | ||
252 | /* If this one fails, we should proceed with random tries */ | |
253 | phase = PHASE_RANDOM; | |
254 | break; | |
255 | ||
256 | case PHASE_RANDOM: | |
257 | ||
258 | /* Pick another random UID, and see if that works for us. */ | |
259 | random_bytes(&candidate, sizeof(candidate)); | |
260 | candidate = UID_CLAMP_INTO_RANGE(candidate); | |
261 | break; | |
262 | ||
263 | default: | |
264 | assert_not_reached("unknown phase"); | |
265 | } | |
266 | ||
267 | /* Make sure whatever we picked here actually is in the right range */ | |
61755fda | 268 | if (!uid_is_dynamic(candidate)) |
da50b85a | 269 | continue; |
29206d46 LP |
270 | |
271 | xsprintf(lock_path, "/run/systemd/dynamic-uid/" UID_FMT, candidate); | |
272 | ||
273 | for (;;) { | |
274 | struct stat st; | |
275 | ||
276 | lock_fd = open(lock_path, O_CREAT|O_RDWR|O_NOFOLLOW|O_CLOEXEC|O_NOCTTY, 0600); | |
277 | if (lock_fd < 0) | |
278 | return -errno; | |
279 | ||
280 | r = flock(lock_fd, LOCK_EX|LOCK_NB); /* Try to get a BSD file lock on the UID lock file */ | |
281 | if (r < 0) { | |
3742095b | 282 | if (IN_SET(errno, EBUSY, EAGAIN)) |
29206d46 LP |
283 | goto next; /* already in use */ |
284 | ||
285 | return -errno; | |
286 | } | |
287 | ||
288 | if (fstat(lock_fd, &st) < 0) | |
289 | return -errno; | |
290 | if (st.st_nlink > 0) | |
291 | break; | |
292 | ||
629ff674 | 293 | /* Oh, bummer, we got the lock, but the file was unlinked between the time we opened it and |
29206d46 LP |
294 | * got the lock. Close it, and try again. */ |
295 | lock_fd = safe_close(lock_fd); | |
296 | } | |
297 | ||
298 | /* Some superficial check whether this UID/GID might already be taken by some static user */ | |
98e4fcec LP |
299 | if (getpwuid(candidate) || |
300 | getgrgid((gid_t) candidate) || | |
301 | search_ipc(candidate, (gid_t) candidate) != 0) { | |
29206d46 | 302 | (void) unlink(lock_path); |
da50b85a | 303 | continue; |
29206d46 LP |
304 | } |
305 | ||
306 | /* Let's store the user name in the lock file, so that we can use it for looking up the username for a UID */ | |
307 | l = pwritev(lock_fd, | |
308 | (struct iovec[2]) { | |
e6a7ec4b LP |
309 | IOVEC_INIT_STRING(name), |
310 | IOVEC_INIT((char[1]) { '\n' }, 1), | |
29206d46 LP |
311 | }, 2, 0); |
312 | if (l < 0) { | |
e53c42ca | 313 | r = -errno; |
29206d46 | 314 | (void) unlink(lock_path); |
e53c42ca | 315 | return r; |
29206d46 LP |
316 | } |
317 | ||
318 | (void) ftruncate(lock_fd, l); | |
fd63e712 | 319 | (void) make_uid_symlinks(candidate, name, true); /* also add direct lookup symlinks */ |
29206d46 LP |
320 | |
321 | *ret_uid = candidate; | |
322 | r = lock_fd; | |
323 | lock_fd = -1; | |
324 | ||
325 | return r; | |
326 | ||
327 | next: | |
da50b85a | 328 | ; |
29206d46 LP |
329 | } |
330 | } | |
331 | ||
332 | static int dynamic_user_pop(DynamicUser *d, uid_t *ret_uid, int *ret_lock_fd) { | |
333 | uid_t uid = UID_INVALID; | |
e6a7ec4b | 334 | struct iovec iov = IOVEC_INIT(&uid, sizeof(uid)); |
29206d46 LP |
335 | union { |
336 | struct cmsghdr cmsghdr; | |
337 | uint8_t buf[CMSG_SPACE(sizeof(int))]; | |
338 | } control = {}; | |
339 | struct msghdr mh = { | |
340 | .msg_control = &control, | |
341 | .msg_controllen = sizeof(control), | |
342 | .msg_iov = &iov, | |
343 | .msg_iovlen = 1, | |
344 | }; | |
345 | struct cmsghdr *cmsg; | |
346 | ||
347 | ssize_t k; | |
348 | int lock_fd = -1; | |
349 | ||
350 | assert(d); | |
351 | assert(ret_uid); | |
352 | assert(ret_lock_fd); | |
353 | ||
354 | /* Read the UID and lock fd that is stored in the storage AF_UNIX socket. This should be called with the lock | |
355 | * on the socket taken. */ | |
356 | ||
357 | k = recvmsg(d->storage_socket[0], &mh, MSG_DONTWAIT|MSG_NOSIGNAL|MSG_CMSG_CLOEXEC); | |
358 | if (k < 0) | |
359 | return -errno; | |
360 | ||
361 | cmsg = cmsg_find(&mh, SOL_SOCKET, SCM_RIGHTS, CMSG_LEN(sizeof(int))); | |
362 | if (cmsg) | |
363 | lock_fd = *(int*) CMSG_DATA(cmsg); | |
364 | else | |
365 | cmsg_close_all(&mh); /* just in case... */ | |
366 | ||
367 | *ret_uid = uid; | |
368 | *ret_lock_fd = lock_fd; | |
369 | ||
370 | return 0; | |
371 | } | |
372 | ||
373 | static int dynamic_user_push(DynamicUser *d, uid_t uid, int lock_fd) { | |
e6a7ec4b | 374 | struct iovec iov = IOVEC_INIT(&uid, sizeof(uid)); |
29206d46 LP |
375 | union { |
376 | struct cmsghdr cmsghdr; | |
377 | uint8_t buf[CMSG_SPACE(sizeof(int))]; | |
378 | } control = {}; | |
379 | struct msghdr mh = { | |
380 | .msg_control = &control, | |
381 | .msg_controllen = sizeof(control), | |
382 | .msg_iov = &iov, | |
383 | .msg_iovlen = 1, | |
384 | }; | |
385 | ssize_t k; | |
386 | ||
387 | assert(d); | |
388 | ||
389 | /* Store the UID and lock_fd in the storage socket. This should be called with the socket pair lock taken. */ | |
390 | ||
391 | if (lock_fd >= 0) { | |
392 | struct cmsghdr *cmsg; | |
393 | ||
394 | cmsg = CMSG_FIRSTHDR(&mh); | |
395 | cmsg->cmsg_level = SOL_SOCKET; | |
396 | cmsg->cmsg_type = SCM_RIGHTS; | |
397 | cmsg->cmsg_len = CMSG_LEN(sizeof(int)); | |
398 | memcpy(CMSG_DATA(cmsg), &lock_fd, sizeof(int)); | |
399 | ||
400 | mh.msg_controllen = CMSG_SPACE(sizeof(int)); | |
401 | } else { | |
402 | mh.msg_control = NULL; | |
403 | mh.msg_controllen = 0; | |
404 | } | |
405 | ||
406 | k = sendmsg(d->storage_socket[1], &mh, MSG_DONTWAIT|MSG_NOSIGNAL); | |
407 | if (k < 0) | |
408 | return -errno; | |
409 | ||
410 | return 0; | |
411 | } | |
412 | ||
fd63e712 | 413 | static void unlink_uid_lock(int lock_fd, uid_t uid, const char *name) { |
fbd0b64f | 414 | char lock_path[STRLEN("/run/systemd/dynamic-uid/") + DECIMAL_STR_MAX(uid_t) + 1]; |
29206d46 LP |
415 | |
416 | if (lock_fd < 0) | |
417 | return; | |
418 | ||
419 | xsprintf(lock_path, "/run/systemd/dynamic-uid/" UID_FMT, uid); | |
fd63e712 LP |
420 | (void) unlink(lock_path); |
421 | ||
422 | (void) make_uid_symlinks(uid, name, false); /* remove direct lookup symlinks */ | |
29206d46 LP |
423 | } |
424 | ||
362d90b7 ZJS |
425 | static int lockfp(int fd, int *fd_lock) { |
426 | if (lockf(fd, F_LOCK, 0) < 0) | |
427 | return -errno; | |
428 | *fd_lock = fd; | |
429 | return 0; | |
430 | } | |
431 | ||
432 | static void unlockfp(int *fd_lock) { | |
433 | if (*fd_lock < 0) | |
434 | return; | |
435 | lockf(*fd_lock, F_ULOCK, 0); | |
436 | *fd_lock = -1; | |
437 | } | |
438 | ||
c2983a7f ZJS |
439 | static int dynamic_user_realize( |
440 | DynamicUser *d, | |
441 | char **suggested_dirs, | |
442 | uid_t *ret_uid, gid_t *ret_gid, | |
443 | bool is_user) { | |
29206d46 | 444 | |
362d90b7 ZJS |
445 | _cleanup_(unlockfp) int storage_socket0_lock = -1; |
446 | _cleanup_close_ int uid_lock_fd = -1; | |
447 | _cleanup_close_ int etc_passwd_lock_fd = -1; | |
c2983a7f ZJS |
448 | uid_t num = UID_INVALID; /* a uid if is_user, and a gid otherwise */ |
449 | gid_t gid = GID_INVALID; /* a gid if is_user, ignored otherwise */ | |
29206d46 LP |
450 | int r; |
451 | ||
452 | assert(d); | |
c2983a7f ZJS |
453 | assert(is_user == !!ret_uid); |
454 | assert(ret_gid); | |
29206d46 LP |
455 | |
456 | /* Acquire a UID for the user name. This will allocate a UID for the user name if the user doesn't exist | |
457 | * yet. If it already exists its existing UID/GID will be reused. */ | |
458 | ||
362d90b7 ZJS |
459 | r = lockfp(d->storage_socket[0], &storage_socket0_lock); |
460 | if (r < 0) | |
461 | return r; | |
29206d46 | 462 | |
c2983a7f | 463 | r = dynamic_user_pop(d, &num, &uid_lock_fd); |
29206d46 LP |
464 | if (r < 0) { |
465 | int new_uid_lock_fd; | |
466 | uid_t new_uid; | |
467 | ||
468 | if (r != -EAGAIN) | |
362d90b7 | 469 | return r; |
29206d46 LP |
470 | |
471 | /* OK, nothing stored yet, let's try to find something useful. While we are working on this release the | |
472 | * lock however, so that nobody else blocks on our NSS lookups. */ | |
362d90b7 | 473 | unlockfp(&storage_socket0_lock); |
29206d46 LP |
474 | |
475 | /* Let's see if a proper, static user or group by this name exists. Try to take the lock on | |
476 | * /etc/passwd, if that fails with EROFS then /etc is read-only. In that case it's fine if we don't | |
477 | * take the lock, given that users can't be added there anyway in this case. */ | |
478 | etc_passwd_lock_fd = take_etc_passwd_lock(NULL); | |
479 | if (etc_passwd_lock_fd < 0 && etc_passwd_lock_fd != -EROFS) | |
480 | return etc_passwd_lock_fd; | |
481 | ||
482 | /* First, let's parse this as numeric UID */ | |
c2983a7f | 483 | r = parse_uid(d->name, &num); |
29206d46 LP |
484 | if (r < 0) { |
485 | struct passwd *p; | |
486 | struct group *g; | |
487 | ||
9ec655cb YW |
488 | if (is_user) { |
489 | /* OK, this is not a numeric UID. Let's see if there's a user by this name */ | |
490 | p = getpwnam(d->name); | |
c2983a7f ZJS |
491 | if (p) { |
492 | num = p->pw_uid; | |
493 | gid = p->pw_gid; | |
494 | } else { | |
9ec655cb YW |
495 | /* if the user does not exist but the group with the same name exists, refuse operation */ |
496 | g = getgrnam(d->name); | |
497 | if (g) | |
498 | return -EILSEQ; | |
499 | } | |
500 | } else { | |
501 | /* Let's see if there's a group by this name */ | |
502 | g = getgrnam(d->name); | |
503 | if (g) | |
c2983a7f | 504 | num = (uid_t) g->gr_gid; |
9ec655cb YW |
505 | else { |
506 | /* if the group does not exist but the user with the same name exists, refuse operation */ | |
507 | p = getpwnam(d->name); | |
508 | if (p) | |
509 | return -EILSEQ; | |
510 | } | |
29206d46 LP |
511 | } |
512 | } | |
513 | ||
c2983a7f | 514 | if (num == UID_INVALID) { |
29206d46 LP |
515 | /* No static UID assigned yet, excellent. Let's pick a new dynamic one, and lock it. */ |
516 | ||
c2983a7f | 517 | uid_lock_fd = pick_uid(suggested_dirs, d->name, &num); |
29206d46 LP |
518 | if (uid_lock_fd < 0) |
519 | return uid_lock_fd; | |
520 | } | |
521 | ||
522 | /* So, we found a working UID/lock combination. Let's see if we actually still need it. */ | |
362d90b7 ZJS |
523 | r = lockfp(d->storage_socket[0], &storage_socket0_lock); |
524 | if (r < 0) { | |
c2983a7f | 525 | unlink_uid_lock(uid_lock_fd, num, d->name); |
362d90b7 | 526 | return r; |
29206d46 LP |
527 | } |
528 | ||
529 | r = dynamic_user_pop(d, &new_uid, &new_uid_lock_fd); | |
530 | if (r < 0) { | |
531 | if (r != -EAGAIN) { | |
532 | /* OK, something bad happened, let's get rid of the bits we acquired. */ | |
c2983a7f | 533 | unlink_uid_lock(uid_lock_fd, num, d->name); |
362d90b7 | 534 | return r; |
29206d46 LP |
535 | } |
536 | ||
537 | /* Great! Nothing is stored here, still. Store our newly acquired data. */ | |
538 | } else { | |
539 | /* Hmm, so as it appears there's now something stored in the storage socket. Throw away what we | |
540 | * acquired, and use what's stored now. */ | |
541 | ||
c2983a7f | 542 | unlink_uid_lock(uid_lock_fd, num, d->name); |
29206d46 LP |
543 | safe_close(uid_lock_fd); |
544 | ||
c2983a7f | 545 | num = new_uid; |
29206d46 LP |
546 | uid_lock_fd = new_uid_lock_fd; |
547 | } | |
548 | } | |
549 | ||
550 | /* If the UID/GID was already allocated dynamically, push the data we popped out back in. If it was already | |
551 | * allocated statically, push the UID back too, but do not push the lock fd in. If we allocated the UID | |
552 | * dynamically right here, push that in along with the lock fd for it. */ | |
c2983a7f | 553 | r = dynamic_user_push(d, num, uid_lock_fd); |
29206d46 | 554 | if (r < 0) |
362d90b7 | 555 | return r; |
29206d46 | 556 | |
c2983a7f ZJS |
557 | if (is_user) { |
558 | *ret_uid = num; | |
559 | *ret_gid = gid != GID_INVALID ? gid : num; | |
560 | } else | |
561 | *ret_gid = num; | |
562 | ||
362d90b7 | 563 | return 0; |
29206d46 LP |
564 | } |
565 | ||
9da440b1 | 566 | static int dynamic_user_current(DynamicUser *d, uid_t *ret) { |
362d90b7 | 567 | _cleanup_(unlockfp) int storage_socket0_lock = -1; |
29206d46 LP |
568 | _cleanup_close_ int lock_fd = -1; |
569 | uid_t uid; | |
570 | int r; | |
571 | ||
572 | assert(d); | |
573 | assert(ret); | |
574 | ||
575 | /* Get the currently assigned UID for the user, if there's any. This simply pops the data from the storage socket, and pushes it back in right-away. */ | |
576 | ||
362d90b7 ZJS |
577 | r = lockfp(d->storage_socket[0], &storage_socket0_lock); |
578 | if (r < 0) | |
579 | return r; | |
29206d46 LP |
580 | |
581 | r = dynamic_user_pop(d, &uid, &lock_fd); | |
582 | if (r < 0) | |
362d90b7 | 583 | return r; |
29206d46 LP |
584 | |
585 | r = dynamic_user_push(d, uid, lock_fd); | |
586 | if (r < 0) | |
362d90b7 | 587 | return r; |
29206d46 LP |
588 | |
589 | *ret = uid; | |
362d90b7 | 590 | return 0; |
29206d46 LP |
591 | } |
592 | ||
9da440b1 | 593 | static DynamicUser* dynamic_user_ref(DynamicUser *d) { |
29206d46 LP |
594 | if (!d) |
595 | return NULL; | |
596 | ||
597 | assert(d->n_ref > 0); | |
598 | d->n_ref++; | |
599 | ||
600 | return d; | |
601 | } | |
602 | ||
9da440b1 | 603 | static DynamicUser* dynamic_user_unref(DynamicUser *d) { |
29206d46 LP |
604 | if (!d) |
605 | return NULL; | |
606 | ||
607 | /* Note that this doesn't actually release any resources itself. If a dynamic user should be fully destroyed | |
608 | * and its UID released, use dynamic_user_destroy() instead. NB: the dynamic user table may contain entries | |
609 | * with no references, which is commonly the case right before a daemon reload. */ | |
610 | ||
611 | assert(d->n_ref > 0); | |
612 | d->n_ref--; | |
613 | ||
614 | return NULL; | |
615 | } | |
616 | ||
617 | static int dynamic_user_close(DynamicUser *d) { | |
362d90b7 | 618 | _cleanup_(unlockfp) int storage_socket0_lock = -1; |
29206d46 LP |
619 | _cleanup_close_ int lock_fd = -1; |
620 | uid_t uid; | |
621 | int r; | |
622 | ||
623 | /* Release the user ID, by releasing the lock on it, and emptying the storage socket. After this the user is | |
624 | * unrealized again, much like it was after it the DynamicUser object was first allocated. */ | |
625 | ||
362d90b7 ZJS |
626 | r = lockfp(d->storage_socket[0], &storage_socket0_lock); |
627 | if (r < 0) | |
628 | return r; | |
29206d46 LP |
629 | |
630 | r = dynamic_user_pop(d, &uid, &lock_fd); | |
362d90b7 | 631 | if (r == -EAGAIN) |
29206d46 | 632 | /* User wasn't realized yet, nothing to do. */ |
362d90b7 | 633 | return 0; |
29206d46 | 634 | if (r < 0) |
362d90b7 | 635 | return r; |
29206d46 LP |
636 | |
637 | /* This dynamic user was realized and dynamically allocated. In this case, let's remove the lock file. */ | |
fd63e712 | 638 | unlink_uid_lock(lock_fd, uid, d->name); |
362d90b7 | 639 | return 1; |
29206d46 LP |
640 | } |
641 | ||
9da440b1 | 642 | static DynamicUser* dynamic_user_destroy(DynamicUser *d) { |
29206d46 LP |
643 | if (!d) |
644 | return NULL; | |
645 | ||
646 | /* Drop a reference to a DynamicUser object, and destroy the user completely if this was the last | |
647 | * reference. This is called whenever a service is shut down and wants its dynamic UID gone. Note that | |
648 | * dynamic_user_unref() is what is called whenever a service is simply freed, for example during a reload | |
649 | * cycle, where the dynamic users should not be destroyed, but our datastructures should. */ | |
650 | ||
651 | dynamic_user_unref(d); | |
652 | ||
653 | if (d->n_ref > 0) | |
654 | return NULL; | |
655 | ||
656 | (void) dynamic_user_close(d); | |
657 | return dynamic_user_free(d); | |
658 | } | |
659 | ||
660 | int dynamic_user_serialize(Manager *m, FILE *f, FDSet *fds) { | |
661 | DynamicUser *d; | |
662 | Iterator i; | |
663 | ||
664 | assert(m); | |
665 | assert(f); | |
666 | assert(fds); | |
667 | ||
668 | /* Dump the dynamic user database into the manager serialization, to deal with daemon reloads. */ | |
669 | ||
670 | HASHMAP_FOREACH(d, m->dynamic_users, i) { | |
671 | int copy0, copy1; | |
672 | ||
673 | copy0 = fdset_put_dup(fds, d->storage_socket[0]); | |
674 | if (copy0 < 0) | |
675 | return copy0; | |
676 | ||
677 | copy1 = fdset_put_dup(fds, d->storage_socket[1]); | |
678 | if (copy1 < 0) | |
679 | return copy1; | |
680 | ||
681 | fprintf(f, "dynamic-user=%s %i %i\n", d->name, copy0, copy1); | |
682 | } | |
683 | ||
684 | return 0; | |
685 | } | |
686 | ||
687 | void dynamic_user_deserialize_one(Manager *m, const char *value, FDSet *fds) { | |
688 | _cleanup_free_ char *name = NULL, *s0 = NULL, *s1 = NULL; | |
689 | int r, fd0, fd1; | |
690 | ||
691 | assert(m); | |
692 | assert(value); | |
693 | assert(fds); | |
694 | ||
695 | /* Parse the serialization again, after a daemon reload */ | |
696 | ||
697 | r = extract_many_words(&value, NULL, 0, &name, &s0, &s1, NULL); | |
698 | if (r != 3 || !isempty(value)) { | |
699 | log_debug("Unable to parse dynamic user line."); | |
700 | return; | |
701 | } | |
702 | ||
703 | if (safe_atoi(s0, &fd0) < 0 || !fdset_contains(fds, fd0)) { | |
704 | log_debug("Unable to process dynamic user fd specification."); | |
705 | return; | |
706 | } | |
707 | ||
708 | if (safe_atoi(s1, &fd1) < 0 || !fdset_contains(fds, fd1)) { | |
709 | log_debug("Unable to process dynamic user fd specification."); | |
710 | return; | |
711 | } | |
712 | ||
713 | r = dynamic_user_add(m, name, (int[]) { fd0, fd1 }, NULL); | |
714 | if (r < 0) { | |
715 | log_debug_errno(r, "Failed to add dynamic user: %m"); | |
716 | return; | |
717 | } | |
718 | ||
719 | (void) fdset_remove(fds, fd0); | |
720 | (void) fdset_remove(fds, fd1); | |
721 | } | |
722 | ||
723 | void dynamic_user_vacuum(Manager *m, bool close_user) { | |
724 | DynamicUser *d; | |
725 | Iterator i; | |
726 | ||
727 | assert(m); | |
728 | ||
729 | /* Empty the dynamic user database, optionally cleaning up orphaned dynamic users, i.e. destroy and free users | |
730 | * to which no reference exist. This is called after a daemon reload finished, in order to destroy users which | |
731 | * might not be referenced anymore. */ | |
732 | ||
733 | HASHMAP_FOREACH(d, m->dynamic_users, i) { | |
734 | if (d->n_ref > 0) | |
735 | continue; | |
736 | ||
737 | if (close_user) { | |
738 | log_debug("Removing orphaned dynamic user %s", d->name); | |
739 | (void) dynamic_user_close(d); | |
740 | } | |
741 | ||
742 | dynamic_user_free(d); | |
743 | } | |
744 | } | |
745 | ||
746 | int dynamic_user_lookup_uid(Manager *m, uid_t uid, char **ret) { | |
fbd0b64f | 747 | char lock_path[STRLEN("/run/systemd/dynamic-uid/") + DECIMAL_STR_MAX(uid_t) + 1]; |
29206d46 LP |
748 | _cleanup_free_ char *user = NULL; |
749 | uid_t check_uid; | |
750 | int r; | |
751 | ||
752 | assert(m); | |
753 | assert(ret); | |
754 | ||
61755fda ZJS |
755 | /* A friendly way to translate a dynamic user's UID into a name. */ |
756 | if (!uid_is_dynamic(uid)) | |
29206d46 LP |
757 | return -ESRCH; |
758 | ||
759 | xsprintf(lock_path, "/run/systemd/dynamic-uid/" UID_FMT, uid); | |
760 | r = read_one_line_file(lock_path, &user); | |
761 | if (r == -ENOENT) | |
762 | return -ESRCH; | |
763 | if (r < 0) | |
764 | return r; | |
765 | ||
766 | /* The lock file might be stale, hence let's verify the data before we return it */ | |
767 | r = dynamic_user_lookup_name(m, user, &check_uid); | |
768 | if (r < 0) | |
769 | return r; | |
770 | if (check_uid != uid) /* lock file doesn't match our own idea */ | |
771 | return -ESRCH; | |
772 | ||
773 | *ret = user; | |
774 | user = NULL; | |
775 | ||
776 | return 0; | |
777 | } | |
778 | ||
779 | int dynamic_user_lookup_name(Manager *m, const char *name, uid_t *ret) { | |
780 | DynamicUser *d; | |
781 | int r; | |
782 | ||
783 | assert(m); | |
784 | assert(name); | |
785 | assert(ret); | |
786 | ||
787 | /* A friendly call for translating a dynamic user's name into its UID */ | |
788 | ||
789 | d = hashmap_get(m->dynamic_users, name); | |
790 | if (!d) | |
791 | return -ESRCH; | |
792 | ||
793 | r = dynamic_user_current(d, ret); | |
794 | if (r == -EAGAIN) /* not realized yet? */ | |
795 | return -ESRCH; | |
796 | ||
797 | return r; | |
798 | } | |
799 | ||
800 | int dynamic_creds_acquire(DynamicCreds *creds, Manager *m, const char *user, const char *group) { | |
801 | bool acquired = false; | |
802 | int r; | |
803 | ||
804 | assert(creds); | |
805 | assert(m); | |
806 | ||
807 | /* A DynamicUser object encapsulates an allocation of both a UID and a GID for a specific name. However, some | |
808 | * services use different user and groups. For cases like that there's DynamicCreds containing a pair of user | |
809 | * and group. This call allocates a pair. */ | |
810 | ||
811 | if (!creds->user && user) { | |
812 | r = dynamic_user_acquire(m, user, &creds->user); | |
813 | if (r < 0) | |
814 | return r; | |
815 | ||
816 | acquired = true; | |
817 | } | |
818 | ||
819 | if (!creds->group) { | |
820 | ||
821 | if (creds->user && (!group || streq_ptr(user, group))) | |
822 | creds->group = dynamic_user_ref(creds->user); | |
823 | else { | |
824 | r = dynamic_user_acquire(m, group, &creds->group); | |
825 | if (r < 0) { | |
826 | if (acquired) | |
827 | creds->user = dynamic_user_unref(creds->user); | |
828 | return r; | |
829 | } | |
830 | } | |
831 | } | |
832 | ||
833 | return 0; | |
834 | } | |
835 | ||
da50b85a | 836 | int dynamic_creds_realize(DynamicCreds *creds, char **suggested_paths, uid_t *uid, gid_t *gid) { |
29206d46 LP |
837 | uid_t u = UID_INVALID; |
838 | gid_t g = GID_INVALID; | |
839 | int r; | |
840 | ||
841 | assert(creds); | |
842 | assert(uid); | |
843 | assert(gid); | |
844 | ||
845 | /* Realize both the referenced user and group */ | |
846 | ||
847 | if (creds->user) { | |
c2983a7f | 848 | r = dynamic_user_realize(creds->user, suggested_paths, &u, &g, true); |
29206d46 LP |
849 | if (r < 0) |
850 | return r; | |
851 | } | |
852 | ||
853 | if (creds->group && creds->group != creds->user) { | |
c2983a7f | 854 | r = dynamic_user_realize(creds->group, suggested_paths, NULL, &g, false); |
29206d46 LP |
855 | if (r < 0) |
856 | return r; | |
c2983a7f | 857 | } |
29206d46 LP |
858 | |
859 | *uid = u; | |
860 | *gid = g; | |
29206d46 LP |
861 | return 0; |
862 | } | |
863 | ||
864 | void dynamic_creds_unref(DynamicCreds *creds) { | |
865 | assert(creds); | |
866 | ||
867 | creds->user = dynamic_user_unref(creds->user); | |
868 | creds->group = dynamic_user_unref(creds->group); | |
869 | } | |
870 | ||
871 | void dynamic_creds_destroy(DynamicCreds *creds) { | |
872 | assert(creds); | |
873 | ||
874 | creds->user = dynamic_user_destroy(creds->user); | |
875 | creds->group = dynamic_user_destroy(creds->group); | |
876 | } |