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53e1b683 | 1 | /* SPDX-License-Identifier: LGPL-2.1+ */ |
b1d4f8e1 LP |
2 | /*** |
3 | This file is part of systemd. | |
4 | ||
5 | Copyright 2010 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 | ||
11c3a366 TA |
21 | #include <alloca.h> |
22 | #include <errno.h> | |
23 | #include <fcntl.h> | |
b1d4f8e1 | 24 | #include <grp.h> |
cf0fbc49 | 25 | #include <pwd.h> |
11c3a366 TA |
26 | #include <stddef.h> |
27 | #include <stdint.h> | |
28 | #include <stdio.h> | |
29 | #include <stdlib.h> | |
30 | #include <string.h> | |
31 | #include <sys/stat.h> | |
32 | #include <unistd.h> | |
e4631b48 | 33 | #include <utmp.h> |
b1d4f8e1 | 34 | |
b5efdb8a | 35 | #include "alloc-util.h" |
e929bee0 | 36 | #include "fd-util.h" |
36d85478 | 37 | #include "fileio.h" |
f97b34a6 | 38 | #include "format-util.h" |
b1d4f8e1 | 39 | #include "macro.h" |
be39ccf3 | 40 | #include "missing.h" |
6bedfcbb | 41 | #include "parse-util.h" |
b1d4f8e1 | 42 | #include "path-util.h" |
6bedfcbb | 43 | #include "string-util.h" |
be39ccf3 | 44 | #include "strv.h" |
6bedfcbb | 45 | #include "user-util.h" |
e4631b48 | 46 | #include "utf8.h" |
b1d4f8e1 LP |
47 | |
48 | bool uid_is_valid(uid_t uid) { | |
49 | ||
1429dfe5 LP |
50 | /* Also see POSIX IEEE Std 1003.1-2008, 2016 Edition, 3.436. */ |
51 | ||
b1d4f8e1 | 52 | /* Some libc APIs use UID_INVALID as special placeholder */ |
b1d52773 | 53 | if (uid == (uid_t) UINT32_C(0xFFFFFFFF)) |
b1d4f8e1 LP |
54 | return false; |
55 | ||
56 | /* A long time ago UIDs where 16bit, hence explicitly avoid the 16bit -1 too */ | |
b1d52773 | 57 | if (uid == (uid_t) UINT32_C(0xFFFF)) |
b1d4f8e1 LP |
58 | return false; |
59 | ||
60 | return true; | |
61 | } | |
62 | ||
b1d52773 LP |
63 | int parse_uid(const char *s, uid_t *ret) { |
64 | uint32_t uid = 0; | |
b1d4f8e1 LP |
65 | int r; |
66 | ||
67 | assert(s); | |
68 | ||
b1d52773 LP |
69 | assert_cc(sizeof(uid_t) == sizeof(uint32_t)); |
70 | r = safe_atou32(s, &uid); | |
b1d4f8e1 LP |
71 | if (r < 0) |
72 | return r; | |
73 | ||
b1d4f8e1 LP |
74 | if (!uid_is_valid(uid)) |
75 | return -ENXIO; /* we return ENXIO instead of EINVAL | |
76 | * here, to make it easy to distuingish | |
ba60af86 | 77 | * invalid numeric uids from invalid |
b1d4f8e1 LP |
78 | * strings. */ |
79 | ||
b1d52773 LP |
80 | if (ret) |
81 | *ret = uid; | |
b1d4f8e1 LP |
82 | |
83 | return 0; | |
84 | } | |
85 | ||
b1d4f8e1 LP |
86 | char* getlogname_malloc(void) { |
87 | uid_t uid; | |
88 | struct stat st; | |
89 | ||
90 | if (isatty(STDIN_FILENO) && fstat(STDIN_FILENO, &st) >= 0) | |
91 | uid = st.st_uid; | |
92 | else | |
93 | uid = getuid(); | |
94 | ||
d0260817 | 95 | return uid_to_name(uid); |
b1d4f8e1 LP |
96 | } |
97 | ||
98 | char *getusername_malloc(void) { | |
99 | const char *e; | |
100 | ||
101 | e = getenv("USER"); | |
102 | if (e) | |
103 | return strdup(e); | |
104 | ||
d0260817 | 105 | return uid_to_name(getuid()); |
b1d4f8e1 LP |
106 | } |
107 | ||
108 | int get_user_creds( | |
109 | const char **username, | |
110 | uid_t *uid, gid_t *gid, | |
111 | const char **home, | |
112 | const char **shell) { | |
113 | ||
114 | struct passwd *p; | |
115 | uid_t u; | |
116 | ||
117 | assert(username); | |
118 | assert(*username); | |
119 | ||
120 | /* We enforce some special rules for uid=0: in order to avoid | |
121 | * NSS lookups for root we hardcode its data. */ | |
122 | ||
123 | if (streq(*username, "root") || streq(*username, "0")) { | |
124 | *username = "root"; | |
125 | ||
126 | if (uid) | |
127 | *uid = 0; | |
128 | ||
129 | if (gid) | |
130 | *gid = 0; | |
131 | ||
132 | if (home) | |
133 | *home = "/root"; | |
134 | ||
135 | if (shell) | |
136 | *shell = "/bin/sh"; | |
137 | ||
138 | return 0; | |
139 | } | |
140 | ||
141 | if (parse_uid(*username, &u) >= 0) { | |
142 | errno = 0; | |
143 | p = getpwuid(u); | |
144 | ||
145 | /* If there are multiple users with the same id, make | |
146 | * sure to leave $USER to the configured value instead | |
147 | * of the first occurrence in the database. However if | |
148 | * the uid was configured by a numeric uid, then let's | |
149 | * pick the real username from /etc/passwd. */ | |
150 | if (p) | |
151 | *username = p->pw_name; | |
152 | } else { | |
153 | errno = 0; | |
154 | p = getpwnam(*username); | |
155 | } | |
156 | ||
157 | if (!p) | |
158 | return errno > 0 ? -errno : -ESRCH; | |
159 | ||
67c7c892 LP |
160 | if (uid) { |
161 | if (!uid_is_valid(p->pw_uid)) | |
162 | return -EBADMSG; | |
163 | ||
b1d4f8e1 | 164 | *uid = p->pw_uid; |
67c7c892 LP |
165 | } |
166 | ||
167 | if (gid) { | |
168 | if (!gid_is_valid(p->pw_gid)) | |
169 | return -EBADMSG; | |
b1d4f8e1 | 170 | |
b1d4f8e1 | 171 | *gid = p->pw_gid; |
67c7c892 | 172 | } |
b1d4f8e1 LP |
173 | |
174 | if (home) | |
175 | *home = p->pw_dir; | |
176 | ||
177 | if (shell) | |
178 | *shell = p->pw_shell; | |
179 | ||
180 | return 0; | |
181 | } | |
182 | ||
be39ccf3 LP |
183 | int get_user_creds_clean( |
184 | const char **username, | |
185 | uid_t *uid, gid_t *gid, | |
186 | const char **home, | |
187 | const char **shell) { | |
188 | ||
189 | int r; | |
190 | ||
191 | /* Like get_user_creds(), but resets home/shell to NULL if they don't contain anything relevant. */ | |
192 | ||
193 | r = get_user_creds(username, uid, gid, home, shell); | |
194 | if (r < 0) | |
195 | return r; | |
196 | ||
197 | if (shell && | |
198 | (isempty(*shell) || PATH_IN_SET(*shell, | |
199 | "/bin/nologin", | |
200 | "/sbin/nologin", | |
201 | "/usr/bin/nologin", | |
202 | "/usr/sbin/nologin"))) | |
203 | *shell = NULL; | |
204 | ||
205 | if (home && | |
206 | (isempty(*home) || path_equal(*home, "/"))) | |
207 | *home = NULL; | |
208 | ||
209 | return 0; | |
210 | } | |
211 | ||
b1d4f8e1 LP |
212 | int get_group_creds(const char **groupname, gid_t *gid) { |
213 | struct group *g; | |
214 | gid_t id; | |
215 | ||
216 | assert(groupname); | |
217 | ||
218 | /* We enforce some special rules for gid=0: in order to avoid | |
219 | * NSS lookups for root we hardcode its data. */ | |
220 | ||
221 | if (streq(*groupname, "root") || streq(*groupname, "0")) { | |
222 | *groupname = "root"; | |
223 | ||
224 | if (gid) | |
225 | *gid = 0; | |
226 | ||
227 | return 0; | |
228 | } | |
229 | ||
230 | if (parse_gid(*groupname, &id) >= 0) { | |
231 | errno = 0; | |
232 | g = getgrgid(id); | |
233 | ||
234 | if (g) | |
235 | *groupname = g->gr_name; | |
236 | } else { | |
237 | errno = 0; | |
238 | g = getgrnam(*groupname); | |
239 | } | |
240 | ||
241 | if (!g) | |
242 | return errno > 0 ? -errno : -ESRCH; | |
243 | ||
67c7c892 LP |
244 | if (gid) { |
245 | if (!gid_is_valid(g->gr_gid)) | |
246 | return -EBADMSG; | |
247 | ||
b1d4f8e1 | 248 | *gid = g->gr_gid; |
67c7c892 | 249 | } |
b1d4f8e1 LP |
250 | |
251 | return 0; | |
252 | } | |
253 | ||
254 | char* uid_to_name(uid_t uid) { | |
d0260817 LP |
255 | char *ret; |
256 | int r; | |
b1d4f8e1 | 257 | |
d0260817 | 258 | /* Shortcut things to avoid NSS lookups */ |
b1d4f8e1 LP |
259 | if (uid == 0) |
260 | return strdup("root"); | |
261 | ||
d0260817 LP |
262 | if (uid_is_valid(uid)) { |
263 | long bufsize; | |
264 | ||
265 | bufsize = sysconf(_SC_GETPW_R_SIZE_MAX); | |
266 | if (bufsize <= 0) | |
267 | bufsize = 4096; | |
268 | ||
269 | for (;;) { | |
270 | struct passwd pwbuf, *pw = NULL; | |
271 | _cleanup_free_ char *buf = NULL; | |
272 | ||
273 | buf = malloc(bufsize); | |
274 | if (!buf) | |
275 | return NULL; | |
276 | ||
277 | r = getpwuid_r(uid, &pwbuf, buf, (size_t) bufsize, &pw); | |
278 | if (r == 0 && pw) | |
279 | return strdup(pw->pw_name); | |
280 | if (r != ERANGE) | |
281 | break; | |
282 | ||
283 | bufsize *= 2; | |
284 | } | |
285 | } | |
b1d4f8e1 | 286 | |
d0260817 | 287 | if (asprintf(&ret, UID_FMT, uid) < 0) |
b1d4f8e1 LP |
288 | return NULL; |
289 | ||
d0260817 | 290 | return ret; |
b1d4f8e1 LP |
291 | } |
292 | ||
293 | char* gid_to_name(gid_t gid) { | |
d0260817 LP |
294 | char *ret; |
295 | int r; | |
b1d4f8e1 LP |
296 | |
297 | if (gid == 0) | |
298 | return strdup("root"); | |
299 | ||
d0260817 LP |
300 | if (gid_is_valid(gid)) { |
301 | long bufsize; | |
302 | ||
303 | bufsize = sysconf(_SC_GETGR_R_SIZE_MAX); | |
304 | if (bufsize <= 0) | |
305 | bufsize = 4096; | |
306 | ||
307 | for (;;) { | |
308 | struct group grbuf, *gr = NULL; | |
309 | _cleanup_free_ char *buf = NULL; | |
310 | ||
311 | buf = malloc(bufsize); | |
312 | if (!buf) | |
313 | return NULL; | |
314 | ||
315 | r = getgrgid_r(gid, &grbuf, buf, (size_t) bufsize, &gr); | |
316 | if (r == 0 && gr) | |
317 | return strdup(gr->gr_name); | |
318 | if (r != ERANGE) | |
319 | break; | |
320 | ||
321 | bufsize *= 2; | |
322 | } | |
323 | } | |
b1d4f8e1 | 324 | |
d0260817 | 325 | if (asprintf(&ret, GID_FMT, gid) < 0) |
b1d4f8e1 LP |
326 | return NULL; |
327 | ||
d0260817 | 328 | return ret; |
b1d4f8e1 LP |
329 | } |
330 | ||
331 | int in_gid(gid_t gid) { | |
332 | gid_t *gids; | |
333 | int ngroups_max, r, i; | |
334 | ||
335 | if (getgid() == gid) | |
336 | return 1; | |
337 | ||
338 | if (getegid() == gid) | |
339 | return 1; | |
340 | ||
67c7c892 LP |
341 | if (!gid_is_valid(gid)) |
342 | return -EINVAL; | |
343 | ||
b1d4f8e1 LP |
344 | ngroups_max = sysconf(_SC_NGROUPS_MAX); |
345 | assert(ngroups_max > 0); | |
346 | ||
347 | gids = alloca(sizeof(gid_t) * ngroups_max); | |
348 | ||
349 | r = getgroups(ngroups_max, gids); | |
350 | if (r < 0) | |
351 | return -errno; | |
352 | ||
353 | for (i = 0; i < r; i++) | |
354 | if (gids[i] == gid) | |
355 | return 1; | |
356 | ||
357 | return 0; | |
358 | } | |
359 | ||
360 | int in_group(const char *name) { | |
361 | int r; | |
362 | gid_t gid; | |
363 | ||
364 | r = get_group_creds(&name, &gid); | |
365 | if (r < 0) | |
366 | return r; | |
367 | ||
368 | return in_gid(gid); | |
369 | } | |
370 | ||
371 | int get_home_dir(char **_h) { | |
372 | struct passwd *p; | |
373 | const char *e; | |
374 | char *h; | |
375 | uid_t u; | |
376 | ||
377 | assert(_h); | |
378 | ||
379 | /* Take the user specified one */ | |
380 | e = secure_getenv("HOME"); | |
381 | if (e && path_is_absolute(e)) { | |
382 | h = strdup(e); | |
383 | if (!h) | |
384 | return -ENOMEM; | |
385 | ||
386 | *_h = h; | |
387 | return 0; | |
388 | } | |
389 | ||
390 | /* Hardcode home directory for root to avoid NSS */ | |
391 | u = getuid(); | |
392 | if (u == 0) { | |
393 | h = strdup("/root"); | |
394 | if (!h) | |
395 | return -ENOMEM; | |
396 | ||
397 | *_h = h; | |
398 | return 0; | |
399 | } | |
400 | ||
401 | /* Check the database... */ | |
402 | errno = 0; | |
403 | p = getpwuid(u); | |
404 | if (!p) | |
405 | return errno > 0 ? -errno : -ESRCH; | |
406 | ||
407 | if (!path_is_absolute(p->pw_dir)) | |
408 | return -EINVAL; | |
409 | ||
410 | h = strdup(p->pw_dir); | |
411 | if (!h) | |
412 | return -ENOMEM; | |
413 | ||
414 | *_h = h; | |
415 | return 0; | |
416 | } | |
417 | ||
418 | int get_shell(char **_s) { | |
419 | struct passwd *p; | |
420 | const char *e; | |
421 | char *s; | |
422 | uid_t u; | |
423 | ||
424 | assert(_s); | |
425 | ||
426 | /* Take the user specified one */ | |
427 | e = getenv("SHELL"); | |
428 | if (e) { | |
429 | s = strdup(e); | |
430 | if (!s) | |
431 | return -ENOMEM; | |
432 | ||
433 | *_s = s; | |
434 | return 0; | |
435 | } | |
436 | ||
437 | /* Hardcode home directory for root to avoid NSS */ | |
438 | u = getuid(); | |
439 | if (u == 0) { | |
440 | s = strdup("/bin/sh"); | |
441 | if (!s) | |
442 | return -ENOMEM; | |
443 | ||
444 | *_s = s; | |
445 | return 0; | |
446 | } | |
447 | ||
448 | /* Check the database... */ | |
449 | errno = 0; | |
450 | p = getpwuid(u); | |
451 | if (!p) | |
452 | return errno > 0 ? -errno : -ESRCH; | |
453 | ||
454 | if (!path_is_absolute(p->pw_shell)) | |
455 | return -EINVAL; | |
456 | ||
457 | s = strdup(p->pw_shell); | |
458 | if (!s) | |
459 | return -ENOMEM; | |
460 | ||
461 | *_s = s; | |
462 | return 0; | |
463 | } | |
464 | ||
465 | int reset_uid_gid(void) { | |
97f0e76f | 466 | int r; |
b1d4f8e1 | 467 | |
97f0e76f LP |
468 | r = maybe_setgroups(0, NULL); |
469 | if (r < 0) | |
470 | return r; | |
b1d4f8e1 LP |
471 | |
472 | if (setresgid(0, 0, 0) < 0) | |
473 | return -errno; | |
474 | ||
475 | if (setresuid(0, 0, 0) < 0) | |
476 | return -errno; | |
477 | ||
478 | return 0; | |
479 | } | |
e929bee0 LP |
480 | |
481 | int take_etc_passwd_lock(const char *root) { | |
482 | ||
483 | struct flock flock = { | |
484 | .l_type = F_WRLCK, | |
485 | .l_whence = SEEK_SET, | |
486 | .l_start = 0, | |
487 | .l_len = 0, | |
488 | }; | |
489 | ||
490 | const char *path; | |
491 | int fd, r; | |
492 | ||
493 | /* This is roughly the same as lckpwdf(), but not as awful. We | |
494 | * don't want to use alarm() and signals, hence we implement | |
495 | * our own trivial version of this. | |
496 | * | |
497 | * Note that shadow-utils also takes per-database locks in | |
498 | * addition to lckpwdf(). However, we don't given that they | |
61233823 | 499 | * are redundant as they invoke lckpwdf() first and keep |
e929bee0 LP |
500 | * it during everything they do. The per-database locks are |
501 | * awfully racy, and thus we just won't do them. */ | |
502 | ||
503 | if (root) | |
504 | path = prefix_roota(root, "/etc/.pwd.lock"); | |
505 | else | |
506 | path = "/etc/.pwd.lock"; | |
507 | ||
508 | fd = open(path, O_WRONLY|O_CREAT|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW, 0600); | |
509 | if (fd < 0) | |
510 | return -errno; | |
511 | ||
512 | r = fcntl(fd, F_SETLKW, &flock); | |
513 | if (r < 0) { | |
514 | safe_close(fd); | |
515 | return -errno; | |
516 | } | |
517 | ||
518 | return fd; | |
519 | } | |
e4631b48 LP |
520 | |
521 | bool valid_user_group_name(const char *u) { | |
522 | const char *i; | |
523 | long sz; | |
524 | ||
1429dfe5 LP |
525 | /* Checks if the specified name is a valid user/group name. Also see POSIX IEEE Std 1003.1-2008, 2016 Edition, |
526 | * 3.437. We are a bit stricter here however. Specifically we deviate from POSIX rules: | |
527 | * | |
528 | * - We don't allow any dots (this would break chown syntax which permits dots as user/group name separator) | |
529 | * - We require that names fit into the appropriate utmp field | |
530 | * - We don't allow empty user names | |
531 | * | |
532 | * Note that other systems are even more restrictive, and don't permit underscores or uppercase characters. | |
533 | */ | |
e4631b48 LP |
534 | |
535 | if (isempty(u)) | |
536 | return false; | |
537 | ||
538 | if (!(u[0] >= 'a' && u[0] <= 'z') && | |
539 | !(u[0] >= 'A' && u[0] <= 'Z') && | |
540 | u[0] != '_') | |
541 | return false; | |
542 | ||
543 | for (i = u+1; *i; i++) { | |
544 | if (!(*i >= 'a' && *i <= 'z') && | |
545 | !(*i >= 'A' && *i <= 'Z') && | |
546 | !(*i >= '0' && *i <= '9') && | |
4c701096 | 547 | !IN_SET(*i, '_', '-')) |
e4631b48 LP |
548 | return false; |
549 | } | |
550 | ||
551 | sz = sysconf(_SC_LOGIN_NAME_MAX); | |
552 | assert_se(sz > 0); | |
553 | ||
554 | if ((size_t) (i-u) > (size_t) sz) | |
555 | return false; | |
556 | ||
557 | if ((size_t) (i-u) > UT_NAMESIZE - 1) | |
558 | return false; | |
559 | ||
560 | return true; | |
561 | } | |
562 | ||
563 | bool valid_user_group_name_or_id(const char *u) { | |
564 | ||
565 | /* Similar as above, but is also fine with numeric UID/GID specifications, as long as they are in the right | |
566 | * range, and not the invalid user ids. */ | |
567 | ||
568 | if (isempty(u)) | |
569 | return false; | |
570 | ||
571 | if (valid_user_group_name(u)) | |
572 | return true; | |
573 | ||
574 | return parse_uid(u, NULL) >= 0; | |
575 | } | |
576 | ||
577 | bool valid_gecos(const char *d) { | |
578 | ||
579 | if (!d) | |
580 | return false; | |
581 | ||
582 | if (!utf8_is_valid(d)) | |
583 | return false; | |
584 | ||
585 | if (string_has_cc(d, NULL)) | |
586 | return false; | |
587 | ||
588 | /* Colons are used as field separators, and hence not OK */ | |
589 | if (strchr(d, ':')) | |
590 | return false; | |
591 | ||
592 | return true; | |
593 | } | |
594 | ||
595 | bool valid_home(const char *p) { | |
596 | ||
597 | if (isempty(p)) | |
598 | return false; | |
599 | ||
600 | if (!utf8_is_valid(p)) | |
601 | return false; | |
602 | ||
603 | if (string_has_cc(p, NULL)) | |
604 | return false; | |
605 | ||
606 | if (!path_is_absolute(p)) | |
607 | return false; | |
608 | ||
609 | if (!path_is_safe(p)) | |
610 | return false; | |
611 | ||
612 | /* Colons are used as field separators, and hence not OK */ | |
613 | if (strchr(p, ':')) | |
614 | return false; | |
615 | ||
616 | return true; | |
617 | } | |
36d85478 GS |
618 | |
619 | int maybe_setgroups(size_t size, const gid_t *list) { | |
97f0e76f LP |
620 | int r; |
621 | ||
622 | /* Check if setgroups is allowed before we try to drop all the auxiliary groups */ | |
623 | if (size == 0) { /* Dropping all aux groups? */ | |
624 | _cleanup_free_ char *setgroups_content = NULL; | |
625 | bool can_setgroups; | |
626 | ||
627 | r = read_one_line_file("/proc/self/setgroups", &setgroups_content); | |
628 | if (r == -ENOENT) | |
629 | /* Old kernels don't have /proc/self/setgroups, so assume we can use setgroups */ | |
630 | can_setgroups = true; | |
631 | else if (r < 0) | |
632 | return r; | |
633 | else | |
634 | can_setgroups = streq(setgroups_content, "allow"); | |
635 | ||
636 | if (!can_setgroups) { | |
637 | log_debug("Skipping setgroups(), /proc/self/setgroups is set to 'deny'"); | |
36d85478 | 638 | return 0; |
97f0e76f | 639 | } |
36d85478 | 640 | } |
97f0e76f LP |
641 | |
642 | if (setgroups(size, list) < 0) | |
643 | return -errno; | |
644 | ||
645 | return 0; | |
36d85478 | 646 | } |