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b1d4f8e1 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 <alloca.h> |
21 | #include <errno.h> | |
22 | #include <fcntl.h> | |
b1d4f8e1 | 23 | #include <grp.h> |
cf0fbc49 | 24 | #include <pwd.h> |
11c3a366 TA |
25 | #include <stddef.h> |
26 | #include <stdint.h> | |
27 | #include <stdio.h> | |
28 | #include <stdlib.h> | |
29 | #include <string.h> | |
30 | #include <sys/stat.h> | |
31 | #include <unistd.h> | |
b1d4f8e1 | 32 | |
0b6b45d5 | 33 | #include "missing.h" |
b5efdb8a | 34 | #include "alloc-util.h" |
e929bee0 | 35 | #include "fd-util.h" |
93cc7779 | 36 | #include "formats-util.h" |
b1d4f8e1 | 37 | #include "macro.h" |
6bedfcbb | 38 | #include "parse-util.h" |
b1d4f8e1 | 39 | #include "path-util.h" |
6bedfcbb LP |
40 | #include "string-util.h" |
41 | #include "user-util.h" | |
b1d4f8e1 LP |
42 | |
43 | bool uid_is_valid(uid_t uid) { | |
44 | ||
45 | /* Some libc APIs use UID_INVALID as special placeholder */ | |
b1d52773 | 46 | if (uid == (uid_t) UINT32_C(0xFFFFFFFF)) |
b1d4f8e1 LP |
47 | return false; |
48 | ||
49 | /* A long time ago UIDs where 16bit, hence explicitly avoid the 16bit -1 too */ | |
b1d52773 | 50 | if (uid == (uid_t) UINT32_C(0xFFFF)) |
b1d4f8e1 LP |
51 | return false; |
52 | ||
53 | return true; | |
54 | } | |
55 | ||
b1d52773 LP |
56 | int parse_uid(const char *s, uid_t *ret) { |
57 | uint32_t uid = 0; | |
b1d4f8e1 LP |
58 | int r; |
59 | ||
60 | assert(s); | |
61 | ||
b1d52773 LP |
62 | assert_cc(sizeof(uid_t) == sizeof(uint32_t)); |
63 | r = safe_atou32(s, &uid); | |
b1d4f8e1 LP |
64 | if (r < 0) |
65 | return r; | |
66 | ||
b1d4f8e1 LP |
67 | if (!uid_is_valid(uid)) |
68 | return -ENXIO; /* we return ENXIO instead of EINVAL | |
69 | * here, to make it easy to distuingish | |
ba60af86 | 70 | * invalid numeric uids from invalid |
b1d4f8e1 LP |
71 | * strings. */ |
72 | ||
b1d52773 LP |
73 | if (ret) |
74 | *ret = uid; | |
b1d4f8e1 LP |
75 | |
76 | return 0; | |
77 | } | |
78 | ||
b1d4f8e1 LP |
79 | char* getlogname_malloc(void) { |
80 | uid_t uid; | |
81 | struct stat st; | |
82 | ||
83 | if (isatty(STDIN_FILENO) && fstat(STDIN_FILENO, &st) >= 0) | |
84 | uid = st.st_uid; | |
85 | else | |
86 | uid = getuid(); | |
87 | ||
d0260817 | 88 | return uid_to_name(uid); |
b1d4f8e1 LP |
89 | } |
90 | ||
91 | char *getusername_malloc(void) { | |
92 | const char *e; | |
93 | ||
94 | e = getenv("USER"); | |
95 | if (e) | |
96 | return strdup(e); | |
97 | ||
d0260817 | 98 | return uid_to_name(getuid()); |
b1d4f8e1 LP |
99 | } |
100 | ||
101 | int get_user_creds( | |
102 | const char **username, | |
103 | uid_t *uid, gid_t *gid, | |
104 | const char **home, | |
105 | const char **shell) { | |
106 | ||
107 | struct passwd *p; | |
108 | uid_t u; | |
109 | ||
110 | assert(username); | |
111 | assert(*username); | |
112 | ||
113 | /* We enforce some special rules for uid=0: in order to avoid | |
114 | * NSS lookups for root we hardcode its data. */ | |
115 | ||
116 | if (streq(*username, "root") || streq(*username, "0")) { | |
117 | *username = "root"; | |
118 | ||
119 | if (uid) | |
120 | *uid = 0; | |
121 | ||
122 | if (gid) | |
123 | *gid = 0; | |
124 | ||
125 | if (home) | |
126 | *home = "/root"; | |
127 | ||
128 | if (shell) | |
129 | *shell = "/bin/sh"; | |
130 | ||
131 | return 0; | |
132 | } | |
133 | ||
134 | if (parse_uid(*username, &u) >= 0) { | |
135 | errno = 0; | |
136 | p = getpwuid(u); | |
137 | ||
138 | /* If there are multiple users with the same id, make | |
139 | * sure to leave $USER to the configured value instead | |
140 | * of the first occurrence in the database. However if | |
141 | * the uid was configured by a numeric uid, then let's | |
142 | * pick the real username from /etc/passwd. */ | |
143 | if (p) | |
144 | *username = p->pw_name; | |
145 | } else { | |
146 | errno = 0; | |
147 | p = getpwnam(*username); | |
148 | } | |
149 | ||
150 | if (!p) | |
151 | return errno > 0 ? -errno : -ESRCH; | |
152 | ||
67c7c892 LP |
153 | if (uid) { |
154 | if (!uid_is_valid(p->pw_uid)) | |
155 | return -EBADMSG; | |
156 | ||
b1d4f8e1 | 157 | *uid = p->pw_uid; |
67c7c892 LP |
158 | } |
159 | ||
160 | if (gid) { | |
161 | if (!gid_is_valid(p->pw_gid)) | |
162 | return -EBADMSG; | |
b1d4f8e1 | 163 | |
b1d4f8e1 | 164 | *gid = p->pw_gid; |
67c7c892 | 165 | } |
b1d4f8e1 LP |
166 | |
167 | if (home) | |
168 | *home = p->pw_dir; | |
169 | ||
170 | if (shell) | |
171 | *shell = p->pw_shell; | |
172 | ||
173 | return 0; | |
174 | } | |
175 | ||
176 | int get_group_creds(const char **groupname, gid_t *gid) { | |
177 | struct group *g; | |
178 | gid_t id; | |
179 | ||
180 | assert(groupname); | |
181 | ||
182 | /* We enforce some special rules for gid=0: in order to avoid | |
183 | * NSS lookups for root we hardcode its data. */ | |
184 | ||
185 | if (streq(*groupname, "root") || streq(*groupname, "0")) { | |
186 | *groupname = "root"; | |
187 | ||
188 | if (gid) | |
189 | *gid = 0; | |
190 | ||
191 | return 0; | |
192 | } | |
193 | ||
194 | if (parse_gid(*groupname, &id) >= 0) { | |
195 | errno = 0; | |
196 | g = getgrgid(id); | |
197 | ||
198 | if (g) | |
199 | *groupname = g->gr_name; | |
200 | } else { | |
201 | errno = 0; | |
202 | g = getgrnam(*groupname); | |
203 | } | |
204 | ||
205 | if (!g) | |
206 | return errno > 0 ? -errno : -ESRCH; | |
207 | ||
67c7c892 LP |
208 | if (gid) { |
209 | if (!gid_is_valid(g->gr_gid)) | |
210 | return -EBADMSG; | |
211 | ||
b1d4f8e1 | 212 | *gid = g->gr_gid; |
67c7c892 | 213 | } |
b1d4f8e1 LP |
214 | |
215 | return 0; | |
216 | } | |
217 | ||
218 | char* uid_to_name(uid_t uid) { | |
d0260817 LP |
219 | char *ret; |
220 | int r; | |
b1d4f8e1 | 221 | |
d0260817 | 222 | /* Shortcut things to avoid NSS lookups */ |
b1d4f8e1 LP |
223 | if (uid == 0) |
224 | return strdup("root"); | |
225 | ||
d0260817 LP |
226 | if (uid_is_valid(uid)) { |
227 | long bufsize; | |
228 | ||
229 | bufsize = sysconf(_SC_GETPW_R_SIZE_MAX); | |
230 | if (bufsize <= 0) | |
231 | bufsize = 4096; | |
232 | ||
233 | for (;;) { | |
234 | struct passwd pwbuf, *pw = NULL; | |
235 | _cleanup_free_ char *buf = NULL; | |
236 | ||
237 | buf = malloc(bufsize); | |
238 | if (!buf) | |
239 | return NULL; | |
240 | ||
241 | r = getpwuid_r(uid, &pwbuf, buf, (size_t) bufsize, &pw); | |
242 | if (r == 0 && pw) | |
243 | return strdup(pw->pw_name); | |
244 | if (r != ERANGE) | |
245 | break; | |
246 | ||
247 | bufsize *= 2; | |
248 | } | |
249 | } | |
b1d4f8e1 | 250 | |
d0260817 | 251 | if (asprintf(&ret, UID_FMT, uid) < 0) |
b1d4f8e1 LP |
252 | return NULL; |
253 | ||
d0260817 | 254 | return ret; |
b1d4f8e1 LP |
255 | } |
256 | ||
257 | char* gid_to_name(gid_t gid) { | |
d0260817 LP |
258 | char *ret; |
259 | int r; | |
b1d4f8e1 LP |
260 | |
261 | if (gid == 0) | |
262 | return strdup("root"); | |
263 | ||
d0260817 LP |
264 | if (gid_is_valid(gid)) { |
265 | long bufsize; | |
266 | ||
267 | bufsize = sysconf(_SC_GETGR_R_SIZE_MAX); | |
268 | if (bufsize <= 0) | |
269 | bufsize = 4096; | |
270 | ||
271 | for (;;) { | |
272 | struct group grbuf, *gr = NULL; | |
273 | _cleanup_free_ char *buf = NULL; | |
274 | ||
275 | buf = malloc(bufsize); | |
276 | if (!buf) | |
277 | return NULL; | |
278 | ||
279 | r = getgrgid_r(gid, &grbuf, buf, (size_t) bufsize, &gr); | |
280 | if (r == 0 && gr) | |
281 | return strdup(gr->gr_name); | |
282 | if (r != ERANGE) | |
283 | break; | |
284 | ||
285 | bufsize *= 2; | |
286 | } | |
287 | } | |
b1d4f8e1 | 288 | |
d0260817 | 289 | if (asprintf(&ret, GID_FMT, gid) < 0) |
b1d4f8e1 LP |
290 | return NULL; |
291 | ||
d0260817 | 292 | return ret; |
b1d4f8e1 LP |
293 | } |
294 | ||
295 | int in_gid(gid_t gid) { | |
296 | gid_t *gids; | |
297 | int ngroups_max, r, i; | |
298 | ||
299 | if (getgid() == gid) | |
300 | return 1; | |
301 | ||
302 | if (getegid() == gid) | |
303 | return 1; | |
304 | ||
67c7c892 LP |
305 | if (!gid_is_valid(gid)) |
306 | return -EINVAL; | |
307 | ||
b1d4f8e1 LP |
308 | ngroups_max = sysconf(_SC_NGROUPS_MAX); |
309 | assert(ngroups_max > 0); | |
310 | ||
311 | gids = alloca(sizeof(gid_t) * ngroups_max); | |
312 | ||
313 | r = getgroups(ngroups_max, gids); | |
314 | if (r < 0) | |
315 | return -errno; | |
316 | ||
317 | for (i = 0; i < r; i++) | |
318 | if (gids[i] == gid) | |
319 | return 1; | |
320 | ||
321 | return 0; | |
322 | } | |
323 | ||
324 | int in_group(const char *name) { | |
325 | int r; | |
326 | gid_t gid; | |
327 | ||
328 | r = get_group_creds(&name, &gid); | |
329 | if (r < 0) | |
330 | return r; | |
331 | ||
332 | return in_gid(gid); | |
333 | } | |
334 | ||
335 | int get_home_dir(char **_h) { | |
336 | struct passwd *p; | |
337 | const char *e; | |
338 | char *h; | |
339 | uid_t u; | |
340 | ||
341 | assert(_h); | |
342 | ||
343 | /* Take the user specified one */ | |
344 | e = secure_getenv("HOME"); | |
345 | if (e && path_is_absolute(e)) { | |
346 | h = strdup(e); | |
347 | if (!h) | |
348 | return -ENOMEM; | |
349 | ||
350 | *_h = h; | |
351 | return 0; | |
352 | } | |
353 | ||
354 | /* Hardcode home directory for root to avoid NSS */ | |
355 | u = getuid(); | |
356 | if (u == 0) { | |
357 | h = strdup("/root"); | |
358 | if (!h) | |
359 | return -ENOMEM; | |
360 | ||
361 | *_h = h; | |
362 | return 0; | |
363 | } | |
364 | ||
365 | /* Check the database... */ | |
366 | errno = 0; | |
367 | p = getpwuid(u); | |
368 | if (!p) | |
369 | return errno > 0 ? -errno : -ESRCH; | |
370 | ||
371 | if (!path_is_absolute(p->pw_dir)) | |
372 | return -EINVAL; | |
373 | ||
374 | h = strdup(p->pw_dir); | |
375 | if (!h) | |
376 | return -ENOMEM; | |
377 | ||
378 | *_h = h; | |
379 | return 0; | |
380 | } | |
381 | ||
382 | int get_shell(char **_s) { | |
383 | struct passwd *p; | |
384 | const char *e; | |
385 | char *s; | |
386 | uid_t u; | |
387 | ||
388 | assert(_s); | |
389 | ||
390 | /* Take the user specified one */ | |
391 | e = getenv("SHELL"); | |
392 | if (e) { | |
393 | s = strdup(e); | |
394 | if (!s) | |
395 | return -ENOMEM; | |
396 | ||
397 | *_s = s; | |
398 | return 0; | |
399 | } | |
400 | ||
401 | /* Hardcode home directory for root to avoid NSS */ | |
402 | u = getuid(); | |
403 | if (u == 0) { | |
404 | s = strdup("/bin/sh"); | |
405 | if (!s) | |
406 | return -ENOMEM; | |
407 | ||
408 | *_s = s; | |
409 | return 0; | |
410 | } | |
411 | ||
412 | /* Check the database... */ | |
413 | errno = 0; | |
414 | p = getpwuid(u); | |
415 | if (!p) | |
416 | return errno > 0 ? -errno : -ESRCH; | |
417 | ||
418 | if (!path_is_absolute(p->pw_shell)) | |
419 | return -EINVAL; | |
420 | ||
421 | s = strdup(p->pw_shell); | |
422 | if (!s) | |
423 | return -ENOMEM; | |
424 | ||
425 | *_s = s; | |
426 | return 0; | |
427 | } | |
428 | ||
429 | int reset_uid_gid(void) { | |
430 | ||
431 | if (setgroups(0, NULL) < 0) | |
432 | return -errno; | |
433 | ||
434 | if (setresgid(0, 0, 0) < 0) | |
435 | return -errno; | |
436 | ||
437 | if (setresuid(0, 0, 0) < 0) | |
438 | return -errno; | |
439 | ||
440 | return 0; | |
441 | } | |
e929bee0 LP |
442 | |
443 | int take_etc_passwd_lock(const char *root) { | |
444 | ||
445 | struct flock flock = { | |
446 | .l_type = F_WRLCK, | |
447 | .l_whence = SEEK_SET, | |
448 | .l_start = 0, | |
449 | .l_len = 0, | |
450 | }; | |
451 | ||
452 | const char *path; | |
453 | int fd, r; | |
454 | ||
455 | /* This is roughly the same as lckpwdf(), but not as awful. We | |
456 | * don't want to use alarm() and signals, hence we implement | |
457 | * our own trivial version of this. | |
458 | * | |
459 | * Note that shadow-utils also takes per-database locks in | |
460 | * addition to lckpwdf(). However, we don't given that they | |
61233823 | 461 | * are redundant as they invoke lckpwdf() first and keep |
e929bee0 LP |
462 | * it during everything they do. The per-database locks are |
463 | * awfully racy, and thus we just won't do them. */ | |
464 | ||
465 | if (root) | |
466 | path = prefix_roota(root, "/etc/.pwd.lock"); | |
467 | else | |
468 | path = "/etc/.pwd.lock"; | |
469 | ||
470 | fd = open(path, O_WRONLY|O_CREAT|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW, 0600); | |
471 | if (fd < 0) | |
472 | return -errno; | |
473 | ||
474 | r = fcntl(fd, F_SETLKW, &flock); | |
475 | if (r < 0) { | |
476 | safe_close(fd); | |
477 | return -errno; | |
478 | } | |
479 | ||
480 | return fd; | |
481 | } |