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b1d4f8e1 LP |
1 | /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/ |
2 | ||
3 | /*** | |
4 | This file is part of systemd. | |
5 | ||
6 | Copyright 2010 Lennart Poettering | |
7 | ||
8 | systemd is free software; you can redistribute it and/or modify it | |
9 | under the terms of the GNU Lesser General Public License as published by | |
10 | the Free Software Foundation; either version 2.1 of the License, or | |
11 | (at your option) any later version. | |
12 | ||
13 | systemd is distributed in the hope that it will be useful, but | |
14 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
16 | Lesser General Public License for more details. | |
17 | ||
18 | You should have received a copy of the GNU Lesser General Public License | |
19 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
20 | ***/ | |
21 | ||
22 | #include <pwd.h> | |
23 | #include <grp.h> | |
24 | ||
b5efdb8a | 25 | #include "alloc-util.h" |
e929bee0 | 26 | #include "fd-util.h" |
b1d4f8e1 | 27 | #include "macro.h" |
6bedfcbb | 28 | #include "parse-util.h" |
b1d4f8e1 | 29 | #include "path-util.h" |
6bedfcbb LP |
30 | #include "string-util.h" |
31 | #include "user-util.h" | |
32 | #include "util.h" | |
b1d4f8e1 LP |
33 | |
34 | bool uid_is_valid(uid_t uid) { | |
35 | ||
36 | /* Some libc APIs use UID_INVALID as special placeholder */ | |
b1d52773 | 37 | if (uid == (uid_t) UINT32_C(0xFFFFFFFF)) |
b1d4f8e1 LP |
38 | return false; |
39 | ||
40 | /* A long time ago UIDs where 16bit, hence explicitly avoid the 16bit -1 too */ | |
b1d52773 | 41 | if (uid == (uid_t) UINT32_C(0xFFFF)) |
b1d4f8e1 LP |
42 | return false; |
43 | ||
44 | return true; | |
45 | } | |
46 | ||
b1d52773 LP |
47 | int parse_uid(const char *s, uid_t *ret) { |
48 | uint32_t uid = 0; | |
b1d4f8e1 LP |
49 | int r; |
50 | ||
51 | assert(s); | |
52 | ||
b1d52773 LP |
53 | assert_cc(sizeof(uid_t) == sizeof(uint32_t)); |
54 | r = safe_atou32(s, &uid); | |
b1d4f8e1 LP |
55 | if (r < 0) |
56 | return r; | |
57 | ||
b1d4f8e1 LP |
58 | if (!uid_is_valid(uid)) |
59 | return -ENXIO; /* we return ENXIO instead of EINVAL | |
60 | * here, to make it easy to distuingish | |
61 | * invalid numeric uids invalid | |
62 | * strings. */ | |
63 | ||
b1d52773 LP |
64 | if (ret) |
65 | *ret = uid; | |
b1d4f8e1 LP |
66 | |
67 | return 0; | |
68 | } | |
69 | ||
b1d4f8e1 LP |
70 | char* getlogname_malloc(void) { |
71 | uid_t uid; | |
72 | struct stat st; | |
73 | ||
74 | if (isatty(STDIN_FILENO) && fstat(STDIN_FILENO, &st) >= 0) | |
75 | uid = st.st_uid; | |
76 | else | |
77 | uid = getuid(); | |
78 | ||
d0260817 | 79 | return uid_to_name(uid); |
b1d4f8e1 LP |
80 | } |
81 | ||
82 | char *getusername_malloc(void) { | |
83 | const char *e; | |
84 | ||
85 | e = getenv("USER"); | |
86 | if (e) | |
87 | return strdup(e); | |
88 | ||
d0260817 | 89 | return uid_to_name(getuid()); |
b1d4f8e1 LP |
90 | } |
91 | ||
92 | int get_user_creds( | |
93 | const char **username, | |
94 | uid_t *uid, gid_t *gid, | |
95 | const char **home, | |
96 | const char **shell) { | |
97 | ||
98 | struct passwd *p; | |
99 | uid_t u; | |
100 | ||
101 | assert(username); | |
102 | assert(*username); | |
103 | ||
104 | /* We enforce some special rules for uid=0: in order to avoid | |
105 | * NSS lookups for root we hardcode its data. */ | |
106 | ||
107 | if (streq(*username, "root") || streq(*username, "0")) { | |
108 | *username = "root"; | |
109 | ||
110 | if (uid) | |
111 | *uid = 0; | |
112 | ||
113 | if (gid) | |
114 | *gid = 0; | |
115 | ||
116 | if (home) | |
117 | *home = "/root"; | |
118 | ||
119 | if (shell) | |
120 | *shell = "/bin/sh"; | |
121 | ||
122 | return 0; | |
123 | } | |
124 | ||
125 | if (parse_uid(*username, &u) >= 0) { | |
126 | errno = 0; | |
127 | p = getpwuid(u); | |
128 | ||
129 | /* If there are multiple users with the same id, make | |
130 | * sure to leave $USER to the configured value instead | |
131 | * of the first occurrence in the database. However if | |
132 | * the uid was configured by a numeric uid, then let's | |
133 | * pick the real username from /etc/passwd. */ | |
134 | if (p) | |
135 | *username = p->pw_name; | |
136 | } else { | |
137 | errno = 0; | |
138 | p = getpwnam(*username); | |
139 | } | |
140 | ||
141 | if (!p) | |
142 | return errno > 0 ? -errno : -ESRCH; | |
143 | ||
67c7c892 LP |
144 | if (uid) { |
145 | if (!uid_is_valid(p->pw_uid)) | |
146 | return -EBADMSG; | |
147 | ||
b1d4f8e1 | 148 | *uid = p->pw_uid; |
67c7c892 LP |
149 | } |
150 | ||
151 | if (gid) { | |
152 | if (!gid_is_valid(p->pw_gid)) | |
153 | return -EBADMSG; | |
b1d4f8e1 | 154 | |
b1d4f8e1 | 155 | *gid = p->pw_gid; |
67c7c892 | 156 | } |
b1d4f8e1 LP |
157 | |
158 | if (home) | |
159 | *home = p->pw_dir; | |
160 | ||
161 | if (shell) | |
162 | *shell = p->pw_shell; | |
163 | ||
164 | return 0; | |
165 | } | |
166 | ||
167 | int get_group_creds(const char **groupname, gid_t *gid) { | |
168 | struct group *g; | |
169 | gid_t id; | |
170 | ||
171 | assert(groupname); | |
172 | ||
173 | /* We enforce some special rules for gid=0: in order to avoid | |
174 | * NSS lookups for root we hardcode its data. */ | |
175 | ||
176 | if (streq(*groupname, "root") || streq(*groupname, "0")) { | |
177 | *groupname = "root"; | |
178 | ||
179 | if (gid) | |
180 | *gid = 0; | |
181 | ||
182 | return 0; | |
183 | } | |
184 | ||
185 | if (parse_gid(*groupname, &id) >= 0) { | |
186 | errno = 0; | |
187 | g = getgrgid(id); | |
188 | ||
189 | if (g) | |
190 | *groupname = g->gr_name; | |
191 | } else { | |
192 | errno = 0; | |
193 | g = getgrnam(*groupname); | |
194 | } | |
195 | ||
196 | if (!g) | |
197 | return errno > 0 ? -errno : -ESRCH; | |
198 | ||
67c7c892 LP |
199 | if (gid) { |
200 | if (!gid_is_valid(g->gr_gid)) | |
201 | return -EBADMSG; | |
202 | ||
b1d4f8e1 | 203 | *gid = g->gr_gid; |
67c7c892 | 204 | } |
b1d4f8e1 LP |
205 | |
206 | return 0; | |
207 | } | |
208 | ||
209 | char* uid_to_name(uid_t uid) { | |
d0260817 LP |
210 | char *ret; |
211 | int r; | |
b1d4f8e1 | 212 | |
d0260817 | 213 | /* Shortcut things to avoid NSS lookups */ |
b1d4f8e1 LP |
214 | if (uid == 0) |
215 | return strdup("root"); | |
216 | ||
d0260817 LP |
217 | if (uid_is_valid(uid)) { |
218 | long bufsize; | |
219 | ||
220 | bufsize = sysconf(_SC_GETPW_R_SIZE_MAX); | |
221 | if (bufsize <= 0) | |
222 | bufsize = 4096; | |
223 | ||
224 | for (;;) { | |
225 | struct passwd pwbuf, *pw = NULL; | |
226 | _cleanup_free_ char *buf = NULL; | |
227 | ||
228 | buf = malloc(bufsize); | |
229 | if (!buf) | |
230 | return NULL; | |
231 | ||
232 | r = getpwuid_r(uid, &pwbuf, buf, (size_t) bufsize, &pw); | |
233 | if (r == 0 && pw) | |
234 | return strdup(pw->pw_name); | |
235 | if (r != ERANGE) | |
236 | break; | |
237 | ||
238 | bufsize *= 2; | |
239 | } | |
240 | } | |
b1d4f8e1 | 241 | |
d0260817 | 242 | if (asprintf(&ret, UID_FMT, uid) < 0) |
b1d4f8e1 LP |
243 | return NULL; |
244 | ||
d0260817 | 245 | return ret; |
b1d4f8e1 LP |
246 | } |
247 | ||
248 | char* gid_to_name(gid_t gid) { | |
d0260817 LP |
249 | char *ret; |
250 | int r; | |
b1d4f8e1 LP |
251 | |
252 | if (gid == 0) | |
253 | return strdup("root"); | |
254 | ||
d0260817 LP |
255 | if (gid_is_valid(gid)) { |
256 | long bufsize; | |
257 | ||
258 | bufsize = sysconf(_SC_GETGR_R_SIZE_MAX); | |
259 | if (bufsize <= 0) | |
260 | bufsize = 4096; | |
261 | ||
262 | for (;;) { | |
263 | struct group grbuf, *gr = NULL; | |
264 | _cleanup_free_ char *buf = NULL; | |
265 | ||
266 | buf = malloc(bufsize); | |
267 | if (!buf) | |
268 | return NULL; | |
269 | ||
270 | r = getgrgid_r(gid, &grbuf, buf, (size_t) bufsize, &gr); | |
271 | if (r == 0 && gr) | |
272 | return strdup(gr->gr_name); | |
273 | if (r != ERANGE) | |
274 | break; | |
275 | ||
276 | bufsize *= 2; | |
277 | } | |
278 | } | |
b1d4f8e1 | 279 | |
d0260817 | 280 | if (asprintf(&ret, GID_FMT, gid) < 0) |
b1d4f8e1 LP |
281 | return NULL; |
282 | ||
d0260817 | 283 | return ret; |
b1d4f8e1 LP |
284 | } |
285 | ||
286 | int in_gid(gid_t gid) { | |
287 | gid_t *gids; | |
288 | int ngroups_max, r, i; | |
289 | ||
290 | if (getgid() == gid) | |
291 | return 1; | |
292 | ||
293 | if (getegid() == gid) | |
294 | return 1; | |
295 | ||
67c7c892 LP |
296 | if (!gid_is_valid(gid)) |
297 | return -EINVAL; | |
298 | ||
b1d4f8e1 LP |
299 | ngroups_max = sysconf(_SC_NGROUPS_MAX); |
300 | assert(ngroups_max > 0); | |
301 | ||
302 | gids = alloca(sizeof(gid_t) * ngroups_max); | |
303 | ||
304 | r = getgroups(ngroups_max, gids); | |
305 | if (r < 0) | |
306 | return -errno; | |
307 | ||
308 | for (i = 0; i < r; i++) | |
309 | if (gids[i] == gid) | |
310 | return 1; | |
311 | ||
312 | return 0; | |
313 | } | |
314 | ||
315 | int in_group(const char *name) { | |
316 | int r; | |
317 | gid_t gid; | |
318 | ||
319 | r = get_group_creds(&name, &gid); | |
320 | if (r < 0) | |
321 | return r; | |
322 | ||
323 | return in_gid(gid); | |
324 | } | |
325 | ||
326 | int get_home_dir(char **_h) { | |
327 | struct passwd *p; | |
328 | const char *e; | |
329 | char *h; | |
330 | uid_t u; | |
331 | ||
332 | assert(_h); | |
333 | ||
334 | /* Take the user specified one */ | |
335 | e = secure_getenv("HOME"); | |
336 | if (e && path_is_absolute(e)) { | |
337 | h = strdup(e); | |
338 | if (!h) | |
339 | return -ENOMEM; | |
340 | ||
341 | *_h = h; | |
342 | return 0; | |
343 | } | |
344 | ||
345 | /* Hardcode home directory for root to avoid NSS */ | |
346 | u = getuid(); | |
347 | if (u == 0) { | |
348 | h = strdup("/root"); | |
349 | if (!h) | |
350 | return -ENOMEM; | |
351 | ||
352 | *_h = h; | |
353 | return 0; | |
354 | } | |
355 | ||
356 | /* Check the database... */ | |
357 | errno = 0; | |
358 | p = getpwuid(u); | |
359 | if (!p) | |
360 | return errno > 0 ? -errno : -ESRCH; | |
361 | ||
362 | if (!path_is_absolute(p->pw_dir)) | |
363 | return -EINVAL; | |
364 | ||
365 | h = strdup(p->pw_dir); | |
366 | if (!h) | |
367 | return -ENOMEM; | |
368 | ||
369 | *_h = h; | |
370 | return 0; | |
371 | } | |
372 | ||
373 | int get_shell(char **_s) { | |
374 | struct passwd *p; | |
375 | const char *e; | |
376 | char *s; | |
377 | uid_t u; | |
378 | ||
379 | assert(_s); | |
380 | ||
381 | /* Take the user specified one */ | |
382 | e = getenv("SHELL"); | |
383 | if (e) { | |
384 | s = strdup(e); | |
385 | if (!s) | |
386 | return -ENOMEM; | |
387 | ||
388 | *_s = s; | |
389 | return 0; | |
390 | } | |
391 | ||
392 | /* Hardcode home directory for root to avoid NSS */ | |
393 | u = getuid(); | |
394 | if (u == 0) { | |
395 | s = strdup("/bin/sh"); | |
396 | if (!s) | |
397 | return -ENOMEM; | |
398 | ||
399 | *_s = s; | |
400 | return 0; | |
401 | } | |
402 | ||
403 | /* Check the database... */ | |
404 | errno = 0; | |
405 | p = getpwuid(u); | |
406 | if (!p) | |
407 | return errno > 0 ? -errno : -ESRCH; | |
408 | ||
409 | if (!path_is_absolute(p->pw_shell)) | |
410 | return -EINVAL; | |
411 | ||
412 | s = strdup(p->pw_shell); | |
413 | if (!s) | |
414 | return -ENOMEM; | |
415 | ||
416 | *_s = s; | |
417 | return 0; | |
418 | } | |
419 | ||
420 | int reset_uid_gid(void) { | |
421 | ||
422 | if (setgroups(0, NULL) < 0) | |
423 | return -errno; | |
424 | ||
425 | if (setresgid(0, 0, 0) < 0) | |
426 | return -errno; | |
427 | ||
428 | if (setresuid(0, 0, 0) < 0) | |
429 | return -errno; | |
430 | ||
431 | return 0; | |
432 | } | |
e929bee0 LP |
433 | |
434 | int take_etc_passwd_lock(const char *root) { | |
435 | ||
436 | struct flock flock = { | |
437 | .l_type = F_WRLCK, | |
438 | .l_whence = SEEK_SET, | |
439 | .l_start = 0, | |
440 | .l_len = 0, | |
441 | }; | |
442 | ||
443 | const char *path; | |
444 | int fd, r; | |
445 | ||
446 | /* This is roughly the same as lckpwdf(), but not as awful. We | |
447 | * don't want to use alarm() and signals, hence we implement | |
448 | * our own trivial version of this. | |
449 | * | |
450 | * Note that shadow-utils also takes per-database locks in | |
451 | * addition to lckpwdf(). However, we don't given that they | |
452 | * are redundant as they they invoke lckpwdf() first and keep | |
453 | * it during everything they do. The per-database locks are | |
454 | * awfully racy, and thus we just won't do them. */ | |
455 | ||
456 | if (root) | |
457 | path = prefix_roota(root, "/etc/.pwd.lock"); | |
458 | else | |
459 | path = "/etc/.pwd.lock"; | |
460 | ||
461 | fd = open(path, O_WRONLY|O_CREAT|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW, 0600); | |
462 | if (fd < 0) | |
463 | return -errno; | |
464 | ||
465 | r = fcntl(fd, F_SETLKW, &flock); | |
466 | if (r < 0) { | |
467 | safe_close(fd); | |
468 | return -errno; | |
469 | } | |
470 | ||
471 | return fd; | |
472 | } |