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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 | ||
25 | #include "macro.h" | |
26 | #include "parse-util.h" | |
27 | #include "path-util.h" | |
28 | #include "string-util.h" | |
29 | #include "user-util.h" | |
30 | #include "util.h" | |
31 | ||
32 | bool uid_is_valid(uid_t uid) { | |
33 | ||
34 | /* Some libc APIs use UID_INVALID as special placeholder */ | |
35 | if (uid == (uid_t) UINT32_C(0xFFFFFFFF)) | |
36 | return false; | |
37 | ||
38 | /* A long time ago UIDs where 16bit, hence explicitly avoid the 16bit -1 too */ | |
39 | if (uid == (uid_t) UINT32_C(0xFFFF)) | |
40 | return false; | |
41 | ||
42 | return true; | |
43 | } | |
44 | ||
45 | int parse_uid(const char *s, uid_t *ret) { | |
46 | uint32_t uid = 0; | |
47 | int r; | |
48 | ||
49 | assert(s); | |
50 | ||
51 | assert_cc(sizeof(uid_t) == sizeof(uint32_t)); | |
52 | r = safe_atou32(s, &uid); | |
53 | if (r < 0) | |
54 | return r; | |
55 | ||
56 | if (!uid_is_valid(uid)) | |
57 | return -ENXIO; /* we return ENXIO instead of EINVAL | |
58 | * here, to make it easy to distuingish | |
59 | * invalid numeric uids invalid | |
60 | * strings. */ | |
61 | ||
62 | if (ret) | |
63 | *ret = uid; | |
64 | ||
65 | return 0; | |
66 | } | |
67 | ||
68 | char* getlogname_malloc(void) { | |
69 | uid_t uid; | |
70 | struct stat st; | |
71 | ||
72 | if (isatty(STDIN_FILENO) && fstat(STDIN_FILENO, &st) >= 0) | |
73 | uid = st.st_uid; | |
74 | else | |
75 | uid = getuid(); | |
76 | ||
77 | return uid_to_name(uid); | |
78 | } | |
79 | ||
80 | char *getusername_malloc(void) { | |
81 | const char *e; | |
82 | ||
83 | e = getenv("USER"); | |
84 | if (e) | |
85 | return strdup(e); | |
86 | ||
87 | return uid_to_name(getuid()); | |
88 | } | |
89 | ||
90 | int get_user_creds( | |
91 | const char **username, | |
92 | uid_t *uid, gid_t *gid, | |
93 | const char **home, | |
94 | const char **shell) { | |
95 | ||
96 | struct passwd *p; | |
97 | uid_t u; | |
98 | ||
99 | assert(username); | |
100 | assert(*username); | |
101 | ||
102 | /* We enforce some special rules for uid=0: in order to avoid | |
103 | * NSS lookups for root we hardcode its data. */ | |
104 | ||
105 | if (streq(*username, "root") || streq(*username, "0")) { | |
106 | *username = "root"; | |
107 | ||
108 | if (uid) | |
109 | *uid = 0; | |
110 | ||
111 | if (gid) | |
112 | *gid = 0; | |
113 | ||
114 | if (home) | |
115 | *home = "/root"; | |
116 | ||
117 | if (shell) | |
118 | *shell = "/bin/sh"; | |
119 | ||
120 | return 0; | |
121 | } | |
122 | ||
123 | if (parse_uid(*username, &u) >= 0) { | |
124 | errno = 0; | |
125 | p = getpwuid(u); | |
126 | ||
127 | /* If there are multiple users with the same id, make | |
128 | * sure to leave $USER to the configured value instead | |
129 | * of the first occurrence in the database. However if | |
130 | * the uid was configured by a numeric uid, then let's | |
131 | * pick the real username from /etc/passwd. */ | |
132 | if (p) | |
133 | *username = p->pw_name; | |
134 | } else { | |
135 | errno = 0; | |
136 | p = getpwnam(*username); | |
137 | } | |
138 | ||
139 | if (!p) | |
140 | return errno > 0 ? -errno : -ESRCH; | |
141 | ||
142 | if (uid) { | |
143 | if (!uid_is_valid(p->pw_uid)) | |
144 | return -EBADMSG; | |
145 | ||
146 | *uid = p->pw_uid; | |
147 | } | |
148 | ||
149 | if (gid) { | |
150 | if (!gid_is_valid(p->pw_gid)) | |
151 | return -EBADMSG; | |
152 | ||
153 | *gid = p->pw_gid; | |
154 | } | |
155 | ||
156 | if (home) | |
157 | *home = p->pw_dir; | |
158 | ||
159 | if (shell) | |
160 | *shell = p->pw_shell; | |
161 | ||
162 | return 0; | |
163 | } | |
164 | ||
165 | int get_group_creds(const char **groupname, gid_t *gid) { | |
166 | struct group *g; | |
167 | gid_t id; | |
168 | ||
169 | assert(groupname); | |
170 | ||
171 | /* We enforce some special rules for gid=0: in order to avoid | |
172 | * NSS lookups for root we hardcode its data. */ | |
173 | ||
174 | if (streq(*groupname, "root") || streq(*groupname, "0")) { | |
175 | *groupname = "root"; | |
176 | ||
177 | if (gid) | |
178 | *gid = 0; | |
179 | ||
180 | return 0; | |
181 | } | |
182 | ||
183 | if (parse_gid(*groupname, &id) >= 0) { | |
184 | errno = 0; | |
185 | g = getgrgid(id); | |
186 | ||
187 | if (g) | |
188 | *groupname = g->gr_name; | |
189 | } else { | |
190 | errno = 0; | |
191 | g = getgrnam(*groupname); | |
192 | } | |
193 | ||
194 | if (!g) | |
195 | return errno > 0 ? -errno : -ESRCH; | |
196 | ||
197 | if (gid) { | |
198 | if (!gid_is_valid(g->gr_gid)) | |
199 | return -EBADMSG; | |
200 | ||
201 | *gid = g->gr_gid; | |
202 | } | |
203 | ||
204 | return 0; | |
205 | } | |
206 | ||
207 | char* uid_to_name(uid_t uid) { | |
208 | char *ret; | |
209 | int r; | |
210 | ||
211 | /* Shortcut things to avoid NSS lookups */ | |
212 | if (uid == 0) | |
213 | return strdup("root"); | |
214 | ||
215 | if (uid_is_valid(uid)) { | |
216 | long bufsize; | |
217 | ||
218 | bufsize = sysconf(_SC_GETPW_R_SIZE_MAX); | |
219 | if (bufsize <= 0) | |
220 | bufsize = 4096; | |
221 | ||
222 | for (;;) { | |
223 | struct passwd pwbuf, *pw = NULL; | |
224 | _cleanup_free_ char *buf = NULL; | |
225 | ||
226 | buf = malloc(bufsize); | |
227 | if (!buf) | |
228 | return NULL; | |
229 | ||
230 | r = getpwuid_r(uid, &pwbuf, buf, (size_t) bufsize, &pw); | |
231 | if (r == 0 && pw) | |
232 | return strdup(pw->pw_name); | |
233 | if (r != ERANGE) | |
234 | break; | |
235 | ||
236 | bufsize *= 2; | |
237 | } | |
238 | } | |
239 | ||
240 | if (asprintf(&ret, UID_FMT, uid) < 0) | |
241 | return NULL; | |
242 | ||
243 | return ret; | |
244 | } | |
245 | ||
246 | char* gid_to_name(gid_t gid) { | |
247 | char *ret; | |
248 | int r; | |
249 | ||
250 | if (gid == 0) | |
251 | return strdup("root"); | |
252 | ||
253 | if (gid_is_valid(gid)) { | |
254 | long bufsize; | |
255 | ||
256 | bufsize = sysconf(_SC_GETGR_R_SIZE_MAX); | |
257 | if (bufsize <= 0) | |
258 | bufsize = 4096; | |
259 | ||
260 | for (;;) { | |
261 | struct group grbuf, *gr = NULL; | |
262 | _cleanup_free_ char *buf = NULL; | |
263 | ||
264 | buf = malloc(bufsize); | |
265 | if (!buf) | |
266 | return NULL; | |
267 | ||
268 | r = getgrgid_r(gid, &grbuf, buf, (size_t) bufsize, &gr); | |
269 | if (r == 0 && gr) | |
270 | return strdup(gr->gr_name); | |
271 | if (r != ERANGE) | |
272 | break; | |
273 | ||
274 | bufsize *= 2; | |
275 | } | |
276 | } | |
277 | ||
278 | if (asprintf(&ret, GID_FMT, gid) < 0) | |
279 | return NULL; | |
280 | ||
281 | return ret; | |
282 | } | |
283 | ||
284 | int in_gid(gid_t gid) { | |
285 | gid_t *gids; | |
286 | int ngroups_max, r, i; | |
287 | ||
288 | if (getgid() == gid) | |
289 | return 1; | |
290 | ||
291 | if (getegid() == gid) | |
292 | return 1; | |
293 | ||
294 | if (!gid_is_valid(gid)) | |
295 | return -EINVAL; | |
296 | ||
297 | ngroups_max = sysconf(_SC_NGROUPS_MAX); | |
298 | assert(ngroups_max > 0); | |
299 | ||
300 | gids = alloca(sizeof(gid_t) * ngroups_max); | |
301 | ||
302 | r = getgroups(ngroups_max, gids); | |
303 | if (r < 0) | |
304 | return -errno; | |
305 | ||
306 | for (i = 0; i < r; i++) | |
307 | if (gids[i] == gid) | |
308 | return 1; | |
309 | ||
310 | return 0; | |
311 | } | |
312 | ||
313 | int in_group(const char *name) { | |
314 | int r; | |
315 | gid_t gid; | |
316 | ||
317 | r = get_group_creds(&name, &gid); | |
318 | if (r < 0) | |
319 | return r; | |
320 | ||
321 | return in_gid(gid); | |
322 | } | |
323 | ||
324 | int get_home_dir(char **_h) { | |
325 | struct passwd *p; | |
326 | const char *e; | |
327 | char *h; | |
328 | uid_t u; | |
329 | ||
330 | assert(_h); | |
331 | ||
332 | /* Take the user specified one */ | |
333 | e = secure_getenv("HOME"); | |
334 | if (e && path_is_absolute(e)) { | |
335 | h = strdup(e); | |
336 | if (!h) | |
337 | return -ENOMEM; | |
338 | ||
339 | *_h = h; | |
340 | return 0; | |
341 | } | |
342 | ||
343 | /* Hardcode home directory for root to avoid NSS */ | |
344 | u = getuid(); | |
345 | if (u == 0) { | |
346 | h = strdup("/root"); | |
347 | if (!h) | |
348 | return -ENOMEM; | |
349 | ||
350 | *_h = h; | |
351 | return 0; | |
352 | } | |
353 | ||
354 | /* Check the database... */ | |
355 | errno = 0; | |
356 | p = getpwuid(u); | |
357 | if (!p) | |
358 | return errno > 0 ? -errno : -ESRCH; | |
359 | ||
360 | if (!path_is_absolute(p->pw_dir)) | |
361 | return -EINVAL; | |
362 | ||
363 | h = strdup(p->pw_dir); | |
364 | if (!h) | |
365 | return -ENOMEM; | |
366 | ||
367 | *_h = h; | |
368 | return 0; | |
369 | } | |
370 | ||
371 | int get_shell(char **_s) { | |
372 | struct passwd *p; | |
373 | const char *e; | |
374 | char *s; | |
375 | uid_t u; | |
376 | ||
377 | assert(_s); | |
378 | ||
379 | /* Take the user specified one */ | |
380 | e = getenv("SHELL"); | |
381 | if (e) { | |
382 | s = strdup(e); | |
383 | if (!s) | |
384 | return -ENOMEM; | |
385 | ||
386 | *_s = s; | |
387 | return 0; | |
388 | } | |
389 | ||
390 | /* Hardcode home directory for root to avoid NSS */ | |
391 | u = getuid(); | |
392 | if (u == 0) { | |
393 | s = strdup("/bin/sh"); | |
394 | if (!s) | |
395 | return -ENOMEM; | |
396 | ||
397 | *_s = s; | |
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_shell)) | |
408 | return -EINVAL; | |
409 | ||
410 | s = strdup(p->pw_shell); | |
411 | if (!s) | |
412 | return -ENOMEM; | |
413 | ||
414 | *_s = s; | |
415 | return 0; | |
416 | } | |
417 | ||
418 | int reset_uid_gid(void) { | |
419 | ||
420 | if (setgroups(0, NULL) < 0) | |
421 | return -errno; | |
422 | ||
423 | if (setresgid(0, 0, 0) < 0) | |
424 | return -errno; | |
425 | ||
426 | if (setresuid(0, 0, 0) < 0) | |
427 | return -errno; | |
428 | ||
429 | return 0; | |
430 | } |