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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 General Public License as published by | |
10 | the Free Software Foundation; either version 2 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 | General Public License for more details. | |
17 | ||
18 | You should have received a copy of the GNU General Public License | |
19 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
20 | ***/ | |
21 | ||
22 | #include <errno.h> | |
23 | #include <fcntl.h> | |
24 | #include <sys/file.h> | |
25 | #include <pwd.h> | |
26 | #include <endian.h> | |
27 | ||
28 | #include <security/pam_modules.h> | |
29 | #include <security/_pam_macros.h> | |
30 | #include <security/pam_modutil.h> | |
31 | #include <security/pam_ext.h> | |
32 | #include <security/pam_misc.h> | |
33 | ||
34 | #include "util.h" | |
35 | #include "cgroup-util.h" | |
36 | #include "macro.h" | |
37 | #include "sd-daemon.h" | |
38 | ||
39 | static int parse_argv(pam_handle_t *handle, | |
40 | int argc, const char **argv, | |
41 | bool *create_session, | |
42 | bool *kill_session, | |
43 | bool *kill_user) { | |
44 | ||
45 | unsigned i; | |
46 | ||
47 | assert(argc >= 0); | |
48 | assert(argc == 0 || argv); | |
49 | ||
50 | for (i = 0; i < (unsigned) argc; i++) { | |
51 | int k; | |
52 | ||
53 | if (startswith(argv[i], "create-session=")) { | |
54 | if ((k = parse_boolean(argv[i] + 15)) < 0) { | |
55 | pam_syslog(handle, LOG_ERR, "Failed to parse create-session= argument."); | |
56 | return k; | |
57 | } | |
58 | ||
59 | if (create_session) | |
60 | *create_session = k; | |
61 | } else if (startswith(argv[i], "kill-session=")) { | |
62 | if ((k = parse_boolean(argv[i] + 13)) < 0) { | |
63 | pam_syslog(handle, LOG_ERR, "Failed to parse kill-session= argument."); | |
64 | return k; | |
65 | } | |
66 | ||
67 | if (kill_session) | |
68 | *kill_session = k; | |
69 | ||
70 | } else if (startswith(argv[i], "kill-user=")) { | |
71 | if ((k = parse_boolean(argv[i] + 10)) < 0) { | |
72 | pam_syslog(handle, LOG_ERR, "Failed to parse kill-user= argument."); | |
73 | return k; | |
74 | } | |
75 | ||
76 | if (kill_user) | |
77 | *kill_user = k; | |
78 | } else { | |
79 | pam_syslog(handle, LOG_ERR, "Unknown parameter '%s'.", argv[i]); | |
80 | return -EINVAL; | |
81 | } | |
82 | } | |
83 | ||
84 | if (kill_session && *kill_session && kill_user) | |
85 | *kill_user = true; | |
86 | ||
87 | return 0; | |
88 | } | |
89 | ||
90 | static int open_file_and_lock(const char *fn) { | |
91 | int fd; | |
92 | ||
93 | assert(fn); | |
94 | ||
95 | if ((fd = open(fn, O_RDWR|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW|O_CREAT, 0600)) < 0) | |
96 | return -errno; | |
97 | ||
98 | /* The BSD socket semantics are a lot nicer than those of | |
99 | * POSIX locks. Which is why we use flock() here. BSD locking | |
100 | * does not work across NFS which however is not needed here | |
101 | * as the filesystems in question should be local, and only | |
102 | * locally accessible, and most likely even tmpfs. */ | |
103 | ||
104 | if (flock(fd, LOCK_EX) < 0) | |
105 | return -errno; | |
106 | ||
107 | return fd; | |
108 | } | |
109 | ||
110 | enum { | |
111 | SESSION_ID_AUDIT = 'a', | |
112 | SESSION_ID_COUNTER = 'c', | |
113 | SESSION_ID_RANDOM = 'r' | |
114 | }; | |
115 | ||
116 | static uint64_t get_session_id(int *mode) { | |
117 | char *s; | |
118 | int fd; | |
119 | ||
120 | assert(mode); | |
121 | ||
122 | /* First attempt: let's use the session ID of the audit | |
123 | * system, if it is available. */ | |
124 | if (read_one_line_file("/proc/self/sessionid", &s) >= 0) { | |
125 | uint32_t u; | |
126 | int r; | |
127 | ||
128 | r = safe_atou32(s, &u); | |
129 | free(s); | |
130 | ||
131 | if (r >= 0 && u != (uint32_t) -1 && u > 0) { | |
132 | *mode = SESSION_ID_AUDIT; | |
133 | return (uint64_t) u; | |
134 | } | |
135 | } | |
136 | ||
137 | /* Second attempt, use our own counter. */ | |
138 | if ((fd = open_file_and_lock(RUNTIME_DIR "/user/.pam-systemd-session")) >= 0) { | |
139 | uint64_t counter; | |
140 | ssize_t r; | |
141 | ||
142 | /* We do a bit of endianess swapping here, just to be | |
143 | * sure. /var should be machine specific anyway, and | |
144 | * /var/run even mounted from tmpfs, so this | |
145 | * byteswapping should really not be necessary. But | |
146 | * then again, you never know, so let's avoid any | |
147 | * risk. */ | |
148 | ||
149 | if (loop_read(fd, &counter, sizeof(counter), false) != sizeof(counter)) | |
150 | counter = 1; | |
151 | else | |
152 | counter = le64toh(counter) + 1; | |
153 | ||
154 | if (lseek(fd, 0, SEEK_SET) == 0) { | |
155 | uint64_t swapped = htole64(counter); | |
156 | ||
157 | r = loop_write(fd, &swapped, sizeof(swapped), false); | |
158 | ||
159 | if (r != sizeof(swapped)) | |
160 | r = -EIO; | |
161 | } else | |
162 | r = -errno; | |
163 | ||
164 | close_nointr_nofail(fd); | |
165 | ||
166 | if (r >= 0) { | |
167 | *mode = SESSION_ID_COUNTER; | |
168 | return counter; | |
169 | } | |
170 | } | |
171 | ||
172 | *mode = SESSION_ID_RANDOM; | |
173 | ||
174 | /* Last attempt, pick a random value */ | |
175 | return (uint64_t) random_ull(); | |
176 | } | |
177 | static int get_user_data( | |
178 | pam_handle_t *handle, | |
179 | const char **ret_username, | |
180 | struct passwd **ret_pw) { | |
181 | ||
182 | const char *username = NULL; | |
183 | struct passwd *pw = NULL; | |
184 | int r; | |
185 | bool have_loginuid = false; | |
186 | char *s; | |
187 | ||
188 | assert(handle); | |
189 | assert(ret_username); | |
190 | assert(ret_pw); | |
191 | ||
192 | if (read_one_line_file("/proc/self/loginuid", &s) >= 0) { | |
193 | uint32_t u; | |
194 | ||
195 | r = safe_atou32(s, &u); | |
196 | free(s); | |
197 | ||
198 | if (r >= 0 && u != (uint32_t) -1 && u > 0) { | |
199 | have_loginuid = true; | |
200 | pw = pam_modutil_getpwuid(handle, u); | |
201 | } | |
202 | } | |
203 | ||
204 | if (!have_loginuid) { | |
205 | if ((r = pam_get_user(handle, &username, NULL)) != PAM_SUCCESS) { | |
206 | pam_syslog(handle, LOG_ERR, "Failed to get user name."); | |
207 | return r; | |
208 | } | |
209 | ||
210 | if (!username || !*username) { | |
211 | pam_syslog(handle, LOG_ERR, "User name not valid."); | |
212 | return PAM_AUTH_ERR; | |
213 | } | |
214 | ||
215 | pw = pam_modutil_getpwnam(handle, username); | |
216 | } | |
217 | ||
218 | if (!pw) { | |
219 | pam_syslog(handle, LOG_ERR, "Failed to get user data."); | |
220 | return PAM_USER_UNKNOWN; | |
221 | } | |
222 | ||
223 | *ret_pw = pw; | |
224 | *ret_username = username ? username : pw->pw_name; | |
225 | ||
226 | return PAM_SUCCESS; | |
227 | } | |
228 | ||
229 | static int create_user_group(pam_handle_t *handle, const char *group, struct passwd *pw, bool attach, bool remember) { | |
230 | int r; | |
231 | ||
232 | assert(handle); | |
233 | assert(group); | |
234 | ||
235 | if (attach) | |
236 | r = cg_create_and_attach(SYSTEMD_CGROUP_CONTROLLER, group, 0); | |
237 | else | |
238 | r = cg_create(SYSTEMD_CGROUP_CONTROLLER, group); | |
239 | ||
240 | if (r < 0) { | |
241 | pam_syslog(handle, LOG_ERR, "Failed to create cgroup: %s", strerror(-r)); | |
242 | return PAM_SESSION_ERR; | |
243 | } | |
244 | ||
245 | if (r > 0 && remember) { | |
246 | /* Remember that it was us who created this group, and | |
247 | * that hence we need to remove it too. This is a | |
248 | * protection against removing the cgroup when run | |
249 | * recursively. */ | |
250 | if ((r = pam_set_data(handle, "systemd.created", INT_TO_PTR(1), NULL)) != PAM_SUCCESS) { | |
251 | pam_syslog(handle, LOG_ERR, "Failed to install created variable."); | |
252 | return r; | |
253 | } | |
254 | } | |
255 | ||
256 | if ((r = cg_set_task_access(SYSTEMD_CGROUP_CONTROLLER, group, 0755, pw->pw_uid, pw->pw_gid)) < 0 || | |
257 | (r = cg_set_group_access(SYSTEMD_CGROUP_CONTROLLER, group, 0755, pw->pw_uid, pw->pw_gid)) < 0) { | |
258 | pam_syslog(handle, LOG_ERR, "Failed to change access modes: %s", strerror(-r)); | |
259 | return PAM_SESSION_ERR; | |
260 | } | |
261 | ||
262 | return PAM_SUCCESS; | |
263 | } | |
264 | ||
265 | _public_ PAM_EXTERN int pam_sm_open_session( | |
266 | pam_handle_t *handle, | |
267 | int flags, | |
268 | int argc, const char **argv) { | |
269 | ||
270 | const char *username = NULL; | |
271 | struct passwd *pw; | |
272 | int r; | |
273 | char *buf = NULL; | |
274 | int lock_fd = -1; | |
275 | bool create_session = true; | |
276 | ||
277 | assert(handle); | |
278 | ||
279 | /* pam_syslog(handle, LOG_DEBUG, "pam-systemd initializing"); */ | |
280 | ||
281 | if (parse_argv(handle, argc, argv, &create_session, NULL, NULL) < 0) | |
282 | return PAM_SESSION_ERR; | |
283 | ||
284 | /* Make this a NOP on non-systemd systems */ | |
285 | if (sd_booted() <= 0) | |
286 | return PAM_SUCCESS; | |
287 | ||
288 | if ((r = get_user_data(handle, &username, &pw)) != PAM_SUCCESS) | |
289 | goto finish; | |
290 | ||
291 | if (safe_mkdir(RUNTIME_DIR "/user", 0755, 0, 0) < 0) { | |
292 | pam_syslog(handle, LOG_ERR, "Failed to create runtime directory: %m"); | |
293 | r = PAM_SYSTEM_ERR; | |
294 | goto finish; | |
295 | } | |
296 | ||
297 | if ((lock_fd = open_file_and_lock(RUNTIME_DIR "/user/.pam-systemd-lock")) < 0) { | |
298 | pam_syslog(handle, LOG_ERR, "Failed to lock runtime directory: %m"); | |
299 | r = PAM_SYSTEM_ERR; | |
300 | goto finish; | |
301 | } | |
302 | ||
303 | /* Create /var/run/$USER */ | |
304 | free(buf); | |
305 | if (asprintf(&buf, RUNTIME_DIR "/user/%s", username) < 0) { | |
306 | r = PAM_BUF_ERR; | |
307 | goto finish; | |
308 | } | |
309 | ||
310 | if (safe_mkdir(buf, 0700, pw->pw_uid, pw->pw_gid) < 0) { | |
311 | pam_syslog(handle, LOG_WARNING, "Failed to create runtime directory: %m"); | |
312 | r = PAM_SYSTEM_ERR; | |
313 | goto finish; | |
314 | } else if ((r = pam_misc_setenv(handle, "XDG_RUNTIME_DIR", buf, 0)) != PAM_SUCCESS) { | |
315 | pam_syslog(handle, LOG_ERR, "Failed to set runtime dir."); | |
316 | goto finish; | |
317 | } | |
318 | ||
319 | free(buf); | |
320 | buf = NULL; | |
321 | ||
322 | if (create_session) { | |
323 | const char *id; | |
324 | ||
325 | /* Reuse or create XDG session ID */ | |
326 | if (!(id = pam_getenv(handle, "XDG_SESSION_ID"))) { | |
327 | int mode; | |
328 | ||
329 | if (asprintf(&buf, "%llux", (unsigned long long) get_session_id(&mode)) < 0) { | |
330 | r = PAM_BUF_ERR; | |
331 | goto finish; | |
332 | } | |
333 | ||
334 | /* To avoid id clashes we add the session id | |
335 | * source to our session ids. Note that the | |
336 | * session id source might change during | |
337 | * runtime, because a filesystem became | |
338 | * writable or the system reconfigured. */ | |
339 | buf[strlen(buf)-1] = | |
340 | mode != SESSION_ID_AUDIT ? (char) mode : 0; | |
341 | ||
342 | if ((r = pam_misc_setenv(handle, "XDG_SESSION_ID", buf, 0)) != PAM_SUCCESS) { | |
343 | pam_syslog(handle, LOG_ERR, "Failed to set session id."); | |
344 | goto finish; | |
345 | } | |
346 | ||
347 | if (!(id = pam_getenv(handle, "XDG_SESSION_ID"))) { | |
348 | pam_syslog(handle, LOG_ERR, "Failed to get session id."); | |
349 | r = PAM_SESSION_ERR; | |
350 | goto finish; | |
351 | } | |
352 | } | |
353 | ||
354 | r = asprintf(&buf, "/user/%s/%s", username, id); | |
355 | } else | |
356 | r = asprintf(&buf, "/user/%s/master", username); | |
357 | ||
358 | if (r < 0) { | |
359 | r = PAM_BUF_ERR; | |
360 | goto finish; | |
361 | } | |
362 | ||
363 | pam_syslog(handle, LOG_INFO, "Moving new user session for %s into control group %s.", username, buf); | |
364 | ||
365 | if ((r = create_user_group(handle, buf, pw, true, true)) != PAM_SUCCESS) | |
366 | goto finish; | |
367 | ||
368 | r = PAM_SUCCESS; | |
369 | ||
370 | finish: | |
371 | free(buf); | |
372 | ||
373 | if (lock_fd >= 0) | |
374 | close_nointr_nofail(lock_fd); | |
375 | ||
376 | return r; | |
377 | } | |
378 | ||
379 | static int session_remains(pam_handle_t *handle, const char *user_path) { | |
380 | int r; | |
381 | bool remains = false; | |
382 | DIR *d; | |
383 | char *subgroup; | |
384 | ||
385 | if ((r = cg_enumerate_subgroups(SYSTEMD_CGROUP_CONTROLLER, user_path, &d)) < 0) | |
386 | return r; | |
387 | ||
388 | while ((r = cg_read_subgroup(d, &subgroup)) > 0) { | |
389 | ||
390 | remains = !streq(subgroup, "master"); | |
391 | free(subgroup); | |
392 | ||
393 | if (remains) | |
394 | break; | |
395 | } | |
396 | ||
397 | closedir(d); | |
398 | ||
399 | if (r < 0) | |
400 | return r; | |
401 | ||
402 | return !!remains; | |
403 | } | |
404 | ||
405 | _public_ PAM_EXTERN int pam_sm_close_session( | |
406 | pam_handle_t *handle, | |
407 | int flags, | |
408 | int argc, const char **argv) { | |
409 | ||
410 | const char *username = NULL; | |
411 | bool kill_session = false; | |
412 | bool kill_user = false; | |
413 | int lock_fd = -1, r; | |
414 | char *session_path = NULL, *nosession_path = NULL, *user_path = NULL; | |
415 | const char *id; | |
416 | struct passwd *pw; | |
417 | const void *created = NULL; | |
418 | ||
419 | assert(handle); | |
420 | ||
421 | if (parse_argv(handle, argc, argv, NULL, &kill_session, &kill_user) < 0) | |
422 | return PAM_SESSION_ERR; | |
423 | ||
424 | /* Make this a NOP on non-systemd systems */ | |
425 | if (sd_booted() <= 0) | |
426 | return PAM_SUCCESS; | |
427 | ||
428 | if ((r = get_user_data(handle, &username, &pw)) != PAM_SUCCESS) | |
429 | goto finish; | |
430 | ||
431 | if ((lock_fd = open_file_and_lock(RUNTIME_DIR "/user/.pam-systemd-lock")) < 0) { | |
432 | pam_syslog(handle, LOG_ERR, "Failed to lock runtime directory: %m"); | |
433 | r = PAM_SYSTEM_ERR; | |
434 | goto finish; | |
435 | } | |
436 | ||
437 | /* We are probably still in some session/user dir. Move ourselves out of the way as first step */ | |
438 | if ((r = cg_attach(SYSTEMD_CGROUP_CONTROLLER, "/user", 0)) < 0) | |
439 | pam_syslog(handle, LOG_ERR, "Failed to move us away: %s", strerror(-r)); | |
440 | ||
441 | if (asprintf(&user_path, "/user/%s", username) < 0) { | |
442 | r = PAM_BUF_ERR; | |
443 | goto finish; | |
444 | } | |
445 | ||
446 | pam_get_data(handle, "systemd.created", &created); | |
447 | ||
448 | if ((id = pam_getenv(handle, "XDG_SESSION_ID")) && created) { | |
449 | ||
450 | if (asprintf(&session_path, "/user/%s/%s", username, id) < 0 || | |
451 | asprintf(&nosession_path, "/user/%s/master", username) < 0) { | |
452 | r = PAM_BUF_ERR; | |
453 | goto finish; | |
454 | } | |
455 | ||
456 | if (kill_session) { | |
457 | pam_syslog(handle, LOG_INFO, "Killing remaining processes of user session %s of %s.", id, username); | |
458 | ||
459 | /* Kill processes in session cgroup, and delete it */ | |
460 | if ((r = cg_kill_recursive_and_wait(SYSTEMD_CGROUP_CONTROLLER, session_path, true)) < 0) | |
461 | pam_syslog(handle, LOG_ERR, "Failed to kill session cgroup: %s", strerror(-r)); | |
462 | } else { | |
463 | pam_syslog(handle, LOG_INFO, "Moving remaining processes of user session %s of %s into control group %s.", id, username, nosession_path); | |
464 | ||
465 | /* Migrate processes from session to user | |
466 | * cgroup. First, try to create the user group | |
467 | * in case it doesn't exist yet. Also, delete | |
468 | * the session group. */ | |
469 | create_user_group(handle, nosession_path, pw, false, false); | |
470 | ||
471 | if ((r = cg_migrate_recursive(SYSTEMD_CGROUP_CONTROLLER, session_path, nosession_path, false, true)) < 0) | |
472 | pam_syslog(handle, LOG_ERR, "Failed to migrate session cgroup: %s", strerror(-r)); | |
473 | } | |
474 | } | |
475 | ||
476 | /* GC user tree */ | |
477 | cg_trim(SYSTEMD_CGROUP_CONTROLLER, user_path, false); | |
478 | ||
479 | if ((r = session_remains(handle, user_path)) < 0) | |
480 | pam_syslog(handle, LOG_ERR, "Failed to determine whether a session remains: %s", strerror(-r)); | |
481 | ||
482 | /* Kill user processes not attached to any session */ | |
483 | if (kill_user && r == 0) { | |
484 | ||
485 | /* Kill user cgroup */ | |
486 | if ((r = cg_kill_recursive_and_wait(SYSTEMD_CGROUP_CONTROLLER, user_path, true)) < 0) | |
487 | pam_syslog(handle, LOG_ERR, "Failed to kill user cgroup: %s", strerror(-r)); | |
488 | } else { | |
489 | ||
490 | if ((r = cg_is_empty_recursive(SYSTEMD_CGROUP_CONTROLLER, user_path, true)) < 0) | |
491 | pam_syslog(handle, LOG_ERR, "Failed to check user cgroup: %s", strerror(-r)); | |
492 | ||
493 | /* Remove user cgroup */ | |
494 | if (r > 0) { | |
495 | if ((r = cg_delete(SYSTEMD_CGROUP_CONTROLLER, user_path)) < 0) | |
496 | pam_syslog(handle, LOG_ERR, "Failed to delete user cgroup: %s", strerror(-r)); | |
497 | ||
498 | /* If we managed to find somebody, don't cleanup the cgroup. */ | |
499 | } else if (r == 0) | |
500 | r = -EBUSY; | |
501 | } | |
502 | ||
503 | if (r >= 0) { | |
504 | const char *runtime_dir; | |
505 | ||
506 | if ((runtime_dir = pam_getenv(handle, "XDG_RUNTIME_DIR"))) | |
507 | if ((r = rm_rf(runtime_dir, false, true)) < 0) | |
508 | pam_syslog(handle, LOG_ERR, "Failed to remove runtime directory: %s", strerror(-r)); | |
509 | } | |
510 | ||
511 | /* pam_syslog(handle, LOG_DEBUG, "pam-systemd done"); */ | |
512 | ||
513 | r = PAM_SUCCESS; | |
514 | ||
515 | finish: | |
516 | if (lock_fd >= 0) | |
517 | close_nointr_nofail(lock_fd); | |
518 | ||
519 | free(session_path); | |
520 | free(nosession_path); | |
521 | free(user_path); | |
522 | ||
523 | return r; | |
524 | } |