blob: 5f264fb5737dcd01329fdeff02a4143584ba9c38
1 | /* Task credentials management - see Documentation/security/credentials.txt |
2 | * |
3 | * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved. |
4 | * Written by David Howells (dhowells@redhat.com) |
5 | * |
6 | * This program is free software; you can redistribute it and/or |
7 | * modify it under the terms of the GNU General Public Licence |
8 | * as published by the Free Software Foundation; either version |
9 | * 2 of the Licence, or (at your option) any later version. |
10 | */ |
11 | #include <linux/export.h> |
12 | #include <linux/cred.h> |
13 | #include <linux/slab.h> |
14 | #include <linux/sched.h> |
15 | #include <linux/key.h> |
16 | #include <linux/keyctl.h> |
17 | #include <linux/init_task.h> |
18 | #include <linux/security.h> |
19 | #include <linux/binfmts.h> |
20 | #include <linux/cn_proc.h> |
21 | |
22 | #if 0 |
23 | #define kdebug(FMT, ...) \ |
24 | printk("[%-5.5s%5u] " FMT "\n", \ |
25 | current->comm, current->pid, ##__VA_ARGS__) |
26 | #else |
27 | #define kdebug(FMT, ...) \ |
28 | do { \ |
29 | if (0) \ |
30 | no_printk("[%-5.5s%5u] " FMT "\n", \ |
31 | current->comm, current->pid, ##__VA_ARGS__); \ |
32 | } while (0) |
33 | #endif |
34 | |
35 | static struct kmem_cache *cred_jar; |
36 | |
37 | /* init to 2 - one for init_task, one to ensure it is never freed */ |
38 | struct group_info init_groups = { .usage = ATOMIC_INIT(2) }; |
39 | |
40 | /* |
41 | * The initial credentials for the initial task |
42 | */ |
43 | struct cred init_cred = { |
44 | .usage = ATOMIC_INIT(4), |
45 | #ifdef CONFIG_DEBUG_CREDENTIALS |
46 | .subscribers = ATOMIC_INIT(2), |
47 | .magic = CRED_MAGIC, |
48 | #endif |
49 | .uid = GLOBAL_ROOT_UID, |
50 | .gid = GLOBAL_ROOT_GID, |
51 | .suid = GLOBAL_ROOT_UID, |
52 | .sgid = GLOBAL_ROOT_GID, |
53 | .euid = GLOBAL_ROOT_UID, |
54 | .egid = GLOBAL_ROOT_GID, |
55 | .fsuid = GLOBAL_ROOT_UID, |
56 | .fsgid = GLOBAL_ROOT_GID, |
57 | .securebits = SECUREBITS_DEFAULT, |
58 | .cap_inheritable = CAP_EMPTY_SET, |
59 | .cap_permitted = CAP_FULL_SET, |
60 | .cap_effective = CAP_FULL_SET, |
61 | .cap_bset = CAP_FULL_SET, |
62 | .user = INIT_USER, |
63 | .user_ns = &init_user_ns, |
64 | .group_info = &init_groups, |
65 | }; |
66 | |
67 | static inline void set_cred_subscribers(struct cred *cred, int n) |
68 | { |
69 | #ifdef CONFIG_DEBUG_CREDENTIALS |
70 | atomic_set(&cred->subscribers, n); |
71 | #endif |
72 | } |
73 | |
74 | static inline int read_cred_subscribers(const struct cred *cred) |
75 | { |
76 | #ifdef CONFIG_DEBUG_CREDENTIALS |
77 | return atomic_read(&cred->subscribers); |
78 | #else |
79 | return 0; |
80 | #endif |
81 | } |
82 | |
83 | static inline void alter_cred_subscribers(const struct cred *_cred, int n) |
84 | { |
85 | #ifdef CONFIG_DEBUG_CREDENTIALS |
86 | struct cred *cred = (struct cred *) _cred; |
87 | |
88 | atomic_add(n, &cred->subscribers); |
89 | #endif |
90 | } |
91 | |
92 | /* |
93 | * The RCU callback to actually dispose of a set of credentials |
94 | */ |
95 | static void put_cred_rcu(struct rcu_head *rcu) |
96 | { |
97 | struct cred *cred = container_of(rcu, struct cred, rcu); |
98 | |
99 | kdebug("put_cred_rcu(%p)", cred); |
100 | |
101 | #ifdef CONFIG_DEBUG_CREDENTIALS |
102 | if (cred->magic != CRED_MAGIC_DEAD || |
103 | atomic_read(&cred->usage) != 0 || |
104 | read_cred_subscribers(cred) != 0) |
105 | panic("CRED: put_cred_rcu() sees %p with" |
106 | " mag %x, put %p, usage %d, subscr %d\n", |
107 | cred, cred->magic, cred->put_addr, |
108 | atomic_read(&cred->usage), |
109 | read_cred_subscribers(cred)); |
110 | #else |
111 | if (atomic_read(&cred->usage) != 0) |
112 | panic("CRED: put_cred_rcu() sees %p with usage %d\n", |
113 | cred, atomic_read(&cred->usage)); |
114 | #endif |
115 | |
116 | security_cred_free(cred); |
117 | key_put(cred->session_keyring); |
118 | key_put(cred->process_keyring); |
119 | key_put(cred->thread_keyring); |
120 | key_put(cred->request_key_auth); |
121 | if (cred->group_info) |
122 | put_group_info(cred->group_info); |
123 | free_uid(cred->user); |
124 | put_user_ns(cred->user_ns); |
125 | kmem_cache_free(cred_jar, cred); |
126 | } |
127 | |
128 | /** |
129 | * __put_cred - Destroy a set of credentials |
130 | * @cred: The record to release |
131 | * |
132 | * Destroy a set of credentials on which no references remain. |
133 | */ |
134 | void __put_cred(struct cred *cred) |
135 | { |
136 | kdebug("__put_cred(%p{%d,%d})", cred, |
137 | atomic_read(&cred->usage), |
138 | read_cred_subscribers(cred)); |
139 | |
140 | BUG_ON(atomic_read(&cred->usage) != 0); |
141 | #ifdef CONFIG_DEBUG_CREDENTIALS |
142 | BUG_ON(read_cred_subscribers(cred) != 0); |
143 | cred->magic = CRED_MAGIC_DEAD; |
144 | cred->put_addr = __builtin_return_address(0); |
145 | #endif |
146 | BUG_ON(cred == current->cred); |
147 | BUG_ON(cred == current->real_cred); |
148 | |
149 | call_rcu(&cred->rcu, put_cred_rcu); |
150 | } |
151 | EXPORT_SYMBOL(__put_cred); |
152 | |
153 | /* |
154 | * Clean up a task's credentials when it exits |
155 | */ |
156 | void exit_creds(struct task_struct *tsk) |
157 | { |
158 | struct cred *cred; |
159 | |
160 | kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred, |
161 | atomic_read(&tsk->cred->usage), |
162 | read_cred_subscribers(tsk->cred)); |
163 | |
164 | cred = (struct cred *) tsk->real_cred; |
165 | tsk->real_cred = NULL; |
166 | validate_creds(cred); |
167 | alter_cred_subscribers(cred, -1); |
168 | put_cred(cred); |
169 | |
170 | cred = (struct cred *) tsk->cred; |
171 | tsk->cred = NULL; |
172 | validate_creds(cred); |
173 | alter_cred_subscribers(cred, -1); |
174 | put_cred(cred); |
175 | } |
176 | |
177 | /** |
178 | * get_task_cred - Get another task's objective credentials |
179 | * @task: The task to query |
180 | * |
181 | * Get the objective credentials of a task, pinning them so that they can't go |
182 | * away. Accessing a task's credentials directly is not permitted. |
183 | * |
184 | * The caller must also make sure task doesn't get deleted, either by holding a |
185 | * ref on task or by holding tasklist_lock to prevent it from being unlinked. |
186 | */ |
187 | const struct cred *get_task_cred(struct task_struct *task) |
188 | { |
189 | const struct cred *cred; |
190 | |
191 | rcu_read_lock(); |
192 | |
193 | do { |
194 | cred = __task_cred((task)); |
195 | BUG_ON(!cred); |
196 | } while (!atomic_inc_not_zero(&((struct cred *)cred)->usage)); |
197 | |
198 | rcu_read_unlock(); |
199 | return cred; |
200 | } |
201 | |
202 | /* |
203 | * Allocate blank credentials, such that the credentials can be filled in at a |
204 | * later date without risk of ENOMEM. |
205 | */ |
206 | struct cred *cred_alloc_blank(void) |
207 | { |
208 | struct cred *new; |
209 | |
210 | new = kmem_cache_zalloc(cred_jar, GFP_KERNEL); |
211 | if (!new) |
212 | return NULL; |
213 | |
214 | atomic_set(&new->usage, 1); |
215 | #ifdef CONFIG_DEBUG_CREDENTIALS |
216 | new->magic = CRED_MAGIC; |
217 | #endif |
218 | |
219 | if (security_cred_alloc_blank(new, GFP_KERNEL) < 0) |
220 | goto error; |
221 | |
222 | return new; |
223 | |
224 | error: |
225 | abort_creds(new); |
226 | return NULL; |
227 | } |
228 | |
229 | /** |
230 | * prepare_creds - Prepare a new set of credentials for modification |
231 | * |
232 | * Prepare a new set of task credentials for modification. A task's creds |
233 | * shouldn't generally be modified directly, therefore this function is used to |
234 | * prepare a new copy, which the caller then modifies and then commits by |
235 | * calling commit_creds(). |
236 | * |
237 | * Preparation involves making a copy of the objective creds for modification. |
238 | * |
239 | * Returns a pointer to the new creds-to-be if successful, NULL otherwise. |
240 | * |
241 | * Call commit_creds() or abort_creds() to clean up. |
242 | */ |
243 | struct cred *prepare_creds(void) |
244 | { |
245 | struct task_struct *task = current; |
246 | const struct cred *old; |
247 | struct cred *new; |
248 | |
249 | validate_process_creds(); |
250 | |
251 | new = kmem_cache_alloc(cred_jar, GFP_KERNEL); |
252 | if (!new) |
253 | return NULL; |
254 | |
255 | kdebug("prepare_creds() alloc %p", new); |
256 | |
257 | old = task->cred; |
258 | memcpy(new, old, sizeof(struct cred)); |
259 | |
260 | atomic_set(&new->usage, 1); |
261 | set_cred_subscribers(new, 0); |
262 | get_group_info(new->group_info); |
263 | get_uid(new->user); |
264 | get_user_ns(new->user_ns); |
265 | |
266 | #ifdef CONFIG_KEYS |
267 | key_get(new->session_keyring); |
268 | key_get(new->process_keyring); |
269 | key_get(new->thread_keyring); |
270 | key_get(new->request_key_auth); |
271 | #endif |
272 | |
273 | #ifdef CONFIG_SECURITY |
274 | new->security = NULL; |
275 | #endif |
276 | |
277 | if (security_prepare_creds(new, old, GFP_KERNEL) < 0) |
278 | goto error; |
279 | validate_creds(new); |
280 | return new; |
281 | |
282 | error: |
283 | abort_creds(new); |
284 | return NULL; |
285 | } |
286 | EXPORT_SYMBOL(prepare_creds); |
287 | |
288 | /* |
289 | * Prepare credentials for current to perform an execve() |
290 | * - The caller must hold ->cred_guard_mutex |
291 | */ |
292 | struct cred *prepare_exec_creds(void) |
293 | { |
294 | struct cred *new; |
295 | |
296 | new = prepare_creds(); |
297 | if (!new) |
298 | return new; |
299 | |
300 | #ifdef CONFIG_KEYS |
301 | /* newly exec'd tasks don't get a thread keyring */ |
302 | key_put(new->thread_keyring); |
303 | new->thread_keyring = NULL; |
304 | |
305 | /* inherit the session keyring; new process keyring */ |
306 | key_put(new->process_keyring); |
307 | new->process_keyring = NULL; |
308 | #endif |
309 | |
310 | return new; |
311 | } |
312 | |
313 | /* |
314 | * Copy credentials for the new process created by fork() |
315 | * |
316 | * We share if we can, but under some circumstances we have to generate a new |
317 | * set. |
318 | * |
319 | * The new process gets the current process's subjective credentials as its |
320 | * objective and subjective credentials |
321 | */ |
322 | int copy_creds(struct task_struct *p, unsigned long clone_flags) |
323 | { |
324 | struct cred *new; |
325 | int ret; |
326 | |
327 | if ( |
328 | #ifdef CONFIG_KEYS |
329 | !p->cred->thread_keyring && |
330 | #endif |
331 | clone_flags & CLONE_THREAD |
332 | ) { |
333 | p->real_cred = get_cred(p->cred); |
334 | get_cred(p->cred); |
335 | alter_cred_subscribers(p->cred, 2); |
336 | kdebug("share_creds(%p{%d,%d})", |
337 | p->cred, atomic_read(&p->cred->usage), |
338 | read_cred_subscribers(p->cred)); |
339 | atomic_inc(&p->cred->user->processes); |
340 | return 0; |
341 | } |
342 | |
343 | new = prepare_creds(); |
344 | if (!new) |
345 | return -ENOMEM; |
346 | |
347 | if (clone_flags & CLONE_NEWUSER) { |
348 | ret = create_user_ns(new); |
349 | if (ret < 0) |
350 | goto error_put; |
351 | } |
352 | |
353 | #ifdef CONFIG_KEYS |
354 | /* new threads get their own thread keyrings if their parent already |
355 | * had one */ |
356 | if (new->thread_keyring) { |
357 | key_put(new->thread_keyring); |
358 | new->thread_keyring = NULL; |
359 | if (clone_flags & CLONE_THREAD) |
360 | install_thread_keyring_to_cred(new); |
361 | } |
362 | |
363 | /* The process keyring is only shared between the threads in a process; |
364 | * anything outside of those threads doesn't inherit. |
365 | */ |
366 | if (!(clone_flags & CLONE_THREAD)) { |
367 | key_put(new->process_keyring); |
368 | new->process_keyring = NULL; |
369 | } |
370 | #endif |
371 | |
372 | atomic_inc(&new->user->processes); |
373 | p->cred = p->real_cred = get_cred(new); |
374 | alter_cred_subscribers(new, 2); |
375 | validate_creds(new); |
376 | return 0; |
377 | |
378 | error_put: |
379 | put_cred(new); |
380 | return ret; |
381 | } |
382 | |
383 | static bool cred_cap_issubset(const struct cred *set, const struct cred *subset) |
384 | { |
385 | const struct user_namespace *set_ns = set->user_ns; |
386 | const struct user_namespace *subset_ns = subset->user_ns; |
387 | |
388 | /* If the two credentials are in the same user namespace see if |
389 | * the capabilities of subset are a subset of set. |
390 | */ |
391 | if (set_ns == subset_ns) |
392 | return cap_issubset(subset->cap_permitted, set->cap_permitted); |
393 | |
394 | /* The credentials are in a different user namespaces |
395 | * therefore one is a subset of the other only if a set is an |
396 | * ancestor of subset and set->euid is owner of subset or one |
397 | * of subsets ancestors. |
398 | */ |
399 | for (;subset_ns != &init_user_ns; subset_ns = subset_ns->parent) { |
400 | if ((set_ns == subset_ns->parent) && |
401 | uid_eq(subset_ns->owner, set->euid)) |
402 | return true; |
403 | } |
404 | |
405 | return false; |
406 | } |
407 | |
408 | /** |
409 | * commit_creds - Install new credentials upon the current task |
410 | * @new: The credentials to be assigned |
411 | * |
412 | * Install a new set of credentials to the current task, using RCU to replace |
413 | * the old set. Both the objective and the subjective credentials pointers are |
414 | * updated. This function may not be called if the subjective credentials are |
415 | * in an overridden state. |
416 | * |
417 | * This function eats the caller's reference to the new credentials. |
418 | * |
419 | * Always returns 0 thus allowing this function to be tail-called at the end |
420 | * of, say, sys_setgid(). |
421 | */ |
422 | int commit_creds(struct cred *new) |
423 | { |
424 | struct task_struct *task = current; |
425 | const struct cred *old = task->real_cred; |
426 | |
427 | kdebug("commit_creds(%p{%d,%d})", new, |
428 | atomic_read(&new->usage), |
429 | read_cred_subscribers(new)); |
430 | |
431 | BUG_ON(task->cred != old); |
432 | #ifdef CONFIG_DEBUG_CREDENTIALS |
433 | BUG_ON(read_cred_subscribers(old) < 2); |
434 | validate_creds(old); |
435 | validate_creds(new); |
436 | #endif |
437 | BUG_ON(atomic_read(&new->usage) < 1); |
438 | |
439 | get_cred(new); /* we will require a ref for the subj creds too */ |
440 | |
441 | /* dumpability changes */ |
442 | if (!uid_eq(old->euid, new->euid) || |
443 | !gid_eq(old->egid, new->egid) || |
444 | !uid_eq(old->fsuid, new->fsuid) || |
445 | !gid_eq(old->fsgid, new->fsgid) || |
446 | !cred_cap_issubset(old, new)) { |
447 | if (task->mm) |
448 | set_dumpable(task->mm, suid_dumpable); |
449 | task->pdeath_signal = 0; |
450 | smp_wmb(); |
451 | } |
452 | |
453 | /* alter the thread keyring */ |
454 | if (!uid_eq(new->fsuid, old->fsuid)) |
455 | key_fsuid_changed(task); |
456 | if (!gid_eq(new->fsgid, old->fsgid)) |
457 | key_fsgid_changed(task); |
458 | |
459 | /* do it |
460 | * RLIMIT_NPROC limits on user->processes have already been checked |
461 | * in set_user(). |
462 | */ |
463 | alter_cred_subscribers(new, 2); |
464 | if (new->user != old->user) |
465 | atomic_inc(&new->user->processes); |
466 | rcu_assign_pointer(task->real_cred, new); |
467 | rcu_assign_pointer(task->cred, new); |
468 | if (new->user != old->user) |
469 | atomic_dec(&old->user->processes); |
470 | alter_cred_subscribers(old, -2); |
471 | |
472 | /* send notifications */ |
473 | if (!uid_eq(new->uid, old->uid) || |
474 | !uid_eq(new->euid, old->euid) || |
475 | !uid_eq(new->suid, old->suid) || |
476 | !uid_eq(new->fsuid, old->fsuid)) |
477 | proc_id_connector(task, PROC_EVENT_UID); |
478 | |
479 | if (!gid_eq(new->gid, old->gid) || |
480 | !gid_eq(new->egid, old->egid) || |
481 | !gid_eq(new->sgid, old->sgid) || |
482 | !gid_eq(new->fsgid, old->fsgid)) |
483 | proc_id_connector(task, PROC_EVENT_GID); |
484 | |
485 | /* release the old obj and subj refs both */ |
486 | put_cred(old); |
487 | put_cred(old); |
488 | return 0; |
489 | } |
490 | EXPORT_SYMBOL(commit_creds); |
491 | |
492 | /** |
493 | * abort_creds - Discard a set of credentials and unlock the current task |
494 | * @new: The credentials that were going to be applied |
495 | * |
496 | * Discard a set of credentials that were under construction and unlock the |
497 | * current task. |
498 | */ |
499 | void abort_creds(struct cred *new) |
500 | { |
501 | kdebug("abort_creds(%p{%d,%d})", new, |
502 | atomic_read(&new->usage), |
503 | read_cred_subscribers(new)); |
504 | |
505 | #ifdef CONFIG_DEBUG_CREDENTIALS |
506 | BUG_ON(read_cred_subscribers(new) != 0); |
507 | #endif |
508 | BUG_ON(atomic_read(&new->usage) < 1); |
509 | put_cred(new); |
510 | } |
511 | EXPORT_SYMBOL(abort_creds); |
512 | |
513 | /** |
514 | * override_creds - Override the current process's subjective credentials |
515 | * @new: The credentials to be assigned |
516 | * |
517 | * Install a set of temporary override subjective credentials on the current |
518 | * process, returning the old set for later reversion. |
519 | */ |
520 | const struct cred *override_creds(const struct cred *new) |
521 | { |
522 | const struct cred *old = current->cred; |
523 | |
524 | kdebug("override_creds(%p{%d,%d})", new, |
525 | atomic_read(&new->usage), |
526 | read_cred_subscribers(new)); |
527 | |
528 | validate_creds(old); |
529 | validate_creds(new); |
530 | get_cred(new); |
531 | alter_cred_subscribers(new, 1); |
532 | rcu_assign_pointer(current->cred, new); |
533 | alter_cred_subscribers(old, -1); |
534 | |
535 | kdebug("override_creds() = %p{%d,%d}", old, |
536 | atomic_read(&old->usage), |
537 | read_cred_subscribers(old)); |
538 | return old; |
539 | } |
540 | EXPORT_SYMBOL(override_creds); |
541 | |
542 | /** |
543 | * revert_creds - Revert a temporary subjective credentials override |
544 | * @old: The credentials to be restored |
545 | * |
546 | * Revert a temporary set of override subjective credentials to an old set, |
547 | * discarding the override set. |
548 | */ |
549 | void revert_creds(const struct cred *old) |
550 | { |
551 | const struct cred *override = current->cred; |
552 | |
553 | kdebug("revert_creds(%p{%d,%d})", old, |
554 | atomic_read(&old->usage), |
555 | read_cred_subscribers(old)); |
556 | |
557 | validate_creds(old); |
558 | validate_creds(override); |
559 | alter_cred_subscribers(old, 1); |
560 | rcu_assign_pointer(current->cred, old); |
561 | alter_cred_subscribers(override, -1); |
562 | put_cred(override); |
563 | } |
564 | EXPORT_SYMBOL(revert_creds); |
565 | |
566 | /* |
567 | * initialise the credentials stuff |
568 | */ |
569 | void __init cred_init(void) |
570 | { |
571 | /* allocate a slab in which we can store credentials */ |
572 | cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), 0, |
573 | SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL); |
574 | } |
575 | |
576 | /** |
577 | * prepare_kernel_cred - Prepare a set of credentials for a kernel service |
578 | * @daemon: A userspace daemon to be used as a reference |
579 | * |
580 | * Prepare a set of credentials for a kernel service. This can then be used to |
581 | * override a task's own credentials so that work can be done on behalf of that |
582 | * task that requires a different subjective context. |
583 | * |
584 | * @daemon is used to provide a base for the security record, but can be NULL. |
585 | * If @daemon is supplied, then the security data will be derived from that; |
586 | * otherwise they'll be set to 0 and no groups, full capabilities and no keys. |
587 | * |
588 | * The caller may change these controls afterwards if desired. |
589 | * |
590 | * Returns the new credentials or NULL if out of memory. |
591 | * |
592 | * Does not take, and does not return holding current->cred_replace_mutex. |
593 | */ |
594 | struct cred *prepare_kernel_cred(struct task_struct *daemon) |
595 | { |
596 | const struct cred *old; |
597 | struct cred *new; |
598 | |
599 | new = kmem_cache_alloc(cred_jar, GFP_KERNEL); |
600 | if (!new) |
601 | return NULL; |
602 | |
603 | kdebug("prepare_kernel_cred() alloc %p", new); |
604 | |
605 | if (daemon) |
606 | old = get_task_cred(daemon); |
607 | else |
608 | old = get_cred(&init_cred); |
609 | |
610 | validate_creds(old); |
611 | |
612 | *new = *old; |
613 | atomic_set(&new->usage, 1); |
614 | set_cred_subscribers(new, 0); |
615 | get_uid(new->user); |
616 | get_user_ns(new->user_ns); |
617 | get_group_info(new->group_info); |
618 | |
619 | #ifdef CONFIG_KEYS |
620 | new->session_keyring = NULL; |
621 | new->process_keyring = NULL; |
622 | new->thread_keyring = NULL; |
623 | new->request_key_auth = NULL; |
624 | new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING; |
625 | #endif |
626 | |
627 | #ifdef CONFIG_SECURITY |
628 | new->security = NULL; |
629 | #endif |
630 | if (security_prepare_creds(new, old, GFP_KERNEL) < 0) |
631 | goto error; |
632 | |
633 | put_cred(old); |
634 | validate_creds(new); |
635 | return new; |
636 | |
637 | error: |
638 | put_cred(new); |
639 | put_cred(old); |
640 | return NULL; |
641 | } |
642 | EXPORT_SYMBOL(prepare_kernel_cred); |
643 | |
644 | /** |
645 | * set_security_override - Set the security ID in a set of credentials |
646 | * @new: The credentials to alter |
647 | * @secid: The LSM security ID to set |
648 | * |
649 | * Set the LSM security ID in a set of credentials so that the subjective |
650 | * security is overridden when an alternative set of credentials is used. |
651 | */ |
652 | int set_security_override(struct cred *new, u32 secid) |
653 | { |
654 | return security_kernel_act_as(new, secid); |
655 | } |
656 | EXPORT_SYMBOL(set_security_override); |
657 | |
658 | /** |
659 | * set_security_override_from_ctx - Set the security ID in a set of credentials |
660 | * @new: The credentials to alter |
661 | * @secctx: The LSM security context to generate the security ID from. |
662 | * |
663 | * Set the LSM security ID in a set of credentials so that the subjective |
664 | * security is overridden when an alternative set of credentials is used. The |
665 | * security ID is specified in string form as a security context to be |
666 | * interpreted by the LSM. |
667 | */ |
668 | int set_security_override_from_ctx(struct cred *new, const char *secctx) |
669 | { |
670 | u32 secid; |
671 | int ret; |
672 | |
673 | ret = security_secctx_to_secid(secctx, strlen(secctx), &secid); |
674 | if (ret < 0) |
675 | return ret; |
676 | |
677 | return set_security_override(new, secid); |
678 | } |
679 | EXPORT_SYMBOL(set_security_override_from_ctx); |
680 | |
681 | /** |
682 | * set_create_files_as - Set the LSM file create context in a set of credentials |
683 | * @new: The credentials to alter |
684 | * @inode: The inode to take the context from |
685 | * |
686 | * Change the LSM file creation context in a set of credentials to be the same |
687 | * as the object context of the specified inode, so that the new inodes have |
688 | * the same MAC context as that inode. |
689 | */ |
690 | int set_create_files_as(struct cred *new, struct inode *inode) |
691 | { |
692 | if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid)) |
693 | return -EINVAL; |
694 | new->fsuid = inode->i_uid; |
695 | new->fsgid = inode->i_gid; |
696 | return security_kernel_create_files_as(new, inode); |
697 | } |
698 | EXPORT_SYMBOL(set_create_files_as); |
699 | |
700 | #ifdef CONFIG_DEBUG_CREDENTIALS |
701 | |
702 | bool creds_are_invalid(const struct cred *cred) |
703 | { |
704 | if (cred->magic != CRED_MAGIC) |
705 | return true; |
706 | #ifdef CONFIG_SECURITY_SELINUX |
707 | /* |
708 | * cred->security == NULL if security_cred_alloc_blank() or |
709 | * security_prepare_creds() returned an error. |
710 | */ |
711 | if (selinux_is_enabled() && cred->security) { |
712 | if ((unsigned long) cred->security < PAGE_SIZE) |
713 | return true; |
714 | if ((*(u32 *)cred->security & 0xffffff00) == |
715 | (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)) |
716 | return true; |
717 | } |
718 | #endif |
719 | return false; |
720 | } |
721 | EXPORT_SYMBOL(creds_are_invalid); |
722 | |
723 | /* |
724 | * dump invalid credentials |
725 | */ |
726 | static void dump_invalid_creds(const struct cred *cred, const char *label, |
727 | const struct task_struct *tsk) |
728 | { |
729 | printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n", |
730 | label, cred, |
731 | cred == &init_cred ? "[init]" : "", |
732 | cred == tsk->real_cred ? "[real]" : "", |
733 | cred == tsk->cred ? "[eff]" : ""); |
734 | printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n", |
735 | cred->magic, cred->put_addr); |
736 | printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n", |
737 | atomic_read(&cred->usage), |
738 | read_cred_subscribers(cred)); |
739 | printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n", |
740 | from_kuid_munged(&init_user_ns, cred->uid), |
741 | from_kuid_munged(&init_user_ns, cred->euid), |
742 | from_kuid_munged(&init_user_ns, cred->suid), |
743 | from_kuid_munged(&init_user_ns, cred->fsuid)); |
744 | printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n", |
745 | from_kgid_munged(&init_user_ns, cred->gid), |
746 | from_kgid_munged(&init_user_ns, cred->egid), |
747 | from_kgid_munged(&init_user_ns, cred->sgid), |
748 | from_kgid_munged(&init_user_ns, cred->fsgid)); |
749 | #ifdef CONFIG_SECURITY |
750 | printk(KERN_ERR "CRED: ->security is %p\n", cred->security); |
751 | if ((unsigned long) cred->security >= PAGE_SIZE && |
752 | (((unsigned long) cred->security & 0xffffff00) != |
753 | (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))) |
754 | printk(KERN_ERR "CRED: ->security {%x, %x}\n", |
755 | ((u32*)cred->security)[0], |
756 | ((u32*)cred->security)[1]); |
757 | #endif |
758 | } |
759 | |
760 | /* |
761 | * report use of invalid credentials |
762 | */ |
763 | void __invalid_creds(const struct cred *cred, const char *file, unsigned line) |
764 | { |
765 | printk(KERN_ERR "CRED: Invalid credentials\n"); |
766 | printk(KERN_ERR "CRED: At %s:%u\n", file, line); |
767 | dump_invalid_creds(cred, "Specified", current); |
768 | BUG(); |
769 | } |
770 | EXPORT_SYMBOL(__invalid_creds); |
771 | |
772 | /* |
773 | * check the credentials on a process |
774 | */ |
775 | void __validate_process_creds(struct task_struct *tsk, |
776 | const char *file, unsigned line) |
777 | { |
778 | if (tsk->cred == tsk->real_cred) { |
779 | if (unlikely(read_cred_subscribers(tsk->cred) < 2 || |
780 | creds_are_invalid(tsk->cred))) |
781 | goto invalid_creds; |
782 | } else { |
783 | if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 || |
784 | read_cred_subscribers(tsk->cred) < 1 || |
785 | creds_are_invalid(tsk->real_cred) || |
786 | creds_are_invalid(tsk->cred))) |
787 | goto invalid_creds; |
788 | } |
789 | return; |
790 | |
791 | invalid_creds: |
792 | printk(KERN_ERR "CRED: Invalid process credentials\n"); |
793 | printk(KERN_ERR "CRED: At %s:%u\n", file, line); |
794 | |
795 | dump_invalid_creds(tsk->real_cred, "Real", tsk); |
796 | if (tsk->cred != tsk->real_cred) |
797 | dump_invalid_creds(tsk->cred, "Effective", tsk); |
798 | else |
799 | printk(KERN_ERR "CRED: Effective creds == Real creds\n"); |
800 | BUG(); |
801 | } |
802 | EXPORT_SYMBOL(__validate_process_creds); |
803 | |
804 | /* |
805 | * check creds for do_exit() |
806 | */ |
807 | void validate_creds_for_do_exit(struct task_struct *tsk) |
808 | { |
809 | kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})", |
810 | tsk->real_cred, tsk->cred, |
811 | atomic_read(&tsk->cred->usage), |
812 | read_cred_subscribers(tsk->cred)); |
813 | |
814 | __validate_process_creds(tsk, __FILE__, __LINE__); |
815 | } |
816 | |
817 | #endif /* CONFIG_DEBUG_CREDENTIALS */ |
818 |