Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0-or-later
2 : /* Task credentials management - see Documentation/security/credentials.rst
3 : *
4 : * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
5 : * Written by David Howells (dhowells@redhat.com)
6 : */
7 : #include <linux/export.h>
8 : #include <linux/cred.h>
9 : #include <linux/slab.h>
10 : #include <linux/sched.h>
11 : #include <linux/sched/coredump.h>
12 : #include <linux/key.h>
13 : #include <linux/keyctl.h>
14 : #include <linux/init_task.h>
15 : #include <linux/security.h>
16 : #include <linux/binfmts.h>
17 : #include <linux/cn_proc.h>
18 : #include <linux/uidgid.h>
19 :
20 : #if 0
21 : #define kdebug(FMT, ...) \
22 : printk("[%-5.5s%5u] " FMT "\n", \
23 : current->comm, current->pid, ##__VA_ARGS__)
24 : #else
25 : #define kdebug(FMT, ...) \
26 : do { \
27 : if (0) \
28 : no_printk("[%-5.5s%5u] " FMT "\n", \
29 : current->comm, current->pid, ##__VA_ARGS__); \
30 : } while (0)
31 : #endif
32 :
33 : static struct kmem_cache *cred_jar;
34 :
35 : /* init to 2 - one for init_task, one to ensure it is never freed */
36 : struct group_info init_groups = { .usage = ATOMIC_INIT(2) };
37 :
38 : /*
39 : * The initial credentials for the initial task
40 : */
41 : struct cred init_cred = {
42 : .usage = ATOMIC_INIT(4),
43 : #ifdef CONFIG_DEBUG_CREDENTIALS
44 : .subscribers = ATOMIC_INIT(2),
45 : .magic = CRED_MAGIC,
46 : #endif
47 : .uid = GLOBAL_ROOT_UID,
48 : .gid = GLOBAL_ROOT_GID,
49 : .suid = GLOBAL_ROOT_UID,
50 : .sgid = GLOBAL_ROOT_GID,
51 : .euid = GLOBAL_ROOT_UID,
52 : .egid = GLOBAL_ROOT_GID,
53 : .fsuid = GLOBAL_ROOT_UID,
54 : .fsgid = GLOBAL_ROOT_GID,
55 : .securebits = SECUREBITS_DEFAULT,
56 : .cap_inheritable = CAP_EMPTY_SET,
57 : .cap_permitted = CAP_FULL_SET,
58 : .cap_effective = CAP_FULL_SET,
59 : .cap_bset = CAP_FULL_SET,
60 : .user = INIT_USER,
61 : .user_ns = &init_user_ns,
62 : .group_info = &init_groups,
63 : };
64 :
65 6183 : static inline void set_cred_subscribers(struct cred *cred, int n)
66 : {
67 : #ifdef CONFIG_DEBUG_CREDENTIALS
68 : atomic_set(&cred->subscribers, n);
69 : #endif
70 6183 : }
71 :
72 : static inline int read_cred_subscribers(const struct cred *cred)
73 : {
74 : #ifdef CONFIG_DEBUG_CREDENTIALS
75 : return atomic_read(&cred->subscribers);
76 : #else
77 : return 0;
78 : #endif
79 : }
80 :
81 18564 : static inline void alter_cred_subscribers(const struct cred *_cred, int n)
82 : {
83 : #ifdef CONFIG_DEBUG_CREDENTIALS
84 : struct cred *cred = (struct cred *) _cred;
85 :
86 : atomic_add(n, &cred->subscribers);
87 : #endif
88 18564 : }
89 :
90 : /*
91 : * The RCU callback to actually dispose of a set of credentials
92 : */
93 6048 : static void put_cred_rcu(struct rcu_head *rcu)
94 : {
95 6048 : struct cred *cred = container_of(rcu, struct cred, rcu);
96 :
97 6048 : kdebug("put_cred_rcu(%p)", cred);
98 :
99 : #ifdef CONFIG_DEBUG_CREDENTIALS
100 : if (cred->magic != CRED_MAGIC_DEAD ||
101 : atomic_read(&cred->usage) != 0 ||
102 : read_cred_subscribers(cred) != 0)
103 : panic("CRED: put_cred_rcu() sees %p with"
104 : " mag %x, put %p, usage %d, subscr %d\n",
105 : cred, cred->magic, cred->put_addr,
106 : atomic_read(&cred->usage),
107 : read_cred_subscribers(cred));
108 : #else
109 6048 : if (atomic_read(&cred->usage) != 0)
110 0 : panic("CRED: put_cred_rcu() sees %p with usage %d\n",
111 0 : cred, atomic_read(&cred->usage));
112 : #endif
113 :
114 6048 : security_cred_free(cred);
115 6049 : key_put(cred->session_keyring);
116 6049 : key_put(cred->process_keyring);
117 6049 : key_put(cred->thread_keyring);
118 6049 : key_put(cred->request_key_auth);
119 6049 : if (cred->group_info)
120 12098 : put_group_info(cred->group_info);
121 6049 : free_uid(cred->user);
122 6049 : put_user_ns(cred->user_ns);
123 6049 : kmem_cache_free(cred_jar, cred);
124 6049 : }
125 :
126 : /**
127 : * __put_cred - Destroy a set of credentials
128 : * @cred: The record to release
129 : *
130 : * Destroy a set of credentials on which no references remain.
131 : */
132 6060 : void __put_cred(struct cred *cred)
133 : {
134 6060 : kdebug("__put_cred(%p{%d,%d})", cred,
135 : atomic_read(&cred->usage),
136 : read_cred_subscribers(cred));
137 :
138 6060 : BUG_ON(atomic_read(&cred->usage) != 0);
139 : #ifdef CONFIG_DEBUG_CREDENTIALS
140 : BUG_ON(read_cred_subscribers(cred) != 0);
141 : cred->magic = CRED_MAGIC_DEAD;
142 : cred->put_addr = __builtin_return_address(0);
143 : #endif
144 6060 : BUG_ON(cred == current->cred);
145 6060 : BUG_ON(cred == current->real_cred);
146 :
147 6060 : if (cred->non_rcu)
148 2941 : put_cred_rcu(&cred->rcu);
149 : else
150 3119 : call_rcu(&cred->rcu, put_cred_rcu);
151 6060 : }
152 : EXPORT_SYMBOL(__put_cred);
153 :
154 : /*
155 : * Clean up a task's credentials when it exits
156 : */
157 882 : void exit_creds(struct task_struct *tsk)
158 : {
159 882 : struct cred *cred;
160 :
161 882 : kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
162 : atomic_read(&tsk->cred->usage),
163 : read_cred_subscribers(tsk->cred));
164 :
165 882 : cred = (struct cred *) tsk->real_cred;
166 882 : tsk->real_cred = NULL;
167 882 : validate_creds(cred);
168 882 : alter_cred_subscribers(cred, -1);
169 882 : put_cred(cred);
170 :
171 882 : cred = (struct cred *) tsk->cred;
172 882 : tsk->cred = NULL;
173 882 : validate_creds(cred);
174 882 : alter_cred_subscribers(cred, -1);
175 882 : put_cred(cred);
176 :
177 : #ifdef CONFIG_KEYS_REQUEST_CACHE
178 : key_put(tsk->cached_requested_key);
179 : tsk->cached_requested_key = NULL;
180 : #endif
181 882 : }
182 :
183 : /**
184 : * get_task_cred - Get another task's objective credentials
185 : * @task: The task to query
186 : *
187 : * Get the objective credentials of a task, pinning them so that they can't go
188 : * away. Accessing a task's credentials directly is not permitted.
189 : *
190 : * The caller must also make sure task doesn't get deleted, either by holding a
191 : * ref on task or by holding tasklist_lock to prevent it from being unlinked.
192 : */
193 152 : const struct cred *get_task_cred(struct task_struct *task)
194 : {
195 152 : const struct cred *cred;
196 :
197 152 : rcu_read_lock();
198 :
199 152 : do {
200 152 : cred = __task_cred((task));
201 152 : BUG_ON(!cred);
202 152 : } while (!get_cred_rcu(cred));
203 :
204 152 : rcu_read_unlock();
205 152 : return cred;
206 : }
207 : EXPORT_SYMBOL(get_task_cred);
208 :
209 : /*
210 : * Allocate blank credentials, such that the credentials can be filled in at a
211 : * later date without risk of ENOMEM.
212 : */
213 0 : struct cred *cred_alloc_blank(void)
214 : {
215 0 : struct cred *new;
216 :
217 0 : new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
218 0 : if (!new)
219 : return NULL;
220 :
221 0 : atomic_set(&new->usage, 1);
222 : #ifdef CONFIG_DEBUG_CREDENTIALS
223 : new->magic = CRED_MAGIC;
224 : #endif
225 :
226 0 : if (security_cred_alloc_blank(new, GFP_KERNEL_ACCOUNT) < 0)
227 0 : goto error;
228 :
229 : return new;
230 :
231 0 : error:
232 0 : abort_creds(new);
233 0 : return NULL;
234 : }
235 :
236 : /**
237 : * prepare_creds - Prepare a new set of credentials for modification
238 : *
239 : * Prepare a new set of task credentials for modification. A task's creds
240 : * shouldn't generally be modified directly, therefore this function is used to
241 : * prepare a new copy, which the caller then modifies and then commits by
242 : * calling commit_creds().
243 : *
244 : * Preparation involves making a copy of the objective creds for modification.
245 : *
246 : * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
247 : *
248 : * Call commit_creds() or abort_creds() to clean up.
249 : */
250 6183 : struct cred *prepare_creds(void)
251 : {
252 6183 : struct task_struct *task = current;
253 6183 : const struct cred *old;
254 6183 : struct cred *new;
255 :
256 6183 : validate_process_creds();
257 :
258 6183 : new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
259 6183 : if (!new)
260 : return NULL;
261 :
262 6183 : kdebug("prepare_creds() alloc %p", new);
263 :
264 6183 : old = task->cred;
265 6183 : memcpy(new, old, sizeof(struct cred));
266 :
267 6183 : new->non_rcu = 0;
268 6183 : atomic_set(&new->usage, 1);
269 6183 : set_cred_subscribers(new, 0);
270 6183 : get_group_info(new->group_info);
271 6183 : get_uid(new->user);
272 6183 : get_user_ns(new->user_ns);
273 :
274 : #ifdef CONFIG_KEYS
275 : key_get(new->session_keyring);
276 : key_get(new->process_keyring);
277 : key_get(new->thread_keyring);
278 : key_get(new->request_key_auth);
279 : #endif
280 :
281 : #ifdef CONFIG_SECURITY
282 6183 : new->security = NULL;
283 : #endif
284 :
285 6183 : if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
286 0 : goto error;
287 6183 : validate_creds(new);
288 : return new;
289 :
290 0 : error:
291 0 : abort_creds(new);
292 0 : return NULL;
293 : }
294 : EXPORT_SYMBOL(prepare_creds);
295 :
296 : /*
297 : * Prepare credentials for current to perform an execve()
298 : * - The caller must hold ->cred_guard_mutex
299 : */
300 1329 : struct cred *prepare_exec_creds(void)
301 : {
302 1329 : struct cred *new;
303 :
304 1329 : new = prepare_creds();
305 1329 : if (!new)
306 : return new;
307 :
308 : #ifdef CONFIG_KEYS
309 : /* newly exec'd tasks don't get a thread keyring */
310 : key_put(new->thread_keyring);
311 : new->thread_keyring = NULL;
312 :
313 : /* inherit the session keyring; new process keyring */
314 : key_put(new->process_keyring);
315 : new->process_keyring = NULL;
316 : #endif
317 :
318 1329 : new->suid = new->fsuid = new->euid;
319 1329 : new->sgid = new->fsgid = new->egid;
320 :
321 1329 : return new;
322 : }
323 :
324 : /*
325 : * Copy credentials for the new process created by fork()
326 : *
327 : * We share if we can, but under some circumstances we have to generate a new
328 : * set.
329 : *
330 : * The new process gets the current process's subjective credentials as its
331 : * objective and subjective credentials
332 : */
333 964 : int copy_creds(struct task_struct *p, unsigned long clone_flags)
334 : {
335 964 : struct cred *new;
336 964 : int ret;
337 :
338 : #ifdef CONFIG_KEYS_REQUEST_CACHE
339 : p->cached_requested_key = NULL;
340 : #endif
341 :
342 964 : if (
343 : #ifdef CONFIG_KEYS
344 : !p->cred->thread_keyring &&
345 : #endif
346 964 : clone_flags & CLONE_THREAD
347 : ) {
348 6 : p->real_cred = get_cred(p->cred);
349 6 : get_cred(p->cred);
350 6 : alter_cred_subscribers(p->cred, 2);
351 6 : kdebug("share_creds(%p{%d,%d})",
352 : p->cred, atomic_read(&p->cred->usage),
353 : read_cred_subscribers(p->cred));
354 6 : atomic_inc(&p->cred->user->processes);
355 6 : return 0;
356 : }
357 :
358 958 : new = prepare_creds();
359 958 : if (!new)
360 : return -ENOMEM;
361 :
362 958 : if (clone_flags & CLONE_NEWUSER) {
363 0 : ret = create_user_ns(new);
364 0 : if (ret < 0)
365 0 : goto error_put;
366 : }
367 :
368 : #ifdef CONFIG_KEYS
369 : /* new threads get their own thread keyrings if their parent already
370 : * had one */
371 : if (new->thread_keyring) {
372 : key_put(new->thread_keyring);
373 : new->thread_keyring = NULL;
374 : if (clone_flags & CLONE_THREAD)
375 : install_thread_keyring_to_cred(new);
376 : }
377 :
378 : /* The process keyring is only shared between the threads in a process;
379 : * anything outside of those threads doesn't inherit.
380 : */
381 : if (!(clone_flags & CLONE_THREAD)) {
382 : key_put(new->process_keyring);
383 : new->process_keyring = NULL;
384 : }
385 : #endif
386 :
387 958 : atomic_inc(&new->user->processes);
388 958 : p->cred = p->real_cred = get_cred(new);
389 958 : alter_cred_subscribers(new, 2);
390 958 : validate_creds(new);
391 958 : return 0;
392 :
393 0 : error_put:
394 0 : put_cred(new);
395 0 : return ret;
396 : }
397 :
398 1492 : static bool cred_cap_issubset(const struct cred *set, const struct cred *subset)
399 : {
400 1492 : const struct user_namespace *set_ns = set->user_ns;
401 1492 : const struct user_namespace *subset_ns = subset->user_ns;
402 :
403 : /* If the two credentials are in the same user namespace see if
404 : * the capabilities of subset are a subset of set.
405 : */
406 1492 : if (set_ns == subset_ns)
407 1492 : return cap_issubset(subset->cap_permitted, set->cap_permitted);
408 :
409 : /* The credentials are in a different user namespaces
410 : * therefore one is a subset of the other only if a set is an
411 : * ancestor of subset and set->euid is owner of subset or one
412 : * of subsets ancestors.
413 : */
414 0 : for (;subset_ns != &init_user_ns; subset_ns = subset_ns->parent) {
415 0 : if ((set_ns == subset_ns->parent) &&
416 0 : uid_eq(subset_ns->owner, set->euid))
417 : return true;
418 : }
419 :
420 : return false;
421 : }
422 :
423 : /**
424 : * commit_creds - Install new credentials upon the current task
425 : * @new: The credentials to be assigned
426 : *
427 : * Install a new set of credentials to the current task, using RCU to replace
428 : * the old set. Both the objective and the subjective credentials pointers are
429 : * updated. This function may not be called if the subjective credentials are
430 : * in an overridden state.
431 : *
432 : * This function eats the caller's reference to the new credentials.
433 : *
434 : * Always returns 0 thus allowing this function to be tail-called at the end
435 : * of, say, sys_setgid().
436 : */
437 1534 : int commit_creds(struct cred *new)
438 : {
439 1534 : struct task_struct *task = current;
440 1534 : const struct cred *old = task->real_cred;
441 :
442 1534 : kdebug("commit_creds(%p{%d,%d})", new,
443 : atomic_read(&new->usage),
444 : read_cred_subscribers(new));
445 :
446 1534 : BUG_ON(task->cred != old);
447 : #ifdef CONFIG_DEBUG_CREDENTIALS
448 : BUG_ON(read_cred_subscribers(old) < 2);
449 : validate_creds(old);
450 : validate_creds(new);
451 : #endif
452 1534 : BUG_ON(atomic_read(&new->usage) < 1);
453 :
454 1534 : get_cred(new); /* we will require a ref for the subj creds too */
455 :
456 : /* dumpability changes */
457 1534 : if (!uid_eq(old->euid, new->euid) ||
458 1513 : !gid_eq(old->egid, new->egid) ||
459 1492 : !uid_eq(old->fsuid, new->fsuid) ||
460 2984 : !gid_eq(old->fsgid, new->fsgid) ||
461 1492 : !cred_cap_issubset(old, new)) {
462 42 : if (task->mm)
463 42 : set_dumpable(task->mm, suid_dumpable);
464 42 : task->pdeath_signal = 0;
465 : /*
466 : * If a task drops privileges and becomes nondumpable,
467 : * the dumpability change must become visible before
468 : * the credential change; otherwise, a __ptrace_may_access()
469 : * racing with this change may be able to attach to a task it
470 : * shouldn't be able to attach to (as if the task had dropped
471 : * privileges without becoming nondumpable).
472 : * Pairs with a read barrier in __ptrace_may_access().
473 : */
474 42 : smp_wmb();
475 : }
476 :
477 : /* alter the thread keyring */
478 1534 : if (!uid_eq(new->fsuid, old->fsuid))
479 1534 : key_fsuid_changed(new);
480 1534 : if (!gid_eq(new->fsgid, old->fsgid))
481 1534 : key_fsgid_changed(new);
482 :
483 : /* do it
484 : * RLIMIT_NPROC limits on user->processes have already been checked
485 : * in set_user().
486 : */
487 1534 : alter_cred_subscribers(new, 2);
488 1534 : if (new->user != old->user)
489 20 : atomic_inc(&new->user->processes);
490 1534 : rcu_assign_pointer(task->real_cred, new);
491 1534 : rcu_assign_pointer(task->cred, new);
492 1534 : if (new->user != old->user)
493 20 : atomic_dec(&old->user->processes);
494 1534 : alter_cred_subscribers(old, -2);
495 :
496 : /* send notifications */
497 1534 : if (!uid_eq(new->uid, old->uid) ||
498 : !uid_eq(new->euid, old->euid) ||
499 : !uid_eq(new->suid, old->suid) ||
500 : !uid_eq(new->fsuid, old->fsuid))
501 1534 : proc_id_connector(task, PROC_EVENT_UID);
502 :
503 1534 : if (!gid_eq(new->gid, old->gid) ||
504 : !gid_eq(new->egid, old->egid) ||
505 : !gid_eq(new->sgid, old->sgid) ||
506 : !gid_eq(new->fsgid, old->fsgid))
507 1534 : proc_id_connector(task, PROC_EVENT_GID);
508 :
509 : /* release the old obj and subj refs both */
510 1534 : put_cred(old);
511 1534 : put_cred(old);
512 1534 : return 0;
513 : }
514 : EXPORT_SYMBOL(commit_creds);
515 :
516 : /**
517 : * abort_creds - Discard a set of credentials and unlock the current task
518 : * @new: The credentials that were going to be applied
519 : *
520 : * Discard a set of credentials that were under construction and unlock the
521 : * current task.
522 : */
523 748 : void abort_creds(struct cred *new)
524 : {
525 748 : kdebug("abort_creds(%p{%d,%d})", new,
526 : atomic_read(&new->usage),
527 : read_cred_subscribers(new));
528 :
529 : #ifdef CONFIG_DEBUG_CREDENTIALS
530 : BUG_ON(read_cred_subscribers(new) != 0);
531 : #endif
532 748 : BUG_ON(atomic_read(&new->usage) < 1);
533 748 : put_cred(new);
534 748 : }
535 : EXPORT_SYMBOL(abort_creds);
536 :
537 : /**
538 : * override_creds - Override the current process's subjective credentials
539 : * @new: The credentials to be assigned
540 : *
541 : * Install a set of temporary override subjective credentials on the current
542 : * process, returning the old set for later reversion.
543 : */
544 3192 : const struct cred *override_creds(const struct cred *new)
545 : {
546 3192 : const struct cred *old = current->cred;
547 :
548 3192 : kdebug("override_creds(%p{%d,%d})", new,
549 : atomic_read(&new->usage),
550 : read_cred_subscribers(new));
551 :
552 3192 : validate_creds(old);
553 3192 : validate_creds(new);
554 :
555 : /*
556 : * NOTE! This uses 'get_new_cred()' rather than 'get_cred()'.
557 : *
558 : * That means that we do not clear the 'non_rcu' flag, since
559 : * we are only installing the cred into the thread-synchronous
560 : * '->cred' pointer, not the '->real_cred' pointer that is
561 : * visible to other threads under RCU.
562 : *
563 : * Also note that we did validate_creds() manually, not depending
564 : * on the validation in 'get_cred()'.
565 : */
566 3192 : get_new_cred((struct cred *)new);
567 3192 : alter_cred_subscribers(new, 1);
568 3192 : rcu_assign_pointer(current->cred, new);
569 3192 : alter_cred_subscribers(old, -1);
570 :
571 3192 : kdebug("override_creds() = %p{%d,%d}", old,
572 : atomic_read(&old->usage),
573 : read_cred_subscribers(old));
574 3192 : return old;
575 : }
576 : EXPORT_SYMBOL(override_creds);
577 :
578 : /**
579 : * revert_creds - Revert a temporary subjective credentials override
580 : * @old: The credentials to be restored
581 : *
582 : * Revert a temporary set of override subjective credentials to an old set,
583 : * discarding the override set.
584 : */
585 3192 : void revert_creds(const struct cred *old)
586 : {
587 3192 : const struct cred *override = current->cred;
588 :
589 3192 : kdebug("revert_creds(%p{%d,%d})", old,
590 : atomic_read(&old->usage),
591 : read_cred_subscribers(old));
592 :
593 3192 : validate_creds(old);
594 3192 : validate_creds(override);
595 3192 : alter_cred_subscribers(old, 1);
596 3192 : rcu_assign_pointer(current->cred, old);
597 3192 : alter_cred_subscribers(override, -1);
598 3192 : put_cred(override);
599 3192 : }
600 : EXPORT_SYMBOL(revert_creds);
601 :
602 : /**
603 : * cred_fscmp - Compare two credentials with respect to filesystem access.
604 : * @a: The first credential
605 : * @b: The second credential
606 : *
607 : * cred_cmp() will return zero if both credentials have the same
608 : * fsuid, fsgid, and supplementary groups. That is, if they will both
609 : * provide the same access to files based on mode/uid/gid.
610 : * If the credentials are different, then either -1 or 1 will
611 : * be returned depending on whether @a comes before or after @b
612 : * respectively in an arbitrary, but stable, ordering of credentials.
613 : *
614 : * Return: -1, 0, or 1 depending on comparison
615 : */
616 0 : int cred_fscmp(const struct cred *a, const struct cred *b)
617 : {
618 0 : struct group_info *ga, *gb;
619 0 : int g;
620 :
621 0 : if (a == b)
622 : return 0;
623 0 : if (uid_lt(a->fsuid, b->fsuid))
624 : return -1;
625 0 : if (uid_gt(a->fsuid, b->fsuid))
626 : return 1;
627 :
628 0 : if (gid_lt(a->fsgid, b->fsgid))
629 : return -1;
630 0 : if (gid_gt(a->fsgid, b->fsgid))
631 : return 1;
632 :
633 0 : ga = a->group_info;
634 0 : gb = b->group_info;
635 0 : if (ga == gb)
636 : return 0;
637 0 : if (ga == NULL)
638 : return -1;
639 0 : if (gb == NULL)
640 : return 1;
641 0 : if (ga->ngroups < gb->ngroups)
642 : return -1;
643 0 : if (ga->ngroups > gb->ngroups)
644 : return 1;
645 :
646 0 : for (g = 0; g < ga->ngroups; g++) {
647 0 : if (gid_lt(ga->gid[g], gb->gid[g]))
648 : return -1;
649 0 : if (gid_gt(ga->gid[g], gb->gid[g]))
650 : return 1;
651 : }
652 : return 0;
653 : }
654 : EXPORT_SYMBOL(cred_fscmp);
655 :
656 : /*
657 : * initialise the credentials stuff
658 : */
659 1 : void __init cred_init(void)
660 : {
661 : /* allocate a slab in which we can store credentials */
662 1 : cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), 0,
663 : SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL);
664 1 : }
665 :
666 : /**
667 : * prepare_kernel_cred - Prepare a set of credentials for a kernel service
668 : * @daemon: A userspace daemon to be used as a reference
669 : *
670 : * Prepare a set of credentials for a kernel service. This can then be used to
671 : * override a task's own credentials so that work can be done on behalf of that
672 : * task that requires a different subjective context.
673 : *
674 : * @daemon is used to provide a base for the security record, but can be NULL.
675 : * If @daemon is supplied, then the security data will be derived from that;
676 : * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
677 : *
678 : * The caller may change these controls afterwards if desired.
679 : *
680 : * Returns the new credentials or NULL if out of memory.
681 : */
682 0 : struct cred *prepare_kernel_cred(struct task_struct *daemon)
683 : {
684 0 : const struct cred *old;
685 0 : struct cred *new;
686 :
687 0 : new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
688 0 : if (!new)
689 : return NULL;
690 :
691 0 : kdebug("prepare_kernel_cred() alloc %p", new);
692 :
693 0 : if (daemon)
694 0 : old = get_task_cred(daemon);
695 : else
696 0 : old = get_cred(&init_cred);
697 :
698 0 : validate_creds(old);
699 :
700 0 : *new = *old;
701 0 : new->non_rcu = 0;
702 0 : atomic_set(&new->usage, 1);
703 0 : set_cred_subscribers(new, 0);
704 0 : get_uid(new->user);
705 0 : get_user_ns(new->user_ns);
706 0 : get_group_info(new->group_info);
707 :
708 : #ifdef CONFIG_KEYS
709 : new->session_keyring = NULL;
710 : new->process_keyring = NULL;
711 : new->thread_keyring = NULL;
712 : new->request_key_auth = NULL;
713 : new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
714 : #endif
715 :
716 : #ifdef CONFIG_SECURITY
717 0 : new->security = NULL;
718 : #endif
719 0 : if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
720 0 : goto error;
721 :
722 0 : put_cred(old);
723 0 : validate_creds(new);
724 0 : return new;
725 :
726 0 : error:
727 0 : put_cred(new);
728 0 : put_cred(old);
729 0 : return NULL;
730 : }
731 : EXPORT_SYMBOL(prepare_kernel_cred);
732 :
733 : /**
734 : * set_security_override - Set the security ID in a set of credentials
735 : * @new: The credentials to alter
736 : * @secid: The LSM security ID to set
737 : *
738 : * Set the LSM security ID in a set of credentials so that the subjective
739 : * security is overridden when an alternative set of credentials is used.
740 : */
741 0 : int set_security_override(struct cred *new, u32 secid)
742 : {
743 0 : return security_kernel_act_as(new, secid);
744 : }
745 : EXPORT_SYMBOL(set_security_override);
746 :
747 : /**
748 : * set_security_override_from_ctx - Set the security ID in a set of credentials
749 : * @new: The credentials to alter
750 : * @secctx: The LSM security context to generate the security ID from.
751 : *
752 : * Set the LSM security ID in a set of credentials so that the subjective
753 : * security is overridden when an alternative set of credentials is used. The
754 : * security ID is specified in string form as a security context to be
755 : * interpreted by the LSM.
756 : */
757 0 : int set_security_override_from_ctx(struct cred *new, const char *secctx)
758 : {
759 0 : u32 secid;
760 0 : int ret;
761 :
762 0 : ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
763 0 : if (ret < 0)
764 : return ret;
765 :
766 0 : return set_security_override(new, secid);
767 : }
768 : EXPORT_SYMBOL(set_security_override_from_ctx);
769 :
770 : /**
771 : * set_create_files_as - Set the LSM file create context in a set of credentials
772 : * @new: The credentials to alter
773 : * @inode: The inode to take the context from
774 : *
775 : * Change the LSM file creation context in a set of credentials to be the same
776 : * as the object context of the specified inode, so that the new inodes have
777 : * the same MAC context as that inode.
778 : */
779 0 : int set_create_files_as(struct cred *new, struct inode *inode)
780 : {
781 0 : if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid))
782 : return -EINVAL;
783 0 : new->fsuid = inode->i_uid;
784 0 : new->fsgid = inode->i_gid;
785 0 : return security_kernel_create_files_as(new, inode);
786 : }
787 : EXPORT_SYMBOL(set_create_files_as);
788 :
789 : #ifdef CONFIG_DEBUG_CREDENTIALS
790 :
791 : bool creds_are_invalid(const struct cred *cred)
792 : {
793 : if (cred->magic != CRED_MAGIC)
794 : return true;
795 : return false;
796 : }
797 : EXPORT_SYMBOL(creds_are_invalid);
798 :
799 : /*
800 : * dump invalid credentials
801 : */
802 : static void dump_invalid_creds(const struct cred *cred, const char *label,
803 : const struct task_struct *tsk)
804 : {
805 : printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
806 : label, cred,
807 : cred == &init_cred ? "[init]" : "",
808 : cred == tsk->real_cred ? "[real]" : "",
809 : cred == tsk->cred ? "[eff]" : "");
810 : printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
811 : cred->magic, cred->put_addr);
812 : printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
813 : atomic_read(&cred->usage),
814 : read_cred_subscribers(cred));
815 : printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
816 : from_kuid_munged(&init_user_ns, cred->uid),
817 : from_kuid_munged(&init_user_ns, cred->euid),
818 : from_kuid_munged(&init_user_ns, cred->suid),
819 : from_kuid_munged(&init_user_ns, cred->fsuid));
820 : printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
821 : from_kgid_munged(&init_user_ns, cred->gid),
822 : from_kgid_munged(&init_user_ns, cred->egid),
823 : from_kgid_munged(&init_user_ns, cred->sgid),
824 : from_kgid_munged(&init_user_ns, cred->fsgid));
825 : #ifdef CONFIG_SECURITY
826 : printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
827 : if ((unsigned long) cred->security >= PAGE_SIZE &&
828 : (((unsigned long) cred->security & 0xffffff00) !=
829 : (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
830 : printk(KERN_ERR "CRED: ->security {%x, %x}\n",
831 : ((u32*)cred->security)[0],
832 : ((u32*)cred->security)[1]);
833 : #endif
834 : }
835 :
836 : /*
837 : * report use of invalid credentials
838 : */
839 : void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
840 : {
841 : printk(KERN_ERR "CRED: Invalid credentials\n");
842 : printk(KERN_ERR "CRED: At %s:%u\n", file, line);
843 : dump_invalid_creds(cred, "Specified", current);
844 : BUG();
845 : }
846 : EXPORT_SYMBOL(__invalid_creds);
847 :
848 : /*
849 : * check the credentials on a process
850 : */
851 : void __validate_process_creds(struct task_struct *tsk,
852 : const char *file, unsigned line)
853 : {
854 : if (tsk->cred == tsk->real_cred) {
855 : if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
856 : creds_are_invalid(tsk->cred)))
857 : goto invalid_creds;
858 : } else {
859 : if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
860 : read_cred_subscribers(tsk->cred) < 1 ||
861 : creds_are_invalid(tsk->real_cred) ||
862 : creds_are_invalid(tsk->cred)))
863 : goto invalid_creds;
864 : }
865 : return;
866 :
867 : invalid_creds:
868 : printk(KERN_ERR "CRED: Invalid process credentials\n");
869 : printk(KERN_ERR "CRED: At %s:%u\n", file, line);
870 :
871 : dump_invalid_creds(tsk->real_cred, "Real", tsk);
872 : if (tsk->cred != tsk->real_cred)
873 : dump_invalid_creds(tsk->cred, "Effective", tsk);
874 : else
875 : printk(KERN_ERR "CRED: Effective creds == Real creds\n");
876 : BUG();
877 : }
878 : EXPORT_SYMBOL(__validate_process_creds);
879 :
880 : /*
881 : * check creds for do_exit()
882 : */
883 : void validate_creds_for_do_exit(struct task_struct *tsk)
884 : {
885 : kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
886 : tsk->real_cred, tsk->cred,
887 : atomic_read(&tsk->cred->usage),
888 : read_cred_subscribers(tsk->cred));
889 :
890 : __validate_process_creds(tsk, __FILE__, __LINE__);
891 : }
892 :
893 : #endif /* CONFIG_DEBUG_CREDENTIALS */
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