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 : static 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 : .ucounts = &init_ucounts,
64 : };
65 :
66 : static inline void set_cred_subscribers(struct cred *cred, int n)
67 : {
68 : #ifdef CONFIG_DEBUG_CREDENTIALS
69 : atomic_set(&cred->subscribers, n);
70 : #endif
71 : }
72 :
73 : static inline int read_cred_subscribers(const struct cred *cred)
74 : {
75 : #ifdef CONFIG_DEBUG_CREDENTIALS
76 : return atomic_read(&cred->subscribers);
77 : #else
78 : return 0;
79 : #endif
80 : }
81 :
82 : static inline void alter_cred_subscribers(const struct cred *_cred, int n)
83 : {
84 : #ifdef CONFIG_DEBUG_CREDENTIALS
85 : struct cred *cred = (struct cred *) _cred;
86 :
87 : atomic_add(n, &cred->subscribers);
88 : #endif
89 : }
90 :
91 : /*
92 : * The RCU callback to actually dispose of a set of credentials
93 : */
94 159 : static void put_cred_rcu(struct rcu_head *rcu)
95 : {
96 159 : struct cred *cred = container_of(rcu, struct cred, rcu);
97 :
98 : kdebug("put_cred_rcu(%p)", cred);
99 :
100 : #ifdef CONFIG_DEBUG_CREDENTIALS
101 : if (cred->magic != CRED_MAGIC_DEAD ||
102 : atomic_read(&cred->usage) != 0 ||
103 : read_cred_subscribers(cred) != 0)
104 : panic("CRED: put_cred_rcu() sees %p with"
105 : " mag %x, put %p, usage %d, subscr %d\n",
106 : cred, cred->magic, cred->put_addr,
107 : atomic_read(&cred->usage),
108 : read_cred_subscribers(cred));
109 : #else
110 318 : if (atomic_read(&cred->usage) != 0)
111 0 : panic("CRED: put_cred_rcu() sees %p with usage %d\n",
112 0 : cred, atomic_read(&cred->usage));
113 : #endif
114 :
115 159 : security_cred_free(cred);
116 : key_put(cred->session_keyring);
117 : key_put(cred->process_keyring);
118 : key_put(cred->thread_keyring);
119 : key_put(cred->request_key_auth);
120 159 : if (cred->group_info)
121 318 : put_group_info(cred->group_info);
122 159 : free_uid(cred->user);
123 159 : if (cred->ucounts)
124 159 : put_ucounts(cred->ucounts);
125 159 : put_user_ns(cred->user_ns);
126 159 : kmem_cache_free(cred_jar, cred);
127 159 : }
128 :
129 : /**
130 : * __put_cred - Destroy a set of credentials
131 : * @cred: The record to release
132 : *
133 : * Destroy a set of credentials on which no references remain.
134 : */
135 159 : void __put_cred(struct cred *cred)
136 : {
137 : kdebug("__put_cred(%p{%d,%d})", cred,
138 : atomic_read(&cred->usage),
139 : read_cred_subscribers(cred));
140 :
141 318 : BUG_ON(atomic_read(&cred->usage) != 0);
142 : #ifdef CONFIG_DEBUG_CREDENTIALS
143 : BUG_ON(read_cred_subscribers(cred) != 0);
144 : cred->magic = CRED_MAGIC_DEAD;
145 : cred->put_addr = __builtin_return_address(0);
146 : #endif
147 159 : BUG_ON(cred == current->cred);
148 159 : BUG_ON(cred == current->real_cred);
149 :
150 159 : if (cred->non_rcu)
151 0 : put_cred_rcu(&cred->rcu);
152 : else
153 159 : call_rcu(&cred->rcu, put_cred_rcu);
154 159 : }
155 : EXPORT_SYMBOL(__put_cred);
156 :
157 : /*
158 : * Clean up a task's credentials when it exits
159 : */
160 159 : void exit_creds(struct task_struct *tsk)
161 : {
162 : struct cred *cred;
163 :
164 : kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
165 : atomic_read(&tsk->cred->usage),
166 : read_cred_subscribers(tsk->cred));
167 :
168 159 : cred = (struct cred *) tsk->real_cred;
169 159 : tsk->real_cred = NULL;
170 159 : validate_creds(cred);
171 159 : alter_cred_subscribers(cred, -1);
172 159 : put_cred(cred);
173 :
174 159 : cred = (struct cred *) tsk->cred;
175 159 : tsk->cred = NULL;
176 159 : validate_creds(cred);
177 159 : alter_cred_subscribers(cred, -1);
178 159 : put_cred(cred);
179 :
180 : #ifdef CONFIG_KEYS_REQUEST_CACHE
181 : key_put(tsk->cached_requested_key);
182 : tsk->cached_requested_key = NULL;
183 : #endif
184 159 : }
185 :
186 : /**
187 : * get_task_cred - Get another task's objective credentials
188 : * @task: The task to query
189 : *
190 : * Get the objective credentials of a task, pinning them so that they can't go
191 : * away. Accessing a task's credentials directly is not permitted.
192 : *
193 : * The caller must also make sure task doesn't get deleted, either by holding a
194 : * ref on task or by holding tasklist_lock to prevent it from being unlinked.
195 : */
196 0 : const struct cred *get_task_cred(struct task_struct *task)
197 : {
198 : const struct cred *cred;
199 :
200 : rcu_read_lock();
201 :
202 : do {
203 0 : cred = __task_cred((task));
204 0 : BUG_ON(!cred);
205 0 : } while (!get_cred_rcu(cred));
206 :
207 : rcu_read_unlock();
208 0 : return cred;
209 : }
210 : EXPORT_SYMBOL(get_task_cred);
211 :
212 : /*
213 : * Allocate blank credentials, such that the credentials can be filled in at a
214 : * later date without risk of ENOMEM.
215 : */
216 0 : struct cred *cred_alloc_blank(void)
217 : {
218 : struct cred *new;
219 :
220 0 : new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
221 0 : if (!new)
222 : return NULL;
223 :
224 0 : atomic_set(&new->usage, 1);
225 : #ifdef CONFIG_DEBUG_CREDENTIALS
226 : new->magic = CRED_MAGIC;
227 : #endif
228 0 : if (security_cred_alloc_blank(new, GFP_KERNEL_ACCOUNT) < 0)
229 : goto error;
230 :
231 0 : return new;
232 :
233 : error:
234 : abort_creds(new);
235 : return NULL;
236 : }
237 :
238 : /**
239 : * prepare_creds - Prepare a new set of credentials for modification
240 : *
241 : * Prepare a new set of task credentials for modification. A task's creds
242 : * shouldn't generally be modified directly, therefore this function is used to
243 : * prepare a new copy, which the caller then modifies and then commits by
244 : * calling commit_creds().
245 : *
246 : * Preparation involves making a copy of the objective creds for modification.
247 : *
248 : * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
249 : *
250 : * Call commit_creds() or abort_creds() to clean up.
251 : */
252 175 : struct cred *prepare_creds(void)
253 : {
254 175 : struct task_struct *task = current;
255 : const struct cred *old;
256 : struct cred *new;
257 :
258 : validate_process_creds();
259 :
260 175 : new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
261 175 : if (!new)
262 : return NULL;
263 :
264 : kdebug("prepare_creds() alloc %p", new);
265 :
266 175 : old = task->cred;
267 350 : memcpy(new, old, sizeof(struct cred));
268 :
269 175 : new->non_rcu = 0;
270 350 : atomic_set(&new->usage, 1);
271 175 : set_cred_subscribers(new, 0);
272 350 : get_group_info(new->group_info);
273 350 : get_uid(new->user);
274 175 : get_user_ns(new->user_ns);
275 :
276 : #ifdef CONFIG_KEYS
277 : key_get(new->session_keyring);
278 : key_get(new->process_keyring);
279 : key_get(new->thread_keyring);
280 : key_get(new->request_key_auth);
281 : #endif
282 :
283 : #ifdef CONFIG_SECURITY
284 : new->security = NULL;
285 : #endif
286 :
287 175 : new->ucounts = get_ucounts(new->ucounts);
288 175 : if (!new->ucounts)
289 : goto error;
290 :
291 : if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
292 : goto error;
293 :
294 : validate_creds(new);
295 : return new;
296 :
297 : error:
298 0 : abort_creds(new);
299 0 : return NULL;
300 : }
301 : EXPORT_SYMBOL(prepare_creds);
302 :
303 : /*
304 : * Prepare credentials for current to perform an execve()
305 : * - The caller must hold ->cred_guard_mutex
306 : */
307 0 : struct cred *prepare_exec_creds(void)
308 : {
309 : struct cred *new;
310 :
311 0 : new = prepare_creds();
312 0 : if (!new)
313 : return new;
314 :
315 : #ifdef CONFIG_KEYS
316 : /* newly exec'd tasks don't get a thread keyring */
317 : key_put(new->thread_keyring);
318 : new->thread_keyring = NULL;
319 :
320 : /* inherit the session keyring; new process keyring */
321 : key_put(new->process_keyring);
322 : new->process_keyring = NULL;
323 : #endif
324 :
325 0 : new->suid = new->fsuid = new->euid;
326 0 : new->sgid = new->fsgid = new->egid;
327 :
328 0 : return new;
329 : }
330 :
331 : /*
332 : * Copy credentials for the new process created by fork()
333 : *
334 : * We share if we can, but under some circumstances we have to generate a new
335 : * set.
336 : *
337 : * The new process gets the current process's subjective credentials as its
338 : * objective and subjective credentials
339 : */
340 175 : int copy_creds(struct task_struct *p, unsigned long clone_flags)
341 : {
342 : struct cred *new;
343 : int ret;
344 :
345 : #ifdef CONFIG_KEYS_REQUEST_CACHE
346 : p->cached_requested_key = NULL;
347 : #endif
348 :
349 175 : if (
350 : #ifdef CONFIG_KEYS
351 : !p->cred->thread_keyring &&
352 : #endif
353 175 : clone_flags & CLONE_THREAD
354 : ) {
355 0 : p->real_cred = get_cred(p->cred);
356 0 : get_cred(p->cred);
357 0 : alter_cred_subscribers(p->cred, 2);
358 : kdebug("share_creds(%p{%d,%d})",
359 : p->cred, atomic_read(&p->cred->usage),
360 : read_cred_subscribers(p->cred));
361 0 : inc_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
362 0 : return 0;
363 : }
364 :
365 175 : new = prepare_creds();
366 175 : if (!new)
367 : return -ENOMEM;
368 :
369 175 : if (clone_flags & CLONE_NEWUSER) {
370 0 : ret = create_user_ns(new);
371 : if (ret < 0)
372 : goto error_put;
373 : ret = set_cred_ucounts(new);
374 : if (ret < 0)
375 : goto error_put;
376 : }
377 :
378 : #ifdef CONFIG_KEYS
379 : /* new threads get their own thread keyrings if their parent already
380 : * had one */
381 : if (new->thread_keyring) {
382 : key_put(new->thread_keyring);
383 : new->thread_keyring = NULL;
384 : if (clone_flags & CLONE_THREAD)
385 : install_thread_keyring_to_cred(new);
386 : }
387 :
388 : /* The process keyring is only shared between the threads in a process;
389 : * anything outside of those threads doesn't inherit.
390 : */
391 : if (!(clone_flags & CLONE_THREAD)) {
392 : key_put(new->process_keyring);
393 : new->process_keyring = NULL;
394 : }
395 : #endif
396 :
397 175 : p->cred = p->real_cred = get_cred(new);
398 350 : inc_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
399 175 : alter_cred_subscribers(new, 2);
400 175 : validate_creds(new);
401 175 : return 0;
402 :
403 : error_put:
404 : put_cred(new);
405 : return ret;
406 : }
407 :
408 : static bool cred_cap_issubset(const struct cred *set, const struct cred *subset)
409 : {
410 0 : const struct user_namespace *set_ns = set->user_ns;
411 0 : const struct user_namespace *subset_ns = subset->user_ns;
412 :
413 : /* If the two credentials are in the same user namespace see if
414 : * the capabilities of subset are a subset of set.
415 : */
416 0 : if (set_ns == subset_ns)
417 : return cap_issubset(subset->cap_permitted, set->cap_permitted);
418 :
419 : /* The credentials are in a different user namespaces
420 : * therefore one is a subset of the other only if a set is an
421 : * ancestor of subset and set->euid is owner of subset or one
422 : * of subsets ancestors.
423 : */
424 0 : for (;subset_ns != &init_user_ns; subset_ns = subset_ns->parent) {
425 0 : if ((set_ns == subset_ns->parent) &&
426 0 : uid_eq(subset_ns->owner, set->euid))
427 : return true;
428 : }
429 :
430 : return false;
431 : }
432 :
433 : /**
434 : * commit_creds - Install new credentials upon the current task
435 : * @new: The credentials to be assigned
436 : *
437 : * Install a new set of credentials to the current task, using RCU to replace
438 : * the old set. Both the objective and the subjective credentials pointers are
439 : * updated. This function may not be called if the subjective credentials are
440 : * in an overridden state.
441 : *
442 : * This function eats the caller's reference to the new credentials.
443 : *
444 : * Always returns 0 thus allowing this function to be tail-called at the end
445 : * of, say, sys_setgid().
446 : */
447 0 : int commit_creds(struct cred *new)
448 : {
449 0 : struct task_struct *task = current;
450 0 : const struct cred *old = task->real_cred;
451 :
452 : kdebug("commit_creds(%p{%d,%d})", new,
453 : atomic_read(&new->usage),
454 : read_cred_subscribers(new));
455 :
456 0 : BUG_ON(task->cred != old);
457 : #ifdef CONFIG_DEBUG_CREDENTIALS
458 : BUG_ON(read_cred_subscribers(old) < 2);
459 : validate_creds(old);
460 : validate_creds(new);
461 : #endif
462 0 : BUG_ON(atomic_read(&new->usage) < 1);
463 :
464 0 : get_cred(new); /* we will require a ref for the subj creds too */
465 :
466 : /* dumpability changes */
467 0 : if (!uid_eq(old->euid, new->euid) ||
468 0 : !gid_eq(old->egid, new->egid) ||
469 0 : !uid_eq(old->fsuid, new->fsuid) ||
470 0 : !gid_eq(old->fsgid, new->fsgid) ||
471 0 : !cred_cap_issubset(old, new)) {
472 0 : if (task->mm)
473 0 : set_dumpable(task->mm, suid_dumpable);
474 0 : task->pdeath_signal = 0;
475 : /*
476 : * If a task drops privileges and becomes nondumpable,
477 : * the dumpability change must become visible before
478 : * the credential change; otherwise, a __ptrace_may_access()
479 : * racing with this change may be able to attach to a task it
480 : * shouldn't be able to attach to (as if the task had dropped
481 : * privileges without becoming nondumpable).
482 : * Pairs with a read barrier in __ptrace_may_access().
483 : */
484 0 : smp_wmb();
485 : }
486 :
487 : /* alter the thread keyring */
488 0 : if (!uid_eq(new->fsuid, old->fsuid))
489 : key_fsuid_changed(new);
490 0 : if (!gid_eq(new->fsgid, old->fsgid))
491 : key_fsgid_changed(new);
492 :
493 : /* do it
494 : * RLIMIT_NPROC limits on user->processes have already been checked
495 : * in set_user().
496 : */
497 0 : alter_cred_subscribers(new, 2);
498 0 : if (new->user != old->user || new->user_ns != old->user_ns)
499 0 : inc_rlimit_ucounts(new->ucounts, UCOUNT_RLIMIT_NPROC, 1);
500 0 : rcu_assign_pointer(task->real_cred, new);
501 0 : rcu_assign_pointer(task->cred, new);
502 0 : if (new->user != old->user || new->user_ns != old->user_ns)
503 0 : dec_rlimit_ucounts(old->ucounts, UCOUNT_RLIMIT_NPROC, 1);
504 0 : alter_cred_subscribers(old, -2);
505 :
506 : /* send notifications */
507 0 : if (!uid_eq(new->uid, old->uid) ||
508 : !uid_eq(new->euid, old->euid) ||
509 : !uid_eq(new->suid, old->suid) ||
510 : !uid_eq(new->fsuid, old->fsuid))
511 : proc_id_connector(task, PROC_EVENT_UID);
512 :
513 0 : if (!gid_eq(new->gid, old->gid) ||
514 : !gid_eq(new->egid, old->egid) ||
515 : !gid_eq(new->sgid, old->sgid) ||
516 : !gid_eq(new->fsgid, old->fsgid))
517 : proc_id_connector(task, PROC_EVENT_GID);
518 :
519 : /* release the old obj and subj refs both */
520 0 : put_cred(old);
521 0 : put_cred(old);
522 0 : return 0;
523 : }
524 : EXPORT_SYMBOL(commit_creds);
525 :
526 : /**
527 : * abort_creds - Discard a set of credentials and unlock the current task
528 : * @new: The credentials that were going to be applied
529 : *
530 : * Discard a set of credentials that were under construction and unlock the
531 : * current task.
532 : */
533 0 : void abort_creds(struct cred *new)
534 : {
535 : kdebug("abort_creds(%p{%d,%d})", new,
536 : atomic_read(&new->usage),
537 : read_cred_subscribers(new));
538 :
539 : #ifdef CONFIG_DEBUG_CREDENTIALS
540 : BUG_ON(read_cred_subscribers(new) != 0);
541 : #endif
542 0 : BUG_ON(atomic_read(&new->usage) < 1);
543 0 : put_cred(new);
544 0 : }
545 : EXPORT_SYMBOL(abort_creds);
546 :
547 : /**
548 : * override_creds - Override the current process's subjective credentials
549 : * @new: The credentials to be assigned
550 : *
551 : * Install a set of temporary override subjective credentials on the current
552 : * process, returning the old set for later reversion.
553 : */
554 0 : const struct cred *override_creds(const struct cred *new)
555 : {
556 0 : const struct cred *old = current->cred;
557 :
558 : kdebug("override_creds(%p{%d,%d})", new,
559 : atomic_read(&new->usage),
560 : read_cred_subscribers(new));
561 :
562 0 : validate_creds(old);
563 0 : validate_creds(new);
564 :
565 : /*
566 : * NOTE! This uses 'get_new_cred()' rather than 'get_cred()'.
567 : *
568 : * That means that we do not clear the 'non_rcu' flag, since
569 : * we are only installing the cred into the thread-synchronous
570 : * '->cred' pointer, not the '->real_cred' pointer that is
571 : * visible to other threads under RCU.
572 : *
573 : * Also note that we did validate_creds() manually, not depending
574 : * on the validation in 'get_cred()'.
575 : */
576 0 : get_new_cred((struct cred *)new);
577 0 : alter_cred_subscribers(new, 1);
578 0 : rcu_assign_pointer(current->cred, new);
579 0 : alter_cred_subscribers(old, -1);
580 :
581 : kdebug("override_creds() = %p{%d,%d}", old,
582 : atomic_read(&old->usage),
583 : read_cred_subscribers(old));
584 0 : return old;
585 : }
586 : EXPORT_SYMBOL(override_creds);
587 :
588 : /**
589 : * revert_creds - Revert a temporary subjective credentials override
590 : * @old: The credentials to be restored
591 : *
592 : * Revert a temporary set of override subjective credentials to an old set,
593 : * discarding the override set.
594 : */
595 0 : void revert_creds(const struct cred *old)
596 : {
597 0 : const struct cred *override = current->cred;
598 :
599 : kdebug("revert_creds(%p{%d,%d})", old,
600 : atomic_read(&old->usage),
601 : read_cred_subscribers(old));
602 :
603 0 : validate_creds(old);
604 0 : validate_creds(override);
605 0 : alter_cred_subscribers(old, 1);
606 0 : rcu_assign_pointer(current->cred, old);
607 0 : alter_cred_subscribers(override, -1);
608 0 : put_cred(override);
609 0 : }
610 : EXPORT_SYMBOL(revert_creds);
611 :
612 : /**
613 : * cred_fscmp - Compare two credentials with respect to filesystem access.
614 : * @a: The first credential
615 : * @b: The second credential
616 : *
617 : * cred_cmp() will return zero if both credentials have the same
618 : * fsuid, fsgid, and supplementary groups. That is, if they will both
619 : * provide the same access to files based on mode/uid/gid.
620 : * If the credentials are different, then either -1 or 1 will
621 : * be returned depending on whether @a comes before or after @b
622 : * respectively in an arbitrary, but stable, ordering of credentials.
623 : *
624 : * Return: -1, 0, or 1 depending on comparison
625 : */
626 0 : int cred_fscmp(const struct cred *a, const struct cred *b)
627 : {
628 : struct group_info *ga, *gb;
629 : int g;
630 :
631 0 : if (a == b)
632 : return 0;
633 0 : if (uid_lt(a->fsuid, b->fsuid))
634 : return -1;
635 0 : if (uid_gt(a->fsuid, b->fsuid))
636 : return 1;
637 :
638 0 : if (gid_lt(a->fsgid, b->fsgid))
639 : return -1;
640 0 : if (gid_gt(a->fsgid, b->fsgid))
641 : return 1;
642 :
643 0 : ga = a->group_info;
644 0 : gb = b->group_info;
645 0 : if (ga == gb)
646 : return 0;
647 0 : if (ga == NULL)
648 : return -1;
649 0 : if (gb == NULL)
650 : return 1;
651 0 : if (ga->ngroups < gb->ngroups)
652 : return -1;
653 0 : if (ga->ngroups > gb->ngroups)
654 : return 1;
655 :
656 0 : for (g = 0; g < ga->ngroups; g++) {
657 0 : if (gid_lt(ga->gid[g], gb->gid[g]))
658 : return -1;
659 0 : if (gid_gt(ga->gid[g], gb->gid[g]))
660 : return 1;
661 : }
662 : return 0;
663 : }
664 : EXPORT_SYMBOL(cred_fscmp);
665 :
666 0 : int set_cred_ucounts(struct cred *new)
667 : {
668 0 : struct ucounts *new_ucounts, *old_ucounts = new->ucounts;
669 :
670 : /*
671 : * This optimization is needed because alloc_ucounts() uses locks
672 : * for table lookups.
673 : */
674 0 : if (old_ucounts->ns == new->user_ns && uid_eq(old_ucounts->uid, new->uid))
675 : return 0;
676 :
677 0 : if (!(new_ucounts = alloc_ucounts(new->user_ns, new->uid)))
678 : return -EAGAIN;
679 :
680 0 : new->ucounts = new_ucounts;
681 0 : put_ucounts(old_ucounts);
682 :
683 0 : return 0;
684 : }
685 :
686 : /*
687 : * initialise the credentials stuff
688 : */
689 1 : void __init cred_init(void)
690 : {
691 : /* allocate a slab in which we can store credentials */
692 1 : cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), 0,
693 : SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL);
694 1 : }
695 :
696 : /**
697 : * prepare_kernel_cred - Prepare a set of credentials for a kernel service
698 : * @daemon: A userspace daemon to be used as a reference
699 : *
700 : * Prepare a set of credentials for a kernel service. This can then be used to
701 : * override a task's own credentials so that work can be done on behalf of that
702 : * task that requires a different subjective context.
703 : *
704 : * @daemon is used to provide a base cred, with the security data derived from
705 : * that; if this is "&init_task", they'll be set to 0, no groups, full
706 : * capabilities, and no keys.
707 : *
708 : * The caller may change these controls afterwards if desired.
709 : *
710 : * Returns the new credentials or NULL if out of memory.
711 : */
712 0 : struct cred *prepare_kernel_cred(struct task_struct *daemon)
713 : {
714 : const struct cred *old;
715 : struct cred *new;
716 :
717 0 : if (WARN_ON_ONCE(!daemon))
718 : return NULL;
719 :
720 0 : new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
721 0 : if (!new)
722 : return NULL;
723 :
724 : kdebug("prepare_kernel_cred() alloc %p", new);
725 :
726 0 : old = get_task_cred(daemon);
727 0 : validate_creds(old);
728 :
729 0 : *new = *old;
730 0 : new->non_rcu = 0;
731 0 : atomic_set(&new->usage, 1);
732 0 : set_cred_subscribers(new, 0);
733 0 : get_uid(new->user);
734 0 : get_user_ns(new->user_ns);
735 0 : get_group_info(new->group_info);
736 :
737 : #ifdef CONFIG_KEYS
738 : new->session_keyring = NULL;
739 : new->process_keyring = NULL;
740 : new->thread_keyring = NULL;
741 : new->request_key_auth = NULL;
742 : new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
743 : #endif
744 :
745 : #ifdef CONFIG_SECURITY
746 : new->security = NULL;
747 : #endif
748 0 : new->ucounts = get_ucounts(new->ucounts);
749 0 : if (!new->ucounts)
750 : goto error;
751 :
752 0 : if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
753 : goto error;
754 :
755 : put_cred(old);
756 : validate_creds(new);
757 : return new;
758 :
759 : error:
760 0 : put_cred(new);
761 : put_cred(old);
762 : return NULL;
763 : }
764 : EXPORT_SYMBOL(prepare_kernel_cred);
765 :
766 : /**
767 : * set_security_override - Set the security ID in a set of credentials
768 : * @new: The credentials to alter
769 : * @secid: The LSM security ID to set
770 : *
771 : * Set the LSM security ID in a set of credentials so that the subjective
772 : * security is overridden when an alternative set of credentials is used.
773 : */
774 0 : int set_security_override(struct cred *new, u32 secid)
775 : {
776 0 : return security_kernel_act_as(new, secid);
777 : }
778 : EXPORT_SYMBOL(set_security_override);
779 :
780 : /**
781 : * set_security_override_from_ctx - Set the security ID in a set of credentials
782 : * @new: The credentials to alter
783 : * @secctx: The LSM security context to generate the security ID from.
784 : *
785 : * Set the LSM security ID in a set of credentials so that the subjective
786 : * security is overridden when an alternative set of credentials is used. The
787 : * security ID is specified in string form as a security context to be
788 : * interpreted by the LSM.
789 : */
790 0 : int set_security_override_from_ctx(struct cred *new, const char *secctx)
791 : {
792 : u32 secid;
793 : int ret;
794 :
795 0 : ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
796 : if (ret < 0)
797 : return ret;
798 :
799 : return set_security_override(new, secid);
800 : }
801 : EXPORT_SYMBOL(set_security_override_from_ctx);
802 :
803 : /**
804 : * set_create_files_as - Set the LSM file create context in a set of credentials
805 : * @new: The credentials to alter
806 : * @inode: The inode to take the context from
807 : *
808 : * Change the LSM file creation context in a set of credentials to be the same
809 : * as the object context of the specified inode, so that the new inodes have
810 : * the same MAC context as that inode.
811 : */
812 0 : int set_create_files_as(struct cred *new, struct inode *inode)
813 : {
814 0 : if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid))
815 : return -EINVAL;
816 0 : new->fsuid = inode->i_uid;
817 0 : new->fsgid = inode->i_gid;
818 0 : return security_kernel_create_files_as(new, inode);
819 : }
820 : EXPORT_SYMBOL(set_create_files_as);
821 :
822 : #ifdef CONFIG_DEBUG_CREDENTIALS
823 :
824 : bool creds_are_invalid(const struct cred *cred)
825 : {
826 : if (cred->magic != CRED_MAGIC)
827 : return true;
828 : return false;
829 : }
830 : EXPORT_SYMBOL(creds_are_invalid);
831 :
832 : /*
833 : * dump invalid credentials
834 : */
835 : static void dump_invalid_creds(const struct cred *cred, const char *label,
836 : const struct task_struct *tsk)
837 : {
838 : printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
839 : label, cred,
840 : cred == &init_cred ? "[init]" : "",
841 : cred == tsk->real_cred ? "[real]" : "",
842 : cred == tsk->cred ? "[eff]" : "");
843 : printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
844 : cred->magic, cred->put_addr);
845 : printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
846 : atomic_read(&cred->usage),
847 : read_cred_subscribers(cred));
848 : printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
849 : from_kuid_munged(&init_user_ns, cred->uid),
850 : from_kuid_munged(&init_user_ns, cred->euid),
851 : from_kuid_munged(&init_user_ns, cred->suid),
852 : from_kuid_munged(&init_user_ns, cred->fsuid));
853 : printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
854 : from_kgid_munged(&init_user_ns, cred->gid),
855 : from_kgid_munged(&init_user_ns, cred->egid),
856 : from_kgid_munged(&init_user_ns, cred->sgid),
857 : from_kgid_munged(&init_user_ns, cred->fsgid));
858 : #ifdef CONFIG_SECURITY
859 : printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
860 : if ((unsigned long) cred->security >= PAGE_SIZE &&
861 : (((unsigned long) cred->security & 0xffffff00) !=
862 : (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
863 : printk(KERN_ERR "CRED: ->security {%x, %x}\n",
864 : ((u32*)cred->security)[0],
865 : ((u32*)cred->security)[1]);
866 : #endif
867 : }
868 :
869 : /*
870 : * report use of invalid credentials
871 : */
872 : void __noreturn __invalid_creds(const struct cred *cred, const char *file, unsigned line)
873 : {
874 : printk(KERN_ERR "CRED: Invalid credentials\n");
875 : printk(KERN_ERR "CRED: At %s:%u\n", file, line);
876 : dump_invalid_creds(cred, "Specified", current);
877 : BUG();
878 : }
879 : EXPORT_SYMBOL(__invalid_creds);
880 :
881 : /*
882 : * check the credentials on a process
883 : */
884 : void __validate_process_creds(struct task_struct *tsk,
885 : const char *file, unsigned line)
886 : {
887 : if (tsk->cred == tsk->real_cred) {
888 : if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
889 : creds_are_invalid(tsk->cred)))
890 : goto invalid_creds;
891 : } else {
892 : if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
893 : read_cred_subscribers(tsk->cred) < 1 ||
894 : creds_are_invalid(tsk->real_cred) ||
895 : creds_are_invalid(tsk->cred)))
896 : goto invalid_creds;
897 : }
898 : return;
899 :
900 : invalid_creds:
901 : printk(KERN_ERR "CRED: Invalid process credentials\n");
902 : printk(KERN_ERR "CRED: At %s:%u\n", file, line);
903 :
904 : dump_invalid_creds(tsk->real_cred, "Real", tsk);
905 : if (tsk->cred != tsk->real_cred)
906 : dump_invalid_creds(tsk->cred, "Effective", tsk);
907 : else
908 : printk(KERN_ERR "CRED: Effective creds == Real creds\n");
909 : BUG();
910 : }
911 : EXPORT_SYMBOL(__validate_process_creds);
912 :
913 : /*
914 : * check creds for do_exit()
915 : */
916 : void validate_creds_for_do_exit(struct task_struct *tsk)
917 : {
918 : kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
919 : tsk->real_cred, tsk->cred,
920 : atomic_read(&tsk->cred->usage),
921 : read_cred_subscribers(tsk->cred));
922 :
923 : __validate_process_creds(tsk, __FILE__, __LINE__);
924 : }
925 :
926 : #endif /* CONFIG_DEBUG_CREDENTIALS */
|
