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