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