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