1 /* Task credentials management - see Documentation/credentials.txt
3 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
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.
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>
22 #define kdebug(FMT, ...) \
23 printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
25 #define kdebug(FMT, ...) \
26 no_printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
29 static struct kmem_cache *cred_jar;
32 * The common credentials for the initial task's thread group
35 static struct thread_group_cred init_tgcred = {
36 .usage = ATOMIC_INIT(2),
38 .lock = SPIN_LOCK_UNLOCKED,
43 * The initial credentials for the initial task
45 struct cred init_cred = {
46 .usage = ATOMIC_INIT(4),
47 #ifdef CONFIG_DEBUG_CREDENTIALS
48 .subscribers = ATOMIC_INIT(2),
51 .securebits = SECUREBITS_DEFAULT,
52 .cap_inheritable = CAP_INIT_INH_SET,
53 .cap_permitted = CAP_FULL_SET,
54 .cap_effective = CAP_INIT_EFF_SET,
55 .cap_bset = CAP_INIT_BSET,
57 .group_info = &init_groups,
59 .tgcred = &init_tgcred,
63 static inline void set_cred_subscribers(struct cred *cred, int n)
65 #ifdef CONFIG_DEBUG_CREDENTIALS
66 atomic_set(&cred->subscribers, n);
70 static inline int read_cred_subscribers(const struct cred *cred)
72 #ifdef CONFIG_DEBUG_CREDENTIALS
73 return atomic_read(&cred->subscribers);
79 static inline void alter_cred_subscribers(const struct cred *_cred, int n)
81 #ifdef CONFIG_DEBUG_CREDENTIALS
82 struct cred *cred = (struct cred *) _cred;
84 atomic_add(n, &cred->subscribers);
89 * Dispose of the shared task group credentials
92 static void release_tgcred_rcu(struct rcu_head *rcu)
94 struct thread_group_cred *tgcred =
95 container_of(rcu, struct thread_group_cred, rcu);
97 BUG_ON(atomic_read(&tgcred->usage) != 0);
99 key_put(tgcred->session_keyring);
100 key_put(tgcred->process_keyring);
106 * Release a set of thread group credentials.
108 static void release_tgcred(struct cred *cred)
111 struct thread_group_cred *tgcred = cred->tgcred;
113 if (atomic_dec_and_test(&tgcred->usage))
114 call_rcu(&tgcred->rcu, release_tgcred_rcu);
119 * The RCU callback to actually dispose of a set of credentials
121 static void put_cred_rcu(struct rcu_head *rcu)
123 struct cred *cred = container_of(rcu, struct cred, rcu);
125 kdebug("put_cred_rcu(%p)", cred);
127 #ifdef CONFIG_DEBUG_CREDENTIALS
128 if (cred->magic != CRED_MAGIC_DEAD ||
129 atomic_read(&cred->usage) != 0 ||
130 read_cred_subscribers(cred) != 0)
131 panic("CRED: put_cred_rcu() sees %p with"
132 " mag %x, put %p, usage %d, subscr %d\n",
133 cred, cred->magic, cred->put_addr,
134 atomic_read(&cred->usage),
135 read_cred_subscribers(cred));
137 if (atomic_read(&cred->usage) != 0)
138 panic("CRED: put_cred_rcu() sees %p with usage %d\n",
139 cred, atomic_read(&cred->usage));
142 security_cred_free(cred);
143 key_put(cred->thread_keyring);
144 key_put(cred->request_key_auth);
145 release_tgcred(cred);
146 if (cred->group_info)
147 put_group_info(cred->group_info);
148 free_uid(cred->user);
149 kmem_cache_free(cred_jar, cred);
153 * __put_cred - Destroy a set of credentials
154 * @cred: The record to release
156 * Destroy a set of credentials on which no references remain.
158 void __put_cred(struct cred *cred)
160 kdebug("__put_cred(%p{%d,%d})", cred,
161 atomic_read(&cred->usage),
162 read_cred_subscribers(cred));
164 BUG_ON(atomic_read(&cred->usage) != 0);
165 #ifdef CONFIG_DEBUG_CREDENTIALS
166 BUG_ON(read_cred_subscribers(cred) != 0);
167 cred->magic = CRED_MAGIC_DEAD;
168 cred->put_addr = __builtin_return_address(0);
170 BUG_ON(cred == current->cred);
171 BUG_ON(cred == current->real_cred);
173 call_rcu(&cred->rcu, put_cred_rcu);
175 EXPORT_SYMBOL(__put_cred);
178 * Clean up a task's credentials when it exits
180 void exit_creds(struct task_struct *tsk)
184 kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
185 atomic_read(&tsk->cred->usage),
186 read_cred_subscribers(tsk->cred));
188 cred = (struct cred *) tsk->real_cred;
189 tsk->real_cred = NULL;
190 validate_creds(cred);
191 alter_cred_subscribers(cred, -1);
194 cred = (struct cred *) tsk->cred;
196 validate_creds(cred);
197 alter_cred_subscribers(cred, -1);
200 cred = (struct cred *) tsk->replacement_session_keyring;
202 tsk->replacement_session_keyring = NULL;
203 validate_creds(cred);
209 * get_task_cred - Get another task's objective credentials
210 * @task: The task to query
212 * Get the objective credentials of a task, pinning them so that they can't go
213 * away. Accessing a task's credentials directly is not permitted.
215 * The caller must also make sure task doesn't get deleted, either by holding a
216 * ref on task or by holding tasklist_lock to prevent it from being unlinked.
218 const struct cred *get_task_cred(struct task_struct *task)
220 const struct cred *cred;
225 cred = __task_cred((task));
227 } while (!atomic_inc_not_zero(&((struct cred *)cred)->usage));
234 * Allocate blank credentials, such that the credentials can be filled in at a
235 * later date without risk of ENOMEM.
237 struct cred *cred_alloc_blank(void)
241 new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
246 new->tgcred = kzalloc(sizeof(*new->tgcred), GFP_KERNEL);
248 kmem_cache_free(cred_jar, new);
251 atomic_set(&new->tgcred->usage, 1);
254 atomic_set(&new->usage, 1);
256 if (security_cred_alloc_blank(new, GFP_KERNEL) < 0)
259 #ifdef CONFIG_DEBUG_CREDENTIALS
260 new->magic = CRED_MAGIC;
270 * prepare_creds - Prepare a new set of credentials for modification
272 * Prepare a new set of task credentials for modification. A task's creds
273 * shouldn't generally be modified directly, therefore this function is used to
274 * prepare a new copy, which the caller then modifies and then commits by
275 * calling commit_creds().
277 * Preparation involves making a copy of the objective creds for modification.
279 * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
281 * Call commit_creds() or abort_creds() to clean up.
283 struct cred *prepare_creds(void)
285 struct task_struct *task = current;
286 const struct cred *old;
289 validate_process_creds();
291 new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
295 kdebug("prepare_creds() alloc %p", new);
298 memcpy(new, old, sizeof(struct cred));
300 atomic_set(&new->usage, 1);
301 set_cred_subscribers(new, 0);
302 get_group_info(new->group_info);
306 key_get(new->thread_keyring);
307 key_get(new->request_key_auth);
308 atomic_inc(&new->tgcred->usage);
311 #ifdef CONFIG_SECURITY
312 new->security = NULL;
315 if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
324 EXPORT_SYMBOL(prepare_creds);
327 * Prepare credentials for current to perform an execve()
328 * - The caller must hold ->cred_guard_mutex
330 struct cred *prepare_exec_creds(void)
332 struct thread_group_cred *tgcred = NULL;
336 tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
341 new = prepare_creds();
348 /* newly exec'd tasks don't get a thread keyring */
349 key_put(new->thread_keyring);
350 new->thread_keyring = NULL;
352 /* create a new per-thread-group creds for all this set of threads to
354 memcpy(tgcred, new->tgcred, sizeof(struct thread_group_cred));
356 atomic_set(&tgcred->usage, 1);
357 spin_lock_init(&tgcred->lock);
359 /* inherit the session keyring; new process keyring */
360 key_get(tgcred->session_keyring);
361 tgcred->process_keyring = NULL;
364 new->tgcred = tgcred;
371 * Copy credentials for the new process created by fork()
373 * We share if we can, but under some circumstances we have to generate a new
376 * The new process gets the current process's subjective credentials as its
377 * objective and subjective credentials
379 int copy_creds(struct task_struct *p, unsigned long clone_flags)
382 struct thread_group_cred *tgcred;
389 !p->cred->thread_keyring &&
391 clone_flags & CLONE_THREAD
393 p->real_cred = get_cred(p->cred);
395 alter_cred_subscribers(p->cred, 2);
396 kdebug("share_creds(%p{%d,%d})",
397 p->cred, atomic_read(&p->cred->usage),
398 read_cred_subscribers(p->cred));
399 atomic_inc(&p->cred->user->processes);
403 new = prepare_creds();
407 if (clone_flags & CLONE_NEWUSER) {
408 ret = create_user_ns(new);
414 /* new threads get their own thread keyrings if their parent already
416 if (new->thread_keyring) {
417 key_put(new->thread_keyring);
418 new->thread_keyring = NULL;
419 if (clone_flags & CLONE_THREAD)
420 install_thread_keyring_to_cred(new);
423 /* we share the process and session keyrings between all the threads in
424 * a process - this is slightly icky as we violate COW credentials a
426 if (!(clone_flags & CLONE_THREAD)) {
427 tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
432 atomic_set(&tgcred->usage, 1);
433 spin_lock_init(&tgcred->lock);
434 tgcred->process_keyring = NULL;
435 tgcred->session_keyring = key_get(new->tgcred->session_keyring);
438 new->tgcred = tgcred;
442 atomic_inc(&new->user->processes);
443 p->cred = p->real_cred = get_cred(new);
444 alter_cred_subscribers(new, 2);
454 * commit_creds - Install new credentials upon the current task
455 * @new: The credentials to be assigned
457 * Install a new set of credentials to the current task, using RCU to replace
458 * the old set. Both the objective and the subjective credentials pointers are
459 * updated. This function may not be called if the subjective credentials are
460 * in an overridden state.
462 * This function eats the caller's reference to the new credentials.
464 * Always returns 0 thus allowing this function to be tail-called at the end
465 * of, say, sys_setgid().
467 int commit_creds(struct cred *new)
469 struct task_struct *task = current;
470 const struct cred *old = task->real_cred;
472 kdebug("commit_creds(%p{%d,%d})", new,
473 atomic_read(&new->usage),
474 read_cred_subscribers(new));
476 BUG_ON(task->cred != old);
477 #ifdef CONFIG_DEBUG_CREDENTIALS
478 BUG_ON(read_cred_subscribers(old) < 2);
482 BUG_ON(atomic_read(&new->usage) < 1);
484 get_cred(new); /* we will require a ref for the subj creds too */
486 /* dumpability changes */
487 if (old->euid != new->euid ||
488 old->egid != new->egid ||
489 old->fsuid != new->fsuid ||
490 old->fsgid != new->fsgid ||
491 !cap_issubset(new->cap_permitted, old->cap_permitted)) {
493 set_dumpable(task->mm, suid_dumpable);
494 task->pdeath_signal = 0;
498 /* alter the thread keyring */
499 if (new->fsuid != old->fsuid)
500 key_fsuid_changed(task);
501 if (new->fsgid != old->fsgid)
502 key_fsgid_changed(task);
505 * - What if a process setreuid()'s and this brings the
506 * new uid over his NPROC rlimit? We can check this now
507 * cheaply with the new uid cache, so if it matters
508 * we should be checking for it. -DaveM
510 alter_cred_subscribers(new, 2);
511 if (new->user != old->user)
512 atomic_inc(&new->user->processes);
513 rcu_assign_pointer(task->real_cred, new);
514 rcu_assign_pointer(task->cred, new);
515 if (new->user != old->user)
516 atomic_dec(&old->user->processes);
517 alter_cred_subscribers(old, -2);
519 /* send notifications */
520 if (new->uid != old->uid ||
521 new->euid != old->euid ||
522 new->suid != old->suid ||
523 new->fsuid != old->fsuid)
524 proc_id_connector(task, PROC_EVENT_UID);
526 if (new->gid != old->gid ||
527 new->egid != old->egid ||
528 new->sgid != old->sgid ||
529 new->fsgid != old->fsgid)
530 proc_id_connector(task, PROC_EVENT_GID);
532 /* release the old obj and subj refs both */
537 EXPORT_SYMBOL(commit_creds);
540 * abort_creds - Discard a set of credentials and unlock the current task
541 * @new: The credentials that were going to be applied
543 * Discard a set of credentials that were under construction and unlock the
546 void abort_creds(struct cred *new)
548 kdebug("abort_creds(%p{%d,%d})", new,
549 atomic_read(&new->usage),
550 read_cred_subscribers(new));
552 #ifdef CONFIG_DEBUG_CREDENTIALS
553 BUG_ON(read_cred_subscribers(new) != 0);
555 BUG_ON(atomic_read(&new->usage) < 1);
558 EXPORT_SYMBOL(abort_creds);
561 * override_creds - Override the current process's subjective credentials
562 * @new: The credentials to be assigned
564 * Install a set of temporary override subjective credentials on the current
565 * process, returning the old set for later reversion.
567 const struct cred *override_creds(const struct cred *new)
569 const struct cred *old = current->cred;
571 kdebug("override_creds(%p{%d,%d})", new,
572 atomic_read(&new->usage),
573 read_cred_subscribers(new));
578 alter_cred_subscribers(new, 1);
579 rcu_assign_pointer(current->cred, new);
580 alter_cred_subscribers(old, -1);
582 kdebug("override_creds() = %p{%d,%d}", old,
583 atomic_read(&old->usage),
584 read_cred_subscribers(old));
587 EXPORT_SYMBOL(override_creds);
590 * revert_creds - Revert a temporary subjective credentials override
591 * @old: The credentials to be restored
593 * Revert a temporary set of override subjective credentials to an old set,
594 * discarding the override set.
596 void revert_creds(const struct cred *old)
598 const struct cred *override = current->cred;
600 kdebug("revert_creds(%p{%d,%d})", old,
601 atomic_read(&old->usage),
602 read_cred_subscribers(old));
605 validate_creds(override);
606 alter_cred_subscribers(old, 1);
607 rcu_assign_pointer(current->cred, old);
608 alter_cred_subscribers(override, -1);
611 EXPORT_SYMBOL(revert_creds);
614 * initialise the credentials stuff
616 void __init cred_init(void)
618 /* allocate a slab in which we can store credentials */
619 cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred),
620 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
624 * prepare_kernel_cred - Prepare a set of credentials for a kernel service
625 * @daemon: A userspace daemon to be used as a reference
627 * Prepare a set of credentials for a kernel service. This can then be used to
628 * override a task's own credentials so that work can be done on behalf of that
629 * task that requires a different subjective context.
631 * @daemon is used to provide a base for the security record, but can be NULL.
632 * If @daemon is supplied, then the security data will be derived from that;
633 * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
635 * The caller may change these controls afterwards if desired.
637 * Returns the new credentials or NULL if out of memory.
639 * Does not take, and does not return holding current->cred_replace_mutex.
641 struct cred *prepare_kernel_cred(struct task_struct *daemon)
643 const struct cred *old;
646 new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
650 kdebug("prepare_kernel_cred() alloc %p", new);
653 old = get_task_cred(daemon);
655 old = get_cred(&init_cred);
661 get_group_info(new->group_info);
664 atomic_inc(&init_tgcred.usage);
665 new->tgcred = &init_tgcred;
666 new->request_key_auth = NULL;
667 new->thread_keyring = NULL;
668 new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
671 #ifdef CONFIG_SECURITY
672 new->security = NULL;
674 if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
677 atomic_set(&new->usage, 1);
678 set_cred_subscribers(new, 0);
688 EXPORT_SYMBOL(prepare_kernel_cred);
691 * set_security_override - Set the security ID in a set of credentials
692 * @new: The credentials to alter
693 * @secid: The LSM security ID to set
695 * Set the LSM security ID in a set of credentials so that the subjective
696 * security is overridden when an alternative set of credentials is used.
698 int set_security_override(struct cred *new, u32 secid)
700 return security_kernel_act_as(new, secid);
702 EXPORT_SYMBOL(set_security_override);
705 * set_security_override_from_ctx - Set the security ID in a set of credentials
706 * @new: The credentials to alter
707 * @secctx: The LSM security context to generate the security ID from.
709 * Set the LSM security ID in a set of credentials so that the subjective
710 * security is overridden when an alternative set of credentials is used. The
711 * security ID is specified in string form as a security context to be
712 * interpreted by the LSM.
714 int set_security_override_from_ctx(struct cred *new, const char *secctx)
719 ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
723 return set_security_override(new, secid);
725 EXPORT_SYMBOL(set_security_override_from_ctx);
728 * set_create_files_as - Set the LSM file create context in a set of credentials
729 * @new: The credentials to alter
730 * @inode: The inode to take the context from
732 * Change the LSM file creation context in a set of credentials to be the same
733 * as the object context of the specified inode, so that the new inodes have
734 * the same MAC context as that inode.
736 int set_create_files_as(struct cred *new, struct inode *inode)
738 new->fsuid = inode->i_uid;
739 new->fsgid = inode->i_gid;
740 return security_kernel_create_files_as(new, inode);
742 EXPORT_SYMBOL(set_create_files_as);
744 #ifdef CONFIG_DEBUG_CREDENTIALS
746 bool creds_are_invalid(const struct cred *cred)
748 if (cred->magic != CRED_MAGIC)
750 #ifdef CONFIG_SECURITY_SELINUX
751 if (selinux_is_enabled()) {
752 if ((unsigned long) cred->security < PAGE_SIZE)
754 if ((*(u32 *)cred->security & 0xffffff00) ==
755 (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
761 EXPORT_SYMBOL(creds_are_invalid);
764 * dump invalid credentials
766 static void dump_invalid_creds(const struct cred *cred, const char *label,
767 const struct task_struct *tsk)
769 printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
771 cred == &init_cred ? "[init]" : "",
772 cred == tsk->real_cred ? "[real]" : "",
773 cred == tsk->cred ? "[eff]" : "");
774 printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
775 cred->magic, cred->put_addr);
776 printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
777 atomic_read(&cred->usage),
778 read_cred_subscribers(cred));
779 printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
780 cred->uid, cred->euid, cred->suid, cred->fsuid);
781 printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
782 cred->gid, cred->egid, cred->sgid, cred->fsgid);
783 #ifdef CONFIG_SECURITY
784 printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
785 if ((unsigned long) cred->security >= PAGE_SIZE &&
786 (((unsigned long) cred->security & 0xffffff00) !=
787 (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
788 printk(KERN_ERR "CRED: ->security {%x, %x}\n",
789 ((u32*)cred->security)[0],
790 ((u32*)cred->security)[1]);
795 * report use of invalid credentials
797 void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
799 printk(KERN_ERR "CRED: Invalid credentials\n");
800 printk(KERN_ERR "CRED: At %s:%u\n", file, line);
801 dump_invalid_creds(cred, "Specified", current);
804 EXPORT_SYMBOL(__invalid_creds);
807 * check the credentials on a process
809 void __validate_process_creds(struct task_struct *tsk,
810 const char *file, unsigned line)
812 if (tsk->cred == tsk->real_cred) {
813 if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
814 creds_are_invalid(tsk->cred)))
817 if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
818 read_cred_subscribers(tsk->cred) < 1 ||
819 creds_are_invalid(tsk->real_cred) ||
820 creds_are_invalid(tsk->cred)))
826 printk(KERN_ERR "CRED: Invalid process credentials\n");
827 printk(KERN_ERR "CRED: At %s:%u\n", file, line);
829 dump_invalid_creds(tsk->real_cred, "Real", tsk);
830 if (tsk->cred != tsk->real_cred)
831 dump_invalid_creds(tsk->cred, "Effective", tsk);
833 printk(KERN_ERR "CRED: Effective creds == Real creds\n");
836 EXPORT_SYMBOL(__validate_process_creds);
839 * check creds for do_exit()
841 void validate_creds_for_do_exit(struct task_struct *tsk)
843 kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
844 tsk->real_cred, tsk->cred,
845 atomic_read(&tsk->cred->usage),
846 read_cred_subscribers(tsk->cred));
848 __validate_process_creds(tsk, __FILE__, __LINE__);
851 #endif /* CONFIG_DEBUG_CREDENTIALS */