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>
20 #include "cred-internals.h"
23 #define kdebug(FMT, ...) \
24 printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
26 static inline __attribute__((format(printf, 1, 2)))
27 void no_printk(const char *fmt, ...)
30 #define kdebug(FMT, ...) \
31 no_printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
34 static struct kmem_cache *cred_jar;
37 * The common credentials for the initial task's thread group
40 static struct thread_group_cred init_tgcred = {
41 .usage = ATOMIC_INIT(2),
43 .lock = SPIN_LOCK_UNLOCKED,
48 * The initial credentials for the initial task
50 struct cred init_cred = {
51 .usage = ATOMIC_INIT(4),
52 #ifdef CONFIG_DEBUG_CREDENTIALS
53 .subscribers = ATOMIC_INIT(2),
56 .securebits = SECUREBITS_DEFAULT,
57 .cap_inheritable = CAP_INIT_INH_SET,
58 .cap_permitted = CAP_FULL_SET,
59 .cap_effective = CAP_INIT_EFF_SET,
60 .cap_bset = CAP_INIT_BSET,
62 .group_info = &init_groups,
64 .tgcred = &init_tgcred,
68 static inline void set_cred_subscribers(struct cred *cred, int n)
70 #ifdef CONFIG_DEBUG_CREDENTIALS
71 atomic_set(&cred->subscribers, n);
75 static inline int read_cred_subscribers(const struct cred *cred)
77 #ifdef CONFIG_DEBUG_CREDENTIALS
78 return atomic_read(&cred->subscribers);
84 static inline void alter_cred_subscribers(const struct cred *_cred, int n)
86 #ifdef CONFIG_DEBUG_CREDENTIALS
87 struct cred *cred = (struct cred *) _cred;
89 atomic_add(n, &cred->subscribers);
94 * Dispose of the shared task group credentials
97 static void release_tgcred_rcu(struct rcu_head *rcu)
99 struct thread_group_cred *tgcred =
100 container_of(rcu, struct thread_group_cred, rcu);
102 BUG_ON(atomic_read(&tgcred->usage) != 0);
104 key_put(tgcred->session_keyring);
105 key_put(tgcred->process_keyring);
111 * Release a set of thread group credentials.
113 static void release_tgcred(struct cred *cred)
116 struct thread_group_cred *tgcred = cred->tgcred;
118 if (atomic_dec_and_test(&tgcred->usage))
119 call_rcu(&tgcred->rcu, release_tgcred_rcu);
124 * The RCU callback to actually dispose of a set of credentials
126 static void put_cred_rcu(struct rcu_head *rcu)
128 struct cred *cred = container_of(rcu, struct cred, rcu);
130 kdebug("put_cred_rcu(%p)", cred);
132 #ifdef CONFIG_DEBUG_CREDENTIALS
133 if (cred->magic != CRED_MAGIC_DEAD ||
134 atomic_read(&cred->usage) != 0 ||
135 read_cred_subscribers(cred) != 0)
136 panic("CRED: put_cred_rcu() sees %p with"
137 " mag %x, put %p, usage %d, subscr %d\n",
138 cred, cred->magic, cred->put_addr,
139 atomic_read(&cred->usage),
140 read_cred_subscribers(cred));
142 if (atomic_read(&cred->usage) != 0)
143 panic("CRED: put_cred_rcu() sees %p with usage %d\n",
144 cred, atomic_read(&cred->usage));
147 security_cred_free(cred);
148 key_put(cred->thread_keyring);
149 key_put(cred->request_key_auth);
150 release_tgcred(cred);
151 if (cred->group_info)
152 put_group_info(cred->group_info);
153 free_uid(cred->user);
154 kmem_cache_free(cred_jar, cred);
158 * __put_cred - Destroy a set of credentials
159 * @cred: The record to release
161 * Destroy a set of credentials on which no references remain.
163 void __put_cred(struct cred *cred)
165 kdebug("__put_cred(%p{%d,%d})", cred,
166 atomic_read(&cred->usage),
167 read_cred_subscribers(cred));
169 BUG_ON(atomic_read(&cred->usage) != 0);
170 #ifdef CONFIG_DEBUG_CREDENTIALS
171 BUG_ON(read_cred_subscribers(cred) != 0);
172 cred->magic = CRED_MAGIC_DEAD;
173 cred->put_addr = __builtin_return_address(0);
175 BUG_ON(cred == current->cred);
176 BUG_ON(cred == current->real_cred);
178 call_rcu(&cred->rcu, put_cred_rcu);
180 EXPORT_SYMBOL(__put_cred);
183 * Clean up a task's credentials when it exits
185 void exit_creds(struct task_struct *tsk)
189 kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
190 atomic_read(&tsk->cred->usage),
191 read_cred_subscribers(tsk->cred));
193 cred = (struct cred *) tsk->real_cred;
194 tsk->real_cred = NULL;
195 validate_creds(cred);
196 alter_cred_subscribers(cred, -1);
199 cred = (struct cred *) tsk->cred;
201 validate_creds(cred);
202 alter_cred_subscribers(cred, -1);
205 cred = (struct cred *) tsk->replacement_session_keyring;
207 tsk->replacement_session_keyring = NULL;
208 validate_creds(cred);
214 * Allocate blank credentials, such that the credentials can be filled in at a
215 * later date without risk of ENOMEM.
217 struct cred *cred_alloc_blank(void)
221 new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
226 new->tgcred = kzalloc(sizeof(*new->tgcred), GFP_KERNEL);
228 kmem_cache_free(cred_jar, new);
231 atomic_set(&new->tgcred->usage, 1);
234 atomic_set(&new->usage, 1);
236 if (security_cred_alloc_blank(new, GFP_KERNEL) < 0)
239 #ifdef CONFIG_DEBUG_CREDENTIALS
240 new->magic = CRED_MAGIC;
250 * prepare_creds - Prepare a new set of credentials for modification
252 * Prepare a new set of task credentials for modification. A task's creds
253 * shouldn't generally be modified directly, therefore this function is used to
254 * prepare a new copy, which the caller then modifies and then commits by
255 * calling commit_creds().
257 * Preparation involves making a copy of the objective creds for modification.
259 * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
261 * Call commit_creds() or abort_creds() to clean up.
263 struct cred *prepare_creds(void)
265 struct task_struct *task = current;
266 const struct cred *old;
269 validate_process_creds();
271 new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
275 kdebug("prepare_creds() alloc %p", new);
278 memcpy(new, old, sizeof(struct cred));
280 atomic_set(&new->usage, 1);
281 set_cred_subscribers(new, 0);
282 get_group_info(new->group_info);
286 key_get(new->thread_keyring);
287 key_get(new->request_key_auth);
288 atomic_inc(&new->tgcred->usage);
291 #ifdef CONFIG_SECURITY
292 new->security = NULL;
295 if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
304 EXPORT_SYMBOL(prepare_creds);
307 * Prepare credentials for current to perform an execve()
308 * - The caller must hold current->cred_guard_mutex
310 struct cred *prepare_exec_creds(void)
312 struct thread_group_cred *tgcred = NULL;
316 tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
321 new = prepare_creds();
328 /* newly exec'd tasks don't get a thread keyring */
329 key_put(new->thread_keyring);
330 new->thread_keyring = NULL;
332 /* create a new per-thread-group creds for all this set of threads to
334 memcpy(tgcred, new->tgcred, sizeof(struct thread_group_cred));
336 atomic_set(&tgcred->usage, 1);
337 spin_lock_init(&tgcred->lock);
339 /* inherit the session keyring; new process keyring */
340 key_get(tgcred->session_keyring);
341 tgcred->process_keyring = NULL;
344 new->tgcred = tgcred;
351 * prepare new credentials for the usermode helper dispatcher
353 struct cred *prepare_usermodehelper_creds(void)
356 struct thread_group_cred *tgcred = NULL;
361 tgcred = kzalloc(sizeof(*new->tgcred), GFP_ATOMIC);
366 new = kmem_cache_alloc(cred_jar, GFP_ATOMIC);
370 kdebug("prepare_usermodehelper_creds() alloc %p", new);
372 memcpy(new, &init_cred, sizeof(struct cred));
374 atomic_set(&new->usage, 1);
375 set_cred_subscribers(new, 0);
376 get_group_info(new->group_info);
380 new->thread_keyring = NULL;
381 new->request_key_auth = NULL;
382 new->jit_keyring = KEY_REQKEY_DEFL_DEFAULT;
384 atomic_set(&tgcred->usage, 1);
385 spin_lock_init(&tgcred->lock);
386 new->tgcred = tgcred;
389 #ifdef CONFIG_SECURITY
390 new->security = NULL;
392 if (security_prepare_creds(new, &init_cred, GFP_ATOMIC) < 0)
396 BUG_ON(atomic_read(&new->usage) != 1);
411 * Copy credentials for the new process created by fork()
413 * We share if we can, but under some circumstances we have to generate a new
416 * The new process gets the current process's subjective credentials as its
417 * objective and subjective credentials
419 int copy_creds(struct task_struct *p, unsigned long clone_flags)
422 struct thread_group_cred *tgcred;
427 mutex_init(&p->cred_guard_mutex);
431 !p->cred->thread_keyring &&
433 clone_flags & CLONE_THREAD
435 p->real_cred = get_cred(p->cred);
437 alter_cred_subscribers(p->cred, 2);
438 kdebug("share_creds(%p{%d,%d})",
439 p->cred, atomic_read(&p->cred->usage),
440 read_cred_subscribers(p->cred));
441 atomic_inc(&p->cred->user->processes);
445 new = prepare_creds();
449 if (clone_flags & CLONE_NEWUSER) {
450 ret = create_user_ns(new);
456 /* new threads get their own thread keyrings if their parent already
458 if (new->thread_keyring) {
459 key_put(new->thread_keyring);
460 new->thread_keyring = NULL;
461 if (clone_flags & CLONE_THREAD)
462 install_thread_keyring_to_cred(new);
465 /* we share the process and session keyrings between all the threads in
466 * a process - this is slightly icky as we violate COW credentials a
468 if (!(clone_flags & CLONE_THREAD)) {
469 tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
474 atomic_set(&tgcred->usage, 1);
475 spin_lock_init(&tgcred->lock);
476 tgcred->process_keyring = NULL;
477 tgcred->session_keyring = key_get(new->tgcred->session_keyring);
480 new->tgcred = tgcred;
484 atomic_inc(&new->user->processes);
485 p->cred = p->real_cred = get_cred(new);
486 alter_cred_subscribers(new, 2);
496 * commit_creds - Install new credentials upon the current task
497 * @new: The credentials to be assigned
499 * Install a new set of credentials to the current task, using RCU to replace
500 * the old set. Both the objective and the subjective credentials pointers are
501 * updated. This function may not be called if the subjective credentials are
502 * in an overridden state.
504 * This function eats the caller's reference to the new credentials.
506 * Always returns 0 thus allowing this function to be tail-called at the end
507 * of, say, sys_setgid().
509 int commit_creds(struct cred *new)
511 struct task_struct *task = current;
512 const struct cred *old = task->real_cred;
514 kdebug("commit_creds(%p{%d,%d})", new,
515 atomic_read(&new->usage),
516 read_cred_subscribers(new));
518 BUG_ON(task->cred != old);
519 #ifdef CONFIG_DEBUG_CREDENTIALS
520 BUG_ON(read_cred_subscribers(old) < 2);
524 BUG_ON(atomic_read(&new->usage) < 1);
526 security_commit_creds(new, old);
528 get_cred(new); /* we will require a ref for the subj creds too */
530 /* dumpability changes */
531 if (old->euid != new->euid ||
532 old->egid != new->egid ||
533 old->fsuid != new->fsuid ||
534 old->fsgid != new->fsgid ||
535 !cap_issubset(new->cap_permitted, old->cap_permitted)) {
537 set_dumpable(task->mm, suid_dumpable);
538 task->pdeath_signal = 0;
542 /* alter the thread keyring */
543 if (new->fsuid != old->fsuid)
544 key_fsuid_changed(task);
545 if (new->fsgid != old->fsgid)
546 key_fsgid_changed(task);
549 * - What if a process setreuid()'s and this brings the
550 * new uid over his NPROC rlimit? We can check this now
551 * cheaply with the new uid cache, so if it matters
552 * we should be checking for it. -DaveM
554 alter_cred_subscribers(new, 2);
555 if (new->user != old->user)
556 atomic_inc(&new->user->processes);
557 rcu_assign_pointer(task->real_cred, new);
558 rcu_assign_pointer(task->cred, new);
559 if (new->user != old->user)
560 atomic_dec(&old->user->processes);
561 alter_cred_subscribers(old, -2);
563 sched_switch_user(task);
565 /* send notifications */
566 if (new->uid != old->uid ||
567 new->euid != old->euid ||
568 new->suid != old->suid ||
569 new->fsuid != old->fsuid)
570 proc_id_connector(task, PROC_EVENT_UID);
572 if (new->gid != old->gid ||
573 new->egid != old->egid ||
574 new->sgid != old->sgid ||
575 new->fsgid != old->fsgid)
576 proc_id_connector(task, PROC_EVENT_GID);
578 /* release the old obj and subj refs both */
583 EXPORT_SYMBOL(commit_creds);
586 * abort_creds - Discard a set of credentials and unlock the current task
587 * @new: The credentials that were going to be applied
589 * Discard a set of credentials that were under construction and unlock the
592 void abort_creds(struct cred *new)
594 kdebug("abort_creds(%p{%d,%d})", new,
595 atomic_read(&new->usage),
596 read_cred_subscribers(new));
598 #ifdef CONFIG_DEBUG_CREDENTIALS
599 BUG_ON(read_cred_subscribers(new) != 0);
601 BUG_ON(atomic_read(&new->usage) < 1);
604 EXPORT_SYMBOL(abort_creds);
607 * override_creds - Override the current process's subjective credentials
608 * @new: The credentials to be assigned
610 * Install a set of temporary override subjective credentials on the current
611 * process, returning the old set for later reversion.
613 const struct cred *override_creds(const struct cred *new)
615 const struct cred *old = current->cred;
617 kdebug("override_creds(%p{%d,%d})", new,
618 atomic_read(&new->usage),
619 read_cred_subscribers(new));
624 alter_cred_subscribers(new, 1);
625 rcu_assign_pointer(current->cred, new);
626 alter_cred_subscribers(old, -1);
628 kdebug("override_creds() = %p{%d,%d}", old,
629 atomic_read(&old->usage),
630 read_cred_subscribers(old));
633 EXPORT_SYMBOL(override_creds);
636 * revert_creds - Revert a temporary subjective credentials override
637 * @old: The credentials to be restored
639 * Revert a temporary set of override subjective credentials to an old set,
640 * discarding the override set.
642 void revert_creds(const struct cred *old)
644 const struct cred *override = current->cred;
646 kdebug("revert_creds(%p{%d,%d})", old,
647 atomic_read(&old->usage),
648 read_cred_subscribers(old));
651 validate_creds(override);
652 alter_cred_subscribers(old, 1);
653 rcu_assign_pointer(current->cred, old);
654 alter_cred_subscribers(override, -1);
657 EXPORT_SYMBOL(revert_creds);
660 * initialise the credentials stuff
662 void __init cred_init(void)
664 /* allocate a slab in which we can store credentials */
665 cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred),
666 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
670 * prepare_kernel_cred - Prepare a set of credentials for a kernel service
671 * @daemon: A userspace daemon to be used as a reference
673 * Prepare a set of credentials for a kernel service. This can then be used to
674 * override a task's own credentials so that work can be done on behalf of that
675 * task that requires a different subjective context.
677 * @daemon is used to provide a base for the security record, but can be NULL.
678 * If @daemon is supplied, then the security data will be derived from that;
679 * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
681 * The caller may change these controls afterwards if desired.
683 * Returns the new credentials or NULL if out of memory.
685 * Does not take, and does not return holding current->cred_replace_mutex.
687 struct cred *prepare_kernel_cred(struct task_struct *daemon)
689 const struct cred *old;
692 new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
696 kdebug("prepare_kernel_cred() alloc %p", new);
699 old = get_task_cred(daemon);
701 old = get_cred(&init_cred);
707 get_group_info(new->group_info);
710 atomic_inc(&init_tgcred.usage);
711 new->tgcred = &init_tgcred;
712 new->request_key_auth = NULL;
713 new->thread_keyring = NULL;
714 new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
717 #ifdef CONFIG_SECURITY
718 new->security = NULL;
720 if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
723 atomic_set(&new->usage, 1);
724 set_cred_subscribers(new, 0);
734 EXPORT_SYMBOL(prepare_kernel_cred);
737 * set_security_override - Set the security ID in a set of credentials
738 * @new: The credentials to alter
739 * @secid: The LSM security ID to set
741 * Set the LSM security ID in a set of credentials so that the subjective
742 * security is overridden when an alternative set of credentials is used.
744 int set_security_override(struct cred *new, u32 secid)
746 return security_kernel_act_as(new, secid);
748 EXPORT_SYMBOL(set_security_override);
751 * set_security_override_from_ctx - Set the security ID in a set of credentials
752 * @new: The credentials to alter
753 * @secctx: The LSM security context to generate the security ID from.
755 * Set the LSM security ID in a set of credentials so that the subjective
756 * security is overridden when an alternative set of credentials is used. The
757 * security ID is specified in string form as a security context to be
758 * interpreted by the LSM.
760 int set_security_override_from_ctx(struct cred *new, const char *secctx)
765 ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
769 return set_security_override(new, secid);
771 EXPORT_SYMBOL(set_security_override_from_ctx);
774 * set_create_files_as - Set the LSM file create context in a set of credentials
775 * @new: The credentials to alter
776 * @inode: The inode to take the context from
778 * Change the LSM file creation context in a set of credentials to be the same
779 * as the object context of the specified inode, so that the new inodes have
780 * the same MAC context as that inode.
782 int set_create_files_as(struct cred *new, struct inode *inode)
784 new->fsuid = inode->i_uid;
785 new->fsgid = inode->i_gid;
786 return security_kernel_create_files_as(new, inode);
788 EXPORT_SYMBOL(set_create_files_as);
790 #ifdef CONFIG_DEBUG_CREDENTIALS
792 bool creds_are_invalid(const struct cred *cred)
794 if (cred->magic != CRED_MAGIC)
796 if (atomic_read(&cred->usage) < atomic_read(&cred->subscribers))
798 #ifdef CONFIG_SECURITY_SELINUX
799 if (selinux_is_enabled()) {
800 if ((unsigned long) cred->security < PAGE_SIZE)
802 if ((*(u32 *)cred->security & 0xffffff00) ==
803 (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
809 EXPORT_SYMBOL(creds_are_invalid);
812 * dump invalid credentials
814 static void dump_invalid_creds(const struct cred *cred, const char *label,
815 const struct task_struct *tsk)
817 printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
819 cred == &init_cred ? "[init]" : "",
820 cred == tsk->real_cred ? "[real]" : "",
821 cred == tsk->cred ? "[eff]" : "");
822 printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
823 cred->magic, cred->put_addr);
824 printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
825 atomic_read(&cred->usage),
826 read_cred_subscribers(cred));
827 printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
828 cred->uid, cred->euid, cred->suid, cred->fsuid);
829 printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
830 cred->gid, cred->egid, cred->sgid, cred->fsgid);
831 #ifdef CONFIG_SECURITY
832 printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
833 if ((unsigned long) cred->security >= PAGE_SIZE &&
834 (((unsigned long) cred->security & 0xffffff00) !=
835 (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
836 printk(KERN_ERR "CRED: ->security {%x, %x}\n",
837 ((u32*)cred->security)[0],
838 ((u32*)cred->security)[1]);
843 * report use of invalid credentials
845 void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
847 printk(KERN_ERR "CRED: Invalid credentials\n");
848 printk(KERN_ERR "CRED: At %s:%u\n", file, line);
849 dump_invalid_creds(cred, "Specified", current);
852 EXPORT_SYMBOL(__invalid_creds);
855 * check the credentials on a process
857 void __validate_process_creds(struct task_struct *tsk,
858 const char *file, unsigned line)
860 if (tsk->cred == tsk->real_cred) {
861 if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
862 creds_are_invalid(tsk->cred)))
865 if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
866 read_cred_subscribers(tsk->cred) < 1 ||
867 creds_are_invalid(tsk->real_cred) ||
868 creds_are_invalid(tsk->cred)))
874 printk(KERN_ERR "CRED: Invalid process credentials\n");
875 printk(KERN_ERR "CRED: At %s:%u\n", file, line);
877 dump_invalid_creds(tsk->real_cred, "Real", tsk);
878 if (tsk->cred != tsk->real_cred)
879 dump_invalid_creds(tsk->cred, "Effective", tsk);
881 printk(KERN_ERR "CRED: Effective creds == Real creds\n");
884 EXPORT_SYMBOL(__validate_process_creds);
887 * check creds for do_exit()
889 void validate_creds_for_do_exit(struct task_struct *tsk)
891 kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
892 tsk->real_cred, tsk->cred,
893 atomic_read(&tsk->cred->usage),
894 read_cred_subscribers(tsk->cred));
896 __validate_process_creds(tsk, __FILE__, __LINE__);
899 #endif /* CONFIG_DEBUG_CREDENTIALS */