1 /* Task credentials management - see Documentation/security/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/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>
23 #define kdebug(FMT, ...) \
24 printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
26 #define kdebug(FMT, ...) \
27 no_printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
30 static struct kmem_cache
*cred_jar
;
33 * The initial credentials for the initial task
35 struct cred init_cred
= {
36 .usage
= ATOMIC_INIT(4),
37 #ifdef CONFIG_DEBUG_CREDENTIALS
38 .subscribers
= ATOMIC_INIT(2),
41 .uid
= GLOBAL_ROOT_UID
,
42 .gid
= GLOBAL_ROOT_GID
,
43 .suid
= GLOBAL_ROOT_UID
,
44 .sgid
= GLOBAL_ROOT_GID
,
45 .euid
= GLOBAL_ROOT_UID
,
46 .egid
= GLOBAL_ROOT_GID
,
47 .fsuid
= GLOBAL_ROOT_UID
,
48 .fsgid
= GLOBAL_ROOT_GID
,
49 .securebits
= SECUREBITS_DEFAULT
,
50 .cap_inheritable
= CAP_EMPTY_SET
,
51 .cap_permitted
= CAP_FULL_SET
,
52 .cap_effective
= CAP_FULL_SET
,
53 .cap_bset
= CAP_FULL_SET
,
55 .user_ns
= &init_user_ns
,
56 .group_info
= &init_groups
,
59 static inline void set_cred_subscribers(struct cred
*cred
, int n
)
61 #ifdef CONFIG_DEBUG_CREDENTIALS
62 atomic_set(&cred
->subscribers
, n
);
66 static inline int read_cred_subscribers(const struct cred
*cred
)
68 #ifdef CONFIG_DEBUG_CREDENTIALS
69 return atomic_read(&cred
->subscribers
);
75 static inline void alter_cred_subscribers(const struct cred
*_cred
, int n
)
77 #ifdef CONFIG_DEBUG_CREDENTIALS
78 struct cred
*cred
= (struct cred
*) _cred
;
80 atomic_add(n
, &cred
->subscribers
);
85 * The RCU callback to actually dispose of a set of credentials
87 static void put_cred_rcu(struct rcu_head
*rcu
)
89 struct cred
*cred
= container_of(rcu
, struct cred
, rcu
);
91 kdebug("put_cred_rcu(%p)", cred
);
93 #ifdef CONFIG_DEBUG_CREDENTIALS
94 if (cred
->magic
!= CRED_MAGIC_DEAD
||
95 atomic_read(&cred
->usage
) != 0 ||
96 read_cred_subscribers(cred
) != 0)
97 panic("CRED: put_cred_rcu() sees %p with"
98 " mag %x, put %p, usage %d, subscr %d\n",
99 cred
, cred
->magic
, cred
->put_addr
,
100 atomic_read(&cred
->usage
),
101 read_cred_subscribers(cred
));
103 if (atomic_read(&cred
->usage
) != 0)
104 panic("CRED: put_cred_rcu() sees %p with usage %d\n",
105 cred
, atomic_read(&cred
->usage
));
108 security_cred_free(cred
);
109 key_put(cred
->session_keyring
);
110 key_put(cred
->process_keyring
);
111 key_put(cred
->thread_keyring
);
112 key_put(cred
->request_key_auth
);
113 if (cred
->group_info
)
114 put_group_info(cred
->group_info
);
115 free_uid(cred
->user
);
116 put_user_ns(cred
->user_ns
);
117 kmem_cache_free(cred_jar
, cred
);
121 * __put_cred - Destroy a set of credentials
122 * @cred: The record to release
124 * Destroy a set of credentials on which no references remain.
126 void __put_cred(struct cred
*cred
)
128 kdebug("__put_cred(%p{%d,%d})", cred
,
129 atomic_read(&cred
->usage
),
130 read_cred_subscribers(cred
));
132 BUG_ON(atomic_read(&cred
->usage
) != 0);
133 #ifdef CONFIG_DEBUG_CREDENTIALS
134 BUG_ON(read_cred_subscribers(cred
) != 0);
135 cred
->magic
= CRED_MAGIC_DEAD
;
136 cred
->put_addr
= __builtin_return_address(0);
138 BUG_ON(cred
== current
->cred
);
139 BUG_ON(cred
== current
->real_cred
);
141 call_rcu(&cred
->rcu
, put_cred_rcu
);
143 EXPORT_SYMBOL(__put_cred
);
146 * Clean up a task's credentials when it exits
148 void exit_creds(struct task_struct
*tsk
)
152 kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk
->pid
, tsk
->real_cred
, tsk
->cred
,
153 atomic_read(&tsk
->cred
->usage
),
154 read_cred_subscribers(tsk
->cred
));
156 cred
= (struct cred
*) tsk
->real_cred
;
157 tsk
->real_cred
= NULL
;
158 validate_creds(cred
);
159 alter_cred_subscribers(cred
, -1);
162 cred
= (struct cred
*) tsk
->cred
;
164 validate_creds(cred
);
165 alter_cred_subscribers(cred
, -1);
170 * get_task_cred - Get another task's objective credentials
171 * @task: The task to query
173 * Get the objective credentials of a task, pinning them so that they can't go
174 * away. Accessing a task's credentials directly is not permitted.
176 * The caller must also make sure task doesn't get deleted, either by holding a
177 * ref on task or by holding tasklist_lock to prevent it from being unlinked.
179 const struct cred
*get_task_cred(struct task_struct
*task
)
181 const struct cred
*cred
;
186 cred
= __task_cred((task
));
188 } while (!atomic_inc_not_zero(&((struct cred
*)cred
)->usage
));
195 * Allocate blank credentials, such that the credentials can be filled in at a
196 * later date without risk of ENOMEM.
198 struct cred
*cred_alloc_blank(void)
202 new = kmem_cache_zalloc(cred_jar
, GFP_KERNEL
);
206 atomic_set(&new->usage
, 1);
207 #ifdef CONFIG_DEBUG_CREDENTIALS
208 new->magic
= CRED_MAGIC
;
211 if (security_cred_alloc_blank(new, GFP_KERNEL
) < 0)
222 * prepare_creds - Prepare a new set of credentials for modification
224 * Prepare a new set of task credentials for modification. A task's creds
225 * shouldn't generally be modified directly, therefore this function is used to
226 * prepare a new copy, which the caller then modifies and then commits by
227 * calling commit_creds().
229 * Preparation involves making a copy of the objective creds for modification.
231 * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
233 * Call commit_creds() or abort_creds() to clean up.
235 struct cred
*prepare_creds(void)
237 struct task_struct
*task
= current
;
238 const struct cred
*old
;
241 validate_process_creds();
243 new = kmem_cache_alloc(cred_jar
, GFP_KERNEL
);
247 kdebug("prepare_creds() alloc %p", new);
250 memcpy(new, old
, sizeof(struct cred
));
252 atomic_set(&new->usage
, 1);
253 set_cred_subscribers(new, 0);
254 get_group_info(new->group_info
);
256 get_user_ns(new->user_ns
);
259 key_get(new->session_keyring
);
260 key_get(new->process_keyring
);
261 key_get(new->thread_keyring
);
262 key_get(new->request_key_auth
);
265 #ifdef CONFIG_SECURITY
266 new->security
= NULL
;
269 if (security_prepare_creds(new, old
, GFP_KERNEL
) < 0)
278 EXPORT_SYMBOL(prepare_creds
);
281 * Prepare credentials for current to perform an execve()
282 * - The caller must hold ->cred_guard_mutex
284 struct cred
*prepare_exec_creds(void)
288 new = prepare_creds();
293 /* newly exec'd tasks don't get a thread keyring */
294 key_put(new->thread_keyring
);
295 new->thread_keyring
= NULL
;
297 /* inherit the session keyring; new process keyring */
298 key_put(new->process_keyring
);
299 new->process_keyring
= NULL
;
306 * Copy credentials for the new process created by fork()
308 * We share if we can, but under some circumstances we have to generate a new
311 * The new process gets the current process's subjective credentials as its
312 * objective and subjective credentials
314 int copy_creds(struct task_struct
*p
, unsigned long clone_flags
)
321 !p
->cred
->thread_keyring
&&
323 clone_flags
& CLONE_THREAD
325 p
->real_cred
= get_cred(p
->cred
);
327 alter_cred_subscribers(p
->cred
, 2);
328 kdebug("share_creds(%p{%d,%d})",
329 p
->cred
, atomic_read(&p
->cred
->usage
),
330 read_cred_subscribers(p
->cred
));
331 atomic_inc(&p
->cred
->user
->processes
);
335 new = prepare_creds();
339 if (clone_flags
& CLONE_NEWUSER
) {
340 ret
= create_user_ns(new);
346 /* new threads get their own thread keyrings if their parent already
348 if (new->thread_keyring
) {
349 key_put(new->thread_keyring
);
350 new->thread_keyring
= NULL
;
351 if (clone_flags
& CLONE_THREAD
)
352 install_thread_keyring_to_cred(new);
355 /* The process keyring is only shared between the threads in a process;
356 * anything outside of those threads doesn't inherit.
358 if (!(clone_flags
& CLONE_THREAD
)) {
359 key_put(new->process_keyring
);
360 new->process_keyring
= NULL
;
364 atomic_inc(&new->user
->processes
);
365 p
->cred
= p
->real_cred
= get_cred(new);
366 alter_cred_subscribers(new, 2);
376 * commit_creds - Install new credentials upon the current task
377 * @new: The credentials to be assigned
379 * Install a new set of credentials to the current task, using RCU to replace
380 * the old set. Both the objective and the subjective credentials pointers are
381 * updated. This function may not be called if the subjective credentials are
382 * in an overridden state.
384 * This function eats the caller's reference to the new credentials.
386 * Always returns 0 thus allowing this function to be tail-called at the end
387 * of, say, sys_setgid().
389 int commit_creds(struct cred
*new)
391 struct task_struct
*task
= current
;
392 const struct cred
*old
= task
->real_cred
;
394 kdebug("commit_creds(%p{%d,%d})", new,
395 atomic_read(&new->usage
),
396 read_cred_subscribers(new));
398 BUG_ON(task
->cred
!= old
);
399 #ifdef CONFIG_DEBUG_CREDENTIALS
400 BUG_ON(read_cred_subscribers(old
) < 2);
404 BUG_ON(atomic_read(&new->usage
) < 1);
406 get_cred(new); /* we will require a ref for the subj creds too */
408 /* dumpability changes */
409 if (!uid_eq(old
->euid
, new->euid
) ||
410 !gid_eq(old
->egid
, new->egid
) ||
411 !uid_eq(old
->fsuid
, new->fsuid
) ||
412 !gid_eq(old
->fsgid
, new->fsgid
) ||
413 !cap_issubset(new->cap_permitted
, old
->cap_permitted
)) {
415 set_dumpable(task
->mm
, suid_dumpable
);
416 task
->pdeath_signal
= 0;
420 /* alter the thread keyring */
421 if (!uid_eq(new->fsuid
, old
->fsuid
))
422 key_fsuid_changed(task
);
423 if (!gid_eq(new->fsgid
, old
->fsgid
))
424 key_fsgid_changed(task
);
427 * RLIMIT_NPROC limits on user->processes have already been checked
430 alter_cred_subscribers(new, 2);
431 if (new->user
!= old
->user
)
432 atomic_inc(&new->user
->processes
);
433 rcu_assign_pointer(task
->real_cred
, new);
434 rcu_assign_pointer(task
->cred
, new);
435 if (new->user
!= old
->user
)
436 atomic_dec(&old
->user
->processes
);
437 alter_cred_subscribers(old
, -2);
439 /* send notifications */
440 if (!uid_eq(new->uid
, old
->uid
) ||
441 !uid_eq(new->euid
, old
->euid
) ||
442 !uid_eq(new->suid
, old
->suid
) ||
443 !uid_eq(new->fsuid
, old
->fsuid
))
444 proc_id_connector(task
, PROC_EVENT_UID
);
446 if (!gid_eq(new->gid
, old
->gid
) ||
447 !gid_eq(new->egid
, old
->egid
) ||
448 !gid_eq(new->sgid
, old
->sgid
) ||
449 !gid_eq(new->fsgid
, old
->fsgid
))
450 proc_id_connector(task
, PROC_EVENT_GID
);
452 /* release the old obj and subj refs both */
457 EXPORT_SYMBOL(commit_creds
);
460 * abort_creds - Discard a set of credentials and unlock the current task
461 * @new: The credentials that were going to be applied
463 * Discard a set of credentials that were under construction and unlock the
466 void abort_creds(struct cred
*new)
468 kdebug("abort_creds(%p{%d,%d})", new,
469 atomic_read(&new->usage
),
470 read_cred_subscribers(new));
472 #ifdef CONFIG_DEBUG_CREDENTIALS
473 BUG_ON(read_cred_subscribers(new) != 0);
475 BUG_ON(atomic_read(&new->usage
) < 1);
478 EXPORT_SYMBOL(abort_creds
);
481 * override_creds - Override the current process's subjective credentials
482 * @new: The credentials to be assigned
484 * Install a set of temporary override subjective credentials on the current
485 * process, returning the old set for later reversion.
487 const struct cred
*override_creds(const struct cred
*new)
489 const struct cred
*old
= current
->cred
;
491 kdebug("override_creds(%p{%d,%d})", new,
492 atomic_read(&new->usage
),
493 read_cred_subscribers(new));
498 alter_cred_subscribers(new, 1);
499 rcu_assign_pointer(current
->cred
, new);
500 alter_cred_subscribers(old
, -1);
502 kdebug("override_creds() = %p{%d,%d}", old
,
503 atomic_read(&old
->usage
),
504 read_cred_subscribers(old
));
507 EXPORT_SYMBOL(override_creds
);
510 * revert_creds - Revert a temporary subjective credentials override
511 * @old: The credentials to be restored
513 * Revert a temporary set of override subjective credentials to an old set,
514 * discarding the override set.
516 void revert_creds(const struct cred
*old
)
518 const struct cred
*override
= current
->cred
;
520 kdebug("revert_creds(%p{%d,%d})", old
,
521 atomic_read(&old
->usage
),
522 read_cred_subscribers(old
));
525 validate_creds(override
);
526 alter_cred_subscribers(old
, 1);
527 rcu_assign_pointer(current
->cred
, old
);
528 alter_cred_subscribers(override
, -1);
531 EXPORT_SYMBOL(revert_creds
);
534 * initialise the credentials stuff
536 void __init
cred_init(void)
538 /* allocate a slab in which we can store credentials */
539 cred_jar
= kmem_cache_create("cred_jar", sizeof(struct cred
),
540 0, SLAB_HWCACHE_ALIGN
|SLAB_PANIC
, NULL
);
544 * prepare_kernel_cred - Prepare a set of credentials for a kernel service
545 * @daemon: A userspace daemon to be used as a reference
547 * Prepare a set of credentials for a kernel service. This can then be used to
548 * override a task's own credentials so that work can be done on behalf of that
549 * task that requires a different subjective context.
551 * @daemon is used to provide a base for the security record, but can be NULL.
552 * If @daemon is supplied, then the security data will be derived from that;
553 * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
555 * The caller may change these controls afterwards if desired.
557 * Returns the new credentials or NULL if out of memory.
559 * Does not take, and does not return holding current->cred_replace_mutex.
561 struct cred
*prepare_kernel_cred(struct task_struct
*daemon
)
563 const struct cred
*old
;
566 new = kmem_cache_alloc(cred_jar
, GFP_KERNEL
);
570 kdebug("prepare_kernel_cred() alloc %p", new);
573 old
= get_task_cred(daemon
);
575 old
= get_cred(&init_cred
);
580 atomic_set(&new->usage
, 1);
581 set_cred_subscribers(new, 0);
583 get_user_ns(new->user_ns
);
584 get_group_info(new->group_info
);
587 new->session_keyring
= NULL
;
588 new->process_keyring
= NULL
;
589 new->thread_keyring
= NULL
;
590 new->request_key_auth
= NULL
;
591 new->jit_keyring
= KEY_REQKEY_DEFL_THREAD_KEYRING
;
594 #ifdef CONFIG_SECURITY
595 new->security
= NULL
;
597 if (security_prepare_creds(new, old
, GFP_KERNEL
) < 0)
609 EXPORT_SYMBOL(prepare_kernel_cred
);
612 * set_security_override - Set the security ID in a set of credentials
613 * @new: The credentials to alter
614 * @secid: The LSM security ID to set
616 * Set the LSM security ID in a set of credentials so that the subjective
617 * security is overridden when an alternative set of credentials is used.
619 int set_security_override(struct cred
*new, u32 secid
)
621 return security_kernel_act_as(new, secid
);
623 EXPORT_SYMBOL(set_security_override
);
626 * set_security_override_from_ctx - Set the security ID in a set of credentials
627 * @new: The credentials to alter
628 * @secctx: The LSM security context to generate the security ID from.
630 * Set the LSM security ID in a set of credentials so that the subjective
631 * security is overridden when an alternative set of credentials is used. The
632 * security ID is specified in string form as a security context to be
633 * interpreted by the LSM.
635 int set_security_override_from_ctx(struct cred
*new, const char *secctx
)
640 ret
= security_secctx_to_secid(secctx
, strlen(secctx
), &secid
);
644 return set_security_override(new, secid
);
646 EXPORT_SYMBOL(set_security_override_from_ctx
);
649 * set_create_files_as - Set the LSM file create context in a set of credentials
650 * @new: The credentials to alter
651 * @inode: The inode to take the context from
653 * Change the LSM file creation context in a set of credentials to be the same
654 * as the object context of the specified inode, so that the new inodes have
655 * the same MAC context as that inode.
657 int set_create_files_as(struct cred
*new, struct inode
*inode
)
659 new->fsuid
= inode
->i_uid
;
660 new->fsgid
= inode
->i_gid
;
661 return security_kernel_create_files_as(new, inode
);
663 EXPORT_SYMBOL(set_create_files_as
);
665 #ifdef CONFIG_DEBUG_CREDENTIALS
667 bool creds_are_invalid(const struct cred
*cred
)
669 if (cred
->magic
!= CRED_MAGIC
)
671 #ifdef CONFIG_SECURITY_SELINUX
673 * cred->security == NULL if security_cred_alloc_blank() or
674 * security_prepare_creds() returned an error.
676 if (selinux_is_enabled() && cred
->security
) {
677 if ((unsigned long) cred
->security
< PAGE_SIZE
)
679 if ((*(u32
*)cred
->security
& 0xffffff00) ==
680 (POISON_FREE
<< 24 | POISON_FREE
<< 16 | POISON_FREE
<< 8))
686 EXPORT_SYMBOL(creds_are_invalid
);
689 * dump invalid credentials
691 static void dump_invalid_creds(const struct cred
*cred
, const char *label
,
692 const struct task_struct
*tsk
)
694 printk(KERN_ERR
"CRED: %s credentials: %p %s%s%s\n",
696 cred
== &init_cred
? "[init]" : "",
697 cred
== tsk
->real_cred
? "[real]" : "",
698 cred
== tsk
->cred
? "[eff]" : "");
699 printk(KERN_ERR
"CRED: ->magic=%x, put_addr=%p\n",
700 cred
->magic
, cred
->put_addr
);
701 printk(KERN_ERR
"CRED: ->usage=%d, subscr=%d\n",
702 atomic_read(&cred
->usage
),
703 read_cred_subscribers(cred
));
704 printk(KERN_ERR
"CRED: ->*uid = { %d,%d,%d,%d }\n",
705 from_kuid_munged(&init_user_ns
, cred
->uid
),
706 from_kuid_munged(&init_user_ns
, cred
->euid
),
707 from_kuid_munged(&init_user_ns
, cred
->suid
),
708 from_kuid_munged(&init_user_ns
, cred
->fsuid
));
709 printk(KERN_ERR
"CRED: ->*gid = { %d,%d,%d,%d }\n",
710 from_kgid_munged(&init_user_ns
, cred
->gid
),
711 from_kgid_munged(&init_user_ns
, cred
->egid
),
712 from_kgid_munged(&init_user_ns
, cred
->sgid
),
713 from_kgid_munged(&init_user_ns
, cred
->fsgid
));
714 #ifdef CONFIG_SECURITY
715 printk(KERN_ERR
"CRED: ->security is %p\n", cred
->security
);
716 if ((unsigned long) cred
->security
>= PAGE_SIZE
&&
717 (((unsigned long) cred
->security
& 0xffffff00) !=
718 (POISON_FREE
<< 24 | POISON_FREE
<< 16 | POISON_FREE
<< 8)))
719 printk(KERN_ERR
"CRED: ->security {%x, %x}\n",
720 ((u32
*)cred
->security
)[0],
721 ((u32
*)cred
->security
)[1]);
726 * report use of invalid credentials
728 void __invalid_creds(const struct cred
*cred
, const char *file
, unsigned line
)
730 printk(KERN_ERR
"CRED: Invalid credentials\n");
731 printk(KERN_ERR
"CRED: At %s:%u\n", file
, line
);
732 dump_invalid_creds(cred
, "Specified", current
);
735 EXPORT_SYMBOL(__invalid_creds
);
738 * check the credentials on a process
740 void __validate_process_creds(struct task_struct
*tsk
,
741 const char *file
, unsigned line
)
743 if (tsk
->cred
== tsk
->real_cred
) {
744 if (unlikely(read_cred_subscribers(tsk
->cred
) < 2 ||
745 creds_are_invalid(tsk
->cred
)))
748 if (unlikely(read_cred_subscribers(tsk
->real_cred
) < 1 ||
749 read_cred_subscribers(tsk
->cred
) < 1 ||
750 creds_are_invalid(tsk
->real_cred
) ||
751 creds_are_invalid(tsk
->cred
)))
757 printk(KERN_ERR
"CRED: Invalid process credentials\n");
758 printk(KERN_ERR
"CRED: At %s:%u\n", file
, line
);
760 dump_invalid_creds(tsk
->real_cred
, "Real", tsk
);
761 if (tsk
->cred
!= tsk
->real_cred
)
762 dump_invalid_creds(tsk
->cred
, "Effective", tsk
);
764 printk(KERN_ERR
"CRED: Effective creds == Real creds\n");
767 EXPORT_SYMBOL(__validate_process_creds
);
770 * check creds for do_exit()
772 void validate_creds_for_do_exit(struct task_struct
*tsk
)
774 kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
775 tsk
->real_cred
, tsk
->cred
,
776 atomic_read(&tsk
->cred
->usage
),
777 read_cred_subscribers(tsk
->cred
));
779 __validate_process_creds(tsk
, __FILE__
, __LINE__
);
782 #endif /* CONFIG_DEBUG_CREDENTIALS */