1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Manage a process's keyrings
4 * Copyright (C) 2004-2005, 2008 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
8 #include <linux/init.h>
9 #include <linux/sched.h>
10 #include <linux/sched/user.h>
11 #include <linux/keyctl.h>
13 #include <linux/err.h>
14 #include <linux/mutex.h>
15 #include <linux/security.h>
16 #include <linux/user_namespace.h>
17 #include <linux/uaccess.h>
18 #include <keys/request_key_auth-type.h>
21 /* Session keyring create vs join semaphore */
22 static DEFINE_MUTEX(key_session_mutex
);
24 /* User keyring creation semaphore */
25 static DEFINE_MUTEX(key_user_keyring_mutex
);
27 /* The root user's tracking struct */
28 struct key_user root_key_user
= {
29 .usage
= REFCOUNT_INIT(3),
30 .cons_lock
= __MUTEX_INITIALIZER(root_key_user
.cons_lock
),
31 .lock
= __SPIN_LOCK_UNLOCKED(root_key_user
.lock
),
32 .nkeys
= ATOMIC_INIT(2),
33 .nikeys
= ATOMIC_INIT(2),
34 .uid
= GLOBAL_ROOT_UID
,
38 * Install the user and user session keyrings for the current process's UID.
40 int install_user_keyrings(void)
42 struct user_struct
*user
;
43 const struct cred
*cred
;
44 struct key
*uid_keyring
, *session_keyring
;
45 key_perm_t user_keyring_perm
;
50 user_keyring_perm
= (KEY_POS_ALL
& ~KEY_POS_SETATTR
) | KEY_USR_ALL
;
51 cred
= current_cred();
53 uid
= from_kuid(cred
->user_ns
, user
->uid
);
55 kenter("%p{%u}", user
, uid
);
57 if (READ_ONCE(user
->uid_keyring
) && READ_ONCE(user
->session_keyring
)) {
58 kleave(" = 0 [exist]");
62 mutex_lock(&key_user_keyring_mutex
);
65 if (!user
->uid_keyring
) {
66 /* get the UID-specific keyring
67 * - there may be one in existence already as it may have been
68 * pinned by a session, but the user_struct pointing to it
69 * may have been destroyed by setuid */
70 sprintf(buf
, "_uid.%u", uid
);
72 uid_keyring
= find_keyring_by_name(buf
, true);
73 if (IS_ERR(uid_keyring
)) {
74 uid_keyring
= keyring_alloc(buf
, user
->uid
, INVALID_GID
,
75 cred
, user_keyring_perm
,
76 KEY_ALLOC_UID_KEYRING
|
79 if (IS_ERR(uid_keyring
)) {
80 ret
= PTR_ERR(uid_keyring
);
85 /* get a default session keyring (which might also exist
87 sprintf(buf
, "_uid_ses.%u", uid
);
89 session_keyring
= find_keyring_by_name(buf
, true);
90 if (IS_ERR(session_keyring
)) {
92 keyring_alloc(buf
, user
->uid
, INVALID_GID
,
93 cred
, user_keyring_perm
,
94 KEY_ALLOC_UID_KEYRING
|
97 if (IS_ERR(session_keyring
)) {
98 ret
= PTR_ERR(session_keyring
);
102 /* we install a link from the user session keyring to
103 * the user keyring */
104 ret
= key_link(session_keyring
, uid_keyring
);
106 goto error_release_both
;
109 /* install the keyrings */
110 /* paired with READ_ONCE() */
111 smp_store_release(&user
->uid_keyring
, uid_keyring
);
112 /* paired with READ_ONCE() */
113 smp_store_release(&user
->session_keyring
, session_keyring
);
116 mutex_unlock(&key_user_keyring_mutex
);
121 key_put(session_keyring
);
123 key_put(uid_keyring
);
125 mutex_unlock(&key_user_keyring_mutex
);
126 kleave(" = %d", ret
);
131 * Install a thread keyring to the given credentials struct if it didn't have
132 * one already. This is allowed to overrun the quota.
134 * Return: 0 if a thread keyring is now present; -errno on failure.
136 int install_thread_keyring_to_cred(struct cred
*new)
140 if (new->thread_keyring
)
143 keyring
= keyring_alloc("_tid", new->uid
, new->gid
, new,
144 KEY_POS_ALL
| KEY_USR_VIEW
,
145 KEY_ALLOC_QUOTA_OVERRUN
,
148 return PTR_ERR(keyring
);
150 new->thread_keyring
= keyring
;
155 * Install a thread keyring to the current task if it didn't have one already.
157 * Return: 0 if a thread keyring is now present; -errno on failure.
159 static int install_thread_keyring(void)
164 new = prepare_creds();
168 ret
= install_thread_keyring_to_cred(new);
174 return commit_creds(new);
178 * Install a process keyring to the given credentials struct if it didn't have
179 * one already. This is allowed to overrun the quota.
181 * Return: 0 if a process keyring is now present; -errno on failure.
183 int install_process_keyring_to_cred(struct cred
*new)
187 if (new->process_keyring
)
190 keyring
= keyring_alloc("_pid", new->uid
, new->gid
, new,
191 KEY_POS_ALL
| KEY_USR_VIEW
,
192 KEY_ALLOC_QUOTA_OVERRUN
,
195 return PTR_ERR(keyring
);
197 new->process_keyring
= keyring
;
202 * Install a process keyring to the current task if it didn't have one already.
204 * Return: 0 if a process keyring is now present; -errno on failure.
206 static int install_process_keyring(void)
211 new = prepare_creds();
215 ret
= install_process_keyring_to_cred(new);
221 return commit_creds(new);
225 * Install the given keyring as the session keyring of the given credentials
226 * struct, replacing the existing one if any. If the given keyring is NULL,
227 * then install a new anonymous session keyring.
228 * @cred can not be in use by any task yet.
230 * Return: 0 on success; -errno on failure.
232 int install_session_keyring_to_cred(struct cred
*cred
, struct key
*keyring
)
239 /* create an empty session keyring */
241 flags
= KEY_ALLOC_QUOTA_OVERRUN
;
242 if (cred
->session_keyring
)
243 flags
= KEY_ALLOC_IN_QUOTA
;
245 keyring
= keyring_alloc("_ses", cred
->uid
, cred
->gid
, cred
,
246 KEY_POS_ALL
| KEY_USR_VIEW
| KEY_USR_READ
,
249 return PTR_ERR(keyring
);
254 /* install the keyring */
255 old
= cred
->session_keyring
;
256 cred
->session_keyring
= keyring
;
265 * Install the given keyring as the session keyring of the current task,
266 * replacing the existing one if any. If the given keyring is NULL, then
267 * install a new anonymous session keyring.
269 * Return: 0 on success; -errno on failure.
271 static int install_session_keyring(struct key
*keyring
)
276 new = prepare_creds();
280 ret
= install_session_keyring_to_cred(new, keyring
);
286 return commit_creds(new);
290 * Handle the fsuid changing.
292 void key_fsuid_changed(struct task_struct
*tsk
)
294 /* update the ownership of the thread keyring */
296 if (tsk
->cred
->thread_keyring
) {
297 down_write(&tsk
->cred
->thread_keyring
->sem
);
298 tsk
->cred
->thread_keyring
->uid
= tsk
->cred
->fsuid
;
299 up_write(&tsk
->cred
->thread_keyring
->sem
);
304 * Handle the fsgid changing.
306 void key_fsgid_changed(struct task_struct
*tsk
)
308 /* update the ownership of the thread keyring */
310 if (tsk
->cred
->thread_keyring
) {
311 down_write(&tsk
->cred
->thread_keyring
->sem
);
312 tsk
->cred
->thread_keyring
->gid
= tsk
->cred
->fsgid
;
313 up_write(&tsk
->cred
->thread_keyring
->sem
);
318 * Search the process keyrings attached to the supplied cred for the first
321 * The search criteria are the type and the match function. The description is
322 * given to the match function as a parameter, but doesn't otherwise influence
323 * the search. Typically the match function will compare the description
324 * parameter to the key's description.
326 * This can only search keyrings that grant Search permission to the supplied
327 * credentials. Keyrings linked to searched keyrings will also be searched if
328 * they grant Search permission too. Keys can only be found if they grant
329 * Search permission to the credentials.
331 * Returns a pointer to the key with the key usage count incremented if
332 * successful, -EAGAIN if we didn't find any matching key or -ENOKEY if we only
333 * matched negative keys.
335 * In the case of a successful return, the possession attribute is set on the
336 * returned key reference.
338 key_ref_t
search_my_process_keyrings(struct keyring_search_context
*ctx
)
340 key_ref_t key_ref
, ret
, err
;
341 const struct cred
*cred
= ctx
->cred
;
343 /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
344 * searchable, but we failed to find a key or we found a negative key;
345 * otherwise we want to return a sample error (probably -EACCES) if
346 * none of the keyrings were searchable
348 * in terms of priority: success > -ENOKEY > -EAGAIN > other error
352 err
= ERR_PTR(-EAGAIN
);
354 /* search the thread keyring first */
355 if (cred
->thread_keyring
) {
356 key_ref
= keyring_search_aux(
357 make_key_ref(cred
->thread_keyring
, 1), ctx
);
358 if (!IS_ERR(key_ref
))
361 switch (PTR_ERR(key_ref
)) {
362 case -EAGAIN
: /* no key */
363 case -ENOKEY
: /* negative key */
372 /* search the process keyring second */
373 if (cred
->process_keyring
) {
374 key_ref
= keyring_search_aux(
375 make_key_ref(cred
->process_keyring
, 1), ctx
);
376 if (!IS_ERR(key_ref
))
379 switch (PTR_ERR(key_ref
)) {
380 case -EAGAIN
: /* no key */
384 case -ENOKEY
: /* negative key */
393 /* search the session keyring */
394 if (cred
->session_keyring
) {
395 key_ref
= keyring_search_aux(
396 make_key_ref(cred
->session_keyring
, 1), ctx
);
398 if (!IS_ERR(key_ref
))
401 switch (PTR_ERR(key_ref
)) {
402 case -EAGAIN
: /* no key */
406 case -ENOKEY
: /* negative key */
414 /* or search the user-session keyring */
415 else if (READ_ONCE(cred
->user
->session_keyring
)) {
416 key_ref
= keyring_search_aux(
417 make_key_ref(READ_ONCE(cred
->user
->session_keyring
), 1),
419 if (!IS_ERR(key_ref
))
422 switch (PTR_ERR(key_ref
)) {
423 case -EAGAIN
: /* no key */
427 case -ENOKEY
: /* negative key */
436 /* no key - decide on the error we're going to go for */
437 key_ref
= ret
? ret
: err
;
444 * Search the process keyrings attached to the supplied cred for the first
445 * matching key in the manner of search_my_process_keyrings(), but also search
446 * the keys attached to the assumed authorisation key using its credentials if
449 * Return same as search_my_process_keyrings().
451 key_ref_t
search_process_keyrings(struct keyring_search_context
*ctx
)
453 struct request_key_auth
*rka
;
454 key_ref_t key_ref
, ret
= ERR_PTR(-EACCES
), err
;
458 key_ref
= search_my_process_keyrings(ctx
);
459 if (!IS_ERR(key_ref
))
463 /* if this process has an instantiation authorisation key, then we also
464 * search the keyrings of the process mentioned there
465 * - we don't permit access to request_key auth keys via this method
467 if (ctx
->cred
->request_key_auth
&&
468 ctx
->cred
== current_cred() &&
469 ctx
->index_key
.type
!= &key_type_request_key_auth
471 const struct cred
*cred
= ctx
->cred
;
473 /* defend against the auth key being revoked */
474 down_read(&cred
->request_key_auth
->sem
);
476 if (key_validate(ctx
->cred
->request_key_auth
) == 0) {
477 rka
= ctx
->cred
->request_key_auth
->payload
.data
[0];
479 ctx
->cred
= rka
->cred
;
480 key_ref
= search_process_keyrings(ctx
);
483 up_read(&cred
->request_key_auth
->sem
);
485 if (!IS_ERR(key_ref
))
490 up_read(&cred
->request_key_auth
->sem
);
494 /* no key - decide on the error we're going to go for */
495 if (err
== ERR_PTR(-ENOKEY
) || ret
== ERR_PTR(-ENOKEY
))
496 key_ref
= ERR_PTR(-ENOKEY
);
497 else if (err
== ERR_PTR(-EACCES
))
507 * See if the key we're looking at is the target key.
509 bool lookup_user_key_possessed(const struct key
*key
,
510 const struct key_match_data
*match_data
)
512 return key
== match_data
->raw_data
;
516 * Look up a key ID given us by userspace with a given permissions mask to get
517 * the key it refers to.
519 * Flags can be passed to request that special keyrings be created if referred
520 * to directly, to permit partially constructed keys to be found and to skip
521 * validity and permission checks on the found key.
523 * Returns a pointer to the key with an incremented usage count if successful;
524 * -EINVAL if the key ID is invalid; -ENOKEY if the key ID does not correspond
525 * to a key or the best found key was a negative key; -EKEYREVOKED or
526 * -EKEYEXPIRED if the best found key was revoked or expired; -EACCES if the
527 * found key doesn't grant the requested permit or the LSM denied access to it;
528 * or -ENOMEM if a special keyring couldn't be created.
530 * In the case of a successful return, the possession attribute is set on the
531 * returned key reference.
533 key_ref_t
lookup_user_key(key_serial_t id
, unsigned long lflags
,
536 struct keyring_search_context ctx
= {
537 .match_data
.cmp
= lookup_user_key_possessed
,
538 .match_data
.lookup_type
= KEYRING_SEARCH_LOOKUP_DIRECT
,
539 .flags
= KEYRING_SEARCH_NO_STATE_CHECK
,
541 struct request_key_auth
*rka
;
543 key_ref_t key_ref
, skey_ref
;
547 ctx
.cred
= get_current_cred();
548 key_ref
= ERR_PTR(-ENOKEY
);
551 case KEY_SPEC_THREAD_KEYRING
:
552 if (!ctx
.cred
->thread_keyring
) {
553 if (!(lflags
& KEY_LOOKUP_CREATE
))
556 ret
= install_thread_keyring();
558 key_ref
= ERR_PTR(ret
);
564 key
= ctx
.cred
->thread_keyring
;
566 key_ref
= make_key_ref(key
, 1);
569 case KEY_SPEC_PROCESS_KEYRING
:
570 if (!ctx
.cred
->process_keyring
) {
571 if (!(lflags
& KEY_LOOKUP_CREATE
))
574 ret
= install_process_keyring();
576 key_ref
= ERR_PTR(ret
);
582 key
= ctx
.cred
->process_keyring
;
584 key_ref
= make_key_ref(key
, 1);
587 case KEY_SPEC_SESSION_KEYRING
:
588 if (!ctx
.cred
->session_keyring
) {
589 /* always install a session keyring upon access if one
590 * doesn't exist yet */
591 ret
= install_user_keyrings();
594 if (lflags
& KEY_LOOKUP_CREATE
)
595 ret
= join_session_keyring(NULL
);
597 ret
= install_session_keyring(
598 ctx
.cred
->user
->session_keyring
);
603 } else if (ctx
.cred
->session_keyring
==
604 READ_ONCE(ctx
.cred
->user
->session_keyring
) &&
605 lflags
& KEY_LOOKUP_CREATE
) {
606 ret
= join_session_keyring(NULL
);
612 key
= ctx
.cred
->session_keyring
;
614 key_ref
= make_key_ref(key
, 1);
617 case KEY_SPEC_USER_KEYRING
:
618 if (!READ_ONCE(ctx
.cred
->user
->uid_keyring
)) {
619 ret
= install_user_keyrings();
624 key
= ctx
.cred
->user
->uid_keyring
;
626 key_ref
= make_key_ref(key
, 1);
629 case KEY_SPEC_USER_SESSION_KEYRING
:
630 if (!READ_ONCE(ctx
.cred
->user
->session_keyring
)) {
631 ret
= install_user_keyrings();
636 key
= ctx
.cred
->user
->session_keyring
;
638 key_ref
= make_key_ref(key
, 1);
641 case KEY_SPEC_GROUP_KEYRING
:
642 /* group keyrings are not yet supported */
643 key_ref
= ERR_PTR(-EINVAL
);
646 case KEY_SPEC_REQKEY_AUTH_KEY
:
647 key
= ctx
.cred
->request_key_auth
;
652 key_ref
= make_key_ref(key
, 1);
655 case KEY_SPEC_REQUESTOR_KEYRING
:
656 if (!ctx
.cred
->request_key_auth
)
659 down_read(&ctx
.cred
->request_key_auth
->sem
);
660 if (test_bit(KEY_FLAG_REVOKED
,
661 &ctx
.cred
->request_key_auth
->flags
)) {
662 key_ref
= ERR_PTR(-EKEYREVOKED
);
665 rka
= ctx
.cred
->request_key_auth
->payload
.data
[0];
666 key
= rka
->dest_keyring
;
669 up_read(&ctx
.cred
->request_key_auth
->sem
);
672 key_ref
= make_key_ref(key
, 1);
676 key_ref
= ERR_PTR(-EINVAL
);
680 key
= key_lookup(id
);
682 key_ref
= ERR_CAST(key
);
686 key_ref
= make_key_ref(key
, 0);
688 /* check to see if we possess the key */
689 ctx
.index_key
.type
= key
->type
;
690 ctx
.index_key
.description
= key
->description
;
691 ctx
.index_key
.desc_len
= strlen(key
->description
);
692 ctx
.match_data
.raw_data
= key
;
693 kdebug("check possessed");
694 skey_ref
= search_process_keyrings(&ctx
);
695 kdebug("possessed=%p", skey_ref
);
697 if (!IS_ERR(skey_ref
)) {
705 /* unlink does not use the nominated key in any way, so can skip all
706 * the permission checks as it is only concerned with the keyring */
707 if (lflags
& KEY_LOOKUP_FOR_UNLINK
) {
712 if (!(lflags
& KEY_LOOKUP_PARTIAL
)) {
713 ret
= wait_for_key_construction(key
, true);
724 ret
= key_validate(key
);
730 if (!(lflags
& KEY_LOOKUP_PARTIAL
) &&
731 key_read_state(key
) == KEY_IS_UNINSTANTIATED
)
734 /* check the permissions */
735 ret
= key_task_permission(key_ref
, ctx
.cred
, perm
);
739 key
->last_used_at
= ktime_get_real_seconds();
746 key_ref_put(key_ref
);
747 key_ref
= ERR_PTR(ret
);
750 /* if we attempted to install a keyring, then it may have caused new
751 * creds to be installed */
756 EXPORT_SYMBOL(lookup_user_key
);
759 * Join the named keyring as the session keyring if possible else attempt to
760 * create a new one of that name and join that.
762 * If the name is NULL, an empty anonymous keyring will be installed as the
765 * Named session keyrings are joined with a semaphore held to prevent the
766 * keyrings from going away whilst the attempt is made to going them and also
767 * to prevent a race in creating compatible session keyrings.
769 long join_session_keyring(const char *name
)
771 const struct cred
*old
;
776 new = prepare_creds();
779 old
= current_cred();
781 /* if no name is provided, install an anonymous keyring */
783 ret
= install_session_keyring_to_cred(new, NULL
);
787 serial
= new->session_keyring
->serial
;
788 ret
= commit_creds(new);
794 /* allow the user to join or create a named keyring */
795 mutex_lock(&key_session_mutex
);
797 /* look for an existing keyring of this name */
798 keyring
= find_keyring_by_name(name
, false);
799 if (PTR_ERR(keyring
) == -ENOKEY
) {
800 /* not found - try and create a new one */
801 keyring
= keyring_alloc(
802 name
, old
->uid
, old
->gid
, old
,
803 KEY_POS_ALL
| KEY_USR_VIEW
| KEY_USR_READ
| KEY_USR_LINK
,
804 KEY_ALLOC_IN_QUOTA
, NULL
, NULL
);
805 if (IS_ERR(keyring
)) {
806 ret
= PTR_ERR(keyring
);
809 } else if (IS_ERR(keyring
)) {
810 ret
= PTR_ERR(keyring
);
812 } else if (keyring
== new->session_keyring
) {
817 /* we've got a keyring - now to install it */
818 ret
= install_session_keyring_to_cred(new, keyring
);
823 mutex_unlock(&key_session_mutex
);
825 ret
= keyring
->serial
;
833 mutex_unlock(&key_session_mutex
);
840 * Replace a process's session keyring on behalf of one of its children when
841 * the target process is about to resume userspace execution.
843 void key_change_session_keyring(struct callback_head
*twork
)
845 const struct cred
*old
= current_cred();
846 struct cred
*new = container_of(twork
, struct cred
, rcu
);
848 if (unlikely(current
->flags
& PF_EXITING
)) {
853 new-> uid
= old
-> uid
;
854 new-> euid
= old
-> euid
;
855 new-> suid
= old
-> suid
;
856 new->fsuid
= old
->fsuid
;
857 new-> gid
= old
-> gid
;
858 new-> egid
= old
-> egid
;
859 new-> sgid
= old
-> sgid
;
860 new->fsgid
= old
->fsgid
;
861 new->user
= get_uid(old
->user
);
862 new->user_ns
= get_user_ns(old
->user_ns
);
863 new->group_info
= get_group_info(old
->group_info
);
865 new->securebits
= old
->securebits
;
866 new->cap_inheritable
= old
->cap_inheritable
;
867 new->cap_permitted
= old
->cap_permitted
;
868 new->cap_effective
= old
->cap_effective
;
869 new->cap_ambient
= old
->cap_ambient
;
870 new->cap_bset
= old
->cap_bset
;
872 new->jit_keyring
= old
->jit_keyring
;
873 new->thread_keyring
= key_get(old
->thread_keyring
);
874 new->process_keyring
= key_get(old
->process_keyring
);
876 security_transfer_creds(new, old
);
882 * Make sure that root's user and user-session keyrings exist.
884 static int __init
init_root_keyring(void)
886 return install_user_keyrings();
889 late_initcall(init_root_keyring
);