1 /* Manage a process's keyrings
3 * Copyright (C) 2004-2005, 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 License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
12 #include <linux/module.h>
13 #include <linux/init.h>
14 #include <linux/sched.h>
15 #include <linux/keyctl.h>
17 #include <linux/err.h>
18 #include <linux/mutex.h>
19 #include <linux/security.h>
20 #include <linux/user_namespace.h>
21 #include <asm/uaccess.h>
24 /* Session keyring create vs join semaphore */
25 static DEFINE_MUTEX(key_session_mutex);
27 /* User keyring creation semaphore */
28 static DEFINE_MUTEX(key_user_keyring_mutex);
30 /* The root user's tracking struct */
31 struct key_user root_key_user = {
32 .usage = ATOMIC_INIT(3),
33 .cons_lock = __MUTEX_INITIALIZER(root_key_user.cons_lock),
34 .lock = __SPIN_LOCK_UNLOCKED(root_key_user.lock),
35 .nkeys = ATOMIC_INIT(2),
36 .nikeys = ATOMIC_INIT(2),
38 .user_ns = &init_user_ns,
42 * Install the user and user session keyrings for the current process's UID.
44 int install_user_keyrings(void)
46 struct user_struct *user;
47 const struct cred *cred;
48 struct key *uid_keyring, *session_keyring;
52 cred = current_cred();
55 kenter("%p{%u}", user, user->uid);
57 if (user->uid_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", user->uid);
72 uid_keyring = find_keyring_by_name(buf, true);
73 if (IS_ERR(uid_keyring)) {
74 uid_keyring = keyring_alloc(buf, user->uid, (gid_t) -1,
75 cred, KEY_ALLOC_IN_QUOTA,
77 if (IS_ERR(uid_keyring)) {
78 ret = PTR_ERR(uid_keyring);
83 /* get a default session keyring (which might also exist
85 sprintf(buf, "_uid_ses.%u", user->uid);
87 session_keyring = find_keyring_by_name(buf, true);
88 if (IS_ERR(session_keyring)) {
90 keyring_alloc(buf, user->uid, (gid_t) -1,
91 cred, KEY_ALLOC_IN_QUOTA, NULL);
92 if (IS_ERR(session_keyring)) {
93 ret = PTR_ERR(session_keyring);
97 /* we install a link from the user session keyring to
99 ret = key_link(session_keyring, uid_keyring);
101 goto error_release_both;
104 /* install the keyrings */
105 user->uid_keyring = uid_keyring;
106 user->session_keyring = session_keyring;
109 mutex_unlock(&key_user_keyring_mutex);
114 key_put(session_keyring);
116 key_put(uid_keyring);
118 mutex_unlock(&key_user_keyring_mutex);
119 kleave(" = %d", ret);
124 * Install a fresh thread keyring directly to new credentials. This keyring is
125 * allowed to overrun the quota.
127 int install_thread_keyring_to_cred(struct cred *new)
131 keyring = keyring_alloc("_tid", new->uid, new->gid, new,
132 KEY_ALLOC_QUOTA_OVERRUN, NULL);
134 return PTR_ERR(keyring);
136 new->thread_keyring = keyring;
141 * Install a fresh thread keyring, discarding the old one.
143 static int install_thread_keyring(void)
148 new = prepare_creds();
152 BUG_ON(new->thread_keyring);
154 ret = install_thread_keyring_to_cred(new);
160 return commit_creds(new);
164 * Install a process keyring directly to a credentials struct.
166 * Returns -EEXIST if there was already a process keyring, 0 if one installed,
167 * and other value on any other error
169 int install_process_keyring_to_cred(struct cred *new)
174 if (new->tgcred->process_keyring)
177 keyring = keyring_alloc("_pid", new->uid, new->gid,
178 new, KEY_ALLOC_QUOTA_OVERRUN, NULL);
180 return PTR_ERR(keyring);
182 spin_lock_irq(&new->tgcred->lock);
183 if (!new->tgcred->process_keyring) {
184 new->tgcred->process_keyring = keyring;
190 spin_unlock_irq(&new->tgcred->lock);
196 * Make sure a process keyring is installed for the current process. The
197 * existing process keyring is not replaced.
199 * Returns 0 if there is a process keyring by the end of this function, some
202 static int install_process_keyring(void)
207 new = prepare_creds();
211 ret = install_process_keyring_to_cred(new);
214 return ret != -EEXIST ? ret : 0;
217 return commit_creds(new);
221 * Install a session keyring directly to a credentials struct.
223 int install_session_keyring_to_cred(struct cred *cred, struct key *keyring)
230 /* create an empty session keyring */
232 flags = KEY_ALLOC_QUOTA_OVERRUN;
233 if (cred->tgcred->session_keyring)
234 flags = KEY_ALLOC_IN_QUOTA;
236 keyring = keyring_alloc("_ses", cred->uid, cred->gid,
239 return PTR_ERR(keyring);
241 atomic_inc(&keyring->usage);
244 /* install the keyring */
245 spin_lock_irq(&cred->tgcred->lock);
246 old = cred->tgcred->session_keyring;
247 rcu_assign_pointer(cred->tgcred->session_keyring, keyring);
248 spin_unlock_irq(&cred->tgcred->lock);
250 /* we're using RCU on the pointer, but there's no point synchronising
251 * on it if it didn't previously point to anything */
261 * Install a session keyring, discarding the old one. If a keyring is not
262 * supplied, an empty one is invented.
264 static int install_session_keyring(struct key *keyring)
269 new = prepare_creds();
273 ret = install_session_keyring_to_cred(new, keyring);
279 return commit_creds(new);
283 * Handle the fsuid changing.
285 void key_fsuid_changed(struct task_struct *tsk)
287 /* update the ownership of the thread keyring */
289 if (tsk->cred->thread_keyring) {
290 down_write(&tsk->cred->thread_keyring->sem);
291 tsk->cred->thread_keyring->uid = tsk->cred->fsuid;
292 up_write(&tsk->cred->thread_keyring->sem);
297 * Handle the fsgid changing.
299 void key_fsgid_changed(struct task_struct *tsk)
301 /* update the ownership of the thread keyring */
303 if (tsk->cred->thread_keyring) {
304 down_write(&tsk->cred->thread_keyring->sem);
305 tsk->cred->thread_keyring->gid = tsk->cred->fsgid;
306 up_write(&tsk->cred->thread_keyring->sem);
311 * Search the process keyrings attached to the supplied cred for the first
314 * The search criteria are the type and the match function. The description is
315 * given to the match function as a parameter, but doesn't otherwise influence
316 * the search. Typically the match function will compare the description
317 * parameter to the key's description.
319 * This can only search keyrings that grant Search permission to the supplied
320 * credentials. Keyrings linked to searched keyrings will also be searched if
321 * they grant Search permission too. Keys can only be found if they grant
322 * Search permission to the credentials.
324 * Returns a pointer to the key with the key usage count incremented if
325 * successful, -EAGAIN if we didn't find any matching key or -ENOKEY if we only
326 * matched negative keys.
328 * In the case of a successful return, the possession attribute is set on the
329 * returned key reference.
331 key_ref_t search_my_process_keyrings(struct key_type *type,
332 const void *description,
333 key_match_func_t match,
335 const struct cred *cred)
337 key_ref_t key_ref, ret, err;
339 /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
340 * searchable, but we failed to find a key or we found a negative key;
341 * otherwise we want to return a sample error (probably -EACCES) if
342 * none of the keyrings were searchable
344 * in terms of priority: success > -ENOKEY > -EAGAIN > other error
348 err = ERR_PTR(-EAGAIN);
350 /* search the thread keyring first */
351 if (cred->thread_keyring) {
352 key_ref = keyring_search_aux(
353 make_key_ref(cred->thread_keyring, 1),
354 cred, type, description, match, no_state_check);
355 if (!IS_ERR(key_ref))
358 switch (PTR_ERR(key_ref)) {
359 case -EAGAIN: /* no key */
362 case -ENOKEY: /* negative key */
371 /* search the process keyring second */
372 if (cred->tgcred->process_keyring) {
373 key_ref = keyring_search_aux(
374 make_key_ref(cred->tgcred->process_keyring, 1),
375 cred, type, description, match, no_state_check);
376 if (!IS_ERR(key_ref))
379 switch (PTR_ERR(key_ref)) {
380 case -EAGAIN: /* no key */
383 case -ENOKEY: /* negative key */
392 /* search the session keyring */
393 if (cred->tgcred->session_keyring) {
395 key_ref = keyring_search_aux(
396 make_key_ref(rcu_dereference(
397 cred->tgcred->session_keyring),
399 cred, type, description, match, no_state_check);
402 if (!IS_ERR(key_ref))
405 switch (PTR_ERR(key_ref)) {
406 case -EAGAIN: /* no key */
409 case -ENOKEY: /* negative key */
417 /* or search the user-session keyring */
418 else if (cred->user->session_keyring) {
419 key_ref = keyring_search_aux(
420 make_key_ref(cred->user->session_keyring, 1),
421 cred, type, description, match, no_state_check);
422 if (!IS_ERR(key_ref))
425 switch (PTR_ERR(key_ref)) {
426 case -EAGAIN: /* no key */
429 case -ENOKEY: /* negative key */
438 /* no key - decide on the error we're going to go for */
439 key_ref = ret ? ret : err;
446 * Search the process keyrings attached to the supplied cred for the first
447 * matching key in the manner of search_my_process_keyrings(), but also search
448 * the keys attached to the assumed authorisation key using its credentials if
451 * Return same as search_my_process_keyrings().
453 key_ref_t search_process_keyrings(struct key_type *type,
454 const void *description,
455 key_match_func_t match,
456 const struct cred *cred)
458 struct request_key_auth *rka;
459 key_ref_t key_ref, ret = ERR_PTR(-EACCES), err;
463 key_ref = search_my_process_keyrings(type, description, match,
465 if (!IS_ERR(key_ref))
469 /* if this process has an instantiation authorisation key, then we also
470 * search the keyrings of the process mentioned there
471 * - we don't permit access to request_key auth keys via this method
473 if (cred->request_key_auth &&
474 cred == current_cred() &&
475 type != &key_type_request_key_auth
477 /* defend against the auth key being revoked */
478 down_read(&cred->request_key_auth->sem);
480 if (key_validate(cred->request_key_auth) == 0) {
481 rka = cred->request_key_auth->payload.data;
483 key_ref = search_process_keyrings(type, description,
486 up_read(&cred->request_key_auth->sem);
488 if (!IS_ERR(key_ref))
493 up_read(&cred->request_key_auth->sem);
497 /* no key - decide on the error we're going to go for */
498 if (err == ERR_PTR(-ENOKEY) || ret == ERR_PTR(-ENOKEY))
499 key_ref = ERR_PTR(-ENOKEY);
500 else if (err == ERR_PTR(-EACCES))
510 * See if the key we're looking at is the target key.
512 int lookup_user_key_possessed(const struct key *key, const void *target)
514 return key == target;
518 * Look up a key ID given us by userspace with a given permissions mask to get
519 * the key it refers to.
521 * Flags can be passed to request that special keyrings be created if referred
522 * to directly, to permit partially constructed keys to be found and to skip
523 * validity and permission checks on the found key.
525 * Returns a pointer to the key with an incremented usage count if successful;
526 * -EINVAL if the key ID is invalid; -ENOKEY if the key ID does not correspond
527 * to a key or the best found key was a negative key; -EKEYREVOKED or
528 * -EKEYEXPIRED if the best found key was revoked or expired; -EACCES if the
529 * found key doesn't grant the requested permit or the LSM denied access to it;
530 * or -ENOMEM if a special keyring couldn't be created.
532 * In the case of a successful return, the possession attribute is set on the
533 * returned key reference.
535 key_ref_t lookup_user_key(key_serial_t id, unsigned long lflags,
538 struct request_key_auth *rka;
539 const struct cred *cred;
541 key_ref_t key_ref, skey_ref;
545 cred = get_current_cred();
546 key_ref = ERR_PTR(-ENOKEY);
549 case KEY_SPEC_THREAD_KEYRING:
550 if (!cred->thread_keyring) {
551 if (!(lflags & KEY_LOOKUP_CREATE))
554 ret = install_thread_keyring();
556 key_ref = ERR_PTR(ret);
562 key = cred->thread_keyring;
563 atomic_inc(&key->usage);
564 key_ref = make_key_ref(key, 1);
567 case KEY_SPEC_PROCESS_KEYRING:
568 if (!cred->tgcred->process_keyring) {
569 if (!(lflags & KEY_LOOKUP_CREATE))
572 ret = install_process_keyring();
574 key_ref = ERR_PTR(ret);
580 key = cred->tgcred->process_keyring;
581 atomic_inc(&key->usage);
582 key_ref = make_key_ref(key, 1);
585 case KEY_SPEC_SESSION_KEYRING:
586 if (!cred->tgcred->session_keyring) {
587 /* always install a session keyring upon access if one
588 * doesn't exist yet */
589 ret = install_user_keyrings();
592 if (lflags & KEY_LOOKUP_CREATE)
593 ret = join_session_keyring(NULL);
595 ret = install_session_keyring(
596 cred->user->session_keyring);
601 } else if (cred->tgcred->session_keyring ==
602 cred->user->session_keyring &&
603 lflags & KEY_LOOKUP_CREATE) {
604 ret = join_session_keyring(NULL);
611 key = rcu_dereference(cred->tgcred->session_keyring);
612 atomic_inc(&key->usage);
614 key_ref = make_key_ref(key, 1);
617 case KEY_SPEC_USER_KEYRING:
618 if (!cred->user->uid_keyring) {
619 ret = install_user_keyrings();
624 key = cred->user->uid_keyring;
625 atomic_inc(&key->usage);
626 key_ref = make_key_ref(key, 1);
629 case KEY_SPEC_USER_SESSION_KEYRING:
630 if (!cred->user->session_keyring) {
631 ret = install_user_keyrings();
636 key = cred->user->session_keyring;
637 atomic_inc(&key->usage);
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 = cred->request_key_auth;
651 atomic_inc(&key->usage);
652 key_ref = make_key_ref(key, 1);
655 case KEY_SPEC_REQUESTOR_KEYRING:
656 if (!cred->request_key_auth)
659 down_read(&cred->request_key_auth->sem);
660 if (test_bit(KEY_FLAG_REVOKED,
661 &cred->request_key_auth->flags)) {
662 key_ref = ERR_PTR(-EKEYREVOKED);
665 rka = cred->request_key_auth->payload.data;
666 key = rka->dest_keyring;
667 atomic_inc(&key->usage);
669 up_read(&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 skey_ref = search_process_keyrings(key->type, key,
690 lookup_user_key_possessed,
693 if (!IS_ERR(skey_ref)) {
701 /* unlink does not use the nominated key in any way, so can skip all
702 * the permission checks as it is only concerned with the keyring */
703 if (lflags & KEY_LOOKUP_FOR_UNLINK) {
708 if (!(lflags & KEY_LOOKUP_PARTIAL)) {
709 ret = wait_for_key_construction(key, true);
720 ret = key_validate(key);
726 if (!(lflags & KEY_LOOKUP_PARTIAL) &&
727 !test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
730 /* check the permissions */
731 ret = key_task_permission(key_ref, cred, perm);
735 key->last_used_at = current_kernel_time().tv_sec;
742 key_ref_put(key_ref);
743 key_ref = ERR_PTR(ret);
746 /* if we attempted to install a keyring, then it may have caused new
747 * creds to be installed */
754 * Join the named keyring as the session keyring if possible else attempt to
755 * create a new one of that name and join that.
757 * If the name is NULL, an empty anonymous keyring will be installed as the
760 * Named session keyrings are joined with a semaphore held to prevent the
761 * keyrings from going away whilst the attempt is made to going them and also
762 * to prevent a race in creating compatible session keyrings.
764 long join_session_keyring(const char *name)
766 const struct cred *old;
771 /* only permit this if there's a single thread in the thread group -
772 * this avoids us having to adjust the creds on all threads and risking
774 if (!current_is_single_threaded())
777 new = prepare_creds();
780 old = current_cred();
782 /* if no name is provided, install an anonymous keyring */
784 ret = install_session_keyring_to_cred(new, NULL);
788 serial = new->tgcred->session_keyring->serial;
789 ret = commit_creds(new);
795 /* allow the user to join or create a named keyring */
796 mutex_lock(&key_session_mutex);
798 /* look for an existing keyring of this name */
799 keyring = find_keyring_by_name(name, false);
800 if (PTR_ERR(keyring) == -ENOKEY) {
801 /* not found - try and create a new one */
802 keyring = keyring_alloc(name, old->uid, old->gid, old,
803 KEY_ALLOC_IN_QUOTA, NULL);
804 if (IS_ERR(keyring)) {
805 ret = PTR_ERR(keyring);
808 } else if (IS_ERR(keyring)) {
809 ret = PTR_ERR(keyring);
813 /* we've got a keyring - now to install it */
814 ret = install_session_keyring_to_cred(new, keyring);
819 mutex_unlock(&key_session_mutex);
821 ret = keyring->serial;
827 mutex_unlock(&key_session_mutex);
834 * Replace a process's session keyring on behalf of one of its children when
835 * the target process is about to resume userspace execution.
837 void key_change_session_keyring(struct callback_head *twork)
839 const struct cred *old = current_cred();
840 struct cred *new = container_of(twork, struct cred, rcu);
842 if (unlikely(current->flags & PF_EXITING)) {
847 new-> uid = old-> uid;
848 new-> euid = old-> euid;
849 new-> suid = old-> suid;
850 new->fsuid = old->fsuid;
851 new-> gid = old-> gid;
852 new-> egid = old-> egid;
853 new-> sgid = old-> sgid;
854 new->fsgid = old->fsgid;
855 new->user = get_uid(old->user);
856 new->user_ns = get_user_ns(new->user_ns);
857 new->group_info = get_group_info(old->group_info);
859 new->securebits = old->securebits;
860 new->cap_inheritable = old->cap_inheritable;
861 new->cap_permitted = old->cap_permitted;
862 new->cap_effective = old->cap_effective;
863 new->cap_bset = old->cap_bset;
865 new->jit_keyring = old->jit_keyring;
866 new->thread_keyring = key_get(old->thread_keyring);
867 new->tgcred->tgid = old->tgcred->tgid;
868 new->tgcred->process_keyring = key_get(old->tgcred->process_keyring);
870 security_transfer_creds(new, old);