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),
37 .uid = GLOBAL_ROOT_UID,
41 * Install the user and user session keyrings for the current process's UID.
43 int install_user_keyrings(void)
45 struct user_struct *user;
46 const struct cred *cred;
47 struct key *uid_keyring, *session_keyring;
52 cred = current_cred();
54 uid = from_kuid(cred->user_ns, user->uid);
56 kenter("%p{%u}", user, uid);
58 if (user->uid_keyring) {
59 kleave(" = 0 [exist]");
63 mutex_lock(&key_user_keyring_mutex);
66 if (!user->uid_keyring) {
67 /* get the UID-specific keyring
68 * - there may be one in existence already as it may have been
69 * pinned by a session, but the user_struct pointing to it
70 * may have been destroyed by setuid */
71 sprintf(buf, "_uid.%u", uid);
73 uid_keyring = find_keyring_by_name(buf, true);
74 if (IS_ERR(uid_keyring)) {
75 uid_keyring = keyring_alloc(buf, user->uid, INVALID_GID,
76 cred, KEY_ALLOC_IN_QUOTA,
78 if (IS_ERR(uid_keyring)) {
79 ret = PTR_ERR(uid_keyring);
84 /* get a default session keyring (which might also exist
86 sprintf(buf, "_uid_ses.%u", uid);
88 session_keyring = find_keyring_by_name(buf, true);
89 if (IS_ERR(session_keyring)) {
91 keyring_alloc(buf, user->uid, INVALID_GID,
92 cred, KEY_ALLOC_IN_QUOTA, NULL);
93 if (IS_ERR(session_keyring)) {
94 ret = PTR_ERR(session_keyring);
98 /* we install a link from the user session keyring to
100 ret = key_link(session_keyring, uid_keyring);
102 goto error_release_both;
105 /* install the keyrings */
106 user->uid_keyring = uid_keyring;
107 user->session_keyring = session_keyring;
110 mutex_unlock(&key_user_keyring_mutex);
115 key_put(session_keyring);
117 key_put(uid_keyring);
119 mutex_unlock(&key_user_keyring_mutex);
120 kleave(" = %d", ret);
125 * Install a fresh thread keyring directly to new credentials. This keyring is
126 * allowed to overrun the quota.
128 int install_thread_keyring_to_cred(struct cred *new)
132 keyring = keyring_alloc("_tid", new->uid, new->gid, new,
133 KEY_ALLOC_QUOTA_OVERRUN, NULL);
135 return PTR_ERR(keyring);
137 new->thread_keyring = keyring;
142 * Install a fresh thread keyring, discarding the old one.
144 static int install_thread_keyring(void)
149 new = prepare_creds();
153 BUG_ON(new->thread_keyring);
155 ret = install_thread_keyring_to_cred(new);
161 return commit_creds(new);
165 * Install a process keyring directly to a credentials struct.
167 * Returns -EEXIST if there was already a process keyring, 0 if one installed,
168 * and other value on any other error
170 int install_process_keyring_to_cred(struct cred *new)
175 if (new->tgcred->process_keyring)
178 keyring = keyring_alloc("_pid", new->uid, new->gid,
179 new, KEY_ALLOC_QUOTA_OVERRUN, NULL);
181 return PTR_ERR(keyring);
183 spin_lock_irq(&new->tgcred->lock);
184 if (!new->tgcred->process_keyring) {
185 new->tgcred->process_keyring = keyring;
191 spin_unlock_irq(&new->tgcred->lock);
197 * Make sure a process keyring is installed for the current process. The
198 * existing process keyring is not replaced.
200 * Returns 0 if there is a process keyring by the end of this function, some
203 static int install_process_keyring(void)
208 new = prepare_creds();
212 ret = install_process_keyring_to_cred(new);
215 return ret != -EEXIST ? ret : 0;
218 return commit_creds(new);
222 * Install a session keyring directly to a credentials struct.
224 int install_session_keyring_to_cred(struct cred *cred, struct key *keyring)
231 /* create an empty session keyring */
233 flags = KEY_ALLOC_QUOTA_OVERRUN;
234 if (cred->tgcred->session_keyring)
235 flags = KEY_ALLOC_IN_QUOTA;
237 keyring = keyring_alloc("_ses", cred->uid, cred->gid,
240 return PTR_ERR(keyring);
242 atomic_inc(&keyring->usage);
245 /* install the keyring */
246 spin_lock_irq(&cred->tgcred->lock);
247 old = cred->tgcred->session_keyring;
248 rcu_assign_pointer(cred->tgcred->session_keyring, keyring);
249 spin_unlock_irq(&cred->tgcred->lock);
251 /* we're using RCU on the pointer, but there's no point synchronising
252 * on it if it didn't previously point to anything */
262 * Install a session keyring, discarding the old one. If a keyring is not
263 * supplied, an empty one is invented.
265 static int install_session_keyring(struct key *keyring)
270 new = prepare_creds();
274 ret = install_session_keyring_to_cred(new, keyring);
280 return commit_creds(new);
284 * Handle the fsuid changing.
286 void key_fsuid_changed(struct task_struct *tsk)
288 /* update the ownership of the thread keyring */
290 if (tsk->cred->thread_keyring) {
291 down_write(&tsk->cred->thread_keyring->sem);
292 tsk->cred->thread_keyring->uid = tsk->cred->fsuid;
293 up_write(&tsk->cred->thread_keyring->sem);
298 * Handle the fsgid changing.
300 void key_fsgid_changed(struct task_struct *tsk)
302 /* update the ownership of the thread keyring */
304 if (tsk->cred->thread_keyring) {
305 down_write(&tsk->cred->thread_keyring->sem);
306 tsk->cred->thread_keyring->gid = tsk->cred->fsgid;
307 up_write(&tsk->cred->thread_keyring->sem);
312 * Search the process keyrings attached to the supplied cred for the first
315 * The search criteria are the type and the match function. The description is
316 * given to the match function as a parameter, but doesn't otherwise influence
317 * the search. Typically the match function will compare the description
318 * parameter to the key's description.
320 * This can only search keyrings that grant Search permission to the supplied
321 * credentials. Keyrings linked to searched keyrings will also be searched if
322 * they grant Search permission too. Keys can only be found if they grant
323 * Search permission to the credentials.
325 * Returns a pointer to the key with the key usage count incremented if
326 * successful, -EAGAIN if we didn't find any matching key or -ENOKEY if we only
327 * matched negative keys.
329 * In the case of a successful return, the possession attribute is set on the
330 * returned key reference.
332 key_ref_t search_my_process_keyrings(struct key_type *type,
333 const void *description,
334 key_match_func_t match,
336 const struct cred *cred)
338 key_ref_t key_ref, ret, err;
340 /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
341 * searchable, but we failed to find a key or we found a negative key;
342 * otherwise we want to return a sample error (probably -EACCES) if
343 * none of the keyrings were searchable
345 * in terms of priority: success > -ENOKEY > -EAGAIN > other error
349 err = ERR_PTR(-EAGAIN);
351 /* search the thread keyring first */
352 if (cred->thread_keyring) {
353 key_ref = keyring_search_aux(
354 make_key_ref(cred->thread_keyring, 1),
355 cred, type, description, match, no_state_check);
356 if (!IS_ERR(key_ref))
359 switch (PTR_ERR(key_ref)) {
360 case -EAGAIN: /* no key */
363 case -ENOKEY: /* negative key */
372 /* search the process keyring second */
373 if (cred->tgcred->process_keyring) {
374 key_ref = keyring_search_aux(
375 make_key_ref(cred->tgcred->process_keyring, 1),
376 cred, type, description, match, no_state_check);
377 if (!IS_ERR(key_ref))
380 switch (PTR_ERR(key_ref)) {
381 case -EAGAIN: /* no key */
384 case -ENOKEY: /* negative key */
393 /* search the session keyring */
394 if (cred->tgcred->session_keyring) {
396 key_ref = keyring_search_aux(
397 make_key_ref(rcu_dereference(
398 cred->tgcred->session_keyring),
400 cred, type, description, match, no_state_check);
403 if (!IS_ERR(key_ref))
406 switch (PTR_ERR(key_ref)) {
407 case -EAGAIN: /* no key */
410 case -ENOKEY: /* negative key */
418 /* or search the user-session keyring */
419 else if (cred->user->session_keyring) {
420 key_ref = keyring_search_aux(
421 make_key_ref(cred->user->session_keyring, 1),
422 cred, type, description, match, no_state_check);
423 if (!IS_ERR(key_ref))
426 switch (PTR_ERR(key_ref)) {
427 case -EAGAIN: /* no key */
430 case -ENOKEY: /* negative key */
439 /* no key - decide on the error we're going to go for */
440 key_ref = ret ? ret : err;
447 * Search the process keyrings attached to the supplied cred for the first
448 * matching key in the manner of search_my_process_keyrings(), but also search
449 * the keys attached to the assumed authorisation key using its credentials if
452 * Return same as search_my_process_keyrings().
454 key_ref_t search_process_keyrings(struct key_type *type,
455 const void *description,
456 key_match_func_t match,
457 const struct cred *cred)
459 struct request_key_auth *rka;
460 key_ref_t key_ref, ret = ERR_PTR(-EACCES), err;
464 key_ref = search_my_process_keyrings(type, description, match,
466 if (!IS_ERR(key_ref))
470 /* if this process has an instantiation authorisation key, then we also
471 * search the keyrings of the process mentioned there
472 * - we don't permit access to request_key auth keys via this method
474 if (cred->request_key_auth &&
475 cred == current_cred() &&
476 type != &key_type_request_key_auth
478 /* defend against the auth key being revoked */
479 down_read(&cred->request_key_auth->sem);
481 if (key_validate(cred->request_key_auth) == 0) {
482 rka = cred->request_key_auth->payload.data;
484 key_ref = search_process_keyrings(type, description,
487 up_read(&cred->request_key_auth->sem);
489 if (!IS_ERR(key_ref))
494 up_read(&cred->request_key_auth->sem);
498 /* no key - decide on the error we're going to go for */
499 if (err == ERR_PTR(-ENOKEY) || ret == ERR_PTR(-ENOKEY))
500 key_ref = ERR_PTR(-ENOKEY);
501 else if (err == ERR_PTR(-EACCES))
511 * See if the key we're looking at is the target key.
513 int lookup_user_key_possessed(const struct key *key, const void *target)
515 return key == target;
519 * Look up a key ID given us by userspace with a given permissions mask to get
520 * the key it refers to.
522 * Flags can be passed to request that special keyrings be created if referred
523 * to directly, to permit partially constructed keys to be found and to skip
524 * validity and permission checks on the found key.
526 * Returns a pointer to the key with an incremented usage count if successful;
527 * -EINVAL if the key ID is invalid; -ENOKEY if the key ID does not correspond
528 * to a key or the best found key was a negative key; -EKEYREVOKED or
529 * -EKEYEXPIRED if the best found key was revoked or expired; -EACCES if the
530 * found key doesn't grant the requested permit or the LSM denied access to it;
531 * or -ENOMEM if a special keyring couldn't be created.
533 * In the case of a successful return, the possession attribute is set on the
534 * returned key reference.
536 key_ref_t lookup_user_key(key_serial_t id, unsigned long lflags,
539 struct request_key_auth *rka;
540 const struct cred *cred;
542 key_ref_t key_ref, skey_ref;
546 cred = get_current_cred();
547 key_ref = ERR_PTR(-ENOKEY);
550 case KEY_SPEC_THREAD_KEYRING:
551 if (!cred->thread_keyring) {
552 if (!(lflags & KEY_LOOKUP_CREATE))
555 ret = install_thread_keyring();
557 key_ref = ERR_PTR(ret);
563 key = cred->thread_keyring;
564 atomic_inc(&key->usage);
565 key_ref = make_key_ref(key, 1);
568 case KEY_SPEC_PROCESS_KEYRING:
569 if (!cred->tgcred->process_keyring) {
570 if (!(lflags & KEY_LOOKUP_CREATE))
573 ret = install_process_keyring();
575 key_ref = ERR_PTR(ret);
581 key = cred->tgcred->process_keyring;
582 atomic_inc(&key->usage);
583 key_ref = make_key_ref(key, 1);
586 case KEY_SPEC_SESSION_KEYRING:
587 if (!cred->tgcred->session_keyring) {
588 /* always install a session keyring upon access if one
589 * doesn't exist yet */
590 ret = install_user_keyrings();
593 if (lflags & KEY_LOOKUP_CREATE)
594 ret = join_session_keyring(NULL);
596 ret = install_session_keyring(
597 cred->user->session_keyring);
602 } else if (cred->tgcred->session_keyring ==
603 cred->user->session_keyring &&
604 lflags & KEY_LOOKUP_CREATE) {
605 ret = join_session_keyring(NULL);
612 key = rcu_dereference(cred->tgcred->session_keyring);
613 atomic_inc(&key->usage);
615 key_ref = make_key_ref(key, 1);
618 case KEY_SPEC_USER_KEYRING:
619 if (!cred->user->uid_keyring) {
620 ret = install_user_keyrings();
625 key = cred->user->uid_keyring;
626 atomic_inc(&key->usage);
627 key_ref = make_key_ref(key, 1);
630 case KEY_SPEC_USER_SESSION_KEYRING:
631 if (!cred->user->session_keyring) {
632 ret = install_user_keyrings();
637 key = cred->user->session_keyring;
638 atomic_inc(&key->usage);
639 key_ref = make_key_ref(key, 1);
642 case KEY_SPEC_GROUP_KEYRING:
643 /* group keyrings are not yet supported */
644 key_ref = ERR_PTR(-EINVAL);
647 case KEY_SPEC_REQKEY_AUTH_KEY:
648 key = cred->request_key_auth;
652 atomic_inc(&key->usage);
653 key_ref = make_key_ref(key, 1);
656 case KEY_SPEC_REQUESTOR_KEYRING:
657 if (!cred->request_key_auth)
660 down_read(&cred->request_key_auth->sem);
661 if (test_bit(KEY_FLAG_REVOKED,
662 &cred->request_key_auth->flags)) {
663 key_ref = ERR_PTR(-EKEYREVOKED);
666 rka = cred->request_key_auth->payload.data;
667 key = rka->dest_keyring;
668 atomic_inc(&key->usage);
670 up_read(&cred->request_key_auth->sem);
673 key_ref = make_key_ref(key, 1);
677 key_ref = ERR_PTR(-EINVAL);
681 key = key_lookup(id);
683 key_ref = ERR_CAST(key);
687 key_ref = make_key_ref(key, 0);
689 /* check to see if we possess the key */
690 skey_ref = search_process_keyrings(key->type, key,
691 lookup_user_key_possessed,
694 if (!IS_ERR(skey_ref)) {
702 /* unlink does not use the nominated key in any way, so can skip all
703 * the permission checks as it is only concerned with the keyring */
704 if (lflags & KEY_LOOKUP_FOR_UNLINK) {
709 if (!(lflags & KEY_LOOKUP_PARTIAL)) {
710 ret = wait_for_key_construction(key, true);
721 ret = key_validate(key);
727 if (!(lflags & KEY_LOOKUP_PARTIAL) &&
728 !test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
731 /* check the permissions */
732 ret = key_task_permission(key_ref, cred, perm);
736 key->last_used_at = current_kernel_time().tv_sec;
743 key_ref_put(key_ref);
744 key_ref = ERR_PTR(ret);
747 /* if we attempted to install a keyring, then it may have caused new
748 * creds to be installed */
755 * Join the named keyring as the session keyring if possible else attempt to
756 * create a new one of that name and join that.
758 * If the name is NULL, an empty anonymous keyring will be installed as the
761 * Named session keyrings are joined with a semaphore held to prevent the
762 * keyrings from going away whilst the attempt is made to going them and also
763 * to prevent a race in creating compatible session keyrings.
765 long join_session_keyring(const char *name)
767 const struct cred *old;
772 /* only permit this if there's a single thread in the thread group -
773 * this avoids us having to adjust the creds on all threads and risking
775 if (!current_is_single_threaded())
778 new = prepare_creds();
781 old = current_cred();
783 /* if no name is provided, install an anonymous keyring */
785 ret = install_session_keyring_to_cred(new, NULL);
789 serial = new->tgcred->session_keyring->serial;
790 ret = commit_creds(new);
796 /* allow the user to join or create a named keyring */
797 mutex_lock(&key_session_mutex);
799 /* look for an existing keyring of this name */
800 keyring = find_keyring_by_name(name, false);
801 if (PTR_ERR(keyring) == -ENOKEY) {
802 /* not found - try and create a new one */
803 keyring = keyring_alloc(name, old->uid, old->gid, old,
804 KEY_ALLOC_IN_QUOTA, NULL);
805 if (IS_ERR(keyring)) {
806 ret = PTR_ERR(keyring);
809 } else if (IS_ERR(keyring)) {
810 ret = PTR_ERR(keyring);
814 /* we've got a keyring - now to install it */
815 ret = install_session_keyring_to_cred(new, keyring);
820 mutex_unlock(&key_session_mutex);
822 ret = keyring->serial;
828 mutex_unlock(&key_session_mutex);
835 * Replace a process's session keyring on behalf of one of its children when
836 * the target process is about to resume userspace execution.
838 void key_change_session_keyring(struct callback_head *twork)
840 const struct cred *old = current_cred();
841 struct cred *new = container_of(twork, struct cred, rcu);
843 if (unlikely(current->flags & PF_EXITING)) {
848 new-> uid = old-> uid;
849 new-> euid = old-> euid;
850 new-> suid = old-> suid;
851 new->fsuid = old->fsuid;
852 new-> gid = old-> gid;
853 new-> egid = old-> egid;
854 new-> sgid = old-> sgid;
855 new->fsgid = old->fsgid;
856 new->user = get_uid(old->user);
857 new->user_ns = get_user_ns(new->user_ns);
858 new->group_info = get_group_info(old->group_info);
860 new->securebits = old->securebits;
861 new->cap_inheritable = old->cap_inheritable;
862 new->cap_permitted = old->cap_permitted;
863 new->cap_effective = old->cap_effective;
864 new->cap_bset = old->cap_bset;
866 new->jit_keyring = old->jit_keyring;
867 new->thread_keyring = key_get(old->thread_keyring);
868 new->tgcred->tgid = old->tgcred->tgid;
869 new->tgcred->process_keyring = key_get(old->tgcred->process_keyring);
871 security_transfer_creds(new, old);