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, NULL);
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,
334 const struct cred *cred)
336 key_ref_t key_ref, ret, err;
338 /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
339 * searchable, but we failed to find a key or we found a negative key;
340 * otherwise we want to return a sample error (probably -EACCES) if
341 * none of the keyrings were searchable
343 * in terms of priority: success > -ENOKEY > -EAGAIN > other error
347 err = ERR_PTR(-EAGAIN);
349 /* search the thread keyring first */
350 if (cred->thread_keyring) {
351 key_ref = keyring_search_aux(
352 make_key_ref(cred->thread_keyring, 1),
353 cred, type, description, match);
354 if (!IS_ERR(key_ref))
357 switch (PTR_ERR(key_ref)) {
358 case -EAGAIN: /* no key */
361 case -ENOKEY: /* negative key */
370 /* search the process keyring second */
371 if (cred->tgcred->process_keyring) {
372 key_ref = keyring_search_aux(
373 make_key_ref(cred->tgcred->process_keyring, 1),
374 cred, type, description, match);
375 if (!IS_ERR(key_ref))
378 switch (PTR_ERR(key_ref)) {
379 case -EAGAIN: /* no key */
382 case -ENOKEY: /* negative key */
391 /* search the session keyring */
392 if (cred->tgcred->session_keyring) {
394 key_ref = keyring_search_aux(
395 make_key_ref(rcu_dereference(
396 cred->tgcred->session_keyring),
398 cred, type, description, match);
401 if (!IS_ERR(key_ref))
404 switch (PTR_ERR(key_ref)) {
405 case -EAGAIN: /* no key */
408 case -ENOKEY: /* negative key */
416 /* or search the user-session keyring */
417 else if (cred->user->session_keyring) {
418 key_ref = keyring_search_aux(
419 make_key_ref(cred->user->session_keyring, 1),
420 cred, type, description, match);
421 if (!IS_ERR(key_ref))
424 switch (PTR_ERR(key_ref)) {
425 case -EAGAIN: /* no key */
428 case -ENOKEY: /* negative key */
437 /* no key - decide on the error we're going to go for */
438 key_ref = ret ? ret : err;
445 * Search the process keyrings attached to the supplied cred for the first
446 * matching key in the manner of search_my_process_keyrings(), but also search
447 * the keys attached to the assumed authorisation key using its credentials if
450 * Return same as search_my_process_keyrings().
452 key_ref_t search_process_keyrings(struct key_type *type,
453 const void *description,
454 key_match_func_t match,
455 const struct cred *cred)
457 struct request_key_auth *rka;
458 key_ref_t key_ref, ret = ERR_PTR(-EACCES), err;
462 key_ref = search_my_process_keyrings(type, description, match, cred);
463 if (!IS_ERR(key_ref))
467 /* if this process has an instantiation authorisation key, then we also
468 * search the keyrings of the process mentioned there
469 * - we don't permit access to request_key auth keys via this method
471 if (cred->request_key_auth &&
472 cred == current_cred() &&
473 type != &key_type_request_key_auth
475 /* defend against the auth key being revoked */
476 down_read(&cred->request_key_auth->sem);
478 if (key_validate(cred->request_key_auth) == 0) {
479 rka = cred->request_key_auth->payload.data;
481 key_ref = search_process_keyrings(type, description,
484 up_read(&cred->request_key_auth->sem);
486 if (!IS_ERR(key_ref))
491 up_read(&cred->request_key_auth->sem);
495 /* no key - decide on the error we're going to go for */
496 if (err == ERR_PTR(-ENOKEY) || ret == ERR_PTR(-ENOKEY))
497 key_ref = ERR_PTR(-ENOKEY);
498 else if (err == ERR_PTR(-EACCES))
508 * See if the key we're looking at is the target key.
510 int lookup_user_key_possessed(const struct key *key, const void *target)
512 return key == target;
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 request_key_auth *rka;
537 const struct cred *cred;
539 key_ref_t key_ref, skey_ref;
543 cred = get_current_cred();
544 key_ref = ERR_PTR(-ENOKEY);
547 case KEY_SPEC_THREAD_KEYRING:
548 if (!cred->thread_keyring) {
549 if (!(lflags & KEY_LOOKUP_CREATE))
552 ret = install_thread_keyring();
554 key_ref = ERR_PTR(ret);
560 key = cred->thread_keyring;
561 atomic_inc(&key->usage);
562 key_ref = make_key_ref(key, 1);
565 case KEY_SPEC_PROCESS_KEYRING:
566 if (!cred->tgcred->process_keyring) {
567 if (!(lflags & KEY_LOOKUP_CREATE))
570 ret = install_process_keyring();
572 key_ref = ERR_PTR(ret);
578 key = cred->tgcred->process_keyring;
579 atomic_inc(&key->usage);
580 key_ref = make_key_ref(key, 1);
583 case KEY_SPEC_SESSION_KEYRING:
584 if (!cred->tgcred->session_keyring) {
585 /* always install a session keyring upon access if one
586 * doesn't exist yet */
587 ret = install_user_keyrings();
590 ret = install_session_keyring(
591 cred->user->session_keyring);
599 key = rcu_dereference(cred->tgcred->session_keyring);
600 atomic_inc(&key->usage);
602 key_ref = make_key_ref(key, 1);
605 case KEY_SPEC_USER_KEYRING:
606 if (!cred->user->uid_keyring) {
607 ret = install_user_keyrings();
612 key = cred->user->uid_keyring;
613 atomic_inc(&key->usage);
614 key_ref = make_key_ref(key, 1);
617 case KEY_SPEC_USER_SESSION_KEYRING:
618 if (!cred->user->session_keyring) {
619 ret = install_user_keyrings();
624 key = cred->user->session_keyring;
625 atomic_inc(&key->usage);
626 key_ref = make_key_ref(key, 1);
629 case KEY_SPEC_GROUP_KEYRING:
630 /* group keyrings are not yet supported */
631 key_ref = ERR_PTR(-EINVAL);
634 case KEY_SPEC_REQKEY_AUTH_KEY:
635 key = cred->request_key_auth;
639 atomic_inc(&key->usage);
640 key_ref = make_key_ref(key, 1);
643 case KEY_SPEC_REQUESTOR_KEYRING:
644 if (!cred->request_key_auth)
647 down_read(&cred->request_key_auth->sem);
648 if (cred->request_key_auth->flags & KEY_FLAG_REVOKED) {
649 key_ref = ERR_PTR(-EKEYREVOKED);
652 rka = cred->request_key_auth->payload.data;
653 key = rka->dest_keyring;
654 atomic_inc(&key->usage);
656 up_read(&cred->request_key_auth->sem);
659 key_ref = make_key_ref(key, 1);
663 key_ref = ERR_PTR(-EINVAL);
667 key = key_lookup(id);
669 key_ref = ERR_CAST(key);
673 key_ref = make_key_ref(key, 0);
675 /* check to see if we possess the key */
676 skey_ref = search_process_keyrings(key->type, key,
677 lookup_user_key_possessed,
680 if (!IS_ERR(skey_ref)) {
688 /* unlink does not use the nominated key in any way, so can skip all
689 * the permission checks as it is only concerned with the keyring */
690 if (lflags & KEY_LOOKUP_FOR_UNLINK) {
695 if (!(lflags & KEY_LOOKUP_PARTIAL)) {
696 ret = wait_for_key_construction(key, true);
707 ret = key_validate(key);
713 if (!(lflags & KEY_LOOKUP_PARTIAL) &&
714 !test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
717 /* check the permissions */
718 ret = key_task_permission(key_ref, cred, perm);
727 key_ref_put(key_ref);
728 key_ref = ERR_PTR(ret);
731 /* if we attempted to install a keyring, then it may have caused new
732 * creds to be installed */
739 * Join the named keyring as the session keyring if possible else attempt to
740 * create a new one of that name and join that.
742 * If the name is NULL, an empty anonymous keyring will be installed as the
745 * Named session keyrings are joined with a semaphore held to prevent the
746 * keyrings from going away whilst the attempt is made to going them and also
747 * to prevent a race in creating compatible session keyrings.
749 long join_session_keyring(const char *name)
751 const struct cred *old;
756 /* only permit this if there's a single thread in the thread group -
757 * this avoids us having to adjust the creds on all threads and risking
759 if (!current_is_single_threaded())
762 new = prepare_creds();
765 old = current_cred();
767 /* if no name is provided, install an anonymous keyring */
769 ret = install_session_keyring_to_cred(new, NULL);
773 serial = new->tgcred->session_keyring->serial;
774 ret = commit_creds(new);
780 /* allow the user to join or create a named keyring */
781 mutex_lock(&key_session_mutex);
783 /* look for an existing keyring of this name */
784 keyring = find_keyring_by_name(name, false);
785 if (PTR_ERR(keyring) == -ENOKEY) {
786 /* not found - try and create a new one */
787 keyring = keyring_alloc(name, old->uid, old->gid, old,
788 KEY_ALLOC_IN_QUOTA, NULL);
789 if (IS_ERR(keyring)) {
790 ret = PTR_ERR(keyring);
793 } else if (IS_ERR(keyring)) {
794 ret = PTR_ERR(keyring);
798 /* we've got a keyring - now to install it */
799 ret = install_session_keyring_to_cred(new, keyring);
804 mutex_unlock(&key_session_mutex);
806 ret = keyring->serial;
812 mutex_unlock(&key_session_mutex);
819 * Replace a process's session keyring on behalf of one of its children when
820 * the target process is about to resume userspace execution.
822 void key_replace_session_keyring(void)
824 const struct cred *old;
827 if (!current->replacement_session_keyring)
830 write_lock_irq(&tasklist_lock);
831 new = current->replacement_session_keyring;
832 current->replacement_session_keyring = NULL;
833 write_unlock_irq(&tasklist_lock);
838 old = current_cred();
839 new-> uid = old-> uid;
840 new-> euid = old-> euid;
841 new-> suid = old-> suid;
842 new->fsuid = old->fsuid;
843 new-> gid = old-> gid;
844 new-> egid = old-> egid;
845 new-> sgid = old-> sgid;
846 new->fsgid = old->fsgid;
847 new->user = get_uid(old->user);
848 new->group_info = get_group_info(old->group_info);
850 new->securebits = old->securebits;
851 new->cap_inheritable = old->cap_inheritable;
852 new->cap_permitted = old->cap_permitted;
853 new->cap_effective = old->cap_effective;
854 new->cap_bset = old->cap_bset;
856 new->jit_keyring = old->jit_keyring;
857 new->thread_keyring = key_get(old->thread_keyring);
858 new->tgcred->tgid = old->tgcred->tgid;
859 new->tgcred->process_keyring = key_get(old->tgcred->process_keyring);
861 security_transfer_creds(new, old);