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 cred *new_cred)
294 /* update the ownership of the thread keyring */
295 if (new_cred->thread_keyring) {
296 down_write(&new_cred->thread_keyring->sem);
297 new_cred->thread_keyring->uid = new_cred->fsuid;
298 up_write(&new_cred->thread_keyring->sem);
303 * Handle the fsgid changing.
305 void key_fsgid_changed(struct cred *new_cred)
307 /* update the ownership of the thread keyring */
308 if (new_cred->thread_keyring) {
309 down_write(&new_cred->thread_keyring->sem);
310 new_cred->thread_keyring->gid = new_cred->fsgid;
311 up_write(&new_cred->thread_keyring->sem);
316 * Search the process keyrings attached to the supplied cred for the first
317 * matching key under RCU conditions (the caller must be holding the RCU read
320 * The search criteria are the type and the match function. The description is
321 * given to the match function as a parameter, but doesn't otherwise influence
322 * the search. Typically the match function will compare the description
323 * parameter to the key's description.
325 * This can only search keyrings that grant Search permission to the supplied
326 * credentials. Keyrings linked to searched keyrings will also be searched if
327 * they grant Search permission too. Keys can only be found if they grant
328 * Search permission to the credentials.
330 * Returns a pointer to the key with the key usage count incremented if
331 * successful, -EAGAIN if we didn't find any matching key or -ENOKEY if we only
332 * matched negative keys.
334 * In the case of a successful return, the possession attribute is set on the
335 * returned key reference.
337 key_ref_t search_cred_keyrings_rcu(struct keyring_search_context *ctx)
339 key_ref_t key_ref, ret, err;
340 const struct cred *cred = ctx->cred;
342 /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
343 * searchable, but we failed to find a key or we found a negative key;
344 * otherwise we want to return a sample error (probably -EACCES) if
345 * none of the keyrings were searchable
347 * in terms of priority: success > -ENOKEY > -EAGAIN > other error
351 err = ERR_PTR(-EAGAIN);
353 /* search the thread keyring first */
354 if (cred->thread_keyring) {
355 key_ref = keyring_search_rcu(
356 make_key_ref(cred->thread_keyring, 1), ctx);
357 if (!IS_ERR(key_ref))
360 switch (PTR_ERR(key_ref)) {
361 case -EAGAIN: /* no key */
362 case -ENOKEY: /* negative key */
371 /* search the process keyring second */
372 if (cred->process_keyring) {
373 key_ref = keyring_search_rcu(
374 make_key_ref(cred->process_keyring, 1), ctx);
375 if (!IS_ERR(key_ref))
378 switch (PTR_ERR(key_ref)) {
379 case -EAGAIN: /* no key */
383 case -ENOKEY: /* negative key */
392 /* search the session keyring */
393 if (cred->session_keyring) {
394 key_ref = keyring_search_rcu(
395 make_key_ref(cred->session_keyring, 1), ctx);
397 if (!IS_ERR(key_ref))
400 switch (PTR_ERR(key_ref)) {
401 case -EAGAIN: /* no key */
405 case -ENOKEY: /* negative key */
413 /* or search the user-session keyring */
414 else if (READ_ONCE(cred->user->session_keyring)) {
415 key_ref = keyring_search_rcu(
416 make_key_ref(READ_ONCE(cred->user->session_keyring), 1),
418 if (!IS_ERR(key_ref))
421 switch (PTR_ERR(key_ref)) {
422 case -EAGAIN: /* no key */
426 case -ENOKEY: /* negative key */
435 /* no key - decide on the error we're going to go for */
436 key_ref = ret ? ret : err;
443 * Search the process keyrings attached to the supplied cred for the first
444 * matching key in the manner of search_my_process_keyrings(), but also search
445 * the keys attached to the assumed authorisation key using its credentials if
448 * The caller must be holding the RCU read lock.
450 * Return same as search_cred_keyrings_rcu().
452 key_ref_t search_process_keyrings_rcu(struct keyring_search_context *ctx)
454 struct request_key_auth *rka;
455 key_ref_t key_ref, ret = ERR_PTR(-EACCES), err;
457 key_ref = search_cred_keyrings_rcu(ctx);
458 if (!IS_ERR(key_ref))
462 /* if this process has an instantiation authorisation key, then we also
463 * search the keyrings of the process mentioned there
464 * - we don't permit access to request_key auth keys via this method
466 if (ctx->cred->request_key_auth &&
467 ctx->cred == current_cred() &&
468 ctx->index_key.type != &key_type_request_key_auth
470 const struct cred *cred = ctx->cred;
472 if (key_validate(cred->request_key_auth) == 0) {
473 rka = ctx->cred->request_key_auth->payload.data[0];
475 //// was search_process_keyrings() [ie. recursive]
476 ctx->cred = rka->cred;
477 key_ref = search_cred_keyrings_rcu(ctx);
480 if (!IS_ERR(key_ref))
486 /* no key - decide on the error we're going to go for */
487 if (err == ERR_PTR(-ENOKEY) || ret == ERR_PTR(-ENOKEY))
488 key_ref = ERR_PTR(-ENOKEY);
489 else if (err == ERR_PTR(-EACCES))
498 * See if the key we're looking at is the target key.
500 bool lookup_user_key_possessed(const struct key *key,
501 const struct key_match_data *match_data)
503 return key == match_data->raw_data;
507 * Look up a key ID given us by userspace with a given permissions mask to get
508 * the key it refers to.
510 * Flags can be passed to request that special keyrings be created if referred
511 * to directly, to permit partially constructed keys to be found and to skip
512 * validity and permission checks on the found key.
514 * Returns a pointer to the key with an incremented usage count if successful;
515 * -EINVAL if the key ID is invalid; -ENOKEY if the key ID does not correspond
516 * to a key or the best found key was a negative key; -EKEYREVOKED or
517 * -EKEYEXPIRED if the best found key was revoked or expired; -EACCES if the
518 * found key doesn't grant the requested permit or the LSM denied access to it;
519 * or -ENOMEM if a special keyring couldn't be created.
521 * In the case of a successful return, the possession attribute is set on the
522 * returned key reference.
524 key_ref_t lookup_user_key(key_serial_t id, unsigned long lflags,
527 struct keyring_search_context ctx = {
528 .match_data.cmp = lookup_user_key_possessed,
529 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
530 .flags = KEYRING_SEARCH_NO_STATE_CHECK,
532 struct request_key_auth *rka;
534 key_ref_t key_ref, skey_ref;
538 ctx.cred = get_current_cred();
539 key_ref = ERR_PTR(-ENOKEY);
542 case KEY_SPEC_THREAD_KEYRING:
543 if (!ctx.cred->thread_keyring) {
544 if (!(lflags & KEY_LOOKUP_CREATE))
547 ret = install_thread_keyring();
549 key_ref = ERR_PTR(ret);
555 key = ctx.cred->thread_keyring;
557 key_ref = make_key_ref(key, 1);
560 case KEY_SPEC_PROCESS_KEYRING:
561 if (!ctx.cred->process_keyring) {
562 if (!(lflags & KEY_LOOKUP_CREATE))
565 ret = install_process_keyring();
567 key_ref = ERR_PTR(ret);
573 key = ctx.cred->process_keyring;
575 key_ref = make_key_ref(key, 1);
578 case KEY_SPEC_SESSION_KEYRING:
579 if (!ctx.cred->session_keyring) {
580 /* always install a session keyring upon access if one
581 * doesn't exist yet */
582 ret = install_user_keyrings();
585 if (lflags & KEY_LOOKUP_CREATE)
586 ret = join_session_keyring(NULL);
588 ret = install_session_keyring(
589 ctx.cred->user->session_keyring);
594 } else if (ctx.cred->session_keyring ==
595 READ_ONCE(ctx.cred->user->session_keyring) &&
596 lflags & KEY_LOOKUP_CREATE) {
597 ret = join_session_keyring(NULL);
603 key = ctx.cred->session_keyring;
605 key_ref = make_key_ref(key, 1);
608 case KEY_SPEC_USER_KEYRING:
609 if (!READ_ONCE(ctx.cred->user->uid_keyring)) {
610 ret = install_user_keyrings();
615 key = ctx.cred->user->uid_keyring;
617 key_ref = make_key_ref(key, 1);
620 case KEY_SPEC_USER_SESSION_KEYRING:
621 if (!READ_ONCE(ctx.cred->user->session_keyring)) {
622 ret = install_user_keyrings();
627 key = ctx.cred->user->session_keyring;
629 key_ref = make_key_ref(key, 1);
632 case KEY_SPEC_GROUP_KEYRING:
633 /* group keyrings are not yet supported */
634 key_ref = ERR_PTR(-EINVAL);
637 case KEY_SPEC_REQKEY_AUTH_KEY:
638 key = ctx.cred->request_key_auth;
643 key_ref = make_key_ref(key, 1);
646 case KEY_SPEC_REQUESTOR_KEYRING:
647 if (!ctx.cred->request_key_auth)
650 down_read(&ctx.cred->request_key_auth->sem);
651 if (test_bit(KEY_FLAG_REVOKED,
652 &ctx.cred->request_key_auth->flags)) {
653 key_ref = ERR_PTR(-EKEYREVOKED);
656 rka = ctx.cred->request_key_auth->payload.data[0];
657 key = rka->dest_keyring;
660 up_read(&ctx.cred->request_key_auth->sem);
663 key_ref = make_key_ref(key, 1);
667 key_ref = ERR_PTR(-EINVAL);
671 key = key_lookup(id);
673 key_ref = ERR_CAST(key);
677 key_ref = make_key_ref(key, 0);
679 /* check to see if we possess the key */
680 ctx.index_key = key->index_key;
681 ctx.match_data.raw_data = key;
682 kdebug("check possessed");
684 skey_ref = search_process_keyrings_rcu(&ctx);
686 kdebug("possessed=%p", skey_ref);
688 if (!IS_ERR(skey_ref)) {
696 /* unlink does not use the nominated key in any way, so can skip all
697 * the permission checks as it is only concerned with the keyring */
698 if (lflags & KEY_LOOKUP_FOR_UNLINK) {
703 if (!(lflags & KEY_LOOKUP_PARTIAL)) {
704 ret = wait_for_key_construction(key, true);
715 ret = key_validate(key);
721 if (!(lflags & KEY_LOOKUP_PARTIAL) &&
722 key_read_state(key) == KEY_IS_UNINSTANTIATED)
725 /* check the permissions */
726 ret = key_task_permission(key_ref, ctx.cred, perm);
730 key->last_used_at = ktime_get_real_seconds();
737 key_ref_put(key_ref);
738 key_ref = ERR_PTR(ret);
741 /* if we attempted to install a keyring, then it may have caused new
742 * creds to be installed */
747 EXPORT_SYMBOL(lookup_user_key);
750 * Join the named keyring as the session keyring if possible else attempt to
751 * create a new one of that name and join that.
753 * If the name is NULL, an empty anonymous keyring will be installed as the
756 * Named session keyrings are joined with a semaphore held to prevent the
757 * keyrings from going away whilst the attempt is made to going them and also
758 * to prevent a race in creating compatible session keyrings.
760 long join_session_keyring(const char *name)
762 const struct cred *old;
767 new = prepare_creds();
770 old = current_cred();
772 /* if no name is provided, install an anonymous keyring */
774 ret = install_session_keyring_to_cred(new, NULL);
778 serial = new->session_keyring->serial;
779 ret = commit_creds(new);
785 /* allow the user to join or create a named keyring */
786 mutex_lock(&key_session_mutex);
788 /* look for an existing keyring of this name */
789 keyring = find_keyring_by_name(name, false);
790 if (PTR_ERR(keyring) == -ENOKEY) {
791 /* not found - try and create a new one */
792 keyring = keyring_alloc(
793 name, old->uid, old->gid, old,
794 KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ | KEY_USR_LINK,
795 KEY_ALLOC_IN_QUOTA, NULL, NULL);
796 if (IS_ERR(keyring)) {
797 ret = PTR_ERR(keyring);
800 } else if (IS_ERR(keyring)) {
801 ret = PTR_ERR(keyring);
803 } else if (keyring == new->session_keyring) {
808 /* we've got a keyring - now to install it */
809 ret = install_session_keyring_to_cred(new, keyring);
814 mutex_unlock(&key_session_mutex);
816 ret = keyring->serial;
824 mutex_unlock(&key_session_mutex);
831 * Replace a process's session keyring on behalf of one of its children when
832 * the target process is about to resume userspace execution.
834 void key_change_session_keyring(struct callback_head *twork)
836 const struct cred *old = current_cred();
837 struct cred *new = container_of(twork, struct cred, rcu);
839 if (unlikely(current->flags & PF_EXITING)) {
844 new-> uid = old-> uid;
845 new-> euid = old-> euid;
846 new-> suid = old-> suid;
847 new->fsuid = old->fsuid;
848 new-> gid = old-> gid;
849 new-> egid = old-> egid;
850 new-> sgid = old-> sgid;
851 new->fsgid = old->fsgid;
852 new->user = get_uid(old->user);
853 new->user_ns = get_user_ns(old->user_ns);
854 new->group_info = get_group_info(old->group_info);
856 new->securebits = old->securebits;
857 new->cap_inheritable = old->cap_inheritable;
858 new->cap_permitted = old->cap_permitted;
859 new->cap_effective = old->cap_effective;
860 new->cap_ambient = old->cap_ambient;
861 new->cap_bset = old->cap_bset;
863 new->jit_keyring = old->jit_keyring;
864 new->thread_keyring = key_get(old->thread_keyring);
865 new->process_keyring = key_get(old->process_keyring);
867 security_transfer_creds(new, old);
873 * Make sure that root's user and user-session keyrings exist.
875 static int __init init_root_keyring(void)
877 return install_user_keyrings();
880 late_initcall(init_root_keyring);