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/init.h>
13 #include <linux/sched.h>
14 #include <linux/sched/user.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 <linux/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 = REFCOUNT_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;
48 key_perm_t user_keyring_perm;
53 user_keyring_perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL;
54 cred = current_cred();
56 uid = from_kuid(cred->user_ns, user->uid);
58 kenter("%p{%u}", user, uid);
60 if (user->uid_keyring && user->session_keyring) {
61 kleave(" = 0 [exist]");
65 mutex_lock(&key_user_keyring_mutex);
68 if (!user->uid_keyring) {
69 /* get the UID-specific keyring
70 * - there may be one in existence already as it may have been
71 * pinned by a session, but the user_struct pointing to it
72 * may have been destroyed by setuid */
73 sprintf(buf, "_uid.%u", uid);
75 uid_keyring = find_keyring_by_name(buf, true);
76 if (IS_ERR(uid_keyring)) {
77 uid_keyring = keyring_alloc(buf, user->uid, INVALID_GID,
78 cred, user_keyring_perm,
79 KEY_ALLOC_UID_KEYRING |
82 if (IS_ERR(uid_keyring)) {
83 ret = PTR_ERR(uid_keyring);
88 /* get a default session keyring (which might also exist
90 sprintf(buf, "_uid_ses.%u", uid);
92 session_keyring = find_keyring_by_name(buf, true);
93 if (IS_ERR(session_keyring)) {
95 keyring_alloc(buf, user->uid, INVALID_GID,
96 cred, user_keyring_perm,
97 KEY_ALLOC_UID_KEYRING |
100 if (IS_ERR(session_keyring)) {
101 ret = PTR_ERR(session_keyring);
105 /* we install a link from the user session keyring to
106 * the user keyring */
107 ret = key_link(session_keyring, uid_keyring);
109 goto error_release_both;
112 /* install the keyrings */
113 user->uid_keyring = uid_keyring;
114 user->session_keyring = session_keyring;
117 mutex_unlock(&key_user_keyring_mutex);
122 key_put(session_keyring);
124 key_put(uid_keyring);
126 mutex_unlock(&key_user_keyring_mutex);
127 kleave(" = %d", ret);
132 * Install a thread keyring to the given credentials struct if it didn't have
133 * one already. This is allowed to overrun the quota.
135 * Return: 0 if a thread keyring is now present; -errno on failure.
137 int install_thread_keyring_to_cred(struct cred *new)
141 if (new->thread_keyring)
144 keyring = keyring_alloc("_tid", new->uid, new->gid, new,
145 KEY_POS_ALL | KEY_USR_VIEW,
146 KEY_ALLOC_QUOTA_OVERRUN,
149 return PTR_ERR(keyring);
151 new->thread_keyring = keyring;
156 * Install a thread keyring to the current task if it didn't have one already.
158 * Return: 0 if a thread keyring is now present; -errno on failure.
160 static int install_thread_keyring(void)
165 new = prepare_creds();
169 ret = install_thread_keyring_to_cred(new);
175 return commit_creds(new);
179 * Install a process keyring to the given credentials struct if it didn't have
180 * one already. This is allowed to overrun the quota.
182 * Return: 0 if a process keyring is now present; -errno on failure.
184 int install_process_keyring_to_cred(struct cred *new)
188 if (new->process_keyring)
191 keyring = keyring_alloc("_pid", new->uid, new->gid, new,
192 KEY_POS_ALL | KEY_USR_VIEW,
193 KEY_ALLOC_QUOTA_OVERRUN,
196 return PTR_ERR(keyring);
198 new->process_keyring = keyring;
203 * Install a process keyring to the current task if it didn't have one already.
205 * Return: 0 if a process keyring is now present; -errno on failure.
207 static int install_process_keyring(void)
212 new = prepare_creds();
216 ret = install_process_keyring_to_cred(new);
222 return commit_creds(new);
226 * Install the given keyring as the session keyring of the given credentials
227 * struct, replacing the existing one if any. If the given keyring is NULL,
228 * then install a new anonymous session keyring.
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 rcu_assign_pointer(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;
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 (ctx->cred->thread_keyring) {
355 key_ref = keyring_search_aux(
356 make_key_ref(ctx->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 (ctx->cred->process_keyring) {
373 key_ref = keyring_search_aux(
374 make_key_ref(ctx->cred->process_keyring, 1), ctx);
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 (ctx->cred->session_keyring) {
394 key_ref = keyring_search_aux(
395 make_key_ref(rcu_dereference(ctx->cred->session_keyring), 1),
399 if (!IS_ERR(key_ref))
402 switch (PTR_ERR(key_ref)) {
403 case -EAGAIN: /* no key */
406 case -ENOKEY: /* negative key */
414 /* or search the user-session keyring */
415 else if (ctx->cred->user->session_keyring) {
416 key_ref = keyring_search_aux(
417 make_key_ref(ctx->cred->user->session_keyring, 1),
419 if (!IS_ERR(key_ref))
422 switch (PTR_ERR(key_ref)) {
423 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 * Return same as search_my_process_keyrings().
450 key_ref_t search_process_keyrings(struct keyring_search_context *ctx)
452 struct request_key_auth *rka;
453 key_ref_t key_ref, ret = ERR_PTR(-EACCES), err;
457 key_ref = search_my_process_keyrings(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 /* defend against the auth key being revoked */
473 down_read(&cred->request_key_auth->sem);
475 if (key_validate(ctx->cred->request_key_auth) == 0) {
476 rka = ctx->cred->request_key_auth->payload.data[0];
478 ctx->cred = rka->cred;
479 key_ref = search_process_keyrings(ctx);
482 up_read(&cred->request_key_auth->sem);
484 if (!IS_ERR(key_ref))
489 up_read(&cred->request_key_auth->sem);
493 /* no key - decide on the error we're going to go for */
494 if (err == ERR_PTR(-ENOKEY) || ret == ERR_PTR(-ENOKEY))
495 key_ref = ERR_PTR(-ENOKEY);
496 else if (err == ERR_PTR(-EACCES))
506 * See if the key we're looking at is the target key.
508 bool lookup_user_key_possessed(const struct key *key,
509 const struct key_match_data *match_data)
511 return key == match_data->raw_data;
515 * Look up a key ID given us by userspace with a given permissions mask to get
516 * the key it refers to.
518 * Flags can be passed to request that special keyrings be created if referred
519 * to directly, to permit partially constructed keys to be found and to skip
520 * validity and permission checks on the found key.
522 * Returns a pointer to the key with an incremented usage count if successful;
523 * -EINVAL if the key ID is invalid; -ENOKEY if the key ID does not correspond
524 * to a key or the best found key was a negative key; -EKEYREVOKED or
525 * -EKEYEXPIRED if the best found key was revoked or expired; -EACCES if the
526 * found key doesn't grant the requested permit or the LSM denied access to it;
527 * or -ENOMEM if a special keyring couldn't be created.
529 * In the case of a successful return, the possession attribute is set on the
530 * returned key reference.
532 key_ref_t lookup_user_key(key_serial_t id, unsigned long lflags,
535 struct keyring_search_context ctx = {
536 .match_data.cmp = lookup_user_key_possessed,
537 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
538 .flags = KEYRING_SEARCH_NO_STATE_CHECK,
540 struct request_key_auth *rka;
542 key_ref_t key_ref, skey_ref;
546 ctx.cred = get_current_cred();
547 key_ref = ERR_PTR(-ENOKEY);
550 case KEY_SPEC_THREAD_KEYRING:
551 if (!ctx.cred->thread_keyring) {
552 if (!(lflags & KEY_LOOKUP_CREATE))
555 ret = install_thread_keyring();
557 key_ref = ERR_PTR(ret);
563 key = ctx.cred->thread_keyring;
565 key_ref = make_key_ref(key, 1);
568 case KEY_SPEC_PROCESS_KEYRING:
569 if (!ctx.cred->process_keyring) {
570 if (!(lflags & KEY_LOOKUP_CREATE))
573 ret = install_process_keyring();
575 key_ref = ERR_PTR(ret);
581 key = ctx.cred->process_keyring;
583 key_ref = make_key_ref(key, 1);
586 case KEY_SPEC_SESSION_KEYRING:
587 if (!ctx.cred->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 ctx.cred->user->session_keyring);
602 } else if (ctx.cred->session_keyring ==
603 ctx.cred->user->session_keyring &&
604 lflags & KEY_LOOKUP_CREATE) {
605 ret = join_session_keyring(NULL);
612 key = rcu_dereference(ctx.cred->session_keyring);
615 key_ref = make_key_ref(key, 1);
618 case KEY_SPEC_USER_KEYRING:
619 if (!ctx.cred->user->uid_keyring) {
620 ret = install_user_keyrings();
625 key = ctx.cred->user->uid_keyring;
627 key_ref = make_key_ref(key, 1);
630 case KEY_SPEC_USER_SESSION_KEYRING:
631 if (!ctx.cred->user->session_keyring) {
632 ret = install_user_keyrings();
637 key = ctx.cred->user->session_keyring;
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 = ctx.cred->request_key_auth;
653 key_ref = make_key_ref(key, 1);
656 case KEY_SPEC_REQUESTOR_KEYRING:
657 if (!ctx.cred->request_key_auth)
660 down_read(&ctx.cred->request_key_auth->sem);
661 if (test_bit(KEY_FLAG_REVOKED,
662 &ctx.cred->request_key_auth->flags)) {
663 key_ref = ERR_PTR(-EKEYREVOKED);
666 rka = ctx.cred->request_key_auth->payload.data[0];
667 key = rka->dest_keyring;
670 up_read(&ctx.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 ctx.index_key.type = key->type;
691 ctx.index_key.description = key->description;
692 ctx.index_key.desc_len = strlen(key->description);
693 ctx.match_data.raw_data = key;
694 kdebug("check possessed");
695 skey_ref = search_process_keyrings(&ctx);
696 kdebug("possessed=%p", skey_ref);
698 if (!IS_ERR(skey_ref)) {
706 /* unlink does not use the nominated key in any way, so can skip all
707 * the permission checks as it is only concerned with the keyring */
708 if (lflags & KEY_LOOKUP_FOR_UNLINK) {
713 if (!(lflags & KEY_LOOKUP_PARTIAL)) {
714 ret = wait_for_key_construction(key, true);
725 ret = key_validate(key);
731 if (!(lflags & KEY_LOOKUP_PARTIAL) &&
732 key_read_state(key) == KEY_IS_UNINSTANTIATED)
735 /* check the permissions */
736 ret = key_task_permission(key_ref, ctx.cred, perm);
740 key->last_used_at = ktime_get_real_seconds();
747 key_ref_put(key_ref);
748 key_ref = ERR_PTR(ret);
751 /* if we attempted to install a keyring, then it may have caused new
752 * creds to be installed */
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);