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>
22 #include <keys/request_key_auth-type.h>
25 /* Session keyring create vs join semaphore */
26 static DEFINE_MUTEX(key_session_mutex);
28 /* User keyring creation semaphore */
29 static DEFINE_MUTEX(key_user_keyring_mutex);
31 /* The root user's tracking struct */
32 struct key_user root_key_user = {
33 .usage = REFCOUNT_INIT(3),
34 .cons_lock = __MUTEX_INITIALIZER(root_key_user.cons_lock),
35 .lock = __SPIN_LOCK_UNLOCKED(root_key_user.lock),
36 .nkeys = ATOMIC_INIT(2),
37 .nikeys = ATOMIC_INIT(2),
38 .uid = GLOBAL_ROOT_UID,
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;
49 key_perm_t user_keyring_perm;
54 user_keyring_perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL;
55 cred = current_cred();
57 uid = from_kuid(cred->user_ns, user->uid);
59 kenter("%p{%u}", user, uid);
61 if (user->uid_keyring && user->session_keyring) {
62 kleave(" = 0 [exist]");
66 mutex_lock(&key_user_keyring_mutex);
69 if (!user->uid_keyring) {
70 /* get the UID-specific keyring
71 * - there may be one in existence already as it may have been
72 * pinned by a session, but the user_struct pointing to it
73 * may have been destroyed by setuid */
74 sprintf(buf, "_uid.%u", uid);
76 uid_keyring = find_keyring_by_name(buf, true);
77 if (IS_ERR(uid_keyring)) {
78 uid_keyring = keyring_alloc(buf, user->uid, INVALID_GID,
79 cred, user_keyring_perm,
80 KEY_ALLOC_UID_KEYRING |
83 if (IS_ERR(uid_keyring)) {
84 ret = PTR_ERR(uid_keyring);
89 /* get a default session keyring (which might also exist
91 sprintf(buf, "_uid_ses.%u", uid);
93 session_keyring = find_keyring_by_name(buf, true);
94 if (IS_ERR(session_keyring)) {
96 keyring_alloc(buf, user->uid, INVALID_GID,
97 cred, user_keyring_perm,
98 KEY_ALLOC_UID_KEYRING |
101 if (IS_ERR(session_keyring)) {
102 ret = PTR_ERR(session_keyring);
106 /* we install a link from the user session keyring to
107 * the user keyring */
108 ret = key_link(session_keyring, uid_keyring);
110 goto error_release_both;
113 /* install the keyrings */
114 user->uid_keyring = uid_keyring;
115 user->session_keyring = session_keyring;
118 mutex_unlock(&key_user_keyring_mutex);
123 key_put(session_keyring);
125 key_put(uid_keyring);
127 mutex_unlock(&key_user_keyring_mutex);
128 kleave(" = %d", ret);
133 * Install a thread keyring to the given credentials struct if it didn't have
134 * one already. This is allowed to overrun the quota.
136 * Return: 0 if a thread keyring is now present; -errno on failure.
138 int install_thread_keyring_to_cred(struct cred *new)
142 if (new->thread_keyring)
145 keyring = keyring_alloc("_tid", new->uid, new->gid, new,
146 KEY_POS_ALL | KEY_USR_VIEW,
147 KEY_ALLOC_QUOTA_OVERRUN,
150 return PTR_ERR(keyring);
152 new->thread_keyring = keyring;
157 * Install a thread keyring to the current task if it didn't have one already.
159 * Return: 0 if a thread keyring is now present; -errno on failure.
161 static int install_thread_keyring(void)
166 new = prepare_creds();
170 ret = install_thread_keyring_to_cred(new);
176 return commit_creds(new);
180 * Install a process keyring to the given credentials struct if it didn't have
181 * one already. This is allowed to overrun the quota.
183 * Return: 0 if a process keyring is now present; -errno on failure.
185 int install_process_keyring_to_cred(struct cred *new)
189 if (new->process_keyring)
192 keyring = keyring_alloc("_pid", new->uid, new->gid, new,
193 KEY_POS_ALL | KEY_USR_VIEW,
194 KEY_ALLOC_QUOTA_OVERRUN,
197 return PTR_ERR(keyring);
199 new->process_keyring = keyring;
204 * Install a process keyring to the current task if it didn't have one already.
206 * Return: 0 if a process keyring is now present; -errno on failure.
208 static int install_process_keyring(void)
213 new = prepare_creds();
217 ret = install_process_keyring_to_cred(new);
223 return commit_creds(new);
227 * Install the given keyring as the session keyring of the given credentials
228 * struct, replacing the existing one if any. If the given keyring is NULL,
229 * then install a new anonymous session keyring.
231 * Return: 0 on success; -errno on failure.
233 int install_session_keyring_to_cred(struct cred *cred, struct key *keyring)
240 /* create an empty session keyring */
242 flags = KEY_ALLOC_QUOTA_OVERRUN;
243 if (cred->session_keyring)
244 flags = KEY_ALLOC_IN_QUOTA;
246 keyring = keyring_alloc("_ses", cred->uid, cred->gid, cred,
247 KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ,
250 return PTR_ERR(keyring);
255 /* install the keyring */
256 old = cred->session_keyring;
257 rcu_assign_pointer(cred->session_keyring, keyring);
266 * Install the given keyring as the session keyring of the current task,
267 * replacing the existing one if any. If the given keyring is NULL, then
268 * install a new anonymous session keyring.
270 * Return: 0 on success; -errno on failure.
272 static int install_session_keyring(struct key *keyring)
277 new = prepare_creds();
281 ret = install_session_keyring_to_cred(new, keyring);
287 return commit_creds(new);
291 * Handle the fsuid changing.
293 void key_fsuid_changed(struct task_struct *tsk)
295 /* update the ownership of the thread keyring */
297 if (tsk->cred->thread_keyring) {
298 down_write(&tsk->cred->thread_keyring->sem);
299 tsk->cred->thread_keyring->uid = tsk->cred->fsuid;
300 up_write(&tsk->cred->thread_keyring->sem);
305 * Handle the fsgid changing.
307 void key_fsgid_changed(struct task_struct *tsk)
309 /* update the ownership of the thread keyring */
311 if (tsk->cred->thread_keyring) {
312 down_write(&tsk->cred->thread_keyring->sem);
313 tsk->cred->thread_keyring->gid = tsk->cred->fsgid;
314 up_write(&tsk->cred->thread_keyring->sem);
319 * Search the process keyrings attached to the supplied cred for the first
322 * The search criteria are the type and the match function. The description is
323 * given to the match function as a parameter, but doesn't otherwise influence
324 * the search. Typically the match function will compare the description
325 * parameter to the key's description.
327 * This can only search keyrings that grant Search permission to the supplied
328 * credentials. Keyrings linked to searched keyrings will also be searched if
329 * they grant Search permission too. Keys can only be found if they grant
330 * Search permission to the credentials.
332 * Returns a pointer to the key with the key usage count incremented if
333 * successful, -EAGAIN if we didn't find any matching key or -ENOKEY if we only
334 * matched negative keys.
336 * In the case of a successful return, the possession attribute is set on the
337 * returned key reference.
339 key_ref_t search_my_process_keyrings(struct keyring_search_context *ctx)
341 key_ref_t key_ref, ret, err;
343 /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
344 * searchable, but we failed to find a key or we found a negative key;
345 * otherwise we want to return a sample error (probably -EACCES) if
346 * none of the keyrings were searchable
348 * in terms of priority: success > -ENOKEY > -EAGAIN > other error
352 err = ERR_PTR(-EAGAIN);
354 /* search the thread keyring first */
355 if (ctx->cred->thread_keyring) {
356 key_ref = keyring_search_aux(
357 make_key_ref(ctx->cred->thread_keyring, 1), ctx);
358 if (!IS_ERR(key_ref))
361 switch (PTR_ERR(key_ref)) {
362 case -EAGAIN: /* no key */
363 case -ENOKEY: /* negative key */
372 /* search the process keyring second */
373 if (ctx->cred->process_keyring) {
374 key_ref = keyring_search_aux(
375 make_key_ref(ctx->cred->process_keyring, 1), ctx);
376 if (!IS_ERR(key_ref))
379 switch (PTR_ERR(key_ref)) {
380 case -EAGAIN: /* no key */
384 case -ENOKEY: /* negative key */
393 /* search the session keyring */
394 if (ctx->cred->session_keyring) {
396 key_ref = keyring_search_aux(
397 make_key_ref(rcu_dereference(ctx->cred->session_keyring), 1),
401 if (!IS_ERR(key_ref))
404 switch (PTR_ERR(key_ref)) {
405 case -EAGAIN: /* no key */
409 case -ENOKEY: /* negative key */
417 /* or search the user-session keyring */
418 else if (ctx->cred->user->session_keyring) {
419 key_ref = keyring_search_aux(
420 make_key_ref(ctx->cred->user->session_keyring, 1),
422 if (!IS_ERR(key_ref))
425 switch (PTR_ERR(key_ref)) {
426 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 keyring_search_context *ctx)
456 struct request_key_auth *rka;
457 key_ref_t key_ref, ret = ERR_PTR(-EACCES), err;
461 key_ref = search_my_process_keyrings(ctx);
462 if (!IS_ERR(key_ref))
466 /* if this process has an instantiation authorisation key, then we also
467 * search the keyrings of the process mentioned there
468 * - we don't permit access to request_key auth keys via this method
470 if (ctx->cred->request_key_auth &&
471 ctx->cred == current_cred() &&
472 ctx->index_key.type != &key_type_request_key_auth
474 const struct cred *cred = ctx->cred;
476 /* defend against the auth key being revoked */
477 down_read(&cred->request_key_auth->sem);
479 if (key_validate(ctx->cred->request_key_auth) == 0) {
480 rka = ctx->cred->request_key_auth->payload.data[0];
482 ctx->cred = rka->cred;
483 key_ref = search_process_keyrings(ctx);
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 bool lookup_user_key_possessed(const struct key *key,
513 const struct key_match_data *match_data)
515 return key == match_data->raw_data;
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 keyring_search_context ctx = {
540 .match_data.cmp = lookup_user_key_possessed,
541 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
542 .flags = KEYRING_SEARCH_NO_STATE_CHECK,
544 struct request_key_auth *rka;
546 key_ref_t key_ref, skey_ref;
550 ctx.cred = get_current_cred();
551 key_ref = ERR_PTR(-ENOKEY);
554 case KEY_SPEC_THREAD_KEYRING:
555 if (!ctx.cred->thread_keyring) {
556 if (!(lflags & KEY_LOOKUP_CREATE))
559 ret = install_thread_keyring();
561 key_ref = ERR_PTR(ret);
567 key = ctx.cred->thread_keyring;
569 key_ref = make_key_ref(key, 1);
572 case KEY_SPEC_PROCESS_KEYRING:
573 if (!ctx.cred->process_keyring) {
574 if (!(lflags & KEY_LOOKUP_CREATE))
577 ret = install_process_keyring();
579 key_ref = ERR_PTR(ret);
585 key = ctx.cred->process_keyring;
587 key_ref = make_key_ref(key, 1);
590 case KEY_SPEC_SESSION_KEYRING:
591 if (!ctx.cred->session_keyring) {
592 /* always install a session keyring upon access if one
593 * doesn't exist yet */
594 ret = install_user_keyrings();
597 if (lflags & KEY_LOOKUP_CREATE)
598 ret = join_session_keyring(NULL);
600 ret = install_session_keyring(
601 ctx.cred->user->session_keyring);
606 } else if (ctx.cred->session_keyring ==
607 ctx.cred->user->session_keyring &&
608 lflags & KEY_LOOKUP_CREATE) {
609 ret = join_session_keyring(NULL);
616 key = rcu_dereference(ctx.cred->session_keyring);
619 key_ref = make_key_ref(key, 1);
622 case KEY_SPEC_USER_KEYRING:
623 if (!ctx.cred->user->uid_keyring) {
624 ret = install_user_keyrings();
629 key = ctx.cred->user->uid_keyring;
631 key_ref = make_key_ref(key, 1);
634 case KEY_SPEC_USER_SESSION_KEYRING:
635 if (!ctx.cred->user->session_keyring) {
636 ret = install_user_keyrings();
641 key = ctx.cred->user->session_keyring;
643 key_ref = make_key_ref(key, 1);
646 case KEY_SPEC_GROUP_KEYRING:
647 /* group keyrings are not yet supported */
648 key_ref = ERR_PTR(-EINVAL);
651 case KEY_SPEC_REQKEY_AUTH_KEY:
652 key = ctx.cred->request_key_auth;
657 key_ref = make_key_ref(key, 1);
660 case KEY_SPEC_REQUESTOR_KEYRING:
661 if (!ctx.cred->request_key_auth)
664 down_read(&ctx.cred->request_key_auth->sem);
665 if (test_bit(KEY_FLAG_REVOKED,
666 &ctx.cred->request_key_auth->flags)) {
667 key_ref = ERR_PTR(-EKEYREVOKED);
670 rka = ctx.cred->request_key_auth->payload.data[0];
671 key = rka->dest_keyring;
674 up_read(&ctx.cred->request_key_auth->sem);
677 key_ref = make_key_ref(key, 1);
681 key_ref = ERR_PTR(-EINVAL);
685 key = key_lookup(id);
687 key_ref = ERR_CAST(key);
691 key_ref = make_key_ref(key, 0);
693 /* check to see if we possess the key */
694 ctx.index_key.type = key->type;
695 ctx.index_key.description = key->description;
696 ctx.index_key.desc_len = strlen(key->description);
697 ctx.match_data.raw_data = key;
698 kdebug("check possessed");
699 skey_ref = search_process_keyrings(&ctx);
700 kdebug("possessed=%p", skey_ref);
702 if (!IS_ERR(skey_ref)) {
710 /* unlink does not use the nominated key in any way, so can skip all
711 * the permission checks as it is only concerned with the keyring */
712 if (lflags & KEY_LOOKUP_FOR_UNLINK) {
717 if (!(lflags & KEY_LOOKUP_PARTIAL)) {
718 ret = wait_for_key_construction(key, true);
729 ret = key_validate(key);
735 if (!(lflags & KEY_LOOKUP_PARTIAL) &&
736 key_read_state(key) == KEY_IS_UNINSTANTIATED)
739 /* check the permissions */
740 ret = key_task_permission(key_ref, ctx.cred, perm);
744 key->last_used_at = ktime_get_real_seconds();
751 key_ref_put(key_ref);
752 key_ref = ERR_PTR(ret);
755 /* if we attempted to install a keyring, then it may have caused new
756 * creds to be installed */
761 EXPORT_SYMBOL(lookup_user_key);
764 * Join the named keyring as the session keyring if possible else attempt to
765 * create a new one of that name and join that.
767 * If the name is NULL, an empty anonymous keyring will be installed as the
770 * Named session keyrings are joined with a semaphore held to prevent the
771 * keyrings from going away whilst the attempt is made to going them and also
772 * to prevent a race in creating compatible session keyrings.
774 long join_session_keyring(const char *name)
776 const struct cred *old;
781 new = prepare_creds();
784 old = current_cred();
786 /* if no name is provided, install an anonymous keyring */
788 ret = install_session_keyring_to_cred(new, NULL);
792 serial = new->session_keyring->serial;
793 ret = commit_creds(new);
799 /* allow the user to join or create a named keyring */
800 mutex_lock(&key_session_mutex);
802 /* look for an existing keyring of this name */
803 keyring = find_keyring_by_name(name, false);
804 if (PTR_ERR(keyring) == -ENOKEY) {
805 /* not found - try and create a new one */
806 keyring = keyring_alloc(
807 name, old->uid, old->gid, old,
808 KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ | KEY_USR_LINK,
809 KEY_ALLOC_IN_QUOTA, NULL, NULL);
810 if (IS_ERR(keyring)) {
811 ret = PTR_ERR(keyring);
814 } else if (IS_ERR(keyring)) {
815 ret = PTR_ERR(keyring);
817 } else if (keyring == new->session_keyring) {
822 /* we've got a keyring - now to install it */
823 ret = install_session_keyring_to_cred(new, keyring);
828 mutex_unlock(&key_session_mutex);
830 ret = keyring->serial;
838 mutex_unlock(&key_session_mutex);
845 * Replace a process's session keyring on behalf of one of its children when
846 * the target process is about to resume userspace execution.
848 void key_change_session_keyring(struct callback_head *twork)
850 const struct cred *old = current_cred();
851 struct cred *new = container_of(twork, struct cred, rcu);
853 if (unlikely(current->flags & PF_EXITING)) {
858 new-> uid = old-> uid;
859 new-> euid = old-> euid;
860 new-> suid = old-> suid;
861 new->fsuid = old->fsuid;
862 new-> gid = old-> gid;
863 new-> egid = old-> egid;
864 new-> sgid = old-> sgid;
865 new->fsgid = old->fsgid;
866 new->user = get_uid(old->user);
867 new->user_ns = get_user_ns(old->user_ns);
868 new->group_info = get_group_info(old->group_info);
870 new->securebits = old->securebits;
871 new->cap_inheritable = old->cap_inheritable;
872 new->cap_permitted = old->cap_permitted;
873 new->cap_effective = old->cap_effective;
874 new->cap_ambient = old->cap_ambient;
875 new->cap_bset = old->cap_bset;
877 new->jit_keyring = old->jit_keyring;
878 new->thread_keyring = key_get(old->thread_keyring);
879 new->process_keyring = key_get(old->process_keyring);
881 security_transfer_creds(new, old);
887 * Make sure that root's user and user-session keyrings exist.
889 static int __init init_root_keyring(void)
891 return install_user_keyrings();
894 late_initcall(init_root_keyring);