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 (READ_ONCE(user->uid_keyring) && READ_ONCE(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 /* paired with READ_ONCE() */
115 smp_store_release(&user->uid_keyring, uid_keyring);
116 /* paired with READ_ONCE() */
117 smp_store_release(&user->session_keyring, session_keyring);
120 mutex_unlock(&key_user_keyring_mutex);
125 key_put(session_keyring);
127 key_put(uid_keyring);
129 mutex_unlock(&key_user_keyring_mutex);
130 kleave(" = %d", ret);
135 * Install a thread keyring to the given credentials struct if it didn't have
136 * one already. This is allowed to overrun the quota.
138 * Return: 0 if a thread keyring is now present; -errno on failure.
140 int install_thread_keyring_to_cred(struct cred *new)
144 if (new->thread_keyring)
147 keyring = keyring_alloc("_tid", new->uid, new->gid, new,
148 KEY_POS_ALL | KEY_USR_VIEW,
149 KEY_ALLOC_QUOTA_OVERRUN,
152 return PTR_ERR(keyring);
154 new->thread_keyring = keyring;
159 * Install a thread keyring to the current task if it didn't have one already.
161 * Return: 0 if a thread keyring is now present; -errno on failure.
163 static int install_thread_keyring(void)
168 new = prepare_creds();
172 ret = install_thread_keyring_to_cred(new);
178 return commit_creds(new);
182 * Install a process keyring to the given credentials struct if it didn't have
183 * one already. This is allowed to overrun the quota.
185 * Return: 0 if a process keyring is now present; -errno on failure.
187 int install_process_keyring_to_cred(struct cred *new)
191 if (new->process_keyring)
194 keyring = keyring_alloc("_pid", new->uid, new->gid, new,
195 KEY_POS_ALL | KEY_USR_VIEW,
196 KEY_ALLOC_QUOTA_OVERRUN,
199 return PTR_ERR(keyring);
201 new->process_keyring = keyring;
206 * Install a process keyring to the current task if it didn't have one already.
208 * Return: 0 if a process keyring is now present; -errno on failure.
210 static int install_process_keyring(void)
215 new = prepare_creds();
219 ret = install_process_keyring_to_cred(new);
225 return commit_creds(new);
229 * Install the given keyring as the session keyring of the given credentials
230 * struct, replacing the existing one if any. If the given keyring is NULL,
231 * then install a new anonymous session keyring.
232 * @cred can not be in use by any task yet.
234 * Return: 0 on success; -errno on failure.
236 int install_session_keyring_to_cred(struct cred *cred, struct key *keyring)
243 /* create an empty session keyring */
245 flags = KEY_ALLOC_QUOTA_OVERRUN;
246 if (cred->session_keyring)
247 flags = KEY_ALLOC_IN_QUOTA;
249 keyring = keyring_alloc("_ses", cred->uid, cred->gid, cred,
250 KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ,
253 return PTR_ERR(keyring);
258 /* install the keyring */
259 old = cred->session_keyring;
260 cred->session_keyring = keyring;
269 * Install the given keyring as the session keyring of the current task,
270 * replacing the existing one if any. If the given keyring is NULL, then
271 * install a new anonymous session keyring.
273 * Return: 0 on success; -errno on failure.
275 static int install_session_keyring(struct key *keyring)
280 new = prepare_creds();
284 ret = install_session_keyring_to_cred(new, keyring);
290 return commit_creds(new);
294 * Handle the fsuid changing.
296 void key_fsuid_changed(struct task_struct *tsk)
298 /* update the ownership of the thread keyring */
300 if (tsk->cred->thread_keyring) {
301 down_write(&tsk->cred->thread_keyring->sem);
302 tsk->cred->thread_keyring->uid = tsk->cred->fsuid;
303 up_write(&tsk->cred->thread_keyring->sem);
308 * Handle the fsgid changing.
310 void key_fsgid_changed(struct task_struct *tsk)
312 /* update the ownership of the thread keyring */
314 if (tsk->cred->thread_keyring) {
315 down_write(&tsk->cred->thread_keyring->sem);
316 tsk->cred->thread_keyring->gid = tsk->cred->fsgid;
317 up_write(&tsk->cred->thread_keyring->sem);
322 * Search the process keyrings attached to the supplied cred for the first
325 * The search criteria are the type and the match function. The description is
326 * given to the match function as a parameter, but doesn't otherwise influence
327 * the search. Typically the match function will compare the description
328 * parameter to the key's description.
330 * This can only search keyrings that grant Search permission to the supplied
331 * credentials. Keyrings linked to searched keyrings will also be searched if
332 * they grant Search permission too. Keys can only be found if they grant
333 * Search permission to the credentials.
335 * Returns a pointer to the key with the key usage count incremented if
336 * successful, -EAGAIN if we didn't find any matching key or -ENOKEY if we only
337 * matched negative keys.
339 * In the case of a successful return, the possession attribute is set on the
340 * returned key reference.
342 key_ref_t search_my_process_keyrings(struct keyring_search_context *ctx)
344 key_ref_t key_ref, ret, err;
345 const struct cred *cred = ctx->cred;
347 /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
348 * searchable, but we failed to find a key or we found a negative key;
349 * otherwise we want to return a sample error (probably -EACCES) if
350 * none of the keyrings were searchable
352 * in terms of priority: success > -ENOKEY > -EAGAIN > other error
356 err = ERR_PTR(-EAGAIN);
358 /* search the thread keyring first */
359 if (cred->thread_keyring) {
360 key_ref = keyring_search_aux(
361 make_key_ref(cred->thread_keyring, 1), ctx);
362 if (!IS_ERR(key_ref))
365 switch (PTR_ERR(key_ref)) {
366 case -EAGAIN: /* no key */
367 case -ENOKEY: /* negative key */
376 /* search the process keyring second */
377 if (cred->process_keyring) {
378 key_ref = keyring_search_aux(
379 make_key_ref(cred->process_keyring, 1), ctx);
380 if (!IS_ERR(key_ref))
383 switch (PTR_ERR(key_ref)) {
384 case -EAGAIN: /* no key */
388 case -ENOKEY: /* negative key */
397 /* search the session keyring */
398 if (cred->session_keyring) {
399 key_ref = keyring_search_aux(
400 make_key_ref(cred->session_keyring, 1), ctx);
402 if (!IS_ERR(key_ref))
405 switch (PTR_ERR(key_ref)) {
406 case -EAGAIN: /* no key */
410 case -ENOKEY: /* negative key */
418 /* or search the user-session keyring */
419 else if (READ_ONCE(cred->user->session_keyring)) {
420 key_ref = keyring_search_aux(
421 make_key_ref(READ_ONCE(cred->user->session_keyring), 1),
423 if (!IS_ERR(key_ref))
426 switch (PTR_ERR(key_ref)) {
427 case -EAGAIN: /* no key */
431 case -ENOKEY: /* negative key */
440 /* no key - decide on the error we're going to go for */
441 key_ref = ret ? ret : err;
448 * Search the process keyrings attached to the supplied cred for the first
449 * matching key in the manner of search_my_process_keyrings(), but also search
450 * the keys attached to the assumed authorisation key using its credentials if
453 * Return same as search_my_process_keyrings().
455 key_ref_t search_process_keyrings(struct keyring_search_context *ctx)
457 struct request_key_auth *rka;
458 key_ref_t key_ref, ret = ERR_PTR(-EACCES), err;
462 key_ref = search_my_process_keyrings(ctx);
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 (ctx->cred->request_key_auth &&
472 ctx->cred == current_cred() &&
473 ctx->index_key.type != &key_type_request_key_auth
475 const struct cred *cred = ctx->cred;
477 /* defend against the auth key being revoked */
478 down_read(&cred->request_key_auth->sem);
480 if (key_validate(ctx->cred->request_key_auth) == 0) {
481 rka = ctx->cred->request_key_auth->payload.data[0];
483 ctx->cred = rka->cred;
484 key_ref = search_process_keyrings(ctx);
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 bool lookup_user_key_possessed(const struct key *key,
514 const struct key_match_data *match_data)
516 return key == match_data->raw_data;
520 * Look up a key ID given us by userspace with a given permissions mask to get
521 * the key it refers to.
523 * Flags can be passed to request that special keyrings be created if referred
524 * to directly, to permit partially constructed keys to be found and to skip
525 * validity and permission checks on the found key.
527 * Returns a pointer to the key with an incremented usage count if successful;
528 * -EINVAL if the key ID is invalid; -ENOKEY if the key ID does not correspond
529 * to a key or the best found key was a negative key; -EKEYREVOKED or
530 * -EKEYEXPIRED if the best found key was revoked or expired; -EACCES if the
531 * found key doesn't grant the requested permit or the LSM denied access to it;
532 * or -ENOMEM if a special keyring couldn't be created.
534 * In the case of a successful return, the possession attribute is set on the
535 * returned key reference.
537 key_ref_t lookup_user_key(key_serial_t id, unsigned long lflags,
540 struct keyring_search_context ctx = {
541 .match_data.cmp = lookup_user_key_possessed,
542 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
543 .flags = KEYRING_SEARCH_NO_STATE_CHECK,
545 struct request_key_auth *rka;
547 key_ref_t key_ref, skey_ref;
551 ctx.cred = get_current_cred();
552 key_ref = ERR_PTR(-ENOKEY);
555 case KEY_SPEC_THREAD_KEYRING:
556 if (!ctx.cred->thread_keyring) {
557 if (!(lflags & KEY_LOOKUP_CREATE))
560 ret = install_thread_keyring();
562 key_ref = ERR_PTR(ret);
568 key = ctx.cred->thread_keyring;
570 key_ref = make_key_ref(key, 1);
573 case KEY_SPEC_PROCESS_KEYRING:
574 if (!ctx.cred->process_keyring) {
575 if (!(lflags & KEY_LOOKUP_CREATE))
578 ret = install_process_keyring();
580 key_ref = ERR_PTR(ret);
586 key = ctx.cred->process_keyring;
588 key_ref = make_key_ref(key, 1);
591 case KEY_SPEC_SESSION_KEYRING:
592 if (!ctx.cred->session_keyring) {
593 /* always install a session keyring upon access if one
594 * doesn't exist yet */
595 ret = install_user_keyrings();
598 if (lflags & KEY_LOOKUP_CREATE)
599 ret = join_session_keyring(NULL);
601 ret = install_session_keyring(
602 ctx.cred->user->session_keyring);
607 } else if (ctx.cred->session_keyring ==
608 READ_ONCE(ctx.cred->user->session_keyring) &&
609 lflags & KEY_LOOKUP_CREATE) {
610 ret = join_session_keyring(NULL);
616 key = ctx.cred->session_keyring;
618 key_ref = make_key_ref(key, 1);
621 case KEY_SPEC_USER_KEYRING:
622 if (!READ_ONCE(ctx.cred->user->uid_keyring)) {
623 ret = install_user_keyrings();
628 key = ctx.cred->user->uid_keyring;
630 key_ref = make_key_ref(key, 1);
633 case KEY_SPEC_USER_SESSION_KEYRING:
634 if (!READ_ONCE(ctx.cred->user->session_keyring)) {
635 ret = install_user_keyrings();
640 key = ctx.cred->user->session_keyring;
642 key_ref = make_key_ref(key, 1);
645 case KEY_SPEC_GROUP_KEYRING:
646 /* group keyrings are not yet supported */
647 key_ref = ERR_PTR(-EINVAL);
650 case KEY_SPEC_REQKEY_AUTH_KEY:
651 key = ctx.cred->request_key_auth;
656 key_ref = make_key_ref(key, 1);
659 case KEY_SPEC_REQUESTOR_KEYRING:
660 if (!ctx.cred->request_key_auth)
663 down_read(&ctx.cred->request_key_auth->sem);
664 if (test_bit(KEY_FLAG_REVOKED,
665 &ctx.cred->request_key_auth->flags)) {
666 key_ref = ERR_PTR(-EKEYREVOKED);
669 rka = ctx.cred->request_key_auth->payload.data[0];
670 key = rka->dest_keyring;
673 up_read(&ctx.cred->request_key_auth->sem);
676 key_ref = make_key_ref(key, 1);
680 key_ref = ERR_PTR(-EINVAL);
684 key = key_lookup(id);
686 key_ref = ERR_CAST(key);
690 key_ref = make_key_ref(key, 0);
692 /* check to see if we possess the key */
693 ctx.index_key.type = key->type;
694 ctx.index_key.description = key->description;
695 ctx.index_key.desc_len = strlen(key->description);
696 ctx.match_data.raw_data = key;
697 kdebug("check possessed");
698 skey_ref = search_process_keyrings(&ctx);
699 kdebug("possessed=%p", skey_ref);
701 if (!IS_ERR(skey_ref)) {
709 /* unlink does not use the nominated key in any way, so can skip all
710 * the permission checks as it is only concerned with the keyring */
711 if (lflags & KEY_LOOKUP_FOR_UNLINK) {
716 if (!(lflags & KEY_LOOKUP_PARTIAL)) {
717 ret = wait_for_key_construction(key, true);
728 ret = key_validate(key);
734 if (!(lflags & KEY_LOOKUP_PARTIAL) &&
735 key_read_state(key) == KEY_IS_UNINSTANTIATED)
738 /* check the permissions */
739 ret = key_task_permission(key_ref, ctx.cred, perm);
743 key->last_used_at = ktime_get_real_seconds();
750 key_ref_put(key_ref);
751 key_ref = ERR_PTR(ret);
754 /* if we attempted to install a keyring, then it may have caused new
755 * creds to be installed */
760 EXPORT_SYMBOL(lookup_user_key);
763 * Join the named keyring as the session keyring if possible else attempt to
764 * create a new one of that name and join that.
766 * If the name is NULL, an empty anonymous keyring will be installed as the
769 * Named session keyrings are joined with a semaphore held to prevent the
770 * keyrings from going away whilst the attempt is made to going them and also
771 * to prevent a race in creating compatible session keyrings.
773 long join_session_keyring(const char *name)
775 const struct cred *old;
780 new = prepare_creds();
783 old = current_cred();
785 /* if no name is provided, install an anonymous keyring */
787 ret = install_session_keyring_to_cred(new, NULL);
791 serial = new->session_keyring->serial;
792 ret = commit_creds(new);
798 /* allow the user to join or create a named keyring */
799 mutex_lock(&key_session_mutex);
801 /* look for an existing keyring of this name */
802 keyring = find_keyring_by_name(name, false);
803 if (PTR_ERR(keyring) == -ENOKEY) {
804 /* not found - try and create a new one */
805 keyring = keyring_alloc(
806 name, old->uid, old->gid, old,
807 KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ | KEY_USR_LINK,
808 KEY_ALLOC_IN_QUOTA, NULL, NULL);
809 if (IS_ERR(keyring)) {
810 ret = PTR_ERR(keyring);
813 } else if (IS_ERR(keyring)) {
814 ret = PTR_ERR(keyring);
816 } else if (keyring == new->session_keyring) {
821 /* we've got a keyring - now to install it */
822 ret = install_session_keyring_to_cred(new, keyring);
827 mutex_unlock(&key_session_mutex);
829 ret = keyring->serial;
837 mutex_unlock(&key_session_mutex);
844 * Replace a process's session keyring on behalf of one of its children when
845 * the target process is about to resume userspace execution.
847 void key_change_session_keyring(struct callback_head *twork)
849 const struct cred *old = current_cred();
850 struct cred *new = container_of(twork, struct cred, rcu);
852 if (unlikely(current->flags & PF_EXITING)) {
857 new-> uid = old-> uid;
858 new-> euid = old-> euid;
859 new-> suid = old-> suid;
860 new->fsuid = old->fsuid;
861 new-> gid = old-> gid;
862 new-> egid = old-> egid;
863 new-> sgid = old-> sgid;
864 new->fsgid = old->fsgid;
865 new->user = get_uid(old->user);
866 new->user_ns = get_user_ns(old->user_ns);
867 new->group_info = get_group_info(old->group_info);
869 new->securebits = old->securebits;
870 new->cap_inheritable = old->cap_inheritable;
871 new->cap_permitted = old->cap_permitted;
872 new->cap_effective = old->cap_effective;
873 new->cap_ambient = old->cap_ambient;
874 new->cap_bset = old->cap_bset;
876 new->jit_keyring = old->jit_keyring;
877 new->thread_keyring = key_get(old->thread_keyring);
878 new->process_keyring = key_get(old->process_keyring);
880 security_transfer_creds(new, old);
886 * Make sure that root's user and user-session keyrings exist.
888 static int __init init_root_keyring(void)
890 return install_user_keyrings();
893 late_initcall(init_root_keyring);