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/sched/user.h>
16 #include <linux/keyctl.h>
18 #include <linux/err.h>
19 #include <linux/mutex.h>
20 #include <linux/security.h>
21 #include <linux/user_namespace.h>
22 #include <linux/uaccess.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,
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,
99 if (IS_ERR(session_keyring)) {
100 ret = PTR_ERR(session_keyring);
104 /* we install a link from the user session keyring to
105 * the user keyring */
106 ret = key_link(session_keyring, uid_keyring);
108 goto error_release_both;
111 /* install the keyrings */
112 user->uid_keyring = uid_keyring;
113 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.
229 * Return: 0 on success; -errno on failure.
231 int install_session_keyring_to_cred(struct cred *cred, struct key *keyring)
238 /* create an empty session keyring */
240 flags = KEY_ALLOC_QUOTA_OVERRUN;
241 if (cred->session_keyring)
242 flags = KEY_ALLOC_IN_QUOTA;
244 keyring = keyring_alloc("_ses", cred->uid, cred->gid, cred,
245 KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ,
248 return PTR_ERR(keyring);
253 /* install the keyring */
254 old = cred->session_keyring;
255 rcu_assign_pointer(cred->session_keyring, keyring);
264 * Install the given keyring as the session keyring of the current task,
265 * replacing the existing one if any. If the given keyring is NULL, then
266 * install a new anonymous session keyring.
268 * Return: 0 on success; -errno on failure.
270 static int install_session_keyring(struct key *keyring)
275 new = prepare_creds();
279 ret = install_session_keyring_to_cred(new, keyring);
285 return commit_creds(new);
289 * Handle the fsuid changing.
291 void key_fsuid_changed(struct task_struct *tsk)
293 /* update the ownership of the thread keyring */
295 if (tsk->cred->thread_keyring) {
296 down_write(&tsk->cred->thread_keyring->sem);
297 tsk->cred->thread_keyring->uid = tsk->cred->fsuid;
298 up_write(&tsk->cred->thread_keyring->sem);
303 * Handle the fsgid changing.
305 void key_fsgid_changed(struct task_struct *tsk)
307 /* update the ownership of the thread keyring */
309 if (tsk->cred->thread_keyring) {
310 down_write(&tsk->cred->thread_keyring->sem);
311 tsk->cred->thread_keyring->gid = tsk->cred->fsgid;
312 up_write(&tsk->cred->thread_keyring->sem);
317 * Search the process keyrings attached to the supplied cred for the first
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_my_process_keyrings(struct keyring_search_context *ctx)
339 key_ref_t key_ref, ret, err;
341 /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
342 * searchable, but we failed to find a key or we found a negative key;
343 * otherwise we want to return a sample error (probably -EACCES) if
344 * none of the keyrings were searchable
346 * in terms of priority: success > -ENOKEY > -EAGAIN > other error
350 err = ERR_PTR(-EAGAIN);
352 /* search the thread keyring first */
353 if (ctx->cred->thread_keyring) {
354 key_ref = keyring_search_aux(
355 make_key_ref(ctx->cred->thread_keyring, 1), ctx);
356 if (!IS_ERR(key_ref))
359 switch (PTR_ERR(key_ref)) {
360 case -EAGAIN: /* no key */
361 case -ENOKEY: /* negative key */
370 /* search the process keyring second */
371 if (ctx->cred->process_keyring) {
372 key_ref = keyring_search_aux(
373 make_key_ref(ctx->cred->process_keyring, 1), ctx);
374 if (!IS_ERR(key_ref))
377 switch (PTR_ERR(key_ref)) {
378 case -EAGAIN: /* no key */
381 case -ENOKEY: /* negative key */
390 /* search the session keyring */
391 if (ctx->cred->session_keyring) {
393 key_ref = keyring_search_aux(
394 make_key_ref(rcu_dereference(ctx->cred->session_keyring), 1),
398 if (!IS_ERR(key_ref))
401 switch (PTR_ERR(key_ref)) {
402 case -EAGAIN: /* no key */
405 case -ENOKEY: /* negative key */
413 /* or search the user-session keyring */
414 else if (ctx->cred->user->session_keyring) {
415 key_ref = keyring_search_aux(
416 make_key_ref(ctx->cred->user->session_keyring, 1),
418 if (!IS_ERR(key_ref))
421 switch (PTR_ERR(key_ref)) {
422 case -EAGAIN: /* no key */
425 case -ENOKEY: /* negative key */
434 /* no key - decide on the error we're going to go for */
435 key_ref = ret ? ret : err;
442 * Search the process keyrings attached to the supplied cred for the first
443 * matching key in the manner of search_my_process_keyrings(), but also search
444 * the keys attached to the assumed authorisation key using its credentials if
447 * Return same as search_my_process_keyrings().
449 key_ref_t search_process_keyrings(struct keyring_search_context *ctx)
451 struct request_key_auth *rka;
452 key_ref_t key_ref, ret = ERR_PTR(-EACCES), err;
456 key_ref = search_my_process_keyrings(ctx);
457 if (!IS_ERR(key_ref))
461 /* if this process has an instantiation authorisation key, then we also
462 * search the keyrings of the process mentioned there
463 * - we don't permit access to request_key auth keys via this method
465 if (ctx->cred->request_key_auth &&
466 ctx->cred == current_cred() &&
467 ctx->index_key.type != &key_type_request_key_auth
469 const struct cred *cred = ctx->cred;
471 /* defend against the auth key being revoked */
472 down_read(&cred->request_key_auth->sem);
474 if (key_validate(ctx->cred->request_key_auth) == 0) {
475 rka = ctx->cred->request_key_auth->payload.data[0];
477 ctx->cred = rka->cred;
478 key_ref = search_process_keyrings(ctx);
481 up_read(&cred->request_key_auth->sem);
483 if (!IS_ERR(key_ref))
488 up_read(&cred->request_key_auth->sem);
492 /* no key - decide on the error we're going to go for */
493 if (err == ERR_PTR(-ENOKEY) || ret == ERR_PTR(-ENOKEY))
494 key_ref = ERR_PTR(-ENOKEY);
495 else if (err == ERR_PTR(-EACCES))
505 * See if the key we're looking at is the target key.
507 bool lookup_user_key_possessed(const struct key *key,
508 const struct key_match_data *match_data)
510 return key == match_data->raw_data;
514 * Look up a key ID given us by userspace with a given permissions mask to get
515 * the key it refers to.
517 * Flags can be passed to request that special keyrings be created if referred
518 * to directly, to permit partially constructed keys to be found and to skip
519 * validity and permission checks on the found key.
521 * Returns a pointer to the key with an incremented usage count if successful;
522 * -EINVAL if the key ID is invalid; -ENOKEY if the key ID does not correspond
523 * to a key or the best found key was a negative key; -EKEYREVOKED or
524 * -EKEYEXPIRED if the best found key was revoked or expired; -EACCES if the
525 * found key doesn't grant the requested permit or the LSM denied access to it;
526 * or -ENOMEM if a special keyring couldn't be created.
528 * In the case of a successful return, the possession attribute is set on the
529 * returned key reference.
531 key_ref_t lookup_user_key(key_serial_t id, unsigned long lflags,
534 struct keyring_search_context ctx = {
535 .match_data.cmp = lookup_user_key_possessed,
536 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
537 .flags = KEYRING_SEARCH_NO_STATE_CHECK,
539 struct request_key_auth *rka;
541 key_ref_t key_ref, skey_ref;
545 ctx.cred = get_current_cred();
546 key_ref = ERR_PTR(-ENOKEY);
549 case KEY_SPEC_THREAD_KEYRING:
550 if (!ctx.cred->thread_keyring) {
551 if (!(lflags & KEY_LOOKUP_CREATE))
554 ret = install_thread_keyring();
556 key_ref = ERR_PTR(ret);
562 key = ctx.cred->thread_keyring;
564 key_ref = make_key_ref(key, 1);
567 case KEY_SPEC_PROCESS_KEYRING:
568 if (!ctx.cred->process_keyring) {
569 if (!(lflags & KEY_LOOKUP_CREATE))
572 ret = install_process_keyring();
574 key_ref = ERR_PTR(ret);
580 key = ctx.cred->process_keyring;
582 key_ref = make_key_ref(key, 1);
585 case KEY_SPEC_SESSION_KEYRING:
586 if (!ctx.cred->session_keyring) {
587 /* always install a session keyring upon access if one
588 * doesn't exist yet */
589 ret = install_user_keyrings();
592 if (lflags & KEY_LOOKUP_CREATE)
593 ret = join_session_keyring(NULL);
595 ret = install_session_keyring(
596 ctx.cred->user->session_keyring);
601 } else if (ctx.cred->session_keyring ==
602 ctx.cred->user->session_keyring &&
603 lflags & KEY_LOOKUP_CREATE) {
604 ret = join_session_keyring(NULL);
611 key = rcu_dereference(ctx.cred->session_keyring);
614 key_ref = make_key_ref(key, 1);
617 case KEY_SPEC_USER_KEYRING:
618 if (!ctx.cred->user->uid_keyring) {
619 ret = install_user_keyrings();
624 key = ctx.cred->user->uid_keyring;
626 key_ref = make_key_ref(key, 1);
629 case KEY_SPEC_USER_SESSION_KEYRING:
630 if (!ctx.cred->user->session_keyring) {
631 ret = install_user_keyrings();
636 key = ctx.cred->user->session_keyring;
638 key_ref = make_key_ref(key, 1);
641 case KEY_SPEC_GROUP_KEYRING:
642 /* group keyrings are not yet supported */
643 key_ref = ERR_PTR(-EINVAL);
646 case KEY_SPEC_REQKEY_AUTH_KEY:
647 key = ctx.cred->request_key_auth;
652 key_ref = make_key_ref(key, 1);
655 case KEY_SPEC_REQUESTOR_KEYRING:
656 if (!ctx.cred->request_key_auth)
659 down_read(&ctx.cred->request_key_auth->sem);
660 if (test_bit(KEY_FLAG_REVOKED,
661 &ctx.cred->request_key_auth->flags)) {
662 key_ref = ERR_PTR(-EKEYREVOKED);
665 rka = ctx.cred->request_key_auth->payload.data[0];
666 key = rka->dest_keyring;
669 up_read(&ctx.cred->request_key_auth->sem);
672 key_ref = make_key_ref(key, 1);
676 key_ref = ERR_PTR(-EINVAL);
680 key = key_lookup(id);
682 key_ref = ERR_CAST(key);
686 key_ref = make_key_ref(key, 0);
688 /* check to see if we possess the key */
689 ctx.index_key.type = key->type;
690 ctx.index_key.description = key->description;
691 ctx.index_key.desc_len = strlen(key->description);
692 ctx.match_data.raw_data = key;
693 kdebug("check possessed");
694 skey_ref = search_process_keyrings(&ctx);
695 kdebug("possessed=%p", skey_ref);
697 if (!IS_ERR(skey_ref)) {
705 /* unlink does not use the nominated key in any way, so can skip all
706 * the permission checks as it is only concerned with the keyring */
707 if (lflags & KEY_LOOKUP_FOR_UNLINK) {
712 if (!(lflags & KEY_LOOKUP_PARTIAL)) {
713 ret = wait_for_key_construction(key, true);
724 ret = key_validate(key);
730 if (!(lflags & KEY_LOOKUP_PARTIAL) &&
731 !test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
734 /* check the permissions */
735 ret = key_task_permission(key_ref, ctx.cred, perm);
739 key->last_used_at = current_kernel_time().tv_sec;
746 key_ref_put(key_ref);
747 key_ref = ERR_PTR(ret);
750 /* if we attempted to install a keyring, then it may have caused new
751 * creds to be installed */
758 * Join the named keyring as the session keyring if possible else attempt to
759 * create a new one of that name and join that.
761 * If the name is NULL, an empty anonymous keyring will be installed as the
764 * Named session keyrings are joined with a semaphore held to prevent the
765 * keyrings from going away whilst the attempt is made to going them and also
766 * to prevent a race in creating compatible session keyrings.
768 long join_session_keyring(const char *name)
770 const struct cred *old;
775 new = prepare_creds();
778 old = current_cred();
780 /* if no name is provided, install an anonymous keyring */
782 ret = install_session_keyring_to_cred(new, NULL);
786 serial = new->session_keyring->serial;
787 ret = commit_creds(new);
793 /* allow the user to join or create a named keyring */
794 mutex_lock(&key_session_mutex);
796 /* look for an existing keyring of this name */
797 keyring = find_keyring_by_name(name, false);
798 if (PTR_ERR(keyring) == -ENOKEY) {
799 /* not found - try and create a new one */
800 keyring = keyring_alloc(
801 name, old->uid, old->gid, old,
802 KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ | KEY_USR_LINK,
803 KEY_ALLOC_IN_QUOTA, NULL, NULL);
804 if (IS_ERR(keyring)) {
805 ret = PTR_ERR(keyring);
808 } else if (IS_ERR(keyring)) {
809 ret = PTR_ERR(keyring);
811 } 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;
831 mutex_unlock(&key_session_mutex);
838 * Replace a process's session keyring on behalf of one of its children when
839 * the target process is about to resume userspace execution.
841 void key_change_session_keyring(struct callback_head *twork)
843 const struct cred *old = current_cred();
844 struct cred *new = container_of(twork, struct cred, rcu);
846 if (unlikely(current->flags & PF_EXITING)) {
851 new-> uid = old-> uid;
852 new-> euid = old-> euid;
853 new-> suid = old-> suid;
854 new->fsuid = old->fsuid;
855 new-> gid = old-> gid;
856 new-> egid = old-> egid;
857 new-> sgid = old-> sgid;
858 new->fsgid = old->fsgid;
859 new->user = get_uid(old->user);
860 new->user_ns = get_user_ns(old->user_ns);
861 new->group_info = get_group_info(old->group_info);
863 new->securebits = old->securebits;
864 new->cap_inheritable = old->cap_inheritable;
865 new->cap_permitted = old->cap_permitted;
866 new->cap_effective = old->cap_effective;
867 new->cap_ambient = old->cap_ambient;
868 new->cap_bset = old->cap_bset;
870 new->jit_keyring = old->jit_keyring;
871 new->thread_keyring = key_get(old->thread_keyring);
872 new->process_keyring = key_get(old->process_keyring);
874 security_transfer_creds(new, old);
880 * Make sure that root's user and user-session keyrings exist.
882 static int __init init_root_keyring(void)
884 return install_user_keyrings();
887 late_initcall(init_root_keyring);