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/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 <asm/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 = ATOMIC_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_IN_QUOTA, NULL);
80 if (IS_ERR(uid_keyring)) {
81 ret = PTR_ERR(uid_keyring);
86 /* get a default session keyring (which might also exist
88 sprintf(buf, "_uid_ses.%u", uid);
90 session_keyring = find_keyring_by_name(buf, true);
91 if (IS_ERR(session_keyring)) {
93 keyring_alloc(buf, user->uid, INVALID_GID,
94 cred, user_keyring_perm,
95 KEY_ALLOC_IN_QUOTA, NULL);
96 if (IS_ERR(session_keyring)) {
97 ret = PTR_ERR(session_keyring);
101 /* we install a link from the user session keyring to
102 * the user keyring */
103 ret = key_link(session_keyring, uid_keyring);
105 goto error_release_both;
108 /* install the keyrings */
109 user->uid_keyring = uid_keyring;
110 user->session_keyring = session_keyring;
113 mutex_unlock(&key_user_keyring_mutex);
118 key_put(session_keyring);
120 key_put(uid_keyring);
122 mutex_unlock(&key_user_keyring_mutex);
123 kleave(" = %d", ret);
128 * Install a thread keyring to the given credentials struct if it didn't have
129 * one already. This is allowed to overrun the quota.
131 * Return: 0 if a thread keyring is now present; -errno on failure.
133 int install_thread_keyring_to_cred(struct cred *new)
137 if (new->thread_keyring)
140 keyring = keyring_alloc("_tid", new->uid, new->gid, new,
141 KEY_POS_ALL | KEY_USR_VIEW,
142 KEY_ALLOC_QUOTA_OVERRUN, NULL);
144 return PTR_ERR(keyring);
146 new->thread_keyring = keyring;
151 * Install a thread keyring to the current task if it didn't have one already.
153 * Return: 0 if a thread keyring is now present; -errno on failure.
155 static int install_thread_keyring(void)
160 new = prepare_creds();
164 ret = install_thread_keyring_to_cred(new);
170 return commit_creds(new);
174 * Install a process keyring to the given credentials struct if it didn't have
175 * one already. This is allowed to overrun the quota.
177 * Return: 0 if a process keyring is now present; -errno on failure.
179 int install_process_keyring_to_cred(struct cred *new)
183 if (new->process_keyring)
186 keyring = keyring_alloc("_pid", new->uid, new->gid, new,
187 KEY_POS_ALL | KEY_USR_VIEW,
188 KEY_ALLOC_QUOTA_OVERRUN, NULL);
190 return PTR_ERR(keyring);
192 new->process_keyring = keyring;
197 * Install a process keyring to the current task if it didn't have one already.
199 * Return: 0 if a process keyring is now present; -errno on failure.
201 static int install_process_keyring(void)
206 new = prepare_creds();
210 ret = install_process_keyring_to_cred(new);
216 return commit_creds(new);
220 * Install the given keyring as the session keyring of the given credentials
221 * struct, replacing the existing one if any. If the given keyring is NULL,
222 * then install a new anonymous session keyring.
224 * Return: 0 on success; -errno on failure.
226 int install_session_keyring_to_cred(struct cred *cred, struct key *keyring)
233 /* create an empty session keyring */
235 flags = KEY_ALLOC_QUOTA_OVERRUN;
236 if (cred->session_keyring)
237 flags = KEY_ALLOC_IN_QUOTA;
239 keyring = keyring_alloc("_ses", cred->uid, cred->gid, cred,
240 KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ,
243 return PTR_ERR(keyring);
248 /* install the keyring */
249 old = cred->session_keyring;
250 rcu_assign_pointer(cred->session_keyring, keyring);
259 * Install the given keyring as the session keyring of the current task,
260 * replacing the existing one if any. If the given keyring is NULL, then
261 * install a new anonymous session keyring.
263 * Return: 0 on success; -errno on failure.
265 static int install_session_keyring(struct key *keyring)
270 new = prepare_creds();
274 ret = install_session_keyring_to_cred(new, keyring);
280 return commit_creds(new);
284 * Handle the fsuid changing.
286 void key_fsuid_changed(struct task_struct *tsk)
288 /* update the ownership of the thread keyring */
290 if (tsk->cred->thread_keyring) {
291 down_write(&tsk->cred->thread_keyring->sem);
292 tsk->cred->thread_keyring->uid = tsk->cred->fsuid;
293 up_write(&tsk->cred->thread_keyring->sem);
298 * Handle the fsgid changing.
300 void key_fsgid_changed(struct task_struct *tsk)
302 /* update the ownership of the thread keyring */
304 if (tsk->cred->thread_keyring) {
305 down_write(&tsk->cred->thread_keyring->sem);
306 tsk->cred->thread_keyring->gid = tsk->cred->fsgid;
307 up_write(&tsk->cred->thread_keyring->sem);
312 * Search the process keyrings attached to the supplied cred for the first
315 * The search criteria are the type and the match function. The description is
316 * given to the match function as a parameter, but doesn't otherwise influence
317 * the search. Typically the match function will compare the description
318 * parameter to the key's description.
320 * This can only search keyrings that grant Search permission to the supplied
321 * credentials. Keyrings linked to searched keyrings will also be searched if
322 * they grant Search permission too. Keys can only be found if they grant
323 * Search permission to the credentials.
325 * Returns a pointer to the key with the key usage count incremented if
326 * successful, -EAGAIN if we didn't find any matching key or -ENOKEY if we only
327 * matched negative keys.
329 * In the case of a successful return, the possession attribute is set on the
330 * returned key reference.
332 key_ref_t search_my_process_keyrings(struct keyring_search_context *ctx)
334 key_ref_t key_ref, ret, err;
336 /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
337 * searchable, but we failed to find a key or we found a negative key;
338 * otherwise we want to return a sample error (probably -EACCES) if
339 * none of the keyrings were searchable
341 * in terms of priority: success > -ENOKEY > -EAGAIN > other error
345 err = ERR_PTR(-EAGAIN);
347 /* search the thread keyring first */
348 if (ctx->cred->thread_keyring) {
349 key_ref = keyring_search_aux(
350 make_key_ref(ctx->cred->thread_keyring, 1), ctx);
351 if (!IS_ERR(key_ref))
354 switch (PTR_ERR(key_ref)) {
355 case -EAGAIN: /* no key */
356 case -ENOKEY: /* negative key */
365 /* search the process keyring second */
366 if (ctx->cred->process_keyring) {
367 key_ref = keyring_search_aux(
368 make_key_ref(ctx->cred->process_keyring, 1), ctx);
369 if (!IS_ERR(key_ref))
372 switch (PTR_ERR(key_ref)) {
373 case -EAGAIN: /* no key */
376 case -ENOKEY: /* negative key */
385 /* search the session keyring */
386 if (ctx->cred->session_keyring) {
388 key_ref = keyring_search_aux(
389 make_key_ref(rcu_dereference(ctx->cred->session_keyring), 1),
393 if (!IS_ERR(key_ref))
396 switch (PTR_ERR(key_ref)) {
397 case -EAGAIN: /* no key */
400 case -ENOKEY: /* negative key */
408 /* or search the user-session keyring */
409 else if (ctx->cred->user->session_keyring) {
410 key_ref = keyring_search_aux(
411 make_key_ref(ctx->cred->user->session_keyring, 1),
413 if (!IS_ERR(key_ref))
416 switch (PTR_ERR(key_ref)) {
417 case -EAGAIN: /* no key */
420 case -ENOKEY: /* negative key */
429 /* no key - decide on the error we're going to go for */
430 key_ref = ret ? ret : err;
437 * Search the process keyrings attached to the supplied cred for the first
438 * matching key in the manner of search_my_process_keyrings(), but also search
439 * the keys attached to the assumed authorisation key using its credentials if
442 * Return same as search_my_process_keyrings().
444 key_ref_t search_process_keyrings(struct keyring_search_context *ctx)
446 struct request_key_auth *rka;
447 key_ref_t key_ref, ret = ERR_PTR(-EACCES), err;
451 key_ref = search_my_process_keyrings(ctx);
452 if (!IS_ERR(key_ref))
456 /* if this process has an instantiation authorisation key, then we also
457 * search the keyrings of the process mentioned there
458 * - we don't permit access to request_key auth keys via this method
460 if (ctx->cred->request_key_auth &&
461 ctx->cred == current_cred() &&
462 ctx->index_key.type != &key_type_request_key_auth
464 const struct cred *cred = ctx->cred;
466 /* defend against the auth key being revoked */
467 down_read(&cred->request_key_auth->sem);
469 if (key_validate(ctx->cred->request_key_auth) == 0) {
470 rka = ctx->cred->request_key_auth->payload.data[0];
472 ctx->cred = rka->cred;
473 key_ref = search_process_keyrings(ctx);
476 up_read(&cred->request_key_auth->sem);
478 if (!IS_ERR(key_ref))
483 up_read(&cred->request_key_auth->sem);
487 /* no key - decide on the error we're going to go for */
488 if (err == ERR_PTR(-ENOKEY) || ret == ERR_PTR(-ENOKEY))
489 key_ref = ERR_PTR(-ENOKEY);
490 else if (err == ERR_PTR(-EACCES))
500 * See if the key we're looking at is the target key.
502 bool lookup_user_key_possessed(const struct key *key,
503 const struct key_match_data *match_data)
505 return key == match_data->raw_data;
509 * Look up a key ID given us by userspace with a given permissions mask to get
510 * the key it refers to.
512 * Flags can be passed to request that special keyrings be created if referred
513 * to directly, to permit partially constructed keys to be found and to skip
514 * validity and permission checks on the found key.
516 * Returns a pointer to the key with an incremented usage count if successful;
517 * -EINVAL if the key ID is invalid; -ENOKEY if the key ID does not correspond
518 * to a key or the best found key was a negative key; -EKEYREVOKED or
519 * -EKEYEXPIRED if the best found key was revoked or expired; -EACCES if the
520 * found key doesn't grant the requested permit or the LSM denied access to it;
521 * or -ENOMEM if a special keyring couldn't be created.
523 * In the case of a successful return, the possession attribute is set on the
524 * returned key reference.
526 key_ref_t lookup_user_key(key_serial_t id, unsigned long lflags,
529 struct keyring_search_context ctx = {
530 .match_data.cmp = lookup_user_key_possessed,
531 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
532 .flags = KEYRING_SEARCH_NO_STATE_CHECK,
534 struct request_key_auth *rka;
536 key_ref_t key_ref, skey_ref;
540 ctx.cred = get_current_cred();
541 key_ref = ERR_PTR(-ENOKEY);
544 case KEY_SPEC_THREAD_KEYRING:
545 if (!ctx.cred->thread_keyring) {
546 if (!(lflags & KEY_LOOKUP_CREATE))
549 ret = install_thread_keyring();
551 key_ref = ERR_PTR(ret);
557 key = ctx.cred->thread_keyring;
559 key_ref = make_key_ref(key, 1);
562 case KEY_SPEC_PROCESS_KEYRING:
563 if (!ctx.cred->process_keyring) {
564 if (!(lflags & KEY_LOOKUP_CREATE))
567 ret = install_process_keyring();
569 key_ref = ERR_PTR(ret);
575 key = ctx.cred->process_keyring;
577 key_ref = make_key_ref(key, 1);
580 case KEY_SPEC_SESSION_KEYRING:
581 if (!ctx.cred->session_keyring) {
582 /* always install a session keyring upon access if one
583 * doesn't exist yet */
584 ret = install_user_keyrings();
587 if (lflags & KEY_LOOKUP_CREATE)
588 ret = join_session_keyring(NULL);
590 ret = install_session_keyring(
591 ctx.cred->user->session_keyring);
596 } else if (ctx.cred->session_keyring ==
597 ctx.cred->user->session_keyring &&
598 lflags & KEY_LOOKUP_CREATE) {
599 ret = join_session_keyring(NULL);
606 key = rcu_dereference(ctx.cred->session_keyring);
609 key_ref = make_key_ref(key, 1);
612 case KEY_SPEC_USER_KEYRING:
613 if (!ctx.cred->user->uid_keyring) {
614 ret = install_user_keyrings();
619 key = ctx.cred->user->uid_keyring;
621 key_ref = make_key_ref(key, 1);
624 case KEY_SPEC_USER_SESSION_KEYRING:
625 if (!ctx.cred->user->session_keyring) {
626 ret = install_user_keyrings();
631 key = ctx.cred->user->session_keyring;
633 key_ref = make_key_ref(key, 1);
636 case KEY_SPEC_GROUP_KEYRING:
637 /* group keyrings are not yet supported */
638 key_ref = ERR_PTR(-EINVAL);
641 case KEY_SPEC_REQKEY_AUTH_KEY:
642 key = ctx.cred->request_key_auth;
647 key_ref = make_key_ref(key, 1);
650 case KEY_SPEC_REQUESTOR_KEYRING:
651 if (!ctx.cred->request_key_auth)
654 down_read(&ctx.cred->request_key_auth->sem);
655 if (test_bit(KEY_FLAG_REVOKED,
656 &ctx.cred->request_key_auth->flags)) {
657 key_ref = ERR_PTR(-EKEYREVOKED);
660 rka = ctx.cred->request_key_auth->payload.data[0];
661 key = rka->dest_keyring;
664 up_read(&ctx.cred->request_key_auth->sem);
667 key_ref = make_key_ref(key, 1);
671 key_ref = ERR_PTR(-EINVAL);
675 key = key_lookup(id);
677 key_ref = ERR_CAST(key);
681 key_ref = make_key_ref(key, 0);
683 /* check to see if we possess the key */
684 ctx.index_key.type = key->type;
685 ctx.index_key.description = key->description;
686 ctx.index_key.desc_len = strlen(key->description);
687 ctx.match_data.raw_data = key;
688 kdebug("check possessed");
689 skey_ref = search_process_keyrings(&ctx);
690 kdebug("possessed=%p", skey_ref);
692 if (!IS_ERR(skey_ref)) {
700 /* unlink does not use the nominated key in any way, so can skip all
701 * the permission checks as it is only concerned with the keyring */
702 if (lflags & KEY_LOOKUP_FOR_UNLINK) {
707 if (!(lflags & KEY_LOOKUP_PARTIAL)) {
708 ret = wait_for_key_construction(key, true);
719 ret = key_validate(key);
725 if (!(lflags & KEY_LOOKUP_PARTIAL) &&
726 !test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
729 /* check the permissions */
730 ret = key_task_permission(key_ref, ctx.cred, perm);
734 key->last_used_at = current_kernel_time().tv_sec;
741 key_ref_put(key_ref);
742 key_ref = ERR_PTR(ret);
745 /* if we attempted to install a keyring, then it may have caused new
746 * creds to be installed */
753 * Join the named keyring as the session keyring if possible else attempt to
754 * create a new one of that name and join that.
756 * If the name is NULL, an empty anonymous keyring will be installed as the
759 * Named session keyrings are joined with a semaphore held to prevent the
760 * keyrings from going away whilst the attempt is made to going them and also
761 * to prevent a race in creating compatible session keyrings.
763 long join_session_keyring(const char *name)
765 const struct cred *old;
770 new = prepare_creds();
773 old = current_cred();
775 /* if no name is provided, install an anonymous keyring */
777 ret = install_session_keyring_to_cred(new, NULL);
781 serial = new->session_keyring->serial;
782 ret = commit_creds(new);
788 /* allow the user to join or create a named keyring */
789 mutex_lock(&key_session_mutex);
791 /* look for an existing keyring of this name */
792 keyring = find_keyring_by_name(name, false);
793 if (PTR_ERR(keyring) == -ENOKEY) {
794 /* not found - try and create a new one */
795 keyring = keyring_alloc(
796 name, old->uid, old->gid, old,
797 KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ | KEY_USR_LINK,
798 KEY_ALLOC_IN_QUOTA, NULL);
799 if (IS_ERR(keyring)) {
800 ret = PTR_ERR(keyring);
803 } else if (IS_ERR(keyring)) {
804 ret = PTR_ERR(keyring);
806 } else if (keyring == new->session_keyring) {
812 /* we've got a keyring - now to install it */
813 ret = install_session_keyring_to_cred(new, keyring);
818 mutex_unlock(&key_session_mutex);
820 ret = keyring->serial;
826 mutex_unlock(&key_session_mutex);
833 * Replace a process's session keyring on behalf of one of its children when
834 * the target process is about to resume userspace execution.
836 void key_change_session_keyring(struct callback_head *twork)
838 const struct cred *old = current_cred();
839 struct cred *new = container_of(twork, struct cred, rcu);
841 if (unlikely(current->flags & PF_EXITING)) {
846 new-> uid = old-> uid;
847 new-> euid = old-> euid;
848 new-> suid = old-> suid;
849 new->fsuid = old->fsuid;
850 new-> gid = old-> gid;
851 new-> egid = old-> egid;
852 new-> sgid = old-> sgid;
853 new->fsgid = old->fsgid;
854 new->user = get_uid(old->user);
855 new->user_ns = get_user_ns(old->user_ns);
856 new->group_info = get_group_info(old->group_info);
858 new->securebits = old->securebits;
859 new->cap_inheritable = old->cap_inheritable;
860 new->cap_permitted = old->cap_permitted;
861 new->cap_effective = old->cap_effective;
862 new->cap_ambient = old->cap_ambient;
863 new->cap_bset = old->cap_bset;
865 new->jit_keyring = old->jit_keyring;
866 new->thread_keyring = key_get(old->thread_keyring);
867 new->process_keyring = key_get(old->process_keyring);
869 security_transfer_creds(new, old);
875 * Make sure that root's user and user-session keyrings exist.
877 static int __init init_root_keyring(void)
879 return install_user_keyrings();
882 late_initcall(init_root_keyring);