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,
81 if (IS_ERR(uid_keyring)) {
82 ret = PTR_ERR(uid_keyring);
87 /* get a default session keyring (which might also exist
89 sprintf(buf, "_uid_ses.%u", uid);
91 session_keyring = find_keyring_by_name(buf, true);
92 if (IS_ERR(session_keyring)) {
94 keyring_alloc(buf, user->uid, INVALID_GID,
95 cred, user_keyring_perm,
98 if (IS_ERR(session_keyring)) {
99 ret = PTR_ERR(session_keyring);
103 /* we install a link from the user session keyring to
104 * the user keyring */
105 ret = key_link(session_keyring, uid_keyring);
107 goto error_release_both;
110 /* install the keyrings */
111 user->uid_keyring = uid_keyring;
112 user->session_keyring = session_keyring;
115 mutex_unlock(&key_user_keyring_mutex);
120 key_put(session_keyring);
122 key_put(uid_keyring);
124 mutex_unlock(&key_user_keyring_mutex);
125 kleave(" = %d", ret);
130 * Install a fresh thread keyring directly to new credentials. This keyring is
131 * allowed to overrun the quota.
133 int install_thread_keyring_to_cred(struct cred *new)
137 keyring = keyring_alloc("_tid", new->uid, new->gid, new,
138 KEY_POS_ALL | KEY_USR_VIEW,
139 KEY_ALLOC_QUOTA_OVERRUN,
142 return PTR_ERR(keyring);
144 new->thread_keyring = keyring;
149 * Install a fresh thread keyring, discarding the old one.
151 static int install_thread_keyring(void)
156 new = prepare_creds();
160 BUG_ON(new->thread_keyring);
162 ret = install_thread_keyring_to_cred(new);
168 return commit_creds(new);
172 * Install a process keyring directly to a credentials struct.
174 * Returns -EEXIST if there was already a process keyring, 0 if one installed,
175 * and other value on any other error
177 int install_process_keyring_to_cred(struct cred *new)
181 if (new->process_keyring)
184 keyring = keyring_alloc("_pid", new->uid, new->gid, new,
185 KEY_POS_ALL | KEY_USR_VIEW,
186 KEY_ALLOC_QUOTA_OVERRUN,
189 return PTR_ERR(keyring);
191 new->process_keyring = keyring;
196 * Make sure a process keyring is installed for the current process. The
197 * existing process keyring is not replaced.
199 * Returns 0 if there is a process keyring by the end of this function, some
202 static int install_process_keyring(void)
207 new = prepare_creds();
211 ret = install_process_keyring_to_cred(new);
214 return ret != -EEXIST ? ret : 0;
217 return commit_creds(new);
221 * Install a session keyring directly to a credentials struct.
223 int install_session_keyring_to_cred(struct cred *cred, struct key *keyring)
230 /* create an empty session keyring */
232 flags = KEY_ALLOC_QUOTA_OVERRUN;
233 if (cred->session_keyring)
234 flags = KEY_ALLOC_IN_QUOTA;
236 keyring = keyring_alloc("_ses", cred->uid, cred->gid, cred,
237 KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ,
240 return PTR_ERR(keyring);
245 /* install the keyring */
246 old = cred->session_keyring;
247 rcu_assign_pointer(cred->session_keyring, keyring);
256 * Install a session keyring, discarding the old one. If a keyring is not
257 * supplied, an empty one is invented.
259 static int install_session_keyring(struct key *keyring)
264 new = prepare_creds();
268 ret = install_session_keyring_to_cred(new, keyring);
274 return commit_creds(new);
278 * Handle the fsuid changing.
280 void key_fsuid_changed(struct task_struct *tsk)
282 /* update the ownership of the thread keyring */
284 if (tsk->cred->thread_keyring) {
285 down_write(&tsk->cred->thread_keyring->sem);
286 tsk->cred->thread_keyring->uid = tsk->cred->fsuid;
287 up_write(&tsk->cred->thread_keyring->sem);
292 * Handle the fsgid changing.
294 void key_fsgid_changed(struct task_struct *tsk)
296 /* update the ownership of the thread keyring */
298 if (tsk->cred->thread_keyring) {
299 down_write(&tsk->cred->thread_keyring->sem);
300 tsk->cred->thread_keyring->gid = tsk->cred->fsgid;
301 up_write(&tsk->cred->thread_keyring->sem);
306 * Search the process keyrings attached to the supplied cred for the first
309 * The search criteria are the type and the match function. The description is
310 * given to the match function as a parameter, but doesn't otherwise influence
311 * the search. Typically the match function will compare the description
312 * parameter to the key's description.
314 * This can only search keyrings that grant Search permission to the supplied
315 * credentials. Keyrings linked to searched keyrings will also be searched if
316 * they grant Search permission too. Keys can only be found if they grant
317 * Search permission to the credentials.
319 * Returns a pointer to the key with the key usage count incremented if
320 * successful, -EAGAIN if we didn't find any matching key or -ENOKEY if we only
321 * matched negative keys.
323 * In the case of a successful return, the possession attribute is set on the
324 * returned key reference.
326 key_ref_t search_my_process_keyrings(struct keyring_search_context *ctx)
328 key_ref_t key_ref, ret, err;
330 /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
331 * searchable, but we failed to find a key or we found a negative key;
332 * otherwise we want to return a sample error (probably -EACCES) if
333 * none of the keyrings were searchable
335 * in terms of priority: success > -ENOKEY > -EAGAIN > other error
339 err = ERR_PTR(-EAGAIN);
341 /* search the thread keyring first */
342 if (ctx->cred->thread_keyring) {
343 key_ref = keyring_search_aux(
344 make_key_ref(ctx->cred->thread_keyring, 1), ctx);
345 if (!IS_ERR(key_ref))
348 switch (PTR_ERR(key_ref)) {
349 case -EAGAIN: /* no key */
350 case -ENOKEY: /* negative key */
359 /* search the process keyring second */
360 if (ctx->cred->process_keyring) {
361 key_ref = keyring_search_aux(
362 make_key_ref(ctx->cred->process_keyring, 1), ctx);
363 if (!IS_ERR(key_ref))
366 switch (PTR_ERR(key_ref)) {
367 case -EAGAIN: /* no key */
370 case -ENOKEY: /* negative key */
379 /* search the session keyring */
380 if (ctx->cred->session_keyring) {
382 key_ref = keyring_search_aux(
383 make_key_ref(rcu_dereference(ctx->cred->session_keyring), 1),
387 if (!IS_ERR(key_ref))
390 switch (PTR_ERR(key_ref)) {
391 case -EAGAIN: /* no key */
394 case -ENOKEY: /* negative key */
402 /* or search the user-session keyring */
403 else if (ctx->cred->user->session_keyring) {
404 key_ref = keyring_search_aux(
405 make_key_ref(ctx->cred->user->session_keyring, 1),
407 if (!IS_ERR(key_ref))
410 switch (PTR_ERR(key_ref)) {
411 case -EAGAIN: /* no key */
414 case -ENOKEY: /* negative key */
423 /* no key - decide on the error we're going to go for */
424 key_ref = ret ? ret : err;
431 * Search the process keyrings attached to the supplied cred for the first
432 * matching key in the manner of search_my_process_keyrings(), but also search
433 * the keys attached to the assumed authorisation key using its credentials if
436 * Return same as search_my_process_keyrings().
438 key_ref_t search_process_keyrings(struct keyring_search_context *ctx)
440 struct request_key_auth *rka;
441 key_ref_t key_ref, ret = ERR_PTR(-EACCES), err;
445 key_ref = search_my_process_keyrings(ctx);
446 if (!IS_ERR(key_ref))
450 /* if this process has an instantiation authorisation key, then we also
451 * search the keyrings of the process mentioned there
452 * - we don't permit access to request_key auth keys via this method
454 if (ctx->cred->request_key_auth &&
455 ctx->cred == current_cred() &&
456 ctx->index_key.type != &key_type_request_key_auth
458 const struct cred *cred = ctx->cred;
460 /* defend against the auth key being revoked */
461 down_read(&cred->request_key_auth->sem);
463 if (key_validate(ctx->cred->request_key_auth) == 0) {
464 rka = ctx->cred->request_key_auth->payload.data[0];
466 ctx->cred = rka->cred;
467 key_ref = search_process_keyrings(ctx);
470 up_read(&cred->request_key_auth->sem);
472 if (!IS_ERR(key_ref))
477 up_read(&cred->request_key_auth->sem);
481 /* no key - decide on the error we're going to go for */
482 if (err == ERR_PTR(-ENOKEY) || ret == ERR_PTR(-ENOKEY))
483 key_ref = ERR_PTR(-ENOKEY);
484 else if (err == ERR_PTR(-EACCES))
494 * See if the key we're looking at is the target key.
496 bool lookup_user_key_possessed(const struct key *key,
497 const struct key_match_data *match_data)
499 return key == match_data->raw_data;
503 * Look up a key ID given us by userspace with a given permissions mask to get
504 * the key it refers to.
506 * Flags can be passed to request that special keyrings be created if referred
507 * to directly, to permit partially constructed keys to be found and to skip
508 * validity and permission checks on the found key.
510 * Returns a pointer to the key with an incremented usage count if successful;
511 * -EINVAL if the key ID is invalid; -ENOKEY if the key ID does not correspond
512 * to a key or the best found key was a negative key; -EKEYREVOKED or
513 * -EKEYEXPIRED if the best found key was revoked or expired; -EACCES if the
514 * found key doesn't grant the requested permit or the LSM denied access to it;
515 * or -ENOMEM if a special keyring couldn't be created.
517 * In the case of a successful return, the possession attribute is set on the
518 * returned key reference.
520 key_ref_t lookup_user_key(key_serial_t id, unsigned long lflags,
523 struct keyring_search_context ctx = {
524 .match_data.cmp = lookup_user_key_possessed,
525 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
526 .flags = KEYRING_SEARCH_NO_STATE_CHECK,
528 struct request_key_auth *rka;
530 key_ref_t key_ref, skey_ref;
534 ctx.cred = get_current_cred();
535 key_ref = ERR_PTR(-ENOKEY);
538 case KEY_SPEC_THREAD_KEYRING:
539 if (!ctx.cred->thread_keyring) {
540 if (!(lflags & KEY_LOOKUP_CREATE))
543 ret = install_thread_keyring();
545 key_ref = ERR_PTR(ret);
551 key = ctx.cred->thread_keyring;
553 key_ref = make_key_ref(key, 1);
556 case KEY_SPEC_PROCESS_KEYRING:
557 if (!ctx.cred->process_keyring) {
558 if (!(lflags & KEY_LOOKUP_CREATE))
561 ret = install_process_keyring();
563 key_ref = ERR_PTR(ret);
569 key = ctx.cred->process_keyring;
571 key_ref = make_key_ref(key, 1);
574 case KEY_SPEC_SESSION_KEYRING:
575 if (!ctx.cred->session_keyring) {
576 /* always install a session keyring upon access if one
577 * doesn't exist yet */
578 ret = install_user_keyrings();
581 if (lflags & KEY_LOOKUP_CREATE)
582 ret = join_session_keyring(NULL);
584 ret = install_session_keyring(
585 ctx.cred->user->session_keyring);
590 } else if (ctx.cred->session_keyring ==
591 ctx.cred->user->session_keyring &&
592 lflags & KEY_LOOKUP_CREATE) {
593 ret = join_session_keyring(NULL);
600 key = rcu_dereference(ctx.cred->session_keyring);
603 key_ref = make_key_ref(key, 1);
606 case KEY_SPEC_USER_KEYRING:
607 if (!ctx.cred->user->uid_keyring) {
608 ret = install_user_keyrings();
613 key = ctx.cred->user->uid_keyring;
615 key_ref = make_key_ref(key, 1);
618 case KEY_SPEC_USER_SESSION_KEYRING:
619 if (!ctx.cred->user->session_keyring) {
620 ret = install_user_keyrings();
625 key = ctx.cred->user->session_keyring;
627 key_ref = make_key_ref(key, 1);
630 case KEY_SPEC_GROUP_KEYRING:
631 /* group keyrings are not yet supported */
632 key_ref = ERR_PTR(-EINVAL);
635 case KEY_SPEC_REQKEY_AUTH_KEY:
636 key = ctx.cred->request_key_auth;
641 key_ref = make_key_ref(key, 1);
644 case KEY_SPEC_REQUESTOR_KEYRING:
645 if (!ctx.cred->request_key_auth)
648 down_read(&ctx.cred->request_key_auth->sem);
649 if (test_bit(KEY_FLAG_REVOKED,
650 &ctx.cred->request_key_auth->flags)) {
651 key_ref = ERR_PTR(-EKEYREVOKED);
654 rka = ctx.cred->request_key_auth->payload.data[0];
655 key = rka->dest_keyring;
658 up_read(&ctx.cred->request_key_auth->sem);
661 key_ref = make_key_ref(key, 1);
665 key_ref = ERR_PTR(-EINVAL);
669 key = key_lookup(id);
671 key_ref = ERR_CAST(key);
675 key_ref = make_key_ref(key, 0);
677 /* check to see if we possess the key */
678 ctx.index_key.type = key->type;
679 ctx.index_key.description = key->description;
680 ctx.index_key.desc_len = strlen(key->description);
681 ctx.match_data.raw_data = key;
682 kdebug("check possessed");
683 skey_ref = search_process_keyrings(&ctx);
684 kdebug("possessed=%p", skey_ref);
686 if (!IS_ERR(skey_ref)) {
694 /* unlink does not use the nominated key in any way, so can skip all
695 * the permission checks as it is only concerned with the keyring */
696 if (lflags & KEY_LOOKUP_FOR_UNLINK) {
701 if (!(lflags & KEY_LOOKUP_PARTIAL)) {
702 ret = wait_for_key_construction(key, true);
713 ret = key_validate(key);
719 if (!(lflags & KEY_LOOKUP_PARTIAL) &&
720 !test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
723 /* check the permissions */
724 ret = key_task_permission(key_ref, ctx.cred, perm);
728 key->last_used_at = current_kernel_time().tv_sec;
735 key_ref_put(key_ref);
736 key_ref = ERR_PTR(ret);
739 /* if we attempted to install a keyring, then it may have caused new
740 * creds to be installed */
747 * Join the named keyring as the session keyring if possible else attempt to
748 * create a new one of that name and join that.
750 * If the name is NULL, an empty anonymous keyring will be installed as the
753 * Named session keyrings are joined with a semaphore held to prevent the
754 * keyrings from going away whilst the attempt is made to going them and also
755 * to prevent a race in creating compatible session keyrings.
757 long join_session_keyring(const char *name)
759 const struct cred *old;
764 new = prepare_creds();
767 old = current_cred();
769 /* if no name is provided, install an anonymous keyring */
771 ret = install_session_keyring_to_cred(new, NULL);
775 serial = new->session_keyring->serial;
776 ret = commit_creds(new);
782 /* allow the user to join or create a named keyring */
783 mutex_lock(&key_session_mutex);
785 /* look for an existing keyring of this name */
786 keyring = find_keyring_by_name(name, false);
787 if (PTR_ERR(keyring) == -ENOKEY) {
788 /* not found - try and create a new one */
789 keyring = keyring_alloc(
790 name, old->uid, old->gid, old,
791 KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ | KEY_USR_LINK,
792 KEY_ALLOC_IN_QUOTA, NULL, NULL);
793 if (IS_ERR(keyring)) {
794 ret = PTR_ERR(keyring);
797 } else if (IS_ERR(keyring)) {
798 ret = PTR_ERR(keyring);
800 } else if (keyring == new->session_keyring) {
806 /* we've got a keyring - now to install it */
807 ret = install_session_keyring_to_cred(new, keyring);
812 mutex_unlock(&key_session_mutex);
814 ret = keyring->serial;
820 mutex_unlock(&key_session_mutex);
827 * Replace a process's session keyring on behalf of one of its children when
828 * the target process is about to resume userspace execution.
830 void key_change_session_keyring(struct callback_head *twork)
832 const struct cred *old = current_cred();
833 struct cred *new = container_of(twork, struct cred, rcu);
835 if (unlikely(current->flags & PF_EXITING)) {
840 new-> uid = old-> uid;
841 new-> euid = old-> euid;
842 new-> suid = old-> suid;
843 new->fsuid = old->fsuid;
844 new-> gid = old-> gid;
845 new-> egid = old-> egid;
846 new-> sgid = old-> sgid;
847 new->fsgid = old->fsgid;
848 new->user = get_uid(old->user);
849 new->user_ns = get_user_ns(old->user_ns);
850 new->group_info = get_group_info(old->group_info);
852 new->securebits = old->securebits;
853 new->cap_inheritable = old->cap_inheritable;
854 new->cap_permitted = old->cap_permitted;
855 new->cap_effective = old->cap_effective;
856 new->cap_ambient = old->cap_ambient;
857 new->cap_bset = old->cap_bset;
859 new->jit_keyring = old->jit_keyring;
860 new->thread_keyring = key_get(old->thread_keyring);
861 new->process_keyring = key_get(old->process_keyring);
863 security_transfer_creds(new, old);
869 * Make sure that root's user and user-session keyrings exist.
871 static int __init init_root_keyring(void)
873 return install_user_keyrings();
876 late_initcall(init_root_keyring);