1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Request a key from userspace
4 * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
7 * See Documentation/security/keys/request-key.rst
10 #include <linux/export.h>
11 #include <linux/sched.h>
12 #include <linux/kmod.h>
13 #include <linux/err.h>
14 #include <linux/keyctl.h>
15 #include <linux/slab.h>
16 #include <net/net_namespace.h>
18 #include <keys/request_key_auth-type.h>
20 #define key_negative_timeout 60 /* default timeout on a negative key's existence */
22 static struct key *check_cached_key(struct keyring_search_context *ctx)
24 #ifdef CONFIG_KEYS_REQUEST_CACHE
25 struct key *key = current->cached_requested_key;
28 ctx->match_data.cmp(key, &ctx->match_data) &&
29 !(key->flags & ((1 << KEY_FLAG_INVALIDATED) |
30 (1 << KEY_FLAG_REVOKED))))
36 static void cache_requested_key(struct key *key)
38 #ifdef CONFIG_KEYS_REQUEST_CACHE
39 struct task_struct *t = current;
41 /* Do not cache key if it is a kernel thread */
42 if (!(t->flags & PF_KTHREAD)) {
43 key_put(t->cached_requested_key);
44 t->cached_requested_key = key_get(key);
45 set_tsk_thread_flag(t, TIF_NOTIFY_RESUME);
51 * complete_request_key - Complete the construction of a key.
52 * @authkey: The authorisation key.
53 * @error: The success or failute of the construction.
55 * Complete the attempt to construct a key. The key will be negated
56 * if an error is indicated. The authorisation key will be revoked
59 void complete_request_key(struct key *authkey, int error)
61 struct request_key_auth *rka = get_request_key_auth(authkey);
62 struct key *key = rka->target_key;
64 kenter("%d{%d},%d", authkey->serial, key->serial, error);
67 key_negate_and_link(key, key_negative_timeout, NULL, authkey);
71 EXPORT_SYMBOL(complete_request_key);
74 * Initialise a usermode helper that is going to have a specific session
77 * This is called in context of freshly forked kthread before kernel_execve(),
78 * so we can simply install the desired session_keyring at this point.
80 static int umh_keys_init(struct subprocess_info *info, struct cred *cred)
82 struct key *keyring = info->data;
84 return install_session_keyring_to_cred(cred, keyring);
88 * Clean up a usermode helper with session keyring.
90 static void umh_keys_cleanup(struct subprocess_info *info)
92 struct key *keyring = info->data;
97 * Call a usermode helper with a specific session keyring.
99 static int call_usermodehelper_keys(const char *path, char **argv, char **envp,
100 struct key *session_keyring, int wait)
102 struct subprocess_info *info;
104 info = call_usermodehelper_setup(path, argv, envp, GFP_KERNEL,
105 umh_keys_init, umh_keys_cleanup,
110 key_get(session_keyring);
111 return call_usermodehelper_exec(info, wait);
115 * Request userspace finish the construction of a key
116 * - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring>"
118 static int call_sbin_request_key(struct key *authkey, void *aux)
120 static char const request_key[] = "/sbin/request-key";
121 struct request_key_auth *rka = get_request_key_auth(authkey);
122 const struct cred *cred = current_cred();
123 key_serial_t prkey, sskey;
124 struct key *key = rka->target_key, *keyring, *session, *user_session;
125 char *argv[9], *envp[3], uid_str[12], gid_str[12];
126 char key_str[12], keyring_str[3][12];
130 kenter("{%d},{%d},%s", key->serial, authkey->serial, rka->op);
132 ret = look_up_user_keyrings(NULL, &user_session);
136 /* allocate a new session keyring */
137 sprintf(desc, "_req.%u", key->serial);
139 cred = get_current_cred();
140 keyring = keyring_alloc(desc, cred->fsuid, cred->fsgid, cred,
141 KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ,
142 KEY_ALLOC_QUOTA_OVERRUN, NULL, NULL);
144 if (IS_ERR(keyring)) {
145 ret = PTR_ERR(keyring);
149 /* attach the auth key to the session keyring */
150 ret = key_link(keyring, authkey);
154 /* record the UID and GID */
155 sprintf(uid_str, "%d", from_kuid(&init_user_ns, cred->fsuid));
156 sprintf(gid_str, "%d", from_kgid(&init_user_ns, cred->fsgid));
158 /* we say which key is under construction */
159 sprintf(key_str, "%d", key->serial);
161 /* we specify the process's default keyrings */
162 sprintf(keyring_str[0], "%d",
163 cred->thread_keyring ? cred->thread_keyring->serial : 0);
166 if (cred->process_keyring)
167 prkey = cred->process_keyring->serial;
168 sprintf(keyring_str[1], "%d", prkey);
170 session = cred->session_keyring;
172 session = user_session;
173 sskey = session->serial;
175 sprintf(keyring_str[2], "%d", sskey);
177 /* set up a minimal environment */
179 envp[i++] = "HOME=/";
180 envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
183 /* set up the argument list */
185 argv[i++] = (char *)request_key;
186 argv[i++] = (char *)rka->op;
190 argv[i++] = keyring_str[0];
191 argv[i++] = keyring_str[1];
192 argv[i++] = keyring_str[2];
196 ret = call_usermodehelper_keys(request_key, argv, envp, keyring,
198 kdebug("usermode -> 0x%x", ret);
200 /* ret is the exit/wait code */
201 if (test_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags) ||
202 key_validate(key) < 0)
205 /* ignore any errors from userspace if the key was
214 key_put(user_session);
216 complete_request_key(authkey, ret);
217 kleave(" = %d", ret);
222 * Call out to userspace for key construction.
224 * Program failure is ignored in favour of key status.
226 static int construct_key(struct key *key, const void *callout_info,
227 size_t callout_len, void *aux,
228 struct key *dest_keyring)
230 request_key_actor_t actor;
234 kenter("%d,%p,%zu,%p", key->serial, callout_info, callout_len, aux);
236 /* allocate an authorisation key */
237 authkey = request_key_auth_new(key, "create", callout_info, callout_len,
240 return PTR_ERR(authkey);
243 actor = call_sbin_request_key;
244 if (key->type->request_key)
245 actor = key->type->request_key;
247 ret = actor(authkey, aux);
249 /* check that the actor called complete_request_key() prior to
250 * returning an error */
252 !test_bit(KEY_FLAG_INVALIDATED, &authkey->flags));
255 kleave(" = %d", ret);
260 * Get the appropriate destination keyring for the request.
262 * The keyring selected is returned with an extra reference upon it which the
263 * caller must release.
265 static int construct_get_dest_keyring(struct key **_dest_keyring)
267 struct request_key_auth *rka;
268 const struct cred *cred = current_cred();
269 struct key *dest_keyring = *_dest_keyring, *authkey;
272 kenter("%p", dest_keyring);
274 /* find the appropriate keyring */
276 /* the caller supplied one */
277 key_get(dest_keyring);
279 bool do_perm_check = true;
281 /* use a default keyring; falling through the cases until we
282 * find one that we actually have */
283 switch (cred->jit_keyring) {
284 case KEY_REQKEY_DEFL_DEFAULT:
285 case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
286 if (cred->request_key_auth) {
287 authkey = cred->request_key_auth;
288 down_read(&authkey->sem);
289 rka = get_request_key_auth(authkey);
290 if (!test_bit(KEY_FLAG_REVOKED,
293 key_get(rka->dest_keyring);
294 up_read(&authkey->sem);
296 do_perm_check = false;
302 case KEY_REQKEY_DEFL_THREAD_KEYRING:
303 dest_keyring = key_get(cred->thread_keyring);
308 case KEY_REQKEY_DEFL_PROCESS_KEYRING:
309 dest_keyring = key_get(cred->process_keyring);
314 case KEY_REQKEY_DEFL_SESSION_KEYRING:
315 dest_keyring = key_get(cred->session_keyring);
321 case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
322 ret = look_up_user_keyrings(NULL, &dest_keyring);
327 case KEY_REQKEY_DEFL_USER_KEYRING:
328 ret = look_up_user_keyrings(&dest_keyring, NULL);
333 case KEY_REQKEY_DEFL_GROUP_KEYRING:
339 * Require Write permission on the keyring. This is essential
340 * because the default keyring may be the session keyring, and
341 * joining a keyring only requires Search permission.
343 * However, this check is skipped for the "requestor keyring" so
344 * that /sbin/request-key can itself use request_key() to add
345 * keys to the original requestor's destination keyring.
347 if (dest_keyring && do_perm_check) {
348 ret = key_permission(make_key_ref(dest_keyring, 1),
351 key_put(dest_keyring);
357 *_dest_keyring = dest_keyring;
358 kleave(" [dk %d]", key_serial(dest_keyring));
363 * Allocate a new key in under-construction state and attempt to link it in to
364 * the requested keyring.
366 * May return a key that's already under construction instead if there was a
367 * race between two thread calling request_key().
369 static int construct_alloc_key(struct keyring_search_context *ctx,
370 struct key *dest_keyring,
372 struct key_user *user,
375 struct assoc_array_edit *edit = NULL;
382 ctx->index_key.type->name, ctx->index_key.description);
385 mutex_lock(&user->cons_lock);
387 perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
388 perm |= KEY_USR_VIEW;
389 if (ctx->index_key.type->read)
390 perm |= KEY_POS_READ;
391 if (ctx->index_key.type == &key_type_keyring ||
392 ctx->index_key.type->update)
393 perm |= KEY_POS_WRITE;
395 key = key_alloc(ctx->index_key.type, ctx->index_key.description,
396 ctx->cred->fsuid, ctx->cred->fsgid, ctx->cred,
401 set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
404 ret = __key_link_lock(dest_keyring, &key->index_key);
406 goto link_lock_failed;
410 * Attach the key to the destination keyring under lock, but we do need
411 * to do another check just in case someone beat us to it whilst we
414 * The caller might specify a comparison function which looks for keys
415 * that do not exactly match but are still equivalent from the caller's
416 * perspective. The __key_link_begin() operation must be done only after
417 * an actual key is determined.
419 mutex_lock(&key_construction_mutex);
422 key_ref = search_process_keyrings_rcu(ctx);
424 if (!IS_ERR(key_ref))
425 goto key_already_present;
428 ret = __key_link_begin(dest_keyring, &key->index_key, &edit);
430 goto link_alloc_failed;
431 __key_link(dest_keyring, key, &edit);
434 mutex_unlock(&key_construction_mutex);
436 __key_link_end(dest_keyring, &key->index_key, edit);
437 mutex_unlock(&user->cons_lock);
439 kleave(" = 0 [%d]", key_serial(key));
442 /* the key is now present - we tell the caller that we found it by
443 * returning -EINPROGRESS */
446 mutex_unlock(&key_construction_mutex);
447 key = key_ref_to_ptr(key_ref);
449 ret = __key_link_begin(dest_keyring, &key->index_key, &edit);
451 goto link_alloc_failed_unlocked;
452 ret = __key_link_check_live_key(dest_keyring, key);
454 __key_link(dest_keyring, key, &edit);
455 __key_link_end(dest_keyring, &key->index_key, edit);
457 goto link_check_failed;
459 mutex_unlock(&user->cons_lock);
461 kleave(" = -EINPROGRESS [%d]", key_serial(key));
465 mutex_unlock(&user->cons_lock);
467 kleave(" = %d [linkcheck]", ret);
471 mutex_unlock(&key_construction_mutex);
472 link_alloc_failed_unlocked:
473 __key_link_end(dest_keyring, &key->index_key, edit);
475 mutex_unlock(&user->cons_lock);
477 kleave(" = %d [prelink]", ret);
481 mutex_unlock(&user->cons_lock);
482 kleave(" = %ld", PTR_ERR(key));
487 * Commence key construction.
489 static struct key *construct_key_and_link(struct keyring_search_context *ctx,
490 const char *callout_info,
493 struct key *dest_keyring,
496 struct key_user *user;
502 if (ctx->index_key.type == &key_type_keyring)
503 return ERR_PTR(-EPERM);
505 ret = construct_get_dest_keyring(&dest_keyring);
509 user = key_user_lookup(current_fsuid());
512 goto error_put_dest_keyring;
515 ret = construct_alloc_key(ctx, dest_keyring, flags, user, &key);
519 ret = construct_key(key, callout_info, callout_len, aux,
522 kdebug("cons failed");
523 goto construction_failed;
525 } else if (ret == -EINPROGRESS) {
528 goto error_put_dest_keyring;
531 key_put(dest_keyring);
532 kleave(" = key %d", key_serial(key));
536 key_negate_and_link(key, key_negative_timeout, NULL, NULL);
538 error_put_dest_keyring:
539 key_put(dest_keyring);
541 kleave(" = %d", ret);
546 * request_key_and_link - Request a key and cache it in a keyring.
547 * @type: The type of key we want.
548 * @description: The searchable description of the key.
549 * @domain_tag: The domain in which the key operates.
550 * @callout_info: The data to pass to the instantiation upcall (or NULL).
551 * @callout_len: The length of callout_info.
552 * @aux: Auxiliary data for the upcall.
553 * @dest_keyring: Where to cache the key.
554 * @flags: Flags to key_alloc().
556 * A key matching the specified criteria (type, description, domain_tag) is
557 * searched for in the process's keyrings and returned with its usage count
558 * incremented if found. Otherwise, if callout_info is not NULL, a key will be
559 * allocated and some service (probably in userspace) will be asked to
562 * If successfully found or created, the key will be linked to the destination
563 * keyring if one is provided.
565 * Returns a pointer to the key if successful; -EACCES, -ENOKEY, -EKEYREVOKED
566 * or -EKEYEXPIRED if an inaccessible, negative, revoked or expired key was
567 * found; -ENOKEY if no key was found and no @callout_info was given; -EDQUOT
568 * if insufficient key quota was available to create a new key; or -ENOMEM if
569 * insufficient memory was available.
571 * If the returned key was created, then it may still be under construction,
572 * and wait_for_key_construction() should be used to wait for that to complete.
574 struct key *request_key_and_link(struct key_type *type,
575 const char *description,
576 struct key_tag *domain_tag,
577 const void *callout_info,
580 struct key *dest_keyring,
583 struct keyring_search_context ctx = {
584 .index_key.type = type,
585 .index_key.domain_tag = domain_tag,
586 .index_key.description = description,
587 .index_key.desc_len = strlen(description),
588 .cred = current_cred(),
589 .match_data.cmp = key_default_cmp,
590 .match_data.raw_data = description,
591 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
592 .flags = (KEYRING_SEARCH_DO_STATE_CHECK |
593 KEYRING_SEARCH_SKIP_EXPIRED |
594 KEYRING_SEARCH_RECURSE),
600 kenter("%s,%s,%p,%zu,%p,%p,%lx",
601 ctx.index_key.type->name, ctx.index_key.description,
602 callout_info, callout_len, aux, dest_keyring, flags);
604 if (type->match_preparse) {
605 ret = type->match_preparse(&ctx.match_data);
612 key = check_cached_key(&ctx);
616 /* search all the process keyrings for a key */
618 key_ref = search_process_keyrings_rcu(&ctx);
621 if (!IS_ERR(key_ref)) {
623 ret = key_task_permission(key_ref, current_cred(),
626 key_ref_put(key_ref);
632 key = key_ref_to_ptr(key_ref);
634 ret = key_link(dest_keyring, key);
642 /* Only cache the key on immediate success */
643 cache_requested_key(key);
644 } else if (PTR_ERR(key_ref) != -EAGAIN) {
645 key = ERR_CAST(key_ref);
647 /* the search failed, but the keyrings were searchable, so we
648 * should consult userspace if we can */
649 key = ERR_PTR(-ENOKEY);
653 key = construct_key_and_link(&ctx, callout_info, callout_len,
654 aux, dest_keyring, flags);
658 if (type->match_free)
659 type->match_free(&ctx.match_data);
661 kleave(" = %p", key);
666 * wait_for_key_construction - Wait for construction of a key to complete
667 * @key: The key being waited for.
668 * @intr: Whether to wait interruptibly.
670 * Wait for a key to finish being constructed.
672 * Returns 0 if successful; -ERESTARTSYS if the wait was interrupted; -ENOKEY
673 * if the key was negated; or -EKEYREVOKED or -EKEYEXPIRED if the key was
674 * revoked or expired.
676 int wait_for_key_construction(struct key *key, bool intr)
680 ret = wait_on_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT,
681 intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
684 ret = key_read_state(key);
687 return key_validate(key);
689 EXPORT_SYMBOL(wait_for_key_construction);
692 * request_key_tag - Request a key and wait for construction
693 * @type: Type of key.
694 * @description: The searchable description of the key.
695 * @domain_tag: The domain in which the key operates.
696 * @callout_info: The data to pass to the instantiation upcall (or NULL).
698 * As for request_key_and_link() except that it does not add the returned key
699 * to a keyring if found, new keys are always allocated in the user's quota,
700 * the callout_info must be a NUL-terminated string and no auxiliary data can
703 * Furthermore, it then works as wait_for_key_construction() to wait for the
704 * completion of keys undergoing construction with a non-interruptible wait.
706 struct key *request_key_tag(struct key_type *type,
707 const char *description,
708 struct key_tag *domain_tag,
709 const char *callout_info)
712 size_t callout_len = 0;
716 callout_len = strlen(callout_info);
717 key = request_key_and_link(type, description, domain_tag,
718 callout_info, callout_len,
719 NULL, NULL, KEY_ALLOC_IN_QUOTA);
721 ret = wait_for_key_construction(key, false);
729 EXPORT_SYMBOL(request_key_tag);
732 * request_key_with_auxdata - Request a key with auxiliary data for the upcaller
733 * @type: The type of key we want.
734 * @description: The searchable description of the key.
735 * @domain_tag: The domain in which the key operates.
736 * @callout_info: The data to pass to the instantiation upcall (or NULL).
737 * @callout_len: The length of callout_info.
738 * @aux: Auxiliary data for the upcall.
740 * As for request_key_and_link() except that it does not add the returned key
741 * to a keyring if found and new keys are always allocated in the user's quota.
743 * Furthermore, it then works as wait_for_key_construction() to wait for the
744 * completion of keys undergoing construction with a non-interruptible wait.
746 struct key *request_key_with_auxdata(struct key_type *type,
747 const char *description,
748 struct key_tag *domain_tag,
749 const void *callout_info,
756 key = request_key_and_link(type, description, domain_tag,
757 callout_info, callout_len,
758 aux, NULL, KEY_ALLOC_IN_QUOTA);
760 ret = wait_for_key_construction(key, false);
768 EXPORT_SYMBOL(request_key_with_auxdata);
771 * request_key_rcu - Request key from RCU-read-locked context
772 * @type: The type of key we want.
773 * @description: The name of the key we want.
774 * @domain_tag: The domain in which the key operates.
776 * Request a key from a context that we may not sleep in (such as RCU-mode
777 * pathwalk). Keys under construction are ignored.
779 * Return a pointer to the found key if successful, -ENOKEY if we couldn't find
780 * a key or some other error if the key found was unsuitable or inaccessible.
782 struct key *request_key_rcu(struct key_type *type,
783 const char *description,
784 struct key_tag *domain_tag)
786 struct keyring_search_context ctx = {
787 .index_key.type = type,
788 .index_key.domain_tag = domain_tag,
789 .index_key.description = description,
790 .index_key.desc_len = strlen(description),
791 .cred = current_cred(),
792 .match_data.cmp = key_default_cmp,
793 .match_data.raw_data = description,
794 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
795 .flags = (KEYRING_SEARCH_DO_STATE_CHECK |
796 KEYRING_SEARCH_SKIP_EXPIRED),
801 kenter("%s,%s", type->name, description);
803 key = check_cached_key(&ctx);
807 /* search all the process keyrings for a key */
808 key_ref = search_process_keyrings_rcu(&ctx);
809 if (IS_ERR(key_ref)) {
810 key = ERR_CAST(key_ref);
811 if (PTR_ERR(key_ref) == -EAGAIN)
812 key = ERR_PTR(-ENOKEY);
814 key = key_ref_to_ptr(key_ref);
815 cache_requested_key(key);
818 kleave(" = %p", key);
821 EXPORT_SYMBOL(request_key_rcu);