1 /* Request a key from userspace
3 * Copyright (C) 2004-2007 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.
11 * See Documentation/security/keys/request-key.rst
14 #include <linux/module.h>
15 #include <linux/sched.h>
16 #include <linux/kmod.h>
17 #include <linux/err.h>
18 #include <linux/keyctl.h>
19 #include <linux/slab.h>
21 #include <keys/request_key_auth-type.h>
23 #define key_negative_timeout 60 /* default timeout on a negative key's existence */
26 * complete_request_key - Complete the construction of a key.
27 * @auth_key: The authorisation key.
28 * @error: The success or failute of the construction.
30 * Complete the attempt to construct a key. The key will be negated
31 * if an error is indicated. The authorisation key will be revoked
34 void complete_request_key(struct key *authkey, int error)
36 struct request_key_auth *rka = get_request_key_auth(authkey);
37 struct key *key = rka->target_key;
39 kenter("%d{%d},%d", authkey->serial, key->serial, error);
42 key_negate_and_link(key, key_negative_timeout, NULL, authkey);
46 EXPORT_SYMBOL(complete_request_key);
49 * Initialise a usermode helper that is going to have a specific session
52 * This is called in context of freshly forked kthread before kernel_execve(),
53 * so we can simply install the desired session_keyring at this point.
55 static int umh_keys_init(struct subprocess_info *info, struct cred *cred)
57 struct key *keyring = info->data;
59 return install_session_keyring_to_cred(cred, keyring);
63 * Clean up a usermode helper with session keyring.
65 static void umh_keys_cleanup(struct subprocess_info *info)
67 struct key *keyring = info->data;
72 * Call a usermode helper with a specific session keyring.
74 static int call_usermodehelper_keys(const char *path, char **argv, char **envp,
75 struct key *session_keyring, int wait)
77 struct subprocess_info *info;
79 info = call_usermodehelper_setup(path, argv, envp, GFP_KERNEL,
80 umh_keys_init, umh_keys_cleanup,
85 key_get(session_keyring);
86 return call_usermodehelper_exec(info, wait);
90 * Request userspace finish the construction of a key
91 * - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring>"
93 static int call_sbin_request_key(struct key *authkey, void *aux)
95 static char const request_key[] = "/sbin/request-key";
96 struct request_key_auth *rka = get_request_key_auth(authkey);
97 const struct cred *cred = current_cred();
98 key_serial_t prkey, sskey;
99 struct key *key = rka->target_key, *keyring, *session;
100 char *argv[9], *envp[3], uid_str[12], gid_str[12];
101 char key_str[12], keyring_str[3][12];
105 kenter("{%d},{%d},%s", key->serial, authkey->serial, rka->op);
107 ret = install_user_keyrings();
111 /* allocate a new session keyring */
112 sprintf(desc, "_req.%u", key->serial);
114 cred = get_current_cred();
115 keyring = keyring_alloc(desc, cred->fsuid, cred->fsgid, cred,
116 KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ,
117 KEY_ALLOC_QUOTA_OVERRUN, NULL, NULL);
119 if (IS_ERR(keyring)) {
120 ret = PTR_ERR(keyring);
124 /* attach the auth key to the session keyring */
125 ret = key_link(keyring, authkey);
129 /* record the UID and GID */
130 sprintf(uid_str, "%d", from_kuid(&init_user_ns, cred->fsuid));
131 sprintf(gid_str, "%d", from_kgid(&init_user_ns, cred->fsgid));
133 /* we say which key is under construction */
134 sprintf(key_str, "%d", key->serial);
136 /* we specify the process's default keyrings */
137 sprintf(keyring_str[0], "%d",
138 cred->thread_keyring ? cred->thread_keyring->serial : 0);
141 if (cred->process_keyring)
142 prkey = cred->process_keyring->serial;
143 sprintf(keyring_str[1], "%d", prkey);
146 session = rcu_dereference(cred->session_keyring);
148 session = cred->user->session_keyring;
149 sskey = session->serial;
152 sprintf(keyring_str[2], "%d", sskey);
154 /* set up a minimal environment */
156 envp[i++] = "HOME=/";
157 envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
160 /* set up the argument list */
162 argv[i++] = (char *)request_key;
163 argv[i++] = (char *)rka->op;
167 argv[i++] = keyring_str[0];
168 argv[i++] = keyring_str[1];
169 argv[i++] = keyring_str[2];
173 ret = call_usermodehelper_keys(request_key, argv, envp, keyring,
175 kdebug("usermode -> 0x%x", ret);
177 /* ret is the exit/wait code */
178 if (test_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags) ||
179 key_validate(key) < 0)
182 /* ignore any errors from userspace if the key was
191 complete_request_key(authkey, ret);
192 kleave(" = %d", ret);
197 * Call out to userspace for key construction.
199 * Program failure is ignored in favour of key status.
201 static int construct_key(struct key *key, const void *callout_info,
202 size_t callout_len, void *aux,
203 struct key *dest_keyring)
205 request_key_actor_t actor;
209 kenter("%d,%p,%zu,%p", key->serial, callout_info, callout_len, aux);
211 /* allocate an authorisation key */
212 authkey = request_key_auth_new(key, "create", callout_info, callout_len,
215 return PTR_ERR(authkey);
218 actor = call_sbin_request_key;
219 if (key->type->request_key)
220 actor = key->type->request_key;
222 ret = actor(authkey, aux);
224 /* check that the actor called complete_request_key() prior to
225 * returning an error */
227 !test_bit(KEY_FLAG_REVOKED, &authkey->flags));
230 kleave(" = %d", ret);
235 * Get the appropriate destination keyring for the request.
237 * The keyring selected is returned with an extra reference upon it which the
238 * caller must release.
240 static int construct_get_dest_keyring(struct key **_dest_keyring)
242 struct request_key_auth *rka;
243 const struct cred *cred = current_cred();
244 struct key *dest_keyring = *_dest_keyring, *authkey;
247 kenter("%p", dest_keyring);
249 /* find the appropriate keyring */
251 /* the caller supplied one */
252 key_get(dest_keyring);
254 bool do_perm_check = true;
256 /* use a default keyring; falling through the cases until we
257 * find one that we actually have */
258 switch (cred->jit_keyring) {
259 case KEY_REQKEY_DEFL_DEFAULT:
260 case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
261 if (cred->request_key_auth) {
262 authkey = cred->request_key_auth;
263 down_read(&authkey->sem);
264 rka = get_request_key_auth(authkey);
265 if (!test_bit(KEY_FLAG_REVOKED,
268 key_get(rka->dest_keyring);
269 up_read(&authkey->sem);
271 do_perm_check = false;
276 case KEY_REQKEY_DEFL_THREAD_KEYRING:
277 dest_keyring = key_get(cred->thread_keyring);
281 case KEY_REQKEY_DEFL_PROCESS_KEYRING:
282 dest_keyring = key_get(cred->process_keyring);
286 case KEY_REQKEY_DEFL_SESSION_KEYRING:
288 dest_keyring = key_get(
289 rcu_dereference(cred->session_keyring));
295 case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
297 key_get(cred->user->session_keyring);
300 case KEY_REQKEY_DEFL_USER_KEYRING:
301 dest_keyring = key_get(cred->user->uid_keyring);
304 case KEY_REQKEY_DEFL_GROUP_KEYRING:
310 * Require Write permission on the keyring. This is essential
311 * because the default keyring may be the session keyring, and
312 * joining a keyring only requires Search permission.
314 * However, this check is skipped for the "requestor keyring" so
315 * that /sbin/request-key can itself use request_key() to add
316 * keys to the original requestor's destination keyring.
318 if (dest_keyring && do_perm_check) {
319 ret = key_permission(make_key_ref(dest_keyring, 1),
322 key_put(dest_keyring);
328 *_dest_keyring = dest_keyring;
329 kleave(" [dk %d]", key_serial(dest_keyring));
334 * Allocate a new key in under-construction state and attempt to link it in to
335 * the requested keyring.
337 * May return a key that's already under construction instead if there was a
338 * race between two thread calling request_key().
340 static int construct_alloc_key(struct keyring_search_context *ctx,
341 struct key *dest_keyring,
343 struct key_user *user,
346 struct assoc_array_edit *edit;
353 ctx->index_key.type->name, ctx->index_key.description);
356 mutex_lock(&user->cons_lock);
358 perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
359 perm |= KEY_USR_VIEW;
360 if (ctx->index_key.type->read)
361 perm |= KEY_POS_READ;
362 if (ctx->index_key.type == &key_type_keyring ||
363 ctx->index_key.type->update)
364 perm |= KEY_POS_WRITE;
366 key = key_alloc(ctx->index_key.type, ctx->index_key.description,
367 ctx->cred->fsuid, ctx->cred->fsgid, ctx->cred,
372 set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
375 ret = __key_link_begin(dest_keyring, &ctx->index_key, &edit);
377 goto link_prealloc_failed;
380 /* attach the key to the destination keyring under lock, but we do need
381 * to do another check just in case someone beat us to it whilst we
382 * waited for locks */
383 mutex_lock(&key_construction_mutex);
385 key_ref = search_process_keyrings(ctx);
386 if (!IS_ERR(key_ref))
387 goto key_already_present;
390 __key_link(key, &edit);
392 mutex_unlock(&key_construction_mutex);
394 __key_link_end(dest_keyring, &ctx->index_key, edit);
395 mutex_unlock(&user->cons_lock);
397 kleave(" = 0 [%d]", key_serial(key));
400 /* the key is now present - we tell the caller that we found it by
401 * returning -EINPROGRESS */
404 mutex_unlock(&key_construction_mutex);
405 key = key_ref_to_ptr(key_ref);
407 ret = __key_link_check_live_key(dest_keyring, key);
409 __key_link(key, &edit);
410 __key_link_end(dest_keyring, &ctx->index_key, edit);
412 goto link_check_failed;
414 mutex_unlock(&user->cons_lock);
416 kleave(" = -EINPROGRESS [%d]", key_serial(key));
420 mutex_unlock(&user->cons_lock);
422 kleave(" = %d [linkcheck]", ret);
425 link_prealloc_failed:
426 mutex_unlock(&user->cons_lock);
428 kleave(" = %d [prelink]", ret);
432 mutex_unlock(&user->cons_lock);
433 kleave(" = %ld", PTR_ERR(key));
438 * Commence key construction.
440 static struct key *construct_key_and_link(struct keyring_search_context *ctx,
441 const char *callout_info,
444 struct key *dest_keyring,
447 struct key_user *user;
453 if (ctx->index_key.type == &key_type_keyring)
454 return ERR_PTR(-EPERM);
456 ret = construct_get_dest_keyring(&dest_keyring);
460 user = key_user_lookup(current_fsuid());
463 goto error_put_dest_keyring;
466 ret = construct_alloc_key(ctx, dest_keyring, flags, user, &key);
470 ret = construct_key(key, callout_info, callout_len, aux,
473 kdebug("cons failed");
474 goto construction_failed;
476 } else if (ret == -EINPROGRESS) {
479 goto error_put_dest_keyring;
482 key_put(dest_keyring);
483 kleave(" = key %d", key_serial(key));
487 key_negate_and_link(key, key_negative_timeout, NULL, NULL);
489 error_put_dest_keyring:
490 key_put(dest_keyring);
492 kleave(" = %d", ret);
497 * request_key_and_link - Request a key and cache it in a keyring.
498 * @type: The type of key we want.
499 * @description: The searchable description of the key.
500 * @callout_info: The data to pass to the instantiation upcall (or NULL).
501 * @callout_len: The length of callout_info.
502 * @aux: Auxiliary data for the upcall.
503 * @dest_keyring: Where to cache the key.
504 * @flags: Flags to key_alloc().
506 * A key matching the specified criteria is searched for in the process's
507 * keyrings and returned with its usage count incremented if found. Otherwise,
508 * if callout_info is not NULL, a key will be allocated and some service
509 * (probably in userspace) will be asked to instantiate it.
511 * If successfully found or created, the key will be linked to the destination
512 * keyring if one is provided.
514 * Returns a pointer to the key if successful; -EACCES, -ENOKEY, -EKEYREVOKED
515 * or -EKEYEXPIRED if an inaccessible, negative, revoked or expired key was
516 * found; -ENOKEY if no key was found and no @callout_info was given; -EDQUOT
517 * if insufficient key quota was available to create a new key; or -ENOMEM if
518 * insufficient memory was available.
520 * If the returned key was created, then it may still be under construction,
521 * and wait_for_key_construction() should be used to wait for that to complete.
523 struct key *request_key_and_link(struct key_type *type,
524 const char *description,
525 const void *callout_info,
528 struct key *dest_keyring,
531 struct keyring_search_context ctx = {
532 .index_key.type = type,
533 .index_key.description = description,
534 .index_key.desc_len = strlen(description),
535 .cred = current_cred(),
536 .match_data.cmp = key_default_cmp,
537 .match_data.raw_data = description,
538 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
539 .flags = (KEYRING_SEARCH_DO_STATE_CHECK |
540 KEYRING_SEARCH_SKIP_EXPIRED),
546 kenter("%s,%s,%p,%zu,%p,%p,%lx",
547 ctx.index_key.type->name, ctx.index_key.description,
548 callout_info, callout_len, aux, dest_keyring, flags);
550 if (type->match_preparse) {
551 ret = type->match_preparse(&ctx.match_data);
558 /* search all the process keyrings for a key */
559 key_ref = search_process_keyrings(&ctx);
561 if (!IS_ERR(key_ref)) {
562 key = key_ref_to_ptr(key_ref);
564 construct_get_dest_keyring(&dest_keyring);
565 ret = key_link(dest_keyring, key);
566 key_put(dest_keyring);
573 } else if (PTR_ERR(key_ref) != -EAGAIN) {
574 key = ERR_CAST(key_ref);
576 /* the search failed, but the keyrings were searchable, so we
577 * should consult userspace if we can */
578 key = ERR_PTR(-ENOKEY);
582 key = construct_key_and_link(&ctx, callout_info, callout_len,
583 aux, dest_keyring, flags);
587 if (type->match_free)
588 type->match_free(&ctx.match_data);
590 kleave(" = %p", key);
595 * wait_for_key_construction - Wait for construction of a key to complete
596 * @key: The key being waited for.
597 * @intr: Whether to wait interruptibly.
599 * Wait for a key to finish being constructed.
601 * Returns 0 if successful; -ERESTARTSYS if the wait was interrupted; -ENOKEY
602 * if the key was negated; or -EKEYREVOKED or -EKEYEXPIRED if the key was
603 * revoked or expired.
605 int wait_for_key_construction(struct key *key, bool intr)
609 ret = wait_on_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT,
610 intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
613 ret = key_read_state(key);
616 return key_validate(key);
618 EXPORT_SYMBOL(wait_for_key_construction);
621 * request_key - Request a key and wait for construction
622 * @type: Type of key.
623 * @description: The searchable description of the key.
624 * @callout_info: The data to pass to the instantiation upcall (or NULL).
626 * As for request_key_and_link() except that it does not add the returned key
627 * to a keyring if found, new keys are always allocated in the user's quota,
628 * the callout_info must be a NUL-terminated string and no auxiliary data can
631 * Furthermore, it then works as wait_for_key_construction() to wait for the
632 * completion of keys undergoing construction with a non-interruptible wait.
634 struct key *request_key(struct key_type *type,
635 const char *description,
636 const char *callout_info)
639 size_t callout_len = 0;
643 callout_len = strlen(callout_info);
644 key = request_key_and_link(type, description, callout_info, callout_len,
645 NULL, NULL, KEY_ALLOC_IN_QUOTA);
647 ret = wait_for_key_construction(key, false);
655 EXPORT_SYMBOL(request_key);
658 * request_key_with_auxdata - Request a key with auxiliary data for the upcaller
659 * @type: The type of key we want.
660 * @description: The searchable description of the key.
661 * @callout_info: The data to pass to the instantiation upcall (or NULL).
662 * @callout_len: The length of callout_info.
663 * @aux: Auxiliary data for the upcall.
665 * As for request_key_and_link() except that it does not add the returned key
666 * to a keyring if found and new keys are always allocated in the user's quota.
668 * Furthermore, it then works as wait_for_key_construction() to wait for the
669 * completion of keys undergoing construction with a non-interruptible wait.
671 struct key *request_key_with_auxdata(struct key_type *type,
672 const char *description,
673 const void *callout_info,
680 key = request_key_and_link(type, description, callout_info, callout_len,
681 aux, NULL, KEY_ALLOC_IN_QUOTA);
683 ret = wait_for_key_construction(key, false);
691 EXPORT_SYMBOL(request_key_with_auxdata);
694 * request_key_async - Request a key (allow async construction)
695 * @type: Type of key.
696 * @description: The searchable description of the key.
697 * @callout_info: The data to pass to the instantiation upcall (or NULL).
698 * @callout_len: The length of callout_info.
700 * As for request_key_and_link() except that it does not add the returned key
701 * to a keyring if found, new keys are always allocated in the user's quota and
702 * no auxiliary data can be passed.
704 * The caller should call wait_for_key_construction() to wait for the
705 * completion of the returned key if it is still undergoing construction.
707 struct key *request_key_async(struct key_type *type,
708 const char *description,
709 const void *callout_info,
712 return request_key_and_link(type, description, callout_info,
713 callout_len, NULL, NULL,
716 EXPORT_SYMBOL(request_key_async);
719 * request a key with auxiliary data for the upcaller (allow async construction)
720 * @type: Type of key.
721 * @description: The searchable description of the key.
722 * @callout_info: The data to pass to the instantiation upcall (or NULL).
723 * @callout_len: The length of callout_info.
724 * @aux: Auxiliary data for the upcall.
726 * As for request_key_and_link() except that it does not add the returned key
727 * to a keyring if found and new keys are always allocated in the user's quota.
729 * The caller should call wait_for_key_construction() to wait for the
730 * completion of the returned key if it is still undergoing construction.
732 struct key *request_key_async_with_auxdata(struct key_type *type,
733 const char *description,
734 const void *callout_info,
738 return request_key_and_link(type, description, callout_info,
739 callout_len, aux, NULL, KEY_ALLOC_IN_QUOTA);
741 EXPORT_SYMBOL(request_key_async_with_auxdata);