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.txt
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>
22 #define key_negative_timeout 60 /* default timeout on a negative key's existence */
25 * wait_on_bit() sleep function for uninterruptible waiting
27 static int key_wait_bit(void *flags)
34 * wait_on_bit() sleep function for interruptible waiting
36 static int key_wait_bit_intr(void *flags)
39 return signal_pending(current) ? -ERESTARTSYS : 0;
43 * complete_request_key - Complete the construction of a key.
44 * @cons: The key construction record.
45 * @error: The success or failute of the construction.
47 * Complete the attempt to construct a key. The key will be negated
48 * if an error is indicated. The authorisation key will be revoked
51 void complete_request_key(struct key_construction *cons, int error)
53 kenter("{%d,%d},%d", cons->key->serial, cons->authkey->serial, error);
56 key_negate_and_link(cons->key, key_negative_timeout, NULL,
59 key_revoke(cons->authkey);
62 key_put(cons->authkey);
65 EXPORT_SYMBOL(complete_request_key);
68 * Initialise a usermode helper that is going to have a specific session
71 * This is called in context of freshly forked kthread before kernel_execve(),
72 * so we can simply install the desired session_keyring at this point.
74 static int umh_keys_init(struct subprocess_info *info, struct cred *cred)
76 struct key *keyring = info->data;
78 return install_session_keyring_to_cred(cred, keyring);
82 * Clean up a usermode helper with session keyring.
84 static void umh_keys_cleanup(struct subprocess_info *info)
86 struct key *keyring = info->data;
91 * Call a usermode helper with a specific session keyring.
93 static int call_usermodehelper_keys(char *path, char **argv, char **envp,
94 struct key *session_keyring, enum umh_wait wait)
96 gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL;
97 struct subprocess_info *info =
98 call_usermodehelper_setup(path, argv, envp, gfp_mask);
103 call_usermodehelper_setfns(info, umh_keys_init, umh_keys_cleanup,
104 key_get(session_keyring));
105 return call_usermodehelper_exec(info, wait);
109 * Request userspace finish the construction of a key
110 * - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring>"
112 static int call_sbin_request_key(struct key_construction *cons,
116 const struct cred *cred = current_cred();
117 key_serial_t prkey, sskey;
118 struct key *key = cons->key, *authkey = cons->authkey, *keyring,
120 char *argv[9], *envp[3], uid_str[12], gid_str[12];
121 char key_str[12], keyring_str[3][12];
125 kenter("{%d},{%d},%s", key->serial, authkey->serial, op);
127 ret = install_user_keyrings();
131 /* allocate a new session keyring */
132 sprintf(desc, "_req.%u", key->serial);
134 cred = get_current_cred();
135 keyring = keyring_alloc(desc, cred->fsuid, cred->fsgid, cred,
136 KEY_ALLOC_QUOTA_OVERRUN, NULL);
138 if (IS_ERR(keyring)) {
139 ret = PTR_ERR(keyring);
143 /* attach the auth key to the session keyring */
144 ret = key_link(keyring, authkey);
148 /* record the UID and GID */
149 sprintf(uid_str, "%d", cred->fsuid);
150 sprintf(gid_str, "%d", cred->fsgid);
152 /* we say which key is under construction */
153 sprintf(key_str, "%d", key->serial);
155 /* we specify the process's default keyrings */
156 sprintf(keyring_str[0], "%d",
157 cred->thread_keyring ? cred->thread_keyring->serial : 0);
160 if (cred->tgcred->process_keyring)
161 prkey = cred->tgcred->process_keyring->serial;
162 sprintf(keyring_str[1], "%d", prkey);
165 session = rcu_dereference(cred->tgcred->session_keyring);
167 session = cred->user->session_keyring;
168 sskey = session->serial;
171 sprintf(keyring_str[2], "%d", sskey);
173 /* set up a minimal environment */
175 envp[i++] = "HOME=/";
176 envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
179 /* set up the argument list */
181 argv[i++] = "/sbin/request-key";
182 argv[i++] = (char *) op;
186 argv[i++] = keyring_str[0];
187 argv[i++] = keyring_str[1];
188 argv[i++] = keyring_str[2];
192 ret = call_usermodehelper_keys(argv[0], argv, envp, keyring,
194 kdebug("usermode -> 0x%x", ret);
196 /* ret is the exit/wait code */
197 if (test_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags) ||
198 key_validate(key) < 0)
201 /* ignore any errors from userspace if the key was
210 complete_request_key(cons, ret);
211 kleave(" = %d", ret);
216 * Call out to userspace for key construction.
218 * Program failure is ignored in favour of key status.
220 static int construct_key(struct key *key, const void *callout_info,
221 size_t callout_len, void *aux,
222 struct key *dest_keyring)
224 struct key_construction *cons;
225 request_key_actor_t actor;
229 kenter("%d,%p,%zu,%p", key->serial, callout_info, callout_len, aux);
231 cons = kmalloc(sizeof(*cons), GFP_KERNEL);
235 /* allocate an authorisation key */
236 authkey = request_key_auth_new(key, callout_info, callout_len,
238 if (IS_ERR(authkey)) {
240 ret = PTR_ERR(authkey);
243 cons->authkey = key_get(authkey);
244 cons->key = key_get(key);
247 actor = call_sbin_request_key;
248 if (key->type->request_key)
249 actor = key->type->request_key;
251 ret = actor(cons, "create", aux);
253 /* check that the actor called complete_request_key() prior to
254 * returning an error */
256 !test_bit(KEY_FLAG_REVOKED, &authkey->flags));
260 kleave(" = %d", ret);
265 * Get the appropriate destination keyring for the request.
267 * The keyring selected is returned with an extra reference upon it which the
268 * caller must release.
270 static int construct_get_dest_keyring(struct key **_dest_keyring)
272 struct request_key_auth *rka;
273 const struct cred *cred = current_cred();
274 struct key *dest_keyring = *_dest_keyring, *authkey;
277 kenter("%p", dest_keyring);
279 /* find the appropriate keyring */
281 /* the caller supplied one */
282 key_get(dest_keyring);
284 bool do_perm_check = true;
286 /* use a default keyring; falling through the cases until we
287 * find one that we actually have */
288 switch (cred->jit_keyring) {
289 case KEY_REQKEY_DEFL_DEFAULT:
290 case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
291 if (cred->request_key_auth) {
292 authkey = cred->request_key_auth;
293 down_read(&authkey->sem);
294 rka = authkey->payload.data;
295 if (!test_bit(KEY_FLAG_REVOKED,
298 key_get(rka->dest_keyring);
299 up_read(&authkey->sem);
301 do_perm_check = false;
306 case KEY_REQKEY_DEFL_THREAD_KEYRING:
307 dest_keyring = key_get(cred->thread_keyring);
311 case KEY_REQKEY_DEFL_PROCESS_KEYRING:
312 dest_keyring = key_get(cred->tgcred->process_keyring);
316 case KEY_REQKEY_DEFL_SESSION_KEYRING:
318 dest_keyring = key_get(
319 rcu_dereference(cred->tgcred->session_keyring));
325 case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
327 key_get(cred->user->session_keyring);
330 case KEY_REQKEY_DEFL_USER_KEYRING:
331 dest_keyring = key_get(cred->user->uid_keyring);
334 case KEY_REQKEY_DEFL_GROUP_KEYRING:
340 * Require Write permission on the keyring. This is essential
341 * because the default keyring may be the session keyring, and
342 * joining a keyring only requires Search permission.
344 * However, this check is skipped for the "requestor keyring" so
345 * that /sbin/request-key can itself use request_key() to add
346 * keys to the original requestor's destination keyring.
348 if (dest_keyring && do_perm_check) {
349 ret = key_permission(make_key_ref(dest_keyring, 1),
352 key_put(dest_keyring);
358 *_dest_keyring = dest_keyring;
359 kleave(" [dk %d]", key_serial(dest_keyring));
364 * Allocate a new key in under-construction state and attempt to link it in to
365 * the requested keyring.
367 * May return a key that's already under construction instead if there was a
368 * race between two thread calling request_key().
370 static int construct_alloc_key(struct key_type *type,
371 const char *description,
372 struct key *dest_keyring,
374 struct key_user *user,
377 const struct cred *cred = current_cred();
378 unsigned long prealloc;
383 kenter("%s,%s,,,", type->name, description);
386 mutex_lock(&user->cons_lock);
388 key = key_alloc(type, description, cred->fsuid, cred->fsgid, cred,
393 set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
396 ret = __key_link_begin(dest_keyring, type, description,
399 goto link_prealloc_failed;
402 /* attach the key to the destination keyring under lock, but we do need
403 * to do another check just in case someone beat us to it whilst we
404 * waited for locks */
405 mutex_lock(&key_construction_mutex);
407 key_ref = search_process_keyrings(type, description, type->match, cred);
408 if (!IS_ERR(key_ref))
409 goto key_already_present;
412 __key_link(dest_keyring, key, &prealloc);
414 mutex_unlock(&key_construction_mutex);
416 __key_link_end(dest_keyring, type, prealloc);
417 mutex_unlock(&user->cons_lock);
419 kleave(" = 0 [%d]", key_serial(key));
422 /* the key is now present - we tell the caller that we found it by
423 * returning -EINPROGRESS */
426 mutex_unlock(&key_construction_mutex);
427 key = key_ref_to_ptr(key_ref);
429 ret = __key_link_check_live_key(dest_keyring, key);
431 __key_link(dest_keyring, key, &prealloc);
432 __key_link_end(dest_keyring, type, prealloc);
434 goto link_check_failed;
436 mutex_unlock(&user->cons_lock);
438 kleave(" = -EINPROGRESS [%d]", key_serial(key));
442 mutex_unlock(&user->cons_lock);
444 kleave(" = %d [linkcheck]", ret);
447 link_prealloc_failed:
448 mutex_unlock(&user->cons_lock);
449 kleave(" = %d [prelink]", ret);
453 mutex_unlock(&user->cons_lock);
454 kleave(" = %ld", PTR_ERR(key));
459 * Commence key construction.
461 static struct key *construct_key_and_link(struct key_type *type,
462 const char *description,
463 const char *callout_info,
466 struct key *dest_keyring,
469 struct key_user *user;
475 ret = construct_get_dest_keyring(&dest_keyring);
479 user = key_user_lookup(current_fsuid(), current_user_ns());
482 goto error_put_dest_keyring;
485 ret = construct_alloc_key(type, description, dest_keyring, flags, user,
490 ret = construct_key(key, callout_info, callout_len, aux,
493 kdebug("cons failed");
494 goto construction_failed;
496 } else if (ret == -EINPROGRESS) {
499 goto error_put_dest_keyring;
502 key_put(dest_keyring);
503 kleave(" = key %d", key_serial(key));
507 key_negate_and_link(key, key_negative_timeout, NULL, NULL);
509 error_put_dest_keyring:
510 key_put(dest_keyring);
512 kleave(" = %d", ret);
517 * request_key_and_link - Request a key and cache it in a keyring.
518 * @type: The type of key we want.
519 * @description: The searchable description of the key.
520 * @callout_info: The data to pass to the instantiation upcall (or NULL).
521 * @callout_len: The length of callout_info.
522 * @aux: Auxiliary data for the upcall.
523 * @dest_keyring: Where to cache the key.
524 * @flags: Flags to key_alloc().
526 * A key matching the specified criteria is searched for in the process's
527 * keyrings and returned with its usage count incremented if found. Otherwise,
528 * if callout_info is not NULL, a key will be allocated and some service
529 * (probably in userspace) will be asked to instantiate it.
531 * If successfully found or created, the key will be linked to the destination
532 * keyring if one is provided.
534 * Returns a pointer to the key if successful; -EACCES, -ENOKEY, -EKEYREVOKED
535 * or -EKEYEXPIRED if an inaccessible, negative, revoked or expired key was
536 * found; -ENOKEY if no key was found and no @callout_info was given; -EDQUOT
537 * if insufficient key quota was available to create a new key; or -ENOMEM if
538 * insufficient memory was available.
540 * If the returned key was created, then it may still be under construction,
541 * and wait_for_key_construction() should be used to wait for that to complete.
543 struct key *request_key_and_link(struct key_type *type,
544 const char *description,
545 const void *callout_info,
548 struct key *dest_keyring,
551 const struct cred *cred = current_cred();
556 kenter("%s,%s,%p,%zu,%p,%p,%lx",
557 type->name, description, callout_info, callout_len, aux,
558 dest_keyring, flags);
560 /* search all the process keyrings for a key */
561 key_ref = search_process_keyrings(type, description, type->match, cred);
563 if (!IS_ERR(key_ref)) {
564 key = key_ref_to_ptr(key_ref);
566 construct_get_dest_keyring(&dest_keyring);
567 ret = key_link(dest_keyring, key);
568 key_put(dest_keyring);
575 } else if (PTR_ERR(key_ref) != -EAGAIN) {
576 key = ERR_CAST(key_ref);
578 /* the search failed, but the keyrings were searchable, so we
579 * should consult userspace if we can */
580 key = ERR_PTR(-ENOKEY);
584 key = construct_key_and_link(type, description, callout_info,
585 callout_len, aux, dest_keyring,
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 ? key_wait_bit_intr : key_wait_bit,
611 intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
614 if (test_bit(KEY_FLAG_NEGATIVE, &key->flags))
615 return key->type_data.reject_error;
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);