1 /* keyring.c: keyring handling
3 * Copyright (C) 2004-5 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/slab.h>
16 #include <linux/security.h>
17 #include <linux/seq_file.h>
18 #include <linux/err.h>
19 #include <asm/uaccess.h>
23 * when plumbing the depths of the key tree, this sets a hard limit set on how
24 * deep we're willing to go
26 #define KEYRING_SEARCH_MAX_DEPTH 6
29 * we keep all named keyrings in a hash to speed looking them up
31 #define KEYRING_NAME_HASH_SIZE (1 << 5)
33 static struct list_head keyring_name_hash[KEYRING_NAME_HASH_SIZE];
34 static DEFINE_RWLOCK(keyring_name_lock);
36 static inline unsigned keyring_hash(const char *desc)
41 bucket += (unsigned char) *desc;
43 return bucket & (KEYRING_NAME_HASH_SIZE - 1);
47 * the keyring type definition
49 static int keyring_instantiate(struct key *keyring,
50 const void *data, size_t datalen);
51 static int keyring_match(const struct key *keyring, const void *criterion);
52 static void keyring_destroy(struct key *keyring);
53 static void keyring_describe(const struct key *keyring, struct seq_file *m);
54 static long keyring_read(const struct key *keyring,
55 char __user *buffer, size_t buflen);
57 struct key_type key_type_keyring = {
59 .def_datalen = sizeof(struct keyring_list),
60 .instantiate = keyring_instantiate,
61 .match = keyring_match,
62 .destroy = keyring_destroy,
63 .describe = keyring_describe,
68 * semaphore to serialise link/link calls to prevent two link calls in parallel
71 DECLARE_RWSEM(keyring_serialise_link_sem);
73 /*****************************************************************************/
75 * publish the name of a keyring so that it can be found by name (if it has
78 void keyring_publish_name(struct key *keyring)
82 if (keyring->description) {
83 bucket = keyring_hash(keyring->description);
85 write_lock(&keyring_name_lock);
87 if (!keyring_name_hash[bucket].next)
88 INIT_LIST_HEAD(&keyring_name_hash[bucket]);
90 list_add_tail(&keyring->type_data.link,
91 &keyring_name_hash[bucket]);
93 write_unlock(&keyring_name_lock);
96 } /* end keyring_publish_name() */
98 /*****************************************************************************/
100 * initialise a keyring
101 * - we object if we were given any data
103 static int keyring_instantiate(struct key *keyring,
104 const void *data, size_t datalen)
110 /* make the keyring available by name if it has one */
111 keyring_publish_name(keyring);
117 } /* end keyring_instantiate() */
119 /*****************************************************************************/
121 * match keyrings on their name
123 static int keyring_match(const struct key *keyring, const void *description)
125 return keyring->description &&
126 strcmp(keyring->description, description) == 0;
128 } /* end keyring_match() */
130 /*****************************************************************************/
132 * dispose of the data dangling from the corpse of a keyring
134 static void keyring_destroy(struct key *keyring)
136 struct keyring_list *klist;
139 if (keyring->description) {
140 write_lock(&keyring_name_lock);
142 if (keyring->type_data.link.next != NULL &&
143 !list_empty(&keyring->type_data.link))
144 list_del(&keyring->type_data.link);
146 write_unlock(&keyring_name_lock);
149 klist = rcu_dereference(keyring->payload.subscriptions);
151 for (loop = klist->nkeys - 1; loop >= 0; loop--)
152 key_put(klist->keys[loop]);
156 } /* end keyring_destroy() */
158 /*****************************************************************************/
160 * describe the keyring
162 static void keyring_describe(const struct key *keyring, struct seq_file *m)
164 struct keyring_list *klist;
166 if (keyring->description) {
167 seq_puts(m, keyring->description);
170 seq_puts(m, "[anon]");
174 klist = rcu_dereference(keyring->payload.subscriptions);
176 seq_printf(m, ": %u/%u", klist->nkeys, klist->maxkeys);
178 seq_puts(m, ": empty");
181 } /* end keyring_describe() */
183 /*****************************************************************************/
185 * read a list of key IDs from the keyring's contents
186 * - the keyring's semaphore is read-locked
188 static long keyring_read(const struct key *keyring,
189 char __user *buffer, size_t buflen)
191 struct keyring_list *klist;
197 klist = rcu_dereference(keyring->payload.subscriptions);
200 /* calculate how much data we could return */
201 qty = klist->nkeys * sizeof(key_serial_t);
203 if (buffer && buflen > 0) {
207 /* copy the IDs of the subscribed keys into the
211 for (loop = 0; loop < klist->nkeys; loop++) {
212 key = klist->keys[loop];
214 tmp = sizeof(key_serial_t);
218 if (copy_to_user(buffer,
236 } /* end keyring_read() */
238 /*****************************************************************************/
240 * allocate a keyring and link into the destination keyring
242 struct key *keyring_alloc(const char *description, uid_t uid, gid_t gid,
243 int not_in_quota, struct key *dest)
248 keyring = key_alloc(&key_type_keyring, description,
250 (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL,
253 if (!IS_ERR(keyring)) {
254 ret = key_instantiate_and_link(keyring, NULL, 0, dest, NULL);
257 keyring = ERR_PTR(ret);
263 } /* end keyring_alloc() */
265 /*****************************************************************************/
267 * search the supplied keyring tree for a key that matches the criterion
268 * - perform a breadth-then-depth search up to the prescribed limit
269 * - we only find keys on which we have search permission
270 * - we use the supplied match function to see if the description (or other
271 * feature of interest) matches
272 * - we rely on RCU to prevent the keyring lists from disappearing on us
273 * - we return -EAGAIN if we didn't find any matching key
274 * - we return -ENOKEY if we only found negative matching keys
275 * - we propagate the possession attribute from the keyring ref to the key ref
277 key_ref_t keyring_search_aux(key_ref_t keyring_ref,
278 struct task_struct *context,
279 struct key_type *type,
280 const void *description,
281 key_match_func_t match)
284 struct keyring_list *keylist;
286 } stack[KEYRING_SEARCH_MAX_DEPTH];
288 struct keyring_list *keylist;
290 unsigned long possessed;
291 struct key *keyring, *key;
296 keyring = key_ref_to_ptr(keyring_ref);
297 possessed = is_key_possessed(keyring_ref);
300 /* top keyring must have search permission to begin the search */
301 err = key_task_permission(keyring_ref, context, KEY_SEARCH);
303 key_ref = ERR_PTR(err);
307 key_ref = ERR_PTR(-ENOTDIR);
308 if (keyring->type != &key_type_keyring)
313 now = current_kernel_time();
317 /* start processing a new keyring */
319 if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
320 goto not_this_keyring;
322 keylist = rcu_dereference(keyring->payload.subscriptions);
324 goto not_this_keyring;
326 /* iterate through the keys in this keyring first */
327 for (kix = 0; kix < keylist->nkeys; kix++) {
328 key = keylist->keys[kix];
330 /* ignore keys not of this type */
331 if (key->type != type)
334 /* skip revoked keys and expired keys */
335 if (test_bit(KEY_FLAG_REVOKED, &key->flags))
338 if (key->expiry && now.tv_sec >= key->expiry)
341 /* keys that don't match */
342 if (!match(key, description))
345 /* key must have search permissions */
346 if (key_task_permission(make_key_ref(key, possessed),
347 context, KEY_SEARCH) < 0)
350 /* we set a different error code if we find a negative key */
351 if (test_bit(KEY_FLAG_NEGATIVE, &key->flags)) {
359 /* search through the keyrings nested in this one */
362 for (; kix < keylist->nkeys; kix++) {
363 key = keylist->keys[kix];
364 if (key->type != &key_type_keyring)
367 /* recursively search nested keyrings
368 * - only search keyrings for which we have search permission
370 if (sp >= KEYRING_SEARCH_MAX_DEPTH)
373 if (key_task_permission(make_key_ref(key, possessed),
374 context, KEY_SEARCH) < 0)
377 /* stack the current position */
378 stack[sp].keylist = keylist;
382 /* begin again with the new keyring */
387 /* the keyring we're looking at was disqualified or didn't contain a
391 /* resume the processing of a keyring higher up in the tree */
393 keylist = stack[sp].keylist;
394 kix = stack[sp].kix + 1;
398 key_ref = ERR_PTR(err);
401 /* we found a viable match */
403 atomic_inc(&key->usage);
405 key_ref = make_key_ref(key, possessed);
411 } /* end keyring_search_aux() */
413 /*****************************************************************************/
415 * search the supplied keyring tree for a key that matches the criterion
416 * - perform a breadth-then-depth search up to the prescribed limit
417 * - we only find keys on which we have search permission
418 * - we readlock the keyrings as we search down the tree
419 * - we return -EAGAIN if we didn't find any matching key
420 * - we return -ENOKEY if we only found negative matching keys
422 key_ref_t keyring_search(key_ref_t keyring,
423 struct key_type *type,
424 const char *description)
427 return ERR_PTR(-ENOKEY);
429 return keyring_search_aux(keyring, current,
430 type, description, type->match);
432 } /* end keyring_search() */
434 EXPORT_SYMBOL(keyring_search);
436 /*****************************************************************************/
438 * search the given keyring only (no recursion)
439 * - keyring must be locked by caller
441 key_ref_t __keyring_search_one(key_ref_t keyring_ref,
442 const struct key_type *ktype,
443 const char *description,
446 struct keyring_list *klist;
447 unsigned long possessed;
448 struct key *keyring, *key;
451 keyring = key_ref_to_ptr(keyring_ref);
452 possessed = is_key_possessed(keyring_ref);
456 klist = rcu_dereference(keyring->payload.subscriptions);
458 for (loop = 0; loop < klist->nkeys; loop++) {
459 key = klist->keys[loop];
461 if (key->type == ktype &&
462 (!key->type->match ||
463 key->type->match(key, description)) &&
464 key_permission(make_key_ref(key, possessed),
466 !test_bit(KEY_FLAG_REVOKED, &key->flags)
473 return ERR_PTR(-ENOKEY);
476 atomic_inc(&key->usage);
478 return make_key_ref(key, possessed);
480 } /* end __keyring_search_one() */
482 /*****************************************************************************/
484 * search for an instantiation authorisation key matching a target key
485 * - the RCU read lock must be held by the caller
486 * - a target_id of zero specifies any valid token
488 struct key *keyring_search_instkey(struct key *keyring,
489 key_serial_t target_id)
491 struct request_key_auth *rka;
492 struct keyring_list *klist;
496 klist = rcu_dereference(keyring->payload.subscriptions);
498 for (loop = 0; loop < klist->nkeys; loop++) {
499 instkey = klist->keys[loop];
501 if (instkey->type != &key_type_request_key_auth)
504 rka = instkey->payload.data;
505 if (target_id && rka->target_key->serial != target_id)
508 /* the auth key is revoked during instantiation */
509 if (!test_bit(KEY_FLAG_REVOKED, &instkey->flags))
512 instkey = ERR_PTR(-EKEYREVOKED);
517 instkey = ERR_PTR(-EACCES);
521 atomic_inc(&instkey->usage);
525 } /* end keyring_search_instkey() */
527 /*****************************************************************************/
529 * find a keyring with the specified name
530 * - all named keyrings are searched
531 * - only find keyrings with search permission for the process
532 * - only find keyrings with a serial number greater than the one specified
534 struct key *find_keyring_by_name(const char *name, key_serial_t bound)
539 keyring = ERR_PTR(-EINVAL);
543 bucket = keyring_hash(name);
545 read_lock(&keyring_name_lock);
547 if (keyring_name_hash[bucket].next) {
548 /* search this hash bucket for a keyring with a matching name
549 * that's readable and that hasn't been revoked */
550 list_for_each_entry(keyring,
551 &keyring_name_hash[bucket],
554 if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
557 if (strcmp(keyring->description, name) != 0)
560 if (key_permission(make_key_ref(keyring, 0),
564 /* found a potential candidate, but we still need to
565 * check the serial number */
566 if (keyring->serial <= bound)
569 /* we've got a match */
570 atomic_inc(&keyring->usage);
571 read_unlock(&keyring_name_lock);
576 read_unlock(&keyring_name_lock);
577 keyring = ERR_PTR(-ENOKEY);
582 } /* end find_keyring_by_name() */
584 /*****************************************************************************/
586 * see if a cycle will will be created by inserting acyclic tree B in acyclic
587 * tree A at the topmost level (ie: as a direct child of A)
588 * - since we are adding B to A at the top level, checking for cycles should
589 * just be a matter of seeing if node A is somewhere in tree B
591 static int keyring_detect_cycle(struct key *A, struct key *B)
594 struct keyring_list *keylist;
596 } stack[KEYRING_SEARCH_MAX_DEPTH];
598 struct keyring_list *keylist;
599 struct key *subtree, *key;
611 /* start processing a new keyring */
613 if (test_bit(KEY_FLAG_REVOKED, &subtree->flags))
614 goto not_this_keyring;
616 keylist = rcu_dereference(subtree->payload.subscriptions);
618 goto not_this_keyring;
622 /* iterate through the remaining keys in this keyring */
623 for (; kix < keylist->nkeys; kix++) {
624 key = keylist->keys[kix];
629 /* recursively check nested keyrings */
630 if (key->type == &key_type_keyring) {
631 if (sp >= KEYRING_SEARCH_MAX_DEPTH)
634 /* stack the current position */
635 stack[sp].keylist = keylist;
639 /* begin again with the new keyring */
645 /* the keyring we're looking at was disqualified or didn't contain a
649 /* resume the checking of a keyring higher up in the tree */
651 keylist = stack[sp].keylist;
652 kix = stack[sp].kix + 1;
656 ret = 0; /* no cycles detected */
670 } /* end keyring_detect_cycle() */
672 /*****************************************************************************/
674 * dispose of a keyring list after the RCU grace period
676 static void keyring_link_rcu_disposal(struct rcu_head *rcu)
678 struct keyring_list *klist =
679 container_of(rcu, struct keyring_list, rcu);
683 } /* end keyring_link_rcu_disposal() */
685 /*****************************************************************************/
687 * link a key into to a keyring
688 * - must be called with the keyring's semaphore write-locked
690 int __key_link(struct key *keyring, struct key *key)
692 struct keyring_list *klist, *nklist;
698 if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
702 if (keyring->type != &key_type_keyring)
705 /* serialise link/link calls to prevent parallel calls causing a
706 * cycle when applied to two keyring in opposite orders */
707 down_write(&keyring_serialise_link_sem);
709 /* check that we aren't going to create a cycle adding one keyring to
711 if (key->type == &key_type_keyring) {
712 ret = keyring_detect_cycle(keyring, key);
717 /* check that we aren't going to overrun the user's quota */
718 ret = key_payload_reserve(keyring,
719 keyring->datalen + KEYQUOTA_LINK_BYTES);
723 klist = keyring->payload.subscriptions;
725 if (klist && klist->nkeys < klist->maxkeys) {
726 /* there's sufficient slack space to add directly */
727 atomic_inc(&key->usage);
729 klist->keys[klist->nkeys] = key;
737 /* grow the key list */
740 max += klist->maxkeys;
745 size = sizeof(*klist) + sizeof(struct key *) * max;
746 if (size > PAGE_SIZE)
750 nklist = kmalloc(size, GFP_KERNEL);
753 nklist->maxkeys = max;
757 nklist->nkeys = klist->nkeys;
760 sizeof(struct key *) * klist->nkeys);
763 /* add the key into the new space */
764 atomic_inc(&key->usage);
765 nklist->keys[nklist->nkeys++] = key;
767 rcu_assign_pointer(keyring->payload.subscriptions, nklist);
769 /* dispose of the old keyring list */
771 call_rcu(&klist->rcu, keyring_link_rcu_disposal);
777 up_write(&keyring_serialise_link_sem);
782 /* undo the quota changes */
783 key_payload_reserve(keyring,
784 keyring->datalen - KEYQUOTA_LINK_BYTES);
787 } /* end __key_link() */
789 /*****************************************************************************/
791 * link a key to a keyring
793 int key_link(struct key *keyring, struct key *key)
800 down_write(&keyring->sem);
801 ret = __key_link(keyring, key);
802 up_write(&keyring->sem);
806 } /* end key_link() */
808 EXPORT_SYMBOL(key_link);
810 /*****************************************************************************/
812 * dispose of a keyring list after the RCU grace period, freeing the unlinked
815 static void keyring_unlink_rcu_disposal(struct rcu_head *rcu)
817 struct keyring_list *klist =
818 container_of(rcu, struct keyring_list, rcu);
820 key_put(klist->keys[klist->delkey]);
823 } /* end keyring_unlink_rcu_disposal() */
825 /*****************************************************************************/
827 * unlink the first link to a key from a keyring
829 int key_unlink(struct key *keyring, struct key *key)
831 struct keyring_list *klist, *nklist;
838 if (keyring->type != &key_type_keyring)
841 down_write(&keyring->sem);
843 klist = keyring->payload.subscriptions;
845 /* search the keyring for the key */
846 for (loop = 0; loop < klist->nkeys; loop++)
847 if (klist->keys[loop] == key)
851 up_write(&keyring->sem);
856 /* we need to copy the key list for RCU purposes */
857 nklist = kmalloc(sizeof(*klist) +
858 sizeof(struct key *) * klist->maxkeys,
862 nklist->maxkeys = klist->maxkeys;
863 nklist->nkeys = klist->nkeys - 1;
866 memcpy(&nklist->keys[0],
868 loop * sizeof(struct key *));
870 if (loop < nklist->nkeys)
871 memcpy(&nklist->keys[loop],
872 &klist->keys[loop + 1],
873 (nklist->nkeys - loop) * sizeof(struct key *));
875 /* adjust the user's quota */
876 key_payload_reserve(keyring,
877 keyring->datalen - KEYQUOTA_LINK_BYTES);
879 rcu_assign_pointer(keyring->payload.subscriptions, nklist);
881 up_write(&keyring->sem);
883 /* schedule for later cleanup */
884 klist->delkey = loop;
885 call_rcu(&klist->rcu, keyring_unlink_rcu_disposal);
893 up_write(&keyring->sem);
896 } /* end key_unlink() */
898 EXPORT_SYMBOL(key_unlink);
900 /*****************************************************************************/
902 * dispose of a keyring list after the RCU grace period, releasing the keys it
905 static void keyring_clear_rcu_disposal(struct rcu_head *rcu)
907 struct keyring_list *klist;
910 klist = container_of(rcu, struct keyring_list, rcu);
912 for (loop = klist->nkeys - 1; loop >= 0; loop--)
913 key_put(klist->keys[loop]);
917 } /* end keyring_clear_rcu_disposal() */
919 /*****************************************************************************/
921 * clear the specified process keyring
922 * - implements keyctl(KEYCTL_CLEAR)
924 int keyring_clear(struct key *keyring)
926 struct keyring_list *klist;
930 if (keyring->type == &key_type_keyring) {
931 /* detach the pointer block with the locks held */
932 down_write(&keyring->sem);
934 klist = keyring->payload.subscriptions;
936 /* adjust the quota */
937 key_payload_reserve(keyring,
938 sizeof(struct keyring_list));
940 rcu_assign_pointer(keyring->payload.subscriptions,
944 up_write(&keyring->sem);
946 /* free the keys after the locks have been dropped */
948 call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
955 } /* end keyring_clear() */
957 EXPORT_SYMBOL(keyring_clear);