1 /* Basic authentication token and access key management
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.
12 #include <linux/module.h>
13 #include <linux/init.h>
14 #include <linux/poison.h>
15 #include <linux/sched.h>
16 #include <linux/slab.h>
17 #include <linux/security.h>
18 #include <linux/workqueue.h>
19 #include <linux/random.h>
20 #include <linux/err.h>
23 static struct kmem_cache *key_jar;
24 struct rb_root key_serial_tree; /* tree of keys indexed by serial */
25 DEFINE_SPINLOCK(key_serial_lock);
27 struct rb_root key_user_tree; /* tree of quota records indexed by UID */
28 DEFINE_SPINLOCK(key_user_lock);
30 static LIST_HEAD(key_types_list);
31 static DECLARE_RWSEM(key_types_sem);
33 static void key_cleanup(struct work_struct *work);
34 static DECLARE_WORK(key_cleanup_task, key_cleanup);
36 /* we serialise key instantiation and link */
37 DEFINE_MUTEX(key_construction_mutex);
39 /* any key who's type gets unegistered will be re-typed to this */
40 static struct key_type key_type_dead = {
45 void __key_check(const struct key *key)
47 printk("__key_check: key %p {%08x} should be {%08x}\n",
48 key, key->magic, KEY_DEBUG_MAGIC);
53 /*****************************************************************************/
55 * get the key quota record for a user, allocating a new record if one doesn't
58 struct key_user *key_user_lookup(uid_t uid)
60 struct key_user *candidate = NULL, *user;
61 struct rb_node *parent = NULL;
65 p = &key_user_tree.rb_node;
66 spin_lock(&key_user_lock);
68 /* search the tree for a user record with a matching UID */
71 user = rb_entry(parent, struct key_user, node);
75 else if (uid > user->uid)
81 /* if we get here, we failed to find a match in the tree */
83 /* allocate a candidate user record if we don't already have
85 spin_unlock(&key_user_lock);
88 candidate = kmalloc(sizeof(struct key_user), GFP_KERNEL);
89 if (unlikely(!candidate))
92 /* the allocation may have scheduled, so we need to repeat the
93 * search lest someone else added the record whilst we were
98 /* if we get here, then the user record still hadn't appeared on the
99 * second pass - so we use the candidate record */
100 atomic_set(&candidate->usage, 1);
101 atomic_set(&candidate->nkeys, 0);
102 atomic_set(&candidate->nikeys, 0);
103 candidate->uid = uid;
104 candidate->qnkeys = 0;
105 candidate->qnbytes = 0;
106 spin_lock_init(&candidate->lock);
107 mutex_init(&candidate->cons_lock);
109 rb_link_node(&candidate->node, parent, p);
110 rb_insert_color(&candidate->node, &key_user_tree);
111 spin_unlock(&key_user_lock);
115 /* okay - we found a user record for this UID */
117 atomic_inc(&user->usage);
118 spin_unlock(&key_user_lock);
123 } /* end key_user_lookup() */
125 /*****************************************************************************/
127 * dispose of a user structure
129 void key_user_put(struct key_user *user)
131 if (atomic_dec_and_lock(&user->usage, &key_user_lock)) {
132 rb_erase(&user->node, &key_user_tree);
133 spin_unlock(&key_user_lock);
138 } /* end key_user_put() */
140 /*****************************************************************************/
142 * insert a key with a fixed serial number
144 static void __init __key_insert_serial(struct key *key)
146 struct rb_node *parent, **p;
150 p = &key_serial_tree.rb_node;
154 xkey = rb_entry(parent, struct key, serial_node);
156 if (key->serial < xkey->serial)
158 else if (key->serial > xkey->serial)
164 /* we've found a suitable hole - arrange for this key to occupy it */
165 rb_link_node(&key->serial_node, parent, p);
166 rb_insert_color(&key->serial_node, &key_serial_tree);
168 } /* end __key_insert_serial() */
170 /*****************************************************************************/
172 * assign a key the next unique serial number
173 * - these are assigned randomly to avoid security issues through covert
176 static inline void key_alloc_serial(struct key *key)
178 struct rb_node *parent, **p;
181 /* propose a random serial number and look for a hole for it in the
182 * serial number tree */
184 get_random_bytes(&key->serial, sizeof(key->serial));
186 key->serial >>= 1; /* negative numbers are not permitted */
187 } while (key->serial < 3);
189 spin_lock(&key_serial_lock);
193 p = &key_serial_tree.rb_node;
197 xkey = rb_entry(parent, struct key, serial_node);
199 if (key->serial < xkey->serial)
201 else if (key->serial > xkey->serial)
207 /* we've found a suitable hole - arrange for this key to occupy it */
208 rb_link_node(&key->serial_node, parent, p);
209 rb_insert_color(&key->serial_node, &key_serial_tree);
211 spin_unlock(&key_serial_lock);
214 /* we found a key with the proposed serial number - walk the tree from
215 * that point looking for the next unused serial number */
219 if (key->serial < 3) {
221 goto attempt_insertion;
224 parent = rb_next(parent);
226 goto attempt_insertion;
228 xkey = rb_entry(parent, struct key, serial_node);
229 if (key->serial < xkey->serial)
230 goto attempt_insertion;
233 } /* end key_alloc_serial() */
235 /*****************************************************************************/
237 * allocate a key of the specified type
238 * - update the user's quota to reflect the existence of the key
239 * - called from a key-type operation with key_types_sem read-locked by
240 * key_create_or_update()
241 * - this prevents unregistration of the key type
242 * - upon return the key is as yet uninstantiated; the caller needs to either
243 * instantiate the key or discard it before returning
245 struct key *key_alloc(struct key_type *type, const char *desc,
246 uid_t uid, gid_t gid, struct task_struct *ctx,
247 key_perm_t perm, unsigned long flags)
249 struct key_user *user = NULL;
251 size_t desclen, quotalen;
254 key = ERR_PTR(-EINVAL);
258 desclen = strlen(desc) + 1;
259 quotalen = desclen + type->def_datalen;
261 /* get hold of the key tracking for this user */
262 user = key_user_lookup(uid);
266 /* check that the user's quota permits allocation of another key and
268 if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
269 spin_lock(&user->lock);
270 if (!(flags & KEY_ALLOC_QUOTA_OVERRUN)) {
271 if (user->qnkeys + 1 >= KEYQUOTA_MAX_KEYS ||
272 user->qnbytes + quotalen >= KEYQUOTA_MAX_BYTES
278 user->qnbytes += quotalen;
279 spin_unlock(&user->lock);
282 /* allocate and initialise the key and its description */
283 key = kmem_cache_alloc(key_jar, GFP_KERNEL);
288 key->description = kmemdup(desc, desclen, GFP_KERNEL);
289 if (!key->description)
293 atomic_set(&key->usage, 1);
294 init_rwsem(&key->sem);
297 key->quotalen = quotalen;
298 key->datalen = type->def_datalen;
304 key->payload.data = NULL;
305 key->security = NULL;
307 if (!(flags & KEY_ALLOC_NOT_IN_QUOTA))
308 key->flags |= 1 << KEY_FLAG_IN_QUOTA;
310 memset(&key->type_data, 0, sizeof(key->type_data));
313 key->magic = KEY_DEBUG_MAGIC;
316 /* let the security module know about the key */
317 ret = security_key_alloc(key, ctx, flags);
321 /* publish the key by giving it a serial number */
322 atomic_inc(&user->nkeys);
323 key_alloc_serial(key);
329 kfree(key->description);
330 kmem_cache_free(key_jar, key);
331 if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
332 spin_lock(&user->lock);
334 user->qnbytes -= quotalen;
335 spin_unlock(&user->lock);
342 kmem_cache_free(key_jar, key);
344 if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
345 spin_lock(&user->lock);
347 user->qnbytes -= quotalen;
348 spin_unlock(&user->lock);
352 key = ERR_PTR(-ENOMEM);
356 spin_unlock(&user->lock);
358 key = ERR_PTR(-EDQUOT);
361 } /* end key_alloc() */
363 EXPORT_SYMBOL(key_alloc);
365 /*****************************************************************************/
367 * reserve an amount of quota for the key's payload
369 int key_payload_reserve(struct key *key, size_t datalen)
371 int delta = (int) datalen - key->datalen;
376 /* contemplate the quota adjustment */
377 if (delta != 0 && test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
378 spin_lock(&key->user->lock);
381 key->user->qnbytes + delta > KEYQUOTA_MAX_BYTES
386 key->user->qnbytes += delta;
387 key->quotalen += delta;
389 spin_unlock(&key->user->lock);
392 /* change the recorded data length if that didn't generate an error */
394 key->datalen = datalen;
398 } /* end key_payload_reserve() */
400 EXPORT_SYMBOL(key_payload_reserve);
402 /*****************************************************************************/
404 * instantiate a key and link it into the target keyring atomically
405 * - called with the target keyring's semaphore writelocked
407 static int __key_instantiate_and_link(struct key *key,
421 mutex_lock(&key_construction_mutex);
423 /* can't instantiate twice */
424 if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
425 /* instantiate the key */
426 ret = key->type->instantiate(key, data, datalen);
429 /* mark the key as being instantiated */
430 atomic_inc(&key->user->nikeys);
431 set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
433 if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
436 /* and link it into the destination keyring */
438 ret = __key_link(keyring, key);
440 /* disable the authorisation key */
446 mutex_unlock(&key_construction_mutex);
448 /* wake up anyone waiting for a key to be constructed */
450 wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
454 } /* end __key_instantiate_and_link() */
456 /*****************************************************************************/
458 * instantiate a key and link it into the target keyring atomically
460 int key_instantiate_and_link(struct key *key,
469 down_write(&keyring->sem);
471 ret = __key_instantiate_and_link(key, data, datalen, keyring, instkey);
474 up_write(&keyring->sem);
478 } /* end key_instantiate_and_link() */
480 EXPORT_SYMBOL(key_instantiate_and_link);
482 /*****************************************************************************/
484 * negatively instantiate a key and link it into the target keyring atomically
486 int key_negate_and_link(struct key *key,
501 down_write(&keyring->sem);
503 mutex_lock(&key_construction_mutex);
505 /* can't instantiate twice */
506 if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
507 /* mark the key as being negatively instantiated */
508 atomic_inc(&key->user->nikeys);
509 set_bit(KEY_FLAG_NEGATIVE, &key->flags);
510 set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
511 now = current_kernel_time();
512 key->expiry = now.tv_sec + timeout;
514 if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
519 /* and link it into the destination keyring */
521 ret = __key_link(keyring, key);
523 /* disable the authorisation key */
528 mutex_unlock(&key_construction_mutex);
531 up_write(&keyring->sem);
533 /* wake up anyone waiting for a key to be constructed */
535 wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
539 } /* end key_negate_and_link() */
541 EXPORT_SYMBOL(key_negate_and_link);
543 /*****************************************************************************/
545 * do cleaning up in process context so that we don't have to disable
546 * interrupts all over the place
548 static void key_cleanup(struct work_struct *work)
554 /* look for a dead key in the tree */
555 spin_lock(&key_serial_lock);
557 for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
558 key = rb_entry(_n, struct key, serial_node);
560 if (atomic_read(&key->usage) == 0)
564 spin_unlock(&key_serial_lock);
568 /* we found a dead key - once we've removed it from the tree, we can
570 rb_erase(&key->serial_node, &key_serial_tree);
571 spin_unlock(&key_serial_lock);
575 security_key_free(key);
577 /* deal with the user's key tracking and quota */
578 if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
579 spin_lock(&key->user->lock);
581 key->user->qnbytes -= key->quotalen;
582 spin_unlock(&key->user->lock);
585 atomic_dec(&key->user->nkeys);
586 if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
587 atomic_dec(&key->user->nikeys);
589 key_user_put(key->user);
591 /* now throw away the key memory */
592 if (key->type->destroy)
593 key->type->destroy(key);
595 kfree(key->description);
598 key->magic = KEY_DEBUG_MAGIC_X;
600 kmem_cache_free(key_jar, key);
602 /* there may, of course, be more than one key to destroy */
605 } /* end key_cleanup() */
607 /*****************************************************************************/
609 * dispose of a reference to a key
610 * - when all the references are gone, we schedule the cleanup task to come and
611 * pull it out of the tree in definite process context
613 void key_put(struct key *key)
618 if (atomic_dec_and_test(&key->usage))
619 schedule_work(&key_cleanup_task);
622 } /* end key_put() */
624 EXPORT_SYMBOL(key_put);
626 /*****************************************************************************/
628 * find a key by its serial number
630 struct key *key_lookup(key_serial_t id)
635 spin_lock(&key_serial_lock);
637 /* search the tree for the specified key */
638 n = key_serial_tree.rb_node;
640 key = rb_entry(n, struct key, serial_node);
642 if (id < key->serial)
644 else if (id > key->serial)
651 key = ERR_PTR(-ENOKEY);
655 /* pretend it doesn't exist if it's dead */
656 if (atomic_read(&key->usage) == 0 ||
657 test_bit(KEY_FLAG_DEAD, &key->flags) ||
658 key->type == &key_type_dead)
661 /* this races with key_put(), but that doesn't matter since key_put()
662 * doesn't actually change the key
664 atomic_inc(&key->usage);
667 spin_unlock(&key_serial_lock);
670 } /* end key_lookup() */
672 /*****************************************************************************/
674 * find and lock the specified key type against removal
675 * - we return with the sem readlocked
677 struct key_type *key_type_lookup(const char *type)
679 struct key_type *ktype;
681 down_read(&key_types_sem);
683 /* look up the key type to see if it's one of the registered kernel
685 list_for_each_entry(ktype, &key_types_list, link) {
686 if (strcmp(ktype->name, type) == 0)
687 goto found_kernel_type;
690 up_read(&key_types_sem);
691 ktype = ERR_PTR(-ENOKEY);
696 } /* end key_type_lookup() */
698 /*****************************************************************************/
702 void key_type_put(struct key_type *ktype)
704 up_read(&key_types_sem);
706 } /* end key_type_put() */
708 /*****************************************************************************/
710 * attempt to update an existing key
711 * - the key has an incremented refcount
712 * - we need to put the key if we get an error
714 static inline key_ref_t __key_update(key_ref_t key_ref,
715 const void *payload, size_t plen)
717 struct key *key = key_ref_to_ptr(key_ref);
720 /* need write permission on the key to update it */
721 ret = key_permission(key_ref, KEY_WRITE);
726 if (!key->type->update)
729 down_write(&key->sem);
731 ret = key->type->update(key, payload, plen);
733 /* updating a negative key instantiates it */
734 clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
745 key_ref = ERR_PTR(ret);
748 } /* end __key_update() */
750 /*****************************************************************************/
752 * search the specified keyring for a key of the same description; if one is
753 * found, update it, otherwise add a new one
755 key_ref_t key_create_or_update(key_ref_t keyring_ref,
757 const char *description,
763 struct key_type *ktype;
764 struct key *keyring, *key = NULL;
768 /* look up the key type to see if it's one of the registered kernel
770 ktype = key_type_lookup(type);
772 key_ref = ERR_PTR(-ENODEV);
776 key_ref = ERR_PTR(-EINVAL);
777 if (!ktype->match || !ktype->instantiate)
780 keyring = key_ref_to_ptr(keyring_ref);
784 key_ref = ERR_PTR(-ENOTDIR);
785 if (keyring->type != &key_type_keyring)
788 down_write(&keyring->sem);
790 /* if we're going to allocate a new key, we're going to have
791 * to modify the keyring */
792 ret = key_permission(keyring_ref, KEY_WRITE);
794 key_ref = ERR_PTR(ret);
798 /* if it's possible to update this type of key, search for an existing
799 * key of the same type and description in the destination keyring and
800 * update that instead if possible
803 key_ref = __keyring_search_one(keyring_ref, ktype, description,
805 if (!IS_ERR(key_ref))
806 goto found_matching_key;
809 /* if the client doesn't provide, decide on the permissions we want */
810 if (perm == KEY_PERM_UNDEF) {
811 perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
812 perm |= KEY_USR_VIEW | KEY_USR_SEARCH | KEY_USR_LINK | KEY_USR_SETATTR;
815 perm |= KEY_POS_READ | KEY_USR_READ;
817 if (ktype == &key_type_keyring || ktype->update)
818 perm |= KEY_USR_WRITE;
821 /* allocate a new key */
822 key = key_alloc(ktype, description, current->fsuid, current->fsgid,
823 current, perm, flags);
825 key_ref = ERR_CAST(key);
829 /* instantiate it and link it into the target keyring */
830 ret = __key_instantiate_and_link(key, payload, plen, keyring, NULL);
833 key_ref = ERR_PTR(ret);
837 key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
840 up_write(&keyring->sem);
847 /* we found a matching key, so we're going to try to update it
848 * - we can drop the locks first as we have the key pinned
850 up_write(&keyring->sem);
853 key_ref = __key_update(key_ref, payload, plen);
856 } /* end key_create_or_update() */
858 EXPORT_SYMBOL(key_create_or_update);
860 /*****************************************************************************/
864 int key_update(key_ref_t key_ref, const void *payload, size_t plen)
866 struct key *key = key_ref_to_ptr(key_ref);
871 /* the key must be writable */
872 ret = key_permission(key_ref, KEY_WRITE);
876 /* attempt to update it if supported */
878 if (key->type->update) {
879 down_write(&key->sem);
881 ret = key->type->update(key, payload, plen);
883 /* updating a negative key instantiates it */
884 clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
892 } /* end key_update() */
894 EXPORT_SYMBOL(key_update);
896 /*****************************************************************************/
900 void key_revoke(struct key *key)
904 /* make sure no one's trying to change or use the key when we mark it
905 * - we tell lockdep that we might nest because we might be revoking an
906 * authorisation key whilst holding the sem on a key we've just
909 down_write_nested(&key->sem, 1);
910 if (!test_and_set_bit(KEY_FLAG_REVOKED, &key->flags) &&
912 key->type->revoke(key);
916 } /* end key_revoke() */
918 EXPORT_SYMBOL(key_revoke);
920 /*****************************************************************************/
922 * register a type of key
924 int register_key_type(struct key_type *ktype)
930 down_write(&key_types_sem);
932 /* disallow key types with the same name */
933 list_for_each_entry(p, &key_types_list, link) {
934 if (strcmp(p->name, ktype->name) == 0)
939 list_add(&ktype->link, &key_types_list);
943 up_write(&key_types_sem);
946 } /* end register_key_type() */
948 EXPORT_SYMBOL(register_key_type);
950 /*****************************************************************************/
952 * unregister a type of key
954 void unregister_key_type(struct key_type *ktype)
959 down_write(&key_types_sem);
961 /* withdraw the key type */
962 list_del_init(&ktype->link);
964 /* mark all the keys of this type dead */
965 spin_lock(&key_serial_lock);
967 for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
968 key = rb_entry(_n, struct key, serial_node);
970 if (key->type == ktype)
971 key->type = &key_type_dead;
974 spin_unlock(&key_serial_lock);
976 /* make sure everyone revalidates their keys */
979 /* we should now be able to destroy the payloads of all the keys of
980 * this type with impunity */
981 spin_lock(&key_serial_lock);
983 for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
984 key = rb_entry(_n, struct key, serial_node);
986 if (key->type == ktype) {
989 memset(&key->payload, KEY_DESTROY, sizeof(key->payload));
993 spin_unlock(&key_serial_lock);
994 up_write(&key_types_sem);
996 } /* end unregister_key_type() */
998 EXPORT_SYMBOL(unregister_key_type);
1000 /*****************************************************************************/
1002 * initialise the key management stuff
1004 void __init key_init(void)
1006 /* allocate a slab in which we can store keys */
1007 key_jar = kmem_cache_create("key_jar", sizeof(struct key),
1008 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1010 /* add the special key types */
1011 list_add_tail(&key_type_keyring.link, &key_types_list);
1012 list_add_tail(&key_type_dead.link, &key_types_list);
1013 list_add_tail(&key_type_user.link, &key_types_list);
1015 /* record the root user tracking */
1016 rb_link_node(&root_key_user.node,
1018 &key_user_tree.rb_node);
1020 rb_insert_color(&root_key_user.node,
1023 /* record root's user standard keyrings */
1024 key_check(&root_user_keyring);
1025 key_check(&root_session_keyring);
1027 __key_insert_serial(&root_user_keyring);
1028 __key_insert_serial(&root_session_keyring);
1030 keyring_publish_name(&root_user_keyring);
1031 keyring_publish_name(&root_session_keyring);
1033 /* link the two root keyrings together */
1034 key_link(&root_session_keyring, &root_user_keyring);
1036 } /* end key_init() */