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 static 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
440 * - caller must guarantee that the keyring is a keyring
442 key_ref_t
__keyring_search_one(key_ref_t keyring_ref
,
443 const struct key_type
*ktype
,
444 const char *description
,
447 struct keyring_list
*klist
;
448 unsigned long possessed
;
449 struct key
*keyring
, *key
;
452 keyring
= key_ref_to_ptr(keyring_ref
);
453 possessed
= is_key_possessed(keyring_ref
);
457 klist
= rcu_dereference(keyring
->payload
.subscriptions
);
459 for (loop
= 0; loop
< klist
->nkeys
; loop
++) {
460 key
= klist
->keys
[loop
];
462 if (key
->type
== ktype
&&
463 (!key
->type
->match
||
464 key
->type
->match(key
, description
)) &&
465 key_permission(make_key_ref(key
, possessed
),
467 !test_bit(KEY_FLAG_REVOKED
, &key
->flags
)
474 return ERR_PTR(-ENOKEY
);
477 atomic_inc(&key
->usage
);
479 return make_key_ref(key
, possessed
);
481 } /* end __keyring_search_one() */
483 /*****************************************************************************/
485 * find a keyring with the specified name
486 * - all named keyrings are searched
487 * - only find keyrings with search permission for the process
488 * - only find keyrings with a serial number greater than the one specified
490 struct key
*find_keyring_by_name(const char *name
, key_serial_t bound
)
495 keyring
= ERR_PTR(-EINVAL
);
499 bucket
= keyring_hash(name
);
501 read_lock(&keyring_name_lock
);
503 if (keyring_name_hash
[bucket
].next
) {
504 /* search this hash bucket for a keyring with a matching name
505 * that's readable and that hasn't been revoked */
506 list_for_each_entry(keyring
,
507 &keyring_name_hash
[bucket
],
510 if (test_bit(KEY_FLAG_REVOKED
, &keyring
->flags
))
513 if (strcmp(keyring
->description
, name
) != 0)
516 if (key_permission(make_key_ref(keyring
, 0),
520 /* found a potential candidate, but we still need to
521 * check the serial number */
522 if (keyring
->serial
<= bound
)
525 /* we've got a match */
526 atomic_inc(&keyring
->usage
);
527 read_unlock(&keyring_name_lock
);
532 read_unlock(&keyring_name_lock
);
533 keyring
= ERR_PTR(-ENOKEY
);
538 } /* end find_keyring_by_name() */
540 /*****************************************************************************/
542 * see if a cycle will will be created by inserting acyclic tree B in acyclic
543 * tree A at the topmost level (ie: as a direct child of A)
544 * - since we are adding B to A at the top level, checking for cycles should
545 * just be a matter of seeing if node A is somewhere in tree B
547 static int keyring_detect_cycle(struct key
*A
, struct key
*B
)
550 struct keyring_list
*keylist
;
552 } stack
[KEYRING_SEARCH_MAX_DEPTH
];
554 struct keyring_list
*keylist
;
555 struct key
*subtree
, *key
;
567 /* start processing a new keyring */
569 if (test_bit(KEY_FLAG_REVOKED
, &subtree
->flags
))
570 goto not_this_keyring
;
572 keylist
= rcu_dereference(subtree
->payload
.subscriptions
);
574 goto not_this_keyring
;
578 /* iterate through the remaining keys in this keyring */
579 for (; kix
< keylist
->nkeys
; kix
++) {
580 key
= keylist
->keys
[kix
];
585 /* recursively check nested keyrings */
586 if (key
->type
== &key_type_keyring
) {
587 if (sp
>= KEYRING_SEARCH_MAX_DEPTH
)
590 /* stack the current position */
591 stack
[sp
].keylist
= keylist
;
595 /* begin again with the new keyring */
601 /* the keyring we're looking at was disqualified or didn't contain a
605 /* resume the checking of a keyring higher up in the tree */
607 keylist
= stack
[sp
].keylist
;
608 kix
= stack
[sp
].kix
+ 1;
612 ret
= 0; /* no cycles detected */
626 } /* end keyring_detect_cycle() */
628 /*****************************************************************************/
630 * dispose of a keyring list after the RCU grace period
632 static void keyring_link_rcu_disposal(struct rcu_head
*rcu
)
634 struct keyring_list
*klist
=
635 container_of(rcu
, struct keyring_list
, rcu
);
639 } /* end keyring_link_rcu_disposal() */
641 /*****************************************************************************/
643 * dispose of a keyring list after the RCU grace period, freeing the unlinked
646 static void keyring_unlink_rcu_disposal(struct rcu_head
*rcu
)
648 struct keyring_list
*klist
=
649 container_of(rcu
, struct keyring_list
, rcu
);
651 key_put(klist
->keys
[klist
->delkey
]);
654 } /* end keyring_unlink_rcu_disposal() */
656 /*****************************************************************************/
658 * link a key into to a keyring
659 * - must be called with the keyring's semaphore write-locked
660 * - discard already extant link to matching key if there is one
662 int __key_link(struct key
*keyring
, struct key
*key
)
664 struct keyring_list
*klist
, *nklist
;
670 if (test_bit(KEY_FLAG_REVOKED
, &keyring
->flags
))
674 if (keyring
->type
!= &key_type_keyring
)
677 /* serialise link/link calls to prevent parallel calls causing a
678 * cycle when applied to two keyring in opposite orders */
679 down_write(&keyring_serialise_link_sem
);
681 /* check that we aren't going to create a cycle adding one keyring to
683 if (key
->type
== &key_type_keyring
) {
684 ret
= keyring_detect_cycle(keyring
, key
);
689 /* see if there's a matching key we can displace */
690 klist
= keyring
->payload
.subscriptions
;
692 if (klist
&& klist
->nkeys
> 0) {
693 struct key_type
*type
= key
->type
;
695 for (loop
= klist
->nkeys
- 1; loop
>= 0; loop
--) {
696 if (klist
->keys
[loop
]->type
== type
&&
697 strcmp(klist
->keys
[loop
]->description
,
698 key
->description
) == 0
700 /* found a match - replace with new key */
701 size
= sizeof(struct key
*) * klist
->maxkeys
;
702 size
+= sizeof(*klist
);
703 BUG_ON(size
> PAGE_SIZE
);
706 nklist
= kmalloc(size
, GFP_KERNEL
);
710 memcpy(nklist
, klist
, size
);
712 /* replace matched key */
713 atomic_inc(&key
->usage
);
714 nklist
->keys
[loop
] = key
;
717 keyring
->payload
.subscriptions
,
720 /* dispose of the old keyring list and the
722 klist
->delkey
= loop
;
723 call_rcu(&klist
->rcu
,
724 keyring_unlink_rcu_disposal
);
731 /* check that we aren't going to overrun the user's quota */
732 ret
= key_payload_reserve(keyring
,
733 keyring
->datalen
+ KEYQUOTA_LINK_BYTES
);
737 klist
= keyring
->payload
.subscriptions
;
739 if (klist
&& klist
->nkeys
< klist
->maxkeys
) {
740 /* there's sufficient slack space to add directly */
741 atomic_inc(&key
->usage
);
743 klist
->keys
[klist
->nkeys
] = key
;
749 /* grow the key list */
752 max
+= klist
->maxkeys
;
757 size
= sizeof(*klist
) + sizeof(struct key
*) * max
;
758 if (size
> PAGE_SIZE
)
762 nklist
= kmalloc(size
, GFP_KERNEL
);
765 nklist
->maxkeys
= max
;
769 nklist
->nkeys
= klist
->nkeys
;
772 sizeof(struct key
*) * klist
->nkeys
);
775 /* add the key into the new space */
776 atomic_inc(&key
->usage
);
777 nklist
->keys
[nklist
->nkeys
++] = key
;
779 rcu_assign_pointer(keyring
->payload
.subscriptions
, nklist
);
781 /* dispose of the old keyring list */
783 call_rcu(&klist
->rcu
, keyring_link_rcu_disposal
);
789 up_write(&keyring_serialise_link_sem
);
794 /* undo the quota changes */
795 key_payload_reserve(keyring
,
796 keyring
->datalen
- KEYQUOTA_LINK_BYTES
);
799 } /* end __key_link() */
801 /*****************************************************************************/
803 * link a key to a keyring
805 int key_link(struct key
*keyring
, struct key
*key
)
812 down_write(&keyring
->sem
);
813 ret
= __key_link(keyring
, key
);
814 up_write(&keyring
->sem
);
818 } /* end key_link() */
820 EXPORT_SYMBOL(key_link
);
822 /*****************************************************************************/
824 * unlink the first link to a key from a keyring
826 int key_unlink(struct key
*keyring
, struct key
*key
)
828 struct keyring_list
*klist
, *nklist
;
835 if (keyring
->type
!= &key_type_keyring
)
838 down_write(&keyring
->sem
);
840 klist
= keyring
->payload
.subscriptions
;
842 /* search the keyring for the key */
843 for (loop
= 0; loop
< klist
->nkeys
; loop
++)
844 if (klist
->keys
[loop
] == key
)
848 up_write(&keyring
->sem
);
853 /* we need to copy the key list for RCU purposes */
854 nklist
= kmalloc(sizeof(*klist
) +
855 sizeof(struct key
*) * klist
->maxkeys
,
859 nklist
->maxkeys
= klist
->maxkeys
;
860 nklist
->nkeys
= klist
->nkeys
- 1;
863 memcpy(&nklist
->keys
[0],
865 loop
* sizeof(struct key
*));
867 if (loop
< nklist
->nkeys
)
868 memcpy(&nklist
->keys
[loop
],
869 &klist
->keys
[loop
+ 1],
870 (nklist
->nkeys
- loop
) * sizeof(struct key
*));
872 /* adjust the user's quota */
873 key_payload_reserve(keyring
,
874 keyring
->datalen
- KEYQUOTA_LINK_BYTES
);
876 rcu_assign_pointer(keyring
->payload
.subscriptions
, nklist
);
878 up_write(&keyring
->sem
);
880 /* schedule for later cleanup */
881 klist
->delkey
= loop
;
882 call_rcu(&klist
->rcu
, keyring_unlink_rcu_disposal
);
890 up_write(&keyring
->sem
);
893 } /* end key_unlink() */
895 EXPORT_SYMBOL(key_unlink
);
897 /*****************************************************************************/
899 * dispose of a keyring list after the RCU grace period, releasing the keys it
902 static void keyring_clear_rcu_disposal(struct rcu_head
*rcu
)
904 struct keyring_list
*klist
;
907 klist
= container_of(rcu
, struct keyring_list
, rcu
);
909 for (loop
= klist
->nkeys
- 1; loop
>= 0; loop
--)
910 key_put(klist
->keys
[loop
]);
914 } /* end keyring_clear_rcu_disposal() */
916 /*****************************************************************************/
918 * clear the specified process keyring
919 * - implements keyctl(KEYCTL_CLEAR)
921 int keyring_clear(struct key
*keyring
)
923 struct keyring_list
*klist
;
927 if (keyring
->type
== &key_type_keyring
) {
928 /* detach the pointer block with the locks held */
929 down_write(&keyring
->sem
);
931 klist
= keyring
->payload
.subscriptions
;
933 /* adjust the quota */
934 key_payload_reserve(keyring
,
935 sizeof(struct keyring_list
));
937 rcu_assign_pointer(keyring
->payload
.subscriptions
,
941 up_write(&keyring
->sem
);
943 /* free the keys after the locks have been dropped */
945 call_rcu(&klist
->rcu
, keyring_clear_rcu_disposal
);
952 } /* end keyring_clear() */
954 EXPORT_SYMBOL(keyring_clear
);