Loading...
1/* Keyring handling
2 *
3 * Copyright (C) 2004-2005, 2008 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
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.
10 */
11
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 <keys/keyring-type.h>
20#include <linux/uaccess.h>
21#include "internal.h"
22
23#define rcu_dereference_locked_keyring(keyring) \
24 (rcu_dereference_protected( \
25 (keyring)->payload.subscriptions, \
26 rwsem_is_locked((struct rw_semaphore *)&(keyring)->sem)))
27
28#define rcu_deref_link_locked(klist, index, keyring) \
29 (rcu_dereference_protected( \
30 (klist)->keys[index], \
31 rwsem_is_locked((struct rw_semaphore *)&(keyring)->sem)))
32
33#define MAX_KEYRING_LINKS \
34 min_t(size_t, USHRT_MAX - 1, \
35 ((PAGE_SIZE - sizeof(struct keyring_list)) / sizeof(struct key *)))
36
37#define KEY_LINK_FIXQUOTA 1UL
38
39/*
40 * When plumbing the depths of the key tree, this sets a hard limit
41 * set on how deep we're willing to go.
42 */
43#define KEYRING_SEARCH_MAX_DEPTH 6
44
45/*
46 * We keep all named keyrings in a hash to speed looking them up.
47 */
48#define KEYRING_NAME_HASH_SIZE (1 << 5)
49
50static struct list_head keyring_name_hash[KEYRING_NAME_HASH_SIZE];
51static DEFINE_RWLOCK(keyring_name_lock);
52
53static inline unsigned keyring_hash(const char *desc)
54{
55 unsigned bucket = 0;
56
57 for (; *desc; desc++)
58 bucket += (unsigned char)*desc;
59
60 return bucket & (KEYRING_NAME_HASH_SIZE - 1);
61}
62
63/*
64 * The keyring key type definition. Keyrings are simply keys of this type and
65 * can be treated as ordinary keys in addition to having their own special
66 * operations.
67 */
68static int keyring_instantiate(struct key *keyring,
69 const void *data, size_t datalen);
70static int keyring_match(const struct key *keyring, const void *criterion);
71static void keyring_revoke(struct key *keyring);
72static void keyring_destroy(struct key *keyring);
73static void keyring_describe(const struct key *keyring, struct seq_file *m);
74static long keyring_read(const struct key *keyring,
75 char __user *buffer, size_t buflen);
76
77struct key_type key_type_keyring = {
78 .name = "keyring",
79 .def_datalen = sizeof(struct keyring_list),
80 .instantiate = keyring_instantiate,
81 .match = keyring_match,
82 .revoke = keyring_revoke,
83 .destroy = keyring_destroy,
84 .describe = keyring_describe,
85 .read = keyring_read,
86};
87EXPORT_SYMBOL(key_type_keyring);
88
89/*
90 * Semaphore to serialise link/link calls to prevent two link calls in parallel
91 * introducing a cycle.
92 */
93static DECLARE_RWSEM(keyring_serialise_link_sem);
94
95/*
96 * Publish the name of a keyring so that it can be found by name (if it has
97 * one).
98 */
99static void keyring_publish_name(struct key *keyring)
100{
101 int bucket;
102
103 if (keyring->description) {
104 bucket = keyring_hash(keyring->description);
105
106 write_lock(&keyring_name_lock);
107
108 if (!keyring_name_hash[bucket].next)
109 INIT_LIST_HEAD(&keyring_name_hash[bucket]);
110
111 list_add_tail(&keyring->type_data.link,
112 &keyring_name_hash[bucket]);
113
114 write_unlock(&keyring_name_lock);
115 }
116}
117
118/*
119 * Initialise a keyring.
120 *
121 * Returns 0 on success, -EINVAL if given any data.
122 */
123static int keyring_instantiate(struct key *keyring,
124 const void *data, size_t datalen)
125{
126 int ret;
127
128 ret = -EINVAL;
129 if (datalen == 0) {
130 /* make the keyring available by name if it has one */
131 keyring_publish_name(keyring);
132 ret = 0;
133 }
134
135 return ret;
136}
137
138/*
139 * Match keyrings on their name
140 */
141static int keyring_match(const struct key *keyring, const void *description)
142{
143 return keyring->description &&
144 strcmp(keyring->description, description) == 0;
145}
146
147/*
148 * Clean up a keyring when it is destroyed. Unpublish its name if it had one
149 * and dispose of its data.
150 *
151 * The garbage collector detects the final key_put(), removes the keyring from
152 * the serial number tree and then does RCU synchronisation before coming here,
153 * so we shouldn't need to worry about code poking around here with the RCU
154 * readlock held by this time.
155 */
156static void keyring_destroy(struct key *keyring)
157{
158 struct keyring_list *klist;
159 int loop;
160
161 if (keyring->description) {
162 write_lock(&keyring_name_lock);
163
164 if (keyring->type_data.link.next != NULL &&
165 !list_empty(&keyring->type_data.link))
166 list_del(&keyring->type_data.link);
167
168 write_unlock(&keyring_name_lock);
169 }
170
171 klist = rcu_access_pointer(keyring->payload.subscriptions);
172 if (klist) {
173 for (loop = klist->nkeys - 1; loop >= 0; loop--)
174 key_put(rcu_access_pointer(klist->keys[loop]));
175 kfree(klist);
176 }
177}
178
179/*
180 * Describe a keyring for /proc.
181 */
182static void keyring_describe(const struct key *keyring, struct seq_file *m)
183{
184 struct keyring_list *klist;
185
186 if (keyring->description)
187 seq_puts(m, keyring->description);
188 else
189 seq_puts(m, "[anon]");
190
191 if (key_is_instantiated(keyring)) {
192 rcu_read_lock();
193 klist = rcu_dereference(keyring->payload.subscriptions);
194 if (klist)
195 seq_printf(m, ": %u/%u", klist->nkeys, klist->maxkeys);
196 else
197 seq_puts(m, ": empty");
198 rcu_read_unlock();
199 }
200}
201
202/*
203 * Read a list of key IDs from the keyring's contents in binary form
204 *
205 * The keyring's semaphore is read-locked by the caller.
206 */
207static long keyring_read(const struct key *keyring,
208 char __user *buffer, size_t buflen)
209{
210 struct keyring_list *klist;
211 struct key *key;
212 size_t qty, tmp;
213 int loop, ret;
214
215 ret = 0;
216 klist = rcu_dereference_locked_keyring(keyring);
217 if (klist) {
218 /* calculate how much data we could return */
219 qty = klist->nkeys * sizeof(key_serial_t);
220
221 if (buffer && buflen > 0) {
222 if (buflen > qty)
223 buflen = qty;
224
225 /* copy the IDs of the subscribed keys into the
226 * buffer */
227 ret = -EFAULT;
228
229 for (loop = 0; loop < klist->nkeys; loop++) {
230 key = rcu_deref_link_locked(klist, loop,
231 keyring);
232
233 tmp = sizeof(key_serial_t);
234 if (tmp > buflen)
235 tmp = buflen;
236
237 if (copy_to_user(buffer,
238 &key->serial,
239 tmp) != 0)
240 goto error;
241
242 buflen -= tmp;
243 if (buflen == 0)
244 break;
245 buffer += tmp;
246 }
247 }
248
249 ret = qty;
250 }
251
252error:
253 return ret;
254}
255
256/*
257 * Allocate a keyring and link into the destination keyring.
258 */
259struct key *keyring_alloc(const char *description, uid_t uid, gid_t gid,
260 const struct cred *cred, unsigned long flags,
261 struct key *dest)
262{
263 struct key *keyring;
264 int ret;
265
266 keyring = key_alloc(&key_type_keyring, description,
267 uid, gid, cred,
268 (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL,
269 flags);
270
271 if (!IS_ERR(keyring)) {
272 ret = key_instantiate_and_link(keyring, NULL, 0, dest, NULL);
273 if (ret < 0) {
274 key_put(keyring);
275 keyring = ERR_PTR(ret);
276 }
277 }
278
279 return keyring;
280}
281
282/**
283 * keyring_search_aux - Search a keyring tree for a key matching some criteria
284 * @keyring_ref: A pointer to the keyring with possession indicator.
285 * @cred: The credentials to use for permissions checks.
286 * @type: The type of key to search for.
287 * @description: Parameter for @match.
288 * @match: Function to rule on whether or not a key is the one required.
289 * @no_state_check: Don't check if a matching key is bad
290 *
291 * Search the supplied keyring tree for a key that matches the criteria given.
292 * The root keyring and any linked keyrings must grant Search permission to the
293 * caller to be searchable and keys can only be found if they too grant Search
294 * to the caller. The possession flag on the root keyring pointer controls use
295 * of the possessor bits in permissions checking of the entire tree. In
296 * addition, the LSM gets to forbid keyring searches and key matches.
297 *
298 * The search is performed as a breadth-then-depth search up to the prescribed
299 * limit (KEYRING_SEARCH_MAX_DEPTH).
300 *
301 * Keys are matched to the type provided and are then filtered by the match
302 * function, which is given the description to use in any way it sees fit. The
303 * match function may use any attributes of a key that it wishes to to
304 * determine the match. Normally the match function from the key type would be
305 * used.
306 *
307 * RCU is used to prevent the keyring key lists from disappearing without the
308 * need to take lots of locks.
309 *
310 * Returns a pointer to the found key and increments the key usage count if
311 * successful; -EAGAIN if no matching keys were found, or if expired or revoked
312 * keys were found; -ENOKEY if only negative keys were found; -ENOTDIR if the
313 * specified keyring wasn't a keyring.
314 *
315 * In the case of a successful return, the possession attribute from
316 * @keyring_ref is propagated to the returned key reference.
317 */
318key_ref_t keyring_search_aux(key_ref_t keyring_ref,
319 const struct cred *cred,
320 struct key_type *type,
321 const void *description,
322 key_match_func_t match,
323 bool no_state_check)
324{
325 struct {
326 /* Need a separate keylist pointer for RCU purposes */
327 struct key *keyring;
328 struct keyring_list *keylist;
329 int kix;
330 } stack[KEYRING_SEARCH_MAX_DEPTH];
331
332 struct keyring_list *keylist;
333 struct timespec now;
334 unsigned long possessed, kflags;
335 struct key *keyring, *key;
336 key_ref_t key_ref;
337 long err;
338 int sp, nkeys, kix;
339
340 keyring = key_ref_to_ptr(keyring_ref);
341 possessed = is_key_possessed(keyring_ref);
342 key_check(keyring);
343
344 /* top keyring must have search permission to begin the search */
345 err = key_task_permission(keyring_ref, cred, KEY_SEARCH);
346 if (err < 0) {
347 key_ref = ERR_PTR(err);
348 goto error;
349 }
350
351 key_ref = ERR_PTR(-ENOTDIR);
352 if (keyring->type != &key_type_keyring)
353 goto error;
354
355 rcu_read_lock();
356
357 now = current_kernel_time();
358 err = -EAGAIN;
359 sp = 0;
360
361 /* firstly we should check to see if this top-level keyring is what we
362 * are looking for */
363 key_ref = ERR_PTR(-EAGAIN);
364 kflags = keyring->flags;
365 if (keyring->type == type && match(keyring, description)) {
366 key = keyring;
367 if (no_state_check)
368 goto found;
369
370 /* check it isn't negative and hasn't expired or been
371 * revoked */
372 if (kflags & (1 << KEY_FLAG_REVOKED))
373 goto error_2;
374 if (key->expiry && now.tv_sec >= key->expiry)
375 goto error_2;
376 key_ref = ERR_PTR(key->type_data.reject_error);
377 if (kflags & (1 << KEY_FLAG_NEGATIVE))
378 goto error_2;
379 goto found;
380 }
381
382 /* otherwise, the top keyring must not be revoked, expired, or
383 * negatively instantiated if we are to search it */
384 key_ref = ERR_PTR(-EAGAIN);
385 if (kflags & ((1 << KEY_FLAG_INVALIDATED) |
386 (1 << KEY_FLAG_REVOKED) |
387 (1 << KEY_FLAG_NEGATIVE)) ||
388 (keyring->expiry && now.tv_sec >= keyring->expiry))
389 goto error_2;
390
391 /* start processing a new keyring */
392descend:
393 kflags = keyring->flags;
394 if (kflags & ((1 << KEY_FLAG_INVALIDATED) |
395 (1 << KEY_FLAG_REVOKED)))
396 goto not_this_keyring;
397
398 keylist = rcu_dereference(keyring->payload.subscriptions);
399 if (!keylist)
400 goto not_this_keyring;
401
402 /* iterate through the keys in this keyring first */
403 nkeys = keylist->nkeys;
404 smp_rmb();
405 for (kix = 0; kix < nkeys; kix++) {
406 key = rcu_dereference(keylist->keys[kix]);
407 kflags = key->flags;
408
409 /* ignore keys not of this type */
410 if (key->type != type)
411 continue;
412
413 /* skip invalidated, revoked and expired keys */
414 if (!no_state_check) {
415 if (kflags & ((1 << KEY_FLAG_INVALIDATED) |
416 (1 << KEY_FLAG_REVOKED)))
417 continue;
418
419 if (key->expiry && now.tv_sec >= key->expiry)
420 continue;
421 }
422
423 /* keys that don't match */
424 if (!match(key, description))
425 continue;
426
427 /* key must have search permissions */
428 if (key_task_permission(make_key_ref(key, possessed),
429 cred, KEY_SEARCH) < 0)
430 continue;
431
432 if (no_state_check)
433 goto found;
434
435 /* we set a different error code if we pass a negative key */
436 if (kflags & (1 << KEY_FLAG_NEGATIVE)) {
437 err = key->type_data.reject_error;
438 continue;
439 }
440
441 goto found;
442 }
443
444 /* search through the keyrings nested in this one */
445 kix = 0;
446ascend:
447 nkeys = keylist->nkeys;
448 smp_rmb();
449 for (; kix < nkeys; kix++) {
450 key = rcu_dereference(keylist->keys[kix]);
451 if (key->type != &key_type_keyring)
452 continue;
453
454 /* recursively search nested keyrings
455 * - only search keyrings for which we have search permission
456 */
457 if (sp >= KEYRING_SEARCH_MAX_DEPTH)
458 continue;
459
460 if (key_task_permission(make_key_ref(key, possessed),
461 cred, KEY_SEARCH) < 0)
462 continue;
463
464 /* stack the current position */
465 stack[sp].keyring = keyring;
466 stack[sp].keylist = keylist;
467 stack[sp].kix = kix;
468 sp++;
469
470 /* begin again with the new keyring */
471 keyring = key;
472 goto descend;
473 }
474
475 /* the keyring we're looking at was disqualified or didn't contain a
476 * matching key */
477not_this_keyring:
478 if (sp > 0) {
479 /* resume the processing of a keyring higher up in the tree */
480 sp--;
481 keyring = stack[sp].keyring;
482 keylist = stack[sp].keylist;
483 kix = stack[sp].kix + 1;
484 goto ascend;
485 }
486
487 key_ref = ERR_PTR(err);
488 goto error_2;
489
490 /* we found a viable match */
491found:
492 atomic_inc(&key->usage);
493 key->last_used_at = now.tv_sec;
494 keyring->last_used_at = now.tv_sec;
495 while (sp > 0)
496 stack[--sp].keyring->last_used_at = now.tv_sec;
497 key_check(key);
498 key_ref = make_key_ref(key, possessed);
499error_2:
500 rcu_read_unlock();
501error:
502 return key_ref;
503}
504
505/**
506 * keyring_search - Search the supplied keyring tree for a matching key
507 * @keyring: The root of the keyring tree to be searched.
508 * @type: The type of keyring we want to find.
509 * @description: The name of the keyring we want to find.
510 *
511 * As keyring_search_aux() above, but using the current task's credentials and
512 * type's default matching function.
513 */
514key_ref_t keyring_search(key_ref_t keyring,
515 struct key_type *type,
516 const char *description)
517{
518 if (!type->match)
519 return ERR_PTR(-ENOKEY);
520
521 return keyring_search_aux(keyring, current->cred,
522 type, description, type->match, false);
523}
524EXPORT_SYMBOL(keyring_search);
525
526/*
527 * Search the given keyring only (no recursion).
528 *
529 * The caller must guarantee that the keyring is a keyring and that the
530 * permission is granted to search the keyring as no check is made here.
531 *
532 * RCU is used to make it unnecessary to lock the keyring key list here.
533 *
534 * Returns a pointer to the found key with usage count incremented if
535 * successful and returns -ENOKEY if not found. Revoked keys and keys not
536 * providing the requested permission are skipped over.
537 *
538 * If successful, the possession indicator is propagated from the keyring ref
539 * to the returned key reference.
540 */
541key_ref_t __keyring_search_one(key_ref_t keyring_ref,
542 const struct key_type *ktype,
543 const char *description,
544 key_perm_t perm)
545{
546 struct keyring_list *klist;
547 unsigned long possessed;
548 struct key *keyring, *key;
549 int nkeys, loop;
550
551 keyring = key_ref_to_ptr(keyring_ref);
552 possessed = is_key_possessed(keyring_ref);
553
554 rcu_read_lock();
555
556 klist = rcu_dereference(keyring->payload.subscriptions);
557 if (klist) {
558 nkeys = klist->nkeys;
559 smp_rmb();
560 for (loop = 0; loop < nkeys ; loop++) {
561 key = rcu_dereference(klist->keys[loop]);
562 if (key->type == ktype &&
563 (!key->type->match ||
564 key->type->match(key, description)) &&
565 key_permission(make_key_ref(key, possessed),
566 perm) == 0 &&
567 !(key->flags & ((1 << KEY_FLAG_INVALIDATED) |
568 (1 << KEY_FLAG_REVOKED)))
569 )
570 goto found;
571 }
572 }
573
574 rcu_read_unlock();
575 return ERR_PTR(-ENOKEY);
576
577found:
578 atomic_inc(&key->usage);
579 keyring->last_used_at = key->last_used_at =
580 current_kernel_time().tv_sec;
581 rcu_read_unlock();
582 return make_key_ref(key, possessed);
583}
584
585/*
586 * Find a keyring with the specified name.
587 *
588 * All named keyrings in the current user namespace are searched, provided they
589 * grant Search permission directly to the caller (unless this check is
590 * skipped). Keyrings whose usage points have reached zero or who have been
591 * revoked are skipped.
592 *
593 * Returns a pointer to the keyring with the keyring's refcount having being
594 * incremented on success. -ENOKEY is returned if a key could not be found.
595 */
596struct key *find_keyring_by_name(const char *name, bool skip_perm_check)
597{
598 struct key *keyring;
599 int bucket;
600
601 if (!name)
602 return ERR_PTR(-EINVAL);
603
604 bucket = keyring_hash(name);
605
606 read_lock(&keyring_name_lock);
607
608 if (keyring_name_hash[bucket].next) {
609 /* search this hash bucket for a keyring with a matching name
610 * that's readable and that hasn't been revoked */
611 list_for_each_entry(keyring,
612 &keyring_name_hash[bucket],
613 type_data.link
614 ) {
615 if (keyring->user->user_ns != current_user_ns())
616 continue;
617
618 if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
619 continue;
620
621 if (strcmp(keyring->description, name) != 0)
622 continue;
623
624 if (!skip_perm_check &&
625 key_permission(make_key_ref(keyring, 0),
626 KEY_SEARCH) < 0)
627 continue;
628
629 /* we've got a match but we might end up racing with
630 * key_cleanup() if the keyring is currently 'dead'
631 * (ie. it has a zero usage count) */
632 if (!atomic_inc_not_zero(&keyring->usage))
633 continue;
634 keyring->last_used_at = current_kernel_time().tv_sec;
635 goto out;
636 }
637 }
638
639 keyring = ERR_PTR(-ENOKEY);
640out:
641 read_unlock(&keyring_name_lock);
642 return keyring;
643}
644
645/*
646 * See if a cycle will will be created by inserting acyclic tree B in acyclic
647 * tree A at the topmost level (ie: as a direct child of A).
648 *
649 * Since we are adding B to A at the top level, checking for cycles should just
650 * be a matter of seeing if node A is somewhere in tree B.
651 */
652static int keyring_detect_cycle(struct key *A, struct key *B)
653{
654 struct {
655 struct keyring_list *keylist;
656 int kix;
657 } stack[KEYRING_SEARCH_MAX_DEPTH];
658
659 struct keyring_list *keylist;
660 struct key *subtree, *key;
661 int sp, nkeys, kix, ret;
662
663 rcu_read_lock();
664
665 ret = -EDEADLK;
666 if (A == B)
667 goto cycle_detected;
668
669 subtree = B;
670 sp = 0;
671
672 /* start processing a new keyring */
673descend:
674 if (test_bit(KEY_FLAG_REVOKED, &subtree->flags))
675 goto not_this_keyring;
676
677 keylist = rcu_dereference(subtree->payload.subscriptions);
678 if (!keylist)
679 goto not_this_keyring;
680 kix = 0;
681
682ascend:
683 /* iterate through the remaining keys in this keyring */
684 nkeys = keylist->nkeys;
685 smp_rmb();
686 for (; kix < nkeys; kix++) {
687 key = rcu_dereference(keylist->keys[kix]);
688
689 if (key == A)
690 goto cycle_detected;
691
692 /* recursively check nested keyrings */
693 if (key->type == &key_type_keyring) {
694 if (sp >= KEYRING_SEARCH_MAX_DEPTH)
695 goto too_deep;
696
697 /* stack the current position */
698 stack[sp].keylist = keylist;
699 stack[sp].kix = kix;
700 sp++;
701
702 /* begin again with the new keyring */
703 subtree = key;
704 goto descend;
705 }
706 }
707
708 /* the keyring we're looking at was disqualified or didn't contain a
709 * matching key */
710not_this_keyring:
711 if (sp > 0) {
712 /* resume the checking of a keyring higher up in the tree */
713 sp--;
714 keylist = stack[sp].keylist;
715 kix = stack[sp].kix + 1;
716 goto ascend;
717 }
718
719 ret = 0; /* no cycles detected */
720
721error:
722 rcu_read_unlock();
723 return ret;
724
725too_deep:
726 ret = -ELOOP;
727 goto error;
728
729cycle_detected:
730 ret = -EDEADLK;
731 goto error;
732}
733
734/*
735 * Dispose of a keyring list after the RCU grace period, freeing the unlinked
736 * key
737 */
738static void keyring_unlink_rcu_disposal(struct rcu_head *rcu)
739{
740 struct keyring_list *klist =
741 container_of(rcu, struct keyring_list, rcu);
742
743 if (klist->delkey != USHRT_MAX)
744 key_put(rcu_access_pointer(klist->keys[klist->delkey]));
745 kfree(klist);
746}
747
748/*
749 * Preallocate memory so that a key can be linked into to a keyring.
750 */
751int __key_link_begin(struct key *keyring, const struct key_type *type,
752 const char *description, unsigned long *_prealloc)
753 __acquires(&keyring->sem)
754{
755 struct keyring_list *klist, *nklist;
756 unsigned long prealloc;
757 unsigned max;
758 time_t lowest_lru;
759 size_t size;
760 int loop, lru, ret;
761
762 kenter("%d,%s,%s,", key_serial(keyring), type->name, description);
763
764 if (keyring->type != &key_type_keyring)
765 return -ENOTDIR;
766
767 down_write(&keyring->sem);
768
769 ret = -EKEYREVOKED;
770 if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
771 goto error_krsem;
772
773 /* serialise link/link calls to prevent parallel calls causing a cycle
774 * when linking two keyring in opposite orders */
775 if (type == &key_type_keyring)
776 down_write(&keyring_serialise_link_sem);
777
778 klist = rcu_dereference_locked_keyring(keyring);
779
780 /* see if there's a matching key we can displace */
781 lru = -1;
782 if (klist && klist->nkeys > 0) {
783 lowest_lru = TIME_T_MAX;
784 for (loop = klist->nkeys - 1; loop >= 0; loop--) {
785 struct key *key = rcu_deref_link_locked(klist, loop,
786 keyring);
787 if (key->type == type &&
788 strcmp(key->description, description) == 0) {
789 /* Found a match - we'll replace the link with
790 * one to the new key. We record the slot
791 * position.
792 */
793 klist->delkey = loop;
794 prealloc = 0;
795 goto done;
796 }
797 if (key->last_used_at < lowest_lru) {
798 lowest_lru = key->last_used_at;
799 lru = loop;
800 }
801 }
802 }
803
804 /* If the keyring is full then do an LRU discard */
805 if (klist &&
806 klist->nkeys == klist->maxkeys &&
807 klist->maxkeys >= MAX_KEYRING_LINKS) {
808 kdebug("LRU discard %d\n", lru);
809 klist->delkey = lru;
810 prealloc = 0;
811 goto done;
812 }
813
814 /* check that we aren't going to overrun the user's quota */
815 ret = key_payload_reserve(keyring,
816 keyring->datalen + KEYQUOTA_LINK_BYTES);
817 if (ret < 0)
818 goto error_sem;
819
820 if (klist && klist->nkeys < klist->maxkeys) {
821 /* there's sufficient slack space to append directly */
822 klist->delkey = klist->nkeys;
823 prealloc = KEY_LINK_FIXQUOTA;
824 } else {
825 /* grow the key list */
826 max = 4;
827 if (klist) {
828 max += klist->maxkeys;
829 if (max > MAX_KEYRING_LINKS)
830 max = MAX_KEYRING_LINKS;
831 BUG_ON(max <= klist->maxkeys);
832 }
833
834 size = sizeof(*klist) + sizeof(struct key *) * max;
835
836 ret = -ENOMEM;
837 nklist = kmalloc(size, GFP_KERNEL);
838 if (!nklist)
839 goto error_quota;
840
841 nklist->maxkeys = max;
842 if (klist) {
843 memcpy(nklist->keys, klist->keys,
844 sizeof(struct key *) * klist->nkeys);
845 nklist->delkey = klist->nkeys;
846 nklist->nkeys = klist->nkeys + 1;
847 klist->delkey = USHRT_MAX;
848 } else {
849 nklist->nkeys = 1;
850 nklist->delkey = 0;
851 }
852
853 /* add the key into the new space */
854 RCU_INIT_POINTER(nklist->keys[nklist->delkey], NULL);
855 prealloc = (unsigned long)nklist | KEY_LINK_FIXQUOTA;
856 }
857
858done:
859 *_prealloc = prealloc;
860 kleave(" = 0");
861 return 0;
862
863error_quota:
864 /* undo the quota changes */
865 key_payload_reserve(keyring,
866 keyring->datalen - KEYQUOTA_LINK_BYTES);
867error_sem:
868 if (type == &key_type_keyring)
869 up_write(&keyring_serialise_link_sem);
870error_krsem:
871 up_write(&keyring->sem);
872 kleave(" = %d", ret);
873 return ret;
874}
875
876/*
877 * Check already instantiated keys aren't going to be a problem.
878 *
879 * The caller must have called __key_link_begin(). Don't need to call this for
880 * keys that were created since __key_link_begin() was called.
881 */
882int __key_link_check_live_key(struct key *keyring, struct key *key)
883{
884 if (key->type == &key_type_keyring)
885 /* check that we aren't going to create a cycle by linking one
886 * keyring to another */
887 return keyring_detect_cycle(keyring, key);
888 return 0;
889}
890
891/*
892 * Link a key into to a keyring.
893 *
894 * Must be called with __key_link_begin() having being called. Discards any
895 * already extant link to matching key if there is one, so that each keyring
896 * holds at most one link to any given key of a particular type+description
897 * combination.
898 */
899void __key_link(struct key *keyring, struct key *key,
900 unsigned long *_prealloc)
901{
902 struct keyring_list *klist, *nklist;
903 struct key *discard;
904
905 nklist = (struct keyring_list *)(*_prealloc & ~KEY_LINK_FIXQUOTA);
906 *_prealloc = 0;
907
908 kenter("%d,%d,%p", keyring->serial, key->serial, nklist);
909
910 klist = rcu_dereference_locked_keyring(keyring);
911
912 atomic_inc(&key->usage);
913 keyring->last_used_at = key->last_used_at =
914 current_kernel_time().tv_sec;
915
916 /* there's a matching key we can displace or an empty slot in a newly
917 * allocated list we can fill */
918 if (nklist) {
919 kdebug("reissue %hu/%hu/%hu",
920 nklist->delkey, nklist->nkeys, nklist->maxkeys);
921
922 RCU_INIT_POINTER(nklist->keys[nklist->delkey], key);
923
924 rcu_assign_pointer(keyring->payload.subscriptions, nklist);
925
926 /* dispose of the old keyring list and, if there was one, the
927 * displaced key */
928 if (klist) {
929 kdebug("dispose %hu/%hu/%hu",
930 klist->delkey, klist->nkeys, klist->maxkeys);
931 call_rcu(&klist->rcu, keyring_unlink_rcu_disposal);
932 }
933 } else if (klist->delkey < klist->nkeys) {
934 kdebug("replace %hu/%hu/%hu",
935 klist->delkey, klist->nkeys, klist->maxkeys);
936
937 discard = rcu_dereference_protected(
938 klist->keys[klist->delkey],
939 rwsem_is_locked(&keyring->sem));
940 rcu_assign_pointer(klist->keys[klist->delkey], key);
941 /* The garbage collector will take care of RCU
942 * synchronisation */
943 key_put(discard);
944 } else {
945 /* there's sufficient slack space to append directly */
946 kdebug("append %hu/%hu/%hu",
947 klist->delkey, klist->nkeys, klist->maxkeys);
948
949 RCU_INIT_POINTER(klist->keys[klist->delkey], key);
950 smp_wmb();
951 klist->nkeys++;
952 }
953}
954
955/*
956 * Finish linking a key into to a keyring.
957 *
958 * Must be called with __key_link_begin() having being called.
959 */
960void __key_link_end(struct key *keyring, struct key_type *type,
961 unsigned long prealloc)
962 __releases(&keyring->sem)
963{
964 BUG_ON(type == NULL);
965 BUG_ON(type->name == NULL);
966 kenter("%d,%s,%lx", keyring->serial, type->name, prealloc);
967
968 if (type == &key_type_keyring)
969 up_write(&keyring_serialise_link_sem);
970
971 if (prealloc) {
972 if (prealloc & KEY_LINK_FIXQUOTA)
973 key_payload_reserve(keyring,
974 keyring->datalen -
975 KEYQUOTA_LINK_BYTES);
976 kfree((struct keyring_list *)(prealloc & ~KEY_LINK_FIXQUOTA));
977 }
978 up_write(&keyring->sem);
979}
980
981/**
982 * key_link - Link a key to a keyring
983 * @keyring: The keyring to make the link in.
984 * @key: The key to link to.
985 *
986 * Make a link in a keyring to a key, such that the keyring holds a reference
987 * on that key and the key can potentially be found by searching that keyring.
988 *
989 * This function will write-lock the keyring's semaphore and will consume some
990 * of the user's key data quota to hold the link.
991 *
992 * Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring,
993 * -EKEYREVOKED if the keyring has been revoked, -ENFILE if the keyring is
994 * full, -EDQUOT if there is insufficient key data quota remaining to add
995 * another link or -ENOMEM if there's insufficient memory.
996 *
997 * It is assumed that the caller has checked that it is permitted for a link to
998 * be made (the keyring should have Write permission and the key Link
999 * permission).
1000 */
1001int key_link(struct key *keyring, struct key *key)
1002{
1003 unsigned long prealloc;
1004 int ret;
1005
1006 key_check(keyring);
1007 key_check(key);
1008
1009 ret = __key_link_begin(keyring, key->type, key->description, &prealloc);
1010 if (ret == 0) {
1011 ret = __key_link_check_live_key(keyring, key);
1012 if (ret == 0)
1013 __key_link(keyring, key, &prealloc);
1014 __key_link_end(keyring, key->type, prealloc);
1015 }
1016
1017 return ret;
1018}
1019EXPORT_SYMBOL(key_link);
1020
1021/**
1022 * key_unlink - Unlink the first link to a key from a keyring.
1023 * @keyring: The keyring to remove the link from.
1024 * @key: The key the link is to.
1025 *
1026 * Remove a link from a keyring to a key.
1027 *
1028 * This function will write-lock the keyring's semaphore.
1029 *
1030 * Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring, -ENOENT if
1031 * the key isn't linked to by the keyring or -ENOMEM if there's insufficient
1032 * memory.
1033 *
1034 * It is assumed that the caller has checked that it is permitted for a link to
1035 * be removed (the keyring should have Write permission; no permissions are
1036 * required on the key).
1037 */
1038int key_unlink(struct key *keyring, struct key *key)
1039{
1040 struct keyring_list *klist, *nklist;
1041 int loop, ret;
1042
1043 key_check(keyring);
1044 key_check(key);
1045
1046 ret = -ENOTDIR;
1047 if (keyring->type != &key_type_keyring)
1048 goto error;
1049
1050 down_write(&keyring->sem);
1051
1052 klist = rcu_dereference_locked_keyring(keyring);
1053 if (klist) {
1054 /* search the keyring for the key */
1055 for (loop = 0; loop < klist->nkeys; loop++)
1056 if (rcu_access_pointer(klist->keys[loop]) == key)
1057 goto key_is_present;
1058 }
1059
1060 up_write(&keyring->sem);
1061 ret = -ENOENT;
1062 goto error;
1063
1064key_is_present:
1065 /* we need to copy the key list for RCU purposes */
1066 nklist = kmalloc(sizeof(*klist) +
1067 sizeof(struct key *) * klist->maxkeys,
1068 GFP_KERNEL);
1069 if (!nklist)
1070 goto nomem;
1071 nklist->maxkeys = klist->maxkeys;
1072 nklist->nkeys = klist->nkeys - 1;
1073
1074 if (loop > 0)
1075 memcpy(&nklist->keys[0],
1076 &klist->keys[0],
1077 loop * sizeof(struct key *));
1078
1079 if (loop < nklist->nkeys)
1080 memcpy(&nklist->keys[loop],
1081 &klist->keys[loop + 1],
1082 (nklist->nkeys - loop) * sizeof(struct key *));
1083
1084 /* adjust the user's quota */
1085 key_payload_reserve(keyring,
1086 keyring->datalen - KEYQUOTA_LINK_BYTES);
1087
1088 rcu_assign_pointer(keyring->payload.subscriptions, nklist);
1089
1090 up_write(&keyring->sem);
1091
1092 /* schedule for later cleanup */
1093 klist->delkey = loop;
1094 call_rcu(&klist->rcu, keyring_unlink_rcu_disposal);
1095
1096 ret = 0;
1097
1098error:
1099 return ret;
1100nomem:
1101 ret = -ENOMEM;
1102 up_write(&keyring->sem);
1103 goto error;
1104}
1105EXPORT_SYMBOL(key_unlink);
1106
1107/*
1108 * Dispose of a keyring list after the RCU grace period, releasing the keys it
1109 * links to.
1110 */
1111static void keyring_clear_rcu_disposal(struct rcu_head *rcu)
1112{
1113 struct keyring_list *klist;
1114 int loop;
1115
1116 klist = container_of(rcu, struct keyring_list, rcu);
1117
1118 for (loop = klist->nkeys - 1; loop >= 0; loop--)
1119 key_put(rcu_access_pointer(klist->keys[loop]));
1120
1121 kfree(klist);
1122}
1123
1124/**
1125 * keyring_clear - Clear a keyring
1126 * @keyring: The keyring to clear.
1127 *
1128 * Clear the contents of the specified keyring.
1129 *
1130 * Returns 0 if successful or -ENOTDIR if the keyring isn't a keyring.
1131 */
1132int keyring_clear(struct key *keyring)
1133{
1134 struct keyring_list *klist;
1135 int ret;
1136
1137 ret = -ENOTDIR;
1138 if (keyring->type == &key_type_keyring) {
1139 /* detach the pointer block with the locks held */
1140 down_write(&keyring->sem);
1141
1142 klist = rcu_dereference_locked_keyring(keyring);
1143 if (klist) {
1144 /* adjust the quota */
1145 key_payload_reserve(keyring,
1146 sizeof(struct keyring_list));
1147
1148 rcu_assign_pointer(keyring->payload.subscriptions,
1149 NULL);
1150 }
1151
1152 up_write(&keyring->sem);
1153
1154 /* free the keys after the locks have been dropped */
1155 if (klist)
1156 call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
1157
1158 ret = 0;
1159 }
1160
1161 return ret;
1162}
1163EXPORT_SYMBOL(keyring_clear);
1164
1165/*
1166 * Dispose of the links from a revoked keyring.
1167 *
1168 * This is called with the key sem write-locked.
1169 */
1170static void keyring_revoke(struct key *keyring)
1171{
1172 struct keyring_list *klist;
1173
1174 klist = rcu_dereference_locked_keyring(keyring);
1175
1176 /* adjust the quota */
1177 key_payload_reserve(keyring, 0);
1178
1179 if (klist) {
1180 rcu_assign_pointer(keyring->payload.subscriptions, NULL);
1181 call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
1182 }
1183}
1184
1185/*
1186 * Collect garbage from the contents of a keyring, replacing the old list with
1187 * a new one with the pointers all shuffled down.
1188 *
1189 * Dead keys are classed as oned that are flagged as being dead or are revoked,
1190 * expired or negative keys that were revoked or expired before the specified
1191 * limit.
1192 */
1193void keyring_gc(struct key *keyring, time_t limit)
1194{
1195 struct keyring_list *klist, *new;
1196 struct key *key;
1197 int loop, keep, max;
1198
1199 kenter("{%x,%s}", key_serial(keyring), keyring->description);
1200
1201 down_write(&keyring->sem);
1202
1203 klist = rcu_dereference_locked_keyring(keyring);
1204 if (!klist)
1205 goto no_klist;
1206
1207 /* work out how many subscriptions we're keeping */
1208 keep = 0;
1209 for (loop = klist->nkeys - 1; loop >= 0; loop--)
1210 if (!key_is_dead(rcu_deref_link_locked(klist, loop, keyring),
1211 limit))
1212 keep++;
1213
1214 if (keep == klist->nkeys)
1215 goto just_return;
1216
1217 /* allocate a new keyring payload */
1218 max = roundup(keep, 4);
1219 new = kmalloc(sizeof(struct keyring_list) + max * sizeof(struct key *),
1220 GFP_KERNEL);
1221 if (!new)
1222 goto nomem;
1223 new->maxkeys = max;
1224 new->nkeys = 0;
1225 new->delkey = 0;
1226
1227 /* install the live keys
1228 * - must take care as expired keys may be updated back to life
1229 */
1230 keep = 0;
1231 for (loop = klist->nkeys - 1; loop >= 0; loop--) {
1232 key = rcu_deref_link_locked(klist, loop, keyring);
1233 if (!key_is_dead(key, limit)) {
1234 if (keep >= max)
1235 goto discard_new;
1236 RCU_INIT_POINTER(new->keys[keep++], key_get(key));
1237 }
1238 }
1239 new->nkeys = keep;
1240
1241 /* adjust the quota */
1242 key_payload_reserve(keyring,
1243 sizeof(struct keyring_list) +
1244 KEYQUOTA_LINK_BYTES * keep);
1245
1246 if (keep == 0) {
1247 rcu_assign_pointer(keyring->payload.subscriptions, NULL);
1248 kfree(new);
1249 } else {
1250 rcu_assign_pointer(keyring->payload.subscriptions, new);
1251 }
1252
1253 up_write(&keyring->sem);
1254
1255 call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
1256 kleave(" [yes]");
1257 return;
1258
1259discard_new:
1260 new->nkeys = keep;
1261 keyring_clear_rcu_disposal(&new->rcu);
1262 up_write(&keyring->sem);
1263 kleave(" [discard]");
1264 return;
1265
1266just_return:
1267 up_write(&keyring->sem);
1268 kleave(" [no dead]");
1269 return;
1270
1271no_klist:
1272 up_write(&keyring->sem);
1273 kleave(" [no_klist]");
1274 return;
1275
1276nomem:
1277 up_write(&keyring->sem);
1278 kleave(" [oom]");
1279}