aboutsummaryrefslogtreecommitdiffstats
path: root/security/keys/key.c
blob: a30e927349051ce651e6f0872861cdda881e5bce (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
/* Basic authentication token and access key management
 *
 * Copyright (C) 2004-2008 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/poison.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/security.h>
#include <linux/workqueue.h>
#include <linux/random.h>
#include <linux/err.h>
#include "internal.h"

struct kmem_cache *key_jar;
struct rb_root		key_serial_tree; /* tree of keys indexed by serial */
DEFINE_SPINLOCK(key_serial_lock);

struct rb_root	key_user_tree; /* tree of quota records indexed by UID */
DEFINE_SPINLOCK(key_user_lock);

unsigned int key_quota_root_maxkeys = 200;	/* root's key count quota */
unsigned int key_quota_root_maxbytes = 20000;	/* root's key space quota */
unsigned int key_quota_maxkeys = 200;		/* general key count quota */
unsigned int key_quota_maxbytes = 20000;	/* general key space quota */

static LIST_HEAD(key_types_list);
static DECLARE_RWSEM(key_types_sem);

/* We serialise key instantiation and link */
DEFINE_MUTEX(key_construction_mutex);

#ifdef KEY_DEBUGGING
void __key_check(const struct key *key)
{
	printk("__key_check: key %p {%08x} should be {%08x}\n",
	       key, key->magic, KEY_DEBUG_MAGIC);
	BUG();
}
#endif

/*
 * Get the key quota record for a user, allocating a new record if one doesn't
 * already exist.
 */
struct key_user *key_user_lookup(kuid_t uid)
{
	struct key_user *candidate = NULL, *user;
	struct rb_node *parent = NULL;
	struct rb_node **p;

try_again:
	p = &key_user_tree.rb_node;
	spin_lock(&key_user_lock);

	/* search the tree for a user record with a matching UID */
	while (*p) {
		parent = *p;
		user = rb_entry(parent, struct key_user, node);

		if (uid_lt(uid, user->uid))
			p = &(*p)->rb_left;
		else if (uid_gt(uid, user->uid))
			p = &(*p)->rb_right;
		else
			goto found;
	}

	/* if we get here, we failed to find a match in the tree */
	if (!candidate) {
		/* allocate a candidate user record if we don't already have
		 * one */
		spin_unlock(&key_user_lock);

		user = NULL;
		candidate = kmalloc(sizeof(struct key_user), GFP_KERNEL);
		if (unlikely(!candidate))
			goto out;

		/* the allocation may have scheduled, so we need to repeat the
		 * search lest someone else added the record whilst we were
		 * asleep */
		goto try_again;
	}

	/* if we get here, then the user record still hadn't appeared on the
	 * second pass - so we use the candidate record */
	atomic_set(&candidate->usage, 1);
	atomic_set(&candidate->nkeys, 0);
	atomic_set(&candidate->nikeys, 0);
	candidate->uid = uid;
	candidate->qnkeys = 0;
	candidate->qnbytes = 0;
	spin_lock_init(&candidate->lock);
	mutex_init(&candidate->cons_lock);

	rb_link_node(&candidate->node, parent, p);
	rb_insert_color(&candidate->node, &key_user_tree);
	spin_unlock(&key_user_lock);
	user = candidate;
	goto out;

	/* okay - we found a user record for this UID */
found:
	atomic_inc(&user->usage);
	spin_unlock(&key_user_lock);
	kfree(candidate);
out:
	return user;
}

/*
 * Dispose of a user structure
 */
void key_user_put(struct key_user *user)
{
	if (atomic_dec_and_lock(&user->usage, &key_user_lock)) {
		rb_erase(&user->node, &key_user_tree);
		spin_unlock(&key_user_lock);

		kfree(user);
	}
}

/*
 * Allocate a serial number for a key.  These are assigned randomly to avoid
 * security issues through covert channel problems.
 */
static inline void key_alloc_serial(struct key *key)
{
	struct rb_node *parent, **p;
	struct key *xkey;

	/* propose a random serial number and look for a hole for it in the
	 * serial number tree */
	do {
		get_random_bytes(&key->serial, sizeof(key->serial));

		key->serial >>= 1; /* negative numbers are not permitted */
	} while (key->serial < 3);

	spin_lock(&key_serial_lock);

attempt_insertion:
	parent = NULL;
	p = &key_serial_tree.rb_node;

	while (*p) {
		parent = *p;
		xkey = rb_entry(parent, struct key, serial_node);

		if (key->serial < xkey->serial)
			p = &(*p)->rb_left;
		else if (key->serial > xkey->serial)
			p = &(*p)->rb_right;
		else
			goto serial_exists;
	}

	/* we've found a suitable hole - arrange for this key to occupy it */
	rb_link_node(&key->serial_node, parent, p);
	rb_insert_color(&key->serial_node, &key_serial_tree);

	spin_unlock(&key_serial_lock);
	return;

	/* we found a key with the proposed serial number - walk the tree from
	 * that point looking for the next unused serial number */
serial_exists:
	for (;;) {
		key->serial++;
		if (key->serial < 3) {
			key->serial = 3;
			goto attempt_insertion;
		}

		parent = rb_next(parent);
		if (!parent)
			goto attempt_insertion;

		xkey = rb_entry(parent, struct key, serial_node);
		if (key->serial < xkey->serial)
			goto attempt_insertion;
	}
}

/**
 * key_alloc - Allocate a key of the specified type.
 * @type: The type of key to allocate.
 * @desc: The key description to allow the key to be searched out.
 * @uid: The owner of the new key.
 * @gid: The group ID for the new key's group permissions.
 * @cred: The credentials specifying UID namespace.
 * @perm: The permissions mask of the new key.
 * @flags: Flags specifying quota properties.
 *
 * Allocate a key of the specified type with the attributes given.  The key is
 * returned in an uninstantiated state and the caller needs to instantiate the
 * key before returning.
 *
 * The user's key count quota is updated to reflect the creation of the key and
 * the user's key data quota has the default for the key type reserved.  The
 * instantiation function should amend this as necessary.  If insufficient
 * quota is available, -EDQUOT will be returned.
 *
 * The LSM security modules can prevent a key being created, in which case
 * -EACCES will be returned.
 *
 * Returns a pointer to the new key if successful and an error code otherwise.
 *
 * Note that the caller needs to ensure the key type isn't uninstantiated.
 * Internally this can be done by locking key_types_sem.  Externally, this can
 * be done by either never unregistering the key type, or making sure
 * key_alloc() calls don't race with module unloading.
 */
struct key *key_alloc(struct key_type *type, const char *desc,
		      kuid_t uid, kgid_t gid, const struct cred *cred,
		      key_perm_t perm, unsigned long flags)
{
	struct key_user *user = NULL;
	struct key *key;
	size_t desclen, quotalen;
	int ret;

	key = ERR_PTR(-EINVAL);
	if (!desc || !*desc)
		goto error;

	if (type->vet_description) {
		ret = type->vet_description(desc);
		if (ret < 0) {
			key = ERR_PTR(ret);
			goto error;
		}
	}

	desclen = strlen(desc) + 1;
	quotalen = desclen + type->def_datalen;

	/* get hold of the key tracking for this user */
	user = key_user_lookup(uid);
	if (!user)
		goto no_memory_1;

	/* check that the user's quota permits allocation of another key and
	 * its description */
	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
		unsigned maxkeys = uid_eq(uid, GLOBAL_ROOT_UID) ?
			key_quota_root_maxkeys : key_quota_maxkeys;
		unsigned maxbytes = uid_eq(uid, GLOBAL_ROOT_UID) ?
			key_quota_root_maxbytes : key_quota_maxbytes;

		spin_lock(&user->lock);
		if (!(flags & KEY_ALLOC_QUOTA_OVERRUN)) {
			if (user->qnkeys + 1 >= maxkeys ||
			    user->qnbytes + quotalen >= maxbytes ||
			    user->qnbytes + quotalen < user->qnbytes)
				goto no_quota;
		}

		user->qnkeys++;
		user->qnbytes += quotalen;
		spin_unlock(&user->lock);
	}

	/* allocate and initialise the key and its description */
	key = kmem_cache_alloc(key_jar, GFP_KERNEL);
	if (!key)
		goto no_memory_2;

	if (desc) {
		key->description = kmemdup(desc, desclen, GFP_KERNEL);
		if (!key->description)
			goto no_memory_3;
	}

	atomic_set(&key->usage, 1);
	init_rwsem(&key->sem);
	lockdep_set_class(&key->sem, &type->lock_class);
	key->type = type;
	key->user = user;
	key->quotalen = quotalen;
	key->datalen = type->def_datalen;
	key->uid = uid;
	key->gid = gid;
	key->perm = perm;
	key->flags = 0;
	key->expiry = 0;
	key->payload.data = NULL;
	key->security = NULL;

	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA))
		key->flags |= 1 << KEY_FLAG_IN_QUOTA;

	memset(&key->type_data, 0, sizeof(key->type_data));

#ifdef KEY_DEBUGGING
	key->magic = KEY_DEBUG_MAGIC;
#endif

	/* let the security module know about the key */
	ret = security_key_alloc(key, cred, flags);
	if (ret < 0)
		goto security_error;

	/* publish the key by giving it a serial number */
	atomic_inc(&user->nkeys);
	key_alloc_serial(key);

error:
	return key;

security_error:
	kfree(key->description);
	kmem_cache_free(key_jar, key);
	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
		spin_lock(&user->lock);
		user->qnkeys--;
		user->qnbytes -= quotalen;
		spin_unlock(&user->lock);
	}
	key_user_put(user);
	key = ERR_PTR(ret);
	goto error;

no_memory_3:
	kmem_cache_free(key_jar, key);
no_memory_2:
	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
		spin_lock(&user->lock);
		user->qnkeys--;
		user->qnbytes -= quotalen;
		spin_unlock(&user->lock);
	}
	key_user_put(user);
no_memory_1:
	key = ERR_PTR(-ENOMEM);
	goto error;

no_quota:
	spin_unlock(&user->lock);
	key_user_put(user);
	key = ERR_PTR(-EDQUOT);
	goto error;
}
EXPORT_SYMBOL(key_alloc);

/**
 * key_payload_reserve - Adjust data quota reservation for the key's payload
 * @key: The key to make the reservation for.
 * @datalen: The amount of data payload the caller now wants.
 *
 * Adjust the amount of the owning user's key data quota that a key reserves.
 * If the amount is increased, then -EDQUOT may be returned if there isn't
 * enough free quota available.
 *
 * If successful, 0 is returned.
 */
int key_payload_reserve(struct key *key, size_t datalen)
{
	int delta = (int)datalen - key->datalen;
	int ret = 0;

	key_check(key);

	/* contemplate the quota adjustment */
	if (delta != 0 && test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
		unsigned maxbytes = uid_eq(key->user->uid, GLOBAL_ROOT_UID) ?
			key_quota_root_maxbytes : key_quota_maxbytes;

		spin_lock(&key->user->lock);

		if (delta > 0 &&
		    (key->user->qnbytes + delta >= maxbytes ||
		     key->user->qnbytes + delta < key->user->qnbytes)) {
			ret = -EDQUOT;
		}
		else {
			key->user->qnbytes += delta;
			key->quotalen += delta;
		}
		spin_unlock(&key->user->lock);
	}

	/* change the recorded data length if that didn't generate an error */
	if (ret == 0)
		key->datalen = datalen;

	return ret;
}
EXPORT_SYMBOL(key_payload_reserve);

/*
 * Instantiate a key and link it into the target keyring atomically.  Must be
 * called with the target keyring's semaphore writelocked.  The target key's
 * semaphore need not be locked as instantiation is serialised by
 * key_construction_mutex.
 */
static int __key_instantiate_and_link(struct key *key,
				      const void *data,
				      size_t datalen,
				      struct key *keyring,
				      struct key *authkey,
				      unsigned long *_prealloc)
{
	int ret, awaken;

	key_check(key);
	key_check(keyring);

	awaken = 0;
	ret = -EBUSY;

	mutex_lock(&key_construction_mutex);

	/* can't instantiate twice */
	if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
		/* instantiate the key */
		ret = key->type->instantiate(key, data, datalen);

		if (ret == 0) {
			/* mark the key as being instantiated */
			atomic_inc(&key->user->nikeys);
			set_bit(KEY_FLAG_INSTANTIATED, &key->flags);

			if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
				awaken = 1;

			/* and link it into the destination keyring */
			if (keyring)
				__key_link(keyring, key, _prealloc);

			/* disable the authorisation key */
			if (authkey)
				key_revoke(authkey);
		}
	}

	mutex_unlock(&key_construction_mutex);

	/* wake up anyone waiting for a key to be constructed */
	if (awaken)
		wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);

	return ret;
}

/**
 * key_instantiate_and_link - Instantiate a key and link it into the keyring.
 * @key: The key to instantiate.
 * @data: The data to use to instantiate the keyring.
 * @datalen: The length of @data.
 * @keyring: Keyring to create a link in on success (or NULL).
 * @authkey: The authorisation token permitting instantiation.
 *
 * Instantiate a key that's in the uninstantiated state using the provided data
 * and, if successful, link it in to the destination keyring if one is
 * supplied.
 *
 * If successful, 0 is returned, the authorisation token is revoked and anyone
 * waiting for the key is woken up.  If the key was already instantiated,
 * -EBUSY will be returned.
 */
int key_instantiate_and_link(struct key *key,
			     const void *data,
			     size_t datalen,
			     struct key *keyring,
			     struct key *authkey)
{
	unsigned long prealloc;
	int ret;

	if (keyring) {
		ret = __key_link_begin(keyring, key->type, key->description,
				       &prealloc);
		if (ret < 0)
			return ret;
	}

	ret = __key_instantiate_and_link(key, data, datalen, keyring, authkey,
					 &prealloc);

	if (keyring)
		__key_link_end(keyring, key->type, prealloc);

	return ret;
}

EXPORT_SYMBOL(key_instantiate_and_link);

/**
 * key_reject_and_link - Negatively instantiate a key and link it into the keyring.
 * @key: The key to instantiate.
 * @timeout: The timeout on the negative key.
 * @error: The error to return when the key is hit.
 * @keyring: Keyring to create a link in on success (or NULL).
 * @authkey: The authorisation token permitting instantiation.
 *
 * Negatively instantiate a key that's in the uninstantiated state and, if
 * successful, set its timeout and stored error and link it in to the
 * destination keyring if one is supplied.  The key and any links to the key
 * will be automatically garbage collected after the timeout expires.
 *
 * Negative keys are used to rate limit repeated request_key() calls by causing
 * them to return the stored error code (typically ENOKEY) until the negative
 * key expires.
 *
 * If successful, 0 is returned, the authorisation token is revoked and anyone
 * waiting for the key is woken up.  If the key was already instantiated,
 * -EBUSY will be returned.
 */
int key_reject_and_link(struct key *key,
			unsigned timeout,
			unsigned error,
			struct key *keyring,
			struct key *authkey)
{
	unsigned long prealloc;
	struct timespec now;
	int ret, awaken, link_ret = 0;

	key_check(key);
	key_check(keyring);

	awaken = 0;
	ret = -EBUSY;

	if (keyring)
		link_ret = __key_link_begin(keyring, key->type,
					    key->description, &prealloc);

	mutex_lock(&key_construction_mutex);

	/* can't instantiate twice */
	if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
		/* mark the key as being negatively instantiated */
		atomic_inc(&key->user->nikeys);
		set_bit(KEY_FLAG_NEGATIVE, &key->flags);
		set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
		key->type_data.reject_error = -error;
		now = current_kernel_time();
		key->expiry = now.tv_sec + timeout;
		key_schedule_gc(key->expiry + key_gc_delay);

		if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
			awaken = 1;

		ret = 0;

		/* and link it into the destination keyring */
		if (keyring && link_ret == 0)
			__key_link(keyring, key, &prealloc);

		/* disable the authorisation key */
		if (authkey)
			key_revoke(authkey);
	}

	mutex_unlock(&key_construction_mutex);

	if (keyring)
		__key_link_end(keyring, key->type, prealloc);

	/* wake up anyone waiting for a key to be constructed */
	if (awaken)
		wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);

	return ret == 0 ? link_ret : ret;
}
EXPORT_SYMBOL(key_reject_and_link);

/**
 * key_put - Discard a reference to a key.
 * @key: The key to discard a reference from.
 *
 * Discard a reference to a key, and when all the references are gone, we
 * schedule the cleanup task to come and pull it out of the tree in process
 * context at some later time.
 */
void key_put(struct key *key)
{
	if (key) {
		key_check(key);

		if (atomic_dec_and_test(&key->usage))
			schedule_work(&key_gc_work);
	}
}
EXPORT_SYMBOL(key_put);

/*
 * Find a key by its serial number.
 */
struct key *key_lookup(key_serial_t id)
{
	struct rb_node *n;
	struct key *key;

	spin_lock(&key_serial_lock);

	/* search the tree for the specified key */
	n = key_serial_tree.rb_node;
	while (n) {
		key = rb_entry(n, struct key, serial_node);

		if (id < key->serial)
			n = n->rb_left;
		else if (id > key->serial)
			n = n->rb_right;
		else
			goto found;
	}

not_found:
	key = ERR_PTR(-ENOKEY);
	goto error;

found:
	/* pretend it doesn't exist if it is awaiting deletion */
	if (atomic_read(&key->usage) == 0)
		goto not_found;

	/* this races with key_put(), but that doesn't matter since key_put()
	 * doesn't actually change the key
	 */
	atomic_inc(&key->usage);

error:
	spin_unlock(&key_serial_lock);
	return key;
}

/*
 * Find and lock the specified key type against removal.
 *
 * We return with the sem read-locked if successful.  If the type wasn't
 * available -ENOKEY is returned instead.
 */
struct key_type *key_type_lookup(const char *type)
{
	struct key_type *ktype;

	down_read(&key_types_sem);

	/* look up the key type to see if it's one of the registered kernel
	 * types */
	list_for_each_entry(ktype, &key_types_list, link) {
		if (strcmp(ktype->name, type) == 0)
			goto found_kernel_type;
	}

	up_read(&key_types_sem);
	ktype = ERR_PTR(-ENOKEY);

found_kernel_type:
	return ktype;
}

void key_set_timeout(struct key *key, unsigned timeout)
{
	struct timespec now;
	time_t expiry = 0;

	/* make the changes with the locks held to prevent races */
	down_write(&key->sem);

	if (timeout > 0) {
		now = current_kernel_time();
		expiry = now.tv_sec + timeout;
	}

	key->expiry = expiry;
	key_schedule_gc(key->expiry + key_gc_delay);

	up_write(&key->sem);
}
EXPORT_SYMBOL_GPL(key_set_timeout);

/*
 * Unlock a key type locked by key_type_lookup().
 */
void key_type_put(struct key_type *ktype)
{
	up_read(&key_types_sem);
}

/*
 * Attempt to update an existing key.
 *
 * The key is given to us with an incremented refcount that we need to discard
 * if we get an error.
 */
static inline key_ref_t __key_update(key_ref_t key_ref,
				     const void *payload, size_t plen)
{
	struct key *key = key_ref_to_ptr(key_ref);
	int ret;

	/* need write permission on the key to update it */
	ret = key_permission(key_ref, KEY_WRITE);
	if (ret < 0)
		goto error;

	ret = -EEXIST;
	if (!key->type->update)
		goto error;

	down_write(&key->sem);

	ret = key->type->update(key, payload, plen);
	if (ret == 0)
		/* updating a negative key instantiates it */
		clear_bit(KEY_FLAG_NEGATIVE, &key->flags);

	up_write(&key->sem);

	if (ret < 0)
		goto error;
out:
	return key_ref;

error:
	key_put(key);
	key_ref = ERR_PTR(ret);
	goto out;
}

/**
 * key_create_or_update - Update or create and instantiate a key.
 * @keyring_ref: A pointer to the destination keyring with possession flag.
 * @type: The type of key.
 * @description: The searchable description for the key.
 * @payload: The data to use to instantiate or update the key.
 * @plen: The length of @payload.
 * @perm: The permissions mask for a new key.
 * @flags: The quota flags for a new key.
 *
 * Search the destination keyring for a key of the same description and if one
 * is found, update it, otherwise create and instantiate a new one and create a
 * link to it from that keyring.
 *
 * If perm is KEY_PERM_UNDEF then an appropriate key permissions mask will be
 * concocted.
 *
 * Returns a pointer to the new key if successful, -ENODEV if the key type
 * wasn't available, -ENOTDIR if the keyring wasn't a keyring, -EACCES if the
 * caller isn't permitted to modify the keyring or the LSM did not permit
 * creation of the key.
 *
 * On success, the possession flag from the keyring ref will be tacked on to
 * the key ref before it is returned.
 */
key_ref_t key_create_or_update(key_ref_t keyring_ref,
			       const char *type,
			       const char *description,
			       const void *payload,
			       size_t plen,
			       key_perm_t perm,
			       unsigned long flags)
{
	unsigned long prealloc;
	const struct cred *cred = current_cred();
	struct key_type *ktype;
	struct key *keyring, *key = NULL;
	key_ref_t key_ref;
	int ret;

	/* look up the key type to see if it's one of the registered kernel
	 * types */
	ktype = key_type_lookup(type);
	if (IS_ERR(ktype)) {
		key_ref = ERR_PTR(-ENODEV);
		goto error;
	}

	key_ref = ERR_PTR(-EINVAL);
	if (!ktype->match || !ktype->instantiate)
		goto error_2;

	keyring = key_ref_to_ptr(keyring_ref);

	key_check(keyring);

	key_ref = ERR_PTR(-ENOTDIR);
	if (keyring->type != &key_type_keyring)
		goto error_2;

	ret = __key_link_begin(keyring, ktype, description, &prealloc);
	if (ret < 0)
		goto error_2;

	/* if we're going to allocate a new key, we're going to have
	 * to modify the keyring */
	ret = key_permission(keyring_ref, KEY_WRITE);
	if (ret < 0) {
		key_ref = ERR_PTR(ret);
		goto error_3;
	}

	/* if it's possible to update this type of key, search for an existing
	 * key of the same type and description in the destination keyring and
	 * update that instead if possible
	 */
	if (ktype->update) {
		key_ref = __keyring_search_one(keyring_ref, ktype, description,
					       0);
		if (!IS_ERR(key_ref))
			goto found_matching_key;
	}

	/* if the client doesn't provide, decide on the permissions we want */
	if (perm == KEY_PERM_UNDEF) {
		perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
		perm |= KEY_USR_VIEW | KEY_USR_SEARCH | KEY_USR_LINK | KEY_USR_SETATTR;

		if (ktype->read)
			perm |= KEY_POS_READ | KEY_USR_READ;

		if (ktype == &key_type_keyring || ktype->update)
			perm |= KEY_USR_WRITE;
	}

	/* allocate a new key */
	key = key_alloc(ktype, description, cred->fsuid, cred->fsgid, cred,
			perm, flags);
	if (IS_ERR(key)) {
		key_ref = ERR_CAST(key);
		goto error_3;
	}

	/* instantiate it and link it into the target keyring */
	ret = __key_instantiate_and_link(key, payload, plen, keyring, NULL,
					 &prealloc);
	if (ret < 0) {
		key_put(key);
		key_ref = ERR_PTR(ret);
		goto error_3;
	}

	key_ref = make_key_ref(key, is_key_possessed(keyring_ref));

 error_3:
	__key_link_end(keyring, ktype, prealloc);
 error_2:
	key_type_put(ktype);
 error:
	return key_ref;

 found_matching_key:
	/* we found a matching key, so we're going to try to update it
	 * - we can drop the locks first as we have the key pinned
	 */
	__key_link_end(keyring, ktype, prealloc);
	key_type_put(ktype);

	key_ref = __key_update(key_ref, payload, plen);
	goto error;
}
EXPORT_SYMBOL(key_create_or_update);

/**
 * key_update - Update a key's contents.
 * @key_ref: The pointer (plus possession flag) to the key.
 * @payload: The data to be used to update the key.
 * @plen: The length of @payload.
 *
 * Attempt to update the contents of a key with the given payload data.  The
 * caller must be granted Write permission on the key.  Negative keys can be
 * instantiated by this method.
 *
 * Returns 0 on success, -EACCES if not permitted and -EOPNOTSUPP if the key
 * type does not support updating.  The key type may return other errors.
 */
int key_update(key_ref_t key_ref, const void *payload, size_t plen)
{
	struct key *key = key_ref_to_ptr(key_ref);
	int ret;

	key_check(key);

	/* the key must be writable */
	ret = key_permission(key_ref, KEY_WRITE);
	if (ret < 0)
		goto error;

	/* attempt to update it if supported */
	ret = -EOPNOTSUPP;
	if (key->type->update) {
		down_write(&key->sem);

		ret = key->type->update(key, payload, plen);
		if (ret == 0)
			/* updating a negative key instantiates it */
			clear_bit(KEY_FLAG_NEGATIVE, &key->flags);

		up_write(&key->sem);
	}

 error:
	return ret;
}
EXPORT_SYMBOL(key_update);

/**
 * key_revoke - Revoke a key.
 * @key: The key to be revoked.
 *
 * Mark a key as being revoked and ask the type to free up its resources.  The
 * revocation timeout is set and the key and all its links will be
 * automatically garbage collected after key_gc_delay amount of time if they
 * are not manually dealt with first.
 */
void key_revoke(struct key *key)
{
	struct timespec now;
	time_t time;

	key_check(key);

	/* make sure no one's trying to change or use the key when we mark it
	 * - we tell lockdep that we might nest because we might be revoking an
	 *   authorisation key whilst holding the sem on a key we've just
	 *   instantiated
	 */
	down_write_nested(&key->sem, 1);
	if (!test_and_set_bit(KEY_FLAG_REVOKED, &key->flags) &&
	    key->type->revoke)
		key->type->revoke(key);

	/* set the death time to no more than the expiry time */
	now = current_kernel_time();
	time = now.tv_sec;
	if (key->revoked_at == 0 || key->revoked_at > time) {
		key->revoked_at = time;
		key_schedule_gc(key->revoked_at + key_gc_delay);
	}

	up_write(&key->sem);
}
EXPORT_SYMBOL(key_revoke);

/**
 * key_invalidate - Invalidate a key.
 * @key: The key to be invalidated.
 *
 * Mark a key as being invalidated and have it cleaned up immediately.  The key
 * is ignored by all searches and other operations from this point.
 */
void key_invalidate(struct key *key)
{
	kenter("%d", key_serial(key));

	key_check(key);

	if (!test_bit(KEY_FLAG_INVALIDATED, &key->flags)) {
		down_write_nested(&key->sem, 1);
		if (!test_and_set_bit(KEY_FLAG_INVALIDATED, &key->flags))
			key_schedule_gc_links();
		up_write(&key->sem);
	}
}
EXPORT_SYMBOL(key_invalidate);

/**
 * register_key_type - Register a type of key.
 * @ktype: The new key type.
 *
 * Register a new key type.
 *
 * Returns 0 on success or -EEXIST if a type of this name already exists.
 */
int register_key_type(struct key_type *ktype)
{
	struct key_type *p;
	int ret;

	memset(&ktype->lock_class, 0, sizeof(ktype->lock_class));

	ret = -EEXIST;
	down_write(&key_types_sem);

	/* disallow key types with the same name */
	list_for_each_entry(p, &key_types_list, link) {
		if (strcmp(p->name, ktype->name) == 0)
			goto out;
	}

	/* store the type */
	list_add(&ktype->link, &key_types_list);

	pr_notice("Key type %s registered\n", ktype->name);
	ret = 0;

out:
	up_write(&key_types_sem);
	return ret;
}
EXPORT_SYMBOL(register_key_type);

/**
 * unregister_key_type - Unregister a type of key.
 * @ktype: The key type.
 *
 * Unregister a key type and mark all the extant keys of this type as dead.
 * Those keys of this type are then destroyed to get rid of their payloads and
 * they and their links will be garbage collected as soon as possible.
 */
void unregister_key_type(struct key_type *ktype)
{
	down_write(&key_types_sem);
	list_del_init(&ktype->link);
	downgrade_write(&key_types_sem);
	key_gc_keytype(ktype);
	pr_notice("Key type %s unregistered\n", ktype->name);
	up_read(&key_types_sem);
}
EXPORT_SYMBOL(unregister_key_type);

/*
 * Initialise the key management state.
 */
void __init key_init(void)
{
	/* allocate a slab in which we can store keys */
	key_jar = kmem_cache_create("key_jar", sizeof(struct key),
			0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);

	/* add the special key types */
	list_add_tail(&key_type_keyring.link, &key_types_list);
	list_add_tail(&key_type_dead.link, &key_types_list);
	list_add_tail(&key_type_user.link, &key_types_list);
	list_add_tail(&key_type_logon.link, &key_types_list);

	/* record the root user tracking */
	rb_link_node(&root_key_user.node,
		     NULL,
		     &key_user_tree.rb_node);

	rb_insert_color(&root_key_user.node,
			&key_user_tree);
}