xref: /openbmc/linux/security/keys/key.c (revision 4161b450)
1 /* Basic authentication token and access key management
2  *
3  * Copyright (C) 2004-2008 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/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>
21 #include "internal.h"
22 
23 struct kmem_cache *key_jar;
24 struct rb_root		key_serial_tree; /* tree of keys indexed by serial */
25 DEFINE_SPINLOCK(key_serial_lock);
26 
27 struct rb_root	key_user_tree; /* tree of quota records indexed by UID */
28 DEFINE_SPINLOCK(key_user_lock);
29 
30 unsigned int key_quota_root_maxkeys = 1000000;	/* root's key count quota */
31 unsigned int key_quota_root_maxbytes = 25000000; /* root's key space quota */
32 unsigned int key_quota_maxkeys = 200;		/* general key count quota */
33 unsigned int key_quota_maxbytes = 20000;	/* general key space quota */
34 
35 static LIST_HEAD(key_types_list);
36 static DECLARE_RWSEM(key_types_sem);
37 
38 /* We serialise key instantiation and link */
39 DEFINE_MUTEX(key_construction_mutex);
40 
41 #ifdef KEY_DEBUGGING
42 void __key_check(const struct key *key)
43 {
44 	printk("__key_check: key %p {%08x} should be {%08x}\n",
45 	       key, key->magic, KEY_DEBUG_MAGIC);
46 	BUG();
47 }
48 #endif
49 
50 /*
51  * Get the key quota record for a user, allocating a new record if one doesn't
52  * already exist.
53  */
54 struct key_user *key_user_lookup(kuid_t uid)
55 {
56 	struct key_user *candidate = NULL, *user;
57 	struct rb_node *parent = NULL;
58 	struct rb_node **p;
59 
60 try_again:
61 	p = &key_user_tree.rb_node;
62 	spin_lock(&key_user_lock);
63 
64 	/* search the tree for a user record with a matching UID */
65 	while (*p) {
66 		parent = *p;
67 		user = rb_entry(parent, struct key_user, node);
68 
69 		if (uid_lt(uid, user->uid))
70 			p = &(*p)->rb_left;
71 		else if (uid_gt(uid, user->uid))
72 			p = &(*p)->rb_right;
73 		else
74 			goto found;
75 	}
76 
77 	/* if we get here, we failed to find a match in the tree */
78 	if (!candidate) {
79 		/* allocate a candidate user record if we don't already have
80 		 * one */
81 		spin_unlock(&key_user_lock);
82 
83 		user = NULL;
84 		candidate = kmalloc(sizeof(struct key_user), GFP_KERNEL);
85 		if (unlikely(!candidate))
86 			goto out;
87 
88 		/* the allocation may have scheduled, so we need to repeat the
89 		 * search lest someone else added the record whilst we were
90 		 * asleep */
91 		goto try_again;
92 	}
93 
94 	/* if we get here, then the user record still hadn't appeared on the
95 	 * second pass - so we use the candidate record */
96 	atomic_set(&candidate->usage, 1);
97 	atomic_set(&candidate->nkeys, 0);
98 	atomic_set(&candidate->nikeys, 0);
99 	candidate->uid = uid;
100 	candidate->qnkeys = 0;
101 	candidate->qnbytes = 0;
102 	spin_lock_init(&candidate->lock);
103 	mutex_init(&candidate->cons_lock);
104 
105 	rb_link_node(&candidate->node, parent, p);
106 	rb_insert_color(&candidate->node, &key_user_tree);
107 	spin_unlock(&key_user_lock);
108 	user = candidate;
109 	goto out;
110 
111 	/* okay - we found a user record for this UID */
112 found:
113 	atomic_inc(&user->usage);
114 	spin_unlock(&key_user_lock);
115 	kfree(candidate);
116 out:
117 	return user;
118 }
119 
120 /*
121  * Dispose of a user structure
122  */
123 void key_user_put(struct key_user *user)
124 {
125 	if (atomic_dec_and_lock(&user->usage, &key_user_lock)) {
126 		rb_erase(&user->node, &key_user_tree);
127 		spin_unlock(&key_user_lock);
128 
129 		kfree(user);
130 	}
131 }
132 
133 /*
134  * Allocate a serial number for a key.  These are assigned randomly to avoid
135  * security issues through covert channel problems.
136  */
137 static inline void key_alloc_serial(struct key *key)
138 {
139 	struct rb_node *parent, **p;
140 	struct key *xkey;
141 
142 	/* propose a random serial number and look for a hole for it in the
143 	 * serial number tree */
144 	do {
145 		get_random_bytes(&key->serial, sizeof(key->serial));
146 
147 		key->serial >>= 1; /* negative numbers are not permitted */
148 	} while (key->serial < 3);
149 
150 	spin_lock(&key_serial_lock);
151 
152 attempt_insertion:
153 	parent = NULL;
154 	p = &key_serial_tree.rb_node;
155 
156 	while (*p) {
157 		parent = *p;
158 		xkey = rb_entry(parent, struct key, serial_node);
159 
160 		if (key->serial < xkey->serial)
161 			p = &(*p)->rb_left;
162 		else if (key->serial > xkey->serial)
163 			p = &(*p)->rb_right;
164 		else
165 			goto serial_exists;
166 	}
167 
168 	/* we've found a suitable hole - arrange for this key to occupy it */
169 	rb_link_node(&key->serial_node, parent, p);
170 	rb_insert_color(&key->serial_node, &key_serial_tree);
171 
172 	spin_unlock(&key_serial_lock);
173 	return;
174 
175 	/* we found a key with the proposed serial number - walk the tree from
176 	 * that point looking for the next unused serial number */
177 serial_exists:
178 	for (;;) {
179 		key->serial++;
180 		if (key->serial < 3) {
181 			key->serial = 3;
182 			goto attempt_insertion;
183 		}
184 
185 		parent = rb_next(parent);
186 		if (!parent)
187 			goto attempt_insertion;
188 
189 		xkey = rb_entry(parent, struct key, serial_node);
190 		if (key->serial < xkey->serial)
191 			goto attempt_insertion;
192 	}
193 }
194 
195 /**
196  * key_alloc - Allocate a key of the specified type.
197  * @type: The type of key to allocate.
198  * @desc: The key description to allow the key to be searched out.
199  * @uid: The owner of the new key.
200  * @gid: The group ID for the new key's group permissions.
201  * @cred: The credentials specifying UID namespace.
202  * @perm: The permissions mask of the new key.
203  * @flags: Flags specifying quota properties.
204  *
205  * Allocate a key of the specified type with the attributes given.  The key is
206  * returned in an uninstantiated state and the caller needs to instantiate the
207  * key before returning.
208  *
209  * The user's key count quota is updated to reflect the creation of the key and
210  * the user's key data quota has the default for the key type reserved.  The
211  * instantiation function should amend this as necessary.  If insufficient
212  * quota is available, -EDQUOT will be returned.
213  *
214  * The LSM security modules can prevent a key being created, in which case
215  * -EACCES will be returned.
216  *
217  * Returns a pointer to the new key if successful and an error code otherwise.
218  *
219  * Note that the caller needs to ensure the key type isn't uninstantiated.
220  * Internally this can be done by locking key_types_sem.  Externally, this can
221  * be done by either never unregistering the key type, or making sure
222  * key_alloc() calls don't race with module unloading.
223  */
224 struct key *key_alloc(struct key_type *type, const char *desc,
225 		      kuid_t uid, kgid_t gid, const struct cred *cred,
226 		      key_perm_t perm, unsigned long flags)
227 {
228 	struct key_user *user = NULL;
229 	struct key *key;
230 	size_t desclen, quotalen;
231 	int ret;
232 
233 	key = ERR_PTR(-EINVAL);
234 	if (!desc || !*desc)
235 		goto error;
236 
237 	if (type->vet_description) {
238 		ret = type->vet_description(desc);
239 		if (ret < 0) {
240 			key = ERR_PTR(ret);
241 			goto error;
242 		}
243 	}
244 
245 	desclen = strlen(desc);
246 	quotalen = desclen + 1 + type->def_datalen;
247 
248 	/* get hold of the key tracking for this user */
249 	user = key_user_lookup(uid);
250 	if (!user)
251 		goto no_memory_1;
252 
253 	/* check that the user's quota permits allocation of another key and
254 	 * its description */
255 	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
256 		unsigned maxkeys = uid_eq(uid, GLOBAL_ROOT_UID) ?
257 			key_quota_root_maxkeys : key_quota_maxkeys;
258 		unsigned maxbytes = uid_eq(uid, GLOBAL_ROOT_UID) ?
259 			key_quota_root_maxbytes : key_quota_maxbytes;
260 
261 		spin_lock(&user->lock);
262 		if (!(flags & KEY_ALLOC_QUOTA_OVERRUN)) {
263 			if (user->qnkeys + 1 >= maxkeys ||
264 			    user->qnbytes + quotalen >= maxbytes ||
265 			    user->qnbytes + quotalen < user->qnbytes)
266 				goto no_quota;
267 		}
268 
269 		user->qnkeys++;
270 		user->qnbytes += quotalen;
271 		spin_unlock(&user->lock);
272 	}
273 
274 	/* allocate and initialise the key and its description */
275 	key = kmem_cache_zalloc(key_jar, GFP_KERNEL);
276 	if (!key)
277 		goto no_memory_2;
278 
279 	key->index_key.desc_len = desclen;
280 	key->index_key.description = kmemdup(desc, desclen + 1, GFP_KERNEL);
281 	if (!key->description)
282 		goto no_memory_3;
283 
284 	atomic_set(&key->usage, 1);
285 	init_rwsem(&key->sem);
286 	lockdep_set_class(&key->sem, &type->lock_class);
287 	key->index_key.type = type;
288 	key->user = user;
289 	key->quotalen = quotalen;
290 	key->datalen = type->def_datalen;
291 	key->uid = uid;
292 	key->gid = gid;
293 	key->perm = perm;
294 
295 	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA))
296 		key->flags |= 1 << KEY_FLAG_IN_QUOTA;
297 	if (flags & KEY_ALLOC_TRUSTED)
298 		key->flags |= 1 << KEY_FLAG_TRUSTED;
299 
300 #ifdef KEY_DEBUGGING
301 	key->magic = KEY_DEBUG_MAGIC;
302 #endif
303 
304 	/* let the security module know about the key */
305 	ret = security_key_alloc(key, cred, flags);
306 	if (ret < 0)
307 		goto security_error;
308 
309 	/* publish the key by giving it a serial number */
310 	atomic_inc(&user->nkeys);
311 	key_alloc_serial(key);
312 
313 error:
314 	return key;
315 
316 security_error:
317 	kfree(key->description);
318 	kmem_cache_free(key_jar, key);
319 	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
320 		spin_lock(&user->lock);
321 		user->qnkeys--;
322 		user->qnbytes -= quotalen;
323 		spin_unlock(&user->lock);
324 	}
325 	key_user_put(user);
326 	key = ERR_PTR(ret);
327 	goto error;
328 
329 no_memory_3:
330 	kmem_cache_free(key_jar, key);
331 no_memory_2:
332 	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
333 		spin_lock(&user->lock);
334 		user->qnkeys--;
335 		user->qnbytes -= quotalen;
336 		spin_unlock(&user->lock);
337 	}
338 	key_user_put(user);
339 no_memory_1:
340 	key = ERR_PTR(-ENOMEM);
341 	goto error;
342 
343 no_quota:
344 	spin_unlock(&user->lock);
345 	key_user_put(user);
346 	key = ERR_PTR(-EDQUOT);
347 	goto error;
348 }
349 EXPORT_SYMBOL(key_alloc);
350 
351 /**
352  * key_payload_reserve - Adjust data quota reservation for the key's payload
353  * @key: The key to make the reservation for.
354  * @datalen: The amount of data payload the caller now wants.
355  *
356  * Adjust the amount of the owning user's key data quota that a key reserves.
357  * If the amount is increased, then -EDQUOT may be returned if there isn't
358  * enough free quota available.
359  *
360  * If successful, 0 is returned.
361  */
362 int key_payload_reserve(struct key *key, size_t datalen)
363 {
364 	int delta = (int)datalen - key->datalen;
365 	int ret = 0;
366 
367 	key_check(key);
368 
369 	/* contemplate the quota adjustment */
370 	if (delta != 0 && test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
371 		unsigned maxbytes = uid_eq(key->user->uid, GLOBAL_ROOT_UID) ?
372 			key_quota_root_maxbytes : key_quota_maxbytes;
373 
374 		spin_lock(&key->user->lock);
375 
376 		if (delta > 0 &&
377 		    (key->user->qnbytes + delta >= maxbytes ||
378 		     key->user->qnbytes + delta < key->user->qnbytes)) {
379 			ret = -EDQUOT;
380 		}
381 		else {
382 			key->user->qnbytes += delta;
383 			key->quotalen += delta;
384 		}
385 		spin_unlock(&key->user->lock);
386 	}
387 
388 	/* change the recorded data length if that didn't generate an error */
389 	if (ret == 0)
390 		key->datalen = datalen;
391 
392 	return ret;
393 }
394 EXPORT_SYMBOL(key_payload_reserve);
395 
396 /*
397  * Instantiate a key and link it into the target keyring atomically.  Must be
398  * called with the target keyring's semaphore writelocked.  The target key's
399  * semaphore need not be locked as instantiation is serialised by
400  * key_construction_mutex.
401  */
402 static int __key_instantiate_and_link(struct key *key,
403 				      struct key_preparsed_payload *prep,
404 				      struct key *keyring,
405 				      struct key *authkey,
406 				      struct assoc_array_edit **_edit)
407 {
408 	int ret, awaken;
409 
410 	key_check(key);
411 	key_check(keyring);
412 
413 	awaken = 0;
414 	ret = -EBUSY;
415 
416 	mutex_lock(&key_construction_mutex);
417 
418 	/* can't instantiate twice */
419 	if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
420 		/* instantiate the key */
421 		ret = key->type->instantiate(key, prep);
422 
423 		if (ret == 0) {
424 			/* mark the key as being instantiated */
425 			atomic_inc(&key->user->nikeys);
426 			set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
427 
428 			if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
429 				awaken = 1;
430 
431 			/* and link it into the destination keyring */
432 			if (keyring)
433 				__key_link(key, _edit);
434 
435 			/* disable the authorisation key */
436 			if (authkey)
437 				key_revoke(authkey);
438 
439 			if (prep->expiry != TIME_T_MAX) {
440 				key->expiry = prep->expiry;
441 				key_schedule_gc(prep->expiry + key_gc_delay);
442 			}
443 		}
444 	}
445 
446 	mutex_unlock(&key_construction_mutex);
447 
448 	/* wake up anyone waiting for a key to be constructed */
449 	if (awaken)
450 		wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
451 
452 	return ret;
453 }
454 
455 /**
456  * key_instantiate_and_link - Instantiate a key and link it into the keyring.
457  * @key: The key to instantiate.
458  * @data: The data to use to instantiate the keyring.
459  * @datalen: The length of @data.
460  * @keyring: Keyring to create a link in on success (or NULL).
461  * @authkey: The authorisation token permitting instantiation.
462  *
463  * Instantiate a key that's in the uninstantiated state using the provided data
464  * and, if successful, link it in to the destination keyring if one is
465  * supplied.
466  *
467  * If successful, 0 is returned, the authorisation token is revoked and anyone
468  * waiting for the key is woken up.  If the key was already instantiated,
469  * -EBUSY will be returned.
470  */
471 int key_instantiate_and_link(struct key *key,
472 			     const void *data,
473 			     size_t datalen,
474 			     struct key *keyring,
475 			     struct key *authkey)
476 {
477 	struct key_preparsed_payload prep;
478 	struct assoc_array_edit *edit;
479 	int ret;
480 
481 	memset(&prep, 0, sizeof(prep));
482 	prep.data = data;
483 	prep.datalen = datalen;
484 	prep.quotalen = key->type->def_datalen;
485 	prep.expiry = TIME_T_MAX;
486 	if (key->type->preparse) {
487 		ret = key->type->preparse(&prep);
488 		if (ret < 0)
489 			goto error;
490 	}
491 
492 	if (keyring) {
493 		ret = __key_link_begin(keyring, &key->index_key, &edit);
494 		if (ret < 0)
495 			goto error;
496 	}
497 
498 	ret = __key_instantiate_and_link(key, &prep, keyring, authkey, &edit);
499 
500 	if (keyring)
501 		__key_link_end(keyring, &key->index_key, edit);
502 
503 error:
504 	if (key->type->preparse)
505 		key->type->free_preparse(&prep);
506 	return ret;
507 }
508 
509 EXPORT_SYMBOL(key_instantiate_and_link);
510 
511 /**
512  * key_reject_and_link - Negatively instantiate a key and link it into the keyring.
513  * @key: The key to instantiate.
514  * @timeout: The timeout on the negative key.
515  * @error: The error to return when the key is hit.
516  * @keyring: Keyring to create a link in on success (or NULL).
517  * @authkey: The authorisation token permitting instantiation.
518  *
519  * Negatively instantiate a key that's in the uninstantiated state and, if
520  * successful, set its timeout and stored error and link it in to the
521  * destination keyring if one is supplied.  The key and any links to the key
522  * will be automatically garbage collected after the timeout expires.
523  *
524  * Negative keys are used to rate limit repeated request_key() calls by causing
525  * them to return the stored error code (typically ENOKEY) until the negative
526  * key expires.
527  *
528  * If successful, 0 is returned, the authorisation token is revoked and anyone
529  * waiting for the key is woken up.  If the key was already instantiated,
530  * -EBUSY will be returned.
531  */
532 int key_reject_and_link(struct key *key,
533 			unsigned timeout,
534 			unsigned error,
535 			struct key *keyring,
536 			struct key *authkey)
537 {
538 	struct assoc_array_edit *edit;
539 	struct timespec now;
540 	int ret, awaken, link_ret = 0;
541 
542 	key_check(key);
543 	key_check(keyring);
544 
545 	awaken = 0;
546 	ret = -EBUSY;
547 
548 	if (keyring)
549 		link_ret = __key_link_begin(keyring, &key->index_key, &edit);
550 
551 	mutex_lock(&key_construction_mutex);
552 
553 	/* can't instantiate twice */
554 	if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
555 		/* mark the key as being negatively instantiated */
556 		atomic_inc(&key->user->nikeys);
557 		key->type_data.reject_error = -error;
558 		smp_wmb();
559 		set_bit(KEY_FLAG_NEGATIVE, &key->flags);
560 		set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
561 		now = current_kernel_time();
562 		key->expiry = now.tv_sec + timeout;
563 		key_schedule_gc(key->expiry + key_gc_delay);
564 
565 		if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
566 			awaken = 1;
567 
568 		ret = 0;
569 
570 		/* and link it into the destination keyring */
571 		if (keyring && link_ret == 0)
572 			__key_link(key, &edit);
573 
574 		/* disable the authorisation key */
575 		if (authkey)
576 			key_revoke(authkey);
577 	}
578 
579 	mutex_unlock(&key_construction_mutex);
580 
581 	if (keyring)
582 		__key_link_end(keyring, &key->index_key, edit);
583 
584 	/* wake up anyone waiting for a key to be constructed */
585 	if (awaken)
586 		wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
587 
588 	return ret == 0 ? link_ret : ret;
589 }
590 EXPORT_SYMBOL(key_reject_and_link);
591 
592 /**
593  * key_put - Discard a reference to a key.
594  * @key: The key to discard a reference from.
595  *
596  * Discard a reference to a key, and when all the references are gone, we
597  * schedule the cleanup task to come and pull it out of the tree in process
598  * context at some later time.
599  */
600 void key_put(struct key *key)
601 {
602 	if (key) {
603 		key_check(key);
604 
605 		if (atomic_dec_and_test(&key->usage))
606 			schedule_work(&key_gc_work);
607 	}
608 }
609 EXPORT_SYMBOL(key_put);
610 
611 /*
612  * Find a key by its serial number.
613  */
614 struct key *key_lookup(key_serial_t id)
615 {
616 	struct rb_node *n;
617 	struct key *key;
618 
619 	spin_lock(&key_serial_lock);
620 
621 	/* search the tree for the specified key */
622 	n = key_serial_tree.rb_node;
623 	while (n) {
624 		key = rb_entry(n, struct key, serial_node);
625 
626 		if (id < key->serial)
627 			n = n->rb_left;
628 		else if (id > key->serial)
629 			n = n->rb_right;
630 		else
631 			goto found;
632 	}
633 
634 not_found:
635 	key = ERR_PTR(-ENOKEY);
636 	goto error;
637 
638 found:
639 	/* pretend it doesn't exist if it is awaiting deletion */
640 	if (atomic_read(&key->usage) == 0)
641 		goto not_found;
642 
643 	/* this races with key_put(), but that doesn't matter since key_put()
644 	 * doesn't actually change the key
645 	 */
646 	__key_get(key);
647 
648 error:
649 	spin_unlock(&key_serial_lock);
650 	return key;
651 }
652 
653 /*
654  * Find and lock the specified key type against removal.
655  *
656  * We return with the sem read-locked if successful.  If the type wasn't
657  * available -ENOKEY is returned instead.
658  */
659 struct key_type *key_type_lookup(const char *type)
660 {
661 	struct key_type *ktype;
662 
663 	down_read(&key_types_sem);
664 
665 	/* look up the key type to see if it's one of the registered kernel
666 	 * types */
667 	list_for_each_entry(ktype, &key_types_list, link) {
668 		if (strcmp(ktype->name, type) == 0)
669 			goto found_kernel_type;
670 	}
671 
672 	up_read(&key_types_sem);
673 	ktype = ERR_PTR(-ENOKEY);
674 
675 found_kernel_type:
676 	return ktype;
677 }
678 
679 void key_set_timeout(struct key *key, unsigned timeout)
680 {
681 	struct timespec now;
682 	time_t expiry = 0;
683 
684 	/* make the changes with the locks held to prevent races */
685 	down_write(&key->sem);
686 
687 	if (timeout > 0) {
688 		now = current_kernel_time();
689 		expiry = now.tv_sec + timeout;
690 	}
691 
692 	key->expiry = expiry;
693 	key_schedule_gc(key->expiry + key_gc_delay);
694 
695 	up_write(&key->sem);
696 }
697 EXPORT_SYMBOL_GPL(key_set_timeout);
698 
699 /*
700  * Unlock a key type locked by key_type_lookup().
701  */
702 void key_type_put(struct key_type *ktype)
703 {
704 	up_read(&key_types_sem);
705 }
706 
707 /*
708  * Attempt to update an existing key.
709  *
710  * The key is given to us with an incremented refcount that we need to discard
711  * if we get an error.
712  */
713 static inline key_ref_t __key_update(key_ref_t key_ref,
714 				     struct key_preparsed_payload *prep)
715 {
716 	struct key *key = key_ref_to_ptr(key_ref);
717 	int ret;
718 
719 	/* need write permission on the key to update it */
720 	ret = key_permission(key_ref, KEY_NEED_WRITE);
721 	if (ret < 0)
722 		goto error;
723 
724 	ret = -EEXIST;
725 	if (!key->type->update)
726 		goto error;
727 
728 	down_write(&key->sem);
729 
730 	ret = key->type->update(key, prep);
731 	if (ret == 0)
732 		/* updating a negative key instantiates it */
733 		clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
734 
735 	up_write(&key->sem);
736 
737 	if (ret < 0)
738 		goto error;
739 out:
740 	return key_ref;
741 
742 error:
743 	key_put(key);
744 	key_ref = ERR_PTR(ret);
745 	goto out;
746 }
747 
748 /**
749  * key_create_or_update - Update or create and instantiate a key.
750  * @keyring_ref: A pointer to the destination keyring with possession flag.
751  * @type: The type of key.
752  * @description: The searchable description for the key.
753  * @payload: The data to use to instantiate or update the key.
754  * @plen: The length of @payload.
755  * @perm: The permissions mask for a new key.
756  * @flags: The quota flags for a new key.
757  *
758  * Search the destination keyring for a key of the same description and if one
759  * is found, update it, otherwise create and instantiate a new one and create a
760  * link to it from that keyring.
761  *
762  * If perm is KEY_PERM_UNDEF then an appropriate key permissions mask will be
763  * concocted.
764  *
765  * Returns a pointer to the new key if successful, -ENODEV if the key type
766  * wasn't available, -ENOTDIR if the keyring wasn't a keyring, -EACCES if the
767  * caller isn't permitted to modify the keyring or the LSM did not permit
768  * creation of the key.
769  *
770  * On success, the possession flag from the keyring ref will be tacked on to
771  * the key ref before it is returned.
772  */
773 key_ref_t key_create_or_update(key_ref_t keyring_ref,
774 			       const char *type,
775 			       const char *description,
776 			       const void *payload,
777 			       size_t plen,
778 			       key_perm_t perm,
779 			       unsigned long flags)
780 {
781 	struct keyring_index_key index_key = {
782 		.description	= description,
783 	};
784 	struct key_preparsed_payload prep;
785 	struct assoc_array_edit *edit;
786 	const struct cred *cred = current_cred();
787 	struct key *keyring, *key = NULL;
788 	key_ref_t key_ref;
789 	int ret;
790 
791 	/* look up the key type to see if it's one of the registered kernel
792 	 * types */
793 	index_key.type = key_type_lookup(type);
794 	if (IS_ERR(index_key.type)) {
795 		key_ref = ERR_PTR(-ENODEV);
796 		goto error;
797 	}
798 
799 	key_ref = ERR_PTR(-EINVAL);
800 	if (!index_key.type->instantiate ||
801 	    (!index_key.description && !index_key.type->preparse))
802 		goto error_put_type;
803 
804 	keyring = key_ref_to_ptr(keyring_ref);
805 
806 	key_check(keyring);
807 
808 	key_ref = ERR_PTR(-ENOTDIR);
809 	if (keyring->type != &key_type_keyring)
810 		goto error_put_type;
811 
812 	memset(&prep, 0, sizeof(prep));
813 	prep.data = payload;
814 	prep.datalen = plen;
815 	prep.quotalen = index_key.type->def_datalen;
816 	prep.trusted = flags & KEY_ALLOC_TRUSTED;
817 	prep.expiry = TIME_T_MAX;
818 	if (index_key.type->preparse) {
819 		ret = index_key.type->preparse(&prep);
820 		if (ret < 0) {
821 			key_ref = ERR_PTR(ret);
822 			goto error_free_prep;
823 		}
824 		if (!index_key.description)
825 			index_key.description = prep.description;
826 		key_ref = ERR_PTR(-EINVAL);
827 		if (!index_key.description)
828 			goto error_free_prep;
829 	}
830 	index_key.desc_len = strlen(index_key.description);
831 
832 	key_ref = ERR_PTR(-EPERM);
833 	if (!prep.trusted && test_bit(KEY_FLAG_TRUSTED_ONLY, &keyring->flags))
834 		goto error_free_prep;
835 	flags |= prep.trusted ? KEY_ALLOC_TRUSTED : 0;
836 
837 	ret = __key_link_begin(keyring, &index_key, &edit);
838 	if (ret < 0) {
839 		key_ref = ERR_PTR(ret);
840 		goto error_free_prep;
841 	}
842 
843 	/* if we're going to allocate a new key, we're going to have
844 	 * to modify the keyring */
845 	ret = key_permission(keyring_ref, KEY_NEED_WRITE);
846 	if (ret < 0) {
847 		key_ref = ERR_PTR(ret);
848 		goto error_link_end;
849 	}
850 
851 	/* if it's possible to update this type of key, search for an existing
852 	 * key of the same type and description in the destination keyring and
853 	 * update that instead if possible
854 	 */
855 	if (index_key.type->update) {
856 		key_ref = find_key_to_update(keyring_ref, &index_key);
857 		if (key_ref)
858 			goto found_matching_key;
859 	}
860 
861 	/* if the client doesn't provide, decide on the permissions we want */
862 	if (perm == KEY_PERM_UNDEF) {
863 		perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
864 		perm |= KEY_USR_VIEW;
865 
866 		if (index_key.type->read)
867 			perm |= KEY_POS_READ;
868 
869 		if (index_key.type == &key_type_keyring ||
870 		    index_key.type->update)
871 			perm |= KEY_POS_WRITE;
872 	}
873 
874 	/* allocate a new key */
875 	key = key_alloc(index_key.type, index_key.description,
876 			cred->fsuid, cred->fsgid, cred, perm, flags);
877 	if (IS_ERR(key)) {
878 		key_ref = ERR_CAST(key);
879 		goto error_link_end;
880 	}
881 
882 	/* instantiate it and link it into the target keyring */
883 	ret = __key_instantiate_and_link(key, &prep, keyring, NULL, &edit);
884 	if (ret < 0) {
885 		key_put(key);
886 		key_ref = ERR_PTR(ret);
887 		goto error_link_end;
888 	}
889 
890 	key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
891 
892 error_link_end:
893 	__key_link_end(keyring, &index_key, edit);
894 error_free_prep:
895 	if (index_key.type->preparse)
896 		index_key.type->free_preparse(&prep);
897 error_put_type:
898 	key_type_put(index_key.type);
899 error:
900 	return key_ref;
901 
902  found_matching_key:
903 	/* we found a matching key, so we're going to try to update it
904 	 * - we can drop the locks first as we have the key pinned
905 	 */
906 	__key_link_end(keyring, &index_key, edit);
907 
908 	key_ref = __key_update(key_ref, &prep);
909 	goto error_free_prep;
910 }
911 EXPORT_SYMBOL(key_create_or_update);
912 
913 /**
914  * key_update - Update a key's contents.
915  * @key_ref: The pointer (plus possession flag) to the key.
916  * @payload: The data to be used to update the key.
917  * @plen: The length of @payload.
918  *
919  * Attempt to update the contents of a key with the given payload data.  The
920  * caller must be granted Write permission on the key.  Negative keys can be
921  * instantiated by this method.
922  *
923  * Returns 0 on success, -EACCES if not permitted and -EOPNOTSUPP if the key
924  * type does not support updating.  The key type may return other errors.
925  */
926 int key_update(key_ref_t key_ref, const void *payload, size_t plen)
927 {
928 	struct key_preparsed_payload prep;
929 	struct key *key = key_ref_to_ptr(key_ref);
930 	int ret;
931 
932 	key_check(key);
933 
934 	/* the key must be writable */
935 	ret = key_permission(key_ref, KEY_NEED_WRITE);
936 	if (ret < 0)
937 		goto error;
938 
939 	/* attempt to update it if supported */
940 	ret = -EOPNOTSUPP;
941 	if (!key->type->update)
942 		goto error;
943 
944 	memset(&prep, 0, sizeof(prep));
945 	prep.data = payload;
946 	prep.datalen = plen;
947 	prep.quotalen = key->type->def_datalen;
948 	prep.expiry = TIME_T_MAX;
949 	if (key->type->preparse) {
950 		ret = key->type->preparse(&prep);
951 		if (ret < 0)
952 			goto error;
953 	}
954 
955 	down_write(&key->sem);
956 
957 	ret = key->type->update(key, &prep);
958 	if (ret == 0)
959 		/* updating a negative key instantiates it */
960 		clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
961 
962 	up_write(&key->sem);
963 
964 error:
965 	if (key->type->preparse)
966 		key->type->free_preparse(&prep);
967 	return ret;
968 }
969 EXPORT_SYMBOL(key_update);
970 
971 /**
972  * key_revoke - Revoke a key.
973  * @key: The key to be revoked.
974  *
975  * Mark a key as being revoked and ask the type to free up its resources.  The
976  * revocation timeout is set and the key and all its links will be
977  * automatically garbage collected after key_gc_delay amount of time if they
978  * are not manually dealt with first.
979  */
980 void key_revoke(struct key *key)
981 {
982 	struct timespec now;
983 	time_t time;
984 
985 	key_check(key);
986 
987 	/* make sure no one's trying to change or use the key when we mark it
988 	 * - we tell lockdep that we might nest because we might be revoking an
989 	 *   authorisation key whilst holding the sem on a key we've just
990 	 *   instantiated
991 	 */
992 	down_write_nested(&key->sem, 1);
993 	if (!test_and_set_bit(KEY_FLAG_REVOKED, &key->flags) &&
994 	    key->type->revoke)
995 		key->type->revoke(key);
996 
997 	/* set the death time to no more than the expiry time */
998 	now = current_kernel_time();
999 	time = now.tv_sec;
1000 	if (key->revoked_at == 0 || key->revoked_at > time) {
1001 		key->revoked_at = time;
1002 		key_schedule_gc(key->revoked_at + key_gc_delay);
1003 	}
1004 
1005 	up_write(&key->sem);
1006 }
1007 EXPORT_SYMBOL(key_revoke);
1008 
1009 /**
1010  * key_invalidate - Invalidate a key.
1011  * @key: The key to be invalidated.
1012  *
1013  * Mark a key as being invalidated and have it cleaned up immediately.  The key
1014  * is ignored by all searches and other operations from this point.
1015  */
1016 void key_invalidate(struct key *key)
1017 {
1018 	kenter("%d", key_serial(key));
1019 
1020 	key_check(key);
1021 
1022 	if (!test_bit(KEY_FLAG_INVALIDATED, &key->flags)) {
1023 		down_write_nested(&key->sem, 1);
1024 		if (!test_and_set_bit(KEY_FLAG_INVALIDATED, &key->flags))
1025 			key_schedule_gc_links();
1026 		up_write(&key->sem);
1027 	}
1028 }
1029 EXPORT_SYMBOL(key_invalidate);
1030 
1031 /**
1032  * generic_key_instantiate - Simple instantiation of a key from preparsed data
1033  * @key: The key to be instantiated
1034  * @prep: The preparsed data to load.
1035  *
1036  * Instantiate a key from preparsed data.  We assume we can just copy the data
1037  * in directly and clear the old pointers.
1038  *
1039  * This can be pointed to directly by the key type instantiate op pointer.
1040  */
1041 int generic_key_instantiate(struct key *key, struct key_preparsed_payload *prep)
1042 {
1043 	int ret;
1044 
1045 	pr_devel("==>%s()\n", __func__);
1046 
1047 	ret = key_payload_reserve(key, prep->quotalen);
1048 	if (ret == 0) {
1049 		key->type_data.p[0] = prep->type_data[0];
1050 		key->type_data.p[1] = prep->type_data[1];
1051 		rcu_assign_keypointer(key, prep->payload[0]);
1052 		key->payload.data2[1] = prep->payload[1];
1053 		prep->type_data[0] = NULL;
1054 		prep->type_data[1] = NULL;
1055 		prep->payload[0] = NULL;
1056 		prep->payload[1] = NULL;
1057 	}
1058 	pr_devel("<==%s() = %d\n", __func__, ret);
1059 	return ret;
1060 }
1061 EXPORT_SYMBOL(generic_key_instantiate);
1062 
1063 /**
1064  * register_key_type - Register a type of key.
1065  * @ktype: The new key type.
1066  *
1067  * Register a new key type.
1068  *
1069  * Returns 0 on success or -EEXIST if a type of this name already exists.
1070  */
1071 int register_key_type(struct key_type *ktype)
1072 {
1073 	struct key_type *p;
1074 	int ret;
1075 
1076 	memset(&ktype->lock_class, 0, sizeof(ktype->lock_class));
1077 
1078 	ret = -EEXIST;
1079 	down_write(&key_types_sem);
1080 
1081 	/* disallow key types with the same name */
1082 	list_for_each_entry(p, &key_types_list, link) {
1083 		if (strcmp(p->name, ktype->name) == 0)
1084 			goto out;
1085 	}
1086 
1087 	/* store the type */
1088 	list_add(&ktype->link, &key_types_list);
1089 
1090 	pr_notice("Key type %s registered\n", ktype->name);
1091 	ret = 0;
1092 
1093 out:
1094 	up_write(&key_types_sem);
1095 	return ret;
1096 }
1097 EXPORT_SYMBOL(register_key_type);
1098 
1099 /**
1100  * unregister_key_type - Unregister a type of key.
1101  * @ktype: The key type.
1102  *
1103  * Unregister a key type and mark all the extant keys of this type as dead.
1104  * Those keys of this type are then destroyed to get rid of their payloads and
1105  * they and their links will be garbage collected as soon as possible.
1106  */
1107 void unregister_key_type(struct key_type *ktype)
1108 {
1109 	down_write(&key_types_sem);
1110 	list_del_init(&ktype->link);
1111 	downgrade_write(&key_types_sem);
1112 	key_gc_keytype(ktype);
1113 	pr_notice("Key type %s unregistered\n", ktype->name);
1114 	up_read(&key_types_sem);
1115 }
1116 EXPORT_SYMBOL(unregister_key_type);
1117 
1118 /*
1119  * Initialise the key management state.
1120  */
1121 void __init key_init(void)
1122 {
1123 	/* allocate a slab in which we can store keys */
1124 	key_jar = kmem_cache_create("key_jar", sizeof(struct key),
1125 			0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1126 
1127 	/* add the special key types */
1128 	list_add_tail(&key_type_keyring.link, &key_types_list);
1129 	list_add_tail(&key_type_dead.link, &key_types_list);
1130 	list_add_tail(&key_type_user.link, &key_types_list);
1131 	list_add_tail(&key_type_logon.link, &key_types_list);
1132 
1133 	/* record the root user tracking */
1134 	rb_link_node(&root_key_user.node,
1135 		     NULL,
1136 		     &key_user_tree.rb_node);
1137 
1138 	rb_insert_color(&root_key_user.node,
1139 			&key_user_tree);
1140 }
1141