xref: /openbmc/linux/security/keys/key.c (revision b830f94f)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Basic authentication token and access key management
3  *
4  * Copyright (C) 2004-2008 Red Hat, Inc. All Rights Reserved.
5  * Written by David Howells (dhowells@redhat.com)
6  */
7 
8 #include <linux/export.h>
9 #include <linux/init.h>
10 #include <linux/poison.h>
11 #include <linux/sched.h>
12 #include <linux/slab.h>
13 #include <linux/security.h>
14 #include <linux/workqueue.h>
15 #include <linux/random.h>
16 #include <linux/err.h>
17 #include "internal.h"
18 
19 struct kmem_cache *key_jar;
20 struct rb_root		key_serial_tree; /* tree of keys indexed by serial */
21 DEFINE_SPINLOCK(key_serial_lock);
22 
23 struct rb_root	key_user_tree; /* tree of quota records indexed by UID */
24 DEFINE_SPINLOCK(key_user_lock);
25 
26 unsigned int key_quota_root_maxkeys = 1000000;	/* root's key count quota */
27 unsigned int key_quota_root_maxbytes = 25000000; /* root's key space quota */
28 unsigned int key_quota_maxkeys = 200;		/* general key count quota */
29 unsigned int key_quota_maxbytes = 20000;	/* general key space quota */
30 
31 static LIST_HEAD(key_types_list);
32 static DECLARE_RWSEM(key_types_sem);
33 
34 /* We serialise key instantiation and link */
35 DEFINE_MUTEX(key_construction_mutex);
36 
37 #ifdef KEY_DEBUGGING
38 void __key_check(const struct key *key)
39 {
40 	printk("__key_check: key %p {%08x} should be {%08x}\n",
41 	       key, key->magic, KEY_DEBUG_MAGIC);
42 	BUG();
43 }
44 #endif
45 
46 /*
47  * Get the key quota record for a user, allocating a new record if one doesn't
48  * already exist.
49  */
50 struct key_user *key_user_lookup(kuid_t uid)
51 {
52 	struct key_user *candidate = NULL, *user;
53 	struct rb_node *parent, **p;
54 
55 try_again:
56 	parent = NULL;
57 	p = &key_user_tree.rb_node;
58 	spin_lock(&key_user_lock);
59 
60 	/* search the tree for a user record with a matching UID */
61 	while (*p) {
62 		parent = *p;
63 		user = rb_entry(parent, struct key_user, node);
64 
65 		if (uid_lt(uid, user->uid))
66 			p = &(*p)->rb_left;
67 		else if (uid_gt(uid, user->uid))
68 			p = &(*p)->rb_right;
69 		else
70 			goto found;
71 	}
72 
73 	/* if we get here, we failed to find a match in the tree */
74 	if (!candidate) {
75 		/* allocate a candidate user record if we don't already have
76 		 * one */
77 		spin_unlock(&key_user_lock);
78 
79 		user = NULL;
80 		candidate = kmalloc(sizeof(struct key_user), GFP_KERNEL);
81 		if (unlikely(!candidate))
82 			goto out;
83 
84 		/* the allocation may have scheduled, so we need to repeat the
85 		 * search lest someone else added the record whilst we were
86 		 * asleep */
87 		goto try_again;
88 	}
89 
90 	/* if we get here, then the user record still hadn't appeared on the
91 	 * second pass - so we use the candidate record */
92 	refcount_set(&candidate->usage, 1);
93 	atomic_set(&candidate->nkeys, 0);
94 	atomic_set(&candidate->nikeys, 0);
95 	candidate->uid = uid;
96 	candidate->qnkeys = 0;
97 	candidate->qnbytes = 0;
98 	spin_lock_init(&candidate->lock);
99 	mutex_init(&candidate->cons_lock);
100 
101 	rb_link_node(&candidate->node, parent, p);
102 	rb_insert_color(&candidate->node, &key_user_tree);
103 	spin_unlock(&key_user_lock);
104 	user = candidate;
105 	goto out;
106 
107 	/* okay - we found a user record for this UID */
108 found:
109 	refcount_inc(&user->usage);
110 	spin_unlock(&key_user_lock);
111 	kfree(candidate);
112 out:
113 	return user;
114 }
115 
116 /*
117  * Dispose of a user structure
118  */
119 void key_user_put(struct key_user *user)
120 {
121 	if (refcount_dec_and_lock(&user->usage, &key_user_lock)) {
122 		rb_erase(&user->node, &key_user_tree);
123 		spin_unlock(&key_user_lock);
124 
125 		kfree(user);
126 	}
127 }
128 
129 /*
130  * Allocate a serial number for a key.  These are assigned randomly to avoid
131  * security issues through covert channel problems.
132  */
133 static inline void key_alloc_serial(struct key *key)
134 {
135 	struct rb_node *parent, **p;
136 	struct key *xkey;
137 
138 	/* propose a random serial number and look for a hole for it in the
139 	 * serial number tree */
140 	do {
141 		get_random_bytes(&key->serial, sizeof(key->serial));
142 
143 		key->serial >>= 1; /* negative numbers are not permitted */
144 	} while (key->serial < 3);
145 
146 	spin_lock(&key_serial_lock);
147 
148 attempt_insertion:
149 	parent = NULL;
150 	p = &key_serial_tree.rb_node;
151 
152 	while (*p) {
153 		parent = *p;
154 		xkey = rb_entry(parent, struct key, serial_node);
155 
156 		if (key->serial < xkey->serial)
157 			p = &(*p)->rb_left;
158 		else if (key->serial > xkey->serial)
159 			p = &(*p)->rb_right;
160 		else
161 			goto serial_exists;
162 	}
163 
164 	/* we've found a suitable hole - arrange for this key to occupy it */
165 	rb_link_node(&key->serial_node, parent, p);
166 	rb_insert_color(&key->serial_node, &key_serial_tree);
167 
168 	spin_unlock(&key_serial_lock);
169 	return;
170 
171 	/* we found a key with the proposed serial number - walk the tree from
172 	 * that point looking for the next unused serial number */
173 serial_exists:
174 	for (;;) {
175 		key->serial++;
176 		if (key->serial < 3) {
177 			key->serial = 3;
178 			goto attempt_insertion;
179 		}
180 
181 		parent = rb_next(parent);
182 		if (!parent)
183 			goto attempt_insertion;
184 
185 		xkey = rb_entry(parent, struct key, serial_node);
186 		if (key->serial < xkey->serial)
187 			goto attempt_insertion;
188 	}
189 }
190 
191 /**
192  * key_alloc - Allocate a key of the specified type.
193  * @type: The type of key to allocate.
194  * @desc: The key description to allow the key to be searched out.
195  * @uid: The owner of the new key.
196  * @gid: The group ID for the new key's group permissions.
197  * @cred: The credentials specifying UID namespace.
198  * @perm: The permissions mask of the new key.
199  * @flags: Flags specifying quota properties.
200  * @restrict_link: Optional link restriction for new keyrings.
201  *
202  * Allocate a key of the specified type with the attributes given.  The key is
203  * returned in an uninstantiated state and the caller needs to instantiate the
204  * key before returning.
205  *
206  * The restrict_link structure (if not NULL) will be freed when the
207  * keyring is destroyed, so it must be dynamically allocated.
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 		      struct key_restriction *restrict_link)
228 {
229 	struct key_user *user = NULL;
230 	struct key *key;
231 	size_t desclen, quotalen;
232 	int ret;
233 
234 	key = ERR_PTR(-EINVAL);
235 	if (!desc || !*desc)
236 		goto error;
237 
238 	if (type->vet_description) {
239 		ret = type->vet_description(desc);
240 		if (ret < 0) {
241 			key = ERR_PTR(ret);
242 			goto error;
243 		}
244 	}
245 
246 	desclen = strlen(desc);
247 	quotalen = desclen + 1 + type->def_datalen;
248 
249 	/* get hold of the key tracking for this user */
250 	user = key_user_lookup(uid);
251 	if (!user)
252 		goto no_memory_1;
253 
254 	/* check that the user's quota permits allocation of another key and
255 	 * its description */
256 	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
257 		unsigned maxkeys = uid_eq(uid, GLOBAL_ROOT_UID) ?
258 			key_quota_root_maxkeys : key_quota_maxkeys;
259 		unsigned maxbytes = uid_eq(uid, GLOBAL_ROOT_UID) ?
260 			key_quota_root_maxbytes : key_quota_maxbytes;
261 
262 		spin_lock(&user->lock);
263 		if (!(flags & KEY_ALLOC_QUOTA_OVERRUN)) {
264 			if (user->qnkeys + 1 > maxkeys ||
265 			    user->qnbytes + quotalen > maxbytes ||
266 			    user->qnbytes + quotalen < user->qnbytes)
267 				goto no_quota;
268 		}
269 
270 		user->qnkeys++;
271 		user->qnbytes += quotalen;
272 		spin_unlock(&user->lock);
273 	}
274 
275 	/* allocate and initialise the key and its description */
276 	key = kmem_cache_zalloc(key_jar, GFP_KERNEL);
277 	if (!key)
278 		goto no_memory_2;
279 
280 	key->index_key.desc_len = desclen;
281 	key->index_key.description = kmemdup(desc, desclen + 1, GFP_KERNEL);
282 	if (!key->index_key.description)
283 		goto no_memory_3;
284 	key->index_key.type = type;
285 	key_set_index_key(&key->index_key);
286 
287 	refcount_set(&key->usage, 1);
288 	init_rwsem(&key->sem);
289 	lockdep_set_class(&key->sem, &type->lock_class);
290 	key->user = user;
291 	key->quotalen = quotalen;
292 	key->datalen = type->def_datalen;
293 	key->uid = uid;
294 	key->gid = gid;
295 	key->perm = perm;
296 	key->restrict_link = restrict_link;
297 	key->last_used_at = ktime_get_real_seconds();
298 
299 	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA))
300 		key->flags |= 1 << KEY_FLAG_IN_QUOTA;
301 	if (flags & KEY_ALLOC_BUILT_IN)
302 		key->flags |= 1 << KEY_FLAG_BUILTIN;
303 	if (flags & KEY_ALLOC_UID_KEYRING)
304 		key->flags |= 1 << KEY_FLAG_UID_KEYRING;
305 
306 #ifdef KEY_DEBUGGING
307 	key->magic = KEY_DEBUG_MAGIC;
308 #endif
309 
310 	/* let the security module know about the key */
311 	ret = security_key_alloc(key, cred, flags);
312 	if (ret < 0)
313 		goto security_error;
314 
315 	/* publish the key by giving it a serial number */
316 	refcount_inc(&key->domain_tag->usage);
317 	atomic_inc(&user->nkeys);
318 	key_alloc_serial(key);
319 
320 error:
321 	return key;
322 
323 security_error:
324 	kfree(key->description);
325 	kmem_cache_free(key_jar, key);
326 	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
327 		spin_lock(&user->lock);
328 		user->qnkeys--;
329 		user->qnbytes -= quotalen;
330 		spin_unlock(&user->lock);
331 	}
332 	key_user_put(user);
333 	key = ERR_PTR(ret);
334 	goto error;
335 
336 no_memory_3:
337 	kmem_cache_free(key_jar, key);
338 no_memory_2:
339 	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
340 		spin_lock(&user->lock);
341 		user->qnkeys--;
342 		user->qnbytes -= quotalen;
343 		spin_unlock(&user->lock);
344 	}
345 	key_user_put(user);
346 no_memory_1:
347 	key = ERR_PTR(-ENOMEM);
348 	goto error;
349 
350 no_quota:
351 	spin_unlock(&user->lock);
352 	key_user_put(user);
353 	key = ERR_PTR(-EDQUOT);
354 	goto error;
355 }
356 EXPORT_SYMBOL(key_alloc);
357 
358 /**
359  * key_payload_reserve - Adjust data quota reservation for the key's payload
360  * @key: The key to make the reservation for.
361  * @datalen: The amount of data payload the caller now wants.
362  *
363  * Adjust the amount of the owning user's key data quota that a key reserves.
364  * If the amount is increased, then -EDQUOT may be returned if there isn't
365  * enough free quota available.
366  *
367  * If successful, 0 is returned.
368  */
369 int key_payload_reserve(struct key *key, size_t datalen)
370 {
371 	int delta = (int)datalen - key->datalen;
372 	int ret = 0;
373 
374 	key_check(key);
375 
376 	/* contemplate the quota adjustment */
377 	if (delta != 0 && test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
378 		unsigned maxbytes = uid_eq(key->user->uid, GLOBAL_ROOT_UID) ?
379 			key_quota_root_maxbytes : key_quota_maxbytes;
380 
381 		spin_lock(&key->user->lock);
382 
383 		if (delta > 0 &&
384 		    (key->user->qnbytes + delta >= maxbytes ||
385 		     key->user->qnbytes + delta < key->user->qnbytes)) {
386 			ret = -EDQUOT;
387 		}
388 		else {
389 			key->user->qnbytes += delta;
390 			key->quotalen += delta;
391 		}
392 		spin_unlock(&key->user->lock);
393 	}
394 
395 	/* change the recorded data length if that didn't generate an error */
396 	if (ret == 0)
397 		key->datalen = datalen;
398 
399 	return ret;
400 }
401 EXPORT_SYMBOL(key_payload_reserve);
402 
403 /*
404  * Change the key state to being instantiated.
405  */
406 static void mark_key_instantiated(struct key *key, int reject_error)
407 {
408 	/* Commit the payload before setting the state; barrier versus
409 	 * key_read_state().
410 	 */
411 	smp_store_release(&key->state,
412 			  (reject_error < 0) ? reject_error : KEY_IS_POSITIVE);
413 }
414 
415 /*
416  * Instantiate a key and link it into the target keyring atomically.  Must be
417  * called with the target keyring's semaphore writelocked.  The target key's
418  * semaphore need not be locked as instantiation is serialised by
419  * key_construction_mutex.
420  */
421 static int __key_instantiate_and_link(struct key *key,
422 				      struct key_preparsed_payload *prep,
423 				      struct key *keyring,
424 				      struct key *authkey,
425 				      struct assoc_array_edit **_edit)
426 {
427 	int ret, awaken;
428 
429 	key_check(key);
430 	key_check(keyring);
431 
432 	awaken = 0;
433 	ret = -EBUSY;
434 
435 	mutex_lock(&key_construction_mutex);
436 
437 	/* can't instantiate twice */
438 	if (key->state == KEY_IS_UNINSTANTIATED) {
439 		/* instantiate the key */
440 		ret = key->type->instantiate(key, prep);
441 
442 		if (ret == 0) {
443 			/* mark the key as being instantiated */
444 			atomic_inc(&key->user->nikeys);
445 			mark_key_instantiated(key, 0);
446 
447 			if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
448 				awaken = 1;
449 
450 			/* and link it into the destination keyring */
451 			if (keyring) {
452 				if (test_bit(KEY_FLAG_KEEP, &keyring->flags))
453 					set_bit(KEY_FLAG_KEEP, &key->flags);
454 
455 				__key_link(key, _edit);
456 			}
457 
458 			/* disable the authorisation key */
459 			if (authkey)
460 				key_invalidate(authkey);
461 
462 			if (prep->expiry != TIME64_MAX) {
463 				key->expiry = prep->expiry;
464 				key_schedule_gc(prep->expiry + key_gc_delay);
465 			}
466 		}
467 	}
468 
469 	mutex_unlock(&key_construction_mutex);
470 
471 	/* wake up anyone waiting for a key to be constructed */
472 	if (awaken)
473 		wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
474 
475 	return ret;
476 }
477 
478 /**
479  * key_instantiate_and_link - Instantiate a key and link it into the keyring.
480  * @key: The key to instantiate.
481  * @data: The data to use to instantiate the keyring.
482  * @datalen: The length of @data.
483  * @keyring: Keyring to create a link in on success (or NULL).
484  * @authkey: The authorisation token permitting instantiation.
485  *
486  * Instantiate a key that's in the uninstantiated state using the provided data
487  * and, if successful, link it in to the destination keyring if one is
488  * supplied.
489  *
490  * If successful, 0 is returned, the authorisation token is revoked and anyone
491  * waiting for the key is woken up.  If the key was already instantiated,
492  * -EBUSY will be returned.
493  */
494 int key_instantiate_and_link(struct key *key,
495 			     const void *data,
496 			     size_t datalen,
497 			     struct key *keyring,
498 			     struct key *authkey)
499 {
500 	struct key_preparsed_payload prep;
501 	struct assoc_array_edit *edit = NULL;
502 	int ret;
503 
504 	memset(&prep, 0, sizeof(prep));
505 	prep.data = data;
506 	prep.datalen = datalen;
507 	prep.quotalen = key->type->def_datalen;
508 	prep.expiry = TIME64_MAX;
509 	if (key->type->preparse) {
510 		ret = key->type->preparse(&prep);
511 		if (ret < 0)
512 			goto error;
513 	}
514 
515 	if (keyring) {
516 		ret = __key_link_lock(keyring, &key->index_key);
517 		if (ret < 0)
518 			goto error;
519 
520 		ret = __key_link_begin(keyring, &key->index_key, &edit);
521 		if (ret < 0)
522 			goto error_link_end;
523 
524 		if (keyring->restrict_link && keyring->restrict_link->check) {
525 			struct key_restriction *keyres = keyring->restrict_link;
526 
527 			ret = keyres->check(keyring, key->type, &prep.payload,
528 					    keyres->key);
529 			if (ret < 0)
530 				goto error_link_end;
531 		}
532 	}
533 
534 	ret = __key_instantiate_and_link(key, &prep, keyring, authkey, &edit);
535 
536 error_link_end:
537 	if (keyring)
538 		__key_link_end(keyring, &key->index_key, edit);
539 
540 error:
541 	if (key->type->preparse)
542 		key->type->free_preparse(&prep);
543 	return ret;
544 }
545 
546 EXPORT_SYMBOL(key_instantiate_and_link);
547 
548 /**
549  * key_reject_and_link - Negatively instantiate a key and link it into the keyring.
550  * @key: The key to instantiate.
551  * @timeout: The timeout on the negative key.
552  * @error: The error to return when the key is hit.
553  * @keyring: Keyring to create a link in on success (or NULL).
554  * @authkey: The authorisation token permitting instantiation.
555  *
556  * Negatively instantiate a key that's in the uninstantiated state and, if
557  * successful, set its timeout and stored error and link it in to the
558  * destination keyring if one is supplied.  The key and any links to the key
559  * will be automatically garbage collected after the timeout expires.
560  *
561  * Negative keys are used to rate limit repeated request_key() calls by causing
562  * them to return the stored error code (typically ENOKEY) until the negative
563  * key expires.
564  *
565  * If successful, 0 is returned, the authorisation token is revoked and anyone
566  * waiting for the key is woken up.  If the key was already instantiated,
567  * -EBUSY will be returned.
568  */
569 int key_reject_and_link(struct key *key,
570 			unsigned timeout,
571 			unsigned error,
572 			struct key *keyring,
573 			struct key *authkey)
574 {
575 	struct assoc_array_edit *edit = NULL;
576 	int ret, awaken, link_ret = 0;
577 
578 	key_check(key);
579 	key_check(keyring);
580 
581 	awaken = 0;
582 	ret = -EBUSY;
583 
584 	if (keyring) {
585 		if (keyring->restrict_link)
586 			return -EPERM;
587 
588 		link_ret = __key_link_lock(keyring, &key->index_key);
589 		if (link_ret == 0) {
590 			link_ret = __key_link_begin(keyring, &key->index_key, &edit);
591 			if (link_ret < 0)
592 				__key_link_end(keyring, &key->index_key, edit);
593 		}
594 	}
595 
596 	mutex_lock(&key_construction_mutex);
597 
598 	/* can't instantiate twice */
599 	if (key->state == KEY_IS_UNINSTANTIATED) {
600 		/* mark the key as being negatively instantiated */
601 		atomic_inc(&key->user->nikeys);
602 		mark_key_instantiated(key, -error);
603 		key->expiry = ktime_get_real_seconds() + timeout;
604 		key_schedule_gc(key->expiry + key_gc_delay);
605 
606 		if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
607 			awaken = 1;
608 
609 		ret = 0;
610 
611 		/* and link it into the destination keyring */
612 		if (keyring && link_ret == 0)
613 			__key_link(key, &edit);
614 
615 		/* disable the authorisation key */
616 		if (authkey)
617 			key_invalidate(authkey);
618 	}
619 
620 	mutex_unlock(&key_construction_mutex);
621 
622 	if (keyring && link_ret == 0)
623 		__key_link_end(keyring, &key->index_key, edit);
624 
625 	/* wake up anyone waiting for a key to be constructed */
626 	if (awaken)
627 		wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
628 
629 	return ret == 0 ? link_ret : ret;
630 }
631 EXPORT_SYMBOL(key_reject_and_link);
632 
633 /**
634  * key_put - Discard a reference to a key.
635  * @key: The key to discard a reference from.
636  *
637  * Discard a reference to a key, and when all the references are gone, we
638  * schedule the cleanup task to come and pull it out of the tree in process
639  * context at some later time.
640  */
641 void key_put(struct key *key)
642 {
643 	if (key) {
644 		key_check(key);
645 
646 		if (refcount_dec_and_test(&key->usage))
647 			schedule_work(&key_gc_work);
648 	}
649 }
650 EXPORT_SYMBOL(key_put);
651 
652 /*
653  * Find a key by its serial number.
654  */
655 struct key *key_lookup(key_serial_t id)
656 {
657 	struct rb_node *n;
658 	struct key *key;
659 
660 	spin_lock(&key_serial_lock);
661 
662 	/* search the tree for the specified key */
663 	n = key_serial_tree.rb_node;
664 	while (n) {
665 		key = rb_entry(n, struct key, serial_node);
666 
667 		if (id < key->serial)
668 			n = n->rb_left;
669 		else if (id > key->serial)
670 			n = n->rb_right;
671 		else
672 			goto found;
673 	}
674 
675 not_found:
676 	key = ERR_PTR(-ENOKEY);
677 	goto error;
678 
679 found:
680 	/* A key is allowed to be looked up only if someone still owns a
681 	 * reference to it - otherwise it's awaiting the gc.
682 	 */
683 	if (!refcount_inc_not_zero(&key->usage))
684 		goto not_found;
685 
686 error:
687 	spin_unlock(&key_serial_lock);
688 	return key;
689 }
690 
691 /*
692  * Find and lock the specified key type against removal.
693  *
694  * We return with the sem read-locked if successful.  If the type wasn't
695  * available -ENOKEY is returned instead.
696  */
697 struct key_type *key_type_lookup(const char *type)
698 {
699 	struct key_type *ktype;
700 
701 	down_read(&key_types_sem);
702 
703 	/* look up the key type to see if it's one of the registered kernel
704 	 * types */
705 	list_for_each_entry(ktype, &key_types_list, link) {
706 		if (strcmp(ktype->name, type) == 0)
707 			goto found_kernel_type;
708 	}
709 
710 	up_read(&key_types_sem);
711 	ktype = ERR_PTR(-ENOKEY);
712 
713 found_kernel_type:
714 	return ktype;
715 }
716 
717 void key_set_timeout(struct key *key, unsigned timeout)
718 {
719 	time64_t expiry = 0;
720 
721 	/* make the changes with the locks held to prevent races */
722 	down_write(&key->sem);
723 
724 	if (timeout > 0)
725 		expiry = ktime_get_real_seconds() + timeout;
726 
727 	key->expiry = expiry;
728 	key_schedule_gc(key->expiry + key_gc_delay);
729 
730 	up_write(&key->sem);
731 }
732 EXPORT_SYMBOL_GPL(key_set_timeout);
733 
734 /*
735  * Unlock a key type locked by key_type_lookup().
736  */
737 void key_type_put(struct key_type *ktype)
738 {
739 	up_read(&key_types_sem);
740 }
741 
742 /*
743  * Attempt to update an existing key.
744  *
745  * The key is given to us with an incremented refcount that we need to discard
746  * if we get an error.
747  */
748 static inline key_ref_t __key_update(key_ref_t key_ref,
749 				     struct key_preparsed_payload *prep)
750 {
751 	struct key *key = key_ref_to_ptr(key_ref);
752 	int ret;
753 
754 	/* need write permission on the key to update it */
755 	ret = key_permission(key_ref, KEY_NEED_WRITE);
756 	if (ret < 0)
757 		goto error;
758 
759 	ret = -EEXIST;
760 	if (!key->type->update)
761 		goto error;
762 
763 	down_write(&key->sem);
764 
765 	ret = key->type->update(key, prep);
766 	if (ret == 0)
767 		/* Updating a negative key positively instantiates it */
768 		mark_key_instantiated(key, 0);
769 
770 	up_write(&key->sem);
771 
772 	if (ret < 0)
773 		goto error;
774 out:
775 	return key_ref;
776 
777 error:
778 	key_put(key);
779 	key_ref = ERR_PTR(ret);
780 	goto out;
781 }
782 
783 /**
784  * key_create_or_update - Update or create and instantiate a key.
785  * @keyring_ref: A pointer to the destination keyring with possession flag.
786  * @type: The type of key.
787  * @description: The searchable description for the key.
788  * @payload: The data to use to instantiate or update the key.
789  * @plen: The length of @payload.
790  * @perm: The permissions mask for a new key.
791  * @flags: The quota flags for a new key.
792  *
793  * Search the destination keyring for a key of the same description and if one
794  * is found, update it, otherwise create and instantiate a new one and create a
795  * link to it from that keyring.
796  *
797  * If perm is KEY_PERM_UNDEF then an appropriate key permissions mask will be
798  * concocted.
799  *
800  * Returns a pointer to the new key if successful, -ENODEV if the key type
801  * wasn't available, -ENOTDIR if the keyring wasn't a keyring, -EACCES if the
802  * caller isn't permitted to modify the keyring or the LSM did not permit
803  * creation of the key.
804  *
805  * On success, the possession flag from the keyring ref will be tacked on to
806  * the key ref before it is returned.
807  */
808 key_ref_t key_create_or_update(key_ref_t keyring_ref,
809 			       const char *type,
810 			       const char *description,
811 			       const void *payload,
812 			       size_t plen,
813 			       key_perm_t perm,
814 			       unsigned long flags)
815 {
816 	struct keyring_index_key index_key = {
817 		.description	= description,
818 	};
819 	struct key_preparsed_payload prep;
820 	struct assoc_array_edit *edit = NULL;
821 	const struct cred *cred = current_cred();
822 	struct key *keyring, *key = NULL;
823 	key_ref_t key_ref;
824 	int ret;
825 	struct key_restriction *restrict_link = NULL;
826 
827 	/* look up the key type to see if it's one of the registered kernel
828 	 * types */
829 	index_key.type = key_type_lookup(type);
830 	if (IS_ERR(index_key.type)) {
831 		key_ref = ERR_PTR(-ENODEV);
832 		goto error;
833 	}
834 
835 	key_ref = ERR_PTR(-EINVAL);
836 	if (!index_key.type->instantiate ||
837 	    (!index_key.description && !index_key.type->preparse))
838 		goto error_put_type;
839 
840 	keyring = key_ref_to_ptr(keyring_ref);
841 
842 	key_check(keyring);
843 
844 	if (!(flags & KEY_ALLOC_BYPASS_RESTRICTION))
845 		restrict_link = keyring->restrict_link;
846 
847 	key_ref = ERR_PTR(-ENOTDIR);
848 	if (keyring->type != &key_type_keyring)
849 		goto error_put_type;
850 
851 	memset(&prep, 0, sizeof(prep));
852 	prep.data = payload;
853 	prep.datalen = plen;
854 	prep.quotalen = index_key.type->def_datalen;
855 	prep.expiry = TIME64_MAX;
856 	if (index_key.type->preparse) {
857 		ret = index_key.type->preparse(&prep);
858 		if (ret < 0) {
859 			key_ref = ERR_PTR(ret);
860 			goto error_free_prep;
861 		}
862 		if (!index_key.description)
863 			index_key.description = prep.description;
864 		key_ref = ERR_PTR(-EINVAL);
865 		if (!index_key.description)
866 			goto error_free_prep;
867 	}
868 	index_key.desc_len = strlen(index_key.description);
869 	key_set_index_key(&index_key);
870 
871 	ret = __key_link_lock(keyring, &index_key);
872 	if (ret < 0) {
873 		key_ref = ERR_PTR(ret);
874 		goto error_free_prep;
875 	}
876 
877 	ret = __key_link_begin(keyring, &index_key, &edit);
878 	if (ret < 0) {
879 		key_ref = ERR_PTR(ret);
880 		goto error_link_end;
881 	}
882 
883 	if (restrict_link && restrict_link->check) {
884 		ret = restrict_link->check(keyring, index_key.type,
885 					   &prep.payload, restrict_link->key);
886 		if (ret < 0) {
887 			key_ref = ERR_PTR(ret);
888 			goto error_link_end;
889 		}
890 	}
891 
892 	/* if we're going to allocate a new key, we're going to have
893 	 * to modify the keyring */
894 	ret = key_permission(keyring_ref, KEY_NEED_WRITE);
895 	if (ret < 0) {
896 		key_ref = ERR_PTR(ret);
897 		goto error_link_end;
898 	}
899 
900 	/* if it's possible to update this type of key, search for an existing
901 	 * key of the same type and description in the destination keyring and
902 	 * update that instead if possible
903 	 */
904 	if (index_key.type->update) {
905 		key_ref = find_key_to_update(keyring_ref, &index_key);
906 		if (key_ref)
907 			goto found_matching_key;
908 	}
909 
910 	/* if the client doesn't provide, decide on the permissions we want */
911 	if (perm == KEY_PERM_UNDEF) {
912 		perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
913 		perm |= KEY_USR_VIEW;
914 
915 		if (index_key.type->read)
916 			perm |= KEY_POS_READ;
917 
918 		if (index_key.type == &key_type_keyring ||
919 		    index_key.type->update)
920 			perm |= KEY_POS_WRITE;
921 	}
922 
923 	/* allocate a new key */
924 	key = key_alloc(index_key.type, index_key.description,
925 			cred->fsuid, cred->fsgid, cred, perm, flags, NULL);
926 	if (IS_ERR(key)) {
927 		key_ref = ERR_CAST(key);
928 		goto error_link_end;
929 	}
930 
931 	/* instantiate it and link it into the target keyring */
932 	ret = __key_instantiate_and_link(key, &prep, keyring, NULL, &edit);
933 	if (ret < 0) {
934 		key_put(key);
935 		key_ref = ERR_PTR(ret);
936 		goto error_link_end;
937 	}
938 
939 	key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
940 
941 error_link_end:
942 	__key_link_end(keyring, &index_key, edit);
943 error_free_prep:
944 	if (index_key.type->preparse)
945 		index_key.type->free_preparse(&prep);
946 error_put_type:
947 	key_type_put(index_key.type);
948 error:
949 	return key_ref;
950 
951  found_matching_key:
952 	/* we found a matching key, so we're going to try to update it
953 	 * - we can drop the locks first as we have the key pinned
954 	 */
955 	__key_link_end(keyring, &index_key, edit);
956 
957 	key = key_ref_to_ptr(key_ref);
958 	if (test_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags)) {
959 		ret = wait_for_key_construction(key, true);
960 		if (ret < 0) {
961 			key_ref_put(key_ref);
962 			key_ref = ERR_PTR(ret);
963 			goto error_free_prep;
964 		}
965 	}
966 
967 	key_ref = __key_update(key_ref, &prep);
968 	goto error_free_prep;
969 }
970 EXPORT_SYMBOL(key_create_or_update);
971 
972 /**
973  * key_update - Update a key's contents.
974  * @key_ref: The pointer (plus possession flag) to the key.
975  * @payload: The data to be used to update the key.
976  * @plen: The length of @payload.
977  *
978  * Attempt to update the contents of a key with the given payload data.  The
979  * caller must be granted Write permission on the key.  Negative keys can be
980  * instantiated by this method.
981  *
982  * Returns 0 on success, -EACCES if not permitted and -EOPNOTSUPP if the key
983  * type does not support updating.  The key type may return other errors.
984  */
985 int key_update(key_ref_t key_ref, const void *payload, size_t plen)
986 {
987 	struct key_preparsed_payload prep;
988 	struct key *key = key_ref_to_ptr(key_ref);
989 	int ret;
990 
991 	key_check(key);
992 
993 	/* the key must be writable */
994 	ret = key_permission(key_ref, KEY_NEED_WRITE);
995 	if (ret < 0)
996 		return ret;
997 
998 	/* attempt to update it if supported */
999 	if (!key->type->update)
1000 		return -EOPNOTSUPP;
1001 
1002 	memset(&prep, 0, sizeof(prep));
1003 	prep.data = payload;
1004 	prep.datalen = plen;
1005 	prep.quotalen = key->type->def_datalen;
1006 	prep.expiry = TIME64_MAX;
1007 	if (key->type->preparse) {
1008 		ret = key->type->preparse(&prep);
1009 		if (ret < 0)
1010 			goto error;
1011 	}
1012 
1013 	down_write(&key->sem);
1014 
1015 	ret = key->type->update(key, &prep);
1016 	if (ret == 0)
1017 		/* Updating a negative key positively instantiates it */
1018 		mark_key_instantiated(key, 0);
1019 
1020 	up_write(&key->sem);
1021 
1022 error:
1023 	if (key->type->preparse)
1024 		key->type->free_preparse(&prep);
1025 	return ret;
1026 }
1027 EXPORT_SYMBOL(key_update);
1028 
1029 /**
1030  * key_revoke - Revoke a key.
1031  * @key: The key to be revoked.
1032  *
1033  * Mark a key as being revoked and ask the type to free up its resources.  The
1034  * revocation timeout is set and the key and all its links will be
1035  * automatically garbage collected after key_gc_delay amount of time if they
1036  * are not manually dealt with first.
1037  */
1038 void key_revoke(struct key *key)
1039 {
1040 	time64_t time;
1041 
1042 	key_check(key);
1043 
1044 	/* make sure no one's trying to change or use the key when we mark it
1045 	 * - we tell lockdep that we might nest because we might be revoking an
1046 	 *   authorisation key whilst holding the sem on a key we've just
1047 	 *   instantiated
1048 	 */
1049 	down_write_nested(&key->sem, 1);
1050 	if (!test_and_set_bit(KEY_FLAG_REVOKED, &key->flags) &&
1051 	    key->type->revoke)
1052 		key->type->revoke(key);
1053 
1054 	/* set the death time to no more than the expiry time */
1055 	time = ktime_get_real_seconds();
1056 	if (key->revoked_at == 0 || key->revoked_at > time) {
1057 		key->revoked_at = time;
1058 		key_schedule_gc(key->revoked_at + key_gc_delay);
1059 	}
1060 
1061 	up_write(&key->sem);
1062 }
1063 EXPORT_SYMBOL(key_revoke);
1064 
1065 /**
1066  * key_invalidate - Invalidate a key.
1067  * @key: The key to be invalidated.
1068  *
1069  * Mark a key as being invalidated and have it cleaned up immediately.  The key
1070  * is ignored by all searches and other operations from this point.
1071  */
1072 void key_invalidate(struct key *key)
1073 {
1074 	kenter("%d", key_serial(key));
1075 
1076 	key_check(key);
1077 
1078 	if (!test_bit(KEY_FLAG_INVALIDATED, &key->flags)) {
1079 		down_write_nested(&key->sem, 1);
1080 		if (!test_and_set_bit(KEY_FLAG_INVALIDATED, &key->flags))
1081 			key_schedule_gc_links();
1082 		up_write(&key->sem);
1083 	}
1084 }
1085 EXPORT_SYMBOL(key_invalidate);
1086 
1087 /**
1088  * generic_key_instantiate - Simple instantiation of a key from preparsed data
1089  * @key: The key to be instantiated
1090  * @prep: The preparsed data to load.
1091  *
1092  * Instantiate a key from preparsed data.  We assume we can just copy the data
1093  * in directly and clear the old pointers.
1094  *
1095  * This can be pointed to directly by the key type instantiate op pointer.
1096  */
1097 int generic_key_instantiate(struct key *key, struct key_preparsed_payload *prep)
1098 {
1099 	int ret;
1100 
1101 	pr_devel("==>%s()\n", __func__);
1102 
1103 	ret = key_payload_reserve(key, prep->quotalen);
1104 	if (ret == 0) {
1105 		rcu_assign_keypointer(key, prep->payload.data[0]);
1106 		key->payload.data[1] = prep->payload.data[1];
1107 		key->payload.data[2] = prep->payload.data[2];
1108 		key->payload.data[3] = prep->payload.data[3];
1109 		prep->payload.data[0] = NULL;
1110 		prep->payload.data[1] = NULL;
1111 		prep->payload.data[2] = NULL;
1112 		prep->payload.data[3] = NULL;
1113 	}
1114 	pr_devel("<==%s() = %d\n", __func__, ret);
1115 	return ret;
1116 }
1117 EXPORT_SYMBOL(generic_key_instantiate);
1118 
1119 /**
1120  * register_key_type - Register a type of key.
1121  * @ktype: The new key type.
1122  *
1123  * Register a new key type.
1124  *
1125  * Returns 0 on success or -EEXIST if a type of this name already exists.
1126  */
1127 int register_key_type(struct key_type *ktype)
1128 {
1129 	struct key_type *p;
1130 	int ret;
1131 
1132 	memset(&ktype->lock_class, 0, sizeof(ktype->lock_class));
1133 
1134 	ret = -EEXIST;
1135 	down_write(&key_types_sem);
1136 
1137 	/* disallow key types with the same name */
1138 	list_for_each_entry(p, &key_types_list, link) {
1139 		if (strcmp(p->name, ktype->name) == 0)
1140 			goto out;
1141 	}
1142 
1143 	/* store the type */
1144 	list_add(&ktype->link, &key_types_list);
1145 
1146 	pr_notice("Key type %s registered\n", ktype->name);
1147 	ret = 0;
1148 
1149 out:
1150 	up_write(&key_types_sem);
1151 	return ret;
1152 }
1153 EXPORT_SYMBOL(register_key_type);
1154 
1155 /**
1156  * unregister_key_type - Unregister a type of key.
1157  * @ktype: The key type.
1158  *
1159  * Unregister a key type and mark all the extant keys of this type as dead.
1160  * Those keys of this type are then destroyed to get rid of their payloads and
1161  * they and their links will be garbage collected as soon as possible.
1162  */
1163 void unregister_key_type(struct key_type *ktype)
1164 {
1165 	down_write(&key_types_sem);
1166 	list_del_init(&ktype->link);
1167 	downgrade_write(&key_types_sem);
1168 	key_gc_keytype(ktype);
1169 	pr_notice("Key type %s unregistered\n", ktype->name);
1170 	up_read(&key_types_sem);
1171 }
1172 EXPORT_SYMBOL(unregister_key_type);
1173 
1174 /*
1175  * Initialise the key management state.
1176  */
1177 void __init key_init(void)
1178 {
1179 	/* allocate a slab in which we can store keys */
1180 	key_jar = kmem_cache_create("key_jar", sizeof(struct key),
1181 			0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1182 
1183 	/* add the special key types */
1184 	list_add_tail(&key_type_keyring.link, &key_types_list);
1185 	list_add_tail(&key_type_dead.link, &key_types_list);
1186 	list_add_tail(&key_type_user.link, &key_types_list);
1187 	list_add_tail(&key_type_logon.link, &key_types_list);
1188 
1189 	/* record the root user tracking */
1190 	rb_link_node(&root_key_user.node,
1191 		     NULL,
1192 		     &key_user_tree.rb_node);
1193 
1194 	rb_insert_color(&root_key_user.node,
1195 			&key_user_tree);
1196 }
1197