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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
__key_check(const struct key * key)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  */
key_user_lookup(kuid_t uid)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  */
key_user_put(struct key_user * user)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  */
key_alloc_serial(struct key * key)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  */
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_restriction * restrict_link)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 	if (flags & KEY_ALLOC_SET_KEEP)
306 		key->flags |= 1 << KEY_FLAG_KEEP;
307 
308 #ifdef KEY_DEBUGGING
309 	key->magic = KEY_DEBUG_MAGIC;
310 #endif
311 
312 	/* let the security module know about the key */
313 	ret = security_key_alloc(key, cred, flags);
314 	if (ret < 0)
315 		goto security_error;
316 
317 	/* publish the key by giving it a serial number */
318 	refcount_inc(&key->domain_tag->usage);
319 	atomic_inc(&user->nkeys);
320 	key_alloc_serial(key);
321 
322 error:
323 	return key;
324 
325 security_error:
326 	kfree(key->description);
327 	kmem_cache_free(key_jar, key);
328 	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
329 		spin_lock(&user->lock);
330 		user->qnkeys--;
331 		user->qnbytes -= quotalen;
332 		spin_unlock(&user->lock);
333 	}
334 	key_user_put(user);
335 	key = ERR_PTR(ret);
336 	goto error;
337 
338 no_memory_3:
339 	kmem_cache_free(key_jar, key);
340 no_memory_2:
341 	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
342 		spin_lock(&user->lock);
343 		user->qnkeys--;
344 		user->qnbytes -= quotalen;
345 		spin_unlock(&user->lock);
346 	}
347 	key_user_put(user);
348 no_memory_1:
349 	key = ERR_PTR(-ENOMEM);
350 	goto error;
351 
352 no_quota:
353 	spin_unlock(&user->lock);
354 	key_user_put(user);
355 	key = ERR_PTR(-EDQUOT);
356 	goto error;
357 }
358 EXPORT_SYMBOL(key_alloc);
359 
360 /**
361  * key_payload_reserve - Adjust data quota reservation for the key's payload
362  * @key: The key to make the reservation for.
363  * @datalen: The amount of data payload the caller now wants.
364  *
365  * Adjust the amount of the owning user's key data quota that a key reserves.
366  * If the amount is increased, then -EDQUOT may be returned if there isn't
367  * enough free quota available.
368  *
369  * If successful, 0 is returned.
370  */
key_payload_reserve(struct key * key,size_t datalen)371 int key_payload_reserve(struct key *key, size_t datalen)
372 {
373 	int delta = (int)datalen - key->datalen;
374 	int ret = 0;
375 
376 	key_check(key);
377 
378 	/* contemplate the quota adjustment */
379 	if (delta != 0 && test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
380 		unsigned maxbytes = uid_eq(key->user->uid, GLOBAL_ROOT_UID) ?
381 			key_quota_root_maxbytes : key_quota_maxbytes;
382 
383 		spin_lock(&key->user->lock);
384 
385 		if (delta > 0 &&
386 		    (key->user->qnbytes + delta > maxbytes ||
387 		     key->user->qnbytes + delta < key->user->qnbytes)) {
388 			ret = -EDQUOT;
389 		}
390 		else {
391 			key->user->qnbytes += delta;
392 			key->quotalen += delta;
393 		}
394 		spin_unlock(&key->user->lock);
395 	}
396 
397 	/* change the recorded data length if that didn't generate an error */
398 	if (ret == 0)
399 		key->datalen = datalen;
400 
401 	return ret;
402 }
403 EXPORT_SYMBOL(key_payload_reserve);
404 
405 /*
406  * Change the key state to being instantiated.
407  */
mark_key_instantiated(struct key * key,int reject_error)408 static void mark_key_instantiated(struct key *key, int reject_error)
409 {
410 	/* Commit the payload before setting the state; barrier versus
411 	 * key_read_state().
412 	 */
413 	smp_store_release(&key->state,
414 			  (reject_error < 0) ? reject_error : KEY_IS_POSITIVE);
415 }
416 
417 /*
418  * Instantiate a key and link it into the target keyring atomically.  Must be
419  * called with the target keyring's semaphore writelocked.  The target key's
420  * semaphore need not be locked as instantiation is serialised by
421  * key_construction_mutex.
422  */
__key_instantiate_and_link(struct key * key,struct key_preparsed_payload * prep,struct key * keyring,struct key * authkey,struct assoc_array_edit ** _edit)423 static int __key_instantiate_and_link(struct key *key,
424 				      struct key_preparsed_payload *prep,
425 				      struct key *keyring,
426 				      struct key *authkey,
427 				      struct assoc_array_edit **_edit)
428 {
429 	int ret, awaken;
430 
431 	key_check(key);
432 	key_check(keyring);
433 
434 	awaken = 0;
435 	ret = -EBUSY;
436 
437 	mutex_lock(&key_construction_mutex);
438 
439 	/* can't instantiate twice */
440 	if (key->state == KEY_IS_UNINSTANTIATED) {
441 		/* instantiate the key */
442 		ret = key->type->instantiate(key, prep);
443 
444 		if (ret == 0) {
445 			/* mark the key as being instantiated */
446 			atomic_inc(&key->user->nikeys);
447 			mark_key_instantiated(key, 0);
448 
449 			if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
450 				awaken = 1;
451 
452 			/* and link it into the destination keyring */
453 			if (keyring) {
454 				if (test_bit(KEY_FLAG_KEEP, &keyring->flags))
455 					set_bit(KEY_FLAG_KEEP, &key->flags);
456 
457 				__key_link(key, _edit);
458 			}
459 
460 			/* disable the authorisation key */
461 			if (authkey)
462 				key_invalidate(authkey);
463 
464 			if (prep->expiry != TIME64_MAX) {
465 				key->expiry = prep->expiry;
466 				key_schedule_gc(prep->expiry + key_gc_delay);
467 			}
468 		}
469 	}
470 
471 	mutex_unlock(&key_construction_mutex);
472 
473 	/* wake up anyone waiting for a key to be constructed */
474 	if (awaken)
475 		wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
476 
477 	return ret;
478 }
479 
480 /**
481  * key_instantiate_and_link - Instantiate a key and link it into the keyring.
482  * @key: The key to instantiate.
483  * @data: The data to use to instantiate the keyring.
484  * @datalen: The length of @data.
485  * @keyring: Keyring to create a link in on success (or NULL).
486  * @authkey: The authorisation token permitting instantiation.
487  *
488  * Instantiate a key that's in the uninstantiated state using the provided data
489  * and, if successful, link it in to the destination keyring if one is
490  * supplied.
491  *
492  * If successful, 0 is returned, the authorisation token is revoked and anyone
493  * waiting for the key is woken up.  If the key was already instantiated,
494  * -EBUSY will be returned.
495  */
key_instantiate_and_link(struct key * key,const void * data,size_t datalen,struct key * keyring,struct key * authkey)496 int key_instantiate_and_link(struct key *key,
497 			     const void *data,
498 			     size_t datalen,
499 			     struct key *keyring,
500 			     struct key *authkey)
501 {
502 	struct key_preparsed_payload prep;
503 	struct assoc_array_edit *edit = NULL;
504 	int ret;
505 
506 	memset(&prep, 0, sizeof(prep));
507 	prep.data = data;
508 	prep.datalen = datalen;
509 	prep.quotalen = key->type->def_datalen;
510 	prep.expiry = TIME64_MAX;
511 	if (key->type->preparse) {
512 		ret = key->type->preparse(&prep);
513 		if (ret < 0)
514 			goto error;
515 	}
516 
517 	if (keyring) {
518 		ret = __key_link_lock(keyring, &key->index_key);
519 		if (ret < 0)
520 			goto error;
521 
522 		ret = __key_link_begin(keyring, &key->index_key, &edit);
523 		if (ret < 0)
524 			goto error_link_end;
525 
526 		if (keyring->restrict_link && keyring->restrict_link->check) {
527 			struct key_restriction *keyres = keyring->restrict_link;
528 
529 			ret = keyres->check(keyring, key->type, &prep.payload,
530 					    keyres->key);
531 			if (ret < 0)
532 				goto error_link_end;
533 		}
534 	}
535 
536 	ret = __key_instantiate_and_link(key, &prep, keyring, authkey, &edit);
537 
538 error_link_end:
539 	if (keyring)
540 		__key_link_end(keyring, &key->index_key, edit);
541 
542 error:
543 	if (key->type->preparse)
544 		key->type->free_preparse(&prep);
545 	return ret;
546 }
547 
548 EXPORT_SYMBOL(key_instantiate_and_link);
549 
550 /**
551  * key_reject_and_link - Negatively instantiate a key and link it into the keyring.
552  * @key: The key to instantiate.
553  * @timeout: The timeout on the negative key.
554  * @error: The error to return when the key is hit.
555  * @keyring: Keyring to create a link in on success (or NULL).
556  * @authkey: The authorisation token permitting instantiation.
557  *
558  * Negatively instantiate a key that's in the uninstantiated state and, if
559  * successful, set its timeout and stored error and link it in to the
560  * destination keyring if one is supplied.  The key and any links to the key
561  * will be automatically garbage collected after the timeout expires.
562  *
563  * Negative keys are used to rate limit repeated request_key() calls by causing
564  * them to return the stored error code (typically ENOKEY) until the negative
565  * key expires.
566  *
567  * If successful, 0 is returned, the authorisation token is revoked and anyone
568  * waiting for the key is woken up.  If the key was already instantiated,
569  * -EBUSY will be returned.
570  */
key_reject_and_link(struct key * key,unsigned timeout,unsigned error,struct key * keyring,struct key * authkey)571 int key_reject_and_link(struct key *key,
572 			unsigned timeout,
573 			unsigned error,
574 			struct key *keyring,
575 			struct key *authkey)
576 {
577 	struct assoc_array_edit *edit = NULL;
578 	int ret, awaken, link_ret = 0;
579 
580 	key_check(key);
581 	key_check(keyring);
582 
583 	awaken = 0;
584 	ret = -EBUSY;
585 
586 	if (keyring) {
587 		if (keyring->restrict_link)
588 			return -EPERM;
589 
590 		link_ret = __key_link_lock(keyring, &key->index_key);
591 		if (link_ret == 0) {
592 			link_ret = __key_link_begin(keyring, &key->index_key, &edit);
593 			if (link_ret < 0)
594 				__key_link_end(keyring, &key->index_key, edit);
595 		}
596 	}
597 
598 	mutex_lock(&key_construction_mutex);
599 
600 	/* can't instantiate twice */
601 	if (key->state == KEY_IS_UNINSTANTIATED) {
602 		/* mark the key as being negatively instantiated */
603 		atomic_inc(&key->user->nikeys);
604 		mark_key_instantiated(key, -error);
605 		key->expiry = ktime_get_real_seconds() + timeout;
606 		key_schedule_gc(key->expiry + key_gc_delay);
607 
608 		if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
609 			awaken = 1;
610 
611 		ret = 0;
612 
613 		/* and link it into the destination keyring */
614 		if (keyring && link_ret == 0)
615 			__key_link(key, &edit);
616 
617 		/* disable the authorisation key */
618 		if (authkey)
619 			key_invalidate(authkey);
620 	}
621 
622 	mutex_unlock(&key_construction_mutex);
623 
624 	if (keyring && link_ret == 0)
625 		__key_link_end(keyring, &key->index_key, edit);
626 
627 	/* wake up anyone waiting for a key to be constructed */
628 	if (awaken)
629 		wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
630 
631 	return ret == 0 ? link_ret : ret;
632 }
633 EXPORT_SYMBOL(key_reject_and_link);
634 
635 /**
636  * key_put - Discard a reference to a key.
637  * @key: The key to discard a reference from.
638  *
639  * Discard a reference to a key, and when all the references are gone, we
640  * schedule the cleanup task to come and pull it out of the tree in process
641  * context at some later time.
642  */
key_put(struct key * key)643 void key_put(struct key *key)
644 {
645 	if (key) {
646 		key_check(key);
647 
648 		if (refcount_dec_and_test(&key->usage))
649 			schedule_work(&key_gc_work);
650 	}
651 }
652 EXPORT_SYMBOL(key_put);
653 
654 /*
655  * Find a key by its serial number.
656  */
key_lookup(key_serial_t id)657 struct key *key_lookup(key_serial_t id)
658 {
659 	struct rb_node *n;
660 	struct key *key;
661 
662 	spin_lock(&key_serial_lock);
663 
664 	/* search the tree for the specified key */
665 	n = key_serial_tree.rb_node;
666 	while (n) {
667 		key = rb_entry(n, struct key, serial_node);
668 
669 		if (id < key->serial)
670 			n = n->rb_left;
671 		else if (id > key->serial)
672 			n = n->rb_right;
673 		else
674 			goto found;
675 	}
676 
677 not_found:
678 	key = ERR_PTR(-ENOKEY);
679 	goto error;
680 
681 found:
682 	/* A key is allowed to be looked up only if someone still owns a
683 	 * reference to it - otherwise it's awaiting the gc.
684 	 */
685 	if (!refcount_inc_not_zero(&key->usage))
686 		goto not_found;
687 
688 error:
689 	spin_unlock(&key_serial_lock);
690 	return key;
691 }
692 
693 /*
694  * Find and lock the specified key type against removal.
695  *
696  * We return with the sem read-locked if successful.  If the type wasn't
697  * available -ENOKEY is returned instead.
698  */
key_type_lookup(const char * type)699 struct key_type *key_type_lookup(const char *type)
700 {
701 	struct key_type *ktype;
702 
703 	down_read(&key_types_sem);
704 
705 	/* look up the key type to see if it's one of the registered kernel
706 	 * types */
707 	list_for_each_entry(ktype, &key_types_list, link) {
708 		if (strcmp(ktype->name, type) == 0)
709 			goto found_kernel_type;
710 	}
711 
712 	up_read(&key_types_sem);
713 	ktype = ERR_PTR(-ENOKEY);
714 
715 found_kernel_type:
716 	return ktype;
717 }
718 
key_set_timeout(struct key * key,unsigned timeout)719 void key_set_timeout(struct key *key, unsigned timeout)
720 {
721 	time64_t expiry = 0;
722 
723 	/* make the changes with the locks held to prevent races */
724 	down_write(&key->sem);
725 
726 	if (timeout > 0)
727 		expiry = ktime_get_real_seconds() + timeout;
728 
729 	key->expiry = expiry;
730 	key_schedule_gc(key->expiry + key_gc_delay);
731 
732 	up_write(&key->sem);
733 }
734 EXPORT_SYMBOL_GPL(key_set_timeout);
735 
736 /*
737  * Unlock a key type locked by key_type_lookup().
738  */
key_type_put(struct key_type * ktype)739 void key_type_put(struct key_type *ktype)
740 {
741 	up_read(&key_types_sem);
742 }
743 
744 /*
745  * Attempt to update an existing key.
746  *
747  * The key is given to us with an incremented refcount that we need to discard
748  * if we get an error.
749  */
__key_update(key_ref_t key_ref,struct key_preparsed_payload * prep)750 static inline key_ref_t __key_update(key_ref_t key_ref,
751 				     struct key_preparsed_payload *prep)
752 {
753 	struct key *key = key_ref_to_ptr(key_ref);
754 	int ret;
755 
756 	/* need write permission on the key to update it */
757 	ret = key_permission(key_ref, KEY_NEED_WRITE);
758 	if (ret < 0)
759 		goto error;
760 
761 	ret = -EEXIST;
762 	if (!key->type->update)
763 		goto error;
764 
765 	down_write(&key->sem);
766 
767 	ret = key->type->update(key, prep);
768 	if (ret == 0)
769 		/* Updating a negative key positively instantiates it */
770 		mark_key_instantiated(key, 0);
771 
772 	up_write(&key->sem);
773 
774 	if (ret < 0)
775 		goto error;
776 out:
777 	return key_ref;
778 
779 error:
780 	key_put(key);
781 	key_ref = ERR_PTR(ret);
782 	goto out;
783 }
784 
785 /**
786  * key_create_or_update - Update or create and instantiate a key.
787  * @keyring_ref: A pointer to the destination keyring with possession flag.
788  * @type: The type of key.
789  * @description: The searchable description for the key.
790  * @payload: The data to use to instantiate or update the key.
791  * @plen: The length of @payload.
792  * @perm: The permissions mask for a new key.
793  * @flags: The quota flags for a new key.
794  *
795  * Search the destination keyring for a key of the same description and if one
796  * is found, update it, otherwise create and instantiate a new one and create a
797  * link to it from that keyring.
798  *
799  * If perm is KEY_PERM_UNDEF then an appropriate key permissions mask will be
800  * concocted.
801  *
802  * Returns a pointer to the new key if successful, -ENODEV if the key type
803  * wasn't available, -ENOTDIR if the keyring wasn't a keyring, -EACCES if the
804  * caller isn't permitted to modify the keyring or the LSM did not permit
805  * creation of the key.
806  *
807  * On success, the possession flag from the keyring ref will be tacked on to
808  * the key ref before it is returned.
809  */
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)810 key_ref_t key_create_or_update(key_ref_t keyring_ref,
811 			       const char *type,
812 			       const char *description,
813 			       const void *payload,
814 			       size_t plen,
815 			       key_perm_t perm,
816 			       unsigned long flags)
817 {
818 	struct keyring_index_key index_key = {
819 		.description	= description,
820 	};
821 	struct key_preparsed_payload prep;
822 	struct assoc_array_edit *edit = NULL;
823 	const struct cred *cred = current_cred();
824 	struct key *keyring, *key = NULL;
825 	key_ref_t key_ref;
826 	int ret;
827 	struct key_restriction *restrict_link = NULL;
828 
829 	/* look up the key type to see if it's one of the registered kernel
830 	 * types */
831 	index_key.type = key_type_lookup(type);
832 	if (IS_ERR(index_key.type)) {
833 		key_ref = ERR_PTR(-ENODEV);
834 		goto error;
835 	}
836 
837 	key_ref = ERR_PTR(-EINVAL);
838 	if (!index_key.type->instantiate ||
839 	    (!index_key.description && !index_key.type->preparse))
840 		goto error_put_type;
841 
842 	keyring = key_ref_to_ptr(keyring_ref);
843 
844 	key_check(keyring);
845 
846 	if (!(flags & KEY_ALLOC_BYPASS_RESTRICTION))
847 		restrict_link = keyring->restrict_link;
848 
849 	key_ref = ERR_PTR(-ENOTDIR);
850 	if (keyring->type != &key_type_keyring)
851 		goto error_put_type;
852 
853 	memset(&prep, 0, sizeof(prep));
854 	prep.data = payload;
855 	prep.datalen = plen;
856 	prep.quotalen = index_key.type->def_datalen;
857 	prep.expiry = TIME64_MAX;
858 	if (index_key.type->preparse) {
859 		ret = index_key.type->preparse(&prep);
860 		if (ret < 0) {
861 			key_ref = ERR_PTR(ret);
862 			goto error_free_prep;
863 		}
864 		if (!index_key.description)
865 			index_key.description = prep.description;
866 		key_ref = ERR_PTR(-EINVAL);
867 		if (!index_key.description)
868 			goto error_free_prep;
869 	}
870 	index_key.desc_len = strlen(index_key.description);
871 	key_set_index_key(&index_key);
872 
873 	ret = __key_link_lock(keyring, &index_key);
874 	if (ret < 0) {
875 		key_ref = ERR_PTR(ret);
876 		goto error_free_prep;
877 	}
878 
879 	ret = __key_link_begin(keyring, &index_key, &edit);
880 	if (ret < 0) {
881 		key_ref = ERR_PTR(ret);
882 		goto error_link_end;
883 	}
884 
885 	if (restrict_link && restrict_link->check) {
886 		ret = restrict_link->check(keyring, index_key.type,
887 					   &prep.payload, restrict_link->key);
888 		if (ret < 0) {
889 			key_ref = ERR_PTR(ret);
890 			goto error_link_end;
891 		}
892 	}
893 
894 	/* if we're going to allocate a new key, we're going to have
895 	 * to modify the keyring */
896 	ret = key_permission(keyring_ref, KEY_NEED_WRITE);
897 	if (ret < 0) {
898 		key_ref = ERR_PTR(ret);
899 		goto error_link_end;
900 	}
901 
902 	/* if it's possible to update this type of key, search for an existing
903 	 * key of the same type and description in the destination keyring and
904 	 * update that instead if possible
905 	 */
906 	if (index_key.type->update) {
907 		key_ref = find_key_to_update(keyring_ref, &index_key);
908 		if (key_ref)
909 			goto found_matching_key;
910 	}
911 
912 	/* if the client doesn't provide, decide on the permissions we want */
913 	if (perm == KEY_PERM_UNDEF) {
914 		perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
915 		perm |= KEY_USR_VIEW;
916 
917 		if (index_key.type->read)
918 			perm |= KEY_POS_READ;
919 
920 		if (index_key.type == &key_type_keyring ||
921 		    index_key.type->update)
922 			perm |= KEY_POS_WRITE;
923 	}
924 
925 	/* allocate a new key */
926 	key = key_alloc(index_key.type, index_key.description,
927 			cred->fsuid, cred->fsgid, cred, perm, flags, NULL);
928 	if (IS_ERR(key)) {
929 		key_ref = ERR_CAST(key);
930 		goto error_link_end;
931 	}
932 
933 	/* instantiate it and link it into the target keyring */
934 	ret = __key_instantiate_and_link(key, &prep, keyring, NULL, &edit);
935 	if (ret < 0) {
936 		key_put(key);
937 		key_ref = ERR_PTR(ret);
938 		goto error_link_end;
939 	}
940 
941 	key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
942 
943 error_link_end:
944 	__key_link_end(keyring, &index_key, edit);
945 error_free_prep:
946 	if (index_key.type->preparse)
947 		index_key.type->free_preparse(&prep);
948 error_put_type:
949 	key_type_put(index_key.type);
950 error:
951 	return key_ref;
952 
953  found_matching_key:
954 	/* we found a matching key, so we're going to try to update it
955 	 * - we can drop the locks first as we have the key pinned
956 	 */
957 	__key_link_end(keyring, &index_key, edit);
958 
959 	key = key_ref_to_ptr(key_ref);
960 	if (test_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags)) {
961 		ret = wait_for_key_construction(key, true);
962 		if (ret < 0) {
963 			key_ref_put(key_ref);
964 			key_ref = ERR_PTR(ret);
965 			goto error_free_prep;
966 		}
967 	}
968 
969 	key_ref = __key_update(key_ref, &prep);
970 	goto error_free_prep;
971 }
972 EXPORT_SYMBOL(key_create_or_update);
973 
974 /**
975  * key_update - Update a key's contents.
976  * @key_ref: The pointer (plus possession flag) to the key.
977  * @payload: The data to be used to update the key.
978  * @plen: The length of @payload.
979  *
980  * Attempt to update the contents of a key with the given payload data.  The
981  * caller must be granted Write permission on the key.  Negative keys can be
982  * instantiated by this method.
983  *
984  * Returns 0 on success, -EACCES if not permitted and -EOPNOTSUPP if the key
985  * type does not support updating.  The key type may return other errors.
986  */
key_update(key_ref_t key_ref,const void * payload,size_t plen)987 int key_update(key_ref_t key_ref, const void *payload, size_t plen)
988 {
989 	struct key_preparsed_payload prep;
990 	struct key *key = key_ref_to_ptr(key_ref);
991 	int ret;
992 
993 	key_check(key);
994 
995 	/* the key must be writable */
996 	ret = key_permission(key_ref, KEY_NEED_WRITE);
997 	if (ret < 0)
998 		return ret;
999 
1000 	/* attempt to update it if supported */
1001 	if (!key->type->update)
1002 		return -EOPNOTSUPP;
1003 
1004 	memset(&prep, 0, sizeof(prep));
1005 	prep.data = payload;
1006 	prep.datalen = plen;
1007 	prep.quotalen = key->type->def_datalen;
1008 	prep.expiry = TIME64_MAX;
1009 	if (key->type->preparse) {
1010 		ret = key->type->preparse(&prep);
1011 		if (ret < 0)
1012 			goto error;
1013 	}
1014 
1015 	down_write(&key->sem);
1016 
1017 	ret = key->type->update(key, &prep);
1018 	if (ret == 0)
1019 		/* Updating a negative key positively instantiates it */
1020 		mark_key_instantiated(key, 0);
1021 
1022 	up_write(&key->sem);
1023 
1024 error:
1025 	if (key->type->preparse)
1026 		key->type->free_preparse(&prep);
1027 	return ret;
1028 }
1029 EXPORT_SYMBOL(key_update);
1030 
1031 /**
1032  * key_revoke - Revoke a key.
1033  * @key: The key to be revoked.
1034  *
1035  * Mark a key as being revoked and ask the type to free up its resources.  The
1036  * revocation timeout is set and the key and all its links will be
1037  * automatically garbage collected after key_gc_delay amount of time if they
1038  * are not manually dealt with first.
1039  */
key_revoke(struct key * key)1040 void key_revoke(struct key *key)
1041 {
1042 	time64_t time;
1043 
1044 	key_check(key);
1045 
1046 	/* make sure no one's trying to change or use the key when we mark it
1047 	 * - we tell lockdep that we might nest because we might be revoking an
1048 	 *   authorisation key whilst holding the sem on a key we've just
1049 	 *   instantiated
1050 	 */
1051 	down_write_nested(&key->sem, 1);
1052 	if (!test_and_set_bit(KEY_FLAG_REVOKED, &key->flags) &&
1053 	    key->type->revoke)
1054 		key->type->revoke(key);
1055 
1056 	/* set the death time to no more than the expiry time */
1057 	time = ktime_get_real_seconds();
1058 	if (key->revoked_at == 0 || key->revoked_at > time) {
1059 		key->revoked_at = time;
1060 		key_schedule_gc(key->revoked_at + key_gc_delay);
1061 	}
1062 
1063 	up_write(&key->sem);
1064 }
1065 EXPORT_SYMBOL(key_revoke);
1066 
1067 /**
1068  * key_invalidate - Invalidate a key.
1069  * @key: The key to be invalidated.
1070  *
1071  * Mark a key as being invalidated and have it cleaned up immediately.  The key
1072  * is ignored by all searches and other operations from this point.
1073  */
key_invalidate(struct key * key)1074 void key_invalidate(struct key *key)
1075 {
1076 	kenter("%d", key_serial(key));
1077 
1078 	key_check(key);
1079 
1080 	if (!test_bit(KEY_FLAG_INVALIDATED, &key->flags)) {
1081 		down_write_nested(&key->sem, 1);
1082 		if (!test_and_set_bit(KEY_FLAG_INVALIDATED, &key->flags))
1083 			key_schedule_gc_links();
1084 		up_write(&key->sem);
1085 	}
1086 }
1087 EXPORT_SYMBOL(key_invalidate);
1088 
1089 /**
1090  * generic_key_instantiate - Simple instantiation of a key from preparsed data
1091  * @key: The key to be instantiated
1092  * @prep: The preparsed data to load.
1093  *
1094  * Instantiate a key from preparsed data.  We assume we can just copy the data
1095  * in directly and clear the old pointers.
1096  *
1097  * This can be pointed to directly by the key type instantiate op pointer.
1098  */
generic_key_instantiate(struct key * key,struct key_preparsed_payload * prep)1099 int generic_key_instantiate(struct key *key, struct key_preparsed_payload *prep)
1100 {
1101 	int ret;
1102 
1103 	pr_devel("==>%s()\n", __func__);
1104 
1105 	ret = key_payload_reserve(key, prep->quotalen);
1106 	if (ret == 0) {
1107 		rcu_assign_keypointer(key, prep->payload.data[0]);
1108 		key->payload.data[1] = prep->payload.data[1];
1109 		key->payload.data[2] = prep->payload.data[2];
1110 		key->payload.data[3] = prep->payload.data[3];
1111 		prep->payload.data[0] = NULL;
1112 		prep->payload.data[1] = NULL;
1113 		prep->payload.data[2] = NULL;
1114 		prep->payload.data[3] = NULL;
1115 	}
1116 	pr_devel("<==%s() = %d\n", __func__, ret);
1117 	return ret;
1118 }
1119 EXPORT_SYMBOL(generic_key_instantiate);
1120 
1121 /**
1122  * register_key_type - Register a type of key.
1123  * @ktype: The new key type.
1124  *
1125  * Register a new key type.
1126  *
1127  * Returns 0 on success or -EEXIST if a type of this name already exists.
1128  */
register_key_type(struct key_type * ktype)1129 int register_key_type(struct key_type *ktype)
1130 {
1131 	struct key_type *p;
1132 	int ret;
1133 
1134 	memset(&ktype->lock_class, 0, sizeof(ktype->lock_class));
1135 
1136 	ret = -EEXIST;
1137 	down_write(&key_types_sem);
1138 
1139 	/* disallow key types with the same name */
1140 	list_for_each_entry(p, &key_types_list, link) {
1141 		if (strcmp(p->name, ktype->name) == 0)
1142 			goto out;
1143 	}
1144 
1145 	/* store the type */
1146 	list_add(&ktype->link, &key_types_list);
1147 
1148 	pr_notice("Key type %s registered\n", ktype->name);
1149 	ret = 0;
1150 
1151 out:
1152 	up_write(&key_types_sem);
1153 	return ret;
1154 }
1155 EXPORT_SYMBOL(register_key_type);
1156 
1157 /**
1158  * unregister_key_type - Unregister a type of key.
1159  * @ktype: The key type.
1160  *
1161  * Unregister a key type and mark all the extant keys of this type as dead.
1162  * Those keys of this type are then destroyed to get rid of their payloads and
1163  * they and their links will be garbage collected as soon as possible.
1164  */
unregister_key_type(struct key_type * ktype)1165 void unregister_key_type(struct key_type *ktype)
1166 {
1167 	down_write(&key_types_sem);
1168 	list_del_init(&ktype->link);
1169 	downgrade_write(&key_types_sem);
1170 	key_gc_keytype(ktype);
1171 	pr_notice("Key type %s unregistered\n", ktype->name);
1172 	up_read(&key_types_sem);
1173 }
1174 EXPORT_SYMBOL(unregister_key_type);
1175 
1176 /*
1177  * Initialise the key management state.
1178  */
key_init(void)1179 void __init key_init(void)
1180 {
1181 	/* allocate a slab in which we can store keys */
1182 	key_jar = kmem_cache_create("key_jar", sizeof(struct key),
1183 			0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1184 
1185 	/* add the special key types */
1186 	list_add_tail(&key_type_keyring.link, &key_types_list);
1187 	list_add_tail(&key_type_dead.link, &key_types_list);
1188 	list_add_tail(&key_type_user.link, &key_types_list);
1189 	list_add_tail(&key_type_logon.link, &key_types_list);
1190 
1191 	/* record the root user tracking */
1192 	rb_link_node(&root_key_user.node,
1193 		     NULL,
1194 		     &key_user_tree.rb_node);
1195 
1196 	rb_insert_color(&root_key_user.node,
1197 			&key_user_tree);
1198 }
1199