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/ima.h>
17 #include <linux/err.h>
18 #include "internal.h"
19 
20 struct kmem_cache *key_jar;
21 struct rb_root		key_serial_tree; /* tree of keys indexed by serial */
22 DEFINE_SPINLOCK(key_serial_lock);
23 
24 struct rb_root	key_user_tree; /* tree of quota records indexed by UID */
25 DEFINE_SPINLOCK(key_user_lock);
26 
27 unsigned int key_quota_root_maxkeys = 1000000;	/* root's key count quota */
28 unsigned int key_quota_root_maxbytes = 25000000; /* root's key space quota */
29 unsigned int key_quota_maxkeys = 200;		/* general key count quota */
30 unsigned int key_quota_maxbytes = 20000;	/* general key space quota */
31 
32 static LIST_HEAD(key_types_list);
33 static DECLARE_RWSEM(key_types_sem);
34 
35 /* We serialise key instantiation and link */
36 DEFINE_MUTEX(key_construction_mutex);
37 
38 #ifdef KEY_DEBUGGING
__key_check(const struct key * key)39 void __key_check(const struct key *key)
40 {
41 	printk("__key_check: key %p {%08x} should be {%08x}\n",
42 	       key, key->magic, KEY_DEBUG_MAGIC);
43 	BUG();
44 }
45 #endif
46 
47 /*
48  * Get the key quota record for a user, allocating a new record if one doesn't
49  * already exist.
50  */
key_user_lookup(kuid_t uid)51 struct key_user *key_user_lookup(kuid_t uid)
52 {
53 	struct key_user *candidate = NULL, *user;
54 	struct rb_node *parent, **p;
55 
56 try_again:
57 	parent = NULL;
58 	p = &key_user_tree.rb_node;
59 	spin_lock(&key_user_lock);
60 
61 	/* search the tree for a user record with a matching UID */
62 	while (*p) {
63 		parent = *p;
64 		user = rb_entry(parent, struct key_user, node);
65 
66 		if (uid_lt(uid, user->uid))
67 			p = &(*p)->rb_left;
68 		else if (uid_gt(uid, user->uid))
69 			p = &(*p)->rb_right;
70 		else
71 			goto found;
72 	}
73 
74 	/* if we get here, we failed to find a match in the tree */
75 	if (!candidate) {
76 		/* allocate a candidate user record if we don't already have
77 		 * one */
78 		spin_unlock(&key_user_lock);
79 
80 		user = NULL;
81 		candidate = kmalloc(sizeof(struct key_user), GFP_KERNEL);
82 		if (unlikely(!candidate))
83 			goto out;
84 
85 		/* the allocation may have scheduled, so we need to repeat the
86 		 * search lest someone else added the record whilst we were
87 		 * asleep */
88 		goto try_again;
89 	}
90 
91 	/* if we get here, then the user record still hadn't appeared on the
92 	 * second pass - so we use the candidate record */
93 	refcount_set(&candidate->usage, 1);
94 	atomic_set(&candidate->nkeys, 0);
95 	atomic_set(&candidate->nikeys, 0);
96 	candidate->uid = uid;
97 	candidate->qnkeys = 0;
98 	candidate->qnbytes = 0;
99 	spin_lock_init(&candidate->lock);
100 	mutex_init(&candidate->cons_lock);
101 
102 	rb_link_node(&candidate->node, parent, p);
103 	rb_insert_color(&candidate->node, &key_user_tree);
104 	spin_unlock(&key_user_lock);
105 	user = candidate;
106 	goto out;
107 
108 	/* okay - we found a user record for this UID */
109 found:
110 	refcount_inc(&user->usage);
111 	spin_unlock(&key_user_lock);
112 	kfree(candidate);
113 out:
114 	return user;
115 }
116 
117 /*
118  * Dispose of a user structure
119  */
key_user_put(struct key_user * user)120 void key_user_put(struct key_user *user)
121 {
122 	if (refcount_dec_and_lock(&user->usage, &key_user_lock)) {
123 		rb_erase(&user->node, &key_user_tree);
124 		spin_unlock(&key_user_lock);
125 
126 		kfree(user);
127 	}
128 }
129 
130 /*
131  * Allocate a serial number for a key.  These are assigned randomly to avoid
132  * security issues through covert channel problems.
133  */
key_alloc_serial(struct key * key)134 static inline void key_alloc_serial(struct key *key)
135 {
136 	struct rb_node *parent, **p;
137 	struct key *xkey;
138 
139 	/* propose a random serial number and look for a hole for it in the
140 	 * serial number tree */
141 	do {
142 		get_random_bytes(&key->serial, sizeof(key->serial));
143 
144 		key->serial >>= 1; /* negative numbers are not permitted */
145 	} while (key->serial < 3);
146 
147 	spin_lock(&key_serial_lock);
148 
149 attempt_insertion:
150 	parent = NULL;
151 	p = &key_serial_tree.rb_node;
152 
153 	while (*p) {
154 		parent = *p;
155 		xkey = rb_entry(parent, struct key, serial_node);
156 
157 		if (key->serial < xkey->serial)
158 			p = &(*p)->rb_left;
159 		else if (key->serial > xkey->serial)
160 			p = &(*p)->rb_right;
161 		else
162 			goto serial_exists;
163 	}
164 
165 	/* we've found a suitable hole - arrange for this key to occupy it */
166 	rb_link_node(&key->serial_node, parent, p);
167 	rb_insert_color(&key->serial_node, &key_serial_tree);
168 
169 	spin_unlock(&key_serial_lock);
170 	return;
171 
172 	/* we found a key with the proposed serial number - walk the tree from
173 	 * that point looking for the next unused serial number */
174 serial_exists:
175 	for (;;) {
176 		key->serial++;
177 		if (key->serial < 3) {
178 			key->serial = 3;
179 			goto attempt_insertion;
180 		}
181 
182 		parent = rb_next(parent);
183 		if (!parent)
184 			goto attempt_insertion;
185 
186 		xkey = rb_entry(parent, struct key, serial_node);
187 		if (key->serial < xkey->serial)
188 			goto attempt_insertion;
189 	}
190 }
191 
192 /**
193  * key_alloc - Allocate a key of the specified type.
194  * @type: The type of key to allocate.
195  * @desc: The key description to allow the key to be searched out.
196  * @uid: The owner of the new key.
197  * @gid: The group ID for the new key's group permissions.
198  * @cred: The credentials specifying UID namespace.
199  * @perm: The permissions mask of the new key.
200  * @flags: Flags specifying quota properties.
201  * @restrict_link: Optional link restriction for new keyrings.
202  *
203  * Allocate a key of the specified type with the attributes given.  The key is
204  * returned in an uninstantiated state and the caller needs to instantiate the
205  * key before returning.
206  *
207  * The restrict_link structure (if not NULL) will be freed when the
208  * keyring is destroyed, so it must be dynamically allocated.
209  *
210  * The user's key count quota is updated to reflect the creation of the key and
211  * the user's key data quota has the default for the key type reserved.  The
212  * instantiation function should amend this as necessary.  If insufficient
213  * quota is available, -EDQUOT will be returned.
214  *
215  * The LSM security modules can prevent a key being created, in which case
216  * -EACCES will be returned.
217  *
218  * Returns a pointer to the new key if successful and an error code otherwise.
219  *
220  * Note that the caller needs to ensure the key type isn't uninstantiated.
221  * Internally this can be done by locking key_types_sem.  Externally, this can
222  * be done by either never unregistering the key type, or making sure
223  * key_alloc() calls don't race with module unloading.
224  */
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)225 struct key *key_alloc(struct key_type *type, const char *desc,
226 		      kuid_t uid, kgid_t gid, const struct cred *cred,
227 		      key_perm_t perm, unsigned long flags,
228 		      struct key_restriction *restrict_link)
229 {
230 	struct key_user *user = NULL;
231 	struct key *key;
232 	size_t desclen, quotalen;
233 	int ret;
234 
235 	key = ERR_PTR(-EINVAL);
236 	if (!desc || !*desc)
237 		goto error;
238 
239 	if (type->vet_description) {
240 		ret = type->vet_description(desc);
241 		if (ret < 0) {
242 			key = ERR_PTR(ret);
243 			goto error;
244 		}
245 	}
246 
247 	desclen = strlen(desc);
248 	quotalen = desclen + 1 + type->def_datalen;
249 
250 	/* get hold of the key tracking for this user */
251 	user = key_user_lookup(uid);
252 	if (!user)
253 		goto no_memory_1;
254 
255 	/* check that the user's quota permits allocation of another key and
256 	 * its description */
257 	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
258 		unsigned maxkeys = uid_eq(uid, GLOBAL_ROOT_UID) ?
259 			key_quota_root_maxkeys : key_quota_maxkeys;
260 		unsigned maxbytes = uid_eq(uid, GLOBAL_ROOT_UID) ?
261 			key_quota_root_maxbytes : key_quota_maxbytes;
262 
263 		spin_lock(&user->lock);
264 		if (!(flags & KEY_ALLOC_QUOTA_OVERRUN)) {
265 			if (user->qnkeys + 1 > maxkeys ||
266 			    user->qnbytes + quotalen > maxbytes ||
267 			    user->qnbytes + quotalen < user->qnbytes)
268 				goto no_quota;
269 		}
270 
271 		user->qnkeys++;
272 		user->qnbytes += quotalen;
273 		spin_unlock(&user->lock);
274 	}
275 
276 	/* allocate and initialise the key and its description */
277 	key = kmem_cache_zalloc(key_jar, GFP_KERNEL);
278 	if (!key)
279 		goto no_memory_2;
280 
281 	key->index_key.desc_len = desclen;
282 	key->index_key.description = kmemdup(desc, desclen + 1, GFP_KERNEL);
283 	if (!key->index_key.description)
284 		goto no_memory_3;
285 	key->index_key.type = type;
286 	key_set_index_key(&key->index_key);
287 
288 	refcount_set(&key->usage, 1);
289 	init_rwsem(&key->sem);
290 	lockdep_set_class(&key->sem, &type->lock_class);
291 	key->user = user;
292 	key->quotalen = quotalen;
293 	key->datalen = type->def_datalen;
294 	key->uid = uid;
295 	key->gid = gid;
296 	key->perm = perm;
297 	key->expiry = TIME64_MAX;
298 	key->restrict_link = restrict_link;
299 	key->last_used_at = ktime_get_real_seconds();
300 
301 	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA))
302 		key->flags |= 1 << KEY_FLAG_IN_QUOTA;
303 	if (flags & KEY_ALLOC_BUILT_IN)
304 		key->flags |= 1 << KEY_FLAG_BUILTIN;
305 	if (flags & KEY_ALLOC_UID_KEYRING)
306 		key->flags |= 1 << KEY_FLAG_UID_KEYRING;
307 	if (flags & KEY_ALLOC_SET_KEEP)
308 		key->flags |= 1 << KEY_FLAG_KEEP;
309 
310 #ifdef KEY_DEBUGGING
311 	key->magic = KEY_DEBUG_MAGIC;
312 #endif
313 
314 	/* let the security module know about the key */
315 	ret = security_key_alloc(key, cred, flags);
316 	if (ret < 0)
317 		goto security_error;
318 
319 	/* publish the key by giving it a serial number */
320 	refcount_inc(&key->domain_tag->usage);
321 	atomic_inc(&user->nkeys);
322 	key_alloc_serial(key);
323 
324 error:
325 	return key;
326 
327 security_error:
328 	kfree(key->description);
329 	kmem_cache_free(key_jar, key);
330 	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
331 		spin_lock(&user->lock);
332 		user->qnkeys--;
333 		user->qnbytes -= quotalen;
334 		spin_unlock(&user->lock);
335 	}
336 	key_user_put(user);
337 	key = ERR_PTR(ret);
338 	goto error;
339 
340 no_memory_3:
341 	kmem_cache_free(key_jar, key);
342 no_memory_2:
343 	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
344 		spin_lock(&user->lock);
345 		user->qnkeys--;
346 		user->qnbytes -= quotalen;
347 		spin_unlock(&user->lock);
348 	}
349 	key_user_put(user);
350 no_memory_1:
351 	key = ERR_PTR(-ENOMEM);
352 	goto error;
353 
354 no_quota:
355 	spin_unlock(&user->lock);
356 	key_user_put(user);
357 	key = ERR_PTR(-EDQUOT);
358 	goto error;
359 }
360 EXPORT_SYMBOL(key_alloc);
361 
362 /**
363  * key_payload_reserve - Adjust data quota reservation for the key's payload
364  * @key: The key to make the reservation for.
365  * @datalen: The amount of data payload the caller now wants.
366  *
367  * Adjust the amount of the owning user's key data quota that a key reserves.
368  * If the amount is increased, then -EDQUOT may be returned if there isn't
369  * enough free quota available.
370  *
371  * If successful, 0 is returned.
372  */
key_payload_reserve(struct key * key,size_t datalen)373 int key_payload_reserve(struct key *key, size_t datalen)
374 {
375 	int delta = (int)datalen - key->datalen;
376 	int ret = 0;
377 
378 	key_check(key);
379 
380 	/* contemplate the quota adjustment */
381 	if (delta != 0 && test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
382 		unsigned maxbytes = uid_eq(key->user->uid, GLOBAL_ROOT_UID) ?
383 			key_quota_root_maxbytes : key_quota_maxbytes;
384 
385 		spin_lock(&key->user->lock);
386 
387 		if (delta > 0 &&
388 		    (key->user->qnbytes + delta > maxbytes ||
389 		     key->user->qnbytes + delta < key->user->qnbytes)) {
390 			ret = -EDQUOT;
391 		}
392 		else {
393 			key->user->qnbytes += delta;
394 			key->quotalen += delta;
395 		}
396 		spin_unlock(&key->user->lock);
397 	}
398 
399 	/* change the recorded data length if that didn't generate an error */
400 	if (ret == 0)
401 		key->datalen = datalen;
402 
403 	return ret;
404 }
405 EXPORT_SYMBOL(key_payload_reserve);
406 
407 /*
408  * Change the key state to being instantiated.
409  */
mark_key_instantiated(struct key * key,int reject_error)410 static void mark_key_instantiated(struct key *key, int reject_error)
411 {
412 	/* Commit the payload before setting the state; barrier versus
413 	 * key_read_state().
414 	 */
415 	smp_store_release(&key->state,
416 			  (reject_error < 0) ? reject_error : KEY_IS_POSITIVE);
417 }
418 
419 /*
420  * Instantiate a key and link it into the target keyring atomically.  Must be
421  * called with the target keyring's semaphore writelocked.  The target key's
422  * semaphore need not be locked as instantiation is serialised by
423  * key_construction_mutex.
424  */
__key_instantiate_and_link(struct key * key,struct key_preparsed_payload * prep,struct key * keyring,struct key * authkey,struct assoc_array_edit ** _edit)425 static int __key_instantiate_and_link(struct key *key,
426 				      struct key_preparsed_payload *prep,
427 				      struct key *keyring,
428 				      struct key *authkey,
429 				      struct assoc_array_edit **_edit)
430 {
431 	int ret, awaken;
432 
433 	key_check(key);
434 	key_check(keyring);
435 
436 	awaken = 0;
437 	ret = -EBUSY;
438 
439 	mutex_lock(&key_construction_mutex);
440 
441 	/* can't instantiate twice */
442 	if (key->state == KEY_IS_UNINSTANTIATED) {
443 		/* instantiate the key */
444 		ret = key->type->instantiate(key, prep);
445 
446 		if (ret == 0) {
447 			/* mark the key as being instantiated */
448 			atomic_inc(&key->user->nikeys);
449 			mark_key_instantiated(key, 0);
450 			notify_key(key, NOTIFY_KEY_INSTANTIATED, 0);
451 
452 			if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
453 				awaken = 1;
454 
455 			/* and link it into the destination keyring */
456 			if (keyring) {
457 				if (test_bit(KEY_FLAG_KEEP, &keyring->flags))
458 					set_bit(KEY_FLAG_KEEP, &key->flags);
459 
460 				__key_link(keyring, key, _edit);
461 			}
462 
463 			/* disable the authorisation key */
464 			if (authkey)
465 				key_invalidate(authkey);
466 
467 			key_set_expiry(key, prep->expiry);
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.orig_description = key->description;
508 	prep.data = data;
509 	prep.datalen = datalen;
510 	prep.quotalen = key->type->def_datalen;
511 	prep.expiry = TIME64_MAX;
512 	if (key->type->preparse) {
513 		ret = key->type->preparse(&prep);
514 		if (ret < 0)
515 			goto error;
516 	}
517 
518 	if (keyring) {
519 		ret = __key_link_lock(keyring, &key->index_key);
520 		if (ret < 0)
521 			goto error;
522 
523 		ret = __key_link_begin(keyring, &key->index_key, &edit);
524 		if (ret < 0)
525 			goto error_link_end;
526 
527 		if (keyring->restrict_link && keyring->restrict_link->check) {
528 			struct key_restriction *keyres = keyring->restrict_link;
529 
530 			ret = keyres->check(keyring, key->type, &prep.payload,
531 					    keyres->key);
532 			if (ret < 0)
533 				goto error_link_end;
534 		}
535 	}
536 
537 	ret = __key_instantiate_and_link(key, &prep, keyring, authkey, &edit);
538 
539 error_link_end:
540 	if (keyring)
541 		__key_link_end(keyring, &key->index_key, edit);
542 
543 error:
544 	if (key->type->preparse)
545 		key->type->free_preparse(&prep);
546 	return ret;
547 }
548 
549 EXPORT_SYMBOL(key_instantiate_and_link);
550 
551 /**
552  * key_reject_and_link - Negatively instantiate a key and link it into the keyring.
553  * @key: The key to instantiate.
554  * @timeout: The timeout on the negative key.
555  * @error: The error to return when the key is hit.
556  * @keyring: Keyring to create a link in on success (or NULL).
557  * @authkey: The authorisation token permitting instantiation.
558  *
559  * Negatively instantiate a key that's in the uninstantiated state and, if
560  * successful, set its timeout and stored error and link it in to the
561  * destination keyring if one is supplied.  The key and any links to the key
562  * will be automatically garbage collected after the timeout expires.
563  *
564  * Negative keys are used to rate limit repeated request_key() calls by causing
565  * them to return the stored error code (typically ENOKEY) until the negative
566  * key expires.
567  *
568  * If successful, 0 is returned, the authorisation token is revoked and anyone
569  * waiting for the key is woken up.  If the key was already instantiated,
570  * -EBUSY will be returned.
571  */
key_reject_and_link(struct key * key,unsigned timeout,unsigned error,struct key * keyring,struct key * authkey)572 int key_reject_and_link(struct key *key,
573 			unsigned timeout,
574 			unsigned error,
575 			struct key *keyring,
576 			struct key *authkey)
577 {
578 	struct assoc_array_edit *edit = NULL;
579 	int ret, awaken, link_ret = 0;
580 
581 	key_check(key);
582 	key_check(keyring);
583 
584 	awaken = 0;
585 	ret = -EBUSY;
586 
587 	if (keyring) {
588 		if (keyring->restrict_link)
589 			return -EPERM;
590 
591 		link_ret = __key_link_lock(keyring, &key->index_key);
592 		if (link_ret == 0) {
593 			link_ret = __key_link_begin(keyring, &key->index_key, &edit);
594 			if (link_ret < 0)
595 				__key_link_end(keyring, &key->index_key, edit);
596 		}
597 	}
598 
599 	mutex_lock(&key_construction_mutex);
600 
601 	/* can't instantiate twice */
602 	if (key->state == KEY_IS_UNINSTANTIATED) {
603 		/* mark the key as being negatively instantiated */
604 		atomic_inc(&key->user->nikeys);
605 		mark_key_instantiated(key, -error);
606 		notify_key(key, NOTIFY_KEY_INSTANTIATED, -error);
607 		key_set_expiry(key, ktime_get_real_seconds() + timeout);
608 
609 		if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
610 			awaken = 1;
611 
612 		ret = 0;
613 
614 		/* and link it into the destination keyring */
615 		if (keyring && link_ret == 0)
616 			__key_link(keyring, key, &edit);
617 
618 		/* disable the authorisation key */
619 		if (authkey)
620 			key_invalidate(authkey);
621 	}
622 
623 	mutex_unlock(&key_construction_mutex);
624 
625 	if (keyring && link_ret == 0)
626 		__key_link_end(keyring, &key->index_key, edit);
627 
628 	/* wake up anyone waiting for a key to be constructed */
629 	if (awaken)
630 		wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
631 
632 	return ret == 0 ? link_ret : ret;
633 }
634 EXPORT_SYMBOL(key_reject_and_link);
635 
636 /**
637  * key_put - Discard a reference to a key.
638  * @key: The key to discard a reference from.
639  *
640  * Discard a reference to a key, and when all the references are gone, we
641  * schedule the cleanup task to come and pull it out of the tree in process
642  * context at some later time.
643  */
key_put(struct key * key)644 void key_put(struct key *key)
645 {
646 	if (key) {
647 		key_check(key);
648 
649 		if (refcount_dec_and_test(&key->usage))
650 			schedule_work(&key_gc_work);
651 	}
652 }
653 EXPORT_SYMBOL(key_put);
654 
655 /*
656  * Find a key by its serial number.
657  */
key_lookup(key_serial_t id)658 struct key *key_lookup(key_serial_t id)
659 {
660 	struct rb_node *n;
661 	struct key *key;
662 
663 	spin_lock(&key_serial_lock);
664 
665 	/* search the tree for the specified key */
666 	n = key_serial_tree.rb_node;
667 	while (n) {
668 		key = rb_entry(n, struct key, serial_node);
669 
670 		if (id < key->serial)
671 			n = n->rb_left;
672 		else if (id > key->serial)
673 			n = n->rb_right;
674 		else
675 			goto found;
676 	}
677 
678 not_found:
679 	key = ERR_PTR(-ENOKEY);
680 	goto error;
681 
682 found:
683 	/* A key is allowed to be looked up only if someone still owns a
684 	 * reference to it - otherwise it's awaiting the gc.
685 	 */
686 	if (!refcount_inc_not_zero(&key->usage))
687 		goto not_found;
688 
689 error:
690 	spin_unlock(&key_serial_lock);
691 	return key;
692 }
693 
694 /*
695  * Find and lock the specified key type against removal.
696  *
697  * We return with the sem read-locked if successful.  If the type wasn't
698  * available -ENOKEY is returned instead.
699  */
key_type_lookup(const char * type)700 struct key_type *key_type_lookup(const char *type)
701 {
702 	struct key_type *ktype;
703 
704 	down_read(&key_types_sem);
705 
706 	/* look up the key type to see if it's one of the registered kernel
707 	 * types */
708 	list_for_each_entry(ktype, &key_types_list, link) {
709 		if (strcmp(ktype->name, type) == 0)
710 			goto found_kernel_type;
711 	}
712 
713 	up_read(&key_types_sem);
714 	ktype = ERR_PTR(-ENOKEY);
715 
716 found_kernel_type:
717 	return ktype;
718 }
719 
key_set_timeout(struct key * key,unsigned timeout)720 void key_set_timeout(struct key *key, unsigned timeout)
721 {
722 	time64_t expiry = TIME64_MAX;
723 
724 	/* make the changes with the locks held to prevent races */
725 	down_write(&key->sem);
726 
727 	if (timeout > 0)
728 		expiry = ktime_get_real_seconds() + timeout;
729 	key_set_expiry(key, expiry);
730 
731 	up_write(&key->sem);
732 }
733 EXPORT_SYMBOL_GPL(key_set_timeout);
734 
735 /*
736  * Unlock a key type locked by key_type_lookup().
737  */
key_type_put(struct key_type * ktype)738 void key_type_put(struct key_type *ktype)
739 {
740 	up_read(&key_types_sem);
741 }
742 
743 /*
744  * Attempt to update an existing key.
745  *
746  * The key is given to us with an incremented refcount that we need to discard
747  * if we get an error.
748  */
__key_update(key_ref_t key_ref,struct key_preparsed_payload * prep)749 static inline key_ref_t __key_update(key_ref_t key_ref,
750 				     struct key_preparsed_payload *prep)
751 {
752 	struct key *key = key_ref_to_ptr(key_ref);
753 	int ret;
754 
755 	/* need write permission on the key to update it */
756 	ret = key_permission(key_ref, KEY_NEED_WRITE);
757 	if (ret < 0)
758 		goto error;
759 
760 	ret = -EEXIST;
761 	if (!key->type->update)
762 		goto error;
763 
764 	down_write(&key->sem);
765 
766 	ret = key->type->update(key, prep);
767 	if (ret == 0) {
768 		/* Updating a negative key positively instantiates it */
769 		mark_key_instantiated(key, 0);
770 		notify_key(key, NOTIFY_KEY_UPDATED, 0);
771 	}
772 
773 	up_write(&key->sem);
774 
775 	if (ret < 0)
776 		goto error;
777 out:
778 	return key_ref;
779 
780 error:
781 	key_put(key);
782 	key_ref = ERR_PTR(ret);
783 	goto out;
784 }
785 
786 /*
787  * Create or potentially update a key. The combined logic behind
788  * key_create_or_update() and key_create()
789  */
__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,bool allow_update)790 static key_ref_t __key_create_or_update(key_ref_t keyring_ref,
791 					const char *type,
792 					const char *description,
793 					const void *payload,
794 					size_t plen,
795 					key_perm_t perm,
796 					unsigned long flags,
797 					bool allow_update)
798 {
799 	struct keyring_index_key index_key = {
800 		.description	= description,
801 	};
802 	struct key_preparsed_payload prep;
803 	struct assoc_array_edit *edit = NULL;
804 	const struct cred *cred = current_cred();
805 	struct key *keyring, *key = NULL;
806 	key_ref_t key_ref;
807 	int ret;
808 	struct key_restriction *restrict_link = NULL;
809 
810 	/* look up the key type to see if it's one of the registered kernel
811 	 * types */
812 	index_key.type = key_type_lookup(type);
813 	if (IS_ERR(index_key.type)) {
814 		key_ref = ERR_PTR(-ENODEV);
815 		goto error;
816 	}
817 
818 	key_ref = ERR_PTR(-EINVAL);
819 	if (!index_key.type->instantiate ||
820 	    (!index_key.description && !index_key.type->preparse))
821 		goto error_put_type;
822 
823 	keyring = key_ref_to_ptr(keyring_ref);
824 
825 	key_check(keyring);
826 
827 	if (!(flags & KEY_ALLOC_BYPASS_RESTRICTION))
828 		restrict_link = keyring->restrict_link;
829 
830 	key_ref = ERR_PTR(-ENOTDIR);
831 	if (keyring->type != &key_type_keyring)
832 		goto error_put_type;
833 
834 	memset(&prep, 0, sizeof(prep));
835 	prep.orig_description = description;
836 	prep.data = payload;
837 	prep.datalen = plen;
838 	prep.quotalen = index_key.type->def_datalen;
839 	prep.expiry = TIME64_MAX;
840 	if (index_key.type->preparse) {
841 		ret = index_key.type->preparse(&prep);
842 		if (ret < 0) {
843 			key_ref = ERR_PTR(ret);
844 			goto error_free_prep;
845 		}
846 		if (!index_key.description)
847 			index_key.description = prep.description;
848 		key_ref = ERR_PTR(-EINVAL);
849 		if (!index_key.description)
850 			goto error_free_prep;
851 	}
852 	index_key.desc_len = strlen(index_key.description);
853 	key_set_index_key(&index_key);
854 
855 	ret = __key_link_lock(keyring, &index_key);
856 	if (ret < 0) {
857 		key_ref = ERR_PTR(ret);
858 		goto error_free_prep;
859 	}
860 
861 	ret = __key_link_begin(keyring, &index_key, &edit);
862 	if (ret < 0) {
863 		key_ref = ERR_PTR(ret);
864 		goto error_link_end;
865 	}
866 
867 	if (restrict_link && restrict_link->check) {
868 		ret = restrict_link->check(keyring, index_key.type,
869 					   &prep.payload, restrict_link->key);
870 		if (ret < 0) {
871 			key_ref = ERR_PTR(ret);
872 			goto error_link_end;
873 		}
874 	}
875 
876 	/* if we're going to allocate a new key, we're going to have
877 	 * to modify the keyring */
878 	ret = key_permission(keyring_ref, KEY_NEED_WRITE);
879 	if (ret < 0) {
880 		key_ref = ERR_PTR(ret);
881 		goto error_link_end;
882 	}
883 
884 	/* if it's requested and possible to update this type of key, search
885 	 * for an existing key of the same type and description in the
886 	 * destination keyring and update that instead if possible
887 	 */
888 	if (allow_update) {
889 		if (index_key.type->update) {
890 			key_ref = find_key_to_update(keyring_ref, &index_key);
891 			if (key_ref)
892 				goto found_matching_key;
893 		}
894 	} else {
895 		key_ref = find_key_to_update(keyring_ref, &index_key);
896 		if (key_ref) {
897 			key_ref_put(key_ref);
898 			key_ref = ERR_PTR(-EEXIST);
899 			goto error_link_end;
900 		}
901 	}
902 
903 	/* if the client doesn't provide, decide on the permissions we want */
904 	if (perm == KEY_PERM_UNDEF) {
905 		perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
906 		perm |= KEY_USR_VIEW;
907 
908 		if (index_key.type->read)
909 			perm |= KEY_POS_READ;
910 
911 		if (index_key.type == &key_type_keyring ||
912 		    index_key.type->update)
913 			perm |= KEY_POS_WRITE;
914 	}
915 
916 	/* allocate a new key */
917 	key = key_alloc(index_key.type, index_key.description,
918 			cred->fsuid, cred->fsgid, cred, perm, flags, NULL);
919 	if (IS_ERR(key)) {
920 		key_ref = ERR_CAST(key);
921 		goto error_link_end;
922 	}
923 
924 	/* instantiate it and link it into the target keyring */
925 	ret = __key_instantiate_and_link(key, &prep, keyring, NULL, &edit);
926 	if (ret < 0) {
927 		key_put(key);
928 		key_ref = ERR_PTR(ret);
929 		goto error_link_end;
930 	}
931 
932 	ima_post_key_create_or_update(keyring, key, payload, plen,
933 				      flags, true);
934 
935 	key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
936 
937 error_link_end:
938 	__key_link_end(keyring, &index_key, edit);
939 error_free_prep:
940 	if (index_key.type->preparse)
941 		index_key.type->free_preparse(&prep);
942 error_put_type:
943 	key_type_put(index_key.type);
944 error:
945 	return key_ref;
946 
947  found_matching_key:
948 	/* we found a matching key, so we're going to try to update it
949 	 * - we can drop the locks first as we have the key pinned
950 	 */
951 	__key_link_end(keyring, &index_key, edit);
952 
953 	key = key_ref_to_ptr(key_ref);
954 	if (test_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags)) {
955 		ret = wait_for_key_construction(key, true);
956 		if (ret < 0) {
957 			key_ref_put(key_ref);
958 			key_ref = ERR_PTR(ret);
959 			goto error_free_prep;
960 		}
961 	}
962 
963 	key_ref = __key_update(key_ref, &prep);
964 
965 	if (!IS_ERR(key_ref))
966 		ima_post_key_create_or_update(keyring, key,
967 					      payload, plen,
968 					      flags, false);
969 
970 	goto error_free_prep;
971 }
972 
973 /**
974  * key_create_or_update - Update or create and instantiate a key.
975  * @keyring_ref: A pointer to the destination keyring with possession flag.
976  * @type: The type of key.
977  * @description: The searchable description for the key.
978  * @payload: The data to use to instantiate or update the key.
979  * @plen: The length of @payload.
980  * @perm: The permissions mask for a new key.
981  * @flags: The quota flags for a new key.
982  *
983  * Search the destination keyring for a key of the same description and if one
984  * is found, update it, otherwise create and instantiate a new one and create a
985  * link to it from that keyring.
986  *
987  * If perm is KEY_PERM_UNDEF then an appropriate key permissions mask will be
988  * concocted.
989  *
990  * Returns a pointer to the new key if successful, -ENODEV if the key type
991  * wasn't available, -ENOTDIR if the keyring wasn't a keyring, -EACCES if the
992  * caller isn't permitted to modify the keyring or the LSM did not permit
993  * creation of the key.
994  *
995  * On success, the possession flag from the keyring ref will be tacked on to
996  * the key ref before it is returned.
997  */
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)998 key_ref_t key_create_or_update(key_ref_t keyring_ref,
999 			       const char *type,
1000 			       const char *description,
1001 			       const void *payload,
1002 			       size_t plen,
1003 			       key_perm_t perm,
1004 			       unsigned long flags)
1005 {
1006 	return __key_create_or_update(keyring_ref, type, description, payload,
1007 				      plen, perm, flags, true);
1008 }
1009 EXPORT_SYMBOL(key_create_or_update);
1010 
1011 /**
1012  * key_create - Create and instantiate a key.
1013  * @keyring_ref: A pointer to the destination keyring with possession flag.
1014  * @type: The type of key.
1015  * @description: The searchable description for the key.
1016  * @payload: The data to use to instantiate or update the key.
1017  * @plen: The length of @payload.
1018  * @perm: The permissions mask for a new key.
1019  * @flags: The quota flags for a new key.
1020  *
1021  * Create and instantiate a new key and link to it from the destination keyring.
1022  *
1023  * If perm is KEY_PERM_UNDEF then an appropriate key permissions mask will be
1024  * concocted.
1025  *
1026  * Returns a pointer to the new key if successful, -EEXIST if a key with the
1027  * same description already exists, -ENODEV if the key type wasn't available,
1028  * -ENOTDIR if the keyring wasn't a keyring, -EACCES if the caller isn't
1029  * permitted to modify the keyring or the LSM did not permit creation of the
1030  * key.
1031  *
1032  * On success, the possession flag from the keyring ref will be tacked on to
1033  * the key ref before it is returned.
1034  */
key_create(key_ref_t keyring_ref,const char * type,const char * description,const void * payload,size_t plen,key_perm_t perm,unsigned long flags)1035 key_ref_t key_create(key_ref_t keyring_ref,
1036 		     const char *type,
1037 		     const char *description,
1038 		     const void *payload,
1039 		     size_t plen,
1040 		     key_perm_t perm,
1041 		     unsigned long flags)
1042 {
1043 	return __key_create_or_update(keyring_ref, type, description, payload,
1044 				      plen, perm, flags, false);
1045 }
1046 EXPORT_SYMBOL(key_create);
1047 
1048 /**
1049  * key_update - Update a key's contents.
1050  * @key_ref: The pointer (plus possession flag) to the key.
1051  * @payload: The data to be used to update the key.
1052  * @plen: The length of @payload.
1053  *
1054  * Attempt to update the contents of a key with the given payload data.  The
1055  * caller must be granted Write permission on the key.  Negative keys can be
1056  * instantiated by this method.
1057  *
1058  * Returns 0 on success, -EACCES if not permitted and -EOPNOTSUPP if the key
1059  * type does not support updating.  The key type may return other errors.
1060  */
key_update(key_ref_t key_ref,const void * payload,size_t plen)1061 int key_update(key_ref_t key_ref, const void *payload, size_t plen)
1062 {
1063 	struct key_preparsed_payload prep;
1064 	struct key *key = key_ref_to_ptr(key_ref);
1065 	int ret;
1066 
1067 	key_check(key);
1068 
1069 	/* the key must be writable */
1070 	ret = key_permission(key_ref, KEY_NEED_WRITE);
1071 	if (ret < 0)
1072 		return ret;
1073 
1074 	/* attempt to update it if supported */
1075 	if (!key->type->update)
1076 		return -EOPNOTSUPP;
1077 
1078 	memset(&prep, 0, sizeof(prep));
1079 	prep.data = payload;
1080 	prep.datalen = plen;
1081 	prep.quotalen = key->type->def_datalen;
1082 	prep.expiry = TIME64_MAX;
1083 	if (key->type->preparse) {
1084 		ret = key->type->preparse(&prep);
1085 		if (ret < 0)
1086 			goto error;
1087 	}
1088 
1089 	down_write(&key->sem);
1090 
1091 	ret = key->type->update(key, &prep);
1092 	if (ret == 0) {
1093 		/* Updating a negative key positively instantiates it */
1094 		mark_key_instantiated(key, 0);
1095 		notify_key(key, NOTIFY_KEY_UPDATED, 0);
1096 	}
1097 
1098 	up_write(&key->sem);
1099 
1100 error:
1101 	if (key->type->preparse)
1102 		key->type->free_preparse(&prep);
1103 	return ret;
1104 }
1105 EXPORT_SYMBOL(key_update);
1106 
1107 /**
1108  * key_revoke - Revoke a key.
1109  * @key: The key to be revoked.
1110  *
1111  * Mark a key as being revoked and ask the type to free up its resources.  The
1112  * revocation timeout is set and the key and all its links will be
1113  * automatically garbage collected after key_gc_delay amount of time if they
1114  * are not manually dealt with first.
1115  */
key_revoke(struct key * key)1116 void key_revoke(struct key *key)
1117 {
1118 	time64_t time;
1119 
1120 	key_check(key);
1121 
1122 	/* make sure no one's trying to change or use the key when we mark it
1123 	 * - we tell lockdep that we might nest because we might be revoking an
1124 	 *   authorisation key whilst holding the sem on a key we've just
1125 	 *   instantiated
1126 	 */
1127 	down_write_nested(&key->sem, 1);
1128 	if (!test_and_set_bit(KEY_FLAG_REVOKED, &key->flags)) {
1129 		notify_key(key, NOTIFY_KEY_REVOKED, 0);
1130 		if (key->type->revoke)
1131 			key->type->revoke(key);
1132 
1133 		/* set the death time to no more than the expiry time */
1134 		time = ktime_get_real_seconds();
1135 		if (key->revoked_at == 0 || key->revoked_at > time) {
1136 			key->revoked_at = time;
1137 			key_schedule_gc(key->revoked_at + key_gc_delay);
1138 		}
1139 	}
1140 
1141 	up_write(&key->sem);
1142 }
1143 EXPORT_SYMBOL(key_revoke);
1144 
1145 /**
1146  * key_invalidate - Invalidate a key.
1147  * @key: The key to be invalidated.
1148  *
1149  * Mark a key as being invalidated and have it cleaned up immediately.  The key
1150  * is ignored by all searches and other operations from this point.
1151  */
key_invalidate(struct key * key)1152 void key_invalidate(struct key *key)
1153 {
1154 	kenter("%d", key_serial(key));
1155 
1156 	key_check(key);
1157 
1158 	if (!test_bit(KEY_FLAG_INVALIDATED, &key->flags)) {
1159 		down_write_nested(&key->sem, 1);
1160 		if (!test_and_set_bit(KEY_FLAG_INVALIDATED, &key->flags)) {
1161 			notify_key(key, NOTIFY_KEY_INVALIDATED, 0);
1162 			key_schedule_gc_links();
1163 		}
1164 		up_write(&key->sem);
1165 	}
1166 }
1167 EXPORT_SYMBOL(key_invalidate);
1168 
1169 /**
1170  * generic_key_instantiate - Simple instantiation of a key from preparsed data
1171  * @key: The key to be instantiated
1172  * @prep: The preparsed data to load.
1173  *
1174  * Instantiate a key from preparsed data.  We assume we can just copy the data
1175  * in directly and clear the old pointers.
1176  *
1177  * This can be pointed to directly by the key type instantiate op pointer.
1178  */
generic_key_instantiate(struct key * key,struct key_preparsed_payload * prep)1179 int generic_key_instantiate(struct key *key, struct key_preparsed_payload *prep)
1180 {
1181 	int ret;
1182 
1183 	pr_devel("==>%s()\n", __func__);
1184 
1185 	ret = key_payload_reserve(key, prep->quotalen);
1186 	if (ret == 0) {
1187 		rcu_assign_keypointer(key, prep->payload.data[0]);
1188 		key->payload.data[1] = prep->payload.data[1];
1189 		key->payload.data[2] = prep->payload.data[2];
1190 		key->payload.data[3] = prep->payload.data[3];
1191 		prep->payload.data[0] = NULL;
1192 		prep->payload.data[1] = NULL;
1193 		prep->payload.data[2] = NULL;
1194 		prep->payload.data[3] = NULL;
1195 	}
1196 	pr_devel("<==%s() = %d\n", __func__, ret);
1197 	return ret;
1198 }
1199 EXPORT_SYMBOL(generic_key_instantiate);
1200 
1201 /**
1202  * register_key_type - Register a type of key.
1203  * @ktype: The new key type.
1204  *
1205  * Register a new key type.
1206  *
1207  * Returns 0 on success or -EEXIST if a type of this name already exists.
1208  */
register_key_type(struct key_type * ktype)1209 int register_key_type(struct key_type *ktype)
1210 {
1211 	struct key_type *p;
1212 	int ret;
1213 
1214 	memset(&ktype->lock_class, 0, sizeof(ktype->lock_class));
1215 
1216 	ret = -EEXIST;
1217 	down_write(&key_types_sem);
1218 
1219 	/* disallow key types with the same name */
1220 	list_for_each_entry(p, &key_types_list, link) {
1221 		if (strcmp(p->name, ktype->name) == 0)
1222 			goto out;
1223 	}
1224 
1225 	/* store the type */
1226 	list_add(&ktype->link, &key_types_list);
1227 
1228 	pr_notice("Key type %s registered\n", ktype->name);
1229 	ret = 0;
1230 
1231 out:
1232 	up_write(&key_types_sem);
1233 	return ret;
1234 }
1235 EXPORT_SYMBOL(register_key_type);
1236 
1237 /**
1238  * unregister_key_type - Unregister a type of key.
1239  * @ktype: The key type.
1240  *
1241  * Unregister a key type and mark all the extant keys of this type as dead.
1242  * Those keys of this type are then destroyed to get rid of their payloads and
1243  * they and their links will be garbage collected as soon as possible.
1244  */
unregister_key_type(struct key_type * ktype)1245 void unregister_key_type(struct key_type *ktype)
1246 {
1247 	down_write(&key_types_sem);
1248 	list_del_init(&ktype->link);
1249 	downgrade_write(&key_types_sem);
1250 	key_gc_keytype(ktype);
1251 	pr_notice("Key type %s unregistered\n", ktype->name);
1252 	up_read(&key_types_sem);
1253 }
1254 EXPORT_SYMBOL(unregister_key_type);
1255 
1256 /*
1257  * Initialise the key management state.
1258  */
key_init(void)1259 void __init key_init(void)
1260 {
1261 	/* allocate a slab in which we can store keys */
1262 	key_jar = kmem_cache_create("key_jar", sizeof(struct key),
1263 			0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1264 
1265 	/* add the special key types */
1266 	list_add_tail(&key_type_keyring.link, &key_types_list);
1267 	list_add_tail(&key_type_dead.link, &key_types_list);
1268 	list_add_tail(&key_type_user.link, &key_types_list);
1269 	list_add_tail(&key_type_logon.link, &key_types_list);
1270 
1271 	/* record the root user tracking */
1272 	rb_link_node(&root_key_user.node,
1273 		     NULL,
1274 		     &key_user_tree.rb_node);
1275 
1276 	rb_insert_color(&root_key_user.node,
1277 			&key_user_tree);
1278 }
1279