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1 /* Basic authentication token and access key management
2  *
3  * Copyright (C) 2004-2008 Red Hat, Inc. All Rights Reserved.
4  * Written by David Howells (dhowells@redhat.com)
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public License
8  * as published by the Free Software Foundation; either version
9  * 2 of the License, or (at your option) any later version.
10  */
11 
12 #include <linux/module.h>
13 #include <linux/init.h>
14 #include <linux/poison.h>
15 #include <linux/sched.h>
16 #include <linux/slab.h>
17 #include <linux/security.h>
18 #include <linux/workqueue.h>
19 #include <linux/random.h>
20 #include <linux/err.h>
21 #include "internal.h"
22 
23 struct kmem_cache *key_jar;
24 struct rb_root		key_serial_tree; /* tree of keys indexed by serial */
25 DEFINE_SPINLOCK(key_serial_lock);
26 
27 struct rb_root	key_user_tree; /* tree of quota records indexed by UID */
28 DEFINE_SPINLOCK(key_user_lock);
29 
30 unsigned int key_quota_root_maxkeys = 200;	/* root's key count quota */
31 unsigned int key_quota_root_maxbytes = 20000;	/* root's key space quota */
32 unsigned int key_quota_maxkeys = 200;		/* general key count quota */
33 unsigned int key_quota_maxbytes = 20000;	/* general key space quota */
34 
35 static LIST_HEAD(key_types_list);
36 static DECLARE_RWSEM(key_types_sem);
37 
38 /* We serialise key instantiation and link */
39 DEFINE_MUTEX(key_construction_mutex);
40 
41 #ifdef KEY_DEBUGGING
__key_check(const struct key * key)42 void __key_check(const struct key *key)
43 {
44 	printk("__key_check: key %p {%08x} should be {%08x}\n",
45 	       key, key->magic, KEY_DEBUG_MAGIC);
46 	BUG();
47 }
48 #endif
49 
50 /*
51  * Get the key quota record for a user, allocating a new record if one doesn't
52  * already exist.
53  */
key_user_lookup(kuid_t uid)54 struct key_user *key_user_lookup(kuid_t uid)
55 {
56 	struct key_user *candidate = NULL, *user;
57 	struct rb_node *parent = NULL;
58 	struct rb_node **p;
59 
60 try_again:
61 	p = &key_user_tree.rb_node;
62 	spin_lock(&key_user_lock);
63 
64 	/* search the tree for a user record with a matching UID */
65 	while (*p) {
66 		parent = *p;
67 		user = rb_entry(parent, struct key_user, node);
68 
69 		if (uid_lt(uid, user->uid))
70 			p = &(*p)->rb_left;
71 		else if (uid_gt(uid, user->uid))
72 			p = &(*p)->rb_right;
73 		else
74 			goto found;
75 	}
76 
77 	/* if we get here, we failed to find a match in the tree */
78 	if (!candidate) {
79 		/* allocate a candidate user record if we don't already have
80 		 * one */
81 		spin_unlock(&key_user_lock);
82 
83 		user = NULL;
84 		candidate = kmalloc(sizeof(struct key_user), GFP_KERNEL);
85 		if (unlikely(!candidate))
86 			goto out;
87 
88 		/* the allocation may have scheduled, so we need to repeat the
89 		 * search lest someone else added the record whilst we were
90 		 * asleep */
91 		goto try_again;
92 	}
93 
94 	/* if we get here, then the user record still hadn't appeared on the
95 	 * second pass - so we use the candidate record */
96 	atomic_set(&candidate->usage, 1);
97 	atomic_set(&candidate->nkeys, 0);
98 	atomic_set(&candidate->nikeys, 0);
99 	candidate->uid = uid;
100 	candidate->qnkeys = 0;
101 	candidate->qnbytes = 0;
102 	spin_lock_init(&candidate->lock);
103 	mutex_init(&candidate->cons_lock);
104 
105 	rb_link_node(&candidate->node, parent, p);
106 	rb_insert_color(&candidate->node, &key_user_tree);
107 	spin_unlock(&key_user_lock);
108 	user = candidate;
109 	goto out;
110 
111 	/* okay - we found a user record for this UID */
112 found:
113 	atomic_inc(&user->usage);
114 	spin_unlock(&key_user_lock);
115 	kfree(candidate);
116 out:
117 	return user;
118 }
119 
120 /*
121  * Dispose of a user structure
122  */
key_user_put(struct key_user * user)123 void key_user_put(struct key_user *user)
124 {
125 	if (atomic_dec_and_lock(&user->usage, &key_user_lock)) {
126 		rb_erase(&user->node, &key_user_tree);
127 		spin_unlock(&key_user_lock);
128 
129 		kfree(user);
130 	}
131 }
132 
133 /*
134  * Allocate a serial number for a key.  These are assigned randomly to avoid
135  * security issues through covert channel problems.
136  */
key_alloc_serial(struct key * key)137 static inline void key_alloc_serial(struct key *key)
138 {
139 	struct rb_node *parent, **p;
140 	struct key *xkey;
141 
142 	/* propose a random serial number and look for a hole for it in the
143 	 * serial number tree */
144 	do {
145 		get_random_bytes(&key->serial, sizeof(key->serial));
146 
147 		key->serial >>= 1; /* negative numbers are not permitted */
148 	} while (key->serial < 3);
149 
150 	spin_lock(&key_serial_lock);
151 
152 attempt_insertion:
153 	parent = NULL;
154 	p = &key_serial_tree.rb_node;
155 
156 	while (*p) {
157 		parent = *p;
158 		xkey = rb_entry(parent, struct key, serial_node);
159 
160 		if (key->serial < xkey->serial)
161 			p = &(*p)->rb_left;
162 		else if (key->serial > xkey->serial)
163 			p = &(*p)->rb_right;
164 		else
165 			goto serial_exists;
166 	}
167 
168 	/* we've found a suitable hole - arrange for this key to occupy it */
169 	rb_link_node(&key->serial_node, parent, p);
170 	rb_insert_color(&key->serial_node, &key_serial_tree);
171 
172 	spin_unlock(&key_serial_lock);
173 	return;
174 
175 	/* we found a key with the proposed serial number - walk the tree from
176 	 * that point looking for the next unused serial number */
177 serial_exists:
178 	for (;;) {
179 		key->serial++;
180 		if (key->serial < 3) {
181 			key->serial = 3;
182 			goto attempt_insertion;
183 		}
184 
185 		parent = rb_next(parent);
186 		if (!parent)
187 			goto attempt_insertion;
188 
189 		xkey = rb_entry(parent, struct key, serial_node);
190 		if (key->serial < xkey->serial)
191 			goto attempt_insertion;
192 	}
193 }
194 
195 /**
196  * key_alloc - Allocate a key of the specified type.
197  * @type: The type of key to allocate.
198  * @desc: The key description to allow the key to be searched out.
199  * @uid: The owner of the new key.
200  * @gid: The group ID for the new key's group permissions.
201  * @cred: The credentials specifying UID namespace.
202  * @perm: The permissions mask of the new key.
203  * @flags: Flags specifying quota properties.
204  *
205  * Allocate a key of the specified type with the attributes given.  The key is
206  * returned in an uninstantiated state and the caller needs to instantiate the
207  * key before returning.
208  *
209  * The user's key count quota is updated to reflect the creation of the key and
210  * the user's key data quota has the default for the key type reserved.  The
211  * instantiation function should amend this as necessary.  If insufficient
212  * quota is available, -EDQUOT will be returned.
213  *
214  * The LSM security modules can prevent a key being created, in which case
215  * -EACCES will be returned.
216  *
217  * Returns a pointer to the new key if successful and an error code otherwise.
218  *
219  * Note that the caller needs to ensure the key type isn't uninstantiated.
220  * Internally this can be done by locking key_types_sem.  Externally, this can
221  * be done by either never unregistering the key type, or making sure
222  * key_alloc() calls don't race with module unloading.
223  */
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)224 struct key *key_alloc(struct key_type *type, const char *desc,
225 		      kuid_t uid, kgid_t gid, const struct cred *cred,
226 		      key_perm_t perm, unsigned long flags)
227 {
228 	struct key_user *user = NULL;
229 	struct key *key;
230 	size_t desclen, quotalen;
231 	int ret;
232 
233 	key = ERR_PTR(-EINVAL);
234 	if (!desc || !*desc)
235 		goto error;
236 
237 	if (type->vet_description) {
238 		ret = type->vet_description(desc);
239 		if (ret < 0) {
240 			key = ERR_PTR(ret);
241 			goto error;
242 		}
243 	}
244 
245 	desclen = strlen(desc) + 1;
246 	quotalen = desclen + type->def_datalen;
247 
248 	/* get hold of the key tracking for this user */
249 	user = key_user_lookup(uid);
250 	if (!user)
251 		goto no_memory_1;
252 
253 	/* check that the user's quota permits allocation of another key and
254 	 * its description */
255 	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
256 		unsigned maxkeys = uid_eq(uid, GLOBAL_ROOT_UID) ?
257 			key_quota_root_maxkeys : key_quota_maxkeys;
258 		unsigned maxbytes = uid_eq(uid, GLOBAL_ROOT_UID) ?
259 			key_quota_root_maxbytes : key_quota_maxbytes;
260 
261 		spin_lock(&user->lock);
262 		if (!(flags & KEY_ALLOC_QUOTA_OVERRUN)) {
263 			if (user->qnkeys + 1 >= maxkeys ||
264 			    user->qnbytes + quotalen >= maxbytes ||
265 			    user->qnbytes + quotalen < user->qnbytes)
266 				goto no_quota;
267 		}
268 
269 		user->qnkeys++;
270 		user->qnbytes += quotalen;
271 		spin_unlock(&user->lock);
272 	}
273 
274 	/* allocate and initialise the key and its description */
275 	key = kmem_cache_alloc(key_jar, GFP_KERNEL);
276 	if (!key)
277 		goto no_memory_2;
278 
279 	if (desc) {
280 		key->description = kmemdup(desc, desclen, GFP_KERNEL);
281 		if (!key->description)
282 			goto no_memory_3;
283 	}
284 
285 	atomic_set(&key->usage, 1);
286 	init_rwsem(&key->sem);
287 	lockdep_set_class(&key->sem, &type->lock_class);
288 	key->type = type;
289 	key->user = user;
290 	key->quotalen = quotalen;
291 	key->datalen = type->def_datalen;
292 	key->uid = uid;
293 	key->gid = gid;
294 	key->perm = perm;
295 	key->flags = 0;
296 	key->expiry = 0;
297 	key->payload.data = NULL;
298 	key->security = NULL;
299 
300 	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA))
301 		key->flags |= 1 << KEY_FLAG_IN_QUOTA;
302 
303 	memset(&key->type_data, 0, sizeof(key->type_data));
304 
305 #ifdef KEY_DEBUGGING
306 	key->magic = KEY_DEBUG_MAGIC;
307 #endif
308 
309 	/* let the security module know about the key */
310 	ret = security_key_alloc(key, cred, flags);
311 	if (ret < 0)
312 		goto security_error;
313 
314 	/* publish the key by giving it a serial number */
315 	atomic_inc(&user->nkeys);
316 	key_alloc_serial(key);
317 
318 error:
319 	return key;
320 
321 security_error:
322 	kfree(key->description);
323 	kmem_cache_free(key_jar, key);
324 	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
325 		spin_lock(&user->lock);
326 		user->qnkeys--;
327 		user->qnbytes -= quotalen;
328 		spin_unlock(&user->lock);
329 	}
330 	key_user_put(user);
331 	key = ERR_PTR(ret);
332 	goto error;
333 
334 no_memory_3:
335 	kmem_cache_free(key_jar, key);
336 no_memory_2:
337 	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
338 		spin_lock(&user->lock);
339 		user->qnkeys--;
340 		user->qnbytes -= quotalen;
341 		spin_unlock(&user->lock);
342 	}
343 	key_user_put(user);
344 no_memory_1:
345 	key = ERR_PTR(-ENOMEM);
346 	goto error;
347 
348 no_quota:
349 	spin_unlock(&user->lock);
350 	key_user_put(user);
351 	key = ERR_PTR(-EDQUOT);
352 	goto error;
353 }
354 EXPORT_SYMBOL(key_alloc);
355 
356 /**
357  * key_payload_reserve - Adjust data quota reservation for the key's payload
358  * @key: The key to make the reservation for.
359  * @datalen: The amount of data payload the caller now wants.
360  *
361  * Adjust the amount of the owning user's key data quota that a key reserves.
362  * If the amount is increased, then -EDQUOT may be returned if there isn't
363  * enough free quota available.
364  *
365  * If successful, 0 is returned.
366  */
key_payload_reserve(struct key * key,size_t datalen)367 int key_payload_reserve(struct key *key, size_t datalen)
368 {
369 	int delta = (int)datalen - key->datalen;
370 	int ret = 0;
371 
372 	key_check(key);
373 
374 	/* contemplate the quota adjustment */
375 	if (delta != 0 && test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
376 		unsigned maxbytes = uid_eq(key->user->uid, GLOBAL_ROOT_UID) ?
377 			key_quota_root_maxbytes : key_quota_maxbytes;
378 
379 		spin_lock(&key->user->lock);
380 
381 		if (delta > 0 &&
382 		    (key->user->qnbytes + delta >= maxbytes ||
383 		     key->user->qnbytes + delta < key->user->qnbytes)) {
384 			ret = -EDQUOT;
385 		}
386 		else {
387 			key->user->qnbytes += delta;
388 			key->quotalen += delta;
389 		}
390 		spin_unlock(&key->user->lock);
391 	}
392 
393 	/* change the recorded data length if that didn't generate an error */
394 	if (ret == 0)
395 		key->datalen = datalen;
396 
397 	return ret;
398 }
399 EXPORT_SYMBOL(key_payload_reserve);
400 
401 /*
402  * Instantiate a key and link it into the target keyring atomically.  Must be
403  * called with the target keyring's semaphore writelocked.  The target key's
404  * semaphore need not be locked as instantiation is serialised by
405  * key_construction_mutex.
406  */
__key_instantiate_and_link(struct key * key,struct key_preparsed_payload * prep,struct key * keyring,struct key * authkey,unsigned long * _prealloc)407 static int __key_instantiate_and_link(struct key *key,
408 				      struct key_preparsed_payload *prep,
409 				      struct key *keyring,
410 				      struct key *authkey,
411 				      unsigned long *_prealloc)
412 {
413 	int ret, awaken;
414 
415 	key_check(key);
416 	key_check(keyring);
417 
418 	awaken = 0;
419 	ret = -EBUSY;
420 
421 	mutex_lock(&key_construction_mutex);
422 
423 	/* can't instantiate twice */
424 	if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
425 		/* instantiate the key */
426 		ret = key->type->instantiate(key, prep);
427 
428 		if (ret == 0) {
429 			/* mark the key as being instantiated */
430 			atomic_inc(&key->user->nikeys);
431 			set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
432 
433 			if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
434 				awaken = 1;
435 
436 			/* and link it into the destination keyring */
437 			if (keyring)
438 				__key_link(keyring, key, _prealloc);
439 
440 			/* disable the authorisation key */
441 			if (authkey)
442 				key_revoke(authkey);
443 		}
444 	}
445 
446 	mutex_unlock(&key_construction_mutex);
447 
448 	/* wake up anyone waiting for a key to be constructed */
449 	if (awaken)
450 		wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
451 
452 	return ret;
453 }
454 
455 /**
456  * key_instantiate_and_link - Instantiate a key and link it into the keyring.
457  * @key: The key to instantiate.
458  * @data: The data to use to instantiate the keyring.
459  * @datalen: The length of @data.
460  * @keyring: Keyring to create a link in on success (or NULL).
461  * @authkey: The authorisation token permitting instantiation.
462  *
463  * Instantiate a key that's in the uninstantiated state using the provided data
464  * and, if successful, link it in to the destination keyring if one is
465  * supplied.
466  *
467  * If successful, 0 is returned, the authorisation token is revoked and anyone
468  * waiting for the key is woken up.  If the key was already instantiated,
469  * -EBUSY will be returned.
470  */
key_instantiate_and_link(struct key * key,const void * data,size_t datalen,struct key * keyring,struct key * authkey)471 int key_instantiate_and_link(struct key *key,
472 			     const void *data,
473 			     size_t datalen,
474 			     struct key *keyring,
475 			     struct key *authkey)
476 {
477 	struct key_preparsed_payload prep;
478 	unsigned long prealloc;
479 	int ret;
480 
481 	memset(&prep, 0, sizeof(prep));
482 	prep.data = data;
483 	prep.datalen = datalen;
484 	prep.quotalen = key->type->def_datalen;
485 	if (key->type->preparse) {
486 		ret = key->type->preparse(&prep);
487 		if (ret < 0)
488 			goto error;
489 	}
490 
491 	if (keyring) {
492 		ret = __key_link_begin(keyring, key->type, key->description,
493 				       &prealloc);
494 		if (ret < 0)
495 			goto error_free_preparse;
496 	}
497 
498 	ret = __key_instantiate_and_link(key, &prep, keyring, authkey,
499 					 &prealloc);
500 
501 	if (keyring)
502 		__key_link_end(keyring, key->type, prealloc);
503 
504 error_free_preparse:
505 	if (key->type->preparse)
506 		key->type->free_preparse(&prep);
507 error:
508 	return ret;
509 }
510 
511 EXPORT_SYMBOL(key_instantiate_and_link);
512 
513 /**
514  * key_reject_and_link - Negatively instantiate a key and link it into the keyring.
515  * @key: The key to instantiate.
516  * @timeout: The timeout on the negative key.
517  * @error: The error to return when the key is hit.
518  * @keyring: Keyring to create a link in on success (or NULL).
519  * @authkey: The authorisation token permitting instantiation.
520  *
521  * Negatively instantiate a key that's in the uninstantiated state and, if
522  * successful, set its timeout and stored error and link it in to the
523  * destination keyring if one is supplied.  The key and any links to the key
524  * will be automatically garbage collected after the timeout expires.
525  *
526  * Negative keys are used to rate limit repeated request_key() calls by causing
527  * them to return the stored error code (typically ENOKEY) until the negative
528  * key expires.
529  *
530  * If successful, 0 is returned, the authorisation token is revoked and anyone
531  * waiting for the key is woken up.  If the key was already instantiated,
532  * -EBUSY will be returned.
533  */
key_reject_and_link(struct key * key,unsigned timeout,unsigned error,struct key * keyring,struct key * authkey)534 int key_reject_and_link(struct key *key,
535 			unsigned timeout,
536 			unsigned error,
537 			struct key *keyring,
538 			struct key *authkey)
539 {
540 	unsigned long prealloc;
541 	struct timespec now;
542 	int ret, awaken, link_ret = 0;
543 
544 	key_check(key);
545 	key_check(keyring);
546 
547 	awaken = 0;
548 	ret = -EBUSY;
549 
550 	if (keyring)
551 		link_ret = __key_link_begin(keyring, key->type,
552 					    key->description, &prealloc);
553 
554 	mutex_lock(&key_construction_mutex);
555 
556 	/* can't instantiate twice */
557 	if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
558 		/* mark the key as being negatively instantiated */
559 		atomic_inc(&key->user->nikeys);
560 		set_bit(KEY_FLAG_NEGATIVE, &key->flags);
561 		set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
562 		key->type_data.reject_error = -error;
563 		now = current_kernel_time();
564 		key->expiry = now.tv_sec + timeout;
565 		key_schedule_gc(key->expiry + key_gc_delay);
566 
567 		if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
568 			awaken = 1;
569 
570 		ret = 0;
571 
572 		/* and link it into the destination keyring */
573 		if (keyring && link_ret == 0)
574 			__key_link(keyring, key, &prealloc);
575 
576 		/* disable the authorisation key */
577 		if (authkey)
578 			key_revoke(authkey);
579 	}
580 
581 	mutex_unlock(&key_construction_mutex);
582 
583 	if (keyring && link_ret == 0)
584 		__key_link_end(keyring, key->type, prealloc);
585 
586 	/* wake up anyone waiting for a key to be constructed */
587 	if (awaken)
588 		wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
589 
590 	return ret == 0 ? link_ret : ret;
591 }
592 EXPORT_SYMBOL(key_reject_and_link);
593 
594 /**
595  * key_put - Discard a reference to a key.
596  * @key: The key to discard a reference from.
597  *
598  * Discard a reference to a key, and when all the references are gone, we
599  * schedule the cleanup task to come and pull it out of the tree in process
600  * context at some later time.
601  */
key_put(struct key * key)602 void key_put(struct key *key)
603 {
604 	if (key) {
605 		key_check(key);
606 
607 		if (atomic_dec_and_test(&key->usage))
608 			schedule_work(&key_gc_work);
609 	}
610 }
611 EXPORT_SYMBOL(key_put);
612 
613 /*
614  * Find a key by its serial number.
615  */
key_lookup(key_serial_t id)616 struct key *key_lookup(key_serial_t id)
617 {
618 	struct rb_node *n;
619 	struct key *key;
620 
621 	spin_lock(&key_serial_lock);
622 
623 	/* search the tree for the specified key */
624 	n = key_serial_tree.rb_node;
625 	while (n) {
626 		key = rb_entry(n, struct key, serial_node);
627 
628 		if (id < key->serial)
629 			n = n->rb_left;
630 		else if (id > key->serial)
631 			n = n->rb_right;
632 		else
633 			goto found;
634 	}
635 
636 not_found:
637 	key = ERR_PTR(-ENOKEY);
638 	goto error;
639 
640 found:
641 	/* pretend it doesn't exist if it is awaiting deletion */
642 	if (atomic_read(&key->usage) == 0)
643 		goto not_found;
644 
645 	/* this races with key_put(), but that doesn't matter since key_put()
646 	 * doesn't actually change the key
647 	 */
648 	atomic_inc(&key->usage);
649 
650 error:
651 	spin_unlock(&key_serial_lock);
652 	return key;
653 }
654 
655 /*
656  * Find and lock the specified key type against removal.
657  *
658  * We return with the sem read-locked if successful.  If the type wasn't
659  * available -ENOKEY is returned instead.
660  */
key_type_lookup(const char * type)661 struct key_type *key_type_lookup(const char *type)
662 {
663 	struct key_type *ktype;
664 
665 	down_read(&key_types_sem);
666 
667 	/* look up the key type to see if it's one of the registered kernel
668 	 * types */
669 	list_for_each_entry(ktype, &key_types_list, link) {
670 		if (strcmp(ktype->name, type) == 0)
671 			goto found_kernel_type;
672 	}
673 
674 	up_read(&key_types_sem);
675 	ktype = ERR_PTR(-ENOKEY);
676 
677 found_kernel_type:
678 	return ktype;
679 }
680 
key_set_timeout(struct key * key,unsigned timeout)681 void key_set_timeout(struct key *key, unsigned timeout)
682 {
683 	struct timespec now;
684 	time_t expiry = 0;
685 
686 	/* make the changes with the locks held to prevent races */
687 	down_write(&key->sem);
688 
689 	if (timeout > 0) {
690 		now = current_kernel_time();
691 		expiry = now.tv_sec + timeout;
692 	}
693 
694 	key->expiry = expiry;
695 	key_schedule_gc(key->expiry + key_gc_delay);
696 
697 	up_write(&key->sem);
698 }
699 EXPORT_SYMBOL_GPL(key_set_timeout);
700 
701 /*
702  * Unlock a key type locked by key_type_lookup().
703  */
key_type_put(struct key_type * ktype)704 void key_type_put(struct key_type *ktype)
705 {
706 	up_read(&key_types_sem);
707 }
708 
709 /*
710  * Attempt to update an existing key.
711  *
712  * The key is given to us with an incremented refcount that we need to discard
713  * if we get an error.
714  */
__key_update(key_ref_t key_ref,struct key_preparsed_payload * prep)715 static inline key_ref_t __key_update(key_ref_t key_ref,
716 				     struct key_preparsed_payload *prep)
717 {
718 	struct key *key = key_ref_to_ptr(key_ref);
719 	int ret;
720 
721 	/* need write permission on the key to update it */
722 	ret = key_permission(key_ref, KEY_WRITE);
723 	if (ret < 0)
724 		goto error;
725 
726 	ret = -EEXIST;
727 	if (!key->type->update)
728 		goto error;
729 
730 	down_write(&key->sem);
731 
732 	ret = key->type->update(key, prep);
733 	if (ret == 0)
734 		/* updating a negative key instantiates it */
735 		clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
736 
737 	up_write(&key->sem);
738 
739 	if (ret < 0)
740 		goto error;
741 out:
742 	return key_ref;
743 
744 error:
745 	key_put(key);
746 	key_ref = ERR_PTR(ret);
747 	goto out;
748 }
749 
750 /**
751  * key_create_or_update - Update or create and instantiate a key.
752  * @keyring_ref: A pointer to the destination keyring with possession flag.
753  * @type: The type of key.
754  * @description: The searchable description for the key.
755  * @payload: The data to use to instantiate or update the key.
756  * @plen: The length of @payload.
757  * @perm: The permissions mask for a new key.
758  * @flags: The quota flags for a new key.
759  *
760  * Search the destination keyring for a key of the same description and if one
761  * is found, update it, otherwise create and instantiate a new one and create a
762  * link to it from that keyring.
763  *
764  * If perm is KEY_PERM_UNDEF then an appropriate key permissions mask will be
765  * concocted.
766  *
767  * Returns a pointer to the new key if successful, -ENODEV if the key type
768  * wasn't available, -ENOTDIR if the keyring wasn't a keyring, -EACCES if the
769  * caller isn't permitted to modify the keyring or the LSM did not permit
770  * creation of the key.
771  *
772  * On success, the possession flag from the keyring ref will be tacked on to
773  * the key ref before it is returned.
774  */
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)775 key_ref_t key_create_or_update(key_ref_t keyring_ref,
776 			       const char *type,
777 			       const char *description,
778 			       const void *payload,
779 			       size_t plen,
780 			       key_perm_t perm,
781 			       unsigned long flags)
782 {
783 	unsigned long prealloc;
784 	struct key_preparsed_payload prep;
785 	const struct cred *cred = current_cred();
786 	struct key_type *ktype;
787 	struct key *keyring, *key = NULL;
788 	key_ref_t key_ref;
789 	int ret;
790 
791 	/* look up the key type to see if it's one of the registered kernel
792 	 * types */
793 	ktype = key_type_lookup(type);
794 	if (IS_ERR(ktype)) {
795 		key_ref = ERR_PTR(-ENODEV);
796 		goto error;
797 	}
798 
799 	key_ref = ERR_PTR(-EINVAL);
800 	if (!ktype->match || !ktype->instantiate ||
801 	    (!description && !ktype->preparse))
802 		goto error_put_type;
803 
804 	keyring = key_ref_to_ptr(keyring_ref);
805 
806 	key_check(keyring);
807 
808 	key_ref = ERR_PTR(-ENOTDIR);
809 	if (keyring->type != &key_type_keyring)
810 		goto error_put_type;
811 
812 	memset(&prep, 0, sizeof(prep));
813 	prep.data = payload;
814 	prep.datalen = plen;
815 	prep.quotalen = ktype->def_datalen;
816 	if (ktype->preparse) {
817 		ret = ktype->preparse(&prep);
818 		if (ret < 0) {
819 			key_ref = ERR_PTR(ret);
820 			goto error_put_type;
821 		}
822 		if (!description)
823 			description = prep.description;
824 		key_ref = ERR_PTR(-EINVAL);
825 		if (!description)
826 			goto error_free_prep;
827 	}
828 
829 	ret = __key_link_begin(keyring, ktype, description, &prealloc);
830 	if (ret < 0) {
831 		key_ref = ERR_PTR(ret);
832 		goto error_free_prep;
833 	}
834 
835 	/* if we're going to allocate a new key, we're going to have
836 	 * to modify the keyring */
837 	ret = key_permission(keyring_ref, KEY_WRITE);
838 	if (ret < 0) {
839 		key_ref = ERR_PTR(ret);
840 		goto error_link_end;
841 	}
842 
843 	/* if it's possible to update this type of key, search for an existing
844 	 * key of the same type and description in the destination keyring and
845 	 * update that instead if possible
846 	 */
847 	if (ktype->update) {
848 		key_ref = __keyring_search_one(keyring_ref, ktype, description,
849 					       0);
850 		if (!IS_ERR(key_ref))
851 			goto found_matching_key;
852 	}
853 
854 	/* if the client doesn't provide, decide on the permissions we want */
855 	if (perm == KEY_PERM_UNDEF) {
856 		perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
857 		perm |= KEY_USR_VIEW;
858 
859 		if (ktype->read)
860 			perm |= KEY_POS_READ;
861 
862 		if (ktype == &key_type_keyring || ktype->update)
863 			perm |= KEY_POS_WRITE;
864 	}
865 
866 	/* allocate a new key */
867 	key = key_alloc(ktype, description, cred->fsuid, cred->fsgid, cred,
868 			perm, flags);
869 	if (IS_ERR(key)) {
870 		key_ref = ERR_CAST(key);
871 		goto error_link_end;
872 	}
873 
874 	/* instantiate it and link it into the target keyring */
875 	ret = __key_instantiate_and_link(key, &prep, keyring, NULL, &prealloc);
876 	if (ret < 0) {
877 		key_put(key);
878 		key_ref = ERR_PTR(ret);
879 		goto error_link_end;
880 	}
881 
882 	key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
883 
884 error_link_end:
885 	__key_link_end(keyring, ktype, prealloc);
886 error_free_prep:
887 	if (ktype->preparse)
888 		ktype->free_preparse(&prep);
889 error_put_type:
890 	key_type_put(ktype);
891 error:
892 	return key_ref;
893 
894  found_matching_key:
895 	/* we found a matching key, so we're going to try to update it
896 	 * - we can drop the locks first as we have the key pinned
897 	 */
898 	__key_link_end(keyring, ktype, prealloc);
899 
900 	key_ref = __key_update(key_ref, &prep);
901 	goto error_free_prep;
902 }
903 EXPORT_SYMBOL(key_create_or_update);
904 
905 /**
906  * key_update - Update a key's contents.
907  * @key_ref: The pointer (plus possession flag) to the key.
908  * @payload: The data to be used to update the key.
909  * @plen: The length of @payload.
910  *
911  * Attempt to update the contents of a key with the given payload data.  The
912  * caller must be granted Write permission on the key.  Negative keys can be
913  * instantiated by this method.
914  *
915  * Returns 0 on success, -EACCES if not permitted and -EOPNOTSUPP if the key
916  * type does not support updating.  The key type may return other errors.
917  */
key_update(key_ref_t key_ref,const void * payload,size_t plen)918 int key_update(key_ref_t key_ref, const void *payload, size_t plen)
919 {
920 	struct key_preparsed_payload prep;
921 	struct key *key = key_ref_to_ptr(key_ref);
922 	int ret;
923 
924 	key_check(key);
925 
926 	/* the key must be writable */
927 	ret = key_permission(key_ref, KEY_WRITE);
928 	if (ret < 0)
929 		goto error;
930 
931 	/* attempt to update it if supported */
932 	ret = -EOPNOTSUPP;
933 	if (!key->type->update)
934 		goto error;
935 
936 	memset(&prep, 0, sizeof(prep));
937 	prep.data = payload;
938 	prep.datalen = plen;
939 	prep.quotalen = key->type->def_datalen;
940 	if (key->type->preparse) {
941 		ret = key->type->preparse(&prep);
942 		if (ret < 0)
943 			goto error;
944 	}
945 
946 	down_write(&key->sem);
947 
948 	ret = key->type->update(key, &prep);
949 	if (ret == 0)
950 		/* updating a negative key instantiates it */
951 		clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
952 
953 	up_write(&key->sem);
954 
955 	if (key->type->preparse)
956 		key->type->free_preparse(&prep);
957 error:
958 	return ret;
959 }
960 EXPORT_SYMBOL(key_update);
961 
962 /**
963  * key_revoke - Revoke a key.
964  * @key: The key to be revoked.
965  *
966  * Mark a key as being revoked and ask the type to free up its resources.  The
967  * revocation timeout is set and the key and all its links will be
968  * automatically garbage collected after key_gc_delay amount of time if they
969  * are not manually dealt with first.
970  */
key_revoke(struct key * key)971 void key_revoke(struct key *key)
972 {
973 	struct timespec now;
974 	time_t time;
975 
976 	key_check(key);
977 
978 	/* make sure no one's trying to change or use the key when we mark it
979 	 * - we tell lockdep that we might nest because we might be revoking an
980 	 *   authorisation key whilst holding the sem on a key we've just
981 	 *   instantiated
982 	 */
983 	down_write_nested(&key->sem, 1);
984 	if (!test_and_set_bit(KEY_FLAG_REVOKED, &key->flags) &&
985 	    key->type->revoke)
986 		key->type->revoke(key);
987 
988 	/* set the death time to no more than the expiry time */
989 	now = current_kernel_time();
990 	time = now.tv_sec;
991 	if (key->revoked_at == 0 || key->revoked_at > time) {
992 		key->revoked_at = time;
993 		key_schedule_gc(key->revoked_at + key_gc_delay);
994 	}
995 
996 	up_write(&key->sem);
997 }
998 EXPORT_SYMBOL(key_revoke);
999 
1000 /**
1001  * key_invalidate - Invalidate a key.
1002  * @key: The key to be invalidated.
1003  *
1004  * Mark a key as being invalidated and have it cleaned up immediately.  The key
1005  * is ignored by all searches and other operations from this point.
1006  */
key_invalidate(struct key * key)1007 void key_invalidate(struct key *key)
1008 {
1009 	kenter("%d", key_serial(key));
1010 
1011 	key_check(key);
1012 
1013 	if (!test_bit(KEY_FLAG_INVALIDATED, &key->flags)) {
1014 		down_write_nested(&key->sem, 1);
1015 		if (!test_and_set_bit(KEY_FLAG_INVALIDATED, &key->flags))
1016 			key_schedule_gc_links();
1017 		up_write(&key->sem);
1018 	}
1019 }
1020 EXPORT_SYMBOL(key_invalidate);
1021 
1022 /**
1023  * register_key_type - Register a type of key.
1024  * @ktype: The new key type.
1025  *
1026  * Register a new key type.
1027  *
1028  * Returns 0 on success or -EEXIST if a type of this name already exists.
1029  */
register_key_type(struct key_type * ktype)1030 int register_key_type(struct key_type *ktype)
1031 {
1032 	struct key_type *p;
1033 	int ret;
1034 
1035 	memset(&ktype->lock_class, 0, sizeof(ktype->lock_class));
1036 
1037 	ret = -EEXIST;
1038 	down_write(&key_types_sem);
1039 
1040 	/* disallow key types with the same name */
1041 	list_for_each_entry(p, &key_types_list, link) {
1042 		if (strcmp(p->name, ktype->name) == 0)
1043 			goto out;
1044 	}
1045 
1046 	/* store the type */
1047 	list_add(&ktype->link, &key_types_list);
1048 
1049 	pr_notice("Key type %s registered\n", ktype->name);
1050 	ret = 0;
1051 
1052 out:
1053 	up_write(&key_types_sem);
1054 	return ret;
1055 }
1056 EXPORT_SYMBOL(register_key_type);
1057 
1058 /**
1059  * unregister_key_type - Unregister a type of key.
1060  * @ktype: The key type.
1061  *
1062  * Unregister a key type and mark all the extant keys of this type as dead.
1063  * Those keys of this type are then destroyed to get rid of their payloads and
1064  * they and their links will be garbage collected as soon as possible.
1065  */
unregister_key_type(struct key_type * ktype)1066 void unregister_key_type(struct key_type *ktype)
1067 {
1068 	down_write(&key_types_sem);
1069 	list_del_init(&ktype->link);
1070 	downgrade_write(&key_types_sem);
1071 	key_gc_keytype(ktype);
1072 	pr_notice("Key type %s unregistered\n", ktype->name);
1073 	up_read(&key_types_sem);
1074 }
1075 EXPORT_SYMBOL(unregister_key_type);
1076 
1077 /*
1078  * Initialise the key management state.
1079  */
key_init(void)1080 void __init key_init(void)
1081 {
1082 	/* allocate a slab in which we can store keys */
1083 	key_jar = kmem_cache_create("key_jar", sizeof(struct key),
1084 			0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1085 
1086 	/* add the special key types */
1087 	list_add_tail(&key_type_keyring.link, &key_types_list);
1088 	list_add_tail(&key_type_dead.link, &key_types_list);
1089 	list_add_tail(&key_type_user.link, &key_types_list);
1090 	list_add_tail(&key_type_logon.link, &key_types_list);
1091 
1092 	/* record the root user tracking */
1093 	rb_link_node(&root_key_user.node,
1094 		     NULL,
1095 		     &key_user_tree.rb_node);
1096 
1097 	rb_insert_color(&root_key_user.node,
1098 			&key_user_tree);
1099 }
1100