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TOMOYO Linux Cross Reference
Linux/security/keys/key.c

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

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