root/security/keys/key.c

DEFINITIONS

1. __key_check
2. key_user_lookup
3. key_user_put
4. key_alloc_serial
5. key_alloc
6. key_payload_reserve
7. mark_key_instantiated
8. __key_instantiate_and_link
9. key_instantiate_and_link
10. key_reject_and_link
11. key_put
12. key_lookup
13. key_type_lookup
14. key_set_timeout
15. key_type_put
16. __key_update
17. key_create_or_update
18. key_update
19. key_revoke
20. key_invalidate
21. generic_key_instantiate
22. register_key_type
23. unregister_key_type
24. key_init

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* Basic authentication token and access key management
   3  *
   4  * Copyright (C) 2004-2008 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7 
   8 #include <linux/export.h>
   9 #include <linux/init.h>
  10 #include <linux/poison.h>
  11 #include <linux/sched.h>
  12 #include <linux/slab.h>
  13 #include <linux/security.h>
  14 #include <linux/workqueue.h>
  15 #include <linux/random.h>
  16 #include <linux/err.h>
  17 #include "internal.h"
  18 
  19 struct kmem_cache *key_jar;
  20 struct rb_root          key_serial_tree; /* tree of keys indexed by serial */
  21 DEFINE_SPINLOCK(key_serial_lock);
  22 
  23 struct rb_root  key_user_tree; /* tree of quota records indexed by UID */
  24 DEFINE_SPINLOCK(key_user_lock);
  25 
  26 unsigned int key_quota_root_maxkeys = 1000000;  /* root's key count quota */
  27 unsigned int key_quota_root_maxbytes = 25000000; /* root's key space quota */
  28 unsigned int key_quota_maxkeys = 200;           /* general key count quota */
  29 unsigned int key_quota_maxbytes = 20000;        /* general key space quota */
  30 
  31 static LIST_HEAD(key_types_list);
  32 static DECLARE_RWSEM(key_types_sem);
  33 
  34 /* We serialise key instantiation and link */
  35 DEFINE_MUTEX(key_construction_mutex);
  36 
  37 #ifdef KEY_DEBUGGING
  38 void __key_check(const struct key *key)
  39 {
  40         printk("__key_check: key %p {%08x} should be {%08x}\n",
  41                key, key->magic, KEY_DEBUG_MAGIC);
  42         BUG();
  43 }
  44 #endif
  45 
  46 /*
  47  * Get the key quota record for a user, allocating a new record if one doesn't
  48  * already exist.
  49  */
  50 struct key_user *key_user_lookup(kuid_t uid)
  51 {
  52         struct key_user *candidate = NULL, *user;
  53         struct rb_node *parent, **p;
  54 
  55 try_again:
  56         parent = NULL;
  57         p = &key_user_tree.rb_node;
  58         spin_lock(&key_user_lock);
  59 
  60         /* search the tree for a user record with a matching UID */
  61         while (*p) {
  62                 parent = *p;
  63                 user = rb_entry(parent, struct key_user, node);
  64 
  65                 if (uid_lt(uid, user->uid))
  66                         p = &(*p)->rb_left;
  67                 else if (uid_gt(uid, user->uid))
  68                         p = &(*p)->rb_right;
  69                 else
  70                         goto found;
  71         }
  72 
  73         /* if we get here, we failed to find a match in the tree */
  74         if (!candidate) {
  75                 /* allocate a candidate user record if we don't already have
  76                  * one */
  77                 spin_unlock(&key_user_lock);
  78 
  79                 user = NULL;
  80                 candidate = kmalloc(sizeof(struct key_user), GFP_KERNEL);
  81                 if (unlikely(!candidate))
  82                         goto out;
  83 
  84                 /* the allocation may have scheduled, so we need to repeat the
  85                  * search lest someone else added the record whilst we were
  86                  * asleep */
  87                 goto try_again;
  88         }
  89 
  90         /* if we get here, then the user record still hadn't appeared on the
  91          * second pass - so we use the candidate record */
  92         refcount_set(&candidate->usage, 1);
  93         atomic_set(&candidate->nkeys, 0);
  94         atomic_set(&candidate->nikeys, 0);
  95         candidate->uid = uid;
  96         candidate->qnkeys = 0;
  97         candidate->qnbytes = 0;
  98         spin_lock_init(&candidate->lock);
  99         mutex_init(&candidate->cons_lock);
 100 
 101         rb_link_node(&candidate->node, parent, p);
 102         rb_insert_color(&candidate->node, &key_user_tree);
 103         spin_unlock(&key_user_lock);
 104         user = candidate;
 105         goto out;
 106 
 107         /* okay - we found a user record for this UID */
 108 found:
 109         refcount_inc(&user->usage);
 110         spin_unlock(&key_user_lock);
 111         kfree(candidate);
 112 out:
 113         return user;
 114 }
 115 
 116 /*
 117  * Dispose of a user structure
 118  */
 119 void key_user_put(struct key_user *user)
 120 {
 121         if (refcount_dec_and_lock(&user->usage, &key_user_lock)) {
 122                 rb_erase(&user->node, &key_user_tree);
 123                 spin_unlock(&key_user_lock);
 124 
 125                 kfree(user);
 126         }
 127 }
 128 
 129 /*
 130  * Allocate a serial number for a key.  These are assigned randomly to avoid
 131  * security issues through covert channel problems.
 132  */
 133 static inline void key_alloc_serial(struct key *key)
 134 {
 135         struct rb_node *parent, **p;
 136         struct key *xkey;
 137 
 138         /* propose a random serial number and look for a hole for it in the
 139          * serial number tree */
 140         do {
 141                 get_random_bytes(&key->serial, sizeof(key->serial));
 142 
 143                 key->serial >>= 1; /* negative numbers are not permitted */
 144         } while (key->serial < 3);
 145 
 146         spin_lock(&key_serial_lock);
 147 
 148 attempt_insertion:
 149         parent = NULL;
 150         p = &key_serial_tree.rb_node;
 151 
 152         while (*p) {
 153                 parent = *p;
 154                 xkey = rb_entry(parent, struct key, serial_node);
 155 
 156                 if (key->serial < xkey->serial)
 157                         p = &(*p)->rb_left;
 158                 else if (key->serial > xkey->serial)
 159                         p = &(*p)->rb_right;
 160                 else
 161                         goto serial_exists;
 162         }
 163 
 164         /* we've found a suitable hole - arrange for this key to occupy it */
 165         rb_link_node(&key->serial_node, parent, p);
 166         rb_insert_color(&key->serial_node, &key_serial_tree);
 167 
 168         spin_unlock(&key_serial_lock);
 169         return;
 170 
 171         /* we found a key with the proposed serial number - walk the tree from
 172          * that point looking for the next unused serial number */
 173 serial_exists:
 174         for (;;) {
 175                 key->serial++;
 176                 if (key->serial < 3) {
 177                         key->serial = 3;
 178                         goto attempt_insertion;
 179                 }
 180 
 181                 parent = rb_next(parent);
 182                 if (!parent)
 183                         goto attempt_insertion;
 184 
 185                 xkey = rb_entry(parent, struct key, serial_node);
 186                 if (key->serial < xkey->serial)
 187                         goto attempt_insertion;
 188         }
 189 }
 190 
 191 /**
 192  * key_alloc - Allocate a key of the specified type.
 193  * @type: The type of key to allocate.
 194  * @desc: The key description to allow the key to be searched out.
 195  * @uid: The owner of the new key.
 196  * @gid: The group ID for the new key's group permissions.
 197  * @cred: The credentials specifying UID namespace.
 198  * @perm: The permissions mask of the new key.
 199  * @flags: Flags specifying quota properties.
 200  * @restrict_link: Optional link restriction for new keyrings.
 201  *
 202  * Allocate a key of the specified type with the attributes given.  The key is
 203  * returned in an uninstantiated state and the caller needs to instantiate the
 204  * key before returning.
 205  *
 206  * The restrict_link structure (if not NULL) will be freed when the
 207  * keyring is destroyed, so it must be dynamically allocated.
 208  *
 209  * The user's key count quota is updated to reflect the creation of the key and
 210  * the user's key data quota has the default for the key type reserved.  The
 211  * instantiation function should amend this as necessary.  If insufficient
 212  * quota is available, -EDQUOT will be returned.
 213  *
 214  * The LSM security modules can prevent a key being created, in which case
 215  * -EACCES will be returned.
 216  *
 217  * Returns a pointer to the new key if successful and an error code otherwise.
 218  *
 219  * Note that the caller needs to ensure the key type isn't uninstantiated.
 220  * Internally this can be done by locking key_types_sem.  Externally, this can
 221  * be done by either never unregistering the key type, or making sure
 222  * key_alloc() calls don't race with module unloading.
 223  */
 224 struct key *key_alloc(struct key_type *type, const char *desc,
 225                       kuid_t uid, kgid_t gid, const struct cred *cred,
 226                       key_perm_t perm, unsigned long flags,
 227                       struct key_restriction *restrict_link)
 228 {
 229         struct key_user *user = NULL;
 230         struct key *key;
 231         size_t desclen, quotalen;
 232         int ret;
 233 
 234         key = ERR_PTR(-EINVAL);
 235         if (!desc || !*desc)
 236                 goto error;
 237 
 238         if (type->vet_description) {
 239                 ret = type->vet_description(desc);
 240                 if (ret < 0) {
 241                         key = ERR_PTR(ret);
 242                         goto error;
 243                 }
 244         }
 245 
 246         desclen = strlen(desc);
 247         quotalen = desclen + 1 + type->def_datalen;
 248 
 249         /* get hold of the key tracking for this user */
 250         user = key_user_lookup(uid);
 251         if (!user)
 252                 goto no_memory_1;
 253 
 254         /* check that the user's quota permits allocation of another key and
 255          * its description */
 256         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 257                 unsigned maxkeys = uid_eq(uid, GLOBAL_ROOT_UID) ?
 258                         key_quota_root_maxkeys : key_quota_maxkeys;
 259                 unsigned maxbytes = uid_eq(uid, GLOBAL_ROOT_UID) ?
 260                         key_quota_root_maxbytes : key_quota_maxbytes;
 261 
 262                 spin_lock(&user->lock);
 263                 if (!(flags & KEY_ALLOC_QUOTA_OVERRUN)) {
 264                         if (user->qnkeys + 1 > maxkeys ||
 265                             user->qnbytes + quotalen > maxbytes ||
 266                             user->qnbytes + quotalen < user->qnbytes)
 267                                 goto no_quota;
 268                 }
 269 
 270                 user->qnkeys++;
 271                 user->qnbytes += quotalen;
 272                 spin_unlock(&user->lock);
 273         }
 274 
 275         /* allocate and initialise the key and its description */
 276         key = kmem_cache_zalloc(key_jar, GFP_KERNEL);
 277         if (!key)
 278                 goto no_memory_2;
 279 
 280         key->index_key.desc_len = desclen;
 281         key->index_key.description = kmemdup(desc, desclen + 1, GFP_KERNEL);
 282         if (!key->index_key.description)
 283                 goto no_memory_3;
 284         key->index_key.type = type;
 285         key_set_index_key(&key->index_key);
 286 
 287         refcount_set(&key->usage, 1);
 288         init_rwsem(&key->sem);
 289         lockdep_set_class(&key->sem, &type->lock_class);
 290         key->user = user;
 291         key->quotalen = quotalen;
 292         key->datalen = type->def_datalen;
 293         key->uid = uid;
 294         key->gid = gid;
 295         key->perm = perm;
 296         key->restrict_link = restrict_link;
 297         key->last_used_at = ktime_get_real_seconds();
 298 
 299         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA))
 300                 key->flags |= 1 << KEY_FLAG_IN_QUOTA;
 301         if (flags & KEY_ALLOC_BUILT_IN)
 302                 key->flags |= 1 << KEY_FLAG_BUILTIN;
 303         if (flags & KEY_ALLOC_UID_KEYRING)
 304                 key->flags |= 1 << KEY_FLAG_UID_KEYRING;
 305 
 306 #ifdef KEY_DEBUGGING
 307         key->magic = KEY_DEBUG_MAGIC;
 308 #endif
 309 
 310         /* let the security module know about the key */
 311         ret = security_key_alloc(key, cred, flags);
 312         if (ret < 0)
 313                 goto security_error;
 314 
 315         /* publish the key by giving it a serial number */
 316         refcount_inc(&key->domain_tag->usage);
 317         atomic_inc(&user->nkeys);
 318         key_alloc_serial(key);
 319 
 320 error:
 321         return key;
 322 
 323 security_error:
 324         kfree(key->description);
 325         kmem_cache_free(key_jar, key);
 326         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 327                 spin_lock(&user->lock);
 328                 user->qnkeys--;
 329                 user->qnbytes -= quotalen;
 330                 spin_unlock(&user->lock);
 331         }
 332         key_user_put(user);
 333         key = ERR_PTR(ret);
 334         goto error;
 335 
 336 no_memory_3:
 337         kmem_cache_free(key_jar, key);
 338 no_memory_2:
 339         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 340                 spin_lock(&user->lock);
 341                 user->qnkeys--;
 342                 user->qnbytes -= quotalen;
 343                 spin_unlock(&user->lock);
 344         }
 345         key_user_put(user);
 346 no_memory_1:
 347         key = ERR_PTR(-ENOMEM);
 348         goto error;
 349 
 350 no_quota:
 351         spin_unlock(&user->lock);
 352         key_user_put(user);
 353         key = ERR_PTR(-EDQUOT);
 354         goto error;
 355 }
 356 EXPORT_SYMBOL(key_alloc);
 357 
 358 /**
 359  * key_payload_reserve - Adjust data quota reservation for the key's payload
 360  * @key: The key to make the reservation for.
 361  * @datalen: The amount of data payload the caller now wants.
 362  *
 363  * Adjust the amount of the owning user's key data quota that a key reserves.
 364  * If the amount is increased, then -EDQUOT may be returned if there isn't
 365  * enough free quota available.
 366  *
 367  * If successful, 0 is returned.
 368  */
 369 int key_payload_reserve(struct key *key, size_t datalen)
 370 {
 371         int delta = (int)datalen - key->datalen;
 372         int ret = 0;
 373 
 374         key_check(key);
 375 
 376         /* contemplate the quota adjustment */
 377         if (delta != 0 && test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
 378                 unsigned maxbytes = uid_eq(key->user->uid, GLOBAL_ROOT_UID) ?
 379                         key_quota_root_maxbytes : key_quota_maxbytes;
 380 
 381                 spin_lock(&key->user->lock);
 382 
 383                 if (delta > 0 &&
 384                     (key->user->qnbytes + delta > maxbytes ||
 385                      key->user->qnbytes + delta < key->user->qnbytes)) {
 386                         ret = -EDQUOT;
 387                 }
 388                 else {
 389                         key->user->qnbytes += delta;
 390                         key->quotalen += delta;
 391                 }
 392                 spin_unlock(&key->user->lock);
 393         }
 394 
 395         /* change the recorded data length if that didn't generate an error */
 396         if (ret == 0)
 397                 key->datalen = datalen;
 398 
 399         return ret;
 400 }
 401 EXPORT_SYMBOL(key_payload_reserve);
 402 
 403 /*
 404  * Change the key state to being instantiated.
 405  */
 406 static void mark_key_instantiated(struct key *key, int reject_error)
 407 {
 408         /* Commit the payload before setting the state; barrier versus
 409          * key_read_state().
 410          */
 411         smp_store_release(&key->state,
 412                           (reject_error < 0) ? reject_error : KEY_IS_POSITIVE);
 413 }
 414 
 415 /*
 416  * Instantiate a key and link it into the target keyring atomically.  Must be
 417  * called with the target keyring's semaphore writelocked.  The target key's
 418  * semaphore need not be locked as instantiation is serialised by
 419  * key_construction_mutex.
 420  */
 421 static int __key_instantiate_and_link(struct key *key,
 422                                       struct key_preparsed_payload *prep,
 423                                       struct key *keyring,
 424                                       struct key *authkey,
 425                                       struct assoc_array_edit **_edit)
 426 {
 427         int ret, awaken;
 428 
 429         key_check(key);
 430         key_check(keyring);
 431 
 432         awaken = 0;
 433         ret = -EBUSY;
 434 
 435         mutex_lock(&key_construction_mutex);
 436 
 437         /* can't instantiate twice */
 438         if (key->state == KEY_IS_UNINSTANTIATED) {
 439                 /* instantiate the key */
 440                 ret = key->type->instantiate(key, prep);
 441 
 442                 if (ret == 0) {
 443                         /* mark the key as being instantiated */
 444                         atomic_inc(&key->user->nikeys);
 445                         mark_key_instantiated(key, 0);
 446 
 447                         if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
 448                                 awaken = 1;
 449 
 450                         /* and link it into the destination keyring */
 451                         if (keyring) {
 452                                 if (test_bit(KEY_FLAG_KEEP, &keyring->flags))
 453                                         set_bit(KEY_FLAG_KEEP, &key->flags);
 454 
 455                                 __key_link(key, _edit);
 456                         }
 457 
 458                         /* disable the authorisation key */
 459                         if (authkey)
 460                                 key_invalidate(authkey);
 461 
 462                         if (prep->expiry != TIME64_MAX) {
 463                                 key->expiry = prep->expiry;
 464                                 key_schedule_gc(prep->expiry + key_gc_delay);
 465                         }
 466                 }
 467         }
 468 
 469         mutex_unlock(&key_construction_mutex);
 470 
 471         /* wake up anyone waiting for a key to be constructed */
 472         if (awaken)
 473                 wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
 474 
 475         return ret;
 476 }
 477 
 478 /**
 479  * key_instantiate_and_link - Instantiate a key and link it into the keyring.
 480  * @key: The key to instantiate.
 481  * @data: The data to use to instantiate the keyring.
 482  * @datalen: The length of @data.
 483  * @keyring: Keyring to create a link in on success (or NULL).
 484  * @authkey: The authorisation token permitting instantiation.
 485  *
 486  * Instantiate a key that's in the uninstantiated state using the provided data
 487  * and, if successful, link it in to the destination keyring if one is
 488  * supplied.
 489  *
 490  * If successful, 0 is returned, the authorisation token is revoked and anyone
 491  * waiting for the key is woken up.  If the key was already instantiated,
 492  * -EBUSY will be returned.
 493  */
 494 int key_instantiate_and_link(struct key *key,
 495                              const void *data,
 496                              size_t datalen,
 497                              struct key *keyring,
 498                              struct key *authkey)
 499 {
 500         struct key_preparsed_payload prep;
 501         struct assoc_array_edit *edit = NULL;
 502         int ret;
 503 
 504         memset(&prep, 0, sizeof(prep));
 505         prep.data = data;
 506         prep.datalen = datalen;
 507         prep.quotalen = key->type->def_datalen;
 508         prep.expiry = TIME64_MAX;
 509         if (key->type->preparse) {
 510                 ret = key->type->preparse(&prep);
 511                 if (ret < 0)
 512                         goto error;
 513         }
 514 
 515         if (keyring) {
 516                 ret = __key_link_lock(keyring, &key->index_key);
 517                 if (ret < 0)
 518                         goto error;
 519 
 520                 ret = __key_link_begin(keyring, &key->index_key, &edit);
 521                 if (ret < 0)
 522                         goto error_link_end;
 523 
 524                 if (keyring->restrict_link && keyring->restrict_link->check) {
 525                         struct key_restriction *keyres = keyring->restrict_link;
 526 
 527                         ret = keyres->check(keyring, key->type, &prep.payload,
 528                                             keyres->key);
 529                         if (ret < 0)
 530                                 goto error_link_end;
 531                 }
 532         }
 533 
 534         ret = __key_instantiate_and_link(key, &prep, keyring, authkey, &edit);
 535 
 536 error_link_end:
 537         if (keyring)
 538                 __key_link_end(keyring, &key->index_key, edit);
 539 
 540 error:
 541         if (key->type->preparse)
 542                 key->type->free_preparse(&prep);
 543         return ret;
 544 }
 545 
 546 EXPORT_SYMBOL(key_instantiate_and_link);
 547 
 548 /**
 549  * key_reject_and_link - Negatively instantiate a key and link it into the keyring.
 550  * @key: The key to instantiate.
 551  * @timeout: The timeout on the negative key.
 552  * @error: The error to return when the key is hit.
 553  * @keyring: Keyring to create a link in on success (or NULL).
 554  * @authkey: The authorisation token permitting instantiation.
 555  *
 556  * Negatively instantiate a key that's in the uninstantiated state and, if
 557  * successful, set its timeout and stored error and link it in to the
 558  * destination keyring if one is supplied.  The key and any links to the key
 559  * will be automatically garbage collected after the timeout expires.
 560  *
 561  * Negative keys are used to rate limit repeated request_key() calls by causing
 562  * them to return the stored error code (typically ENOKEY) until the negative
 563  * key expires.
 564  *
 565  * If successful, 0 is returned, the authorisation token is revoked and anyone
 566  * waiting for the key is woken up.  If the key was already instantiated,
 567  * -EBUSY will be returned.
 568  */
 569 int key_reject_and_link(struct key *key,
 570                         unsigned timeout,
 571                         unsigned error,
 572                         struct key *keyring,
 573                         struct key *authkey)
 574 {
 575         struct assoc_array_edit *edit = NULL;
 576         int ret, awaken, link_ret = 0;
 577 
 578         key_check(key);
 579         key_check(keyring);
 580 
 581         awaken = 0;
 582         ret = -EBUSY;
 583 
 584         if (keyring) {
 585                 if (keyring->restrict_link)
 586                         return -EPERM;
 587 
 588                 link_ret = __key_link_lock(keyring, &key->index_key);
 589                 if (link_ret == 0) {
 590                         link_ret = __key_link_begin(keyring, &key->index_key, &edit);
 591                         if (link_ret < 0)
 592                                 __key_link_end(keyring, &key->index_key, edit);
 593                 }
 594         }
 595 
 596         mutex_lock(&key_construction_mutex);
 597 
 598         /* can't instantiate twice */
 599         if (key->state == KEY_IS_UNINSTANTIATED) {
 600                 /* mark the key as being negatively instantiated */
 601                 atomic_inc(&key->user->nikeys);
 602                 mark_key_instantiated(key, -error);
 603                 key->expiry = ktime_get_real_seconds() + timeout;
 604                 key_schedule_gc(key->expiry + key_gc_delay);
 605 
 606                 if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
 607                         awaken = 1;
 608 
 609                 ret = 0;
 610 
 611                 /* and link it into the destination keyring */
 612                 if (keyring && link_ret == 0)
 613                         __key_link(key, &edit);
 614 
 615                 /* disable the authorisation key */
 616                 if (authkey)
 617                         key_invalidate(authkey);
 618         }
 619 
 620         mutex_unlock(&key_construction_mutex);
 621 
 622         if (keyring && link_ret == 0)
 623                 __key_link_end(keyring, &key->index_key, edit);
 624 
 625         /* wake up anyone waiting for a key to be constructed */
 626         if (awaken)
 627                 wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
 628 
 629         return ret == 0 ? link_ret : ret;
 630 }
 631 EXPORT_SYMBOL(key_reject_and_link);
 632 
 633 /**
 634  * key_put - Discard a reference to a key.
 635  * @key: The key to discard a reference from.
 636  *
 637  * Discard a reference to a key, and when all the references are gone, we
 638  * schedule the cleanup task to come and pull it out of the tree in process
 639  * context at some later time.
 640  */
 641 void key_put(struct key *key)
 642 {
 643         if (key) {
 644                 key_check(key);
 645 
 646                 if (refcount_dec_and_test(&key->usage))
 647                         schedule_work(&key_gc_work);
 648         }
 649 }
 650 EXPORT_SYMBOL(key_put);
 651 
 652 /*
 653  * Find a key by its serial number.
 654  */
 655 struct key *key_lookup(key_serial_t id)
 656 {
 657         struct rb_node *n;
 658         struct key *key;
 659 
 660         spin_lock(&key_serial_lock);
 661 
 662         /* search the tree for the specified key */
 663         n = key_serial_tree.rb_node;
 664         while (n) {
 665                 key = rb_entry(n, struct key, serial_node);
 666 
 667                 if (id < key->serial)
 668                         n = n->rb_left;
 669                 else if (id > key->serial)
 670                         n = n->rb_right;
 671                 else
 672                         goto found;
 673         }
 674 
 675 not_found:
 676         key = ERR_PTR(-ENOKEY);
 677         goto error;
 678 
 679 found:
 680         /* A key is allowed to be looked up only if someone still owns a
 681          * reference to it - otherwise it's awaiting the gc.
 682          */
 683         if (!refcount_inc_not_zero(&key->usage))
 684                 goto not_found;
 685 
 686 error:
 687         spin_unlock(&key_serial_lock);
 688         return key;
 689 }
 690 
 691 /*
 692  * Find and lock the specified key type against removal.
 693  *
 694  * We return with the sem read-locked if successful.  If the type wasn't
 695  * available -ENOKEY is returned instead.
 696  */
 697 struct key_type *key_type_lookup(const char *type)
 698 {
 699         struct key_type *ktype;
 700 
 701         down_read(&key_types_sem);
 702 
 703         /* look up the key type to see if it's one of the registered kernel
 704          * types */
 705         list_for_each_entry(ktype, &key_types_list, link) {
 706                 if (strcmp(ktype->name, type) == 0)
 707                         goto found_kernel_type;
 708         }
 709 
 710         up_read(&key_types_sem);
 711         ktype = ERR_PTR(-ENOKEY);
 712 
 713 found_kernel_type:
 714         return ktype;
 715 }
 716 
 717 void key_set_timeout(struct key *key, unsigned timeout)
 718 {
 719         time64_t expiry = 0;
 720 
 721         /* make the changes with the locks held to prevent races */
 722         down_write(&key->sem);
 723 
 724         if (timeout > 0)
 725                 expiry = ktime_get_real_seconds() + timeout;
 726 
 727         key->expiry = expiry;
 728         key_schedule_gc(key->expiry + key_gc_delay);
 729 
 730         up_write(&key->sem);
 731 }
 732 EXPORT_SYMBOL_GPL(key_set_timeout);
 733 
 734 /*
 735  * Unlock a key type locked by key_type_lookup().
 736  */
 737 void key_type_put(struct key_type *ktype)
 738 {
 739         up_read(&key_types_sem);
 740 }
 741 
 742 /*
 743  * Attempt to update an existing key.
 744  *
 745  * The key is given to us with an incremented refcount that we need to discard
 746  * if we get an error.
 747  */
 748 static inline key_ref_t __key_update(key_ref_t key_ref,
 749                                      struct key_preparsed_payload *prep)
 750 {
 751         struct key *key = key_ref_to_ptr(key_ref);
 752         int ret;
 753 
 754         /* need write permission on the key to update it */
 755         ret = key_permission(key_ref, KEY_NEED_WRITE);
 756         if (ret < 0)
 757                 goto error;
 758 
 759         ret = -EEXIST;
 760         if (!key->type->update)
 761                 goto error;
 762 
 763         down_write(&key->sem);
 764 
 765         ret = key->type->update(key, prep);
 766         if (ret == 0)
 767                 /* Updating a negative key positively instantiates it */
 768                 mark_key_instantiated(key, 0);
 769 
 770         up_write(&key->sem);
 771 
 772         if (ret < 0)
 773                 goto error;
 774 out:
 775         return key_ref;
 776 
 777 error:
 778         key_put(key);
 779         key_ref = ERR_PTR(ret);
 780         goto out;
 781 }
 782 
 783 /**
 784  * key_create_or_update - Update or create and instantiate a key.
 785  * @keyring_ref: A pointer to the destination keyring with possession flag.
 786  * @type: The type of key.
 787  * @description: The searchable description for the key.
 788  * @payload: The data to use to instantiate or update the key.
 789  * @plen: The length of @payload.
 790  * @perm: The permissions mask for a new key.
 791  * @flags: The quota flags for a new key.
 792  *
 793  * Search the destination keyring for a key of the same description and if one
 794  * is found, update it, otherwise create and instantiate a new one and create a
 795  * link to it from that keyring.
 796  *
 797  * If perm is KEY_PERM_UNDEF then an appropriate key permissions mask will be
 798  * concocted.
 799  *
 800  * Returns a pointer to the new key if successful, -ENODEV if the key type
 801  * wasn't available, -ENOTDIR if the keyring wasn't a keyring, -EACCES if the
 802  * caller isn't permitted to modify the keyring or the LSM did not permit
 803  * creation of the key.
 804  *
 805  * On success, the possession flag from the keyring ref will be tacked on to
 806  * the key ref before it is returned.
 807  */
 808 key_ref_t key_create_or_update(key_ref_t keyring_ref,
 809                                const char *type,
 810                                const char *description,
 811                                const void *payload,
 812                                size_t plen,
 813                                key_perm_t perm,
 814                                unsigned long flags)
 815 {
 816         struct keyring_index_key index_key = {
 817                 .description    = description,
 818         };
 819         struct key_preparsed_payload prep;
 820         struct assoc_array_edit *edit = NULL;
 821         const struct cred *cred = current_cred();
 822         struct key *keyring, *key = NULL;
 823         key_ref_t key_ref;
 824         int ret;
 825         struct key_restriction *restrict_link = NULL;
 826 
 827         /* look up the key type to see if it's one of the registered kernel
 828          * types */
 829         index_key.type = key_type_lookup(type);
 830         if (IS_ERR(index_key.type)) {
 831                 key_ref = ERR_PTR(-ENODEV);
 832                 goto error;
 833         }
 834 
 835         key_ref = ERR_PTR(-EINVAL);
 836         if (!index_key.type->instantiate ||
 837             (!index_key.description && !index_key.type->preparse))
 838                 goto error_put_type;
 839 
 840         keyring = key_ref_to_ptr(keyring_ref);
 841 
 842         key_check(keyring);
 843 
 844         if (!(flags & KEY_ALLOC_BYPASS_RESTRICTION))
 845                 restrict_link = keyring->restrict_link;
 846 
 847         key_ref = ERR_PTR(-ENOTDIR);
 848         if (keyring->type != &key_type_keyring)
 849                 goto error_put_type;
 850 
 851         memset(&prep, 0, sizeof(prep));
 852         prep.data = payload;
 853         prep.datalen = plen;
 854         prep.quotalen = index_key.type->def_datalen;
 855         prep.expiry = TIME64_MAX;
 856         if (index_key.type->preparse) {
 857                 ret = index_key.type->preparse(&prep);
 858                 if (ret < 0) {
 859                         key_ref = ERR_PTR(ret);
 860                         goto error_free_prep;
 861                 }
 862                 if (!index_key.description)
 863                         index_key.description = prep.description;
 864                 key_ref = ERR_PTR(-EINVAL);
 865                 if (!index_key.description)
 866                         goto error_free_prep;
 867         }
 868         index_key.desc_len = strlen(index_key.description);
 869         key_set_index_key(&index_key);
 870 
 871         ret = __key_link_lock(keyring, &index_key);
 872         if (ret < 0) {
 873                 key_ref = ERR_PTR(ret);
 874                 goto error_free_prep;
 875         }
 876 
 877         ret = __key_link_begin(keyring, &index_key, &edit);
 878         if (ret < 0) {
 879                 key_ref = ERR_PTR(ret);
 880                 goto error_link_end;
 881         }
 882 
 883         if (restrict_link && restrict_link->check) {
 884                 ret = restrict_link->check(keyring, index_key.type,
 885                                            &prep.payload, restrict_link->key);
 886                 if (ret < 0) {
 887                         key_ref = ERR_PTR(ret);
 888                         goto error_link_end;
 889                 }
 890         }
 891 
 892         /* if we're going to allocate a new key, we're going to have
 893          * to modify the keyring */
 894         ret = key_permission(keyring_ref, KEY_NEED_WRITE);
 895         if (ret < 0) {
 896                 key_ref = ERR_PTR(ret);
 897                 goto error_link_end;
 898         }
 899 
 900         /* if it's possible to update this type of key, search for an existing
 901          * key of the same type and description in the destination keyring and
 902          * update that instead if possible
 903          */
 904         if (index_key.type->update) {
 905                 key_ref = find_key_to_update(keyring_ref, &index_key);
 906                 if (key_ref)
 907                         goto found_matching_key;
 908         }
 909 
 910         /* if the client doesn't provide, decide on the permissions we want */
 911         if (perm == KEY_PERM_UNDEF) {
 912                 perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
 913                 perm |= KEY_USR_VIEW;
 914 
 915                 if (index_key.type->read)
 916                         perm |= KEY_POS_READ;
 917 
 918                 if (index_key.type == &key_type_keyring ||
 919                     index_key.type->update)
 920                         perm |= KEY_POS_WRITE;
 921         }
 922 
 923         /* allocate a new key */
 924         key = key_alloc(index_key.type, index_key.description,
 925                         cred->fsuid, cred->fsgid, cred, perm, flags, NULL);
 926         if (IS_ERR(key)) {
 927                 key_ref = ERR_CAST(key);
 928                 goto error_link_end;
 929         }
 930 
 931         /* instantiate it and link it into the target keyring */
 932         ret = __key_instantiate_and_link(key, &prep, keyring, NULL, &edit);
 933         if (ret < 0) {
 934                 key_put(key);
 935                 key_ref = ERR_PTR(ret);
 936                 goto error_link_end;
 937         }
 938 
 939         key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
 940 
 941 error_link_end:
 942         __key_link_end(keyring, &index_key, edit);
 943 error_free_prep:
 944         if (index_key.type->preparse)
 945                 index_key.type->free_preparse(&prep);
 946 error_put_type:
 947         key_type_put(index_key.type);
 948 error:
 949         return key_ref;
 950 
 951  found_matching_key:
 952         /* we found a matching key, so we're going to try to update it
 953          * - we can drop the locks first as we have the key pinned
 954          */
 955         __key_link_end(keyring, &index_key, edit);
 956 
 957         key = key_ref_to_ptr(key_ref);
 958         if (test_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags)) {
 959                 ret = wait_for_key_construction(key, true);
 960                 if (ret < 0) {
 961                         key_ref_put(key_ref);
 962                         key_ref = ERR_PTR(ret);
 963                         goto error_free_prep;
 964                 }
 965         }
 966 
 967         key_ref = __key_update(key_ref, &prep);
 968         goto error_free_prep;
 969 }
 970 EXPORT_SYMBOL(key_create_or_update);
 971 
 972 /**
 973  * key_update - Update a key's contents.
 974  * @key_ref: The pointer (plus possession flag) to the key.
 975  * @payload: The data to be used to update the key.
 976  * @plen: The length of @payload.
 977  *
 978  * Attempt to update the contents of a key with the given payload data.  The
 979  * caller must be granted Write permission on the key.  Negative keys can be
 980  * instantiated by this method.
 981  *
 982  * Returns 0 on success, -EACCES if not permitted and -EOPNOTSUPP if the key
 983  * type does not support updating.  The key type may return other errors.
 984  */
 985 int key_update(key_ref_t key_ref, const void *payload, size_t plen)
 986 {
 987         struct key_preparsed_payload prep;
 988         struct key *key = key_ref_to_ptr(key_ref);
 989         int ret;
 990 
 991         key_check(key);
 992 
 993         /* the key must be writable */
 994         ret = key_permission(key_ref, KEY_NEED_WRITE);
 995         if (ret < 0)
 996                 return ret;
 997 
 998         /* attempt to update it if supported */
 999         if (!key->type->update)
1000                 return -EOPNOTSUPP;
1001 
1002         memset(&prep, 0, sizeof(prep));
1003         prep.data = payload;
1004         prep.datalen = plen;
1005         prep.quotalen = key->type->def_datalen;
1006         prep.expiry = TIME64_MAX;
1007         if (key->type->preparse) {
1008                 ret = key->type->preparse(&prep);
1009                 if (ret < 0)
1010                         goto error;
1011         }
1012 
1013         down_write(&key->sem);
1014 
1015         ret = key->type->update(key, &prep);
1016         if (ret == 0)
1017                 /* Updating a negative key positively instantiates it */
1018                 mark_key_instantiated(key, 0);
1019 
1020         up_write(&key->sem);
1021 
1022 error:
1023         if (key->type->preparse)
1024                 key->type->free_preparse(&prep);
1025         return ret;
1026 }
1027 EXPORT_SYMBOL(key_update);
1028 
1029 /**
1030  * key_revoke - Revoke a key.
1031  * @key: The key to be revoked.
1032  *
1033  * Mark a key as being revoked and ask the type to free up its resources.  The
1034  * revocation timeout is set and the key and all its links will be
1035  * automatically garbage collected after key_gc_delay amount of time if they
1036  * are not manually dealt with first.
1037  */
1038 void key_revoke(struct key *key)
1039 {
1040         time64_t time;
1041 
1042         key_check(key);
1043 
1044         /* make sure no one's trying to change or use the key when we mark it
1045          * - we tell lockdep that we might nest because we might be revoking an
1046          *   authorisation key whilst holding the sem on a key we've just
1047          *   instantiated
1048          */
1049         down_write_nested(&key->sem, 1);
1050         if (!test_and_set_bit(KEY_FLAG_REVOKED, &key->flags) &&
1051             key->type->revoke)
1052                 key->type->revoke(key);
1053 
1054         /* set the death time to no more than the expiry time */
1055         time = ktime_get_real_seconds();
1056         if (key->revoked_at == 0 || key->revoked_at > time) {
1057                 key->revoked_at = time;
1058                 key_schedule_gc(key->revoked_at + key_gc_delay);
1059         }
1060 
1061         up_write(&key->sem);
1062 }
1063 EXPORT_SYMBOL(key_revoke);
1064 
1065 /**
1066  * key_invalidate - Invalidate a key.
1067  * @key: The key to be invalidated.
1068  *
1069  * Mark a key as being invalidated and have it cleaned up immediately.  The key
1070  * is ignored by all searches and other operations from this point.
1071  */
1072 void key_invalidate(struct key *key)
1073 {
1074         kenter("%d", key_serial(key));
1075 
1076         key_check(key);
1077 
1078         if (!test_bit(KEY_FLAG_INVALIDATED, &key->flags)) {
1079                 down_write_nested(&key->sem, 1);
1080                 if (!test_and_set_bit(KEY_FLAG_INVALIDATED, &key->flags))
1081                         key_schedule_gc_links();
1082                 up_write(&key->sem);
1083         }
1084 }
1085 EXPORT_SYMBOL(key_invalidate);
1086 
1087 /**
1088  * generic_key_instantiate - Simple instantiation of a key from preparsed data
1089  * @key: The key to be instantiated
1090  * @prep: The preparsed data to load.
1091  *
1092  * Instantiate a key from preparsed data.  We assume we can just copy the data
1093  * in directly and clear the old pointers.
1094  *
1095  * This can be pointed to directly by the key type instantiate op pointer.
1096  */
1097 int generic_key_instantiate(struct key *key, struct key_preparsed_payload *prep)
1098 {
1099         int ret;
1100 
1101         pr_devel("==>%s()\n", __func__);
1102 
1103         ret = key_payload_reserve(key, prep->quotalen);
1104         if (ret == 0) {
1105                 rcu_assign_keypointer(key, prep->payload.data[0]);
1106                 key->payload.data[1] = prep->payload.data[1];
1107                 key->payload.data[2] = prep->payload.data[2];
1108                 key->payload.data[3] = prep->payload.data[3];
1109                 prep->payload.data[0] = NULL;
1110                 prep->payload.data[1] = NULL;
1111                 prep->payload.data[2] = NULL;
1112                 prep->payload.data[3] = NULL;
1113         }
1114         pr_devel("<==%s() = %d\n", __func__, ret);
1115         return ret;
1116 }
1117 EXPORT_SYMBOL(generic_key_instantiate);
1118 
1119 /**
1120  * register_key_type - Register a type of key.
1121  * @ktype: The new key type.
1122  *
1123  * Register a new key type.
1124  *
1125  * Returns 0 on success or -EEXIST if a type of this name already exists.
1126  */
1127 int register_key_type(struct key_type *ktype)
1128 {
1129         struct key_type *p;
1130         int ret;
1131 
1132         memset(&ktype->lock_class, 0, sizeof(ktype->lock_class));
1133 
1134         ret = -EEXIST;
1135         down_write(&key_types_sem);
1136 
1137         /* disallow key types with the same name */
1138         list_for_each_entry(p, &key_types_list, link) {
1139                 if (strcmp(p->name, ktype->name) == 0)
1140                         goto out;
1141         }
1142 
1143         /* store the type */
1144         list_add(&ktype->link, &key_types_list);
1145 
1146         pr_notice("Key type %s registered\n", ktype->name);
1147         ret = 0;
1148 
1149 out:
1150         up_write(&key_types_sem);
1151         return ret;
1152 }
1153 EXPORT_SYMBOL(register_key_type);
1154 
1155 /**
1156  * unregister_key_type - Unregister a type of key.
1157  * @ktype: The key type.
1158  *
1159  * Unregister a key type and mark all the extant keys of this type as dead.
1160  * Those keys of this type are then destroyed to get rid of their payloads and
1161  * they and their links will be garbage collected as soon as possible.
1162  */
1163 void unregister_key_type(struct key_type *ktype)
1164 {
1165         down_write(&key_types_sem);
1166         list_del_init(&ktype->link);
1167         downgrade_write(&key_types_sem);
1168         key_gc_keytype(ktype);
1169         pr_notice("Key type %s unregistered\n", ktype->name);
1170         up_read(&key_types_sem);
1171 }
1172 EXPORT_SYMBOL(unregister_key_type);
1173 
1174 /*
1175  * Initialise the key management state.
1176  */
1177 void __init key_init(void)
1178 {
1179         /* allocate a slab in which we can store keys */
1180         key_jar = kmem_cache_create("key_jar", sizeof(struct key),
1181                         0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1182 
1183         /* add the special key types */
1184         list_add_tail(&key_type_keyring.link, &key_types_list);
1185         list_add_tail(&key_type_dead.link, &key_types_list);
1186         list_add_tail(&key_type_user.link, &key_types_list);
1187         list_add_tail(&key_type_logon.link, &key_types_list);
1188 
1189         /* record the root user tracking */
1190         rb_link_node(&root_key_user.node,
1191                      NULL,
1192                      &key_user_tree.rb_node);
1193 
1194         rb_insert_color(&root_key_user.node,
1195                         &key_user_tree);
1196 }