security/keys/key.c

   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 static 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 static LIST_HEAD(key_types_list);
  31 static DECLARE_RWSEM(key_types_sem);
  32
  33 static void key_cleanup(struct work_struct *work);
  34 static DECLARE_WORK(key_cleanup_task, key_cleanup);
  35
  36 /* we serialise key instantiation and link */
  37 DEFINE_MUTEX(key_construction_mutex);
  38
  39 /* any key who's type gets unegistered will be re-typed to this */
  40 static struct key_type key_type_dead = {
  41         .name           = "dead",
  42 };
  43
  44 #ifdef KEY_DEBUGGING
  45 void __key_check(const struct key *key)
  46 {
  47         printk("__key_check: key %p {%08x} should be {%08x}\n",
  48                key, key->magic, KEY_DEBUG_MAGIC);
  49         BUG();
  50 }
  51 #endif
  52
  53 /*****************************************************************************/
  54 /*
  55  * get the key quota record for a user, allocating a new record if one doesn't
  56  * already exist
  57  */
  58 struct key_user *key_user_lookup(uid_t uid)
  59 {
  60         struct key_user *candidate = NULL, *user;
  61         struct rb_node *parent = NULL;
  62         struct rb_node **p;
  63
  64  try_again:
  65         p = &key_user_tree.rb_node;
  66         spin_lock(&key_user_lock);
  67
  68         /* search the tree for a user record with a matching UID */
  69         while (*p) {
  70                 parent = *p;
  71                 user = rb_entry(parent, struct key_user, node);
  72
  73                 if (uid < user->uid)
  74                         p = &(*p)->rb_left;
  75                 else if (uid > user->uid)
  76                         p = &(*p)->rb_right;
  77                 else
  78                         goto found;
  79         }
  80
  81         /* if we get here, we failed to find a match in the tree */
  82         if (!candidate) {
  83                 /* allocate a candidate user record if we don't already have
  84                  * one */
  85                 spin_unlock(&key_user_lock);
  86
  87                 user = NULL;
  88                 candidate = kmalloc(sizeof(struct key_user), GFP_KERNEL);
  89                 if (unlikely(!candidate))
  90                         goto out;
  91
  92                 /* the allocation may have scheduled, so we need to repeat the
  93                  * search lest someone else added the record whilst we were
  94                  * asleep */
  95                 goto try_again;
  96         }
  97
  98         /* if we get here, then the user record still hadn't appeared on the
  99          * second pass - so we use the candidate record */
 100         atomic_set(&candidate->usage, 1);
 101         atomic_set(&candidate->nkeys, 0);
 102         atomic_set(&candidate->nikeys, 0);
 103         candidate->uid = uid;
 104         candidate->qnkeys = 0;
 105         candidate->qnbytes = 0;
 106         spin_lock_init(&candidate->lock);
 107         mutex_init(&candidate->cons_lock);
 108
 109         rb_link_node(&candidate->node, parent, p);
 110         rb_insert_color(&candidate->node, &key_user_tree);
 111         spin_unlock(&key_user_lock);
 112         user = candidate;
 113         goto out;
 114
 115         /* okay - we found a user record for this UID */
 116  found:
 117         atomic_inc(&user->usage);
 118         spin_unlock(&key_user_lock);
 119         kfree(candidate);
 120  out:
 121         return user;
 122
 123 } /* end key_user_lookup() */
 124
 125 /*****************************************************************************/
 126 /*
 127  * dispose of a user structure
 128  */
 129 void key_user_put(struct key_user *user)
 130 {
 131         if (atomic_dec_and_lock(&user->usage, &key_user_lock)) {
 132                 rb_erase(&user->node, &key_user_tree);
 133                 spin_unlock(&key_user_lock);
 134
 135                 kfree(user);
 136         }
 137
 138 } /* end key_user_put() */
 139
 140 /*****************************************************************************/
 141 /*
 142  * assign a key the next unique serial number
 143  * - these are assigned randomly to avoid security issues through covert
 144  *   channel problems
 145  */
 146 static inline void key_alloc_serial(struct key *key)
 147 {
 148         struct rb_node *parent, **p;
 149         struct key *xkey;
 150
 151         /* propose a random serial number and look for a hole for it in the
 152          * serial number tree */
 153         do {
 154                 get_random_bytes(&key->serial, sizeof(key->serial));
 155
 156                 key->serial >>= 1; /* negative numbers are not permitted */
 157         } while (key->serial < 3);
 158
 159         spin_lock(&key_serial_lock);
 160
 161 attempt_insertion:
 162         parent = NULL;
 163         p = &key_serial_tree.rb_node;
 164
 165         while (*p) {
 166                 parent = *p;
 167                 xkey = rb_entry(parent, struct key, serial_node);
 168
 169                 if (key->serial < xkey->serial)
 170                         p = &(*p)->rb_left;
 171                 else if (key->serial > xkey->serial)
 172                         p = &(*p)->rb_right;
 173                 else
 174                         goto serial_exists;
 175         }
 176
 177         /* we've found a suitable hole - arrange for this key to occupy it */
 178         rb_link_node(&key->serial_node, parent, p);
 179         rb_insert_color(&key->serial_node, &key_serial_tree);
 180
 181         spin_unlock(&key_serial_lock);
 182         return;
 183
 184         /* we found a key with the proposed serial number - walk the tree from
 185          * that point looking for the next unused serial number */
 186 serial_exists:
 187         for (;;) {
 188                 key->serial++;
 189                 if (key->serial < 3) {
 190                         key->serial = 3;
 191                         goto attempt_insertion;
 192                 }
 193
 194                 parent = rb_next(parent);
 195                 if (!parent)
 196                         goto attempt_insertion;
 197
 198                 xkey = rb_entry(parent, struct key, serial_node);
 199                 if (key->serial < xkey->serial)
 200                         goto attempt_insertion;
 201         }
 202
 203 } /* end key_alloc_serial() */
 204
 205 /*****************************************************************************/
 206 /*
 207  * allocate a key of the specified type
 208  * - update the user's quota to reflect the existence of the key
 209  * - called from a key-type operation with key_types_sem read-locked by
 210  *   key_create_or_update()
 211  *   - this prevents unregistration of the key type
 212  * - upon return the key is as yet uninstantiated; the caller needs to either
 213  *   instantiate the key or discard it before returning
 214  */
 215 struct key *key_alloc(struct key_type *type, const char *desc,
 216                       uid_t uid, gid_t gid, struct task_struct *ctx,
 217                       key_perm_t perm, unsigned long flags)
 218 {
 219         struct key_user *user = NULL;
 220         struct key *key;
 221         size_t desclen, quotalen;
 222         int ret;
 223
 224         key = ERR_PTR(-EINVAL);
 225         if (!desc || !*desc)
 226                 goto error;
 227
 228         desclen = strlen(desc) + 1;
 229         quotalen = desclen + type->def_datalen;
 230
 231         /* get hold of the key tracking for this user */
 232         user = key_user_lookup(uid);
 233         if (!user)
 234                 goto no_memory_1;
 235
 236         /* check that the user's quota permits allocation of another key and
 237          * its description */
 238         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 239                 spin_lock(&user->lock);
 240                 if (!(flags & KEY_ALLOC_QUOTA_OVERRUN)) {
 241                         if (user->qnkeys + 1 >= KEYQUOTA_MAX_KEYS ||
 242                             user->qnbytes + quotalen >= KEYQUOTA_MAX_BYTES
 243                             )
 244                                 goto no_quota;
 245                 }
 246
 247                 user->qnkeys++;
 248                 user->qnbytes += quotalen;
 249                 spin_unlock(&user->lock);
 250         }
 251
 252         /* allocate and initialise the key and its description */
 253         key = kmem_cache_alloc(key_jar, GFP_KERNEL);
 254         if (!key)
 255                 goto no_memory_2;
 256
 257         if (desc) {
 258                 key->description = kmemdup(desc, desclen, GFP_KERNEL);
 259                 if (!key->description)
 260                         goto no_memory_3;
 261         }
 262
 263         atomic_set(&key->usage, 1);
 264         init_rwsem(&key->sem);
 265         key->type = type;
 266         key->user = user;
 267         key->quotalen = quotalen;
 268         key->datalen = type->def_datalen;
 269         key->uid = uid;
 270         key->gid = gid;
 271         key->perm = perm;
 272         key->flags = 0;
 273         key->expiry = 0;
 274         key->payload.data = NULL;
 275         key->security = NULL;
 276
 277         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA))
 278                 key->flags |= 1 << KEY_FLAG_IN_QUOTA;
 279
 280         memset(&key->type_data, 0, sizeof(key->type_data));
 281
 282 #ifdef KEY_DEBUGGING
 283         key->magic = KEY_DEBUG_MAGIC;
 284 #endif
 285
 286         /* let the security module know about the key */
 287         ret = security_key_alloc(key, ctx, flags);
 288         if (ret < 0)
 289                 goto security_error;
 290
 291         /* publish the key by giving it a serial number */
 292         atomic_inc(&user->nkeys);
 293         key_alloc_serial(key);
 294
 295 error:
 296         return key;
 297
 298 security_error:
 299         kfree(key->description);
 300         kmem_cache_free(key_jar, key);
 301         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 302                 spin_lock(&user->lock);
 303                 user->qnkeys--;
 304                 user->qnbytes -= quotalen;
 305                 spin_unlock(&user->lock);
 306         }
 307         key_user_put(user);
 308         key = ERR_PTR(ret);
 309         goto error;
 310
 311 no_memory_3:
 312         kmem_cache_free(key_jar, key);
 313 no_memory_2:
 314         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 315                 spin_lock(&user->lock);
 316                 user->qnkeys--;
 317                 user->qnbytes -= quotalen;
 318                 spin_unlock(&user->lock);
 319         }
 320         key_user_put(user);
 321 no_memory_1:
 322         key = ERR_PTR(-ENOMEM);
 323         goto error;
 324
 325 no_quota:
 326         spin_unlock(&user->lock);
 327         key_user_put(user);
 328         key = ERR_PTR(-EDQUOT);
 329         goto error;
 330
 331 } /* end key_alloc() */
 332
 333 EXPORT_SYMBOL(key_alloc);
 334
 335 /*****************************************************************************/
 336 /*
 337  * reserve an amount of quota for the key's payload
 338  */
 339 int key_payload_reserve(struct key *key, size_t datalen)
 340 {
 341         int delta = (int) datalen - key->datalen;
 342         int ret = 0;
 343
 344         key_check(key);
 345
 346         /* contemplate the quota adjustment */
 347         if (delta != 0 && test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
 348                 spin_lock(&key->user->lock);
 349
 350                 if (delta > 0 &&
 351                     key->user->qnbytes + delta > KEYQUOTA_MAX_BYTES
 352                     ) {
 353                         ret = -EDQUOT;
 354                 }
 355                 else {
 356                         key->user->qnbytes += delta;
 357                         key->quotalen += delta;
 358                 }
 359                 spin_unlock(&key->user->lock);
 360         }
 361
 362         /* change the recorded data length if that didn't generate an error */
 363         if (ret == 0)
 364                 key->datalen = datalen;
 365
 366         return ret;
 367
 368 } /* end key_payload_reserve() */
 369
 370 EXPORT_SYMBOL(key_payload_reserve);
 371
 372 /*****************************************************************************/
 373 /*
 374  * instantiate a key and link it into the target keyring atomically
 375  * - called with the target keyring's semaphore writelocked
 376  */
 377 static int __key_instantiate_and_link(struct key *key,
 378                                       const void *data,
 379                                       size_t datalen,
 380                                       struct key *keyring,
 381                                       struct key *instkey)
 382 {
 383         int ret, awaken;
 384
 385         key_check(key);
 386         key_check(keyring);
 387
 388         awaken = 0;
 389         ret = -EBUSY;
 390
 391         mutex_lock(&key_construction_mutex);
 392
 393         /* can't instantiate twice */
 394         if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
 395                 /* instantiate the key */
 396                 ret = key->type->instantiate(key, data, datalen);
 397
 398                 if (ret == 0) {
 399                         /* mark the key as being instantiated */
 400                         atomic_inc(&key->user->nikeys);
 401                         set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
 402
 403                         if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
 404                                 awaken = 1;
 405
 406                         /* and link it into the destination keyring */
 407                         if (keyring)
 408                                 ret = __key_link(keyring, key);
 409
 410                         /* disable the authorisation key */
 411                         if (instkey)
 412                                 key_revoke(instkey);
 413                 }
 414         }
 415
 416         mutex_unlock(&key_construction_mutex);
 417
 418         /* wake up anyone waiting for a key to be constructed */
 419         if (awaken)
 420                 wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
 421
 422         return ret;
 423
 424 } /* end __key_instantiate_and_link() */
 425
 426 /*****************************************************************************/
 427 /*
 428  * instantiate a key and link it into the target keyring atomically
 429  */
 430 int key_instantiate_and_link(struct key *key,
 431                              const void *data,
 432                              size_t datalen,
 433                              struct key *keyring,
 434                              struct key *instkey)
 435 {
 436         int ret;
 437
 438         if (keyring)
 439                 down_write(&keyring->sem);
 440
 441         ret = __key_instantiate_and_link(key, data, datalen, keyring, instkey);
 442
 443         if (keyring)
 444                 up_write(&keyring->sem);
 445
 446         return ret;
 447
 448 } /* end key_instantiate_and_link() */
 449
 450 EXPORT_SYMBOL(key_instantiate_and_link);
 451
 452 /*****************************************************************************/
 453 /*
 454  * negatively instantiate a key and link it into the target keyring atomically
 455  */
 456 int key_negate_and_link(struct key *key,
 457                         unsigned timeout,
 458                         struct key *keyring,
 459                         struct key *instkey)
 460 {
 461         struct timespec now;
 462         int ret, awaken;
 463
 464         key_check(key);
 465         key_check(keyring);
 466
 467         awaken = 0;
 468         ret = -EBUSY;
 469
 470         if (keyring)
 471                 down_write(&keyring->sem);
 472
 473         mutex_lock(&key_construction_mutex);
 474
 475         /* can't instantiate twice */
 476         if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
 477                 /* mark the key as being negatively instantiated */
 478                 atomic_inc(&key->user->nikeys);
 479                 set_bit(KEY_FLAG_NEGATIVE, &key->flags);
 480                 set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
 481                 now = current_kernel_time();
 482                 key->expiry = now.tv_sec + timeout;
 483
 484                 if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
 485                         awaken = 1;
 486
 487                 ret = 0;
 488
 489                 /* and link it into the destination keyring */
 490                 if (keyring)
 491                         ret = __key_link(keyring, key);
 492
 493                 /* disable the authorisation key */
 494                 if (instkey)
 495                         key_revoke(instkey);
 496         }
 497
 498         mutex_unlock(&key_construction_mutex);
 499
 500         if (keyring)
 501                 up_write(&keyring->sem);
 502
 503         /* wake up anyone waiting for a key to be constructed */
 504         if (awaken)
 505                 wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
 506
 507         return ret;
 508
 509 } /* end key_negate_and_link() */
 510
 511 EXPORT_SYMBOL(key_negate_and_link);
 512
 513 /*****************************************************************************/
 514 /*
 515  * do cleaning up in process context so that we don't have to disable
 516  * interrupts all over the place
 517  */
 518 static void key_cleanup(struct work_struct *work)
 519 {
 520         struct rb_node *_n;
 521         struct key *key;
 522
 523  go_again:
 524         /* look for a dead key in the tree */
 525         spin_lock(&key_serial_lock);
 526
 527         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 528                 key = rb_entry(_n, struct key, serial_node);
 529
 530                 if (atomic_read(&key->usage) == 0)
 531                         goto found_dead_key;
 532         }
 533
 534         spin_unlock(&key_serial_lock);
 535         return;
 536
 537  found_dead_key:
 538         /* we found a dead key - once we've removed it from the tree, we can
 539          * drop the lock */
 540         rb_erase(&key->serial_node, &key_serial_tree);
 541         spin_unlock(&key_serial_lock);
 542
 543         key_check(key);
 544
 545         security_key_free(key);
 546
 547         /* deal with the user's key tracking and quota */
 548         if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
 549                 spin_lock(&key->user->lock);
 550                 key->user->qnkeys--;
 551                 key->user->qnbytes -= key->quotalen;
 552                 spin_unlock(&key->user->lock);
 553         }
 554
 555         atomic_dec(&key->user->nkeys);
 556         if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
 557                 atomic_dec(&key->user->nikeys);
 558
 559         key_user_put(key->user);
 560
 561         /* now throw away the key memory */
 562         if (key->type->destroy)
 563                 key->type->destroy(key);
 564
 565         kfree(key->description);
 566
 567 #ifdef KEY_DEBUGGING
 568         key->magic = KEY_DEBUG_MAGIC_X;
 569 #endif
 570         kmem_cache_free(key_jar, key);
 571
 572         /* there may, of course, be more than one key to destroy */
 573         goto go_again;
 574
 575 } /* end key_cleanup() */
 576
 577 /*****************************************************************************/
 578 /*
 579  * dispose of a reference to a key
 580  * - when all the references are gone, we schedule the cleanup task to come and
 581  *   pull it out of the tree in definite process context
 582  */
 583 void key_put(struct key *key)
 584 {
 585         if (key) {
 586                 key_check(key);
 587
 588                 if (atomic_dec_and_test(&key->usage))
 589                         schedule_work(&key_cleanup_task);
 590         }
 591
 592 } /* end key_put() */
 593
 594 EXPORT_SYMBOL(key_put);
 595
 596 /*****************************************************************************/
 597 /*
 598  * find a key by its serial number
 599  */
 600 struct key *key_lookup(key_serial_t id)
 601 {
 602         struct rb_node *n;
 603         struct key *key;
 604
 605         spin_lock(&key_serial_lock);
 606
 607         /* search the tree for the specified key */
 608         n = key_serial_tree.rb_node;
 609         while (n) {
 610                 key = rb_entry(n, struct key, serial_node);
 611
 612                 if (id < key->serial)
 613                         n = n->rb_left;
 614                 else if (id > key->serial)
 615                         n = n->rb_right;
 616                 else
 617                         goto found;
 618         }
 619
 620  not_found:
 621         key = ERR_PTR(-ENOKEY);
 622         goto error;
 623
 624  found:
 625         /* pretend it doesn't exist if it's dead */
 626         if (atomic_read(&key->usage) == 0 ||
 627             test_bit(KEY_FLAG_DEAD, &key->flags) ||
 628             key->type == &key_type_dead)
 629                 goto not_found;
 630
 631         /* this races with key_put(), but that doesn't matter since key_put()
 632          * doesn't actually change the key
 633          */
 634         atomic_inc(&key->usage);
 635
 636  error:
 637         spin_unlock(&key_serial_lock);
 638         return key;
 639
 640 } /* end key_lookup() */
 641
 642 /*****************************************************************************/
 643 /*
 644  * find and lock the specified key type against removal
 645  * - we return with the sem readlocked
 646  */
 647 struct key_type *key_type_lookup(const char *type)
 648 {
 649         struct key_type *ktype;
 650
 651         down_read(&key_types_sem);
 652
 653         /* look up the key type to see if it's one of the registered kernel
 654          * types */
 655         list_for_each_entry(ktype, &key_types_list, link) {
 656                 if (strcmp(ktype->name, type) == 0)
 657                         goto found_kernel_type;
 658         }
 659
 660         up_read(&key_types_sem);
 661         ktype = ERR_PTR(-ENOKEY);
 662
 663  found_kernel_type:
 664         return ktype;
 665
 666 } /* end key_type_lookup() */
 667
 668 /*****************************************************************************/
 669 /*
 670  * unlock a key type
 671  */
 672 void key_type_put(struct key_type *ktype)
 673 {
 674         up_read(&key_types_sem);
 675
 676 } /* end key_type_put() */
 677
 678 /*****************************************************************************/
 679 /*
 680  * attempt to update an existing key
 681  * - the key has an incremented refcount
 682  * - we need to put the key if we get an error
 683  */
 684 static inline key_ref_t __key_update(key_ref_t key_ref,
 685                                      const void *payload, size_t plen)
 686 {
 687         struct key *key = key_ref_to_ptr(key_ref);
 688         int ret;
 689
 690         /* need write permission on the key to update it */
 691         ret = key_permission(key_ref, KEY_WRITE);
 692         if (ret < 0)
 693                 goto error;
 694
 695         ret = -EEXIST;
 696         if (!key->type->update)
 697                 goto error;
 698
 699         down_write(&key->sem);
 700
 701         ret = key->type->update(key, payload, plen);
 702         if (ret == 0)
 703                 /* updating a negative key instantiates it */
 704                 clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
 705
 706         up_write(&key->sem);
 707
 708         if (ret < 0)
 709                 goto error;
 710 out:
 711         return key_ref;
 712
 713 error:
 714         key_put(key);
 715         key_ref = ERR_PTR(ret);
 716         goto out;
 717
 718 } /* end __key_update() */
 719
 720 /*****************************************************************************/
 721 /*
 722  * search the specified keyring for a key of the same description; if one is
 723  * found, update it, otherwise add a new one
 724  */
 725 key_ref_t key_create_or_update(key_ref_t keyring_ref,
 726                                const char *type,
 727                                const char *description,
 728                                const void *payload,
 729                                size_t plen,
 730                                key_perm_t perm,
 731                                unsigned long flags)
 732 {
 733         struct key_type *ktype;
 734         struct key *keyring, *key = NULL;
 735         key_ref_t key_ref;
 736         int ret;
 737
 738         /* look up the key type to see if it's one of the registered kernel
 739          * types */
 740         ktype = key_type_lookup(type);
 741         if (IS_ERR(ktype)) {
 742                 key_ref = ERR_PTR(-ENODEV);
 743                 goto error;
 744         }
 745
 746         key_ref = ERR_PTR(-EINVAL);
 747         if (!ktype->match || !ktype->instantiate)
 748                 goto error_2;
 749
 750         keyring = key_ref_to_ptr(keyring_ref);
 751
 752         key_check(keyring);
 753
 754         key_ref = ERR_PTR(-ENOTDIR);
 755         if (keyring->type != &key_type_keyring)
 756                 goto error_2;
 757
 758         down_write(&keyring->sem);
 759
 760         /* if we're going to allocate a new key, we're going to have
 761          * to modify the keyring */
 762         ret = key_permission(keyring_ref, KEY_WRITE);
 763         if (ret < 0) {
 764                 key_ref = ERR_PTR(ret);
 765                 goto error_3;
 766         }
 767
 768         /* if it's possible to update this type of key, search for an existing
 769          * key of the same type and description in the destination keyring and
 770          * update that instead if possible
 771          */
 772         if (ktype->update) {
 773                 key_ref = __keyring_search_one(keyring_ref, ktype, description,
 774                                                0);
 775                 if (!IS_ERR(key_ref))
 776                         goto found_matching_key;
 777         }
 778
 779         /* if the client doesn't provide, decide on the permissions we want */
 780         if (perm == KEY_PERM_UNDEF) {
 781                 perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
 782                 perm |= KEY_USR_VIEW | KEY_USR_SEARCH | KEY_USR_LINK | KEY_USR_SETATTR;
 783
 784                 if (ktype->read)
 785                         perm |= KEY_POS_READ | KEY_USR_READ;
 786
 787                 if (ktype == &key_type_keyring || ktype->update)
 788                         perm |= KEY_USR_WRITE;
 789         }
 790
 791         /* allocate a new key */
 792         key = key_alloc(ktype, description, current->fsuid, current->fsgid,
 793                         current, perm, flags);
 794         if (IS_ERR(key)) {
 795                 key_ref = ERR_CAST(key);
 796                 goto error_3;
 797         }
 798
 799         /* instantiate it and link it into the target keyring */
 800         ret = __key_instantiate_and_link(key, payload, plen, keyring, NULL);
 801         if (ret < 0) {
 802                 key_put(key);
 803                 key_ref = ERR_PTR(ret);
 804                 goto error_3;
 805         }
 806
 807         key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
 808
 809  error_3:
 810         up_write(&keyring->sem);
 811  error_2:
 812         key_type_put(ktype);
 813  error:
 814         return key_ref;
 815
 816  found_matching_key:
 817         /* we found a matching key, so we're going to try to update it
 818          * - we can drop the locks first as we have the key pinned
 819          */
 820         up_write(&keyring->sem);
 821         key_type_put(ktype);
 822
 823         key_ref = __key_update(key_ref, payload, plen);
 824         goto error;
 825
 826 } /* end key_create_or_update() */
 827
 828 EXPORT_SYMBOL(key_create_or_update);
 829
 830 /*****************************************************************************/
 831 /*
 832  * update a key
 833  */
 834 int key_update(key_ref_t key_ref, const void *payload, size_t plen)
 835 {
 836         struct key *key = key_ref_to_ptr(key_ref);
 837         int ret;
 838
 839         key_check(key);
 840
 841         /* the key must be writable */
 842         ret = key_permission(key_ref, KEY_WRITE);
 843         if (ret < 0)
 844                 goto error;
 845
 846         /* attempt to update it if supported */
 847         ret = -EOPNOTSUPP;
 848         if (key->type->update) {
 849                 down_write(&key->sem);
 850
 851                 ret = key->type->update(key, payload, plen);
 852                 if (ret == 0)
 853                         /* updating a negative key instantiates it */
 854                         clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
 855
 856                 up_write(&key->sem);
 857         }
 858
 859  error:
 860         return ret;
 861
 862 } /* end key_update() */
 863
 864 EXPORT_SYMBOL(key_update);
 865
 866 /*****************************************************************************/
 867 /*
 868  * revoke a key
 869  */
 870 void key_revoke(struct key *key)
 871 {
 872         key_check(key);
 873
 874         /* make sure no one's trying to change or use the key when we mark it
 875          * - we tell lockdep that we might nest because we might be revoking an
 876          *   authorisation key whilst holding the sem on a key we've just
 877          *   instantiated
 878          */
 879         down_write_nested(&key->sem, 1);
 880         if (!test_and_set_bit(KEY_FLAG_REVOKED, &key->flags) &&
 881             key->type->revoke)
 882                 key->type->revoke(key);
 883
 884         up_write(&key->sem);
 885
 886 } /* end key_revoke() */
 887
 888 EXPORT_SYMBOL(key_revoke);
 889
 890 /*****************************************************************************/
 891 /*
 892  * register a type of key
 893  */
 894 int register_key_type(struct key_type *ktype)
 895 {
 896         struct key_type *p;
 897         int ret;
 898
 899         ret = -EEXIST;
 900         down_write(&key_types_sem);
 901
 902         /* disallow key types with the same name */
 903         list_for_each_entry(p, &key_types_list, link) {
 904                 if (strcmp(p->name, ktype->name) == 0)
 905                         goto out;
 906         }
 907
 908         /* store the type */
 909         list_add(&ktype->link, &key_types_list);
 910         ret = 0;
 911
 912  out:
 913         up_write(&key_types_sem);
 914         return ret;
 915
 916 } /* end register_key_type() */
 917
 918 EXPORT_SYMBOL(register_key_type);
 919
 920 /*****************************************************************************/
 921 /*
 922  * unregister a type of key
 923  */
 924 void unregister_key_type(struct key_type *ktype)
 925 {
 926         struct rb_node *_n;
 927         struct key *key;
 928
 929         down_write(&key_types_sem);
 930
 931         /* withdraw the key type */
 932         list_del_init(&ktype->link);
 933
 934         /* mark all the keys of this type dead */
 935         spin_lock(&key_serial_lock);
 936
 937         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 938                 key = rb_entry(_n, struct key, serial_node);
 939
 940                 if (key->type == ktype)
 941                         key->type = &key_type_dead;
 942         }
 943
 944         spin_unlock(&key_serial_lock);
 945
 946         /* make sure everyone revalidates their keys */
 947         synchronize_rcu();
 948
 949         /* we should now be able to destroy the payloads of all the keys of
 950          * this type with impunity */
 951         spin_lock(&key_serial_lock);
 952
 953         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 954                 key = rb_entry(_n, struct key, serial_node);
 955
 956                 if (key->type == ktype) {
 957                         if (ktype->destroy)
 958                                 ktype->destroy(key);
 959                         memset(&key->payload, KEY_DESTROY, sizeof(key->payload));
 960                 }
 961         }
 962
 963         spin_unlock(&key_serial_lock);
 964         up_write(&key_types_sem);
 965
 966 } /* end unregister_key_type() */
 967
 968 EXPORT_SYMBOL(unregister_key_type);
 969
 970 /*****************************************************************************/
 971 /*
 972  * initialise the key management stuff
 973  */
 974 void __init key_init(void)
 975 {
 976         /* allocate a slab in which we can store keys */
 977         key_jar = kmem_cache_create("key_jar", sizeof(struct key),
 978                         0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
 979
 980         /* add the special key types */
 981         list_add_tail(&key_type_keyring.link, &key_types_list);
 982         list_add_tail(&key_type_dead.link, &key_types_list);
 983         list_add_tail(&key_type_user.link, &key_types_list);
 984
 985         /* record the root user tracking */
 986         rb_link_node(&root_key_user.node,
 987                      NULL,
 988                      &key_user_tree.rb_node);
 989
 990         rb_insert_color(&root_key_user.node,
 991                         &key_user_tree);
 992
 993 } /* end key_init() */