security/keys/key.c

   1 /* key.c: basic authentication token and access key management
   2  *
   3  * Copyright (C) 2004-6 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 DECLARE_RWSEM(key_construction_sem);
  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         INIT_LIST_HEAD(&candidate->consq);
 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  * insert a key with a fixed serial number
 143  */
 144 static void __init __key_insert_serial(struct key *key)
 145 {
 146         struct rb_node *parent, **p;
 147         struct key *xkey;
 148
 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                         BUG();
 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 } /* end __key_insert_serial() */
 169
 170 /*****************************************************************************/
 171 /*
 172  * assign a key the next unique serial number
 173  * - these are assigned randomly to avoid security issues through covert
 174  *   channel problems
 175  */
 176 static inline void key_alloc_serial(struct key *key)
 177 {
 178         struct rb_node *parent, **p;
 179         struct key *xkey;
 180
 181         /* propose a random serial number and look for a hole for it in the
 182          * serial number tree */
 183         do {
 184                 get_random_bytes(&key->serial, sizeof(key->serial));
 185
 186                 key->serial >>= 1; /* negative numbers are not permitted */
 187         } while (key->serial < 3);
 188
 189         spin_lock(&key_serial_lock);
 190
 191 attempt_insertion:
 192         parent = NULL;
 193         p = &key_serial_tree.rb_node;
 194
 195         while (*p) {
 196                 parent = *p;
 197                 xkey = rb_entry(parent, struct key, serial_node);
 198
 199                 if (key->serial < xkey->serial)
 200                         p = &(*p)->rb_left;
 201                 else if (key->serial > xkey->serial)
 202                         p = &(*p)->rb_right;
 203                 else
 204                         goto serial_exists;
 205         }
 206
 207         /* we've found a suitable hole - arrange for this key to occupy it */
 208         rb_link_node(&key->serial_node, parent, p);
 209         rb_insert_color(&key->serial_node, &key_serial_tree);
 210
 211         spin_unlock(&key_serial_lock);
 212         return;
 213
 214         /* we found a key with the proposed serial number - walk the tree from
 215          * that point looking for the next unused serial number */
 216 serial_exists:
 217         for (;;) {
 218                 key->serial++;
 219                 if (key->serial < 3) {
 220                         key->serial = 3;
 221                         goto attempt_insertion;
 222                 }
 223
 224                 parent = rb_next(parent);
 225                 if (!parent)
 226                         goto attempt_insertion;
 227
 228                 xkey = rb_entry(parent, struct key, serial_node);
 229                 if (key->serial < xkey->serial)
 230                         goto attempt_insertion;
 231         }
 232
 233 } /* end key_alloc_serial() */
 234
 235 /*****************************************************************************/
 236 /*
 237  * allocate a key of the specified type
 238  * - update the user's quota to reflect the existence of the key
 239  * - called from a key-type operation with key_types_sem read-locked by
 240  *   key_create_or_update()
 241  *   - this prevents unregistration of the key type
 242  * - upon return the key is as yet uninstantiated; the caller needs to either
 243  *   instantiate the key or discard it before returning
 244  */
 245 struct key *key_alloc(struct key_type *type, const char *desc,
 246                       uid_t uid, gid_t gid, struct task_struct *ctx,
 247                       key_perm_t perm, unsigned long flags)
 248 {
 249         struct key_user *user = NULL;
 250         struct key *key;
 251         size_t desclen, quotalen;
 252         int ret;
 253
 254         key = ERR_PTR(-EINVAL);
 255         if (!desc || !*desc)
 256                 goto error;
 257
 258         desclen = strlen(desc) + 1;
 259         quotalen = desclen + type->def_datalen;
 260
 261         /* get hold of the key tracking for this user */
 262         user = key_user_lookup(uid);
 263         if (!user)
 264                 goto no_memory_1;
 265
 266         /* check that the user's quota permits allocation of another key and
 267          * its description */
 268         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 269                 spin_lock(&user->lock);
 270                 if (!(flags & KEY_ALLOC_QUOTA_OVERRUN)) {
 271                         if (user->qnkeys + 1 >= KEYQUOTA_MAX_KEYS ||
 272                             user->qnbytes + quotalen >= KEYQUOTA_MAX_BYTES
 273                             )
 274                                 goto no_quota;
 275                 }
 276
 277                 user->qnkeys++;
 278                 user->qnbytes += quotalen;
 279                 spin_unlock(&user->lock);
 280         }
 281
 282         /* allocate and initialise the key and its description */
 283         key = kmem_cache_alloc(key_jar, GFP_KERNEL);
 284         if (!key)
 285                 goto no_memory_2;
 286
 287         if (desc) {
 288                 key->description = kmemdup(desc, desclen, GFP_KERNEL);
 289                 if (!key->description)
 290                         goto no_memory_3;
 291         }
 292
 293         atomic_set(&key->usage, 1);
 294         init_rwsem(&key->sem);
 295         key->type = type;
 296         key->user = user;
 297         key->quotalen = quotalen;
 298         key->datalen = type->def_datalen;
 299         key->uid = uid;
 300         key->gid = gid;
 301         key->perm = perm;
 302         key->flags = 0;
 303         key->expiry = 0;
 304         key->payload.data = NULL;
 305         key->security = NULL;
 306
 307         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA))
 308                 key->flags |= 1 << KEY_FLAG_IN_QUOTA;
 309
 310         memset(&key->type_data, 0, sizeof(key->type_data));
 311
 312 #ifdef KEY_DEBUGGING
 313         key->magic = KEY_DEBUG_MAGIC;
 314 #endif
 315
 316         /* let the security module know about the key */
 317         ret = security_key_alloc(key, ctx, flags);
 318         if (ret < 0)
 319                 goto security_error;
 320
 321         /* publish the key by giving it a serial number */
 322         atomic_inc(&user->nkeys);
 323         key_alloc_serial(key);
 324
 325 error:
 326         return key;
 327
 328 security_error:
 329         kfree(key->description);
 330         kmem_cache_free(key_jar, key);
 331         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 332                 spin_lock(&user->lock);
 333                 user->qnkeys--;
 334                 user->qnbytes -= quotalen;
 335                 spin_unlock(&user->lock);
 336         }
 337         key_user_put(user);
 338         key = ERR_PTR(ret);
 339         goto error;
 340
 341 no_memory_3:
 342         kmem_cache_free(key_jar, key);
 343 no_memory_2:
 344         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 345                 spin_lock(&user->lock);
 346                 user->qnkeys--;
 347                 user->qnbytes -= quotalen;
 348                 spin_unlock(&user->lock);
 349         }
 350         key_user_put(user);
 351 no_memory_1:
 352         key = ERR_PTR(-ENOMEM);
 353         goto error;
 354
 355 no_quota:
 356         spin_unlock(&user->lock);
 357         key_user_put(user);
 358         key = ERR_PTR(-EDQUOT);
 359         goto error;
 360
 361 } /* end key_alloc() */
 362
 363 EXPORT_SYMBOL(key_alloc);
 364
 365 /*****************************************************************************/
 366 /*
 367  * reserve an amount of quota for the key's payload
 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                 spin_lock(&key->user->lock);
 379
 380                 if (delta > 0 &&
 381                     key->user->qnbytes + delta > KEYQUOTA_MAX_BYTES
 382                     ) {
 383                         ret = -EDQUOT;
 384                 }
 385                 else {
 386                         key->user->qnbytes += delta;
 387                         key->quotalen += delta;
 388                 }
 389                 spin_unlock(&key->user->lock);
 390         }
 391
 392         /* change the recorded data length if that didn't generate an error */
 393         if (ret == 0)
 394                 key->datalen = datalen;
 395
 396         return ret;
 397
 398 } /* end key_payload_reserve() */
 399
 400 EXPORT_SYMBOL(key_payload_reserve);
 401
 402 /*****************************************************************************/
 403 /*
 404  * instantiate a key and link it into the target keyring atomically
 405  * - called with the target keyring's semaphore writelocked
 406  */
 407 static int __key_instantiate_and_link(struct key *key,
 408                                       const void *data,
 409                                       size_t datalen,
 410                                       struct key *keyring,
 411                                       struct key *instkey)
 412 {
 413         int ret, awaken;
 414
 415         key_check(key);
 416         key_check(keyring);
 417
 418         awaken = 0;
 419         ret = -EBUSY;
 420
 421         down_write(&key_construction_sem);
 422
 423         /* can't instantiate twice */
 424         if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
 425                 /* instantiate the key */
 426                 ret = key->type->instantiate(key, data, datalen);
 427
 428                 if (ret == 0) {
 429                         /* mark the key as being instantiated */
 430                         atomic_inc(&key->user->nikeys);
 431                         set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
 432
 433                         if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
 434                                 awaken = 1;
 435
 436                         /* and link it into the destination keyring */
 437                         if (keyring)
 438                                 ret = __key_link(keyring, key);
 439
 440                         /* disable the authorisation key */
 441                         if (instkey)
 442                                 key_revoke(instkey);
 443                 }
 444         }
 445
 446         up_write(&key_construction_sem);
 447
 448         /* wake up anyone waiting for a key to be constructed */
 449         if (awaken)
 450                 wake_up_all(&request_key_conswq);
 451
 452         return ret;
 453
 454 } /* end __key_instantiate_and_link() */
 455
 456 /*****************************************************************************/
 457 /*
 458  * instantiate a key and link it into the target keyring atomically
 459  */
 460 int key_instantiate_and_link(struct key *key,
 461                              const void *data,
 462                              size_t datalen,
 463                              struct key *keyring,
 464                              struct key *instkey)
 465 {
 466         int ret;
 467
 468         if (keyring)
 469                 down_write(&keyring->sem);
 470
 471         ret = __key_instantiate_and_link(key, data, datalen, keyring, instkey);
 472
 473         if (keyring)
 474                 up_write(&keyring->sem);
 475
 476         return ret;
 477
 478 } /* end key_instantiate_and_link() */
 479
 480 EXPORT_SYMBOL(key_instantiate_and_link);
 481
 482 /*****************************************************************************/
 483 /*
 484  * negatively instantiate a key and link it into the target keyring atomically
 485  */
 486 int key_negate_and_link(struct key *key,
 487                         unsigned timeout,
 488                         struct key *keyring,
 489                         struct key *instkey)
 490 {
 491         struct timespec now;
 492         int ret, awaken;
 493
 494         key_check(key);
 495         key_check(keyring);
 496
 497         awaken = 0;
 498         ret = -EBUSY;
 499
 500         if (keyring)
 501                 down_write(&keyring->sem);
 502
 503         down_write(&key_construction_sem);
 504
 505         /* can't instantiate twice */
 506         if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
 507                 /* mark the key as being negatively instantiated */
 508                 atomic_inc(&key->user->nikeys);
 509                 set_bit(KEY_FLAG_NEGATIVE, &key->flags);
 510                 set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
 511                 now = current_kernel_time();
 512                 key->expiry = now.tv_sec + timeout;
 513
 514                 if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
 515                         awaken = 1;
 516
 517                 ret = 0;
 518
 519                 /* and link it into the destination keyring */
 520                 if (keyring)
 521                         ret = __key_link(keyring, key);
 522
 523                 /* disable the authorisation key */
 524                 if (instkey)
 525                         key_revoke(instkey);
 526         }
 527
 528         up_write(&key_construction_sem);
 529
 530         if (keyring)
 531                 up_write(&keyring->sem);
 532
 533         /* wake up anyone waiting for a key to be constructed */
 534         if (awaken)
 535                 wake_up_all(&request_key_conswq);
 536
 537         return ret;
 538
 539 } /* end key_negate_and_link() */
 540
 541 EXPORT_SYMBOL(key_negate_and_link);
 542
 543 /*****************************************************************************/
 544 /*
 545  * do cleaning up in process context so that we don't have to disable
 546  * interrupts all over the place
 547  */
 548 static void key_cleanup(struct work_struct *work)
 549 {
 550         struct rb_node *_n;
 551         struct key *key;
 552
 553  go_again:
 554         /* look for a dead key in the tree */
 555         spin_lock(&key_serial_lock);
 556
 557         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 558                 key = rb_entry(_n, struct key, serial_node);
 559
 560                 if (atomic_read(&key->usage) == 0)
 561                         goto found_dead_key;
 562         }
 563
 564         spin_unlock(&key_serial_lock);
 565         return;
 566
 567  found_dead_key:
 568         /* we found a dead key - once we've removed it from the tree, we can
 569          * drop the lock */
 570         rb_erase(&key->serial_node, &key_serial_tree);
 571         spin_unlock(&key_serial_lock);
 572
 573         key_check(key);
 574
 575         security_key_free(key);
 576
 577         /* deal with the user's key tracking and quota */
 578         if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
 579                 spin_lock(&key->user->lock);
 580                 key->user->qnkeys--;
 581                 key->user->qnbytes -= key->quotalen;
 582                 spin_unlock(&key->user->lock);
 583         }
 584
 585         atomic_dec(&key->user->nkeys);
 586         if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
 587                 atomic_dec(&key->user->nikeys);
 588
 589         key_user_put(key->user);
 590
 591         /* now throw away the key memory */
 592         if (key->type->destroy)
 593                 key->type->destroy(key);
 594
 595         kfree(key->description);
 596
 597 #ifdef KEY_DEBUGGING
 598         key->magic = KEY_DEBUG_MAGIC_X;
 599 #endif
 600         kmem_cache_free(key_jar, key);
 601
 602         /* there may, of course, be more than one key to destroy */
 603         goto go_again;
 604
 605 } /* end key_cleanup() */
 606
 607 /*****************************************************************************/
 608 /*
 609  * dispose of a reference to a key
 610  * - when all the references are gone, we schedule the cleanup task to come and
 611  *   pull it out of the tree in definite process context
 612  */
 613 void key_put(struct key *key)
 614 {
 615         if (key) {
 616                 key_check(key);
 617
 618                 if (atomic_dec_and_test(&key->usage))
 619                         schedule_work(&key_cleanup_task);
 620         }
 621
 622 } /* end key_put() */
 623
 624 EXPORT_SYMBOL(key_put);
 625
 626 /*****************************************************************************/
 627 /*
 628  * find a key by its serial number
 629  */
 630 struct key *key_lookup(key_serial_t id)
 631 {
 632         struct rb_node *n;
 633         struct key *key;
 634
 635         spin_lock(&key_serial_lock);
 636
 637         /* search the tree for the specified key */
 638         n = key_serial_tree.rb_node;
 639         while (n) {
 640                 key = rb_entry(n, struct key, serial_node);
 641
 642                 if (id < key->serial)
 643                         n = n->rb_left;
 644                 else if (id > key->serial)
 645                         n = n->rb_right;
 646                 else
 647                         goto found;
 648         }
 649
 650  not_found:
 651         key = ERR_PTR(-ENOKEY);
 652         goto error;
 653
 654  found:
 655         /* pretend it doesn't exist if it's dead */
 656         if (atomic_read(&key->usage) == 0 ||
 657             test_bit(KEY_FLAG_DEAD, &key->flags) ||
 658             key->type == &key_type_dead)
 659                 goto not_found;
 660
 661         /* this races with key_put(), but that doesn't matter since key_put()
 662          * doesn't actually change the key
 663          */
 664         atomic_inc(&key->usage);
 665
 666  error:
 667         spin_unlock(&key_serial_lock);
 668         return key;
 669
 670 } /* end key_lookup() */
 671
 672 /*****************************************************************************/
 673 /*
 674  * find and lock the specified key type against removal
 675  * - we return with the sem readlocked
 676  */
 677 struct key_type *key_type_lookup(const char *type)
 678 {
 679         struct key_type *ktype;
 680
 681         down_read(&key_types_sem);
 682
 683         /* look up the key type to see if it's one of the registered kernel
 684          * types */
 685         list_for_each_entry(ktype, &key_types_list, link) {
 686                 if (strcmp(ktype->name, type) == 0)
 687                         goto found_kernel_type;
 688         }
 689
 690         up_read(&key_types_sem);
 691         ktype = ERR_PTR(-ENOKEY);
 692
 693  found_kernel_type:
 694         return ktype;
 695
 696 } /* end key_type_lookup() */
 697
 698 /*****************************************************************************/
 699 /*
 700  * unlock a key type
 701  */
 702 void key_type_put(struct key_type *ktype)
 703 {
 704         up_read(&key_types_sem);
 705
 706 } /* end key_type_put() */
 707
 708 /*****************************************************************************/
 709 /*
 710  * attempt to update an existing key
 711  * - the key has an incremented refcount
 712  * - we need to put the key if we get an error
 713  */
 714 static inline key_ref_t __key_update(key_ref_t key_ref,
 715                                      const void *payload, size_t plen)
 716 {
 717         struct key *key = key_ref_to_ptr(key_ref);
 718         int ret;
 719
 720         /* need write permission on the key to update it */
 721         ret = key_permission(key_ref, KEY_WRITE);
 722         if (ret < 0)
 723                 goto error;
 724
 725         ret = -EEXIST;
 726         if (!key->type->update)
 727                 goto error;
 728
 729         down_write(&key->sem);
 730
 731         ret = key->type->update(key, payload, plen);
 732         if (ret == 0)
 733                 /* updating a negative key instantiates it */
 734                 clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
 735
 736         up_write(&key->sem);
 737
 738         if (ret < 0)
 739                 goto error;
 740 out:
 741         return key_ref;
 742
 743 error:
 744         key_put(key);
 745         key_ref = ERR_PTR(ret);
 746         goto out;
 747
 748 } /* end __key_update() */
 749
 750 /*****************************************************************************/
 751 /*
 752  * search the specified keyring for a key of the same description; if one is
 753  * found, update it, otherwise add a new one
 754  */
 755 key_ref_t key_create_or_update(key_ref_t keyring_ref,
 756                                const char *type,
 757                                const char *description,
 758                                const void *payload,
 759                                size_t plen,
 760                                unsigned long flags)
 761 {
 762         struct key_type *ktype;
 763         struct key *keyring, *key = NULL;
 764         key_perm_t perm;
 765         key_ref_t key_ref;
 766         int ret;
 767
 768         /* look up the key type to see if it's one of the registered kernel
 769          * types */
 770         ktype = key_type_lookup(type);
 771         if (IS_ERR(ktype)) {
 772                 key_ref = ERR_PTR(-ENODEV);
 773                 goto error;
 774         }
 775
 776         key_ref = ERR_PTR(-EINVAL);
 777         if (!ktype->match || !ktype->instantiate)
 778                 goto error_2;
 779
 780         keyring = key_ref_to_ptr(keyring_ref);
 781
 782         key_check(keyring);
 783
 784         key_ref = ERR_PTR(-ENOTDIR);
 785         if (keyring->type != &key_type_keyring)
 786                 goto error_2;
 787
 788         down_write(&keyring->sem);
 789
 790         /* if we're going to allocate a new key, we're going to have
 791          * to modify the keyring */
 792         ret = key_permission(keyring_ref, KEY_WRITE);
 793         if (ret < 0) {
 794                 key_ref = ERR_PTR(ret);
 795                 goto error_3;
 796         }
 797
 798         /* if it's possible to update this type of key, search for an existing
 799          * key of the same type and description in the destination keyring and
 800          * update that instead if possible
 801          */
 802         if (ktype->update) {
 803                 key_ref = __keyring_search_one(keyring_ref, ktype, description,
 804                                                0);
 805                 if (!IS_ERR(key_ref))
 806                         goto found_matching_key;
 807         }
 808
 809         /* decide on the permissions we want */
 810         perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
 811         perm |= KEY_USR_VIEW | KEY_USR_SEARCH | KEY_USR_LINK | KEY_USR_SETATTR;
 812
 813         if (ktype->read)
 814                 perm |= KEY_POS_READ | KEY_USR_READ;
 815
 816         if (ktype == &key_type_keyring || ktype->update)
 817                 perm |= KEY_USR_WRITE;
 818
 819         /* allocate a new key */
 820         key = key_alloc(ktype, description, current->fsuid, current->fsgid,
 821                         current, perm, flags);
 822         if (IS_ERR(key)) {
 823                 key_ref = ERR_PTR(PTR_ERR(key));
 824                 goto error_3;
 825         }
 826
 827         /* instantiate it and link it into the target keyring */
 828         ret = __key_instantiate_and_link(key, payload, plen, keyring, NULL);
 829         if (ret < 0) {
 830                 key_put(key);
 831                 key_ref = ERR_PTR(ret);
 832                 goto error_3;
 833         }
 834
 835         key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
 836
 837  error_3:
 838         up_write(&keyring->sem);
 839  error_2:
 840         key_type_put(ktype);
 841  error:
 842         return key_ref;
 843
 844  found_matching_key:
 845         /* we found a matching key, so we're going to try to update it
 846          * - we can drop the locks first as we have the key pinned
 847          */
 848         up_write(&keyring->sem);
 849         key_type_put(ktype);
 850
 851         key_ref = __key_update(key_ref, payload, plen);
 852         goto error;
 853
 854 } /* end key_create_or_update() */
 855
 856 EXPORT_SYMBOL(key_create_or_update);
 857
 858 /*****************************************************************************/
 859 /*
 860  * update a key
 861  */
 862 int key_update(key_ref_t key_ref, const void *payload, size_t plen)
 863 {
 864         struct key *key = key_ref_to_ptr(key_ref);
 865         int ret;
 866
 867         key_check(key);
 868
 869         /* the key must be writable */
 870         ret = key_permission(key_ref, KEY_WRITE);
 871         if (ret < 0)
 872                 goto error;
 873
 874         /* attempt to update it if supported */
 875         ret = -EOPNOTSUPP;
 876         if (key->type->update) {
 877                 down_write(&key->sem);
 878
 879                 ret = key->type->update(key, payload, plen);
 880                 if (ret == 0)
 881                         /* updating a negative key instantiates it */
 882                         clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
 883
 884                 up_write(&key->sem);
 885         }
 886
 887  error:
 888         return ret;
 889
 890 } /* end key_update() */
 891
 892 EXPORT_SYMBOL(key_update);
 893
 894 /*****************************************************************************/
 895 /*
 896  * revoke a key
 897  */
 898 void key_revoke(struct key *key)
 899 {
 900         key_check(key);
 901
 902         /* make sure no one's trying to change or use the key when we mark
 903          * it */
 904         down_write(&key->sem);
 905         set_bit(KEY_FLAG_REVOKED, &key->flags);
 906
 907         if (key->type->revoke)
 908                 key->type->revoke(key);
 909
 910         up_write(&key->sem);
 911
 912 } /* end key_revoke() */
 913
 914 EXPORT_SYMBOL(key_revoke);
 915
 916 /*****************************************************************************/
 917 /*
 918  * register a type of key
 919  */
 920 int register_key_type(struct key_type *ktype)
 921 {
 922         struct key_type *p;
 923         int ret;
 924
 925         ret = -EEXIST;
 926         down_write(&key_types_sem);
 927
 928         /* disallow key types with the same name */
 929         list_for_each_entry(p, &key_types_list, link) {
 930                 if (strcmp(p->name, ktype->name) == 0)
 931                         goto out;
 932         }
 933
 934         /* store the type */
 935         list_add(&ktype->link, &key_types_list);
 936         ret = 0;
 937
 938  out:
 939         up_write(&key_types_sem);
 940         return ret;
 941
 942 } /* end register_key_type() */
 943
 944 EXPORT_SYMBOL(register_key_type);
 945
 946 /*****************************************************************************/
 947 /*
 948  * unregister a type of key
 949  */
 950 void unregister_key_type(struct key_type *ktype)
 951 {
 952         struct rb_node *_n;
 953         struct key *key;
 954
 955         down_write(&key_types_sem);
 956
 957         /* withdraw the key type */
 958         list_del_init(&ktype->link);
 959
 960         /* mark all the keys of this type dead */
 961         spin_lock(&key_serial_lock);
 962
 963         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 964                 key = rb_entry(_n, struct key, serial_node);
 965
 966                 if (key->type == ktype)
 967                         key->type = &key_type_dead;
 968         }
 969
 970         spin_unlock(&key_serial_lock);
 971
 972         /* make sure everyone revalidates their keys */
 973         synchronize_rcu();
 974
 975         /* we should now be able to destroy the payloads of all the keys of
 976          * this type with impunity */
 977         spin_lock(&key_serial_lock);
 978
 979         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 980                 key = rb_entry(_n, struct key, serial_node);
 981
 982                 if (key->type == ktype) {
 983                         if (ktype->destroy)
 984                                 ktype->destroy(key);
 985                         memset(&key->payload, KEY_DESTROY, sizeof(key->payload));
 986                 }
 987         }
 988
 989         spin_unlock(&key_serial_lock);
 990         up_write(&key_types_sem);
 991
 992 } /* end unregister_key_type() */
 993
 994 EXPORT_SYMBOL(unregister_key_type);
 995
 996 /*****************************************************************************/
 997 /*
 998  * initialise the key management stuff
 999  */
1000 void __init key_init(void)
1001 {
1002         /* allocate a slab in which we can store keys */
1003         key_jar = kmem_cache_create("key_jar", sizeof(struct key),
1004                         0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1005
1006         /* add the special key types */
1007         list_add_tail(&key_type_keyring.link, &key_types_list);
1008         list_add_tail(&key_type_dead.link, &key_types_list);
1009         list_add_tail(&key_type_user.link, &key_types_list);
1010
1011         /* record the root user tracking */
1012         rb_link_node(&root_key_user.node,
1013                      NULL,
1014                      &key_user_tree.rb_node);
1015
1016         rb_insert_color(&root_key_user.node,
1017                         &key_user_tree);
1018
1019         /* record root's user standard keyrings */
1020         key_check(&root_user_keyring);
1021         key_check(&root_session_keyring);
1022
1023         __key_insert_serial(&root_user_keyring);
1024         __key_insert_serial(&root_session_keyring);
1025
1026         keyring_publish_name(&root_user_keyring);
1027         keyring_publish_name(&root_session_keyring);
1028
1029         /* link the two root keyrings together */
1030         key_link(&root_session_keyring, &root_user_keyring);
1031
1032 } /* end key_init() */