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 kmem_cache_t     *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         parent = NULL;
 192         p = &key_serial_tree.rb_node;
 193
 194         while (*p) {
 195                 parent = *p;
 196                 xkey = rb_entry(parent, struct key, serial_node);
 197
 198                 if (key->serial < xkey->serial)
 199                         p = &(*p)->rb_left;
 200                 else if (key->serial > xkey->serial)
 201                         p = &(*p)->rb_right;
 202                 else
 203                         goto serial_exists;
 204         }
 205         goto insert_here;
 206
 207         /* we found a key with the proposed serial number - walk the tree from
 208          * that point looking for the next unused serial number */
 209 serial_exists:
 210         for (;;) {
 211                 key->serial++;
 212                 if (key->serial < 2)
 213                         key->serial = 2;
 214
 215                 if (!rb_parent(parent))
 216                         p = &key_serial_tree.rb_node;
 217                 else if (rb_parent(parent)->rb_left == parent)
 218                         p = &(rb_parent(parent)->rb_left);
 219                 else
 220                         p = &(rb_parent(parent)->rb_right);
 221
 222                 parent = rb_next(parent);
 223                 if (!parent)
 224                         break;
 225
 226                 xkey = rb_entry(parent, struct key, serial_node);
 227                 if (key->serial < xkey->serial)
 228                         goto insert_here;
 229         }
 230
 231         /* we've found a suitable hole - arrange for this key to occupy it */
 232 insert_here:
 233         rb_link_node(&key->serial_node, parent, p);
 234         rb_insert_color(&key->serial_node, &key_serial_tree);
 235
 236         spin_unlock(&key_serial_lock);
 237
 238 } /* end key_alloc_serial() */
 239
 240 /*****************************************************************************/
 241 /*
 242  * allocate a key of the specified type
 243  * - update the user's quota to reflect the existence of the key
 244  * - called from a key-type operation with key_types_sem read-locked by
 245  *   key_create_or_update()
 246  *   - this prevents unregistration of the key type
 247  * - upon return the key is as yet uninstantiated; the caller needs to either
 248  *   instantiate the key or discard it before returning
 249  */
 250 struct key *key_alloc(struct key_type *type, const char *desc,
 251                       uid_t uid, gid_t gid, struct task_struct *ctx,
 252                       key_perm_t perm, unsigned long flags)
 253 {
 254         struct key_user *user = NULL;
 255         struct key *key;
 256         size_t desclen, quotalen;
 257         int ret;
 258
 259         key = ERR_PTR(-EINVAL);
 260         if (!desc || !*desc)
 261                 goto error;
 262
 263         desclen = strlen(desc) + 1;
 264         quotalen = desclen + type->def_datalen;
 265
 266         /* get hold of the key tracking for this user */
 267         user = key_user_lookup(uid);
 268         if (!user)
 269                 goto no_memory_1;
 270
 271         /* check that the user's quota permits allocation of another key and
 272          * its description */
 273         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 274                 spin_lock(&user->lock);
 275                 if (!(flags & KEY_ALLOC_QUOTA_OVERRUN)) {
 276                         if (user->qnkeys + 1 >= KEYQUOTA_MAX_KEYS ||
 277                             user->qnbytes + quotalen >= KEYQUOTA_MAX_BYTES
 278                             )
 279                                 goto no_quota;
 280                 }
 281
 282                 user->qnkeys++;
 283                 user->qnbytes += quotalen;
 284                 spin_unlock(&user->lock);
 285         }
 286
 287         /* allocate and initialise the key and its description */
 288         key = kmem_cache_alloc(key_jar, SLAB_KERNEL);
 289         if (!key)
 290                 goto no_memory_2;
 291
 292         if (desc) {
 293                 key->description = kmalloc(desclen, GFP_KERNEL);
 294                 if (!key->description)
 295                         goto no_memory_3;
 296
 297                 memcpy(key->description, desc, desclen);
 298         }
 299
 300         atomic_set(&key->usage, 1);
 301         init_rwsem(&key->sem);
 302         key->type = type;
 303         key->user = user;
 304         key->quotalen = quotalen;
 305         key->datalen = type->def_datalen;
 306         key->uid = uid;
 307         key->gid = gid;
 308         key->perm = perm;
 309         key->flags = 0;
 310         key->expiry = 0;
 311         key->payload.data = NULL;
 312         key->security = NULL;
 313
 314         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA))
 315                 key->flags |= 1 << KEY_FLAG_IN_QUOTA;
 316
 317         memset(&key->type_data, 0, sizeof(key->type_data));
 318
 319 #ifdef KEY_DEBUGGING
 320         key->magic = KEY_DEBUG_MAGIC;
 321 #endif
 322
 323         /* let the security module know about the key */
 324         ret = security_key_alloc(key, ctx, flags);
 325         if (ret < 0)
 326                 goto security_error;
 327
 328         /* publish the key by giving it a serial number */
 329         atomic_inc(&user->nkeys);
 330         key_alloc_serial(key);
 331
 332 error:
 333         return key;
 334
 335 security_error:
 336         kfree(key->description);
 337         kmem_cache_free(key_jar, key);
 338         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 339                 spin_lock(&user->lock);
 340                 user->qnkeys--;
 341                 user->qnbytes -= quotalen;
 342                 spin_unlock(&user->lock);
 343         }
 344         key_user_put(user);
 345         key = ERR_PTR(ret);
 346         goto error;
 347
 348 no_memory_3:
 349         kmem_cache_free(key_jar, key);
 350 no_memory_2:
 351         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 352                 spin_lock(&user->lock);
 353                 user->qnkeys--;
 354                 user->qnbytes -= quotalen;
 355                 spin_unlock(&user->lock);
 356         }
 357         key_user_put(user);
 358 no_memory_1:
 359         key = ERR_PTR(-ENOMEM);
 360         goto error;
 361
 362 no_quota:
 363         spin_unlock(&user->lock);
 364         key_user_put(user);
 365         key = ERR_PTR(-EDQUOT);
 366         goto error;
 367
 368 } /* end key_alloc() */
 369
 370 EXPORT_SYMBOL(key_alloc);
 371
 372 /*****************************************************************************/
 373 /*
 374  * reserve an amount of quota for the key's payload
 375  */
 376 int key_payload_reserve(struct key *key, size_t datalen)
 377 {
 378         int delta = (int) datalen - key->datalen;
 379         int ret = 0;
 380
 381         key_check(key);
 382
 383         /* contemplate the quota adjustment */
 384         if (delta != 0 && test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
 385                 spin_lock(&key->user->lock);
 386
 387                 if (delta > 0 &&
 388                     key->user->qnbytes + delta > KEYQUOTA_MAX_BYTES
 389                     ) {
 390                         ret = -EDQUOT;
 391                 }
 392                 else {
 393                         key->user->qnbytes += delta;
 394                         key->quotalen += delta;
 395                 }
 396                 spin_unlock(&key->user->lock);
 397         }
 398
 399         /* change the recorded data length if that didn't generate an error */
 400         if (ret == 0)
 401                 key->datalen = datalen;
 402
 403         return ret;
 404
 405 } /* end key_payload_reserve() */
 406
 407 EXPORT_SYMBOL(key_payload_reserve);
 408
 409 /*****************************************************************************/
 410 /*
 411  * instantiate a key and link it into the target keyring atomically
 412  * - called with the target keyring's semaphore writelocked
 413  */
 414 static int __key_instantiate_and_link(struct key *key,
 415                                       const void *data,
 416                                       size_t datalen,
 417                                       struct key *keyring,
 418                                       struct key *instkey)
 419 {
 420         int ret, awaken;
 421
 422         key_check(key);
 423         key_check(keyring);
 424
 425         awaken = 0;
 426         ret = -EBUSY;
 427
 428         down_write(&key_construction_sem);
 429
 430         /* can't instantiate twice */
 431         if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
 432                 /* instantiate the key */
 433                 ret = key->type->instantiate(key, data, datalen);
 434
 435                 if (ret == 0) {
 436                         /* mark the key as being instantiated */
 437                         atomic_inc(&key->user->nikeys);
 438                         set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
 439
 440                         if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
 441                                 awaken = 1;
 442
 443                         /* and link it into the destination keyring */
 444                         if (keyring)
 445                                 ret = __key_link(keyring, key);
 446
 447                         /* disable the authorisation key */
 448                         if (instkey)
 449                                 key_revoke(instkey);
 450                 }
 451         }
 452
 453         up_write(&key_construction_sem);
 454
 455         /* wake up anyone waiting for a key to be constructed */
 456         if (awaken)
 457                 wake_up_all(&request_key_conswq);
 458
 459         return ret;
 460
 461 } /* end __key_instantiate_and_link() */
 462
 463 /*****************************************************************************/
 464 /*
 465  * instantiate a key and link it into the target keyring atomically
 466  */
 467 int key_instantiate_and_link(struct key *key,
 468                              const void *data,
 469                              size_t datalen,
 470                              struct key *keyring,
 471                              struct key *instkey)
 472 {
 473         int ret;
 474
 475         if (keyring)
 476                 down_write(&keyring->sem);
 477
 478         ret = __key_instantiate_and_link(key, data, datalen, keyring, instkey);
 479
 480         if (keyring)
 481                 up_write(&keyring->sem);
 482
 483         return ret;
 484
 485 } /* end key_instantiate_and_link() */
 486
 487 EXPORT_SYMBOL(key_instantiate_and_link);
 488
 489 /*****************************************************************************/
 490 /*
 491  * negatively instantiate a key and link it into the target keyring atomically
 492  */
 493 int key_negate_and_link(struct key *key,
 494                         unsigned timeout,
 495                         struct key *keyring,
 496                         struct key *instkey)
 497 {
 498         struct timespec now;
 499         int ret, awaken;
 500
 501         key_check(key);
 502         key_check(keyring);
 503
 504         awaken = 0;
 505         ret = -EBUSY;
 506
 507         if (keyring)
 508                 down_write(&keyring->sem);
 509
 510         down_write(&key_construction_sem);
 511
 512         /* can't instantiate twice */
 513         if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
 514                 /* mark the key as being negatively instantiated */
 515                 atomic_inc(&key->user->nikeys);
 516                 set_bit(KEY_FLAG_NEGATIVE, &key->flags);
 517                 set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
 518                 now = current_kernel_time();
 519                 key->expiry = now.tv_sec + timeout;
 520
 521                 if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
 522                         awaken = 1;
 523
 524                 ret = 0;
 525
 526                 /* and link it into the destination keyring */
 527                 if (keyring)
 528                         ret = __key_link(keyring, key);
 529
 530                 /* disable the authorisation key */
 531                 if (instkey)
 532                         key_revoke(instkey);
 533         }
 534
 535         up_write(&key_construction_sem);
 536
 537         if (keyring)
 538                 up_write(&keyring->sem);
 539
 540         /* wake up anyone waiting for a key to be constructed */
 541         if (awaken)
 542                 wake_up_all(&request_key_conswq);
 543
 544         return ret;
 545
 546 } /* end key_negate_and_link() */
 547
 548 EXPORT_SYMBOL(key_negate_and_link);
 549
 550 /*****************************************************************************/
 551 /*
 552  * do cleaning up in process context so that we don't have to disable
 553  * interrupts all over the place
 554  */
 555 static void key_cleanup(struct work_struct *work)
 556 {
 557         struct rb_node *_n;
 558         struct key *key;
 559
 560  go_again:
 561         /* look for a dead key in the tree */
 562         spin_lock(&key_serial_lock);
 563
 564         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 565                 key = rb_entry(_n, struct key, serial_node);
 566
 567                 if (atomic_read(&key->usage) == 0)
 568                         goto found_dead_key;
 569         }
 570
 571         spin_unlock(&key_serial_lock);
 572         return;
 573
 574  found_dead_key:
 575         /* we found a dead key - once we've removed it from the tree, we can
 576          * drop the lock */
 577         rb_erase(&key->serial_node, &key_serial_tree);
 578         spin_unlock(&key_serial_lock);
 579
 580         key_check(key);
 581
 582         security_key_free(key);
 583
 584         /* deal with the user's key tracking and quota */
 585         if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
 586                 spin_lock(&key->user->lock);
 587                 key->user->qnkeys--;
 588                 key->user->qnbytes -= key->quotalen;
 589                 spin_unlock(&key->user->lock);
 590         }
 591
 592         atomic_dec(&key->user->nkeys);
 593         if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
 594                 atomic_dec(&key->user->nikeys);
 595
 596         key_user_put(key->user);
 597
 598         /* now throw away the key memory */
 599         if (key->type->destroy)
 600                 key->type->destroy(key);
 601
 602         kfree(key->description);
 603
 604 #ifdef KEY_DEBUGGING
 605         key->magic = KEY_DEBUG_MAGIC_X;
 606 #endif
 607         kmem_cache_free(key_jar, key);
 608
 609         /* there may, of course, be more than one key to destroy */
 610         goto go_again;
 611
 612 } /* end key_cleanup() */
 613
 614 /*****************************************************************************/
 615 /*
 616  * dispose of a reference to a key
 617  * - when all the references are gone, we schedule the cleanup task to come and
 618  *   pull it out of the tree in definite process context
 619  */
 620 void key_put(struct key *key)
 621 {
 622         if (key) {
 623                 key_check(key);
 624
 625                 if (atomic_dec_and_test(&key->usage))
 626                         schedule_work(&key_cleanup_task);
 627         }
 628
 629 } /* end key_put() */
 630
 631 EXPORT_SYMBOL(key_put);
 632
 633 /*****************************************************************************/
 634 /*
 635  * find a key by its serial number
 636  */
 637 struct key *key_lookup(key_serial_t id)
 638 {
 639         struct rb_node *n;
 640         struct key *key;
 641
 642         spin_lock(&key_serial_lock);
 643
 644         /* search the tree for the specified key */
 645         n = key_serial_tree.rb_node;
 646         while (n) {
 647                 key = rb_entry(n, struct key, serial_node);
 648
 649                 if (id < key->serial)
 650                         n = n->rb_left;
 651                 else if (id > key->serial)
 652                         n = n->rb_right;
 653                 else
 654                         goto found;
 655         }
 656
 657  not_found:
 658         key = ERR_PTR(-ENOKEY);
 659         goto error;
 660
 661  found:
 662         /* pretend it doesn't exist if it's dead */
 663         if (atomic_read(&key->usage) == 0 ||
 664             test_bit(KEY_FLAG_DEAD, &key->flags) ||
 665             key->type == &key_type_dead)
 666                 goto not_found;
 667
 668         /* this races with key_put(), but that doesn't matter since key_put()
 669          * doesn't actually change the key
 670          */
 671         atomic_inc(&key->usage);
 672
 673  error:
 674         spin_unlock(&key_serial_lock);
 675         return key;
 676
 677 } /* end key_lookup() */
 678
 679 /*****************************************************************************/
 680 /*
 681  * find and lock the specified key type against removal
 682  * - we return with the sem readlocked
 683  */
 684 struct key_type *key_type_lookup(const char *type)
 685 {
 686         struct key_type *ktype;
 687
 688         down_read(&key_types_sem);
 689
 690         /* look up the key type to see if it's one of the registered kernel
 691          * types */
 692         list_for_each_entry(ktype, &key_types_list, link) {
 693                 if (strcmp(ktype->name, type) == 0)
 694                         goto found_kernel_type;
 695         }
 696
 697         up_read(&key_types_sem);
 698         ktype = ERR_PTR(-ENOKEY);
 699
 700  found_kernel_type:
 701         return ktype;
 702
 703 } /* end key_type_lookup() */
 704
 705 /*****************************************************************************/
 706 /*
 707  * unlock a key type
 708  */
 709 void key_type_put(struct key_type *ktype)
 710 {
 711         up_read(&key_types_sem);
 712
 713 } /* end key_type_put() */
 714
 715 /*****************************************************************************/
 716 /*
 717  * attempt to update an existing key
 718  * - the key has an incremented refcount
 719  * - we need to put the key if we get an error
 720  */
 721 static inline key_ref_t __key_update(key_ref_t key_ref,
 722                                      const void *payload, size_t plen)
 723 {
 724         struct key *key = key_ref_to_ptr(key_ref);
 725         int ret;
 726
 727         /* need write permission on the key to update it */
 728         ret = key_permission(key_ref, KEY_WRITE);
 729         if (ret < 0)
 730                 goto error;
 731
 732         ret = -EEXIST;
 733         if (!key->type->update)
 734                 goto error;
 735
 736         down_write(&key->sem);
 737
 738         ret = key->type->update(key, payload, plen);
 739         if (ret == 0)
 740                 /* updating a negative key instantiates it */
 741                 clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
 742
 743         up_write(&key->sem);
 744
 745         if (ret < 0)
 746                 goto error;
 747 out:
 748         return key_ref;
 749
 750 error:
 751         key_put(key);
 752         key_ref = ERR_PTR(ret);
 753         goto out;
 754
 755 } /* end __key_update() */
 756
 757 /*****************************************************************************/
 758 /*
 759  * search the specified keyring for a key of the same description; if one is
 760  * found, update it, otherwise add a new one
 761  */
 762 key_ref_t key_create_or_update(key_ref_t keyring_ref,
 763                                const char *type,
 764                                const char *description,
 765                                const void *payload,
 766                                size_t plen,
 767                                unsigned long flags)
 768 {
 769         struct key_type *ktype;
 770         struct key *keyring, *key = NULL;
 771         key_perm_t perm;
 772         key_ref_t key_ref;
 773         int ret;
 774
 775         /* look up the key type to see if it's one of the registered kernel
 776          * types */
 777         ktype = key_type_lookup(type);
 778         if (IS_ERR(ktype)) {
 779                 key_ref = ERR_PTR(-ENODEV);
 780                 goto error;
 781         }
 782
 783         key_ref = ERR_PTR(-EINVAL);
 784         if (!ktype->match || !ktype->instantiate)
 785                 goto error_2;
 786
 787         keyring = key_ref_to_ptr(keyring_ref);
 788
 789         key_check(keyring);
 790
 791         key_ref = ERR_PTR(-ENOTDIR);
 792         if (keyring->type != &key_type_keyring)
 793                 goto error_2;
 794
 795         down_write(&keyring->sem);
 796
 797         /* if we're going to allocate a new key, we're going to have
 798          * to modify the keyring */
 799         ret = key_permission(keyring_ref, KEY_WRITE);
 800         if (ret < 0) {
 801                 key_ref = ERR_PTR(ret);
 802                 goto error_3;
 803         }
 804
 805         /* if it's possible to update this type of key, search for an existing
 806          * key of the same type and description in the destination keyring and
 807          * update that instead if possible
 808          */
 809         if (ktype->update) {
 810                 key_ref = __keyring_search_one(keyring_ref, ktype, description,
 811                                                0);
 812                 if (!IS_ERR(key_ref))
 813                         goto found_matching_key;
 814         }
 815
 816         /* decide on the permissions we want */
 817         perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
 818         perm |= KEY_USR_VIEW | KEY_USR_SEARCH | KEY_USR_LINK | KEY_USR_SETATTR;
 819
 820         if (ktype->read)
 821                 perm |= KEY_POS_READ | KEY_USR_READ;
 822
 823         if (ktype == &key_type_keyring || ktype->update)
 824                 perm |= KEY_USR_WRITE;
 825
 826         /* allocate a new key */
 827         key = key_alloc(ktype, description, current->fsuid, current->fsgid,
 828                         current, perm, flags);
 829         if (IS_ERR(key)) {
 830                 key_ref = ERR_PTR(PTR_ERR(key));
 831                 goto error_3;
 832         }
 833
 834         /* instantiate it and link it into the target keyring */
 835         ret = __key_instantiate_and_link(key, payload, plen, keyring, NULL);
 836         if (ret < 0) {
 837                 key_put(key);
 838                 key_ref = ERR_PTR(ret);
 839                 goto error_3;
 840         }
 841
 842         key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
 843
 844  error_3:
 845         up_write(&keyring->sem);
 846  error_2:
 847         key_type_put(ktype);
 848  error:
 849         return key_ref;
 850
 851  found_matching_key:
 852         /* we found a matching key, so we're going to try to update it
 853          * - we can drop the locks first as we have the key pinned
 854          */
 855         up_write(&keyring->sem);
 856         key_type_put(ktype);
 857
 858         key_ref = __key_update(key_ref, payload, plen);
 859         goto error;
 860
 861 } /* end key_create_or_update() */
 862
 863 EXPORT_SYMBOL(key_create_or_update);
 864
 865 /*****************************************************************************/
 866 /*
 867  * update a key
 868  */
 869 int key_update(key_ref_t key_ref, const void *payload, size_t plen)
 870 {
 871         struct key *key = key_ref_to_ptr(key_ref);
 872         int ret;
 873
 874         key_check(key);
 875
 876         /* the key must be writable */
 877         ret = key_permission(key_ref, KEY_WRITE);
 878         if (ret < 0)
 879                 goto error;
 880
 881         /* attempt to update it if supported */
 882         ret = -EOPNOTSUPP;
 883         if (key->type->update) {
 884                 down_write(&key->sem);
 885
 886                 ret = key->type->update(key, payload, plen);
 887                 if (ret == 0)
 888                         /* updating a negative key instantiates it */
 889                         clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
 890
 891                 up_write(&key->sem);
 892         }
 893
 894  error:
 895         return ret;
 896
 897 } /* end key_update() */
 898
 899 EXPORT_SYMBOL(key_update);
 900
 901 /*****************************************************************************/
 902 /*
 903  * revoke a key
 904  */
 905 void key_revoke(struct key *key)
 906 {
 907         key_check(key);
 908
 909         /* make sure no one's trying to change or use the key when we mark
 910          * it */
 911         down_write(&key->sem);
 912         set_bit(KEY_FLAG_REVOKED, &key->flags);
 913
 914         if (key->type->revoke)
 915                 key->type->revoke(key);
 916
 917         up_write(&key->sem);
 918
 919 } /* end key_revoke() */
 920
 921 EXPORT_SYMBOL(key_revoke);
 922
 923 /*****************************************************************************/
 924 /*
 925  * register a type of key
 926  */
 927 int register_key_type(struct key_type *ktype)
 928 {
 929         struct key_type *p;
 930         int ret;
 931
 932         ret = -EEXIST;
 933         down_write(&key_types_sem);
 934
 935         /* disallow key types with the same name */
 936         list_for_each_entry(p, &key_types_list, link) {
 937                 if (strcmp(p->name, ktype->name) == 0)
 938                         goto out;
 939         }
 940
 941         /* store the type */
 942         list_add(&ktype->link, &key_types_list);
 943         ret = 0;
 944
 945  out:
 946         up_write(&key_types_sem);
 947         return ret;
 948
 949 } /* end register_key_type() */
 950
 951 EXPORT_SYMBOL(register_key_type);
 952
 953 /*****************************************************************************/
 954 /*
 955  * unregister a type of key
 956  */
 957 void unregister_key_type(struct key_type *ktype)
 958 {
 959         struct rb_node *_n;
 960         struct key *key;
 961
 962         down_write(&key_types_sem);
 963
 964         /* withdraw the key type */
 965         list_del_init(&ktype->link);
 966
 967         /* mark all the keys of this type dead */
 968         spin_lock(&key_serial_lock);
 969
 970         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 971                 key = rb_entry(_n, struct key, serial_node);
 972
 973                 if (key->type == ktype)
 974                         key->type = &key_type_dead;
 975         }
 976
 977         spin_unlock(&key_serial_lock);
 978
 979         /* make sure everyone revalidates their keys */
 980         synchronize_rcu();
 981
 982         /* we should now be able to destroy the payloads of all the keys of
 983          * this type with impunity */
 984         spin_lock(&key_serial_lock);
 985
 986         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 987                 key = rb_entry(_n, struct key, serial_node);
 988
 989                 if (key->type == ktype) {
 990                         if (ktype->destroy)
 991                                 ktype->destroy(key);
 992                         memset(&key->payload, KEY_DESTROY, sizeof(key->payload));
 993                 }
 994         }
 995
 996         spin_unlock(&key_serial_lock);
 997         up_write(&key_types_sem);
 998
 999 } /* end unregister_key_type() */
1000
1001 EXPORT_SYMBOL(unregister_key_type);
1002
1003 /*****************************************************************************/
1004 /*
1005  * initialise the key management stuff
1006  */
1007 void __init key_init(void)
1008 {
1009         /* allocate a slab in which we can store keys */
1010         key_jar = kmem_cache_create("key_jar", sizeof(struct key),
1011                         0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1012
1013         /* add the special key types */
1014         list_add_tail(&key_type_keyring.link, &key_types_list);
1015         list_add_tail(&key_type_dead.link, &key_types_list);
1016         list_add_tail(&key_type_user.link, &key_types_list);
1017
1018         /* record the root user tracking */
1019         rb_link_node(&root_key_user.node,
1020                      NULL,
1021                      &key_user_tree.rb_node);
1022
1023         rb_insert_color(&root_key_user.node,
1024                         &key_user_tree);
1025
1026         /* record root's user standard keyrings */
1027         key_check(&root_user_keyring);
1028         key_check(&root_session_keyring);
1029
1030         __key_insert_serial(&root_user_keyring);
1031         __key_insert_serial(&root_session_keyring);
1032
1033         keyring_publish_name(&root_user_keyring);
1034         keyring_publish_name(&root_session_keyring);
1035
1036         /* link the two root keyrings together */
1037         key_link(&root_session_keyring, &root_user_keyring);
1038
1039 } /* end key_init() */