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