security/keys/key.c

   1 /* key.c: basic authentication token and access key management
   2  *
   3  * Copyright (C) 2004 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/sched.h>
  15 #include <linux/slab.h>
  16 #include <linux/security.h>
  17 #include <linux/workqueue.h>
  18 #include <linux/err.h>
  19 #include "internal.h"
  20
  21 static kmem_cache_t     *key_jar;
  22 static key_serial_t     key_serial_next = 3;
  23 struct rb_root          key_serial_tree; /* tree of keys indexed by serial */
  24 DEFINE_SPINLOCK(key_serial_lock);
  25
  26 struct rb_root  key_user_tree; /* tree of quota records indexed by UID */
  27 DEFINE_SPINLOCK(key_user_lock);
  28
  29 static LIST_HEAD(key_types_list);
  30 static DECLARE_RWSEM(key_types_sem);
  31
  32 static void key_cleanup(void *data);
  33 static DECLARE_WORK(key_cleanup_task, key_cleanup, NULL);
  34
  35 /* we serialise key instantiation and link */
  36 DECLARE_RWSEM(key_construction_sem);
  37
  38 /* any key who's type gets unegistered will be re-typed to this */
  39 struct key_type key_type_dead = {
  40         .name           = "dead",
  41 };
  42
  43 #ifdef KEY_DEBUGGING
  44 void __key_check(const struct key *key)
  45 {
  46         printk("__key_check: key %p {%08x} should be {%08x}\n",
  47                key, key->magic, KEY_DEBUG_MAGIC);
  48         BUG();
  49 }
  50 #endif
  51
  52 /*****************************************************************************/
  53 /*
  54  * get the key quota record for a user, allocating a new record if one doesn't
  55  * already exist
  56  */
  57 struct key_user *key_user_lookup(uid_t uid)
  58 {
  59         struct key_user *candidate = NULL, *user;
  60         struct rb_node *parent = NULL;
  61         struct rb_node **p;
  62
  63  try_again:
  64         p = &key_user_tree.rb_node;
  65         spin_lock(&key_user_lock);
  66
  67         /* search the tree for a user record with a matching UID */
  68         while (*p) {
  69                 parent = *p;
  70                 user = rb_entry(parent, struct key_user, node);
  71
  72                 if (uid < user->uid)
  73                         p = &(*p)->rb_left;
  74                 else if (uid > user->uid)
  75                         p = &(*p)->rb_right;
  76                 else
  77                         goto found;
  78         }
  79
  80         /* if we get here, we failed to find a match in the tree */
  81         if (!candidate) {
  82                 /* allocate a candidate user record if we don't already have
  83                  * one */
  84                 spin_unlock(&key_user_lock);
  85
  86                 user = NULL;
  87                 candidate = kmalloc(sizeof(struct key_user), GFP_KERNEL);
  88                 if (unlikely(!candidate))
  89                         goto out;
  90
  91                 /* the allocation may have scheduled, so we need to repeat the
  92                  * search lest someone else added the record whilst we were
  93                  * asleep */
  94                 goto try_again;
  95         }
  96
  97         /* if we get here, then the user record still hadn't appeared on the
  98          * second pass - so we use the candidate record */
  99         atomic_set(&candidate->usage, 1);
 100         atomic_set(&candidate->nkeys, 0);
 101         atomic_set(&candidate->nikeys, 0);
 102         candidate->uid = uid;
 103         candidate->qnkeys = 0;
 104         candidate->qnbytes = 0;
 105         spin_lock_init(&candidate->lock);
 106         INIT_LIST_HEAD(&candidate->consq);
 107
 108         rb_link_node(&candidate->node, parent, p);
 109         rb_insert_color(&candidate->node, &key_user_tree);
 110         spin_unlock(&key_user_lock);
 111         user = candidate;
 112         goto out;
 113
 114         /* okay - we found a user record for this UID */
 115  found:
 116         atomic_inc(&user->usage);
 117         spin_unlock(&key_user_lock);
 118         if (candidate)
 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  * - we work through all the serial numbers between 2 and 2^31-1 in turn and
 174  *   then wrap
 175  */
 176 static inline void key_alloc_serial(struct key *key)
 177 {
 178         struct rb_node *parent, **p;
 179         struct key *xkey;
 180
 181         spin_lock(&key_serial_lock);
 182
 183         /* propose a likely serial number and look for a hole for it in the
 184          * serial number tree */
 185         key->serial = key_serial_next;
 186         if (key->serial < 3)
 187                 key->serial = 3;
 188         key_serial_next = key->serial + 1;
 189
 190         parent = NULL;
 191         p = &key_serial_tree.rb_node;
 192
 193         while (*p) {
 194                 parent = *p;
 195                 xkey = rb_entry(parent, struct key, serial_node);
 196
 197                 if (key->serial < xkey->serial)
 198                         p = &(*p)->rb_left;
 199                 else if (key->serial > xkey->serial)
 200                         p = &(*p)->rb_right;
 201                 else
 202                         goto serial_exists;
 203         }
 204         goto insert_here;
 205
 206         /* we found a key with the proposed serial number - walk the tree from
 207          * that point looking for the next unused serial number */
 208  serial_exists:
 209         for (;;) {
 210                 key->serial = key_serial_next;
 211                 if (key->serial < 2)
 212                         key->serial = 2;
 213                 key_serial_next = key->serial + 1;
 214
 215                 if (!parent->rb_parent)
 216                         p = &key_serial_tree.rb_node;
 217                 else if (parent->rb_parent->rb_left == parent)
 218                         p = &parent->rb_parent->rb_left;
 219                 else
 220                         p = &parent->rb_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 either
 245  *   key_create_or_update() or by key_duplicate(); this prevents unregistration
 246  *   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, key_perm_t perm,
 252                       int not_in_quota)
 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 (!not_in_quota) {
 274                 spin_lock(&user->lock);
 275                 if (user->qnkeys + 1 >= KEYQUOTA_MAX_KEYS &&
 276                     user->qnbytes + quotalen >= KEYQUOTA_MAX_BYTES
 277                     )
 278                         goto no_quota;
 279
 280                 user->qnkeys++;
 281                 user->qnbytes += quotalen;
 282                 spin_unlock(&user->lock);
 283         }
 284
 285         /* allocate and initialise the key and its description */
 286         key = kmem_cache_alloc(key_jar, SLAB_KERNEL);
 287         if (!key)
 288                 goto no_memory_2;
 289
 290         if (desc) {
 291                 key->description = kmalloc(desclen, GFP_KERNEL);
 292                 if (!key->description)
 293                         goto no_memory_3;
 294
 295                 memcpy(key->description, desc, desclen);
 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 (!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);
 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 (!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 (!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(void *data)
 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                                int not_in_quota)
 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         down_write(&keyring->sem);
 790
 791         /* if we're going to allocate a new key, we're going to have
 792          * to modify the keyring */
 793         ret = key_permission(keyring_ref, KEY_WRITE);
 794         if (ret < 0) {
 795                 key_ref = ERR_PTR(ret);
 796                 goto error_3;
 797         }
 798
 799         /* search for an existing key of the same type and description in the
 800          * destination keyring
 801          */
 802         key_ref = __keyring_search_one(keyring_ref, ktype, description, 0);
 803         if (!IS_ERR(key_ref))
 804                 goto found_matching_key;
 805
 806         /* decide on the permissions we want */
 807         perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
 808         perm |= KEY_USR_VIEW | KEY_USR_SEARCH | KEY_USR_LINK | KEY_USR_SETATTR;
 809
 810         if (ktype->read)
 811                 perm |= KEY_POS_READ | KEY_USR_READ;
 812
 813         if (ktype == &key_type_keyring || ktype->update)
 814                 perm |= KEY_USR_WRITE;
 815
 816         /* allocate a new key */
 817         key = key_alloc(ktype, description, current->fsuid, current->fsgid,
 818                         perm, not_in_quota);
 819         if (IS_ERR(key)) {
 820                 key_ref = ERR_PTR(PTR_ERR(key));
 821                 goto error_3;
 822         }
 823
 824         /* instantiate it and link it into the target keyring */
 825         ret = __key_instantiate_and_link(key, payload, plen, keyring, NULL);
 826         if (ret < 0) {
 827                 key_put(key);
 828                 key_ref = ERR_PTR(ret);
 829                 goto error_3;
 830         }
 831
 832         key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
 833
 834  error_3:
 835         up_write(&keyring->sem);
 836  error_2:
 837         key_type_put(ktype);
 838  error:
 839         return key_ref;
 840
 841  found_matching_key:
 842         /* we found a matching key, so we're going to try to update it
 843          * - we can drop the locks first as we have the key pinned
 844          */
 845         up_write(&keyring->sem);
 846         key_type_put(ktype);
 847
 848         key_ref = __key_update(key_ref, payload, plen);
 849         goto error;
 850
 851 } /* end key_create_or_update() */
 852
 853 EXPORT_SYMBOL(key_create_or_update);
 854
 855 /*****************************************************************************/
 856 /*
 857  * update a key
 858  */
 859 int key_update(key_ref_t key_ref, const void *payload, size_t plen)
 860 {
 861         struct key *key = key_ref_to_ptr(key_ref);
 862         int ret;
 863
 864         key_check(key);
 865
 866         /* the key must be writable */
 867         ret = key_permission(key_ref, KEY_WRITE);
 868         if (ret < 0)
 869                 goto error;
 870
 871         /* attempt to update it if supported */
 872         ret = -EOPNOTSUPP;
 873         if (key->type->update) {
 874                 down_write(&key->sem);
 875
 876                 ret = key->type->update(key, payload, plen);
 877                 if (ret == 0)
 878                         /* updating a negative key instantiates it */
 879                         clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
 880
 881                 up_write(&key->sem);
 882         }
 883
 884  error:
 885         return ret;
 886
 887 } /* end key_update() */
 888
 889 EXPORT_SYMBOL(key_update);
 890
 891 /*****************************************************************************/
 892 /*
 893  * duplicate a key, potentially with a revised description
 894  * - must be supported by the keytype (keyrings for instance can be duplicated)
 895  */
 896 struct key *key_duplicate(struct key *source, const char *desc)
 897 {
 898         struct key *key;
 899         int ret;
 900
 901         key_check(source);
 902
 903         if (!desc)
 904                 desc = source->description;
 905
 906         down_read(&key_types_sem);
 907
 908         ret = -EINVAL;
 909         if (!source->type->duplicate)
 910                 goto error;
 911
 912         /* allocate and instantiate a key */
 913         key = key_alloc(source->type, desc, current->fsuid, current->fsgid,
 914                         source->perm, 0);
 915         if (IS_ERR(key))
 916                 goto error_k;
 917
 918         down_read(&source->sem);
 919         ret = key->type->duplicate(key, source);
 920         up_read(&source->sem);
 921         if (ret < 0)
 922                 goto error2;
 923
 924         atomic_inc(&key->user->nikeys);
 925         set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
 926
 927  error_k:
 928         up_read(&key_types_sem);
 929  out:
 930         return key;
 931
 932  error2:
 933         key_put(key);
 934  error:
 935         up_read(&key_types_sem);
 936         key = ERR_PTR(ret);
 937         goto out;
 938
 939 } /* end key_duplicate() */
 940
 941 /*****************************************************************************/
 942 /*
 943  * revoke a key
 944  */
 945 void key_revoke(struct key *key)
 946 {
 947         key_check(key);
 948
 949         /* make sure no one's trying to change or use the key when we mark
 950          * it */
 951         down_write(&key->sem);
 952         set_bit(KEY_FLAG_REVOKED, &key->flags);
 953         up_write(&key->sem);
 954
 955 } /* end key_revoke() */
 956
 957 EXPORT_SYMBOL(key_revoke);
 958
 959 /*****************************************************************************/
 960 /*
 961  * register a type of key
 962  */
 963 int register_key_type(struct key_type *ktype)
 964 {
 965         struct key_type *p;
 966         int ret;
 967
 968         ret = -EEXIST;
 969         down_write(&key_types_sem);
 970
 971         /* disallow key types with the same name */
 972         list_for_each_entry(p, &key_types_list, link) {
 973                 if (strcmp(p->name, ktype->name) == 0)
 974                         goto out;
 975         }
 976
 977         /* store the type */
 978         list_add(&ktype->link, &key_types_list);
 979         ret = 0;
 980
 981  out:
 982         up_write(&key_types_sem);
 983         return ret;
 984
 985 } /* end register_key_type() */
 986
 987 EXPORT_SYMBOL(register_key_type);
 988
 989 /*****************************************************************************/
 990 /*
 991  * unregister a type of key
 992  */
 993 void unregister_key_type(struct key_type *ktype)
 994 {
 995         struct rb_node *_n;
 996         struct key *key;
 997
 998         down_write(&key_types_sem);
 999
1000         /* withdraw the key type */
1001         list_del_init(&ktype->link);
1002
1003         /* mark all the keys of this type dead */
1004         spin_lock(&key_serial_lock);
1005
1006         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
1007                 key = rb_entry(_n, struct key, serial_node);
1008
1009                 if (key->type == ktype)
1010                         key->type = &key_type_dead;
1011         }
1012
1013         spin_unlock(&key_serial_lock);
1014
1015         /* make sure everyone revalidates their keys */
1016         synchronize_rcu();
1017
1018         /* we should now be able to destroy the payloads of all the keys of
1019          * this type with impunity */
1020         spin_lock(&key_serial_lock);
1021
1022         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
1023                 key = rb_entry(_n, struct key, serial_node);
1024
1025                 if (key->type == ktype) {
1026                         if (ktype->destroy)
1027                                 ktype->destroy(key);
1028                         memset(&key->payload, 0xbd, sizeof(key->payload));
1029                 }
1030         }
1031
1032         spin_unlock(&key_serial_lock);
1033         up_write(&key_types_sem);
1034
1035 } /* end unregister_key_type() */
1036
1037 EXPORT_SYMBOL(unregister_key_type);
1038
1039 /*****************************************************************************/
1040 /*
1041  * initialise the key management stuff
1042  */
1043 void __init key_init(void)
1044 {
1045         /* allocate a slab in which we can store keys */
1046         key_jar = kmem_cache_create("key_jar", sizeof(struct key),
1047                         0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1048
1049         /* add the special key types */
1050         list_add_tail(&key_type_keyring.link, &key_types_list);
1051         list_add_tail(&key_type_dead.link, &key_types_list);
1052         list_add_tail(&key_type_user.link, &key_types_list);
1053
1054         /* record the root user tracking */
1055         rb_link_node(&root_key_user.node,
1056                      NULL,
1057                      &key_user_tree.rb_node);
1058
1059         rb_insert_color(&root_key_user.node,
1060                         &key_user_tree);
1061
1062         /* record root's user standard keyrings */
1063         key_check(&root_user_keyring);
1064         key_check(&root_session_keyring);
1065
1066         __key_insert_serial(&root_user_keyring);
1067         __key_insert_serial(&root_session_keyring);
1068
1069         keyring_publish_name(&root_user_keyring);
1070         keyring_publish_name(&root_session_keyring);
1071
1072         /* link the two root keyrings together */
1073         key_link(&root_session_keyring, &root_user_keyring);
1074
1075 } /* end key_init() */