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/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 static 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         kfree(candidate);
 119  out:
 120         return user;
 121
 122 } /* end key_user_lookup() */
 123
 124 /*****************************************************************************/
 125 /*
 126  * dispose of a user structure
 127  */
 128 void key_user_put(struct key_user *user)
 129 {
 130         if (atomic_dec_and_lock(&user->usage, &key_user_lock)) {
 131                 rb_erase(&user->node, &key_user_tree);
 132                 spin_unlock(&key_user_lock);
 133
 134                 kfree(user);
 135         }
 136
 137 } /* end key_user_put() */
 138
 139 /*****************************************************************************/
 140 /*
 141  * insert a key with a fixed serial number
 142  */
 143 static void __init __key_insert_serial(struct key *key)
 144 {
 145         struct rb_node *parent, **p;
 146         struct key *xkey;
 147
 148         parent = NULL;
 149         p = &key_serial_tree.rb_node;
 150
 151         while (*p) {
 152                 parent = *p;
 153                 xkey = rb_entry(parent, struct key, serial_node);
 154
 155                 if (key->serial < xkey->serial)
 156                         p = &(*p)->rb_left;
 157                 else if (key->serial > xkey->serial)
 158                         p = &(*p)->rb_right;
 159                 else
 160                         BUG();
 161         }
 162
 163         /* we've found a suitable hole - arrange for this key to occupy it */
 164         rb_link_node(&key->serial_node, parent, p);
 165         rb_insert_color(&key->serial_node, &key_serial_tree);
 166
 167 } /* end __key_insert_serial() */
 168
 169 /*****************************************************************************/
 170 /*
 171  * assign a key the next unique serial number
 172  * - we work through all the serial numbers between 2 and 2^31-1 in turn and
 173  *   then wrap
 174  */
 175 static inline void key_alloc_serial(struct key *key)
 176 {
 177         struct rb_node *parent, **p;
 178         struct key *xkey;
 179
 180         spin_lock(&key_serial_lock);
 181
 182         /* propose a likely serial number and look for a hole for it in the
 183          * serial number tree */
 184         key->serial = key_serial_next;
 185         if (key->serial < 3)
 186                 key->serial = 3;
 187         key_serial_next = key->serial + 1;
 188
 189         parent = NULL;
 190         p = &key_serial_tree.rb_node;
 191
 192         while (*p) {
 193                 parent = *p;
 194                 xkey = rb_entry(parent, struct key, serial_node);
 195
 196                 if (key->serial < xkey->serial)
 197                         p = &(*p)->rb_left;
 198                 else if (key->serial > xkey->serial)
 199                         p = &(*p)->rb_right;
 200                 else
 201                         goto serial_exists;
 202         }
 203         goto insert_here;
 204
 205         /* we found a key with the proposed serial number - walk the tree from
 206          * that point looking for the next unused serial number */
 207  serial_exists:
 208         for (;;) {
 209                 key->serial = key_serial_next;
 210                 if (key->serial < 2)
 211                         key->serial = 2;
 212                 key_serial_next = key->serial + 1;
 213
 214                 if (!rb_parent(parent))
 215                         p = &key_serial_tree.rb_node;
 216                 else if (rb_parent(parent)->rb_left == parent)
 217                         p = &(rb_parent(parent)->rb_left);
 218                 else
 219                         p = &(rb_parent(parent)->rb_right);
 220
 221                 parent = rb_next(parent);
 222                 if (!parent)
 223                         break;
 224
 225                 xkey = rb_entry(parent, struct key, serial_node);
 226                 if (key->serial < xkey->serial)
 227                         goto insert_here;
 228         }
 229
 230         /* we've found a suitable hole - arrange for this key to occupy it */
 231  insert_here:
 232         rb_link_node(&key->serial_node, parent, p);
 233         rb_insert_color(&key->serial_node, &key_serial_tree);
 234
 235         spin_unlock(&key_serial_lock);
 236
 237 } /* end key_alloc_serial() */
 238
 239 /*****************************************************************************/
 240 /*
 241  * allocate a key of the specified type
 242  * - update the user's quota to reflect the existence of the key
 243  * - called from a key-type operation with key_types_sem read-locked by
 244  *   key_create_or_update()
 245  *   - this prevents unregistration of the key type
 246  * - upon return the key is as yet uninstantiated; the caller needs to either
 247  *   instantiate the key or discard it before returning
 248  */
 249 struct key *key_alloc(struct key_type *type, const char *desc,
 250                       uid_t uid, gid_t gid, struct task_struct *ctx,
 251                       key_perm_t perm, unsigned long flags)
 252 {
 253         struct key_user *user = NULL;
 254         struct key *key;
 255         size_t desclen, quotalen;
 256         int ret;
 257
 258         key = ERR_PTR(-EINVAL);
 259         if (!desc || !*desc)
 260                 goto error;
 261
 262         desclen = strlen(desc) + 1;
 263         quotalen = desclen + type->def_datalen;
 264
 265         /* get hold of the key tracking for this user */
 266         user = key_user_lookup(uid);
 267         if (!user)
 268                 goto no_memory_1;
 269
 270         /* check that the user's quota permits allocation of another key and
 271          * its description */
 272         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 273                 spin_lock(&user->lock);
 274                 if (!(flags & KEY_ALLOC_QUOTA_OVERRUN)) {
 275                         if (user->qnkeys + 1 >= KEYQUOTA_MAX_KEYS ||
 276                             user->qnbytes + quotalen >= KEYQUOTA_MAX_BYTES
 277                             )
 278                                 goto no_quota;
 279                 }
 280
 281                 user->qnkeys++;
 282                 user->qnbytes += quotalen;
 283                 spin_unlock(&user->lock);
 284         }
 285
 286         /* allocate and initialise the key and its description */
 287         key = kmem_cache_alloc(key_jar, SLAB_KERNEL);
 288         if (!key)
 289                 goto no_memory_2;
 290
 291         if (desc) {
 292                 key->description = kmalloc(desclen, GFP_KERNEL);
 293                 if (!key->description)
 294                         goto no_memory_3;
 295
 296                 memcpy(key->description, desc, desclen);
 297         }
 298
 299         atomic_set(&key->usage, 1);
 300         init_rwsem(&key->sem);
 301         key->type = type;
 302         key->user = user;
 303         key->quotalen = quotalen;
 304         key->datalen = type->def_datalen;
 305         key->uid = uid;
 306         key->gid = gid;
 307         key->perm = perm;
 308         key->flags = 0;
 309         key->expiry = 0;
 310         key->payload.data = NULL;
 311         key->security = NULL;
 312
 313         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA))
 314                 key->flags |= 1 << KEY_FLAG_IN_QUOTA;
 315
 316         memset(&key->type_data, 0, sizeof(key->type_data));
 317
 318 #ifdef KEY_DEBUGGING
 319         key->magic = KEY_DEBUG_MAGIC;
 320 #endif
 321
 322         /* let the security module know about the key */
 323         ret = security_key_alloc(key, ctx, flags);
 324         if (ret < 0)
 325                 goto security_error;
 326
 327         /* publish the key by giving it a serial number */
 328         atomic_inc(&user->nkeys);
 329         key_alloc_serial(key);
 330
 331 error:
 332         return key;
 333
 334 security_error:
 335         kfree(key->description);
 336         kmem_cache_free(key_jar, key);
 337         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 338                 spin_lock(&user->lock);
 339                 user->qnkeys--;
 340                 user->qnbytes -= quotalen;
 341                 spin_unlock(&user->lock);
 342         }
 343         key_user_put(user);
 344         key = ERR_PTR(ret);
 345         goto error;
 346
 347 no_memory_3:
 348         kmem_cache_free(key_jar, key);
 349 no_memory_2:
 350         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 351                 spin_lock(&user->lock);
 352                 user->qnkeys--;
 353                 user->qnbytes -= quotalen;
 354                 spin_unlock(&user->lock);
 355         }
 356         key_user_put(user);
 357 no_memory_1:
 358         key = ERR_PTR(-ENOMEM);
 359         goto error;
 360
 361 no_quota:
 362         spin_unlock(&user->lock);
 363         key_user_put(user);
 364         key = ERR_PTR(-EDQUOT);
 365         goto error;
 366
 367 } /* end key_alloc() */
 368
 369 EXPORT_SYMBOL(key_alloc);
 370
 371 /*****************************************************************************/
 372 /*
 373  * reserve an amount of quota for the key's payload
 374  */
 375 int key_payload_reserve(struct key *key, size_t datalen)
 376 {
 377         int delta = (int) datalen - key->datalen;
 378         int ret = 0;
 379
 380         key_check(key);
 381
 382         /* contemplate the quota adjustment */
 383         if (delta != 0 && test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
 384                 spin_lock(&key->user->lock);
 385
 386                 if (delta > 0 &&
 387                     key->user->qnbytes + delta > KEYQUOTA_MAX_BYTES
 388                     ) {
 389                         ret = -EDQUOT;
 390                 }
 391                 else {
 392                         key->user->qnbytes += delta;
 393                         key->quotalen += delta;
 394                 }
 395                 spin_unlock(&key->user->lock);
 396         }
 397
 398         /* change the recorded data length if that didn't generate an error */
 399         if (ret == 0)
 400                 key->datalen = datalen;
 401
 402         return ret;
 403
 404 } /* end key_payload_reserve() */
 405
 406 EXPORT_SYMBOL(key_payload_reserve);
 407
 408 /*****************************************************************************/
 409 /*
 410  * instantiate a key and link it into the target keyring atomically
 411  * - called with the target keyring's semaphore writelocked
 412  */
 413 static int __key_instantiate_and_link(struct key *key,
 414                                       const void *data,
 415                                       size_t datalen,
 416                                       struct key *keyring,
 417                                       struct key *instkey)
 418 {
 419         int ret, awaken;
 420
 421         key_check(key);
 422         key_check(keyring);
 423
 424         awaken = 0;
 425         ret = -EBUSY;
 426
 427         down_write(&key_construction_sem);
 428
 429         /* can't instantiate twice */
 430         if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
 431                 /* instantiate the key */
 432                 ret = key->type->instantiate(key, data, datalen);
 433
 434                 if (ret == 0) {
 435                         /* mark the key as being instantiated */
 436                         atomic_inc(&key->user->nikeys);
 437                         set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
 438
 439                         if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
 440                                 awaken = 1;
 441
 442                         /* and link it into the destination keyring */
 443                         if (keyring)
 444                                 ret = __key_link(keyring, key);
 445
 446                         /* disable the authorisation key */
 447                         if (instkey)
 448                                 key_revoke(instkey);
 449                 }
 450         }
 451
 452         up_write(&key_construction_sem);
 453
 454         /* wake up anyone waiting for a key to be constructed */
 455         if (awaken)
 456                 wake_up_all(&request_key_conswq);
 457
 458         return ret;
 459
 460 } /* end __key_instantiate_and_link() */
 461
 462 /*****************************************************************************/
 463 /*
 464  * instantiate a key and link it into the target keyring atomically
 465  */
 466 int key_instantiate_and_link(struct key *key,
 467                              const void *data,
 468                              size_t datalen,
 469                              struct key *keyring,
 470                              struct key *instkey)
 471 {
 472         int ret;
 473
 474         if (keyring)
 475                 down_write(&keyring->sem);
 476
 477         ret = __key_instantiate_and_link(key, data, datalen, keyring, instkey);
 478
 479         if (keyring)
 480                 up_write(&keyring->sem);
 481
 482         return ret;
 483
 484 } /* end key_instantiate_and_link() */
 485
 486 EXPORT_SYMBOL(key_instantiate_and_link);
 487
 488 /*****************************************************************************/
 489 /*
 490  * negatively instantiate a key and link it into the target keyring atomically
 491  */
 492 int key_negate_and_link(struct key *key,
 493                         unsigned timeout,
 494                         struct key *keyring,
 495                         struct key *instkey)
 496 {
 497         struct timespec now;
 498         int ret, awaken;
 499
 500         key_check(key);
 501         key_check(keyring);
 502
 503         awaken = 0;
 504         ret = -EBUSY;
 505
 506         if (keyring)
 507                 down_write(&keyring->sem);
 508
 509         down_write(&key_construction_sem);
 510
 511         /* can't instantiate twice */
 512         if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
 513                 /* mark the key as being negatively instantiated */
 514                 atomic_inc(&key->user->nikeys);
 515                 set_bit(KEY_FLAG_NEGATIVE, &key->flags);
 516                 set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
 517                 now = current_kernel_time();
 518                 key->expiry = now.tv_sec + timeout;
 519
 520                 if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
 521                         awaken = 1;
 522
 523                 ret = 0;
 524
 525                 /* and link it into the destination keyring */
 526                 if (keyring)
 527                         ret = __key_link(keyring, key);
 528
 529                 /* disable the authorisation key */
 530                 if (instkey)
 531                         key_revoke(instkey);
 532         }
 533
 534         up_write(&key_construction_sem);
 535
 536         if (keyring)
 537                 up_write(&keyring->sem);
 538
 539         /* wake up anyone waiting for a key to be constructed */
 540         if (awaken)
 541                 wake_up_all(&request_key_conswq);
 542
 543         return ret;
 544
 545 } /* end key_negate_and_link() */
 546
 547 EXPORT_SYMBOL(key_negate_and_link);
 548
 549 /*****************************************************************************/
 550 /*
 551  * do cleaning up in process context so that we don't have to disable
 552  * interrupts all over the place
 553  */
 554 static void key_cleanup(void *data)
 555 {
 556         struct rb_node *_n;
 557         struct key *key;
 558
 559  go_again:
 560         /* look for a dead key in the tree */
 561         spin_lock(&key_serial_lock);
 562
 563         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 564                 key = rb_entry(_n, struct key, serial_node);
 565
 566                 if (atomic_read(&key->usage) == 0)
 567                         goto found_dead_key;
 568         }
 569
 570         spin_unlock(&key_serial_lock);
 571         return;
 572
 573  found_dead_key:
 574         /* we found a dead key - once we've removed it from the tree, we can
 575          * drop the lock */
 576         rb_erase(&key->serial_node, &key_serial_tree);
 577         spin_unlock(&key_serial_lock);
 578
 579         key_check(key);
 580
 581         security_key_free(key);
 582
 583         /* deal with the user's key tracking and quota */
 584         if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
 585                 spin_lock(&key->user->lock);
 586                 key->user->qnkeys--;
 587                 key->user->qnbytes -= key->quotalen;
 588                 spin_unlock(&key->user->lock);
 589         }
 590
 591         atomic_dec(&key->user->nkeys);
 592         if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
 593                 atomic_dec(&key->user->nikeys);
 594
 595         key_user_put(key->user);
 596
 597         /* now throw away the key memory */
 598         if (key->type->destroy)
 599                 key->type->destroy(key);
 600
 601         kfree(key->description);
 602
 603 #ifdef KEY_DEBUGGING
 604         key->magic = KEY_DEBUG_MAGIC_X;
 605 #endif
 606         kmem_cache_free(key_jar, key);
 607
 608         /* there may, of course, be more than one key to destroy */
 609         goto go_again;
 610
 611 } /* end key_cleanup() */
 612
 613 /*****************************************************************************/
 614 /*
 615  * dispose of a reference to a key
 616  * - when all the references are gone, we schedule the cleanup task to come and
 617  *   pull it out of the tree in definite process context
 618  */
 619 void key_put(struct key *key)
 620 {
 621         if (key) {
 622                 key_check(key);
 623
 624                 if (atomic_dec_and_test(&key->usage))
 625                         schedule_work(&key_cleanup_task);
 626         }
 627
 628 } /* end key_put() */
 629
 630 EXPORT_SYMBOL(key_put);
 631
 632 /*****************************************************************************/
 633 /*
 634  * find a key by its serial number
 635  */
 636 struct key *key_lookup(key_serial_t id)
 637 {
 638         struct rb_node *n;
 639         struct key *key;
 640
 641         spin_lock(&key_serial_lock);
 642
 643         /* search the tree for the specified key */
 644         n = key_serial_tree.rb_node;
 645         while (n) {
 646                 key = rb_entry(n, struct key, serial_node);
 647
 648                 if (id < key->serial)
 649                         n = n->rb_left;
 650                 else if (id > key->serial)
 651                         n = n->rb_right;
 652                 else
 653                         goto found;
 654         }
 655
 656  not_found:
 657         key = ERR_PTR(-ENOKEY);
 658         goto error;
 659
 660  found:
 661         /* pretend it doesn't exist if it's dead */
 662         if (atomic_read(&key->usage) == 0 ||
 663             test_bit(KEY_FLAG_DEAD, &key->flags) ||
 664             key->type == &key_type_dead)
 665                 goto not_found;
 666
 667         /* this races with key_put(), but that doesn't matter since key_put()
 668          * doesn't actually change the key
 669          */
 670         atomic_inc(&key->usage);
 671
 672  error:
 673         spin_unlock(&key_serial_lock);
 674         return key;
 675
 676 } /* end key_lookup() */
 677
 678 /*****************************************************************************/
 679 /*
 680  * find and lock the specified key type against removal
 681  * - we return with the sem readlocked
 682  */
 683 struct key_type *key_type_lookup(const char *type)
 684 {
 685         struct key_type *ktype;
 686
 687         down_read(&key_types_sem);
 688
 689         /* look up the key type to see if it's one of the registered kernel
 690          * types */
 691         list_for_each_entry(ktype, &key_types_list, link) {
 692                 if (strcmp(ktype->name, type) == 0)
 693                         goto found_kernel_type;
 694         }
 695
 696         up_read(&key_types_sem);
 697         ktype = ERR_PTR(-ENOKEY);
 698
 699  found_kernel_type:
 700         return ktype;
 701
 702 } /* end key_type_lookup() */
 703
 704 /*****************************************************************************/
 705 /*
 706  * unlock a key type
 707  */
 708 void key_type_put(struct key_type *ktype)
 709 {
 710         up_read(&key_types_sem);
 711
 712 } /* end key_type_put() */
 713
 714 /*****************************************************************************/
 715 /*
 716  * attempt to update an existing key
 717  * - the key has an incremented refcount
 718  * - we need to put the key if we get an error
 719  */
 720 static inline key_ref_t __key_update(key_ref_t key_ref,
 721                                      const void *payload, size_t plen)
 722 {
 723         struct key *key = key_ref_to_ptr(key_ref);
 724         int ret;
 725
 726         /* need write permission on the key to update it */
 727         ret = key_permission(key_ref, KEY_WRITE);
 728         if (ret < 0)
 729                 goto error;
 730
 731         ret = -EEXIST;
 732         if (!key->type->update)
 733                 goto error;
 734
 735         down_write(&key->sem);
 736
 737         ret = key->type->update(key, payload, plen);
 738         if (ret == 0)
 739                 /* updating a negative key instantiates it */
 740                 clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
 741
 742         up_write(&key->sem);
 743
 744         if (ret < 0)
 745                 goto error;
 746 out:
 747         return key_ref;
 748
 749 error:
 750         key_put(key);
 751         key_ref = ERR_PTR(ret);
 752         goto out;
 753
 754 } /* end __key_update() */
 755
 756 /*****************************************************************************/
 757 /*
 758  * search the specified keyring for a key of the same description; if one is
 759  * found, update it, otherwise add a new one
 760  */
 761 key_ref_t key_create_or_update(key_ref_t keyring_ref,
 762                                const char *type,
 763                                const char *description,
 764                                const void *payload,
 765                                size_t plen,
 766                                unsigned long flags)
 767 {
 768         struct key_type *ktype;
 769         struct key *keyring, *key = NULL;
 770         key_perm_t perm;
 771         key_ref_t key_ref;
 772         int ret;
 773
 774         /* look up the key type to see if it's one of the registered kernel
 775          * types */
 776         ktype = key_type_lookup(type);
 777         if (IS_ERR(ktype)) {
 778                 key_ref = ERR_PTR(-ENODEV);
 779                 goto error;
 780         }
 781
 782         key_ref = ERR_PTR(-EINVAL);
 783         if (!ktype->match || !ktype->instantiate)
 784                 goto error_2;
 785
 786         keyring = key_ref_to_ptr(keyring_ref);
 787
 788         key_check(keyring);
 789
 790         key_ref = ERR_PTR(-ENOTDIR);
 791         if (keyring->type != &key_type_keyring)
 792                 goto error_2;
 793
 794         down_write(&keyring->sem);
 795
 796         /* if we're going to allocate a new key, we're going to have
 797          * to modify the keyring */
 798         ret = key_permission(keyring_ref, KEY_WRITE);
 799         if (ret < 0) {
 800                 key_ref = ERR_PTR(ret);
 801                 goto error_3;
 802         }
 803
 804         /* if it's possible to update this type of key, search for an existing
 805          * key of the same type and description in the destination keyring and
 806          * update that instead if possible
 807          */
 808         if (ktype->update) {
 809                 key_ref = __keyring_search_one(keyring_ref, ktype, description,
 810                                                0);
 811                 if (!IS_ERR(key_ref))
 812                         goto found_matching_key;
 813         }
 814
 815         /* decide on the permissions we want */
 816         perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
 817         perm |= KEY_USR_VIEW | KEY_USR_SEARCH | KEY_USR_LINK | KEY_USR_SETATTR;
 818
 819         if (ktype->read)
 820                 perm |= KEY_POS_READ | KEY_USR_READ;
 821
 822         if (ktype == &key_type_keyring || ktype->update)
 823                 perm |= KEY_USR_WRITE;
 824
 825         /* allocate a new key */
 826         key = key_alloc(ktype, description, current->fsuid, current->fsgid,
 827                         current, perm, flags);
 828         if (IS_ERR(key)) {
 829                 key_ref = ERR_PTR(PTR_ERR(key));
 830                 goto error_3;
 831         }
 832
 833         /* instantiate it and link it into the target keyring */
 834         ret = __key_instantiate_and_link(key, payload, plen, keyring, NULL);
 835         if (ret < 0) {
 836                 key_put(key);
 837                 key_ref = ERR_PTR(ret);
 838                 goto error_3;
 839         }
 840
 841         key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
 842
 843  error_3:
 844         up_write(&keyring->sem);
 845  error_2:
 846         key_type_put(ktype);
 847  error:
 848         return key_ref;
 849
 850  found_matching_key:
 851         /* we found a matching key, so we're going to try to update it
 852          * - we can drop the locks first as we have the key pinned
 853          */
 854         up_write(&keyring->sem);
 855         key_type_put(ktype);
 856
 857         key_ref = __key_update(key_ref, payload, plen);
 858         goto error;
 859
 860 } /* end key_create_or_update() */
 861
 862 EXPORT_SYMBOL(key_create_or_update);
 863
 864 /*****************************************************************************/
 865 /*
 866  * update a key
 867  */
 868 int key_update(key_ref_t key_ref, const void *payload, size_t plen)
 869 {
 870         struct key *key = key_ref_to_ptr(key_ref);
 871         int ret;
 872
 873         key_check(key);
 874
 875         /* the key must be writable */
 876         ret = key_permission(key_ref, KEY_WRITE);
 877         if (ret < 0)
 878                 goto error;
 879
 880         /* attempt to update it if supported */
 881         ret = -EOPNOTSUPP;
 882         if (key->type->update) {
 883                 down_write(&key->sem);
 884
 885                 ret = key->type->update(key, payload, plen);
 886                 if (ret == 0)
 887                         /* updating a negative key instantiates it */
 888                         clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
 889
 890                 up_write(&key->sem);
 891         }
 892
 893  error:
 894         return ret;
 895
 896 } /* end key_update() */
 897
 898 EXPORT_SYMBOL(key_update);
 899
 900 /*****************************************************************************/
 901 /*
 902  * revoke a key
 903  */
 904 void key_revoke(struct key *key)
 905 {
 906         key_check(key);
 907
 908         /* make sure no one's trying to change or use the key when we mark
 909          * it */
 910         down_write(&key->sem);
 911         set_bit(KEY_FLAG_REVOKED, &key->flags);
 912
 913         if (key->type->revoke)
 914                 key->type->revoke(key);
 915
 916         up_write(&key->sem);
 917
 918 } /* end key_revoke() */
 919
 920 EXPORT_SYMBOL(key_revoke);
 921
 922 /*****************************************************************************/
 923 /*
 924  * register a type of key
 925  */
 926 int register_key_type(struct key_type *ktype)
 927 {
 928         struct key_type *p;
 929         int ret;
 930
 931         ret = -EEXIST;
 932         down_write(&key_types_sem);
 933
 934         /* disallow key types with the same name */
 935         list_for_each_entry(p, &key_types_list, link) {
 936                 if (strcmp(p->name, ktype->name) == 0)
 937                         goto out;
 938         }
 939
 940         /* store the type */
 941         list_add(&ktype->link, &key_types_list);
 942         ret = 0;
 943
 944  out:
 945         up_write(&key_types_sem);
 946         return ret;
 947
 948 } /* end register_key_type() */
 949
 950 EXPORT_SYMBOL(register_key_type);
 951
 952 /*****************************************************************************/
 953 /*
 954  * unregister a type of key
 955  */
 956 void unregister_key_type(struct key_type *ktype)
 957 {
 958         struct rb_node *_n;
 959         struct key *key;
 960
 961         down_write(&key_types_sem);
 962
 963         /* withdraw the key type */
 964         list_del_init(&ktype->link);
 965
 966         /* mark all the keys of this type dead */
 967         spin_lock(&key_serial_lock);
 968
 969         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 970                 key = rb_entry(_n, struct key, serial_node);
 971
 972                 if (key->type == ktype)
 973                         key->type = &key_type_dead;
 974         }
 975
 976         spin_unlock(&key_serial_lock);
 977
 978         /* make sure everyone revalidates their keys */
 979         synchronize_rcu();
 980
 981         /* we should now be able to destroy the payloads of all the keys of
 982          * this type with impunity */
 983         spin_lock(&key_serial_lock);
 984
 985         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 986                 key = rb_entry(_n, struct key, serial_node);
 987
 988                 if (key->type == ktype) {
 989                         if (ktype->destroy)
 990                                 ktype->destroy(key);
 991                         memset(&key->payload, 0xbd, sizeof(key->payload));
 992                 }
 993         }
 994
 995         spin_unlock(&key_serial_lock);
 996         up_write(&key_types_sem);
 997
 998 } /* end unregister_key_type() */
 999
1000 EXPORT_SYMBOL(unregister_key_type);
1001
1002 /*****************************************************************************/
1003 /*
1004  * initialise the key management stuff
1005  */
1006 void __init key_init(void)
1007 {
1008         /* allocate a slab in which we can store keys */
1009         key_jar = kmem_cache_create("key_jar", sizeof(struct key),
1010                         0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1011
1012         /* add the special key types */
1013         list_add_tail(&key_type_keyring.link, &key_types_list);
1014         list_add_tail(&key_type_dead.link, &key_types_list);
1015         list_add_tail(&key_type_user.link, &key_types_list);
1016
1017         /* record the root user tracking */
1018         rb_link_node(&root_key_user.node,
1019                      NULL,
1020                      &key_user_tree.rb_node);
1021
1022         rb_insert_color(&root_key_user.node,
1023                         &key_user_tree);
1024
1025         /* record root's user standard keyrings */
1026         key_check(&root_user_keyring);
1027         key_check(&root_session_keyring);
1028
1029         __key_insert_serial(&root_user_keyring);
1030         __key_insert_serial(&root_session_keyring);
1031
1032         keyring_publish_name(&root_user_keyring);
1033         keyring_publish_name(&root_session_keyring);
1034
1035         /* link the two root keyrings together */
1036         key_link(&root_session_keyring, &root_user_keyring);
1037
1038 } /* end key_init() */