security/keys/key.c

   1 /* Basic authentication token and access key management
   2  *
   3  * Copyright (C) 2004-2008 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 unsigned int key_quota_root_maxkeys = 200;      /* root's key count quota */
  31 unsigned int key_quota_root_maxbytes = 20000;   /* root's key space quota */
  32 unsigned int key_quota_maxkeys = 200;           /* general key count quota */
  33 unsigned int key_quota_maxbytes = 20000;        /* general key space quota */
  34
  35 static LIST_HEAD(key_types_list);
  36 static DECLARE_RWSEM(key_types_sem);
  37
  38 static void key_cleanup(struct work_struct *work);
  39 static DECLARE_WORK(key_cleanup_task, key_cleanup);
  40
  41 /* we serialise key instantiation and link */
  42 DEFINE_MUTEX(key_construction_mutex);
  43
  44 /* any key who's type gets unegistered will be re-typed to this */
  45 static struct key_type key_type_dead = {
  46         .name           = "dead",
  47 };
  48
  49 #ifdef KEY_DEBUGGING
  50 void __key_check(const struct key *key)
  51 {
  52         printk("__key_check: key %p {%08x} should be {%08x}\n",
  53                key, key->magic, KEY_DEBUG_MAGIC);
  54         BUG();
  55 }
  56 #endif
  57
  58 /*****************************************************************************/
  59 /*
  60  * get the key quota record for a user, allocating a new record if one doesn't
  61  * already exist
  62  */
  63 struct key_user *key_user_lookup(uid_t uid)
  64 {
  65         struct key_user *candidate = NULL, *user;
  66         struct rb_node *parent = NULL;
  67         struct rb_node **p;
  68
  69  try_again:
  70         p = &key_user_tree.rb_node;
  71         spin_lock(&key_user_lock);
  72
  73         /* search the tree for a user record with a matching UID */
  74         while (*p) {
  75                 parent = *p;
  76                 user = rb_entry(parent, struct key_user, node);
  77
  78                 if (uid < user->uid)
  79                         p = &(*p)->rb_left;
  80                 else if (uid > user->uid)
  81                         p = &(*p)->rb_right;
  82                 else
  83                         goto found;
  84         }
  85
  86         /* if we get here, we failed to find a match in the tree */
  87         if (!candidate) {
  88                 /* allocate a candidate user record if we don't already have
  89                  * one */
  90                 spin_unlock(&key_user_lock);
  91
  92                 user = NULL;
  93                 candidate = kmalloc(sizeof(struct key_user), GFP_KERNEL);
  94                 if (unlikely(!candidate))
  95                         goto out;
  96
  97                 /* the allocation may have scheduled, so we need to repeat the
  98                  * search lest someone else added the record whilst we were
  99                  * asleep */
 100                 goto try_again;
 101         }
 102
 103         /* if we get here, then the user record still hadn't appeared on the
 104          * second pass - so we use the candidate record */
 105         atomic_set(&candidate->usage, 1);
 106         atomic_set(&candidate->nkeys, 0);
 107         atomic_set(&candidate->nikeys, 0);
 108         candidate->uid = uid;
 109         candidate->qnkeys = 0;
 110         candidate->qnbytes = 0;
 111         spin_lock_init(&candidate->lock);
 112         mutex_init(&candidate->cons_lock);
 113
 114         rb_link_node(&candidate->node, parent, p);
 115         rb_insert_color(&candidate->node, &key_user_tree);
 116         spin_unlock(&key_user_lock);
 117         user = candidate;
 118         goto out;
 119
 120         /* okay - we found a user record for this UID */
 121  found:
 122         atomic_inc(&user->usage);
 123         spin_unlock(&key_user_lock);
 124         kfree(candidate);
 125  out:
 126         return user;
 127
 128 } /* end key_user_lookup() */
 129
 130 /*****************************************************************************/
 131 /*
 132  * dispose of a user structure
 133  */
 134 void key_user_put(struct key_user *user)
 135 {
 136         if (atomic_dec_and_lock(&user->usage, &key_user_lock)) {
 137                 rb_erase(&user->node, &key_user_tree);
 138                 spin_unlock(&key_user_lock);
 139
 140                 kfree(user);
 141         }
 142
 143 } /* end key_user_put() */
 144
 145 /*****************************************************************************/
 146 /*
 147  * assign a key the next unique serial number
 148  * - these are assigned randomly to avoid security issues through covert
 149  *   channel problems
 150  */
 151 static inline void key_alloc_serial(struct key *key)
 152 {
 153         struct rb_node *parent, **p;
 154         struct key *xkey;
 155
 156         /* propose a random serial number and look for a hole for it in the
 157          * serial number tree */
 158         do {
 159                 get_random_bytes(&key->serial, sizeof(key->serial));
 160
 161                 key->serial >>= 1; /* negative numbers are not permitted */
 162         } while (key->serial < 3);
 163
 164         spin_lock(&key_serial_lock);
 165
 166 attempt_insertion:
 167         parent = NULL;
 168         p = &key_serial_tree.rb_node;
 169
 170         while (*p) {
 171                 parent = *p;
 172                 xkey = rb_entry(parent, struct key, serial_node);
 173
 174                 if (key->serial < xkey->serial)
 175                         p = &(*p)->rb_left;
 176                 else if (key->serial > xkey->serial)
 177                         p = &(*p)->rb_right;
 178                 else
 179                         goto serial_exists;
 180         }
 181
 182         /* we've found a suitable hole - arrange for this key to occupy it */
 183         rb_link_node(&key->serial_node, parent, p);
 184         rb_insert_color(&key->serial_node, &key_serial_tree);
 185
 186         spin_unlock(&key_serial_lock);
 187         return;
 188
 189         /* we found a key with the proposed serial number - walk the tree from
 190          * that point looking for the next unused serial number */
 191 serial_exists:
 192         for (;;) {
 193                 key->serial++;
 194                 if (key->serial < 3) {
 195                         key->serial = 3;
 196                         goto attempt_insertion;
 197                 }
 198
 199                 parent = rb_next(parent);
 200                 if (!parent)
 201                         goto attempt_insertion;
 202
 203                 xkey = rb_entry(parent, struct key, serial_node);
 204                 if (key->serial < xkey->serial)
 205                         goto attempt_insertion;
 206         }
 207
 208 } /* end key_alloc_serial() */
 209
 210 /*****************************************************************************/
 211 /*
 212  * allocate a key of the specified type
 213  * - update the user's quota to reflect the existence of the key
 214  * - called from a key-type operation with key_types_sem read-locked by
 215  *   key_create_or_update()
 216  *   - this prevents unregistration of the key type
 217  * - upon return the key is as yet uninstantiated; the caller needs to either
 218  *   instantiate the key or discard it before returning
 219  */
 220 struct key *key_alloc(struct key_type *type, const char *desc,
 221                       uid_t uid, gid_t gid, const struct cred *cred,
 222                       key_perm_t perm, unsigned long flags)
 223 {
 224         struct key_user *user = NULL;
 225         struct key *key;
 226         size_t desclen, quotalen;
 227         int ret;
 228
 229         key = ERR_PTR(-EINVAL);
 230         if (!desc || !*desc)
 231                 goto error;
 232
 233         desclen = strlen(desc) + 1;
 234         quotalen = desclen + type->def_datalen;
 235
 236         /* get hold of the key tracking for this user */
 237         user = key_user_lookup(uid);
 238         if (!user)
 239                 goto no_memory_1;
 240
 241         /* check that the user's quota permits allocation of another key and
 242          * its description */
 243         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 244                 unsigned maxkeys = (uid == 0) ?
 245                         key_quota_root_maxkeys : key_quota_maxkeys;
 246                 unsigned maxbytes = (uid == 0) ?
 247                         key_quota_root_maxbytes : key_quota_maxbytes;
 248
 249                 spin_lock(&user->lock);
 250                 if (!(flags & KEY_ALLOC_QUOTA_OVERRUN)) {
 251                         if (user->qnkeys + 1 >= maxkeys ||
 252                             user->qnbytes + quotalen >= maxbytes ||
 253                             user->qnbytes + quotalen < user->qnbytes)
 254                                 goto no_quota;
 255                 }
 256
 257                 user->qnkeys++;
 258                 user->qnbytes += quotalen;
 259                 spin_unlock(&user->lock);
 260         }
 261
 262         /* allocate and initialise the key and its description */
 263         key = kmem_cache_alloc(key_jar, GFP_KERNEL);
 264         if (!key)
 265                 goto no_memory_2;
 266
 267         if (desc) {
 268                 key->description = kmemdup(desc, desclen, GFP_KERNEL);
 269                 if (!key->description)
 270                         goto no_memory_3;
 271         }
 272
 273         atomic_set(&key->usage, 1);
 274         init_rwsem(&key->sem);
 275         key->type = type;
 276         key->user = user;
 277         key->quotalen = quotalen;
 278         key->datalen = type->def_datalen;
 279         key->uid = uid;
 280         key->gid = gid;
 281         key->perm = perm;
 282         key->flags = 0;
 283         key->expiry = 0;
 284         key->payload.data = NULL;
 285         key->security = NULL;
 286
 287         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA))
 288                 key->flags |= 1 << KEY_FLAG_IN_QUOTA;
 289
 290         memset(&key->type_data, 0, sizeof(key->type_data));
 291
 292 #ifdef KEY_DEBUGGING
 293         key->magic = KEY_DEBUG_MAGIC;
 294 #endif
 295
 296         /* let the security module know about the key */
 297         ret = security_key_alloc(key, cred, flags);
 298         if (ret < 0)
 299                 goto security_error;
 300
 301         /* publish the key by giving it a serial number */
 302         atomic_inc(&user->nkeys);
 303         key_alloc_serial(key);
 304
 305 error:
 306         return key;
 307
 308 security_error:
 309         kfree(key->description);
 310         kmem_cache_free(key_jar, key);
 311         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 312                 spin_lock(&user->lock);
 313                 user->qnkeys--;
 314                 user->qnbytes -= quotalen;
 315                 spin_unlock(&user->lock);
 316         }
 317         key_user_put(user);
 318         key = ERR_PTR(ret);
 319         goto error;
 320
 321 no_memory_3:
 322         kmem_cache_free(key_jar, key);
 323 no_memory_2:
 324         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 325                 spin_lock(&user->lock);
 326                 user->qnkeys--;
 327                 user->qnbytes -= quotalen;
 328                 spin_unlock(&user->lock);
 329         }
 330         key_user_put(user);
 331 no_memory_1:
 332         key = ERR_PTR(-ENOMEM);
 333         goto error;
 334
 335 no_quota:
 336         spin_unlock(&user->lock);
 337         key_user_put(user);
 338         key = ERR_PTR(-EDQUOT);
 339         goto error;
 340
 341 } /* end key_alloc() */
 342
 343 EXPORT_SYMBOL(key_alloc);
 344
 345 /*****************************************************************************/
 346 /*
 347  * reserve an amount of quota for the key's payload
 348  */
 349 int key_payload_reserve(struct key *key, size_t datalen)
 350 {
 351         int delta = (int) datalen - key->datalen;
 352         int ret = 0;
 353
 354         key_check(key);
 355
 356         /* contemplate the quota adjustment */
 357         if (delta != 0 && test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
 358                 unsigned maxbytes = (key->user->uid == 0) ?
 359                         key_quota_root_maxbytes : key_quota_maxbytes;
 360
 361                 spin_lock(&key->user->lock);
 362
 363                 if (delta > 0 &&
 364                     (key->user->qnbytes + delta >= maxbytes ||
 365                      key->user->qnbytes + delta < key->user->qnbytes)) {
 366                         ret = -EDQUOT;
 367                 }
 368                 else {
 369                         key->user->qnbytes += delta;
 370                         key->quotalen += delta;
 371                 }
 372                 spin_unlock(&key->user->lock);
 373         }
 374
 375         /* change the recorded data length if that didn't generate an error */
 376         if (ret == 0)
 377                 key->datalen = datalen;
 378
 379         return ret;
 380
 381 } /* end key_payload_reserve() */
 382
 383 EXPORT_SYMBOL(key_payload_reserve);
 384
 385 /*****************************************************************************/
 386 /*
 387  * instantiate a key and link it into the target keyring atomically
 388  * - called with the target keyring's semaphore writelocked
 389  */
 390 static int __key_instantiate_and_link(struct key *key,
 391                                       const void *data,
 392                                       size_t datalen,
 393                                       struct key *keyring,
 394                                       struct key *authkey)
 395 {
 396         int ret, awaken;
 397
 398         key_check(key);
 399         key_check(keyring);
 400
 401         awaken = 0;
 402         ret = -EBUSY;
 403
 404         mutex_lock(&key_construction_mutex);
 405
 406         /* can't instantiate twice */
 407         if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
 408                 /* instantiate the key */
 409                 ret = key->type->instantiate(key, data, datalen);
 410
 411                 if (ret == 0) {
 412                         /* mark the key as being instantiated */
 413                         atomic_inc(&key->user->nikeys);
 414                         set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
 415
 416                         if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
 417                                 awaken = 1;
 418
 419                         /* and link it into the destination keyring */
 420                         if (keyring)
 421                                 ret = __key_link(keyring, key);
 422
 423                         /* disable the authorisation key */
 424                         if (authkey)
 425                                 key_revoke(authkey);
 426                 }
 427         }
 428
 429         mutex_unlock(&key_construction_mutex);
 430
 431         /* wake up anyone waiting for a key to be constructed */
 432         if (awaken)
 433                 wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
 434
 435         return ret;
 436
 437 } /* end __key_instantiate_and_link() */
 438
 439 /*****************************************************************************/
 440 /*
 441  * instantiate a key and link it into the target keyring atomically
 442  */
 443 int key_instantiate_and_link(struct key *key,
 444                              const void *data,
 445                              size_t datalen,
 446                              struct key *keyring,
 447                              struct key *authkey)
 448 {
 449         int ret;
 450
 451         if (keyring)
 452                 down_write(&keyring->sem);
 453
 454         ret = __key_instantiate_and_link(key, data, datalen, keyring, authkey);
 455
 456         if (keyring)
 457                 up_write(&keyring->sem);
 458
 459         return ret;
 460
 461 } /* end key_instantiate_and_link() */
 462
 463 EXPORT_SYMBOL(key_instantiate_and_link);
 464
 465 /*****************************************************************************/
 466 /*
 467  * negatively instantiate a key and link it into the target keyring atomically
 468  */
 469 int key_negate_and_link(struct key *key,
 470                         unsigned timeout,
 471                         struct key *keyring,
 472                         struct key *authkey)
 473 {
 474         struct timespec now;
 475         int ret, awaken;
 476
 477         key_check(key);
 478         key_check(keyring);
 479
 480         awaken = 0;
 481         ret = -EBUSY;
 482
 483         if (keyring)
 484                 down_write(&keyring->sem);
 485
 486         mutex_lock(&key_construction_mutex);
 487
 488         /* can't instantiate twice */
 489         if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
 490                 /* mark the key as being negatively instantiated */
 491                 atomic_inc(&key->user->nikeys);
 492                 set_bit(KEY_FLAG_NEGATIVE, &key->flags);
 493                 set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
 494                 now = current_kernel_time();
 495                 key->expiry = now.tv_sec + timeout;
 496
 497                 if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
 498                         awaken = 1;
 499
 500                 ret = 0;
 501
 502                 /* and link it into the destination keyring */
 503                 if (keyring)
 504                         ret = __key_link(keyring, key);
 505
 506                 /* disable the authorisation key */
 507                 if (authkey)
 508                         key_revoke(authkey);
 509         }
 510
 511         mutex_unlock(&key_construction_mutex);
 512
 513         if (keyring)
 514                 up_write(&keyring->sem);
 515
 516         /* wake up anyone waiting for a key to be constructed */
 517         if (awaken)
 518                 wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
 519
 520         return ret;
 521
 522 } /* end key_negate_and_link() */
 523
 524 EXPORT_SYMBOL(key_negate_and_link);
 525
 526 /*****************************************************************************/
 527 /*
 528  * do cleaning up in process context so that we don't have to disable
 529  * interrupts all over the place
 530  */
 531 static void key_cleanup(struct work_struct *work)
 532 {
 533         struct rb_node *_n;
 534         struct key *key;
 535
 536  go_again:
 537         /* look for a dead key in the tree */
 538         spin_lock(&key_serial_lock);
 539
 540         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 541                 key = rb_entry(_n, struct key, serial_node);
 542
 543                 if (atomic_read(&key->usage) == 0)
 544                         goto found_dead_key;
 545         }
 546
 547         spin_unlock(&key_serial_lock);
 548         return;
 549
 550  found_dead_key:
 551         /* we found a dead key - once we've removed it from the tree, we can
 552          * drop the lock */
 553         rb_erase(&key->serial_node, &key_serial_tree);
 554         spin_unlock(&key_serial_lock);
 555
 556         key_check(key);
 557
 558         security_key_free(key);
 559
 560         /* deal with the user's key tracking and quota */
 561         if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
 562                 spin_lock(&key->user->lock);
 563                 key->user->qnkeys--;
 564                 key->user->qnbytes -= key->quotalen;
 565                 spin_unlock(&key->user->lock);
 566         }
 567
 568         atomic_dec(&key->user->nkeys);
 569         if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
 570                 atomic_dec(&key->user->nikeys);
 571
 572         key_user_put(key->user);
 573
 574         /* now throw away the key memory */
 575         if (key->type->destroy)
 576                 key->type->destroy(key);
 577
 578         kfree(key->description);
 579
 580 #ifdef KEY_DEBUGGING
 581         key->magic = KEY_DEBUG_MAGIC_X;
 582 #endif
 583         kmem_cache_free(key_jar, key);
 584
 585         /* there may, of course, be more than one key to destroy */
 586         goto go_again;
 587
 588 } /* end key_cleanup() */
 589
 590 /*****************************************************************************/
 591 /*
 592  * dispose of a reference to a key
 593  * - when all the references are gone, we schedule the cleanup task to come and
 594  *   pull it out of the tree in definite process context
 595  */
 596 void key_put(struct key *key)
 597 {
 598         if (key) {
 599                 key_check(key);
 600
 601                 if (atomic_dec_and_test(&key->usage))
 602                         schedule_work(&key_cleanup_task);
 603         }
 604
 605 } /* end key_put() */
 606
 607 EXPORT_SYMBOL(key_put);
 608
 609 /*****************************************************************************/
 610 /*
 611  * find a key by its serial number
 612  */
 613 struct key *key_lookup(key_serial_t id)
 614 {
 615         struct rb_node *n;
 616         struct key *key;
 617
 618         spin_lock(&key_serial_lock);
 619
 620         /* search the tree for the specified key */
 621         n = key_serial_tree.rb_node;
 622         while (n) {
 623                 key = rb_entry(n, struct key, serial_node);
 624
 625                 if (id < key->serial)
 626                         n = n->rb_left;
 627                 else if (id > key->serial)
 628                         n = n->rb_right;
 629                 else
 630                         goto found;
 631         }
 632
 633  not_found:
 634         key = ERR_PTR(-ENOKEY);
 635         goto error;
 636
 637  found:
 638         /* pretend it doesn't exist if it's dead */
 639         if (atomic_read(&key->usage) == 0 ||
 640             test_bit(KEY_FLAG_DEAD, &key->flags) ||
 641             key->type == &key_type_dead)
 642                 goto not_found;
 643
 644         /* this races with key_put(), but that doesn't matter since key_put()
 645          * doesn't actually change the key
 646          */
 647         atomic_inc(&key->usage);
 648
 649  error:
 650         spin_unlock(&key_serial_lock);
 651         return key;
 652
 653 } /* end key_lookup() */
 654
 655 /*****************************************************************************/
 656 /*
 657  * find and lock the specified key type against removal
 658  * - we return with the sem readlocked
 659  */
 660 struct key_type *key_type_lookup(const char *type)
 661 {
 662         struct key_type *ktype;
 663
 664         down_read(&key_types_sem);
 665
 666         /* look up the key type to see if it's one of the registered kernel
 667          * types */
 668         list_for_each_entry(ktype, &key_types_list, link) {
 669                 if (strcmp(ktype->name, type) == 0)
 670                         goto found_kernel_type;
 671         }
 672
 673         up_read(&key_types_sem);
 674         ktype = ERR_PTR(-ENOKEY);
 675
 676  found_kernel_type:
 677         return ktype;
 678
 679 } /* end key_type_lookup() */
 680
 681 /*****************************************************************************/
 682 /*
 683  * unlock a key type
 684  */
 685 void key_type_put(struct key_type *ktype)
 686 {
 687         up_read(&key_types_sem);
 688
 689 } /* end key_type_put() */
 690
 691 /*****************************************************************************/
 692 /*
 693  * attempt to update an existing key
 694  * - the key has an incremented refcount
 695  * - we need to put the key if we get an error
 696  */
 697 static inline key_ref_t __key_update(key_ref_t key_ref,
 698                                      const void *payload, size_t plen)
 699 {
 700         struct key *key = key_ref_to_ptr(key_ref);
 701         int ret;
 702
 703         /* need write permission on the key to update it */
 704         ret = key_permission(key_ref, KEY_WRITE);
 705         if (ret < 0)
 706                 goto error;
 707
 708         ret = -EEXIST;
 709         if (!key->type->update)
 710                 goto error;
 711
 712         down_write(&key->sem);
 713
 714         ret = key->type->update(key, payload, plen);
 715         if (ret == 0)
 716                 /* updating a negative key instantiates it */
 717                 clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
 718
 719         up_write(&key->sem);
 720
 721         if (ret < 0)
 722                 goto error;
 723 out:
 724         return key_ref;
 725
 726 error:
 727         key_put(key);
 728         key_ref = ERR_PTR(ret);
 729         goto out;
 730
 731 } /* end __key_update() */
 732
 733 /*****************************************************************************/
 734 /*
 735  * search the specified keyring for a key of the same description; if one is
 736  * found, update it, otherwise add a new one
 737  */
 738 key_ref_t key_create_or_update(key_ref_t keyring_ref,
 739                                const char *type,
 740                                const char *description,
 741                                const void *payload,
 742                                size_t plen,
 743                                key_perm_t perm,
 744                                unsigned long flags)
 745 {
 746         const struct cred *cred = current_cred();
 747         struct key_type *ktype;
 748         struct key *keyring, *key = NULL;
 749         key_ref_t key_ref;
 750         int ret;
 751
 752         /* look up the key type to see if it's one of the registered kernel
 753          * types */
 754         ktype = key_type_lookup(type);
 755         if (IS_ERR(ktype)) {
 756                 key_ref = ERR_PTR(-ENODEV);
 757                 goto error;
 758         }
 759
 760         key_ref = ERR_PTR(-EINVAL);
 761         if (!ktype->match || !ktype->instantiate)
 762                 goto error_2;
 763
 764         keyring = key_ref_to_ptr(keyring_ref);
 765
 766         key_check(keyring);
 767
 768         key_ref = ERR_PTR(-ENOTDIR);
 769         if (keyring->type != &key_type_keyring)
 770                 goto error_2;
 771
 772         down_write(&keyring->sem);
 773
 774         /* if we're going to allocate a new key, we're going to have
 775          * to modify the keyring */
 776         ret = key_permission(keyring_ref, KEY_WRITE);
 777         if (ret < 0) {
 778                 key_ref = ERR_PTR(ret);
 779                 goto error_3;
 780         }
 781
 782         /* if it's possible to update this type of key, search for an existing
 783          * key of the same type and description in the destination keyring and
 784          * update that instead if possible
 785          */
 786         if (ktype->update) {
 787                 key_ref = __keyring_search_one(keyring_ref, ktype, description,
 788                                                0);
 789                 if (!IS_ERR(key_ref))
 790                         goto found_matching_key;
 791         }
 792
 793         /* if the client doesn't provide, decide on the permissions we want */
 794         if (perm == KEY_PERM_UNDEF) {
 795                 perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
 796                 perm |= KEY_USR_VIEW | KEY_USR_SEARCH | KEY_USR_LINK | KEY_USR_SETATTR;
 797
 798                 if (ktype->read)
 799                         perm |= KEY_POS_READ | KEY_USR_READ;
 800
 801                 if (ktype == &key_type_keyring || ktype->update)
 802                         perm |= KEY_USR_WRITE;
 803         }
 804
 805         /* allocate a new key */
 806         key = key_alloc(ktype, description, cred->fsuid, cred->fsgid, cred,
 807                         perm, flags);
 808         if (IS_ERR(key)) {
 809                 key_ref = ERR_CAST(key);
 810                 goto error_3;
 811         }
 812
 813         /* instantiate it and link it into the target keyring */
 814         ret = __key_instantiate_and_link(key, payload, plen, keyring, NULL);
 815         if (ret < 0) {
 816                 key_put(key);
 817                 key_ref = ERR_PTR(ret);
 818                 goto error_3;
 819         }
 820
 821         key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
 822
 823  error_3:
 824         up_write(&keyring->sem);
 825  error_2:
 826         key_type_put(ktype);
 827  error:
 828         return key_ref;
 829
 830  found_matching_key:
 831         /* we found a matching key, so we're going to try to update it
 832          * - we can drop the locks first as we have the key pinned
 833          */
 834         up_write(&keyring->sem);
 835         key_type_put(ktype);
 836
 837         key_ref = __key_update(key_ref, payload, plen);
 838         goto error;
 839
 840 } /* end key_create_or_update() */
 841
 842 EXPORT_SYMBOL(key_create_or_update);
 843
 844 /*****************************************************************************/
 845 /*
 846  * update a key
 847  */
 848 int key_update(key_ref_t key_ref, const void *payload, size_t plen)
 849 {
 850         struct key *key = key_ref_to_ptr(key_ref);
 851         int ret;
 852
 853         key_check(key);
 854
 855         /* the key must be writable */
 856         ret = key_permission(key_ref, KEY_WRITE);
 857         if (ret < 0)
 858                 goto error;
 859
 860         /* attempt to update it if supported */
 861         ret = -EOPNOTSUPP;
 862         if (key->type->update) {
 863                 down_write(&key->sem);
 864
 865                 ret = key->type->update(key, payload, plen);
 866                 if (ret == 0)
 867                         /* updating a negative key instantiates it */
 868                         clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
 869
 870                 up_write(&key->sem);
 871         }
 872
 873  error:
 874         return ret;
 875
 876 } /* end key_update() */
 877
 878 EXPORT_SYMBOL(key_update);
 879
 880 /*****************************************************************************/
 881 /*
 882  * revoke a key
 883  */
 884 void key_revoke(struct key *key)
 885 {
 886         key_check(key);
 887
 888         /* make sure no one's trying to change or use the key when we mark it
 889          * - we tell lockdep that we might nest because we might be revoking an
 890          *   authorisation key whilst holding the sem on a key we've just
 891          *   instantiated
 892          */
 893         down_write_nested(&key->sem, 1);
 894         if (!test_and_set_bit(KEY_FLAG_REVOKED, &key->flags) &&
 895             key->type->revoke)
 896                 key->type->revoke(key);
 897
 898         up_write(&key->sem);
 899
 900 } /* end key_revoke() */
 901
 902 EXPORT_SYMBOL(key_revoke);
 903
 904 /*****************************************************************************/
 905 /*
 906  * register a type of key
 907  */
 908 int register_key_type(struct key_type *ktype)
 909 {
 910         struct key_type *p;
 911         int ret;
 912
 913         ret = -EEXIST;
 914         down_write(&key_types_sem);
 915
 916         /* disallow key types with the same name */
 917         list_for_each_entry(p, &key_types_list, link) {
 918                 if (strcmp(p->name, ktype->name) == 0)
 919                         goto out;
 920         }
 921
 922         /* store the type */
 923         list_add(&ktype->link, &key_types_list);
 924         ret = 0;
 925
 926  out:
 927         up_write(&key_types_sem);
 928         return ret;
 929
 930 } /* end register_key_type() */
 931
 932 EXPORT_SYMBOL(register_key_type);
 933
 934 /*****************************************************************************/
 935 /*
 936  * unregister a type of key
 937  */
 938 void unregister_key_type(struct key_type *ktype)
 939 {
 940         struct rb_node *_n;
 941         struct key *key;
 942
 943         down_write(&key_types_sem);
 944
 945         /* withdraw the key type */
 946         list_del_init(&ktype->link);
 947
 948         /* mark all the keys of this type dead */
 949         spin_lock(&key_serial_lock);
 950
 951         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 952                 key = rb_entry(_n, struct key, serial_node);
 953
 954                 if (key->type == ktype)
 955                         key->type = &key_type_dead;
 956         }
 957
 958         spin_unlock(&key_serial_lock);
 959
 960         /* make sure everyone revalidates their keys */
 961         synchronize_rcu();
 962
 963         /* we should now be able to destroy the payloads of all the keys of
 964          * this type with impunity */
 965         spin_lock(&key_serial_lock);
 966
 967         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 968                 key = rb_entry(_n, struct key, serial_node);
 969
 970                 if (key->type == ktype) {
 971                         if (ktype->destroy)
 972                                 ktype->destroy(key);
 973                         memset(&key->payload, KEY_DESTROY, sizeof(key->payload));
 974                 }
 975         }
 976
 977         spin_unlock(&key_serial_lock);
 978         up_write(&key_types_sem);
 979
 980 } /* end unregister_key_type() */
 981
 982 EXPORT_SYMBOL(unregister_key_type);
 983
 984 /*****************************************************************************/
 985 /*
 986  * initialise the key management stuff
 987  */
 988 void __init key_init(void)
 989 {
 990         /* allocate a slab in which we can store keys */
 991         key_jar = kmem_cache_create("key_jar", sizeof(struct key),
 992                         0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
 993
 994         /* add the special key types */
 995         list_add_tail(&key_type_keyring.link, &key_types_list);
 996         list_add_tail(&key_type_dead.link, &key_types_list);
 997         list_add_tail(&key_type_user.link, &key_types_list);
 998
 999         /* record the root user tracking */
1000         rb_link_node(&root_key_user.node,
1001                      NULL,
1002                      &key_user_tree.rb_node);
1003
1004         rb_insert_color(&root_key_user.node,
1005                         &key_user_tree);
1006
1007 } /* end key_init() */