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 <linux/user_namespace.h>
  22 #include "internal.h"
  23
  24 static struct kmem_cache        *key_jar;
  25 struct rb_root          key_serial_tree; /* tree of keys indexed by serial */
  26 DEFINE_SPINLOCK(key_serial_lock);
  27
  28 struct rb_root  key_user_tree; /* tree of quota records indexed by UID */
  29 DEFINE_SPINLOCK(key_user_lock);
  30
  31 unsigned int key_quota_root_maxkeys = 200;      /* root's key count quota */
  32 unsigned int key_quota_root_maxbytes = 20000;   /* root's key space quota */
  33 unsigned int key_quota_maxkeys = 200;           /* general key count quota */
  34 unsigned int key_quota_maxbytes = 20000;        /* general key space quota */
  35
  36 static LIST_HEAD(key_types_list);
  37 static DECLARE_RWSEM(key_types_sem);
  38
  39 static void key_cleanup(struct work_struct *work);
  40 static DECLARE_WORK(key_cleanup_task, key_cleanup);
  41
  42 /* we serialise key instantiation and link */
  43 DEFINE_MUTEX(key_construction_mutex);
  44
  45 /* any key who's type gets unegistered will be re-typed to this */
  46 static struct key_type key_type_dead = {
  47         .name           = "dead",
  48 };
  49
  50 #ifdef KEY_DEBUGGING
  51 void __key_check(const struct key *key)
  52 {
  53         printk("__key_check: key %p {%08x} should be {%08x}\n",
  54                key, key->magic, KEY_DEBUG_MAGIC);
  55         BUG();
  56 }
  57 #endif
  58
  59 /*****************************************************************************/
  60 /*
  61  * get the key quota record for a user, allocating a new record if one doesn't
  62  * already exist
  63  */
  64 struct key_user *key_user_lookup(uid_t uid, struct user_namespace *user_ns)
  65 {
  66         struct key_user *candidate = NULL, *user;
  67         struct rb_node *parent = NULL;
  68         struct rb_node **p;
  69
  70  try_again:
  71         p = &key_user_tree.rb_node;
  72         spin_lock(&key_user_lock);
  73
  74         /* search the tree for a user record with a matching UID */
  75         while (*p) {
  76                 parent = *p;
  77                 user = rb_entry(parent, struct key_user, node);
  78
  79                 if (uid < user->uid)
  80                         p = &(*p)->rb_left;
  81                 else if (uid > user->uid)
  82                         p = &(*p)->rb_right;
  83                 else if (user_ns < user->user_ns)
  84                         p = &(*p)->rb_left;
  85                 else if (user_ns > user->user_ns)
  86                         p = &(*p)->rb_right;
  87                 else
  88                         goto found;
  89         }
  90
  91         /* if we get here, we failed to find a match in the tree */
  92         if (!candidate) {
  93                 /* allocate a candidate user record if we don't already have
  94                  * one */
  95                 spin_unlock(&key_user_lock);
  96
  97                 user = NULL;
  98                 candidate = kmalloc(sizeof(struct key_user), GFP_KERNEL);
  99                 if (unlikely(!candidate))
 100                         goto out;
 101
 102                 /* the allocation may have scheduled, so we need to repeat the
 103                  * search lest someone else added the record whilst we were
 104                  * asleep */
 105                 goto try_again;
 106         }
 107
 108         /* if we get here, then the user record still hadn't appeared on the
 109          * second pass - so we use the candidate record */
 110         atomic_set(&candidate->usage, 1);
 111         atomic_set(&candidate->nkeys, 0);
 112         atomic_set(&candidate->nikeys, 0);
 113         candidate->uid = uid;
 114         candidate->user_ns = get_user_ns(user_ns);
 115         candidate->qnkeys = 0;
 116         candidate->qnbytes = 0;
 117         spin_lock_init(&candidate->lock);
 118         mutex_init(&candidate->cons_lock);
 119
 120         rb_link_node(&candidate->node, parent, p);
 121         rb_insert_color(&candidate->node, &key_user_tree);
 122         spin_unlock(&key_user_lock);
 123         user = candidate;
 124         goto out;
 125
 126         /* okay - we found a user record for this UID */
 127  found:
 128         atomic_inc(&user->usage);
 129         spin_unlock(&key_user_lock);
 130         kfree(candidate);
 131  out:
 132         return user;
 133
 134 } /* end key_user_lookup() */
 135
 136 /*****************************************************************************/
 137 /*
 138  * dispose of a user structure
 139  */
 140 void key_user_put(struct key_user *user)
 141 {
 142         if (atomic_dec_and_lock(&user->usage, &key_user_lock)) {
 143                 rb_erase(&user->node, &key_user_tree);
 144                 spin_unlock(&key_user_lock);
 145                 put_user_ns(user->user_ns);
 146
 147                 kfree(user);
 148         }
 149
 150 } /* end key_user_put() */
 151
 152 /*****************************************************************************/
 153 /*
 154  * assign a key the next unique serial number
 155  * - these are assigned randomly to avoid security issues through covert
 156  *   channel problems
 157  */
 158 static inline void key_alloc_serial(struct key *key)
 159 {
 160         struct rb_node *parent, **p;
 161         struct key *xkey;
 162
 163         /* propose a random serial number and look for a hole for it in the
 164          * serial number tree */
 165         do {
 166                 get_random_bytes(&key->serial, sizeof(key->serial));
 167
 168                 key->serial >>= 1; /* negative numbers are not permitted */
 169         } while (key->serial < 3);
 170
 171         spin_lock(&key_serial_lock);
 172
 173 attempt_insertion:
 174         parent = NULL;
 175         p = &key_serial_tree.rb_node;
 176
 177         while (*p) {
 178                 parent = *p;
 179                 xkey = rb_entry(parent, struct key, serial_node);
 180
 181                 if (key->serial < xkey->serial)
 182                         p = &(*p)->rb_left;
 183                 else if (key->serial > xkey->serial)
 184                         p = &(*p)->rb_right;
 185                 else
 186                         goto serial_exists;
 187         }
 188
 189         /* we've found a suitable hole - arrange for this key to occupy it */
 190         rb_link_node(&key->serial_node, parent, p);
 191         rb_insert_color(&key->serial_node, &key_serial_tree);
 192
 193         spin_unlock(&key_serial_lock);
 194         return;
 195
 196         /* we found a key with the proposed serial number - walk the tree from
 197          * that point looking for the next unused serial number */
 198 serial_exists:
 199         for (;;) {
 200                 key->serial++;
 201                 if (key->serial < 3) {
 202                         key->serial = 3;
 203                         goto attempt_insertion;
 204                 }
 205
 206                 parent = rb_next(parent);
 207                 if (!parent)
 208                         goto attempt_insertion;
 209
 210                 xkey = rb_entry(parent, struct key, serial_node);
 211                 if (key->serial < xkey->serial)
 212                         goto attempt_insertion;
 213         }
 214
 215 } /* end key_alloc_serial() */
 216
 217 /*****************************************************************************/
 218 /*
 219  * allocate a key of the specified type
 220  * - update the user's quota to reflect the existence of the key
 221  * - called from a key-type operation with key_types_sem read-locked by
 222  *   key_create_or_update()
 223  *   - this prevents unregistration of the key type
 224  * - upon return the key is as yet uninstantiated; the caller needs to either
 225  *   instantiate the key or discard it before returning
 226  */
 227 struct key *key_alloc(struct key_type *type, const char *desc,
 228                       uid_t uid, gid_t gid, const struct cred *cred,
 229                       key_perm_t perm, unsigned long flags)
 230 {
 231         struct key_user *user = NULL;
 232         struct key *key;
 233         size_t desclen, quotalen;
 234         int ret;
 235
 236         key = ERR_PTR(-EINVAL);
 237         if (!desc || !*desc)
 238                 goto error;
 239
 240         desclen = strlen(desc) + 1;
 241         quotalen = desclen + type->def_datalen;
 242
 243         /* get hold of the key tracking for this user */
 244         user = key_user_lookup(uid, cred->user->user_ns);
 245         if (!user)
 246                 goto no_memory_1;
 247
 248         /* check that the user's quota permits allocation of another key and
 249          * its description */
 250         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 251                 unsigned maxkeys = (uid == 0) ?
 252                         key_quota_root_maxkeys : key_quota_maxkeys;
 253                 unsigned maxbytes = (uid == 0) ?
 254                         key_quota_root_maxbytes : key_quota_maxbytes;
 255
 256                 spin_lock(&user->lock);
 257                 if (!(flags & KEY_ALLOC_QUOTA_OVERRUN)) {
 258                         if (user->qnkeys + 1 >= maxkeys ||
 259                             user->qnbytes + quotalen >= maxbytes ||
 260                             user->qnbytes + quotalen < user->qnbytes)
 261                                 goto no_quota;
 262                 }
 263
 264                 user->qnkeys++;
 265                 user->qnbytes += quotalen;
 266                 spin_unlock(&user->lock);
 267         }
 268
 269         /* allocate and initialise the key and its description */
 270         key = kmem_cache_alloc(key_jar, GFP_KERNEL);
 271         if (!key)
 272                 goto no_memory_2;
 273
 274         if (desc) {
 275                 key->description = kmemdup(desc, desclen, GFP_KERNEL);
 276                 if (!key->description)
 277                         goto no_memory_3;
 278         }
 279
 280         atomic_set(&key->usage, 1);
 281         init_rwsem(&key->sem);
 282         key->type = type;
 283         key->user = user;
 284         key->quotalen = quotalen;
 285         key->datalen = type->def_datalen;
 286         key->uid = uid;
 287         key->gid = gid;
 288         key->perm = perm;
 289         key->flags = 0;
 290         key->expiry = 0;
 291         key->payload.data = NULL;
 292         key->security = NULL;
 293
 294         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA))
 295                 key->flags |= 1 << KEY_FLAG_IN_QUOTA;
 296
 297         memset(&key->type_data, 0, sizeof(key->type_data));
 298
 299 #ifdef KEY_DEBUGGING
 300         key->magic = KEY_DEBUG_MAGIC;
 301 #endif
 302
 303         /* let the security module know about the key */
 304         ret = security_key_alloc(key, cred, flags);
 305         if (ret < 0)
 306                 goto security_error;
 307
 308         /* publish the key by giving it a serial number */
 309         atomic_inc(&user->nkeys);
 310         key_alloc_serial(key);
 311
 312 error:
 313         return key;
 314
 315 security_error:
 316         kfree(key->description);
 317         kmem_cache_free(key_jar, key);
 318         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 319                 spin_lock(&user->lock);
 320                 user->qnkeys--;
 321                 user->qnbytes -= quotalen;
 322                 spin_unlock(&user->lock);
 323         }
 324         key_user_put(user);
 325         key = ERR_PTR(ret);
 326         goto error;
 327
 328 no_memory_3:
 329         kmem_cache_free(key_jar, key);
 330 no_memory_2:
 331         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 332                 spin_lock(&user->lock);
 333                 user->qnkeys--;
 334                 user->qnbytes -= quotalen;
 335                 spin_unlock(&user->lock);
 336         }
 337         key_user_put(user);
 338 no_memory_1:
 339         key = ERR_PTR(-ENOMEM);
 340         goto error;
 341
 342 no_quota:
 343         spin_unlock(&user->lock);
 344         key_user_put(user);
 345         key = ERR_PTR(-EDQUOT);
 346         goto error;
 347
 348 } /* end key_alloc() */
 349
 350 EXPORT_SYMBOL(key_alloc);
 351
 352 /*****************************************************************************/
 353 /*
 354  * reserve an amount of quota for the key's payload
 355  */
 356 int key_payload_reserve(struct key *key, size_t datalen)
 357 {
 358         int delta = (int) datalen - key->datalen;
 359         int ret = 0;
 360
 361         key_check(key);
 362
 363         /* contemplate the quota adjustment */
 364         if (delta != 0 && test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
 365                 unsigned maxbytes = (key->user->uid == 0) ?
 366                         key_quota_root_maxbytes : key_quota_maxbytes;
 367
 368                 spin_lock(&key->user->lock);
 369
 370                 if (delta > 0 &&
 371                     (key->user->qnbytes + delta >= maxbytes ||
 372                      key->user->qnbytes + delta < key->user->qnbytes)) {
 373                         ret = -EDQUOT;
 374                 }
 375                 else {
 376                         key->user->qnbytes += delta;
 377                         key->quotalen += delta;
 378                 }
 379                 spin_unlock(&key->user->lock);
 380         }
 381
 382         /* change the recorded data length if that didn't generate an error */
 383         if (ret == 0)
 384                 key->datalen = datalen;
 385
 386         return ret;
 387
 388 } /* end key_payload_reserve() */
 389
 390 EXPORT_SYMBOL(key_payload_reserve);
 391
 392 /*****************************************************************************/
 393 /*
 394  * instantiate a key and link it into the target keyring atomically
 395  * - called with the target keyring's semaphore writelocked
 396  */
 397 static int __key_instantiate_and_link(struct key *key,
 398                                       const void *data,
 399                                       size_t datalen,
 400                                       struct key *keyring,
 401                                       struct key *authkey)
 402 {
 403         int ret, awaken;
 404
 405         key_check(key);
 406         key_check(keyring);
 407
 408         awaken = 0;
 409         ret = -EBUSY;
 410
 411         mutex_lock(&key_construction_mutex);
 412
 413         /* can't instantiate twice */
 414         if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
 415                 /* instantiate the key */
 416                 ret = key->type->instantiate(key, data, datalen);
 417
 418                 if (ret == 0) {
 419                         /* mark the key as being instantiated */
 420                         atomic_inc(&key->user->nikeys);
 421                         set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
 422
 423                         if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
 424                                 awaken = 1;
 425
 426                         /* and link it into the destination keyring */
 427                         if (keyring)
 428                                 ret = __key_link(keyring, key);
 429
 430                         /* disable the authorisation key */
 431                         if (authkey)
 432                                 key_revoke(authkey);
 433                 }
 434         }
 435
 436         mutex_unlock(&key_construction_mutex);
 437
 438         /* wake up anyone waiting for a key to be constructed */
 439         if (awaken)
 440                 wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
 441
 442         return ret;
 443
 444 } /* end __key_instantiate_and_link() */
 445
 446 /*****************************************************************************/
 447 /*
 448  * instantiate a key and link it into the target keyring atomically
 449  */
 450 int key_instantiate_and_link(struct key *key,
 451                              const void *data,
 452                              size_t datalen,
 453                              struct key *keyring,
 454                              struct key *authkey)
 455 {
 456         int ret;
 457
 458         if (keyring)
 459                 down_write(&keyring->sem);
 460
 461         ret = __key_instantiate_and_link(key, data, datalen, keyring, authkey);
 462
 463         if (keyring)
 464                 up_write(&keyring->sem);
 465
 466         return ret;
 467
 468 } /* end key_instantiate_and_link() */
 469
 470 EXPORT_SYMBOL(key_instantiate_and_link);
 471
 472 /*****************************************************************************/
 473 /*
 474  * negatively instantiate a key and link it into the target keyring atomically
 475  */
 476 int key_negate_and_link(struct key *key,
 477                         unsigned timeout,
 478                         struct key *keyring,
 479                         struct key *authkey)
 480 {
 481         struct timespec now;
 482         int ret, awaken;
 483
 484         key_check(key);
 485         key_check(keyring);
 486
 487         awaken = 0;
 488         ret = -EBUSY;
 489
 490         if (keyring)
 491                 down_write(&keyring->sem);
 492
 493         mutex_lock(&key_construction_mutex);
 494
 495         /* can't instantiate twice */
 496         if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
 497                 /* mark the key as being negatively instantiated */
 498                 atomic_inc(&key->user->nikeys);
 499                 set_bit(KEY_FLAG_NEGATIVE, &key->flags);
 500                 set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
 501                 now = current_kernel_time();
 502                 key->expiry = now.tv_sec + timeout;
 503                 key_schedule_gc(key->expiry + key_gc_delay);
 504
 505                 if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
 506                         awaken = 1;
 507
 508                 ret = 0;
 509
 510                 /* and link it into the destination keyring */
 511                 if (keyring)
 512                         ret = __key_link(keyring, key);
 513
 514                 /* disable the authorisation key */
 515                 if (authkey)
 516                         key_revoke(authkey);
 517         }
 518
 519         mutex_unlock(&key_construction_mutex);
 520
 521         if (keyring)
 522                 up_write(&keyring->sem);
 523
 524         /* wake up anyone waiting for a key to be constructed */
 525         if (awaken)
 526                 wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
 527
 528         return ret;
 529
 530 } /* end key_negate_and_link() */
 531
 532 EXPORT_SYMBOL(key_negate_and_link);
 533
 534 /*****************************************************************************/
 535 /*
 536  * do cleaning up in process context so that we don't have to disable
 537  * interrupts all over the place
 538  */
 539 static void key_cleanup(struct work_struct *work)
 540 {
 541         struct rb_node *_n;
 542         struct key *key;
 543
 544  go_again:
 545         /* look for a dead key in the tree */
 546         spin_lock(&key_serial_lock);
 547
 548         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 549                 key = rb_entry(_n, struct key, serial_node);
 550
 551                 if (atomic_read(&key->usage) == 0)
 552                         goto found_dead_key;
 553         }
 554
 555         spin_unlock(&key_serial_lock);
 556         return;
 557
 558  found_dead_key:
 559         /* we found a dead key - once we've removed it from the tree, we can
 560          * drop the lock */
 561         rb_erase(&key->serial_node, &key_serial_tree);
 562         spin_unlock(&key_serial_lock);
 563
 564         key_check(key);
 565
 566         security_key_free(key);
 567
 568         /* deal with the user's key tracking and quota */
 569         if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
 570                 spin_lock(&key->user->lock);
 571                 key->user->qnkeys--;
 572                 key->user->qnbytes -= key->quotalen;
 573                 spin_unlock(&key->user->lock);
 574         }
 575
 576         atomic_dec(&key->user->nkeys);
 577         if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
 578                 atomic_dec(&key->user->nikeys);
 579
 580         key_user_put(key->user);
 581
 582         /* now throw away the key memory */
 583         if (key->type->destroy)
 584                 key->type->destroy(key);
 585
 586         kfree(key->description);
 587
 588 #ifdef KEY_DEBUGGING
 589         key->magic = KEY_DEBUG_MAGIC_X;
 590 #endif
 591         kmem_cache_free(key_jar, key);
 592
 593         /* there may, of course, be more than one key to destroy */
 594         goto go_again;
 595
 596 } /* end key_cleanup() */
 597
 598 /*****************************************************************************/
 599 /*
 600  * dispose of a reference to a key
 601  * - when all the references are gone, we schedule the cleanup task to come and
 602  *   pull it out of the tree in definite process context
 603  */
 604 void key_put(struct key *key)
 605 {
 606         if (key) {
 607                 key_check(key);
 608
 609                 if (atomic_dec_and_test(&key->usage))
 610                         schedule_work(&key_cleanup_task);
 611         }
 612
 613 } /* end key_put() */
 614
 615 EXPORT_SYMBOL(key_put);
 616
 617 /*****************************************************************************/
 618 /*
 619  * find a key by its serial number
 620  */
 621 struct key *key_lookup(key_serial_t id)
 622 {
 623         struct rb_node *n;
 624         struct key *key;
 625
 626         spin_lock(&key_serial_lock);
 627
 628         /* search the tree for the specified key */
 629         n = key_serial_tree.rb_node;
 630         while (n) {
 631                 key = rb_entry(n, struct key, serial_node);
 632
 633                 if (id < key->serial)
 634                         n = n->rb_left;
 635                 else if (id > key->serial)
 636                         n = n->rb_right;
 637                 else
 638                         goto found;
 639         }
 640
 641  not_found:
 642         key = ERR_PTR(-ENOKEY);
 643         goto error;
 644
 645  found:
 646         /* pretend it doesn't exist if it is awaiting deletion */
 647         if (atomic_read(&key->usage) == 0)
 648                 goto not_found;
 649
 650         /* this races with key_put(), but that doesn't matter since key_put()
 651          * doesn't actually change the key
 652          */
 653         atomic_inc(&key->usage);
 654
 655  error:
 656         spin_unlock(&key_serial_lock);
 657         return key;
 658
 659 } /* end key_lookup() */
 660
 661 /*****************************************************************************/
 662 /*
 663  * find and lock the specified key type against removal
 664  * - we return with the sem readlocked
 665  */
 666 struct key_type *key_type_lookup(const char *type)
 667 {
 668         struct key_type *ktype;
 669
 670         down_read(&key_types_sem);
 671
 672         /* look up the key type to see if it's one of the registered kernel
 673          * types */
 674         list_for_each_entry(ktype, &key_types_list, link) {
 675                 if (strcmp(ktype->name, type) == 0)
 676                         goto found_kernel_type;
 677         }
 678
 679         up_read(&key_types_sem);
 680         ktype = ERR_PTR(-ENOKEY);
 681
 682  found_kernel_type:
 683         return ktype;
 684
 685 } /* end key_type_lookup() */
 686
 687 /*****************************************************************************/
 688 /*
 689  * unlock a key type
 690  */
 691 void key_type_put(struct key_type *ktype)
 692 {
 693         up_read(&key_types_sem);
 694
 695 } /* end key_type_put() */
 696
 697 /*****************************************************************************/
 698 /*
 699  * attempt to update an existing key
 700  * - the key has an incremented refcount
 701  * - we need to put the key if we get an error
 702  */
 703 static inline key_ref_t __key_update(key_ref_t key_ref,
 704                                      const void *payload, size_t plen)
 705 {
 706         struct key *key = key_ref_to_ptr(key_ref);
 707         int ret;
 708
 709         /* need write permission on the key to update it */
 710         ret = key_permission(key_ref, KEY_WRITE);
 711         if (ret < 0)
 712                 goto error;
 713
 714         ret = -EEXIST;
 715         if (!key->type->update)
 716                 goto error;
 717
 718         down_write(&key->sem);
 719
 720         ret = key->type->update(key, payload, plen);
 721         if (ret == 0)
 722                 /* updating a negative key instantiates it */
 723                 clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
 724
 725         up_write(&key->sem);
 726
 727         if (ret < 0)
 728                 goto error;
 729 out:
 730         return key_ref;
 731
 732 error:
 733         key_put(key);
 734         key_ref = ERR_PTR(ret);
 735         goto out;
 736
 737 } /* end __key_update() */
 738
 739 /*****************************************************************************/
 740 /*
 741  * search the specified keyring for a key of the same description; if one is
 742  * found, update it, otherwise add a new one
 743  */
 744 key_ref_t key_create_or_update(key_ref_t keyring_ref,
 745                                const char *type,
 746                                const char *description,
 747                                const void *payload,
 748                                size_t plen,
 749                                key_perm_t perm,
 750                                unsigned long flags)
 751 {
 752         const struct cred *cred = current_cred();
 753         struct key_type *ktype;
 754         struct key *keyring, *key = NULL;
 755         key_ref_t key_ref;
 756         int ret;
 757
 758         /* look up the key type to see if it's one of the registered kernel
 759          * types */
 760         ktype = key_type_lookup(type);
 761         if (IS_ERR(ktype)) {
 762                 key_ref = ERR_PTR(-ENODEV);
 763                 goto error;
 764         }
 765
 766         key_ref = ERR_PTR(-EINVAL);
 767         if (!ktype->match || !ktype->instantiate)
 768                 goto error_2;
 769
 770         keyring = key_ref_to_ptr(keyring_ref);
 771
 772         key_check(keyring);
 773
 774         key_ref = ERR_PTR(-ENOTDIR);
 775         if (keyring->type != &key_type_keyring)
 776                 goto error_2;
 777
 778         down_write(&keyring->sem);
 779
 780         /* if we're going to allocate a new key, we're going to have
 781          * to modify the keyring */
 782         ret = key_permission(keyring_ref, KEY_WRITE);
 783         if (ret < 0) {
 784                 key_ref = ERR_PTR(ret);
 785                 goto error_3;
 786         }
 787
 788         /* if it's possible to update this type of key, search for an existing
 789          * key of the same type and description in the destination keyring and
 790          * update that instead if possible
 791          */
 792         if (ktype->update) {
 793                 key_ref = __keyring_search_one(keyring_ref, ktype, description,
 794                                                0);
 795                 if (!IS_ERR(key_ref))
 796                         goto found_matching_key;
 797         }
 798
 799         /* if the client doesn't provide, decide on the permissions we want */
 800         if (perm == KEY_PERM_UNDEF) {
 801                 perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
 802                 perm |= KEY_USR_VIEW | KEY_USR_SEARCH | KEY_USR_LINK | KEY_USR_SETATTR;
 803
 804                 if (ktype->read)
 805                         perm |= KEY_POS_READ | KEY_USR_READ;
 806
 807                 if (ktype == &key_type_keyring || ktype->update)
 808                         perm |= KEY_USR_WRITE;
 809         }
 810
 811         /* allocate a new key */
 812         key = key_alloc(ktype, description, cred->fsuid, cred->fsgid, cred,
 813                         perm, flags);
 814         if (IS_ERR(key)) {
 815                 key_ref = ERR_CAST(key);
 816                 goto error_3;
 817         }
 818
 819         /* instantiate it and link it into the target keyring */
 820         ret = __key_instantiate_and_link(key, payload, plen, keyring, NULL);
 821         if (ret < 0) {
 822                 key_put(key);
 823                 key_ref = ERR_PTR(ret);
 824                 goto error_3;
 825         }
 826
 827         key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
 828
 829  error_3:
 830         up_write(&keyring->sem);
 831  error_2:
 832         key_type_put(ktype);
 833  error:
 834         return key_ref;
 835
 836  found_matching_key:
 837         /* we found a matching key, so we're going to try to update it
 838          * - we can drop the locks first as we have the key pinned
 839          */
 840         up_write(&keyring->sem);
 841         key_type_put(ktype);
 842
 843         key_ref = __key_update(key_ref, payload, plen);
 844         goto error;
 845
 846 } /* end key_create_or_update() */
 847
 848 EXPORT_SYMBOL(key_create_or_update);
 849
 850 /*****************************************************************************/
 851 /*
 852  * update a key
 853  */
 854 int key_update(key_ref_t key_ref, const void *payload, size_t plen)
 855 {
 856         struct key *key = key_ref_to_ptr(key_ref);
 857         int ret;
 858
 859         key_check(key);
 860
 861         /* the key must be writable */
 862         ret = key_permission(key_ref, KEY_WRITE);
 863         if (ret < 0)
 864                 goto error;
 865
 866         /* attempt to update it if supported */
 867         ret = -EOPNOTSUPP;
 868         if (key->type->update) {
 869                 down_write(&key->sem);
 870
 871                 ret = key->type->update(key, payload, plen);
 872                 if (ret == 0)
 873                         /* updating a negative key instantiates it */
 874                         clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
 875
 876                 up_write(&key->sem);
 877         }
 878
 879  error:
 880         return ret;
 881
 882 } /* end key_update() */
 883
 884 EXPORT_SYMBOL(key_update);
 885
 886 /*****************************************************************************/
 887 /*
 888  * revoke a key
 889  */
 890 void key_revoke(struct key *key)
 891 {
 892         struct timespec now;
 893         time_t time;
 894
 895         key_check(key);
 896
 897         /* make sure no one's trying to change or use the key when we mark it
 898          * - we tell lockdep that we might nest because we might be revoking an
 899          *   authorisation key whilst holding the sem on a key we've just
 900          *   instantiated
 901          */
 902         down_write_nested(&key->sem, 1);
 903         if (!test_and_set_bit(KEY_FLAG_REVOKED, &key->flags) &&
 904             key->type->revoke)
 905                 key->type->revoke(key);
 906
 907         /* set the death time to no more than the expiry time */
 908         now = current_kernel_time();
 909         time = now.tv_sec;
 910         if (key->revoked_at == 0 || key->revoked_at > time) {
 911                 key->revoked_at = time;
 912                 key_schedule_gc(key->revoked_at + key_gc_delay);
 913         }
 914
 915         up_write(&key->sem);
 916
 917 } /* end key_revoke() */
 918
 919 EXPORT_SYMBOL(key_revoke);
 920
 921 /*****************************************************************************/
 922 /*
 923  * register a type of key
 924  */
 925 int register_key_type(struct key_type *ktype)
 926 {
 927         struct key_type *p;
 928         int ret;
 929
 930         ret = -EEXIST;
 931         down_write(&key_types_sem);
 932
 933         /* disallow key types with the same name */
 934         list_for_each_entry(p, &key_types_list, link) {
 935                 if (strcmp(p->name, ktype->name) == 0)
 936                         goto out;
 937         }
 938
 939         /* store the type */
 940         list_add(&ktype->link, &key_types_list);
 941         ret = 0;
 942
 943  out:
 944         up_write(&key_types_sem);
 945         return ret;
 946
 947 } /* end register_key_type() */
 948
 949 EXPORT_SYMBOL(register_key_type);
 950
 951 /*****************************************************************************/
 952 /*
 953  * unregister a type of key
 954  */
 955 void unregister_key_type(struct key_type *ktype)
 956 {
 957         struct rb_node *_n;
 958         struct key *key;
 959
 960         down_write(&key_types_sem);
 961
 962         /* withdraw the key type */
 963         list_del_init(&ktype->link);
 964
 965         /* mark all the keys of this type dead */
 966         spin_lock(&key_serial_lock);
 967
 968         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 969                 key = rb_entry(_n, struct key, serial_node);
 970
 971                 if (key->type == ktype) {
 972                         key->type = &key_type_dead;
 973                         set_bit(KEY_FLAG_DEAD, &key->flags);
 974                 }
 975         }
 976
 977         spin_unlock(&key_serial_lock);
 978
 979         /* make sure everyone revalidates their keys */
 980         synchronize_rcu();
 981
 982         /* we should now be able to destroy the payloads of all the keys of
 983          * this type with impunity */
 984         spin_lock(&key_serial_lock);
 985
 986         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 987                 key = rb_entry(_n, struct key, serial_node);
 988
 989                 if (key->type == ktype) {
 990                         if (ktype->destroy)
 991                                 ktype->destroy(key);
 992                         memset(&key->payload, KEY_DESTROY, sizeof(key->payload));
 993                 }
 994         }
 995
 996         spin_unlock(&key_serial_lock);
 997         up_write(&key_types_sem);
 998
 999         key_schedule_gc(0);
1000
1001 } /* end unregister_key_type() */
1002
1003 EXPORT_SYMBOL(unregister_key_type);
1004
1005 /*****************************************************************************/
1006 /*
1007  * initialise the key management stuff
1008  */
1009 void __init key_init(void)
1010 {
1011         /* allocate a slab in which we can store keys */
1012         key_jar = kmem_cache_create("key_jar", sizeof(struct key),
1013                         0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1014
1015         /* add the special key types */
1016         list_add_tail(&key_type_keyring.link, &key_types_list);
1017         list_add_tail(&key_type_dead.link, &key_types_list);
1018         list_add_tail(&key_type_user.link, &key_types_list);
1019
1020         /* record the root user tracking */
1021         rb_link_node(&root_key_user.node,
1022                      NULL,
1023                      &key_user_tree.rb_node);
1024
1025         rb_insert_color(&root_key_user.node,
1026                         &key_user_tree);
1027
1028 } /* end key_init() */