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
 504                 if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
 505                         awaken = 1;
 506
 507                 ret = 0;
 508
 509                 /* and link it into the destination keyring */
 510                 if (keyring)
 511                         ret = __key_link(keyring, key);
 512
 513                 /* disable the authorisation key */
 514                 if (authkey)
 515                         key_revoke(authkey);
 516         }
 517
 518         mutex_unlock(&key_construction_mutex);
 519
 520         if (keyring)
 521                 up_write(&keyring->sem);
 522
 523         /* wake up anyone waiting for a key to be constructed */
 524         if (awaken)
 525                 wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
 526
 527         return ret;
 528
 529 } /* end key_negate_and_link() */
 530
 531 EXPORT_SYMBOL(key_negate_and_link);
 532
 533 /*****************************************************************************/
 534 /*
 535  * do cleaning up in process context so that we don't have to disable
 536  * interrupts all over the place
 537  */
 538 static void key_cleanup(struct work_struct *work)
 539 {
 540         struct rb_node *_n;
 541         struct key *key;
 542
 543  go_again:
 544         /* look for a dead key in the tree */
 545         spin_lock(&key_serial_lock);
 546
 547         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 548                 key = rb_entry(_n, struct key, serial_node);
 549
 550                 if (atomic_read(&key->usage) == 0)
 551                         goto found_dead_key;
 552         }
 553
 554         spin_unlock(&key_serial_lock);
 555         return;
 556
 557  found_dead_key:
 558         /* we found a dead key - once we've removed it from the tree, we can
 559          * drop the lock */
 560         rb_erase(&key->serial_node, &key_serial_tree);
 561         spin_unlock(&key_serial_lock);
 562
 563         key_check(key);
 564
 565         security_key_free(key);
 566
 567         /* deal with the user's key tracking and quota */
 568         if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
 569                 spin_lock(&key->user->lock);
 570                 key->user->qnkeys--;
 571                 key->user->qnbytes -= key->quotalen;
 572                 spin_unlock(&key->user->lock);
 573         }
 574
 575         atomic_dec(&key->user->nkeys);
 576         if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
 577                 atomic_dec(&key->user->nikeys);
 578
 579         key_user_put(key->user);
 580
 581         /* now throw away the key memory */
 582         if (key->type->destroy)
 583                 key->type->destroy(key);
 584
 585         kfree(key->description);
 586
 587 #ifdef KEY_DEBUGGING
 588         key->magic = KEY_DEBUG_MAGIC_X;
 589 #endif
 590         kmem_cache_free(key_jar, key);
 591
 592         /* there may, of course, be more than one key to destroy */
 593         goto go_again;
 594
 595 } /* end key_cleanup() */
 596
 597 /*****************************************************************************/
 598 /*
 599  * dispose of a reference to a key
 600  * - when all the references are gone, we schedule the cleanup task to come and
 601  *   pull it out of the tree in definite process context
 602  */
 603 void key_put(struct key *key)
 604 {
 605         if (key) {
 606                 key_check(key);
 607
 608                 if (atomic_dec_and_test(&key->usage))
 609                         schedule_work(&key_cleanup_task);
 610         }
 611
 612 } /* end key_put() */
 613
 614 EXPORT_SYMBOL(key_put);
 615
 616 /*****************************************************************************/
 617 /*
 618  * find a key by its serial number
 619  */
 620 struct key *key_lookup(key_serial_t id)
 621 {
 622         struct rb_node *n;
 623         struct key *key;
 624
 625         spin_lock(&key_serial_lock);
 626
 627         /* search the tree for the specified key */
 628         n = key_serial_tree.rb_node;
 629         while (n) {
 630                 key = rb_entry(n, struct key, serial_node);
 631
 632                 if (id < key->serial)
 633                         n = n->rb_left;
 634                 else if (id > key->serial)
 635                         n = n->rb_right;
 636                 else
 637                         goto found;
 638         }
 639
 640  not_found:
 641         key = ERR_PTR(-ENOKEY);
 642         goto error;
 643
 644  found:
 645         /* pretend it doesn't exist if it's dead */
 646         if (atomic_read(&key->usage) == 0 ||
 647             test_bit(KEY_FLAG_DEAD, &key->flags) ||
 648             key->type == &key_type_dead)
 649                 goto not_found;
 650
 651         /* this races with key_put(), but that doesn't matter since key_put()
 652          * doesn't actually change the key
 653          */
 654         atomic_inc(&key->usage);
 655
 656  error:
 657         spin_unlock(&key_serial_lock);
 658         return key;
 659
 660 } /* end key_lookup() */
 661
 662 /*****************************************************************************/
 663 /*
 664  * find and lock the specified key type against removal
 665  * - we return with the sem readlocked
 666  */
 667 struct key_type *key_type_lookup(const char *type)
 668 {
 669         struct key_type *ktype;
 670
 671         down_read(&key_types_sem);
 672
 673         /* look up the key type to see if it's one of the registered kernel
 674          * types */
 675         list_for_each_entry(ktype, &key_types_list, link) {
 676                 if (strcmp(ktype->name, type) == 0)
 677                         goto found_kernel_type;
 678         }
 679
 680         up_read(&key_types_sem);
 681         ktype = ERR_PTR(-ENOKEY);
 682
 683  found_kernel_type:
 684         return ktype;
 685
 686 } /* end key_type_lookup() */
 687
 688 /*****************************************************************************/
 689 /*
 690  * unlock a key type
 691  */
 692 void key_type_put(struct key_type *ktype)
 693 {
 694         up_read(&key_types_sem);
 695
 696 } /* end key_type_put() */
 697
 698 /*****************************************************************************/
 699 /*
 700  * attempt to update an existing key
 701  * - the key has an incremented refcount
 702  * - we need to put the key if we get an error
 703  */
 704 static inline key_ref_t __key_update(key_ref_t key_ref,
 705                                      const void *payload, size_t plen)
 706 {
 707         struct key *key = key_ref_to_ptr(key_ref);
 708         int ret;
 709
 710         /* need write permission on the key to update it */
 711         ret = key_permission(key_ref, KEY_WRITE);
 712         if (ret < 0)
 713                 goto error;
 714
 715         ret = -EEXIST;
 716         if (!key->type->update)
 717                 goto error;
 718
 719         down_write(&key->sem);
 720
 721         ret = key->type->update(key, payload, plen);
 722         if (ret == 0)
 723                 /* updating a negative key instantiates it */
 724                 clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
 725
 726         up_write(&key->sem);
 727
 728         if (ret < 0)
 729                 goto error;
 730 out:
 731         return key_ref;
 732
 733 error:
 734         key_put(key);
 735         key_ref = ERR_PTR(ret);
 736         goto out;
 737
 738 } /* end __key_update() */
 739
 740 /*****************************************************************************/
 741 /*
 742  * search the specified keyring for a key of the same description; if one is
 743  * found, update it, otherwise add a new one
 744  */
 745 key_ref_t key_create_or_update(key_ref_t keyring_ref,
 746                                const char *type,
 747                                const char *description,
 748                                const void *payload,
 749                                size_t plen,
 750                                key_perm_t perm,
 751                                unsigned long flags)
 752 {
 753         const struct cred *cred = current_cred();
 754         struct key_type *ktype;
 755         struct key *keyring, *key = NULL;
 756         key_ref_t key_ref;
 757         int ret;
 758
 759         /* look up the key type to see if it's one of the registered kernel
 760          * types */
 761         ktype = key_type_lookup(type);
 762         if (IS_ERR(ktype)) {
 763                 key_ref = ERR_PTR(-ENODEV);
 764                 goto error;
 765         }
 766
 767         key_ref = ERR_PTR(-EINVAL);
 768         if (!ktype->match || !ktype->instantiate)
 769                 goto error_2;
 770
 771         keyring = key_ref_to_ptr(keyring_ref);
 772
 773         key_check(keyring);
 774
 775         key_ref = ERR_PTR(-ENOTDIR);
 776         if (keyring->type != &key_type_keyring)
 777                 goto error_2;
 778
 779         down_write(&keyring->sem);
 780
 781         /* if we're going to allocate a new key, we're going to have
 782          * to modify the keyring */
 783         ret = key_permission(keyring_ref, KEY_WRITE);
 784         if (ret < 0) {
 785                 key_ref = ERR_PTR(ret);
 786                 goto error_3;
 787         }
 788
 789         /* if it's possible to update this type of key, search for an existing
 790          * key of the same type and description in the destination keyring and
 791          * update that instead if possible
 792          */
 793         if (ktype->update) {
 794                 key_ref = __keyring_search_one(keyring_ref, ktype, description,
 795                                                0);
 796                 if (!IS_ERR(key_ref))
 797                         goto found_matching_key;
 798         }
 799
 800         /* if the client doesn't provide, decide on the permissions we want */
 801         if (perm == KEY_PERM_UNDEF) {
 802                 perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
 803                 perm |= KEY_USR_VIEW | KEY_USR_SEARCH | KEY_USR_LINK | KEY_USR_SETATTR;
 804
 805                 if (ktype->read)
 806                         perm |= KEY_POS_READ | KEY_USR_READ;
 807
 808                 if (ktype == &key_type_keyring || ktype->update)
 809                         perm |= KEY_USR_WRITE;
 810         }
 811
 812         /* allocate a new key */
 813         key = key_alloc(ktype, description, cred->fsuid, cred->fsgid, cred,
 814                         perm, flags);
 815         if (IS_ERR(key)) {
 816                 key_ref = ERR_CAST(key);
 817                 goto error_3;
 818         }
 819
 820         /* instantiate it and link it into the target keyring */
 821         ret = __key_instantiate_and_link(key, payload, plen, keyring, NULL);
 822         if (ret < 0) {
 823                 key_put(key);
 824                 key_ref = ERR_PTR(ret);
 825                 goto error_3;
 826         }
 827
 828         key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
 829
 830  error_3:
 831         up_write(&keyring->sem);
 832  error_2:
 833         key_type_put(ktype);
 834  error:
 835         return key_ref;
 836
 837  found_matching_key:
 838         /* we found a matching key, so we're going to try to update it
 839          * - we can drop the locks first as we have the key pinned
 840          */
 841         up_write(&keyring->sem);
 842         key_type_put(ktype);
 843
 844         key_ref = __key_update(key_ref, payload, plen);
 845         goto error;
 846
 847 } /* end key_create_or_update() */
 848
 849 EXPORT_SYMBOL(key_create_or_update);
 850
 851 /*****************************************************************************/
 852 /*
 853  * update a key
 854  */
 855 int key_update(key_ref_t key_ref, const void *payload, size_t plen)
 856 {
 857         struct key *key = key_ref_to_ptr(key_ref);
 858         int ret;
 859
 860         key_check(key);
 861
 862         /* the key must be writable */
 863         ret = key_permission(key_ref, KEY_WRITE);
 864         if (ret < 0)
 865                 goto error;
 866
 867         /* attempt to update it if supported */
 868         ret = -EOPNOTSUPP;
 869         if (key->type->update) {
 870                 down_write(&key->sem);
 871
 872                 ret = key->type->update(key, payload, plen);
 873                 if (ret == 0)
 874                         /* updating a negative key instantiates it */
 875                         clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
 876
 877                 up_write(&key->sem);
 878         }
 879
 880  error:
 881         return ret;
 882
 883 } /* end key_update() */
 884
 885 EXPORT_SYMBOL(key_update);
 886
 887 /*****************************************************************************/
 888 /*
 889  * revoke a key
 890  */
 891 void key_revoke(struct key *key)
 892 {
 893         key_check(key);
 894
 895         /* make sure no one's trying to change or use the key when we mark it
 896          * - we tell lockdep that we might nest because we might be revoking an
 897          *   authorisation key whilst holding the sem on a key we've just
 898          *   instantiated
 899          */
 900         down_write_nested(&key->sem, 1);
 901         if (!test_and_set_bit(KEY_FLAG_REVOKED, &key->flags) &&
 902             key->type->revoke)
 903                 key->type->revoke(key);
 904
 905         up_write(&key->sem);
 906
 907 } /* end key_revoke() */
 908
 909 EXPORT_SYMBOL(key_revoke);
 910
 911 /*****************************************************************************/
 912 /*
 913  * register a type of key
 914  */
 915 int register_key_type(struct key_type *ktype)
 916 {
 917         struct key_type *p;
 918         int ret;
 919
 920         ret = -EEXIST;
 921         down_write(&key_types_sem);
 922
 923         /* disallow key types with the same name */
 924         list_for_each_entry(p, &key_types_list, link) {
 925                 if (strcmp(p->name, ktype->name) == 0)
 926                         goto out;
 927         }
 928
 929         /* store the type */
 930         list_add(&ktype->link, &key_types_list);
 931         ret = 0;
 932
 933  out:
 934         up_write(&key_types_sem);
 935         return ret;
 936
 937 } /* end register_key_type() */
 938
 939 EXPORT_SYMBOL(register_key_type);
 940
 941 /*****************************************************************************/
 942 /*
 943  * unregister a type of key
 944  */
 945 void unregister_key_type(struct key_type *ktype)
 946 {
 947         struct rb_node *_n;
 948         struct key *key;
 949
 950         down_write(&key_types_sem);
 951
 952         /* withdraw the key type */
 953         list_del_init(&ktype->link);
 954
 955         /* mark all the keys of this type dead */
 956         spin_lock(&key_serial_lock);
 957
 958         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 959                 key = rb_entry(_n, struct key, serial_node);
 960
 961                 if (key->type == ktype)
 962                         key->type = &key_type_dead;
 963         }
 964
 965         spin_unlock(&key_serial_lock);
 966
 967         /* make sure everyone revalidates their keys */
 968         synchronize_rcu();
 969
 970         /* we should now be able to destroy the payloads of all the keys of
 971          * this type with impunity */
 972         spin_lock(&key_serial_lock);
 973
 974         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 975                 key = rb_entry(_n, struct key, serial_node);
 976
 977                 if (key->type == ktype) {
 978                         if (ktype->destroy)
 979                                 ktype->destroy(key);
 980                         memset(&key->payload, KEY_DESTROY, sizeof(key->payload));
 981                 }
 982         }
 983
 984         spin_unlock(&key_serial_lock);
 985         up_write(&key_types_sem);
 986
 987 } /* end unregister_key_type() */
 988
 989 EXPORT_SYMBOL(unregister_key_type);
 990
 991 /*****************************************************************************/
 992 /*
 993  * initialise the key management stuff
 994  */
 995 void __init key_init(void)
 996 {
 997         /* allocate a slab in which we can store keys */
 998         key_jar = kmem_cache_create("key_jar", sizeof(struct key),
 999                         0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1000
1001         /* add the special key types */
1002         list_add_tail(&key_type_keyring.link, &key_types_list);
1003         list_add_tail(&key_type_dead.link, &key_types_list);
1004         list_add_tail(&key_type_user.link, &key_types_list);
1005
1006         /* record the root user tracking */
1007         rb_link_node(&root_key_user.node,
1008                      NULL,
1009                      &key_user_tree.rb_node);
1010
1011         rb_insert_color(&root_key_user.node,
1012                         &key_user_tree);
1013
1014 } /* end key_init() */