linux/security/keys/key.c
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   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
  23struct kmem_cache *key_jar;
  24struct rb_root          key_serial_tree; /* tree of keys indexed by serial */
  25DEFINE_SPINLOCK(key_serial_lock);
  26
  27struct rb_root  key_user_tree; /* tree of quota records indexed by UID */
  28DEFINE_SPINLOCK(key_user_lock);
  29
  30unsigned int key_quota_root_maxkeys = 200;      /* root's key count quota */
  31unsigned int key_quota_root_maxbytes = 20000;   /* root's key space quota */
  32unsigned int key_quota_maxkeys = 200;           /* general key count quota */
  33unsigned int key_quota_maxbytes = 20000;        /* general key space quota */
  34
  35static LIST_HEAD(key_types_list);
  36static DECLARE_RWSEM(key_types_sem);
  37
  38/* We serialise key instantiation and link */
  39DEFINE_MUTEX(key_construction_mutex);
  40
  41#ifdef KEY_DEBUGGING
  42void __key_check(const struct key *key)
  43{
  44        printk("__key_check: key %p {%08x} should be {%08x}\n",
  45               key, key->magic, KEY_DEBUG_MAGIC);
  46        BUG();
  47}
  48#endif
  49
  50/*
  51 * Get the key quota record for a user, allocating a new record if one doesn't
  52 * already exist.
  53 */
  54struct key_user *key_user_lookup(kuid_t uid)
  55{
  56        struct key_user *candidate = NULL, *user;
  57        struct rb_node *parent = NULL;
  58        struct rb_node **p;
  59
  60try_again:
  61        p = &key_user_tree.rb_node;
  62        spin_lock(&key_user_lock);
  63
  64        /* search the tree for a user record with a matching UID */
  65        while (*p) {
  66                parent = *p;
  67                user = rb_entry(parent, struct key_user, node);
  68
  69                if (uid_lt(uid, user->uid))
  70                        p = &(*p)->rb_left;
  71                else if (uid_gt(uid, user->uid))
  72                        p = &(*p)->rb_right;
  73                else
  74                        goto found;
  75        }
  76
  77        /* if we get here, we failed to find a match in the tree */
  78        if (!candidate) {
  79                /* allocate a candidate user record if we don't already have
  80                 * one */
  81                spin_unlock(&key_user_lock);
  82
  83                user = NULL;
  84                candidate = kmalloc(sizeof(struct key_user), GFP_KERNEL);
  85                if (unlikely(!candidate))
  86                        goto out;
  87
  88                /* the allocation may have scheduled, so we need to repeat the
  89                 * search lest someone else added the record whilst we were
  90                 * asleep */
  91                goto try_again;
  92        }
  93
  94        /* if we get here, then the user record still hadn't appeared on the
  95         * second pass - so we use the candidate record */
  96        atomic_set(&candidate->usage, 1);
  97        atomic_set(&candidate->nkeys, 0);
  98        atomic_set(&candidate->nikeys, 0);
  99        candidate->uid = uid;
 100        candidate->qnkeys = 0;
 101        candidate->qnbytes = 0;
 102        spin_lock_init(&candidate->lock);
 103        mutex_init(&candidate->cons_lock);
 104
 105        rb_link_node(&candidate->node, parent, p);
 106        rb_insert_color(&candidate->node, &key_user_tree);
 107        spin_unlock(&key_user_lock);
 108        user = candidate;
 109        goto out;
 110
 111        /* okay - we found a user record for this UID */
 112found:
 113        atomic_inc(&user->usage);
 114        spin_unlock(&key_user_lock);
 115        kfree(candidate);
 116out:
 117        return user;
 118}
 119
 120/*
 121 * Dispose of a user structure
 122 */
 123void key_user_put(struct key_user *user)
 124{
 125        if (atomic_dec_and_lock(&user->usage, &key_user_lock)) {
 126                rb_erase(&user->node, &key_user_tree);
 127                spin_unlock(&key_user_lock);
 128
 129                kfree(user);
 130        }
 131}
 132
 133/*
 134 * Allocate a serial number for a key.  These are assigned randomly to avoid
 135 * security issues through covert channel problems.
 136 */
 137static inline void key_alloc_serial(struct key *key)
 138{
 139        struct rb_node *parent, **p;
 140        struct key *xkey;
 141
 142        /* propose a random serial number and look for a hole for it in the
 143         * serial number tree */
 144        do {
 145                get_random_bytes(&key->serial, sizeof(key->serial));
 146
 147                key->serial >>= 1; /* negative numbers are not permitted */
 148        } while (key->serial < 3);
 149
 150        spin_lock(&key_serial_lock);
 151
 152attempt_insertion:
 153        parent = NULL;
 154        p = &key_serial_tree.rb_node;
 155
 156        while (*p) {
 157                parent = *p;
 158                xkey = rb_entry(parent, struct key, serial_node);
 159
 160                if (key->serial < xkey->serial)
 161                        p = &(*p)->rb_left;
 162                else if (key->serial > xkey->serial)
 163                        p = &(*p)->rb_right;
 164                else
 165                        goto serial_exists;
 166        }
 167
 168        /* we've found a suitable hole - arrange for this key to occupy it */
 169        rb_link_node(&key->serial_node, parent, p);
 170        rb_insert_color(&key->serial_node, &key_serial_tree);
 171
 172        spin_unlock(&key_serial_lock);
 173        return;
 174
 175        /* we found a key with the proposed serial number - walk the tree from
 176         * that point looking for the next unused serial number */
 177serial_exists:
 178        for (;;) {
 179                key->serial++;
 180                if (key->serial < 3) {
 181                        key->serial = 3;
 182                        goto attempt_insertion;
 183                }
 184
 185                parent = rb_next(parent);
 186                if (!parent)
 187                        goto attempt_insertion;
 188
 189                xkey = rb_entry(parent, struct key, serial_node);
 190                if (key->serial < xkey->serial)
 191                        goto attempt_insertion;
 192        }
 193}
 194
 195/**
 196 * key_alloc - Allocate a key of the specified type.
 197 * @type: The type of key to allocate.
 198 * @desc: The key description to allow the key to be searched out.
 199 * @uid: The owner of the new key.
 200 * @gid: The group ID for the new key's group permissions.
 201 * @cred: The credentials specifying UID namespace.
 202 * @perm: The permissions mask of the new key.
 203 * @flags: Flags specifying quota properties.
 204 *
 205 * Allocate a key of the specified type with the attributes given.  The key is
 206 * returned in an uninstantiated state and the caller needs to instantiate the
 207 * key before returning.
 208 *
 209 * The user's key count quota is updated to reflect the creation of the key and
 210 * the user's key data quota has the default for the key type reserved.  The
 211 * instantiation function should amend this as necessary.  If insufficient
 212 * quota is available, -EDQUOT will be returned.
 213 *
 214 * The LSM security modules can prevent a key being created, in which case
 215 * -EACCES will be returned.
 216 *
 217 * Returns a pointer to the new key if successful and an error code otherwise.
 218 *
 219 * Note that the caller needs to ensure the key type isn't uninstantiated.
 220 * Internally this can be done by locking key_types_sem.  Externally, this can
 221 * be done by either never unregistering the key type, or making sure
 222 * key_alloc() calls don't race with module unloading.
 223 */
 224struct key *key_alloc(struct key_type *type, const char *desc,
 225                      kuid_t uid, kgid_t gid, const struct cred *cred,
 226                      key_perm_t perm, unsigned long flags)
 227{
 228        struct key_user *user = NULL;
 229        struct key *key;
 230        size_t desclen, quotalen;
 231        int ret;
 232
 233        key = ERR_PTR(-EINVAL);
 234        if (!desc || !*desc)
 235                goto error;
 236
 237        if (type->vet_description) {
 238                ret = type->vet_description(desc);
 239                if (ret < 0) {
 240                        key = ERR_PTR(ret);
 241                        goto error;
 242                }
 243        }
 244
 245        desclen = strlen(desc) + 1;
 246        quotalen = desclen + type->def_datalen;
 247
 248        /* get hold of the key tracking for this user */
 249        user = key_user_lookup(uid);
 250        if (!user)
 251                goto no_memory_1;
 252
 253        /* check that the user's quota permits allocation of another key and
 254         * its description */
 255        if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 256                unsigned maxkeys = uid_eq(uid, GLOBAL_ROOT_UID) ?
 257                        key_quota_root_maxkeys : key_quota_maxkeys;
 258                unsigned maxbytes = uid_eq(uid, GLOBAL_ROOT_UID) ?
 259                        key_quota_root_maxbytes : key_quota_maxbytes;
 260
 261                spin_lock(&user->lock);
 262                if (!(flags & KEY_ALLOC_QUOTA_OVERRUN)) {
 263                        if (user->qnkeys + 1 >= maxkeys ||
 264                            user->qnbytes + quotalen >= maxbytes ||
 265                            user->qnbytes + quotalen < user->qnbytes)
 266                                goto no_quota;
 267                }
 268
 269                user->qnkeys++;
 270                user->qnbytes += quotalen;
 271                spin_unlock(&user->lock);
 272        }
 273
 274        /* allocate and initialise the key and its description */
 275        key = kmem_cache_alloc(key_jar, GFP_KERNEL);
 276        if (!key)
 277                goto no_memory_2;
 278
 279        if (desc) {
 280                key->description = kmemdup(desc, desclen, GFP_KERNEL);
 281                if (!key->description)
 282                        goto no_memory_3;
 283        }
 284
 285        atomic_set(&key->usage, 1);
 286        init_rwsem(&key->sem);
 287        lockdep_set_class(&key->sem, &type->lock_class);
 288        key->type = type;
 289        key->user = user;
 290        key->quotalen = quotalen;
 291        key->datalen = type->def_datalen;
 292        key->uid = uid;
 293        key->gid = gid;
 294        key->perm = perm;
 295        key->flags = 0;
 296        key->expiry = 0;
 297        key->payload.data = NULL;
 298        key->security = NULL;
 299
 300        if (!(flags & KEY_ALLOC_NOT_IN_QUOTA))
 301                key->flags |= 1 << KEY_FLAG_IN_QUOTA;
 302
 303        memset(&key->type_data, 0, sizeof(key->type_data));
 304
 305#ifdef KEY_DEBUGGING
 306        key->magic = KEY_DEBUG_MAGIC;
 307#endif
 308
 309        /* let the security module know about the key */
 310        ret = security_key_alloc(key, cred, flags);
 311        if (ret < 0)
 312                goto security_error;
 313
 314        /* publish the key by giving it a serial number */
 315        atomic_inc(&user->nkeys);
 316        key_alloc_serial(key);
 317
 318error:
 319        return key;
 320
 321security_error:
 322        kfree(key->description);
 323        kmem_cache_free(key_jar, key);
 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        key = ERR_PTR(ret);
 332        goto error;
 333
 334no_memory_3:
 335        kmem_cache_free(key_jar, key);
 336no_memory_2:
 337        if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 338                spin_lock(&user->lock);
 339                user->qnkeys--;
 340                user->qnbytes -= quotalen;
 341                spin_unlock(&user->lock);
 342        }
 343        key_user_put(user);
 344no_memory_1:
 345        key = ERR_PTR(-ENOMEM);
 346        goto error;
 347
 348no_quota:
 349        spin_unlock(&user->lock);
 350        key_user_put(user);
 351        key = ERR_PTR(-EDQUOT);
 352        goto error;
 353}
 354EXPORT_SYMBOL(key_alloc);
 355
 356/**
 357 * key_payload_reserve - Adjust data quota reservation for the key's payload
 358 * @key: The key to make the reservation for.
 359 * @datalen: The amount of data payload the caller now wants.
 360 *
 361 * Adjust the amount of the owning user's key data quota that a key reserves.
 362 * If the amount is increased, then -EDQUOT may be returned if there isn't
 363 * enough free quota available.
 364 *
 365 * If successful, 0 is returned.
 366 */
 367int key_payload_reserve(struct key *key, size_t datalen)
 368{
 369        int delta = (int)datalen - key->datalen;
 370        int ret = 0;
 371
 372        key_check(key);
 373
 374        /* contemplate the quota adjustment */
 375        if (delta != 0 && test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
 376                unsigned maxbytes = uid_eq(key->user->uid, GLOBAL_ROOT_UID) ?
 377                        key_quota_root_maxbytes : key_quota_maxbytes;
 378
 379                spin_lock(&key->user->lock);
 380
 381                if (delta > 0 &&
 382                    (key->user->qnbytes + delta >= maxbytes ||
 383                     key->user->qnbytes + delta < key->user->qnbytes)) {
 384                        ret = -EDQUOT;
 385                }
 386                else {
 387                        key->user->qnbytes += delta;
 388                        key->quotalen += delta;
 389                }
 390                spin_unlock(&key->user->lock);
 391        }
 392
 393        /* change the recorded data length if that didn't generate an error */
 394        if (ret == 0)
 395                key->datalen = datalen;
 396
 397        return ret;
 398}
 399EXPORT_SYMBOL(key_payload_reserve);
 400
 401/*
 402 * Instantiate a key and link it into the target keyring atomically.  Must be
 403 * called with the target keyring's semaphore writelocked.  The target key's
 404 * semaphore need not be locked as instantiation is serialised by
 405 * key_construction_mutex.
 406 */
 407static int __key_instantiate_and_link(struct key *key,
 408                                      struct key_preparsed_payload *prep,
 409                                      struct key *keyring,
 410                                      struct key *authkey,
 411                                      unsigned long *_prealloc)
 412{
 413        int ret, awaken;
 414
 415        key_check(key);
 416        key_check(keyring);
 417
 418        awaken = 0;
 419        ret = -EBUSY;
 420
 421        mutex_lock(&key_construction_mutex);
 422
 423        /* can't instantiate twice */
 424        if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
 425                /* instantiate the key */
 426                ret = key->type->instantiate(key, prep);
 427
 428                if (ret == 0) {
 429                        /* mark the key as being instantiated */
 430                        atomic_inc(&key->user->nikeys);
 431                        set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
 432
 433                        if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
 434                                awaken = 1;
 435
 436                        /* and link it into the destination keyring */
 437                        if (keyring)
 438                                __key_link(keyring, key, _prealloc);
 439
 440                        /* disable the authorisation key */
 441                        if (authkey)
 442                                key_revoke(authkey);
 443                }
 444        }
 445
 446        mutex_unlock(&key_construction_mutex);
 447
 448        /* wake up anyone waiting for a key to be constructed */
 449        if (awaken)
 450                wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
 451
 452        return ret;
 453}
 454
 455/**
 456 * key_instantiate_and_link - Instantiate a key and link it into the keyring.
 457 * @key: The key to instantiate.
 458 * @data: The data to use to instantiate the keyring.
 459 * @datalen: The length of @data.
 460 * @keyring: Keyring to create a link in on success (or NULL).
 461 * @authkey: The authorisation token permitting instantiation.
 462 *
 463 * Instantiate a key that's in the uninstantiated state using the provided data
 464 * and, if successful, link it in to the destination keyring if one is
 465 * supplied.
 466 *
 467 * If successful, 0 is returned, the authorisation token is revoked and anyone
 468 * waiting for the key is woken up.  If the key was already instantiated,
 469 * -EBUSY will be returned.
 470 */
 471int key_instantiate_and_link(struct key *key,
 472                             const void *data,
 473                             size_t datalen,
 474                             struct key *keyring,
 475                             struct key *authkey)
 476{
 477        struct key_preparsed_payload prep;
 478        unsigned long prealloc;
 479        int ret;
 480
 481        memset(&prep, 0, sizeof(prep));
 482        prep.data = data;
 483        prep.datalen = datalen;
 484        prep.quotalen = key->type->def_datalen;
 485        if (key->type->preparse) {
 486                ret = key->type->preparse(&prep);
 487                if (ret < 0)
 488                        goto error;
 489        }
 490
 491        if (keyring) {
 492                ret = __key_link_begin(keyring, key->type, key->description,
 493                                       &prealloc);
 494                if (ret < 0)
 495                        goto error_free_preparse;
 496        }
 497
 498        ret = __key_instantiate_and_link(key, &prep, keyring, authkey,
 499                                         &prealloc);
 500
 501        if (keyring)
 502                __key_link_end(keyring, key->type, prealloc);
 503
 504error_free_preparse:
 505        if (key->type->preparse)
 506                key->type->free_preparse(&prep);
 507error:
 508        return ret;
 509}
 510
 511EXPORT_SYMBOL(key_instantiate_and_link);
 512
 513/**
 514 * key_reject_and_link - Negatively instantiate a key and link it into the keyring.
 515 * @key: The key to instantiate.
 516 * @timeout: The timeout on the negative key.
 517 * @error: The error to return when the key is hit.
 518 * @keyring: Keyring to create a link in on success (or NULL).
 519 * @authkey: The authorisation token permitting instantiation.
 520 *
 521 * Negatively instantiate a key that's in the uninstantiated state and, if
 522 * successful, set its timeout and stored error and link it in to the
 523 * destination keyring if one is supplied.  The key and any links to the key
 524 * will be automatically garbage collected after the timeout expires.
 525 *
 526 * Negative keys are used to rate limit repeated request_key() calls by causing
 527 * them to return the stored error code (typically ENOKEY) until the negative
 528 * key expires.
 529 *
 530 * If successful, 0 is returned, the authorisation token is revoked and anyone
 531 * waiting for the key is woken up.  If the key was already instantiated,
 532 * -EBUSY will be returned.
 533 */
 534int key_reject_and_link(struct key *key,
 535                        unsigned timeout,
 536                        unsigned error,
 537                        struct key *keyring,
 538                        struct key *authkey)
 539{
 540        unsigned long prealloc;
 541        struct timespec now;
 542        int ret, awaken, link_ret = 0;
 543
 544        key_check(key);
 545        key_check(keyring);
 546
 547        awaken = 0;
 548        ret = -EBUSY;
 549
 550        if (keyring)
 551                link_ret = __key_link_begin(keyring, key->type,
 552                                            key->description, &prealloc);
 553
 554        mutex_lock(&key_construction_mutex);
 555
 556        /* can't instantiate twice */
 557        if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
 558                /* mark the key as being negatively instantiated */
 559                atomic_inc(&key->user->nikeys);
 560                set_bit(KEY_FLAG_NEGATIVE, &key->flags);
 561                set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
 562                key->type_data.reject_error = -error;
 563                now = current_kernel_time();
 564                key->expiry = now.tv_sec + timeout;
 565                key_schedule_gc(key->expiry + key_gc_delay);
 566
 567                if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
 568                        awaken = 1;
 569
 570                ret = 0;
 571
 572                /* and link it into the destination keyring */
 573                if (keyring && link_ret == 0)
 574                        __key_link(keyring, key, &prealloc);
 575
 576                /* disable the authorisation key */
 577                if (authkey)
 578                        key_revoke(authkey);
 579        }
 580
 581        mutex_unlock(&key_construction_mutex);
 582
 583        if (keyring)
 584                __key_link_end(keyring, key->type, prealloc);
 585
 586        /* wake up anyone waiting for a key to be constructed */
 587        if (awaken)
 588                wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
 589
 590        return ret == 0 ? link_ret : ret;
 591}
 592EXPORT_SYMBOL(key_reject_and_link);
 593
 594/**
 595 * key_put - Discard a reference to a key.
 596 * @key: The key to discard a reference from.
 597 *
 598 * Discard a reference to a key, and when all the references are gone, we
 599 * schedule the cleanup task to come and pull it out of the tree in process
 600 * context at some later time.
 601 */
 602void key_put(struct key *key)
 603{
 604        if (key) {
 605                key_check(key);
 606
 607                if (atomic_dec_and_test(&key->usage))
 608                        schedule_work(&key_gc_work);
 609        }
 610}
 611EXPORT_SYMBOL(key_put);
 612
 613/*
 614 * Find a key by its serial number.
 615 */
 616struct key *key_lookup(key_serial_t id)
 617{
 618        struct rb_node *n;
 619        struct key *key;
 620
 621        spin_lock(&key_serial_lock);
 622
 623        /* search the tree for the specified key */
 624        n = key_serial_tree.rb_node;
 625        while (n) {
 626                key = rb_entry(n, struct key, serial_node);
 627
 628                if (id < key->serial)
 629                        n = n->rb_left;
 630                else if (id > key->serial)
 631                        n = n->rb_right;
 632                else
 633                        goto found;
 634        }
 635
 636not_found:
 637        key = ERR_PTR(-ENOKEY);
 638        goto error;
 639
 640found:
 641        /* pretend it doesn't exist if it is awaiting deletion */
 642        if (atomic_read(&key->usage) == 0)
 643                goto not_found;
 644
 645        /* this races with key_put(), but that doesn't matter since key_put()
 646         * doesn't actually change the key
 647         */
 648        atomic_inc(&key->usage);
 649
 650error:
 651        spin_unlock(&key_serial_lock);
 652        return key;
 653}
 654
 655/*
 656 * Find and lock the specified key type against removal.
 657 *
 658 * We return with the sem read-locked if successful.  If the type wasn't
 659 * available -ENOKEY is returned instead.
 660 */
 661struct key_type *key_type_lookup(const char *type)
 662{
 663        struct key_type *ktype;
 664
 665        down_read(&key_types_sem);
 666
 667        /* look up the key type to see if it's one of the registered kernel
 668         * types */
 669        list_for_each_entry(ktype, &key_types_list, link) {
 670                if (strcmp(ktype->name, type) == 0)
 671                        goto found_kernel_type;
 672        }
 673
 674        up_read(&key_types_sem);
 675        ktype = ERR_PTR(-ENOKEY);
 676
 677found_kernel_type:
 678        return ktype;
 679}
 680
 681void key_set_timeout(struct key *key, unsigned timeout)
 682{
 683        struct timespec now;
 684        time_t expiry = 0;
 685
 686        /* make the changes with the locks held to prevent races */
 687        down_write(&key->sem);
 688
 689        if (timeout > 0) {
 690                now = current_kernel_time();
 691                expiry = now.tv_sec + timeout;
 692        }
 693
 694        key->expiry = expiry;
 695        key_schedule_gc(key->expiry + key_gc_delay);
 696
 697        up_write(&key->sem);
 698}
 699EXPORT_SYMBOL_GPL(key_set_timeout);
 700
 701/*
 702 * Unlock a key type locked by key_type_lookup().
 703 */
 704void key_type_put(struct key_type *ktype)
 705{
 706        up_read(&key_types_sem);
 707}
 708
 709/*
 710 * Attempt to update an existing key.
 711 *
 712 * The key is given to us with an incremented refcount that we need to discard
 713 * if we get an error.
 714 */
 715static inline key_ref_t __key_update(key_ref_t key_ref,
 716                                     struct key_preparsed_payload *prep)
 717{
 718        struct key *key = key_ref_to_ptr(key_ref);
 719        int ret;
 720
 721        /* need write permission on the key to update it */
 722        ret = key_permission(key_ref, KEY_WRITE);
 723        if (ret < 0)
 724                goto error;
 725
 726        ret = -EEXIST;
 727        if (!key->type->update)
 728                goto error;
 729
 730        down_write(&key->sem);
 731
 732        ret = key->type->update(key, prep);
 733        if (ret == 0)
 734                /* updating a negative key instantiates it */
 735                clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
 736
 737        up_write(&key->sem);
 738
 739        if (ret < 0)
 740                goto error;
 741out:
 742        return key_ref;
 743
 744error:
 745        key_put(key);
 746        key_ref = ERR_PTR(ret);
 747        goto out;
 748}
 749
 750/**
 751 * key_create_or_update - Update or create and instantiate a key.
 752 * @keyring_ref: A pointer to the destination keyring with possession flag.
 753 * @type: The type of key.
 754 * @description: The searchable description for the key.
 755 * @payload: The data to use to instantiate or update the key.
 756 * @plen: The length of @payload.
 757 * @perm: The permissions mask for a new key.
 758 * @flags: The quota flags for a new key.
 759 *
 760 * Search the destination keyring for a key of the same description and if one
 761 * is found, update it, otherwise create and instantiate a new one and create a
 762 * link to it from that keyring.
 763 *
 764 * If perm is KEY_PERM_UNDEF then an appropriate key permissions mask will be
 765 * concocted.
 766 *
 767 * Returns a pointer to the new key if successful, -ENODEV if the key type
 768 * wasn't available, -ENOTDIR if the keyring wasn't a keyring, -EACCES if the
 769 * caller isn't permitted to modify the keyring or the LSM did not permit
 770 * creation of the key.
 771 *
 772 * On success, the possession flag from the keyring ref will be tacked on to
 773 * the key ref before it is returned.
 774 */
 775key_ref_t key_create_or_update(key_ref_t keyring_ref,
 776                               const char *type,
 777                               const char *description,
 778                               const void *payload,
 779                               size_t plen,
 780                               key_perm_t perm,
 781                               unsigned long flags)
 782{
 783        unsigned long prealloc;
 784        struct key_preparsed_payload prep;
 785        const struct cred *cred = current_cred();
 786        struct key_type *ktype;
 787        struct key *keyring, *key = NULL;
 788        key_ref_t key_ref;
 789        int ret;
 790
 791        /* look up the key type to see if it's one of the registered kernel
 792         * types */
 793        ktype = key_type_lookup(type);
 794        if (IS_ERR(ktype)) {
 795                key_ref = ERR_PTR(-ENODEV);
 796                goto error;
 797        }
 798
 799        key_ref = ERR_PTR(-EINVAL);
 800        if (!ktype->match || !ktype->instantiate ||
 801            (!description && !ktype->preparse))
 802                goto error_put_type;
 803
 804        keyring = key_ref_to_ptr(keyring_ref);
 805
 806        key_check(keyring);
 807
 808        key_ref = ERR_PTR(-ENOTDIR);
 809        if (keyring->type != &key_type_keyring)
 810                goto error_put_type;
 811
 812        memset(&prep, 0, sizeof(prep));
 813        prep.data = payload;
 814        prep.datalen = plen;
 815        prep.quotalen = ktype->def_datalen;
 816        if (ktype->preparse) {
 817                ret = ktype->preparse(&prep);
 818                if (ret < 0) {
 819                        key_ref = ERR_PTR(ret);
 820                        goto error_put_type;
 821                }
 822                if (!description)
 823                        description = prep.description;
 824                key_ref = ERR_PTR(-EINVAL);
 825                if (!description)
 826                        goto error_free_prep;
 827        }
 828
 829        ret = __key_link_begin(keyring, ktype, description, &prealloc);
 830        if (ret < 0) {
 831                key_ref = ERR_PTR(ret);
 832                goto error_free_prep;
 833        }
 834
 835        /* if we're going to allocate a new key, we're going to have
 836         * to modify the keyring */
 837        ret = key_permission(keyring_ref, KEY_WRITE);
 838        if (ret < 0) {
 839                key_ref = ERR_PTR(ret);
 840                goto error_link_end;
 841        }
 842
 843        /* if it's possible to update this type of key, search for an existing
 844         * key of the same type and description in the destination keyring and
 845         * update that instead if possible
 846         */
 847        if (ktype->update) {
 848                key_ref = __keyring_search_one(keyring_ref, ktype, description,
 849                                               0);
 850                if (!IS_ERR(key_ref))
 851                        goto found_matching_key;
 852        }
 853
 854        /* if the client doesn't provide, decide on the permissions we want */
 855        if (perm == KEY_PERM_UNDEF) {
 856                perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
 857                perm |= KEY_USR_VIEW | KEY_USR_SEARCH | KEY_USR_LINK | KEY_USR_SETATTR;
 858
 859                if (ktype->read)
 860                        perm |= KEY_POS_READ | KEY_USR_READ;
 861
 862                if (ktype == &key_type_keyring || ktype->update)
 863                        perm |= KEY_USR_WRITE;
 864        }
 865
 866        /* allocate a new key */
 867        key = key_alloc(ktype, description, cred->fsuid, cred->fsgid, cred,
 868                        perm, flags);
 869        if (IS_ERR(key)) {
 870                key_ref = ERR_CAST(key);
 871                goto error_link_end;
 872        }
 873
 874        /* instantiate it and link it into the target keyring */
 875        ret = __key_instantiate_and_link(key, &prep, keyring, NULL, &prealloc);
 876        if (ret < 0) {
 877                key_put(key);
 878                key_ref = ERR_PTR(ret);
 879                goto error_link_end;
 880        }
 881
 882        key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
 883
 884error_link_end:
 885        __key_link_end(keyring, ktype, prealloc);
 886error_free_prep:
 887        if (ktype->preparse)
 888                ktype->free_preparse(&prep);
 889error_put_type:
 890        key_type_put(ktype);
 891error:
 892        return key_ref;
 893
 894 found_matching_key:
 895        /* we found a matching key, so we're going to try to update it
 896         * - we can drop the locks first as we have the key pinned
 897         */
 898        __key_link_end(keyring, ktype, prealloc);
 899
 900        key_ref = __key_update(key_ref, &prep);
 901        goto error_free_prep;
 902}
 903EXPORT_SYMBOL(key_create_or_update);
 904
 905/**
 906 * key_update - Update a key's contents.
 907 * @key_ref: The pointer (plus possession flag) to the key.
 908 * @payload: The data to be used to update the key.
 909 * @plen: The length of @payload.
 910 *
 911 * Attempt to update the contents of a key with the given payload data.  The
 912 * caller must be granted Write permission on the key.  Negative keys can be
 913 * instantiated by this method.
 914 *
 915 * Returns 0 on success, -EACCES if not permitted and -EOPNOTSUPP if the key
 916 * type does not support updating.  The key type may return other errors.
 917 */
 918int key_update(key_ref_t key_ref, const void *payload, size_t plen)
 919{
 920        struct key_preparsed_payload prep;
 921        struct key *key = key_ref_to_ptr(key_ref);
 922        int ret;
 923
 924        key_check(key);
 925
 926        /* the key must be writable */
 927        ret = key_permission(key_ref, KEY_WRITE);
 928        if (ret < 0)
 929                goto error;
 930
 931        /* attempt to update it if supported */
 932        ret = -EOPNOTSUPP;
 933        if (!key->type->update)
 934                goto error;
 935
 936        memset(&prep, 0, sizeof(prep));
 937        prep.data = payload;
 938        prep.datalen = plen;
 939        prep.quotalen = key->type->def_datalen;
 940        if (key->type->preparse) {
 941                ret = key->type->preparse(&prep);
 942                if (ret < 0)
 943                        goto error;
 944        }
 945
 946        down_write(&key->sem);
 947
 948        ret = key->type->update(key, &prep);
 949        if (ret == 0)
 950                /* updating a negative key instantiates it */
 951                clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
 952
 953        up_write(&key->sem);
 954
 955        if (key->type->preparse)
 956                key->type->free_preparse(&prep);
 957error:
 958        return ret;
 959}
 960EXPORT_SYMBOL(key_update);
 961
 962/**
 963 * key_revoke - Revoke a key.
 964 * @key: The key to be revoked.
 965 *
 966 * Mark a key as being revoked and ask the type to free up its resources.  The
 967 * revocation timeout is set and the key and all its links will be
 968 * automatically garbage collected after key_gc_delay amount of time if they
 969 * are not manually dealt with first.
 970 */
 971void key_revoke(struct key *key)
 972{
 973        struct timespec now;
 974        time_t time;
 975
 976        key_check(key);
 977
 978        /* make sure no one's trying to change or use the key when we mark it
 979         * - we tell lockdep that we might nest because we might be revoking an
 980         *   authorisation key whilst holding the sem on a key we've just
 981         *   instantiated
 982         */
 983        down_write_nested(&key->sem, 1);
 984        if (!test_and_set_bit(KEY_FLAG_REVOKED, &key->flags) &&
 985            key->type->revoke)
 986                key->type->revoke(key);
 987
 988        /* set the death time to no more than the expiry time */
 989        now = current_kernel_time();
 990        time = now.tv_sec;
 991        if (key->revoked_at == 0 || key->revoked_at > time) {
 992                key->revoked_at = time;
 993                key_schedule_gc(key->revoked_at + key_gc_delay);
 994        }
 995
 996        up_write(&key->sem);
 997}
 998EXPORT_SYMBOL(key_revoke);
 999
1000/**
1001 * key_invalidate - Invalidate a key.
1002 * @key: The key to be invalidated.
1003 *
1004 * Mark a key as being invalidated and have it cleaned up immediately.  The key
1005 * is ignored by all searches and other operations from this point.
1006 */
1007void key_invalidate(struct key *key)
1008{
1009        kenter("%d", key_serial(key));
1010
1011        key_check(key);
1012
1013        if (!test_bit(KEY_FLAG_INVALIDATED, &key->flags)) {
1014                down_write_nested(&key->sem, 1);
1015                if (!test_and_set_bit(KEY_FLAG_INVALIDATED, &key->flags))
1016                        key_schedule_gc_links();
1017                up_write(&key->sem);
1018        }
1019}
1020EXPORT_SYMBOL(key_invalidate);
1021
1022/**
1023 * register_key_type - Register a type of key.
1024 * @ktype: The new key type.
1025 *
1026 * Register a new key type.
1027 *
1028 * Returns 0 on success or -EEXIST if a type of this name already exists.
1029 */
1030int register_key_type(struct key_type *ktype)
1031{
1032        struct key_type *p;
1033        int ret;
1034
1035        memset(&ktype->lock_class, 0, sizeof(ktype->lock_class));
1036
1037        ret = -EEXIST;
1038        down_write(&key_types_sem);
1039
1040        /* disallow key types with the same name */
1041        list_for_each_entry(p, &key_types_list, link) {
1042                if (strcmp(p->name, ktype->name) == 0)
1043                        goto out;
1044        }
1045
1046        /* store the type */
1047        list_add(&ktype->link, &key_types_list);
1048
1049        pr_notice("Key type %s registered\n", ktype->name);
1050        ret = 0;
1051
1052out:
1053        up_write(&key_types_sem);
1054        return ret;
1055}
1056EXPORT_SYMBOL(register_key_type);
1057
1058/**
1059 * unregister_key_type - Unregister a type of key.
1060 * @ktype: The key type.
1061 *
1062 * Unregister a key type and mark all the extant keys of this type as dead.
1063 * Those keys of this type are then destroyed to get rid of their payloads and
1064 * they and their links will be garbage collected as soon as possible.
1065 */
1066void unregister_key_type(struct key_type *ktype)
1067{
1068        down_write(&key_types_sem);
1069        list_del_init(&ktype->link);
1070        downgrade_write(&key_types_sem);
1071        key_gc_keytype(ktype);
1072        pr_notice("Key type %s unregistered\n", ktype->name);
1073        up_read(&key_types_sem);
1074}
1075EXPORT_SYMBOL(unregister_key_type);
1076
1077/*
1078 * Initialise the key management state.
1079 */
1080void __init key_init(void)
1081{
1082        /* allocate a slab in which we can store keys */
1083        key_jar = kmem_cache_create("key_jar", sizeof(struct key),
1084                        0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1085
1086        /* add the special key types */
1087        list_add_tail(&key_type_keyring.link, &key_types_list);
1088        list_add_tail(&key_type_dead.link, &key_types_list);
1089        list_add_tail(&key_type_user.link, &key_types_list);
1090        list_add_tail(&key_type_logon.link, &key_types_list);
1091
1092        /* record the root user tracking */
1093        rb_link_node(&root_key_user.node,
1094                     NULL,
1095                     &key_user_tree.rb_node);
1096
1097        rb_insert_color(&root_key_user.node,
1098                        &key_user_tree);
1099}
1100
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