linux/security/keys/keyring.c
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   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/* Keyring handling
   3 *
   4 * Copyright (C) 2004-2005, 2008, 2013 Red Hat, Inc. All Rights Reserved.
   5 * Written by David Howells (dhowells@redhat.com)
   6 */
   7
   8#include <linux/export.h>
   9#include <linux/init.h>
  10#include <linux/sched.h>
  11#include <linux/slab.h>
  12#include <linux/security.h>
  13#include <linux/seq_file.h>
  14#include <linux/err.h>
  15#include <linux/user_namespace.h>
  16#include <linux/nsproxy.h>
  17#include <keys/keyring-type.h>
  18#include <keys/user-type.h>
  19#include <linux/assoc_array_priv.h>
  20#include <linux/uaccess.h>
  21#include <net/net_namespace.h>
  22#include "internal.h"
  23
  24/*
  25 * When plumbing the depths of the key tree, this sets a hard limit
  26 * set on how deep we're willing to go.
  27 */
  28#define KEYRING_SEARCH_MAX_DEPTH 6
  29
  30/*
  31 * We mark pointers we pass to the associative array with bit 1 set if
  32 * they're keyrings and clear otherwise.
  33 */
  34#define KEYRING_PTR_SUBTYPE     0x2UL
  35
  36static inline bool keyring_ptr_is_keyring(const struct assoc_array_ptr *x)
  37{
  38        return (unsigned long)x & KEYRING_PTR_SUBTYPE;
  39}
  40static inline struct key *keyring_ptr_to_key(const struct assoc_array_ptr *x)
  41{
  42        void *object = assoc_array_ptr_to_leaf(x);
  43        return (struct key *)((unsigned long)object & ~KEYRING_PTR_SUBTYPE);
  44}
  45static inline void *keyring_key_to_ptr(struct key *key)
  46{
  47        if (key->type == &key_type_keyring)
  48                return (void *)((unsigned long)key | KEYRING_PTR_SUBTYPE);
  49        return key;
  50}
  51
  52static DEFINE_RWLOCK(keyring_name_lock);
  53
  54/*
  55 * Clean up the bits of user_namespace that belong to us.
  56 */
  57void key_free_user_ns(struct user_namespace *ns)
  58{
  59        write_lock(&keyring_name_lock);
  60        list_del_init(&ns->keyring_name_list);
  61        write_unlock(&keyring_name_lock);
  62
  63        key_put(ns->user_keyring_register);
  64#ifdef CONFIG_PERSISTENT_KEYRINGS
  65        key_put(ns->persistent_keyring_register);
  66#endif
  67}
  68
  69/*
  70 * The keyring key type definition.  Keyrings are simply keys of this type and
  71 * can be treated as ordinary keys in addition to having their own special
  72 * operations.
  73 */
  74static int keyring_preparse(struct key_preparsed_payload *prep);
  75static void keyring_free_preparse(struct key_preparsed_payload *prep);
  76static int keyring_instantiate(struct key *keyring,
  77                               struct key_preparsed_payload *prep);
  78static void keyring_revoke(struct key *keyring);
  79static void keyring_destroy(struct key *keyring);
  80static void keyring_describe(const struct key *keyring, struct seq_file *m);
  81static long keyring_read(const struct key *keyring,
  82                         char __user *buffer, size_t buflen);
  83
  84struct key_type key_type_keyring = {
  85        .name           = "keyring",
  86        .def_datalen    = 0,
  87        .preparse       = keyring_preparse,
  88        .free_preparse  = keyring_free_preparse,
  89        .instantiate    = keyring_instantiate,
  90        .revoke         = keyring_revoke,
  91        .destroy        = keyring_destroy,
  92        .describe       = keyring_describe,
  93        .read           = keyring_read,
  94};
  95EXPORT_SYMBOL(key_type_keyring);
  96
  97/*
  98 * Semaphore to serialise link/link calls to prevent two link calls in parallel
  99 * introducing a cycle.
 100 */
 101static DEFINE_MUTEX(keyring_serialise_link_lock);
 102
 103/*
 104 * Publish the name of a keyring so that it can be found by name (if it has
 105 * one and it doesn't begin with a dot).
 106 */
 107static void keyring_publish_name(struct key *keyring)
 108{
 109        struct user_namespace *ns = current_user_ns();
 110
 111        if (keyring->description &&
 112            keyring->description[0] &&
 113            keyring->description[0] != '.') {
 114                write_lock(&keyring_name_lock);
 115                list_add_tail(&keyring->name_link, &ns->keyring_name_list);
 116                write_unlock(&keyring_name_lock);
 117        }
 118}
 119
 120/*
 121 * Preparse a keyring payload
 122 */
 123static int keyring_preparse(struct key_preparsed_payload *prep)
 124{
 125        return prep->datalen != 0 ? -EINVAL : 0;
 126}
 127
 128/*
 129 * Free a preparse of a user defined key payload
 130 */
 131static void keyring_free_preparse(struct key_preparsed_payload *prep)
 132{
 133}
 134
 135/*
 136 * Initialise a keyring.
 137 *
 138 * Returns 0 on success, -EINVAL if given any data.
 139 */
 140static int keyring_instantiate(struct key *keyring,
 141                               struct key_preparsed_payload *prep)
 142{
 143        assoc_array_init(&keyring->keys);
 144        /* make the keyring available by name if it has one */
 145        keyring_publish_name(keyring);
 146        return 0;
 147}
 148
 149/*
 150 * Multiply 64-bits by 32-bits to 96-bits and fold back to 64-bit.  Ideally we'd
 151 * fold the carry back too, but that requires inline asm.
 152 */
 153static u64 mult_64x32_and_fold(u64 x, u32 y)
 154{
 155        u64 hi = (u64)(u32)(x >> 32) * y;
 156        u64 lo = (u64)(u32)(x) * y;
 157        return lo + ((u64)(u32)hi << 32) + (u32)(hi >> 32);
 158}
 159
 160/*
 161 * Hash a key type and description.
 162 */
 163static void hash_key_type_and_desc(struct keyring_index_key *index_key)
 164{
 165        const unsigned level_shift = ASSOC_ARRAY_LEVEL_STEP;
 166        const unsigned long fan_mask = ASSOC_ARRAY_FAN_MASK;
 167        const char *description = index_key->description;
 168        unsigned long hash, type;
 169        u32 piece;
 170        u64 acc;
 171        int n, desc_len = index_key->desc_len;
 172
 173        type = (unsigned long)index_key->type;
 174        acc = mult_64x32_and_fold(type, desc_len + 13);
 175        acc = mult_64x32_and_fold(acc, 9207);
 176        piece = (unsigned long)index_key->domain_tag;
 177        acc = mult_64x32_and_fold(acc, piece);
 178        acc = mult_64x32_and_fold(acc, 9207);
 179
 180        for (;;) {
 181                n = desc_len;
 182                if (n <= 0)
 183                        break;
 184                if (n > 4)
 185                        n = 4;
 186                piece = 0;
 187                memcpy(&piece, description, n);
 188                description += n;
 189                desc_len -= n;
 190                acc = mult_64x32_and_fold(acc, piece);
 191                acc = mult_64x32_and_fold(acc, 9207);
 192        }
 193
 194        /* Fold the hash down to 32 bits if need be. */
 195        hash = acc;
 196        if (ASSOC_ARRAY_KEY_CHUNK_SIZE == 32)
 197                hash ^= acc >> 32;
 198
 199        /* Squidge all the keyrings into a separate part of the tree to
 200         * ordinary keys by making sure the lowest level segment in the hash is
 201         * zero for keyrings and non-zero otherwise.
 202         */
 203        if (index_key->type != &key_type_keyring && (hash & fan_mask) == 0)
 204                hash |= (hash >> (ASSOC_ARRAY_KEY_CHUNK_SIZE - level_shift)) | 1;
 205        else if (index_key->type == &key_type_keyring && (hash & fan_mask) != 0)
 206                hash = (hash + (hash << level_shift)) & ~fan_mask;
 207        index_key->hash = hash;
 208}
 209
 210/*
 211 * Finalise an index key to include a part of the description actually in the
 212 * index key, to set the domain tag and to calculate the hash.
 213 */
 214void key_set_index_key(struct keyring_index_key *index_key)
 215{
 216        static struct key_tag default_domain_tag = { .usage = REFCOUNT_INIT(1), };
 217        size_t n = min_t(size_t, index_key->desc_len, sizeof(index_key->desc));
 218
 219        memcpy(index_key->desc, index_key->description, n);
 220
 221        if (!index_key->domain_tag) {
 222                if (index_key->type->flags & KEY_TYPE_NET_DOMAIN)
 223                        index_key->domain_tag = current->nsproxy->net_ns->key_domain;
 224                else
 225                        index_key->domain_tag = &default_domain_tag;
 226        }
 227
 228        hash_key_type_and_desc(index_key);
 229}
 230
 231/**
 232 * key_put_tag - Release a ref on a tag.
 233 * @tag: The tag to release.
 234 *
 235 * This releases a reference the given tag and returns true if that ref was the
 236 * last one.
 237 */
 238bool key_put_tag(struct key_tag *tag)
 239{
 240        if (refcount_dec_and_test(&tag->usage)) {
 241                kfree_rcu(tag, rcu);
 242                return true;
 243        }
 244
 245        return false;
 246}
 247
 248/**
 249 * key_remove_domain - Kill off a key domain and gc its keys
 250 * @domain_tag: The domain tag to release.
 251 *
 252 * This marks a domain tag as being dead and releases a ref on it.  If that
 253 * wasn't the last reference, the garbage collector is poked to try and delete
 254 * all keys that were in the domain.
 255 */
 256void key_remove_domain(struct key_tag *domain_tag)
 257{
 258        domain_tag->removed = true;
 259        if (!key_put_tag(domain_tag))
 260                key_schedule_gc_links();
 261}
 262
 263/*
 264 * Build the next index key chunk.
 265 *
 266 * We return it one word-sized chunk at a time.
 267 */
 268static unsigned long keyring_get_key_chunk(const void *data, int level)
 269{
 270        const struct keyring_index_key *index_key = data;
 271        unsigned long chunk = 0;
 272        const u8 *d;
 273        int desc_len = index_key->desc_len, n = sizeof(chunk);
 274
 275        level /= ASSOC_ARRAY_KEY_CHUNK_SIZE;
 276        switch (level) {
 277        case 0:
 278                return index_key->hash;
 279        case 1:
 280                return index_key->x;
 281        case 2:
 282                return (unsigned long)index_key->type;
 283        case 3:
 284                return (unsigned long)index_key->domain_tag;
 285        default:
 286                level -= 4;
 287                if (desc_len <= sizeof(index_key->desc))
 288                        return 0;
 289
 290                d = index_key->description + sizeof(index_key->desc);
 291                d += level * sizeof(long);
 292                desc_len -= sizeof(index_key->desc);
 293                if (desc_len > n)
 294                        desc_len = n;
 295                do {
 296                        chunk <<= 8;
 297                        chunk |= *d++;
 298                } while (--desc_len > 0);
 299                return chunk;
 300        }
 301}
 302
 303static unsigned long keyring_get_object_key_chunk(const void *object, int level)
 304{
 305        const struct key *key = keyring_ptr_to_key(object);
 306        return keyring_get_key_chunk(&key->index_key, level);
 307}
 308
 309static bool keyring_compare_object(const void *object, const void *data)
 310{
 311        const struct keyring_index_key *index_key = data;
 312        const struct key *key = keyring_ptr_to_key(object);
 313
 314        return key->index_key.type == index_key->type &&
 315                key->index_key.domain_tag == index_key->domain_tag &&
 316                key->index_key.desc_len == index_key->desc_len &&
 317                memcmp(key->index_key.description, index_key->description,
 318                       index_key->desc_len) == 0;
 319}
 320
 321/*
 322 * Compare the index keys of a pair of objects and determine the bit position
 323 * at which they differ - if they differ.
 324 */
 325static int keyring_diff_objects(const void *object, const void *data)
 326{
 327        const struct key *key_a = keyring_ptr_to_key(object);
 328        const struct keyring_index_key *a = &key_a->index_key;
 329        const struct keyring_index_key *b = data;
 330        unsigned long seg_a, seg_b;
 331        int level, i;
 332
 333        level = 0;
 334        seg_a = a->hash;
 335        seg_b = b->hash;
 336        if ((seg_a ^ seg_b) != 0)
 337                goto differ;
 338        level += ASSOC_ARRAY_KEY_CHUNK_SIZE / 8;
 339
 340        /* The number of bits contributed by the hash is controlled by a
 341         * constant in the assoc_array headers.  Everything else thereafter we
 342         * can deal with as being machine word-size dependent.
 343         */
 344        seg_a = a->x;
 345        seg_b = b->x;
 346        if ((seg_a ^ seg_b) != 0)
 347                goto differ;
 348        level += sizeof(unsigned long);
 349
 350        /* The next bit may not work on big endian */
 351        seg_a = (unsigned long)a->type;
 352        seg_b = (unsigned long)b->type;
 353        if ((seg_a ^ seg_b) != 0)
 354                goto differ;
 355        level += sizeof(unsigned long);
 356
 357        seg_a = (unsigned long)a->domain_tag;
 358        seg_b = (unsigned long)b->domain_tag;
 359        if ((seg_a ^ seg_b) != 0)
 360                goto differ;
 361        level += sizeof(unsigned long);
 362
 363        i = sizeof(a->desc);
 364        if (a->desc_len <= i)
 365                goto same;
 366
 367        for (; i < a->desc_len; i++) {
 368                seg_a = *(unsigned char *)(a->description + i);
 369                seg_b = *(unsigned char *)(b->description + i);
 370                if ((seg_a ^ seg_b) != 0)
 371                        goto differ_plus_i;
 372        }
 373
 374same:
 375        return -1;
 376
 377differ_plus_i:
 378        level += i;
 379differ:
 380        i = level * 8 + __ffs(seg_a ^ seg_b);
 381        return i;
 382}
 383
 384/*
 385 * Free an object after stripping the keyring flag off of the pointer.
 386 */
 387static void keyring_free_object(void *object)
 388{
 389        key_put(keyring_ptr_to_key(object));
 390}
 391
 392/*
 393 * Operations for keyring management by the index-tree routines.
 394 */
 395static const struct assoc_array_ops keyring_assoc_array_ops = {
 396        .get_key_chunk          = keyring_get_key_chunk,
 397        .get_object_key_chunk   = keyring_get_object_key_chunk,
 398        .compare_object         = keyring_compare_object,
 399        .diff_objects           = keyring_diff_objects,
 400        .free_object            = keyring_free_object,
 401};
 402
 403/*
 404 * Clean up a keyring when it is destroyed.  Unpublish its name if it had one
 405 * and dispose of its data.
 406 *
 407 * The garbage collector detects the final key_put(), removes the keyring from
 408 * the serial number tree and then does RCU synchronisation before coming here,
 409 * so we shouldn't need to worry about code poking around here with the RCU
 410 * readlock held by this time.
 411 */
 412static void keyring_destroy(struct key *keyring)
 413{
 414        if (keyring->description) {
 415                write_lock(&keyring_name_lock);
 416
 417                if (keyring->name_link.next != NULL &&
 418                    !list_empty(&keyring->name_link))
 419                        list_del(&keyring->name_link);
 420
 421                write_unlock(&keyring_name_lock);
 422        }
 423
 424        if (keyring->restrict_link) {
 425                struct key_restriction *keyres = keyring->restrict_link;
 426
 427                key_put(keyres->key);
 428                kfree(keyres);
 429        }
 430
 431        assoc_array_destroy(&keyring->keys, &keyring_assoc_array_ops);
 432}
 433
 434/*
 435 * Describe a keyring for /proc.
 436 */
 437static void keyring_describe(const struct key *keyring, struct seq_file *m)
 438{
 439        if (keyring->description)
 440                seq_puts(m, keyring->description);
 441        else
 442                seq_puts(m, "[anon]");
 443
 444        if (key_is_positive(keyring)) {
 445                if (keyring->keys.nr_leaves_on_tree != 0)
 446                        seq_printf(m, ": %lu", keyring->keys.nr_leaves_on_tree);
 447                else
 448                        seq_puts(m, ": empty");
 449        }
 450}
 451
 452struct keyring_read_iterator_context {
 453        size_t                  buflen;
 454        size_t                  count;
 455        key_serial_t            *buffer;
 456};
 457
 458static int keyring_read_iterator(const void *object, void *data)
 459{
 460        struct keyring_read_iterator_context *ctx = data;
 461        const struct key *key = keyring_ptr_to_key(object);
 462
 463        kenter("{%s,%d},,{%zu/%zu}",
 464               key->type->name, key->serial, ctx->count, ctx->buflen);
 465
 466        if (ctx->count >= ctx->buflen)
 467                return 1;
 468
 469        *ctx->buffer++ = key->serial;
 470        ctx->count += sizeof(key->serial);
 471        return 0;
 472}
 473
 474/*
 475 * Read a list of key IDs from the keyring's contents in binary form
 476 *
 477 * The keyring's semaphore is read-locked by the caller.  This prevents someone
 478 * from modifying it under us - which could cause us to read key IDs multiple
 479 * times.
 480 */
 481static long keyring_read(const struct key *keyring,
 482                         char *buffer, size_t buflen)
 483{
 484        struct keyring_read_iterator_context ctx;
 485        long ret;
 486
 487        kenter("{%d},,%zu", key_serial(keyring), buflen);
 488
 489        if (buflen & (sizeof(key_serial_t) - 1))
 490                return -EINVAL;
 491
 492        /* Copy as many key IDs as fit into the buffer */
 493        if (buffer && buflen) {
 494                ctx.buffer = (key_serial_t *)buffer;
 495                ctx.buflen = buflen;
 496                ctx.count = 0;
 497                ret = assoc_array_iterate(&keyring->keys,
 498                                          keyring_read_iterator, &ctx);
 499                if (ret < 0) {
 500                        kleave(" = %ld [iterate]", ret);
 501                        return ret;
 502                }
 503        }
 504
 505        /* Return the size of the buffer needed */
 506        ret = keyring->keys.nr_leaves_on_tree * sizeof(key_serial_t);
 507        if (ret <= buflen)
 508                kleave("= %ld [ok]", ret);
 509        else
 510                kleave("= %ld [buffer too small]", ret);
 511        return ret;
 512}
 513
 514/*
 515 * Allocate a keyring and link into the destination keyring.
 516 */
 517struct key *keyring_alloc(const char *description, kuid_t uid, kgid_t gid,
 518                          const struct cred *cred, key_perm_t perm,
 519                          unsigned long flags,
 520                          struct key_restriction *restrict_link,
 521                          struct key *dest)
 522{
 523        struct key *keyring;
 524        int ret;
 525
 526        keyring = key_alloc(&key_type_keyring, description,
 527                            uid, gid, cred, perm, flags, restrict_link);
 528        if (!IS_ERR(keyring)) {
 529                ret = key_instantiate_and_link(keyring, NULL, 0, dest, NULL);
 530                if (ret < 0) {
 531                        key_put(keyring);
 532                        keyring = ERR_PTR(ret);
 533                }
 534        }
 535
 536        return keyring;
 537}
 538EXPORT_SYMBOL(keyring_alloc);
 539
 540/**
 541 * restrict_link_reject - Give -EPERM to restrict link
 542 * @keyring: The keyring being added to.
 543 * @type: The type of key being added.
 544 * @payload: The payload of the key intended to be added.
 545 * @restriction_key: Keys providing additional data for evaluating restriction.
 546 *
 547 * Reject the addition of any links to a keyring.  It can be overridden by
 548 * passing KEY_ALLOC_BYPASS_RESTRICTION to key_instantiate_and_link() when
 549 * adding a key to a keyring.
 550 *
 551 * This is meant to be stored in a key_restriction structure which is passed
 552 * in the restrict_link parameter to keyring_alloc().
 553 */
 554int restrict_link_reject(struct key *keyring,
 555                         const struct key_type *type,
 556                         const union key_payload *payload,
 557                         struct key *restriction_key)
 558{
 559        return -EPERM;
 560}
 561
 562/*
 563 * By default, we keys found by getting an exact match on their descriptions.
 564 */
 565bool key_default_cmp(const struct key *key,
 566                     const struct key_match_data *match_data)
 567{
 568        return strcmp(key->description, match_data->raw_data) == 0;
 569}
 570
 571/*
 572 * Iteration function to consider each key found.
 573 */
 574static int keyring_search_iterator(const void *object, void *iterator_data)
 575{
 576        struct keyring_search_context *ctx = iterator_data;
 577        const struct key *key = keyring_ptr_to_key(object);
 578        unsigned long kflags = READ_ONCE(key->flags);
 579        short state = READ_ONCE(key->state);
 580
 581        kenter("{%d}", key->serial);
 582
 583        /* ignore keys not of this type */
 584        if (key->type != ctx->index_key.type) {
 585                kleave(" = 0 [!type]");
 586                return 0;
 587        }
 588
 589        /* skip invalidated, revoked and expired keys */
 590        if (ctx->flags & KEYRING_SEARCH_DO_STATE_CHECK) {
 591                time64_t expiry = READ_ONCE(key->expiry);
 592
 593                if (kflags & ((1 << KEY_FLAG_INVALIDATED) |
 594                              (1 << KEY_FLAG_REVOKED))) {
 595                        ctx->result = ERR_PTR(-EKEYREVOKED);
 596                        kleave(" = %d [invrev]", ctx->skipped_ret);
 597                        goto skipped;
 598                }
 599
 600                if (expiry && ctx->now >= expiry) {
 601                        if (!(ctx->flags & KEYRING_SEARCH_SKIP_EXPIRED))
 602                                ctx->result = ERR_PTR(-EKEYEXPIRED);
 603                        kleave(" = %d [expire]", ctx->skipped_ret);
 604                        goto skipped;
 605                }
 606        }
 607
 608        /* keys that don't match */
 609        if (!ctx->match_data.cmp(key, &ctx->match_data)) {
 610                kleave(" = 0 [!match]");
 611                return 0;
 612        }
 613
 614        /* key must have search permissions */
 615        if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM) &&
 616            key_task_permission(make_key_ref(key, ctx->possessed),
 617                                ctx->cred, KEY_NEED_SEARCH) < 0) {
 618                ctx->result = ERR_PTR(-EACCES);
 619                kleave(" = %d [!perm]", ctx->skipped_ret);
 620                goto skipped;
 621        }
 622
 623        if (ctx->flags & KEYRING_SEARCH_DO_STATE_CHECK) {
 624                /* we set a different error code if we pass a negative key */
 625                if (state < 0) {
 626                        ctx->result = ERR_PTR(state);
 627                        kleave(" = %d [neg]", ctx->skipped_ret);
 628                        goto skipped;
 629                }
 630        }
 631
 632        /* Found */
 633        ctx->result = make_key_ref(key, ctx->possessed);
 634        kleave(" = 1 [found]");
 635        return 1;
 636
 637skipped:
 638        return ctx->skipped_ret;
 639}
 640
 641/*
 642 * Search inside a keyring for a key.  We can search by walking to it
 643 * directly based on its index-key or we can iterate over the entire
 644 * tree looking for it, based on the match function.
 645 */
 646static int search_keyring(struct key *keyring, struct keyring_search_context *ctx)
 647{
 648        if (ctx->match_data.lookup_type == KEYRING_SEARCH_LOOKUP_DIRECT) {
 649                const void *object;
 650
 651                object = assoc_array_find(&keyring->keys,
 652                                          &keyring_assoc_array_ops,
 653                                          &ctx->index_key);
 654                return object ? ctx->iterator(object, ctx) : 0;
 655        }
 656        return assoc_array_iterate(&keyring->keys, ctx->iterator, ctx);
 657}
 658
 659/*
 660 * Search a tree of keyrings that point to other keyrings up to the maximum
 661 * depth.
 662 */
 663static bool search_nested_keyrings(struct key *keyring,
 664                                   struct keyring_search_context *ctx)
 665{
 666        struct {
 667                struct key *keyring;
 668                struct assoc_array_node *node;
 669                int slot;
 670        } stack[KEYRING_SEARCH_MAX_DEPTH];
 671
 672        struct assoc_array_shortcut *shortcut;
 673        struct assoc_array_node *node;
 674        struct assoc_array_ptr *ptr;
 675        struct key *key;
 676        int sp = 0, slot;
 677
 678        kenter("{%d},{%s,%s}",
 679               keyring->serial,
 680               ctx->index_key.type->name,
 681               ctx->index_key.description);
 682
 683#define STATE_CHECKS (KEYRING_SEARCH_NO_STATE_CHECK | KEYRING_SEARCH_DO_STATE_CHECK)
 684        BUG_ON((ctx->flags & STATE_CHECKS) == 0 ||
 685               (ctx->flags & STATE_CHECKS) == STATE_CHECKS);
 686
 687        if (ctx->index_key.description)
 688                key_set_index_key(&ctx->index_key);
 689
 690        /* Check to see if this top-level keyring is what we are looking for
 691         * and whether it is valid or not.
 692         */
 693        if (ctx->match_data.lookup_type == KEYRING_SEARCH_LOOKUP_ITERATE ||
 694            keyring_compare_object(keyring, &ctx->index_key)) {
 695                ctx->skipped_ret = 2;
 696                switch (ctx->iterator(keyring_key_to_ptr(keyring), ctx)) {
 697                case 1:
 698                        goto found;
 699                case 2:
 700                        return false;
 701                default:
 702                        break;
 703                }
 704        }
 705
 706        ctx->skipped_ret = 0;
 707
 708        /* Start processing a new keyring */
 709descend_to_keyring:
 710        kdebug("descend to %d", keyring->serial);
 711        if (keyring->flags & ((1 << KEY_FLAG_INVALIDATED) |
 712                              (1 << KEY_FLAG_REVOKED)))
 713                goto not_this_keyring;
 714
 715        /* Search through the keys in this keyring before its searching its
 716         * subtrees.
 717         */
 718        if (search_keyring(keyring, ctx))
 719                goto found;
 720
 721        /* Then manually iterate through the keyrings nested in this one.
 722         *
 723         * Start from the root node of the index tree.  Because of the way the
 724         * hash function has been set up, keyrings cluster on the leftmost
 725         * branch of the root node (root slot 0) or in the root node itself.
 726         * Non-keyrings avoid the leftmost branch of the root entirely (root
 727         * slots 1-15).
 728         */
 729        if (!(ctx->flags & KEYRING_SEARCH_RECURSE))
 730                goto not_this_keyring;
 731
 732        ptr = READ_ONCE(keyring->keys.root);
 733        if (!ptr)
 734                goto not_this_keyring;
 735
 736        if (assoc_array_ptr_is_shortcut(ptr)) {
 737                /* If the root is a shortcut, either the keyring only contains
 738                 * keyring pointers (everything clusters behind root slot 0) or
 739                 * doesn't contain any keyring pointers.
 740                 */
 741                shortcut = assoc_array_ptr_to_shortcut(ptr);
 742                if ((shortcut->index_key[0] & ASSOC_ARRAY_FAN_MASK) != 0)
 743                        goto not_this_keyring;
 744
 745                ptr = READ_ONCE(shortcut->next_node);
 746                node = assoc_array_ptr_to_node(ptr);
 747                goto begin_node;
 748        }
 749
 750        node = assoc_array_ptr_to_node(ptr);
 751        ptr = node->slots[0];
 752        if (!assoc_array_ptr_is_meta(ptr))
 753                goto begin_node;
 754
 755descend_to_node:
 756        /* Descend to a more distal node in this keyring's content tree and go
 757         * through that.
 758         */
 759        kdebug("descend");
 760        if (assoc_array_ptr_is_shortcut(ptr)) {
 761                shortcut = assoc_array_ptr_to_shortcut(ptr);
 762                ptr = READ_ONCE(shortcut->next_node);
 763                BUG_ON(!assoc_array_ptr_is_node(ptr));
 764        }
 765        node = assoc_array_ptr_to_node(ptr);
 766
 767begin_node:
 768        kdebug("begin_node");
 769        slot = 0;
 770ascend_to_node:
 771        /* Go through the slots in a node */
 772        for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
 773                ptr = READ_ONCE(node->slots[slot]);
 774
 775                if (assoc_array_ptr_is_meta(ptr) && node->back_pointer)
 776                        goto descend_to_node;
 777
 778                if (!keyring_ptr_is_keyring(ptr))
 779                        continue;
 780
 781                key = keyring_ptr_to_key(ptr);
 782
 783                if (sp >= KEYRING_SEARCH_MAX_DEPTH) {
 784                        if (ctx->flags & KEYRING_SEARCH_DETECT_TOO_DEEP) {
 785                                ctx->result = ERR_PTR(-ELOOP);
 786                                return false;
 787                        }
 788                        goto not_this_keyring;
 789                }
 790
 791                /* Search a nested keyring */
 792                if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM) &&
 793                    key_task_permission(make_key_ref(key, ctx->possessed),
 794                                        ctx->cred, KEY_NEED_SEARCH) < 0)
 795                        continue;
 796
 797                /* stack the current position */
 798                stack[sp].keyring = keyring;
 799                stack[sp].node = node;
 800                stack[sp].slot = slot;
 801                sp++;
 802
 803                /* begin again with the new keyring */
 804                keyring = key;
 805                goto descend_to_keyring;
 806        }
 807
 808        /* We've dealt with all the slots in the current node, so now we need
 809         * to ascend to the parent and continue processing there.
 810         */
 811        ptr = READ_ONCE(node->back_pointer);
 812        slot = node->parent_slot;
 813
 814        if (ptr && assoc_array_ptr_is_shortcut(ptr)) {
 815                shortcut = assoc_array_ptr_to_shortcut(ptr);
 816                ptr = READ_ONCE(shortcut->back_pointer);
 817                slot = shortcut->parent_slot;
 818        }
 819        if (!ptr)
 820                goto not_this_keyring;
 821        node = assoc_array_ptr_to_node(ptr);
 822        slot++;
 823
 824        /* If we've ascended to the root (zero backpointer), we must have just
 825         * finished processing the leftmost branch rather than the root slots -
 826         * so there can't be any more keyrings for us to find.
 827         */
 828        if (node->back_pointer) {
 829                kdebug("ascend %d", slot);
 830                goto ascend_to_node;
 831        }
 832
 833        /* The keyring we're looking at was disqualified or didn't contain a
 834         * matching key.
 835         */
 836not_this_keyring:
 837        kdebug("not_this_keyring %d", sp);
 838        if (sp <= 0) {
 839                kleave(" = false");
 840                return false;
 841        }
 842
 843        /* Resume the processing of a keyring higher up in the tree */
 844        sp--;
 845        keyring = stack[sp].keyring;
 846        node = stack[sp].node;
 847        slot = stack[sp].slot + 1;
 848        kdebug("ascend to %d [%d]", keyring->serial, slot);
 849        goto ascend_to_node;
 850
 851        /* We found a viable match */
 852found:
 853        key = key_ref_to_ptr(ctx->result);
 854        key_check(key);
 855        if (!(ctx->flags & KEYRING_SEARCH_NO_UPDATE_TIME)) {
 856                key->last_used_at = ctx->now;
 857                keyring->last_used_at = ctx->now;
 858                while (sp > 0)
 859                        stack[--sp].keyring->last_used_at = ctx->now;
 860        }
 861        kleave(" = true");
 862        return true;
 863}
 864
 865/**
 866 * keyring_search_rcu - Search a keyring tree for a matching key under RCU
 867 * @keyring_ref: A pointer to the keyring with possession indicator.
 868 * @ctx: The keyring search context.
 869 *
 870 * Search the supplied keyring tree for a key that matches the criteria given.
 871 * The root keyring and any linked keyrings must grant Search permission to the
 872 * caller to be searchable and keys can only be found if they too grant Search
 873 * to the caller. The possession flag on the root keyring pointer controls use
 874 * of the possessor bits in permissions checking of the entire tree.  In
 875 * addition, the LSM gets to forbid keyring searches and key matches.
 876 *
 877 * The search is performed as a breadth-then-depth search up to the prescribed
 878 * limit (KEYRING_SEARCH_MAX_DEPTH).  The caller must hold the RCU read lock to
 879 * prevent keyrings from being destroyed or rearranged whilst they are being
 880 * searched.
 881 *
 882 * Keys are matched to the type provided and are then filtered by the match
 883 * function, which is given the description to use in any way it sees fit.  The
 884 * match function may use any attributes of a key that it wishes to
 885 * determine the match.  Normally the match function from the key type would be
 886 * used.
 887 *
 888 * RCU can be used to prevent the keyring key lists from disappearing without
 889 * the need to take lots of locks.
 890 *
 891 * Returns a pointer to the found key and increments the key usage count if
 892 * successful; -EAGAIN if no matching keys were found, or if expired or revoked
 893 * keys were found; -ENOKEY if only negative keys were found; -ENOTDIR if the
 894 * specified keyring wasn't a keyring.
 895 *
 896 * In the case of a successful return, the possession attribute from
 897 * @keyring_ref is propagated to the returned key reference.
 898 */
 899key_ref_t keyring_search_rcu(key_ref_t keyring_ref,
 900                             struct keyring_search_context *ctx)
 901{
 902        struct key *keyring;
 903        long err;
 904
 905        ctx->iterator = keyring_search_iterator;
 906        ctx->possessed = is_key_possessed(keyring_ref);
 907        ctx->result = ERR_PTR(-EAGAIN);
 908
 909        keyring = key_ref_to_ptr(keyring_ref);
 910        key_check(keyring);
 911
 912        if (keyring->type != &key_type_keyring)
 913                return ERR_PTR(-ENOTDIR);
 914
 915        if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM)) {
 916                err = key_task_permission(keyring_ref, ctx->cred, KEY_NEED_SEARCH);
 917                if (err < 0)
 918                        return ERR_PTR(err);
 919        }
 920
 921        ctx->now = ktime_get_real_seconds();
 922        if (search_nested_keyrings(keyring, ctx))
 923                __key_get(key_ref_to_ptr(ctx->result));
 924        return ctx->result;
 925}
 926
 927/**
 928 * keyring_search - Search the supplied keyring tree for a matching key
 929 * @keyring: The root of the keyring tree to be searched.
 930 * @type: The type of keyring we want to find.
 931 * @description: The name of the keyring we want to find.
 932 * @recurse: True to search the children of @keyring also
 933 *
 934 * As keyring_search_rcu() above, but using the current task's credentials and
 935 * type's default matching function and preferred search method.
 936 */
 937key_ref_t keyring_search(key_ref_t keyring,
 938                         struct key_type *type,
 939                         const char *description,
 940                         bool recurse)
 941{
 942        struct keyring_search_context ctx = {
 943                .index_key.type         = type,
 944                .index_key.description  = description,
 945                .index_key.desc_len     = strlen(description),
 946                .cred                   = current_cred(),
 947                .match_data.cmp         = key_default_cmp,
 948                .match_data.raw_data    = description,
 949                .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
 950                .flags                  = KEYRING_SEARCH_DO_STATE_CHECK,
 951        };
 952        key_ref_t key;
 953        int ret;
 954
 955        if (recurse)
 956                ctx.flags |= KEYRING_SEARCH_RECURSE;
 957        if (type->match_preparse) {
 958                ret = type->match_preparse(&ctx.match_data);
 959                if (ret < 0)
 960                        return ERR_PTR(ret);
 961        }
 962
 963        rcu_read_lock();
 964        key = keyring_search_rcu(keyring, &ctx);
 965        rcu_read_unlock();
 966
 967        if (type->match_free)
 968                type->match_free(&ctx.match_data);
 969        return key;
 970}
 971EXPORT_SYMBOL(keyring_search);
 972
 973static struct key_restriction *keyring_restriction_alloc(
 974        key_restrict_link_func_t check)
 975{
 976        struct key_restriction *keyres =
 977                kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
 978
 979        if (!keyres)
 980                return ERR_PTR(-ENOMEM);
 981
 982        keyres->check = check;
 983
 984        return keyres;
 985}
 986
 987/*
 988 * Semaphore to serialise restriction setup to prevent reference count
 989 * cycles through restriction key pointers.
 990 */
 991static DECLARE_RWSEM(keyring_serialise_restrict_sem);
 992
 993/*
 994 * Check for restriction cycles that would prevent keyring garbage collection.
 995 * keyring_serialise_restrict_sem must be held.
 996 */
 997static bool keyring_detect_restriction_cycle(const struct key *dest_keyring,
 998                                             struct key_restriction *keyres)
 999{
1000        while (keyres && keyres->key &&
1001               keyres->key->type == &key_type_keyring) {
1002                if (keyres->key == dest_keyring)
1003                        return true;
1004
1005                keyres = keyres->key->restrict_link;
1006        }
1007
1008        return false;
1009}
1010
1011/**
1012 * keyring_restrict - Look up and apply a restriction to a keyring
1013 * @keyring_ref: The keyring to be restricted
1014 * @type: The key type that will provide the restriction checker.
1015 * @restriction: The restriction options to apply to the keyring
1016 *
1017 * Look up a keyring and apply a restriction to it.  The restriction is managed
1018 * by the specific key type, but can be configured by the options specified in
1019 * the restriction string.
1020 */
1021int keyring_restrict(key_ref_t keyring_ref, const char *type,
1022                     const char *restriction)
1023{
1024        struct key *keyring;
1025        struct key_type *restrict_type = NULL;
1026        struct key_restriction *restrict_link;
1027        int ret = 0;
1028
1029        keyring = key_ref_to_ptr(keyring_ref);
1030        key_check(keyring);
1031
1032        if (keyring->type != &key_type_keyring)
1033                return -ENOTDIR;
1034
1035        if (!type) {
1036                restrict_link = keyring_restriction_alloc(restrict_link_reject);
1037        } else {
1038                restrict_type = key_type_lookup(type);
1039
1040                if (IS_ERR(restrict_type))
1041                        return PTR_ERR(restrict_type);
1042
1043                if (!restrict_type->lookup_restriction) {
1044                        ret = -ENOENT;
1045                        goto error;
1046                }
1047
1048                restrict_link = restrict_type->lookup_restriction(restriction);
1049        }
1050
1051        if (IS_ERR(restrict_link)) {
1052                ret = PTR_ERR(restrict_link);
1053                goto error;
1054        }
1055
1056        down_write(&keyring->sem);
1057        down_write(&keyring_serialise_restrict_sem);
1058
1059        if (keyring->restrict_link) {
1060                ret = -EEXIST;
1061        } else if (keyring_detect_restriction_cycle(keyring, restrict_link)) {
1062                ret = -EDEADLK;
1063        } else {
1064                keyring->restrict_link = restrict_link;
1065                notify_key(keyring, NOTIFY_KEY_SETATTR, 0);
1066        }
1067
1068        up_write(&keyring_serialise_restrict_sem);
1069        up_write(&keyring->sem);
1070
1071        if (ret < 0) {
1072                key_put(restrict_link->key);
1073                kfree(restrict_link);
1074        }
1075
1076error:
1077        if (restrict_type)
1078                key_type_put(restrict_type);
1079
1080        return ret;
1081}
1082EXPORT_SYMBOL(keyring_restrict);
1083
1084/*
1085 * Search the given keyring for a key that might be updated.
1086 *
1087 * The caller must guarantee that the keyring is a keyring and that the
1088 * permission is granted to modify the keyring as no check is made here.  The
1089 * caller must also hold a lock on the keyring semaphore.
1090 *
1091 * Returns a pointer to the found key with usage count incremented if
1092 * successful and returns NULL if not found.  Revoked and invalidated keys are
1093 * skipped over.
1094 *
1095 * If successful, the possession indicator is propagated from the keyring ref
1096 * to the returned key reference.
1097 */
1098key_ref_t find_key_to_update(key_ref_t keyring_ref,
1099                             const struct keyring_index_key *index_key)
1100{
1101        struct key *keyring, *key;
1102        const void *object;
1103
1104        keyring = key_ref_to_ptr(keyring_ref);
1105
1106        kenter("{%d},{%s,%s}",
1107               keyring->serial, index_key->type->name, index_key->description);
1108
1109        object = assoc_array_find(&keyring->keys, &keyring_assoc_array_ops,
1110                                  index_key);
1111
1112        if (object)
1113                goto found;
1114
1115        kleave(" = NULL");
1116        return NULL;
1117
1118found:
1119        key = keyring_ptr_to_key(object);
1120        if (key->flags & ((1 << KEY_FLAG_INVALIDATED) |
1121                          (1 << KEY_FLAG_REVOKED))) {
1122                kleave(" = NULL [x]");
1123                return NULL;
1124        }
1125        __key_get(key);
1126        kleave(" = {%d}", key->serial);
1127        return make_key_ref(key, is_key_possessed(keyring_ref));
1128}
1129
1130/*
1131 * Find a keyring with the specified name.
1132 *
1133 * Only keyrings that have nonzero refcount, are not revoked, and are owned by a
1134 * user in the current user namespace are considered.  If @uid_keyring is %true,
1135 * the keyring additionally must have been allocated as a user or user session
1136 * keyring; otherwise, it must grant Search permission directly to the caller.
1137 *
1138 * Returns a pointer to the keyring with the keyring's refcount having being
1139 * incremented on success.  -ENOKEY is returned if a key could not be found.
1140 */
1141struct key *find_keyring_by_name(const char *name, bool uid_keyring)
1142{
1143        struct user_namespace *ns = current_user_ns();
1144        struct key *keyring;
1145
1146        if (!name)
1147                return ERR_PTR(-EINVAL);
1148
1149        read_lock(&keyring_name_lock);
1150
1151        /* Search this hash bucket for a keyring with a matching name that
1152         * grants Search permission and that hasn't been revoked
1153         */
1154        list_for_each_entry(keyring, &ns->keyring_name_list, name_link) {
1155                if (!kuid_has_mapping(ns, keyring->user->uid))
1156                        continue;
1157
1158                if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
1159                        continue;
1160
1161                if (strcmp(keyring->description, name) != 0)
1162                        continue;
1163
1164                if (uid_keyring) {
1165                        if (!test_bit(KEY_FLAG_UID_KEYRING,
1166                                      &keyring->flags))
1167                                continue;
1168                } else {
1169                        if (key_permission(make_key_ref(keyring, 0),
1170                                           KEY_NEED_SEARCH) < 0)
1171                                continue;
1172                }
1173
1174                /* we've got a match but we might end up racing with
1175                 * key_cleanup() if the keyring is currently 'dead'
1176                 * (ie. it has a zero usage count) */
1177                if (!refcount_inc_not_zero(&keyring->usage))
1178                        continue;
1179                keyring->last_used_at = ktime_get_real_seconds();
1180                goto out;
1181        }
1182
1183        keyring = ERR_PTR(-ENOKEY);
1184out:
1185        read_unlock(&keyring_name_lock);
1186        return keyring;
1187}
1188
1189static int keyring_detect_cycle_iterator(const void *object,
1190                                         void *iterator_data)
1191{
1192        struct keyring_search_context *ctx = iterator_data;
1193        const struct key *key = keyring_ptr_to_key(object);
1194
1195        kenter("{%d}", key->serial);
1196
1197        /* We might get a keyring with matching index-key that is nonetheless a
1198         * different keyring. */
1199        if (key != ctx->match_data.raw_data)
1200                return 0;
1201
1202        ctx->result = ERR_PTR(-EDEADLK);
1203        return 1;
1204}
1205
1206/*
1207 * See if a cycle will be created by inserting acyclic tree B in acyclic
1208 * tree A at the topmost level (ie: as a direct child of A).
1209 *
1210 * Since we are adding B to A at the top level, checking for cycles should just
1211 * be a matter of seeing if node A is somewhere in tree B.
1212 */
1213static int keyring_detect_cycle(struct key *A, struct key *B)
1214{
1215        struct keyring_search_context ctx = {
1216                .index_key              = A->index_key,
1217                .match_data.raw_data    = A,
1218                .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
1219                .iterator               = keyring_detect_cycle_iterator,
1220                .flags                  = (KEYRING_SEARCH_NO_STATE_CHECK |
1221                                           KEYRING_SEARCH_NO_UPDATE_TIME |
1222                                           KEYRING_SEARCH_NO_CHECK_PERM |
1223                                           KEYRING_SEARCH_DETECT_TOO_DEEP |
1224                                           KEYRING_SEARCH_RECURSE),
1225        };
1226
1227        rcu_read_lock();
1228        search_nested_keyrings(B, &ctx);
1229        rcu_read_unlock();
1230        return PTR_ERR(ctx.result) == -EAGAIN ? 0 : PTR_ERR(ctx.result);
1231}
1232
1233/*
1234 * Lock keyring for link.
1235 */
1236int __key_link_lock(struct key *keyring,
1237                    const struct keyring_index_key *index_key)
1238        __acquires(&keyring->sem)
1239        __acquires(&keyring_serialise_link_lock)
1240{
1241        if (keyring->type != &key_type_keyring)
1242                return -ENOTDIR;
1243
1244        down_write(&keyring->sem);
1245
1246        /* Serialise link/link calls to prevent parallel calls causing a cycle
1247         * when linking two keyring in opposite orders.
1248         */
1249        if (index_key->type == &key_type_keyring)
1250                mutex_lock(&keyring_serialise_link_lock);
1251
1252        return 0;
1253}
1254
1255/*
1256 * Lock keyrings for move (link/unlink combination).
1257 */
1258int __key_move_lock(struct key *l_keyring, struct key *u_keyring,
1259                    const struct keyring_index_key *index_key)
1260        __acquires(&l_keyring->sem)
1261        __acquires(&u_keyring->sem)
1262        __acquires(&keyring_serialise_link_lock)
1263{
1264        if (l_keyring->type != &key_type_keyring ||
1265            u_keyring->type != &key_type_keyring)
1266                return -ENOTDIR;
1267
1268        /* We have to be very careful here to take the keyring locks in the
1269         * right order, lest we open ourselves to deadlocking against another
1270         * move operation.
1271         */
1272        if (l_keyring < u_keyring) {
1273                down_write(&l_keyring->sem);
1274                down_write_nested(&u_keyring->sem, 1);
1275        } else {
1276                down_write(&u_keyring->sem);
1277                down_write_nested(&l_keyring->sem, 1);
1278        }
1279
1280        /* Serialise link/link calls to prevent parallel calls causing a cycle
1281         * when linking two keyring in opposite orders.
1282         */
1283        if (index_key->type == &key_type_keyring)
1284                mutex_lock(&keyring_serialise_link_lock);
1285
1286        return 0;
1287}
1288
1289/*
1290 * Preallocate memory so that a key can be linked into to a keyring.
1291 */
1292int __key_link_begin(struct key *keyring,
1293                     const struct keyring_index_key *index_key,
1294                     struct assoc_array_edit **_edit)
1295{
1296        struct assoc_array_edit *edit;
1297        int ret;
1298
1299        kenter("%d,%s,%s,",
1300               keyring->serial, index_key->type->name, index_key->description);
1301
1302        BUG_ON(index_key->desc_len == 0);
1303        BUG_ON(*_edit != NULL);
1304
1305        *_edit = NULL;
1306
1307        ret = -EKEYREVOKED;
1308        if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
1309                goto error;
1310
1311        /* Create an edit script that will insert/replace the key in the
1312         * keyring tree.
1313         */
1314        edit = assoc_array_insert(&keyring->keys,
1315                                  &keyring_assoc_array_ops,
1316                                  index_key,
1317                                  NULL);
1318        if (IS_ERR(edit)) {
1319                ret = PTR_ERR(edit);
1320                goto error;
1321        }
1322
1323        /* If we're not replacing a link in-place then we're going to need some
1324         * extra quota.
1325         */
1326        if (!edit->dead_leaf) {
1327                ret = key_payload_reserve(keyring,
1328                                          keyring->datalen + KEYQUOTA_LINK_BYTES);
1329                if (ret < 0)
1330                        goto error_cancel;
1331        }
1332
1333        *_edit = edit;
1334        kleave(" = 0");
1335        return 0;
1336
1337error_cancel:
1338        assoc_array_cancel_edit(edit);
1339error:
1340        kleave(" = %d", ret);
1341        return ret;
1342}
1343
1344/*
1345 * Check already instantiated keys aren't going to be a problem.
1346 *
1347 * The caller must have called __key_link_begin(). Don't need to call this for
1348 * keys that were created since __key_link_begin() was called.
1349 */
1350int __key_link_check_live_key(struct key *keyring, struct key *key)
1351{
1352        if (key->type == &key_type_keyring)
1353                /* check that we aren't going to create a cycle by linking one
1354                 * keyring to another */
1355                return keyring_detect_cycle(keyring, key);
1356        return 0;
1357}
1358
1359/*
1360 * Link a key into to a keyring.
1361 *
1362 * Must be called with __key_link_begin() having being called.  Discards any
1363 * already extant link to matching key if there is one, so that each keyring
1364 * holds at most one link to any given key of a particular type+description
1365 * combination.
1366 */
1367void __key_link(struct key *keyring, struct key *key,
1368                struct assoc_array_edit **_edit)
1369{
1370        __key_get(key);
1371        assoc_array_insert_set_object(*_edit, keyring_key_to_ptr(key));
1372        assoc_array_apply_edit(*_edit);
1373        *_edit = NULL;
1374        notify_key(keyring, NOTIFY_KEY_LINKED, key_serial(key));
1375}
1376
1377/*
1378 * Finish linking a key into to a keyring.
1379 *
1380 * Must be called with __key_link_begin() having being called.
1381 */
1382void __key_link_end(struct key *keyring,
1383                    const struct keyring_index_key *index_key,
1384                    struct assoc_array_edit *edit)
1385        __releases(&keyring->sem)
1386        __releases(&keyring_serialise_link_lock)
1387{
1388        BUG_ON(index_key->type == NULL);
1389        kenter("%d,%s,", keyring->serial, index_key->type->name);
1390
1391        if (edit) {
1392                if (!edit->dead_leaf) {
1393                        key_payload_reserve(keyring,
1394                                keyring->datalen - KEYQUOTA_LINK_BYTES);
1395                }
1396                assoc_array_cancel_edit(edit);
1397        }
1398        up_write(&keyring->sem);
1399
1400        if (index_key->type == &key_type_keyring)
1401                mutex_unlock(&keyring_serialise_link_lock);
1402}
1403
1404/*
1405 * Check addition of keys to restricted keyrings.
1406 */
1407static int __key_link_check_restriction(struct key *keyring, struct key *key)
1408{
1409        if (!keyring->restrict_link || !keyring->restrict_link->check)
1410                return 0;
1411        return keyring->restrict_link->check(keyring, key->type, &key->payload,
1412                                             keyring->restrict_link->key);
1413}
1414
1415/**
1416 * key_link - Link a key to a keyring
1417 * @keyring: The keyring to make the link in.
1418 * @key: The key to link to.
1419 *
1420 * Make a link in a keyring to a key, such that the keyring holds a reference
1421 * on that key and the key can potentially be found by searching that keyring.
1422 *
1423 * This function will write-lock the keyring's semaphore and will consume some
1424 * of the user's key data quota to hold the link.
1425 *
1426 * Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring,
1427 * -EKEYREVOKED if the keyring has been revoked, -ENFILE if the keyring is
1428 * full, -EDQUOT if there is insufficient key data quota remaining to add
1429 * another link or -ENOMEM if there's insufficient memory.
1430 *
1431 * It is assumed that the caller has checked that it is permitted for a link to
1432 * be made (the keyring should have Write permission and the key Link
1433 * permission).
1434 */
1435int key_link(struct key *keyring, struct key *key)
1436{
1437        struct assoc_array_edit *edit = NULL;
1438        int ret;
1439
1440        kenter("{%d,%d}", keyring->serial, refcount_read(&keyring->usage));
1441
1442        key_check(keyring);
1443        key_check(key);
1444
1445        ret = __key_link_lock(keyring, &key->index_key);
1446        if (ret < 0)
1447                goto error;
1448
1449        ret = __key_link_begin(keyring, &key->index_key, &edit);
1450        if (ret < 0)
1451                goto error_end;
1452
1453        kdebug("begun {%d,%d}", keyring->serial, refcount_read(&keyring->usage));
1454        ret = __key_link_check_restriction(keyring, key);
1455        if (ret == 0)
1456                ret = __key_link_check_live_key(keyring, key);
1457        if (ret == 0)
1458                __key_link(keyring, key, &edit);
1459
1460error_end:
1461        __key_link_end(keyring, &key->index_key, edit);
1462error:
1463        kleave(" = %d {%d,%d}", ret, keyring->serial, refcount_read(&keyring->usage));
1464        return ret;
1465}
1466EXPORT_SYMBOL(key_link);
1467
1468/*
1469 * Lock a keyring for unlink.
1470 */
1471static int __key_unlink_lock(struct key *keyring)
1472        __acquires(&keyring->sem)
1473{
1474        if (keyring->type != &key_type_keyring)
1475                return -ENOTDIR;
1476
1477        down_write(&keyring->sem);
1478        return 0;
1479}
1480
1481/*
1482 * Begin the process of unlinking a key from a keyring.
1483 */
1484static int __key_unlink_begin(struct key *keyring, struct key *key,
1485                              struct assoc_array_edit **_edit)
1486{
1487        struct assoc_array_edit *edit;
1488
1489        BUG_ON(*_edit != NULL);
1490
1491        edit = assoc_array_delete(&keyring->keys, &keyring_assoc_array_ops,
1492                                  &key->index_key);
1493        if (IS_ERR(edit))
1494                return PTR_ERR(edit);
1495
1496        if (!edit)
1497                return -ENOENT;
1498
1499        *_edit = edit;
1500        return 0;
1501}
1502
1503/*
1504 * Apply an unlink change.
1505 */
1506static void __key_unlink(struct key *keyring, struct key *key,
1507                         struct assoc_array_edit **_edit)
1508{
1509        assoc_array_apply_edit(*_edit);
1510        notify_key(keyring, NOTIFY_KEY_UNLINKED, key_serial(key));
1511        *_edit = NULL;
1512        key_payload_reserve(keyring, keyring->datalen - KEYQUOTA_LINK_BYTES);
1513}
1514
1515/*
1516 * Finish unlinking a key from to a keyring.
1517 */
1518static void __key_unlink_end(struct key *keyring,
1519                             struct key *key,
1520                             struct assoc_array_edit *edit)
1521        __releases(&keyring->sem)
1522{
1523        if (edit)
1524                assoc_array_cancel_edit(edit);
1525        up_write(&keyring->sem);
1526}
1527
1528/**
1529 * key_unlink - Unlink the first link to a key from a keyring.
1530 * @keyring: The keyring to remove the link from.
1531 * @key: The key the link is to.
1532 *
1533 * Remove a link from a keyring to a key.
1534 *
1535 * This function will write-lock the keyring's semaphore.
1536 *
1537 * Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring, -ENOENT if
1538 * the key isn't linked to by the keyring or -ENOMEM if there's insufficient
1539 * memory.
1540 *
1541 * It is assumed that the caller has checked that it is permitted for a link to
1542 * be removed (the keyring should have Write permission; no permissions are
1543 * required on the key).
1544 */
1545int key_unlink(struct key *keyring, struct key *key)
1546{
1547        struct assoc_array_edit *edit = NULL;
1548        int ret;
1549
1550        key_check(keyring);
1551        key_check(key);
1552
1553        ret = __key_unlink_lock(keyring);
1554        if (ret < 0)
1555                return ret;
1556
1557        ret = __key_unlink_begin(keyring, key, &edit);
1558        if (ret == 0)
1559                __key_unlink(keyring, key, &edit);
1560        __key_unlink_end(keyring, key, edit);
1561        return ret;
1562}
1563EXPORT_SYMBOL(key_unlink);
1564
1565/**
1566 * key_move - Move a key from one keyring to another
1567 * @key: The key to move
1568 * @from_keyring: The keyring to remove the link from.
1569 * @to_keyring: The keyring to make the link in.
1570 * @flags: Qualifying flags, such as KEYCTL_MOVE_EXCL.
1571 *
1572 * Make a link in @to_keyring to a key, such that the keyring holds a reference
1573 * on that key and the key can potentially be found by searching that keyring
1574 * whilst simultaneously removing a link to the key from @from_keyring.
1575 *
1576 * This function will write-lock both keyring's semaphores and will consume
1577 * some of the user's key data quota to hold the link on @to_keyring.
1578 *
1579 * Returns 0 if successful, -ENOTDIR if either keyring isn't a keyring,
1580 * -EKEYREVOKED if either keyring has been revoked, -ENFILE if the second
1581 * keyring is full, -EDQUOT if there is insufficient key data quota remaining
1582 * to add another link or -ENOMEM if there's insufficient memory.  If
1583 * KEYCTL_MOVE_EXCL is set, then -EEXIST will be returned if there's already a
1584 * matching key in @to_keyring.
1585 *
1586 * It is assumed that the caller has checked that it is permitted for a link to
1587 * be made (the keyring should have Write permission and the key Link
1588 * permission).
1589 */
1590int key_move(struct key *key,
1591             struct key *from_keyring,
1592             struct key *to_keyring,
1593             unsigned int flags)
1594{
1595        struct assoc_array_edit *from_edit = NULL, *to_edit = NULL;
1596        int ret;
1597
1598        kenter("%d,%d,%d", key->serial, from_keyring->serial, to_keyring->serial);
1599
1600        if (from_keyring == to_keyring)
1601                return 0;
1602
1603        key_check(key);
1604        key_check(from_keyring);
1605        key_check(to_keyring);
1606
1607        ret = __key_move_lock(from_keyring, to_keyring, &key->index_key);
1608        if (ret < 0)
1609                goto out;
1610        ret = __key_unlink_begin(from_keyring, key, &from_edit);
1611        if (ret < 0)
1612                goto error;
1613        ret = __key_link_begin(to_keyring, &key->index_key, &to_edit);
1614        if (ret < 0)
1615                goto error;
1616
1617        ret = -EEXIST;
1618        if (to_edit->dead_leaf && (flags & KEYCTL_MOVE_EXCL))
1619                goto error;
1620
1621        ret = __key_link_check_restriction(to_keyring, key);
1622        if (ret < 0)
1623                goto error;
1624        ret = __key_link_check_live_key(to_keyring, key);
1625        if (ret < 0)
1626                goto error;
1627
1628        __key_unlink(from_keyring, key, &from_edit);
1629        __key_link(to_keyring, key, &to_edit);
1630error:
1631        __key_link_end(to_keyring, &key->index_key, to_edit);
1632        __key_unlink_end(from_keyring, key, from_edit);
1633out:
1634        kleave(" = %d", ret);
1635        return ret;
1636}
1637EXPORT_SYMBOL(key_move);
1638
1639/**
1640 * keyring_clear - Clear a keyring
1641 * @keyring: The keyring to clear.
1642 *
1643 * Clear the contents of the specified keyring.
1644 *
1645 * Returns 0 if successful or -ENOTDIR if the keyring isn't a keyring.
1646 */
1647int keyring_clear(struct key *keyring)
1648{
1649        struct assoc_array_edit *edit;
1650        int ret;
1651
1652        if (keyring->type != &key_type_keyring)
1653                return -ENOTDIR;
1654
1655        down_write(&keyring->sem);
1656
1657        edit = assoc_array_clear(&keyring->keys, &keyring_assoc_array_ops);
1658        if (IS_ERR(edit)) {
1659                ret = PTR_ERR(edit);
1660        } else {
1661                if (edit)
1662                        assoc_array_apply_edit(edit);
1663                notify_key(keyring, NOTIFY_KEY_CLEARED, 0);
1664                key_payload_reserve(keyring, 0);
1665                ret = 0;
1666        }
1667
1668        up_write(&keyring->sem);
1669        return ret;
1670}
1671EXPORT_SYMBOL(keyring_clear);
1672
1673/*
1674 * Dispose of the links from a revoked keyring.
1675 *
1676 * This is called with the key sem write-locked.
1677 */
1678static void keyring_revoke(struct key *keyring)
1679{
1680        struct assoc_array_edit *edit;
1681
1682        edit = assoc_array_clear(&keyring->keys, &keyring_assoc_array_ops);
1683        if (!IS_ERR(edit)) {
1684                if (edit)
1685                        assoc_array_apply_edit(edit);
1686                key_payload_reserve(keyring, 0);
1687        }
1688}
1689
1690static bool keyring_gc_select_iterator(void *object, void *iterator_data)
1691{
1692        struct key *key = keyring_ptr_to_key(object);
1693        time64_t *limit = iterator_data;
1694
1695        if (key_is_dead(key, *limit))
1696                return false;
1697        key_get(key);
1698        return true;
1699}
1700
1701static int keyring_gc_check_iterator(const void *object, void *iterator_data)
1702{
1703        const struct key *key = keyring_ptr_to_key(object);
1704        time64_t *limit = iterator_data;
1705
1706        key_check(key);
1707        return key_is_dead(key, *limit);
1708}
1709
1710/*
1711 * Garbage collect pointers from a keyring.
1712 *
1713 * Not called with any locks held.  The keyring's key struct will not be
1714 * deallocated under us as only our caller may deallocate it.
1715 */
1716void keyring_gc(struct key *keyring, time64_t limit)
1717{
1718        int result;
1719
1720        kenter("%x{%s}", keyring->serial, keyring->description ?: "");
1721
1722        if (keyring->flags & ((1 << KEY_FLAG_INVALIDATED) |
1723                              (1 << KEY_FLAG_REVOKED)))
1724                goto dont_gc;
1725
1726        /* scan the keyring looking for dead keys */
1727        rcu_read_lock();
1728        result = assoc_array_iterate(&keyring->keys,
1729                                     keyring_gc_check_iterator, &limit);
1730        rcu_read_unlock();
1731        if (result == true)
1732                goto do_gc;
1733
1734dont_gc:
1735        kleave(" [no gc]");
1736        return;
1737
1738do_gc:
1739        down_write(&keyring->sem);
1740        assoc_array_gc(&keyring->keys, &keyring_assoc_array_ops,
1741                       keyring_gc_select_iterator, &limit);
1742        up_write(&keyring->sem);
1743        kleave(" [gc]");
1744}
1745
1746/*
1747 * Garbage collect restriction pointers from a keyring.
1748 *
1749 * Keyring restrictions are associated with a key type, and must be cleaned
1750 * up if the key type is unregistered. The restriction is altered to always
1751 * reject additional keys so a keyring cannot be opened up by unregistering
1752 * a key type.
1753 *
1754 * Not called with any keyring locks held. The keyring's key struct will not
1755 * be deallocated under us as only our caller may deallocate it.
1756 *
1757 * The caller is required to hold key_types_sem and dead_type->sem. This is
1758 * fulfilled by key_gc_keytype() holding the locks on behalf of
1759 * key_garbage_collector(), which it invokes on a workqueue.
1760 */
1761void keyring_restriction_gc(struct key *keyring, struct key_type *dead_type)
1762{
1763        struct key_restriction *keyres;
1764
1765        kenter("%x{%s}", keyring->serial, keyring->description ?: "");
1766
1767        /*
1768         * keyring->restrict_link is only assigned at key allocation time
1769         * or with the key type locked, so the only values that could be
1770         * concurrently assigned to keyring->restrict_link are for key
1771         * types other than dead_type. Given this, it's ok to check
1772         * the key type before acquiring keyring->sem.
1773         */
1774        if (!dead_type || !keyring->restrict_link ||
1775            keyring->restrict_link->keytype != dead_type) {
1776                kleave(" [no restriction gc]");
1777                return;
1778        }
1779
1780        /* Lock the keyring to ensure that a link is not in progress */
1781        down_write(&keyring->sem);
1782
1783        keyres = keyring->restrict_link;
1784
1785        keyres->check = restrict_link_reject;
1786
1787        key_put(keyres->key);
1788        keyres->key = NULL;
1789        keyres->keytype = NULL;
1790
1791        up_write(&keyring->sem);
1792
1793        kleave(" [restriction gc]");
1794}
1795