block/blk-crypto.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright 2019 Google LLC
   4  */
   5
   6 /*
   7  * Refer to Documentation/block/inline-encryption.rst for detailed explanation.
   8  */
   9
  10 #define pr_fmt(fmt) "blk-crypto: " fmt
  11
  12 #include <linux/bio.h>
  13 #include <linux/blkdev.h>
  14 #include <linux/blk-crypto-profile.h>
  15 #include <linux/module.h>
  16 #include <linux/slab.h>
  17
  18 #include "blk-crypto-internal.h"
  19
  20 const struct blk_crypto_mode blk_crypto_modes[] = {
  21         [BLK_ENCRYPTION_MODE_AES_256_XTS] = {
  22                 .name = "AES-256-XTS",
  23                 .cipher_str = "xts(aes)",
  24                 .keysize = 64,
  25                 .ivsize = 16,
  26         },
  27         [BLK_ENCRYPTION_MODE_AES_128_CBC_ESSIV] = {
  28                 .name = "AES-128-CBC-ESSIV",
  29                 .cipher_str = "essiv(cbc(aes),sha256)",
  30                 .keysize = 16,
  31                 .ivsize = 16,
  32         },
  33         [BLK_ENCRYPTION_MODE_ADIANTUM] = {
  34                 .name = "Adiantum",
  35                 .cipher_str = "adiantum(xchacha12,aes)",
  36                 .keysize = 32,
  37                 .ivsize = 32,
  38         },
  39         [BLK_ENCRYPTION_MODE_SM4_XTS] = {
  40                 .name = "SM4-XTS",
  41                 .cipher_str = "xts(sm4)",
  42                 .keysize = 32,
  43                 .ivsize = 16,
  44         },
  45 };
  46
  47 /*
  48  * This number needs to be at least (the number of threads doing IO
  49  * concurrently) * (maximum recursive depth of a bio), so that we don't
  50  * deadlock on crypt_ctx allocations. The default is chosen to be the same
  51  * as the default number of post read contexts in both EXT4 and F2FS.
  52  */
  53 static int num_prealloc_crypt_ctxs = 128;
  54
  55 module_param(num_prealloc_crypt_ctxs, int, 0444);
  56 MODULE_PARM_DESC(num_prealloc_crypt_ctxs,
  57                 "Number of bio crypto contexts to preallocate");
  58
  59 static struct kmem_cache *bio_crypt_ctx_cache;
  60 static mempool_t *bio_crypt_ctx_pool;
  61
  62 static int __init bio_crypt_ctx_init(void)
  63 {
  64         size_t i;
  65
  66         bio_crypt_ctx_cache = KMEM_CACHE(bio_crypt_ctx, 0);
  67         if (!bio_crypt_ctx_cache)
  68                 goto out_no_mem;
  69
  70         bio_crypt_ctx_pool = mempool_create_slab_pool(num_prealloc_crypt_ctxs,
  71                                                       bio_crypt_ctx_cache);
  72         if (!bio_crypt_ctx_pool)
  73                 goto out_no_mem;
  74
  75         /* This is assumed in various places. */
  76         BUILD_BUG_ON(BLK_ENCRYPTION_MODE_INVALID != 0);
  77
  78         /* Sanity check that no algorithm exceeds the defined limits. */
  79         for (i = 0; i < BLK_ENCRYPTION_MODE_MAX; i++) {
  80                 BUG_ON(blk_crypto_modes[i].keysize > BLK_CRYPTO_MAX_KEY_SIZE);
  81                 BUG_ON(blk_crypto_modes[i].ivsize > BLK_CRYPTO_MAX_IV_SIZE);
  82         }
  83
  84         return 0;
  85 out_no_mem:
  86         panic("Failed to allocate mem for bio crypt ctxs\n");
  87 }
  88 subsys_initcall(bio_crypt_ctx_init);
  89
  90 void bio_crypt_set_ctx(struct bio *bio, const struct blk_crypto_key *key,
  91                        const u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE], gfp_t gfp_mask)
  92 {
  93         struct bio_crypt_ctx *bc;
  94
  95         /*
  96          * The caller must use a gfp_mask that contains __GFP_DIRECT_RECLAIM so
  97          * that the mempool_alloc() can't fail.
  98          */
  99         WARN_ON_ONCE(!(gfp_mask & __GFP_DIRECT_RECLAIM));
 100
 101         bc = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
 102
 103         bc->bc_key = key;
 104         memcpy(bc->bc_dun, dun, sizeof(bc->bc_dun));
 105
 106         bio->bi_crypt_context = bc;
 107 }
 108
 109 void __bio_crypt_free_ctx(struct bio *bio)
 110 {
 111         mempool_free(bio->bi_crypt_context, bio_crypt_ctx_pool);
 112         bio->bi_crypt_context = NULL;
 113 }
 114
 115 int __bio_crypt_clone(struct bio *dst, struct bio *src, gfp_t gfp_mask)
 116 {
 117         dst->bi_crypt_context = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
 118         if (!dst->bi_crypt_context)
 119                 return -ENOMEM;
 120         *dst->bi_crypt_context = *src->bi_crypt_context;
 121         return 0;
 122 }
 123
 124 /* Increments @dun by @inc, treating @dun as a multi-limb integer. */
 125 void bio_crypt_dun_increment(u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE],
 126                              unsigned int inc)
 127 {
 128         int i;
 129
 130         for (i = 0; inc && i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++) {
 131                 dun[i] += inc;
 132                 /*
 133                  * If the addition in this limb overflowed, then we need to
 134                  * carry 1 into the next limb. Else the carry is 0.
 135                  */
 136                 if (dun[i] < inc)
 137                         inc = 1;
 138                 else
 139                         inc = 0;
 140         }
 141 }
 142
 143 void __bio_crypt_advance(struct bio *bio, unsigned int bytes)
 144 {
 145         struct bio_crypt_ctx *bc = bio->bi_crypt_context;
 146
 147         bio_crypt_dun_increment(bc->bc_dun,
 148                                 bytes >> bc->bc_key->data_unit_size_bits);
 149 }
 150
 151 /*
 152  * Returns true if @bc->bc_dun plus @bytes converted to data units is equal to
 153  * @next_dun, treating the DUNs as multi-limb integers.
 154  */
 155 bool bio_crypt_dun_is_contiguous(const struct bio_crypt_ctx *bc,
 156                                  unsigned int bytes,
 157                                  const u64 next_dun[BLK_CRYPTO_DUN_ARRAY_SIZE])
 158 {
 159         int i;
 160         unsigned int carry = bytes >> bc->bc_key->data_unit_size_bits;
 161
 162         for (i = 0; i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++) {
 163                 if (bc->bc_dun[i] + carry != next_dun[i])
 164                         return false;
 165                 /*
 166                  * If the addition in this limb overflowed, then we need to
 167                  * carry 1 into the next limb. Else the carry is 0.
 168                  */
 169                 if ((bc->bc_dun[i] + carry) < carry)
 170                         carry = 1;
 171                 else
 172                         carry = 0;
 173         }
 174
 175         /* If the DUN wrapped through 0, don't treat it as contiguous. */
 176         return carry == 0;
 177 }
 178
 179 /*
 180  * Checks that two bio crypt contexts are compatible - i.e. that
 181  * they are mergeable except for data_unit_num continuity.
 182  */
 183 static bool bio_crypt_ctx_compatible(struct bio_crypt_ctx *bc1,
 184                                      struct bio_crypt_ctx *bc2)
 185 {
 186         if (!bc1)
 187                 return !bc2;
 188
 189         return bc2 && bc1->bc_key == bc2->bc_key;
 190 }
 191
 192 bool bio_crypt_rq_ctx_compatible(struct request *rq, struct bio *bio)
 193 {
 194         return bio_crypt_ctx_compatible(rq->crypt_ctx, bio->bi_crypt_context);
 195 }
 196
 197 /*
 198  * Checks that two bio crypt contexts are compatible, and also
 199  * that their data_unit_nums are continuous (and can hence be merged)
 200  * in the order @bc1 followed by @bc2.
 201  */
 202 bool bio_crypt_ctx_mergeable(struct bio_crypt_ctx *bc1, unsigned int bc1_bytes,
 203                              struct bio_crypt_ctx *bc2)
 204 {
 205         if (!bio_crypt_ctx_compatible(bc1, bc2))
 206                 return false;
 207
 208         return !bc1 || bio_crypt_dun_is_contiguous(bc1, bc1_bytes, bc2->bc_dun);
 209 }
 210
 211 /* Check that all I/O segments are data unit aligned. */
 212 static bool bio_crypt_check_alignment(struct bio *bio)
 213 {
 214         const unsigned int data_unit_size =
 215                 bio->bi_crypt_context->bc_key->crypto_cfg.data_unit_size;
 216         struct bvec_iter iter;
 217         struct bio_vec bv;
 218
 219         bio_for_each_segment(bv, bio, iter) {
 220                 if (!IS_ALIGNED(bv.bv_len | bv.bv_offset, data_unit_size))
 221                         return false;
 222         }
 223
 224         return true;
 225 }
 226
 227 blk_status_t __blk_crypto_init_request(struct request *rq)
 228 {
 229         return blk_crypto_get_keyslot(rq->q->crypto_profile,
 230                                       rq->crypt_ctx->bc_key,
 231                                       &rq->crypt_keyslot);
 232 }
 233
 234 /**
 235  * __blk_crypto_free_request - Uninitialize the crypto fields of a request.
 236  *
 237  * @rq: The request whose crypto fields to uninitialize.
 238  *
 239  * Completely uninitializes the crypto fields of a request. If a keyslot has
 240  * been programmed into some inline encryption hardware, that keyslot is
 241  * released. The rq->crypt_ctx is also freed.
 242  */
 243 void __blk_crypto_free_request(struct request *rq)
 244 {
 245         blk_crypto_put_keyslot(rq->crypt_keyslot);
 246         mempool_free(rq->crypt_ctx, bio_crypt_ctx_pool);
 247         blk_crypto_rq_set_defaults(rq);
 248 }
 249
 250 /**
 251  * __blk_crypto_bio_prep - Prepare bio for inline encryption
 252  *
 253  * @bio_ptr: pointer to original bio pointer
 254  *
 255  * If the bio crypt context provided for the bio is supported by the underlying
 256  * device's inline encryption hardware, do nothing.
 257  *
 258  * Otherwise, try to perform en/decryption for this bio by falling back to the
 259  * kernel crypto API. When the crypto API fallback is used for encryption,
 260  * blk-crypto may choose to split the bio into 2 - the first one that will
 261  * continue to be processed and the second one that will be resubmitted via
 262  * submit_bio_noacct. A bounce bio will be allocated to encrypt the contents
 263  * of the aforementioned "first one", and *bio_ptr will be updated to this
 264  * bounce bio.
 265  *
 266  * Caller must ensure bio has bio_crypt_ctx.
 267  *
 268  * Return: true on success; false on error (and bio->bi_status will be set
 269  *         appropriately, and bio_endio() will have been called so bio
 270  *         submission should abort).
 271  */
 272 bool __blk_crypto_bio_prep(struct bio **bio_ptr)
 273 {
 274         struct bio *bio = *bio_ptr;
 275         const struct blk_crypto_key *bc_key = bio->bi_crypt_context->bc_key;
 276
 277         /* Error if bio has no data. */
 278         if (WARN_ON_ONCE(!bio_has_data(bio))) {
 279                 bio->bi_status = BLK_STS_IOERR;
 280                 goto fail;
 281         }
 282
 283         if (!bio_crypt_check_alignment(bio)) {
 284                 bio->bi_status = BLK_STS_IOERR;
 285                 goto fail;
 286         }
 287
 288         /*
 289          * Success if device supports the encryption context, or if we succeeded
 290          * in falling back to the crypto API.
 291          */
 292         if (blk_crypto_config_supported_natively(bio->bi_bdev,
 293                                                  &bc_key->crypto_cfg))
 294                 return true;
 295         if (blk_crypto_fallback_bio_prep(bio_ptr))
 296                 return true;
 297 fail:
 298         bio_endio(*bio_ptr);
 299         return false;
 300 }
 301
 302 int __blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
 303                              gfp_t gfp_mask)
 304 {
 305         if (!rq->crypt_ctx) {
 306                 rq->crypt_ctx = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
 307                 if (!rq->crypt_ctx)
 308                         return -ENOMEM;
 309         }
 310         *rq->crypt_ctx = *bio->bi_crypt_context;
 311         return 0;
 312 }
 313
 314 /**
 315  * blk_crypto_init_key() - Prepare a key for use with blk-crypto
 316  * @blk_key: Pointer to the blk_crypto_key to initialize.
 317  * @raw_key: Pointer to the raw key. Must be the correct length for the chosen
 318  *           @crypto_mode; see blk_crypto_modes[].
 319  * @crypto_mode: identifier for the encryption algorithm to use
 320  * @dun_bytes: number of bytes that will be used to specify the DUN when this
 321  *             key is used
 322  * @data_unit_size: the data unit size to use for en/decryption
 323  *
 324  * Return: 0 on success, -errno on failure.  The caller is responsible for
 325  *         zeroizing both blk_key and raw_key when done with them.
 326  */
 327 int blk_crypto_init_key(struct blk_crypto_key *blk_key, const u8 *raw_key,
 328                         enum blk_crypto_mode_num crypto_mode,
 329                         unsigned int dun_bytes,
 330                         unsigned int data_unit_size)
 331 {
 332         const struct blk_crypto_mode *mode;
 333
 334         memset(blk_key, 0, sizeof(*blk_key));
 335
 336         if (crypto_mode >= ARRAY_SIZE(blk_crypto_modes))
 337                 return -EINVAL;
 338
 339         mode = &blk_crypto_modes[crypto_mode];
 340         if (mode->keysize == 0)
 341                 return -EINVAL;
 342
 343         if (dun_bytes == 0 || dun_bytes > mode->ivsize)
 344                 return -EINVAL;
 345
 346         if (!is_power_of_2(data_unit_size))
 347                 return -EINVAL;
 348
 349         blk_key->crypto_cfg.crypto_mode = crypto_mode;
 350         blk_key->crypto_cfg.dun_bytes = dun_bytes;
 351         blk_key->crypto_cfg.data_unit_size = data_unit_size;
 352         blk_key->data_unit_size_bits = ilog2(data_unit_size);
 353         blk_key->size = mode->keysize;
 354         memcpy(blk_key->raw, raw_key, mode->keysize);
 355
 356         return 0;
 357 }
 358
 359 bool blk_crypto_config_supported_natively(struct block_device *bdev,
 360                                           const struct blk_crypto_config *cfg)
 361 {
 362         return __blk_crypto_cfg_supported(bdev_get_queue(bdev)->crypto_profile,
 363                                           cfg);
 364 }
 365
 366 /*
 367  * Check if bios with @cfg can be en/decrypted by blk-crypto (i.e. either the
 368  * block_device it's submitted to supports inline crypto, or the
 369  * blk-crypto-fallback is enabled and supports the cfg).
 370  */
 371 bool blk_crypto_config_supported(struct block_device *bdev,
 372                                  const struct blk_crypto_config *cfg)
 373 {
 374         return IS_ENABLED(CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK) ||
 375                blk_crypto_config_supported_natively(bdev, cfg);
 376 }
 377
 378 /**
 379  * blk_crypto_start_using_key() - Start using a blk_crypto_key on a device
 380  * @bdev: block device to operate on
 381  * @key: A key to use on the device
 382  *
 383  * Upper layers must call this function to ensure that either the hardware
 384  * supports the key's crypto settings, or the crypto API fallback has transforms
 385  * for the needed mode allocated and ready to go. This function may allocate
 386  * an skcipher, and *should not* be called from the data path, since that might
 387  * cause a deadlock
 388  *
 389  * Return: 0 on success; -ENOPKG if the hardware doesn't support the key and
 390  *         blk-crypto-fallback is either disabled or the needed algorithm
 391  *         is disabled in the crypto API; or another -errno code.
 392  */
 393 int blk_crypto_start_using_key(struct block_device *bdev,
 394                                const struct blk_crypto_key *key)
 395 {
 396         if (blk_crypto_config_supported_natively(bdev, &key->crypto_cfg))
 397                 return 0;
 398         return blk_crypto_fallback_start_using_mode(key->crypto_cfg.crypto_mode);
 399 }
 400
 401 /**
 402  * blk_crypto_evict_key() - Evict a key from any inline encryption hardware
 403  *                          it may have been programmed into
 404  * @bdev: The block_device who's associated inline encryption hardware this key
 405  *     might have been programmed into
 406  * @key: The key to evict
 407  *
 408  * Upper layers (filesystems) must call this function to ensure that a key is
 409  * evicted from any hardware that it might have been programmed into.  The key
 410  * must not be in use by any in-flight IO when this function is called.
 411  *
 412  * Return: 0 on success or if the key wasn't in any keyslot; -errno on error.
 413  */
 414 int blk_crypto_evict_key(struct block_device *bdev,
 415                          const struct blk_crypto_key *key)
 416 {
 417         struct request_queue *q = bdev_get_queue(bdev);
 418
 419         if (blk_crypto_config_supported_natively(bdev, &key->crypto_cfg))
 420                 return __blk_crypto_evict_key(q->crypto_profile, key);
 421
 422         /*
 423          * If the block_device didn't support the key, then blk-crypto-fallback
 424          * may have been used, so try to evict the key from blk-crypto-fallback.
 425          */
 426         return blk_crypto_fallback_evict_key(key);
 427 }
 428 EXPORT_SYMBOL_GPL(blk_crypto_evict_key);