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/ratelimit.h>
  17 #include <linux/slab.h>
  18
  19 #include "blk-crypto-internal.h"
  20
  21 const struct blk_crypto_mode blk_crypto_modes[] = {
  22         [BLK_ENCRYPTION_MODE_AES_256_XTS] = {
  23                 .name = "AES-256-XTS",
  24                 .cipher_str = "xts(aes)",
  25                 .keysize = 64,
  26                 .ivsize = 16,
  27         },
  28         [BLK_ENCRYPTION_MODE_AES_128_CBC_ESSIV] = {
  29                 .name = "AES-128-CBC-ESSIV",
  30                 .cipher_str = "essiv(cbc(aes),sha256)",
  31                 .keysize = 16,
  32                 .ivsize = 16,
  33         },
  34         [BLK_ENCRYPTION_MODE_ADIANTUM] = {
  35                 .name = "Adiantum",
  36                 .cipher_str = "adiantum(xchacha12,aes)",
  37                 .keysize = 32,
  38                 .ivsize = 32,
  39         },
  40         [BLK_ENCRYPTION_MODE_SM4_XTS] = {
  41                 .name = "SM4-XTS",
  42                 .cipher_str = "xts(sm4)",
  43                 .keysize = 32,
  44                 .ivsize = 16,
  45         },
  46 };
  47
  48 /*
  49  * This number needs to be at least (the number of threads doing IO
  50  * concurrently) * (maximum recursive depth of a bio), so that we don't
  51  * deadlock on crypt_ctx allocations. The default is chosen to be the same
  52  * as the default number of post read contexts in both EXT4 and F2FS.
  53  */
  54 static int num_prealloc_crypt_ctxs = 128;
  55
  56 module_param(num_prealloc_crypt_ctxs, int, 0444);
  57 MODULE_PARM_DESC(num_prealloc_crypt_ctxs,
  58                 "Number of bio crypto contexts to preallocate");
  59
  60 static struct kmem_cache *bio_crypt_ctx_cache;
  61 static mempool_t *bio_crypt_ctx_pool;
  62
  63 static int __init bio_crypt_ctx_init(void)
  64 {
  65         size_t i;
  66
  67         bio_crypt_ctx_cache = KMEM_CACHE(bio_crypt_ctx, 0);
  68         if (!bio_crypt_ctx_cache)
  69                 goto out_no_mem;
  70
  71         bio_crypt_ctx_pool = mempool_create_slab_pool(num_prealloc_crypt_ctxs,
  72                                                       bio_crypt_ctx_cache);
  73         if (!bio_crypt_ctx_pool)
  74                 goto out_no_mem;
  75
  76         /* This is assumed in various places. */
  77         BUILD_BUG_ON(BLK_ENCRYPTION_MODE_INVALID != 0);
  78
  79         /* Sanity check that no algorithm exceeds the defined limits. */
  80         for (i = 0; i < BLK_ENCRYPTION_MODE_MAX; i++) {
  81                 BUG_ON(blk_crypto_modes[i].keysize > BLK_CRYPTO_MAX_KEY_SIZE);
  82                 BUG_ON(blk_crypto_modes[i].ivsize > BLK_CRYPTO_MAX_IV_SIZE);
  83         }
  84
  85         return 0;
  86 out_no_mem:
  87         panic("Failed to allocate mem for bio crypt ctxs\n");
  88 }
  89 subsys_initcall(bio_crypt_ctx_init);
  90
  91 void bio_crypt_set_ctx(struct bio *bio, const struct blk_crypto_key *key,
  92                        const u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE], gfp_t gfp_mask)
  93 {
  94         struct bio_crypt_ctx *bc;
  95
  96         /*
  97          * The caller must use a gfp_mask that contains __GFP_DIRECT_RECLAIM so
  98          * that the mempool_alloc() can't fail.
  99          */
 100         WARN_ON_ONCE(!(gfp_mask & __GFP_DIRECT_RECLAIM));
 101
 102         bc = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
 103
 104         bc->bc_key = key;
 105         memcpy(bc->bc_dun, dun, sizeof(bc->bc_dun));
 106
 107         bio->bi_crypt_context = bc;
 108 }
 109
 110 void __bio_crypt_free_ctx(struct bio *bio)
 111 {
 112         mempool_free(bio->bi_crypt_context, bio_crypt_ctx_pool);
 113         bio->bi_crypt_context = NULL;
 114 }
 115
 116 int __bio_crypt_clone(struct bio *dst, struct bio *src, gfp_t gfp_mask)
 117 {
 118         dst->bi_crypt_context = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
 119         if (!dst->bi_crypt_context)
 120                 return -ENOMEM;
 121         *dst->bi_crypt_context = *src->bi_crypt_context;
 122         return 0;
 123 }
 124
 125 /* Increments @dun by @inc, treating @dun as a multi-limb integer. */
 126 void bio_crypt_dun_increment(u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE],
 127                              unsigned int inc)
 128 {
 129         int i;
 130
 131         for (i = 0; inc && i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++) {
 132                 dun[i] += inc;
 133                 /*
 134                  * If the addition in this limb overflowed, then we need to
 135                  * carry 1 into the next limb. Else the carry is 0.
 136                  */
 137                 if (dun[i] < inc)
 138                         inc = 1;
 139                 else
 140                         inc = 0;
 141         }
 142 }
 143
 144 void __bio_crypt_advance(struct bio *bio, unsigned int bytes)
 145 {
 146         struct bio_crypt_ctx *bc = bio->bi_crypt_context;
 147
 148         bio_crypt_dun_increment(bc->bc_dun,
 149                                 bytes >> bc->bc_key->data_unit_size_bits);
 150 }
 151
 152 /*
 153  * Returns true if @bc->bc_dun plus @bytes converted to data units is equal to
 154  * @next_dun, treating the DUNs as multi-limb integers.
 155  */
 156 bool bio_crypt_dun_is_contiguous(const struct bio_crypt_ctx *bc,
 157                                  unsigned int bytes,
 158                                  const u64 next_dun[BLK_CRYPTO_DUN_ARRAY_SIZE])
 159 {
 160         int i;
 161         unsigned int carry = bytes >> bc->bc_key->data_unit_size_bits;
 162
 163         for (i = 0; i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++) {
 164                 if (bc->bc_dun[i] + carry != next_dun[i])
 165                         return false;
 166                 /*
 167                  * If the addition in this limb overflowed, then we need to
 168                  * carry 1 into the next limb. Else the carry is 0.
 169                  */
 170                 if ((bc->bc_dun[i] + carry) < carry)
 171                         carry = 1;
 172                 else
 173                         carry = 0;
 174         }
 175
 176         /* If the DUN wrapped through 0, don't treat it as contiguous. */
 177         return carry == 0;
 178 }
 179
 180 /*
 181  * Checks that two bio crypt contexts are compatible - i.e. that
 182  * they are mergeable except for data_unit_num continuity.
 183  */
 184 static bool bio_crypt_ctx_compatible(struct bio_crypt_ctx *bc1,
 185                                      struct bio_crypt_ctx *bc2)
 186 {
 187         if (!bc1)
 188                 return !bc2;
 189
 190         return bc2 && bc1->bc_key == bc2->bc_key;
 191 }
 192
 193 bool bio_crypt_rq_ctx_compatible(struct request *rq, struct bio *bio)
 194 {
 195         return bio_crypt_ctx_compatible(rq->crypt_ctx, bio->bi_crypt_context);
 196 }
 197
 198 /*
 199  * Checks that two bio crypt contexts are compatible, and also
 200  * that their data_unit_nums are continuous (and can hence be merged)
 201  * in the order @bc1 followed by @bc2.
 202  */
 203 bool bio_crypt_ctx_mergeable(struct bio_crypt_ctx *bc1, unsigned int bc1_bytes,
 204                              struct bio_crypt_ctx *bc2)
 205 {
 206         if (!bio_crypt_ctx_compatible(bc1, bc2))
 207                 return false;
 208
 209         return !bc1 || bio_crypt_dun_is_contiguous(bc1, bc1_bytes, bc2->bc_dun);
 210 }
 211
 212 /* Check that all I/O segments are data unit aligned. */
 213 static bool bio_crypt_check_alignment(struct bio *bio)
 214 {
 215         const unsigned int data_unit_size =
 216                 bio->bi_crypt_context->bc_key->crypto_cfg.data_unit_size;
 217         struct bvec_iter iter;
 218         struct bio_vec bv;
 219
 220         bio_for_each_segment(bv, bio, iter) {
 221                 if (!IS_ALIGNED(bv.bv_len | bv.bv_offset, data_unit_size))
 222                         return false;
 223         }
 224
 225         return true;
 226 }
 227
 228 blk_status_t __blk_crypto_rq_get_keyslot(struct request *rq)
 229 {
 230         return blk_crypto_get_keyslot(rq->q->crypto_profile,
 231                                       rq->crypt_ctx->bc_key,
 232                                       &rq->crypt_keyslot);
 233 }
 234
 235 void __blk_crypto_rq_put_keyslot(struct request *rq)
 236 {
 237         blk_crypto_put_keyslot(rq->crypt_keyslot);
 238         rq->crypt_keyslot = NULL;
 239 }
 240
 241 void __blk_crypto_free_request(struct request *rq)
 242 {
 243         /* The keyslot, if one was needed, should have been released earlier. */
 244         if (WARN_ON_ONCE(rq->crypt_keyslot))
 245                 __blk_crypto_rq_put_keyslot(rq);
 246
 247         mempool_free(rq->crypt_ctx, bio_crypt_ctx_pool);
 248         rq->crypt_ctx = NULL;
 249 }
 250
 251 /**
 252  * __blk_crypto_bio_prep - Prepare bio for inline encryption
 253  *
 254  * @bio_ptr: pointer to original bio pointer
 255  *
 256  * If the bio crypt context provided for the bio is supported by the underlying
 257  * device's inline encryption hardware, do nothing.
 258  *
 259  * Otherwise, try to perform en/decryption for this bio by falling back to the
 260  * kernel crypto API. When the crypto API fallback is used for encryption,
 261  * blk-crypto may choose to split the bio into 2 - the first one that will
 262  * continue to be processed and the second one that will be resubmitted via
 263  * submit_bio_noacct. A bounce bio will be allocated to encrypt the contents
 264  * of the aforementioned "first one", and *bio_ptr will be updated to this
 265  * bounce bio.
 266  *
 267  * Caller must ensure bio has bio_crypt_ctx.
 268  *
 269  * Return: true on success; false on error (and bio->bi_status will be set
 270  *         appropriately, and bio_endio() will have been called so bio
 271  *         submission should abort).
 272  */
 273 bool __blk_crypto_bio_prep(struct bio **bio_ptr)
 274 {
 275         struct bio *bio = *bio_ptr;
 276         const struct blk_crypto_key *bc_key = bio->bi_crypt_context->bc_key;
 277
 278         /* Error if bio has no data. */
 279         if (WARN_ON_ONCE(!bio_has_data(bio))) {
 280                 bio->bi_status = BLK_STS_IOERR;
 281                 goto fail;
 282         }
 283
 284         if (!bio_crypt_check_alignment(bio)) {
 285                 bio->bi_status = BLK_STS_IOERR;
 286                 goto fail;
 287         }
 288
 289         /*
 290          * Success if device supports the encryption context, or if we succeeded
 291          * in falling back to the crypto API.
 292          */
 293         if (blk_crypto_config_supported_natively(bio->bi_bdev,
 294                                                  &bc_key->crypto_cfg))
 295                 return true;
 296         if (blk_crypto_fallback_bio_prep(bio_ptr))
 297                 return true;
 298 fail:
 299         bio_endio(*bio_ptr);
 300         return false;
 301 }
 302
 303 int __blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
 304                              gfp_t gfp_mask)
 305 {
 306         if (!rq->crypt_ctx) {
 307                 rq->crypt_ctx = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
 308                 if (!rq->crypt_ctx)
 309                         return -ENOMEM;
 310         }
 311         *rq->crypt_ctx = *bio->bi_crypt_context;
 312         return 0;
 313 }
 314
 315 /**
 316  * blk_crypto_init_key() - Prepare a key for use with blk-crypto
 317  * @blk_key: Pointer to the blk_crypto_key to initialize.
 318  * @raw_key: Pointer to the raw key. Must be the correct length for the chosen
 319  *           @crypto_mode; see blk_crypto_modes[].
 320  * @crypto_mode: identifier for the encryption algorithm to use
 321  * @dun_bytes: number of bytes that will be used to specify the DUN when this
 322  *             key is used
 323  * @data_unit_size: the data unit size to use for en/decryption
 324  *
 325  * Return: 0 on success, -errno on failure.  The caller is responsible for
 326  *         zeroizing both blk_key and raw_key when done with them.
 327  */
 328 int blk_crypto_init_key(struct blk_crypto_key *blk_key, const u8 *raw_key,
 329                         enum blk_crypto_mode_num crypto_mode,
 330                         unsigned int dun_bytes,
 331                         unsigned int data_unit_size)
 332 {
 333         const struct blk_crypto_mode *mode;
 334
 335         memset(blk_key, 0, sizeof(*blk_key));
 336
 337         if (crypto_mode >= ARRAY_SIZE(blk_crypto_modes))
 338                 return -EINVAL;
 339
 340         mode = &blk_crypto_modes[crypto_mode];
 341         if (mode->keysize == 0)
 342                 return -EINVAL;
 343
 344         if (dun_bytes == 0 || dun_bytes > mode->ivsize)
 345                 return -EINVAL;
 346
 347         if (!is_power_of_2(data_unit_size))
 348                 return -EINVAL;
 349
 350         blk_key->crypto_cfg.crypto_mode = crypto_mode;
 351         blk_key->crypto_cfg.dun_bytes = dun_bytes;
 352         blk_key->crypto_cfg.data_unit_size = data_unit_size;
 353         blk_key->data_unit_size_bits = ilog2(data_unit_size);
 354         blk_key->size = mode->keysize;
 355         memcpy(blk_key->raw, raw_key, mode->keysize);
 356
 357         return 0;
 358 }
 359
 360 bool blk_crypto_config_supported_natively(struct block_device *bdev,
 361                                           const struct blk_crypto_config *cfg)
 362 {
 363         return __blk_crypto_cfg_supported(bdev_get_queue(bdev)->crypto_profile,
 364                                           cfg);
 365 }
 366
 367 /*
 368  * Check if bios with @cfg can be en/decrypted by blk-crypto (i.e. either the
 369  * block_device it's submitted to supports inline crypto, or the
 370  * blk-crypto-fallback is enabled and supports the cfg).
 371  */
 372 bool blk_crypto_config_supported(struct block_device *bdev,
 373                                  const struct blk_crypto_config *cfg)
 374 {
 375         return IS_ENABLED(CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK) ||
 376                blk_crypto_config_supported_natively(bdev, cfg);
 377 }
 378
 379 /**
 380  * blk_crypto_start_using_key() - Start using a blk_crypto_key on a device
 381  * @bdev: block device to operate on
 382  * @key: A key to use on the device
 383  *
 384  * Upper layers must call this function to ensure that either the hardware
 385  * supports the key's crypto settings, or the crypto API fallback has transforms
 386  * for the needed mode allocated and ready to go. This function may allocate
 387  * an skcipher, and *should not* be called from the data path, since that might
 388  * cause a deadlock
 389  *
 390  * Return: 0 on success; -ENOPKG if the hardware doesn't support the key and
 391  *         blk-crypto-fallback is either disabled or the needed algorithm
 392  *         is disabled in the crypto API; or another -errno code.
 393  */
 394 int blk_crypto_start_using_key(struct block_device *bdev,
 395                                const struct blk_crypto_key *key)
 396 {
 397         if (blk_crypto_config_supported_natively(bdev, &key->crypto_cfg))
 398                 return 0;
 399         return blk_crypto_fallback_start_using_mode(key->crypto_cfg.crypto_mode);
 400 }
 401
 402 /**
 403  * blk_crypto_evict_key() - Evict a blk_crypto_key from a block_device
 404  * @bdev: a block_device on which I/O using the key may have been done
 405  * @key: the key to evict
 406  *
 407  * For a given block_device, this function removes the given blk_crypto_key from
 408  * the keyslot management structures and evicts it from any underlying hardware
 409  * keyslot(s) or blk-crypto-fallback keyslot it may have been programmed into.
 410  *
 411  * Upper layers must call this before freeing the blk_crypto_key.  It must be
 412  * called for every block_device the key may have been used on.  The key must no
 413  * longer be in use by any I/O when this function is called.
 414  *
 415  * Context: May sleep.
 416  */
 417 void blk_crypto_evict_key(struct block_device *bdev,
 418                           const struct blk_crypto_key *key)
 419 {
 420         struct request_queue *q = bdev_get_queue(bdev);
 421         int err;
 422
 423         if (blk_crypto_config_supported_natively(bdev, &key->crypto_cfg))
 424                 err = __blk_crypto_evict_key(q->crypto_profile, key);
 425         else
 426                 err = blk_crypto_fallback_evict_key(key);
 427         /*
 428          * An error can only occur here if the key failed to be evicted from a
 429          * keyslot (due to a hardware or driver issue) or is allegedly still in
 430          * use by I/O (due to a kernel bug).  Even in these cases, the key is
 431          * still unlinked from the keyslot management structures, and the caller
 432          * is allowed and expected to free it right away.  There's nothing
 433          * callers can do to handle errors, so just log them and return void.
 434          */
 435         if (err)
 436                 pr_warn_ratelimited("%pg: error %d evicting key\n", bdev, err);
 437 }
 438 EXPORT_SYMBOL_GPL(blk_crypto_evict_key);