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