// SPDX-License-Identifier: GPL-2.0
  /*
   * Copyright 2019 Google LLC
   */
  
  /*
   * Refer to Documentation/block/inline-encryption.rst for detailed explanation.
   */
  
  #define pr_fmt(fmt) "blk-crypto: " fmt
  
  #include <linux/bio.h>
  #include <linux/blkdev.h>
  #include <linux/keyslot-manager.h>
  #include <linux/module.h>
  #include <linux/slab.h>
  
  #include "blk-crypto-internal.h"
  
  const struct blk_crypto_mode blk_crypto_modes[] = {
  	[BLK_ENCRYPTION_MODE_AES_256_XTS] = {

  		.cipher_str = "xts(aes)",

  		.keysize = 64,
  		.ivsize = 16,
  	},
  	[BLK_ENCRYPTION_MODE_AES_128_CBC_ESSIV] = {

  		.cipher_str = "essiv(cbc(aes),sha256)",

  		.keysize = 16,
  		.ivsize = 16,
  	},
  	[BLK_ENCRYPTION_MODE_ADIANTUM] = {

  		.cipher_str = "adiantum(xchacha12,aes)",

  		.keysize = 32,
  		.ivsize = 32,
  	},
  };
  
  /*
   * This number needs to be at least (the number of threads doing IO
   * concurrently) * (maximum recursive depth of a bio), so that we don't
   * deadlock on crypt_ctx allocations. The default is chosen to be the same
   * as the default number of post read contexts in both EXT4 and F2FS.
   */
  static int num_prealloc_crypt_ctxs = 128;
  
  module_param(num_prealloc_crypt_ctxs, int, 0444);
  MODULE_PARM_DESC(num_prealloc_crypt_ctxs,
  		"Number of bio crypto contexts to preallocate");
  
  static struct kmem_cache *bio_crypt_ctx_cache;
  static mempool_t *bio_crypt_ctx_pool;
  
  static int __init bio_crypt_ctx_init(void)
  {
  	size_t i;
  
  	bio_crypt_ctx_cache = KMEM_CACHE(bio_crypt_ctx, 0);
  	if (!bio_crypt_ctx_cache)
  		goto out_no_mem;
  
  	bio_crypt_ctx_pool = mempool_create_slab_pool(num_prealloc_crypt_ctxs,
  						      bio_crypt_ctx_cache);
  	if (!bio_crypt_ctx_pool)
  		goto out_no_mem;
  
  	/* This is assumed in various places. */
  	BUILD_BUG_ON(BLK_ENCRYPTION_MODE_INVALID != 0);
  
  	/* Sanity check that no algorithm exceeds the defined limits. */
  	for (i = 0; i < BLK_ENCRYPTION_MODE_MAX; i++) {
  		BUG_ON(blk_crypto_modes[i].keysize > BLK_CRYPTO_MAX_KEY_SIZE);
  		BUG_ON(blk_crypto_modes[i].ivsize > BLK_CRYPTO_MAX_IV_SIZE);
  	}
  
  	return 0;
  out_no_mem:
  	panic("Failed to allocate mem for bio crypt ctxs
  ");
  }
  subsys_initcall(bio_crypt_ctx_init);
  
  void bio_crypt_set_ctx(struct bio *bio, const struct blk_crypto_key *key,
  		       const u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE], gfp_t gfp_mask)
  {

  	struct bio_crypt_ctx *bc;
  
  	/*
  	 * The caller must use a gfp_mask that contains __GFP_DIRECT_RECLAIM so
  	 * that the mempool_alloc() can't fail.
  	 */
  	WARN_ON_ONCE(!(gfp_mask & __GFP_DIRECT_RECLAIM));
  
  	bc = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);

  
  	bc->bc_key = key;
  	memcpy(bc->bc_dun, dun, sizeof(bc->bc_dun));
  
  	bio->bi_crypt_context = bc;
  }
  
  void __bio_crypt_free_ctx(struct bio *bio)
  {
  	mempool_free(bio->bi_crypt_context, bio_crypt_ctx_pool);
  	bio->bi_crypt_context = NULL;
  }

  int __bio_crypt_clone(struct bio *dst, struct bio *src, gfp_t gfp_mask)

  {
  	dst->bi_crypt_context = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);

  	if (!dst->bi_crypt_context)
  		return -ENOMEM;

  	*dst->bi_crypt_context = *src->bi_crypt_context;

  	return 0;

  }
  EXPORT_SYMBOL_GPL(__bio_crypt_clone);
  
  /* Increments @dun by @inc, treating @dun as a multi-limb integer. */
  void bio_crypt_dun_increment(u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE],
  			     unsigned int inc)
  {
  	int i;
  
  	for (i = 0; inc && i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++) {
  		dun[i] += inc;
  		/*
  		 * If the addition in this limb overflowed, then we need to
  		 * carry 1 into the next limb. Else the carry is 0.
  		 */
  		if (dun[i] < inc)
  			inc = 1;
  		else
  			inc = 0;
  	}
  }
  
  void __bio_crypt_advance(struct bio *bio, unsigned int bytes)
  {
  	struct bio_crypt_ctx *bc = bio->bi_crypt_context;
  
  	bio_crypt_dun_increment(bc->bc_dun,
  				bytes >> bc->bc_key->data_unit_size_bits);
  }
  
  /*
   * Returns true if @bc->bc_dun plus @bytes converted to data units is equal to
   * @next_dun, treating the DUNs as multi-limb integers.
   */
  bool bio_crypt_dun_is_contiguous(const struct bio_crypt_ctx *bc,
  				 unsigned int bytes,
  				 const u64 next_dun[BLK_CRYPTO_DUN_ARRAY_SIZE])
  {
  	int i;
  	unsigned int carry = bytes >> bc->bc_key->data_unit_size_bits;
  
  	for (i = 0; i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++) {
  		if (bc->bc_dun[i] + carry != next_dun[i])
  			return false;
  		/*
  		 * If the addition in this limb overflowed, then we need to
  		 * carry 1 into the next limb. Else the carry is 0.
  		 */
  		if ((bc->bc_dun[i] + carry) < carry)
  			carry = 1;
  		else
  			carry = 0;
  	}
  
  	/* If the DUN wrapped through 0, don't treat it as contiguous. */
  	return carry == 0;
  }
  
  /*
   * Checks that two bio crypt contexts are compatible - i.e. that
   * they are mergeable except for data_unit_num continuity.
   */
  static bool bio_crypt_ctx_compatible(struct bio_crypt_ctx *bc1,
  				     struct bio_crypt_ctx *bc2)
  {
  	if (!bc1)
  		return !bc2;
  
  	return bc2 && bc1->bc_key == bc2->bc_key;
  }
  
  bool bio_crypt_rq_ctx_compatible(struct request *rq, struct bio *bio)
  {
  	return bio_crypt_ctx_compatible(rq->crypt_ctx, bio->bi_crypt_context);
  }
  
  /*
   * Checks that two bio crypt contexts are compatible, and also
   * that their data_unit_nums are continuous (and can hence be merged)
   * in the order @bc1 followed by @bc2.
   */
  bool bio_crypt_ctx_mergeable(struct bio_crypt_ctx *bc1, unsigned int bc1_bytes,
  			     struct bio_crypt_ctx *bc2)
  {
  	if (!bio_crypt_ctx_compatible(bc1, bc2))
  		return false;
  
  	return !bc1 || bio_crypt_dun_is_contiguous(bc1, bc1_bytes, bc2->bc_dun);
  }
  
  /* Check that all I/O segments are data unit aligned. */
  static bool bio_crypt_check_alignment(struct bio *bio)
  {
  	const unsigned int data_unit_size =
  		bio->bi_crypt_context->bc_key->crypto_cfg.data_unit_size;
  	struct bvec_iter iter;
  	struct bio_vec bv;
  
  	bio_for_each_segment(bv, bio, iter) {
  		if (!IS_ALIGNED(bv.bv_len | bv.bv_offset, data_unit_size))
  			return false;
  	}
  
  	return true;
  }
  
  blk_status_t __blk_crypto_init_request(struct request *rq)
  {
  	return blk_ksm_get_slot_for_key(rq->q->ksm, rq->crypt_ctx->bc_key,
  					&rq->crypt_keyslot);
  }
  
  /**
   * __blk_crypto_free_request - Uninitialize the crypto fields of a request.
   *
   * @rq: The request whose crypto fields to uninitialize.
   *
   * Completely uninitializes the crypto fields of a request. If a keyslot has
   * been programmed into some inline encryption hardware, that keyslot is
   * released. The rq->crypt_ctx is also freed.
   */
  void __blk_crypto_free_request(struct request *rq)
  {
  	blk_ksm_put_slot(rq->crypt_keyslot);
  	mempool_free(rq->crypt_ctx, bio_crypt_ctx_pool);
  	blk_crypto_rq_set_defaults(rq);
  }
  
  /**
   * __blk_crypto_bio_prep - Prepare bio for inline encryption
   *
   * @bio_ptr: pointer to original bio pointer
   *

   * If the bio crypt context provided for the bio is supported by the underlying
   * device's inline encryption hardware, do nothing.
   *
   * Otherwise, try to perform en/decryption for this bio by falling back to the
   * kernel crypto API. When the crypto API fallback is used for encryption,
   * blk-crypto may choose to split the bio into 2 - the first one that will
   * continue to be processed and the second one that will be resubmitted via

   * submit_bio_noacct. A bounce bio will be allocated to encrypt the contents

   * of the aforementioned "first one", and *bio_ptr will be updated to this
   * bounce bio.

   *
   * Caller must ensure bio has bio_crypt_ctx.
   *
   * Return: true on success; false on error (and bio->bi_status will be set
   *	   appropriately, and bio_endio() will have been called so bio
   *	   submission should abort).
   */
  bool __blk_crypto_bio_prep(struct bio **bio_ptr)
  {
  	struct bio *bio = *bio_ptr;
  	const struct blk_crypto_key *bc_key = bio->bi_crypt_context->bc_key;

  
  	/* Error if bio has no data. */

  	if (WARN_ON_ONCE(!bio_has_data(bio))) {
  		bio->bi_status = BLK_STS_IOERR;

  		goto fail;

  	}

  	if (!bio_crypt_check_alignment(bio)) {
  		bio->bi_status = BLK_STS_IOERR;

  		goto fail;

  	}

  
  	/*

  	 * Success if device supports the encryption context, or if we succeeded
  	 * in falling back to the crypto API.

  	 */

  	if (blk_ksm_crypto_cfg_supported(bio->bi_bdev->bd_disk->queue->ksm,

  					 &bc_key->crypto_cfg))
  		return true;

  	if (blk_crypto_fallback_bio_prep(bio_ptr))
  		return true;

  fail:

  	bio_endio(*bio_ptr);
  	return false;
  }

  int __blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
  			     gfp_t gfp_mask)

  {

  	if (!rq->crypt_ctx) {

  		rq->crypt_ctx = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);

  		if (!rq->crypt_ctx)
  			return -ENOMEM;
  	}

  	*rq->crypt_ctx = *bio->bi_crypt_context;

  	return 0;

  }
  
  /**
   * blk_crypto_init_key() - Prepare a key for use with blk-crypto
   * @blk_key: Pointer to the blk_crypto_key to initialize.
   * @raw_key: Pointer to the raw key. Must be the correct length for the chosen
   *	     @crypto_mode; see blk_crypto_modes[].
   * @crypto_mode: identifier for the encryption algorithm to use
   * @dun_bytes: number of bytes that will be used to specify the DUN when this
   *	       key is used
   * @data_unit_size: the data unit size to use for en/decryption
   *
   * Return: 0 on success, -errno on failure.  The caller is responsible for
   *	   zeroizing both blk_key and raw_key when done with them.
   */
  int blk_crypto_init_key(struct blk_crypto_key *blk_key, const u8 *raw_key,
  			enum blk_crypto_mode_num crypto_mode,
  			unsigned int dun_bytes,
  			unsigned int data_unit_size)
  {
  	const struct blk_crypto_mode *mode;
  
  	memset(blk_key, 0, sizeof(*blk_key));
  
  	if (crypto_mode >= ARRAY_SIZE(blk_crypto_modes))
  		return -EINVAL;
  
  	mode = &blk_crypto_modes[crypto_mode];
  	if (mode->keysize == 0)
  		return -EINVAL;

  	if (dun_bytes == 0 || dun_bytes > mode->ivsize)

  		return -EINVAL;
  
  	if (!is_power_of_2(data_unit_size))
  		return -EINVAL;
  
  	blk_key->crypto_cfg.crypto_mode = crypto_mode;
  	blk_key->crypto_cfg.dun_bytes = dun_bytes;
  	blk_key->crypto_cfg.data_unit_size = data_unit_size;
  	blk_key->data_unit_size_bits = ilog2(data_unit_size);
  	blk_key->size = mode->keysize;
  	memcpy(blk_key->raw, raw_key, mode->keysize);
  
  	return 0;
  }

  /*
   * Check if bios with @cfg can be en/decrypted by blk-crypto (i.e. either the
   * request queue it's submitted to supports inline crypto, or the
   * blk-crypto-fallback is enabled and supports the cfg).
   */

  bool blk_crypto_config_supported(struct request_queue *q,
  				 const struct blk_crypto_config *cfg)
  {

  	return IS_ENABLED(CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK) ||
  	       blk_ksm_crypto_cfg_supported(q->ksm, cfg);

  }
  
  /**
   * blk_crypto_start_using_key() - Start using a blk_crypto_key on a device
   * @key: A key to use on the device
   * @q: the request queue for the device
   *

   * Upper layers must call this function to ensure that either the hardware
   * supports the key's crypto settings, or the crypto API fallback has transforms
   * for the needed mode allocated and ready to go. This function may allocate
   * an skcipher, and *should not* be called from the data path, since that might
   * cause a deadlock

   *

   * Return: 0 on success; -ENOPKG if the hardware doesn't support the key and
   *	   blk-crypto-fallback is either disabled or the needed algorithm
   *	   is disabled in the crypto API; or another -errno code.

   */
  int blk_crypto_start_using_key(const struct blk_crypto_key *key,
  			       struct request_queue *q)
  {
  	if (blk_ksm_crypto_cfg_supported(q->ksm, &key->crypto_cfg))
  		return 0;

  	return blk_crypto_fallback_start_using_mode(key->crypto_cfg.crypto_mode);

  }
  
  /**
   * blk_crypto_evict_key() - Evict a key from any inline encryption hardware
   *			    it may have been programmed into
   * @q: The request queue who's associated inline encryption hardware this key
   *     might have been programmed into
   * @key: The key to evict
   *
   * Upper layers (filesystems) must call this function to ensure that a key is
   * evicted from any hardware that it might have been programmed into.  The key
   * must not be in use by any in-flight IO when this function is called.
   *
   * Return: 0 on success or if key is not present in the q's ksm, -err on error.
   */
  int blk_crypto_evict_key(struct request_queue *q,
  			 const struct blk_crypto_key *key)
  {
  	if (blk_ksm_crypto_cfg_supported(q->ksm, &key->crypto_cfg))
  		return blk_ksm_evict_key(q->ksm, key);

  	/*
  	 * If the request queue's associated inline encryption hardware didn't
  	 * have support for the key, then the key might have been programmed
  	 * into the fallback keyslot manager, so try to evict from there.
  	 */
  	return blk_crypto_fallback_evict_key(key);

  }

  EXPORT_SYMBOL_GPL(blk_crypto_evict_key);