[PATCH 03/16] blk-crypto: Allow control over whether hardware is used

fscrypt uses inline encryption hardware only when the "inlinecrypt"
mount option is given.  I'd like to keep that behavior even after
standardizing on the blk-crypto API for file contents encryption.  That
is, the default should continue to be the well-tested CPU-based
encryption code, and the use of inline encryption hardware should
continue to be an opt-in feature for systems where it's beneficial and
has been fully validated (including verifying ciphertext correctness).

To support this use case, add an allow_hw field to struct
blk_crypto_config.

For now it's always set to true.  Later commits will change that.

Signed-off-by: Eric Biggers <[email protected]>
---
 block/blk-crypto.c          | 8 +++++++-
 drivers/md/dm-inlinecrypt.c | 2 +-
 fs/crypto/inline_crypt.c    | 3 ++-
 include/linux/blk-crypto.h  | 6 +++++-
 4 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/block/blk-crypto.c b/block/blk-crypto.c
index dd83fc5af282..c157db869183 100644
--- a/block/blk-crypto.c
+++ b/block/blk-crypto.c
@@ -298,20 +298,21 @@ int __blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
  * @key_type: type of the key -- either raw or hardware-wrapped
  * @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
+ * @allow_hw: true if using inline encryption hardware is allowed
  *
  * Return: 0 on success, -errno on failure.  The caller is responsible for
  *	   zeroizing both blk_key and key_bytes when done with them.
  */
 int blk_crypto_init_key(struct blk_crypto_key *blk_key,
 			const u8 *key_bytes, size_t key_size,
 			enum blk_crypto_key_type key_type,
 			enum blk_crypto_mode_num crypto_mode,
 			unsigned int dun_bytes,
-			unsigned int data_unit_size)
+			unsigned int data_unit_size, bool allow_hw)
 {
 	const struct blk_crypto_mode *mode;
 
 	memset(blk_key, 0, sizeof(*blk_key));
 
@@ -326,10 +327,12 @@ int blk_crypto_init_key(struct blk_crypto_key *blk_key,
 		break;
 	case BLK_CRYPTO_KEY_TYPE_HW_WRAPPED:
 		if (key_size < mode->security_strength ||
 		    key_size > BLK_CRYPTO_MAX_HW_WRAPPED_KEY_SIZE)
 			return -EINVAL;
+		if (!allow_hw)
+			return -EINVAL;
 		break;
 	default:
 		return -EINVAL;
 	}
 
@@ -341,10 +344,11 @@ int blk_crypto_init_key(struct blk_crypto_key *blk_key,
 
 	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->crypto_cfg.key_type = key_type;
+	blk_key->crypto_cfg.allow_hw = allow_hw;
 	blk_key->data_unit_size_bits = ilog2(data_unit_size);
 	blk_key->size = key_size;
 	memcpy(blk_key->bytes, key_bytes, key_size);
 
 	return 0;
@@ -366,10 +370,12 @@ bool blk_crypto_config_supported_natively(struct block_device *bdev,
 {
 	struct blk_crypto_profile *profile = bdev_get_queue(bdev)->crypto_profile;
 
 	if (!profile)
 		return false;
+	if (!cfg->allow_hw)
+		return false;
 	if (!(profile->modes_supported[cfg->crypto_mode] & cfg->data_unit_size))
 		return false;
 	if (profile->max_dun_bytes_supported < cfg->dun_bytes)
 		return false;
 	if (!(profile->key_types_supported & cfg->key_type))
diff --git a/drivers/md/dm-inlinecrypt.c b/drivers/md/dm-inlinecrypt.c
index be1b4aa8f28b..a0f039c1e153 100644
--- a/drivers/md/dm-inlinecrypt.c
+++ b/drivers/md/dm-inlinecrypt.c
@@ -404,11 +404,11 @@ static int inlinecrypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 		       (ctx->sector_bits - SECTOR_SHIFT);
 	dun_bytes = DIV_ROUND_UP(fls64(ctx->max_dun), 8);
 
 	err = blk_crypto_init_key(&ctx->key, key_bytes, ctx->key_size,
 				  ctx->key_type, cipher->mode_num,
-				  dun_bytes, ctx->sector_size);
+				  dun_bytes, ctx->sector_size, true);
 	if (err) {
 		ti->error = "Error initializing blk-crypto key";
 		goto bad;
 	}
 
diff --git a/fs/crypto/inline_crypt.c b/fs/crypto/inline_crypt.c
index 47324062fee5..0d4c0dd04d20 100644
--- a/fs/crypto/inline_crypt.c
+++ b/fs/crypto/inline_crypt.c
@@ -132,10 +132,11 @@ int fscrypt_select_encryption_impl(struct fscrypt_inode_info *ci,
 	crypto_cfg.crypto_mode = ci->ci_mode->blk_crypto_mode;
 	crypto_cfg.data_unit_size = 1U << ci->ci_data_unit_bits;
 	crypto_cfg.dun_bytes = fscrypt_get_dun_bytes(ci);
 	crypto_cfg.key_type = is_hw_wrapped_key ?
 		BLK_CRYPTO_KEY_TYPE_HW_WRAPPED : BLK_CRYPTO_KEY_TYPE_RAW;
+	crypto_cfg.allow_hw = true;
 
 	devs = fscrypt_get_devices(sb, &num_devs);
 	if (IS_ERR(devs))
 		return PTR_ERR(devs);
 
@@ -173,11 +174,11 @@ int fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,
 	if (!blk_key)
 		return -ENOMEM;
 
 	err = blk_crypto_init_key(blk_key, key_bytes, key_size, key_type,
 				  crypto_mode, fscrypt_get_dun_bytes(ci),
-				  1U << ci->ci_data_unit_bits);
+				  1U << ci->ci_data_unit_bits, true);
 	if (err) {
 		fscrypt_err(inode, "error %d initializing blk-crypto key", err);
 		goto fail;
 	}
 
diff --git a/include/linux/blk-crypto.h b/include/linux/blk-crypto.h
index f7c3cb4a342f..7b9dca89aec9 100644
--- a/include/linux/blk-crypto.h
+++ b/include/linux/blk-crypto.h
@@ -75,16 +75,20 @@ enum blk_crypto_key_type {
  *	key.  This is the size in bytes of each individual plaintext and
  *	ciphertext.  This is always a power of 2.  It might be e.g. the
  *	filesystem block size or the disk sector size.
  * @dun_bytes: the maximum number of bytes of DUN used when using this key
  * @key_type: the type of this key -- either raw or hardware-wrapped
+ * @allow_hw: true if inline encryption hardware will be used if available;
+ *	      false to always use CPU-based encryption (requires
+ *	      CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK)
  */
 struct blk_crypto_config {
 	enum blk_crypto_mode_num crypto_mode;
 	unsigned int data_unit_size;
 	unsigned int dun_bytes;
 	enum blk_crypto_key_type key_type;
+	bool allow_hw;
 };
 
 /**
  * struct blk_crypto_key - an inline encryption key
  * @crypto_cfg: the crypto mode, data unit size, key type, and other
@@ -148,11 +152,11 @@ bool bio_crypt_dun_is_contiguous(const struct bio_crypt_ctx *bc,
 int blk_crypto_init_key(struct blk_crypto_key *blk_key,
 			const u8 *key_bytes, size_t key_size,
 			enum blk_crypto_key_type key_type,
 			enum blk_crypto_mode_num crypto_mode,
 			unsigned int dun_bytes,
-			unsigned int data_unit_size);
+			unsigned int data_unit_size, bool allow_hw);
 
 int blk_crypto_start_using_key(struct block_device *bdev,
 			       const struct blk_crypto_key *key);
 
 void blk_crypto_evict_key(struct block_device *bdev,
-- 
2.54.0