[PATCH v3 03/17] 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, extend blk_crypto_config with a new flag
BLK_CRYPTO_CFG_ALLOW_HW.

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

Signed-off-by: Eric Biggers <[email protected]>
---
 block/blk-crypto.c          | 11 ++++++++++-
 drivers/md/dm-inlinecrypt.c |  3 ++-
 fs/crypto/inline_crypt.c    |  4 +++-
 include/linux/blk-crypto.h  | 13 ++++++++++++-
 4 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/block/blk-crypto.c b/block/blk-crypto.c
index de60f03b4d4b..0fe6ef0eea1d 100644
--- a/block/blk-crypto.c
+++ b/block/blk-crypto.c
@@ -300,6 +300,7 @@ int __blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
  * @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
+ * @flags: BLK_CRYPTO_CFG_* flags
  *
  * Return: 0 on success, -errno on failure.  The caller is responsible for
  *	   zeroizing both blk_key and key_bytes when done with them.
@@ -309,7 +310,7 @@ int blk_crypto_init_key(struct blk_crypto_key *blk_key,
 			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, int flags)
 {
 	const struct blk_crypto_mode *mode;
 
@@ -318,6 +319,9 @@ int blk_crypto_init_key(struct blk_crypto_key *blk_key,
 	if (crypto_mode >= ARRAY_SIZE(blk_crypto_modes))
 		return -EINVAL;
 
+	if (flags & ~BLK_CRYPTO_CFG_ALLOW_HW)
+		return -EINVAL;
+
 	mode = &blk_crypto_modes[crypto_mode];
 	switch (key_type) {
 	case BLK_CRYPTO_KEY_TYPE_RAW:
@@ -328,6 +332,8 @@ int blk_crypto_init_key(struct blk_crypto_key *blk_key,
 		if (key_size < mode->security_strength ||
 		    key_size > BLK_CRYPTO_MAX_HW_WRAPPED_KEY_SIZE)
 			return -EINVAL;
+		if (!(flags & BLK_CRYPTO_CFG_ALLOW_HW))
+			return -EINVAL;
 		break;
 	default:
 		return -EINVAL;
@@ -343,6 +349,7 @@ int blk_crypto_init_key(struct blk_crypto_key *blk_key,
 	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.flags = flags;
 	blk_key->data_unit_size_bits = ilog2(data_unit_size);
 	blk_key->size = key_size;
 	memcpy(blk_key->bytes, key_bytes, key_size);
@@ -368,6 +375,8 @@ bool blk_crypto_config_supported_natively(struct block_device *bdev,
 
 	if (!profile)
 		return false;
+	if (!(cfg->flags & BLK_CRYPTO_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)
diff --git a/drivers/md/dm-inlinecrypt.c b/drivers/md/dm-inlinecrypt.c
index be1b4aa8f28b..35379f5c84df 100644
--- a/drivers/md/dm-inlinecrypt.c
+++ b/drivers/md/dm-inlinecrypt.c
@@ -406,7 +406,8 @@ static int inlinecrypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 
 	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,
+				  BLK_CRYPTO_CFG_ALLOW_HW);
 	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..aaf71f6068b0 100644
--- a/fs/crypto/inline_crypt.c
+++ b/fs/crypto/inline_crypt.c
@@ -134,6 +134,7 @@ int fscrypt_select_encryption_impl(struct fscrypt_inode_info *ci,
 	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.flags = BLK_CRYPTO_CFG_ALLOW_HW;
 
 	devs = fscrypt_get_devices(sb, &num_devs);
 	if (IS_ERR(devs))
@@ -175,7 +176,8 @@ int fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,
 
 	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,
+				  BLK_CRYPTO_CFG_ALLOW_HW);
 	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..5f40821f99cd 100644
--- a/include/linux/blk-crypto.h
+++ b/include/linux/blk-crypto.h
@@ -68,6 +68,15 @@ enum blk_crypto_key_type {
  */
 #define BLK_CRYPTO_SW_SECRET_SIZE	32
 
+/* Flags for blk_crypto_config::flags: */
+
+/*
+ * If set, inline encryption hardware will be used if available.
+ * If unset, CPU-based encryption will always be used (requires
+ * CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK)
+ */
+#define BLK_CRYPTO_CFG_ALLOW_HW		(1 << 0)
+
 /**
  * struct blk_crypto_config - an inline encryption key's crypto configuration
  * @crypto_mode: encryption algorithm this key is for
@@ -77,12 +86,14 @@ enum blk_crypto_key_type {
  *	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
+ * @flags: BLK_CRYPTO_CFG_* flags
  */
 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;
+	int flags;
 };
 
 /**
@@ -150,7 +161,7 @@ int blk_crypto_init_key(struct blk_crypto_key *blk_key,
 			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, int flags);
 
 int blk_crypto_start_using_key(struct block_device *bdev,
 			       const struct blk_crypto_key *key);
-- 
2.55.0