blk-crypto: add basic hardware-wrapped key support

To prevent keys from being compromised if an attacker acquires read
access to kernel memory, some inline encryption hardware can accept keys
which are wrapped by a per-boot hardware-internal key.  This avoids
needing to keep the raw keys in kernel memory, without limiting the
number of keys that can be used.  Such hardware also supports deriving a
"software secret" for cryptographic tasks that can't be handled by
inline encryption; this is needed for fscrypt to work properly.

To support this hardware, allow struct blk_crypto_key to represent a
hardware-wrapped key as an alternative to a raw key, and make drivers
set flags in struct blk_crypto_profile to indicate which types of keys
they support.  Also add the ->derive_sw_secret() low-level operation,
which drivers supporting wrapped keys must implement.

For more information, see the detailed documentation which this patch
adds to Documentation/block/inline-encryption.rst.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Tested-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org> # sm8650
Link: https://lore.kernel.org/r/20250204060041.409950-2-ebiggers@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

3 files changed, 8 insertions, 5 deletions

diff --git a/drivers/ufs/core/ufshcd-crypto.c b/drivers/ufs/core/ufshcd-crypto.c
index 694ff7578fc1..9e63a9d3cb7e 100644
--- a/drivers/ufs/core/ufshcd-crypto.c
+++ b/drivers/ufs/core/ufshcd-crypto.c
@@ -72,11 +72,11 @@ static int ufshcd_crypto_keyslot_program(struct blk_crypto_profile *profile,
 
 	if (ccap_array[cap_idx].algorithm_id == UFS_CRYPTO_ALG_AES_XTS) {
 		/* In XTS mode, the blk_crypto_key's size is already doubled */
-		memcpy(cfg.crypto_key, key->raw, key->size/2);
+		memcpy(cfg.crypto_key, key->bytes, key->size/2);
 		memcpy(cfg.crypto_key + UFS_CRYPTO_KEY_MAX_SIZE/2,
-		       key->raw + key->size/2, key->size/2);
+		       key->bytes + key->size/2, key->size/2);
 	} else {
-		memcpy(cfg.crypto_key, key->raw, key->size);
+		memcpy(cfg.crypto_key, key->bytes, key->size);
 	}
 
 	ufshcd_program_key(hba, &cfg, slot);
@@ -185,6 +185,7 @@ int ufshcd_hba_init_crypto_capabilities(struct ufs_hba *hba)
 	hba->crypto_profile.ll_ops = ufshcd_crypto_ops;
 	/* UFS only supports 8 bytes for any DUN */
 	hba->crypto_profile.max_dun_bytes_supported = 8;
+	hba->crypto_profile.key_types_supported = BLK_CRYPTO_KEY_TYPE_RAW;
 	hba->crypto_profile.dev = hba->dev;
 
 	/*
diff --git a/drivers/ufs/host/ufs-exynos.c b/drivers/ufs/host/ufs-exynos.c
index 13dd5dfc03eb..6a415d9bdc85 100644
--- a/drivers/ufs/host/ufs-exynos.c
+++ b/drivers/ufs/host/ufs-exynos.c
@@ -1320,6 +1320,7 @@ static void exynos_ufs_fmp_init(struct ufs_hba *hba, struct exynos_ufs *ufs)
 		return;
 	}
 	profile->max_dun_bytes_supported = AES_BLOCK_SIZE;
+	profile->key_types_supported = BLK_CRYPTO_KEY_TYPE_RAW;
 	profile->dev = hba->dev;
 	profile->modes_supported[BLK_ENCRYPTION_MODE_AES_256_XTS] =
 		DATA_UNIT_SIZE;
@@ -1366,7 +1367,7 @@ static int exynos_ufs_fmp_fill_prdt(struct ufs_hba *hba,
 				    void *prdt, unsigned int num_segments)
 {
 	struct fmp_sg_entry *fmp_prdt = prdt;
-	const u8 *enckey = crypt_ctx->bc_key->raw;
+	const u8 *enckey = crypt_ctx->bc_key->bytes;
 	const u8 *twkey = enckey + AES_KEYSIZE_256;
 	u64 dun_lo = crypt_ctx->bc_dun[0];
 	u64 dun_hi = crypt_ctx->bc_dun[1];
diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
index 23b9f6efa047..c3f0aa81ff98 100644
--- a/drivers/ufs/host/ufs-qcom.c
+++ b/drivers/ufs/host/ufs-qcom.c
@@ -147,6 +147,7 @@ static int ufs_qcom_ice_init(struct ufs_qcom_host *host)
 
 	profile->ll_ops = ufs_qcom_crypto_ops;
 	profile->max_dun_bytes_supported = 8;
+	profile->key_types_supported = BLK_CRYPTO_KEY_TYPE_RAW;
 	profile->dev = dev;
 
 	/*
@@ -202,7 +203,7 @@ static int ufs_qcom_ice_keyslot_program(struct blk_crypto_profile *profile,
 	err = qcom_ice_program_key(host->ice,
 				   QCOM_ICE_CRYPTO_ALG_AES_XTS,
 				   QCOM_ICE_CRYPTO_KEY_SIZE_256,
-				   key->raw,
+				   key->bytes,
 				   key->crypto_cfg.data_unit_size / 512,
 				   slot);
 	ufshcd_release(hba);