diff options
Diffstat (limited to 'include/linux/blk-crypto.h')
| -rw-r--r-- | include/linux/blk-crypto.h | 73 |
1 files changed, 66 insertions, 7 deletions
diff --git a/include/linux/blk-crypto.h b/include/linux/blk-crypto.h index 5e5822c18ee4..58b0c5254a67 100644 --- a/include/linux/blk-crypto.h +++ b/include/linux/blk-crypto.h @@ -6,7 +6,9 @@ #ifndef __LINUX_BLK_CRYPTO_H #define __LINUX_BLK_CRYPTO_H +#include <linux/minmax.h> #include <linux/types.h> +#include <uapi/linux/blk-crypto.h> enum blk_crypto_mode_num { BLK_ENCRYPTION_MODE_INVALID, @@ -17,7 +19,55 @@ enum blk_crypto_mode_num { BLK_ENCRYPTION_MODE_MAX, }; -#define BLK_CRYPTO_MAX_KEY_SIZE 64 +/* + * Supported types of keys. Must be bitflags due to their use in + * blk_crypto_profile::key_types_supported. + */ +enum blk_crypto_key_type { + /* + * Raw keys (i.e. "software keys"). These keys are simply kept in raw, + * plaintext form in kernel memory. + */ + BLK_CRYPTO_KEY_TYPE_RAW = 0x1, + + /* + * Hardware-wrapped keys. These keys are only present in kernel memory + * in ephemerally-wrapped form, and they can only be unwrapped by + * dedicated hardware. For details, see the "Hardware-wrapped keys" + * section of Documentation/block/inline-encryption.rst. + */ + BLK_CRYPTO_KEY_TYPE_HW_WRAPPED = 0x2, +}; + +/* + * Currently the maximum raw key size is 64 bytes, as that is the key size of + * BLK_ENCRYPTION_MODE_AES_256_XTS which takes the longest key. + * + * The maximum hardware-wrapped key size depends on the hardware's key wrapping + * algorithm, which is a hardware implementation detail, so it isn't precisely + * specified. But currently 128 bytes is plenty in practice. Implementations + * are recommended to wrap a 32-byte key for the hardware KDF with AES-256-GCM, + * which should result in a size closer to 64 bytes than 128. + * + * Both of these values can trivially be increased if ever needed. + */ +#define BLK_CRYPTO_MAX_RAW_KEY_SIZE 64 +#define BLK_CRYPTO_MAX_HW_WRAPPED_KEY_SIZE 128 + +#define BLK_CRYPTO_MAX_ANY_KEY_SIZE \ + MAX(BLK_CRYPTO_MAX_RAW_KEY_SIZE, BLK_CRYPTO_MAX_HW_WRAPPED_KEY_SIZE) + +/* + * Size of the "software secret" which can be derived from a hardware-wrapped + * key. This is currently always 32 bytes. Note, the choice of 32 bytes + * assumes that the software secret is only used directly for algorithms that + * don't require more than a 256-bit key to get the desired security strength. + * If it were to be used e.g. directly as an AES-256-XTS key, then this would + * need to be increased (which is possible if hardware supports it, but care + * would need to be taken to avoid breaking users who need exactly 32 bytes). + */ +#define BLK_CRYPTO_SW_SECRET_SIZE 32 + /** * struct blk_crypto_config - an inline encryption key's crypto configuration * @crypto_mode: encryption algorithm this key is for @@ -26,20 +76,23 @@ enum blk_crypto_mode_num { * 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 */ 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; }; /** * struct blk_crypto_key - an inline encryption key - * @crypto_cfg: the crypto configuration (like crypto_mode, key size) for this - * key + * @crypto_cfg: the crypto mode, data unit size, key type, and other + * characteristics of this key and how it will be used * @data_unit_size_bits: log2 of data_unit_size - * @size: size of this key in bytes (determined by @crypto_cfg.crypto_mode) - * @raw: the raw bytes of this key. Only the first @size bytes are used. + * @size: size of this key in bytes. The size of a raw key is fixed for a given + * crypto mode, but the size of a hardware-wrapped key can vary. + * @bytes: the bytes of this key. Only the first @size bytes are significant. * * A blk_crypto_key is immutable once created, and many bios can reference it at * the same time. It must not be freed until all bios using it have completed @@ -49,7 +102,7 @@ struct blk_crypto_key { struct blk_crypto_config crypto_cfg; unsigned int data_unit_size_bits; unsigned int size; - u8 raw[BLK_CRYPTO_MAX_KEY_SIZE]; + u8 bytes[BLK_CRYPTO_MAX_ANY_KEY_SIZE]; }; #define BLK_CRYPTO_MAX_IV_SIZE 32 @@ -87,7 +140,9 @@ 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 blk_crypto_init_key(struct blk_crypto_key *blk_key, const u8 *raw_key, +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); @@ -103,6 +158,10 @@ bool blk_crypto_config_supported_natively(struct block_device *bdev, bool blk_crypto_config_supported(struct block_device *bdev, const struct blk_crypto_config *cfg); +int blk_crypto_derive_sw_secret(struct block_device *bdev, + const u8 *eph_key, size_t eph_key_size, + u8 sw_secret[BLK_CRYPTO_SW_SECRET_SIZE]); + #else /* CONFIG_BLK_INLINE_ENCRYPTION */ static inline bool bio_has_crypt_ctx(struct bio *bio) |