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authorEric Biggers <ebiggers@google.com>2019-10-24 14:54:36 -0700
committerEric Biggers <ebiggers@google.com>2019-11-06 12:34:36 -0800
commitb103fb7653fff09e7a6fb6ba9398a41584e7ae36 (patch)
tree76a36a85c9d27f1a8e58e6cbf751844958ab1867 /fs/crypto/fscrypt_private.h
parentff73c2c016f8569b728eb1e9ebfab383545e4d65 (diff)
fscrypt: add support for IV_INO_LBLK_64 policies
Inline encryption hardware compliant with the UFS v2.1 standard or with the upcoming version of the eMMC standard has the following properties: (1) Per I/O request, the encryption key is specified by a previously loaded keyslot. There might be only a small number of keyslots. (2) Per I/O request, the starting IV is specified by a 64-bit "data unit number" (DUN). IV bits 64-127 are assumed to be 0. The hardware automatically increments the DUN for each "data unit" of configurable size in the request, e.g. for each filesystem block. Property (1) makes it inefficient to use the traditional fscrypt per-file keys. Property (2) precludes the use of the existing DIRECT_KEY fscrypt policy flag, which needs at least 192 IV bits. Therefore, add a new fscrypt policy flag IV_INO_LBLK_64 which causes the encryption to modified as follows: - The encryption keys are derived from the master key, encryption mode number, and filesystem UUID. - The IVs are chosen as (inode_number << 32) | file_logical_block_num. For filenames encryption, file_logical_block_num is 0. Since the file nonces aren't used in the key derivation, many files may share the same encryption key. This is much more efficient on the target hardware. Including the inode number in the IVs and mixing the filesystem UUID into the keys ensures that data in different files is nevertheless still encrypted differently. Additionally, limiting the inode and block numbers to 32 bits and placing the block number in the low bits maintains compatibility with the 64-bit DUN convention (property (2) above). Since this scheme assumes that inode numbers are stable (which may preclude filesystem shrinking) and that inode and file logical block numbers are at most 32-bit, IV_INO_LBLK_64 will only be allowed on filesystems that meet these constraints. These are acceptable limitations for the cases where this format would actually be used. Note that IV_INO_LBLK_64 is an on-disk format, not an implementation. This patch just adds support for it using the existing filesystem layer encryption. A later patch will add support for inline encryption. Reviewed-by: Paul Crowley <paulcrowley@google.com> Co-developed-by: Satya Tangirala <satyat@google.com> Signed-off-by: Satya Tangirala <satyat@google.com> Signed-off-by: Eric Biggers <ebiggers@google.com>
Diffstat (limited to 'fs/crypto/fscrypt_private.h')
-rw-r--r--fs/crypto/fscrypt_private.h16
1 files changed, 13 insertions, 3 deletions
diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index d9a3e8614049..130b50e5a011 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -163,6 +163,9 @@ struct fscrypt_info {
/* The actual crypto transform used for encryption and decryption */
struct crypto_skcipher *ci_ctfm;
+ /* True if the key should be freed when this fscrypt_info is freed */
+ bool ci_owns_key;
+
/*
* Encryption mode used for this inode. It corresponds to either the
* contents or filenames encryption mode, depending on the inode type.
@@ -281,7 +284,8 @@ extern int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key,
*/
#define HKDF_CONTEXT_KEY_IDENTIFIER 1
#define HKDF_CONTEXT_PER_FILE_KEY 2
-#define HKDF_CONTEXT_PER_MODE_KEY 3
+#define HKDF_CONTEXT_DIRECT_KEY 3
+#define HKDF_CONTEXT_IV_INO_LBLK_64_KEY 4
extern int fscrypt_hkdf_expand(struct fscrypt_hkdf *hkdf, u8 context,
const u8 *info, unsigned int infolen,
@@ -378,8 +382,14 @@ struct fscrypt_master_key {
struct list_head mk_decrypted_inodes;
spinlock_t mk_decrypted_inodes_lock;
- /* Per-mode tfms for DIRECT_KEY policies, allocated on-demand */
- struct crypto_skcipher *mk_mode_keys[__FSCRYPT_MODE_MAX + 1];
+ /* Crypto API transforms for DIRECT_KEY policies, allocated on-demand */
+ struct crypto_skcipher *mk_direct_tfms[__FSCRYPT_MODE_MAX + 1];
+
+ /*
+ * Crypto API transforms for filesystem-layer implementation of
+ * IV_INO_LBLK_64 policies, allocated on-demand.
+ */
+ struct crypto_skcipher *mk_iv_ino_lblk_64_tfms[__FSCRYPT_MODE_MAX + 1];
} __randomize_layout;