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author | Daniel Walter <dwalter@sigma-star.at> | 2017-06-19 10:27:58 +0300 |
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committer | Theodore Ts'o <tytso@mit.edu> | 2017-06-24 03:05:07 +0300 |
commit | b7e7cf7a66a27e62c5f873a0068cee34094bf5d7 (patch) | |
tree | e86d2bbc849e8a854e7f3a22846a08bef49423b9 /fs/crypto/fscrypt_private.h | |
parent | 27e47a6342e21b005a15a1f0afea0b6f179e0a71 (diff) | |
download | linux-b7e7cf7a66a27e62c5f873a0068cee34094bf5d7.tar.xz |
fscrypt: add support for AES-128-CBC
fscrypt provides facilities to use different encryption algorithms which
are selectable by userspace when setting the encryption policy. Currently,
only AES-256-XTS for file contents and AES-256-CBC-CTS for file names are
implemented. This is a clear case of kernel offers the mechanism and
userspace selects a policy. Similar to what dm-crypt and ecryptfs have.
This patch adds support for using AES-128-CBC for file contents and
AES-128-CBC-CTS for file name encryption. To mitigate watermarking
attacks, IVs are generated using the ESSIV algorithm. While AES-CBC is
actually slightly less secure than AES-XTS from a security point of view,
there is more widespread hardware support. Using AES-CBC gives us the
acceptable performance while still providing a moderate level of security
for persistent storage.
Especially low-powered embedded devices with crypto accelerators such as
CAAM or CESA often only support AES-CBC. Since using AES-CBC over AES-XTS
is basically thought of a last resort, we use AES-128-CBC over AES-256-CBC
since it has less encryption rounds and yields noticeable better
performance starting from a file size of just a few kB.
Signed-off-by: Daniel Walter <dwalter@sigma-star.at>
[david@sigma-star.at: addressed review comments]
Signed-off-by: David Gstir <david@sigma-star.at>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs/crypto/fscrypt_private.h')
-rw-r--r-- | fs/crypto/fscrypt_private.h | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h index 1e1f8a361b75..a1d5021c31ef 100644 --- a/fs/crypto/fscrypt_private.h +++ b/fs/crypto/fscrypt_private.h @@ -12,10 +12,13 @@ #define _FSCRYPT_PRIVATE_H #include <linux/fscrypt_supp.h> +#include <crypto/hash.h> /* Encryption parameters */ -#define FS_XTS_TWEAK_SIZE 16 +#define FS_IV_SIZE 16 #define FS_AES_128_ECB_KEY_SIZE 16 +#define FS_AES_128_CBC_KEY_SIZE 16 +#define FS_AES_128_CTS_KEY_SIZE 16 #define FS_AES_256_GCM_KEY_SIZE 32 #define FS_AES_256_CBC_KEY_SIZE 32 #define FS_AES_256_CTS_KEY_SIZE 32 @@ -54,6 +57,7 @@ struct fscrypt_info { u8 ci_filename_mode; u8 ci_flags; struct crypto_skcipher *ci_ctfm; + struct crypto_cipher *ci_essiv_tfm; u8 ci_master_key[FS_KEY_DESCRIPTOR_SIZE]; }; @@ -87,4 +91,7 @@ extern int fscrypt_do_page_crypto(const struct inode *inode, extern struct page *fscrypt_alloc_bounce_page(struct fscrypt_ctx *ctx, gfp_t gfp_flags); +/* keyinfo.c */ +extern void __exit fscrypt_essiv_cleanup(void); + #endif /* _FSCRYPT_PRIVATE_H */ |