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authorDaniel Walter <dwalter@sigma-star.at>2017-06-19 09:27:58 +0200
committerTheodore Ts'o <tytso@mit.edu>2017-06-23 20:05:07 -0400
commitb7e7cf7a66a27e62c5f873a0068cee34094bf5d7 (patch)
treee86d2bbc849e8a854e7f3a22846a08bef49423b9 /include/uapi
parent27e47a6342e21b005a15a1f0afea0b6f179e0a71 (diff)
downloadop-kernel-dev-b7e7cf7a66a27e62c5f873a0068cee34094bf5d7.zip
op-kernel-dev-b7e7cf7a66a27e62c5f873a0068cee34094bf5d7.tar.gz
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 'include/uapi')
-rw-r--r--include/uapi/linux/fs.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index 24e61a5..a2a3ffb 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -272,6 +272,8 @@ struct fsxattr {
#define FS_ENCRYPTION_MODE_AES_256_GCM 2
#define FS_ENCRYPTION_MODE_AES_256_CBC 3
#define FS_ENCRYPTION_MODE_AES_256_CTS 4
+#define FS_ENCRYPTION_MODE_AES_128_CBC 5
+#define FS_ENCRYPTION_MODE_AES_128_CTS 6
struct fscrypt_policy {
__u8 version;
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