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| author | Daniel Walter <dwalter@sigma-star.at> | 2017-06-19 10:27:58 +0300 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2017-06-24 03:05:07 +0300 |
| commit | b7e7cf7a66a27e62c5f873a0068cee34094bf5d7 (patch) | |
| tree | e86d2bbc849e8a854e7f3a22846a08bef49423b9 /fs/crypto/policy.c | |
| 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/policy.c')
| -rw-r--r-- | fs/crypto/policy.c | 8 |
1 files changed, 2 insertions, 6 deletions
diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c index 210976e7a269..9914d51dff86 100644 --- a/fs/crypto/policy.c +++ b/fs/crypto/policy.c @@ -38,12 +38,8 @@ static int create_encryption_context_from_policy(struct inode *inode, memcpy(ctx.master_key_descriptor, policy->master_key_descriptor, FS_KEY_DESCRIPTOR_SIZE); - if (!fscrypt_valid_contents_enc_mode( - policy->contents_encryption_mode)) - return -EINVAL; - - if (!fscrypt_valid_filenames_enc_mode( - policy->filenames_encryption_mode)) + if (!fscrypt_valid_enc_modes(policy->contents_encryption_mode, + policy->filenames_encryption_mode)) return -EINVAL; if (policy->flags & ~FS_POLICY_FLAGS_VALID) |