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| author |   Eric Biggers <ebiggers@google.com> | 2020-07-21 11:10:12 -0700 |
|---|---|---|
| committer | Eric Biggers <ebiggers@google.com> | 2020-07-21 11:12:57 -0700 |
| commit | f000223c981a7c75f6f3ab7288f0be7b571c3644 (patch) | |
| tree | 7c0c19405b6ee653b4cc3e9cdc05936eca0dd833 /fs/crypto | |
| parent | fscrypt: rename FS_KEY_DERIVATION_NONCE_SIZE (diff) | |
| download | linux-dev-f000223c981a7c75f6f3ab7288f0be7b571c3644.tar.xz linux-dev-f000223c981a7c75f6f3ab7288f0be7b571c3644.zip | |
fscrypt: restrict IV_INO_LBLK_* to AES-256-XTS
IV_INO_LBLK_* exist only because of hardware limitations, and currently
the only known use case for them involves AES-256-XTS. Therefore, for
now only allow them in combination with AES-256-XTS. This way we don't
have to worry about them being combined with other encryption modes.
(To be clear, combining IV_INO_LBLK_* with other encryption modes
*should* work just fine. It's just not being tested, so we can't be
100% sure it works. So with no known use case, it's best to disallow it
for now, just like we don't allow other weird combinations like
AES-256-XTS contents encryption with Adiantum filenames encryption.)
This can be relaxed later if a use case for other combinations arises.
Fixes: b103fb7653ff ("fscrypt: add support for IV_INO_LBLK_64 policies")
Fixes: e3b1078bedd3 ("fscrypt: add support for IV_INO_LBLK_32 policies")
Link: https://lore.kernel.org/r/20200721181012.39308-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Diffstat (limited to 'fs/crypto')
| -rw-r--r-- | fs/crypto/policy.c | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c index 8a8ad0e44bb8..8e667aadf271 100644 --- a/fs/crypto/policy.c +++ b/fs/crypto/policy.c @@ -78,6 +78,20 @@ static bool supported_iv_ino_lblk_policy(const struct fscrypt_policy_v2 *policy, int ino_bits = 64, lblk_bits = 64; /* + * IV_INO_LBLK_* exist only because of hardware limitations, and + * currently the only known use case for them involves AES-256-XTS. + * That's also all we test currently. For these reasons, for now only + * allow AES-256-XTS here. This can be relaxed later if a use case for + * IV_INO_LBLK_* with other encryption modes arises. + */ + if (policy->contents_encryption_mode != FSCRYPT_MODE_AES_256_XTS) { + fscrypt_warn(inode, + "Can't use %s policy with contents mode other than AES-256-XTS", + type); + return false; + } + + /* * It's unsafe to include inode numbers in the IVs if the filesystem can * potentially renumber inodes, e.g. via filesystem shrinking. */ |