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authorEric Biggers <ebiggers@google.com>2020-07-21 11:10:12 -0700
committerEric Biggers <ebiggers@google.com>2020-07-21 11:12:57 -0700
commitf000223c981a7c75f6f3ab7288f0be7b571c3644 (patch)
tree7c0c19405b6ee653b4cc3e9cdc05936eca0dd833 /fs/crypto
parent1d6217a4f9905917ee63315c8ea3d63833792f51 (diff)
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.c14
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.
*/