On 10/17/24 9:44 PM, Eric Biggers wrote:
On Wed, Oct 16, 2024 at 04:27:48PM -0700, Eric Biggers wrote:
Add a new device-mapper target "dm-inlinecrypt" that is similar to
dm-crypt but uses the blk-crypto API instead of the regular crypto API.
This allows it to take advantage of inline encryption hardware such as
that commonly built into UFS host controllers.
A slight difference in behavior vs. dm-crypt that I just became aware of:
dm-crypt allows XTS keys whose first half equals the second half, i.e.
cipher key == tweak key. dm-inlinecrypt typically will not allow this. Inline
encryption hardware typically rejects such keys, and blk-crypto-fallback rejects
them too because it uses CRYPTO_TFM_REQ_FORBID_WEAK_KEYS.
IMO, rejecting these weak keys is desirable, and the fact that dm-inlinecrypt
fixes this issue with dm-crypt will just need to be documented.
Hm, I thought this is already rejected in crypto API (at least in FIPS mode)...
It should be rejected exactly as you described even for dm-crypt,
just the check should be (IMO) part of crypto API (set keys), not dm-crypt itself.
And here I think we should not be backward "compatible" as it is security issue,
both XTS keys just must not be the same.
Milan
