On Thu, May 27, 2021 at 03:55:25PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@xxxxxxxxxx>
>
> Typically, the cryptographic APIs that fscrypt uses take keys as byte
> arrays, which avoids endianness issues. However, siphash_key_t is an
> exception. It is defined as 'u64 key[2];', i.e. the 128-bit key is
> expected to be given directly as two 64-bit words in CPU endianness.
>
> fscrypt_derive_dirhash_key() forgot to take this into account.
> Therefore, the SipHash keys used to index encrypted+casefolded
> directories differ on big endian vs. little endian platforms.
> This makes such directories non-portable between these platforms.
>
> Fix this by always using the little endian order. This is a breaking
> change for big endian platforms, but this should be fine in practice
> since the encrypt+casefold support isn't known to actually be used on
> any big endian platforms yet.
>
> Fixes: aa408f835d02 ("fscrypt: derive dirhash key for casefolded directories")
> Cc: <stable@xxxxxxxxxxxxxxx> # v5.6+
> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
> ---
> fs/crypto/keysetup.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
I missed that fscrypt_setup_iv_ino_lblk_32_key() has the same bug too.
I'll send out a new patch which fixes both of these...
- Eric
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