On Sat, Jun 05, 2021 at 12:50:33AM -0700, Eric Biggers wrote:
From: Eric Biggers ebiggers@google.com
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() and fscrypt_setup_iv_ino_lblk_32_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, as do the SipHash keys used to hash inode numbers for IV_INO_LBLK_32-encrypted directories. 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 these features (encrypt+casefold support, and the IV_INO_LBLK_32 flag) aren't known to actually be used on any big endian platforms yet.
Fixes: aa408f835d02 ("fscrypt: derive dirhash key for casefolded directories") Fixes: e3b1078bedd3 ("fscrypt: add support for IV_INO_LBLK_32 policies") Cc: stable@vger.kernel.org # v5.6+ Signed-off-by: Eric Biggers ebiggers@google.com
v2: Fixed fscrypt_setup_iv_ino_lblk_32_key() too, not just fscrypt_derive_dirhash_key().
fs/crypto/keysetup.c | 40 ++++++++++++++++++++++++++++++++-------- 1 file changed, 32 insertions(+), 8 deletions(-)
Applied to fscrypt.git#master for 5.14.
- Eric