From 6b2a51ff03bf0c54cbc699ee85a9a49eb203ebfc Mon Sep 17 00:00:00 2001 From: Nathan Huckleberry Date: Fri, 20 May 2022 18:15:01 +0000 Subject: fscrypt: Add HCTR2 support for filename encryption HCTR2 is a tweakable, length-preserving encryption mode that is intended for use on CPUs with dedicated crypto instructions. HCTR2 has the property that a bitflip in the plaintext changes the entire ciphertext. This property fixes a known weakness with filename encryption: when two filenames in the same directory share a prefix of >= 16 bytes, with AES-CTS-CBC their encrypted filenames share a common substring, leaking information. HCTR2 does not have this problem. More information on HCTR2 can be found here: "Length-preserving encryption with HCTR2": https://eprint.iacr.org/2021/1441.pdf Signed-off-by: Nathan Huckleberry Reviewed-by: Ard Biesheuvel Acked-by: Eric Biggers Signed-off-by: Herbert Xu --- include/uapi/linux/fscrypt.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'include/uapi/linux') diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h index 9f4428be3e36..a756b29afcc2 100644 --- a/include/uapi/linux/fscrypt.h +++ b/include/uapi/linux/fscrypt.h @@ -27,7 +27,8 @@ #define FSCRYPT_MODE_AES_128_CBC 5 #define FSCRYPT_MODE_AES_128_CTS 6 #define FSCRYPT_MODE_ADIANTUM 9 -/* If adding a mode number > 9, update FSCRYPT_MODE_MAX in fscrypt_private.h */ +#define FSCRYPT_MODE_AES_256_HCTR2 10 +/* If adding a mode number > 10, update FSCRYPT_MODE_MAX in fscrypt_private.h */ /* * Legacy policy version; ad-hoc KDF and no key verification. -- cgit v1.2.3