evie/android_kernel_oneplus_msm8998
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

ANDROID: ext4: allow encrypting filenames using HEH algorithm

Browse source 
Update ext4 encryption to allow filenames to be encrypted using the
Hash-Encrypt-Hash (HEH) block cipher mode of operation, which is
believed to be more secure than CBC, particularly within the constant
initialization vector (IV) constraint of filename encryption.  Notably,
HEH avoids the "common prefix" problem of CBC.  Both algorithms use
AES-256 as the underlying block cipher and take a 256-bit key.

We assign mode number 126 to HEH, just below 127
(EXT4_ENCRYPTION_MODE_PRIVATE) which in some kernels is reserved for
inline encryption on MSM chipsets.  Note that these modes are not yet
upstream, which is why these numbers are being used; it's preferable to
avoid collisions with modes that may be added upstream.  Also, although
HEH is not hardware-specific, we aren't currently reserving mode number
5 for HEH upstream, since for now we are tying HEH to the new key
derivation method which might become an independent flag upstream, and
there's also a chance that details of HEH will change after it gets
wider review.

Bug: 32975945
Signed-off-by: Eric Biggers <ebiggers@google.com>
Change-Id: I81418709d47da0e0ac607ae3f91088063c2d5dd4
This commit is contained in:
Eric Biggers 2017-01-10 17:02:39 -08:00
parent 0223de3a24
commit 3e0dd6ec69
5 changed files with 10 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

1
fs/ext4/Kconfig
View file

@ -106,6 +106,7 @@ config EXT4_ENCRYPTION
select CRYPTO_ECB
select CRYPTO_XTS
select CRYPTO_CTS
select CRYPTO_HEH
select CRYPTO_CTR
select CRYPTO_SHA256
select KEYS

3
fs/ext4/crypto_fname.c
View file

@ -44,7 +44,8 @@ static void ext4_dir_crypt_complete(struct crypto_async_request *req, int res)
bool ext4_valid_filenames_enc_mode(uint32_t mode)
{
return (mode == EXT4_ENCRYPTION_MODE_AES_256_CTS);
return (mode == EXT4_ENCRYPTION_MODE_AES_256_CTS ||
mode == EXT4_ENCRYPTION_MODE_AES_256_HEH);
}
static unsigned max_name_len(struct inode *inode)

3
fs/ext4/crypto_key.c
View file

@ -182,6 +182,9 @@ retry:
case EXT4_ENCRYPTION_MODE_AES_256_CTS:
cipher_str = "cts(cbc(aes))";
break;
case EXT4_ENCRYPTION_MODE_AES_256_HEH:
cipher_str = "heh(aes)";
break;
default:
printk_once(KERN_WARNING
"ext4: unsupported key mode %d (ino %u)\n",

1
fs/ext4/ext4.h
View file

@ -588,6 +588,7 @@ enum {
#define EXT4_ENCRYPTION_MODE_AES_256_GCM 2
#define EXT4_ENCRYPTION_MODE_AES_256_CBC 3
#define EXT4_ENCRYPTION_MODE_AES_256_CTS 4
#define EXT4_ENCRYPTION_MODE_AES_256_HEH 126
#include "ext4_crypto.h"

3
fs/ext4/ext4_crypto.h
View file

@ -60,6 +60,7 @@ struct ext4_encryption_context {
#define EXT4_AES_256_GCM_KEY_SIZE 32
#define EXT4_AES_256_CBC_KEY_SIZE 32
#define EXT4_AES_256_CTS_KEY_SIZE 32
#define EXT4_AES_256_HEH_KEY_SIZE 32
#define EXT4_AES_256_XTS_KEY_SIZE 64
#define EXT4_MAX_KEY_SIZE 64
@ -121,6 +122,8 @@ static inline int ext4_encryption_key_size(int mode)
return EXT4_AES_256_CBC_KEY_SIZE;
case EXT4_ENCRYPTION_MODE_AES_256_CTS:
return EXT4_AES_256_CTS_KEY_SIZE;
case EXT4_ENCRYPTION_MODE_AES_256_HEH:
return EXT4_AES_256_HEH_KEY_SIZE;
default:
BUG();
}