Commit e0cefada authored by Tianjia Zhang's avatar Tianjia Zhang Committed by Eric Biggers
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fscrypt: Add SM4 XTS/CTS symmetric algorithm support 



Add support for XTS and CTS mode variant of SM4 algorithm. The former is
used to encrypt file contents, while the latter (SM4-CTS-CBC) is used to
encrypt filenames.

SM4 is a symmetric algorithm widely used in China, and is even mandatory
algorithm in some special scenarios. We need to provide these users with
the ability to encrypt files or disks using SM4-XTS.

Signed-off-by: default avatarTianjia Zhang <tianjia.zhang@linux.alibaba.com>
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20221201125819.36932-3-tianjia.zhang@linux.alibaba.com
parent d209ce35

Documentation/filesystems/fscrypt.rst

+1 −0
Original line number Diff line number Diff line
@@ -338,6 +338,7 @@ Currently, the following pairs of encryption modes are supported: 
- AES-128-CBC for contents and AES-128-CTS-CBC for filenames

- Adiantum for both contents and filenames

- AES-256-XTS for contents and AES-256-HCTR2 for filenames (v2 policies only)

- SM4-XTS for contents and SM4-CTS-CBC for filenames (v2 policies only)



If unsure, you should use the (AES-256-XTS, AES-256-CTS-CBC) pair.

fs/crypto/keysetup.c

+15 −0
Original line number Diff line number Diff line
@@ -44,6 +44,21 @@ struct fscrypt_mode fscrypt_modes[] = { 
		.security_strength = 16,

		.ivsize = 16,

	},

	[FSCRYPT_MODE_SM4_XTS] = {

		.friendly_name = "SM4-XTS",

		.cipher_str = "xts(sm4)",

		.keysize = 32,

		.security_strength = 16,

		.ivsize = 16,

		.blk_crypto_mode = BLK_ENCRYPTION_MODE_SM4_XTS,

	},

	[FSCRYPT_MODE_SM4_CTS] = {

		.friendly_name = "SM4-CTS-CBC",

		.cipher_str = "cts(cbc(sm4))",

		.keysize = 16,

		.security_strength = 16,

		.ivsize = 16,

	},

	[FSCRYPT_MODE_ADIANTUM] = {

		.friendly_name = "Adiantum",

		.cipher_str = "adiantum(xchacha12,aes)",

fs/crypto/policy.c

+5 −0
Original line number Diff line number Diff line
@@ -90,6 +90,11 @@ static bool fscrypt_valid_enc_modes_v2(u32 contents_mode, u32 filenames_mode) 
	if (contents_mode == FSCRYPT_MODE_AES_256_XTS &&

	    filenames_mode == FSCRYPT_MODE_AES_256_HCTR2)

		return true;



	if (contents_mode == FSCRYPT_MODE_SM4_XTS &&

	    filenames_mode == FSCRYPT_MODE_SM4_CTS)

		return true;



	return fscrypt_valid_enc_modes_v1(contents_mode, filenames_mode);

}

include/uapi/linux/fscrypt.h

+2 −0
Original line number Diff line number Diff line
@@ -26,6 +26,8 @@ 
#define FSCRYPT_MODE_AES_256_CTS		4

#define FSCRYPT_MODE_AES_128_CBC		5

#define FSCRYPT_MODE_AES_128_CTS		6

#define FSCRYPT_MODE_SM4_XTS			7

#define FSCRYPT_MODE_SM4_CTS			8

#define FSCRYPT_MODE_ADIANTUM			9

#define FSCRYPT_MODE_AES_256_HCTR2		10

/* If adding a mode number > 10, update FSCRYPT_MODE_MAX in fscrypt_private.h */