linux-kernel - [PATCH v4 2/2] fscrypt: Add SM4 XTS/CTS symmetric algorithm support

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Message-Id: <20221201125819.36932-3-tianjia.zhang@linux.alibaba.com>
Date:   Thu,  1 Dec 2022 20:58:19 +0800
From:   Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>
To:     Eric Biggers <ebiggers@...nel.org>,
        "Theodore Y. Ts o" <tytso@....edu>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        Jonathan Corbet <corbet@....net>, Jens Axboe <axboe@...nel.dk>,
        Ard Biesheuvel <ardb@...nel.org>,
        Bagas Sanjaya <bagasdotme@...il.com>,
        linux-fscrypt@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-block@...r.kernel.org
Cc:     Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>
Subject: [PATCH v4 2/2] fscrypt: Add SM4 XTS/CTS symmetric algorithm support

Add support for XTS and CTS mode variant of SM4 algorithm, in similar
fashion to SM2 and SM3. The former is used to encrypt file contents,
while the latter (SM4-CBC-CTS) 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: Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>
---
 Documentation/filesystems/fscrypt.rst |  1 +
 fs/crypto/keysetup.c                  | 15 +++++++++++++++
 fs/crypto/policy.c                    |  5 +++++
 include/uapi/linux/fscrypt.h          |  2 ++
 4 files changed, 23 insertions(+)

diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst
index 5ba5817c17c2..c0784ec05553 100644
--- a/Documentation/filesystems/fscrypt.rst
+++ b/Documentation/filesystems/fscrypt.rst
@@ -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.
 
diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index f7407071a952..24e55c95abc3 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -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",
+		.cipher_str = "cts(cbc(sm4))",
+		.keysize = 16,
+		.security_strength = 16,
+		.ivsize = 16,
+	},
 	[FSCRYPT_MODE_ADIANTUM] = {
 		.friendly_name = "Adiantum",
 		.cipher_str = "adiantum(xchacha12,aes)",
diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c
index 46757c3052ef..ec19066128e5 100644
--- a/fs/crypto/policy.c
+++ b/fs/crypto/policy.c
@@ -83,6 +83,11 @@ 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);
 }
 
diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h
index a756b29afcc2..47dbd1994bfe 100644
--- a/include/uapi/linux/fscrypt.h
+++ b/include/uapi/linux/fscrypt.h
@@ -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 */
-- 
2.24.3 (Apple Git-128)