[PATCH 2/2] fscrypt: Add SM4 XTS/CTS symmetric algorithm support

[Tianjia Zhang]

SM4 is a symmetric algorithm widely used in China, this patch enables
to use SM4-XTS mode to encrypt file content, and use SM4-CBC-CTS to
encrypt filename.

Signed-off-by: Tianjia Zhang <tianjia.zhang@xxxxxxxxxxxxxxxxx>
---
 Documentation/filesystems/fscrypt.rst |  1 +
 fs/crypto/fscrypt_private.h           |  2 +-
 fs/crypto/keysetup.c                  | 15 +++++++++++++++
 fs/crypto/policy.c                    |  4 ++++
 include/uapi/linux/fscrypt.h          |  4 +++-
 5 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst
index 5ba5817c17c2..af27e7b2c74f 100644
--- a/Documentation/filesystems/fscrypt.rst
+++ b/Documentation/filesystems/fscrypt.rst
@@ -336,6 +336,7 @@ Currently, the following pairs of encryption modes are supported:
 
 - AES-256-XTS for contents and AES-256-CTS-CBC for filenames
 - AES-128-CBC for contents and AES-128-CTS-CBC for filenames
+- SM4-XTS for contents and SM4-CTS-CBC for filenames
 - Adiantum for both contents and filenames
 - AES-256-XTS for contents and AES-256-HCTR2 for filenames (v2 policies only)
 
diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index d5f68a0c5d15..e79a701de028 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -31,7 +31,7 @@
 #define FSCRYPT_CONTEXT_V2	2
 
 /* Keep this in sync with include/uapi/linux/fscrypt.h */
-#define FSCRYPT_MODE_MAX	FSCRYPT_MODE_AES_256_HCTR2
+#define FSCRYPT_MODE_MAX	FSCRYPT_MODE_SM4_CTS
 
 struct fscrypt_context_v1 {
 	u8 version; /* FSCRYPT_CONTEXT_V1 */
diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index f7407071a952..c0a3f882f5a4 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -59,6 +59,21 @@ struct fscrypt_mode fscrypt_modes[] = {
 		.security_strength = 32,
 		.ivsize = 32,
 	},
+	[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,
+	},
 };
 
 static DEFINE_MUTEX(fscrypt_mode_key_setup_mutex);
diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c
index 46757c3052ef..4881fd3af6ee 100644
--- a/fs/crypto/policy.c
+++ b/fs/crypto/policy.c
@@ -75,6 +75,10 @@ static bool fscrypt_valid_enc_modes_v1(u32 contents_mode, u32 filenames_mode)
 	    filenames_mode == FSCRYPT_MODE_ADIANTUM)
 		return true;
 
+	if (contents_mode == FSCRYPT_MODE_SM4_XTS &&
+	    filenames_mode == FSCRYPT_MODE_SM4_CTS)
+		return true;
+
 	return false;
 }
 
diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h
index a756b29afcc2..34d791bd162c 100644
--- a/include/uapi/linux/fscrypt.h
+++ b/include/uapi/linux/fscrypt.h
@@ -28,7 +28,9 @@
 #define FSCRYPT_MODE_AES_128_CTS		6
 #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 */
+#define FSCRYPT_MODE_SM4_XTS			11
+#define FSCRYPT_MODE_SM4_CTS			12
+/* If adding a mode number > 12, update FSCRYPT_MODE_MAX in fscrypt_private.h */
 
 /*
  * Legacy policy version; ad-hoc KDF and no key verification.
-- 
2.24.3 (Apple Git-128)