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: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20221201125819.36932-3-tianjia.zhang@linux.alibaba.com

diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst
index 5ba5817..c0784ec 100644 (file)
--- 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 9e44dc0..94757cc 100644 (file)
--- 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-CBC",
+               .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 84fa516..893661b 100644 (file)
--- a/fs/crypto/policy.c
+++ b/fs/crypto/policy.c
@@ -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);
 }
 

diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h
index a756b29..47dbd19 100644 (file)
--- 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 */