2022-11-16 08:55:19

by Tianjia Zhang

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

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 <[email protected]>
---
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)

2022-11-17 03:04:21

by Tianjia Zhang

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

Hi Eric,

On 11/17/22 1:26 AM, Eric Biggers wrote:
> On Wed, Nov 16, 2022 at 04:24:16PM +0800, Tianjia Zhang wrote:
>> SM4 is a symmetric algorithm widely used in China
>
> So?
>
> What is the use case for adding this to fscrypt specifically?
>
> Just because an algorithm is widely used doesn't necessarily mean it is useful
> or appropriate to support with fscrypt.
>

We want to provide our users with the ability to encrypt disks and files
using SM4-XTS, the ability to sign SM2/3, and the ability to use
SM4-GCM/CCM with TLS (of course this belongs to other parts), quite a
few users need these features.

>> , 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 <[email protected]>
>> ---
>> 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 */
>
> This might be a good time to reclaim some of the unused mode numbers. Maybe 7-8
> which were very briefly used for Speck128/256. (Irony not lost?)
>

This looks awesome, I'll reclaim the gaps in the next version if
possible.

Cheers,
Tianjia