[PATCH] IMA hash algorithm supports sm3-256

The algorithm name sm3-256 referenced by IMA is implemented in crypto as sm3,
which causes IMA to not use sm3-256 algorithm. This patch solves this problem
by adding an alias name sm3-256 to sm3 algorithm, and let IMA hash algorithm
configuration list supports sm3.

The name sm3-256 is defined in hash_algo_name in hash_info, but the
algorithm name implemented in sm3_generic.c is sm3, which will cause
the sm3-256 algorithm to be not found in some application scenarios of
the hash algorithm, and an ENOENT error will occur. For example,
IMA, keys, and other subsystems that reference hash_algo_name cannot use
the hash algorithm of sm3. This patch adds an alias name sm3-256 to sm3,
which can better solve the above problems.

Signed-off-by: Tianjia Zhang <redacted>
---
 crypto/sm3_generic.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/crypto/sm3_generic.c b/crypto/sm3_generic.c
index 3468975215ca..ded41031bd5f 100644
--- a/crypto/sm3_generic.c
+++ b/crypto/sm3_generic.c

@@ -163,7 +163,7 @@ int crypto_sm3_finup(struct shash_desc *desc, const u8 *data,
 }
 EXPORT_SYMBOL(crypto_sm3_finup);
 
-static struct shash_alg sm3_alg = {
+static struct shash_alg sm3_algs[2] = { {
 	.digestsize	=	SM3_DIGEST_SIZE,
 	.init		=	sm3_base_init,
 	.update		=	crypto_sm3_update,

@@ -176,16 +176,28 @@ static struct shash_alg sm3_alg = {
 		.cra_blocksize	 =	SM3_BLOCK_SIZE,
 		.cra_module	 =	THIS_MODULE,
 	}
-};
+}, {
+	.digestsize	=	SM3_DIGEST_SIZE,
+	.init		=	sm3_base_init,
+	.update		=	crypto_sm3_update,
+	.final		=	sm3_final,
+	.finup		=	crypto_sm3_finup,
+	.descsize	=	sizeof(struct sm3_state),
+	.base		=	{
+		.cra_name	 =	"sm3-256",
+		.cra_blocksize	 =	SM3_BLOCK_SIZE,
+		.cra_module	 =	THIS_MODULE,
+	}
+} };
 
 static int __init sm3_generic_mod_init(void)
 {
-	return crypto_register_shash(&sm3_alg);
+	return crypto_register_shashes(sm3_algs, ARRAY_SIZE(sm3_algs));
 }
 
 static void __exit sm3_generic_mod_fini(void)
 {
-	crypto_unregister_shash(&sm3_alg);
+	crypto_unregister_shashes(sm3_algs, ARRAY_SIZE(sm3_algs));
 }
 
 subsys_initcall(sm3_generic_mod_init);

@@ -196,3 +208,4 @@ MODULE_DESCRIPTION("SM3 Secure Hash Algorithm");
 
 MODULE_ALIAS_CRYPTO("sm3");
 MODULE_ALIAS_CRYPTO("sm3-generic");
+MODULE_ALIAS_CRYPTO("sm3-256");

-- 
2.17.1

On Fri, Feb 07, 2020 at 05:22:18PM +0800, Tianjia Zhang wrote:

According to https://tools.ietf.org/id/draft-oscca-cfrg-sm3-01.html,
SM3 always produces a 256-bit hash value.  E.g., it says:

	"SM3 produces an output hash value of 256 bits long"

and

	"SM3 is a hash function that generates a 256-bit hash value."

I don't see any mention of "SM3-256".

So why not just keep it as "sm3" and change hash_info.c instead?
Since the name there is currently wrong, no one can be using it yet.

- Eric

On 2/9/2020 10:17 PM, Eric Biggers wrote:

According to https://tools.ietf.org/id/draft-oscca-cfrg-sm3-01.html,
SM3 always produces a 256-bit hash value.  E.g., it says:

	"SM3 produces an output hash value of 256 bits long"

and

	"SM3 is a hash function that generates a 256-bit hash value."

I don't see any mention of "SM3-256".

So why not just keep it as "sm3" and change hash_info.c instead?
Since the name there is currently wrong, no one can be using it yet.

Question:  Is 256 bits fundamental to SM3?  Could there ever be a 
variant in the future that's e.g., 512 bits?

On Mon, 2020-02-10 at 11:30 -0500, Ken Goldman wrote:

On 2/9/2020 10:17 PM, Eric Biggers wrote:

quoted

According to https://tools.ietf.org/id/draft-oscca-cfrg-sm3-01.html
,
SM3 always produces a 256-bit hash value.  E.g., it says:

	"SM3 produces an output hash value of 256 bits long"

and

	"SM3 is a hash function that generates a 256-bit hash value."

I don't see any mention of "SM3-256".

So why not just keep it as "sm3" and change hash_info.c instead?
Since the name there is currently wrong, no one can be using it
yet.

Question:  Is 256 bits fundamental to SM3?

No.

  Could there ever be a 
variant in the future that's e.g., 512 bits?

Yes, SM3 like SHA-3 is based on a 512  bit input blocks.  However,
what's left of the standard:

https://www.ietf.org/archive/id/draft-sca-cfrg-sm3-02.txt

Currently only defines a 256 output (via compression from the final 512
bit output).  In theory, like SHA-3, SM3 could support 384 and 512
output variants.  However, there's no evidence anyone is working on
adding this.

James

sm3-256 has been supported by the ima hash algorithm, but it is not
yet in the Kconfig configuration list. After adding, both ima and tpm2
can support sm3-256 well.

Signed-off-by: Tianjia Zhang <redacted>
---
 security/integrity/ima/Kconfig | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
index 838476d780e5..27b5df895808 100644
--- a/security/integrity/ima/Kconfig
+++ b/security/integrity/ima/Kconfig

@@ -112,6 +112,10 @@ choice
 	config IMA_DEFAULT_HASH_WP512
 		bool "WP512"
 		depends on CRYPTO_WP512=y && !IMA_TEMPLATE
+
+	config IMA_DEFAULT_HASH_SM3_256
+		bool "SM3_256"
+		depends on CRYPTO_SM3=y && !IMA_TEMPLATE
 endchoice
 
 config IMA_DEFAULT_HASH

@@ -121,6 +125,7 @@ config IMA_DEFAULT_HASH
 	default "sha256" if IMA_DEFAULT_HASH_SHA256
 	default "sha512" if IMA_DEFAULT_HASH_SHA512
 	default "wp512" if IMA_DEFAULT_HASH_WP512
+	default "sm3-256" if IMA_DEFAULT_HASH_SM3_256
 
 config IMA_WRITE_POLICY
 	bool "Enable multiple writes to the IMA policy"

-- 
2.17.1