crypto: sm2 - introduce OSCCA SM2 asymmetric cipher algorithm

This new module implement the SM2 public key algorithm. It was
published by State Encryption Management Bureau, China.
List of specifications for SM2 elliptic curve public key cryptography:

* GM/T 0003.1-2012
* GM/T 0003.2-2012
* GM/T 0003.3-2012
* GM/T 0003.4-2012
* GM/T 0003.5-2012

IETF: https://tools.ietf.org/html/draft-shen-sm2-ecdsa-02
oscca: http://www.oscca.gov.cn/sca/xxgk/2010-12/17/content_1002386.shtml
scctc: http://www.gmbz.org.cn/main/bzlb.html

Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Tested-by: Xufeng Zhang <yunbo.xufeng@linux.alibaba.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/Kconfig

@@ -260,6 +260,23 @@ config CRYPTO_ECRDSA
 	  standard algorithms (called GOST algorithms). Only signature verification
 	  is implemented.
 
+config CRYPTO_SM2
+	tristate "SM2 algorithm"
+	select CRYPTO_SM3
+	select CRYPTO_AKCIPHER
+	select CRYPTO_MANAGER
+	select MPILIB
+	select ASN1
+	help
+	  Generic implementation of the SM2 public key algorithm. It was
+	  published by State Encryption Management Bureau, China.
+	  as specified by OSCCA GM/T 0003.1-2012 -- 0003.5-2012.
+
+	  References:
+	  https://tools.ietf.org/html/draft-shen-sm2-ecdsa-02
+	  http://www.oscca.gov.cn/sca/xxgk/2010-12/17/content_1002386.shtml
+	  http://www.gmbz.org.cn/main/bzlb.html
+
 config CRYPTO_CURVE25519
 	tristate "Curve25519 algorithm"
 	select CRYPTO_KPP

crypto/Makefile

@@ -42,6 +42,14 @@ rsa_generic-y += rsa_helper.o
 rsa_generic-y += rsa-pkcs1pad.o
 obj-$(CONFIG_CRYPTO_RSA) += rsa_generic.o
 
+$(obj)/sm2signature.asn1.o: $(obj)/sm2signature.asn1.c $(obj)/sm2signature.asn1.h
+$(obj)/sm2.o: $(obj)/sm2signature.asn1.h
+
+sm2_generic-y += sm2signature.asn1.o
+sm2_generic-y += sm2.o
+
+obj-$(CONFIG_CRYPTO_SM2) += sm2_generic.o
+
 crypto_acompress-y := acompress.o
 crypto_acompress-y += scompress.o
 obj-$(CONFIG_CRYPTO_ACOMP2) += crypto_acompress.o