smx509: refactor p8 parse and pkix public key parse

docs/sm2.md

@@ -7,6 +7,7 @@
 * 《GB/T 32918.4-2016 信息安全技术 SM2椭圆曲线公钥密码算法 第4部分：公钥加密算法》
 * 《GB/T 32918.5-2016 信息安全技术 SM2椭圆曲线公钥密码算法 第5部分：参数定义》
 * 《GB/T 35276-2017 信息安全技术 SM2密码算法使用规范》
+* 《GB/T 33560-2017 信息安全技术 密码应用标识规范》
 * 《GB/T 35275-2017 信息安全技术 SM2密码算法加密签名消息语法规范》(对应PKCS#7)
 
 您可以从[国家标准全文公开系统](https://openstd.samr.gov.cn/)在线阅读这些标准。

smx509/parser.go

@@ -21,6 +21,7 @@ import (
 	"unicode/utf16"
 	"unicode/utf8"
 
+	"github.com/emmansun/gmsm/sm2"
 	"golang.org/x/crypto/cryptobyte"
 	cryptobyte_asn1 "golang.org/x/crypto/cryptobyte/asn1"
 )
@@ -288,6 +289,27 @@ func parsePublicKey(keyData *publicKeyInfo) (any, error) {
 			Y:     y,
 		}
 		return pub, nil
+	case oid.Equal(oidPublicKeySM2):
+		paramsDer := cryptobyte.String(params.FullBytes)
+		namedCurveOID := new(asn1.ObjectIdentifier)
+		if !paramsDer.ReadASN1ObjectIdentifier(namedCurveOID) {
+			return nil, errors.New("x509: invalid SM2 parameters")
+		}
+		namedCurve := namedCurveFromOID(*namedCurveOID)
+		if namedCurve != sm2.P256() {
+			return nil, errors.New("x509: unsupported SM2 curve")
+		}
+		x, y := elliptic.Unmarshal(namedCurve, der)
+		if x == nil {
+			return nil, errors.New("x509: failed to unmarshal SM2 curve point")
+		}
+		pub := &ecdsa.PublicKey{
+			Curve: namedCurve,
+			X:     x,
+			Y:     y,
+		}
+		return pub, nil
+
 	case oid.Equal(oidPublicKeyEd25519):
 		// RFC 8410, Section 3
 		// > For all of the OIDs, the parameters MUST be absent.

smx509/parser_test.go

@@ -2,6 +2,7 @@ package smx509
 
 import (
 	"encoding/asn1"
+	"encoding/hex"
 	"testing"
 
 	cryptobyte_asn1 "golang.org/x/crypto/cryptobyte/asn1"
@@ -97,3 +98,31 @@ func TestParseASN1String(t *testing.T) {
 		})
 	}
 }
+
+// The SM2 public key with alg = oidPublicKeySM2 and SM2 curve
+var sm2PublicKeyHex = "305a301406082a811ccf5501822d06082a811ccf5501822d0342000409586fff35c1f805b5c74f7281c3ade8fe211ffa70bf0ddd1c7268f62ae664331410e3039eeb03209afdc7fa834235c7b3ef528d32bf8b401eb98d32f498b4b7"
+
+// The SM2 public key with alg = oidPublicKeySM2 and NIST P256 curve
+var sm2NistP256PubulicKeyHex = "305a301406082a811ccf5501822d06082a8648ce3d0301070342000476110a45e7e86c1e96ba3c3300da61049a529c20a7ea7f026e50a2dbed60558087346bcb04cb0f0f8dcab8cca9967b8c7cc5aa0c874f024b73208b28f408bfca"
+
+func TestParseSM2PublicKey(t *testing.T) {
+	der, err := hex.DecodeString(sm2PublicKeyHex)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = ParsePKIXPublicKey(der)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestParseSM2PublicKeyWithNistP256(t *testing.T) {
+	der, err := hex.DecodeString(sm2NistP256PubulicKeyHex)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = ParsePKIXPublicKey(der)
+	if err == nil || err.Error() != "x509: unsupported SM2 curve" {
+		t.Fatal("should throw x509: unsupported SM2 curve")
+	}
+}

smx509/pkcs8.go

@@ -46,27 +46,42 @@ func ParsePKCS8PrivateKey(der []byte) (key any, err error) {
 		}
 		return nil, err
 	}
-	if privKey.Algo.Algorithm.Equal(oidSM9) || privKey.Algo.Algorithm.Equal(oidSM9Sign) || privKey.Algo.Algorithm.Equal(oidSM9Enc) {
+	switch {
+	case privKey.Algo.Algorithm.Equal(oidPublicKeySM2):
+		bytes := privKey.Algo.Parameters.FullBytes
+		namedCurveOID := new(asn1.ObjectIdentifier)
+		if _, err := asn1.Unmarshal(bytes, namedCurveOID); err != nil {
+			namedCurveOID = nil
+		}
+		ecKey, err := parseECPrivateKey(namedCurveOID, privKey.PrivateKey)
+		if err != nil {
+			return nil, errors.New("x509: failed to parse SM2 private key embedded in PKCS#8: " + err.Error())
+		}
+		if ecKey.Curve != sm2.P256() {
+			return nil, errors.New("x509: unsupported SM2 curve")
+		}
+		return new(sm2.PrivateKey).FromECPrivateKey(ecKey)
+	case privKey.Algo.Algorithm.Equal(oidSM9), privKey.Algo.Algorithm.Equal(oidSM9Sign), privKey.Algo.Algorithm.Equal(oidSM9Enc):
 		return parseSM9PrivateKey(privKey)
-	}
-	if !privKey.Algo.Algorithm.Equal(oidPublicKeyECDSA) && !privKey.Algo.Algorithm.Equal(oidNamedCurveP256SM2) {
+	case privKey.Algo.Algorithm.Equal(oidPublicKeyECDSA):
+		bytes := privKey.Algo.Parameters.FullBytes
+		namedCurveOID := new(asn1.ObjectIdentifier)
+		if _, err := asn1.Unmarshal(bytes, namedCurveOID); err != nil {
+			namedCurveOID = nil
+		}
+		ecKey, err := parseECPrivateKey(namedCurveOID, privKey.PrivateKey)
+		if err != nil {
+			return nil, errors.New("x509: failed to parse EC private key embedded in PKCS#8: " + err.Error())
+		}
+		// convert *ecdsa.PrivateKey to *sm2.PrivateKey
+		if ecKey.Curve == sm2.P256() {
+			return new(sm2.PrivateKey).FromECPrivateKey(ecKey)
+		}
+		return ecKey, err
+	default:
+		// fallback to golang sdk
 		return x509.ParsePKCS8PrivateKey(der)
 	}
-	bytes := privKey.Algo.Parameters.FullBytes
-	namedCurveOID := new(asn1.ObjectIdentifier)
-	if _, err := asn1.Unmarshal(bytes, namedCurveOID); err != nil {
-		namedCurveOID = nil
-	}
-	ecKey, err := parseECPrivateKey(namedCurveOID, privKey.PrivateKey)
-	if err != nil {
-		return nil, errors.New("x509: failed to parse EC private key embedded in PKCS#8: " + err.Error())
-	}
-	if namedCurveOID.Equal(oidNamedCurveP256SM2) {
-		key, err = new(sm2.PrivateKey).FromECPrivateKey(ecKey)
-	} else {
-		key = ecKey
-	}
-	return key, err
 }
 
 func parseSM9PrivateKey(privKey pkcs8) (key any, err error) {

smx509/x509.go

@@ -462,6 +462,9 @@ var (
 	//	id-ecPublicKey OBJECT IDENTIFIER ::= {
 	//		iso(1) member-body(2) us(840) ansi-X9-62(10045) keyType(2) 1 }
 	oidPublicKeyECDSA = asn1.ObjectIdentifier{1, 2, 840, 10045, 2, 1}
+	// GB/T 33560-2017 信息安全技术 密码应用标识规范
+	// 附录A（规范性附录）商用密码领域中的相关OID定义
+	oidPublicKeySM2 = asn1.ObjectIdentifier{1, 2, 156, 10197, 1, 301}
 	// RFC 8410, Section 3
 	//
 	//	id-X25519    OBJECT IDENTIFIER ::= { 1 3 101 110 }