src/crypto/x509/pkcs8.go | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++--

diff --git a/src/crypto/x509/pkcs8.go b/src/crypto/x509/pkcs8.go
index a5ee4cfbfeff14be4c8610671b51945f89b12b5c..fb83da81bfcc913abaad14837656fa448d95aba3 100644
--- a/src/crypto/x509/pkcs8.go
+++ b/src/crypto/x509/pkcs8.go
@@ -12,6 +12,11 @@ 	"crypto/x509/pkix"
 	"encoding/asn1"
 	"errors"
 	"fmt"
+
+	"golang.org/x/crypto/cryptobyte"
+	cryptobyte_asn1 "golang.org/x/crypto/cryptobyte/asn1"
+
+	"crypto/go.cypherpunks.ru/gogost/v5/gost3410"
 )
 
 // pkcs8 reflects an ASN.1, PKCS #8 PrivateKey. See
@@ -81,8 +86,8 @@ }
 
 // MarshalPKCS8PrivateKey converts a private key to PKCS #8, ASN.1 DER form.
 //
-// The following key types are currently supported: *rsa.PrivateKey, *ecdsa.PrivateKey
-// and ed25519.PrivateKey. Unsupported key types result in an error.
+// The following key types are currently supported: *rsa.PrivateKey, *ecdsa.PrivateKey,
+// GOST R 34.10-2012 and ed25519.PrivateKey. Unsupported key types result in an error.
 //
 // This kind of key is commonly encoded in PEM blocks of type "PRIVATE KEY".
 func MarshalPKCS8PrivateKey(key interface{}) ([]byte, error) {
@@ -127,6 +132,57 @@ 		if err != nil {
 			return nil, fmt.Errorf("x509: failed to marshal private key: %v", err)
 		}
 		privKey.PrivateKey = curvePrivateKey
+
+	case *gost3410.PrivateKey:
+		builder := cryptobyte.NewBuilder(nil)
+		switch k.C.Name {
+		case "id-tc26-gost-3410-2012-256-paramSetA":
+			privKey.Algo.Algorithm = oidTc26Gost34102012256
+			builder.AddASN1(cryptobyte_asn1.SEQUENCE, func(b *cryptobyte.Builder) {
+				b.AddASN1ObjectIdentifier(oidTc26Gost34102012256ParamSetA)
+			})
+		case "id-tc26-gost-3410-2012-256-paramSetB":
+			privKey.Algo.Algorithm = oidTc26Gost34102012256
+			builder.AddASN1(cryptobyte_asn1.SEQUENCE, func(b *cryptobyte.Builder) {
+				b.AddASN1ObjectIdentifier(oidTc26Gost34102012256ParamSetB)
+			})
+		case "id-tc26-gost-3410-2012-256-paramSetC":
+			privKey.Algo.Algorithm = oidTc26Gost34102012256
+			builder.AddASN1(cryptobyte_asn1.SEQUENCE, func(b *cryptobyte.Builder) {
+				b.AddASN1ObjectIdentifier(oidTc26Gost34102012256ParamSetC)
+			})
+		case "id-tc26-gost-3410-2012-256-paramSetD":
+			privKey.Algo.Algorithm = oidTc26Gost34102012256
+			builder.AddASN1(cryptobyte_asn1.SEQUENCE, func(b *cryptobyte.Builder) {
+				b.AddASN1ObjectIdentifier(oidTc26Gost34102012256ParamSetD)
+			})
+		case "id-tc26-gost-3410-12-512-paramSetA":
+			privKey.Algo.Algorithm = oidTc26Gost34102012512
+			builder.AddASN1(cryptobyte_asn1.SEQUENCE, func(b *cryptobyte.Builder) {
+				b.AddASN1ObjectIdentifier(oidTc26Gost34102012512ParamSetA)
+			})
+		case "id-tc26-gost-3410-12-512-paramSetB":
+			privKey.Algo.Algorithm = oidTc26Gost34102012512
+			builder.AddASN1(cryptobyte_asn1.SEQUENCE, func(b *cryptobyte.Builder) {
+				b.AddASN1ObjectIdentifier(oidTc26Gost34102012512ParamSetB)
+			})
+		case "id-tc26-gost-3410-2012-512-paramSetC":
+			privKey.Algo.Algorithm = oidTc26Gost34102012512
+			builder.AddASN1(cryptobyte_asn1.SEQUENCE, func(b *cryptobyte.Builder) {
+				b.AddASN1ObjectIdentifier(oidTc26Gost34102012512ParamSetC)
+			})
+		}
+		var err error
+		privKey.Algo.Parameters.FullBytes, err = builder.Bytes()
+		if err != nil {
+			return nil, err
+		}
+		builder = cryptobyte.NewBuilder(nil)
+		builder.AddASN1OctetString(k.Raw())
+		privKey.PrivateKey, err = builder.Bytes()
+		if err != nil {
+			return nil, err
+		}
 
 	default:
 		return nil, fmt.Errorf("x509: unknown key type while marshaling PKCS#8: %T", key)