Reuse Connect.parseSigner.Adds change from #8898

Co-authored-by: Aliaksandr Mianzhynski <amenzhinsky@gmail.com>

tlsutil/generate.go

@@ -4,8 +4,8 @@ import (
 	"bytes"
 	"crypto"
 	"crypto/ecdsa"
-	"crypto/rsa"
 	"crypto/rand"
+	"crypto/rsa"
 	"crypto/sha256"
 	"crypto/x509"
 	"crypto/x509/pkix"
@@ -175,10 +175,22 @@ func ParseSigner(pemValue string) (crypto.Signer, error) {
 	switch block.Type {
 	case "EC PRIVATE KEY":
 		return x509.ParseECPrivateKey(block.Bytes)
-		
+
 	case "RSA PRIVATE KEY":
 		return x509.ParsePKCS1PrivateKey(block.Bytes)
-		
+
+	case "PRIVATE KEY":
+		signer, err := x509.ParsePKCS8PrivateKey(block.Bytes)
+		if err != nil {
+			return nil, err
+		}
+		pk, ok := signer.(crypto.Signer)
+		if !ok {
+			return nil, fmt.Errorf("private key is not a valid format")
+		}
+
+		return pk, nil
+
 	default:
 		return nil, fmt.Errorf("unknown PEM block type for signing key: %s", block.Type)
 	}