fix: try parse private key instead of checking for error

DecryptPEMBlock may not return error due to format quirks
Try parse key instead, and if fail use legacy passowrd to open it

Signed-off-by: Artur Troian <troian.ap@gmail.com>

x/cert/utils/key_pair_manager.go

@@ -264,6 +264,7 @@ func (kpm *keyPairManager) readImpl(fin io.Reader) ([]byte, []byte, []byte, erro
 	}
 
 	var privKeyPlaintext []byte
+	var privKeyI interface{}
 
 	// PKCS#8 header defined in RFC7468 section 11
 	// nolint: gocritic
@@ -272,21 +273,26 @@ func (kpm *keyPairManager) readImpl(fin io.Reader) ([]byte, []byte, []byte, erro
 	} else if block.Headers["Proc-Type"] == "4,ENCRYPTED" {
 		// nolint: staticcheck
 		privKeyPlaintext, err = x509.DecryptPEMBlock(block, kpm.passwordBytes)
-		if errors.Is(err, x509.IncorrectPasswordError) {
+
+		// DecryptPEMBlock may not return IncorrectPasswordError.
+		// Try parse private key instead and if it fails give another try with legacy password
+		privKeyI, err = x509.ParsePKCS8PrivateKey(privKeyPlaintext)
+
+		if err != nil {
 			// nolint: staticcheck
 			privKeyPlaintext, err = x509.DecryptPEMBlock(block, kpm.passwordLegacy)
 		}
 	} else {
 		return nil, nil, nil, errUnsupportedEncryptedPEM
 	}
-
 	if err != nil {
 		return nil, nil, nil, fmt.Errorf("%w: failed decrypting x509 block with private key", err)
 	}
 
-	var privKeyI interface{}
-	if privKeyI, err = x509.ParsePKCS8PrivateKey(privKeyPlaintext); err != nil {
-		return nil, nil, nil, fmt.Errorf("%w: failed parsing private key data", err)
+	if privKeyI == nil {
+		if privKeyI, err = x509.ParsePKCS8PrivateKey(privKeyPlaintext); err != nil {
+			return nil, nil, nil, fmt.Errorf("%w: failed parsing private key data", err)
+		}
 	}
 
 	eckey, valid := privKeyI.(*ecdsa.PrivateKey)