include connection code in mqtt

modules/mqtt/scan.go

@@ -181,11 +181,16 @@ func (s *scan) Grab() *zgrab2.ScanError {
 	}
 
 	client := paho.NewClient(options)
-	if t := client.Connect(); t.Wait() && t.Error() != nil {
+	t := client.Connect()
+	if t.Wait() && t.Error() != nil {
 		return zgrab2.NewScanError(zgrab2.SCAN_CONNECTION_REFUSED, t.Error())
 	}
 	defer client.Disconnect(250)
 
+	if t := t.(*paho.ConnectToken); t != nil {
+		s.result.ConnectionCode = t.ReturnCode()
+	}
+
 	s.SetFilters()
 	handler := s.makeMessageHandler()
 	client.SubscribeMultiple(s.filters, handler)

modules/mqtt/scanner.go

@@ -59,10 +59,14 @@ func (module *Module) Description() string {
 
 // A Result object returned from the MQTT module's Scanner.Scan().
 type Result struct {
-	Topics       map[string][]string `json:"topics,omitempty"`
-	Certificates [][]byte            `json:"certificate,omitempty"`
-	Scheme       string              `json:"scheme"`
-	Error        any                 `json:"error,omitempty"`
+	ConnectionCode byte                `json:"connection-code"`
+	Topics         map[string][]string `json:"topics,omitempty"`
+	Certificates   [][]byte            `json:"certificate,omitempty"`
+	Scheme         string              `json:"scheme"`
+	Error          any                 `json:"error,omitempty"`
+
+	// TODO: divide this by scheme. Each result should be enclosed in the given scheme.
+	// E.g.: tls {connection-code: 0, topics: {}}, ssl {connection-code: 1, topics: {$SYS/broker/version: mosquitto}}...
 }
 
 // Scanner implements the zgrab2.Scanner interface.