Validate lower/upper limit in mailserver request (#1058)

mailserver/mailserver.go

@@ -294,6 +294,11 @@ func (s *WMailServer) validateRequest(peerID []byte, request *whisper.Envelope)
 	lower := binary.BigEndian.Uint32(decrypted.Payload[:4])
 	upper := binary.BigEndian.Uint32(decrypted.Payload[4:8])
 
+	if upper < lower {
+		log.Error(fmt.Sprintf("Query range is invalid: from > to (%d > %d)", lower, upper))
+		return false, 0, 0, nil
+	}
+
 	lowerTime := time.Unix(int64(lower), 0)
 	upperTime := time.Unix(int64(upper), 0)
 	if upperTime.Sub(lowerTime) > maxQueryRange {

mailserver/mailserver_test.go

@@ -209,7 +209,7 @@ func (s *MailserverSuite) TestMailServer() {
 		{
 			params: func() *ServerTestParams {
 				params := s.defaultServerParams(env)
-				params.low = 0
+				params.low = params.birth
 				params.upp = params.birth - 1
 
 				return params