client: decrease security issues with AnyPortEnable

When AnyPortEnable is true, store the port of the first incoming packet
and check that following packets use the same port

client.go

@@ -1247,29 +1247,33 @@ func (c *Client) doSetup(
 			}
 		}
 
-		cm.udpRTPListener.readIP = func() net.IP {
-			if thRes.Source != nil {
-				return *thRes.Source
-			}
-			return c.nconn.RemoteAddr().(*net.TCPAddr).IP
-		}()
+		if thRes.Source != nil {
+			cm.udpRTPListener.readIP = *thRes.Source
+		} else {
+			cm.udpRTPListener.readIP = c.nconn.RemoteAddr().(*net.TCPAddr).IP
+		}
+
 		if thRes.ServerPorts != nil {
-			cm.udpRTPListener.readPort = thRes.ServerPorts[0]
+			if !c.AnyPortEnable {
+				cm.udpRTPListener.readPort = thRes.ServerPorts[0]
+			}
 			cm.udpRTPListener.writeAddr = &net.UDPAddr{
 				IP:   c.nconn.RemoteAddr().(*net.TCPAddr).IP,
 				Zone: c.nconn.RemoteAddr().(*net.TCPAddr).Zone,
 				Port: thRes.ServerPorts[0],
 			}
 		}
 
-		cm.udpRTCPListener.readIP = func() net.IP {
-			if thRes.Source != nil {
-				return *thRes.Source
-			}
-			return c.nconn.RemoteAddr().(*net.TCPAddr).IP
-		}()
+		if thRes.Source != nil {
+			cm.udpRTCPListener.readIP = *thRes.Source
+		} else {
+			cm.udpRTCPListener.readIP = c.nconn.RemoteAddr().(*net.TCPAddr).IP
+		}
+
 		if thRes.ServerPorts != nil {
-			cm.udpRTCPListener.readPort = thRes.ServerPorts[1]
+			if !c.AnyPortEnable {
+				cm.udpRTCPListener.readPort = thRes.ServerPorts[1]
+			}
 			cm.udpRTCPListener.writeAddr = &net.UDPAddr{
 				IP:   c.nconn.RemoteAddr().(*net.TCPAddr).IP,
 				Zone: c.nconn.RemoteAddr().(*net.TCPAddr).Zone,

clientudpl.go

@@ -186,7 +186,15 @@ func (u *clientUDPListener) runReader(forPlay bool) {
 
 		uaddr := addr.(*net.UDPAddr)
 
-		if !u.readIP.Equal(uaddr.IP) || (!u.anyPortEnable && u.readPort != uaddr.Port) {
+		if !u.readIP.Equal(uaddr.IP) {
+			continue
+		}
+
+		// in case of anyPortEnable, store the port of the first packet we receive.
+		// this reduces security issues
+		if u.anyPortEnable && u.readPort == 0 {
+			u.readPort = uaddr.Port
+		} else if u.readPort != uaddr.Port {
 			continue
 		}