From f49c299d772b5ab3514802c16d3b021046dbcaf8 Mon Sep 17 00:00:00 2001
From: braginini <bangvalo@gmail.com>
Date: Tue, 6 Sep 2022 21:07:21 +0200
Subject: [PATCH] Check for stun packet with a fixed size

---
 iface/bind.go              | 2 +-
 iface/udp_mux.go           | 2 +-
 iface/udp_mux_universal.go | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/iface/bind.go b/iface/bind.go
index 09160d5bd..15f6efe88 100644
--- a/iface/bind.go
+++ b/iface/bind.go
@@ -114,7 +114,7 @@ func (b *ICEBind) makeReceiveIPv4(c net.PacketConn, bindMux BindMux) conn.Receiv
 		if err != nil {
 			return 0, nil, err
 		}
-		if !stun.IsMessage(buff[:n]) {
+		if !stun.IsMessage(buff[:20]) {
 			// WireGuard traffic
 			return n, (*conn.StdNetEndpoint)(&net.UDPAddr{
 				IP:   e.Addr().AsSlice(),
diff --git a/iface/udp_mux.go b/iface/udp_mux.go
index 040a216e0..da44d521d 100644
--- a/iface/udp_mux.go
+++ b/iface/udp_mux.go
@@ -85,7 +85,7 @@ func (m *UDPMuxDefault) HandlePacket(p []byte, n int, addr net.Addr) error {
 	m.addressMapMu.Unlock()
 
 	// If we haven't seen this address before but is a STUN packet lookup by ufrag
-	if destinationConn == nil && stun.IsMessage(p[:n]) {
+	if destinationConn == nil && stun.IsMessage(p[:20]) {
 		msg := &stun.Message{
 			Raw: append([]byte{}, p[:n]...),
 		}
diff --git a/iface/udp_mux_universal.go b/iface/udp_mux_universal.go
index d33bb4171..f24f66253 100644
--- a/iface/udp_mux_universal.go
+++ b/iface/udp_mux_universal.go
@@ -80,7 +80,7 @@ func (m *UniversalUDPMuxDefault) Type() string {
 }
 
 func (m *UniversalUDPMuxDefault) HandlePacket(p []byte, n int, addr net.Addr) error {
-	if stun.IsMessage(p[:n]) {
+	if stun.IsMessage(p[:20]) {
 		msg := &stun.Message{
 			Raw: append([]byte{}, p[:n]...),
 		}