From 4f674c91e101a44aa0d60a12a00328cc3d8e435f Mon Sep 17 00:00:00 2001
From: Reese Norris <reese.norris@gmail.com>
Date: Mon, 15 Apr 2024 14:16:54 -0700
Subject: [PATCH] verify client callsign does not collide with a privileged
 callsign

---
 fsd_client.go | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fsd_client.go b/fsd_client.go
index 367b06a..1caf359 100644
--- a/fsd_client.go
+++ b/fsd_client.go
@@ -284,6 +284,13 @@ func HandleConnection(conn *net.TCPConn) {
 		return
 	}
 
+	// Verify callsign
+	switch clientIdentPDU.From {
+	case protocol.ServerCallsign, protocol.ClientQueryBroadcastRecipient, protocol.ClientQueryBroadcastRecipientPilots:
+		conn.Write([]byte(protocol.NewGenericFSDError(protocol.CallsignInvalidError).Serialize()))
+		return
+	}
+
 	// Verify protocol revision
 	if addPilotPDU.ProtocolRevision != protocol.ProtoRevisionVatsim2022 {
 		conn.Write([]byte(protocol.NewGenericFSDError(protocol.InvalidProtocolRevisionError).Serialize()))