Authentication Bypass by Primary Weakness Affecting tshock package, versions [,5.2.1)

Affected versions of this package are vulnerable to Authentication Bypass by Primary Weakness due to the management of client connections by OTAPI, which allows stale UUIDs to remain on RemoteClient instances after a player disconnects. An attacker can assume the login state of a previously connected player by connecting with a modified client that omits the ClientUUID#68 packet.

Note: This is only exploitable if the server has UUID login enabled, an authenticated player disconnects, and the server assigns the same RemoteClient object to the newly connected player.

This vulnerability can be mitigated by implementing a RemoteClient reset event handler in a plugin.

public override void Initialize()
{
        On.Terraria.RemoteClient.Reset += RemoteClient_Reset;
}

private static void RemoteClient_Reset(On.Terraria.RemoteClient.orig_Reset orig, RemoteClient client)
{
    client.ClientUUID = null;
        orig(client);
}

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