ChatGuard mod 0.0.1

gistfile1.lua

--
-- ChatGuard server protection mod
--
-- This mod checks players chat messages for oversized or to frequent 
-- messages. Players abusing chat will be kicked or even baned.
--
-- Serverconfig:
-- chatguard_max_message_length = nil
--   maximum allowed length of a message (check disabled by default)
--
-- chatguard_max_overlength_messages = 10
--   amount of overlenth messages causing a player to be kicked
--
-- chatguard_max_messages = nil
--   maximum amount of messages allowed to be sent per second and player
-- 
-- chatguard_max_overcount_messages = 50
--   maximum number of messages a player may send more then allowed per second prior beeing kicked
--
-- chatguard_ban_overcount_players = nil
--   set to true to automaticaly ban players exceeding number of messages per second
--


local version = "0.0.1"

local chat_guard_data = {
	max_message_length               = core.setting_get("chatguard_max_message_length"),
	player_overlength_kick_threshold = core.setting_get("chatguard_max_overlength_messages") or 10,
	max_messages_per_second          = core.setting_get("chatguard_max_messages") or -1,
	player_overcount_kick_threshold  = core.setting_get("chatguard_max_overcount_messages") or 50,
	ban_overcount                    = core.setting_get("chatguard_ban_overcount_players"),
	playerlist = {},
	toadd = 0
}

-- initialize player chat quota on join
core.register_on_joinplayer(function(player)

	if not player:is_player() then
		core.log("error", "ChatGuard: on_joinplayer called without valid player object")
		return
	end
	
	local playername = player:get_player_name()
	
	if playername == "" then
		core.log("error", "ChatGuard: on_joinplayer failed to get player name")
		return
	end
	
	chat_guard_data.playerlist[playername] = {
		message_quota = max_messages_per_second,
		overlength_messages = 0
	}
end)

-- cleanup internal data on player leaving
core.register_on_leaveplayer(function(player)

	if not player:is_player() then
		core.log("error", "ChatGuard: on_leaveplayer called without valid player object")
		return
	end
	
	local playername = player:get_player_name()
	
	if playername == "" then
		core.log("error", "ChatGuard: on_leaveplayer failed to get player name")
		return
	end
	
	chat_guard_data.playerlist[playername] = nil
end)

-- check players chat messages
core.register_on_chat_message(function(playername, message)

	if chat_guard_data.playerlist[playername] == nil then
		core.log("action", "ChatGuard: message by unknown player \"" .. playername .. "\", discarding")
		return true
	end

	-- only do this if length is configured
	if chat_guard_data.max_message_length ~= nil and
		message:length() > chat_guard_data.max_message_length then
		chat_guard_data.playerlist[playername].overlength_messages = 
			chat_guard_data.playerlist[playername].overlength_messages +1
		
		if chat_guard_data.playerlist[playername].overlength_messages > 
			chat_guard_data.player_overlength_kick_threshold then
			core.kick_player(playername,"ChatGuard: too many overlength chat messages")
		else
			core.chat_send_player(playername, "ChatGuard: your message was to long. Don't do this again or you will be kicked!")
		end
		return true
	end
	
	-- check if message count check is disabled
	if chat_guard_data.max_messages_per_second < 0 then
		return false
	end
	
	chat_guard_data.playerlist[playername].message_quota = 
		chat_guard_data.playerlist[playername].message_quota -1
		
	if chat_guard_data.playerlist[playername].message_quota < 
		-chat_guard_data.player_overcount_kick_threshold then
		core.kick_player(playername, "ChatGuard: Kicked due to excessive spawning!")
		
		if chat_guard_data.ban_overcount then
			core.ban_player(playername)
		end
	end
	
	-- player has still messages left to be sent
	if chat_guard_data.playerlist[playername].message_quota > -1 then
		return false
	end
	
	-- player exceeded his quota don't send this message
	return true
end)

-- give credit back to players
core.register_globalstep(function(dtime)

	-- don't do anything if message amount limiting is disabled
	if chat_guard_data.max_messages_per_second < 0 then
		return
	end
	
	chat_guard_data.toadd = chat_guard_data.toadd + 
		dtime * chat_guard_data.max_messages_per_second

	if chat_guard_data.toadd > 1 then
		for k,v in pairs(chat_guard_data.playerlist) do
			v.message_quota = math.min(
				v.message_quota + chat_guard_data.toadd,
				chat_guard_data.max_messages_per_second)
		end
		chat_guard_data.toadd = 0
	end
end)

core.log("action", "ChatGuard mod version " .. version .. " initialized ...")