--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/plugins/mod_register_limits.lua	Sat Dec 09 19:35:08 2017 +0100
@@ -0,0 +1,71 @@
+-- Prosody IM
+-- Copyright (C) 2008-2010 Matthew Wild
+-- Copyright (C) 2008-2010 Waqas Hussain
+--
+-- This project is MIT/X11 licensed. Please see the
+-- COPYING file in the source package for more information.
+--
+
+
+local create_throttle = require "util.throttle".create;
+local new_cache = require "util.cache".new;
+local ip_util = require "util.ip";
+local new_ip = ip_util.new_ip;
+local match_ip = ip_util.match;
+local parse_cidr = ip_util.parse_cidr;
+
+local min_seconds_between_registrations = module:get_option_number("min_seconds_between_registrations");
+local whitelist_only = module:get_option_boolean("whitelist_registration_only");
+local whitelisted_ips = module:get_option_set("registration_whitelist", { "127.0.0.1", "::1" })._items;
+local blacklisted_ips = module:get_option_set("registration_blacklist", {})._items;
+
+local throttle_max = module:get_option_number("registration_throttle_max", min_seconds_between_registrations and 1);
+local throttle_period = module:get_option_number("registration_throttle_period", min_seconds_between_registrations);
+local throttle_cache_size = module:get_option_number("registration_throttle_cache_size", 100);
+local blacklist_overflow = module:get_option_boolean("blacklist_on_registration_throttle_overload", false);
+
+local throttle_cache = new_cache(throttle_cache_size, blacklist_overflow and function (ip, throttle)
+	if not throttle:peek() then
+		module:log("info", "Adding ip %s to registration blacklist", ip);
+		blacklisted_ips[ip] = true;
+	end
+end or nil);
+
+local function check_throttle(ip)
+	if not throttle_max then return true end
+	local throttle = throttle_cache:get(ip);
+	if not throttle then
+		throttle = create_throttle(throttle_max, throttle_period);
+	end
+	throttle_cache:set(ip, throttle);
+	return throttle:poll(1);
+end
+
+local function ip_in_set(set, ip)
+	if set[ip] then
+		return true;
+	end
+	ip = new_ip(ip);
+	for in_set in pairs(set) do
+		if match_ip(ip, parse_cidr(in_set)) then
+			return true;
+		end
+	end
+	return false;
+end
+
+module:hook("user-registering", function (event)
+	local session = event.session;
+	local ip = event.ip or session and session.ip;
+	local log = session and session.log or module._log;
+	if not ip then
+		log("debug", "User's IP not known; can't apply blacklist/whitelist");
+	elseif ip_in_set(blacklisted_ips, event.ip) or (whitelist_only and not ip_in_set(whitelisted_ips, ip)) then
+		event.allowed = false;
+	elseif throttle_max and not ip_in_set(whitelisted_ips, ip) then
+		if not check_throttle(event.ip) then
+			log("debug", "Registrations over limit for ip %s", ip or "?");
+			event.allowed = false;
+		end
+	end
+end);