--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mod_net_proxy/mod_net_proxy.lua	Thu Mar 15 15:26:30 2018 +0100
@@ -0,0 +1,378 @@
+-- mod_net_proxy.lua
+-- Copyright (C) 2018 Pascal Mathis <mail@pascalmathis.com>
+--
+-- Implementation of PROXY protocol versions 1 and 2
+-- Specifications: https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt
+
+module:set_global();
+
+-- Imports
+local softreq = require "util.dependencies".softreq;
+local bit = assert(softreq "bit" or softreq "bit32", "No bit module found. See https://prosody.im/doc/depends#bitop");
+local hex = require "util.hex";
+local ip = require "util.ip";
+local net = require "util.net";
+local portmanager = require "core.portmanager";
+
+-- Utility Functions
+local function _table_invert(input)
+	local output = {};
+	for key, value in pairs(input) do
+		output[value] = key;
+	end
+	return output;
+end
+
+-- Constants
+local ADDR_FAMILY = { UNSPEC = 0x0, INET = 0x1, INET6 = 0x2, UNIX = 0x3 };
+local ADDR_FAMILY_STR = _table_invert(ADDR_FAMILY);
+local TRANSPORT = { UNSPEC = 0x0, STREAM = 0x1, DGRAM = 0x2 };
+local TRANSPORT_STR = _table_invert(TRANSPORT);
+
+local PROTO_MAX_HEADER_LENGTH = 256;
+local PROTO_HANDLERS = {
+	PROXYv1 = { signature = hex.from("50524F5859"), callback = nil },
+	PROXYv2 = { signature = hex.from("0D0A0D0A000D0A515549540A"), callback = nil }
+};
+local PROTO_HANDLER_STATUS = { SUCCESS = 0, POSTPONE = 1, FAILURE = 2 };
+
+-- Persistent In-Memory Storage
+local sessions = {};
+local mappings = {};
+
+-- Proxy Data Methods
+local proxy_data_mt = {}; proxy_data_mt.__index = proxy_data_mt;
+
+function proxy_data_mt:describe()
+	return string.format("proto=%s/%s src=%s:%d dst=%s:%d",
+		self:addr_family_str(), self:transport_str(), self:src_addr(), self:src_port(), self:dst_addr(), self:dst_port());
+end
+
+function proxy_data_mt:addr_family_str()
+	return ADDR_FAMILY_STR[self._addr_family] or ADDR_FAMILY_STR[ADDR_FAMILY.UNSPEC];
+end
+
+function proxy_data_mt:transport_str()
+	return TRANSPORT_STR[self._transport] or TRANSPORT_STR[TRANSPORT.UNSPEC];
+end
+
+function proxy_data_mt:version()
+	return self._version;
+end
+
+function proxy_data_mt:addr_family()
+	return self._addr_family;
+end
+
+function proxy_data_mt:transport()
+	return self._transport;
+end
+
+function proxy_data_mt:src_addr()
+	return self._src_addr;
+end
+
+function proxy_data_mt:src_port()
+	return self._src_port;
+end
+
+function proxy_data_mt:dst_addr()
+	return self._dst_addr;
+end
+
+function proxy_data_mt:dst_port()
+	return self._dst_port;
+end
+
+-- Protocol Handler Functions
+PROTO_HANDLERS["PROXYv1"].callback = function(conn, session)
+	local addr_family_mappings = { TCP4 = ADDR_FAMILY.INET, TCP6 = ADDR_FAMILY.INET6 };
+
+	-- Postpone processing if CRLF (PROXYv1 header terminator) does not exist within buffer
+	if session.buffer:find("\r\n") == nil then
+		return PROTO_HANDLER_STATUS.POSTPONE, nil;
+	end
+
+	-- Declare header pattern and match current buffer against pattern
+	local header_pattern = "^PROXY (%S+) (%S+) (%S+) (%d+) (%d+)\r\n";
+	local addr_family, src_addr, dst_addr, src_port, dst_port = session.buffer:match(header_pattern);
+	src_port, dst_port = tonumber(src_port), tonumber(dst_port);
+
+	-- Ensure that header was successfully parsed and contains a valid address family
+	if addr_family == nil or src_addr == nil or dst_addr == nil or src_port == nil or dst_port == nil then
+		module:log("warn", "Received unparseable PROXYv1 header from %s", conn:ip());
+		return PROTO_HANDLER_STATUS.FAILURE, nil;
+	end
+	if addr_family_mappings[addr_family] == nil then
+		module:log("warn", "Received invalid PROXYv1 address family from %s: %s", conn:ip(), addr_family);
+		return PROTO_HANDLER_STATUS.FAILURE, nil;
+	end
+
+	-- Ensure that received source and destination ports are within 1 and 65535 (0xFFFF)
+	if src_port <= 0 or src_port >= 0xFFFF then
+		module:log("warn", "Received invalid PROXYv1 source port from %s: %d", conn:ip(), src_port);
+		return PROTO_HANDLER_STATUS.FAILURE, nil;
+	end
+	if dst_port <= 0 or dst_port >= 0xFFFF then
+		module:log("warn", "Received invalid PROXYv1 destination port from %s: %d", conn:ip(), dst_port);
+		return PROTO_HANDLER_STATUS.FAILURE, nil;
+	end
+
+	-- Ensure that received source and destination address can be parsed
+	local _, err = ip.new_ip(src_addr);
+	if err ~= nil then
+		module:log("warn", "Received unparseable PROXYv1 source address from %s: %s", conn:ip(), src_addr);
+	end
+	_, err = ip.new_ip(dst_addr);
+	if err ~= nil then
+		module:log("warn", "Received unparseable PROXYv1 destination address from %s: %s", conn:ip(), dst_addr);
+		return PROTO_HANDLER_STATUS.FAILURE, nil;
+	end
+
+	-- Strip parsed header from session buffer and build proxy data
+	session.buffer = session.buffer:gsub(header_pattern, "");
+
+	local proxy_data = {
+		_version = 1,
+		_addr_family = addr_family, _transport = TRANSPORT.STREAM,
+		_src_addr = src_addr, _src_port = src_port,
+		_dst_addr = dst_addr, _dst_port = dst_port
+	};
+	setmetatable(proxy_data, proxy_data_mt);
+
+	-- Return successful response with gathered proxy data
+	return PROTO_HANDLER_STATUS.SUCCESS, proxy_data;
+end
+
+PROTO_HANDLERS["PROXYv2"].callback = function(conn, session)
+	-- Postpone processing if less than 16 bytes are available
+	if #session.buffer < 16 then
+		return PROTO_HANDLER_STATUS.POSTPONE, nil;
+	end
+
+	-- Parse first 16 bytes of protocol header
+	local version = bit.rshift(bit.band(session.buffer:byte(13), 0xF0), 4);
+	local command = bit.band(session.buffer:byte(13), 0x0F);
+	local addr_family = bit.rshift(bit.band(session.buffer:byte(14), 0xF0), 4);
+	local transport = bit.band(session.buffer:byte(14), 0x0F);
+	local length = bit.bor(session.buffer:byte(16), bit.lshift(session.buffer:byte(15), 8));
+
+	-- Postpone processing if less than 16+<length> bytes are available
+	if #session.buffer < 16 + length then
+		return PROTO_HANDLER_STATUS.POSTPONE, nil;
+	end
+
+	-- Ensure that version number is correct
+	if version ~= 0x2 then
+		module:log("error", "Received unsupported PROXYv2 version from %s: %d", conn:ip(), version);
+		return PROTO_HANDLER_STATUS.FAILURE, nil;
+	end
+
+	local payload = session.buffer:sub(17);
+	if command == 0x0 then
+		-- Gather source/destination addresses and ports from local socket
+		local src_addr, src_port = conn:socket():getpeername();
+		local dst_addr, dst_port = conn:socket():getsockname();
+
+		-- Build proxy data based on real connection information
+		local proxy_data = {
+			_version = version,
+			_addr_family = addr_family, _transport = transport,
+			_src_addr = src_addr, _src_port = src_port,
+			_dst_addr = dst_addr, _dst_port = dst_port
+		};
+		setmetatable(proxy_data, proxy_data_mt);
+
+		-- Return successful response with gathered proxy data
+		return PROTO_HANDLER_STATUS.SUCCESS, proxy_data;
+	elseif command == 0x1 then
+		local offset = 1;
+		local src_addr, src_port, dst_addr, dst_port;
+
+		-- Verify transport protocol is either STREAM or DGRAM
+		if transport ~= TRANSPORT.STREAM and transport ~= TRANSPORT.DGRAM then
+			module:log("warn", "Received unsupported PROXYv2 transport from %s: 0x%02X", conn:ip(), transport);
+			return PROTO_HANDLER_STATUS.FAILURE, nil;
+		end
+
+		-- Parse source and destination addresses
+		if addr_family == ADDR_FAMILY.INET then
+			src_addr = net.ntop(payload:sub(offset, offset + 3)); offset = offset + 4;
+			dst_addr = net.ntop(payload:sub(offset, offset + 3)); offset = offset + 4;
+		elseif addr_family == ADDR_FAMILY.INET6 then
+			src_addr = net.ntop(payload:sub(offset, offset + 15)); offset = offset + 16;
+			dst_addr = net.ntop(payload:sub(offset, offset + 15)); offset = offset + 16;
+		elseif addr_family == ADDR_FAMILY.UNIX then
+			src_addr = payload:sub(offset, offset + 107); offset = offset + 108;
+			dst_addr = payload:sub(offset, offset + 107); offset = offset + 108;
+		end
+
+		-- Parse source and destination ports
+		if addr_family == ADDR_FAMILY.INET or addr_family == ADDR_FAMILY.INET6 then
+			src_port = bit.bor(payload:byte(offset + 1), bit.lshift(payload:byte(offset), 8)); offset = offset + 2;
+			-- luacheck: ignore 311
+			dst_port = bit.bor(payload:byte(offset + 1), bit.lshift(payload:byte(offset), 8)); offset = offset + 2;
+		end
+
+		-- Strip parsed header from session buffer and build proxy data
+		session.buffer = session.buffer:sub(17 + length);
+
+		local proxy_data = {
+			_version = version,
+			_addr_family = addr_family, _transport = transport,
+			_src_addr = src_addr, _src_port = src_port,
+			_dst_addr = dst_addr, _dst_port = dst_port
+		};
+		setmetatable(proxy_data, proxy_data_mt);
+
+		-- Return successful response with gathered proxy data
+		return PROTO_HANDLER_STATUS.SUCCESS, proxy_data;
+	else
+		module:log("error", "Received unsupported PROXYv2 command from %s: 0x%02X", conn:ip(), command);
+		return PROTO_HANDLER_STATUS.FAILURE, nil;
+	end
+end
+
+-- Wrap an existing connection with the provided proxy data. This will override several methods of the 'conn' object to
+-- return the proxied source instead of the source which initiated the TCP connection. Afterwards, the listener of the
+-- connection gets set according to the globally defined port<>service mappings and the methods 'onconnect' and
+-- 'onincoming' are being called manually with the current session buffer.
+local function wrap_proxy_connection(conn, session, proxy_data)
+	-- Override and add functions of 'conn' object when source information has been collected
+	conn.proxyip, conn.proxyport = conn.ip, conn.port;
+	if proxy_data:src_addr() ~= nil and proxy_data:src_port() ~= nil then
+		conn.ip = function()
+			return proxy_data:src_addr();
+		end
+		conn.port = function()
+			return proxy_data:src_port();
+		end
+		conn.clientport = conn.port;
+	end
+
+	-- Attempt to find service by processing port<>service mappings
+	local mapping = mappings[conn:serverport()];
+	if mapping == nil then
+		conn:close();
+		module:log("error", "Connection %s@%s terminated: Could not find mapping for port %d",
+			conn:ip(), conn:proxyip(), conn:serverport());
+		return;
+	end
+
+	if mapping.service == nil then
+		local service = portmanager.get_service(mapping.service_name);
+
+		if service ~= nil then
+			mapping.service = service;
+		else
+			conn:close();
+			module:log("error", "Connection %s@%s terminated: Could not process mapping for unknown service %s",
+				conn:ip(), conn:proxyip(), mapping.service_name);
+			return;
+		end
+	end
+
+	-- Pass connection to actual service listener and simulate onconnect/onincoming callbacks
+	local service_listener = mapping.service.listener;
+
+	module:log("info", "Passing proxied connection %s:%d to service %s", conn:ip(), conn:port(), mapping.service_name);
+	conn:setlistener(service_listener);
+	if service_listener.onconnect then
+		service_listener.onconnect(conn);
+	end
+	return service_listener.onincoming(conn, session.buffer);
+end
+
+-- Network Listener Methods
+local listener = {};
+
+function listener.onconnect(conn)
+	sessions[conn] = {
+		handler = nil;
+		buffer = nil;
+	};
+end
+
+function listener.onincoming(conn, data)
+	-- Abort processing if no data has been received
+	if not data then
+		return;
+	end
+
+	-- Lookup session for connection and append received data to buffer
+	local session = sessions[conn];
+	session.buffer = session.buffer and session.buffer .. data or data;
+
+	-- Attempt to determine protocol handler if not done previously
+	if session.handler == nil then
+		-- Match current session buffer against all known protocol signatures to determine protocol handler
+		for handler_name, handler in pairs(PROTO_HANDLERS) do
+			if session.buffer:find("^" .. handler.signature) ~= nil then
+				session.handler = handler.callback;
+				module:log("debug", "Detected %s connection from %s:%d", handler_name, conn:ip(), conn:port());
+				break;
+			end
+		end
+
+		-- Decide between waiting for a complete header signature or terminating the connection when no handler has been found
+		if session.handler == nil then
+			-- Terminate connection if buffer size has exceeded tolerable maximum size
+			if #session.buffer > PROTO_MAX_HEADER_LENGTH then
+				conn:close();
+				module:log("warn", "Connection %s:%d terminated: No valid PROXY header within %d bytes",
+					conn:ip(), conn:port(), PROTO_MAX_HEADER_LENGTH);
+			end
+
+			-- Skip further processing without a valid protocol handler
+			module:log("debug", "No valid header signature detected from %s:%d, waiting for more data...",
+				conn:ip(), conn:port());
+			return;
+		end
+	end
+
+	-- Execute proxy protocol handler and process response
+	local response, proxy_data = session.handler(conn, session);
+	if response == PROTO_HANDLER_STATUS.SUCCESS then
+		module:log("info", "Received PROXY header from %s: %s", conn:ip(), proxy_data:describe());
+		return wrap_proxy_connection(conn, session, proxy_data);
+	elseif response == PROTO_HANDLER_STATUS.POSTPONE then
+		module:log("debug", "Postponed parsing of incomplete PROXY header received from %s", conn:ip());
+		return;
+	elseif response == PROTO_HANDLER_STATUS.FAILURE then
+		conn:close();
+		module:log("warn", "Connection %s terminated: Could not process PROXY header from client, " +
+			"see previous log messages.", conn:ip());
+		return;
+	else
+		-- This code should be never reached, but is included for completeness
+		conn:close();
+		module:log("error", "Connection terminated: Received invalid protocol handler response with code %d", response);
+		return;
+	end
+end
+
+function listener.ondisconnect(conn)
+	sessions[conn] = nil;
+end
+
+listener.ondetach = listener.ondisconnect;
+
+-- Initialize the module by processing all configured port mappings
+local config_ports = module:get_option_set("proxy_ports", {});
+local config_mappings = module:get_option("proxy_port_mappings", {});
+for port in config_ports do
+	if config_mappings[port] ~= nil then
+		mappings[port] = {
+			service_name = config_mappings[port],
+			service = nil
+		};
+	else
+		module:log("warn", "No port<>service mapping found for port: %d", port);
+	end
+end
+
+-- Register the previously declared network listener
+module:provides("net", {
+	name = "proxy";
+	listener = listener;
+});