view mod_net_proxy/mod_net_proxy.lua @ 4047:36b6e3e3f9e2

mod_conversejs: Disable automatic BOSH/WS endpoint discovery Converse.js 7.0 will enable this by default, but when using this module the BOSH and WebSocket endpoints are provided in the generated HTML, so automatic discovery is not needed and unlikely to work without an additional module.
author Kim Alvefur <zash@zash.se>
date Thu, 18 Jun 2020 15:24:34 +0200
parents b33b2fbdc713
children 9d65eb3fcb15
line wrap: on
line source

-- 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 set = require "util.set";
local portmanager = require "core.portmanager";

-- Backwards Compatibility
local function net_ntop_bc(input)
	if input:len() == 4 then
		return string.format("%d.%d.%d.%d", input:byte(1, 4));
	elseif input:len() == 16 then
		local octets = { nil, nil, nil, nil, nil, nil, nil, nil };

		-- Convert received bytes into IPv6 address and skip leading zeroes for each group
		for index = 1, 8 do
			local high, low = input:byte(index * 2 - 1, index * 2);
			octets[index] = string.format("%x", high * 256 + low);
		end
		local address = table.concat(octets, ":", 1, 8);

		-- Search for the longest sequence of zeroes
		local token;
		local length = (address:match("^0:[0:]+()") or 1) - 1;
		for s in address:gmatch(":0:[0:]+") do
			if length < #s then
				length, token = #s, s;
			end
		end

		-- Return the shortened IPv6 address
		return address:gsub(token or "^0:[0:]+", "::", 1);
	end
end

local net_ntop = net.ntop or net_ntop_bc

-- 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 };

-- Configuration Variables
local config_mappings = module:get_option("proxy_port_mappings", {});
local config_ports = module:get_option_set("proxy_ports", {});
local config_trusted_proxies = module:get_option_set("proxy_trusted_proxies", {"127.0.0.1", "::1"});

-- Persistent In-Memory Storage
local sessions = {};
local mappings = {};
local trusted_networks = set.new();

-- 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);
		return PROTO_HANDLER_STATUS.FAILURE, nil;
	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("warn", "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("warn", "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[tonumber(conn:serverport())];
	if mapping == nil then
		conn:close();
		module:log("warn", "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("warn", "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

local function is_trusted_proxy(conn)
	-- If no trusted proxies were configured, trust any incoming connection
	-- While this may seem insecure, the module defaults to only trusting 127.0.0.1 and ::1
	if trusted_networks:empty() then
		return true;
	end

	-- Iterate through all trusted proxies and check for match against connected IP address
	local conn_ip = ip.new_ip(conn:ip());
	for trusted_network in trusted_networks:items() do
		if ip.match(trusted_network.ip, conn_ip, trusted_network.cidr) then
			return true;
		end
	end

	-- Connection does not match any trusted proxy
	return false;
end

-- Network Listener Methods
local listener = {};

function listener.onconnect(conn)
	-- Silently drop connections with an IP address of <nil>, which can happen when the socket was closed before the
	-- responsible net.server backend was able to grab the IP address of the connecting client.
	if conn:ip() == nil then
		conn:close();
		return;
	end

	-- Check if connection is coming from a trusted proxy
	if not is_trusted_proxy(conn) then
		conn:close();
		module:log("warn", "Dropped connection from untrusted proxy: %s", conn:ip());
		return;
	end

	-- Initialize session variables
	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("warn", "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;

-- Parse trusted proxies which can either contain single hosts or networks
if not config_trusted_proxies:empty() then
	for trusted_proxy in config_trusted_proxies:items() do
		local network = {};
		network.ip, network.cidr = ip.parse_cidr(trusted_proxy);
		trusted_networks:add(network);
	end
else
	module:log("warn", "No trusted proxies configured, all connections will be accepted - this might be dangerous");
end

-- Process all configured port mappings and generate a list of mapped ports
local mapped_ports = {};
for port, mapping in pairs(config_mappings) do
	port = tonumber(port);
	table.insert(mapped_ports, port);
	mappings[port] = {
		service_name = mapping,
		service = nil,
	};
end

-- Log error message when user manually specifies ports without configuring the necessary port mappings
if not config_ports:empty() then
	local missing_ports = config_ports - set.new(mapped_ports);
	if not missing_ports:empty() then
		module:log("error", "Missing port<>service mappings for these ports: %s", tostring(missing_ports));
	end
end

-- Register the previously declared network listener
module:provides("net", {
	name = "proxy";
	listener = listener;
	default_ports = mapped_ports;
});