-- Prosody IM

-- Copyright (C) 2012-2014 Florian Zeitz

--

-- This project is MIT/X11 licensed. Please see the

-- COPYING file in the source package for more information.

--

-- luacheck: ignore 431/log

module:set_global();

local add_task = require "util.timer".add_task;

local add_filter = require "util.filters".add_filter;

local sha1 = require "util.hashes".sha1;

local base64 = require "util.encodings".base64.encode;

local st = require "util.stanza";

local parse_xml = require "util.xml".parse;

local contains_token = require "util.http".contains_token;

local portmanager = require "core.portmanager";

local sm_destroy_session = require"core.sessionmanager".destroy_session;

local log = module._log;

local dbuffer = require "util.dbuffer";

local websocket_frames = require"net.websocket.frames";

local parse_frame = websocket_frames.parse;

local build_frame = websocket_frames.build;

local build_close = websocket_frames.build_close;

local parse_close = websocket_frames.parse_close;

local t_concat = table.concat;

local stanza_size_limit = module:get_option_number("c2s_stanza_size_limit", 10 * 1024 * 1024);

local frame_buffer_limit = module:get_option_number("websocket_frame_buffer_limit", 2 * stanza_size_limit);

local frame_fragment_limit = module:get_option_number("websocket_frame_fragment_limit", 8);

local stream_close_timeout = module:get_option_number("c2s_close_timeout", 5);

local consider_websocket_secure = module:get_option_boolean("consider_websocket_secure");

local cross_domain = module:get_option("cross_domain_websocket");

if cross_domain ~= nil then

	module:log("info", "The 'cross_domain_websocket' option has been deprecated");

end

local xmlns_framing = "urn:ietf:params:xml:ns:xmpp-framing";

local xmlns_streams = "http://etherx.jabber.org/streams";

local xmlns_client = "jabber:client";

local stream_xmlns_attr = {xmlns='urn:ietf:params:xml:ns:xmpp-streams'};

module:depends("c2s")

local sessions = module:shared("c2s/sessions");

local c2s_listener = portmanager.get_service("c2s").listener;

--- Session methods

local function session_open_stream(session, from, to)

	local attr = {

		xmlns = xmlns_framing,

		["xml:lang"] = "en",

		version = "1.0",

		id = session.streamid or "",

		from = from or session.host, to = to,

	};

	if session.stream_attrs then

		session:stream_attrs(from, to, attr)

	end

	session.send(st.stanza("open", attr));

end

local function session_close(session, reason)

	local log = session.log or log;

	if session.conn then

		if session.notopen then

			session:open_stream();

		end

		if reason then -- nil == no err, initiated by us, false == initiated by client

			local stream_error = st.stanza("stream:error");

			if type(reason) == "string" then -- assume stream error

				stream_error:tag(reason, {xmlns = 'urn:ietf:params:xml:ns:xmpp-streams' });

			elseif type(reason) == "table" then

				if reason.condition then

					stream_error:tag(reason.condition, stream_xmlns_attr):up();

					if reason.text then

						stream_error:tag("text", stream_xmlns_attr):text(reason.text):up();

					end

					if reason.extra then

						stream_error:add_child(reason.extra);

					end

				elseif reason.name then -- a stanza

					stream_error = reason;

				end

			end

			log("debug", "Disconnecting client, <stream:error> is: %s", stream_error);

			session.send(stream_error);

		end

		session.send(st.stanza("close", { xmlns = xmlns_framing }));

		function session.send() return false; end

		-- luacheck: ignore 422/reason

		-- FIXME reason should be handled in common place

		local reason = (reason and (reason.name or reason.text or reason.condition)) or reason;

		session.log("debug", "c2s stream for %s closed: %s", session.full_jid or ("<"..session.ip..">"), reason or "session closed");

		-- Authenticated incoming stream may still be sending us stanzas, so wait for </stream:stream> from remote

		local conn = session.conn;

		if reason == nil and not session.notopen and session.type == "c2s" then

			-- Grace time to process data from authenticated cleanly-closed stream

			add_task(stream_close_timeout, function ()

				if not session.destroyed then

					session.log("warn", "Failed to receive a stream close response, closing connection anyway...");

					sm_destroy_session(session, reason);

					conn:write(build_close(1000, "Stream closed"));

					conn:close();

				end

			end);

		else

			sm_destroy_session(session, reason);

			conn:write(build_close(1000, "Stream closed"));

			conn:close();

		end

	end

end

--- Filters

local function filter_open_close(data)

	if not data:find(xmlns_framing, 1, true) then return data; end

	local oc = parse_xml(data);

	if not oc then return data; end

	if oc.attr.xmlns ~= xmlns_framing then return data; end

	if oc.name == "close" then return "</stream:stream>"; end

	if oc.name == "open" then

		oc.name = "stream:stream";

		oc.attr.xmlns = nil;

		oc.attr["xmlns:stream"] = xmlns_streams;

		return oc:top_tag();

	end

	return data;

end

local default_get_response_body = [[<!DOCTYPE html><html><head><title>Websocket</title></head><body>

<p>It works! Now point your WebSocket client to this URL to connect to Prosody.</p>

</body></html>]]

local websocket_get_response_body = module:get_option_string("websocket_get_response_body", default_get_response_body)

local function validate_frame(frame, max_length)

	local opcode, length = frame.opcode, frame.length;

	if max_length and length > max_length then

		return false, 1009, "Payload too large";

	end

	-- Error cases

	if frame.RSV1 or frame.RSV2 or frame.RSV3 then -- Reserved bits non zero

		return false, 1002, "Reserved bits not zero";

	end

	if opcode == 0x8 and frame.data then -- close frame

		if length == 1 then

			return false, 1002, "Close frame with payload, but too short for status code";

		elseif length >= 2 then

			local status_code = parse_close(frame.data)

			if status_code < 1000 then

				return false, 1002, "Closed with invalid status code";

			elseif ((status_code > 1003 and status_code < 1007) or status_code > 1011) and status_code < 3000 then

				return false, 1002, "Closed with reserved status code";

			end

		end

	end

	if opcode >= 0x8 then

		if length > 125 then -- Control frame with too much payload

			return false, 1002, "Payload too large";

		end

		if not frame.FIN then -- Fragmented control frame

			return false, 1002, "Fragmented control frame";

		end

	end

	if (opcode > 0x2 and opcode < 0x8) or (opcode > 0xA) then

		return false, 1002, "Reserved opcode";

	end

	-- Check opcode

	if opcode == 0x2 then -- Binary frame

		return false, 1003, "Only text frames are supported, RFC 7395 3.2";

	elseif opcode == 0x8 then -- Close request

		return false, 1000, "Goodbye";

	end

	-- Other (XMPP-specific) validity checks

	if not frame.FIN then

		return false, 1003, "Continuation frames are not supported, RFC 7395 3.3.3";

	end

	if opcode == 0x01 and frame.data and frame.data:byte(1, 1) ~= 60 then

		return false, 1007, "Invalid payload start character, RFC 7395 3.3.3";

	end

	return true;

end

function handle_request(event)

	local request, response = event.request, event.response;

	local conn = response.conn;

	conn.starttls = false; -- Prevent mod_tls from believing starttls can be done

	if not request.headers.sec_websocket_key or request.method ~= "GET" then

		response.headers.content_type = "text/html";

		return websocket_get_response_body;

	end

	local wants_xmpp = contains_token(request.headers.sec_websocket_protocol or "", "xmpp");

	if not wants_xmpp then

		module:log("debug", "Client didn't want to talk XMPP, list of protocols was %s", request.headers.sec_websocket_protocol or "(empty)");

		return 501;

	end

	local function websocket_close(code, message)

		conn:write(build_close(code, message));

		conn:close();

	end

	local function websocket_handle_error(session, code, message)

		if code == 1009 then -- stanza size limit exceeded

			-- we close the session, rather than the connection,

			-- otherwise a resuming client will simply resend the

			-- offending stanza

			session:close({ condition = "policy-violation", text = "stanza too large" });

		else

			websocket_close(code, message);

		end

	end

	local function handle_frame(frame)

		module:log("debug", "Websocket received frame: opcode=%0x, %i bytes", frame.opcode, #frame.data);

		-- Check frame makes sense

		local frame_ok, err_status, err_text = validate_frame(frame, stanza_size_limit);

		if not frame_ok then

			return frame_ok, err_status, err_text;

		end

		local opcode = frame.opcode;

		if opcode == 0x9 then -- Ping frame

			frame.opcode = 0xA;

			frame.MASK = false; -- Clients send masked frames, servers don't, see #1484

			conn:write(build_frame(frame));

			return "";

		elseif opcode == 0xA then -- Pong frame, MAY be sent unsolicited, eg as keepalive

			return "";

		elseif opcode ~= 0x1 then -- Not text frame (which is all we support)

			log("warn", "Received frame with unsupported opcode %i", opcode);

			return "";

		end

		return frame.data;

	end

	conn:setlistener(c2s_listener);

	c2s_listener.onconnect(conn);

	local session = sessions[conn];

	-- Use upstream IP if a HTTP proxy was used

	-- See mod_http and #540

	session.ip = request.ip;

	session.secure = consider_websocket_secure or session.secure;

	session.websocket_request = request;

	session.open_stream = session_open_stream;

	session.close = session_close;

	local frameBuffer = dbuffer.new(frame_buffer_limit, frame_fragment_limit);

	add_filter(session, "bytes/in", function(data)

		if not frameBuffer:write(data) then

			session.log("warn", "websocket frame buffer full - terminating session");

			session:close({ condition = "resource-constraint", text = "frame buffer exceeded" });

			return;

		end

		local cache = {};

		local frame, length, partial = parse_frame(frameBuffer);

		while frame do

			frameBuffer:discard(length);

			local result, err_status, err_text = handle_frame(frame);

			if not result then

				websocket_handle_error(session, err_status, err_text);

				break;

			end

			cache[#cache+1] = filter_open_close(result);

			frame, length, partial = parse_frame(frameBuffer);

		end

		if partial then

			-- The header of the next frame is already in the buffer, run

			-- some early validation here

			local frame_ok, err_status, err_text = validate_frame(partial, stanza_size_limit);

			if not frame_ok then

				websocket_handle_error(session, err_status, err_text);

			end

		end

		return t_concat(cache, "");

	end);

	add_filter(session, "stanzas/out", function(stanza)

		stanza = st.clone(stanza);

		local attr = stanza.attr;

		attr.xmlns = attr.xmlns or xmlns_client;

		if stanza.name:find("^stream:") then

			attr["xmlns:stream"] = attr["xmlns:stream"] or xmlns_streams;

		end

		return stanza;

	end, -1000);

	add_filter(session, "bytes/out", function(data)

		return build_frame({ FIN = true, opcode = 0x01, data = tostring(data)});

	end);

	response.status_code = 101;

	response.headers.upgrade = "websocket";

	response.headers.connection = "Upgrade";

	response.headers.sec_webSocket_accept = base64(sha1(request.headers.sec_websocket_key .. "258EAFA5-E914-47DA-95CA-C5AB0DC85B11"));

	response.headers.sec_webSocket_protocol = "xmpp";

	module:fire_event("websocket-session", { session = session, request = request });

	session.log("debug", "Sending WebSocket handshake");

	return "";

end

local function keepalive(event)

	local session = event.session;

	if session.open_stream == session_open_stream then

		return session.conn:write(build_frame({ opcode = 0x9, FIN = true }));

	end

end

module:hook("c2s-read-timeout", keepalive, -0.9);

module:depends("http");

module:provides("http", {

	name = "websocket";

	default_path = "xmpp-websocket";

	route = {

		["GET"] = handle_request;

		["GET /"] = handle_request;

	};

});

function module.add_host(module)

	module:hook("c2s-read-timeout", keepalive, -0.9);

end