core/s2smanager.lua

-- 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 hosts = hosts;

local sessions = sessions;

local core_process_stanza = function(a, b) core_process_stanza(a, b); end

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

local socket = require "socket";

local format = string.format;

local t_insert, t_sort = table.insert, table.sort;

local get_traceback = debug.traceback;

local tostring, pairs, ipairs, getmetatable, newproxy, error, tonumber, setmetatable

    = tostring, pairs, ipairs, getmetatable, newproxy, error, tonumber, setmetatable;

local idna_to_ascii = require "util.encodings".idna.to_ascii;

local connlisteners_get = require "net.connlisteners".get;

local initialize_filters = require "util.filters".initialize;

local wrapclient = require "net.server".wrapclient;

local modulemanager = require "core.modulemanager";

local st = require "stanza";

local stanza = st.stanza;

local nameprep = require "util.encodings".stringprep.nameprep;

local cert_verify_identity = require "util.x509".verify_identity;

local fire_event = prosody.events.fire_event;

local uuid_gen = require "util.uuid".generate;

local logger_init = require "util.logger".init;

local log = logger_init("s2smanager");

local sha256_hash = require "util.hashes".sha256;

local adns, dns = require "net.adns", require "net.dns";

local config = require "core.configmanager";

local connect_timeout = config.get("*", "core", "s2s_timeout") or 60;

local dns_timeout = config.get("*", "core", "dns_timeout") or 15;

local max_dns_depth = config.get("*", "core", "dns_max_depth") or 3;

dns.settimeout(dns_timeout);

local prosody = _G.prosody;

incoming_s2s = {};

prosody.incoming_s2s = incoming_s2s;

local incoming_s2s = incoming_s2s;

module "s2smanager"

function compare_srv_priorities(a,b)

	return a.priority < b.priority or (a.priority == b.priority and a.weight > b.weight);

end

local bouncy_stanzas = { message = true, presence = true, iq = true };

local function bounce_sendq(session, reason)

	local sendq = session.sendq;

	if sendq then

		session.log("info", "sending error replies for "..#sendq.." queued stanzas because of failed outgoing connection to "..tostring(session.to_host));

		local dummy = {

			type = "s2sin";

			send = function(s)

				(session.log or log)("error", "Replying to to an s2s error reply, please report this! Traceback: %s", get_traceback());

			end;

			dummy = true;

		};

		for i, data in ipairs(sendq) do

			local reply = data[2];

			local xmlns = reply.attr.xmlns;

			if not(xmlns) and bouncy_stanzas[reply.name] then

				reply.attr.type = "error";

				reply:tag("error", {type = "cancel"})

					:tag("remote-server-not-found", {xmlns = "urn:ietf:params:xml:ns:xmpp-stanzas"}):up();

				if reason then

					reply:tag("text", {xmlns = "urn:ietf:params:xml:ns:xmpp-stanzas"}):text("Connection failed: "..reason):up();

				end

				core_process_stanza(dummy, reply);

			end

			sendq[i] = nil;

		end

		session.sendq = nil;

	end

end

function send_to_host(from_host, to_host, data)

	if not hosts[from_host] then

		log("warn", "Attempt to send stanza from %s - a host we don't serve", from_host);

		return false;

	end

	local host = hosts[from_host].s2sout[to_host];

	if host then

		-- We have a connection to this host already

		if host.type == "s2sout_unauthed" and (data.name ~= "db:verify" or not host.dialback_key) then

			(host.log or log)("debug", "trying to send over unauthed s2sout to "..to_host);

			-- Queue stanza until we are able to send it

			if host.sendq then t_insert(host.sendq, {tostring(data), st.reply(data)});

			else host.sendq = { {tostring(data), st.reply(data)} }; end

			host.log("debug", "stanza [%s] queued ", data.name);

		elseif host.type == "local" or host.type == "component" then

			log("error", "Trying to send a stanza to ourselves??")

			log("error", "Traceback: %s", get_traceback());

			log("error", "Stanza: %s", tostring(data));

			return false;

		else

			(host.log or log)("debug", "going to send stanza to "..to_host.." from "..from_host);

			-- FIXME

			if host.from_host ~= from_host then

				log("error", "WARNING! This might, possibly, be a bug, but it might not...");

				log("error", "We are going to send from %s instead of %s", tostring(host.from_host), tostring(from_host));

			end

			host.sends2s(data);

			host.log("debug", "stanza sent over "..host.type);

		end

	else

		log("debug", "opening a new outgoing connection for this stanza");

		local host_session = new_outgoing(from_host, to_host);

		-- Store in buffer

		host_session.sendq = { {tostring(data), st.reply(data)} };

		log("debug", "stanza [%s] queued until connection complete", tostring(data.name));

		if (not host_session.connecting) and (not host_session.conn) then

			log("warn", "Connection to %s failed already, destroying session...", to_host);

			if not destroy_session(host_session, "Connection failed") then

				-- Already destroyed, we need to bounce our stanza

				bounce_sendq(host_session, host_session.destruction_reason);

			end

			return false;

		end

	end

	return true;

end

local open_sessions = 0;

function new_incoming(conn)

	local session = { conn = conn, type = "s2sin_unauthed", direction = "incoming", hosts = {} };

	if true then

		session.trace = newproxy(true);

		getmetatable(session.trace).__gc = function () open_sessions = open_sessions - 1; end;

	end

	open_sessions = open_sessions + 1;

	local w, log = conn.write, logger_init("s2sin"..tostring(conn):match("[a-f0-9]+$"));

	session.log = log;

	local filter = initialize_filters(session);

	session.sends2s = function (t)

		log("debug", "sending: %s", t.top_tag and t:top_tag() or t:match("^([^>]*>?)"));

		if t.name then

			t = filter("stanzas/out", t);

		end

		if t then

			t = filter("bytes/out", tostring(t));

			if t then

				return w(conn, t);

			end

		end

	end

	incoming_s2s[session] = true;

	add_task(connect_timeout, function ()

		if session.conn ~= conn or

		   session.type == "s2sin" then

			return; -- Ok, we're connect[ed|ing]

		end

		-- Not connected, need to close session and clean up

		(session.log or log)("warn", "Destroying incomplete session %s->%s due to inactivity",

		    session.from_host or "(unknown)", session.to_host or "(unknown)");

		session:close("connection-timeout");

	end);

	return session;

end

function new_outgoing(from_host, to_host, connect)

		local host_session = { to_host = to_host, from_host = from_host, host = from_host,

		                       notopen = true, type = "s2sout_unauthed", direction = "outgoing",

		                       open_stream = session_open_stream };

		hosts[from_host].s2sout[to_host] = host_session;

		host_session.close = destroy_session; -- This gets replaced by xmppserver_listener later

		local log;

		do

			local conn_name = "s2sout"..tostring(host_session):match("[a-f0-9]*$");

			log = logger_init(conn_name);

			host_session.log = log;

		end

		initialize_filters(host_session);

		if connect ~= false then

			-- Kick the connection attempting machine into life

			if not attempt_connection(host_session) then

				-- Intentionally not returning here, the

				-- session is needed, connected or not

				destroy_session(host_session);

			end

		end

		if not host_session.sends2s then

			-- A sends2s which buffers data (until the stream is opened)

			-- note that data in this buffer will be sent before the stream is authed

			-- and will not be ack'd in any way, successful or otherwise

			local buffer;

			function host_session.sends2s(data)

				if not buffer then

					buffer = {};

					host_session.send_buffer = buffer;

				end

				log("debug", "Buffering data on unconnected s2sout to %s", to_host);

				buffer[#buffer+1] = data;

				log("debug", "Buffered item %d: %s", #buffer, tostring(data));

			end

		end

		return host_session;

end

function attempt_connection(host_session, err)

	local from_host, to_host = host_session.from_host, host_session.to_host;

	local connect_host, connect_port = to_host and idna_to_ascii(to_host), 5269;

	if not connect_host then

		return false;

	end

	if not err then -- This is our first attempt

		log("debug", "First attempt to connect to %s, starting with SRV lookup...", to_host);

		host_session.connecting = true;

		local handle;

		handle = adns.lookup(function (answer)

			handle = nil;

			host_session.connecting = nil;

			if answer then

				log("debug", to_host.." has SRV records, handling...");

				local srv_hosts = {};

				host_session.srv_hosts = srv_hosts;

				for _, record in ipairs(answer) do

					t_insert(srv_hosts, record.srv);

				end

				t_sort(srv_hosts, compare_srv_priorities);

				local srv_choice = srv_hosts[1];

				host_session.srv_choice = 1;

				if srv_choice then

					connect_host, connect_port = srv_choice.target or to_host, srv_choice.port or connect_port;

					log("debug", "Best record found, will connect to %s:%d", connect_host, connect_port);

				end

			else

				log("debug", to_host.." has no SRV records, falling back to A");

			end

			-- Try with SRV, or just the plain hostname if no SRV

			local ok, err = try_connect(host_session, connect_host, connect_port);

			if not ok then

				if not attempt_connection(host_session, err) then

					-- No more attempts will be made

					destroy_session(host_session, err);

				end

			end

		end, "_xmpp-server._tcp."..connect_host..".", "SRV");

		return true; -- Attempt in progress

	elseif host_session.srv_hosts and #host_session.srv_hosts > host_session.srv_choice then -- Not our first attempt, and we also have SRV

		host_session.srv_choice = host_session.srv_choice + 1;

		local srv_choice = host_session.srv_hosts[host_session.srv_choice];

		connect_host, connect_port = srv_choice.target or to_host, srv_choice.port or connect_port;

		host_session.log("info", "Connection failed (%s). Attempt #%d: This time to %s:%d", tostring(err), host_session.srv_choice, connect_host, connect_port);

	else

		host_session.log("info", "Out of connection options, can't connect to %s", tostring(host_session.to_host));

		-- We're out of options

		return false;

	end

	if not (connect_host and connect_port) then

		-- Likely we couldn't resolve DNS

		log("warn", "Hmm, we're without a host (%s) and port (%s) to connect to for %s, giving up :(", tostring(connect_host), tostring(connect_port), tostring(to_host));

		return false;

	end

	return try_connect(host_session, connect_host, connect_port);

end

function try_connect(host_session, connect_host, connect_port)

	host_session.connecting = true;

	local handle;

	handle = adns.lookup(function (reply, err)

		handle = nil;

		host_session.connecting = nil;

		-- COMPAT: This is a compromise for all you CNAME-(ab)users :)

		if not (reply and reply[#reply] and reply[#reply].a) then

			local count = max_dns_depth;

			reply = dns.peek(connect_host, "CNAME", "IN");

			while count > 0 and reply and reply[#reply] and not reply[#reply].a and reply[#reply].cname do

				log("debug", "Looking up %s (DNS depth is %d)", tostring(reply[#reply].cname), count);

				reply = dns.peek(reply[#reply].cname, "A", "IN") or dns.peek(reply[#reply].cname, "CNAME", "IN");

				count = count - 1;

			end

		end

		-- end of CNAME resolving

		if reply and reply[#reply] and reply[#reply].a then

			log("debug", "DNS reply for %s gives us %s", connect_host, reply[#reply].a);

			local ok, err = make_connect(host_session, reply[#reply].a, connect_port);

			if not ok then

				if not attempt_connection(host_session, err or "closed") then

					err = err and (": "..err) or "";

					destroy_session(host_session, "Connection failed"..err);

				end

			end

		else

			log("debug", "DNS lookup failed to get a response for %s", connect_host);

			if not attempt_connection(host_session, "name resolution failed") then -- Retry if we can

				log("debug", "No other records to try for %s - destroying", host_session.to_host);

				err = err and (": "..err) or "";

				destroy_session(host_session, "DNS resolution failed"..err); -- End of the line, we can't

			end

		end

	end, connect_host, "A", "IN");

	return true;

end

function make_connect(host_session, connect_host, connect_port)

	(host_session.log or log)("info", "Beginning new connection attempt to %s (%s:%d)", host_session.to_host, connect_host, connect_port);

	-- Ok, we're going to try to connect

	local from_host, to_host = host_session.from_host, host_session.to_host;

	local conn, handler = socket.tcp();

	if not conn then

		log("warn", "Failed to create outgoing connection, system error: %s", handler);

		return false, handler;

	end

	conn:settimeout(0);

	local success, err = conn:connect(connect_host, connect_port);

	if not success and err ~= "timeout" then

		log("warn", "s2s connect() to %s (%s:%d) failed: %s", host_session.to_host, connect_host, connect_port, err);

		return false, err;

	end

	local cl = connlisteners_get("xmppserver");

	conn = wrapclient(conn, connect_host, connect_port, cl, cl.default_mode or 1 );

	host_session.conn = conn;

	local filter = initialize_filters(host_session);

	local w, log = conn.write, host_session.log;

	host_session.sends2s = function (t)

		log("debug", "sending: %s", (t.top_tag and t:top_tag()) or t:match("^[^>]*>?"));

		if t.name then

			t = filter("stanzas/out", t);

		end

		if t then

			t = filter("bytes/out", tostring(t));

			if t then

				return w(conn, tostring(t));

			end

		end

	end

	-- Register this outgoing connection so that xmppserver_listener knows about it

	-- otherwise it will assume it is a new incoming connection

	cl.register_outgoing(conn, host_session);

	host_session:open_stream(from_host, to_host);

	log("debug", "Connection attempt in progress...");

	add_task(connect_timeout, function ()

		if host_session.conn ~= conn or

		   host_session.type == "s2sout" or

		   host_session.connecting then

			return; -- Ok, we're connect[ed|ing]

		end

		-- Not connected, need to close session and clean up

		(host_session.log or log)("warn", "Destroying incomplete session %s->%s due to inactivity",

		    host_session.from_host or "(unknown)", host_session.to_host or "(unknown)");

		host_session:close("connection-timeout");

	end);

	return true;

end

function session_open_stream(session, from, to)

	session.sends2s(st.stanza("stream:stream", {

		xmlns='jabber:server', ["xmlns:db"]='jabber:server:dialback',

		["xmlns:stream"]='http://etherx.jabber.org/streams',

		from=from, to=to, version='1.0', ["xml:lang"]='en'}):top_tag());

end

local function check_cert_status(session)

	local conn = session.conn:socket()

	local cert

	if conn.getpeercertificate then

		cert = conn:getpeercertificate()

	end

	if cert then

		local chain_valid, err = conn:getpeerchainvalid()

		if not chain_valid then

			session.cert_chain_status = "invalid";

			(session.log or log)("debug", "certificate chain validation result: %s", err);

		else

			session.cert_chain_status = "valid";

			local host = session.direction == "incoming" and session.from_host or session.to_host

			-- We'll go ahead and verify the asserted identity if the

			-- connecting server specified one.

			if host then

				if cert_verify_identity(host, "xmpp-server", cert) then

					session.cert_identity_status = "valid"

				else

					session.cert_identity_status = "invalid"

				end

			end

		end

	end

end

function streamopened(session, attr)

	local send = session.sends2s;

	-- TODO: #29: SASL/TLS on s2s streams

	session.version = tonumber(attr.version) or 0;

	-- TODO: Rename session.secure to session.encrypted

	if session.secure == false then

		session.secure = true;

	end

	if session.direction == "incoming" then

		-- Send a reply stream header

		session.to_host = attr.to and nameprep(attr.to);

		session.from_host = attr.from and nameprep(attr.from);

		session.streamid = uuid_gen();

		(session.log or log)("debug", "incoming s2s received <stream:stream>");

		if session.to_host then

			if not hosts[session.to_host] then

				-- Attempting to connect to a host we don't serve

				session:close({

					condition = "host-unknown";

					text = "This host does not serve "..session.to_host

				});

				return;

			elseif hosts[session.to_host].disallow_s2s then

				-- Attempting to connect to a host that disallows s2s

				session:close({

					condition = "policy-violation";

					text = "Server-to-server communication is not allowed to this host";

				});

				return;

			end

		end

		if session.secure and not session.cert_chain_status then check_cert_status(session); end

		send("<?xml version='1.0'?>");

		send(stanza("stream:stream", { xmlns='jabber:server', ["xmlns:db"]='jabber:server:dialback',

				["xmlns:stream"]='http://etherx.jabber.org/streams', id=session.streamid, from=session.to_host, to=session.from_host, version=(session.version > 0 and "1.0" or nil) }):top_tag());

		if session.version >= 1.0 then

			local features = st.stanza("stream:features");

			if session.to_host then

				hosts[session.to_host].events.fire_event("s2s-stream-features", { origin = session, features = features });

			else

				(session.log or log)("warn", "No 'to' on stream header from %s means we can't offer any features", session.from_host or "unknown host");

			end

			log("debug", "Sending stream features: %s", tostring(features));

			send(features);

		end

	elseif session.direction == "outgoing" then

		-- If we are just using the connection for verifying dialback keys, we won't try and auth it

		if not attr.id then error("stream response did not give us a streamid!!!"); end

		session.streamid = attr.id;

		if session.secure and not session.cert_chain_status then check_cert_status(session); end

		-- Send unauthed buffer

		-- (stanzas which are fine to send before dialback)

		-- Note that this is *not* the stanza queue (which

		-- we can only send if auth succeeds) :)

		local send_buffer = session.send_buffer;

		if send_buffer and #send_buffer > 0 then

			log("debug", "Sending s2s send_buffer now...");

			for i, data in ipairs(send_buffer) do

				session.sends2s(tostring(data));

				send_buffer[i] = nil;

			end

		end

		session.send_buffer = nil;

		-- If server is pre-1.0, don't wait for features, just do dialback

		if session.version < 1.0 then

			if not session.dialback_verifying then

				log("debug", "Initiating dialback...");

				initiate_dialback(session);

			else

				mark_connected(session);

			end

		end

	end

	session.notopen = nil;

end

function streamclosed(session)

	(session.log or log)("debug", "Received </stream:stream>");

	session:close();

end

function initiate_dialback(session)

	-- generate dialback key

	session.dialback_key = generate_dialback(session.streamid, session.to_host, session.from_host);

	session.sends2s(format("<db:result from='%s' to='%s'>%s</db:result>", session.from_host, session.to_host, session.dialback_key));

	session.log("info", "sent dialback key on outgoing s2s stream");

end

function generate_dialback(id, to, from)

	return sha256_hash(id..to..from..hosts[from].dialback_secret, true);

end

function verify_dialback(id, to, from, key)

	return key == generate_dialback(id, to, from);

end

function make_authenticated(session, host)

	if not session.secure then

		local local_host = session.direction == "incoming" and session.to_host or session.from_host;

		if config.get(local_host, "core", "s2s_require_encryption") then

			session:close({

				condition = "policy-violation",

				text = "Encrypted server-to-server communication is required but was not "

				       ..((session.direction == "outgoing" and "offered") or "used")

			});

		end

	end

	if session.type == "s2sout_unauthed" then

		session.type = "s2sout";

	elseif session.type == "s2sin_unauthed" then

		session.type = "s2sin";

		if host then

			if not session.hosts[host] then session.hosts[host] = {}; end

			session.hosts[host].authed = true;

		end

	elseif session.type == "s2sin" and host then

		if not session.hosts[host] then session.hosts[host] = {}; end

		session.hosts[host].authed = true;

	else

		return false;

	end

	session.log("debug", "connection %s->%s is now authenticated", session.from_host or "(unknown)", session.to_host or "(unknown)");

	mark_connected(session);

	return true;

end

-- Stream is authorised, and ready for normal stanzas

function mark_connected(session)

	local sendq, send = session.sendq, session.sends2s;

	local from, to = session.from_host, session.to_host;

	session.log("info", session.direction.." s2s connection "..from.."->"..to.." complete");

	local send_to_host = send_to_host;

	function session.send(data) return send_to_host(to, from, data); end

	local event_data = { session = session };

	if session.type == "s2sout" then

		prosody.events.fire_event("s2sout-established", event_data);

		hosts[session.from_host].events.fire_event("s2sout-established", event_data);

	else

		prosody.events.fire_event("s2sin-established", event_data);

		hosts[session.to_host].events.fire_event("s2sin-established", event_data);

	end

	if session.direction == "outgoing" then

		if sendq then

			session.log("debug", "sending "..#sendq.." queued stanzas across new outgoing connection to "..session.to_host);

			for i, data in ipairs(sendq) do

				send(data[1]);

				sendq[i] = nil;

			end

			session.sendq = nil;

		end

		session.srv_hosts = nil;

	end

end

local resting_session = { -- Resting, not dead

		destroyed = true;

		type = "s2s_destroyed";

		open_stream = function (session)

			session.log("debug", "Attempt to open stream on resting session");

		end;

		close = function (session)

			session.log("debug", "Attempt to close already-closed session");

		end;

		filter = function (type, data) return data; end;

	}; resting_session.__index = resting_session;

function retire_session(session, reason)

	local log = session.log or log;

	for k in pairs(session) do

		if k ~= "trace" and k ~= "log" and k ~= "id" then

			session[k] = nil;

		end

	end

	session.destruction_reason = reason;

	function session.send(data) log("debug", "Discarding data sent to resting session: %s", tostring(data)); end

	function session.data(data) log("debug", "Discarding data received from resting session: %s", tostring(data)); end

	return setmetatable(session, resting_session);

end

function destroy_session(session, reason)

	if session.destroyed then return; end

	(session.log or log)("info", "Destroying "..tostring(session.direction).." session "..tostring(session.from_host).."->"..tostring(session.to_host));

	if session.direction == "outgoing" then

		hosts[session.from_host].s2sout[session.to_host] = nil;

		bounce_sendq(session, reason);

	elseif session.direction == "incoming" then

		incoming_s2s[session] = nil;

	end

	local event_data = { session = session, reason = reason };

	if session.type == "s2sout" then

		prosody.events.fire_event("s2sout-destroyed", event_data);

		if hosts[session.from_host] then

			hosts[session.from_host].events.fire_event("s2sout-destroyed", event_data);

		end

	elseif session.type == "s2sin" then

		prosody.events.fire_event("s2sin-destroyed", event_data);

		if hosts[session.to_host] then

			hosts[session.to_host].events.fire_event("s2sin-destroyed", event_data);

		end

	end

	retire_session(session, reason); -- Clean session until it is GC'd

	return true;

end

return _M;