aboutsummaryrefslogtreecommitdiffstats
path: root/core/s2smanager.lua
blob: acb0baebbdf6aa066ee5292980b5583f3c78e403 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
-- 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, type, error, tonumber, setmetatable
    = tostring, pairs, ipairs, getmetatable, newproxy, type, 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 st = require "stanza";
local stanza = st.stanza;
local nameprep = require "util.encodings".stringprep.nameprep;
local cert_verify_identity = require "util.x509".verify_identity;
local new_ip = require "util.ip".new_ip;
local rfc3484_dest = require "util.rfc3484".destination;

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;
local sources;

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];
			if reply and not(reply.attr.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("Server-to-server 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), data.attr.type ~= "error" and data.attr.type ~= "result" and st.reply(data)});
			else host.sendq = { {tostring(data), data.attr.type ~= "error" and data.attr.type ~= "result" and 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), data.attr.type ~= "error" and data.attr.type ~= "result" and 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)("debug", "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
				if #srv_hosts == 1 and srv_hosts[1].target == "." then
					log("debug", to_host.." does not provide a XMPP service");
					destroy_session(host_session, err); -- Nothing to see here
					return;
				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.ip_hosts then
		return try_connect(host_session, connect_host, connect_port, err);
	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_next_ip(host_session)
	host_session.connecting = nil;
	host_session.ip_choice = host_session.ip_choice + 1;
	local ip = host_session.ip_hosts[host_session.ip_choice];
	local ok, err= make_connect(host_session, ip.ip, ip.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
end

function try_connect(host_session, connect_host, connect_port, err)
	host_session.connecting = true;

	if not err then
		local IPs = {};
		host_session.ip_hosts = IPs;
		local handle4, handle6;
		local has_other = false;

		if not sources then
			sources =  {};
			local cfg_sources = config.get("*", "core", "interface") or connlisteners_get("xmppserver").default_interface;
			if type(cfg_sources) == "string" then
				cfg_sources = { cfg_sources };
			end
			for i, source in ipairs(cfg_sources) do
				if source == "*" then
					sources[i] = new_ip("0.0.0.0", "IPv4");
				else
					sources[i] = new_ip(source, (source:find(":") and "IPv6") or "IPv4");
				end
			end
		end

		handle4 = adns.lookup(function (reply, err)
			handle4 = 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
				for _, ip in ipairs(reply) do
					log("debug", "DNS reply for %s gives us %s", connect_host, ip.a);
					IPs[#IPs+1] = new_ip(ip.a, "IPv4");
				end
			end

			if has_other then
				if #IPs > 0 then
					rfc3484_dest(host_session.ip_hosts, sources);
					for i = 1, #IPs do
						IPs[i] = {ip = IPs[i], port = connect_port};
					end
					host_session.ip_choice = 0;
					try_next_ip(host_session);
				else
					log("debug", "DNS lookup failed to get a response for %s", connect_host);
					host_session.ip_hosts = nil;
					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
			else
				has_other = true;
			end
		end, connect_host, "A", "IN");

		handle6 = adns.lookup(function (reply, err)
			handle6 = nil;

			if reply and reply[#reply] and reply[#reply].aaaa then
				for _, ip in ipairs(reply) do
					log("debug", "DNS reply for %s gives us %s", connect_host, ip.aaaa);
					IPs[#IPs+1] = new_ip(ip.aaaa, "IPv6");
				end
			end

			if has_other then
				if #IPs > 0 then
					rfc3484_dest(host_session.ip_hosts, sources);
					for i = 1, #IPs do
						IPs[i] = {ip = IPs[i], port = connect_port};
					end
					host_session.ip_choice = 0;
					try_next_ip(host_session);
				else
					log("debug", "DNS lookup failed to get a response for %s", connect_host);
					host_session.ip_hosts = nil;
					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
			else
				has_other = true;
			end
		end, connect_host, "AAAA", "IN");

		return true;
	elseif host_session.ip_hosts and #host_session.ip_hosts > host_session.ip_choice then -- Not our first attempt, and we also have IPs left to try
		try_next_ip(host_session);
	else
		host_session.ip_hosts = nil;
		if not attempt_connection(host_session, "out of IP addresses") 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, "Connecting failed"..err); -- End of the line, we can't
			return false;
		end
	end

	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.addr, 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;
	if connect_host.proto == "IPv4" then
		conn, handler = socket.tcp();
	elseif socket.tcp6 then
		conn, handler = socket.tcp6();
	end
	
	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.addr, 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.addr, connect_port, err);
		return false, err;
	end
	
	local cl = connlisteners_get("xmppserver");
	conn = wrapclient(conn, connect_host.addr, 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, errors = conn:getpeerverification()
		-- Is there any interest in printing out all/the number of errors here?
		if not chain_valid then
			(session.log or log)("debug", "certificate chain validation result: invalid");
			session.cert_chain_status = "invalid";
		else
			(session.log or log)("debug", "certificate chain validation result: valid");
			session.cert_chain_status = "valid";

			local host;
			if session.direction == "incoming" then
				host = session.from_host;
			else
				host = session.to_host;
			end

			-- 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 %s", st.stanza("stream:stream", attr):top_tag());
		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 for %s", session.from_host or "(unknown)", session.to_host or "(unknown)", host);
	
	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)("debug", "Destroying "..tostring(session.direction).." session "..tostring(session.from_host).."->"..tostring(session.to_host)..(reason and (": "..reason) or ""));
	
	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;