aboutsummaryrefslogtreecommitdiff
path: root/common.c
blob: 1d6c1f773b25138701216b805ee90ff606cc145a (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
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
/*
 * common.c: common functionality
 *
 * Copyright (c) 2014 - 2015, Přemysl Janouch <p.janouch@gmail.com>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 */

#define LIBERTY_WANT_SSL
#define LIBERTY_WANT_ASYNC
#define LIBERTY_WANT_POLLER
#define LIBERTY_WANT_PROTO_IRC

#ifdef WANT_SYSLOG_LOGGING
	#define print_fatal_data    ((void *) LOG_ERR)
	#define print_error_data    ((void *) LOG_ERR)
	#define print_warning_data  ((void *) LOG_WARNING)
	#define print_status_data   ((void *) LOG_INFO)
	#define print_debug_data    ((void *) LOG_DEBUG)
#endif // WANT_SYSLOG_LOGGING

#include "liberty/liberty.c"
#include <arpa/inet.h>
#include <netinet/tcp.h>

static void
init_openssl (void)
{
#if OPENSSL_VERSION_NUMBER < 0x10100000L || LIBRESSL_VERSION_NUMBER
	SSL_library_init ();
	// XXX: this list is probably not complete
	atexit (EVP_cleanup);
	SSL_load_error_strings ();
	atexit (ERR_free_strings);
#else
	// Cleanup is done automatically via atexit()
	OPENSSL_init_ssl (0, NULL);
#endif
}

// --- To be moved to liberty --------------------------------------------------

static ssize_t
str_vector_find (const struct str_vector *v, const char *s)
{
	for (size_t i = 0; i < v->len; i++)
		if (!strcmp (v->vector[i], s))
			return i;
	return -1;
}

static time_t
unixtime_msec (long *msec)
{
#ifdef _POSIX_TIMERS
        struct timespec tp;
        hard_assert (clock_gettime (CLOCK_REALTIME, &tp) != -1);
        *msec = tp.tv_nsec / 1000000;
#else // ! _POSIX_TIMERS
        struct timeval tp;
        hard_assert (gettimeofday (&tp, NULL) != -1);
        *msec = tp.tv_usec / 1000;
#endif // ! _POSIX_TIMERS
        return tp.tv_sec;
}

/// This differs from the non-unique version in that we expect the filename
/// to be something like a pattern for mkstemp(), so the resulting path can
/// reside in a system-wide directory with no risk of a conflict.
static char *
resolve_relative_runtime_unique_filename (const char *filename)
{
	struct str path;
	str_init (&path);

	const char *runtime_dir = getenv ("XDG_RUNTIME_DIR");
	const char *tmpdir = getenv ("TMPDIR");
	if (runtime_dir && *runtime_dir == '/')
		str_append (&path, runtime_dir);
	else if (tmpdir && *tmpdir == '/')
		str_append (&path, tmpdir);
	else
		str_append (&path, "/tmp");
	str_append_printf (&path, "/%s/%s", PROGRAM_NAME, filename);

	// Try to create the file's ancestors;
	// typically the user will want to immediately create a file in there
	const char *last_slash = strrchr (path.str, '/');
	if (last_slash && last_slash != path.str)
	{
		char *copy = xstrndup (path.str, last_slash - path.str);
		(void) mkdir_with_parents (copy, NULL);
		free (copy);
	}
	return str_steal (&path);
}

static bool
xwrite (int fd, const char *data, size_t len, struct error **e)
{
	size_t written = 0;
	while (written < len)
	{
		ssize_t res = write (fd, data + written, len - written);
		if (res >= 0)
			written += res;
		else if (errno != EINTR)
			return error_set (e, "%s", strerror (errno));
	}
	return true;
}

// --- Logging -----------------------------------------------------------------

static void
log_message_syslog (void *user_data, const char *quote, const char *fmt,
	va_list ap)
{
	int prio = (int) (intptr_t) user_data;

	va_list va;
	va_copy (va, ap);
	int size = vsnprintf (NULL, 0, fmt, va);
	va_end (va);
	if (size < 0)
		return;

	char buf[size + 1];
	if (vsnprintf (buf, sizeof buf, fmt, ap) >= 0)
		syslog (prio, "%s%s", quote, buf);
}

// --- SOCKS 5/4a --------------------------------------------------------------

// Asynchronous SOCKS connector.  Adds more stuff on top of the regular one.

// Note that the `username' is used differently in SOCKS 4a and 5.  In the
// former version, it is the username that you can get ident'ed against.
// In the latter version, it forms a pair with the password field and doesn't
// need to be an actual user on your machine.

struct socks_addr
{
	enum socks_addr_type
	{
		SOCKS_IPV4 = 1,                 ///< IPv4 address
		SOCKS_DOMAIN = 3,               ///< Domain name to be resolved
		SOCKS_IPV6 = 4                  ///< IPv6 address
	}
	type;                               ///< The type of this address
	union
	{
		uint8_t ipv4[4];                ///< IPv4 address, network octet order
		char *domain;                   ///< Domain name
		uint8_t ipv6[16];               ///< IPv6 address, network octet order
	}
	data;                               ///< The address itself
};

static void
socks_addr_free (struct socks_addr *self)
{
	if (self->type == SOCKS_DOMAIN)
		free (self->data.domain);
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

struct socks_target
{
	LIST_HEADER (struct socks_target)

	char *address_str;                  ///< Target address as a string
	struct socks_addr address;          ///< Target address
	uint16_t port;                      ///< Target service port
};

enum socks_protocol
{
	SOCKS_5,                            ///< SOCKS5
	SOCKS_4A,                           ///< SOCKS4A
	SOCKS_MAX                           ///< End of protocol
};

static inline const char *
socks_protocol_to_string (enum socks_protocol self)
{
	switch (self)
	{
	case SOCKS_5:   return "SOCKS5";
	case SOCKS_4A:  return "SOCKS4A";
	default:        return NULL;
	}
}

struct socks_connector
{
	struct connector *connector;        ///< Proxy server iterator (effectively)
	enum socks_protocol protocol_iter;  ///< Protocol iterator
	struct socks_target *targets_iter;  ///< Targets iterator

	// Negotiation:

	struct poller_timer timeout;        ///< Timeout timer

	int socket_fd;                      ///< Current socket file descriptor
	struct poller_fd socket_event;      ///< Socket can be read from/written to
	struct str read_buffer;             ///< Read buffer
	struct str write_buffer;            ///< Write buffer

	bool done;                          ///< Tunnel succesfully established
	uint8_t bound_address_len;          ///< Length of domain name
	size_t data_needed;                 ///< How much data "on_data" needs

	/// Process incoming data if there's enough of it available
	bool (*on_data) (struct socks_connector *, struct msg_unpacker *);

	// Configuration:

	char *hostname;                     ///< SOCKS server hostname
	char *service;                      ///< SOCKS server service name or port

	char *username;                     ///< Username for authentication
	char *password;                     ///< Password for authentication

	struct socks_target *targets;       ///< Targets
	struct socks_target *targets_tail;  ///< Tail of targets

	void *user_data;                    ///< User data for callbacks

	// Additional results:

	struct socks_addr bound_address;    ///< Bound address at the server
	uint16_t bound_port;                ///< Bound port at the server

	// You may destroy the connector object in these two main callbacks:

	/// Connection has been successfully established
	void (*on_connected) (void *user_data, int socket, const char *hostname);
	/// Failed to establish a connection to either target
	void (*on_failure) (void *user_data);

	// Optional:

	/// Connecting to a new address
	void (*on_connecting) (void *user_data,
		const char *address, const char *via, const char *version);
	/// Connecting to the last address has failed
	void (*on_error) (void *user_data, const char *error);
};

// I've tried to make the actual protocol handlers as simple as possible

#define SOCKS_FAIL(...)                                                        \
	BLOCK_START                                                                \
		char *error = xstrdup_printf (__VA_ARGS__);                            \
		if (self->on_error)                                                    \
			self->on_error (self->user_data, error);                           \
		free (error);                                                          \
		return false;                                                          \
	BLOCK_END

#define SOCKS_DATA_CB(name) static bool name                                   \
	(struct socks_connector *self, struct msg_unpacker *unpacker)

#define SOCKS_GO(name, data_needed_)                                           \
	self->on_data = name;                                                      \
	self->data_needed = data_needed_;                                          \
	return true

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

SOCKS_DATA_CB (socks_4a_finish)
{
	uint8_t null, status;
	hard_assert (msg_unpacker_u8 (unpacker, &null));
	hard_assert (msg_unpacker_u8 (unpacker, &status));

	if (null != 0)
		SOCKS_FAIL ("protocol error");

	switch (status)
	{
	case 90:
		self->done = true;
		return false;
	case 91:
		SOCKS_FAIL ("request rejected or failed");
	case 92:
		SOCKS_FAIL ("%s: %s", "request rejected",
			"SOCKS server cannot connect to identd on the client");
	case 93:
		SOCKS_FAIL ("%s: %s", "request rejected",
			"identd reports different user-id");
	default:
		SOCKS_FAIL ("protocol error");
	}
}

static bool
socks_4a_start (struct socks_connector *self)
{
	struct socks_target *target = self->targets_iter;
	const void *dest_ipv4 = "\x00\x00\x00\x01";
	const char *dest_domain = NULL;

	char buf[INET6_ADDRSTRLEN];
	switch (target->address.type)
	{
	case SOCKS_IPV4:
		dest_ipv4 = target->address.data.ipv4;
		break;
	case SOCKS_IPV6:
		// About the best thing we can do, not sure if it works anywhere at all
		if (!inet_ntop (AF_INET6, &target->address.data.ipv6, buf, sizeof buf))
			SOCKS_FAIL ("%s: %s", "inet_ntop", strerror (errno));
		dest_domain = buf;
		break;
	case SOCKS_DOMAIN:
		dest_domain = target->address.data.domain;
	}

	struct str *wb = &self->write_buffer;
	str_pack_u8 (wb, 4);                  // version
	str_pack_u8 (wb, 1);                  // connect

	str_pack_u16 (wb, target->port);      // port
	str_append_data (wb, dest_ipv4, 4);   // destination address

	if (self->username)
		str_append (wb, self->username);
	str_append_c (wb, '\0');

	if (dest_domain)
	{
		str_append (wb, dest_domain);
		str_append_c (wb, '\0');
	}

	SOCKS_GO (socks_4a_finish, 8);
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

SOCKS_DATA_CB (socks_5_request_port)
{
	hard_assert (msg_unpacker_u16 (unpacker, &self->bound_port));
	self->done = true;
	return false;
}

SOCKS_DATA_CB (socks_5_request_ipv4)
{
	memcpy (self->bound_address.data.ipv4, unpacker->data, unpacker->len);
	SOCKS_GO (socks_5_request_port, 2);
}

SOCKS_DATA_CB (socks_5_request_ipv6)
{
	memcpy (self->bound_address.data.ipv6, unpacker->data, unpacker->len);
	SOCKS_GO (socks_5_request_port, 2);
}

SOCKS_DATA_CB (socks_5_request_domain_data)
{
	self->bound_address.data.domain = xstrndup (unpacker->data, unpacker->len);
	SOCKS_GO (socks_5_request_port, 2);
}

SOCKS_DATA_CB (socks_5_request_domain)
{
	hard_assert (msg_unpacker_u8 (unpacker, &self->bound_address_len));
	SOCKS_GO (socks_5_request_domain_data, self->bound_address_len);
}

SOCKS_DATA_CB (socks_5_request_finish)
{
	uint8_t version, status, reserved, type;
	hard_assert (msg_unpacker_u8 (unpacker, &version));
	hard_assert (msg_unpacker_u8 (unpacker, &status));
	hard_assert (msg_unpacker_u8 (unpacker, &reserved));
	hard_assert (msg_unpacker_u8 (unpacker, &type));

	if (version != 0x05)
		SOCKS_FAIL ("protocol error");

	switch (status)
	{
	case 0x00:
		break;
	case 0x01:  SOCKS_FAIL ("general SOCKS server failure");
	case 0x02:  SOCKS_FAIL ("connection not allowed by ruleset");
	case 0x03:  SOCKS_FAIL ("network unreachable");
	case 0x04:  SOCKS_FAIL ("host unreachable");
	case 0x05:  SOCKS_FAIL ("connection refused");
	case 0x06:  SOCKS_FAIL ("TTL expired");
	case 0x07:  SOCKS_FAIL ("command not supported");
	case 0x08:  SOCKS_FAIL ("address type not supported");
	default:    SOCKS_FAIL ("protocol error");
	}

	switch ((self->bound_address.type = type))
	{
	case SOCKS_IPV4:
		SOCKS_GO (socks_5_request_ipv4, sizeof self->bound_address.data.ipv4);
	case SOCKS_IPV6:
		SOCKS_GO (socks_5_request_ipv6, sizeof self->bound_address.data.ipv6);
	case SOCKS_DOMAIN:
		SOCKS_GO (socks_5_request_domain, 1);
	default:
		SOCKS_FAIL ("protocol error");
	}
}

static bool
socks_5_request_start (struct socks_connector *self)
{
	struct socks_target *target = self->targets_iter;
	struct str *wb = &self->write_buffer;
	str_pack_u8 (wb, 0x05);  // version
	str_pack_u8 (wb, 0x01);  // connect
	str_pack_u8 (wb, 0x00);  // reserved
	str_pack_u8 (wb, target->address.type);

	switch (target->address.type)
	{
	case SOCKS_IPV4:
		str_append_data (wb,
			target->address.data.ipv4, sizeof target->address.data.ipv4);
		break;
	case SOCKS_DOMAIN:
	{
		size_t dlen = strlen (target->address.data.domain);
		if (dlen > 255)
			dlen = 255;

		str_pack_u8 (wb, dlen);
		str_append_data (wb, target->address.data.domain, dlen);
		break;
	}
	case SOCKS_IPV6:
		str_append_data (wb,
			target->address.data.ipv6, sizeof target->address.data.ipv6);
		break;
	}
	str_pack_u16 (wb, target->port);

	SOCKS_GO (socks_5_request_finish, 4);
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

SOCKS_DATA_CB (socks_5_userpass_finish)
{
	uint8_t version, status;
	hard_assert (msg_unpacker_u8 (unpacker, &version));
	hard_assert (msg_unpacker_u8 (unpacker, &status));

	if (version != 0x01)
		SOCKS_FAIL ("protocol error");
	if (status != 0x00)
		SOCKS_FAIL ("authentication failure");

	return socks_5_request_start (self);
}

static bool
socks_5_userpass_start (struct socks_connector *self)
{
	size_t ulen = strlen (self->username);
	if (ulen > 255)
		ulen = 255;

	size_t plen = strlen (self->password);
	if (plen > 255)
		plen = 255;

	struct str *wb = &self->write_buffer;
	str_pack_u8 (wb, 0x01);  // version
	str_pack_u8 (wb, ulen);  // username length
	str_append_data (wb, self->username, ulen);
	str_pack_u8 (wb, plen);  // password length
	str_append_data (wb, self->password, plen);

	SOCKS_GO (socks_5_userpass_finish, 2);
}

SOCKS_DATA_CB (socks_5_auth_finish)
{
	uint8_t version, method;
	hard_assert (msg_unpacker_u8 (unpacker, &version));
	hard_assert (msg_unpacker_u8 (unpacker, &method));

	if (version != 0x05)
		SOCKS_FAIL ("protocol error");

	bool can_auth = self->username && self->password;

	switch (method)
	{
	case 0x02:
		if (!can_auth)
			SOCKS_FAIL ("protocol error");

		return socks_5_userpass_start (self);
	case 0x00:
		return socks_5_request_start (self);
	case 0xFF:
		SOCKS_FAIL ("no acceptable authentication methods");
	default:
		SOCKS_FAIL ("protocol error");
	}
}

static bool
socks_5_auth_start (struct socks_connector *self)
{
	bool can_auth = self->username && self->password;

	struct str *wb = &self->write_buffer;
	str_pack_u8 (wb, 0x05);          // version
	str_pack_u8 (wb, 1 + can_auth);  // number of authentication methods
	str_pack_u8 (wb, 0x00);          // no authentication required
	if (can_auth)
		str_pack_u8 (wb, 0x02);      // username/password

	SOCKS_GO (socks_5_auth_finish, 2);
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

static void socks_connector_start (struct socks_connector *self);

static void
socks_connector_destroy_connector (struct socks_connector *self)
{
	if (self->connector)
	{
		connector_free (self->connector);
		free (self->connector);
		self->connector = NULL;
	}
}

static void
socks_connector_cancel_events (struct socks_connector *self)
{
	// Before calling the final callbacks, we should cancel events that
	// could potentially fire; caller should destroy us immediately, though
	poller_fd_reset (&self->socket_event);
	poller_timer_reset (&self->timeout);
}

static void
socks_connector_fail (struct socks_connector *self)
{
	socks_connector_cancel_events (self);
	self->on_failure (self->user_data);
}

static bool
socks_connector_step_iterators (struct socks_connector *self)
{
	// At the lowest level we iterate over all addresses for the SOCKS server
	// and just try to connect; this is done automatically by the connector

	// Then we iterate over available protocols
	if (++self->protocol_iter != SOCKS_MAX)
		return true;

	// At the highest level we iterate over possible targets
	self->protocol_iter = 0;
	if (self->targets_iter && (self->targets_iter = self->targets_iter->next))
		return true;

	return false;
}

static void
socks_connector_step (struct socks_connector *self)
{
	if (self->socket_fd != -1)
	{
		poller_fd_reset (&self->socket_event);
		xclose (self->socket_fd);
		self->socket_fd = -1;
	}

	socks_connector_destroy_connector (self);
	if (socks_connector_step_iterators (self))
		socks_connector_start (self);
	else
		socks_connector_fail (self);
}

static void
socks_connector_on_timeout (struct socks_connector *self)
{
	if (self->on_error)
		self->on_error (self->user_data, "timeout");

	socks_connector_destroy_connector (self);
	socks_connector_fail (self);
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

static void
socks_connector_on_connected
	(void *user_data, int socket_fd, const char *hostname)
{
	set_blocking (socket_fd, false);
	(void) hostname;

	struct socks_connector *self = user_data;
	self->socket_fd = socket_fd;
	self->socket_event.fd = socket_fd;
	poller_fd_set (&self->socket_event, POLLIN | POLLOUT);
	str_reset (&self->read_buffer);
	str_reset (&self->write_buffer);

	if (!(self->protocol_iter == SOCKS_5  && socks_5_auth_start (self))
	 && !(self->protocol_iter == SOCKS_4A && socks_4a_start     (self)))
		socks_connector_fail (self);
}

static void
socks_connector_on_failure (void *user_data)
{
	struct socks_connector *self = user_data;
	// TODO: skip SOCKS server on connection failure
	socks_connector_step (self);
}

static void
socks_connector_on_connecting (void *user_data, const char *via)
{
	struct socks_connector *self = user_data;
	if (!self->on_connecting)
		return;

	struct socks_target *target = self->targets_iter;
	char *port = xstrdup_printf ("%u", target->port);
	char *address = format_host_port_pair (target->address_str, port);
	free (port);
	self->on_connecting (self->user_data, address, via,
		socks_protocol_to_string (self->protocol_iter));
	free (address);
}

static void
socks_connector_on_error (void *user_data, const char *error)
{
	struct socks_connector *self = user_data;
	// TODO: skip protocol on protocol failure
	if (self->on_error)
		self->on_error (self->user_data, error);
}

static void
socks_connector_start (struct socks_connector *self)
{
	hard_assert (!self->connector);

	struct connector *connector =
		self->connector = xcalloc (1, sizeof *connector);
	connector_init (connector, self->socket_event.poller);

	connector->user_data     = self;
	connector->on_connected  = socks_connector_on_connected;
	connector->on_connecting = socks_connector_on_connecting;
	connector->on_error      = socks_connector_on_error;
	connector->on_failure    = socks_connector_on_failure;

	connector_add_target (connector, self->hostname, self->service);
	poller_timer_set (&self->timeout, 60 * 1000);
	self->done = false;

	self->bound_port = 0;
	socks_addr_free (&self->bound_address);
	memset (&self->bound_address, 0, sizeof self->bound_address);
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

static bool
socks_try_fill_read_buffer (struct socks_connector *self, size_t n)
{
	ssize_t remains = (ssize_t) n - (ssize_t) self->read_buffer.len;
	if (remains <= 0)
		return true;

	ssize_t received;
	str_ensure_space (&self->read_buffer, remains);
	do
		received = recv (self->socket_fd,
			self->read_buffer.str + self->read_buffer.len, remains, 0);
	while ((received == -1) && errno == EINTR);

	if (received == 0)
		SOCKS_FAIL ("%s: %s", "protocol error", "unexpected EOF");
	if (received == -1 && errno != EAGAIN)
		SOCKS_FAIL ("%s: %s", "recv", strerror (errno));
	if (received > 0)
		self->read_buffer.len += received;
	return true;
}

static bool
socks_call_on_data (struct socks_connector *self)
{
	size_t to_consume = self->data_needed;
	if (!socks_try_fill_read_buffer (self, to_consume))
		return false;
	if (self->read_buffer.len < to_consume)
		return true;

	struct msg_unpacker unpacker;
	msg_unpacker_init (&unpacker, self->read_buffer.str, self->read_buffer.len);
	bool result = self->on_data (self, &unpacker);
	str_remove_slice (&self->read_buffer, 0, to_consume);
	return result;
}

static bool
socks_try_flush_write_buffer (struct socks_connector *self)
{
	struct str *wb = &self->write_buffer;
	ssize_t n_written;

	while (wb->len)
	{
		n_written = send (self->socket_fd, wb->str, wb->len, 0);
		if (n_written >= 0)
		{
			str_remove_slice (wb, 0, n_written);
			continue;
		}

		if (errno == EAGAIN)
			break;
		if (errno == EINTR)
			continue;

		SOCKS_FAIL ("%s: %s", "send", strerror (errno));
	}
	return true;
}

static void
socks_connector_on_ready
	(const struct pollfd *pfd, struct socks_connector *self)
{
	(void) pfd;

	if (socks_call_on_data (self) && socks_try_flush_write_buffer (self))
	{
		poller_fd_set (&self->socket_event,
			self->write_buffer.len ? (POLLIN | POLLOUT) : POLLIN);
	}
	else if (self->done)
	{
		socks_connector_cancel_events (self);

		int fd = self->socket_fd;
		self->socket_fd = -1;

		struct socks_target *target = self->targets_iter;
		set_blocking (fd, true);
		self->on_connected (self->user_data, fd, target->address_str);
	}
	else
		// We've failed this target, let's try to move on
		socks_connector_step (self);
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

static void
socks_connector_init (struct socks_connector *self, struct poller *poller)
{
	memset (self, 0, sizeof *self);

	poller_fd_init (&self->socket_event, poller, (self->socket_fd = -1));
	self->socket_event.dispatcher = (poller_fd_fn) socks_connector_on_ready;
	self->socket_event.user_data = self;

	poller_timer_init (&self->timeout, poller);
	self->timeout.dispatcher = (poller_timer_fn) socks_connector_on_timeout;
	self->timeout.user_data = self;

	str_init (&self->read_buffer);
	str_init (&self->write_buffer);
}

static void
socks_connector_free (struct socks_connector *self)
{
	socks_connector_destroy_connector (self);
	socks_connector_cancel_events (self);

	if (self->socket_fd != -1)
		xclose (self->socket_fd);

	str_free (&self->read_buffer);
	str_free (&self->write_buffer);

	free (self->hostname);
	free (self->service);
	free (self->username);
	free (self->password);

	LIST_FOR_EACH (struct socks_target, iter, self->targets)
	{
		socks_addr_free (&iter->address);
		free (iter->address_str);
		free (iter);
	}

	socks_addr_free (&self->bound_address);
}

static bool
socks_connector_add_target (struct socks_connector *self,
	const char *host, const char *service, struct error **e)
{
	unsigned long port;
	const struct servent *serv;
	if ((serv = getservbyname (service, "tcp")))
		port = (uint16_t) ntohs (serv->s_port);
	else if (!xstrtoul (&port, service, 10) || !port || port > UINT16_MAX)
	{
		error_set (e, "invalid port number");
		return false;
	}

	struct socks_target *target = xcalloc (1, sizeof *target);
	if      (inet_pton (AF_INET,  host, &target->address.data.ipv4) == 1)
		target->address.type = SOCKS_IPV4;
	else if (inet_pton (AF_INET6, host, &target->address.data.ipv6) == 1)
		target->address.type = SOCKS_IPV6;
	else
	{
		target->address.type = SOCKS_DOMAIN;
		target->address.data.domain = xstrdup (host);
	}

	target->port = port;
	target->address_str = xstrdup (host);
	LIST_APPEND_WITH_TAIL (self->targets, self->targets_tail, target);
	return true;
}

static void
socks_connector_run (struct socks_connector *self,
	const char *host, const char *service,
	const char *username, const char *password)
{
	hard_assert (self->targets);
	hard_assert (host && service);

	self->hostname = xstrdup (host);
	self->service  = xstrdup (service);

	if (username)  self->username = xstrdup (username);
	if (password)  self->password = xstrdup (password);

	self->targets_iter = self->targets;
	self->protocol_iter = 0;
	// XXX: this can fail immediately from an error creating the connector
	socks_connector_start (self);
}

// --- CTCP decoding -----------------------------------------------------------

#define CTCP_M_QUOTE '\020'
#define CTCP_X_DELIM '\001'
#define CTCP_X_QUOTE '\\'

struct ctcp_chunk
{
	LIST_HEADER (struct ctcp_chunk)

	bool is_extended;                   ///< Is this a tagged extended message?
	bool is_partial;                    ///< Unterminated extended message
	struct str tag;                     ///< The tag, if any
	struct str text;                    ///< Message contents
};

static struct ctcp_chunk *
ctcp_chunk_new (void)
{
	struct ctcp_chunk *self = xcalloc (1, sizeof *self);
	str_init (&self->tag);
	str_init (&self->text);
	return self;
}

static void
ctcp_chunk_destroy (struct ctcp_chunk *self)
{
	str_free (&self->tag);
	str_free (&self->text);
	free (self);
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

static void
ctcp_low_level_decode (const char *message, struct str *output)
{
	bool escape = false;
	for (const char *p = message; *p; p++)
	{
		if (escape)
		{
			switch (*p)
			{
			case '0': str_append_c (output, '\0'); break;
			case 'r': str_append_c (output, '\r'); break;
			case 'n': str_append_c (output, '\n'); break;
			default:  str_append_c (output, *p);
			}
			escape = false;
		}
		else if (*p == CTCP_M_QUOTE)
			escape = true;
		else
			str_append_c (output, *p);
	}
}

static void
ctcp_intra_decode (const char *chunk, size_t len, struct str *output)
{
	bool escape = false;
	for (size_t i = 0; i < len; i++)
	{
		char c = chunk[i];
		if (escape)
		{
			if (c == 'a')
				str_append_c (output, CTCP_X_DELIM);
			else
				str_append_c (output, c);
			escape = false;
		}
		else if (c == CTCP_X_QUOTE)
			escape = true;
		else
			str_append_c (output, c);
	}
}

// According to the original CTCP specification we should use
// ctcp_intra_decode() on all parts, however no one seems to use that
// and it breaks normal text with backslashes
#ifndef SUPPORT_CTCP_X_QUOTES
#define ctcp_intra_decode(s, len, output) str_append_data (output, s, len)
#endif

static void
ctcp_parse_tagged (const char *chunk, size_t len, struct ctcp_chunk *output)
{
	// We may search for the space before doing the higher level decoding,
	// as it doesn't concern space characters at all
	size_t tag_end = len;
	for (size_t i = 0; i < len; i++)
		if (chunk[i] == ' ')
		{
			tag_end = i;
			break;
		}

	output->is_extended = true;
	ctcp_intra_decode (chunk, tag_end, &output->tag);
	if (tag_end++ != len)
		ctcp_intra_decode (chunk + tag_end, len - tag_end, &output->text);
}

static struct ctcp_chunk *
ctcp_parse (const char *message)
{
	struct str m;
	str_init (&m);
	ctcp_low_level_decode (message, &m);

	struct ctcp_chunk *result = NULL, *result_tail = NULL;

	size_t start = 0;
	bool in_ctcp = false;
	for (size_t i = 0; i < m.len; i++)
	{
		char c = m.str[i];
		if (c != CTCP_X_DELIM)
			continue;

		// Remember the current state
		size_t my_start = start;
		bool my_is_ctcp = in_ctcp;

		start = i + 1;
		in_ctcp = !in_ctcp;

		// Skip empty chunks
		if (my_start == i)
			continue;

		struct ctcp_chunk *chunk = ctcp_chunk_new ();
		if (my_is_ctcp)
			ctcp_parse_tagged (m.str + my_start, i - my_start, chunk);
		else
			ctcp_intra_decode (m.str + my_start, i - my_start, &chunk->text);
		LIST_APPEND_WITH_TAIL (result, result_tail, chunk);
	}

	// Finish the last part.  Unended tagged chunks are marked as such.
	if (start != m.len)
	{
		struct ctcp_chunk *chunk = ctcp_chunk_new ();
		if (in_ctcp)
		{
			ctcp_parse_tagged (m.str + start, m.len - start, chunk);
			chunk->is_partial = true;
		}
		else
			ctcp_intra_decode (m.str + start, m.len - start, &chunk->text);
		LIST_APPEND_WITH_TAIL (result, result_tail, chunk);
	}

	str_free (&m);
	return result;
}

static void
ctcp_destroy (struct ctcp_chunk *list)
{
	LIST_FOR_EACH (struct ctcp_chunk, iter, list)
		ctcp_chunk_destroy (iter);
}