summaryrefslogtreecommitdiff
path: root/channels.c
blob: 853d34ba2c8d76c691280749279f027c66ae87bd (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
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
/*

channels.c

Author: Tatu Ylonen <ylo@cs.hut.fi>

Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
                   All rights reserved

Created: Fri Mar 24 16:35:24 1995 ylo

This file contains functions for generic socket connection forwarding.
There is also code for initiating connection forwarding for X11 connections,
arbitrary tcp/ip connections, and the authentication agent connection.

*/

#include "includes.h"
RCSID("$Id: channels.c,v 1.1.1.1 1999/10/27 03:42:44 damien Exp $");

#include "ssh.h"
#include "packet.h"
#include "xmalloc.h"
#include "buffer.h"
#include "authfd.h"
#include "uidswap.h"
#include "servconf.h"

#include "channels.h"
#include "nchan.h"
#include "compat.h"

/* Maximum number of fake X11 displays to try. */
#define MAX_DISPLAYS  1000

/* Max len of agent socket */
#define MAX_SOCKET_NAME 100

/* Pointer to an array containing all allocated channels.  The array is
   dynamically extended as needed. */
static Channel *channels = NULL;

/* Size of the channel array.  All slots of the array must always be
   initialized (at least the type field); unused slots are marked with
   type SSH_CHANNEL_FREE. */
static int channels_alloc = 0;

/* Maximum file descriptor value used in any of the channels.  This is updated
   in channel_allocate. */
static int channel_max_fd_value = 0;

/* Name and directory of socket for authentication agent forwarding. */
static char *channel_forwarded_auth_socket_name = NULL;
static char *channel_forwarded_auth_socket_dir  = NULL;

/* Saved X11 authentication protocol name. */
char *x11_saved_proto = NULL;

/* Saved X11 authentication data.  This is the real data. */
char *x11_saved_data = NULL;
unsigned int x11_saved_data_len = 0;

/* Fake X11 authentication data.  This is what the server will be sending
   us; we should replace any occurrences of this by the real data. */
char *x11_fake_data = NULL;
unsigned int x11_fake_data_len;

/* Data structure for storing which hosts are permitted for forward requests.
   The local sides of any remote forwards are stored in this array to prevent
   a corrupt remote server from accessing arbitrary TCP/IP ports on our
   local network (which might be behind a firewall). */
typedef struct
{
  char *host;		/* Host name. */
  int port;		/* Port number. */
} ForwardPermission;

/* List of all permitted host/port pairs to connect. */
static ForwardPermission permitted_opens[SSH_MAX_FORWARDS_PER_DIRECTION];
/* Number of permitted host/port pairs in the array. */
static int num_permitted_opens = 0;
/* If this is true, all opens are permitted.  This is the case on the
   server on which we have to trust the client anyway, and the user could
   do anything after logging in anyway. */
static int all_opens_permitted = 0;

/* This is set to true if both sides support SSH_PROTOFLAG_HOST_IN_FWD_OPEN. */
static int have_hostname_in_open = 0;

/* Sets specific protocol options. */

void channel_set_options(int hostname_in_open)
{
  have_hostname_in_open = hostname_in_open;
}

/* Permits opening to any host/port in SSH_MSG_PORT_OPEN.  This is usually
   called by the server, because the user could connect to any port anyway,
   and the server has no way to know but to trust the client anyway. */

void channel_permit_all_opens()
{
  all_opens_permitted = 1;
}

/* Allocate a new channel object and set its type and socket. 
   This will cause remote_name to be freed. */

int channel_allocate(int type, int sock, char *remote_name)
{
  int i, old_channels;

  /* Update the maximum file descriptor value. */
  if (sock > channel_max_fd_value)
    channel_max_fd_value = sock;

  /* Do initial allocation if this is the first call. */
  if (channels_alloc == 0)
    {
      channels_alloc = 10;
      channels = xmalloc(channels_alloc * sizeof(Channel));
      for (i = 0; i < channels_alloc; i++)
	channels[i].type = SSH_CHANNEL_FREE;

      /* Kludge: arrange a call to channel_stop_listening if we terminate
	 with fatal(). */
      fatal_add_cleanup((void (*)(void *))channel_stop_listening, NULL);
    }

  /* Try to find a free slot where to put the new channel. */
  for (i = 0; i < channels_alloc; i++)
    if (channels[i].type == SSH_CHANNEL_FREE)
      {
	/* Found a free slot.  Initialize the fields and return its number. */
	buffer_init(&channels[i].input);
	buffer_init(&channels[i].output);
	channels[i].self = i;
	channels[i].type = type;
	channels[i].x11 = 0;
	channels[i].sock = sock;
	channels[i].remote_id = -1;
	channels[i].remote_name = remote_name;
        chan_init_iostates(&channels[i]);
	return i;
      }

  /* There are no free slots.  Must expand the array. */
  old_channels = channels_alloc;
  channels_alloc += 10;
  channels = xrealloc(channels, channels_alloc * sizeof(Channel));
  for (i = old_channels; i < channels_alloc; i++)
    channels[i].type = SSH_CHANNEL_FREE;

  /* We know that the next one after the old maximum channel number is now
     available.  Initialize and return its number. */
  buffer_init(&channels[old_channels].input);
  buffer_init(&channels[old_channels].output);
  channels[old_channels].self = old_channels;
  channels[old_channels].type = type;
  channels[old_channels].x11 = 0;
  channels[old_channels].sock = sock;
  channels[old_channels].remote_id = -1;
  channels[old_channels].remote_name = remote_name;
  chan_init_iostates(&channels[old_channels]);
  return old_channels;
}

/* Free the channel and close its socket. */

void channel_free(int channel)
{
  assert(channel >= 0 && channel < channels_alloc &&
	 channels[channel].type != SSH_CHANNEL_FREE);
  if(compat13)
    shutdown(channels[channel].sock, SHUT_RDWR);
  close(channels[channel].sock);
  buffer_free(&channels[channel].input);
  buffer_free(&channels[channel].output);
  channels[channel].type = SSH_CHANNEL_FREE;
  if (channels[channel].remote_name)
    {
      xfree(channels[channel].remote_name);
      channels[channel].remote_name = NULL;
    }
}

/* This is called just before select() to add any bits relevant to
   channels in the select bitmasks. */

void channel_prepare_select(fd_set *readset, fd_set *writeset)
{
  int i;
  Channel *ch;
  unsigned char *ucp;
  unsigned int proto_len, data_len;

  for (i = 0; i < channels_alloc; i++)
    {
      ch = &channels[i];
    redo:
      switch (ch->type)
	{
	case SSH_CHANNEL_X11_LISTENER:
	case SSH_CHANNEL_PORT_LISTENER:
	case SSH_CHANNEL_AUTH_SOCKET:
	  FD_SET(ch->sock, readset);
	  break;

	case SSH_CHANNEL_OPEN:
	  if(compat13){
	    if (buffer_len(&ch->input) < 32768)
	      FD_SET(ch->sock, readset);
	    if (buffer_len(&ch->output) > 0)
	      FD_SET(ch->sock, writeset);
	    break;
	  }
	  /* test whether sockets are 'alive' for read/write */
          if (ch->istate == CHAN_INPUT_OPEN)
            if (buffer_len(&ch->input) < 32768)
              FD_SET(ch->sock, readset);
          if (ch->ostate == CHAN_OUTPUT_OPEN || ch->ostate == CHAN_OUTPUT_WAIT_DRAIN){
            if (buffer_len(&ch->output) > 0){
              FD_SET(ch->sock, writeset);
            }else if(ch->ostate == CHAN_OUTPUT_WAIT_DRAIN) {
              chan_obuf_empty(ch);
            }
          }
          break;

	case SSH_CHANNEL_INPUT_DRAINING:
 	  if (!compat13)
	    fatal("cannot happen: IN_DRAIN");
	  if (buffer_len(&ch->input) == 0)
	    {
	      packet_start(SSH_MSG_CHANNEL_CLOSE);
	      packet_put_int(ch->remote_id);
	      packet_send();
	      ch->type = SSH_CHANNEL_CLOSED;
	      debug("Closing channel %d after input drain.", i);
	      break;
	    }
	  break;

	case SSH_CHANNEL_OUTPUT_DRAINING:
 	  if (!compat13)
	    fatal("cannot happen: OUT_DRAIN");
	  if (buffer_len(&ch->output) == 0)
	    {
	      /* debug("Freeing channel %d after output drain.", i); */
	      channel_free(i);
	      break;
	    }
	  FD_SET(ch->sock, writeset);
	  break;

	case SSH_CHANNEL_X11_OPEN:
	  /* This is a special state for X11 authentication spoofing.  An
	     opened X11 connection (when authentication spoofing is being
	     done) remains in this state until the first packet has been
	     completely read.  The authentication data in that packet is
	     then substituted by the real data if it matches the fake data,
	     and the channel is put into normal mode. */

	  /* Check if the fixed size part of the packet is in buffer. */
	  if (buffer_len(&ch->output) < 12)
	    break;

	  /* Parse the lengths of variable-length fields. */
	  ucp = (unsigned char *)buffer_ptr(&ch->output);
	  if (ucp[0] == 0x42)
	    { /* Byte order MSB first. */
	      proto_len = 256 * ucp[6] + ucp[7];
	      data_len = 256 * ucp[8] + ucp[9];
	    }
	  else
	    if (ucp[0] == 0x6c)
	      { /* Byte order LSB first. */
		proto_len = ucp[6] + 256 * ucp[7];
		data_len = ucp[8] + 256 * ucp[9];
	      }
	    else
	      {
		debug("Initial X11 packet contains bad byte order byte: 0x%x",
		      ucp[0]);
		ch->type = SSH_CHANNEL_OPEN;
		goto reject;
	      }

	  /* Check if the whole packet is in buffer. */
	  if (buffer_len(&ch->output) <
	      12 + ((proto_len + 3) & ~3) + ((data_len + 3) & ~3))
	    break;
	  
	  /* Check if authentication protocol matches. */
	  if (proto_len != strlen(x11_saved_proto) || 
	      memcmp(ucp + 12, x11_saved_proto, proto_len) != 0)
	    {
	      debug("X11 connection uses different authentication protocol.");
	      ch->type = SSH_CHANNEL_OPEN;
	      goto reject;
	    }

	  /* Check if authentication data matches our fake data. */
	  if (data_len != x11_fake_data_len ||
	      memcmp(ucp + 12 + ((proto_len + 3) & ~3),
		     x11_fake_data, x11_fake_data_len) != 0)
	    {
	      debug("X11 auth data does not match fake data.");
	      ch->type = SSH_CHANNEL_OPEN;
	      goto reject;
	    }

	  /* Received authentication protocol and data match our fake data.
	     Substitute the fake data with real data. */
	  assert(x11_fake_data_len == x11_saved_data_len);
	  memcpy(ucp + 12 + ((proto_len + 3) & ~3),
		 x11_saved_data, x11_saved_data_len);

	  /* Start normal processing for the channel. */
	  ch->type = SSH_CHANNEL_OPEN;
	  /* Enable X11 Problem FIX */
	  ch->x11 = 1;
	  goto redo;
	  
	reject:
	  /* We have received an X11 connection that has bad authentication
	     information. */
	  log("X11 connection rejected because of wrong authentication.\r\n");
	  buffer_clear(&ch->input);
	  buffer_clear(&ch->output);
	  if (compat13) {
            close(ch->sock);
            ch->sock = -1;
            ch->type = SSH_CHANNEL_CLOSED;
            packet_start(SSH_MSG_CHANNEL_CLOSE);
            packet_put_int(ch->remote_id);
            packet_send();
          }else{
	    debug("X11 rejected %d 0x%x 0x%x", ch->self, ch->istate, ch->ostate);
	    chan_read_failed(ch);
	    chan_write_failed(ch);
	    debug("X11 rejected %d 0x%x 0x%x", ch->self, ch->istate, ch->ostate);
	  }
	  break;

	case SSH_CHANNEL_FREE:
	default:
	  continue;
	}
    }
}

/* After select, perform any appropriate operations for channels which
   have events pending. */

void channel_after_select(fd_set *readset, fd_set *writeset)
{
  struct sockaddr addr;
  int addrlen, newsock, i, newch, len;
  Channel *ch;
  char buf[16384], *remote_hostname;
  
  /* Loop over all channels... */
  for (i = 0; i < channels_alloc; i++)
    {
      ch = &channels[i];
      switch (ch->type)
	{
	case SSH_CHANNEL_X11_LISTENER:
	  /* This is our fake X11 server socket. */
	  if (FD_ISSET(ch->sock, readset))
	    {
	      debug("X11 connection requested.");
	      addrlen = sizeof(addr);
	      newsock = accept(ch->sock, &addr, &addrlen);
	      if (newsock < 0)
		{
		  error("accept: %.100s", strerror(errno));
		  break;
		}
	      remote_hostname = get_remote_hostname(newsock);
	      snprintf(buf, sizeof buf, "X11 connection from %.200s port %d",
		      remote_hostname, get_peer_port(newsock));
	      xfree(remote_hostname);
	      newch = channel_allocate(SSH_CHANNEL_OPENING, newsock, 
				       xstrdup(buf));
	      packet_start(SSH_SMSG_X11_OPEN);
	      packet_put_int(newch);
	      if (have_hostname_in_open)
		packet_put_string(buf, strlen(buf));
	      packet_send();
	    }
	  break;
	  
	case SSH_CHANNEL_PORT_LISTENER:
	  /* This socket is listening for connections to a forwarded TCP/IP
	     port. */
	  if (FD_ISSET(ch->sock, readset))
	    {
	      debug("Connection to port %d forwarding to %.100s:%d requested.",
		    ch->listening_port, ch->path, ch->host_port);
	      addrlen = sizeof(addr);
	      newsock = accept(ch->sock, &addr, &addrlen);
	      if (newsock < 0)
		{
		  error("accept: %.100s", strerror(errno));
		  break;
		}
	      remote_hostname = get_remote_hostname(newsock);
	      snprintf(buf, sizeof buf, "port %d, connection from %.200s port %d",
		      ch->listening_port, remote_hostname,
		      get_peer_port(newsock));
	      xfree(remote_hostname);
	      newch = channel_allocate(SSH_CHANNEL_OPENING, newsock, 
				       xstrdup(buf));
	      packet_start(SSH_MSG_PORT_OPEN);
	      packet_put_int(newch);
	      packet_put_string(ch->path, strlen(ch->path));
	      packet_put_int(ch->host_port);
	      if (have_hostname_in_open)
		packet_put_string(buf, strlen(buf));
	      packet_send();
	    }
	  break;

	case SSH_CHANNEL_AUTH_SOCKET:
	  /* This is the authentication agent socket listening for connections
	     from clients. */
	  if (FD_ISSET(ch->sock, readset))
	    {
	      int nchan;
	      len = sizeof(addr);
	      newsock = accept(ch->sock, &addr, &len);
	      if (newsock < 0)
		{
		  error("accept from auth socket: %.100s", strerror(errno));
		  break;
		}

	      nchan = channel_allocate(SSH_CHANNEL_OPENING, newsock,
				     xstrdup("accepted auth socket"));
	      packet_start(SSH_SMSG_AGENT_OPEN);
	      packet_put_int(nchan);
	      packet_send();
	    }
	  break;

	case SSH_CHANNEL_OPEN:
	  /* This is an open two-way communication channel.  It is not of
	     interest to us at this point what kind of data is being
	     transmitted. */

	  /* Read available incoming data and append it to buffer;
	     shutdown socket, if read or write failes */
	  if (FD_ISSET(ch->sock, readset))
	    {
	      len = read(ch->sock, buf, sizeof(buf));
	      if (len <= 0)
		{
		  if (compat13) {
                    buffer_consume(&ch->output, buffer_len(&ch->output));
                    ch->type = SSH_CHANNEL_INPUT_DRAINING;
                    debug("Channel %d status set to input draining.", i);
                  }else{
                    chan_read_failed(ch);
		  }
		  break;
		}
	      buffer_append(&ch->input, buf, len);
	    }
	  /* Send buffered output data to the socket. */
	  if (FD_ISSET(ch->sock, writeset) && buffer_len(&ch->output) > 0)
	    {
	      len = write(ch->sock, buffer_ptr(&ch->output),
			  buffer_len(&ch->output));
	      if (len <= 0)
		{
		  if (compat13) {
                    buffer_consume(&ch->output, buffer_len(&ch->output));
                    debug("Channel %d status set to input draining.", i);
                    ch->type = SSH_CHANNEL_INPUT_DRAINING;
                  }else{
                    chan_write_failed(ch);
		  }
		  break;
		}
	      buffer_consume(&ch->output, len);
	    }
	  break;

	case SSH_CHANNEL_OUTPUT_DRAINING:
 	  if (!compat13)
		fatal("cannot happen: OUT_DRAIN");
	  /* Send buffered output data to the socket. */
	  if (FD_ISSET(ch->sock, writeset) && buffer_len(&ch->output) > 0)
	    {
	      len = write(ch->sock, buffer_ptr(&ch->output),
			  buffer_len(&ch->output));
	      if (len <= 0)
		buffer_consume(&ch->output, buffer_len(&ch->output));
	      else
		buffer_consume(&ch->output, len);
	    }
	  break;

	case SSH_CHANNEL_X11_OPEN:
	case SSH_CHANNEL_FREE:
	default:
	  continue;
	}
    }
}

/* If there is data to send to the connection, send some of it now. */

void channel_output_poll()
{
  int len, i;
  Channel *ch;

  for (i = 0; i < channels_alloc; i++)
    {
      ch = &channels[i];
      /* We are only interested in channels that can have buffered incoming
	 data. */
      if (ch->type != SSH_CHANNEL_OPEN && 
	  ch->type != SSH_CHANNEL_INPUT_DRAINING)
	continue;

      /* Get the amount of buffered data for this channel. */
      len = buffer_len(&ch->input);
      if (len > 0)
	{
	  /* Send some data for the other side over the secure connection. */
	  if (packet_is_interactive())
	    {
	      if (len > 1024)
		len = 512;
	    }
	  else
	    {
	      if (len > 16384)
		len = 16384;  /* Keep the packets at reasonable size. */
	    }
	  packet_start(SSH_MSG_CHANNEL_DATA);
	  packet_put_int(ch->remote_id);
	  packet_put_string(buffer_ptr(&ch->input), len);
	  packet_send();
	  buffer_consume(&ch->input, len);
	}
      else if(ch->istate == CHAN_INPUT_WAIT_DRAIN)
     	{
 	  if (compat13)
	     fatal("cannot happen: istate == INPUT_WAIT_DRAIN for proto 1.3");
	  /* input-buffer is empty and read-socket shutdown:
	     tell peer, that we will not send more data: send IEOF */
	  chan_ibuf_empty(ch);
     	}
    }
}

/* This is called when a packet of type CHANNEL_DATA has just been received.
   The message type has already been consumed, but channel number and data
   is still there. */

void channel_input_data(int payload_len)
{
  int channel;
  char *data;
  unsigned int data_len;

  /* Get the channel number and verify it. */
  channel = packet_get_int();
  if (channel < 0 || channel >= channels_alloc ||
      channels[channel].type == SSH_CHANNEL_FREE)
    packet_disconnect("Received data for nonexistent channel %d.", channel);

  /* Ignore any data for non-open channels (might happen on close) */
  if (channels[channel].type != SSH_CHANNEL_OPEN &&
      channels[channel].type != SSH_CHANNEL_X11_OPEN)
    return; 

  /* Get the data. */
  data = packet_get_string(&data_len);
  packet_integrity_check(payload_len, 4 + 4+data_len, SSH_MSG_CHANNEL_DATA);
  buffer_append(&channels[channel].output, data, data_len);
  xfree(data);
}

/* Returns true if no channel has too much buffered data, and false if
   one or more channel is overfull. */

int channel_not_very_much_buffered_data()
{
  unsigned int i;
  Channel *ch;
  
  for (i = 0; i < channels_alloc; i++)
    {
      ch = &channels[i];
      switch (ch->type)
	{
	case SSH_CHANNEL_X11_LISTENER:
	case SSH_CHANNEL_PORT_LISTENER:
	case SSH_CHANNEL_AUTH_SOCKET:
	  continue;
	case SSH_CHANNEL_OPEN:
	  if (buffer_len(&ch->input) > 32768)
	    return 0;
	  if (buffer_len(&ch->output) > 32768)
	    return 0;
	  continue;
	case SSH_CHANNEL_INPUT_DRAINING:
	case SSH_CHANNEL_OUTPUT_DRAINING:
	case SSH_CHANNEL_X11_OPEN:
	case SSH_CHANNEL_FREE:
	default:
	  continue;
	}
    }
  return 1;
}

/* This is called after receiving CHANNEL_CLOSE/IEOF. */

void channel_input_close()
{
  int channel;

  /* Get the channel number and verify it. */
  channel = packet_get_int();
  if (channel < 0 || channel >= channels_alloc ||
      channels[channel].type == SSH_CHANNEL_FREE)
    packet_disconnect("Received data for nonexistent channel %d.", channel);

  if(!compat13){
    /* proto version 1.5 overloads CLOSE with IEOF */
    chan_rcvd_ieof(&channels[channel]);
    return;
  }

  /* Send a confirmation that we have closed the channel and no more data is
     coming for it. */
  packet_start(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION);
  packet_put_int(channels[channel].remote_id);
  packet_send();

  /* If the channel is in closed state, we have sent a close request, and
     the other side will eventually respond with a confirmation.  Thus,
     we cannot free the channel here, because then there would be no-one to
     receive the confirmation.  The channel gets freed when the confirmation
     arrives. */
  if (channels[channel].type != SSH_CHANNEL_CLOSED)
    {
      /* Not a closed channel - mark it as draining, which will cause it to
	 be freed later. */
      buffer_consume(&channels[channel].input, 
		     buffer_len(&channels[channel].input));
      channels[channel].type = SSH_CHANNEL_OUTPUT_DRAINING;
      /* debug("Setting status to output draining; output len = %d",
	 buffer_len(&channels[channel].output)); */
    }
}

/* This is called after receiving CHANNEL_CLOSE_CONFIRMATION/OCLOSE. */

void channel_input_close_confirmation()
{
  int channel;

  /* Get the channel number and verify it. */
  channel = packet_get_int();
  if (channel < 0 || channel >= channels_alloc)
    packet_disconnect("Received close confirmation for out-of-range channel %d.",
		      channel);

  if(!compat13){
    /* proto version 1.5 overloads CLOSE_CONFIRMATION with OCLOSE */
    chan_rcvd_oclose(&channels[channel]);
    return;
  }

  if (channels[channel].type != SSH_CHANNEL_CLOSED)
    packet_disconnect("Received close confirmation for non-closed channel %d (type %d).",
		      channel, channels[channel].type);

  /* Free the channel. */
  channel_free(channel);
}

/* This is called after receiving CHANNEL_OPEN_CONFIRMATION. */

void channel_input_open_confirmation()
{
  int channel, remote_channel;

  /* Get the channel number and verify it. */
  channel = packet_get_int();
  if (channel < 0 || channel >= channels_alloc ||
      channels[channel].type != SSH_CHANNEL_OPENING)
    packet_disconnect("Received open confirmation for non-opening channel %d.",
		      channel);

  /* Get remote side's id for this channel. */
  remote_channel = packet_get_int();

  /* Record the remote channel number and mark that the channel is now open. */
  channels[channel].remote_id = remote_channel;
  channels[channel].type = SSH_CHANNEL_OPEN;
}

/* This is called after receiving CHANNEL_OPEN_FAILURE from the other side. */

void channel_input_open_failure()
{
  int channel;

  /* Get the channel number and verify it. */
  channel = packet_get_int();
  if (channel < 0 || channel >= channels_alloc ||
      channels[channel].type != SSH_CHANNEL_OPENING)
    packet_disconnect("Received open failure for non-opening channel %d.",
		      channel);
  
  /* Free the channel.  This will also close the socket. */
  channel_free(channel);
}

/* Stops listening for channels, and removes any unix domain sockets that
   we might have. */

void channel_stop_listening()
{
  int i;
  for (i = 0; i < channels_alloc; i++)
    {
      switch (channels[i].type)
	{
	case SSH_CHANNEL_AUTH_SOCKET:
	  close(channels[i].sock);
	  remove(channels[i].path);
	  channel_free(i);
	  break;
	case SSH_CHANNEL_PORT_LISTENER:
	case SSH_CHANNEL_X11_LISTENER:
	  close(channels[i].sock);
	  channel_free(i);
	  break;
	default:
	  break;
	}
    }
}

/* Closes the sockets of all channels.  This is used to close extra file
   descriptors after a fork. */

void channel_close_all()
{
  int i;
  for (i = 0; i < channels_alloc; i++)
    {
      if (channels[i].type != SSH_CHANNEL_FREE)
	close(channels[i].sock);
    }
}

/* Returns the maximum file descriptor number used by the channels. */

int channel_max_fd()
{
  return channel_max_fd_value;
}

/* Returns true if any channel is still open. */

int channel_still_open()
{
  unsigned int i;
  for (i = 0; i < channels_alloc; i++)
    switch (channels[i].type)
      {
      case SSH_CHANNEL_FREE:
      case SSH_CHANNEL_X11_LISTENER:
      case SSH_CHANNEL_PORT_LISTENER:
      case SSH_CHANNEL_CLOSED:
      case SSH_CHANNEL_AUTH_SOCKET:
	continue;
      case SSH_CHANNEL_OPENING:
      case SSH_CHANNEL_OPEN:
      case SSH_CHANNEL_X11_OPEN:
	return 1;
      case SSH_CHANNEL_INPUT_DRAINING:
      case SSH_CHANNEL_OUTPUT_DRAINING:
 	if (!compat13)
	  fatal("cannot happen: OUT_DRAIN");
	return 1;
      default:
	fatal("channel_still_open: bad channel type %d", channels[i].type);
	/*NOTREACHED*/
      }
  return 0;
}

/* Returns a message describing the currently open forwarded
   connections, suitable for sending to the client.  The message
   contains crlf pairs for newlines. */

char *channel_open_message()
{
  Buffer buffer;
  int i;
  char buf[512], *cp;

  buffer_init(&buffer);
  snprintf(buf, sizeof buf, "The following connections are open:\r\n");
  buffer_append(&buffer, buf, strlen(buf));
  for (i = 0; i < channels_alloc; i++){
    Channel *c=&channels[i];
    switch (c->type)
      {
      case SSH_CHANNEL_FREE:
      case SSH_CHANNEL_X11_LISTENER:
      case SSH_CHANNEL_PORT_LISTENER:
      case SSH_CHANNEL_CLOSED:
      case SSH_CHANNEL_AUTH_SOCKET:
	continue;
      case SSH_CHANNEL_OPENING:
      case SSH_CHANNEL_OPEN:
      case SSH_CHANNEL_X11_OPEN:
      case SSH_CHANNEL_INPUT_DRAINING:
      case SSH_CHANNEL_OUTPUT_DRAINING:
	snprintf(buf, sizeof buf, "  #%d/%d %.300s\r\n",
		 c->self,c->type,c->remote_name);
	buffer_append(&buffer, buf, strlen(buf));
	continue;
      default:
	fatal("channel_still_open: bad channel type %d", c->type);
	/*NOTREACHED*/
      }
  }
  buffer_append(&buffer, "\0", 1);
  cp = xstrdup(buffer_ptr(&buffer));
  buffer_free(&buffer);
  return cp;
}

/* Initiate forwarding of connections to local port "port" through the secure
   channel to host:port from remote side. */

void channel_request_local_forwarding(int port, const char *host,
				      int host_port)
{
  int ch, sock;
  struct sockaddr_in sin;
  extern Options options;

  if (strlen(host) > sizeof(channels[0].path) - 1)
    packet_disconnect("Forward host name too long.");
  
  /* Create a port to listen for the host. */
  sock = socket(AF_INET, SOCK_STREAM, 0);
  if (sock < 0)
    packet_disconnect("socket: %.100s", strerror(errno));

  /* Initialize socket address. */
  memset(&sin, 0, sizeof(sin));
  sin.sin_family = AF_INET;
  if (options.gateway_ports == 1)
    sin.sin_addr.s_addr = htonl(INADDR_ANY);
  else
    sin.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
  sin.sin_port = htons(port);
  
  /* Bind the socket to the address. */
  if (bind(sock, (struct sockaddr *)&sin, sizeof(sin)) < 0)
    packet_disconnect("bind: %.100s", strerror(errno));
      
  /* Start listening for connections on the socket. */
  if (listen(sock, 5) < 0)
    packet_disconnect("listen: %.100s", strerror(errno));
	    
  /* Allocate a channel number for the socket. */
  ch = channel_allocate(SSH_CHANNEL_PORT_LISTENER, sock,
			xstrdup("port listener"));
  strcpy(channels[ch].path, host); /* note: host name stored here */
  channels[ch].host_port = host_port; /* port on host to connect to */
  channels[ch].listening_port = port; /* port being listened */
}  

/* Initiate forwarding of connections to port "port" on remote host through
   the secure channel to host:port from local side. */

void channel_request_remote_forwarding(int port, const char *host,
				       int remote_port)
{
  int payload_len;
  /* Record locally that connection to this host/port is permitted. */
  if (num_permitted_opens >= SSH_MAX_FORWARDS_PER_DIRECTION)
    fatal("channel_request_remote_forwarding: too many forwards");
  permitted_opens[num_permitted_opens].host = xstrdup(host);
  permitted_opens[num_permitted_opens].port = remote_port;
  num_permitted_opens++;

  /* Send the forward request to the remote side. */
  packet_start(SSH_CMSG_PORT_FORWARD_REQUEST);
  packet_put_int(port);
  packet_put_string(host, strlen(host));
  packet_put_int(remote_port);
  packet_send();
  packet_write_wait();
  
  /* Wait for response from the remote side.  It will send a disconnect
     message on failure, and we will never see it here. */
  packet_read_expect(&payload_len, SSH_SMSG_SUCCESS);
}

/* This is called after receiving CHANNEL_FORWARDING_REQUEST.  This initates
   listening for the port, and sends back a success reply (or disconnect
   message if there was an error).  This never returns if there was an 
   error. */

void channel_input_port_forward_request(int is_root)
{
  int port, host_port;
  char *hostname;
  
  /* Get arguments from the packet. */
  port = packet_get_int();
  hostname = packet_get_string(NULL);
  host_port = packet_get_int();
  
  /* Port numbers are 16 bit quantities. */
  if ((port & 0xffff) != port)
    packet_disconnect("Requested forwarding of nonexistent port %d.", port);

  /* Check that an unprivileged user is not trying to forward a privileged
     port. */
  if (port < IPPORT_RESERVED && !is_root)
    packet_disconnect("Requested forwarding of port %d but user is not root.",
		      port);

  /* Initiate forwarding. */
  channel_request_local_forwarding(port, hostname, host_port);

  /* Free the argument string. */
  xfree(hostname);
}

/* This is called after receiving PORT_OPEN message.  This attempts to connect
   to the given host:port, and sends back CHANNEL_OPEN_CONFIRMATION or
   CHANNEL_OPEN_FAILURE. */

void channel_input_port_open(int payload_len)
{
  int remote_channel, sock, newch, host_port, i;
  struct sockaddr_in sin;
  char *host, *originator_string;
  struct hostent *hp;
  int host_len, originator_len;

  /* Get remote channel number. */
  remote_channel = packet_get_int();

  /* Get host name to connect to. */
  host = packet_get_string(&host_len);

  /* Get port to connect to. */
  host_port = packet_get_int();

  /* Get remote originator name. */
  if (have_hostname_in_open)
    originator_string = packet_get_string(&originator_len);
  else
    originator_string = xstrdup("unknown (remote did not supply name)");

  packet_integrity_check(payload_len,
			 4 + 4 + host_len + 4 + 4 + originator_len,
			 SSH_MSG_PORT_OPEN);

  /* Check if opening that port is permitted. */
  if (!all_opens_permitted)
    {
      /* Go trough all permitted ports. */
      for (i = 0; i < num_permitted_opens; i++)
	if (permitted_opens[i].port == host_port &&
	    strcmp(permitted_opens[i].host, host) == 0)
	  break;

      /* Check if we found the requested port among those permitted. */
      if (i >= num_permitted_opens)
	{
	  /* The port is not permitted. */
	  log("Received request to connect to %.100s:%d, but the request was denied.",
	      host, host_port);
	  packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
	  packet_put_int(remote_channel);
	  packet_send();
	}
    }
  
  memset(&sin, 0, sizeof(sin));
  sin.sin_addr.s_addr = inet_addr(host);
  if ((sin.sin_addr.s_addr & 0xffffffff) != 0xffffffff)
    {
      /* It was a valid numeric host address. */
      sin.sin_family = AF_INET;
    }
  else
    {
      /* Look up the host address from the name servers. */
      hp = gethostbyname(host);
      if (!hp)
	{
	  error("%.100s: unknown host.", host);
	  goto fail;
	}
      if (!hp->h_addr_list[0])
	{
	  error("%.100s: host has no IP address.", host);
	  goto fail;
	}
      sin.sin_family = hp->h_addrtype;
      memcpy(&sin.sin_addr, hp->h_addr_list[0], 
	     sizeof(sin.sin_addr));
    }
  sin.sin_port = htons(host_port);

  /* Create the socket. */
  sock = socket(sin.sin_family, SOCK_STREAM, 0);
  if (sock < 0)
    {
      error("socket: %.100s", strerror(errno));
      goto fail;
    }

  /* Connect to the host/port. */
  if (connect(sock, (struct sockaddr *)&sin, sizeof(sin)) < 0)
    {
      error("connect %.100s:%d: %.100s", host, host_port,
	    strerror(errno));
      close(sock);
      goto fail;
    }

  /* Successful connection. */

  /* Allocate a channel for this connection. */
  newch = channel_allocate(SSH_CHANNEL_OPEN, sock, originator_string);
  channels[newch].remote_id = remote_channel;
  
  /* Send a confirmation to the remote host. */
  packet_start(SSH_MSG_CHANNEL_OPEN_CONFIRMATION);
  packet_put_int(remote_channel);
  packet_put_int(newch);
  packet_send();

  /* Free the argument string. */
  xfree(host);
  
  return;

 fail:
  /* Free the argument string. */
  xfree(host);

  /* Send refusal to the remote host. */
  packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
  packet_put_int(remote_channel);
  packet_send();
}

/* Creates an internet domain socket for listening for X11 connections. 
   Returns a suitable value for the DISPLAY variable, or NULL if an error
   occurs. */

char *x11_create_display_inet(int screen_number)
{
  extern ServerOptions options;
  int display_number, port, sock;
  struct sockaddr_in sin;
  char buf[512];
  char hostname[MAXHOSTNAMELEN];

  for (display_number = options.x11_display_offset; display_number < MAX_DISPLAYS; display_number++)
    {
      port = 6000 + display_number;
      memset(&sin, 0, sizeof(sin));
      sin.sin_family = AF_INET;
      sin.sin_addr.s_addr = htonl(INADDR_ANY);
      sin.sin_port = htons(port);
      
      sock = socket(AF_INET, SOCK_STREAM, 0);
      if (sock < 0)
	{
	  error("socket: %.100s", strerror(errno));
	  return NULL;
	}
      
      if (bind(sock, (struct sockaddr *)&sin, sizeof(sin)) < 0)
	{
	  debug("bind port %d: %.100s", port, strerror(errno));
	  shutdown(sock, SHUT_RDWR);
	  close(sock);
	  continue;
	}
      break;
    }
  if (display_number >= MAX_DISPLAYS)
    {
      error("Failed to allocate internet-domain X11 display socket.");
      return NULL;
    }

  /* Start listening for connections on the socket. */
  if (listen(sock, 5) < 0)
    {
      error("listen: %.100s", strerror(errno));
      shutdown(sock, SHUT_RDWR);
      close(sock);
      return NULL;
    }

  /* Set up a suitable value for the DISPLAY variable. */
  if (gethostname(hostname, sizeof(hostname)) < 0)
    fatal("gethostname: %.100s", strerror(errno));
  snprintf(buf, sizeof buf, "%.400s:%d.%d", hostname,
    display_number, screen_number);
	    
  /* Allocate a channel for the socket. */
  (void)channel_allocate(SSH_CHANNEL_X11_LISTENER, sock,
			 xstrdup("X11 inet listener"));

  /* Return a suitable value for the DISPLAY environment variable. */
  return xstrdup(buf);
}

#ifndef X_UNIX_PATH
#define X_UNIX_PATH "/tmp/.X11-unix/X"
#endif

static
int
connect_local_xsocket(unsigned dnr)
{
  static const char *const x_sockets[] = {
    X_UNIX_PATH "%u",
    "/var/X/.X11-unix/X" "%u",
    "/usr/spool/sockets/X11/" "%u",
    NULL
  };
  int sock;
  struct sockaddr_un addr;
  const char *const *path;

  for (path = x_sockets; *path; ++path)
    {
      sock = socket(AF_UNIX, SOCK_STREAM, 0);
      if (sock < 0)
	error("socket: %.100s", strerror(errno));
      memset(&addr, 0, sizeof(addr));
      addr.sun_family = AF_UNIX;
      snprintf(addr.sun_path, sizeof addr.sun_path, *path, dnr);
      if (connect(sock, (struct sockaddr *)&addr, sizeof(addr)) == 0)
	return sock;
      close(sock);
    }
  error("connect %.100s: %.100s", addr.sun_path, strerror(errno));
  return -1;
}


/* This is called when SSH_SMSG_X11_OPEN is received.  The packet contains
   the remote channel number.  We should do whatever we want, and respond
   with either SSH_MSG_OPEN_CONFIRMATION or SSH_MSG_OPEN_FAILURE. */

void x11_input_open(int payload_len)
{
  int remote_channel, display_number, sock, newch;
  const char *display;
  struct sockaddr_in sin;
  char buf[1024], *cp, *remote_host;
  struct hostent *hp;
  int remote_len;

  /* Get remote channel number. */
  remote_channel = packet_get_int();

  /* Get remote originator name. */
  if (have_hostname_in_open)
    remote_host = packet_get_string(&remote_len);
  else
    remote_host = xstrdup("unknown (remote did not supply name)");

  debug("Received X11 open request.");
  packet_integrity_check(payload_len, 4 + 4+remote_len, SSH_SMSG_X11_OPEN);

  /* Try to open a socket for the local X server. */
  display = getenv("DISPLAY");
  if (!display)
    {
      error("DISPLAY not set.");
      goto fail;
    }
  
  /* Now we decode the value of the DISPLAY variable and make a connection
     to the real X server. */

  /* Check if it is a unix domain socket.  Unix domain displays are in one
     of the following formats: unix:d[.s], :d[.s], ::d[.s] */
  if (strncmp(display, "unix:", 5) == 0 ||
      display[0] == ':')
    {
      /* Connect to the unix domain socket. */
      if (sscanf(strrchr(display, ':') + 1, "%d", &display_number) != 1)
	{
	  error("Could not parse display number from DISPLAY: %.100s",
		display);
	  goto fail;
	}
      /* Create a socket. */
      sock = connect_local_xsocket(display_number);
      if (sock < 0)
	goto fail;

      /* OK, we now have a connection to the display. */
      goto success;
    }
  
  /* Connect to an inet socket.  The DISPLAY value is supposedly
      hostname:d[.s], where hostname may also be numeric IP address. */
  strncpy(buf, display, sizeof(buf));
  buf[sizeof(buf) - 1] = 0;
  cp = strchr(buf, ':');
  if (!cp)
    {
      error("Could not find ':' in DISPLAY: %.100s", display);
      goto fail;
    }
  *cp = 0;
  /* buf now contains the host name.  But first we parse the display number. */
  if (sscanf(cp + 1, "%d", &display_number) != 1)
    {
       error("Could not parse display number from DISPLAY: %.100s",
	     display);
      goto fail;
    }
  
  /* Try to parse the host name as a numeric IP address. */
  memset(&sin, 0, sizeof(sin));
  sin.sin_addr.s_addr = inet_addr(buf);
  if ((sin.sin_addr.s_addr & 0xffffffff) != 0xffffffff)
    {
      /* It was a valid numeric host address. */
      sin.sin_family = AF_INET;
    }
  else
    {
      /* Not a numeric IP address. */
      /* Look up the host address from the name servers. */
      hp = gethostbyname(buf);
      if (!hp)
	{
	  error("%.100s: unknown host.", buf);
	  goto fail;
	}
      if (!hp->h_addr_list[0])
	{
	  error("%.100s: host has no IP address.", buf);
	  goto fail;
	}
      sin.sin_family = hp->h_addrtype;
      memcpy(&sin.sin_addr, hp->h_addr_list[0], 
	     sizeof(sin.sin_addr));
    }
  /* Set port number. */
  sin.sin_port = htons(6000 + display_number);

  /* Create a socket. */
  sock = socket(sin.sin_family, SOCK_STREAM, 0);
  if (sock < 0)
    {
      error("socket: %.100s", strerror(errno));
      goto fail;
    }
  /* Connect it to the display. */
  if (connect(sock, (struct sockaddr *)&sin, sizeof(sin)) < 0)
    {
      error("connect %.100s:%d: %.100s", buf, 6000 + display_number, 
	    strerror(errno));
      close(sock);
      goto fail;
    }

 success:
  /* We have successfully obtained a connection to the real X display. */
  
  /* Allocate a channel for this connection. */
  if (x11_saved_proto == NULL)
    newch = channel_allocate(SSH_CHANNEL_OPEN, sock, remote_host);
  else
    newch = channel_allocate(SSH_CHANNEL_X11_OPEN, sock, remote_host);
  channels[newch].remote_id = remote_channel;
  
  /* Send a confirmation to the remote host. */
  packet_start(SSH_MSG_CHANNEL_OPEN_CONFIRMATION);
  packet_put_int(remote_channel);
  packet_put_int(newch);
  packet_send();
  
  return;

 fail:
  /* Send refusal to the remote host. */
  packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
  packet_put_int(remote_channel);
  packet_send();
}

/* Requests forwarding of X11 connections, generates fake authentication
   data, and enables authentication spoofing. */

void x11_request_forwarding_with_spoofing(const char *proto, const char *data)
{
  unsigned int data_len = (unsigned int)strlen(data) / 2;
  unsigned int i, value;
  char *new_data;
  int screen_number;
  const char *cp;
  u_int32_t rand = 0;

  cp = getenv("DISPLAY");
  if (cp)
    cp = strchr(cp, ':');
  if (cp)
    cp = strchr(cp, '.');
  if (cp)
    screen_number = atoi(cp + 1);
  else
    screen_number = 0;

  /* Save protocol name. */
  x11_saved_proto = xstrdup(proto);

  /* Extract real authentication data and generate fake data of the same
     length. */
  x11_saved_data = xmalloc(data_len);
  x11_fake_data = xmalloc(data_len);
  for (i = 0; i < data_len; i++)
    {
      if (sscanf(data + 2 * i, "%2x", &value) != 1)
	fatal("x11_request_forwarding: bad authentication data: %.100s", data);
      if (i % 4 == 0)
	rand = arc4random();
      x11_saved_data[i] = value;
      x11_fake_data[i] = rand & 0xff;
      rand >>= 8;
    }
  x11_saved_data_len = data_len;
  x11_fake_data_len = data_len;

  /* Convert the fake data into hex. */
  new_data = xmalloc(2 * data_len + 1);
  for (i = 0; i < data_len; i++)
    sprintf(new_data + 2 * i, "%02x", (unsigned char)x11_fake_data[i]);

  /* Send the request packet. */
  packet_start(SSH_CMSG_X11_REQUEST_FORWARDING);
  packet_put_string(proto, strlen(proto));
  packet_put_string(new_data, strlen(new_data));
  packet_put_int(screen_number);
  packet_send();
  packet_write_wait();
  xfree(new_data);
}

/* Sends a message to the server to request authentication fd forwarding. */

void auth_request_forwarding()
{
  packet_start(SSH_CMSG_AGENT_REQUEST_FORWARDING);
  packet_send();
  packet_write_wait();
}

/* Returns the name of the forwarded authentication socket.  Returns NULL
   if there is no forwarded authentication socket.  The returned value
   points to a static buffer. */

char *auth_get_socket_name()
{
  return channel_forwarded_auth_socket_name;
}

/* removes the agent forwarding socket */

void cleanup_socket(void) {
  remove(channel_forwarded_auth_socket_name);
  rmdir(channel_forwarded_auth_socket_dir);
}

/* This if called to process SSH_CMSG_AGENT_REQUEST_FORWARDING on the server.
   This starts forwarding authentication requests. */

void auth_input_request_forwarding(struct passwd *pw)
{
  int sock, newch;
  struct sockaddr_un sunaddr;
  
  if (auth_get_socket_name() != NULL)
    fatal("Protocol error: authentication forwarding requested twice.");

  /* Temporarily drop privileged uid for mkdir/bind. */
  temporarily_use_uid(pw->pw_uid);

  /* Allocate a buffer for the socket name, and format the name. */
  channel_forwarded_auth_socket_name = xmalloc(MAX_SOCKET_NAME);
  channel_forwarded_auth_socket_dir  = xmalloc(MAX_SOCKET_NAME);
  strlcpy(channel_forwarded_auth_socket_dir, "/tmp/ssh-XXXXXXXX", MAX_SOCKET_NAME);

  /* Create private directory for socket */
  if (mkdtemp(channel_forwarded_auth_socket_dir) == NULL)
    packet_disconnect("mkdtemp: %.100s", strerror(errno));
  snprintf(channel_forwarded_auth_socket_name, MAX_SOCKET_NAME,
	   "%s/agent.%d", channel_forwarded_auth_socket_dir, (int)getpid());

  if (atexit(cleanup_socket) < 0) {
    int saved=errno;
    cleanup_socket();
    packet_disconnect("socket: %.100s", strerror(saved));
  }

  /* Create the socket. */
  sock = socket(AF_UNIX, SOCK_STREAM, 0);
  if (sock < 0)
    packet_disconnect("socket: %.100s", strerror(errno));

  /* Bind it to the name. */
  memset(&sunaddr, 0, sizeof(sunaddr));
  sunaddr.sun_family = AF_UNIX;
  strncpy(sunaddr.sun_path, channel_forwarded_auth_socket_name, 
          sizeof(sunaddr.sun_path));

  if (bind(sock, (struct sockaddr *)&sunaddr, sizeof(sunaddr)) < 0)
    packet_disconnect("bind: %.100s", strerror(errno));

  /* Restore the privileged uid. */
  restore_uid();

  /* Start listening on the socket. */
  if (listen(sock, 5) < 0)
    packet_disconnect("listen: %.100s", strerror(errno));

  /* Allocate a channel for the authentication agent socket. */
  newch = channel_allocate(SSH_CHANNEL_AUTH_SOCKET, sock,
    		       xstrdup("auth socket"));
  strcpy(channels[newch].path, channel_forwarded_auth_socket_name);
}

/* This is called to process an SSH_SMSG_AGENT_OPEN message. */

void auth_input_open_request()
{
  int remch, sock, newch;
  char *dummyname;

  /* Read the remote channel number from the message. */
  remch = packet_get_int();
  
  /* Get a connection to the local authentication agent (this may again get
     forwarded). */
  sock = ssh_get_authentication_socket();

  /* If we could not connect the agent, send an error message back to
     the server. This should never happen unless the agent
     dies, because authentication forwarding is only enabled if we have an
     agent. */
  if (sock < 0){
    packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
    packet_put_int(remch);
    packet_send();
    return;
  }

  debug("Forwarding authentication connection.");

  /* Dummy host name.  This will be freed when the channel is freed; it will
     still be valid in the packet_put_string below since the channel cannot
     yet be freed at that point. */
  dummyname = xstrdup("authentication agent connection");
  
  newch = channel_allocate(SSH_CHANNEL_OPEN, sock, dummyname);
  channels[newch].remote_id = remch;
  
  /* Send a confirmation to the remote host. */
  packet_start(SSH_MSG_CHANNEL_OPEN_CONFIRMATION);
  packet_put_int(remch);
  packet_put_int(newch);
  packet_send();
}