summaryrefslogtreecommitdiff
path: root/sshconnect.c
blob: bca0bf43afdb88fb56222ad208688ac3baa62c73 (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
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
/*
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 * Created: Sat Mar 18 22:15:47 1995 ylo
 * Code to connect to a remote host, and to perform the client side of the
 * login (authentication) dialog.
 *
 * SSH2 support added by Markus Friedl.
 */

#include "includes.h"
RCSID("$OpenBSD: sshconnect.c,v 1.68 2000/04/14 10:30:33 markus Exp $");

#ifdef HAVE_OPENSSL
#include <openssl/bn.h>
#include <openssl/rsa.h>
#include <openssl/dsa.h>
#include <openssl/md5.h>
#endif
#ifdef HAVE_SSL
#include <ssl/bn.h>
#include <ssl/rsa.h>
#include <ssl/dsa.h>
#include <ssl/md5.h>
#endif

#include "xmalloc.h"
#include "rsa.h"
#include "ssh.h"
#include "buffer.h"
#include "packet.h"
#include "authfd.h"
#include "cipher.h"
#include "mpaux.h"
#include "uidswap.h"
#include "compat.h"
#include "readconf.h"

#include "bufaux.h"

#include "ssh2.h"
#include "kex.h"
#include "myproposal.h"
#include "key.h"
#include "dsa.h"
#include "hostfile.h"

/* Session id for the current session. */
unsigned char session_id[16];

/* authentications supported by server */
unsigned int supported_authentications;

static char *client_version_string = NULL;
static char *server_version_string = NULL;

extern Options options;
extern char *__progname;

/*
 * Connect to the given ssh server using a proxy command.
 */
int
ssh_proxy_connect(const char *host, u_short port, uid_t original_real_uid,
		  const char *proxy_command)
{
	Buffer command;
	const char *cp;
	char *command_string;
	int pin[2], pout[2];
	int pid;
	char strport[NI_MAXSERV];

	/* Convert the port number into a string. */
	snprintf(strport, sizeof strport, "%hu", port);

	/* Build the final command string in the buffer by making the
	   appropriate substitutions to the given proxy command. */
	buffer_init(&command);
	for (cp = proxy_command; *cp; cp++) {
		if (cp[0] == '%' && cp[1] == '%') {
			buffer_append(&command, "%", 1);
			cp++;
			continue;
		}
		if (cp[0] == '%' && cp[1] == 'h') {
			buffer_append(&command, host, strlen(host));
			cp++;
			continue;
		}
		if (cp[0] == '%' && cp[1] == 'p') {
			buffer_append(&command, strport, strlen(strport));
			cp++;
			continue;
		}
		buffer_append(&command, cp, 1);
	}
	buffer_append(&command, "\0", 1);

	/* Get the final command string. */
	command_string = buffer_ptr(&command);

	/* Create pipes for communicating with the proxy. */
	if (pipe(pin) < 0 || pipe(pout) < 0)
		fatal("Could not create pipes to communicate with the proxy: %.100s",
		      strerror(errno));

	debug("Executing proxy command: %.500s", command_string);

	/* Fork and execute the proxy command. */
	if ((pid = fork()) == 0) {
		char *argv[10];

		/* Child.  Permanently give up superuser privileges. */
		permanently_set_uid(original_real_uid);

		/* Redirect stdin and stdout. */
		close(pin[1]);
		if (pin[0] != 0) {
			if (dup2(pin[0], 0) < 0)
				perror("dup2 stdin");
			close(pin[0]);
		}
		close(pout[0]);
		if (dup2(pout[1], 1) < 0)
			perror("dup2 stdout");
		/* Cannot be 1 because pin allocated two descriptors. */
		close(pout[1]);

		/* Stderr is left as it is so that error messages get
		   printed on the user's terminal. */
		argv[0] = "/bin/sh";
		argv[1] = "-c";
		argv[2] = command_string;
		argv[3] = NULL;

		/* Execute the proxy command.  Note that we gave up any
		   extra privileges above. */
		execv("/bin/sh", argv);
		perror("/bin/sh");
		exit(1);
	}
	/* Parent. */
	if (pid < 0)
		fatal("fork failed: %.100s", strerror(errno));

	/* Close child side of the descriptors. */
	close(pin[0]);
	close(pout[1]);

	/* Free the command name. */
	buffer_free(&command);

	/* Set the connection file descriptors. */
	packet_set_connection(pout[0], pin[1]);

	return 1;
}

/*
 * Creates a (possibly privileged) socket for use as the ssh connection.
 */
int
ssh_create_socket(uid_t original_real_uid, int privileged, int family)
{
	int sock;

	/*
	 * If we are running as root and want to connect to a privileged
	 * port, bind our own socket to a privileged port.
	 */
	if (privileged) {
		int p = IPPORT_RESERVED - 1;
		sock = rresvport_af(&p, family);
		if (sock < 0)
			error("rresvport: af=%d %.100s", family, strerror(errno));
		else
			debug("Allocated local port %d.", p);
	} else {
		/*
		 * Just create an ordinary socket on arbitrary port.  We use
		 * the user's uid to create the socket.
		 */
		temporarily_use_uid(original_real_uid);
		sock = socket(family, SOCK_STREAM, 0);
		if (sock < 0)
			error("socket: %.100s", strerror(errno));
		restore_uid();
	}
	return sock;
}

/*
 * Opens a TCP/IP connection to the remote server on the given host.
 * The address of the remote host will be returned in hostaddr.
 * If port is 0, the default port will be used.  If anonymous is zero,
 * a privileged port will be allocated to make the connection.
 * This requires super-user privileges if anonymous is false.
 * Connection_attempts specifies the maximum number of tries (one per
 * second).  If proxy_command is non-NULL, it specifies the command (with %h
 * and %p substituted for host and port, respectively) to use to contact
 * the daemon.
 */
int
ssh_connect(const char *host, struct sockaddr_storage * hostaddr,
	    u_short port, int connection_attempts,
	    int anonymous, uid_t original_real_uid,
	    const char *proxy_command)
{
	int sock = -1, attempt;
	struct servent *sp;
	struct addrinfo hints, *ai, *aitop;
	char ntop[NI_MAXHOST], strport[NI_MAXSERV];
	int gaierr;
	struct linger linger;

	debug("ssh_connect: getuid %d geteuid %d anon %d",
	      (int) getuid(), (int) geteuid(), anonymous);

	/* Get default port if port has not been set. */
	if (port == 0) {
		sp = getservbyname(SSH_SERVICE_NAME, "tcp");
		if (sp)
			port = ntohs(sp->s_port);
		else
			port = SSH_DEFAULT_PORT;
	}
	/* If a proxy command is given, connect using it. */
	if (proxy_command != NULL)
		return ssh_proxy_connect(host, port, original_real_uid, proxy_command);

	/* No proxy command. */

	memset(&hints, 0, sizeof(hints));
	hints.ai_family = IPv4or6;
	hints.ai_socktype = SOCK_STREAM;
	snprintf(strport, sizeof strport, "%d", port);
	if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0)
		fatal("%s: %.100s: %s", __progname, host,
		    gai_strerror(gaierr));

	/*
	 * Try to connect several times.  On some machines, the first time
	 * will sometimes fail.  In general socket code appears to behave
	 * quite magically on many machines.
	 */
	for (attempt = 0; attempt < connection_attempts; attempt++) {
		if (attempt > 0)
			debug("Trying again...");

		/* Loop through addresses for this host, and try each one in
		   sequence until the connection succeeds. */
		for (ai = aitop; ai; ai = ai->ai_next) {
			if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
				continue;
			if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
			    ntop, sizeof(ntop), strport, sizeof(strport),
			    NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
				error("ssh_connect: getnameinfo failed");
				continue;
			}
			debug("Connecting to %.200s [%.100s] port %s.",
				host, ntop, strport);

			/* Create a socket for connecting. */
			sock = ssh_create_socket(original_real_uid,
			    !anonymous && geteuid() == 0 && port < IPPORT_RESERVED,
			    ai->ai_family);
			if (sock < 0)
				continue;

			/* Connect to the host.  We use the user's uid in the
			 * hope that it will help with tcp_wrappers showing
			 * the remote uid as root.
			 */
			temporarily_use_uid(original_real_uid);
			if (connect(sock, ai->ai_addr, ai->ai_addrlen) >= 0) {
				/* Successful connection. */
				memcpy(hostaddr, ai->ai_addr, sizeof(*(ai->ai_addr)));
				restore_uid();
				break;
			} else {
				debug("connect: %.100s", strerror(errno));
				restore_uid();
				/*
				 * Close the failed socket; there appear to
				 * be some problems when reusing a socket for
				 * which connect() has already returned an
				 * error.
				 */
				shutdown(sock, SHUT_RDWR);
				close(sock);
			}
		}
		if (ai)
			break;	/* Successful connection. */

		/* Sleep a moment before retrying. */
		sleep(1);
	}

	freeaddrinfo(aitop);

	/* Return failure if we didn't get a successful connection. */
	if (attempt >= connection_attempts)
		return 0;

	debug("Connection established.");

	/*
	 * Set socket options.  We would like the socket to disappear as soon
	 * as it has been closed for whatever reason.
	 */
	/* setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
	linger.l_onoff = 1;
	linger.l_linger = 5;
	setsockopt(sock, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));

	/* Set the connection. */
	packet_set_connection(sock, sock);

	return 1;
}

/*
 * Checks if the user has an authentication agent, and if so, tries to
 * authenticate using the agent.
 */
int
try_agent_authentication()
{
	int status, type;
	char *comment;
	AuthenticationConnection *auth;
	unsigned char response[16];
	unsigned int i;
	BIGNUM *e, *n, *challenge;

	/* Get connection to the agent. */
	auth = ssh_get_authentication_connection();
	if (!auth)
		return 0;

	e = BN_new();
	n = BN_new();
	challenge = BN_new();

	/* Loop through identities served by the agent. */
	for (status = ssh_get_first_identity(auth, e, n, &comment);
	     status;
	     status = ssh_get_next_identity(auth, e, n, &comment)) {
		int plen, clen;

		/* Try this identity. */
		debug("Trying RSA authentication via agent with '%.100s'", comment);
		xfree(comment);

		/* Tell the server that we are willing to authenticate using this key. */
		packet_start(SSH_CMSG_AUTH_RSA);
		packet_put_bignum(n);
		packet_send();
		packet_write_wait();

		/* Wait for server's response. */
		type = packet_read(&plen);

		/* The server sends failure if it doesn\'t like our key or
		   does not support RSA authentication. */
		if (type == SSH_SMSG_FAILURE) {
			debug("Server refused our key.");
			continue;
		}
		/* Otherwise it should have sent a challenge. */
		if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
			packet_disconnect("Protocol error during RSA authentication: %d",
					  type);

		packet_get_bignum(challenge, &clen);

		packet_integrity_check(plen, clen, type);

		debug("Received RSA challenge from server.");

		/* Ask the agent to decrypt the challenge. */
		if (!ssh_decrypt_challenge(auth, e, n, challenge,
					   session_id, 1, response)) {
			/* The agent failed to authenticate this identifier although it
			   advertised it supports this.  Just return a wrong value. */
			log("Authentication agent failed to decrypt challenge.");
			memset(response, 0, sizeof(response));
		}
		debug("Sending response to RSA challenge.");

		/* Send the decrypted challenge back to the server. */
		packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
		for (i = 0; i < 16; i++)
			packet_put_char(response[i]);
		packet_send();
		packet_write_wait();

		/* Wait for response from the server. */
		type = packet_read(&plen);

		/* The server returns success if it accepted the authentication. */
		if (type == SSH_SMSG_SUCCESS) {
			debug("RSA authentication accepted by server.");
			BN_clear_free(e);
			BN_clear_free(n);
			BN_clear_free(challenge);
			return 1;
		}
		/* Otherwise it should return failure. */
		if (type != SSH_SMSG_FAILURE)
			packet_disconnect("Protocol error waiting RSA auth response: %d",
					  type);
	}

	BN_clear_free(e);
	BN_clear_free(n);
	BN_clear_free(challenge);

	debug("RSA authentication using agent refused.");
	return 0;
}

/*
 * Computes the proper response to a RSA challenge, and sends the response to
 * the server.
 */
void
respond_to_rsa_challenge(BIGNUM * challenge, RSA * prv)
{
	unsigned char buf[32], response[16];
	MD5_CTX md;
	int i, len;

	/* Decrypt the challenge using the private key. */
	rsa_private_decrypt(challenge, challenge, prv);

	/* Compute the response. */
	/* The response is MD5 of decrypted challenge plus session id. */
	len = BN_num_bytes(challenge);
	if (len <= 0 || len > sizeof(buf))
		packet_disconnect("respond_to_rsa_challenge: bad challenge length %d",
				  len);

	memset(buf, 0, sizeof(buf));
	BN_bn2bin(challenge, buf + sizeof(buf) - len);
	MD5_Init(&md);
	MD5_Update(&md, buf, 32);
	MD5_Update(&md, session_id, 16);
	MD5_Final(response, &md);

	debug("Sending response to host key RSA challenge.");

	/* Send the response back to the server. */
	packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
	for (i = 0; i < 16; i++)
		packet_put_char(response[i]);
	packet_send();
	packet_write_wait();

	memset(buf, 0, sizeof(buf));
	memset(response, 0, sizeof(response));
	memset(&md, 0, sizeof(md));
}

/*
 * Checks if the user has authentication file, and if so, tries to authenticate
 * the user using it.
 */
int
try_rsa_authentication(const char *authfile)
{
	BIGNUM *challenge;
	RSA *private_key;
	RSA *public_key;
	char *passphrase, *comment;
	int type, i;
	int plen, clen;

	/* Try to load identification for the authentication key. */
	public_key = RSA_new();
	if (!load_public_key(authfile, public_key, &comment)) {
		RSA_free(public_key);
		/* Could not load it.  Fail. */
		return 0;
	}
	debug("Trying RSA authentication with key '%.100s'", comment);

	/* Tell the server that we are willing to authenticate using this key. */
	packet_start(SSH_CMSG_AUTH_RSA);
	packet_put_bignum(public_key->n);
	packet_send();
	packet_write_wait();

	/* We no longer need the public key. */
	RSA_free(public_key);

	/* Wait for server's response. */
	type = packet_read(&plen);

	/*
	 * The server responds with failure if it doesn\'t like our key or
	 * doesn\'t support RSA authentication.
	 */
	if (type == SSH_SMSG_FAILURE) {
		debug("Server refused our key.");
		xfree(comment);
		return 0;
	}
	/* Otherwise, the server should respond with a challenge. */
	if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
		packet_disconnect("Protocol error during RSA authentication: %d", type);

	/* Get the challenge from the packet. */
	challenge = BN_new();
	packet_get_bignum(challenge, &clen);

	packet_integrity_check(plen, clen, type);

	debug("Received RSA challenge from server.");

	private_key = RSA_new();
	/*
	 * Load the private key.  Try first with empty passphrase; if it
	 * fails, ask for a passphrase.
	 */
	if (!load_private_key(authfile, "", private_key, NULL)) {
		char buf[300];
		snprintf(buf, sizeof buf, "Enter passphrase for RSA key '%.100s': ",
		    comment);
		if (!options.batch_mode)
			passphrase = read_passphrase(buf, 0);
		else {
			debug("Will not query passphrase for %.100s in batch mode.",
			      comment);
			passphrase = xstrdup("");
		}

		/* Load the authentication file using the pasphrase. */
		if (!load_private_key(authfile, passphrase, private_key, NULL)) {
			memset(passphrase, 0, strlen(passphrase));
			xfree(passphrase);
			error("Bad passphrase.");

			/* Send a dummy response packet to avoid protocol error. */
			packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
			for (i = 0; i < 16; i++)
				packet_put_char(0);
			packet_send();
			packet_write_wait();

			/* Expect the server to reject it... */
			packet_read_expect(&plen, SSH_SMSG_FAILURE);
			xfree(comment);
			return 0;
		}
		/* Destroy the passphrase. */
		memset(passphrase, 0, strlen(passphrase));
		xfree(passphrase);
	}
	/* We no longer need the comment. */
	xfree(comment);

	/* Compute and send a response to the challenge. */
	respond_to_rsa_challenge(challenge, private_key);

	/* Destroy the private key. */
	RSA_free(private_key);

	/* We no longer need the challenge. */
	BN_clear_free(challenge);

	/* Wait for response from the server. */
	type = packet_read(&plen);
	if (type == SSH_SMSG_SUCCESS) {
		debug("RSA authentication accepted by server.");
		return 1;
	}
	if (type != SSH_SMSG_FAILURE)
		packet_disconnect("Protocol error waiting RSA auth response: %d", type);
	debug("RSA authentication refused.");
	return 0;
}

/*
 * Tries to authenticate the user using combined rhosts or /etc/hosts.equiv
 * authentication and RSA host authentication.
 */
int
try_rhosts_rsa_authentication(const char *local_user, RSA * host_key)
{
	int type;
	BIGNUM *challenge;
	int plen, clen;

	debug("Trying rhosts or /etc/hosts.equiv with RSA host authentication.");

	/* Tell the server that we are willing to authenticate using this key. */
	packet_start(SSH_CMSG_AUTH_RHOSTS_RSA);
	packet_put_string(local_user, strlen(local_user));
	packet_put_int(BN_num_bits(host_key->n));
	packet_put_bignum(host_key->e);
	packet_put_bignum(host_key->n);
	packet_send();
	packet_write_wait();

	/* Wait for server's response. */
	type = packet_read(&plen);

	/* The server responds with failure if it doesn't admit our
	   .rhosts authentication or doesn't know our host key. */
	if (type == SSH_SMSG_FAILURE) {
		debug("Server refused our rhosts authentication or host key.");
		return 0;
	}
	/* Otherwise, the server should respond with a challenge. */
	if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
		packet_disconnect("Protocol error during RSA authentication: %d", type);

	/* Get the challenge from the packet. */
	challenge = BN_new();
	packet_get_bignum(challenge, &clen);

	packet_integrity_check(plen, clen, type);

	debug("Received RSA challenge for host key from server.");

	/* Compute a response to the challenge. */
	respond_to_rsa_challenge(challenge, host_key);

	/* We no longer need the challenge. */
	BN_clear_free(challenge);

	/* Wait for response from the server. */
	type = packet_read(&plen);
	if (type == SSH_SMSG_SUCCESS) {
		debug("Rhosts or /etc/hosts.equiv with RSA host authentication accepted by server.");
		return 1;
	}
	if (type != SSH_SMSG_FAILURE)
		packet_disconnect("Protocol error waiting RSA auth response: %d", type);
	debug("Rhosts or /etc/hosts.equiv with RSA host authentication refused.");
	return 0;
}

#ifdef KRB4
int
try_kerberos_authentication()
{
	KTEXT_ST auth;		/* Kerberos data */
	char *reply;
	char inst[INST_SZ];
	char *realm;
	CREDENTIALS cred;
	int r, type, plen;
	socklen_t slen;
	Key_schedule schedule;
	u_long checksum, cksum;
	MSG_DAT msg_data;
	struct sockaddr_in local, foreign;
	struct stat st;

	/* Don't do anything if we don't have any tickets. */
	if (stat(tkt_string(), &st) < 0)
		return 0;

	strncpy(inst, (char *) krb_get_phost(get_canonical_hostname()), INST_SZ);

	realm = (char *) krb_realmofhost(get_canonical_hostname());
	if (!realm) {
		debug("Kerberos V4: no realm for %s", get_canonical_hostname());
		return 0;
	}
	/* This can really be anything. */
	checksum = (u_long) getpid();

	r = krb_mk_req(&auth, KRB4_SERVICE_NAME, inst, realm, checksum);
	if (r != KSUCCESS) {
		debug("Kerberos V4 krb_mk_req failed: %s", krb_err_txt[r]);
		return 0;
	}
	/* Get session key to decrypt the server's reply with. */
	r = krb_get_cred(KRB4_SERVICE_NAME, inst, realm, &cred);
	if (r != KSUCCESS) {
		debug("get_cred failed: %s", krb_err_txt[r]);
		return 0;
	}
	des_key_sched((des_cblock *) cred.session, schedule);

	/* Send authentication info to server. */
	packet_start(SSH_CMSG_AUTH_KERBEROS);
	packet_put_string((char *) auth.dat, auth.length);
	packet_send();
	packet_write_wait();

	/* Zero the buffer. */
	(void) memset(auth.dat, 0, MAX_KTXT_LEN);

	slen = sizeof(local);
	memset(&local, 0, sizeof(local));
	if (getsockname(packet_get_connection_in(),
			(struct sockaddr *) & local, &slen) < 0)
		debug("getsockname failed: %s", strerror(errno));

	slen = sizeof(foreign);
	memset(&foreign, 0, sizeof(foreign));
	if (getpeername(packet_get_connection_in(),
			(struct sockaddr *) & foreign, &slen) < 0) {
		debug("getpeername failed: %s", strerror(errno));
		fatal_cleanup();
	}
	/* Get server reply. */
	type = packet_read(&plen);
	switch (type) {
	case SSH_SMSG_FAILURE:
		/* Should really be SSH_SMSG_AUTH_KERBEROS_FAILURE */
		debug("Kerberos V4 authentication failed.");
		return 0;
		break;

	case SSH_SMSG_AUTH_KERBEROS_RESPONSE:
		/* SSH_SMSG_AUTH_KERBEROS_SUCCESS */
		debug("Kerberos V4 authentication accepted.");

		/* Get server's response. */
		reply = packet_get_string((unsigned int *) &auth.length);
		memcpy(auth.dat, reply, auth.length);
		xfree(reply);

		packet_integrity_check(plen, 4 + auth.length, type);

		/*
		 * If his response isn't properly encrypted with the session
		 * key, and the decrypted checksum fails to match, he's
		 * bogus. Bail out.
		 */
		r = krb_rd_priv(auth.dat, auth.length, schedule, &cred.session,
				&foreign, &local, &msg_data);
		if (r != KSUCCESS) {
			debug("Kerberos V4 krb_rd_priv failed: %s", krb_err_txt[r]);
			packet_disconnect("Kerberos V4 challenge failed!");
		}
		/* Fetch the (incremented) checksum that we supplied in the request. */
		(void) memcpy((char *) &cksum, (char *) msg_data.app_data, sizeof(cksum));
		cksum = ntohl(cksum);

		/* If it matches, we're golden. */
		if (cksum == checksum + 1) {
			debug("Kerberos V4 challenge successful.");
			return 1;
		} else
			packet_disconnect("Kerberos V4 challenge failed!");
		break;

	default:
		packet_disconnect("Protocol error on Kerberos V4 response: %d", type);
	}
	return 0;
}

#endif /* KRB4 */

#ifdef AFS
int
send_kerberos_tgt()
{
	CREDENTIALS *creds;
	char pname[ANAME_SZ], pinst[INST_SZ], prealm[REALM_SZ];
	int r, type, plen;
	char buffer[8192];
	struct stat st;

	/* Don't do anything if we don't have any tickets. */
	if (stat(tkt_string(), &st) < 0)
		return 0;

	creds = xmalloc(sizeof(*creds));

	if ((r = krb_get_tf_fullname(TKT_FILE, pname, pinst, prealm)) != KSUCCESS) {
		debug("Kerberos V4 tf_fullname failed: %s", krb_err_txt[r]);
		return 0;
	}
	if ((r = krb_get_cred("krbtgt", prealm, prealm, creds)) != GC_OK) {
		debug("Kerberos V4 get_cred failed: %s", krb_err_txt[r]);
		return 0;
	}
	if (time(0) > krb_life_to_time(creds->issue_date, creds->lifetime)) {
		debug("Kerberos V4 ticket expired: %s", TKT_FILE);
		return 0;
	}
	creds_to_radix(creds, (unsigned char *)buffer);
	xfree(creds);

	packet_start(SSH_CMSG_HAVE_KERBEROS_TGT);
	packet_put_string(buffer, strlen(buffer));
	packet_send();
	packet_write_wait();

	type = packet_read(&plen);

	if (type == SSH_SMSG_FAILURE)
		debug("Kerberos TGT for realm %s rejected.", prealm);
	else if (type != SSH_SMSG_SUCCESS)
		packet_disconnect("Protocol error on Kerberos TGT response: %d", type);

	return 1;
}

void
send_afs_tokens(void)
{
	CREDENTIALS creds;
	struct ViceIoctl parms;
	struct ClearToken ct;
	int i, type, len, plen;
	char buf[2048], *p, *server_cell;
	char buffer[8192];

	/* Move over ktc_GetToken, here's something leaner. */
	for (i = 0; i < 100; i++) {	/* just in case */
		parms.in = (char *) &i;
		parms.in_size = sizeof(i);
		parms.out = buf;
		parms.out_size = sizeof(buf);
		if (k_pioctl(0, VIOCGETTOK, &parms, 0) != 0)
			break;
		p = buf;

		/* Get secret token. */
		memcpy(&creds.ticket_st.length, p, sizeof(unsigned int));
		if (creds.ticket_st.length > MAX_KTXT_LEN)
			break;
		p += sizeof(unsigned int);
		memcpy(creds.ticket_st.dat, p, creds.ticket_st.length);
		p += creds.ticket_st.length;

		/* Get clear token. */
		memcpy(&len, p, sizeof(len));
		if (len != sizeof(struct ClearToken))
			break;
		p += sizeof(len);
		memcpy(&ct, p, len);
		p += len;
		p += sizeof(len);	/* primary flag */
		server_cell = p;

		/* Flesh out our credentials. */
		strlcpy(creds.service, "afs", sizeof creds.service);
		creds.instance[0] = '\0';
		strlcpy(creds.realm, server_cell, REALM_SZ);
		memcpy(creds.session, ct.HandShakeKey, DES_KEY_SZ);
		creds.issue_date = ct.BeginTimestamp;
		creds.lifetime = krb_time_to_life(creds.issue_date, ct.EndTimestamp);
		creds.kvno = ct.AuthHandle;
		snprintf(creds.pname, sizeof(creds.pname), "AFS ID %d", ct.ViceId);
		creds.pinst[0] = '\0';

		/* Encode token, ship it off. */
		if (!creds_to_radix(&creds, (unsigned char*) buffer))
			break;
		packet_start(SSH_CMSG_HAVE_AFS_TOKEN);
		packet_put_string(buffer, strlen(buffer));
		packet_send();
		packet_write_wait();

		/* Roger, Roger. Clearance, Clarence. What's your vector,
		   Victor? */
		type = packet_read(&plen);

		if (type == SSH_SMSG_FAILURE)
			debug("AFS token for cell %s rejected.", server_cell);
		else if (type != SSH_SMSG_SUCCESS)
			packet_disconnect("Protocol error on AFS token response: %d", type);
	}
}

#endif /* AFS */

/*
 * Tries to authenticate with any string-based challenge/response system.
 * Note that the client code is not tied to s/key or TIS.
 */
int
try_skey_authentication()
{
	int type, i;
	int payload_len;
	unsigned int clen;
	char *challenge, *response;

	debug("Doing skey authentication.");

	/* request a challenge */
	packet_start(SSH_CMSG_AUTH_TIS);
	packet_send();
	packet_write_wait();

	type = packet_read(&payload_len);
	if (type != SSH_SMSG_FAILURE &&
	    type != SSH_SMSG_AUTH_TIS_CHALLENGE) {
		packet_disconnect("Protocol error: got %d in response "
				  "to skey-auth", type);
	}
	if (type != SSH_SMSG_AUTH_TIS_CHALLENGE) {
		debug("No challenge for skey authentication.");
		return 0;
	}
	challenge = packet_get_string(&clen);
	packet_integrity_check(payload_len, (4 + clen), type);
	if (options.cipher == SSH_CIPHER_NONE)
		log("WARNING: Encryption is disabled! "
		    "Reponse will be transmitted in clear text.");
	fprintf(stderr, "%s\n", challenge);
	xfree(challenge);
	fflush(stderr);
	for (i = 0; i < options.number_of_password_prompts; i++) {
		if (i != 0)
			error("Permission denied, please try again.");
		response = read_passphrase("Response: ", 0);
		packet_start(SSH_CMSG_AUTH_TIS_RESPONSE);
		packet_put_string(response, strlen(response));
		memset(response, 0, strlen(response));
		xfree(response);
		packet_send();
		packet_write_wait();
		type = packet_read(&payload_len);
		if (type == SSH_SMSG_SUCCESS)
			return 1;
		if (type != SSH_SMSG_FAILURE)
			packet_disconnect("Protocol error: got %d in response "
					  "to skey-auth-reponse", type);
	}
	/* failure */
	return 0;
}

/*
 * Tries to authenticate with plain passwd authentication.
 */
int
try_password_authentication(char *prompt)
{
	int type, i, payload_len;
	char *password;

	debug("Doing password authentication.");
	if (options.cipher == SSH_CIPHER_NONE)
		log("WARNING: Encryption is disabled! Password will be transmitted in clear text.");
	for (i = 0; i < options.number_of_password_prompts; i++) {
		if (i != 0)
			error("Permission denied, please try again.");
		password = read_passphrase(prompt, 0);
		packet_start(SSH_CMSG_AUTH_PASSWORD);
		packet_put_string(password, strlen(password));
		memset(password, 0, strlen(password));
		xfree(password);
		packet_send();
		packet_write_wait();

		type = packet_read(&payload_len);
		if (type == SSH_SMSG_SUCCESS)
			return 1;
		if (type != SSH_SMSG_FAILURE)
			packet_disconnect("Protocol error: got %d in response to passwd auth", type);
	}
	/* failure */
	return 0;
}

char *
chop(char *s)
{
	char *t = s;
	while (*t) {
		if(*t == '\n' || *t == '\r') {
			*t = '\0';
			return s;
		}
		t++;
	}
	return s;

}

/*
 * Waits for the server identification string, and sends our own
 * identification string.
 */
void
ssh_exchange_identification()
{
	char buf[256], remote_version[256];	/* must be same size! */
	int remote_major, remote_minor, i, mismatch;
	int connection_in = packet_get_connection_in();
	int connection_out = packet_get_connection_out();

	/* Read other side\'s version identification. */
	for (i = 0; i < sizeof(buf) - 1; i++) {
		int len = read(connection_in, &buf[i], 1);
		if (len < 0)
			fatal("ssh_exchange_identification: read: %.100s", strerror(errno));
		if (len != 1)
			fatal("ssh_exchange_identification: Connection closed by remote host");
		if (buf[i] == '\r') {
			buf[i] = '\n';
			buf[i + 1] = 0;
			continue;		/**XXX wait for \n */
		}
		if (buf[i] == '\n') {
			buf[i + 1] = 0;
			break;
		}
	}
	buf[sizeof(buf) - 1] = 0;
	server_version_string = xstrdup(buf);

	/*
	 * Check that the versions match.  In future this might accept
	 * several versions and set appropriate flags to handle them.
	 */
	if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
	    &remote_major, &remote_minor, remote_version) != 3)
		fatal("Bad remote protocol version identification: '%.100s'", buf);
	debug("Remote protocol version %d.%d, remote software version %.100s",
	      remote_major, remote_minor, remote_version);

	compat_datafellows(remote_version);
	mismatch = 0;

	switch(remote_major) {
	case 1:
		if (remote_minor == 99 &&
		    (options.protocol & SSH_PROTO_2) &&
		    !(options.protocol & SSH_PROTO_1_PREFERRED)) {
			enable_compat20();
			break;
		}
		if (!(options.protocol & SSH_PROTO_1)) {
			mismatch = 1;
			break;
		}
		if (remote_minor < 3) {
			fatal("Remote machine has too old SSH software version.");
		} else if (remote_minor == 3) {
			/* We speak 1.3, too. */
			enable_compat13();
			if (options.forward_agent) {
				log("Agent forwarding disabled for protocol 1.3");
				options.forward_agent = 0;
			}
		}
		break;
	case 2:
		if (options.protocol & SSH_PROTO_2) {
			enable_compat20();
			break;
		}
		/* FALLTHROUGH */
	default:
		mismatch = 1;
		break;
	}
	if (mismatch)
		fatal("Protocol major versions differ: %d vs. %d",
		    (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
		    remote_major);

	/* Send our own protocol version identification. */
	snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n",
	    compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
	    compat20 ? PROTOCOL_MINOR_2 : PROTOCOL_MINOR_1,
	    SSH_VERSION);
	if (atomicio(write, connection_out, buf, strlen(buf)) != strlen(buf))
		fatal("write: %.100s", strerror(errno));
	client_version_string = xstrdup(buf);
	chop(client_version_string);
	chop(server_version_string);
	debug("Local version string %.100s", client_version_string);
}

int
read_yes_or_no(const char *prompt, int defval)
{
	char buf[1024];
	FILE *f;
	int retval = -1;

	if (isatty(0))
		f = stdin;
	else
		f = fopen("/dev/tty", "rw");

	if (f == NULL)
		return 0;

	fflush(stdout);

	while (1) {
		fprintf(stderr, "%s", prompt);
		if (fgets(buf, sizeof(buf), f) == NULL) {
			/* Print a newline (the prompt probably didn\'t have one). */
			fprintf(stderr, "\n");
			strlcpy(buf, "no", sizeof buf);
		}
		/* Remove newline from response. */
		if (strchr(buf, '\n'))
			*strchr(buf, '\n') = 0;

		if (buf[0] == 0)
			retval = defval;
		if (strcmp(buf, "yes") == 0)
			retval = 1;
		if (strcmp(buf, "no") == 0)
			retval = 0;

		if (retval != -1) {
			if (f != stdin)
				fclose(f);
			return retval;
		}
	}
}

/*
 * check whether the supplied host key is valid, return only if ok.
 */

void
check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
{
	Key *file_key;
	char *ip = NULL;
	char hostline[1000], *hostp;
	HostStatus host_status;
	HostStatus ip_status;
	int local = 0, host_ip_differ = 0;
	int salen;
	char ntop[NI_MAXHOST];

	/*
	 * Force accepting of the host key for loopback/localhost. The
	 * problem is that if the home directory is NFS-mounted to multiple
	 * machines, localhost will refer to a different machine in each of
	 * them, and the user will get bogus HOST_CHANGED warnings.  This
	 * essentially disables host authentication for localhost; however,
	 * this is probably not a real problem.
	 */
	switch (hostaddr->sa_family) {
	case AF_INET:
		local = (ntohl(((struct sockaddr_in *)hostaddr)->sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
		salen = sizeof(struct sockaddr_in);
		break;
	case AF_INET6:
		local = IN6_IS_ADDR_LOOPBACK(&(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
		salen = sizeof(struct sockaddr_in6);
		break;
	default:
		local = 0;
		salen = sizeof(struct sockaddr_storage);
		break;
	}
	if (local) {
		debug("Forcing accepting of host key for loopback/localhost.");
		return;
	}

	/*
	 * Turn off check_host_ip for proxy connects, since
	 * we don't have the remote ip-address
	 */
	if (options.proxy_command != NULL && options.check_host_ip)
		options.check_host_ip = 0;

	if (options.check_host_ip) {
		if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop),
		    NULL, 0, NI_NUMERICHOST) != 0)
			fatal("check_host_key: getnameinfo failed");
		ip = xstrdup(ntop);
	}

	/*
	 * Store the host key from the known host file in here so that we can
	 * compare it with the key for the IP address.
	 */
	file_key = key_new(host_key->type);

	/*
	 * Check if the host key is present in the user\'s list of known
	 * hosts or in the systemwide list.
	 */
	host_status = check_host_in_hostfile(options.user_hostfile, host, host_key, file_key);
	if (host_status == HOST_NEW)
		host_status = check_host_in_hostfile(options.system_hostfile, host, host_key, file_key);
	/*
	 * Also perform check for the ip address, skip the check if we are
	 * localhost or the hostname was an ip address to begin with
	 */
	if (options.check_host_ip && !local && strcmp(host, ip)) {
		Key *ip_key = key_new(host_key->type);
		ip_status = check_host_in_hostfile(options.user_hostfile, ip, host_key, ip_key);

		if (ip_status == HOST_NEW)
			ip_status = check_host_in_hostfile(options.system_hostfile, ip, host_key, ip_key);
		if (host_status == HOST_CHANGED &&
		    (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key)))
			host_ip_differ = 1;

		key_free(ip_key);
	} else
		ip_status = host_status;

	key_free(file_key);

	switch (host_status) {
	case HOST_OK:
		/* The host is known and the key matches. */
		debug("Host '%.200s' is known and matches the host key.", host);
		if (options.check_host_ip) {
			if (ip_status == HOST_NEW) {
				if (!add_host_to_hostfile(options.user_hostfile, ip, host_key))
					log("Failed to add the host key for IP address '%.30s' to the list of known hosts (%.30s).",
					    ip, options.user_hostfile);
				else
					log("Warning: Permanently added host key for IP address '%.30s' to the list of known hosts.",
					    ip);
			} else if (ip_status != HOST_OK)
				log("Warning: the host key for '%.200s' differs from the key for the IP address '%.30s'",
				    host, ip);
		}
		break;
	case HOST_NEW:
		/* The host is new. */
		if (options.strict_host_key_checking == 1) {
			/* User has requested strict host key checking.  We will not add the host key
			   automatically.  The only alternative left is to abort. */
			fatal("No host key is known for %.200s and you have requested strict checking.", host);
		} else if (options.strict_host_key_checking == 2) {
			/* The default */
			char prompt[1024];
			char *fp = key_fingerprint(host_key);
			snprintf(prompt, sizeof(prompt),
			    "The authenticity of host '%.200s' can't be established.\n"
			    "Key fingerprint is %s.\n"
			    "Are you sure you want to continue connecting (yes/no)? ",
			    host, fp);
			if (!read_yes_or_no(prompt, -1))
				fatal("Aborted by user!\n");
		}
		if (options.check_host_ip && ip_status == HOST_NEW && strcmp(host, ip)) {
			snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
			hostp = hostline;
		} else
			hostp = host;

		/* If not in strict mode, add the key automatically to the local known_hosts file. */
		if (!add_host_to_hostfile(options.user_hostfile, hostp, host_key))
			log("Failed to add the host to the list of known hosts (%.500s).",
			    options.user_hostfile);
		else
			log("Warning: Permanently added '%.200s' to the list of known hosts.",
			    hostp);
		break;
	case HOST_CHANGED:
		if (options.check_host_ip && host_ip_differ) {
			char *msg;
			if (ip_status == HOST_NEW)
				msg = "is unknown";
			else if (ip_status == HOST_OK)
				msg = "is unchanged";
			else
				msg = "has a different value";
			error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
			error("@       WARNING: POSSIBLE DNS SPOOFING DETECTED!          @");
			error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
			error("The host key for %s has changed,", host);
			error("and the key for the according IP address %s", ip);
			error("%s. This could either mean that", msg);
			error("DNS SPOOFING is happening or the IP address for the host");
			error("and its host key have changed at the same time");
		}
		/* The host key has changed. */
		error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
		error("@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @");
		error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
		error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
		error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
		error("It is also possible that the host key has just been changed.");
		error("Please contact your system administrator.");
		error("Add correct host key in %.100s to get rid of this message.",
		      options.user_hostfile);

		/*
		 * If strict host key checking is in use, the user will have
		 * to edit the key manually and we can only abort.
		 */
		if (options.strict_host_key_checking)
			fatal("Host key for %.200s has changed and you have requested strict checking.", host);

		/*
		 * If strict host key checking has not been requested, allow
		 * the connection but without password authentication or
		 * agent forwarding.
		 */
		if (options.password_authentication) {
			error("Password authentication is disabled to avoid trojan horses.");
			options.password_authentication = 0;
		}
		if (options.forward_agent) {
			error("Agent forwarding is disabled to avoid trojan horses.");
			options.forward_agent = 0;
		}
		/*
		 * XXX Should permit the user to change to use the new id.
		 * This could be done by converting the host key to an
		 * identifying sentence, tell that the host identifies itself
		 * by that sentence, and ask the user if he/she whishes to
		 * accept the authentication.
		 */
		break;
	}
	if (options.check_host_ip)
		xfree(ip);
}
void
check_rsa_host_key(char *host, struct sockaddr *hostaddr, RSA *host_key)
{
	Key k;
	k.type = KEY_RSA;
	k.rsa = host_key;
	check_host_key(host, hostaddr, &k);
}

/*
 * SSH2 key exchange
 */
void
ssh_kex2(char *host, struct sockaddr *hostaddr)
{
	Kex *kex;
	char *cprop[PROPOSAL_MAX];
	char *sprop[PROPOSAL_MAX];
	Buffer *client_kexinit;
	Buffer *server_kexinit;
	int payload_len, dlen;
	unsigned int klen, kout;
	char *ptr;
	char *signature = NULL;
	unsigned int slen;
	char *server_host_key_blob = NULL;
	Key *server_host_key;
	unsigned int sbloblen;
	DH *dh;
	BIGNUM *dh_server_pub = 0;
	BIGNUM *shared_secret = 0;
	int i;
	unsigned char *kbuf;
	unsigned char *hash;

/* KEXINIT */

	debug("Sending KEX init.");
	if (options.ciphers != NULL) {
		myproposal[PROPOSAL_ENC_ALGS_CTOS] =
		myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
	} else if (
	    options.cipher == SSH_CIPHER_ARCFOUR ||
	    options.cipher == SSH_CIPHER_3DES_CBC ||
	    options.cipher == SSH_CIPHER_CAST128_CBC ||
	    options.cipher == SSH_CIPHER_BLOWFISH_CBC) {
		myproposal[PROPOSAL_ENC_ALGS_CTOS] =
		myproposal[PROPOSAL_ENC_ALGS_STOC] = cipher_name(options.cipher);
	}
	if (options.compression) {
		myproposal[PROPOSAL_COMP_ALGS_CTOS] = "zlib";
		myproposal[PROPOSAL_COMP_ALGS_STOC] = "zlib";
	} else {
		myproposal[PROPOSAL_COMP_ALGS_CTOS] = "none";
		myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
	}
	for (i = 0; i < PROPOSAL_MAX; i++)
		cprop[i] = xstrdup(myproposal[i]);

	client_kexinit = kex_init(cprop);
	packet_start(SSH2_MSG_KEXINIT);
	packet_put_raw(buffer_ptr(client_kexinit), buffer_len(client_kexinit));	
	packet_send();
	packet_write_wait();

	debug("done");

	packet_read_expect(&payload_len, SSH2_MSG_KEXINIT);

	/* save payload for session_id */
	server_kexinit = xmalloc(sizeof(*server_kexinit));
	buffer_init(server_kexinit);
	ptr = packet_get_raw(&payload_len);
	buffer_append(server_kexinit, ptr, payload_len);

	/* skip cookie */
	for (i = 0; i < 16; i++)
		(void) packet_get_char();
	/* kex init proposal strings */
	for (i = 0; i < PROPOSAL_MAX; i++) {
		sprop[i] = packet_get_string(NULL);
		debug("got kexinit string: %s", sprop[i]);
	}
	i = (int) packet_get_char();
	debug("first kex follow == %d", i);
	i = packet_get_int();
	debug("reserved == %d", i);
	packet_done();

	debug("done read kexinit");
	kex = kex_choose_conf(cprop, sprop, 0);

/* KEXDH */

	debug("Sending SSH2_MSG_KEXDH_INIT.");

	/* generate and send 'e', client DH public key */
	dh = dh_new_group1();
	packet_start(SSH2_MSG_KEXDH_INIT);
	packet_put_bignum2(dh->pub_key);
	packet_send();
	packet_write_wait();

#ifdef DEBUG_KEXDH
	fprintf(stderr, "\np= ");
	bignum_print(dh->p);
	fprintf(stderr, "\ng= ");
	bignum_print(dh->g);
	fprintf(stderr, "\npub= ");
	bignum_print(dh->pub_key);
	fprintf(stderr, "\n");
	DHparams_print_fp(stderr, dh);
#endif

	debug("Wait SSH2_MSG_KEXDH_REPLY.");

	packet_read_expect(&payload_len, SSH2_MSG_KEXDH_REPLY);

	debug("Got SSH2_MSG_KEXDH_REPLY.");

	/* key, cert */
	server_host_key_blob = packet_get_string(&sbloblen);
	server_host_key = dsa_serverkey_from_blob(server_host_key_blob, sbloblen);
	if (server_host_key == NULL)
		fatal("cannot decode server_host_key_blob");

	check_host_key(host, hostaddr, server_host_key);

	/* DH paramter f, server public DH key */
	dh_server_pub = BN_new();
	if (dh_server_pub == NULL)
		fatal("dh_server_pub == NULL");
	packet_get_bignum2(dh_server_pub, &dlen);

#ifdef DEBUG_KEXDH
	fprintf(stderr, "\ndh_server_pub= ");
	bignum_print(dh_server_pub);
	fprintf(stderr, "\n");
	debug("bits %d", BN_num_bits(dh_server_pub));
#endif

	/* signed H */
	signature = packet_get_string(&slen);
	packet_done();

	if (!dh_pub_is_valid(dh, dh_server_pub))
		packet_disconnect("bad server public DH value");

	klen = DH_size(dh);
	kbuf = xmalloc(klen);
	kout = DH_compute_key(kbuf, dh_server_pub, dh);
#ifdef DEBUG_KEXDH
	debug("shared secret: len %d/%d", klen, kout);
	fprintf(stderr, "shared secret == ");
	for (i = 0; i< kout; i++)
		fprintf(stderr, "%02x", (kbuf[i])&0xff);
	fprintf(stderr, "\n");
#endif
	shared_secret = BN_new();

	BN_bin2bn(kbuf, kout, shared_secret);
	memset(kbuf, 0, klen);
	xfree(kbuf);

	/* calc and verify H */
	hash = kex_hash(
	    client_version_string,
	    server_version_string,
	    buffer_ptr(client_kexinit), buffer_len(client_kexinit),
	    buffer_ptr(server_kexinit), buffer_len(server_kexinit),
	    server_host_key_blob, sbloblen,
	    dh->pub_key,
	    dh_server_pub,
	    shared_secret
	);
	buffer_free(client_kexinit);
	buffer_free(server_kexinit);
	xfree(client_kexinit);
	xfree(server_kexinit);
#ifdef DEBUG_KEXDH
	fprintf(stderr, "hash == ");
	for (i = 0; i< 20; i++)
		fprintf(stderr, "%02x", (hash[i])&0xff);
	fprintf(stderr, "\n");
#endif
	dsa_verify(server_host_key, (unsigned char *)signature, slen, hash, 20);
	key_free(server_host_key);

	kex_derive_keys(kex, hash, shared_secret);
	packet_set_kex(kex);

	/* have keys, free DH */
	DH_free(dh);

	debug("Wait SSH2_MSG_NEWKEYS.");
	packet_read_expect(&payload_len, SSH2_MSG_NEWKEYS);
	packet_done();
	debug("GOT SSH2_MSG_NEWKEYS.");

	debug("send SSH2_MSG_NEWKEYS.");
	packet_start(SSH2_MSG_NEWKEYS);
	packet_send();
	packet_write_wait();
	debug("done: send SSH2_MSG_NEWKEYS.");

#ifdef DEBUG_KEXDH
	/* send 1st encrypted/maced/compressed message */
	packet_start(SSH2_MSG_IGNORE);
	packet_put_cstring("markus");
	packet_send();
	packet_write_wait();
#endif
	debug("done: KEX2.");
}
/*
 * Authenticate user
 */
void
ssh_userauth2(int host_key_valid, RSA *own_host_key,
    uid_t original_real_uid, char *host)
{
	int type;
	int plen;
	unsigned int dlen;
	int partial;
	struct passwd *pw;
	char prompt[80];
	char *server_user, *local_user;
	char *auths;
	char *password;
	char *service = "ssh-connection";		/* service name */

	debug("send SSH2_MSG_SERVICE_REQUEST");
	packet_start(SSH2_MSG_SERVICE_REQUEST);
	packet_put_cstring("ssh-userauth");
	packet_send();
	packet_write_wait();

	type = packet_read(&plen);
	if (type != SSH2_MSG_SERVICE_ACCEPT) {
		fatal("denied SSH2_MSG_SERVICE_ACCEPT: %d", type);
	}
	if (packet_remaining() > 0) {
		char *reply = packet_get_string(&plen);
		debug("service_accept: %s", reply);
		xfree(reply);
	} else {
		/* payload empty for ssh-2.0.13 ?? */
		log("buggy server: service_accept w/o service");
	}
	packet_done();
	debug("got SSH2_MSG_SERVICE_ACCEPT");

	/*XX COMMONCODE: */
	/* Get local user name.  Use it as server user if no user name was given. */
	pw = getpwuid(original_real_uid);
	if (!pw)
		fatal("User id %d not found from user database.", original_real_uid);
	local_user = xstrdup(pw->pw_name);
	server_user = options.user ? options.user : local_user;

	/* INITIAL request for auth */
	packet_start(SSH2_MSG_USERAUTH_REQUEST);
	packet_put_cstring(server_user);
	packet_put_cstring(service);
	packet_put_cstring("none");
	packet_send();
	packet_write_wait();

	for (;;) {
		type = packet_read(&plen);
		if (type == SSH2_MSG_USERAUTH_SUCCESS)
			break;
		if (type != SSH2_MSG_USERAUTH_FAILURE)
			fatal("access denied: %d", type);
		/* SSH2_MSG_USERAUTH_FAILURE means: try again */
		auths = packet_get_string(&dlen);
		debug("authentications that can continue: %s", auths);
		partial = packet_get_char();
		packet_done();
		if (partial)
			debug("partial success");
		if (strstr(auths, "password") == NULL)
			fatal("passwd auth not supported: %s", auths);
		xfree(auths);
		/* try passwd */
		snprintf(prompt, sizeof(prompt), "%.30s@%.40s's password: ",
		    server_user, host);
		password = read_passphrase(prompt, 0);
		packet_start(SSH2_MSG_USERAUTH_REQUEST);
		packet_put_cstring(server_user);
		packet_put_cstring(service);
		packet_put_cstring("password");
		packet_put_char(0);
		packet_put_cstring(password);
		memset(password, 0, strlen(password));
		xfree(password);
		packet_send();
		packet_write_wait();
	}
	packet_done();
	debug("ssh-userauth2 successfull");
}

/*
 * SSH1 key exchange
 */
void
ssh_kex(char *host, struct sockaddr *hostaddr)
{
	int i;
	BIGNUM *key;
	RSA *host_key;
	RSA *public_key;
	int bits, rbits;
	int ssh_cipher_default = SSH_CIPHER_3DES;
	unsigned char session_key[SSH_SESSION_KEY_LENGTH];
	unsigned char cookie[8];
	unsigned int supported_ciphers;
	unsigned int server_flags, client_flags;
	int payload_len, clen, sum_len = 0;
	u_int32_t rand = 0;

	debug("Waiting for server public key.");

	/* Wait for a public key packet from the server. */
	packet_read_expect(&payload_len, SSH_SMSG_PUBLIC_KEY);

	/* Get cookie from the packet. */
	for (i = 0; i < 8; i++)
		cookie[i] = packet_get_char();

	/* Get the public key. */
	public_key = RSA_new();
	bits = packet_get_int();/* bits */
	public_key->e = BN_new();
	packet_get_bignum(public_key->e, &clen);
	sum_len += clen;
	public_key->n = BN_new();
	packet_get_bignum(public_key->n, &clen);
	sum_len += clen;

	rbits = BN_num_bits(public_key->n);
	if (bits != rbits) {
		log("Warning: Server lies about size of server public key: "
		    "actual size is %d bits vs. announced %d.", rbits, bits);
		log("Warning: This may be due to an old implementation of ssh.");
	}
	/* Get the host key. */
	host_key = RSA_new();
	bits = packet_get_int();/* bits */
	host_key->e = BN_new();
	packet_get_bignum(host_key->e, &clen);
	sum_len += clen;
	host_key->n = BN_new();
	packet_get_bignum(host_key->n, &clen);
	sum_len += clen;

	rbits = BN_num_bits(host_key->n);
	if (bits != rbits) {
		log("Warning: Server lies about size of server host key: "
		    "actual size is %d bits vs. announced %d.", rbits, bits);
		log("Warning: This may be due to an old implementation of ssh.");
	}

	/* Get protocol flags. */
	server_flags = packet_get_int();
	packet_set_protocol_flags(server_flags);

	supported_ciphers = packet_get_int();
	supported_authentications = packet_get_int();

	debug("Received server public key (%d bits) and host key (%d bits).",
	      BN_num_bits(public_key->n), BN_num_bits(host_key->n));

	packet_integrity_check(payload_len,
			       8 + 4 + sum_len + 0 + 4 + 0 + 0 + 4 + 4 + 4,
			       SSH_SMSG_PUBLIC_KEY);

	check_rsa_host_key(host, hostaddr, host_key);

	client_flags = SSH_PROTOFLAG_SCREEN_NUMBER | SSH_PROTOFLAG_HOST_IN_FWD_OPEN;

	compute_session_id(session_id, cookie, host_key->n, public_key->n);

	/* Generate a session key. */
	arc4random_stir();

	/*
	 * Generate an encryption key for the session.   The key is a 256 bit
	 * random number, interpreted as a 32-byte key, with the least
	 * significant 8 bits being the first byte of the key.
	 */
	for (i = 0; i < 32; i++) {
		if (i % 4 == 0)
			rand = arc4random();
		session_key[i] = rand & 0xff;
		rand >>= 8;
	}

	/*
	 * According to the protocol spec, the first byte of the session key
	 * is the highest byte of the integer.  The session key is xored with
	 * the first 16 bytes of the session id.
	 */
	key = BN_new();
	BN_set_word(key, 0);
	for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
		BN_lshift(key, key, 8);
		if (i < 16)
			BN_add_word(key, session_key[i] ^ session_id[i]);
		else
			BN_add_word(key, session_key[i]);
	}

	/*
	 * Encrypt the integer using the public key and host key of the
	 * server (key with smaller modulus first).
	 */
	if (BN_cmp(public_key->n, host_key->n) < 0) {
		/* Public key has smaller modulus. */
		if (BN_num_bits(host_key->n) <
		    BN_num_bits(public_key->n) + SSH_KEY_BITS_RESERVED) {
			fatal("respond_to_rsa_challenge: host_key %d < public_key %d + "
			      "SSH_KEY_BITS_RESERVED %d",
			      BN_num_bits(host_key->n),
			      BN_num_bits(public_key->n),
			      SSH_KEY_BITS_RESERVED);
		}
		rsa_public_encrypt(key, key, public_key);
		rsa_public_encrypt(key, key, host_key);
	} else {
		/* Host key has smaller modulus (or they are equal). */
		if (BN_num_bits(public_key->n) <
		    BN_num_bits(host_key->n) + SSH_KEY_BITS_RESERVED) {
			fatal("respond_to_rsa_challenge: public_key %d < host_key %d + "
			      "SSH_KEY_BITS_RESERVED %d",
			      BN_num_bits(public_key->n),
			      BN_num_bits(host_key->n),
			      SSH_KEY_BITS_RESERVED);
		}
		rsa_public_encrypt(key, key, host_key);
		rsa_public_encrypt(key, key, public_key);
	}

	/* Destroy the public keys since we no longer need them. */
	RSA_free(public_key);
	RSA_free(host_key);

	if (options.cipher == SSH_CIPHER_NOT_SET) {
		if (cipher_mask1() & supported_ciphers & (1 << ssh_cipher_default))
			options.cipher = ssh_cipher_default;
		else {
			debug("Cipher %s not supported, using %.100s instead.",
			      cipher_name(ssh_cipher_default),
			      cipher_name(SSH_FALLBACK_CIPHER));
			options.cipher = SSH_FALLBACK_CIPHER;
		}
	}
	/* Check that the selected cipher is supported. */
	if (!(supported_ciphers & (1 << options.cipher)))
		fatal("Selected cipher type %.100s not supported by server.",
		      cipher_name(options.cipher));

	debug("Encryption type: %.100s", cipher_name(options.cipher));

	/* Send the encrypted session key to the server. */
	packet_start(SSH_CMSG_SESSION_KEY);
	packet_put_char(options.cipher);

	/* Send the cookie back to the server. */
	for (i = 0; i < 8; i++)
		packet_put_char(cookie[i]);

	/* Send and destroy the encrypted encryption key integer. */
	packet_put_bignum(key);
	BN_clear_free(key);

	/* Send protocol flags. */
	packet_put_int(client_flags);

	/* Send the packet now. */
	packet_send();
	packet_write_wait();

	debug("Sent encrypted session key.");

	/* Set the encryption key. */
	packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, options.cipher);

	/* We will no longer need the session key here.  Destroy any extra copies. */
	memset(session_key, 0, sizeof(session_key));

	/*
	 * Expect a success message from the server.  Note that this message
	 * will be received in encrypted form.
	 */
	packet_read_expect(&payload_len, SSH_SMSG_SUCCESS);

	debug("Received encrypted confirmation.");
}

/*
 * Authenticate user
 */
void
ssh_userauth(int host_key_valid, RSA *own_host_key,
    uid_t original_real_uid, char *host)
{
	int i, type;
	int payload_len;
	struct passwd *pw;
	const char *server_user, *local_user;

	/* Get local user name.  Use it as server user if no user name was given. */
	pw = getpwuid(original_real_uid);
	if (!pw)
		fatal("User id %d not found from user database.", original_real_uid);
	local_user = xstrdup(pw->pw_name);
	server_user = options.user ? options.user : local_user;

	/* Send the name of the user to log in as on the server. */
	packet_start(SSH_CMSG_USER);
	packet_put_string(server_user, strlen(server_user));
	packet_send();
	packet_write_wait();

	/*
	 * The server should respond with success if no authentication is
	 * needed (the user has no password).  Otherwise the server responds
	 * with failure.
	 */
	type = packet_read(&payload_len);

	/* check whether the connection was accepted without authentication. */
	if (type == SSH_SMSG_SUCCESS)
		return;
	if (type != SSH_SMSG_FAILURE)
		packet_disconnect("Protocol error: got %d in response to SSH_CMSG_USER",
				  type);

#ifdef AFS
	/* Try Kerberos tgt passing if the server supports it. */
	if ((supported_authentications & (1 << SSH_PASS_KERBEROS_TGT)) &&
	    options.kerberos_tgt_passing) {
		if (options.cipher == SSH_CIPHER_NONE)
			log("WARNING: Encryption is disabled! Ticket will be transmitted in the clear!");
		(void) send_kerberos_tgt();
	}
	/* Try AFS token passing if the server supports it. */
	if ((supported_authentications & (1 << SSH_PASS_AFS_TOKEN)) &&
	    options.afs_token_passing && k_hasafs()) {
		if (options.cipher == SSH_CIPHER_NONE)
			log("WARNING: Encryption is disabled! Token will be transmitted in the clear!");
		send_afs_tokens();
	}
#endif /* AFS */

#ifdef KRB4
	if ((supported_authentications & (1 << SSH_AUTH_KERBEROS)) &&
	    options.kerberos_authentication) {
		debug("Trying Kerberos authentication.");
		if (try_kerberos_authentication()) {
			/* The server should respond with success or failure. */
			type = packet_read(&payload_len);
			if (type == SSH_SMSG_SUCCESS)
				return;
			if (type != SSH_SMSG_FAILURE)
				packet_disconnect("Protocol error: got %d in response to Kerberos auth", type);
		}
	}
#endif /* KRB4 */

	/*
	 * Use rhosts authentication if running in privileged socket and we
	 * do not wish to remain anonymous.
	 */
	if ((supported_authentications & (1 << SSH_AUTH_RHOSTS)) &&
	    options.rhosts_authentication) {
		debug("Trying rhosts authentication.");
		packet_start(SSH_CMSG_AUTH_RHOSTS);
		packet_put_string(local_user, strlen(local_user));
		packet_send();
		packet_write_wait();

		/* The server should respond with success or failure. */
		type = packet_read(&payload_len);
		if (type == SSH_SMSG_SUCCESS)
			return;
		if (type != SSH_SMSG_FAILURE)
			packet_disconnect("Protocol error: got %d in response to rhosts auth",
					  type);
	}
	/*
	 * Try .rhosts or /etc/hosts.equiv authentication with RSA host
	 * authentication.
	 */
	if ((supported_authentications & (1 << SSH_AUTH_RHOSTS_RSA)) &&
	    options.rhosts_rsa_authentication && host_key_valid) {
		if (try_rhosts_rsa_authentication(local_user, own_host_key))
			return;
	}
	/* Try RSA authentication if the server supports it. */
	if ((supported_authentications & (1 << SSH_AUTH_RSA)) &&
	    options.rsa_authentication) {
		/*
		 * Try RSA authentication using the authentication agent. The
		 * agent is tried first because no passphrase is needed for
		 * it, whereas identity files may require passphrases.
		 */
		if (try_agent_authentication())
			return;

		/* Try RSA authentication for each identity. */
		for (i = 0; i < options.num_identity_files; i++)
			if (try_rsa_authentication(options.identity_files[i]))
				return;
	}
	/* Try skey authentication if the server supports it. */
	if ((supported_authentications & (1 << SSH_AUTH_TIS)) &&
	    options.skey_authentication && !options.batch_mode) {
		if (try_skey_authentication())
			return;
	}
	/* Try password authentication if the server supports it. */
	if ((supported_authentications & (1 << SSH_AUTH_PASSWORD)) &&
	    options.password_authentication && !options.batch_mode) {
		char prompt[80];

		snprintf(prompt, sizeof(prompt), "%.30s@%.40s's password: ",
		    server_user, host);
		if (try_password_authentication(prompt))
			return;
	}
	/* All authentication methods have failed.  Exit with an error message. */
	fatal("Permission denied.");
	/* NOTREACHED */
}
/*
 * Starts a dialog with the server, and authenticates the current user on the
 * server.  This does not need any extra privileges.  The basic connection
 * to the server must already have been established before this is called.
 * If login fails, this function prints an error and never returns.
 * This function does not require super-user privileges.
 */
void
ssh_login(int host_key_valid, RSA *own_host_key, const char *orighost,
    struct sockaddr *hostaddr, uid_t original_real_uid)
{
	char *host, *cp;

	/* Convert the user-supplied hostname into all lowercase. */
	host = xstrdup(orighost);
	for (cp = host; *cp; cp++)
		if (isupper(*cp))
			*cp = tolower(*cp);

	/* Exchange protocol version identification strings with the server. */
	ssh_exchange_identification();

	/* Put the connection into non-blocking mode. */
	packet_set_nonblocking();

	/* key exchange */
	/* authenticate user */
	if (compat20) {
		ssh_kex2(host, hostaddr);
		ssh_userauth2(host_key_valid, own_host_key, original_real_uid, host);
	} else {
		supported_authentications = 0;
		ssh_kex(host, hostaddr);
		if (supported_authentications == 0)
			fatal("supported_authentications == 0.");
		ssh_userauth(host_key_valid, own_host_key, original_real_uid, host);
	}
}