summaryrefslogtreecommitdiffstats
path: root/crypto/openssh/sshd.c
blob: d3f5bb81540b3234dae6dcb575fdf21be0f2070f (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
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
/* $OpenBSD: sshd.c,v 1.375 2010/04/16 01:47:26 djm Exp $ */
/*
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 * This program is the ssh daemon.  It listens for connections from clients,
 * and performs authentication, executes use commands or shell, and forwards
 * information to/from the application to the user client over an encrypted
 * connection.  This can also handle forwarding of X11, TCP/IP, and
 * authentication agent connections.
 *
 * As far as I am concerned, the code I have written for this software
 * can be used freely for any purpose.  Any derived versions of this
 * software must be clearly marked as such, and if the derived work is
 * incompatible with the protocol description in the RFC file, it must be
 * called by a name other than "ssh" or "Secure Shell".
 *
 * SSH2 implementation:
 * Privilege Separation:
 *
 * Copyright (c) 2000, 2001, 2002 Markus Friedl.  All rights reserved.
 * Copyright (c) 2002 Niels Provos.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "includes.h"
__RCSID("$FreeBSD$");

#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/socket.h>
#ifdef HAVE_SYS_STAT_H
# include <sys/stat.h>
#endif
#ifdef HAVE_SYS_TIME_H
# include <sys/time.h>
#endif
#include "openbsd-compat/sys-tree.h"
#include "openbsd-compat/sys-queue.h"
#include <sys/wait.h>

#include <errno.h>
#include <fcntl.h>
#include <netdb.h>
#ifdef HAVE_PATHS_H
#include <paths.h>
#endif
#include <grp.h>
#include <pwd.h>
#include <signal.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <openssl/dh.h>
#include <openssl/bn.h>
#include <openssl/md5.h>
#include <openssl/rand.h>
#include "openbsd-compat/openssl-compat.h"

#ifdef HAVE_SECUREWARE
#include <sys/security.h>
#include <prot.h>
#endif

#ifdef __FreeBSD__
#include <resolv.h>
#if defined(GSSAPI) && defined(HAVE_GSSAPI_H)
#include <gssapi.h>
#elif defined(GSSAPI) && defined(HAVE_GSSAPI_GSSAPI_H)
#include <gssapi/gssapi.h>
#endif
#endif

#include "xmalloc.h"
#include "ssh.h"
#include "ssh1.h"
#include "ssh2.h"
#include "rsa.h"
#include "sshpty.h"
#include "packet.h"
#include "log.h"
#include "buffer.h"
#include "servconf.h"
#include "uidswap.h"
#include "compat.h"
#include "cipher.h"
#include "key.h"
#include "kex.h"
#include "dh.h"
#include "myproposal.h"
#include "authfile.h"
#include "pathnames.h"
#include "atomicio.h"
#include "canohost.h"
#include "hostfile.h"
#include "auth.h"
#include "misc.h"
#include "msg.h"
#include "dispatch.h"
#include "channels.h"
#include "session.h"
#include "monitor_mm.h"
#include "monitor.h"
#ifdef GSSAPI
#include "ssh-gss.h"
#endif
#include "monitor_wrap.h"
#include "roaming.h"
#include "version.h"

#ifdef LIBWRAP
#include <tcpd.h>
#include <syslog.h>
int allow_severity;
int deny_severity;
#endif /* LIBWRAP */

#ifndef O_NOCTTY
#define O_NOCTTY	0
#endif

/* Re-exec fds */
#define REEXEC_DEVCRYPTO_RESERVED_FD	(STDERR_FILENO + 1)
#define REEXEC_STARTUP_PIPE_FD		(STDERR_FILENO + 2)
#define REEXEC_CONFIG_PASS_FD		(STDERR_FILENO + 3)
#define REEXEC_MIN_FREE_FD		(STDERR_FILENO + 4)

extern char *__progname;

/* Server configuration options. */
ServerOptions options;

/* Name of the server configuration file. */
char *config_file_name = _PATH_SERVER_CONFIG_FILE;

/*
 * Debug mode flag.  This can be set on the command line.  If debug
 * mode is enabled, extra debugging output will be sent to the system
 * log, the daemon will not go to background, and will exit after processing
 * the first connection.
 */
int debug_flag = 0;

/* Flag indicating that the daemon should only test the configuration and keys. */
int test_flag = 0;

/* Flag indicating that the daemon is being started from inetd. */
int inetd_flag = 0;

/* Flag indicating that sshd should not detach and become a daemon. */
int no_daemon_flag = 0;

/* debug goes to stderr unless inetd_flag is set */
int log_stderr = 0;

/* Saved arguments to main(). */
char **saved_argv;
int saved_argc;

/* re-exec */
int rexeced_flag = 0;
int rexec_flag = 1;
int rexec_argc = 0;
char **rexec_argv;

/*
 * The sockets that the server is listening; this is used in the SIGHUP
 * signal handler.
 */
#define	MAX_LISTEN_SOCKS	16
int listen_socks[MAX_LISTEN_SOCKS];
int num_listen_socks = 0;

/*
 * the client's version string, passed by sshd2 in compat mode. if != NULL,
 * sshd will skip the version-number exchange
 */
char *client_version_string = NULL;
char *server_version_string = NULL;

/* for rekeying XXX fixme */
Kex *xxx_kex;

/*
 * Any really sensitive data in the application is contained in this
 * structure. The idea is that this structure could be locked into memory so
 * that the pages do not get written into swap.  However, there are some
 * problems. The private key contains BIGNUMs, and we do not (in principle)
 * have access to the internals of them, and locking just the structure is
 * not very useful.  Currently, memory locking is not implemented.
 */
struct {
	Key	*server_key;		/* ephemeral server key */
	Key	*ssh1_host_key;		/* ssh1 host key */
	Key	**host_keys;		/* all private host keys */
	Key	**host_certificates;	/* all public host certificates */
	int	have_ssh1_key;
	int	have_ssh2_key;
	u_char	ssh1_cookie[SSH_SESSION_KEY_LENGTH];
} sensitive_data;

/*
 * Flag indicating whether the RSA server key needs to be regenerated.
 * Is set in the SIGALRM handler and cleared when the key is regenerated.
 */
static volatile sig_atomic_t key_do_regen = 0;

/* This is set to true when a signal is received. */
static volatile sig_atomic_t received_sighup = 0;
static volatile sig_atomic_t received_sigterm = 0;

/* session identifier, used by RSA-auth */
u_char session_id[16];

/* same for ssh2 */
u_char *session_id2 = NULL;
u_int session_id2_len = 0;

/* record remote hostname or ip */
u_int utmp_len = MAXHOSTNAMELEN;

/* options.max_startup sized array of fd ints */
int *startup_pipes = NULL;
int startup_pipe;		/* in child */

/* variables used for privilege separation */
int use_privsep = -1;
struct monitor *pmonitor = NULL;

/* global authentication context */
Authctxt *the_authctxt = NULL;

/* sshd_config buffer */
Buffer cfg;

/* message to be displayed after login */
Buffer loginmsg;

/* Unprivileged user */
struct passwd *privsep_pw = NULL;

/* Prototypes for various functions defined later in this file. */
void destroy_sensitive_data(void);
void demote_sensitive_data(void);

static void do_ssh1_kex(void);
static void do_ssh2_kex(void);

/*
 * Close all listening sockets
 */
static void
close_listen_socks(void)
{
	int i;

	for (i = 0; i < num_listen_socks; i++)
		close(listen_socks[i]);
	num_listen_socks = -1;
}

static void
close_startup_pipes(void)
{
	int i;

	if (startup_pipes)
		for (i = 0; i < options.max_startups; i++)
			if (startup_pipes[i] != -1)
				close(startup_pipes[i]);
}

/*
 * Signal handler for SIGHUP.  Sshd execs itself when it receives SIGHUP;
 * the effect is to reread the configuration file (and to regenerate
 * the server key).
 */

/*ARGSUSED*/
static void
sighup_handler(int sig)
{
	int save_errno = errno;

	received_sighup = 1;
	signal(SIGHUP, sighup_handler);
	errno = save_errno;
}

/*
 * Called from the main program after receiving SIGHUP.
 * Restarts the server.
 */
static void
sighup_restart(void)
{
	logit("Received SIGHUP; restarting.");
	close_listen_socks();
	close_startup_pipes();
	alarm(0);  /* alarm timer persists across exec */
	signal(SIGHUP, SIG_IGN); /* will be restored after exec */
	execv(saved_argv[0], saved_argv);
	logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0],
	    strerror(errno));
	exit(1);
}

/*
 * Generic signal handler for terminating signals in the master daemon.
 */
/*ARGSUSED*/
static void
sigterm_handler(int sig)
{
	received_sigterm = sig;
}

/*
 * SIGCHLD handler.  This is called whenever a child dies.  This will then
 * reap any zombies left by exited children.
 */
/*ARGSUSED*/
static void
main_sigchld_handler(int sig)
{
	int save_errno = errno;
	pid_t pid;
	int status;

	while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
	    (pid < 0 && errno == EINTR))
		;

	signal(SIGCHLD, main_sigchld_handler);
	errno = save_errno;
}

/*
 * Signal handler for the alarm after the login grace period has expired.
 */
/*ARGSUSED*/
static void
grace_alarm_handler(int sig)
{
	if (use_privsep && pmonitor != NULL && pmonitor->m_pid > 0)
		kill(pmonitor->m_pid, SIGALRM);

	/* Log error and exit. */
	sigdie("Timeout before authentication for %s", get_remote_ipaddr());
}

/*
 * Signal handler for the key regeneration alarm.  Note that this
 * alarm only occurs in the daemon waiting for connections, and it does not
 * do anything with the private key or random state before forking.
 * Thus there should be no concurrency control/asynchronous execution
 * problems.
 */
static void
generate_ephemeral_server_key(void)
{
	verbose("Generating %s%d bit RSA key.",
	    sensitive_data.server_key ? "new " : "", options.server_key_bits);
	if (sensitive_data.server_key != NULL)
		key_free(sensitive_data.server_key);
	sensitive_data.server_key = key_generate(KEY_RSA1,
	    options.server_key_bits);
	verbose("RSA key generation complete.");

	arc4random_buf(sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
	arc4random_stir();
}

/*ARGSUSED*/
static void
key_regeneration_alarm(int sig)
{
	int save_errno = errno;

	signal(SIGALRM, SIG_DFL);
	errno = save_errno;
	key_do_regen = 1;
}

static void
sshd_exchange_identification(int sock_in, int sock_out)
{
	u_int i;
	int mismatch;
	int remote_major, remote_minor;
	int major, minor;
	char *s, *newline = "\n";
	char buf[256];			/* Must not be larger than remote_version. */
	char remote_version[256];	/* Must be at least as big as buf. */

	if ((options.protocol & SSH_PROTO_1) &&
	    (options.protocol & SSH_PROTO_2)) {
		major = PROTOCOL_MAJOR_1;
		minor = 99;
	} else if (options.protocol & SSH_PROTO_2) {
		major = PROTOCOL_MAJOR_2;
		minor = PROTOCOL_MINOR_2;
		newline = "\r\n";
	} else {
		major = PROTOCOL_MAJOR_1;
		minor = PROTOCOL_MINOR_1;
	}
	snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s%s", major, minor,
	    SSH_VERSION, newline);
	server_version_string = xstrdup(buf);

	/* Send our protocol version identification. */
	if (roaming_atomicio(vwrite, sock_out, server_version_string,
	    strlen(server_version_string))
	    != strlen(server_version_string)) {
		logit("Could not write ident string to %s", get_remote_ipaddr());
		cleanup_exit(255);
	}

	/* Read other sides version identification. */
	memset(buf, 0, sizeof(buf));
	for (i = 0; i < sizeof(buf) - 1; i++) {
		if (roaming_atomicio(read, sock_in, &buf[i], 1) != 1) {
			logit("Did not receive identification string from %s",
			    get_remote_ipaddr());
			cleanup_exit(255);
		}
		if (buf[i] == '\r') {
			buf[i] = 0;
			/* Kludge for F-Secure Macintosh < 1.0.2 */
			if (i == 12 &&
			    strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
				break;
			continue;
		}
		if (buf[i] == '\n') {
			buf[i] = 0;
			break;
		}
	}
	buf[sizeof(buf) - 1] = 0;
	client_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(client_version_string, "SSH-%d.%d-%[^\n]\n",
	    &remote_major, &remote_minor, remote_version) != 3) {
		s = "Protocol mismatch.\n";
		(void) atomicio(vwrite, sock_out, s, strlen(s));
		close(sock_in);
		close(sock_out);
		logit("Bad protocol version identification '%.100s' from %s",
		    client_version_string, get_remote_ipaddr());
		cleanup_exit(255);
	}
	debug("Client protocol version %d.%d; client software version %.100s",
	    remote_major, remote_minor, remote_version);

	compat_datafellows(remote_version);

	if (datafellows & SSH_BUG_PROBE) {
		logit("probed from %s with %s.  Don't panic.",
		    get_remote_ipaddr(), client_version_string);
		cleanup_exit(255);
	}

	if (datafellows & SSH_BUG_SCANNER) {
		logit("scanned from %s with %s.  Don't panic.",
		    get_remote_ipaddr(), client_version_string);
		cleanup_exit(255);
	}

	mismatch = 0;
	switch (remote_major) {
	case 1:
		if (remote_minor == 99) {
			if (options.protocol & SSH_PROTO_2)
				enable_compat20();
			else
				mismatch = 1;
			break;
		}
		if (!(options.protocol & SSH_PROTO_1)) {
			mismatch = 1;
			break;
		}
		if (remote_minor < 3) {
			packet_disconnect("Your ssh version is too old and "
			    "is no longer supported.  Please install a newer version.");
		} else if (remote_minor == 3) {
			/* note that this disables agent-forwarding */
			enable_compat13();
		}
		break;
	case 2:
		if (options.protocol & SSH_PROTO_2) {
			enable_compat20();
			break;
		}
		/* FALLTHROUGH */
	default:
		mismatch = 1;
		break;
	}
	chop(server_version_string);
	debug("Local version string %.200s", server_version_string);

	if (mismatch) {
		s = "Protocol major versions differ.\n";
		(void) atomicio(vwrite, sock_out, s, strlen(s));
		close(sock_in);
		close(sock_out);
		logit("Protocol major versions differ for %s: %.200s vs. %.200s",
		    get_remote_ipaddr(),
		    server_version_string, client_version_string);
		cleanup_exit(255);
	}
}

/* Destroy the host and server keys.  They will no longer be needed. */
void
destroy_sensitive_data(void)
{
	int i;

	if (sensitive_data.server_key) {
		key_free(sensitive_data.server_key);
		sensitive_data.server_key = NULL;
	}
	for (i = 0; i < options.num_host_key_files; i++) {
		if (sensitive_data.host_keys[i]) {
			key_free(sensitive_data.host_keys[i]);
			sensitive_data.host_keys[i] = NULL;
		}
		if (sensitive_data.host_certificates[i]) {
			key_free(sensitive_data.host_certificates[i]);
			sensitive_data.host_certificates[i] = NULL;
		}
	}
	sensitive_data.ssh1_host_key = NULL;
	memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
}

/* Demote private to public keys for network child */
void
demote_sensitive_data(void)
{
	Key *tmp;
	int i;

	if (sensitive_data.server_key) {
		tmp = key_demote(sensitive_data.server_key);
		key_free(sensitive_data.server_key);
		sensitive_data.server_key = tmp;
	}

	for (i = 0; i < options.num_host_key_files; i++) {
		if (sensitive_data.host_keys[i]) {
			tmp = key_demote(sensitive_data.host_keys[i]);
			key_free(sensitive_data.host_keys[i]);
			sensitive_data.host_keys[i] = tmp;
			if (tmp->type == KEY_RSA1)
				sensitive_data.ssh1_host_key = tmp;
		}
		/* Certs do not need demotion */
	}

	/* We do not clear ssh1_host key and cookie.  XXX - Okay Niels? */
}

static void
privsep_preauth_child(void)
{
	u_int32_t rnd[256];
	gid_t gidset[1];

	/* Enable challenge-response authentication for privilege separation */
	privsep_challenge_enable();

	arc4random_stir();
	arc4random_buf(rnd, sizeof(rnd));
	RAND_seed(rnd, sizeof(rnd));

	/* Demote the private keys to public keys. */
	demote_sensitive_data();

	/* Change our root directory */
	if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1)
		fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR,
		    strerror(errno));
	if (chdir("/") == -1)
		fatal("chdir(\"/\"): %s", strerror(errno));

	/* Drop our privileges */
	debug3("privsep user:group %u:%u", (u_int)privsep_pw->pw_uid,
	    (u_int)privsep_pw->pw_gid);
#if 0
	/* XXX not ready, too heavy after chroot */
	do_setusercontext(privsep_pw);
#else
	gidset[0] = privsep_pw->pw_gid;
	if (setgroups(1, gidset) < 0)
		fatal("setgroups: %.100s", strerror(errno));
	permanently_set_uid(privsep_pw);
#endif
}

static int
privsep_preauth(Authctxt *authctxt)
{
	int status;
	pid_t pid;

	/* Set up unprivileged child process to deal with network data */
	pmonitor = monitor_init();
	/* Store a pointer to the kex for later rekeying */
	pmonitor->m_pkex = &xxx_kex;

	pid = fork();
	if (pid == -1) {
		fatal("fork of unprivileged child failed");
	} else if (pid != 0) {
		debug2("Network child is on pid %ld", (long)pid);

		close(pmonitor->m_recvfd);
		pmonitor->m_pid = pid;
		monitor_child_preauth(authctxt, pmonitor);
		close(pmonitor->m_sendfd);

		/* Sync memory */
		monitor_sync(pmonitor);

		/* Wait for the child's exit status */
		while (waitpid(pid, &status, 0) < 0)
			if (errno != EINTR)
				break;
		return (1);
	} else {
		/* child */

		close(pmonitor->m_sendfd);

		/* Demote the child */
		if (getuid() == 0 || geteuid() == 0)
			privsep_preauth_child();
		setproctitle("%s", "[net]");
	}
	return (0);
}

static void
privsep_postauth(Authctxt *authctxt)
{
	u_int32_t rnd[256];

#ifdef DISABLE_FD_PASSING
	if (1) {
#else
	if (authctxt->pw->pw_uid == 0 || options.use_login) {
#endif
		/* File descriptor passing is broken or root login */
		use_privsep = 0;
		goto skip;
	}

	/* New socket pair */
	monitor_reinit(pmonitor);

	pmonitor->m_pid = fork();
	if (pmonitor->m_pid == -1)
		fatal("fork of unprivileged child failed");
	else if (pmonitor->m_pid != 0) {
		verbose("User child is on pid %ld", (long)pmonitor->m_pid);
		close(pmonitor->m_recvfd);
		buffer_clear(&loginmsg);
		monitor_child_postauth(pmonitor);

		/* NEVERREACHED */
		exit(0);
	}

	close(pmonitor->m_sendfd);

	/* Demote the private keys to public keys. */
	demote_sensitive_data();

	arc4random_stir();
	arc4random_buf(rnd, sizeof(rnd));
	RAND_seed(rnd, sizeof(rnd));

	/* Drop privileges */
	do_setusercontext(authctxt->pw);

 skip:
	/* It is safe now to apply the key state */
	monitor_apply_keystate(pmonitor);

	/*
	 * Tell the packet layer that authentication was successful, since
	 * this information is not part of the key state.
	 */
	packet_set_authenticated();
}

static char *
list_hostkey_types(void)
{
	Buffer b;
	const char *p;
	char *ret;
	int i;
	Key *key;

	buffer_init(&b);
	for (i = 0; i < options.num_host_key_files; i++) {
		key = sensitive_data.host_keys[i];
		if (key == NULL)
			continue;
		switch (key->type) {
		case KEY_RSA:
		case KEY_DSA:
			if (buffer_len(&b) > 0)
				buffer_append(&b, ",", 1);
			p = key_ssh_name(key);
			buffer_append(&b, p, strlen(p));
			break;
		}
		/* If the private key has a cert peer, then list that too */
		key = sensitive_data.host_certificates[i];
		if (key == NULL)
			continue;
		switch (key->type) {
		case KEY_RSA_CERT_V00:
		case KEY_DSA_CERT_V00:
		case KEY_RSA_CERT:
		case KEY_DSA_CERT:
			if (buffer_len(&b) > 0)
				buffer_append(&b, ",", 1);
			p = key_ssh_name(key);
			buffer_append(&b, p, strlen(p));
			break;
		}
	}
	buffer_append(&b, "\0", 1);
	ret = xstrdup(buffer_ptr(&b));
	buffer_free(&b);
	debug("list_hostkey_types: %s", ret);
	return ret;
}

static Key *
get_hostkey_by_type(int type, int need_private)
{
	int i;
	Key *key;

	for (i = 0; i < options.num_host_key_files; i++) {
		switch (type) {
		case KEY_RSA_CERT_V00:
		case KEY_DSA_CERT_V00:
		case KEY_RSA_CERT:
		case KEY_DSA_CERT:
			key = sensitive_data.host_certificates[i];
			break;
		default:
			key = sensitive_data.host_keys[i];
			break;
		}
		if (key != NULL && key->type == type)
			return need_private ?
			    sensitive_data.host_keys[i] : key;
	}
	return NULL;
}

Key *
get_hostkey_public_by_type(int type)
{
	return get_hostkey_by_type(type, 0);
}

Key *
get_hostkey_private_by_type(int type)
{
	return get_hostkey_by_type(type, 1);
}

Key *
get_hostkey_by_index(int ind)
{
	if (ind < 0 || ind >= options.num_host_key_files)
		return (NULL);
	return (sensitive_data.host_keys[ind]);
}

int
get_hostkey_index(Key *key)
{
	int i;

	for (i = 0; i < options.num_host_key_files; i++) {
		if (key_is_cert(key)) {
			if (key == sensitive_data.host_certificates[i])
				return (i);
		} else {
			if (key == sensitive_data.host_keys[i])
				return (i);
		}
	}
	return (-1);
}

/*
 * returns 1 if connection should be dropped, 0 otherwise.
 * dropping starts at connection #max_startups_begin with a probability
 * of (max_startups_rate/100). the probability increases linearly until
 * all connections are dropped for startups > max_startups
 */
static int
drop_connection(int startups)
{
	int p, r;

	if (startups < options.max_startups_begin)
		return 0;
	if (startups >= options.max_startups)
		return 1;
	if (options.max_startups_rate == 100)
		return 1;

	p  = 100 - options.max_startups_rate;
	p *= startups - options.max_startups_begin;
	p /= options.max_startups - options.max_startups_begin;
	p += options.max_startups_rate;
	r = arc4random_uniform(100);

	debug("drop_connection: p %d, r %d", p, r);
	return (r < p) ? 1 : 0;
}

static void
usage(void)
{
	fprintf(stderr, "%s, %s\n",
	    SSH_RELEASE, SSLeay_version(SSLEAY_VERSION));
	fprintf(stderr,
"usage: sshd [-46DdeiqTt] [-b bits] [-C connection_spec] [-c host_cert_file]\n"
"            [-f config_file] [-g login_grace_time] [-h host_key_file]\n"
"            [-k key_gen_time] [-o option] [-p port] [-u len]\n"
	);
	exit(1);
}

static void
send_rexec_state(int fd, Buffer *conf)
{
	Buffer m;

	debug3("%s: entering fd = %d config len %d", __func__, fd,
	    buffer_len(conf));

	/*
	 * Protocol from reexec master to child:
	 *	string	configuration
	 *	u_int	ephemeral_key_follows
	 *	bignum	e		(only if ephemeral_key_follows == 1)
	 *	bignum	n			"
	 *	bignum	d			"
	 *	bignum	iqmp			"
	 *	bignum	p			"
	 *	bignum	q			"
	 *	string rngseed		(only if OpenSSL is not self-seeded)
	 */
	buffer_init(&m);
	buffer_put_cstring(&m, buffer_ptr(conf));

	if (sensitive_data.server_key != NULL &&
	    sensitive_data.server_key->type == KEY_RSA1) {
		buffer_put_int(&m, 1);
		buffer_put_bignum(&m, sensitive_data.server_key->rsa->e);
		buffer_put_bignum(&m, sensitive_data.server_key->rsa->n);
		buffer_put_bignum(&m, sensitive_data.server_key->rsa->d);
		buffer_put_bignum(&m, sensitive_data.server_key->rsa->iqmp);
		buffer_put_bignum(&m, sensitive_data.server_key->rsa->p);
		buffer_put_bignum(&m, sensitive_data.server_key->rsa->q);
	} else
		buffer_put_int(&m, 0);

#ifndef OPENSSL_PRNG_ONLY
	rexec_send_rng_seed(&m);
#endif

	if (ssh_msg_send(fd, 0, &m) == -1)
		fatal("%s: ssh_msg_send failed", __func__);

	buffer_free(&m);

	debug3("%s: done", __func__);
}

static void
recv_rexec_state(int fd, Buffer *conf)
{
	Buffer m;
	char *cp;
	u_int len;

	debug3("%s: entering fd = %d", __func__, fd);

	buffer_init(&m);

	if (ssh_msg_recv(fd, &m) == -1)
		fatal("%s: ssh_msg_recv failed", __func__);
	if (buffer_get_char(&m) != 0)
		fatal("%s: rexec version mismatch", __func__);

	cp = buffer_get_string(&m, &len);
	if (conf != NULL)
		buffer_append(conf, cp, len + 1);
	xfree(cp);

	if (buffer_get_int(&m)) {
		if (sensitive_data.server_key != NULL)
			key_free(sensitive_data.server_key);
		sensitive_data.server_key = key_new_private(KEY_RSA1);
		buffer_get_bignum(&m, sensitive_data.server_key->rsa->e);
		buffer_get_bignum(&m, sensitive_data.server_key->rsa->n);
		buffer_get_bignum(&m, sensitive_data.server_key->rsa->d);
		buffer_get_bignum(&m, sensitive_data.server_key->rsa->iqmp);
		buffer_get_bignum(&m, sensitive_data.server_key->rsa->p);
		buffer_get_bignum(&m, sensitive_data.server_key->rsa->q);
		rsa_generate_additional_parameters(
		    sensitive_data.server_key->rsa);
	}

#ifndef OPENSSL_PRNG_ONLY
	rexec_recv_rng_seed(&m);
#endif

	buffer_free(&m);

	debug3("%s: done", __func__);
}

/* Accept a connection from inetd */
static void
server_accept_inetd(int *sock_in, int *sock_out)
{
	int fd;

	startup_pipe = -1;
	if (rexeced_flag) {
		close(REEXEC_CONFIG_PASS_FD);
		*sock_in = *sock_out = dup(STDIN_FILENO);
		if (!debug_flag) {
			startup_pipe = dup(REEXEC_STARTUP_PIPE_FD);
			close(REEXEC_STARTUP_PIPE_FD);
		}
	} else {
		*sock_in = dup(STDIN_FILENO);
		*sock_out = dup(STDOUT_FILENO);
	}
	/*
	 * We intentionally do not close the descriptors 0, 1, and 2
	 * as our code for setting the descriptors won't work if
	 * ttyfd happens to be one of those.
	 */
	if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
		dup2(fd, STDIN_FILENO);
		dup2(fd, STDOUT_FILENO);
		if (fd > STDOUT_FILENO)
			close(fd);
	}
	debug("inetd sockets after dupping: %d, %d", *sock_in, *sock_out);
}

/*
 * Listen for TCP connections
 */
static void
server_listen(void)
{
	int ret, listen_sock, on = 1;
	struct addrinfo *ai;
	char ntop[NI_MAXHOST], strport[NI_MAXSERV];

	for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
		if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
			continue;
		if (num_listen_socks >= MAX_LISTEN_SOCKS)
			fatal("Too many listen sockets. "
			    "Enlarge MAX_LISTEN_SOCKS");
		if ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen,
		    ntop, sizeof(ntop), strport, sizeof(strport),
		    NI_NUMERICHOST|NI_NUMERICSERV)) != 0) {
			error("getnameinfo failed: %.100s",
			    ssh_gai_strerror(ret));
			continue;
		}
		/* Create socket for listening. */
		listen_sock = socket(ai->ai_family, ai->ai_socktype,
		    ai->ai_protocol);
		if (listen_sock < 0) {
			/* kernel may not support ipv6 */
			verbose("socket: %.100s", strerror(errno));
			continue;
		}
		if (set_nonblock(listen_sock) == -1) {
			close(listen_sock);
			continue;
		}
		/*
		 * Set socket options.
		 * Allow local port reuse in TIME_WAIT.
		 */
		if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
		    &on, sizeof(on)) == -1)
			error("setsockopt SO_REUSEADDR: %s", strerror(errno));

		/* Only communicate in IPv6 over AF_INET6 sockets. */
		if (ai->ai_family == AF_INET6)
			sock_set_v6only(listen_sock);

		debug("Bind to port %s on %s.", strport, ntop);

		/* Bind the socket to the desired port. */
		if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
			error("Bind to port %s on %s failed: %.200s.",
			    strport, ntop, strerror(errno));
			close(listen_sock);
			continue;
		}
		listen_socks[num_listen_socks] = listen_sock;
		num_listen_socks++;

		/* Start listening on the port. */
		if (listen(listen_sock, SSH_LISTEN_BACKLOG) < 0)
			fatal("listen on [%s]:%s: %.100s",
			    ntop, strport, strerror(errno));
		logit("Server listening on %s port %s.", ntop, strport);
	}
	freeaddrinfo(options.listen_addrs);

	if (!num_listen_socks)
		fatal("Cannot bind any address.");
}

/*
 * The main TCP accept loop. Note that, for the non-debug case, returns
 * from this function are in a forked subprocess.
 */
static void
server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s)
{
	fd_set *fdset;
	int i, j, ret, maxfd;
	int key_used = 0, startups = 0;
	int startup_p[2] = { -1 , -1 };
	struct sockaddr_storage from;
	socklen_t fromlen;
	pid_t pid;

	/* setup fd set for accept */
	fdset = NULL;
	maxfd = 0;
	for (i = 0; i < num_listen_socks; i++)
		if (listen_socks[i] > maxfd)
			maxfd = listen_socks[i];
	/* pipes connected to unauthenticated childs */
	startup_pipes = xcalloc(options.max_startups, sizeof(int));
	for (i = 0; i < options.max_startups; i++)
		startup_pipes[i] = -1;

	/*
	 * Stay listening for connections until the system crashes or
	 * the daemon is killed with a signal.
	 */
	for (;;) {
		if (received_sighup)
			sighup_restart();
		if (fdset != NULL)
			xfree(fdset);
		fdset = (fd_set *)xcalloc(howmany(maxfd + 1, NFDBITS),
		    sizeof(fd_mask));

		for (i = 0; i < num_listen_socks; i++)
			FD_SET(listen_socks[i], fdset);
		for (i = 0; i < options.max_startups; i++)
			if (startup_pipes[i] != -1)
				FD_SET(startup_pipes[i], fdset);

		/* Wait in select until there is a connection. */
		ret = select(maxfd+1, fdset, NULL, NULL, NULL);
		if (ret < 0 && errno != EINTR)
			error("select: %.100s", strerror(errno));
		if (received_sigterm) {
			logit("Received signal %d; terminating.",
			    (int) received_sigterm);
			close_listen_socks();
			unlink(options.pid_file);
			exit(255);
		}
		if (key_used && key_do_regen) {
			generate_ephemeral_server_key();
			key_used = 0;
			key_do_regen = 0;
		}
		if (ret < 0)
			continue;

		for (i = 0; i < options.max_startups; i++)
			if (startup_pipes[i] != -1 &&
			    FD_ISSET(startup_pipes[i], fdset)) {
				/*
				 * the read end of the pipe is ready
				 * if the child has closed the pipe
				 * after successful authentication
				 * or if the child has died
				 */
				close(startup_pipes[i]);
				startup_pipes[i] = -1;
				startups--;
			}
		for (i = 0; i < num_listen_socks; i++) {
			if (!FD_ISSET(listen_socks[i], fdset))
				continue;
			fromlen = sizeof(from);
			*newsock = accept(listen_socks[i],
			    (struct sockaddr *)&from, &fromlen);
			if (*newsock < 0) {
				if (errno != EINTR && errno != EAGAIN &&
				    errno != EWOULDBLOCK)
					error("accept: %.100s", strerror(errno));
				continue;
			}
			if (unset_nonblock(*newsock) == -1) {
				close(*newsock);
				continue;
			}
			if (drop_connection(startups) == 1) {
				debug("drop connection #%d", startups);
				close(*newsock);
				continue;
			}
			if (pipe(startup_p) == -1) {
				close(*newsock);
				continue;
			}

			if (rexec_flag && socketpair(AF_UNIX,
			    SOCK_STREAM, 0, config_s) == -1) {
				error("reexec socketpair: %s",
				    strerror(errno));
				close(*newsock);
				close(startup_p[0]);
				close(startup_p[1]);
				continue;
			}

			for (j = 0; j < options.max_startups; j++)
				if (startup_pipes[j] == -1) {
					startup_pipes[j] = startup_p[0];
					if (maxfd < startup_p[0])
						maxfd = startup_p[0];
					startups++;
					break;
				}

			/*
			 * Got connection.  Fork a child to handle it, unless
			 * we are in debugging mode.
			 */
			if (debug_flag) {
				/*
				 * In debugging mode.  Close the listening
				 * socket, and start processing the
				 * connection without forking.
				 */
				debug("Server will not fork when running in debugging mode.");
				close_listen_socks();
				*sock_in = *newsock;
				*sock_out = *newsock;
				close(startup_p[0]);
				close(startup_p[1]);
				startup_pipe = -1;
				pid = getpid();
				if (rexec_flag) {
					send_rexec_state(config_s[0],
					    &cfg);
					close(config_s[0]);
				}
				break;
			}

			/*
			 * Normal production daemon.  Fork, and have
			 * the child process the connection. The
			 * parent continues listening.
			 */
			platform_pre_fork();
			if ((pid = fork()) == 0) {
				/*
				 * Child.  Close the listening and
				 * max_startup sockets.  Start using
				 * the accepted socket. Reinitialize
				 * logging (since our pid has changed).
				 * We break out of the loop to handle
				 * the connection.
				 */
				platform_post_fork_child();
				startup_pipe = startup_p[1];
				close_startup_pipes();
				close_listen_socks();
				*sock_in = *newsock;
				*sock_out = *newsock;
				log_init(__progname,
				    options.log_level,
				    options.log_facility,
				    log_stderr);
				if (rexec_flag)
					close(config_s[0]);
				break;
			}

			/* Parent.  Stay in the loop. */
			platform_post_fork_parent(pid);
			if (pid < 0)
				error("fork: %.100s", strerror(errno));
			else
				debug("Forked child %ld.", (long)pid);

			close(startup_p[1]);

			if (rexec_flag) {
				send_rexec_state(config_s[0], &cfg);
				close(config_s[0]);
				close(config_s[1]);
			}

			/*
			 * Mark that the key has been used (it
			 * was "given" to the child).
			 */
			if ((options.protocol & SSH_PROTO_1) &&
			    key_used == 0) {
				/* Schedule server key regeneration alarm. */
				signal(SIGALRM, key_regeneration_alarm);
				alarm(options.key_regeneration_time);
				key_used = 1;
			}

			close(*newsock);

			/*
			 * Ensure that our random state differs
			 * from that of the child
			 */
			arc4random_stir();
		}

		/* child process check (or debug mode) */
		if (num_listen_socks < 0)
			break;
	}
}


/*
 * Main program for the daemon.
 */
int
main(int ac, char **av)
{
	extern char *optarg;
	extern int optind;
	int opt, i, j, on = 1;
	int sock_in = -1, sock_out = -1, newsock = -1;
	const char *remote_ip;
	char *test_user = NULL, *test_host = NULL, *test_addr = NULL;
	int remote_port;
	char *line, *p, *cp;
	int config_s[2] = { -1 , -1 };
	u_int64_t ibytes, obytes;
	mode_t new_umask;
	Key *key;
	Authctxt *authctxt;

#ifdef HAVE_SECUREWARE
	(void)set_auth_parameters(ac, av);
#endif
	__progname = ssh_get_progname(av[0]);
	init_rng();

	/* Save argv. Duplicate so setproctitle emulation doesn't clobber it */
	saved_argc = ac;
	rexec_argc = ac;
	saved_argv = xcalloc(ac + 1, sizeof(*saved_argv));
	for (i = 0; i < ac; i++)
		saved_argv[i] = xstrdup(av[i]);
	saved_argv[i] = NULL;

#ifndef HAVE_SETPROCTITLE
	/* Prepare for later setproctitle emulation */
	compat_init_setproctitle(ac, av);
	av = saved_argv;
#endif

	if (geteuid() == 0 && setgroups(0, NULL) == -1)
		debug("setgroups(): %.200s", strerror(errno));

	/* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
	sanitise_stdfd();

	/* Initialize configuration options to their default values. */
	initialize_server_options(&options);

	/* Parse command-line arguments. */
	while ((opt = getopt(ac, av, "f:p:b:k:h:g:u:o:C:dDeiqrtQRT46")) != -1) {
		switch (opt) {
		case '4':
			options.address_family = AF_INET;
			break;
		case '6':
			options.address_family = AF_INET6;
			break;
		case 'f':
			config_file_name = optarg;
			break;
		case 'c':
			if (options.num_host_cert_files >= MAX_HOSTCERTS) {
				fprintf(stderr, "too many host certificates.\n");
				exit(1);
			}
			options.host_cert_files[options.num_host_cert_files++] =
			   derelativise_path(optarg);
			break;
		case 'd':
			if (debug_flag == 0) {
				debug_flag = 1;
				options.log_level = SYSLOG_LEVEL_DEBUG1;
			} else if (options.log_level < SYSLOG_LEVEL_DEBUG3)
				options.log_level++;
			break;
		case 'D':
			no_daemon_flag = 1;
			break;
		case 'e':
			log_stderr = 1;
			break;
		case 'i':
			inetd_flag = 1;
			break;
		case 'r':
			rexec_flag = 0;
			break;
		case 'R':
			rexeced_flag = 1;
			inetd_flag = 1;
			break;
		case 'Q':
			/* ignored */
			break;
		case 'q':
			options.log_level = SYSLOG_LEVEL_QUIET;
			break;
		case 'b':
			options.server_key_bits = (int)strtonum(optarg, 256,
			    32768, NULL);
			break;
		case 'p':
			options.ports_from_cmdline = 1;
			if (options.num_ports >= MAX_PORTS) {
				fprintf(stderr, "too many ports.\n");
				exit(1);
			}
			options.ports[options.num_ports++] = a2port(optarg);
			if (options.ports[options.num_ports-1] <= 0) {
				fprintf(stderr, "Bad port number.\n");
				exit(1);
			}
			break;
		case 'g':
			if ((options.login_grace_time = convtime(optarg)) == -1) {
				fprintf(stderr, "Invalid login grace time.\n");
				exit(1);
			}
			break;
		case 'k':
			if ((options.key_regeneration_time = convtime(optarg)) == -1) {
				fprintf(stderr, "Invalid key regeneration interval.\n");
				exit(1);
			}
			break;
		case 'h':
			if (options.num_host_key_files >= MAX_HOSTKEYS) {
				fprintf(stderr, "too many host keys.\n");
				exit(1);
			}
			options.host_key_files[options.num_host_key_files++] = 
			   derelativise_path(optarg);
			break;
		case 't':
			test_flag = 1;
			break;
		case 'T':
			test_flag = 2;
			break;
		case 'C':
			cp = optarg;
			while ((p = strsep(&cp, ",")) && *p != '\0') {
				if (strncmp(p, "addr=", 5) == 0)
					test_addr = xstrdup(p + 5);
				else if (strncmp(p, "host=", 5) == 0)
					test_host = xstrdup(p + 5);
				else if (strncmp(p, "user=", 5) == 0)
					test_user = xstrdup(p + 5);
				else {
					fprintf(stderr, "Invalid test "
					    "mode specification %s\n", p);
					exit(1);
				}
			}
			break;
		case 'u':
			utmp_len = (u_int)strtonum(optarg, 0, MAXHOSTNAMELEN+1, NULL);
			if (utmp_len > MAXHOSTNAMELEN) {
				fprintf(stderr, "Invalid utmp length.\n");
				exit(1);
			}
			break;
		case 'o':
			line = xstrdup(optarg);
			if (process_server_config_line(&options, line,
			    "command-line", 0, NULL, NULL, NULL, NULL) != 0)
				exit(1);
			xfree(line);
			break;
		case '?':
		default:
			usage();
			break;
		}
	}
	if (rexeced_flag || inetd_flag)
		rexec_flag = 0;
	if (!test_flag && (rexec_flag && (av[0] == NULL || *av[0] != '/')))
		fatal("sshd re-exec requires execution with an absolute path");
	if (rexeced_flag)
		closefrom(REEXEC_MIN_FREE_FD);
	else
		closefrom(REEXEC_DEVCRYPTO_RESERVED_FD);

	SSLeay_add_all_algorithms();

	/*
	 * Force logging to stderr until we have loaded the private host
	 * key (unless started from inetd)
	 */
	log_init(__progname,
	    options.log_level == SYSLOG_LEVEL_NOT_SET ?
	    SYSLOG_LEVEL_INFO : options.log_level,
	    options.log_facility == SYSLOG_FACILITY_NOT_SET ?
	    SYSLOG_FACILITY_AUTH : options.log_facility,
	    log_stderr || !inetd_flag);

	/*
	 * Unset KRB5CCNAME, otherwise the user's session may inherit it from
	 * root's environment
	 */
	if (getenv("KRB5CCNAME") != NULL)
		unsetenv("KRB5CCNAME");

#ifdef _UNICOS
	/* Cray can define user privs drop all privs now!
	 * Not needed on PRIV_SU systems!
	 */
	drop_cray_privs();
#endif

	sensitive_data.server_key = NULL;
	sensitive_data.ssh1_host_key = NULL;
	sensitive_data.have_ssh1_key = 0;
	sensitive_data.have_ssh2_key = 0;

	/*
	 * If we're doing an extended config test, make sure we have all of
	 * the parameters we need.  If we're not doing an extended test,
	 * do not silently ignore connection test params.
	 */
	if (test_flag >= 2 &&
	   (test_user != NULL || test_host != NULL || test_addr != NULL)
	    && (test_user == NULL || test_host == NULL || test_addr == NULL))
		fatal("user, host and addr are all required when testing "
		   "Match configs");
	if (test_flag < 2 && (test_user != NULL || test_host != NULL ||
	    test_addr != NULL))
		fatal("Config test connection parameter (-C) provided without "
		   "test mode (-T)");

	/* Fetch our configuration */
	buffer_init(&cfg);
	if (rexeced_flag)
		recv_rexec_state(REEXEC_CONFIG_PASS_FD, &cfg);
	else
		load_server_config(config_file_name, &cfg);

	parse_server_config(&options, rexeced_flag ? "rexec" : config_file_name,
	    &cfg, NULL, NULL, NULL);

	seed_rng();

	/* Fill in default values for those options not explicitly set. */
	fill_default_server_options(&options);

	/* challenge-response is implemented via keyboard interactive */
	if (options.challenge_response_authentication)
		options.kbd_interactive_authentication = 1;

	/* set default channel AF */
	channel_set_af(options.address_family);

	/* Check that there are no remaining arguments. */
	if (optind < ac) {
		fprintf(stderr, "Extra argument %s.\n", av[optind]);
		exit(1);
	}

	debug("sshd version %.100s", SSH_RELEASE);

	/* Store privilege separation user for later use if required. */
	if ((privsep_pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) {
		if (use_privsep || options.kerberos_authentication)
			fatal("Privilege separation user %s does not exist",
			    SSH_PRIVSEP_USER);
	} else {
		memset(privsep_pw->pw_passwd, 0, strlen(privsep_pw->pw_passwd));
		privsep_pw = pwcopy(privsep_pw);
		xfree(privsep_pw->pw_passwd);
		privsep_pw->pw_passwd = xstrdup("*");
	}
	endpwent();

	/* load private host keys */
	sensitive_data.host_keys = xcalloc(options.num_host_key_files,
	    sizeof(Key *));
	for (i = 0; i < options.num_host_key_files; i++)
		sensitive_data.host_keys[i] = NULL;

	for (i = 0; i < options.num_host_key_files; i++) {
		key = key_load_private(options.host_key_files[i], "", NULL);
		sensitive_data.host_keys[i] = key;
		if (key == NULL) {
			error("Could not load host key: %s",
			    options.host_key_files[i]);
			sensitive_data.host_keys[i] = NULL;
			continue;
		}
		switch (key->type) {
		case KEY_RSA1:
			sensitive_data.ssh1_host_key = key;
			sensitive_data.have_ssh1_key = 1;
			break;
		case KEY_RSA:
		case KEY_DSA:
			sensitive_data.have_ssh2_key = 1;
			break;
		}
		debug("private host key: #%d type %d %s", i, key->type,
		    key_type(key));
	}
	if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
		logit("Disabling protocol version 1. Could not load host key");
		options.protocol &= ~SSH_PROTO_1;
	}
	if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
		logit("Disabling protocol version 2. Could not load host key");
		options.protocol &= ~SSH_PROTO_2;
	}
	if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
		logit("sshd: no hostkeys available -- exiting.");
		exit(1);
	}

	/*
	 * Load certificates. They are stored in an array at identical
	 * indices to the public keys that they relate to.
	 */
	sensitive_data.host_certificates = xcalloc(options.num_host_key_files,
	    sizeof(Key *));
	for (i = 0; i < options.num_host_key_files; i++)
		sensitive_data.host_certificates[i] = NULL;

	for (i = 0; i < options.num_host_cert_files; i++) {
		key = key_load_public(options.host_cert_files[i], NULL);
		if (key == NULL) {
			error("Could not load host certificate: %s",
			    options.host_cert_files[i]);
			continue;
		}
		if (!key_is_cert(key)) {
			error("Certificate file is not a certificate: %s",
			    options.host_cert_files[i]);
			key_free(key);
			continue;
		}
		/* Find matching private key */
		for (j = 0; j < options.num_host_key_files; j++) {
			if (key_equal_public(key,
			    sensitive_data.host_keys[j])) {
				sensitive_data.host_certificates[j] = key;
				break;
			}
		}
		if (j >= options.num_host_key_files) {
			error("No matching private key for certificate: %s",
			    options.host_cert_files[i]);
			key_free(key);
			continue;
		}
		sensitive_data.host_certificates[j] = key;
		debug("host certificate: #%d type %d %s", j, key->type,
		    key_type(key));
	}
	/* Check certain values for sanity. */
	if (options.protocol & SSH_PROTO_1) {
		if (options.server_key_bits < 512 ||
		    options.server_key_bits > 32768) {
			fprintf(stderr, "Bad server key size.\n");
			exit(1);
		}
		/*
		 * Check that server and host key lengths differ sufficiently. This
		 * is necessary to make double encryption work with rsaref. Oh, I
		 * hate software patents. I dont know if this can go? Niels
		 */
		if (options.server_key_bits >
		    BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) -
		    SSH_KEY_BITS_RESERVED && options.server_key_bits <
		    BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
		    SSH_KEY_BITS_RESERVED) {
			options.server_key_bits =
			    BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
			    SSH_KEY_BITS_RESERVED;
			debug("Forcing server key to %d bits to make it differ from host key.",
			    options.server_key_bits);
		}
	}

	if (use_privsep) {
		struct stat st;

		if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) ||
		    (S_ISDIR(st.st_mode) == 0))
			fatal("Missing privilege separation directory: %s",
			    _PATH_PRIVSEP_CHROOT_DIR);

#ifdef HAVE_CYGWIN
		if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) &&
		    (st.st_uid != getuid () ||
		    (st.st_mode & (S_IWGRP|S_IWOTH)) != 0))
#else
		if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)
#endif
			fatal("%s must be owned by root and not group or "
			    "world-writable.", _PATH_PRIVSEP_CHROOT_DIR);
	}

	if (test_flag > 1) {
		if (test_user != NULL && test_addr != NULL && test_host != NULL)
			parse_server_match_config(&options, test_user,
			    test_host, test_addr);
		dump_config(&options);
	}

	/* Configuration looks good, so exit if in test mode. */
	if (test_flag)
		exit(0);

	/*
	 * Clear out any supplemental groups we may have inherited.  This
	 * prevents inadvertent creation of files with bad modes (in the
	 * portable version at least, it's certainly possible for PAM
	 * to create a file, and we can't control the code in every
	 * module which might be used).
	 */
	if (setgroups(0, NULL) < 0)
		debug("setgroups() failed: %.200s", strerror(errno));

	if (rexec_flag) {
		rexec_argv = xcalloc(rexec_argc + 2, sizeof(char *));
		for (i = 0; i < rexec_argc; i++) {
			debug("rexec_argv[%d]='%s'", i, saved_argv[i]);
			rexec_argv[i] = saved_argv[i];
		}
		rexec_argv[rexec_argc] = "-R";
		rexec_argv[rexec_argc + 1] = NULL;
	}

	/* Ensure that umask disallows at least group and world write */
	new_umask = umask(0077) | 0022;
	(void) umask(new_umask);

	/* Initialize the log (it is reinitialized below in case we forked). */
	if (debug_flag && (!inetd_flag || rexeced_flag))
		log_stderr = 1;
	log_init(__progname, options.log_level, options.log_facility, log_stderr);

	/*
	 * If not in debugging mode, and not started from inetd, disconnect
	 * from the controlling terminal, and fork.  The original process
	 * exits.
	 */
	if (!(debug_flag || inetd_flag || no_daemon_flag)) {
#ifdef TIOCNOTTY
		int fd;
#endif /* TIOCNOTTY */
		if (daemon(0, 0) < 0)
			fatal("daemon() failed: %.200s", strerror(errno));

		/* Disconnect from the controlling tty. */
#ifdef TIOCNOTTY
		fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
		if (fd >= 0) {
			(void) ioctl(fd, TIOCNOTTY, NULL);
			close(fd);
		}
#endif /* TIOCNOTTY */
	}
	/* Reinitialize the log (because of the fork above). */
	log_init(__progname, options.log_level, options.log_facility, log_stderr);

	/* Avoid killing the process in high-pressure swapping environments. */
	if (!inetd_flag && madvise(NULL, 0, MADV_PROTECT) != 0)
		debug("madvise(): %.200s", strerror(errno));

	/* Initialize the random number generator. */
	arc4random_stir();

	/* Chdir to the root directory so that the current disk can be
	   unmounted if desired. */
	chdir("/");

	/* ignore SIGPIPE */
	signal(SIGPIPE, SIG_IGN);

	/* Get a connection, either from inetd or a listening TCP socket */
	if (inetd_flag) {
		server_accept_inetd(&sock_in, &sock_out);
	} else {
		platform_pre_listen();
		server_listen();

		if (options.protocol & SSH_PROTO_1)
			generate_ephemeral_server_key();

		signal(SIGHUP, sighup_handler);
		signal(SIGCHLD, main_sigchld_handler);
		signal(SIGTERM, sigterm_handler);
		signal(SIGQUIT, sigterm_handler);

		/*
		 * Write out the pid file after the sigterm handler
		 * is setup and the listen sockets are bound
		 */
		if (!debug_flag) {
			FILE *f = fopen(options.pid_file, "w");

			if (f == NULL) {
				error("Couldn't create pid file \"%s\": %s",
				    options.pid_file, strerror(errno));
			} else {
				fprintf(f, "%ld\n", (long) getpid());
				fclose(f);
			}
		}

		/* Accept a connection and return in a forked child */
		server_accept_loop(&sock_in, &sock_out,
		    &newsock, config_s);
	}

	/* This is the child processing a new connection. */
	setproctitle("%s", "[accepted]");

	/*
	 * Create a new session and process group since the 4.4BSD
	 * setlogin() affects the entire process group.  We don't
	 * want the child to be able to affect the parent.
	 */
#if !defined(SSHD_ACQUIRES_CTTY)
	/*
	 * If setsid is called, on some platforms sshd will later acquire a
	 * controlling terminal which will result in "could not set
	 * controlling tty" errors.
	 */
	if (!debug_flag && !inetd_flag && setsid() < 0)
		error("setsid: %.100s", strerror(errno));
#endif

	if (rexec_flag) {
		int fd;

		debug("rexec start in %d out %d newsock %d pipe %d sock %d",
		    sock_in, sock_out, newsock, startup_pipe, config_s[0]);
		dup2(newsock, STDIN_FILENO);
		dup2(STDIN_FILENO, STDOUT_FILENO);
		if (startup_pipe == -1)
			close(REEXEC_STARTUP_PIPE_FD);
		else
			dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD);

		dup2(config_s[1], REEXEC_CONFIG_PASS_FD);
		close(config_s[1]);
		if (startup_pipe != -1)
			close(startup_pipe);

		execv(rexec_argv[0], rexec_argv);

		/* Reexec has failed, fall back and continue */
		error("rexec of %s failed: %s", rexec_argv[0], strerror(errno));
		recv_rexec_state(REEXEC_CONFIG_PASS_FD, NULL);
		log_init(__progname, options.log_level,
		    options.log_facility, log_stderr);

		/* Clean up fds */
		startup_pipe = REEXEC_STARTUP_PIPE_FD;
		close(config_s[1]);
		close(REEXEC_CONFIG_PASS_FD);
		newsock = sock_out = sock_in = dup(STDIN_FILENO);
		if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
			dup2(fd, STDIN_FILENO);
			dup2(fd, STDOUT_FILENO);
			if (fd > STDERR_FILENO)
				close(fd);
		}
		debug("rexec cleanup in %d out %d newsock %d pipe %d sock %d",
		    sock_in, sock_out, newsock, startup_pipe, config_s[0]);
	}

	/* Executed child processes don't need these. */
	fcntl(sock_out, F_SETFD, FD_CLOEXEC);
	fcntl(sock_in, F_SETFD, FD_CLOEXEC);

	/*
	 * Disable the key regeneration alarm.  We will not regenerate the
	 * key since we are no longer in a position to give it to anyone. We
	 * will not restart on SIGHUP since it no longer makes sense.
	 */
	alarm(0);
	signal(SIGALRM, SIG_DFL);
	signal(SIGHUP, SIG_DFL);
	signal(SIGTERM, SIG_DFL);
	signal(SIGQUIT, SIG_DFL);
	signal(SIGCHLD, SIG_DFL);
	signal(SIGINT, SIG_DFL);

#ifdef __FreeBSD__
	/*
	 * Initialize the resolver.  This may not happen automatically
	 * before privsep chroot().                                   
	 */
	if ((_res.options & RES_INIT) == 0) {
		debug("res_init()");         
		res_init();         
	}
#ifdef GSSAPI
	/*
	 * Force GSS-API to parse its configuration and load any
	 * mechanism plugins.
	 */
	{
		gss_OID_set mechs;
		OM_uint32 minor_status;
		gss_indicate_mechs(&minor_status, &mechs);
		gss_release_oid_set(&minor_status, &mechs);
	}
#endif
#endif

	/*
	 * Register our connection.  This turns encryption off because we do
	 * not have a key.
	 */
	packet_set_connection(sock_in, sock_out);
	packet_set_server();

	/* Set SO_KEEPALIVE if requested. */
	if (options.tcp_keep_alive && packet_connection_is_on_socket() &&
	    setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) < 0)
		error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));

	if ((remote_port = get_remote_port()) < 0) {
		debug("get_remote_port failed");
		cleanup_exit(255);
	}

	/*
	 * We use get_canonical_hostname with usedns = 0 instead of
	 * get_remote_ipaddr here so IP options will be checked.
	 */
	(void) get_canonical_hostname(0);
	/*
	 * The rest of the code depends on the fact that
	 * get_remote_ipaddr() caches the remote ip, even if
	 * the socket goes away.
	 */
	remote_ip = get_remote_ipaddr();

#ifdef SSH_AUDIT_EVENTS
	audit_connection_from(remote_ip, remote_port);
#endif
#ifdef LIBWRAP
	allow_severity = options.log_facility|LOG_INFO;
	deny_severity = options.log_facility|LOG_WARNING;
	/* Check whether logins are denied from this host. */
	if (packet_connection_is_on_socket()) {
		struct request_info req;

		request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0);
		fromhost(&req);

		if (!hosts_access(&req)) {
			debug("Connection refused by tcp wrapper");
			refuse(&req);
			/* NOTREACHED */
			fatal("libwrap refuse returns");
		}
	}
#endif /* LIBWRAP */

	/* Log the connection. */
	verbose("Connection from %.500s port %d", remote_ip, remote_port);

	/*
	 * We don't want to listen forever unless the other side
	 * successfully authenticates itself.  So we set up an alarm which is
	 * cleared after successful authentication.  A limit of zero
	 * indicates no limit. Note that we don't set the alarm in debugging
	 * mode; it is just annoying to have the server exit just when you
	 * are about to discover the bug.
	 */
	signal(SIGALRM, grace_alarm_handler);
	if (!debug_flag)
		alarm(options.login_grace_time);

	sshd_exchange_identification(sock_in, sock_out);

	/* In inetd mode, generate ephemeral key only for proto 1 connections */
	if (!compat20 && inetd_flag && sensitive_data.server_key == NULL)
		generate_ephemeral_server_key();

	packet_set_nonblocking();

	/* allocate authentication context */
	authctxt = xcalloc(1, sizeof(*authctxt));

	authctxt->loginmsg = &loginmsg;

	/* XXX global for cleanup, access from other modules */
	the_authctxt = authctxt;

	/* prepare buffer to collect messages to display to user after login */
	buffer_init(&loginmsg);
	auth_debug_reset();

	if (use_privsep)
		if (privsep_preauth(authctxt) == 1)
			goto authenticated;

	/* perform the key exchange */
	/* authenticate user and start session */
	if (compat20) {
		do_ssh2_kex();
		do_authentication2(authctxt);
	} else {
		do_ssh1_kex();
		do_authentication(authctxt);
	}
	/*
	 * If we use privilege separation, the unprivileged child transfers
	 * the current keystate and exits
	 */
	if (use_privsep) {
		mm_send_keystate(pmonitor);
		exit(0);
	}

 authenticated:
	/*
	 * Cancel the alarm we set to limit the time taken for
	 * authentication.
	 */
	alarm(0);
	signal(SIGALRM, SIG_DFL);
	authctxt->authenticated = 1;
	if (startup_pipe != -1) {
		close(startup_pipe);
		startup_pipe = -1;
	}

#ifdef SSH_AUDIT_EVENTS
	audit_event(SSH_AUTH_SUCCESS);
#endif

#ifdef GSSAPI
	if (options.gss_authentication) {
		temporarily_use_uid(authctxt->pw);
		ssh_gssapi_storecreds();
		restore_uid();
	}
#endif
#ifdef USE_PAM
	if (options.use_pam) {
		do_pam_setcred(1);
		do_pam_session();
	}
#endif

	/*
	 * In privilege separation, we fork another child and prepare
	 * file descriptor passing.
	 */
	if (use_privsep) {
		privsep_postauth(authctxt);
		/* the monitor process [priv] will not return */
		if (!compat20)
			destroy_sensitive_data();
	}

	packet_set_timeout(options.client_alive_interval,
	    options.client_alive_count_max);

	/* Start session. */
	do_authenticated(authctxt);

	/* The connection has been terminated. */
	packet_get_state(MODE_IN, NULL, NULL, NULL, &ibytes);
	packet_get_state(MODE_OUT, NULL, NULL, NULL, &obytes);
	verbose("Transferred: sent %llu, received %llu bytes", obytes, ibytes);

	verbose("Closing connection to %.500s port %d", remote_ip, remote_port);

#ifdef USE_PAM
	if (options.use_pam)
		finish_pam();
#endif /* USE_PAM */

#ifdef SSH_AUDIT_EVENTS
	PRIVSEP(audit_event(SSH_CONNECTION_CLOSE));
#endif

	packet_close();

	if (use_privsep)
		mm_terminate();

	exit(0);
}

/*
 * Decrypt session_key_int using our private server key and private host key
 * (key with larger modulus first).
 */
int
ssh1_session_key(BIGNUM *session_key_int)
{
	int rsafail = 0;

	if (BN_cmp(sensitive_data.server_key->rsa->n,
	    sensitive_data.ssh1_host_key->rsa->n) > 0) {
		/* Server key has bigger modulus. */
		if (BN_num_bits(sensitive_data.server_key->rsa->n) <
		    BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
		    SSH_KEY_BITS_RESERVED) {
			fatal("do_connection: %s: "
			    "server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
			    get_remote_ipaddr(),
			    BN_num_bits(sensitive_data.server_key->rsa->n),
			    BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
			    SSH_KEY_BITS_RESERVED);
		}
		if (rsa_private_decrypt(session_key_int, session_key_int,
		    sensitive_data.server_key->rsa) <= 0)
			rsafail++;
		if (rsa_private_decrypt(session_key_int, session_key_int,
		    sensitive_data.ssh1_host_key->rsa) <= 0)
			rsafail++;
	} else {
		/* Host key has bigger modulus (or they are equal). */
		if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
		    BN_num_bits(sensitive_data.server_key->rsa->n) +
		    SSH_KEY_BITS_RESERVED) {
			fatal("do_connection: %s: "
			    "host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
			    get_remote_ipaddr(),
			    BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
			    BN_num_bits(sensitive_data.server_key->rsa->n),
			    SSH_KEY_BITS_RESERVED);
		}
		if (rsa_private_decrypt(session_key_int, session_key_int,
		    sensitive_data.ssh1_host_key->rsa) < 0)
			rsafail++;
		if (rsa_private_decrypt(session_key_int, session_key_int,
		    sensitive_data.server_key->rsa) < 0)
			rsafail++;
	}
	return (rsafail);
}
/*
 * SSH1 key exchange
 */
static void
do_ssh1_kex(void)
{
	int i, len;
	int rsafail = 0;
	BIGNUM *session_key_int;
	u_char session_key[SSH_SESSION_KEY_LENGTH];
	u_char cookie[8];
	u_int cipher_type, auth_mask, protocol_flags;

	/*
	 * Generate check bytes that the client must send back in the user
	 * packet in order for it to be accepted; this is used to defy ip
	 * spoofing attacks.  Note that this only works against somebody
	 * doing IP spoofing from a remote machine; any machine on the local
	 * network can still see outgoing packets and catch the random
	 * cookie.  This only affects rhosts authentication, and this is one
	 * of the reasons why it is inherently insecure.
	 */
	arc4random_buf(cookie, sizeof(cookie));

	/*
	 * Send our public key.  We include in the packet 64 bits of random
	 * data that must be matched in the reply in order to prevent IP
	 * spoofing.
	 */
	packet_start(SSH_SMSG_PUBLIC_KEY);
	for (i = 0; i < 8; i++)
		packet_put_char(cookie[i]);

	/* Store our public server RSA key. */
	packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
	packet_put_bignum(sensitive_data.server_key->rsa->e);
	packet_put_bignum(sensitive_data.server_key->rsa->n);

	/* Store our public host RSA key. */
	packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
	packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
	packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);

	/* Put protocol flags. */
	packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);

	/* Declare which ciphers we support. */
	packet_put_int(cipher_mask_ssh1(0));

	/* Declare supported authentication types. */
	auth_mask = 0;
	if (options.rhosts_rsa_authentication)
		auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
	if (options.rsa_authentication)
		auth_mask |= 1 << SSH_AUTH_RSA;
	if (options.challenge_response_authentication == 1)
		auth_mask |= 1 << SSH_AUTH_TIS;
	if (options.password_authentication)
		auth_mask |= 1 << SSH_AUTH_PASSWORD;
	packet_put_int(auth_mask);

	/* Send the packet and wait for it to be sent. */
	packet_send();
	packet_write_wait();

	debug("Sent %d bit server key and %d bit host key.",
	    BN_num_bits(sensitive_data.server_key->rsa->n),
	    BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));

	/* Read clients reply (cipher type and session key). */
	packet_read_expect(SSH_CMSG_SESSION_KEY);

	/* Get cipher type and check whether we accept this. */
	cipher_type = packet_get_char();

	if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
		packet_disconnect("Warning: client selects unsupported cipher.");

	/* Get check bytes from the packet.  These must match those we
	   sent earlier with the public key packet. */
	for (i = 0; i < 8; i++)
		if (cookie[i] != packet_get_char())
			packet_disconnect("IP Spoofing check bytes do not match.");

	debug("Encryption type: %.200s", cipher_name(cipher_type));

	/* Get the encrypted integer. */
	if ((session_key_int = BN_new()) == NULL)
		fatal("do_ssh1_kex: BN_new failed");
	packet_get_bignum(session_key_int);

	protocol_flags = packet_get_int();
	packet_set_protocol_flags(protocol_flags);
	packet_check_eom();

	/* Decrypt session_key_int using host/server keys */
	rsafail = PRIVSEP(ssh1_session_key(session_key_int));

	/*
	 * Extract session key from the decrypted integer.  The key is in the
	 * least significant 256 bits of the integer; the first byte of the
	 * key is in the highest bits.
	 */
	if (!rsafail) {
		(void) BN_mask_bits(session_key_int, sizeof(session_key) * 8);
		len = BN_num_bytes(session_key_int);
		if (len < 0 || (u_int)len > sizeof(session_key)) {
			error("do_ssh1_kex: bad session key len from %s: "
			    "session_key_int %d > sizeof(session_key) %lu",
			    get_remote_ipaddr(), len, (u_long)sizeof(session_key));
			rsafail++;
		} else {
			memset(session_key, 0, sizeof(session_key));
			BN_bn2bin(session_key_int,
			    session_key + sizeof(session_key) - len);

			derive_ssh1_session_id(
			    sensitive_data.ssh1_host_key->rsa->n,
			    sensitive_data.server_key->rsa->n,
			    cookie, session_id);
			/*
			 * Xor the first 16 bytes of the session key with the
			 * session id.
			 */
			for (i = 0; i < 16; i++)
				session_key[i] ^= session_id[i];
		}
	}
	if (rsafail) {
		int bytes = BN_num_bytes(session_key_int);
		u_char *buf = xmalloc(bytes);
		MD5_CTX md;

		logit("do_connection: generating a fake encryption key");
		BN_bn2bin(session_key_int, buf);
		MD5_Init(&md);
		MD5_Update(&md, buf, bytes);
		MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
		MD5_Final(session_key, &md);
		MD5_Init(&md);
		MD5_Update(&md, session_key, 16);
		MD5_Update(&md, buf, bytes);
		MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
		MD5_Final(session_key + 16, &md);
		memset(buf, 0, bytes);
		xfree(buf);
		for (i = 0; i < 16; i++)
			session_id[i] = session_key[i] ^ session_key[i + 16];
	}
	/* Destroy the private and public keys. No longer. */
	destroy_sensitive_data();

	if (use_privsep)
		mm_ssh1_session_id(session_id);

	/* Destroy the decrypted integer.  It is no longer needed. */
	BN_clear_free(session_key_int);

	/* Set the session key.  From this on all communications will be encrypted. */
	packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);

	/* Destroy our copy of the session key.  It is no longer needed. */
	memset(session_key, 0, sizeof(session_key));

	debug("Received session key; encryption turned on.");

	/* Send an acknowledgment packet.  Note that this packet is sent encrypted. */
	packet_start(SSH_SMSG_SUCCESS);
	packet_send();
	packet_write_wait();
}

/*
 * SSH2 key exchange: diffie-hellman-group1-sha1
 */
static void
do_ssh2_kex(void)
{
	Kex *kex;

	if (options.ciphers != NULL) {
		myproposal[PROPOSAL_ENC_ALGS_CTOS] =
		myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
	}
	myproposal[PROPOSAL_ENC_ALGS_CTOS] =
	    compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
	myproposal[PROPOSAL_ENC_ALGS_STOC] =
	    compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);

	if (options.macs != NULL) {
		myproposal[PROPOSAL_MAC_ALGS_CTOS] =
		myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
	}
	if (options.compression == COMP_NONE) {
		myproposal[PROPOSAL_COMP_ALGS_CTOS] =
		myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
	} else if (options.compression == COMP_DELAYED) {
		myproposal[PROPOSAL_COMP_ALGS_CTOS] =
		myproposal[PROPOSAL_COMP_ALGS_STOC] = "none,zlib@openssh.com";
	}

	myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();

	/* start key exchange */
	kex = kex_setup(myproposal);
	kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server;
	kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server;
	kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
	kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
	kex->server = 1;
	kex->client_version_string=client_version_string;
	kex->server_version_string=server_version_string;
	kex->load_host_public_key=&get_hostkey_public_by_type;
	kex->load_host_private_key=&get_hostkey_private_by_type;
	kex->host_key_index=&get_hostkey_index;

	xxx_kex = kex;

	dispatch_run(DISPATCH_BLOCK, &kex->done, kex);

	session_id2 = kex->session_id;
	session_id2_len = kex->session_id_len;

#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("KEX done");
}

/* server specific fatal cleanup */
void
cleanup_exit(int i)
{
	if (the_authctxt)
		do_cleanup(the_authctxt);
#ifdef SSH_AUDIT_EVENTS
	/* done after do_cleanup so it can cancel the PAM auth 'thread' */
	if (!use_privsep || mm_is_monitor())
		audit_event(SSH_CONNECTION_ABANDON);
#endif
	_exit(i);
}
OpenPOWER on IntegriCloud