summaryrefslogtreecommitdiff
path: root/ssh.c
blob: cffd56676a2926e2cfc0c5c084797cfa10d847ff (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
/*
 * 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 16:36:11 1995 ylo
 * Ssh client program.  This program can be used to log into a remote machine.
 * The software supports strong authentication, encryption, and forwarding
 * of X11, TCP/IP, and authentication connections.
 *
 * Modified to work with SSL by Niels Provos <provos@citi.umich.edu> in Canada.
 */

#include "includes.h"
RCSID("$Id: ssh.c,v 1.28 2000/04/30 00:00:54 damien Exp $");

#include <openssl/evp.h>
#include <openssl/dsa.h>
#include <openssl/rsa.h>

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

#include "ssh2.h"
#include "compat.h"
#include "channels.h"
#include "key.h"
#include "authfile.h"

#ifdef HAVE___PROGNAME
extern char *__progname;
#else /* HAVE___PROGNAME */
const char *__progname = "ssh";
#endif /* HAVE___PROGNAME */

/* Flag indicating whether IPv4 or IPv6.  This can be set on the command line.
   Default value is AF_UNSPEC means both IPv4 and IPv6. */
#ifdef IPV4_DEFAULT
int IPv4or6 = AF_INET;
#else
int IPv4or6 = AF_UNSPEC;
#endif

/* Flag indicating whether debug mode is on.  This can be set on the command line. */
int debug_flag = 0;

/* Flag indicating whether a tty should be allocated */
int tty_flag = 0;

/* don't exec a shell */
int no_shell_flag = 0;
int no_tty_flag = 0;

/*
 * Flag indicating that nothing should be read from stdin.  This can be set
 * on the command line.
 */
int stdin_null_flag = 0;

/*
 * Flag indicating that ssh should fork after authentication.  This is useful
 * so that the pasphrase can be entered manually, and then ssh goes to the
 * background.
 */
int fork_after_authentication_flag = 0;

/*
 * General data structure for command line options and options configurable
 * in configuration files.  See readconf.h.
 */
Options options;

/*
 * Name of the host we are connecting to.  This is the name given on the
 * command line, or the HostName specified for the user-supplied name in a
 * configuration file.
 */
char *host;

/* socket address the host resolves to */
struct sockaddr_storage hostaddr;

/*
 * Flag to indicate that we have received a window change signal which has
 * not yet been processed.  This will cause a message indicating the new
 * window size to be sent to the server a little later.  This is volatile
 * because this is updated in a signal handler.
 */
volatile int received_window_change_signal = 0;

/* Value of argv[0] (set in the main program). */
char *av0;

/* Flag indicating whether we have a valid host private key loaded. */
int host_private_key_loaded = 0;

/* Host private key. */
RSA *host_private_key = NULL;

/* Original real UID. */
uid_t original_real_uid;

/* command to be executed */
Buffer command;

/* Prints a help message to the user.  This function never returns. */

void
usage()
{
	fprintf(stderr, "Usage: %s [options] host [command]\n", av0);
	fprintf(stderr, "Options:\n");
	fprintf(stderr, "  -l user     Log in using this user name.\n");
	fprintf(stderr, "  -n          Redirect input from /dev/null.\n");
	fprintf(stderr, "  -a          Disable authentication agent forwarding.\n");
#ifdef AFS
	fprintf(stderr, "  -k          Disable Kerberos ticket and AFS token forwarding.\n");
#endif				/* AFS */
	fprintf(stderr, "  -x          Disable X11 connection forwarding.\n");
	fprintf(stderr, "  -i file     Identity for RSA authentication (default: ~/.ssh/identity).\n");
	fprintf(stderr, "  -t          Tty; allocate a tty even if command is given.\n");
	fprintf(stderr, "  -T          Do not allocate a tty.\n");
	fprintf(stderr, "  -v          Verbose; display verbose debugging messages.\n");
	fprintf(stderr, "  -V          Display version number only.\n");
	fprintf(stderr, "  -P          Don't allocate a privileged port.\n");
	fprintf(stderr, "  -q          Quiet; don't display any warning messages.\n");
	fprintf(stderr, "  -f          Fork into background after authentication.\n");
	fprintf(stderr, "  -e char     Set escape character; ``none'' = disable (default: ~).\n");

	fprintf(stderr, "  -c cipher   Select encryption algorithm: "
			"``3des'', "
			"``blowfish''\n");
	fprintf(stderr, "  -p port     Connect to this port.  Server must be on the same port.\n");
	fprintf(stderr, "  -L listen-port:host:port   Forward local port to remote address\n");
	fprintf(stderr, "  -R listen-port:host:port   Forward remote port to local address\n");
	fprintf(stderr, "              These cause %s to listen for connections on a port, and\n", av0);
	fprintf(stderr, "              forward them to the other side by connecting to host:port.\n");
	fprintf(stderr, "  -C          Enable compression.\n");
	fprintf(stderr, "  -N          Do not execute a shell or command.\n");
	fprintf(stderr, "  -g          Allow remote hosts to connect to forwarded ports.\n");
	fprintf(stderr, "  -4          Use IPv4 only.\n");
	fprintf(stderr, "  -6          Use IPv6 only.\n");
	fprintf(stderr, "  -2          Force protocol version 2.\n");
	fprintf(stderr, "  -o 'option' Process the option as if it was read from a configuration file.\n");
	exit(1);
}

/*
 * Connects to the given host using rsh (or prints an error message and exits
 * if rsh is not available).  This function never returns.
 */
void
rsh_connect(char *host, char *user, Buffer * command)
{
	char *args[10];
	int i;

	log("Using rsh.  WARNING: Connection will not be encrypted.");
	/* Build argument list for rsh. */
	i = 0;
	args[i++] = _PATH_RSH;
	/* host may have to come after user on some systems */
	args[i++] = host;
	if (user) {
		args[i++] = "-l";
		args[i++] = user;
	}
	if (buffer_len(command) > 0) {
		buffer_append(command, "\0", 1);
		args[i++] = buffer_ptr(command);
	}
	args[i++] = NULL;
	if (debug_flag) {
		for (i = 0; args[i]; i++) {
			if (i != 0)
				fprintf(stderr, " ");
			fprintf(stderr, "%s", args[i]);
		}
		fprintf(stderr, "\n");
	}
	execv(_PATH_RSH, args);
	perror(_PATH_RSH);
	exit(1);
}

int ssh_session(void);
int ssh_session2(void);

/*
 * Main program for the ssh client.
 */
int
main(int ac, char **av)
{
	int i, opt, optind, exit_status, ok;
	u_short fwd_port, fwd_host_port;
	char *optarg, *cp, buf[256];
	struct stat st;
	struct passwd *pw, pwcopy;
	int dummy;
	uid_t original_effective_uid;

	/*
	 * Save the original real uid.  It will be needed later (uid-swapping
	 * may clobber the real uid).
	 */
	original_real_uid = getuid();
	original_effective_uid = geteuid();

	/* If we are installed setuid root be careful to not drop core. */
	if (original_real_uid != original_effective_uid) {
		struct rlimit rlim;
		rlim.rlim_cur = rlim.rlim_max = 0;
		if (setrlimit(RLIMIT_CORE, &rlim) < 0)
			fatal("setrlimit failed: %.100s", strerror(errno));
	}
	/*
	 * Use uid-swapping to give up root privileges for the duration of
	 * option processing.  We will re-instantiate the rights when we are
	 * ready to create the privileged port, and will permanently drop
	 * them when the port has been created (actually, when the connection
	 * has been made, as we may need to create the port several times).
	 */
	temporarily_use_uid(original_real_uid);

	/*
	 * Set our umask to something reasonable, as some files are created
	 * with the default umask.  This will make them world-readable but
	 * writable only by the owner, which is ok for all files for which we
	 * don't set the modes explicitly.
	 */
	umask(022);

	/* Save our own name. */
	av0 = av[0];

	/* Initialize option structure to indicate that no values have been set. */
	initialize_options(&options);

	/* Parse command-line arguments. */
	host = NULL;

	/* If program name is not one of the standard names, use it as host name. */
	if (strchr(av0, '/'))
		cp = strrchr(av0, '/') + 1;
	else
		cp = av0;
	if (strcmp(cp, "rsh") != 0 && strcmp(cp, "ssh") != 0 &&
	    strcmp(cp, "rlogin") != 0 && strcmp(cp, "slogin") != 0)
		host = cp;

	for (optind = 1; optind < ac; optind++) {
		if (av[optind][0] != '-') {
			if (host)
				break;
			if ((cp = strchr(av[optind], '@'))) {
				if(cp == av[optind])
					usage();
				options.user = av[optind];
				*cp = '\0';
				host = ++cp;
			} else
				host = av[optind];
			continue;
		}
		opt = av[optind][1];
		if (!opt)
			usage();
		if (strchr("eilcpLRo", opt)) {	/* options with arguments */
			optarg = av[optind] + 2;
			if (strcmp(optarg, "") == 0) {
				if (optind >= ac - 1)
					usage();
				optarg = av[++optind];
			}
		} else {
			if (av[optind][2])
				usage();
			optarg = NULL;
		}
		switch (opt) {
		case '2':
			options.protocol = SSH_PROTO_2;
			break;
		case '4':
			IPv4or6 = AF_INET;
			break;
		case '6':
			IPv4or6 = AF_INET6;
			break;
		case 'n':
			stdin_null_flag = 1;
			break;
		case 'f':
			fork_after_authentication_flag = 1;
			stdin_null_flag = 1;
			break;
		case 'x':
			options.forward_x11 = 0;
			break;
		case 'X':
			options.forward_x11 = 1;
			break;
		case 'g':
			options.gateway_ports = 1;
			break;
		case 'P':
			options.use_privileged_port = 0;
			break;
		case 'a':
			options.forward_agent = 0;
			break;
#ifdef AFS
		case 'k':
			options.kerberos_tgt_passing = 0;
			options.afs_token_passing = 0;
			break;
#endif
		case 'i':
			if (stat(optarg, &st) < 0) {
				fprintf(stderr, "Warning: Identity file %s does not exist.\n",
					optarg);
				break;
			}
			if (options.num_identity_files >= SSH_MAX_IDENTITY_FILES)
				fatal("Too many identity files specified (max %d)",
				      SSH_MAX_IDENTITY_FILES);
			options.identity_files[options.num_identity_files++] =
				xstrdup(optarg);
			break;
		case 't':
			tty_flag = 1;
			break;
		case 'v':
		case 'V':
			fprintf(stderr, "SSH Version %s, protocol versions %d.%d/%d.%d.\n",
			    SSH_VERSION,
			    PROTOCOL_MAJOR_1, PROTOCOL_MINOR_1,
			    PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2);
			fprintf(stderr, "Compiled with SSL (0x%8.8lx).\n", SSLeay());
			if (opt == 'V')
				exit(0);
			debug_flag = 1;
			options.log_level = SYSLOG_LEVEL_DEBUG;
			break;
		case 'q':
			options.log_level = SYSLOG_LEVEL_QUIET;
			break;
		case 'e':
			if (optarg[0] == '^' && optarg[2] == 0 &&
			    (unsigned char) optarg[1] >= 64 && (unsigned char) optarg[1] < 128)
				options.escape_char = (unsigned char) optarg[1] & 31;
			else if (strlen(optarg) == 1)
				options.escape_char = (unsigned char) optarg[0];
			else if (strcmp(optarg, "none") == 0)
				options.escape_char = -2;
			else {
				fprintf(stderr, "Bad escape character '%s'.\n", optarg);
				exit(1);
			}
			break;
		case 'c':
			if (ciphers_valid(optarg)) {
				/* SSH2 only */
				options.ciphers = xstrdup(optarg);
			} else {
				/* SSH1 only */
				options.cipher = cipher_number(optarg);
				if (options.cipher == -1) {
					fprintf(stderr, "Unknown cipher type '%s'\n", optarg);
					exit(1);
				}
			}
			break;
		case 'p':
			options.port = atoi(optarg);
			break;
		case 'l':
			options.user = optarg;
			break;
		case 'R':
			if (sscanf(optarg, "%hu/%255[^/]/%hu", &fwd_port, buf,
			    &fwd_host_port) != 3 &&
			    sscanf(optarg, "%hu:%255[^:]:%hu", &fwd_port, buf,
			    &fwd_host_port) != 3) {
				fprintf(stderr, "Bad forwarding specification '%s'.\n", optarg);
				usage();
				/* NOTREACHED */
			}
			add_remote_forward(&options, fwd_port, buf, fwd_host_port);
			break;
		case 'L':
			if (sscanf(optarg, "%hu/%255[^/]/%hu", &fwd_port, buf,
			    &fwd_host_port) != 3 &&
			    sscanf(optarg, "%hu:%255[^:]:%hu", &fwd_port, buf,
			    &fwd_host_port) != 3) {
				fprintf(stderr, "Bad forwarding specification '%s'.\n", optarg);
				usage();
				/* NOTREACHED */
			}
			add_local_forward(&options, fwd_port, buf, fwd_host_port);
			break;
		case 'C':
			options.compression = 1;
			break;
		case 'N':
			no_shell_flag = 1;
			no_tty_flag = 1;
			break;
		case 'T':
			no_tty_flag = 1;
			break;
		case 'o':
			dummy = 1;
			if (process_config_line(&options, host ? host : "", optarg,
					 "command-line", 0, &dummy) != 0)
				exit(1);
			break;
		default:
			usage();
		}
	}

	/* Check that we got a host name. */
	if (!host)
		usage();

	/* Initialize the command to execute on remote host. */
	buffer_init(&command);

	OpenSSL_add_all_algorithms();
	
	/*
	 * Save the command to execute on the remote host in a buffer. There
	 * is no limit on the length of the command, except by the maximum
	 * packet size.  Also sets the tty flag if there is no command.
	 */
	if (optind == ac) {
		/* No command specified - execute shell on a tty. */
		tty_flag = 1;
	} else {
		/* A command has been specified.  Store it into the
		   buffer. */
		for (i = optind; i < ac; i++) {
			if (i > optind)
				buffer_append(&command, " ", 1);
			buffer_append(&command, av[i], strlen(av[i]));
		}
	}

	/* Cannot fork to background if no command. */
	if (fork_after_authentication_flag && buffer_len(&command) == 0)
		fatal("Cannot fork into background without a command to execute.");

	/* Allocate a tty by default if no command specified. */
	if (buffer_len(&command) == 0)
		tty_flag = 1;

	/* Do not allocate a tty if stdin is not a tty. */
	if (!isatty(fileno(stdin))) {
		if (tty_flag)
			fprintf(stderr, "Pseudo-terminal will not be allocated because stdin is not a terminal.\n");
		tty_flag = 0;
	}
	/* force */
	if (no_tty_flag)
		tty_flag = 0;

	/* Get user data. */
	pw = getpwuid(original_real_uid);
	if (!pw) {
		fprintf(stderr, "You don't exist, go away!\n");
		exit(1);
	}
	/* Take a copy of the returned structure. */
	memset(&pwcopy, 0, sizeof(pwcopy));
	pwcopy.pw_name = xstrdup(pw->pw_name);
	pwcopy.pw_passwd = xstrdup(pw->pw_passwd);
	pwcopy.pw_uid = pw->pw_uid;
	pwcopy.pw_gid = pw->pw_gid;
	pwcopy.pw_dir = xstrdup(pw->pw_dir);
	pwcopy.pw_shell = xstrdup(pw->pw_shell);
	pw = &pwcopy;

	/* Initialize "log" output.  Since we are the client all output
	   actually goes to the terminal. */
	log_init(av[0], options.log_level, SYSLOG_FACILITY_USER, 0);

	/* Read per-user configuration file. */
	snprintf(buf, sizeof buf, "%.100s/%.100s", pw->pw_dir, SSH_USER_CONFFILE);
	read_config_file(buf, host, &options);

	/* Read systemwide configuration file. */
	read_config_file(HOST_CONFIG_FILE, host, &options);

	/* Fill configuration defaults. */
	fill_default_options(&options);

	/* reinit */
	log_init(av[0], options.log_level, SYSLOG_FACILITY_USER, 0);

	/* check if RSA support exists */
	if ((options.protocol & SSH_PROTO_1) &&
	    rsa_alive() == 0) {
		log("%s: no RSA support in libssl and libcrypto.  See ssl(8).",
		    __progname);
		log("Disabling protocol version 1");
		options.protocol &= ~ (SSH_PROTO_1|SSH_PROTO_1_PREFERRED);
	}
	if (! options.protocol & (SSH_PROTO_1|SSH_PROTO_2)) {
		fprintf(stderr, "%s: No protocol version available.\n",
		    __progname);
 		exit(1);
	}

	if (options.user == NULL)
		options.user = xstrdup(pw->pw_name);

	if (options.hostname != NULL)
		host = options.hostname;

	/* Find canonic host name. */
	if (strchr(host, '.') == 0) {
		struct addrinfo hints;
		struct addrinfo *ai = NULL;
		int errgai;
		memset(&hints, 0, sizeof(hints));
		hints.ai_family = IPv4or6;
		hints.ai_flags = AI_CANONNAME;
		hints.ai_socktype = SOCK_STREAM;
		errgai = getaddrinfo(host, NULL, &hints, &ai);
		if (errgai == 0) {
			if (ai->ai_canonname != NULL)
				host = xstrdup(ai->ai_canonname);
			freeaddrinfo(ai);
		}
	}
	/* Disable rhosts authentication if not running as root. */
	if (original_effective_uid != 0 || !options.use_privileged_port) {
		options.rhosts_authentication = 0;
		options.rhosts_rsa_authentication = 0;
	}
	/*
	 * If using rsh has been selected, exec it now (without trying
	 * anything else).  Note that we must release privileges first.
	 */
	if (options.use_rsh) {
		/*
		 * Restore our superuser privileges.  This must be done
		 * before permanently setting the uid.
		 */
		restore_uid();

		/* Switch to the original uid permanently. */
		permanently_set_uid(original_real_uid);

		/* Execute rsh. */
		rsh_connect(host, options.user, &command);
		fatal("rsh_connect returned");
	}
	/* Restore our superuser privileges. */
	restore_uid();

	/*
	 * Open a connection to the remote host.  This needs root privileges
	 * if rhosts_{rsa_}authentication is enabled.
	 */

	ok = ssh_connect(host, &hostaddr, options.port,
			 options.connection_attempts,
			 !options.rhosts_authentication &&
			 !options.rhosts_rsa_authentication,
			 original_real_uid,
			 options.proxy_command);

	/*
	 * If we successfully made the connection, load the host private key
	 * in case we will need it later for combined rsa-rhosts
	 * authentication. This must be done before releasing extra
	 * privileges, because the file is only readable by root.
	 */
	if (ok && (options.protocol & SSH_PROTO_1)) {
		Key k;
		host_private_key = RSA_new();
		k.type = KEY_RSA;
		k.rsa = host_private_key;
		if (load_private_key(HOST_KEY_FILE, "", &k, NULL))
			host_private_key_loaded = 1;
	}
	/*
	 * Get rid of any extra privileges that we may have.  We will no
	 * longer need them.  Also, extra privileges could make it very hard
	 * to read identity files and other non-world-readable files from the
	 * user's home directory if it happens to be on a NFS volume where
	 * root is mapped to nobody.
	 */

	/*
	 * Note that some legacy systems need to postpone the following call
	 * to permanently_set_uid() until the private hostkey is destroyed
	 * with RSA_free().  Otherwise the calling user could ptrace() the
	 * process, read the private hostkey and impersonate the host.
	 * OpenBSD does not allow ptracing of setuid processes.
	 */
	permanently_set_uid(original_real_uid);

	/*
	 * Now that we are back to our own permissions, create ~/.ssh
	 * directory if it doesn\'t already exist.
	 */
	snprintf(buf, sizeof buf, "%.100s/%.100s", pw->pw_dir, SSH_USER_DIR);
	if (stat(buf, &st) < 0)
		if (mkdir(buf, 0755) < 0)
			error("Could not create directory '%.200s'.", buf);

	/* Check if the connection failed, and try "rsh" if appropriate. */
	if (!ok) {
		if (options.port != 0)
			log("Secure connection to %.100s on port %hu refused%.100s.",
			    host, options.port,
			    options.fallback_to_rsh ? "; reverting to insecure method" : "");
		else
			log("Secure connection to %.100s refused%.100s.", host,
			    options.fallback_to_rsh ? "; reverting to insecure method" : "");

		if (options.fallback_to_rsh) {
			rsh_connect(host, options.user, &command);
			fatal("rsh_connect returned");
		}
		exit(1);
	}
	/* Expand ~ in options.identity_files. */
	/* XXX mem-leaks */
	for (i = 0; i < options.num_identity_files; i++)
		options.identity_files[i] =
			tilde_expand_filename(options.identity_files[i], original_real_uid);
	for (i = 0; i < options.num_identity_files2; i++)
		options.identity_files2[i] =
			tilde_expand_filename(options.identity_files2[i], original_real_uid);
	/* Expand ~ in known host file names. */
	options.system_hostfile = tilde_expand_filename(options.system_hostfile,
	    original_real_uid);
	options.user_hostfile = tilde_expand_filename(options.user_hostfile,
	    original_real_uid);
	options.system_hostfile2 = tilde_expand_filename(options.system_hostfile2,
	    original_real_uid);
	options.user_hostfile2 = tilde_expand_filename(options.user_hostfile2,
	    original_real_uid);

	/* Log into the remote system.  This never returns if the login fails. */
	ssh_login(host_private_key_loaded, host_private_key,
		  host, (struct sockaddr *)&hostaddr, original_real_uid);

	/* We no longer need the host private key.  Clear it now. */
	if (host_private_key_loaded)
		RSA_free(host_private_key);	/* Destroys contents safely */

	exit_status = compat20 ? ssh_session2() : ssh_session();
	packet_close();
	return exit_status;
}

void
x11_get_proto(char *proto, int proto_len, char *data, int data_len)
{
	char line[512];
	FILE *f;
	int got_data = 0, i;

#ifdef XAUTH_PATH
	/* Try to get Xauthority information for the display. */
	snprintf(line, sizeof line, "%.100s list %.200s 2>/dev/null",
		 XAUTH_PATH, getenv("DISPLAY"));
	f = popen(line, "r");
	if (f && fgets(line, sizeof(line), f) &&
	    sscanf(line, "%*s %s %s", proto, data) == 2)
		got_data = 1;
	if (f)
		pclose(f);
#endif /* XAUTH_PATH */
	/*
	 * If we didn't get authentication data, just make up some
	 * data.  The forwarding code will check the validity of the
	 * response anyway, and substitute this data.  The X11
	 * server, however, will ignore this fake data and use
	 * whatever authentication mechanisms it was using otherwise
	 * for the local connection.
	 */
	if (!got_data) {
		u_int32_t rand = 0;

		strlcpy(proto, "MIT-MAGIC-COOKIE-1", proto_len);
		for (i = 0; i < 16; i++) {
			if (i % 4 == 0)
				rand = arc4random();
			snprintf(data + 2 * i, data_len - 2 * i, "%02x", rand & 0xff);
			rand >>= 8;
		}
	}
}

int
ssh_session(void)
{
	int type;
	int i;
	int plen;
	int interactive = 0;
	int have_tty = 0;
	struct winsize ws;
	int authfd;
	char *cp;

	/* Enable compression if requested. */
	if (options.compression) {
		debug("Requesting compression at level %d.", options.compression_level);

		if (options.compression_level < 1 || options.compression_level > 9)
			fatal("Compression level must be from 1 (fast) to 9 (slow, best).");

		/* Send the request. */
		packet_start(SSH_CMSG_REQUEST_COMPRESSION);
		packet_put_int(options.compression_level);
		packet_send();
		packet_write_wait();
		type = packet_read(&plen);
		if (type == SSH_SMSG_SUCCESS)
			packet_start_compression(options.compression_level);
		else if (type == SSH_SMSG_FAILURE)
			log("Warning: Remote host refused compression.");
		else
			packet_disconnect("Protocol error waiting for compression response.");
	}
	/* Allocate a pseudo tty if appropriate. */
	if (tty_flag) {
		debug("Requesting pty.");

		/* Start the packet. */
		packet_start(SSH_CMSG_REQUEST_PTY);

		/* Store TERM in the packet.  There is no limit on the
		   length of the string. */
		cp = getenv("TERM");
		if (!cp)
			cp = "";
		packet_put_string(cp, strlen(cp));

		/* Store window size in the packet. */
		if (ioctl(fileno(stdin), TIOCGWINSZ, &ws) < 0)
			memset(&ws, 0, sizeof(ws));
		packet_put_int(ws.ws_row);
		packet_put_int(ws.ws_col);
		packet_put_int(ws.ws_xpixel);
		packet_put_int(ws.ws_ypixel);

		/* Store tty modes in the packet. */
		tty_make_modes(fileno(stdin));

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

		/* Read response from the server. */
		type = packet_read(&plen);
		if (type == SSH_SMSG_SUCCESS) {
			interactive = 1;
			have_tty = 1;
		} else if (type == SSH_SMSG_FAILURE)
			log("Warning: Remote host failed or refused to allocate a pseudo tty.");
		else
			packet_disconnect("Protocol error waiting for pty request response.");
	}
	/* Request X11 forwarding if enabled and DISPLAY is set. */
	if (options.forward_x11 && getenv("DISPLAY") != NULL) {
		char proto[512], data[512];
		/* Get reasonable local authentication information. */
		x11_get_proto(proto, sizeof proto, data, sizeof data);
		/* Request forwarding with authentication spoofing. */
		debug("Requesting X11 forwarding with authentication spoofing.");
		x11_request_forwarding_with_spoofing(0, proto, data);

		/* Read response from the server. */
		type = packet_read(&plen);
		if (type == SSH_SMSG_SUCCESS) {
			interactive = 1;
		} else if (type == SSH_SMSG_FAILURE) {
			log("Warning: Remote host denied X11 forwarding.");
		} else {
			packet_disconnect("Protocol error waiting for X11 forwarding");
		}
	}
	/* Tell the packet module whether this is an interactive session. */
	packet_set_interactive(interactive, options.keepalives);

	/* Clear agent forwarding if we don\'t have an agent. */
	authfd = ssh_get_authentication_socket();
	if (authfd < 0)
		options.forward_agent = 0;
	else
		ssh_close_authentication_socket(authfd);

	/* Request authentication agent forwarding if appropriate. */
	if (options.forward_agent) {
		debug("Requesting authentication agent forwarding.");
		auth_request_forwarding();

		/* Read response from the server. */
		type = packet_read(&plen);
		packet_integrity_check(plen, 0, type);
		if (type != SSH_SMSG_SUCCESS)
			log("Warning: Remote host denied authentication agent forwarding.");
	}
	/* Initiate local TCP/IP port forwardings. */
	for (i = 0; i < options.num_local_forwards; i++) {
		debug("Connections to local port %d forwarded to remote address %.200s:%d",
		      options.local_forwards[i].port,
		      options.local_forwards[i].host,
		      options.local_forwards[i].host_port);
		channel_request_local_forwarding(options.local_forwards[i].port,
						 options.local_forwards[i].host,
						 options.local_forwards[i].host_port,
						 options.gateway_ports);
	}

	/* Initiate remote TCP/IP port forwardings. */
	for (i = 0; i < options.num_remote_forwards; i++) {
		debug("Connections to remote port %d forwarded to local address %.200s:%d",
		      options.remote_forwards[i].port,
		      options.remote_forwards[i].host,
		      options.remote_forwards[i].host_port);
		channel_request_remote_forwarding(options.remote_forwards[i].port,
						  options.remote_forwards[i].host,
						  options.remote_forwards[i].host_port);
	}

	/* If requested, let ssh continue in the background. */
	if (fork_after_authentication_flag)
		if (daemon(1, 1) < 0)
			fatal("daemon() failed: %.200s", strerror(errno));

	/*
	 * If a command was specified on the command line, execute the
	 * command now. Otherwise request the server to start a shell.
	 */
	if (buffer_len(&command) > 0) {
		int len = buffer_len(&command);
		if (len > 900)
			len = 900;
		debug("Sending command: %.*s", len, buffer_ptr(&command));
		packet_start(SSH_CMSG_EXEC_CMD);
		packet_put_string(buffer_ptr(&command), buffer_len(&command));
		packet_send();
		packet_write_wait();
	} else {
		debug("Requesting shell.");
		packet_start(SSH_CMSG_EXEC_SHELL);
		packet_send();
		packet_write_wait();
	}

	/* Enter the interactive session. */
	return client_loop(have_tty, tty_flag ? options.escape_char : -1);
}

void
init_local_fwd(void)
{
	int i;
	/* Initiate local TCP/IP port forwardings. */
	for (i = 0; i < options.num_local_forwards; i++) {
		debug("Connections to local port %d forwarded to remote address %.200s:%d",
		      options.local_forwards[i].port,
		      options.local_forwards[i].host,
		      options.local_forwards[i].host_port);
		channel_request_local_forwarding(options.local_forwards[i].port,
						 options.local_forwards[i].host,
						 options.local_forwards[i].host_port,
						 options.gateway_ports);
	}
}

extern void client_set_session_ident(int id);

void
client_init(int id, void *arg)
{
	int len;
	debug("client_init id %d arg %d", id, (int)arg);

	if (no_shell_flag)
		goto done;

	if (tty_flag) {
		struct winsize ws;
		char *cp;
		cp = getenv("TERM");
		if (!cp)
			cp = "";
		/* Store window size in the packet. */
		if (ioctl(fileno(stdin), TIOCGWINSZ, &ws) < 0)
			memset(&ws, 0, sizeof(ws));

		channel_request_start(id, "pty-req", 0);
		packet_put_cstring(cp);
		packet_put_int(ws.ws_col);
		packet_put_int(ws.ws_row);
		packet_put_int(ws.ws_xpixel);
		packet_put_int(ws.ws_ypixel);
		packet_put_cstring("");		/* XXX: encode terminal modes */
		packet_send();
		/* XXX wait for reply */
	}
	if (options.forward_x11 &&
	    getenv("DISPLAY") != NULL) {
		char proto[512], data[512];
		/* Get reasonable local authentication information. */
		x11_get_proto(proto, sizeof proto, data, sizeof data);
		/* Request forwarding with authentication spoofing. */
		debug("Requesting X11 forwarding with authentication spoofing.");
		x11_request_forwarding_with_spoofing(id, proto, data);
		/* XXX wait for reply */
	}

	len = buffer_len(&command);
	if (len > 0) {
		if (len > 900)
			len = 900;
		debug("Sending command: %.*s", len, buffer_ptr(&command));
		channel_request_start(id, "exec", 0);
		packet_put_string(buffer_ptr(&command), len);
		packet_send();
	} else {
		channel_request(id, "shell", 0);
	}
	/* channel_callback(id, SSH2_MSG_OPEN_CONFIGMATION, client_init, 0); */
done:
	/* register different callback, etc. XXX */
	client_set_session_ident(id);
}

int
ssh_session2(void)
{
	int window, packetmax, id;
	int in  = dup(STDIN_FILENO);
	int out = dup(STDOUT_FILENO);
	int err = dup(STDERR_FILENO);

	if (in < 0 || out < 0 || err < 0)
		fatal("dump in/out/err failed");

	/* should be pre-session */
	init_local_fwd();
	
	window = 32*1024;
	if (tty_flag) {
		packetmax = window/8;
	} else {
		window *= 2;
		packetmax = window/2;
	}

	id = channel_new(
	    "session", SSH_CHANNEL_OPENING, in, out, err,
	    window, packetmax, CHAN_EXTENDED_WRITE, xstrdup("client-session"));


	channel_open(id);
	channel_register_callback(id, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, client_init, (void *)0);

	return client_loop(tty_flag, tty_flag ? options.escape_char : -1);
}