summaryrefslogtreecommitdiff
path: root/sshconnect.c
blob: 2a2aa98e7ac4a13ad34fa3fc1e0c937e9d0c9e1d (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
/*
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 * Code to connect to a remote host, and to perform the client side of the
 * login (authentication) dialog.
 *
 * 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".
 */

#include "includes.h"
RCSID("$OpenBSD: sshconnect.c,v 1.92 2001/01/30 22:48:52 djm Exp $");

#include <openssl/bn.h>

#include "ssh.h"
#include "xmalloc.h"
#include "rsa.h"
#include "buffer.h"
#include "packet.h"
#include "uidswap.h"
#include "compat.h"
#include "key.h"
#include "sshconnect.h"
#include "hostfile.h"
#include "log.h"
#include "readconf.h"
#include "atomicio.h"
#include "misc.h"

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

extern Options options;
extern char *__progname;

/* AF_UNSPEC or AF_INET or AF_INET6 */
extern int IPv4or6;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

	return 1;
}

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

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

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

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

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

	/* No proxy command. */

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

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

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

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

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

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

	freeaddrinfo(aitop);

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

	debug("Connection established.");

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

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

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

	return 1;
}

/*
 * Waits for the server identification string, and sends our own
 * identification string.
 */
void
ssh_exchange_identification()
{
	char buf[256], remote_version[256];	/* must be same size! */
	int remote_major, remote_minor, i, mismatch;
	int connection_in = packet_get_connection_in();
	int connection_out = packet_get_connection_out();
	int minor1 = PROTOCOL_MINOR_1; 

	/* Read other side\'s version identification. */
	for (;;) {
		for (i = 0; i < sizeof(buf) - 1; i++) {
			int len = atomicio(read, connection_in, &buf[i], 1);
			if (len < 0)
				fatal("ssh_exchange_identification: read: %.100s", strerror(errno));
			if (len != 1)
				fatal("ssh_exchange_identification: Connection closed by remote host");
			if (buf[i] == '\r') {
				buf[i] = '\n';
				buf[i + 1] = 0;
				continue;		/**XXX wait for \n */
			}
			if (buf[i] == '\n') {
				buf[i + 1] = 0;
				break;
			}
		}
		buf[sizeof(buf) - 1] = 0;
		if (strncmp(buf, "SSH-", 4) == 0)
			break;
		debug("ssh_exchange_identification: %s", buf);
	}
	server_version_string = xstrdup(buf);

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

	compat_datafellows(remote_version);
	mismatch = 0;

	switch(remote_major) {
	case 1:
		if (remote_minor == 99 &&
		    (options.protocol & SSH_PROTO_2) &&
		    !(options.protocol & SSH_PROTO_1_PREFERRED)) {
			enable_compat20();
			break;
		}
		if (!(options.protocol & SSH_PROTO_1)) {
			mismatch = 1;
			break;
		}
		if (remote_minor < 3) {
			fatal("Remote machine has too old SSH software version.");
		} else if (remote_minor == 3 || remote_minor == 4) {
			/* We speak 1.3, too. */
			enable_compat13();
			minor1 = 3;
			if (options.forward_agent) {
				log("Agent forwarding disabled for protocol 1.3");
				options.forward_agent = 0;
			}
		}
		break;
	case 2:
		if (options.protocol & SSH_PROTO_2) {
			enable_compat20();
			break;
		}
		/* FALLTHROUGH */
	default:
		mismatch = 1;
		break;
	}
	if (mismatch)
		fatal("Protocol major versions differ: %d vs. %d",
		    (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
		    remote_major);
	if (compat20)
		packet_set_ssh2_format();
	/* Send our own protocol version identification. */
	snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n",
	    compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
	    compat20 ? PROTOCOL_MINOR_2 : minor1,
	    SSH_VERSION);
	if (atomicio(write, connection_out, buf, strlen(buf)) != strlen(buf))
		fatal("write: %.100s", strerror(errno));
	client_version_string = xstrdup(buf);
	chop(client_version_string);
	chop(server_version_string);
	debug("Local version string %.100s", client_version_string);
}

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

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

	if (f == NULL)
		return 0;

	fflush(stdout);

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

		if (buf[0] == 0)
			retval = defval;
		if (strcmp(buf, "yes") == 0)
			retval = 1;
		else if (strcmp(buf, "no") == 0)
			retval = 0;
		else
			fprintf(stderr, "Please type 'yes' or 'no'.\n");

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

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

void
check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key,
	const char *user_hostfile, const char *system_hostfile)
{
	Key *file_key;
	char *type = key_type(host_key);
	char *ip = NULL;
	char hostline[1000], *hostp;
	HostStatus host_status;
	HostStatus ip_status;
	int local = 0, host_ip_differ = 0;
	int salen;
	char ntop[NI_MAXHOST];
	int host_line, ip_line;
	const char *host_file = NULL, *ip_file = NULL;

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

	/*
	 * We don't have the remote ip-address for connections
	 * using a proxy command
	 */
	if (options.proxy_command == NULL) {
		if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop),
		    NULL, 0, NI_NUMERICHOST) != 0)
			fatal("check_host_key: getnameinfo failed");
		ip = xstrdup(ntop);
	} else {
		ip = xstrdup("<no hostip for proxy command>");
	}
	/*
	 * Turn off check_host_ip if the connection is to localhost, via proxy
	 * command or if we don't have a hostname to compare with
	 */
	if (options.check_host_ip &&
	    (local || strcmp(host, ip) == 0 || options.proxy_command != NULL))
		options.check_host_ip = 0;

	/*
	 * Allow the user to record the key under a different name. This is
	 * useful for ssh tunneling over forwarded connections or if you run
	 * multiple sshd's on different ports on the same machine.
	 */
	if (options.host_key_alias != NULL) {
		host = options.host_key_alias;
		debug("using hostkeyalias: %s", host);
	}

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

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

		ip_file = user_hostfile;
		ip_status = check_host_in_hostfile(ip_file, ip, host_key, ip_key, &ip_line);
		if (ip_status == HOST_NEW) {
			ip_file = system_hostfile;
			ip_status = check_host_in_hostfile(ip_file, ip, host_key, ip_key, &ip_line);
		}
		if (host_status == HOST_CHANGED &&
		    (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key)))
			host_ip_differ = 1;

		key_free(ip_key);
	} else
		ip_status = host_status;

	key_free(file_key);

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

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

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

		/*
		 * If strict host key checking has not been requested, allow
		 * the connection but without password authentication or
		 * agent forwarding.
		 */
		if (options.password_authentication) {
			error("Password authentication is disabled to avoid trojan horses.");
			options.password_authentication = 0;
		}
		if (options.forward_agent) {
			error("Agent forwarding is disabled to avoid trojan horses.");
			options.forward_agent = 0;
		}
		if (options.forward_x11) {
			error("X11 forwarding is disabled to avoid trojan horses.");
			options.forward_x11 = 0;
		}
	        if (options.num_local_forwards > 0 || options.num_remote_forwards > 0) {
			error("Port forwarding is disabled to avoid trojan horses.");
			options.num_local_forwards = options.num_remote_forwards = 0;
		}
		/*
		 * XXX Should permit the user to change to use the new id.
		 * This could be done by converting the host key to an
		 * identifying sentence, tell that the host identifies itself
		 * by that sentence, and ask the user if he/she whishes to
		 * accept the authentication.
		 */
		break;
	}

	if (options.check_host_ip && host_status != HOST_CHANGED &&
	    ip_status == HOST_CHANGED) {
		log("Warning: the %s host key for '%.200s' "
		    "differs from the key for the IP address '%.30s'",
		    type, host, ip);
		if (host_status == HOST_OK)
			log("Matching host key in %s:%d", host_file, host_line);
		log("Offending key for IP in %s:%d", ip_file, ip_line);
		if (options.strict_host_key_checking == 1) {
			fatal("Exiting, you have requested strict checking.");
		} else if (options.strict_host_key_checking == 2) {
			if (!read_yes_or_no("Are you sure you want " \
			    "to continue connecting (yes/no)? ", -1))
				fatal("Aborted by user!\n");
		}
	}

	xfree(ip);
}

/*
 * Starts a dialog with the server, and authenticates the current user on the
 * server.  This does not need any extra privileges.  The basic connection
 * to the server must already have been established before this is called.
 * If login fails, this function prints an error and never returns.
 * This function does not require super-user privileges.
 */
void
ssh_login(int host_key_valid, RSA *own_host_key, const char *orighost,
    struct sockaddr *hostaddr, uid_t original_real_uid)
{
	struct passwd *pw;
	char *host, *cp;
	char *server_user, *local_user;

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

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

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

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

	/* key exchange */
	/* authenticate user */
	if (compat20) {
		ssh_kex2(host, hostaddr);
		ssh_userauth2(server_user, host);
	} else {
		ssh_kex(host, hostaddr);
		ssh_userauth(local_user, server_user, host, host_key_valid, own_host_key);
	}
}