sshconnect.c revision 285980
1/* $OpenBSD: sshconnect.c,v 1.246 2014/02/06 22:21:01 djm Exp $ */
2/* $FreeBSD: releng/9.3/crypto/openssh/sshconnect.c 285980 2015-07-28 19:59:22Z delphij $ */
3/*
4 * Author: Tatu Ylonen <ylo@cs.hut.fi>
5 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
6 *                    All rights reserved
7 * Code to connect to a remote host, and to perform the client side of the
8 * login (authentication) dialog.
9 *
10 * As far as I am concerned, the code I have written for this software
11 * can be used freely for any purpose.  Any derived versions of this
12 * software must be clearly marked as such, and if the derived work is
13 * incompatible with the protocol description in the RFC file, it must be
14 * called by a name other than "ssh" or "Secure Shell".
15 */
16
17#include "includes.h"
18__RCSID("$FreeBSD: releng/9.3/crypto/openssh/sshconnect.c 285980 2015-07-28 19:59:22Z delphij $");
19
20#include <sys/types.h>
21#include <sys/wait.h>
22#include <sys/stat.h>
23#include <sys/socket.h>
24#ifdef HAVE_SYS_TIME_H
25# include <sys/time.h>
26#endif
27
28#include <netinet/in.h>
29#include <arpa/inet.h>
30#include <rpc/rpc.h>
31
32#include <ctype.h>
33#include <errno.h>
34#include <fcntl.h>
35#include <netdb.h>
36#ifdef HAVE_PATHS_H
37#include <paths.h>
38#endif
39#include <pwd.h>
40#include <signal.h>
41#include <stdarg.h>
42#include <stdio.h>
43#include <stdlib.h>
44#include <string.h>
45#include <unistd.h>
46
47#include "xmalloc.h"
48#include "key.h"
49#include "hostfile.h"
50#include "ssh.h"
51#include "rsa.h"
52#include "buffer.h"
53#include "packet.h"
54#include "uidswap.h"
55#include "compat.h"
56#include "key.h"
57#include "sshconnect.h"
58#include "hostfile.h"
59#include "log.h"
60#include "readconf.h"
61#include "atomicio.h"
62#include "misc.h"
63#include "dns.h"
64#include "roaming.h"
65#include "monitor_fdpass.h"
66#include "ssh2.h"
67#include "version.h"
68
69char *client_version_string = NULL;
70char *server_version_string = NULL;
71
72static int matching_host_key_dns = 0;
73
74static pid_t proxy_command_pid = 0;
75
76/* import */
77extern Options options;
78extern char *__progname;
79extern uid_t original_real_uid;
80extern uid_t original_effective_uid;
81
82static int show_other_keys(struct hostkeys *, Key *);
83static void warn_changed_key(Key *);
84
85/* Expand a proxy command */
86static char *
87expand_proxy_command(const char *proxy_command, const char *user,
88    const char *host, int port)
89{
90	char *tmp, *ret, strport[NI_MAXSERV];
91
92	snprintf(strport, sizeof strport, "%d", port);
93	xasprintf(&tmp, "exec %s", proxy_command);
94	ret = percent_expand(tmp, "h", host, "p", strport,
95	    "r", options.user, (char *)NULL);
96	free(tmp);
97	return ret;
98}
99
100/*
101 * Connect to the given ssh server using a proxy command that passes a
102 * a connected fd back to us.
103 */
104static int
105ssh_proxy_fdpass_connect(const char *host, u_short port,
106    const char *proxy_command)
107{
108	char *command_string;
109	int sp[2], sock;
110	pid_t pid;
111	char *shell;
112
113	if ((shell = getenv("SHELL")) == NULL)
114		shell = _PATH_BSHELL;
115
116	if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) < 0)
117		fatal("Could not create socketpair to communicate with "
118		    "proxy dialer: %.100s", strerror(errno));
119
120	command_string = expand_proxy_command(proxy_command, options.user,
121	    host, port);
122	debug("Executing proxy dialer command: %.500s", command_string);
123
124	/* Fork and execute the proxy command. */
125	if ((pid = fork()) == 0) {
126		char *argv[10];
127
128		/* Child.  Permanently give up superuser privileges. */
129		permanently_drop_suid(original_real_uid);
130
131		close(sp[1]);
132		/* Redirect stdin and stdout. */
133		if (sp[0] != 0) {
134			if (dup2(sp[0], 0) < 0)
135				perror("dup2 stdin");
136		}
137		if (sp[0] != 1) {
138			if (dup2(sp[0], 1) < 0)
139				perror("dup2 stdout");
140		}
141		if (sp[0] >= 2)
142			close(sp[0]);
143
144		/*
145		 * Stderr is left as it is so that error messages get
146		 * printed on the user's terminal.
147		 */
148		argv[0] = shell;
149		argv[1] = "-c";
150		argv[2] = command_string;
151		argv[3] = NULL;
152
153		/*
154		 * Execute the proxy command.
155		 * Note that we gave up any extra privileges above.
156		 */
157		execv(argv[0], argv);
158		perror(argv[0]);
159		exit(1);
160	}
161	/* Parent. */
162	if (pid < 0)
163		fatal("fork failed: %.100s", strerror(errno));
164	close(sp[0]);
165	free(command_string);
166
167	if ((sock = mm_receive_fd(sp[1])) == -1)
168		fatal("proxy dialer did not pass back a connection");
169
170	while (waitpid(pid, NULL, 0) == -1)
171		if (errno != EINTR)
172			fatal("Couldn't wait for child: %s", strerror(errno));
173
174	/* Set the connection file descriptors. */
175	packet_set_connection(sock, sock);
176
177	return 0;
178}
179
180/*
181 * Connect to the given ssh server using a proxy command.
182 */
183static int
184ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
185{
186	char *command_string;
187	int pin[2], pout[2];
188	pid_t pid;
189	char *shell;
190
191	if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
192		shell = _PATH_BSHELL;
193
194	/* Create pipes for communicating with the proxy. */
195	if (pipe(pin) < 0 || pipe(pout) < 0)
196		fatal("Could not create pipes to communicate with the proxy: %.100s",
197		    strerror(errno));
198
199	command_string = expand_proxy_command(proxy_command, options.user,
200	    host, port);
201	debug("Executing proxy command: %.500s", command_string);
202
203	/* Fork and execute the proxy command. */
204	if ((pid = fork()) == 0) {
205		char *argv[10];
206
207		/* Child.  Permanently give up superuser privileges. */
208		permanently_drop_suid(original_real_uid);
209
210		/* Redirect stdin and stdout. */
211		close(pin[1]);
212		if (pin[0] != 0) {
213			if (dup2(pin[0], 0) < 0)
214				perror("dup2 stdin");
215			close(pin[0]);
216		}
217		close(pout[0]);
218		if (dup2(pout[1], 1) < 0)
219			perror("dup2 stdout");
220		/* Cannot be 1 because pin allocated two descriptors. */
221		close(pout[1]);
222
223		/* Stderr is left as it is so that error messages get
224		   printed on the user's terminal. */
225		argv[0] = shell;
226		argv[1] = "-c";
227		argv[2] = command_string;
228		argv[3] = NULL;
229
230		/* Execute the proxy command.  Note that we gave up any
231		   extra privileges above. */
232		signal(SIGPIPE, SIG_DFL);
233		execv(argv[0], argv);
234		perror(argv[0]);
235		exit(1);
236	}
237	/* Parent. */
238	if (pid < 0)
239		fatal("fork failed: %.100s", strerror(errno));
240	else
241		proxy_command_pid = pid; /* save pid to clean up later */
242
243	/* Close child side of the descriptors. */
244	close(pin[0]);
245	close(pout[1]);
246
247	/* Free the command name. */
248	free(command_string);
249
250	/* Set the connection file descriptors. */
251	packet_set_connection(pout[0], pin[1]);
252
253	/* Indicate OK return */
254	return 0;
255}
256
257void
258ssh_kill_proxy_command(void)
259{
260	/*
261	 * Send SIGHUP to proxy command if used. We don't wait() in
262	 * case it hangs and instead rely on init to reap the child
263	 */
264	if (proxy_command_pid > 1)
265		kill(proxy_command_pid, SIGHUP);
266}
267
268/*
269 * Set TCP receive buffer if requested.
270 * Note: tuning needs to happen after the socket is created but before the
271 * connection happens so winscale is negotiated properly.
272 */
273static void
274ssh_set_socket_recvbuf(int sock)
275{
276	void *buf = (void *)&options.tcp_rcv_buf;
277	int socksize, sz = sizeof(options.tcp_rcv_buf);
278	socklen_t len = sizeof(int);
279
280	debug("setsockopt attempting to set SO_RCVBUF to %d",
281	    options.tcp_rcv_buf);
282	if (setsockopt(sock, SOL_SOCKET, SO_RCVBUF, buf, sz) >= 0) {
283		getsockopt(sock, SOL_SOCKET, SO_RCVBUF, &socksize, &len);
284		debug("setsockopt SO_RCVBUF: %.100s %d", strerror(errno),
285		    socksize);
286	} else
287		error("Couldn't set socket receive buffer to %d: %.100s",
288		    options.tcp_rcv_buf, strerror(errno));
289}
290
291/*
292 * Creates a (possibly privileged) socket for use as the ssh connection.
293 */
294static int
295ssh_create_socket(int privileged, struct addrinfo *ai)
296{
297	int sock, r, gaierr;
298	struct addrinfo hints, *res = NULL;
299
300	sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
301	if (sock < 0) {
302		error("socket: %s", strerror(errno));
303		return -1;
304	}
305	fcntl(sock, F_SETFD, FD_CLOEXEC);
306
307	if (options.tcp_rcv_buf > 0)
308		ssh_set_socket_recvbuf(sock);
309
310	/* Bind the socket to an alternative local IP address */
311	if (options.bind_address == NULL && !privileged)
312		return sock;
313
314	if (options.bind_address) {
315		memset(&hints, 0, sizeof(hints));
316		hints.ai_family = ai->ai_family;
317		hints.ai_socktype = ai->ai_socktype;
318		hints.ai_protocol = ai->ai_protocol;
319		hints.ai_flags = AI_PASSIVE;
320		gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res);
321		if (gaierr) {
322			error("getaddrinfo: %s: %s", options.bind_address,
323			    ssh_gai_strerror(gaierr));
324			close(sock);
325			return -1;
326		}
327	}
328	/*
329	 * If we are running as root and want to connect to a privileged
330	 * port, bind our own socket to a privileged port.
331	 */
332	if (privileged) {
333		PRIV_START;
334		r = bindresvport_sa(sock, res ? res->ai_addr : NULL);
335		PRIV_END;
336		if (r < 0) {
337			error("bindresvport_sa: af=%d %s", ai->ai_family,
338			    strerror(errno));
339			goto fail;
340		}
341	} else {
342		if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
343			error("bind: %s: %s", options.bind_address,
344			    strerror(errno));
345 fail:
346			close(sock);
347			freeaddrinfo(res);
348			return -1;
349		}
350	}
351	if (res != NULL)
352		freeaddrinfo(res);
353	return sock;
354}
355
356static int
357timeout_connect(int sockfd, const struct sockaddr *serv_addr,
358    socklen_t addrlen, int *timeoutp)
359{
360	fd_set *fdset;
361	struct timeval tv, t_start;
362	socklen_t optlen;
363	int optval, rc, result = -1;
364
365	gettimeofday(&t_start, NULL);
366
367	if (*timeoutp <= 0) {
368		result = connect(sockfd, serv_addr, addrlen);
369		goto done;
370	}
371
372	set_nonblock(sockfd);
373	rc = connect(sockfd, serv_addr, addrlen);
374	if (rc == 0) {
375		unset_nonblock(sockfd);
376		result = 0;
377		goto done;
378	}
379	if (errno != EINPROGRESS) {
380		result = -1;
381		goto done;
382	}
383
384	fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS),
385	    sizeof(fd_mask));
386	FD_SET(sockfd, fdset);
387	ms_to_timeval(&tv, *timeoutp);
388
389	for (;;) {
390		rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
391		if (rc != -1 || errno != EINTR)
392			break;
393	}
394
395	switch (rc) {
396	case 0:
397		/* Timed out */
398		errno = ETIMEDOUT;
399		break;
400	case -1:
401		/* Select error */
402		debug("select: %s", strerror(errno));
403		break;
404	case 1:
405		/* Completed or failed */
406		optval = 0;
407		optlen = sizeof(optval);
408		if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
409		    &optlen) == -1) {
410			debug("getsockopt: %s", strerror(errno));
411			break;
412		}
413		if (optval != 0) {
414			errno = optval;
415			break;
416		}
417		result = 0;
418		unset_nonblock(sockfd);
419		break;
420	default:
421		/* Should not occur */
422		fatal("Bogus return (%d) from select()", rc);
423	}
424
425	free(fdset);
426
427 done:
428 	if (result == 0 && *timeoutp > 0) {
429		ms_subtract_diff(&t_start, timeoutp);
430		if (*timeoutp <= 0) {
431			errno = ETIMEDOUT;
432			result = -1;
433		}
434	}
435
436	return (result);
437}
438
439/*
440 * Opens a TCP/IP connection to the remote server on the given host.
441 * The address of the remote host will be returned in hostaddr.
442 * If port is 0, the default port will be used.  If needpriv is true,
443 * a privileged port will be allocated to make the connection.
444 * This requires super-user privileges if needpriv is true.
445 * Connection_attempts specifies the maximum number of tries (one per
446 * second).  If proxy_command is non-NULL, it specifies the command (with %h
447 * and %p substituted for host and port, respectively) to use to contact
448 * the daemon.
449 */
450static int
451ssh_connect_direct(const char *host, struct addrinfo *aitop,
452    struct sockaddr_storage *hostaddr, u_short port, int family,
453    int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv)
454{
455	int on = 1;
456	int sock = -1, attempt;
457	char ntop[NI_MAXHOST], strport[NI_MAXSERV];
458	struct addrinfo *ai;
459
460	debug2("ssh_connect: needpriv %d", needpriv);
461
462	for (attempt = 0; attempt < connection_attempts; attempt++) {
463		if (attempt > 0) {
464			/* Sleep a moment before retrying. */
465			sleep(1);
466			debug("Trying again...");
467		}
468		/*
469		 * Loop through addresses for this host, and try each one in
470		 * sequence until the connection succeeds.
471		 */
472		for (ai = aitop; ai; ai = ai->ai_next) {
473			if (ai->ai_family != AF_INET &&
474			    ai->ai_family != AF_INET6)
475				continue;
476			if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
477			    ntop, sizeof(ntop), strport, sizeof(strport),
478			    NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
479				error("ssh_connect: getnameinfo failed");
480				continue;
481			}
482			debug("Connecting to %.200s [%.100s] port %s.",
483				host, ntop, strport);
484
485			/* Create a socket for connecting. */
486			sock = ssh_create_socket(needpriv, ai);
487			if (sock < 0)
488				/* Any error is already output */
489				continue;
490
491			if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
492			    timeout_ms) >= 0) {
493				/* Successful connection. */
494				memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
495				break;
496			} else {
497				debug("connect to address %s port %s: %s",
498				    ntop, strport, strerror(errno));
499				close(sock);
500				sock = -1;
501			}
502		}
503		if (sock != -1)
504			break;	/* Successful connection. */
505	}
506
507	/* Return failure if we didn't get a successful connection. */
508	if (sock == -1) {
509		error("ssh: connect to host %s port %s: %s",
510		    host, strport, strerror(errno));
511		return (-1);
512	}
513
514	debug("Connection established.");
515
516	/* Set SO_KEEPALIVE if requested. */
517	if (want_keepalive &&
518	    setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
519	    sizeof(on)) < 0)
520		error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
521
522	/* Set the connection. */
523	packet_set_connection(sock, sock);
524
525	return 0;
526}
527
528int
529ssh_connect(const char *host, struct addrinfo *addrs,
530    struct sockaddr_storage *hostaddr, u_short port, int family,
531    int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv)
532{
533	if (options.proxy_command == NULL) {
534		return ssh_connect_direct(host, addrs, hostaddr, port, family,
535		    connection_attempts, timeout_ms, want_keepalive, needpriv);
536	} else if (strcmp(options.proxy_command, "-") == 0) {
537		packet_set_connection(STDIN_FILENO, STDOUT_FILENO);
538		return 0; /* Always succeeds */
539	} else if (options.proxy_use_fdpass) {
540		return ssh_proxy_fdpass_connect(host, port,
541		    options.proxy_command);
542	}
543	return ssh_proxy_connect(host, port, options.proxy_command);
544}
545
546static void
547send_client_banner(int connection_out, int minor1)
548{
549	/* Send our own protocol version identification. */
550	xasprintf(&client_version_string, "SSH-%d.%d-%.100s%s%s%s%s",
551	    compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
552	    compat20 ? PROTOCOL_MINOR_2 : minor1,
553	    SSH_VERSION, options.hpn_disabled ? "" : SSH_VERSION_HPN,
554	    *options.version_addendum == '\0' ? "" : " ",
555	    options.version_addendum, compat20 ? "\r\n" : "\n");
556	if (roaming_atomicio(vwrite, connection_out, client_version_string,
557	    strlen(client_version_string)) != strlen(client_version_string))
558		fatal("write: %.100s", strerror(errno));
559	chop(client_version_string);
560	debug("Local version string %.100s", client_version_string);
561}
562
563/*
564 * Waits for the server identification string, and sends our own
565 * identification string.
566 */
567void
568ssh_exchange_identification(int timeout_ms)
569{
570	char buf[256], remote_version[256];	/* must be same size! */
571	int remote_major, remote_minor, mismatch;
572	int connection_in = packet_get_connection_in();
573	int connection_out = packet_get_connection_out();
574	int minor1 = PROTOCOL_MINOR_1, client_banner_sent = 0;
575	u_int i, n;
576	size_t len;
577	int fdsetsz, remaining, rc;
578	struct timeval t_start, t_remaining;
579	fd_set *fdset;
580
581	fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask);
582	fdset = xcalloc(1, fdsetsz);
583
584	/*
585	 * If we are SSH2-only then we can send the banner immediately and
586	 * save a round-trip.
587	 */
588	if (options.protocol == SSH_PROTO_2) {
589		enable_compat20();
590		send_client_banner(connection_out, 0);
591		client_banner_sent = 1;
592	}
593
594	/* Read other side's version identification. */
595	remaining = timeout_ms;
596	for (n = 0;;) {
597		for (i = 0; i < sizeof(buf) - 1; i++) {
598			if (timeout_ms > 0) {
599				gettimeofday(&t_start, NULL);
600				ms_to_timeval(&t_remaining, remaining);
601				FD_SET(connection_in, fdset);
602				rc = select(connection_in + 1, fdset, NULL,
603				    fdset, &t_remaining);
604				ms_subtract_diff(&t_start, &remaining);
605				if (rc == 0 || remaining <= 0)
606					fatal("Connection timed out during "
607					    "banner exchange");
608				if (rc == -1) {
609					if (errno == EINTR)
610						continue;
611					fatal("ssh_exchange_identification: "
612					    "select: %s", strerror(errno));
613				}
614			}
615
616			len = roaming_atomicio(read, connection_in, &buf[i], 1);
617
618			if (len != 1 && errno == EPIPE)
619				fatal("ssh_exchange_identification: "
620				    "Connection closed by remote host");
621			else if (len != 1)
622				fatal("ssh_exchange_identification: "
623				    "read: %.100s", strerror(errno));
624			if (buf[i] == '\r') {
625				buf[i] = '\n';
626				buf[i + 1] = 0;
627				continue;		/**XXX wait for \n */
628			}
629			if (buf[i] == '\n') {
630				buf[i + 1] = 0;
631				break;
632			}
633			if (++n > 65536)
634				fatal("ssh_exchange_identification: "
635				    "No banner received");
636		}
637		buf[sizeof(buf) - 1] = 0;
638		if (strncmp(buf, "SSH-", 4) == 0)
639			break;
640		debug("ssh_exchange_identification: %s", buf);
641	}
642	server_version_string = xstrdup(buf);
643	free(fdset);
644
645	/*
646	 * Check that the versions match.  In future this might accept
647	 * several versions and set appropriate flags to handle them.
648	 */
649	if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
650	    &remote_major, &remote_minor, remote_version) != 3)
651		fatal("Bad remote protocol version identification: '%.100s'", buf);
652	debug("Remote protocol version %d.%d, remote software version %.100s",
653	    remote_major, remote_minor, remote_version);
654
655	compat_datafellows(remote_version);
656	mismatch = 0;
657
658	switch (remote_major) {
659	case 1:
660		if (remote_minor == 99 &&
661		    (options.protocol & SSH_PROTO_2) &&
662		    !(options.protocol & SSH_PROTO_1_PREFERRED)) {
663			enable_compat20();
664			break;
665		}
666		if (!(options.protocol & SSH_PROTO_1)) {
667			mismatch = 1;
668			break;
669		}
670		if (remote_minor < 3) {
671			fatal("Remote machine has too old SSH software version.");
672		} else if (remote_minor == 3 || remote_minor == 4) {
673			/* We speak 1.3, too. */
674			enable_compat13();
675			minor1 = 3;
676			if (options.forward_agent) {
677				logit("Agent forwarding disabled for protocol 1.3");
678				options.forward_agent = 0;
679			}
680		}
681		break;
682	case 2:
683		if (options.protocol & SSH_PROTO_2) {
684			enable_compat20();
685			break;
686		}
687		/* FALLTHROUGH */
688	default:
689		mismatch = 1;
690		break;
691	}
692	if (mismatch)
693		fatal("Protocol major versions differ: %d vs. %d",
694		    (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
695		    remote_major);
696	if ((datafellows & SSH_BUG_DERIVEKEY) != 0)
697		fatal("Server version \"%.100s\" uses unsafe key agreement; "
698		    "refusing connection", remote_version);
699	if ((datafellows & SSH_BUG_RSASIGMD5) != 0)
700		logit("Server version \"%.100s\" uses unsafe RSA signature "
701		    "scheme; disabling use of RSA keys", remote_version);
702	if (!client_banner_sent)
703		send_client_banner(connection_out, minor1);
704	chop(server_version_string);
705}
706
707/* defaults to 'no' */
708static int
709confirm(const char *prompt)
710{
711	const char *msg, *again = "Please type 'yes' or 'no': ";
712	char *p;
713	int ret = -1;
714
715	if (options.batch_mode)
716		return 0;
717	for (msg = prompt;;msg = again) {
718		p = read_passphrase(msg, RP_ECHO);
719		if (p == NULL ||
720		    (p[0] == '\0') || (p[0] == '\n') ||
721		    strncasecmp(p, "no", 2) == 0)
722			ret = 0;
723		if (p && strncasecmp(p, "yes", 3) == 0)
724			ret = 1;
725		free(p);
726		if (ret != -1)
727			return ret;
728	}
729}
730
731static int
732check_host_cert(const char *host, const Key *host_key)
733{
734	const char *reason;
735
736	if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) {
737		error("%s", reason);
738		return 0;
739	}
740	if (buffer_len(&host_key->cert->critical) != 0) {
741		error("Certificate for %s contains unsupported "
742		    "critical options(s)", host);
743		return 0;
744	}
745	return 1;
746}
747
748static int
749sockaddr_is_local(struct sockaddr *hostaddr)
750{
751	switch (hostaddr->sa_family) {
752	case AF_INET:
753		return (ntohl(((struct sockaddr_in *)hostaddr)->
754		    sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
755	case AF_INET6:
756		return IN6_IS_ADDR_LOOPBACK(
757		    &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
758	default:
759		return 0;
760	}
761}
762
763/*
764 * Prepare the hostname and ip address strings that are used to lookup
765 * host keys in known_hosts files. These may have a port number appended.
766 */
767void
768get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr,
769    u_short port, char **hostfile_hostname, char **hostfile_ipaddr)
770{
771	char ntop[NI_MAXHOST];
772	socklen_t addrlen;
773
774	switch (hostaddr == NULL ? -1 : hostaddr->sa_family) {
775	case -1:
776		addrlen = 0;
777		break;
778	case AF_INET:
779		addrlen = sizeof(struct sockaddr_in);
780		break;
781	case AF_INET6:
782		addrlen = sizeof(struct sockaddr_in6);
783		break;
784	default:
785		addrlen = sizeof(struct sockaddr);
786		break;
787	}
788
789	/*
790	 * We don't have the remote ip-address for connections
791	 * using a proxy command
792	 */
793	if (hostfile_ipaddr != NULL) {
794		if (options.proxy_command == NULL) {
795			if (getnameinfo(hostaddr, addrlen,
796			    ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0)
797			fatal("check_host_key: getnameinfo failed");
798			*hostfile_ipaddr = put_host_port(ntop, port);
799		} else {
800			*hostfile_ipaddr = xstrdup("<no hostip for proxy "
801			    "command>");
802		}
803	}
804
805	/*
806	 * Allow the user to record the key under a different name or
807	 * differentiate a non-standard port.  This is useful for ssh
808	 * tunneling over forwarded connections or if you run multiple
809	 * sshd's on different ports on the same machine.
810	 */
811	if (hostfile_hostname != NULL) {
812		if (options.host_key_alias != NULL) {
813			*hostfile_hostname = xstrdup(options.host_key_alias);
814			debug("using hostkeyalias: %s", *hostfile_hostname);
815		} else {
816			*hostfile_hostname = put_host_port(hostname, port);
817		}
818	}
819}
820
821/*
822 * check whether the supplied host key is valid, return -1 if the key
823 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true.
824 */
825#define RDRW	0
826#define RDONLY	1
827#define ROQUIET	2
828static int
829check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
830    Key *host_key, int readonly,
831    char **user_hostfiles, u_int num_user_hostfiles,
832    char **system_hostfiles, u_int num_system_hostfiles)
833{
834	HostStatus host_status;
835	HostStatus ip_status;
836	Key *raw_key = NULL;
837	char *ip = NULL, *host = NULL;
838	char hostline[1000], *hostp, *fp, *ra;
839	char msg[1024];
840	const char *type;
841	const struct hostkey_entry *host_found, *ip_found;
842	int len, cancelled_forwarding = 0;
843	int local = sockaddr_is_local(hostaddr);
844	int r, want_cert = key_is_cert(host_key), host_ip_differ = 0;
845	struct hostkeys *host_hostkeys, *ip_hostkeys;
846	u_int i;
847
848	/*
849	 * Force accepting of the host key for loopback/localhost. The
850	 * problem is that if the home directory is NFS-mounted to multiple
851	 * machines, localhost will refer to a different machine in each of
852	 * them, and the user will get bogus HOST_CHANGED warnings.  This
853	 * essentially disables host authentication for localhost; however,
854	 * this is probably not a real problem.
855	 */
856	if (options.no_host_authentication_for_localhost == 1 && local &&
857	    options.host_key_alias == NULL) {
858		debug("Forcing accepting of host key for "
859		    "loopback/localhost.");
860		return 0;
861	}
862
863	/*
864	 * Prepare the hostname and address strings used for hostkey lookup.
865	 * In some cases, these will have a port number appended.
866	 */
867	get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip);
868
869	/*
870	 * Turn off check_host_ip if the connection is to localhost, via proxy
871	 * command or if we don't have a hostname to compare with
872	 */
873	if (options.check_host_ip && (local ||
874	    strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
875		options.check_host_ip = 0;
876
877	host_hostkeys = init_hostkeys();
878	for (i = 0; i < num_user_hostfiles; i++)
879		load_hostkeys(host_hostkeys, host, user_hostfiles[i]);
880	for (i = 0; i < num_system_hostfiles; i++)
881		load_hostkeys(host_hostkeys, host, system_hostfiles[i]);
882
883	ip_hostkeys = NULL;
884	if (!want_cert && options.check_host_ip) {
885		ip_hostkeys = init_hostkeys();
886		for (i = 0; i < num_user_hostfiles; i++)
887			load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]);
888		for (i = 0; i < num_system_hostfiles; i++)
889			load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]);
890	}
891
892 retry:
893	/* Reload these as they may have changed on cert->key downgrade */
894	want_cert = key_is_cert(host_key);
895	type = key_type(host_key);
896
897	/*
898	 * Check if the host key is present in the user's list of known
899	 * hosts or in the systemwide list.
900	 */
901	host_status = check_key_in_hostkeys(host_hostkeys, host_key,
902	    &host_found);
903
904	/*
905	 * Also perform check for the ip address, skip the check if we are
906	 * localhost, looking for a certificate, or the hostname was an ip
907	 * address to begin with.
908	 */
909	if (!want_cert && ip_hostkeys != NULL) {
910		ip_status = check_key_in_hostkeys(ip_hostkeys, host_key,
911		    &ip_found);
912		if (host_status == HOST_CHANGED &&
913		    (ip_status != HOST_CHANGED ||
914		    (ip_found != NULL &&
915		    !key_equal(ip_found->key, host_found->key))))
916			host_ip_differ = 1;
917	} else
918		ip_status = host_status;
919
920	switch (host_status) {
921	case HOST_OK:
922		/* The host is known and the key matches. */
923		debug("Host '%.200s' is known and matches the %s host %s.",
924		    host, type, want_cert ? "certificate" : "key");
925		debug("Found %s in %s:%lu", want_cert ? "CA key" : "key",
926		    host_found->file, host_found->line);
927		if (want_cert && !check_host_cert(hostname, host_key))
928			goto fail;
929		if (options.check_host_ip && ip_status == HOST_NEW) {
930			if (readonly || want_cert)
931				logit("%s host key for IP address "
932				    "'%.128s' not in list of known hosts.",
933				    type, ip);
934			else if (!add_host_to_hostfile(user_hostfiles[0], ip,
935			    host_key, options.hash_known_hosts))
936				logit("Failed to add the %s host key for IP "
937				    "address '%.128s' to the list of known "
938				    "hosts (%.30s).", type, ip,
939				    user_hostfiles[0]);
940			else
941				logit("Warning: Permanently added the %s host "
942				    "key for IP address '%.128s' to the list "
943				    "of known hosts.", type, ip);
944		} else if (options.visual_host_key) {
945			fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
946			ra = key_fingerprint(host_key, SSH_FP_MD5,
947			    SSH_FP_RANDOMART);
948			logit("Host key fingerprint is %s\n%s\n", fp, ra);
949			free(ra);
950			free(fp);
951		}
952		break;
953	case HOST_NEW:
954		if (options.host_key_alias == NULL && port != 0 &&
955		    port != SSH_DEFAULT_PORT) {
956			debug("checking without port identifier");
957			if (check_host_key(hostname, hostaddr, 0, host_key,
958			    ROQUIET, user_hostfiles, num_user_hostfiles,
959			    system_hostfiles, num_system_hostfiles) == 0) {
960				debug("found matching key w/out port");
961				break;
962			}
963		}
964		if (readonly || want_cert)
965			goto fail;
966		/* The host is new. */
967		if (options.strict_host_key_checking == 1) {
968			/*
969			 * User has requested strict host key checking.  We
970			 * will not add the host key automatically.  The only
971			 * alternative left is to abort.
972			 */
973			error("No %s host key is known for %.200s and you "
974			    "have requested strict checking.", type, host);
975			goto fail;
976		} else if (options.strict_host_key_checking == 2) {
977			char msg1[1024], msg2[1024];
978
979			if (show_other_keys(host_hostkeys, host_key))
980				snprintf(msg1, sizeof(msg1),
981				    "\nbut keys of different type are already"
982				    " known for this host.");
983			else
984				snprintf(msg1, sizeof(msg1), ".");
985			/* The default */
986			fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
987			ra = key_fingerprint(host_key, SSH_FP_MD5,
988			    SSH_FP_RANDOMART);
989			msg2[0] = '\0';
990			if (options.verify_host_key_dns) {
991				if (matching_host_key_dns)
992					snprintf(msg2, sizeof(msg2),
993					    "Matching host key fingerprint"
994					    " found in DNS.\n");
995				else
996					snprintf(msg2, sizeof(msg2),
997					    "No matching host key fingerprint"
998					    " found in DNS.\n");
999			}
1000			snprintf(msg, sizeof(msg),
1001			    "The authenticity of host '%.200s (%s)' can't be "
1002			    "established%s\n"
1003			    "%s key fingerprint is %s.%s%s\n%s"
1004			    "Are you sure you want to continue connecting "
1005			    "(yes/no)? ",
1006			    host, ip, msg1, type, fp,
1007			    options.visual_host_key ? "\n" : "",
1008			    options.visual_host_key ? ra : "",
1009			    msg2);
1010			free(ra);
1011			free(fp);
1012			if (!confirm(msg))
1013				goto fail;
1014		}
1015		/*
1016		 * If not in strict mode, add the key automatically to the
1017		 * local known_hosts file.
1018		 */
1019		if (options.check_host_ip && ip_status == HOST_NEW) {
1020			snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
1021			hostp = hostline;
1022			if (options.hash_known_hosts) {
1023				/* Add hash of host and IP separately */
1024				r = add_host_to_hostfile(user_hostfiles[0],
1025				    host, host_key, options.hash_known_hosts) &&
1026				    add_host_to_hostfile(user_hostfiles[0], ip,
1027				    host_key, options.hash_known_hosts);
1028			} else {
1029				/* Add unhashed "host,ip" */
1030				r = add_host_to_hostfile(user_hostfiles[0],
1031				    hostline, host_key,
1032				    options.hash_known_hosts);
1033			}
1034		} else {
1035			r = add_host_to_hostfile(user_hostfiles[0], host,
1036			    host_key, options.hash_known_hosts);
1037			hostp = host;
1038		}
1039
1040		if (!r)
1041			logit("Failed to add the host to the list of known "
1042			    "hosts (%.500s).", user_hostfiles[0]);
1043		else
1044			logit("Warning: Permanently added '%.200s' (%s) to the "
1045			    "list of known hosts.", hostp, type);
1046		break;
1047	case HOST_REVOKED:
1048		error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1049		error("@       WARNING: REVOKED HOST KEY DETECTED!               @");
1050		error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1051		error("The %s host key for %s is marked as revoked.", type, host);
1052		error("This could mean that a stolen key is being used to");
1053		error("impersonate this host.");
1054
1055		/*
1056		 * If strict host key checking is in use, the user will have
1057		 * to edit the key manually and we can only abort.
1058		 */
1059		if (options.strict_host_key_checking) {
1060			error("%s host key for %.200s was revoked and you have "
1061			    "requested strict checking.", type, host);
1062			goto fail;
1063		}
1064		goto continue_unsafe;
1065
1066	case HOST_CHANGED:
1067		if (want_cert) {
1068			/*
1069			 * This is only a debug() since it is valid to have
1070			 * CAs with wildcard DNS matches that don't match
1071			 * all hosts that one might visit.
1072			 */
1073			debug("Host certificate authority does not "
1074			    "match %s in %s:%lu", CA_MARKER,
1075			    host_found->file, host_found->line);
1076			goto fail;
1077		}
1078		if (readonly == ROQUIET)
1079			goto fail;
1080		if (options.check_host_ip && host_ip_differ) {
1081			char *key_msg;
1082			if (ip_status == HOST_NEW)
1083				key_msg = "is unknown";
1084			else if (ip_status == HOST_OK)
1085				key_msg = "is unchanged";
1086			else
1087				key_msg = "has a different value";
1088			error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1089			error("@       WARNING: POSSIBLE DNS SPOOFING DETECTED!          @");
1090			error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1091			error("The %s host key for %s has changed,", type, host);
1092			error("and the key for the corresponding IP address %s", ip);
1093			error("%s. This could either mean that", key_msg);
1094			error("DNS SPOOFING is happening or the IP address for the host");
1095			error("and its host key have changed at the same time.");
1096			if (ip_status != HOST_NEW)
1097				error("Offending key for IP in %s:%lu",
1098				    ip_found->file, ip_found->line);
1099		}
1100		/* The host key has changed. */
1101		warn_changed_key(host_key);
1102		error("Add correct host key in %.100s to get rid of this message.",
1103		    user_hostfiles[0]);
1104		error("Offending %s key in %s:%lu", key_type(host_found->key),
1105		    host_found->file, host_found->line);
1106
1107		/*
1108		 * If strict host key checking is in use, the user will have
1109		 * to edit the key manually and we can only abort.
1110		 */
1111		if (options.strict_host_key_checking) {
1112			error("%s host key for %.200s has changed and you have "
1113			    "requested strict checking.", type, host);
1114			goto fail;
1115		}
1116
1117 continue_unsafe:
1118		/*
1119		 * If strict host key checking has not been requested, allow
1120		 * the connection but without MITM-able authentication or
1121		 * forwarding.
1122		 */
1123		if (options.password_authentication) {
1124			error("Password authentication is disabled to avoid "
1125			    "man-in-the-middle attacks.");
1126			options.password_authentication = 0;
1127			cancelled_forwarding = 1;
1128		}
1129		if (options.kbd_interactive_authentication) {
1130			error("Keyboard-interactive authentication is disabled"
1131			    " to avoid man-in-the-middle attacks.");
1132			options.kbd_interactive_authentication = 0;
1133			options.challenge_response_authentication = 0;
1134			cancelled_forwarding = 1;
1135		}
1136		if (options.challenge_response_authentication) {
1137			error("Challenge/response authentication is disabled"
1138			    " to avoid man-in-the-middle attacks.");
1139			options.challenge_response_authentication = 0;
1140			cancelled_forwarding = 1;
1141		}
1142		if (options.forward_agent) {
1143			error("Agent forwarding is disabled to avoid "
1144			    "man-in-the-middle attacks.");
1145			options.forward_agent = 0;
1146			cancelled_forwarding = 1;
1147		}
1148		if (options.forward_x11) {
1149			error("X11 forwarding is disabled to avoid "
1150			    "man-in-the-middle attacks.");
1151			options.forward_x11 = 0;
1152			cancelled_forwarding = 1;
1153		}
1154		if (options.num_local_forwards > 0 ||
1155		    options.num_remote_forwards > 0) {
1156			error("Port forwarding is disabled to avoid "
1157			    "man-in-the-middle attacks.");
1158			options.num_local_forwards =
1159			    options.num_remote_forwards = 0;
1160			cancelled_forwarding = 1;
1161		}
1162		if (options.tun_open != SSH_TUNMODE_NO) {
1163			error("Tunnel forwarding is disabled to avoid "
1164			    "man-in-the-middle attacks.");
1165			options.tun_open = SSH_TUNMODE_NO;
1166			cancelled_forwarding = 1;
1167		}
1168		if (options.exit_on_forward_failure && cancelled_forwarding)
1169			fatal("Error: forwarding disabled due to host key "
1170			    "check failure");
1171
1172		/*
1173		 * XXX Should permit the user to change to use the new id.
1174		 * This could be done by converting the host key to an
1175		 * identifying sentence, tell that the host identifies itself
1176		 * by that sentence, and ask the user if he/she wishes to
1177		 * accept the authentication.
1178		 */
1179		break;
1180	case HOST_FOUND:
1181		fatal("internal error");
1182		break;
1183	}
1184
1185	if (options.check_host_ip && host_status != HOST_CHANGED &&
1186	    ip_status == HOST_CHANGED) {
1187		snprintf(msg, sizeof(msg),
1188		    "Warning: the %s host key for '%.200s' "
1189		    "differs from the key for the IP address '%.128s'"
1190		    "\nOffending key for IP in %s:%lu",
1191		    type, host, ip, ip_found->file, ip_found->line);
1192		if (host_status == HOST_OK) {
1193			len = strlen(msg);
1194			snprintf(msg + len, sizeof(msg) - len,
1195			    "\nMatching host key in %s:%lu",
1196			    host_found->file, host_found->line);
1197		}
1198		if (options.strict_host_key_checking == 1) {
1199			logit("%s", msg);
1200			error("Exiting, you have requested strict checking.");
1201			goto fail;
1202		} else if (options.strict_host_key_checking == 2) {
1203			strlcat(msg, "\nAre you sure you want "
1204			    "to continue connecting (yes/no)? ", sizeof(msg));
1205			if (!confirm(msg))
1206				goto fail;
1207		} else {
1208			logit("%s", msg);
1209		}
1210	}
1211
1212	free(ip);
1213	free(host);
1214	if (host_hostkeys != NULL)
1215		free_hostkeys(host_hostkeys);
1216	if (ip_hostkeys != NULL)
1217		free_hostkeys(ip_hostkeys);
1218	return 0;
1219
1220fail:
1221	if (want_cert && host_status != HOST_REVOKED) {
1222		/*
1223		 * No matching certificate. Downgrade cert to raw key and
1224		 * search normally.
1225		 */
1226		debug("No matching CA found. Retry with plain key");
1227		raw_key = key_from_private(host_key);
1228		if (key_drop_cert(raw_key) != 0)
1229			fatal("Couldn't drop certificate");
1230		host_key = raw_key;
1231		goto retry;
1232	}
1233	if (raw_key != NULL)
1234		key_free(raw_key);
1235	free(ip);
1236	free(host);
1237	if (host_hostkeys != NULL)
1238		free_hostkeys(host_hostkeys);
1239	if (ip_hostkeys != NULL)
1240		free_hostkeys(ip_hostkeys);
1241	return -1;
1242}
1243
1244/* returns 0 if key verifies or -1 if key does NOT verify */
1245int
1246verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
1247{
1248	int flags = 0;
1249	char *fp;
1250	Key *plain = NULL;
1251
1252	fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1253	debug("Server host key: %s %s", key_type(host_key), fp);
1254	free(fp);
1255
1256	if (options.verify_host_key_dns) {
1257		/*
1258		 * XXX certs are not yet supported for DNS, so downgrade
1259		 * them and try the plain key.
1260		 */
1261		plain = key_from_private(host_key);
1262		if (key_is_cert(plain))
1263			key_drop_cert(plain);
1264		if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) {
1265			if (flags & DNS_VERIFY_FOUND) {
1266				if (options.verify_host_key_dns == 1 &&
1267				    flags & DNS_VERIFY_MATCH &&
1268				    flags & DNS_VERIFY_SECURE) {
1269					key_free(plain);
1270					return 0;
1271				}
1272				if (flags & DNS_VERIFY_MATCH) {
1273					matching_host_key_dns = 1;
1274				} else {
1275					warn_changed_key(plain);
1276					error("Update the SSHFP RR in DNS "
1277					    "with the new host key to get rid "
1278					    "of this message.");
1279				}
1280			}
1281		}
1282		key_free(plain);
1283	}
1284
1285	return check_host_key(host, hostaddr, options.port, host_key, RDRW,
1286	    options.user_hostfiles, options.num_user_hostfiles,
1287	    options.system_hostfiles, options.num_system_hostfiles);
1288}
1289
1290/*
1291 * Starts a dialog with the server, and authenticates the current user on the
1292 * server.  This does not need any extra privileges.  The basic connection
1293 * to the server must already have been established before this is called.
1294 * If login fails, this function prints an error and never returns.
1295 * This function does not require super-user privileges.
1296 */
1297void
1298ssh_login(Sensitive *sensitive, const char *orighost,
1299    struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms)
1300{
1301	char *host;
1302	char *server_user, *local_user;
1303
1304	local_user = xstrdup(pw->pw_name);
1305	server_user = options.user ? options.user : local_user;
1306
1307	/* Convert the user-supplied hostname into all lowercase. */
1308	host = xstrdup(orighost);
1309	lowercase(host);
1310
1311	/* Exchange protocol version identification strings with the server. */
1312	ssh_exchange_identification(timeout_ms);
1313
1314	/* Put the connection into non-blocking mode. */
1315	packet_set_nonblocking();
1316
1317	/* key exchange */
1318	/* authenticate user */
1319	if (compat20) {
1320		ssh_kex2(host, hostaddr, port);
1321		ssh_userauth2(local_user, server_user, host, sensitive);
1322	} else {
1323		ssh_kex(host, hostaddr);
1324		ssh_userauth1(local_user, server_user, host, sensitive);
1325	}
1326	free(local_user);
1327}
1328
1329void
1330ssh_put_password(char *password)
1331{
1332	int size;
1333	char *padded;
1334
1335	if (datafellows & SSH_BUG_PASSWORDPAD) {
1336		packet_put_cstring(password);
1337		return;
1338	}
1339	size = roundup(strlen(password) + 1, 32);
1340	padded = xcalloc(1, size);
1341	strlcpy(padded, password, size);
1342	packet_put_string(padded, size);
1343	explicit_bzero(padded, size);
1344	free(padded);
1345}
1346
1347/* print all known host keys for a given host, but skip keys of given type */
1348static int
1349show_other_keys(struct hostkeys *hostkeys, Key *key)
1350{
1351	int type[] = {
1352		KEY_RSA1,
1353		KEY_RSA,
1354		KEY_DSA,
1355		KEY_ECDSA,
1356		KEY_ED25519,
1357		-1
1358	};
1359	int i, ret = 0;
1360	char *fp, *ra;
1361	const struct hostkey_entry *found;
1362
1363	for (i = 0; type[i] != -1; i++) {
1364		if (type[i] == key->type)
1365			continue;
1366		if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found))
1367			continue;
1368		fp = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_HEX);
1369		ra = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_RANDOMART);
1370		logit("WARNING: %s key found for host %s\n"
1371		    "in %s:%lu\n"
1372		    "%s key fingerprint %s.",
1373		    key_type(found->key),
1374		    found->host, found->file, found->line,
1375		    key_type(found->key), fp);
1376		if (options.visual_host_key)
1377			logit("%s", ra);
1378		free(ra);
1379		free(fp);
1380		ret = 1;
1381	}
1382	return ret;
1383}
1384
1385static void
1386warn_changed_key(Key *host_key)
1387{
1388	char *fp;
1389
1390	fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1391
1392	error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1393	error("@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @");
1394	error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1395	error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1396	error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1397	error("It is also possible that a host key has just been changed.");
1398	error("The fingerprint for the %s key sent by the remote host is\n%s.",
1399	    key_type(host_key), fp);
1400	error("Please contact your system administrator.");
1401
1402	free(fp);
1403}
1404
1405/*
1406 * Execute a local command
1407 */
1408int
1409ssh_local_cmd(const char *args)
1410{
1411	char *shell;
1412	pid_t pid;
1413	int status;
1414	void (*osighand)(int);
1415
1416	if (!options.permit_local_command ||
1417	    args == NULL || !*args)
1418		return (1);
1419
1420	if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
1421		shell = _PATH_BSHELL;
1422
1423	osighand = signal(SIGCHLD, SIG_DFL);
1424	pid = fork();
1425	if (pid == 0) {
1426		signal(SIGPIPE, SIG_DFL);
1427		debug3("Executing %s -c \"%s\"", shell, args);
1428		execl(shell, shell, "-c", args, (char *)NULL);
1429		error("Couldn't execute %s -c \"%s\": %s",
1430		    shell, args, strerror(errno));
1431		_exit(1);
1432	} else if (pid == -1)
1433		fatal("fork failed: %.100s", strerror(errno));
1434	while (waitpid(pid, &status, 0) == -1)
1435		if (errno != EINTR)
1436			fatal("Couldn't wait for child: %s", strerror(errno));
1437	signal(SIGCHLD, osighand);
1438
1439	if (!WIFEXITED(status))
1440		return (1);
1441
1442	return (WEXITSTATUS(status));
1443}
1444