xref: /freebsd/crypto/openssh/sshconnect.c (revision 3e0efd2ec4fcb4cd68fb8ccf8aea6fc6151c454b)
1 /* $OpenBSD: sshconnect.c,v 1.234 2011/05/24 07:15:47 djm Exp $ */
2 /* $FreeBSD$ */
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 
19 #include <sys/types.h>
20 #include <sys/wait.h>
21 #include <sys/stat.h>
22 #include <sys/socket.h>
23 #ifdef HAVE_SYS_TIME_H
24 # include <sys/time.h>
25 #endif
26 
27 #include <netinet/in.h>
28 #include <arpa/inet.h>
29 
30 #include <ctype.h>
31 #include <errno.h>
32 #include <fcntl.h>
33 #include <netdb.h>
34 #ifdef HAVE_PATHS_H
35 #include <paths.h>
36 #endif
37 #include <pwd.h>
38 #include <signal.h>
39 #include <stdarg.h>
40 #include <stdio.h>
41 #include <stdlib.h>
42 #include <string.h>
43 #include <unistd.h>
44 
45 #include "xmalloc.h"
46 #include "key.h"
47 #include "hostfile.h"
48 #include "ssh.h"
49 #include "rsa.h"
50 #include "buffer.h"
51 #include "packet.h"
52 #include "uidswap.h"
53 #include "compat.h"
54 #include "key.h"
55 #include "sshconnect.h"
56 #include "hostfile.h"
57 #include "log.h"
58 #include "readconf.h"
59 #include "atomicio.h"
60 #include "misc.h"
61 #include "dns.h"
62 #include "roaming.h"
63 #include "ssh2.h"
64 #include "version.h"
65 
66 char *client_version_string = NULL;
67 char *server_version_string = NULL;
68 
69 static int matching_host_key_dns = 0;
70 
71 static pid_t proxy_command_pid = 0;
72 
73 /* import */
74 extern Options options;
75 extern char *__progname;
76 extern uid_t original_real_uid;
77 extern uid_t original_effective_uid;
78 
79 static int show_other_keys(struct hostkeys *, Key *);
80 static void warn_changed_key(Key *);
81 
82 /*
83  * Connect to the given ssh server using a proxy command.
84  */
85 static int
86 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
87 {
88 	char *command_string, *tmp;
89 	int pin[2], pout[2];
90 	pid_t pid;
91 	char *shell, strport[NI_MAXSERV];
92 
93 	if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
94 		shell = _PATH_BSHELL;
95 
96 	/* Convert the port number into a string. */
97 	snprintf(strport, sizeof strport, "%hu", port);
98 
99 	/*
100 	 * Build the final command string in the buffer by making the
101 	 * appropriate substitutions to the given proxy command.
102 	 *
103 	 * Use "exec" to avoid "sh -c" processes on some platforms
104 	 * (e.g. Solaris)
105 	 */
106 	xasprintf(&tmp, "exec %s", proxy_command);
107 	command_string = percent_expand(tmp, "h", host, "p", strport,
108 	    "r", options.user, (char *)NULL);
109 	xfree(tmp);
110 
111 	/* Create pipes for communicating with the proxy. */
112 	if (pipe(pin) < 0 || pipe(pout) < 0)
113 		fatal("Could not create pipes to communicate with the proxy: %.100s",
114 		    strerror(errno));
115 
116 	debug("Executing proxy command: %.500s", command_string);
117 
118 	/* Fork and execute the proxy command. */
119 	if ((pid = fork()) == 0) {
120 		char *argv[10];
121 
122 		/* Child.  Permanently give up superuser privileges. */
123 		permanently_drop_suid(original_real_uid);
124 
125 		/* Redirect stdin and stdout. */
126 		close(pin[1]);
127 		if (pin[0] != 0) {
128 			if (dup2(pin[0], 0) < 0)
129 				perror("dup2 stdin");
130 			close(pin[0]);
131 		}
132 		close(pout[0]);
133 		if (dup2(pout[1], 1) < 0)
134 			perror("dup2 stdout");
135 		/* Cannot be 1 because pin allocated two descriptors. */
136 		close(pout[1]);
137 
138 		/* Stderr is left as it is so that error messages get
139 		   printed on the user's terminal. */
140 		argv[0] = shell;
141 		argv[1] = "-c";
142 		argv[2] = command_string;
143 		argv[3] = NULL;
144 
145 		/* Execute the proxy command.  Note that we gave up any
146 		   extra privileges above. */
147 		signal(SIGPIPE, SIG_DFL);
148 		execv(argv[0], argv);
149 		perror(argv[0]);
150 		exit(1);
151 	}
152 	/* Parent. */
153 	if (pid < 0)
154 		fatal("fork failed: %.100s", strerror(errno));
155 	else
156 		proxy_command_pid = pid; /* save pid to clean up later */
157 
158 	/* Close child side of the descriptors. */
159 	close(pin[0]);
160 	close(pout[1]);
161 
162 	/* Free the command name. */
163 	xfree(command_string);
164 
165 	/* Set the connection file descriptors. */
166 	packet_set_connection(pout[0], pin[1]);
167 	packet_set_timeout(options.server_alive_interval,
168 	    options.server_alive_count_max);
169 
170 	/* Indicate OK return */
171 	return 0;
172 }
173 
174 void
175 ssh_kill_proxy_command(void)
176 {
177 	/*
178 	 * Send SIGHUP to proxy command if used. We don't wait() in
179 	 * case it hangs and instead rely on init to reap the child
180 	 */
181 	if (proxy_command_pid > 1)
182 		kill(proxy_command_pid, SIGHUP);
183 }
184 
185 /*
186  * Set TCP receive buffer if requested.
187  * Note: tuning needs to happen after the socket is created but before the
188  * connection happens so winscale is negotiated properly.
189  */
190 static void
191 ssh_set_socket_recvbuf(int sock)
192 {
193 	void *buf = (void *)&options.tcp_rcv_buf;
194 	int socksize, sz = sizeof(options.tcp_rcv_buf);
195 	socklen_t len = sizeof(int);
196 
197 	debug("setsockopt attempting to set SO_RCVBUF to %d",
198 	    options.tcp_rcv_buf);
199 	if (setsockopt(sock, SOL_SOCKET, SO_RCVBUF, buf, sz) >= 0) {
200 		getsockopt(sock, SOL_SOCKET, SO_RCVBUF, &socksize, &len);
201 		debug("setsockopt SO_RCVBUF: %.100s %d", strerror(errno),
202 		    socksize);
203 	} else
204 		error("Couldn't set socket receive buffer to %d: %.100s",
205 		    options.tcp_rcv_buf, strerror(errno));
206 }
207 
208 /*
209  * Creates a (possibly privileged) socket for use as the ssh connection.
210  */
211 static int
212 ssh_create_socket(int privileged, struct addrinfo *ai)
213 {
214 	int sock, gaierr;
215 	struct addrinfo hints, *res;
216 
217 	/*
218 	 * If we are running as root and want to connect to a privileged
219 	 * port, bind our own socket to a privileged port.
220 	 */
221 	if (privileged) {
222 		int p = IPPORT_RESERVED - 1;
223 		PRIV_START;
224 		sock = rresvport_af(&p, ai->ai_family);
225 		PRIV_END;
226 		if (sock < 0)
227 			error("rresvport: af=%d %.100s", ai->ai_family,
228 			    strerror(errno));
229 		else
230 			debug("Allocated local port %d.", p);
231 		if (options.tcp_rcv_buf > 0)
232 			ssh_set_socket_recvbuf(sock);
233 		return sock;
234 	}
235 	sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
236 	if (sock < 0) {
237 		error("socket: %.100s", strerror(errno));
238 		return -1;
239 	}
240 	fcntl(sock, F_SETFD, FD_CLOEXEC);
241 
242 	if (options.tcp_rcv_buf > 0)
243 		ssh_set_socket_recvbuf(sock);
244 
245 	/* Bind the socket to an alternative local IP address */
246 	if (options.bind_address == NULL)
247 		return sock;
248 
249 	memset(&hints, 0, sizeof(hints));
250 	hints.ai_family = ai->ai_family;
251 	hints.ai_socktype = ai->ai_socktype;
252 	hints.ai_protocol = ai->ai_protocol;
253 	hints.ai_flags = AI_PASSIVE;
254 	gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res);
255 	if (gaierr) {
256 		error("getaddrinfo: %s: %s", options.bind_address,
257 		    ssh_gai_strerror(gaierr));
258 		close(sock);
259 		return -1;
260 	}
261 	if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
262 		error("bind: %s: %s", options.bind_address, strerror(errno));
263 		close(sock);
264 		freeaddrinfo(res);
265 		return -1;
266 	}
267 	freeaddrinfo(res);
268 	return sock;
269 }
270 
271 static int
272 timeout_connect(int sockfd, const struct sockaddr *serv_addr,
273     socklen_t addrlen, int *timeoutp)
274 {
275 	fd_set *fdset;
276 	struct timeval tv, t_start;
277 	socklen_t optlen;
278 	int optval, rc, result = -1;
279 
280 	gettimeofday(&t_start, NULL);
281 
282 	if (*timeoutp <= 0) {
283 		result = connect(sockfd, serv_addr, addrlen);
284 		goto done;
285 	}
286 
287 	set_nonblock(sockfd);
288 	rc = connect(sockfd, serv_addr, addrlen);
289 	if (rc == 0) {
290 		unset_nonblock(sockfd);
291 		result = 0;
292 		goto done;
293 	}
294 	if (errno != EINPROGRESS) {
295 		result = -1;
296 		goto done;
297 	}
298 
299 	fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS),
300 	    sizeof(fd_mask));
301 	FD_SET(sockfd, fdset);
302 	ms_to_timeval(&tv, *timeoutp);
303 
304 	for (;;) {
305 		rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
306 		if (rc != -1 || errno != EINTR)
307 			break;
308 	}
309 
310 	switch (rc) {
311 	case 0:
312 		/* Timed out */
313 		errno = ETIMEDOUT;
314 		break;
315 	case -1:
316 		/* Select error */
317 		debug("select: %s", strerror(errno));
318 		break;
319 	case 1:
320 		/* Completed or failed */
321 		optval = 0;
322 		optlen = sizeof(optval);
323 		if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
324 		    &optlen) == -1) {
325 			debug("getsockopt: %s", strerror(errno));
326 			break;
327 		}
328 		if (optval != 0) {
329 			errno = optval;
330 			break;
331 		}
332 		result = 0;
333 		unset_nonblock(sockfd);
334 		break;
335 	default:
336 		/* Should not occur */
337 		fatal("Bogus return (%d) from select()", rc);
338 	}
339 
340 	xfree(fdset);
341 
342  done:
343  	if (result == 0 && *timeoutp > 0) {
344 		ms_subtract_diff(&t_start, timeoutp);
345 		if (*timeoutp <= 0) {
346 			errno = ETIMEDOUT;
347 			result = -1;
348 		}
349 	}
350 
351 	return (result);
352 }
353 
354 /*
355  * Opens a TCP/IP connection to the remote server on the given host.
356  * The address of the remote host will be returned in hostaddr.
357  * If port is 0, the default port will be used.  If needpriv is true,
358  * a privileged port will be allocated to make the connection.
359  * This requires super-user privileges if needpriv is true.
360  * Connection_attempts specifies the maximum number of tries (one per
361  * second).  If proxy_command is non-NULL, it specifies the command (with %h
362  * and %p substituted for host and port, respectively) to use to contact
363  * the daemon.
364  */
365 int
366 ssh_connect(const char *host, struct sockaddr_storage * hostaddr,
367     u_short port, int family, int connection_attempts, int *timeout_ms,
368     int want_keepalive, int needpriv, const char *proxy_command)
369 {
370 	int gaierr;
371 	int on = 1;
372 	int sock = -1, attempt;
373 	char ntop[NI_MAXHOST], strport[NI_MAXSERV];
374 	struct addrinfo hints, *ai, *aitop;
375 
376 	debug2("ssh_connect: needpriv %d", needpriv);
377 
378 	/* If a proxy command is given, connect using it. */
379 	if (proxy_command != NULL)
380 		return ssh_proxy_connect(host, port, proxy_command);
381 
382 	/* No proxy command. */
383 
384 	memset(&hints, 0, sizeof(hints));
385 	hints.ai_family = family;
386 	hints.ai_socktype = SOCK_STREAM;
387 	snprintf(strport, sizeof strport, "%u", port);
388 	if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0)
389 		fatal("%s: Could not resolve hostname %.100s: %s", __progname,
390 		    host, ssh_gai_strerror(gaierr));
391 
392 	for (attempt = 0; attempt < connection_attempts; attempt++) {
393 		if (attempt > 0) {
394 			/* Sleep a moment before retrying. */
395 			sleep(1);
396 			debug("Trying again...");
397 		}
398 		/*
399 		 * Loop through addresses for this host, and try each one in
400 		 * sequence until the connection succeeds.
401 		 */
402 		for (ai = aitop; ai; ai = ai->ai_next) {
403 			if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
404 				continue;
405 			if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
406 			    ntop, sizeof(ntop), strport, sizeof(strport),
407 			    NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
408 				error("ssh_connect: getnameinfo failed");
409 				continue;
410 			}
411 			debug("Connecting to %.200s [%.100s] port %s.",
412 				host, ntop, strport);
413 
414 			/* Create a socket for connecting. */
415 			sock = ssh_create_socket(needpriv, ai);
416 			if (sock < 0)
417 				/* Any error is already output */
418 				continue;
419 
420 			if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
421 			    timeout_ms) >= 0) {
422 				/* Successful connection. */
423 				memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
424 				break;
425 			} else {
426 				debug("connect to address %s port %s: %s",
427 				    ntop, strport, strerror(errno));
428 				close(sock);
429 				sock = -1;
430 			}
431 		}
432 		if (sock != -1)
433 			break;	/* Successful connection. */
434 	}
435 
436 	freeaddrinfo(aitop);
437 
438 	/* Return failure if we didn't get a successful connection. */
439 	if (sock == -1) {
440 		error("ssh: connect to host %s port %s: %s",
441 		    host, strport, strerror(errno));
442 		return (-1);
443 	}
444 
445 	debug("Connection established.");
446 
447 	/* Set SO_KEEPALIVE if requested. */
448 	if (want_keepalive &&
449 	    setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
450 	    sizeof(on)) < 0)
451 		error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
452 
453 	/* Set the connection. */
454 	packet_set_connection(sock, sock);
455 	packet_set_timeout(options.server_alive_interval,
456 	    options.server_alive_count_max);
457 
458 	return 0;
459 }
460 
461 /*
462  * Waits for the server identification string, and sends our own
463  * identification string.
464  */
465 void
466 ssh_exchange_identification(int timeout_ms)
467 {
468 	char buf[256], remote_version[256];	/* must be same size! */
469 	int remote_major, remote_minor, mismatch;
470 	int connection_in = packet_get_connection_in();
471 	int connection_out = packet_get_connection_out();
472 	int minor1 = PROTOCOL_MINOR_1;
473 	u_int i, n;
474 	size_t len;
475 	int fdsetsz, remaining, rc;
476 	struct timeval t_start, t_remaining;
477 	fd_set *fdset;
478 
479 	fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask);
480 	fdset = xcalloc(1, fdsetsz);
481 
482 	/* Read other side's version identification. */
483 	remaining = timeout_ms;
484 	for (n = 0;;) {
485 		for (i = 0; i < sizeof(buf) - 1; i++) {
486 			if (timeout_ms > 0) {
487 				gettimeofday(&t_start, NULL);
488 				ms_to_timeval(&t_remaining, remaining);
489 				FD_SET(connection_in, fdset);
490 				rc = select(connection_in + 1, fdset, NULL,
491 				    fdset, &t_remaining);
492 				ms_subtract_diff(&t_start, &remaining);
493 				if (rc == 0 || remaining <= 0)
494 					fatal("Connection timed out during "
495 					    "banner exchange");
496 				if (rc == -1) {
497 					if (errno == EINTR)
498 						continue;
499 					fatal("ssh_exchange_identification: "
500 					    "select: %s", strerror(errno));
501 				}
502 			}
503 
504 			len = roaming_atomicio(read, connection_in, &buf[i], 1);
505 
506 			if (len != 1 && errno == EPIPE)
507 				fatal("ssh_exchange_identification: "
508 				    "Connection closed by remote host");
509 			else if (len != 1)
510 				fatal("ssh_exchange_identification: "
511 				    "read: %.100s", strerror(errno));
512 			if (buf[i] == '\r') {
513 				buf[i] = '\n';
514 				buf[i + 1] = 0;
515 				continue;		/**XXX wait for \n */
516 			}
517 			if (buf[i] == '\n') {
518 				buf[i + 1] = 0;
519 				break;
520 			}
521 			if (++n > 65536)
522 				fatal("ssh_exchange_identification: "
523 				    "No banner received");
524 		}
525 		buf[sizeof(buf) - 1] = 0;
526 		if (strncmp(buf, "SSH-", 4) == 0)
527 			break;
528 		debug("ssh_exchange_identification: %s", buf);
529 	}
530 	server_version_string = xstrdup(buf);
531 	xfree(fdset);
532 
533 	/*
534 	 * Check that the versions match.  In future this might accept
535 	 * several versions and set appropriate flags to handle them.
536 	 */
537 	if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
538 	    &remote_major, &remote_minor, remote_version) != 3)
539 		fatal("Bad remote protocol version identification: '%.100s'", buf);
540 	debug("Remote protocol version %d.%d, remote software version %.100s",
541 	    remote_major, remote_minor, remote_version);
542 
543 	compat_datafellows(remote_version);
544 	mismatch = 0;
545 
546 	switch (remote_major) {
547 	case 1:
548 		if (remote_minor == 99 &&
549 		    (options.protocol & SSH_PROTO_2) &&
550 		    !(options.protocol & SSH_PROTO_1_PREFERRED)) {
551 			enable_compat20();
552 			break;
553 		}
554 		if (!(options.protocol & SSH_PROTO_1)) {
555 			mismatch = 1;
556 			break;
557 		}
558 		if (remote_minor < 3) {
559 			fatal("Remote machine has too old SSH software version.");
560 		} else if (remote_minor == 3 || remote_minor == 4) {
561 			/* We speak 1.3, too. */
562 			enable_compat13();
563 			minor1 = 3;
564 			if (options.forward_agent) {
565 				logit("Agent forwarding disabled for protocol 1.3");
566 				options.forward_agent = 0;
567 			}
568 		}
569 		break;
570 	case 2:
571 		if (options.protocol & SSH_PROTO_2) {
572 			enable_compat20();
573 			break;
574 		}
575 		/* FALLTHROUGH */
576 	default:
577 		mismatch = 1;
578 		break;
579 	}
580 	if (mismatch)
581 		fatal("Protocol major versions differ: %d vs. %d",
582 		    (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
583 		    remote_major);
584 	/* Send our own protocol version identification. */
585 	snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s%s",
586 	    compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
587 	    compat20 ? PROTOCOL_MINOR_2 : minor1,
588 	    ssh_version_get(options.hpn_disabled), compat20 ? "\r\n" : "\n");
589 	if (roaming_atomicio(vwrite, connection_out, buf, strlen(buf))
590 	    != strlen(buf))
591 		fatal("write: %.100s", strerror(errno));
592 	client_version_string = xstrdup(buf);
593 	chop(client_version_string);
594 	chop(server_version_string);
595 	debug("Local version string %.100s", client_version_string);
596 }
597 
598 /* defaults to 'no' */
599 static int
600 confirm(const char *prompt)
601 {
602 	const char *msg, *again = "Please type 'yes' or 'no': ";
603 	char *p;
604 	int ret = -1;
605 
606 	if (options.batch_mode)
607 		return 0;
608 	for (msg = prompt;;msg = again) {
609 		p = read_passphrase(msg, RP_ECHO);
610 		if (p == NULL ||
611 		    (p[0] == '\0') || (p[0] == '\n') ||
612 		    strncasecmp(p, "no", 2) == 0)
613 			ret = 0;
614 		if (p && strncasecmp(p, "yes", 3) == 0)
615 			ret = 1;
616 		if (p)
617 			xfree(p);
618 		if (ret != -1)
619 			return ret;
620 	}
621 }
622 
623 static int
624 check_host_cert(const char *host, const Key *host_key)
625 {
626 	const char *reason;
627 
628 	if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) {
629 		error("%s", reason);
630 		return 0;
631 	}
632 	if (buffer_len(&host_key->cert->critical) != 0) {
633 		error("Certificate for %s contains unsupported "
634 		    "critical options(s)", host);
635 		return 0;
636 	}
637 	return 1;
638 }
639 
640 static int
641 sockaddr_is_local(struct sockaddr *hostaddr)
642 {
643 	switch (hostaddr->sa_family) {
644 	case AF_INET:
645 		return (ntohl(((struct sockaddr_in *)hostaddr)->
646 		    sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
647 	case AF_INET6:
648 		return IN6_IS_ADDR_LOOPBACK(
649 		    &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
650 	default:
651 		return 0;
652 	}
653 }
654 
655 /*
656  * Prepare the hostname and ip address strings that are used to lookup
657  * host keys in known_hosts files. These may have a port number appended.
658  */
659 void
660 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr,
661     u_short port, char **hostfile_hostname, char **hostfile_ipaddr)
662 {
663 	char ntop[NI_MAXHOST];
664 	socklen_t addrlen;
665 
666 	switch (hostaddr == NULL ? -1 : hostaddr->sa_family) {
667 	case -1:
668 		addrlen = 0;
669 		break;
670 	case AF_INET:
671 		addrlen = sizeof(struct sockaddr_in);
672 		break;
673 	case AF_INET6:
674 		addrlen = sizeof(struct sockaddr_in6);
675 		break;
676 	default:
677 		addrlen = sizeof(struct sockaddr);
678 		break;
679 	}
680 
681 	/*
682 	 * We don't have the remote ip-address for connections
683 	 * using a proxy command
684 	 */
685 	if (hostfile_ipaddr != NULL) {
686 		if (options.proxy_command == NULL) {
687 			if (getnameinfo(hostaddr, addrlen,
688 			    ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0)
689 			fatal("check_host_key: getnameinfo failed");
690 			*hostfile_ipaddr = put_host_port(ntop, port);
691 		} else {
692 			*hostfile_ipaddr = xstrdup("<no hostip for proxy "
693 			    "command>");
694 		}
695 	}
696 
697 	/*
698 	 * Allow the user to record the key under a different name or
699 	 * differentiate a non-standard port.  This is useful for ssh
700 	 * tunneling over forwarded connections or if you run multiple
701 	 * sshd's on different ports on the same machine.
702 	 */
703 	if (hostfile_hostname != NULL) {
704 		if (options.host_key_alias != NULL) {
705 			*hostfile_hostname = xstrdup(options.host_key_alias);
706 			debug("using hostkeyalias: %s", *hostfile_hostname);
707 		} else {
708 			*hostfile_hostname = put_host_port(hostname, port);
709 		}
710 	}
711 }
712 
713 /*
714  * check whether the supplied host key is valid, return -1 if the key
715  * is not valid. user_hostfile[0] will not be updated if 'readonly' is true.
716  */
717 #define RDRW	0
718 #define RDONLY	1
719 #define ROQUIET	2
720 static int
721 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
722     Key *host_key, int readonly,
723     char **user_hostfiles, u_int num_user_hostfiles,
724     char **system_hostfiles, u_int num_system_hostfiles)
725 {
726 	HostStatus host_status;
727 	HostStatus ip_status;
728 	Key *raw_key = NULL;
729 	char *ip = NULL, *host = NULL;
730 	char hostline[1000], *hostp, *fp, *ra;
731 	char msg[1024];
732 	const char *type;
733 	const struct hostkey_entry *host_found, *ip_found;
734 	int len, cancelled_forwarding = 0;
735 	int local = sockaddr_is_local(hostaddr);
736 	int r, want_cert = key_is_cert(host_key), host_ip_differ = 0;
737 	struct hostkeys *host_hostkeys, *ip_hostkeys;
738 	u_int i;
739 
740 	/*
741 	 * Force accepting of the host key for loopback/localhost. The
742 	 * problem is that if the home directory is NFS-mounted to multiple
743 	 * machines, localhost will refer to a different machine in each of
744 	 * them, and the user will get bogus HOST_CHANGED warnings.  This
745 	 * essentially disables host authentication for localhost; however,
746 	 * this is probably not a real problem.
747 	 */
748 	if (options.no_host_authentication_for_localhost == 1 && local &&
749 	    options.host_key_alias == NULL) {
750 		debug("Forcing accepting of host key for "
751 		    "loopback/localhost.");
752 		return 0;
753 	}
754 
755 	/*
756 	 * Prepare the hostname and address strings used for hostkey lookup.
757 	 * In some cases, these will have a port number appended.
758 	 */
759 	get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip);
760 
761 	/*
762 	 * Turn off check_host_ip if the connection is to localhost, via proxy
763 	 * command or if we don't have a hostname to compare with
764 	 */
765 	if (options.check_host_ip && (local ||
766 	    strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
767 		options.check_host_ip = 0;
768 
769 	host_hostkeys = init_hostkeys();
770 	for (i = 0; i < num_user_hostfiles; i++)
771 		load_hostkeys(host_hostkeys, host, user_hostfiles[i]);
772 	for (i = 0; i < num_system_hostfiles; i++)
773 		load_hostkeys(host_hostkeys, host, system_hostfiles[i]);
774 
775 	ip_hostkeys = NULL;
776 	if (!want_cert && options.check_host_ip) {
777 		ip_hostkeys = init_hostkeys();
778 		for (i = 0; i < num_user_hostfiles; i++)
779 			load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]);
780 		for (i = 0; i < num_system_hostfiles; i++)
781 			load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]);
782 	}
783 
784  retry:
785 	/* Reload these as they may have changed on cert->key downgrade */
786 	want_cert = key_is_cert(host_key);
787 	type = key_type(host_key);
788 
789 	/*
790 	 * Check if the host key is present in the user's list of known
791 	 * hosts or in the systemwide list.
792 	 */
793 	host_status = check_key_in_hostkeys(host_hostkeys, host_key,
794 	    &host_found);
795 
796 	/*
797 	 * Also perform check for the ip address, skip the check if we are
798 	 * localhost, looking for a certificate, or the hostname was an ip
799 	 * address to begin with.
800 	 */
801 	if (!want_cert && ip_hostkeys != NULL) {
802 		ip_status = check_key_in_hostkeys(ip_hostkeys, host_key,
803 		    &ip_found);
804 		if (host_status == HOST_CHANGED &&
805 		    (ip_status != HOST_CHANGED ||
806 		    (ip_found != NULL &&
807 		    !key_equal(ip_found->key, host_found->key))))
808 			host_ip_differ = 1;
809 	} else
810 		ip_status = host_status;
811 
812 	switch (host_status) {
813 	case HOST_OK:
814 		/* The host is known and the key matches. */
815 		debug("Host '%.200s' is known and matches the %s host %s.",
816 		    host, type, want_cert ? "certificate" : "key");
817 		debug("Found %s in %s:%lu", want_cert ? "CA key" : "key",
818 		    host_found->file, host_found->line);
819 		if (want_cert && !check_host_cert(hostname, host_key))
820 			goto fail;
821 		if (options.check_host_ip && ip_status == HOST_NEW) {
822 			if (readonly || want_cert)
823 				logit("%s host key for IP address "
824 				    "'%.128s' not in list of known hosts.",
825 				    type, ip);
826 			else if (!add_host_to_hostfile(user_hostfiles[0], ip,
827 			    host_key, options.hash_known_hosts))
828 				logit("Failed to add the %s host key for IP "
829 				    "address '%.128s' to the list of known "
830 				    "hosts (%.30s).", type, ip,
831 				    user_hostfiles[0]);
832 			else
833 				logit("Warning: Permanently added the %s host "
834 				    "key for IP address '%.128s' to the list "
835 				    "of known hosts.", type, ip);
836 		} else if (options.visual_host_key) {
837 			fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
838 			ra = key_fingerprint(host_key, SSH_FP_MD5,
839 			    SSH_FP_RANDOMART);
840 			logit("Host key fingerprint is %s\n%s\n", fp, ra);
841 			xfree(ra);
842 			xfree(fp);
843 		}
844 		break;
845 	case HOST_NEW:
846 		if (options.host_key_alias == NULL && port != 0 &&
847 		    port != SSH_DEFAULT_PORT) {
848 			debug("checking without port identifier");
849 			if (check_host_key(hostname, hostaddr, 0, host_key,
850 			    ROQUIET, user_hostfiles, num_user_hostfiles,
851 			    system_hostfiles, num_system_hostfiles) == 0) {
852 				debug("found matching key w/out port");
853 				break;
854 			}
855 		}
856 		if (readonly || want_cert)
857 			goto fail;
858 		/* The host is new. */
859 		if (options.strict_host_key_checking == 1) {
860 			/*
861 			 * User has requested strict host key checking.  We
862 			 * will not add the host key automatically.  The only
863 			 * alternative left is to abort.
864 			 */
865 			error("No %s host key is known for %.200s and you "
866 			    "have requested strict checking.", type, host);
867 			goto fail;
868 		} else if (options.strict_host_key_checking == 2) {
869 			char msg1[1024], msg2[1024];
870 
871 			if (show_other_keys(host_hostkeys, host_key))
872 				snprintf(msg1, sizeof(msg1),
873 				    "\nbut keys of different type are already"
874 				    " known for this host.");
875 			else
876 				snprintf(msg1, sizeof(msg1), ".");
877 			/* The default */
878 			fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
879 			ra = key_fingerprint(host_key, SSH_FP_MD5,
880 			    SSH_FP_RANDOMART);
881 			msg2[0] = '\0';
882 			if (options.verify_host_key_dns) {
883 				if (matching_host_key_dns)
884 					snprintf(msg2, sizeof(msg2),
885 					    "Matching host key fingerprint"
886 					    " found in DNS.\n");
887 				else
888 					snprintf(msg2, sizeof(msg2),
889 					    "No matching host key fingerprint"
890 					    " found in DNS.\n");
891 			}
892 			snprintf(msg, sizeof(msg),
893 			    "The authenticity of host '%.200s (%s)' can't be "
894 			    "established%s\n"
895 			    "%s key fingerprint is %s.%s%s\n%s"
896 			    "Are you sure you want to continue connecting "
897 			    "(yes/no)? ",
898 			    host, ip, msg1, type, fp,
899 			    options.visual_host_key ? "\n" : "",
900 			    options.visual_host_key ? ra : "",
901 			    msg2);
902 			xfree(ra);
903 			xfree(fp);
904 			if (!confirm(msg))
905 				goto fail;
906 		}
907 		/*
908 		 * If not in strict mode, add the key automatically to the
909 		 * local known_hosts file.
910 		 */
911 		if (options.check_host_ip && ip_status == HOST_NEW) {
912 			snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
913 			hostp = hostline;
914 			if (options.hash_known_hosts) {
915 				/* Add hash of host and IP separately */
916 				r = add_host_to_hostfile(user_hostfiles[0],
917 				    host, host_key, options.hash_known_hosts) &&
918 				    add_host_to_hostfile(user_hostfiles[0], ip,
919 				    host_key, options.hash_known_hosts);
920 			} else {
921 				/* Add unhashed "host,ip" */
922 				r = add_host_to_hostfile(user_hostfiles[0],
923 				    hostline, host_key,
924 				    options.hash_known_hosts);
925 			}
926 		} else {
927 			r = add_host_to_hostfile(user_hostfiles[0], host,
928 			    host_key, options.hash_known_hosts);
929 			hostp = host;
930 		}
931 
932 		if (!r)
933 			logit("Failed to add the host to the list of known "
934 			    "hosts (%.500s).", user_hostfiles[0]);
935 		else
936 			logit("Warning: Permanently added '%.200s' (%s) to the "
937 			    "list of known hosts.", hostp, type);
938 		break;
939 	case HOST_REVOKED:
940 		error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
941 		error("@       WARNING: REVOKED HOST KEY DETECTED!               @");
942 		error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
943 		error("The %s host key for %s is marked as revoked.", type, host);
944 		error("This could mean that a stolen key is being used to");
945 		error("impersonate this host.");
946 
947 		/*
948 		 * If strict host key checking is in use, the user will have
949 		 * to edit the key manually and we can only abort.
950 		 */
951 		if (options.strict_host_key_checking) {
952 			error("%s host key for %.200s was revoked and you have "
953 			    "requested strict checking.", type, host);
954 			goto fail;
955 		}
956 		goto continue_unsafe;
957 
958 	case HOST_CHANGED:
959 		if (want_cert) {
960 			/*
961 			 * This is only a debug() since it is valid to have
962 			 * CAs with wildcard DNS matches that don't match
963 			 * all hosts that one might visit.
964 			 */
965 			debug("Host certificate authority does not "
966 			    "match %s in %s:%lu", CA_MARKER,
967 			    host_found->file, host_found->line);
968 			goto fail;
969 		}
970 		if (readonly == ROQUIET)
971 			goto fail;
972 		if (options.check_host_ip && host_ip_differ) {
973 			char *key_msg;
974 			if (ip_status == HOST_NEW)
975 				key_msg = "is unknown";
976 			else if (ip_status == HOST_OK)
977 				key_msg = "is unchanged";
978 			else
979 				key_msg = "has a different value";
980 			error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
981 			error("@       WARNING: POSSIBLE DNS SPOOFING DETECTED!          @");
982 			error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
983 			error("The %s host key for %s has changed,", type, host);
984 			error("and the key for the corresponding IP address %s", ip);
985 			error("%s. This could either mean that", key_msg);
986 			error("DNS SPOOFING is happening or the IP address for the host");
987 			error("and its host key have changed at the same time.");
988 			if (ip_status != HOST_NEW)
989 				error("Offending key for IP in %s:%lu",
990 				    ip_found->file, ip_found->line);
991 		}
992 		/* The host key has changed. */
993 		warn_changed_key(host_key);
994 		error("Add correct host key in %.100s to get rid of this message.",
995 		    user_hostfiles[0]);
996 		error("Offending %s key in %s:%lu", key_type(host_found->key),
997 		    host_found->file, host_found->line);
998 
999 		/*
1000 		 * If strict host key checking is in use, the user will have
1001 		 * to edit the key manually and we can only abort.
1002 		 */
1003 		if (options.strict_host_key_checking) {
1004 			error("%s host key for %.200s has changed and you have "
1005 			    "requested strict checking.", type, host);
1006 			goto fail;
1007 		}
1008 
1009  continue_unsafe:
1010 		/*
1011 		 * If strict host key checking has not been requested, allow
1012 		 * the connection but without MITM-able authentication or
1013 		 * forwarding.
1014 		 */
1015 		if (options.password_authentication) {
1016 			error("Password authentication is disabled to avoid "
1017 			    "man-in-the-middle attacks.");
1018 			options.password_authentication = 0;
1019 			cancelled_forwarding = 1;
1020 		}
1021 		if (options.kbd_interactive_authentication) {
1022 			error("Keyboard-interactive authentication is disabled"
1023 			    " to avoid man-in-the-middle attacks.");
1024 			options.kbd_interactive_authentication = 0;
1025 			options.challenge_response_authentication = 0;
1026 			cancelled_forwarding = 1;
1027 		}
1028 		if (options.challenge_response_authentication) {
1029 			error("Challenge/response authentication is disabled"
1030 			    " to avoid man-in-the-middle attacks.");
1031 			options.challenge_response_authentication = 0;
1032 			cancelled_forwarding = 1;
1033 		}
1034 		if (options.forward_agent) {
1035 			error("Agent forwarding is disabled to avoid "
1036 			    "man-in-the-middle attacks.");
1037 			options.forward_agent = 0;
1038 			cancelled_forwarding = 1;
1039 		}
1040 		if (options.forward_x11) {
1041 			error("X11 forwarding is disabled to avoid "
1042 			    "man-in-the-middle attacks.");
1043 			options.forward_x11 = 0;
1044 			cancelled_forwarding = 1;
1045 		}
1046 		if (options.num_local_forwards > 0 ||
1047 		    options.num_remote_forwards > 0) {
1048 			error("Port forwarding is disabled to avoid "
1049 			    "man-in-the-middle attacks.");
1050 			options.num_local_forwards =
1051 			    options.num_remote_forwards = 0;
1052 			cancelled_forwarding = 1;
1053 		}
1054 		if (options.tun_open != SSH_TUNMODE_NO) {
1055 			error("Tunnel forwarding is disabled to avoid "
1056 			    "man-in-the-middle attacks.");
1057 			options.tun_open = SSH_TUNMODE_NO;
1058 			cancelled_forwarding = 1;
1059 		}
1060 		if (options.exit_on_forward_failure && cancelled_forwarding)
1061 			fatal("Error: forwarding disabled due to host key "
1062 			    "check failure");
1063 
1064 		/*
1065 		 * XXX Should permit the user to change to use the new id.
1066 		 * This could be done by converting the host key to an
1067 		 * identifying sentence, tell that the host identifies itself
1068 		 * by that sentence, and ask the user if he/she wishes to
1069 		 * accept the authentication.
1070 		 */
1071 		break;
1072 	case HOST_FOUND:
1073 		fatal("internal error");
1074 		break;
1075 	}
1076 
1077 	if (options.check_host_ip && host_status != HOST_CHANGED &&
1078 	    ip_status == HOST_CHANGED) {
1079 		snprintf(msg, sizeof(msg),
1080 		    "Warning: the %s host key for '%.200s' "
1081 		    "differs from the key for the IP address '%.128s'"
1082 		    "\nOffending key for IP in %s:%lu",
1083 		    type, host, ip, ip_found->file, ip_found->line);
1084 		if (host_status == HOST_OK) {
1085 			len = strlen(msg);
1086 			snprintf(msg + len, sizeof(msg) - len,
1087 			    "\nMatching host key in %s:%lu",
1088 			    host_found->file, host_found->line);
1089 		}
1090 		if (options.strict_host_key_checking == 1) {
1091 			logit("%s", msg);
1092 			error("Exiting, you have requested strict checking.");
1093 			goto fail;
1094 		} else if (options.strict_host_key_checking == 2) {
1095 			strlcat(msg, "\nAre you sure you want "
1096 			    "to continue connecting (yes/no)? ", sizeof(msg));
1097 			if (!confirm(msg))
1098 				goto fail;
1099 		} else {
1100 			logit("%s", msg);
1101 		}
1102 	}
1103 
1104 	xfree(ip);
1105 	xfree(host);
1106 	if (host_hostkeys != NULL)
1107 		free_hostkeys(host_hostkeys);
1108 	if (ip_hostkeys != NULL)
1109 		free_hostkeys(ip_hostkeys);
1110 	return 0;
1111 
1112 fail:
1113 	if (want_cert && host_status != HOST_REVOKED) {
1114 		/*
1115 		 * No matching certificate. Downgrade cert to raw key and
1116 		 * search normally.
1117 		 */
1118 		debug("No matching CA found. Retry with plain key");
1119 		raw_key = key_from_private(host_key);
1120 		if (key_drop_cert(raw_key) != 0)
1121 			fatal("Couldn't drop certificate");
1122 		host_key = raw_key;
1123 		goto retry;
1124 	}
1125 	if (raw_key != NULL)
1126 		key_free(raw_key);
1127 	xfree(ip);
1128 	xfree(host);
1129 	if (host_hostkeys != NULL)
1130 		free_hostkeys(host_hostkeys);
1131 	if (ip_hostkeys != NULL)
1132 		free_hostkeys(ip_hostkeys);
1133 	return -1;
1134 }
1135 
1136 /* returns 0 if key verifies or -1 if key does NOT verify */
1137 int
1138 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
1139 {
1140 	int flags = 0;
1141 	char *fp;
1142 
1143 	fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1144 	debug("Server host key: %s %s", key_type(host_key), fp);
1145 	xfree(fp);
1146 
1147 	/* XXX certs are not yet supported for DNS */
1148 	if (!key_is_cert(host_key) && options.verify_host_key_dns &&
1149 	    verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) {
1150 		if (flags & DNS_VERIFY_FOUND) {
1151 
1152 			if (options.verify_host_key_dns == 1 &&
1153 			    flags & DNS_VERIFY_MATCH &&
1154 			    flags & DNS_VERIFY_SECURE)
1155 				return 0;
1156 
1157 			if (flags & DNS_VERIFY_MATCH) {
1158 				matching_host_key_dns = 1;
1159 			} else {
1160 				warn_changed_key(host_key);
1161 				error("Update the SSHFP RR in DNS with the new "
1162 				    "host key to get rid of this message.");
1163 			}
1164 		}
1165 	}
1166 
1167 	return check_host_key(host, hostaddr, options.port, host_key, RDRW,
1168 	    options.user_hostfiles, options.num_user_hostfiles,
1169 	    options.system_hostfiles, options.num_system_hostfiles);
1170 }
1171 
1172 /*
1173  * Starts a dialog with the server, and authenticates the current user on the
1174  * server.  This does not need any extra privileges.  The basic connection
1175  * to the server must already have been established before this is called.
1176  * If login fails, this function prints an error and never returns.
1177  * This function does not require super-user privileges.
1178  */
1179 void
1180 ssh_login(Sensitive *sensitive, const char *orighost,
1181     struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms)
1182 {
1183 	char *host, *cp;
1184 	char *server_user, *local_user;
1185 
1186 	local_user = xstrdup(pw->pw_name);
1187 	server_user = options.user ? options.user : local_user;
1188 
1189 	/* Convert the user-supplied hostname into all lowercase. */
1190 	host = xstrdup(orighost);
1191 	for (cp = host; *cp; cp++)
1192 		if (isupper(*cp))
1193 			*cp = (char)tolower(*cp);
1194 
1195 	/* Exchange protocol version identification strings with the server. */
1196 	ssh_exchange_identification(timeout_ms);
1197 
1198 	/* Put the connection into non-blocking mode. */
1199 	packet_set_nonblocking();
1200 
1201 	/* key exchange */
1202 	/* authenticate user */
1203 	if (compat20) {
1204 		ssh_kex2(host, hostaddr, port);
1205 		ssh_userauth2(local_user, server_user, host, sensitive);
1206 	} else {
1207 		ssh_kex(host, hostaddr);
1208 		ssh_userauth1(local_user, server_user, host, sensitive);
1209 	}
1210 	xfree(local_user);
1211 }
1212 
1213 void
1214 ssh_put_password(char *password)
1215 {
1216 	int size;
1217 	char *padded;
1218 
1219 	if (datafellows & SSH_BUG_PASSWORDPAD) {
1220 		packet_put_cstring(password);
1221 		return;
1222 	}
1223 	size = roundup(strlen(password) + 1, 32);
1224 	padded = xcalloc(1, size);
1225 	strlcpy(padded, password, size);
1226 	packet_put_string(padded, size);
1227 	memset(padded, 0, size);
1228 	xfree(padded);
1229 }
1230 
1231 /* print all known host keys for a given host, but skip keys of given type */
1232 static int
1233 show_other_keys(struct hostkeys *hostkeys, Key *key)
1234 {
1235 	int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, KEY_ECDSA, -1};
1236 	int i, ret = 0;
1237 	char *fp, *ra;
1238 	const struct hostkey_entry *found;
1239 
1240 	for (i = 0; type[i] != -1; i++) {
1241 		if (type[i] == key->type)
1242 			continue;
1243 		if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found))
1244 			continue;
1245 		fp = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_HEX);
1246 		ra = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_RANDOMART);
1247 		logit("WARNING: %s key found for host %s\n"
1248 		    "in %s:%lu\n"
1249 		    "%s key fingerprint %s.",
1250 		    key_type(found->key),
1251 		    found->host, found->file, found->line,
1252 		    key_type(found->key), fp);
1253 		if (options.visual_host_key)
1254 			logit("%s", ra);
1255 		xfree(ra);
1256 		xfree(fp);
1257 		ret = 1;
1258 	}
1259 	return ret;
1260 }
1261 
1262 static void
1263 warn_changed_key(Key *host_key)
1264 {
1265 	char *fp;
1266 
1267 	fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1268 
1269 	error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1270 	error("@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @");
1271 	error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1272 	error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1273 	error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1274 	error("It is also possible that a host key has just been changed.");
1275 	error("The fingerprint for the %s key sent by the remote host is\n%s.",
1276 	    key_type(host_key), fp);
1277 	error("Please contact your system administrator.");
1278 
1279 	xfree(fp);
1280 }
1281 
1282 /*
1283  * Execute a local command
1284  */
1285 int
1286 ssh_local_cmd(const char *args)
1287 {
1288 	char *shell;
1289 	pid_t pid;
1290 	int status;
1291 	void (*osighand)(int);
1292 
1293 	if (!options.permit_local_command ||
1294 	    args == NULL || !*args)
1295 		return (1);
1296 
1297 	if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
1298 		shell = _PATH_BSHELL;
1299 
1300 	osighand = signal(SIGCHLD, SIG_DFL);
1301 	pid = fork();
1302 	if (pid == 0) {
1303 		signal(SIGPIPE, SIG_DFL);
1304 		debug3("Executing %s -c \"%s\"", shell, args);
1305 		execl(shell, shell, "-c", args, (char *)NULL);
1306 		error("Couldn't execute %s -c \"%s\": %s",
1307 		    shell, args, strerror(errno));
1308 		_exit(1);
1309 	} else if (pid == -1)
1310 		fatal("fork failed: %.100s", strerror(errno));
1311 	while (waitpid(pid, &status, 0) == -1)
1312 		if (errno != EINTR)
1313 			fatal("Couldn't wait for child: %s", strerror(errno));
1314 	signal(SIGCHLD, osighand);
1315 
1316 	if (!WIFEXITED(status))
1317 		return (1);
1318 
1319 	return (WEXITSTATUS(status));
1320 }
1321