xref: /openssh-portable/sshconnect.c (revision 5a878a71)
1 /* $OpenBSD: sshconnect.c,v 1.350 2021/01/26 00:49:30 djm Exp $ */
2 /*
3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5  *                    All rights reserved
6  * Code to connect to a remote host, and to perform the client side of the
7  * login (authentication) dialog.
8  *
9  * As far as I am concerned, the code I have written for this software
10  * can be used freely for any purpose.  Any derived versions of this
11  * software must be clearly marked as such, and if the derived work is
12  * incompatible with the protocol description in the RFC file, it must be
13  * called by a name other than "ssh" or "Secure Shell".
14  */
15 
16 #include "includes.h"
17 
18 #include <sys/types.h>
19 #include <sys/wait.h>
20 #include <sys/stat.h>
21 #include <sys/socket.h>
22 #ifdef HAVE_SYS_TIME_H
23 # include <sys/time.h>
24 #endif
25 
26 #include <net/if.h>
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 <limits.h>
34 #include <netdb.h>
35 #ifdef HAVE_PATHS_H
36 #include <paths.h>
37 #endif
38 #include <pwd.h>
39 #ifdef HAVE_POLL_H
40 #include <poll.h>
41 #endif
42 #include <signal.h>
43 #include <stdio.h>
44 #include <stdlib.h>
45 #include <stdarg.h>
46 #include <string.h>
47 #include <unistd.h>
48 #ifdef HAVE_IFADDRS_H
49 # include <ifaddrs.h>
50 #endif
51 
52 #include "xmalloc.h"
53 #include "hostfile.h"
54 #include "ssh.h"
55 #include "sshbuf.h"
56 #include "packet.h"
57 #include "compat.h"
58 #include "sshkey.h"
59 #include "sshconnect.h"
60 #include "log.h"
61 #include "misc.h"
62 #include "readconf.h"
63 #include "atomicio.h"
64 #include "dns.h"
65 #include "monitor_fdpass.h"
66 #include "ssh2.h"
67 #include "version.h"
68 #include "authfile.h"
69 #include "ssherr.h"
70 #include "authfd.h"
71 #include "kex.h"
72 
73 struct sshkey *previous_host_key = NULL;
74 
75 static int matching_host_key_dns = 0;
76 
77 static pid_t proxy_command_pid = 0;
78 
79 /* import */
80 extern int debug_flag;
81 extern Options options;
82 extern char *__progname;
83 
84 static int show_other_keys(struct hostkeys *, struct sshkey *);
85 static void warn_changed_key(struct sshkey *);
86 
87 /* Expand a proxy command */
88 static char *
89 expand_proxy_command(const char *proxy_command, const char *user,
90     const char *host, const char *host_arg, int port)
91 {
92 	char *tmp, *ret, strport[NI_MAXSERV];
93 	const char *keyalias = options.host_key_alias ?
94 	     options.host_key_alias : host_arg;
95 
96 	snprintf(strport, sizeof strport, "%d", port);
97 	xasprintf(&tmp, "exec %s", proxy_command);
98 	ret = percent_expand(tmp,
99 	    "h", host,
100 	    "k", keyalias,
101 	    "n", host_arg,
102 	    "p", strport,
103 	    "r", options.user,
104 	    (char *)NULL);
105 	free(tmp);
106 	return ret;
107 }
108 
109 /*
110  * Connect to the given ssh server using a proxy command that passes a
111  * a connected fd back to us.
112  */
113 static int
114 ssh_proxy_fdpass_connect(struct ssh *ssh, const char *host,
115     const char *host_arg, u_short port, const char *proxy_command)
116 {
117 	char *command_string;
118 	int sp[2], sock;
119 	pid_t pid;
120 	char *shell;
121 
122 	if ((shell = getenv("SHELL")) == NULL)
123 		shell = _PATH_BSHELL;
124 
125 	if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) == -1)
126 		fatal("Could not create socketpair to communicate with "
127 		    "proxy dialer: %.100s", strerror(errno));
128 
129 	command_string = expand_proxy_command(proxy_command, options.user,
130 	    host, host_arg, port);
131 	debug("Executing proxy dialer command: %.500s", command_string);
132 
133 	/* Fork and execute the proxy command. */
134 	if ((pid = fork()) == 0) {
135 		char *argv[10];
136 
137 		close(sp[1]);
138 		/* Redirect stdin and stdout. */
139 		if (sp[0] != 0) {
140 			if (dup2(sp[0], 0) == -1)
141 				perror("dup2 stdin");
142 		}
143 		if (sp[0] != 1) {
144 			if (dup2(sp[0], 1) == -1)
145 				perror("dup2 stdout");
146 		}
147 		if (sp[0] >= 2)
148 			close(sp[0]);
149 
150 		/*
151 		 * Stderr is left for non-ControlPersist connections is so
152 		 * error messages may be printed on the user's terminal.
153 		 */
154 		if (!debug_flag && options.control_path != NULL &&
155 		    options.control_persist && stdfd_devnull(0, 0, 1) == -1)
156 			error_f("stdfd_devnull failed");
157 
158 		argv[0] = shell;
159 		argv[1] = "-c";
160 		argv[2] = command_string;
161 		argv[3] = NULL;
162 
163 		/*
164 		 * Execute the proxy command.
165 		 * Note that we gave up any extra privileges above.
166 		 */
167 		execv(argv[0], argv);
168 		perror(argv[0]);
169 		exit(1);
170 	}
171 	/* Parent. */
172 	if (pid == -1)
173 		fatal("fork failed: %.100s", strerror(errno));
174 	close(sp[0]);
175 	free(command_string);
176 
177 	if ((sock = mm_receive_fd(sp[1])) == -1)
178 		fatal("proxy dialer did not pass back a connection");
179 	close(sp[1]);
180 
181 	while (waitpid(pid, NULL, 0) == -1)
182 		if (errno != EINTR)
183 			fatal("Couldn't wait for child: %s", strerror(errno));
184 
185 	/* Set the connection file descriptors. */
186 	if (ssh_packet_set_connection(ssh, sock, sock) == NULL)
187 		return -1; /* ssh_packet_set_connection logs error */
188 
189 	return 0;
190 }
191 
192 /*
193  * Connect to the given ssh server using a proxy command.
194  */
195 static int
196 ssh_proxy_connect(struct ssh *ssh, const char *host, const char *host_arg,
197     u_short port, const char *proxy_command)
198 {
199 	char *command_string;
200 	int pin[2], pout[2];
201 	pid_t pid;
202 	char *shell;
203 
204 	if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
205 		shell = _PATH_BSHELL;
206 
207 	/* Create pipes for communicating with the proxy. */
208 	if (pipe(pin) == -1 || pipe(pout) == -1)
209 		fatal("Could not create pipes to communicate with the proxy: %.100s",
210 		    strerror(errno));
211 
212 	command_string = expand_proxy_command(proxy_command, options.user,
213 	    host, host_arg, port);
214 	debug("Executing proxy command: %.500s", command_string);
215 
216 	/* Fork and execute the proxy command. */
217 	if ((pid = fork()) == 0) {
218 		char *argv[10];
219 
220 		/* Redirect stdin and stdout. */
221 		close(pin[1]);
222 		if (pin[0] != 0) {
223 			if (dup2(pin[0], 0) == -1)
224 				perror("dup2 stdin");
225 			close(pin[0]);
226 		}
227 		close(pout[0]);
228 		if (dup2(pout[1], 1) == -1)
229 			perror("dup2 stdout");
230 		/* Cannot be 1 because pin allocated two descriptors. */
231 		close(pout[1]);
232 
233 		/*
234 		 * Stderr is left for non-ControlPersist connections is so
235 		 * error messages may be printed on the user's terminal.
236 		 */
237 		if (!debug_flag && options.control_path != NULL &&
238 		    options.control_persist && stdfd_devnull(0, 0, 1) == -1)
239 			error_f("stdfd_devnull failed");
240 
241 		argv[0] = shell;
242 		argv[1] = "-c";
243 		argv[2] = command_string;
244 		argv[3] = NULL;
245 
246 		/* Execute the proxy command.  Note that we gave up any
247 		   extra privileges above. */
248 		ssh_signal(SIGPIPE, SIG_DFL);
249 		execv(argv[0], argv);
250 		perror(argv[0]);
251 		exit(1);
252 	}
253 	/* Parent. */
254 	if (pid == -1)
255 		fatal("fork failed: %.100s", strerror(errno));
256 	else
257 		proxy_command_pid = pid; /* save pid to clean up later */
258 
259 	/* Close child side of the descriptors. */
260 	close(pin[0]);
261 	close(pout[1]);
262 
263 	/* Free the command name. */
264 	free(command_string);
265 
266 	/* Set the connection file descriptors. */
267 	if (ssh_packet_set_connection(ssh, pout[0], pin[1]) == NULL)
268 		return -1; /* ssh_packet_set_connection logs error */
269 
270 	return 0;
271 }
272 
273 void
274 ssh_kill_proxy_command(void)
275 {
276 	/*
277 	 * Send SIGHUP to proxy command if used. We don't wait() in
278 	 * case it hangs and instead rely on init to reap the child
279 	 */
280 	if (proxy_command_pid > 1)
281 		kill(proxy_command_pid, SIGHUP);
282 }
283 
284 #ifdef HAVE_IFADDRS_H
285 /*
286  * Search a interface address list (returned from getifaddrs(3)) for an
287  * address that matches the desired address family on the specified interface.
288  * Returns 0 and fills in *resultp and *rlenp on success. Returns -1 on failure.
289  */
290 static int
291 check_ifaddrs(const char *ifname, int af, const struct ifaddrs *ifaddrs,
292     struct sockaddr_storage *resultp, socklen_t *rlenp)
293 {
294 	struct sockaddr_in6 *sa6;
295 	struct sockaddr_in *sa;
296 	struct in6_addr *v6addr;
297 	const struct ifaddrs *ifa;
298 	int allow_local;
299 
300 	/*
301 	 * Prefer addresses that are not loopback or linklocal, but use them
302 	 * if nothing else matches.
303 	 */
304 	for (allow_local = 0; allow_local < 2; allow_local++) {
305 		for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) {
306 			if (ifa->ifa_addr == NULL || ifa->ifa_name == NULL ||
307 			    (ifa->ifa_flags & IFF_UP) == 0 ||
308 			    ifa->ifa_addr->sa_family != af ||
309 			    strcmp(ifa->ifa_name, options.bind_interface) != 0)
310 				continue;
311 			switch (ifa->ifa_addr->sa_family) {
312 			case AF_INET:
313 				sa = (struct sockaddr_in *)ifa->ifa_addr;
314 				if (!allow_local && sa->sin_addr.s_addr ==
315 				    htonl(INADDR_LOOPBACK))
316 					continue;
317 				if (*rlenp < sizeof(struct sockaddr_in)) {
318 					error_f("v4 addr doesn't fit");
319 					return -1;
320 				}
321 				*rlenp = sizeof(struct sockaddr_in);
322 				memcpy(resultp, sa, *rlenp);
323 				return 0;
324 			case AF_INET6:
325 				sa6 = (struct sockaddr_in6 *)ifa->ifa_addr;
326 				v6addr = &sa6->sin6_addr;
327 				if (!allow_local &&
328 				    (IN6_IS_ADDR_LINKLOCAL(v6addr) ||
329 				    IN6_IS_ADDR_LOOPBACK(v6addr)))
330 					continue;
331 				if (*rlenp < sizeof(struct sockaddr_in6)) {
332 					error_f("v6 addr doesn't fit");
333 					return -1;
334 				}
335 				*rlenp = sizeof(struct sockaddr_in6);
336 				memcpy(resultp, sa6, *rlenp);
337 				return 0;
338 			}
339 		}
340 	}
341 	return -1;
342 }
343 #endif
344 
345 /*
346  * Creates a socket for use as the ssh connection.
347  */
348 static int
349 ssh_create_socket(struct addrinfo *ai)
350 {
351 	int sock, r;
352 	struct sockaddr_storage bindaddr;
353 	socklen_t bindaddrlen = 0;
354 	struct addrinfo hints, *res = NULL;
355 #ifdef HAVE_IFADDRS_H
356 	struct ifaddrs *ifaddrs = NULL;
357 #endif
358 	char ntop[NI_MAXHOST];
359 
360 	sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
361 	if (sock == -1) {
362 		error("socket: %s", strerror(errno));
363 		return -1;
364 	}
365 	fcntl(sock, F_SETFD, FD_CLOEXEC);
366 
367 	/* Use interactive QOS (if specified) until authentication completed */
368 	if (options.ip_qos_interactive != INT_MAX)
369 		set_sock_tos(sock, options.ip_qos_interactive);
370 
371 	/* Bind the socket to an alternative local IP address */
372 	if (options.bind_address == NULL && options.bind_interface == NULL)
373 		return sock;
374 
375 	if (options.bind_address != NULL) {
376 		memset(&hints, 0, sizeof(hints));
377 		hints.ai_family = ai->ai_family;
378 		hints.ai_socktype = ai->ai_socktype;
379 		hints.ai_protocol = ai->ai_protocol;
380 		hints.ai_flags = AI_PASSIVE;
381 		if ((r = getaddrinfo(options.bind_address, NULL,
382 		    &hints, &res)) != 0) {
383 			error("getaddrinfo: %s: %s", options.bind_address,
384 			    ssh_gai_strerror(r));
385 			goto fail;
386 		}
387 		if (res == NULL) {
388 			error("getaddrinfo: no addrs");
389 			goto fail;
390 		}
391 		memcpy(&bindaddr, res->ai_addr, res->ai_addrlen);
392 		bindaddrlen = res->ai_addrlen;
393 
394 		/*'-B' option*/
395 		if (options.bind_interface != NULL) {
396 			if (setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, options.bind_interface, strlen(options.bind_interface) + 1))
397 				debug("error: setsockopt SO_BINDTODEVICE");
398 		}
399 	} else if (options.bind_interface != NULL) {
400 #ifdef HAVE_IFADDRS_H
401 		if ((r = getifaddrs(&ifaddrs)) != 0) {
402 			error("getifaddrs: %s: %s", options.bind_interface,
403 			      strerror(errno));
404 			goto fail;
405 		}
406 		bindaddrlen = sizeof(bindaddr);
407 		if (check_ifaddrs(options.bind_interface, ai->ai_family,
408 		    ifaddrs, &bindaddr, &bindaddrlen) != 0) {
409 			logit("getifaddrs: %s: no suitable addresses",
410 			      options.bind_interface);
411 			goto fail;
412 		}
413 #else
414 		error("BindInterface not supported on this platform.");
415 #endif
416 	}
417 	if ((r = getnameinfo((struct sockaddr *)&bindaddr, bindaddrlen,
418 	    ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST)) != 0) {
419 		error_f("getnameinfo failed: %s", ssh_gai_strerror(r));
420 		goto fail;
421 	}
422 	if (bind(sock, (struct sockaddr *)&bindaddr, bindaddrlen) != 0) {
423 		error("bind %s: %s", ntop, strerror(errno));
424 		goto fail;
425 	}
426 	debug_f("bound to %s", ntop);
427 	/* success */
428 	goto out;
429 fail:
430 	close(sock);
431 	sock = -1;
432  out:
433 	if (res != NULL)
434 		freeaddrinfo(res);
435 #ifdef HAVE_IFADDRS_H
436 	if (ifaddrs != NULL)
437 		freeifaddrs(ifaddrs);
438 #endif
439 	return sock;
440 }
441 
442 /*
443  * Opens a TCP/IP connection to the remote server on the given host.
444  * The address of the remote host will be returned in hostaddr.
445  * If port is 0, the default port will be used.
446  * Connection_attempts specifies the maximum number of tries (one per
447  * second).  If proxy_command is non-NULL, it specifies the command (with %h
448  * and %p substituted for host and port, respectively) to use to contact
449  * the daemon.
450  */
451 static int
452 ssh_connect_direct(struct ssh *ssh, const char *host, struct addrinfo *aitop,
453     struct sockaddr_storage *hostaddr, u_short port, int connection_attempts,
454     int *timeout_ms, int want_keepalive)
455 {
456 	int on = 1, saved_timeout_ms = *timeout_ms;
457 	int oerrno, sock = -1, attempt;
458 	char ntop[NI_MAXHOST], strport[NI_MAXSERV];
459 	struct addrinfo *ai;
460 
461 	debug3_f("entering");
462 	memset(ntop, 0, sizeof(ntop));
463 	memset(strport, 0, sizeof(strport));
464 
465 	for (attempt = 0; attempt < connection_attempts; attempt++) {
466 		if (attempt > 0) {
467 			/* Sleep a moment before retrying. */
468 			sleep(1);
469 			debug("Trying again...");
470 		}
471 		/*
472 		 * Loop through addresses for this host, and try each one in
473 		 * sequence until the connection succeeds.
474 		 */
475 		for (ai = aitop; ai; ai = ai->ai_next) {
476 			if (ai->ai_family != AF_INET &&
477 			    ai->ai_family != AF_INET6) {
478 				errno = EAFNOSUPPORT;
479 				continue;
480 			}
481 			if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
482 			    ntop, sizeof(ntop), strport, sizeof(strport),
483 			    NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
484 				oerrno = errno;
485 				error_f("getnameinfo failed");
486 				errno = oerrno;
487 				continue;
488 			}
489 			debug("Connecting to %.200s [%.100s] port %s.",
490 				host, ntop, strport);
491 
492 			/* Create a socket for connecting. */
493 			sock = ssh_create_socket(ai);
494 			if (sock < 0) {
495 				/* Any error is already output */
496 				errno = 0;
497 				continue;
498 			}
499 
500 			*timeout_ms = saved_timeout_ms;
501 			if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
502 			    timeout_ms) >= 0) {
503 				/* Successful connection. */
504 				memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
505 				break;
506 			} else {
507 				oerrno = errno;
508 				debug("connect to address %s port %s: %s",
509 				    ntop, strport, strerror(errno));
510 				close(sock);
511 				sock = -1;
512 				errno = oerrno;
513 			}
514 		}
515 		if (sock != -1)
516 			break;	/* Successful connection. */
517 	}
518 
519 	/* Return failure if we didn't get a successful connection. */
520 	if (sock == -1) {
521 		error("ssh: connect to host %s port %s: %s",
522 		    host, strport, errno == 0 ? "failure" : strerror(errno));
523 		return -1;
524 	}
525 
526 	debug("Connection established.");
527 
528 	/* Set SO_KEEPALIVE if requested. */
529 	if (want_keepalive &&
530 	    setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
531 	    sizeof(on)) == -1)
532 		error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
533 
534 	/* Set the connection. */
535 	if (ssh_packet_set_connection(ssh, sock, sock) == NULL)
536 		return -1; /* ssh_packet_set_connection logs error */
537 
538 	return 0;
539 }
540 
541 int
542 ssh_connect(struct ssh *ssh, const char *host, const char *host_arg,
543     struct addrinfo *addrs, struct sockaddr_storage *hostaddr, u_short port,
544     int connection_attempts, int *timeout_ms, int want_keepalive)
545 {
546 	int in, out;
547 
548 	if (options.proxy_command == NULL) {
549 		return ssh_connect_direct(ssh, host, addrs, hostaddr, port,
550 		    connection_attempts, timeout_ms, want_keepalive);
551 	} else if (strcmp(options.proxy_command, "-") == 0) {
552 		if ((in = dup(STDIN_FILENO)) == -1 ||
553 		    (out = dup(STDOUT_FILENO)) == -1) {
554 			if (in >= 0)
555 				close(in);
556 			error_f("dup() in/out failed");
557 			return -1; /* ssh_packet_set_connection logs error */
558 		}
559 		if ((ssh_packet_set_connection(ssh, in, out)) == NULL)
560 			return -1; /* ssh_packet_set_connection logs error */
561 		return 0;
562 	} else if (options.proxy_use_fdpass) {
563 		return ssh_proxy_fdpass_connect(ssh, host, host_arg, port,
564 		    options.proxy_command);
565 	}
566 	return ssh_proxy_connect(ssh, host, host_arg, port,
567 	    options.proxy_command);
568 }
569 
570 /* defaults to 'no' */
571 static int
572 confirm(const char *prompt, const char *fingerprint)
573 {
574 	const char *msg, *again = "Please type 'yes' or 'no': ";
575 	const char *again_fp = "Please type 'yes', 'no' or the fingerprint: ";
576 	char *p, *cp;
577 	int ret = -1;
578 
579 	if (options.batch_mode)
580 		return 0;
581 	for (msg = prompt;;msg = fingerprint ? again_fp : again) {
582 		cp = p = read_passphrase(msg, RP_ECHO);
583 		if (p == NULL)
584 			return 0;
585 		p += strspn(p, " \t"); /* skip leading whitespace */
586 		p[strcspn(p, " \t\n")] = '\0'; /* remove trailing whitespace */
587 		if (p[0] == '\0' || strcasecmp(p, "no") == 0)
588 			ret = 0;
589 		else if (strcasecmp(p, "yes") == 0 || (fingerprint != NULL &&
590 		    strcmp(p, fingerprint) == 0))
591 			ret = 1;
592 		free(cp);
593 		if (ret != -1)
594 			return ret;
595 	}
596 }
597 
598 static int
599 sockaddr_is_local(struct sockaddr *hostaddr)
600 {
601 	switch (hostaddr->sa_family) {
602 	case AF_INET:
603 		return (ntohl(((struct sockaddr_in *)hostaddr)->
604 		    sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
605 	case AF_INET6:
606 		return IN6_IS_ADDR_LOOPBACK(
607 		    &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
608 	default:
609 		return 0;
610 	}
611 }
612 
613 /*
614  * Prepare the hostname and ip address strings that are used to lookup
615  * host keys in known_hosts files. These may have a port number appended.
616  */
617 void
618 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr,
619     u_short port, char **hostfile_hostname, char **hostfile_ipaddr)
620 {
621 	char ntop[NI_MAXHOST];
622 	socklen_t addrlen;
623 
624 	switch (hostaddr == NULL ? -1 : hostaddr->sa_family) {
625 	case -1:
626 		addrlen = 0;
627 		break;
628 	case AF_INET:
629 		addrlen = sizeof(struct sockaddr_in);
630 		break;
631 	case AF_INET6:
632 		addrlen = sizeof(struct sockaddr_in6);
633 		break;
634 	default:
635 		addrlen = sizeof(struct sockaddr);
636 		break;
637 	}
638 
639 	/*
640 	 * We don't have the remote ip-address for connections
641 	 * using a proxy command
642 	 */
643 	if (hostfile_ipaddr != NULL) {
644 		if (options.proxy_command == NULL) {
645 			if (getnameinfo(hostaddr, addrlen,
646 			    ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0)
647 			fatal_f("getnameinfo failed");
648 			*hostfile_ipaddr = put_host_port(ntop, port);
649 		} else {
650 			*hostfile_ipaddr = xstrdup("<no hostip for proxy "
651 			    "command>");
652 		}
653 	}
654 
655 	/*
656 	 * Allow the user to record the key under a different name or
657 	 * differentiate a non-standard port.  This is useful for ssh
658 	 * tunneling over forwarded connections or if you run multiple
659 	 * sshd's on different ports on the same machine.
660 	 */
661 	if (hostfile_hostname != NULL) {
662 		if (options.host_key_alias != NULL) {
663 			*hostfile_hostname = xstrdup(options.host_key_alias);
664 			debug("using hostkeyalias: %s", *hostfile_hostname);
665 		} else {
666 			*hostfile_hostname = put_host_port(hostname, port);
667 		}
668 	}
669 }
670 
671 /* returns non-zero if path appears in hostfiles, or 0 if not. */
672 static int
673 path_in_hostfiles(const char *path, char **hostfiles, u_int num_hostfiles)
674 {
675 	u_int i;
676 
677 	for (i = 0; i < num_hostfiles; i++) {
678 		if (strcmp(path, hostfiles[i]) == 0)
679 			return 1;
680 	}
681 	return 0;
682 }
683 
684 struct find_by_key_ctx {
685 	const char *host, *ip;
686 	const struct sshkey *key;
687 	char **names;
688 	u_int nnames;
689 };
690 
691 /* Try to replace home directory prefix (per $HOME) with a ~/ sequence */
692 static char *
693 try_tilde_unexpand(const char *path)
694 {
695 	char *home, *ret = NULL;
696 	size_t l;
697 
698 	if (*path != '/')
699 		return xstrdup(path);
700 	if ((home = getenv("HOME")) == NULL || (l = strlen(home)) == 0)
701 		return xstrdup(path);
702 	if (strncmp(path, home, l) != 0)
703 		return xstrdup(path);
704 	/*
705 	 * ensure we have matched on a path boundary: either the $HOME that
706 	 * we just compared ends with a '/' or the next character of the path
707 	 * must be a '/'.
708 	 */
709 	if (home[l - 1] != '/' && path[l] != '/')
710 		return xstrdup(path);
711 	if (path[l] == '/')
712 		l++;
713 	xasprintf(&ret, "~/%s", path + l);
714 	return ret;
715 }
716 
717 static int
718 hostkeys_find_by_key_cb(struct hostkey_foreach_line *l, void *_ctx)
719 {
720 	struct find_by_key_ctx *ctx = (struct find_by_key_ctx *)_ctx;
721 	char *path;
722 
723 	/* we are looking for keys with names that *do not* match */
724 	if ((l->match & HKF_MATCH_HOST) != 0)
725 		return 0;
726 	/* not interested in marker lines */
727 	if (l->marker != MRK_NONE)
728 		return 0;
729 	/* we are only interested in exact key matches */
730 	if (l->key == NULL || !sshkey_equal(ctx->key, l->key))
731 		return 0;
732 	path = try_tilde_unexpand(l->path);
733 	debug_f("found matching key in %s:%lu", path, l->linenum);
734 	ctx->names = xrecallocarray(ctx->names,
735 	    ctx->nnames, ctx->nnames + 1, sizeof(*ctx->names));
736 	xasprintf(&ctx->names[ctx->nnames], "%s:%lu: %s", path, l->linenum,
737 	    strncmp(l->hosts, HASH_MAGIC, strlen(HASH_MAGIC)) == 0 ?
738 	    "[hashed name]" : l->hosts);
739 	ctx->nnames++;
740 	free(path);
741 	return 0;
742 }
743 
744 static int
745 hostkeys_find_by_key_hostfile(const char *file, const char *which,
746     struct find_by_key_ctx *ctx)
747 {
748 	int r;
749 
750 	debug3_f("trying %s hostfile \"%s\"", which, file);
751 	if ((r = hostkeys_foreach(file, hostkeys_find_by_key_cb, ctx,
752 	    ctx->host, ctx->ip, HKF_WANT_PARSE_KEY, 0)) != 0) {
753 		if (r == SSH_ERR_SYSTEM_ERROR && errno == ENOENT) {
754 			debug_f("hostkeys file %s does not exist", file);
755 			return 0;
756 		}
757 		error_fr(r, "hostkeys_foreach failed for %s", file);
758 		return r;
759 	}
760 	return 0;
761 }
762 
763 /*
764  * Find 'key' in known hosts file(s) that do not match host/ip.
765  * Used to display also-known-as information for previously-unseen hostkeys.
766  */
767 static void
768 hostkeys_find_by_key(const char *host, const char *ip, const struct sshkey *key,
769     char **user_hostfiles, u_int num_user_hostfiles,
770     char **system_hostfiles, u_int num_system_hostfiles,
771     char ***names, u_int *nnames)
772 {
773 	struct find_by_key_ctx ctx = {0, 0, 0, 0, 0};
774 	u_int i;
775 
776 	*names = NULL;
777 	*nnames = 0;
778 
779 	if (key == NULL || sshkey_is_cert(key))
780 		return;
781 
782 	ctx.host = host;
783 	ctx.ip = ip;
784 	ctx.key = key;
785 
786 	for (i = 0; i < num_user_hostfiles; i++) {
787 		if (hostkeys_find_by_key_hostfile(user_hostfiles[i],
788 		    "user", &ctx) != 0)
789 			goto fail;
790 	}
791 	for (i = 0; i < num_system_hostfiles; i++) {
792 		if (hostkeys_find_by_key_hostfile(system_hostfiles[i],
793 		    "system", &ctx) != 0)
794 			goto fail;
795 	}
796 	/* success */
797 	*names = ctx.names;
798 	*nnames = ctx.nnames;
799 	ctx.names = NULL;
800 	ctx.nnames = 0;
801 	return;
802  fail:
803 	for (i = 0; i < ctx.nnames; i++)
804 		free(ctx.names[i]);
805 	free(ctx.names);
806 }
807 
808 #define MAX_OTHER_NAMES	8 /* Maximum number of names to list */
809 static char *
810 other_hostkeys_message(const char *host, const char *ip,
811     const struct sshkey *key,
812     char **user_hostfiles, u_int num_user_hostfiles,
813     char **system_hostfiles, u_int num_system_hostfiles)
814 {
815 	char *ret = NULL, **othernames = NULL;
816 	u_int i, n, num_othernames = 0;
817 
818 	hostkeys_find_by_key(host, ip, key,
819 	    user_hostfiles, num_user_hostfiles,
820 	    system_hostfiles, num_system_hostfiles,
821 	    &othernames, &num_othernames);
822 	if (num_othernames == 0)
823 		return xstrdup("This key is not known by any other names");
824 
825 	xasprintf(&ret, "This host key is known by the following other "
826 	    "names/addresses:");
827 
828 	n = num_othernames;
829 	if (n > MAX_OTHER_NAMES)
830 		n = MAX_OTHER_NAMES;
831 	for (i = 0; i < n; i++) {
832 		xextendf(&ret, "\n", "    %s", othernames[i]);
833 	}
834 	if (n < num_othernames) {
835 		xextendf(&ret, "\n", "    (%d additional names ommitted)",
836 		    num_othernames - n);
837 	}
838 	for (i = 0; i < num_othernames; i++)
839 		free(othernames[i]);
840 	free(othernames);
841 	return ret;
842 }
843 
844 void
845 load_hostkeys_command(struct hostkeys *hostkeys, const char *command_template,
846     const char *invocation, const struct ssh_conn_info *cinfo,
847     const struct sshkey *host_key, const char *hostfile_hostname)
848 {
849 	int r, i, ac = 0;
850 	char *key_fp = NULL, *keytext = NULL, *tmp;
851 	char *command = NULL, *tag = NULL, **av = NULL;
852 	FILE *f = NULL;
853 	pid_t pid;
854 	void (*osigchld)(int);
855 
856 	xasprintf(&tag, "KnownHostsCommand-%s", invocation);
857 
858 	if (host_key != NULL) {
859 		if ((key_fp = sshkey_fingerprint(host_key,
860 		    options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
861 			fatal_f("sshkey_fingerprint failed");
862 		if ((r = sshkey_to_base64(host_key, &keytext)) != 0)
863 			fatal_fr(r, "sshkey_to_base64 failed");
864 	}
865 	/*
866 	 * NB. all returns later this function should go via "out" to
867 	 * ensure the original SIGCHLD handler is restored properly.
868 	 */
869 	osigchld = ssh_signal(SIGCHLD, SIG_DFL);
870 
871 	/* Turn the command into an argument vector */
872 	if (argv_split(command_template, &ac, &av) != 0) {
873 		error("%s \"%s\" contains invalid quotes", tag,
874 		   command_template);
875 		goto out;
876 	}
877 	if (ac == 0) {
878 		error("%s \"%s\" yielded no arguments", tag,
879 		    command_template);
880 		goto out;
881 	}
882 	for (i = 1; i < ac; i++) {
883 		tmp = percent_dollar_expand(av[i],
884 		    DEFAULT_CLIENT_PERCENT_EXPAND_ARGS(cinfo),
885 		    "H", hostfile_hostname,
886 		    "I", invocation,
887 		    "t", host_key == NULL ? "NONE" : sshkey_ssh_name(host_key),
888 		    "f", key_fp == NULL ? "NONE" : key_fp,
889 		    "K", keytext == NULL ? "NONE" : keytext,
890 		    (char *)NULL);
891 		if (tmp == NULL)
892 			fatal_f("percent_expand failed");
893 		free(av[i]);
894 		av[i] = tmp;
895 	}
896 	/* Prepare a printable command for logs, etc. */
897 	command = argv_assemble(ac, av);
898 
899 	if ((pid = subprocess(tag, command, ac, av, &f,
900 	    SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_UNSAFE_PATH|
901 	    SSH_SUBPROCESS_PRESERVE_ENV, NULL, NULL, NULL)) == 0)
902 		goto out;
903 
904 	load_hostkeys_file(hostkeys, hostfile_hostname, tag, f, 1);
905 
906 	if (exited_cleanly(pid, tag, command, 0) != 0)
907 		fatal("KnownHostsCommand failed");
908 
909  out:
910 	if (f != NULL)
911 		fclose(f);
912 	ssh_signal(SIGCHLD, osigchld);
913 	for (i = 0; i < ac; i++)
914 		free(av[i]);
915 	free(av);
916 	free(tag);
917 	free(command);
918 	free(key_fp);
919 	free(keytext);
920 }
921 
922 /*
923  * check whether the supplied host key is valid, return -1 if the key
924  * is not valid. user_hostfile[0] will not be updated if 'readonly' is true.
925  */
926 #define RDRW	0
927 #define RDONLY	1
928 #define ROQUIET	2
929 static int
930 check_host_key(char *hostname, const struct ssh_conn_info *cinfo,
931     struct sockaddr *hostaddr, u_short port,
932     struct sshkey *host_key, int readonly, int clobber_port,
933     char **user_hostfiles, u_int num_user_hostfiles,
934     char **system_hostfiles, u_int num_system_hostfiles,
935     const char *hostfile_command)
936 {
937 	HostStatus host_status = -1, ip_status = -1;
938 	struct sshkey *raw_key = NULL;
939 	char *ip = NULL, *host = NULL;
940 	char hostline[1000], *hostp, *fp, *ra;
941 	char msg[1024];
942 	const char *type, *fail_reason;
943 	const struct hostkey_entry *host_found = NULL, *ip_found = NULL;
944 	int len, cancelled_forwarding = 0, confirmed;
945 	int local = sockaddr_is_local(hostaddr);
946 	int r, want_cert = sshkey_is_cert(host_key), host_ip_differ = 0;
947 	int hostkey_trusted = 0; /* Known or explicitly accepted by user */
948 	struct hostkeys *host_hostkeys, *ip_hostkeys;
949 	u_int i;
950 
951 	/*
952 	 * Force accepting of the host key for loopback/localhost. The
953 	 * problem is that if the home directory is NFS-mounted to multiple
954 	 * machines, localhost will refer to a different machine in each of
955 	 * them, and the user will get bogus HOST_CHANGED warnings.  This
956 	 * essentially disables host authentication for localhost; however,
957 	 * this is probably not a real problem.
958 	 */
959 	if (options.no_host_authentication_for_localhost == 1 && local &&
960 	    options.host_key_alias == NULL) {
961 		debug("Forcing accepting of host key for "
962 		    "loopback/localhost.");
963 		options.update_hostkeys = 0;
964 		return 0;
965 	}
966 
967 	/*
968 	 * Prepare the hostname and address strings used for hostkey lookup.
969 	 * In some cases, these will have a port number appended.
970 	 */
971 	get_hostfile_hostname_ipaddr(hostname, hostaddr,
972 	    clobber_port ? 0 : port, &host, &ip);
973 
974 	/*
975 	 * Turn off check_host_ip if the connection is to localhost, via proxy
976 	 * command or if we don't have a hostname to compare with
977 	 */
978 	if (options.check_host_ip && (local ||
979 	    strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
980 		options.check_host_ip = 0;
981 
982 	host_hostkeys = init_hostkeys();
983 	for (i = 0; i < num_user_hostfiles; i++)
984 		load_hostkeys(host_hostkeys, host, user_hostfiles[i], 0);
985 	for (i = 0; i < num_system_hostfiles; i++)
986 		load_hostkeys(host_hostkeys, host, system_hostfiles[i], 0);
987 	if (hostfile_command != NULL && !clobber_port) {
988 		load_hostkeys_command(host_hostkeys, hostfile_command,
989 		    "HOSTNAME", cinfo, host_key, host);
990 	}
991 
992 	ip_hostkeys = NULL;
993 	if (!want_cert && options.check_host_ip) {
994 		ip_hostkeys = init_hostkeys();
995 		for (i = 0; i < num_user_hostfiles; i++)
996 			load_hostkeys(ip_hostkeys, ip, user_hostfiles[i], 0);
997 		for (i = 0; i < num_system_hostfiles; i++)
998 			load_hostkeys(ip_hostkeys, ip, system_hostfiles[i], 0);
999 		if (hostfile_command != NULL && !clobber_port) {
1000 			load_hostkeys_command(ip_hostkeys, hostfile_command,
1001 			    "ADDRESS", cinfo, host_key, ip);
1002 		}
1003 	}
1004 
1005  retry:
1006 	/* Reload these as they may have changed on cert->key downgrade */
1007 	want_cert = sshkey_is_cert(host_key);
1008 	type = sshkey_type(host_key);
1009 
1010 	/*
1011 	 * Check if the host key is present in the user's list of known
1012 	 * hosts or in the systemwide list.
1013 	 */
1014 	host_status = check_key_in_hostkeys(host_hostkeys, host_key,
1015 	    &host_found);
1016 
1017 	/*
1018 	 * If there are no hostfiles, or if the hostkey was found via
1019 	 * KnownHostsCommand, then don't try to touch the disk.
1020 	 */
1021 	if (!readonly && (num_user_hostfiles == 0 ||
1022 	    (host_found != NULL && host_found->note != 0)))
1023 		readonly = RDONLY;
1024 
1025 	/*
1026 	 * Also perform check for the ip address, skip the check if we are
1027 	 * localhost, looking for a certificate, or the hostname was an ip
1028 	 * address to begin with.
1029 	 */
1030 	if (!want_cert && ip_hostkeys != NULL) {
1031 		ip_status = check_key_in_hostkeys(ip_hostkeys, host_key,
1032 		    &ip_found);
1033 		if (host_status == HOST_CHANGED &&
1034 		    (ip_status != HOST_CHANGED ||
1035 		    (ip_found != NULL &&
1036 		    !sshkey_equal(ip_found->key, host_found->key))))
1037 			host_ip_differ = 1;
1038 	} else
1039 		ip_status = host_status;
1040 
1041 	switch (host_status) {
1042 	case HOST_OK:
1043 		/* The host is known and the key matches. */
1044 		debug("Host '%.200s' is known and matches the %s host %s.",
1045 		    host, type, want_cert ? "certificate" : "key");
1046 		debug("Found %s in %s:%lu", want_cert ? "CA key" : "key",
1047 		    host_found->file, host_found->line);
1048 		if (want_cert) {
1049 			if (sshkey_cert_check_host(host_key,
1050 			    options.host_key_alias == NULL ?
1051 			    hostname : options.host_key_alias, 0,
1052 			    options.ca_sign_algorithms, &fail_reason) != 0) {
1053 				error("%s", fail_reason);
1054 				goto fail;
1055 			}
1056 			/*
1057 			 * Do not attempt hostkey update if a certificate was
1058 			 * successfully matched.
1059 			 */
1060 			if (options.update_hostkeys != 0) {
1061 				options.update_hostkeys = 0;
1062 				debug3_f("certificate host key in use; "
1063 				    "disabling UpdateHostkeys");
1064 			}
1065 		}
1066 		/* Turn off UpdateHostkeys if key was in system known_hosts */
1067 		if (options.update_hostkeys != 0 &&
1068 		    (path_in_hostfiles(host_found->file,
1069 		    system_hostfiles, num_system_hostfiles) ||
1070 		    (ip_status == HOST_OK && ip_found != NULL &&
1071 		    path_in_hostfiles(ip_found->file,
1072 		    system_hostfiles, num_system_hostfiles)))) {
1073 			options.update_hostkeys = 0;
1074 			debug3_f("host key found in GlobalKnownHostsFile; "
1075 			    "disabling UpdateHostkeys");
1076 		}
1077 		if (options.update_hostkeys != 0 && host_found->note) {
1078 			options.update_hostkeys = 0;
1079 			debug3_f("host key found via KnownHostsCommand; "
1080 			    "disabling UpdateHostkeys");
1081 		}
1082 		if (options.check_host_ip && ip_status == HOST_NEW) {
1083 			if (readonly || want_cert)
1084 				logit("%s host key for IP address "
1085 				    "'%.128s' not in list of known hosts.",
1086 				    type, ip);
1087 			else if (!add_host_to_hostfile(user_hostfiles[0], ip,
1088 			    host_key, options.hash_known_hosts))
1089 				logit("Failed to add the %s host key for IP "
1090 				    "address '%.128s' to the list of known "
1091 				    "hosts (%.500s).", type, ip,
1092 				    user_hostfiles[0]);
1093 			else
1094 				logit("Warning: Permanently added the %s host "
1095 				    "key for IP address '%.128s' to the list "
1096 				    "of known hosts.", type, ip);
1097 		} else if (options.visual_host_key) {
1098 			fp = sshkey_fingerprint(host_key,
1099 			    options.fingerprint_hash, SSH_FP_DEFAULT);
1100 			ra = sshkey_fingerprint(host_key,
1101 			    options.fingerprint_hash, SSH_FP_RANDOMART);
1102 			if (fp == NULL || ra == NULL)
1103 				fatal_f("sshkey_fingerprint failed");
1104 			logit("Host key fingerprint is %s\n%s", fp, ra);
1105 			free(ra);
1106 			free(fp);
1107 		}
1108 		hostkey_trusted = 1;
1109 		break;
1110 	case HOST_NEW:
1111 		if (options.host_key_alias == NULL && port != 0 &&
1112 		    port != SSH_DEFAULT_PORT && !clobber_port) {
1113 			debug("checking without port identifier");
1114 			if (check_host_key(hostname, cinfo, hostaddr, 0,
1115 			    host_key, ROQUIET, 1,
1116 			    user_hostfiles, num_user_hostfiles,
1117 			    system_hostfiles, num_system_hostfiles,
1118 			    hostfile_command) == 0) {
1119 				debug("found matching key w/out port");
1120 				break;
1121 			}
1122 		}
1123 		if (readonly || want_cert)
1124 			goto fail;
1125 		/* The host is new. */
1126 		if (options.strict_host_key_checking ==
1127 		    SSH_STRICT_HOSTKEY_YES) {
1128 			/*
1129 			 * User has requested strict host key checking.  We
1130 			 * will not add the host key automatically.  The only
1131 			 * alternative left is to abort.
1132 			 */
1133 			error("No %s host key is known for %.200s and you "
1134 			    "have requested strict checking.", type, host);
1135 			goto fail;
1136 		} else if (options.strict_host_key_checking ==
1137 		    SSH_STRICT_HOSTKEY_ASK) {
1138 			char *msg1 = NULL, *msg2 = NULL;
1139 
1140 			xasprintf(&msg1, "The authenticity of host "
1141 			    "'%.200s (%s)' can't be established", host, ip);
1142 
1143 			if (show_other_keys(host_hostkeys, host_key)) {
1144 				xextendf(&msg1, "\n", "but keys of different "
1145 				    "type are already known for this host.");
1146 			} else
1147 				xextendf(&msg1, "", ".");
1148 
1149 			fp = sshkey_fingerprint(host_key,
1150 			    options.fingerprint_hash, SSH_FP_DEFAULT);
1151 			ra = sshkey_fingerprint(host_key,
1152 			    options.fingerprint_hash, SSH_FP_RANDOMART);
1153 			if (fp == NULL || ra == NULL)
1154 				fatal_f("sshkey_fingerprint failed");
1155 			xextendf(&msg1, "\n", "%s key fingerprint is %s.",
1156 			    type, fp);
1157 			if (options.visual_host_key)
1158 				xextendf(&msg1, "\n", "%s", ra);
1159 			if (options.verify_host_key_dns) {
1160 				xextendf(&msg1, "\n",
1161 				    "%s host key fingerprint found in DNS.",
1162 				    matching_host_key_dns ?
1163 				    "Matching" : "No matching");
1164 			}
1165 			/* msg2 informs for other names matching this key */
1166 			if ((msg2 = other_hostkeys_message(host, ip, host_key,
1167 			    user_hostfiles, num_user_hostfiles,
1168 			    system_hostfiles, num_system_hostfiles)) != NULL)
1169 				xextendf(&msg1, "\n", "%s", msg2);
1170 
1171 			xextendf(&msg1, "\n",
1172 			    "Are you sure you want to continue connecting "
1173 			    "(yes/no/[fingerprint])? ");
1174 
1175 			confirmed = confirm(msg1, fp);
1176 			free(ra);
1177 			free(fp);
1178 			free(msg1);
1179 			free(msg2);
1180 			if (!confirmed)
1181 				goto fail;
1182 			hostkey_trusted = 1; /* user explicitly confirmed */
1183 		}
1184 		/*
1185 		 * If in "new" or "off" strict mode, add the key automatically
1186 		 * to the local known_hosts file.
1187 		 */
1188 		if (options.check_host_ip && ip_status == HOST_NEW) {
1189 			snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
1190 			hostp = hostline;
1191 			if (options.hash_known_hosts) {
1192 				/* Add hash of host and IP separately */
1193 				r = add_host_to_hostfile(user_hostfiles[0],
1194 				    host, host_key, options.hash_known_hosts) &&
1195 				    add_host_to_hostfile(user_hostfiles[0], ip,
1196 				    host_key, options.hash_known_hosts);
1197 			} else {
1198 				/* Add unhashed "host,ip" */
1199 				r = add_host_to_hostfile(user_hostfiles[0],
1200 				    hostline, host_key,
1201 				    options.hash_known_hosts);
1202 			}
1203 		} else {
1204 			r = add_host_to_hostfile(user_hostfiles[0], host,
1205 			    host_key, options.hash_known_hosts);
1206 			hostp = host;
1207 		}
1208 
1209 		if (!r)
1210 			logit("Failed to add the host to the list of known "
1211 			    "hosts (%.500s).", user_hostfiles[0]);
1212 		else
1213 			logit("Warning: Permanently added '%.200s' (%s) to the "
1214 			    "list of known hosts.", hostp, type);
1215 		break;
1216 	case HOST_REVOKED:
1217 		error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1218 		error("@       WARNING: REVOKED HOST KEY DETECTED!               @");
1219 		error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1220 		error("The %s host key for %s is marked as revoked.", type, host);
1221 		error("This could mean that a stolen key is being used to");
1222 		error("impersonate this host.");
1223 
1224 		/*
1225 		 * If strict host key checking is in use, the user will have
1226 		 * to edit the key manually and we can only abort.
1227 		 */
1228 		if (options.strict_host_key_checking !=
1229 		    SSH_STRICT_HOSTKEY_OFF) {
1230 			error("%s host key for %.200s was revoked and you have "
1231 			    "requested strict checking.", type, host);
1232 			goto fail;
1233 		}
1234 		goto continue_unsafe;
1235 
1236 	case HOST_CHANGED:
1237 		if (want_cert) {
1238 			/*
1239 			 * This is only a debug() since it is valid to have
1240 			 * CAs with wildcard DNS matches that don't match
1241 			 * all hosts that one might visit.
1242 			 */
1243 			debug("Host certificate authority does not "
1244 			    "match %s in %s:%lu", CA_MARKER,
1245 			    host_found->file, host_found->line);
1246 			goto fail;
1247 		}
1248 		if (readonly == ROQUIET)
1249 			goto fail;
1250 		if (options.check_host_ip && host_ip_differ) {
1251 			char *key_msg;
1252 			if (ip_status == HOST_NEW)
1253 				key_msg = "is unknown";
1254 			else if (ip_status == HOST_OK)
1255 				key_msg = "is unchanged";
1256 			else
1257 				key_msg = "has a different value";
1258 			error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1259 			error("@       WARNING: POSSIBLE DNS SPOOFING DETECTED!          @");
1260 			error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1261 			error("The %s host key for %s has changed,", type, host);
1262 			error("and the key for the corresponding IP address %s", ip);
1263 			error("%s. This could either mean that", key_msg);
1264 			error("DNS SPOOFING is happening or the IP address for the host");
1265 			error("and its host key have changed at the same time.");
1266 			if (ip_status != HOST_NEW)
1267 				error("Offending key for IP in %s:%lu",
1268 				    ip_found->file, ip_found->line);
1269 		}
1270 		/* The host key has changed. */
1271 		warn_changed_key(host_key);
1272 		error("Add correct host key in %.100s to get rid of this message.",
1273 		    user_hostfiles[0]);
1274 		error("Offending %s key in %s:%lu",
1275 		    sshkey_type(host_found->key),
1276 		    host_found->file, host_found->line);
1277 
1278 		/*
1279 		 * If strict host key checking is in use, the user will have
1280 		 * to edit the key manually and we can only abort.
1281 		 */
1282 		if (options.strict_host_key_checking !=
1283 		    SSH_STRICT_HOSTKEY_OFF) {
1284 			error("Host key for %.200s has changed and you have "
1285 			    "requested strict checking.", host);
1286 			goto fail;
1287 		}
1288 
1289  continue_unsafe:
1290 		/*
1291 		 * If strict host key checking has not been requested, allow
1292 		 * the connection but without MITM-able authentication or
1293 		 * forwarding.
1294 		 */
1295 		if (options.password_authentication) {
1296 			error("Password authentication is disabled to avoid "
1297 			    "man-in-the-middle attacks.");
1298 			options.password_authentication = 0;
1299 			cancelled_forwarding = 1;
1300 		}
1301 		if (options.kbd_interactive_authentication) {
1302 			error("Keyboard-interactive authentication is disabled"
1303 			    " to avoid man-in-the-middle attacks.");
1304 			options.kbd_interactive_authentication = 0;
1305 			options.challenge_response_authentication = 0;
1306 			cancelled_forwarding = 1;
1307 		}
1308 		if (options.challenge_response_authentication) {
1309 			error("Challenge/response authentication is disabled"
1310 			    " to avoid man-in-the-middle attacks.");
1311 			options.challenge_response_authentication = 0;
1312 			cancelled_forwarding = 1;
1313 		}
1314 		if (options.forward_agent) {
1315 			error("Agent forwarding is disabled to avoid "
1316 			    "man-in-the-middle attacks.");
1317 			options.forward_agent = 0;
1318 			cancelled_forwarding = 1;
1319 		}
1320 		if (options.forward_x11) {
1321 			error("X11 forwarding is disabled to avoid "
1322 			    "man-in-the-middle attacks.");
1323 			options.forward_x11 = 0;
1324 			cancelled_forwarding = 1;
1325 		}
1326 		if (options.num_local_forwards > 0 ||
1327 		    options.num_remote_forwards > 0) {
1328 			error("Port forwarding is disabled to avoid "
1329 			    "man-in-the-middle attacks.");
1330 			options.num_local_forwards =
1331 			    options.num_remote_forwards = 0;
1332 			cancelled_forwarding = 1;
1333 		}
1334 		if (options.tun_open != SSH_TUNMODE_NO) {
1335 			error("Tunnel forwarding is disabled to avoid "
1336 			    "man-in-the-middle attacks.");
1337 			options.tun_open = SSH_TUNMODE_NO;
1338 			cancelled_forwarding = 1;
1339 		}
1340 		if (options.update_hostkeys != 0) {
1341 			error("UpdateHostkeys is disabled because the host "
1342 			    "key is not trusted.");
1343 			options.update_hostkeys = 0;
1344 		}
1345 		if (options.exit_on_forward_failure && cancelled_forwarding)
1346 			fatal("Error: forwarding disabled due to host key "
1347 			    "check failure");
1348 
1349 		/*
1350 		 * XXX Should permit the user to change to use the new id.
1351 		 * This could be done by converting the host key to an
1352 		 * identifying sentence, tell that the host identifies itself
1353 		 * by that sentence, and ask the user if he/she wishes to
1354 		 * accept the authentication.
1355 		 */
1356 		break;
1357 	case HOST_FOUND:
1358 		fatal("internal error");
1359 		break;
1360 	}
1361 
1362 	if (options.check_host_ip && host_status != HOST_CHANGED &&
1363 	    ip_status == HOST_CHANGED) {
1364 		snprintf(msg, sizeof(msg),
1365 		    "Warning: the %s host key for '%.200s' "
1366 		    "differs from the key for the IP address '%.128s'"
1367 		    "\nOffending key for IP in %s:%lu",
1368 		    type, host, ip, ip_found->file, ip_found->line);
1369 		if (host_status == HOST_OK) {
1370 			len = strlen(msg);
1371 			snprintf(msg + len, sizeof(msg) - len,
1372 			    "\nMatching host key in %s:%lu",
1373 			    host_found->file, host_found->line);
1374 		}
1375 		if (options.strict_host_key_checking ==
1376 		    SSH_STRICT_HOSTKEY_ASK) {
1377 			strlcat(msg, "\nAre you sure you want "
1378 			    "to continue connecting (yes/no)? ", sizeof(msg));
1379 			if (!confirm(msg, NULL))
1380 				goto fail;
1381 		} else if (options.strict_host_key_checking !=
1382 		    SSH_STRICT_HOSTKEY_OFF) {
1383 			logit("%s", msg);
1384 			error("Exiting, you have requested strict checking.");
1385 			goto fail;
1386 		} else {
1387 			logit("%s", msg);
1388 		}
1389 	}
1390 
1391 	if (!hostkey_trusted && options.update_hostkeys) {
1392 		debug_f("hostkey not known or explicitly trusted: "
1393 		    "disabling UpdateHostkeys");
1394 		options.update_hostkeys = 0;
1395 	}
1396 
1397 	free(ip);
1398 	free(host);
1399 	if (host_hostkeys != NULL)
1400 		free_hostkeys(host_hostkeys);
1401 	if (ip_hostkeys != NULL)
1402 		free_hostkeys(ip_hostkeys);
1403 	return 0;
1404 
1405 fail:
1406 	if (want_cert && host_status != HOST_REVOKED) {
1407 		/*
1408 		 * No matching certificate. Downgrade cert to raw key and
1409 		 * search normally.
1410 		 */
1411 		debug("No matching CA found. Retry with plain key");
1412 		if ((r = sshkey_from_private(host_key, &raw_key)) != 0)
1413 			fatal_fr(r, "decode key");
1414 		if ((r = sshkey_drop_cert(raw_key)) != 0)
1415 			fatal_r(r, "Couldn't drop certificate");
1416 		host_key = raw_key;
1417 		goto retry;
1418 	}
1419 	sshkey_free(raw_key);
1420 	free(ip);
1421 	free(host);
1422 	if (host_hostkeys != NULL)
1423 		free_hostkeys(host_hostkeys);
1424 	if (ip_hostkeys != NULL)
1425 		free_hostkeys(ip_hostkeys);
1426 	return -1;
1427 }
1428 
1429 /* returns 0 if key verifies or -1 if key does NOT verify */
1430 int
1431 verify_host_key(char *host, struct sockaddr *hostaddr, struct sshkey *host_key,
1432     const struct ssh_conn_info *cinfo)
1433 {
1434 	u_int i;
1435 	int r = -1, flags = 0;
1436 	char valid[64], *fp = NULL, *cafp = NULL;
1437 	struct sshkey *plain = NULL;
1438 
1439 	if ((fp = sshkey_fingerprint(host_key,
1440 	    options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1441 		error_fr(r, "fingerprint host key");
1442 		r = -1;
1443 		goto out;
1444 	}
1445 
1446 	if (sshkey_is_cert(host_key)) {
1447 		if ((cafp = sshkey_fingerprint(host_key->cert->signature_key,
1448 		    options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1449 			error_fr(r, "fingerprint CA key");
1450 			r = -1;
1451 			goto out;
1452 		}
1453 		sshkey_format_cert_validity(host_key->cert,
1454 		    valid, sizeof(valid));
1455 		debug("Server host certificate: %s %s, serial %llu "
1456 		    "ID \"%s\" CA %s %s valid %s",
1457 		    sshkey_ssh_name(host_key), fp,
1458 		    (unsigned long long)host_key->cert->serial,
1459 		    host_key->cert->key_id,
1460 		    sshkey_ssh_name(host_key->cert->signature_key), cafp,
1461 		    valid);
1462 		for (i = 0; i < host_key->cert->nprincipals; i++) {
1463 			debug2("Server host certificate hostname: %s",
1464 			    host_key->cert->principals[i]);
1465 		}
1466 	} else {
1467 		debug("Server host key: %s %s", sshkey_ssh_name(host_key), fp);
1468 	}
1469 
1470 	if (sshkey_equal(previous_host_key, host_key)) {
1471 		debug2_f("server host key %s %s matches cached key",
1472 		    sshkey_type(host_key), fp);
1473 		r = 0;
1474 		goto out;
1475 	}
1476 
1477 	/* Check in RevokedHostKeys file if specified */
1478 	if (options.revoked_host_keys != NULL) {
1479 		r = sshkey_check_revoked(host_key, options.revoked_host_keys);
1480 		switch (r) {
1481 		case 0:
1482 			break; /* not revoked */
1483 		case SSH_ERR_KEY_REVOKED:
1484 			error("Host key %s %s revoked by file %s",
1485 			    sshkey_type(host_key), fp,
1486 			    options.revoked_host_keys);
1487 			r = -1;
1488 			goto out;
1489 		default:
1490 			error_r(r, "Error checking host key %s %s in "
1491 			    "revoked keys file %s", sshkey_type(host_key),
1492 			    fp, options.revoked_host_keys);
1493 			r = -1;
1494 			goto out;
1495 		}
1496 	}
1497 
1498 	if (options.verify_host_key_dns) {
1499 		/*
1500 		 * XXX certs are not yet supported for DNS, so downgrade
1501 		 * them and try the plain key.
1502 		 */
1503 		if ((r = sshkey_from_private(host_key, &plain)) != 0)
1504 			goto out;
1505 		if (sshkey_is_cert(plain))
1506 			sshkey_drop_cert(plain);
1507 		if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) {
1508 			if (flags & DNS_VERIFY_FOUND) {
1509 				if (options.verify_host_key_dns == 1 &&
1510 				    flags & DNS_VERIFY_MATCH &&
1511 				    flags & DNS_VERIFY_SECURE) {
1512 					r = 0;
1513 					goto out;
1514 				}
1515 				if (flags & DNS_VERIFY_MATCH) {
1516 					matching_host_key_dns = 1;
1517 				} else {
1518 					warn_changed_key(plain);
1519 					error("Update the SSHFP RR in DNS "
1520 					    "with the new host key to get rid "
1521 					    "of this message.");
1522 				}
1523 			}
1524 		}
1525 	}
1526 	r = check_host_key(host, cinfo, hostaddr, options.port, host_key,
1527 	    RDRW, 0, options.user_hostfiles, options.num_user_hostfiles,
1528 	    options.system_hostfiles, options.num_system_hostfiles,
1529 	    options.known_hosts_command);
1530 
1531 out:
1532 	sshkey_free(plain);
1533 	free(fp);
1534 	free(cafp);
1535 	if (r == 0 && host_key != NULL) {
1536 		sshkey_free(previous_host_key);
1537 		r = sshkey_from_private(host_key, &previous_host_key);
1538 	}
1539 
1540 	return r;
1541 }
1542 
1543 /*
1544  * Starts a dialog with the server, and authenticates the current user on the
1545  * server.  This does not need any extra privileges.  The basic connection
1546  * to the server must already have been established before this is called.
1547  * If login fails, this function prints an error and never returns.
1548  * This function does not require super-user privileges.
1549  */
1550 void
1551 ssh_login(struct ssh *ssh, Sensitive *sensitive, const char *orighost,
1552     struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms,
1553     const struct ssh_conn_info *cinfo)
1554 {
1555 	char *host;
1556 	char *server_user, *local_user;
1557 	int r;
1558 
1559 	local_user = xstrdup(pw->pw_name);
1560 	server_user = options.user ? options.user : local_user;
1561 
1562 	/* Convert the user-supplied hostname into all lowercase. */
1563 	host = xstrdup(orighost);
1564 	lowercase(host);
1565 
1566 	/* Exchange protocol version identification strings with the server. */
1567 	if ((r = kex_exchange_identification(ssh, timeout_ms, NULL)) != 0)
1568 		sshpkt_fatal(ssh, r, "banner exchange");
1569 
1570 	/* Put the connection into non-blocking mode. */
1571 	ssh_packet_set_nonblocking(ssh);
1572 
1573 	/* key exchange */
1574 	/* authenticate user */
1575 	debug("Authenticating to %s:%d as '%s'", host, port, server_user);
1576 	ssh_kex2(ssh, host, hostaddr, port, cinfo);
1577 	ssh_userauth2(ssh, local_user, server_user, host, sensitive);
1578 	free(local_user);
1579 	free(host);
1580 }
1581 
1582 /* print all known host keys for a given host, but skip keys of given type */
1583 static int
1584 show_other_keys(struct hostkeys *hostkeys, struct sshkey *key)
1585 {
1586 	int type[] = {
1587 		KEY_RSA,
1588 		KEY_DSA,
1589 		KEY_ECDSA,
1590 		KEY_ED25519,
1591 		KEY_XMSS,
1592 		-1
1593 	};
1594 	int i, ret = 0;
1595 	char *fp, *ra;
1596 	const struct hostkey_entry *found;
1597 
1598 	for (i = 0; type[i] != -1; i++) {
1599 		if (type[i] == key->type)
1600 			continue;
1601 		if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i],
1602 		    -1, &found))
1603 			continue;
1604 		fp = sshkey_fingerprint(found->key,
1605 		    options.fingerprint_hash, SSH_FP_DEFAULT);
1606 		ra = sshkey_fingerprint(found->key,
1607 		    options.fingerprint_hash, SSH_FP_RANDOMART);
1608 		if (fp == NULL || ra == NULL)
1609 			fatal_f("sshkey_fingerprint fail");
1610 		logit("WARNING: %s key found for host %s\n"
1611 		    "in %s:%lu\n"
1612 		    "%s key fingerprint %s.",
1613 		    sshkey_type(found->key),
1614 		    found->host, found->file, found->line,
1615 		    sshkey_type(found->key), fp);
1616 		if (options.visual_host_key)
1617 			logit("%s", ra);
1618 		free(ra);
1619 		free(fp);
1620 		ret = 1;
1621 	}
1622 	return ret;
1623 }
1624 
1625 static void
1626 warn_changed_key(struct sshkey *host_key)
1627 {
1628 	char *fp;
1629 
1630 	fp = sshkey_fingerprint(host_key, options.fingerprint_hash,
1631 	    SSH_FP_DEFAULT);
1632 	if (fp == NULL)
1633 		fatal_f("sshkey_fingerprint fail");
1634 
1635 	error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1636 	error("@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @");
1637 	error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1638 	error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1639 	error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1640 	error("It is also possible that a host key has just been changed.");
1641 	error("The fingerprint for the %s key sent by the remote host is\n%s.",
1642 	    sshkey_type(host_key), fp);
1643 	error("Please contact your system administrator.");
1644 
1645 	free(fp);
1646 }
1647 
1648 /*
1649  * Execute a local command
1650  */
1651 int
1652 ssh_local_cmd(const char *args)
1653 {
1654 	char *shell;
1655 	pid_t pid;
1656 	int status;
1657 	void (*osighand)(int);
1658 
1659 	if (!options.permit_local_command ||
1660 	    args == NULL || !*args)
1661 		return (1);
1662 
1663 	if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
1664 		shell = _PATH_BSHELL;
1665 
1666 	osighand = ssh_signal(SIGCHLD, SIG_DFL);
1667 	pid = fork();
1668 	if (pid == 0) {
1669 		ssh_signal(SIGPIPE, SIG_DFL);
1670 		debug3("Executing %s -c \"%s\"", shell, args);
1671 		execl(shell, shell, "-c", args, (char *)NULL);
1672 		error("Couldn't execute %s -c \"%s\": %s",
1673 		    shell, args, strerror(errno));
1674 		_exit(1);
1675 	} else if (pid == -1)
1676 		fatal("fork failed: %.100s", strerror(errno));
1677 	while (waitpid(pid, &status, 0) == -1)
1678 		if (errno != EINTR)
1679 			fatal("Couldn't wait for child: %s", strerror(errno));
1680 	ssh_signal(SIGCHLD, osighand);
1681 
1682 	if (!WIFEXITED(status))
1683 		return (1);
1684 
1685 	return (WEXITSTATUS(status));
1686 }
1687 
1688 void
1689 maybe_add_key_to_agent(const char *authfile, struct sshkey *private,
1690     const char *comment, const char *passphrase)
1691 {
1692 	int auth_sock = -1, r;
1693 	const char *skprovider = NULL;
1694 
1695 	if (options.add_keys_to_agent == 0)
1696 		return;
1697 
1698 	if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) {
1699 		debug3("no authentication agent, not adding key");
1700 		return;
1701 	}
1702 
1703 	if (options.add_keys_to_agent == 2 &&
1704 	    !ask_permission("Add key %s (%s) to agent?", authfile, comment)) {
1705 		debug3("user denied adding this key");
1706 		close(auth_sock);
1707 		return;
1708 	}
1709 	if (sshkey_is_sk(private))
1710 		skprovider = options.sk_provider;
1711 	if ((r = ssh_add_identity_constrained(auth_sock, private,
1712 	    comment == NULL ? authfile : comment,
1713 	    options.add_keys_to_agent_lifespan,
1714 	    (options.add_keys_to_agent == 3), 0, skprovider)) == 0)
1715 		debug("identity added to agent: %s", authfile);
1716 	else
1717 		debug("could not add identity to agent: %s (%d)", authfile, r);
1718 	close(auth_sock);
1719 }
1720