xref: /openssh-portable/sshconnect.c (revision cffd0338)
1 /* $OpenBSD: sshconnect.c,v 1.351 2021/03/03 21:40:16 sthen 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 	} else if (options.bind_interface != NULL) {
394 #ifdef HAVE_IFADDRS_H
395 		if ((r = getifaddrs(&ifaddrs)) != 0) {
396 			error("getifaddrs: %s: %s", options.bind_interface,
397 			      strerror(errno));
398 			goto fail;
399 		}
400 		bindaddrlen = sizeof(bindaddr);
401 		if (check_ifaddrs(options.bind_interface, ai->ai_family,
402 		    ifaddrs, &bindaddr, &bindaddrlen) != 0) {
403 			logit("getifaddrs: %s: no suitable addresses",
404 			      options.bind_interface);
405 			goto fail;
406 		}
407 #else
408 		error("BindInterface not supported on this platform.");
409 #endif
410 	}
411 	if ((r = getnameinfo((struct sockaddr *)&bindaddr, bindaddrlen,
412 	    ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST)) != 0) {
413 		error_f("getnameinfo failed: %s", ssh_gai_strerror(r));
414 		goto fail;
415 	}
416 	if (bind(sock, (struct sockaddr *)&bindaddr, bindaddrlen) != 0) {
417 		error("bind %s: %s", ntop, strerror(errno));
418 		goto fail;
419 	}
420 	debug_f("bound to %s", ntop);
421 	/* success */
422 	goto out;
423 fail:
424 	close(sock);
425 	sock = -1;
426  out:
427 	if (res != NULL)
428 		freeaddrinfo(res);
429 #ifdef HAVE_IFADDRS_H
430 	if (ifaddrs != NULL)
431 		freeifaddrs(ifaddrs);
432 #endif
433 	return sock;
434 }
435 
436 /*
437  * Opens a TCP/IP connection to the remote server on the given host.
438  * The address of the remote host will be returned in hostaddr.
439  * If port is 0, the default port will be used.
440  * Connection_attempts specifies the maximum number of tries (one per
441  * second).  If proxy_command is non-NULL, it specifies the command (with %h
442  * and %p substituted for host and port, respectively) to use to contact
443  * the daemon.
444  */
445 static int
446 ssh_connect_direct(struct ssh *ssh, const char *host, struct addrinfo *aitop,
447     struct sockaddr_storage *hostaddr, u_short port, int connection_attempts,
448     int *timeout_ms, int want_keepalive)
449 {
450 	int on = 1, saved_timeout_ms = *timeout_ms;
451 	int oerrno, sock = -1, attempt;
452 	char ntop[NI_MAXHOST], strport[NI_MAXSERV];
453 	struct addrinfo *ai;
454 
455 	debug3_f("entering");
456 	memset(ntop, 0, sizeof(ntop));
457 	memset(strport, 0, sizeof(strport));
458 
459 	for (attempt = 0; attempt < connection_attempts; attempt++) {
460 		if (attempt > 0) {
461 			/* Sleep a moment before retrying. */
462 			sleep(1);
463 			debug("Trying again...");
464 		}
465 		/*
466 		 * Loop through addresses for this host, and try each one in
467 		 * sequence until the connection succeeds.
468 		 */
469 		for (ai = aitop; ai; ai = ai->ai_next) {
470 			if (ai->ai_family != AF_INET &&
471 			    ai->ai_family != AF_INET6) {
472 				errno = EAFNOSUPPORT;
473 				continue;
474 			}
475 			if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
476 			    ntop, sizeof(ntop), strport, sizeof(strport),
477 			    NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
478 				oerrno = errno;
479 				error_f("getnameinfo failed");
480 				errno = oerrno;
481 				continue;
482 			}
483 			debug("Connecting to %.200s [%.100s] port %s.",
484 				host, ntop, strport);
485 
486 			/* Create a socket for connecting. */
487 			sock = ssh_create_socket(ai);
488 			if (sock < 0) {
489 				/* Any error is already output */
490 				errno = 0;
491 				continue;
492 			}
493 
494 			*timeout_ms = saved_timeout_ms;
495 			if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
496 			    timeout_ms) >= 0) {
497 				/* Successful connection. */
498 				memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
499 				break;
500 			} else {
501 				oerrno = errno;
502 				debug("connect to address %s port %s: %s",
503 				    ntop, strport, strerror(errno));
504 				close(sock);
505 				sock = -1;
506 				errno = oerrno;
507 			}
508 		}
509 		if (sock != -1)
510 			break;	/* Successful connection. */
511 	}
512 
513 	/* Return failure if we didn't get a successful connection. */
514 	if (sock == -1) {
515 		error("ssh: connect to host %s port %s: %s",
516 		    host, strport, errno == 0 ? "failure" : strerror(errno));
517 		return -1;
518 	}
519 
520 	debug("Connection established.");
521 
522 	/* Set SO_KEEPALIVE if requested. */
523 	if (want_keepalive &&
524 	    setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
525 	    sizeof(on)) == -1)
526 		error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
527 
528 	/* Set the connection. */
529 	if (ssh_packet_set_connection(ssh, sock, sock) == NULL)
530 		return -1; /* ssh_packet_set_connection logs error */
531 
532 	return 0;
533 }
534 
535 int
536 ssh_connect(struct ssh *ssh, const char *host, const char *host_arg,
537     struct addrinfo *addrs, struct sockaddr_storage *hostaddr, u_short port,
538     int connection_attempts, int *timeout_ms, int want_keepalive)
539 {
540 	int in, out;
541 
542 	if (options.proxy_command == NULL) {
543 		return ssh_connect_direct(ssh, host, addrs, hostaddr, port,
544 		    connection_attempts, timeout_ms, want_keepalive);
545 	} else if (strcmp(options.proxy_command, "-") == 0) {
546 		if ((in = dup(STDIN_FILENO)) == -1 ||
547 		    (out = dup(STDOUT_FILENO)) == -1) {
548 			if (in >= 0)
549 				close(in);
550 			error_f("dup() in/out failed");
551 			return -1; /* ssh_packet_set_connection logs error */
552 		}
553 		if ((ssh_packet_set_connection(ssh, in, out)) == NULL)
554 			return -1; /* ssh_packet_set_connection logs error */
555 		return 0;
556 	} else if (options.proxy_use_fdpass) {
557 		return ssh_proxy_fdpass_connect(ssh, host, host_arg, port,
558 		    options.proxy_command);
559 	}
560 	return ssh_proxy_connect(ssh, host, host_arg, port,
561 	    options.proxy_command);
562 }
563 
564 /* defaults to 'no' */
565 static int
566 confirm(const char *prompt, const char *fingerprint)
567 {
568 	const char *msg, *again = "Please type 'yes' or 'no': ";
569 	const char *again_fp = "Please type 'yes', 'no' or the fingerprint: ";
570 	char *p, *cp;
571 	int ret = -1;
572 
573 	if (options.batch_mode)
574 		return 0;
575 	for (msg = prompt;;msg = fingerprint ? again_fp : again) {
576 		cp = p = read_passphrase(msg, RP_ECHO);
577 		if (p == NULL)
578 			return 0;
579 		p += strspn(p, " \t"); /* skip leading whitespace */
580 		p[strcspn(p, " \t\n")] = '\0'; /* remove trailing whitespace */
581 		if (p[0] == '\0' || strcasecmp(p, "no") == 0)
582 			ret = 0;
583 		else if (strcasecmp(p, "yes") == 0 || (fingerprint != NULL &&
584 		    strcmp(p, fingerprint) == 0))
585 			ret = 1;
586 		free(cp);
587 		if (ret != -1)
588 			return ret;
589 	}
590 }
591 
592 static int
593 sockaddr_is_local(struct sockaddr *hostaddr)
594 {
595 	switch (hostaddr->sa_family) {
596 	case AF_INET:
597 		return (ntohl(((struct sockaddr_in *)hostaddr)->
598 		    sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
599 	case AF_INET6:
600 		return IN6_IS_ADDR_LOOPBACK(
601 		    &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
602 	default:
603 		return 0;
604 	}
605 }
606 
607 /*
608  * Prepare the hostname and ip address strings that are used to lookup
609  * host keys in known_hosts files. These may have a port number appended.
610  */
611 void
612 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr,
613     u_short port, char **hostfile_hostname, char **hostfile_ipaddr)
614 {
615 	char ntop[NI_MAXHOST];
616 	socklen_t addrlen;
617 
618 	switch (hostaddr == NULL ? -1 : hostaddr->sa_family) {
619 	case -1:
620 		addrlen = 0;
621 		break;
622 	case AF_INET:
623 		addrlen = sizeof(struct sockaddr_in);
624 		break;
625 	case AF_INET6:
626 		addrlen = sizeof(struct sockaddr_in6);
627 		break;
628 	default:
629 		addrlen = sizeof(struct sockaddr);
630 		break;
631 	}
632 
633 	/*
634 	 * We don't have the remote ip-address for connections
635 	 * using a proxy command
636 	 */
637 	if (hostfile_ipaddr != NULL) {
638 		if (options.proxy_command == NULL) {
639 			if (getnameinfo(hostaddr, addrlen,
640 			    ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0)
641 			fatal_f("getnameinfo failed");
642 			*hostfile_ipaddr = put_host_port(ntop, port);
643 		} else {
644 			*hostfile_ipaddr = xstrdup("<no hostip for proxy "
645 			    "command>");
646 		}
647 	}
648 
649 	/*
650 	 * Allow the user to record the key under a different name or
651 	 * differentiate a non-standard port.  This is useful for ssh
652 	 * tunneling over forwarded connections or if you run multiple
653 	 * sshd's on different ports on the same machine.
654 	 */
655 	if (hostfile_hostname != NULL) {
656 		if (options.host_key_alias != NULL) {
657 			*hostfile_hostname = xstrdup(options.host_key_alias);
658 			debug("using hostkeyalias: %s", *hostfile_hostname);
659 		} else {
660 			*hostfile_hostname = put_host_port(hostname, port);
661 		}
662 	}
663 }
664 
665 /* returns non-zero if path appears in hostfiles, or 0 if not. */
666 static int
667 path_in_hostfiles(const char *path, char **hostfiles, u_int num_hostfiles)
668 {
669 	u_int i;
670 
671 	for (i = 0; i < num_hostfiles; i++) {
672 		if (strcmp(path, hostfiles[i]) == 0)
673 			return 1;
674 	}
675 	return 0;
676 }
677 
678 struct find_by_key_ctx {
679 	const char *host, *ip;
680 	const struct sshkey *key;
681 	char **names;
682 	u_int nnames;
683 };
684 
685 /* Try to replace home directory prefix (per $HOME) with a ~/ sequence */
686 static char *
687 try_tilde_unexpand(const char *path)
688 {
689 	char *home, *ret = NULL;
690 	size_t l;
691 
692 	if (*path != '/')
693 		return xstrdup(path);
694 	if ((home = getenv("HOME")) == NULL || (l = strlen(home)) == 0)
695 		return xstrdup(path);
696 	if (strncmp(path, home, l) != 0)
697 		return xstrdup(path);
698 	/*
699 	 * ensure we have matched on a path boundary: either the $HOME that
700 	 * we just compared ends with a '/' or the next character of the path
701 	 * must be a '/'.
702 	 */
703 	if (home[l - 1] != '/' && path[l] != '/')
704 		return xstrdup(path);
705 	if (path[l] == '/')
706 		l++;
707 	xasprintf(&ret, "~/%s", path + l);
708 	return ret;
709 }
710 
711 static int
712 hostkeys_find_by_key_cb(struct hostkey_foreach_line *l, void *_ctx)
713 {
714 	struct find_by_key_ctx *ctx = (struct find_by_key_ctx *)_ctx;
715 	char *path;
716 
717 	/* we are looking for keys with names that *do not* match */
718 	if ((l->match & HKF_MATCH_HOST) != 0)
719 		return 0;
720 	/* not interested in marker lines */
721 	if (l->marker != MRK_NONE)
722 		return 0;
723 	/* we are only interested in exact key matches */
724 	if (l->key == NULL || !sshkey_equal(ctx->key, l->key))
725 		return 0;
726 	path = try_tilde_unexpand(l->path);
727 	debug_f("found matching key in %s:%lu", path, l->linenum);
728 	ctx->names = xrecallocarray(ctx->names,
729 	    ctx->nnames, ctx->nnames + 1, sizeof(*ctx->names));
730 	xasprintf(&ctx->names[ctx->nnames], "%s:%lu: %s", path, l->linenum,
731 	    strncmp(l->hosts, HASH_MAGIC, strlen(HASH_MAGIC)) == 0 ?
732 	    "[hashed name]" : l->hosts);
733 	ctx->nnames++;
734 	free(path);
735 	return 0;
736 }
737 
738 static int
739 hostkeys_find_by_key_hostfile(const char *file, const char *which,
740     struct find_by_key_ctx *ctx)
741 {
742 	int r;
743 
744 	debug3_f("trying %s hostfile \"%s\"", which, file);
745 	if ((r = hostkeys_foreach(file, hostkeys_find_by_key_cb, ctx,
746 	    ctx->host, ctx->ip, HKF_WANT_PARSE_KEY, 0)) != 0) {
747 		if (r == SSH_ERR_SYSTEM_ERROR && errno == ENOENT) {
748 			debug_f("hostkeys file %s does not exist", file);
749 			return 0;
750 		}
751 		error_fr(r, "hostkeys_foreach failed for %s", file);
752 		return r;
753 	}
754 	return 0;
755 }
756 
757 /*
758  * Find 'key' in known hosts file(s) that do not match host/ip.
759  * Used to display also-known-as information for previously-unseen hostkeys.
760  */
761 static void
762 hostkeys_find_by_key(const char *host, const char *ip, const struct sshkey *key,
763     char **user_hostfiles, u_int num_user_hostfiles,
764     char **system_hostfiles, u_int num_system_hostfiles,
765     char ***names, u_int *nnames)
766 {
767 	struct find_by_key_ctx ctx = {0, 0, 0, 0, 0};
768 	u_int i;
769 
770 	*names = NULL;
771 	*nnames = 0;
772 
773 	if (key == NULL || sshkey_is_cert(key))
774 		return;
775 
776 	ctx.host = host;
777 	ctx.ip = ip;
778 	ctx.key = key;
779 
780 	for (i = 0; i < num_user_hostfiles; i++) {
781 		if (hostkeys_find_by_key_hostfile(user_hostfiles[i],
782 		    "user", &ctx) != 0)
783 			goto fail;
784 	}
785 	for (i = 0; i < num_system_hostfiles; i++) {
786 		if (hostkeys_find_by_key_hostfile(system_hostfiles[i],
787 		    "system", &ctx) != 0)
788 			goto fail;
789 	}
790 	/* success */
791 	*names = ctx.names;
792 	*nnames = ctx.nnames;
793 	ctx.names = NULL;
794 	ctx.nnames = 0;
795 	return;
796  fail:
797 	for (i = 0; i < ctx.nnames; i++)
798 		free(ctx.names[i]);
799 	free(ctx.names);
800 }
801 
802 #define MAX_OTHER_NAMES	8 /* Maximum number of names to list */
803 static char *
804 other_hostkeys_message(const char *host, const char *ip,
805     const struct sshkey *key,
806     char **user_hostfiles, u_int num_user_hostfiles,
807     char **system_hostfiles, u_int num_system_hostfiles)
808 {
809 	char *ret = NULL, **othernames = NULL;
810 	u_int i, n, num_othernames = 0;
811 
812 	hostkeys_find_by_key(host, ip, key,
813 	    user_hostfiles, num_user_hostfiles,
814 	    system_hostfiles, num_system_hostfiles,
815 	    &othernames, &num_othernames);
816 	if (num_othernames == 0)
817 		return xstrdup("This key is not known by any other names");
818 
819 	xasprintf(&ret, "This host key is known by the following other "
820 	    "names/addresses:");
821 
822 	n = num_othernames;
823 	if (n > MAX_OTHER_NAMES)
824 		n = MAX_OTHER_NAMES;
825 	for (i = 0; i < n; i++) {
826 		xextendf(&ret, "\n", "    %s", othernames[i]);
827 	}
828 	if (n < num_othernames) {
829 		xextendf(&ret, "\n", "    (%d additional names omitted)",
830 		    num_othernames - n);
831 	}
832 	for (i = 0; i < num_othernames; i++)
833 		free(othernames[i]);
834 	free(othernames);
835 	return ret;
836 }
837 
838 void
839 load_hostkeys_command(struct hostkeys *hostkeys, const char *command_template,
840     const char *invocation, const struct ssh_conn_info *cinfo,
841     const struct sshkey *host_key, const char *hostfile_hostname)
842 {
843 	int r, i, ac = 0;
844 	char *key_fp = NULL, *keytext = NULL, *tmp;
845 	char *command = NULL, *tag = NULL, **av = NULL;
846 	FILE *f = NULL;
847 	pid_t pid;
848 	void (*osigchld)(int);
849 
850 	xasprintf(&tag, "KnownHostsCommand-%s", invocation);
851 
852 	if (host_key != NULL) {
853 		if ((key_fp = sshkey_fingerprint(host_key,
854 		    options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
855 			fatal_f("sshkey_fingerprint failed");
856 		if ((r = sshkey_to_base64(host_key, &keytext)) != 0)
857 			fatal_fr(r, "sshkey_to_base64 failed");
858 	}
859 	/*
860 	 * NB. all returns later this function should go via "out" to
861 	 * ensure the original SIGCHLD handler is restored properly.
862 	 */
863 	osigchld = ssh_signal(SIGCHLD, SIG_DFL);
864 
865 	/* Turn the command into an argument vector */
866 	if (argv_split(command_template, &ac, &av) != 0) {
867 		error("%s \"%s\" contains invalid quotes", tag,
868 		   command_template);
869 		goto out;
870 	}
871 	if (ac == 0) {
872 		error("%s \"%s\" yielded no arguments", tag,
873 		    command_template);
874 		goto out;
875 	}
876 	for (i = 1; i < ac; i++) {
877 		tmp = percent_dollar_expand(av[i],
878 		    DEFAULT_CLIENT_PERCENT_EXPAND_ARGS(cinfo),
879 		    "H", hostfile_hostname,
880 		    "I", invocation,
881 		    "t", host_key == NULL ? "NONE" : sshkey_ssh_name(host_key),
882 		    "f", key_fp == NULL ? "NONE" : key_fp,
883 		    "K", keytext == NULL ? "NONE" : keytext,
884 		    (char *)NULL);
885 		if (tmp == NULL)
886 			fatal_f("percent_expand failed");
887 		free(av[i]);
888 		av[i] = tmp;
889 	}
890 	/* Prepare a printable command for logs, etc. */
891 	command = argv_assemble(ac, av);
892 
893 	if ((pid = subprocess(tag, command, ac, av, &f,
894 	    SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_UNSAFE_PATH|
895 	    SSH_SUBPROCESS_PRESERVE_ENV, NULL, NULL, NULL)) == 0)
896 		goto out;
897 
898 	load_hostkeys_file(hostkeys, hostfile_hostname, tag, f, 1);
899 
900 	if (exited_cleanly(pid, tag, command, 0) != 0)
901 		fatal("KnownHostsCommand failed");
902 
903  out:
904 	if (f != NULL)
905 		fclose(f);
906 	ssh_signal(SIGCHLD, osigchld);
907 	for (i = 0; i < ac; i++)
908 		free(av[i]);
909 	free(av);
910 	free(tag);
911 	free(command);
912 	free(key_fp);
913 	free(keytext);
914 }
915 
916 /*
917  * check whether the supplied host key is valid, return -1 if the key
918  * is not valid. user_hostfile[0] will not be updated if 'readonly' is true.
919  */
920 #define RDRW	0
921 #define RDONLY	1
922 #define ROQUIET	2
923 static int
924 check_host_key(char *hostname, const struct ssh_conn_info *cinfo,
925     struct sockaddr *hostaddr, u_short port,
926     struct sshkey *host_key, int readonly, int clobber_port,
927     char **user_hostfiles, u_int num_user_hostfiles,
928     char **system_hostfiles, u_int num_system_hostfiles,
929     const char *hostfile_command)
930 {
931 	HostStatus host_status = -1, ip_status = -1;
932 	struct sshkey *raw_key = NULL;
933 	char *ip = NULL, *host = NULL;
934 	char hostline[1000], *hostp, *fp, *ra;
935 	char msg[1024];
936 	const char *type, *fail_reason;
937 	const struct hostkey_entry *host_found = NULL, *ip_found = NULL;
938 	int len, cancelled_forwarding = 0, confirmed;
939 	int local = sockaddr_is_local(hostaddr);
940 	int r, want_cert = sshkey_is_cert(host_key), host_ip_differ = 0;
941 	int hostkey_trusted = 0; /* Known or explicitly accepted by user */
942 	struct hostkeys *host_hostkeys, *ip_hostkeys;
943 	u_int i;
944 
945 	/*
946 	 * Force accepting of the host key for loopback/localhost. The
947 	 * problem is that if the home directory is NFS-mounted to multiple
948 	 * machines, localhost will refer to a different machine in each of
949 	 * them, and the user will get bogus HOST_CHANGED warnings.  This
950 	 * essentially disables host authentication for localhost; however,
951 	 * this is probably not a real problem.
952 	 */
953 	if (options.no_host_authentication_for_localhost == 1 && local &&
954 	    options.host_key_alias == NULL) {
955 		debug("Forcing accepting of host key for "
956 		    "loopback/localhost.");
957 		options.update_hostkeys = 0;
958 		return 0;
959 	}
960 
961 	/*
962 	 * Prepare the hostname and address strings used for hostkey lookup.
963 	 * In some cases, these will have a port number appended.
964 	 */
965 	get_hostfile_hostname_ipaddr(hostname, hostaddr,
966 	    clobber_port ? 0 : port, &host, &ip);
967 
968 	/*
969 	 * Turn off check_host_ip if the connection is to localhost, via proxy
970 	 * command or if we don't have a hostname to compare with
971 	 */
972 	if (options.check_host_ip && (local ||
973 	    strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
974 		options.check_host_ip = 0;
975 
976 	host_hostkeys = init_hostkeys();
977 	for (i = 0; i < num_user_hostfiles; i++)
978 		load_hostkeys(host_hostkeys, host, user_hostfiles[i], 0);
979 	for (i = 0; i < num_system_hostfiles; i++)
980 		load_hostkeys(host_hostkeys, host, system_hostfiles[i], 0);
981 	if (hostfile_command != NULL && !clobber_port) {
982 		load_hostkeys_command(host_hostkeys, hostfile_command,
983 		    "HOSTNAME", cinfo, host_key, host);
984 	}
985 
986 	ip_hostkeys = NULL;
987 	if (!want_cert && options.check_host_ip) {
988 		ip_hostkeys = init_hostkeys();
989 		for (i = 0; i < num_user_hostfiles; i++)
990 			load_hostkeys(ip_hostkeys, ip, user_hostfiles[i], 0);
991 		for (i = 0; i < num_system_hostfiles; i++)
992 			load_hostkeys(ip_hostkeys, ip, system_hostfiles[i], 0);
993 		if (hostfile_command != NULL && !clobber_port) {
994 			load_hostkeys_command(ip_hostkeys, hostfile_command,
995 			    "ADDRESS", cinfo, host_key, ip);
996 		}
997 	}
998 
999  retry:
1000 	/* Reload these as they may have changed on cert->key downgrade */
1001 	want_cert = sshkey_is_cert(host_key);
1002 	type = sshkey_type(host_key);
1003 
1004 	/*
1005 	 * Check if the host key is present in the user's list of known
1006 	 * hosts or in the systemwide list.
1007 	 */
1008 	host_status = check_key_in_hostkeys(host_hostkeys, host_key,
1009 	    &host_found);
1010 
1011 	/*
1012 	 * If there are no hostfiles, or if the hostkey was found via
1013 	 * KnownHostsCommand, then don't try to touch the disk.
1014 	 */
1015 	if (!readonly && (num_user_hostfiles == 0 ||
1016 	    (host_found != NULL && host_found->note != 0)))
1017 		readonly = RDONLY;
1018 
1019 	/*
1020 	 * Also perform check for the ip address, skip the check if we are
1021 	 * localhost, looking for a certificate, or the hostname was an ip
1022 	 * address to begin with.
1023 	 */
1024 	if (!want_cert && ip_hostkeys != NULL) {
1025 		ip_status = check_key_in_hostkeys(ip_hostkeys, host_key,
1026 		    &ip_found);
1027 		if (host_status == HOST_CHANGED &&
1028 		    (ip_status != HOST_CHANGED ||
1029 		    (ip_found != NULL &&
1030 		    !sshkey_equal(ip_found->key, host_found->key))))
1031 			host_ip_differ = 1;
1032 	} else
1033 		ip_status = host_status;
1034 
1035 	switch (host_status) {
1036 	case HOST_OK:
1037 		/* The host is known and the key matches. */
1038 		debug("Host '%.200s' is known and matches the %s host %s.",
1039 		    host, type, want_cert ? "certificate" : "key");
1040 		debug("Found %s in %s:%lu", want_cert ? "CA key" : "key",
1041 		    host_found->file, host_found->line);
1042 		if (want_cert) {
1043 			if (sshkey_cert_check_host(host_key,
1044 			    options.host_key_alias == NULL ?
1045 			    hostname : options.host_key_alias, 0,
1046 			    options.ca_sign_algorithms, &fail_reason) != 0) {
1047 				error("%s", fail_reason);
1048 				goto fail;
1049 			}
1050 			/*
1051 			 * Do not attempt hostkey update if a certificate was
1052 			 * successfully matched.
1053 			 */
1054 			if (options.update_hostkeys != 0) {
1055 				options.update_hostkeys = 0;
1056 				debug3_f("certificate host key in use; "
1057 				    "disabling UpdateHostkeys");
1058 			}
1059 		}
1060 		/* Turn off UpdateHostkeys if key was in system known_hosts */
1061 		if (options.update_hostkeys != 0 &&
1062 		    (path_in_hostfiles(host_found->file,
1063 		    system_hostfiles, num_system_hostfiles) ||
1064 		    (ip_status == HOST_OK && ip_found != NULL &&
1065 		    path_in_hostfiles(ip_found->file,
1066 		    system_hostfiles, num_system_hostfiles)))) {
1067 			options.update_hostkeys = 0;
1068 			debug3_f("host key found in GlobalKnownHostsFile; "
1069 			    "disabling UpdateHostkeys");
1070 		}
1071 		if (options.update_hostkeys != 0 && host_found->note) {
1072 			options.update_hostkeys = 0;
1073 			debug3_f("host key found via KnownHostsCommand; "
1074 			    "disabling UpdateHostkeys");
1075 		}
1076 		if (options.check_host_ip && ip_status == HOST_NEW) {
1077 			if (readonly || want_cert)
1078 				logit("%s host key for IP address "
1079 				    "'%.128s' not in list of known hosts.",
1080 				    type, ip);
1081 			else if (!add_host_to_hostfile(user_hostfiles[0], ip,
1082 			    host_key, options.hash_known_hosts))
1083 				logit("Failed to add the %s host key for IP "
1084 				    "address '%.128s' to the list of known "
1085 				    "hosts (%.500s).", type, ip,
1086 				    user_hostfiles[0]);
1087 			else
1088 				logit("Warning: Permanently added the %s host "
1089 				    "key for IP address '%.128s' to the list "
1090 				    "of known hosts.", type, ip);
1091 		} else if (options.visual_host_key) {
1092 			fp = sshkey_fingerprint(host_key,
1093 			    options.fingerprint_hash, SSH_FP_DEFAULT);
1094 			ra = sshkey_fingerprint(host_key,
1095 			    options.fingerprint_hash, SSH_FP_RANDOMART);
1096 			if (fp == NULL || ra == NULL)
1097 				fatal_f("sshkey_fingerprint failed");
1098 			logit("Host key fingerprint is %s\n%s", fp, ra);
1099 			free(ra);
1100 			free(fp);
1101 		}
1102 		hostkey_trusted = 1;
1103 		break;
1104 	case HOST_NEW:
1105 		if (options.host_key_alias == NULL && port != 0 &&
1106 		    port != SSH_DEFAULT_PORT && !clobber_port) {
1107 			debug("checking without port identifier");
1108 			if (check_host_key(hostname, cinfo, hostaddr, 0,
1109 			    host_key, ROQUIET, 1,
1110 			    user_hostfiles, num_user_hostfiles,
1111 			    system_hostfiles, num_system_hostfiles,
1112 			    hostfile_command) == 0) {
1113 				debug("found matching key w/out port");
1114 				break;
1115 			}
1116 		}
1117 		if (readonly || want_cert)
1118 			goto fail;
1119 		/* The host is new. */
1120 		if (options.strict_host_key_checking ==
1121 		    SSH_STRICT_HOSTKEY_YES) {
1122 			/*
1123 			 * User has requested strict host key checking.  We
1124 			 * will not add the host key automatically.  The only
1125 			 * alternative left is to abort.
1126 			 */
1127 			error("No %s host key is known for %.200s and you "
1128 			    "have requested strict checking.", type, host);
1129 			goto fail;
1130 		} else if (options.strict_host_key_checking ==
1131 		    SSH_STRICT_HOSTKEY_ASK) {
1132 			char *msg1 = NULL, *msg2 = NULL;
1133 
1134 			xasprintf(&msg1, "The authenticity of host "
1135 			    "'%.200s (%s)' can't be established", host, ip);
1136 
1137 			if (show_other_keys(host_hostkeys, host_key)) {
1138 				xextendf(&msg1, "\n", "but keys of different "
1139 				    "type are already known for this host.");
1140 			} else
1141 				xextendf(&msg1, "", ".");
1142 
1143 			fp = sshkey_fingerprint(host_key,
1144 			    options.fingerprint_hash, SSH_FP_DEFAULT);
1145 			ra = sshkey_fingerprint(host_key,
1146 			    options.fingerprint_hash, SSH_FP_RANDOMART);
1147 			if (fp == NULL || ra == NULL)
1148 				fatal_f("sshkey_fingerprint failed");
1149 			xextendf(&msg1, "\n", "%s key fingerprint is %s.",
1150 			    type, fp);
1151 			if (options.visual_host_key)
1152 				xextendf(&msg1, "\n", "%s", ra);
1153 			if (options.verify_host_key_dns) {
1154 				xextendf(&msg1, "\n",
1155 				    "%s host key fingerprint found in DNS.",
1156 				    matching_host_key_dns ?
1157 				    "Matching" : "No matching");
1158 			}
1159 			/* msg2 informs for other names matching this key */
1160 			if ((msg2 = other_hostkeys_message(host, ip, host_key,
1161 			    user_hostfiles, num_user_hostfiles,
1162 			    system_hostfiles, num_system_hostfiles)) != NULL)
1163 				xextendf(&msg1, "\n", "%s", msg2);
1164 
1165 			xextendf(&msg1, "\n",
1166 			    "Are you sure you want to continue connecting "
1167 			    "(yes/no/[fingerprint])? ");
1168 
1169 			confirmed = confirm(msg1, fp);
1170 			free(ra);
1171 			free(fp);
1172 			free(msg1);
1173 			free(msg2);
1174 			if (!confirmed)
1175 				goto fail;
1176 			hostkey_trusted = 1; /* user explicitly confirmed */
1177 		}
1178 		/*
1179 		 * If in "new" or "off" strict mode, add the key automatically
1180 		 * to the local known_hosts file.
1181 		 */
1182 		if (options.check_host_ip && ip_status == HOST_NEW) {
1183 			snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
1184 			hostp = hostline;
1185 			if (options.hash_known_hosts) {
1186 				/* Add hash of host and IP separately */
1187 				r = add_host_to_hostfile(user_hostfiles[0],
1188 				    host, host_key, options.hash_known_hosts) &&
1189 				    add_host_to_hostfile(user_hostfiles[0], ip,
1190 				    host_key, options.hash_known_hosts);
1191 			} else {
1192 				/* Add unhashed "host,ip" */
1193 				r = add_host_to_hostfile(user_hostfiles[0],
1194 				    hostline, host_key,
1195 				    options.hash_known_hosts);
1196 			}
1197 		} else {
1198 			r = add_host_to_hostfile(user_hostfiles[0], host,
1199 			    host_key, options.hash_known_hosts);
1200 			hostp = host;
1201 		}
1202 
1203 		if (!r)
1204 			logit("Failed to add the host to the list of known "
1205 			    "hosts (%.500s).", user_hostfiles[0]);
1206 		else
1207 			logit("Warning: Permanently added '%.200s' (%s) to the "
1208 			    "list of known hosts.", hostp, type);
1209 		break;
1210 	case HOST_REVOKED:
1211 		error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1212 		error("@       WARNING: REVOKED HOST KEY DETECTED!               @");
1213 		error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1214 		error("The %s host key for %s is marked as revoked.", type, host);
1215 		error("This could mean that a stolen key is being used to");
1216 		error("impersonate this host.");
1217 
1218 		/*
1219 		 * If strict host key checking is in use, the user will have
1220 		 * to edit the key manually and we can only abort.
1221 		 */
1222 		if (options.strict_host_key_checking !=
1223 		    SSH_STRICT_HOSTKEY_OFF) {
1224 			error("%s host key for %.200s was revoked and you have "
1225 			    "requested strict checking.", type, host);
1226 			goto fail;
1227 		}
1228 		goto continue_unsafe;
1229 
1230 	case HOST_CHANGED:
1231 		if (want_cert) {
1232 			/*
1233 			 * This is only a debug() since it is valid to have
1234 			 * CAs with wildcard DNS matches that don't match
1235 			 * all hosts that one might visit.
1236 			 */
1237 			debug("Host certificate authority does not "
1238 			    "match %s in %s:%lu", CA_MARKER,
1239 			    host_found->file, host_found->line);
1240 			goto fail;
1241 		}
1242 		if (readonly == ROQUIET)
1243 			goto fail;
1244 		if (options.check_host_ip && host_ip_differ) {
1245 			char *key_msg;
1246 			if (ip_status == HOST_NEW)
1247 				key_msg = "is unknown";
1248 			else if (ip_status == HOST_OK)
1249 				key_msg = "is unchanged";
1250 			else
1251 				key_msg = "has a different value";
1252 			error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1253 			error("@       WARNING: POSSIBLE DNS SPOOFING DETECTED!          @");
1254 			error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1255 			error("The %s host key for %s has changed,", type, host);
1256 			error("and the key for the corresponding IP address %s", ip);
1257 			error("%s. This could either mean that", key_msg);
1258 			error("DNS SPOOFING is happening or the IP address for the host");
1259 			error("and its host key have changed at the same time.");
1260 			if (ip_status != HOST_NEW)
1261 				error("Offending key for IP in %s:%lu",
1262 				    ip_found->file, ip_found->line);
1263 		}
1264 		/* The host key has changed. */
1265 		warn_changed_key(host_key);
1266 		error("Add correct host key in %.100s to get rid of this message.",
1267 		    user_hostfiles[0]);
1268 		error("Offending %s key in %s:%lu",
1269 		    sshkey_type(host_found->key),
1270 		    host_found->file, host_found->line);
1271 
1272 		/*
1273 		 * If strict host key checking is in use, the user will have
1274 		 * to edit the key manually and we can only abort.
1275 		 */
1276 		if (options.strict_host_key_checking !=
1277 		    SSH_STRICT_HOSTKEY_OFF) {
1278 			error("Host key for %.200s has changed and you have "
1279 			    "requested strict checking.", host);
1280 			goto fail;
1281 		}
1282 
1283  continue_unsafe:
1284 		/*
1285 		 * If strict host key checking has not been requested, allow
1286 		 * the connection but without MITM-able authentication or
1287 		 * forwarding.
1288 		 */
1289 		if (options.password_authentication) {
1290 			error("Password authentication is disabled to avoid "
1291 			    "man-in-the-middle attacks.");
1292 			options.password_authentication = 0;
1293 			cancelled_forwarding = 1;
1294 		}
1295 		if (options.kbd_interactive_authentication) {
1296 			error("Keyboard-interactive authentication is disabled"
1297 			    " to avoid man-in-the-middle attacks.");
1298 			options.kbd_interactive_authentication = 0;
1299 			options.challenge_response_authentication = 0;
1300 			cancelled_forwarding = 1;
1301 		}
1302 		if (options.challenge_response_authentication) {
1303 			error("Challenge/response authentication is disabled"
1304 			    " to avoid man-in-the-middle attacks.");
1305 			options.challenge_response_authentication = 0;
1306 			cancelled_forwarding = 1;
1307 		}
1308 		if (options.forward_agent) {
1309 			error("Agent forwarding is disabled to avoid "
1310 			    "man-in-the-middle attacks.");
1311 			options.forward_agent = 0;
1312 			cancelled_forwarding = 1;
1313 		}
1314 		if (options.forward_x11) {
1315 			error("X11 forwarding is disabled to avoid "
1316 			    "man-in-the-middle attacks.");
1317 			options.forward_x11 = 0;
1318 			cancelled_forwarding = 1;
1319 		}
1320 		if (options.num_local_forwards > 0 ||
1321 		    options.num_remote_forwards > 0) {
1322 			error("Port forwarding is disabled to avoid "
1323 			    "man-in-the-middle attacks.");
1324 			options.num_local_forwards =
1325 			    options.num_remote_forwards = 0;
1326 			cancelled_forwarding = 1;
1327 		}
1328 		if (options.tun_open != SSH_TUNMODE_NO) {
1329 			error("Tunnel forwarding is disabled to avoid "
1330 			    "man-in-the-middle attacks.");
1331 			options.tun_open = SSH_TUNMODE_NO;
1332 			cancelled_forwarding = 1;
1333 		}
1334 		if (options.update_hostkeys != 0) {
1335 			error("UpdateHostkeys is disabled because the host "
1336 			    "key is not trusted.");
1337 			options.update_hostkeys = 0;
1338 		}
1339 		if (options.exit_on_forward_failure && cancelled_forwarding)
1340 			fatal("Error: forwarding disabled due to host key "
1341 			    "check failure");
1342 
1343 		/*
1344 		 * XXX Should permit the user to change to use the new id.
1345 		 * This could be done by converting the host key to an
1346 		 * identifying sentence, tell that the host identifies itself
1347 		 * by that sentence, and ask the user if he/she wishes to
1348 		 * accept the authentication.
1349 		 */
1350 		break;
1351 	case HOST_FOUND:
1352 		fatal("internal error");
1353 		break;
1354 	}
1355 
1356 	if (options.check_host_ip && host_status != HOST_CHANGED &&
1357 	    ip_status == HOST_CHANGED) {
1358 		snprintf(msg, sizeof(msg),
1359 		    "Warning: the %s host key for '%.200s' "
1360 		    "differs from the key for the IP address '%.128s'"
1361 		    "\nOffending key for IP in %s:%lu",
1362 		    type, host, ip, ip_found->file, ip_found->line);
1363 		if (host_status == HOST_OK) {
1364 			len = strlen(msg);
1365 			snprintf(msg + len, sizeof(msg) - len,
1366 			    "\nMatching host key in %s:%lu",
1367 			    host_found->file, host_found->line);
1368 		}
1369 		if (options.strict_host_key_checking ==
1370 		    SSH_STRICT_HOSTKEY_ASK) {
1371 			strlcat(msg, "\nAre you sure you want "
1372 			    "to continue connecting (yes/no)? ", sizeof(msg));
1373 			if (!confirm(msg, NULL))
1374 				goto fail;
1375 		} else if (options.strict_host_key_checking !=
1376 		    SSH_STRICT_HOSTKEY_OFF) {
1377 			logit("%s", msg);
1378 			error("Exiting, you have requested strict checking.");
1379 			goto fail;
1380 		} else {
1381 			logit("%s", msg);
1382 		}
1383 	}
1384 
1385 	if (!hostkey_trusted && options.update_hostkeys) {
1386 		debug_f("hostkey not known or explicitly trusted: "
1387 		    "disabling UpdateHostkeys");
1388 		options.update_hostkeys = 0;
1389 	}
1390 
1391 	free(ip);
1392 	free(host);
1393 	if (host_hostkeys != NULL)
1394 		free_hostkeys(host_hostkeys);
1395 	if (ip_hostkeys != NULL)
1396 		free_hostkeys(ip_hostkeys);
1397 	return 0;
1398 
1399 fail:
1400 	if (want_cert && host_status != HOST_REVOKED) {
1401 		/*
1402 		 * No matching certificate. Downgrade cert to raw key and
1403 		 * search normally.
1404 		 */
1405 		debug("No matching CA found. Retry with plain key");
1406 		if ((r = sshkey_from_private(host_key, &raw_key)) != 0)
1407 			fatal_fr(r, "decode key");
1408 		if ((r = sshkey_drop_cert(raw_key)) != 0)
1409 			fatal_r(r, "Couldn't drop certificate");
1410 		host_key = raw_key;
1411 		goto retry;
1412 	}
1413 	sshkey_free(raw_key);
1414 	free(ip);
1415 	free(host);
1416 	if (host_hostkeys != NULL)
1417 		free_hostkeys(host_hostkeys);
1418 	if (ip_hostkeys != NULL)
1419 		free_hostkeys(ip_hostkeys);
1420 	return -1;
1421 }
1422 
1423 /* returns 0 if key verifies or -1 if key does NOT verify */
1424 int
1425 verify_host_key(char *host, struct sockaddr *hostaddr, struct sshkey *host_key,
1426     const struct ssh_conn_info *cinfo)
1427 {
1428 	u_int i;
1429 	int r = -1, flags = 0;
1430 	char valid[64], *fp = NULL, *cafp = NULL;
1431 	struct sshkey *plain = NULL;
1432 
1433 	if ((fp = sshkey_fingerprint(host_key,
1434 	    options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1435 		error_fr(r, "fingerprint host key");
1436 		r = -1;
1437 		goto out;
1438 	}
1439 
1440 	if (sshkey_is_cert(host_key)) {
1441 		if ((cafp = sshkey_fingerprint(host_key->cert->signature_key,
1442 		    options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1443 			error_fr(r, "fingerprint CA key");
1444 			r = -1;
1445 			goto out;
1446 		}
1447 		sshkey_format_cert_validity(host_key->cert,
1448 		    valid, sizeof(valid));
1449 		debug("Server host certificate: %s %s, serial %llu "
1450 		    "ID \"%s\" CA %s %s valid %s",
1451 		    sshkey_ssh_name(host_key), fp,
1452 		    (unsigned long long)host_key->cert->serial,
1453 		    host_key->cert->key_id,
1454 		    sshkey_ssh_name(host_key->cert->signature_key), cafp,
1455 		    valid);
1456 		for (i = 0; i < host_key->cert->nprincipals; i++) {
1457 			debug2("Server host certificate hostname: %s",
1458 			    host_key->cert->principals[i]);
1459 		}
1460 	} else {
1461 		debug("Server host key: %s %s", sshkey_ssh_name(host_key), fp);
1462 	}
1463 
1464 	if (sshkey_equal(previous_host_key, host_key)) {
1465 		debug2_f("server host key %s %s matches cached key",
1466 		    sshkey_type(host_key), fp);
1467 		r = 0;
1468 		goto out;
1469 	}
1470 
1471 	/* Check in RevokedHostKeys file if specified */
1472 	if (options.revoked_host_keys != NULL) {
1473 		r = sshkey_check_revoked(host_key, options.revoked_host_keys);
1474 		switch (r) {
1475 		case 0:
1476 			break; /* not revoked */
1477 		case SSH_ERR_KEY_REVOKED:
1478 			error("Host key %s %s revoked by file %s",
1479 			    sshkey_type(host_key), fp,
1480 			    options.revoked_host_keys);
1481 			r = -1;
1482 			goto out;
1483 		default:
1484 			error_r(r, "Error checking host key %s %s in "
1485 			    "revoked keys file %s", sshkey_type(host_key),
1486 			    fp, options.revoked_host_keys);
1487 			r = -1;
1488 			goto out;
1489 		}
1490 	}
1491 
1492 	if (options.verify_host_key_dns) {
1493 		/*
1494 		 * XXX certs are not yet supported for DNS, so downgrade
1495 		 * them and try the plain key.
1496 		 */
1497 		if ((r = sshkey_from_private(host_key, &plain)) != 0)
1498 			goto out;
1499 		if (sshkey_is_cert(plain))
1500 			sshkey_drop_cert(plain);
1501 		if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) {
1502 			if (flags & DNS_VERIFY_FOUND) {
1503 				if (options.verify_host_key_dns == 1 &&
1504 				    flags & DNS_VERIFY_MATCH &&
1505 				    flags & DNS_VERIFY_SECURE) {
1506 					r = 0;
1507 					goto out;
1508 				}
1509 				if (flags & DNS_VERIFY_MATCH) {
1510 					matching_host_key_dns = 1;
1511 				} else {
1512 					warn_changed_key(plain);
1513 					error("Update the SSHFP RR in DNS "
1514 					    "with the new host key to get rid "
1515 					    "of this message.");
1516 				}
1517 			}
1518 		}
1519 	}
1520 	r = check_host_key(host, cinfo, hostaddr, options.port, host_key,
1521 	    RDRW, 0, options.user_hostfiles, options.num_user_hostfiles,
1522 	    options.system_hostfiles, options.num_system_hostfiles,
1523 	    options.known_hosts_command);
1524 
1525 out:
1526 	sshkey_free(plain);
1527 	free(fp);
1528 	free(cafp);
1529 	if (r == 0 && host_key != NULL) {
1530 		sshkey_free(previous_host_key);
1531 		r = sshkey_from_private(host_key, &previous_host_key);
1532 	}
1533 
1534 	return r;
1535 }
1536 
1537 /*
1538  * Starts a dialog with the server, and authenticates the current user on the
1539  * server.  This does not need any extra privileges.  The basic connection
1540  * to the server must already have been established before this is called.
1541  * If login fails, this function prints an error and never returns.
1542  * This function does not require super-user privileges.
1543  */
1544 void
1545 ssh_login(struct ssh *ssh, Sensitive *sensitive, const char *orighost,
1546     struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms,
1547     const struct ssh_conn_info *cinfo)
1548 {
1549 	char *host;
1550 	char *server_user, *local_user;
1551 	int r;
1552 
1553 	local_user = xstrdup(pw->pw_name);
1554 	server_user = options.user ? options.user : local_user;
1555 
1556 	/* Convert the user-supplied hostname into all lowercase. */
1557 	host = xstrdup(orighost);
1558 	lowercase(host);
1559 
1560 	/* Exchange protocol version identification strings with the server. */
1561 	if ((r = kex_exchange_identification(ssh, timeout_ms, NULL)) != 0)
1562 		sshpkt_fatal(ssh, r, "banner exchange");
1563 
1564 	/* Put the connection into non-blocking mode. */
1565 	ssh_packet_set_nonblocking(ssh);
1566 
1567 	/* key exchange */
1568 	/* authenticate user */
1569 	debug("Authenticating to %s:%d as '%s'", host, port, server_user);
1570 	ssh_kex2(ssh, host, hostaddr, port, cinfo);
1571 	ssh_userauth2(ssh, local_user, server_user, host, sensitive);
1572 	free(local_user);
1573 	free(host);
1574 }
1575 
1576 /* print all known host keys for a given host, but skip keys of given type */
1577 static int
1578 show_other_keys(struct hostkeys *hostkeys, struct sshkey *key)
1579 {
1580 	int type[] = {
1581 		KEY_RSA,
1582 		KEY_DSA,
1583 		KEY_ECDSA,
1584 		KEY_ED25519,
1585 		KEY_XMSS,
1586 		-1
1587 	};
1588 	int i, ret = 0;
1589 	char *fp, *ra;
1590 	const struct hostkey_entry *found;
1591 
1592 	for (i = 0; type[i] != -1; i++) {
1593 		if (type[i] == key->type)
1594 			continue;
1595 		if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i],
1596 		    -1, &found))
1597 			continue;
1598 		fp = sshkey_fingerprint(found->key,
1599 		    options.fingerprint_hash, SSH_FP_DEFAULT);
1600 		ra = sshkey_fingerprint(found->key,
1601 		    options.fingerprint_hash, SSH_FP_RANDOMART);
1602 		if (fp == NULL || ra == NULL)
1603 			fatal_f("sshkey_fingerprint fail");
1604 		logit("WARNING: %s key found for host %s\n"
1605 		    "in %s:%lu\n"
1606 		    "%s key fingerprint %s.",
1607 		    sshkey_type(found->key),
1608 		    found->host, found->file, found->line,
1609 		    sshkey_type(found->key), fp);
1610 		if (options.visual_host_key)
1611 			logit("%s", ra);
1612 		free(ra);
1613 		free(fp);
1614 		ret = 1;
1615 	}
1616 	return ret;
1617 }
1618 
1619 static void
1620 warn_changed_key(struct sshkey *host_key)
1621 {
1622 	char *fp;
1623 
1624 	fp = sshkey_fingerprint(host_key, options.fingerprint_hash,
1625 	    SSH_FP_DEFAULT);
1626 	if (fp == NULL)
1627 		fatal_f("sshkey_fingerprint fail");
1628 
1629 	error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1630 	error("@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @");
1631 	error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1632 	error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1633 	error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1634 	error("It is also possible that a host key has just been changed.");
1635 	error("The fingerprint for the %s key sent by the remote host is\n%s.",
1636 	    sshkey_type(host_key), fp);
1637 	error("Please contact your system administrator.");
1638 
1639 	free(fp);
1640 }
1641 
1642 /*
1643  * Execute a local command
1644  */
1645 int
1646 ssh_local_cmd(const char *args)
1647 {
1648 	char *shell;
1649 	pid_t pid;
1650 	int status;
1651 	void (*osighand)(int);
1652 
1653 	if (!options.permit_local_command ||
1654 	    args == NULL || !*args)
1655 		return (1);
1656 
1657 	if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
1658 		shell = _PATH_BSHELL;
1659 
1660 	osighand = ssh_signal(SIGCHLD, SIG_DFL);
1661 	pid = fork();
1662 	if (pid == 0) {
1663 		ssh_signal(SIGPIPE, SIG_DFL);
1664 		debug3("Executing %s -c \"%s\"", shell, args);
1665 		execl(shell, shell, "-c", args, (char *)NULL);
1666 		error("Couldn't execute %s -c \"%s\": %s",
1667 		    shell, args, strerror(errno));
1668 		_exit(1);
1669 	} else if (pid == -1)
1670 		fatal("fork failed: %.100s", strerror(errno));
1671 	while (waitpid(pid, &status, 0) == -1)
1672 		if (errno != EINTR)
1673 			fatal("Couldn't wait for child: %s", strerror(errno));
1674 	ssh_signal(SIGCHLD, osighand);
1675 
1676 	if (!WIFEXITED(status))
1677 		return (1);
1678 
1679 	return (WEXITSTATUS(status));
1680 }
1681 
1682 void
1683 maybe_add_key_to_agent(const char *authfile, struct sshkey *private,
1684     const char *comment, const char *passphrase)
1685 {
1686 	int auth_sock = -1, r;
1687 	const char *skprovider = NULL;
1688 
1689 	if (options.add_keys_to_agent == 0)
1690 		return;
1691 
1692 	if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) {
1693 		debug3("no authentication agent, not adding key");
1694 		return;
1695 	}
1696 
1697 	if (options.add_keys_to_agent == 2 &&
1698 	    !ask_permission("Add key %s (%s) to agent?", authfile, comment)) {
1699 		debug3("user denied adding this key");
1700 		close(auth_sock);
1701 		return;
1702 	}
1703 	if (sshkey_is_sk(private))
1704 		skprovider = options.sk_provider;
1705 	if ((r = ssh_add_identity_constrained(auth_sock, private,
1706 	    comment == NULL ? authfile : comment,
1707 	    options.add_keys_to_agent_lifespan,
1708 	    (options.add_keys_to_agent == 3), 0, skprovider)) == 0)
1709 		debug("identity added to agent: %s", authfile);
1710 	else
1711 		debug("could not add identity to agent: %s (%d)", authfile, r);
1712 	close(auth_sock);
1713 }
1714