1 /* $OpenBSD: sshconnect.c,v 1.384 2026/07/06 07:49:58 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/socket.h>
21
22 #include <net/if.h>
23 #include <netinet/in.h>
24 #include <arpa/inet.h>
25
26 #include <errno.h>
27 #include <fcntl.h>
28 #include <limits.h>
29 #include <netdb.h>
30 #include <paths.h>
31 #include <pwd.h>
32 #include <poll.h>
33 #include <signal.h>
34 #include <stdio.h>
35 #include <stdlib.h>
36 #include <stdarg.h>
37 #include <string.h>
38 #include <unistd.h>
39 #include <ifaddrs.h>
40
41 #include "xmalloc.h"
42 #include "hostfile.h"
43 #include "ssh.h"
44 #include "compat.h"
45 #include "packet.h"
46 #include "sshkey.h"
47 #include "sshconnect.h"
48 #include "log.h"
49 #include "match.h"
50 #include "misc.h"
51 #include "readconf.h"
52 #include "dns.h"
53 #include "monitor_fdpass.h"
54 #include "authfile.h"
55 #include "ssherr.h"
56 #include "authfd.h"
57 #include "kex.h"
58
59 struct sshkey *previous_host_key = NULL;
60
61 static int matching_host_key_dns = 0;
62
63 static pid_t proxy_command_pid = 0;
64
65 /* import */
66 extern int debug_flag;
67 extern Options options;
68 extern char *__progname;
69
70 static int show_other_keys(struct hostkeys *, struct sshkey *);
71 static void warn_changed_key(struct sshkey *);
72
73 void
ssh_conn_info_free(struct ssh_conn_info * cinfo)74 ssh_conn_info_free(struct ssh_conn_info *cinfo)
75 {
76 if (cinfo == NULL)
77 return;
78 free(cinfo->conn_hash_hex);
79 free(cinfo->shorthost);
80 free(cinfo->uidstr);
81 free(cinfo->keyalias);
82 free(cinfo->thishost);
83 free(cinfo->host_arg);
84 free(cinfo->portstr);
85 free(cinfo->remhost);
86 free(cinfo->remuser);
87 free(cinfo->homedir);
88 free(cinfo->locuser);
89 free(cinfo->jmphost);
90 freezero(cinfo, sizeof(*cinfo));
91 }
92
93 struct ssh_conn_info *
ssh_conn_info_dup(const struct ssh_conn_info * cinfo)94 ssh_conn_info_dup(const struct ssh_conn_info *cinfo)
95 {
96 struct ssh_conn_info *ret;
97
98 if (cinfo == NULL)
99 return NULL;
100 ret = xcalloc(1, sizeof(*ret));
101 ret->conn_hash_hex = xstrdup(cinfo->conn_hash_hex);
102 ret->shorthost = xstrdup(cinfo->shorthost);
103 ret->uidstr = xstrdup(cinfo->uidstr);
104 ret->keyalias = xstrdup(cinfo->keyalias);
105 ret->thishost = xstrdup(cinfo->thishost);
106 ret->host_arg = xstrdup(cinfo->host_arg);
107 ret->portstr = xstrdup(cinfo->portstr);
108 ret->remhost = xstrdup(cinfo->remhost);
109 ret->remuser = xstrdup(cinfo->remuser);
110 ret->homedir = xstrdup(cinfo->homedir);
111 ret->locuser = xstrdup(cinfo->locuser);
112 ret->jmphost = xstrdup(cinfo->jmphost);
113 return ret;
114 }
115
116 /* Expand a proxy command */
117 static char *
expand_proxy_command(const char * proxy_command,const char * user,const char * host,const char * host_arg,int port)118 expand_proxy_command(const char *proxy_command, const char *user,
119 const char *host, const char *host_arg, int port)
120 {
121 char *tmp, *ret, strport[NI_MAXSERV];
122 const char *keyalias = options.host_key_alias ?
123 options.host_key_alias : host_arg;
124
125 snprintf(strport, sizeof strport, "%d", port);
126 xasprintf(&tmp, "exec %s", proxy_command);
127 ret = percent_expand(tmp,
128 "h", host,
129 "k", keyalias,
130 "n", host_arg,
131 "p", strport,
132 "r", options.user,
133 (char *)NULL);
134 free(tmp);
135 return ret;
136 }
137
138 /*
139 * Connect to the given ssh server using a proxy command that passes a
140 * a connected fd back to us.
141 */
142 static int
ssh_proxy_fdpass_connect(struct ssh * ssh,const char * host,const char * host_arg,u_short port,const char * proxy_command)143 ssh_proxy_fdpass_connect(struct ssh *ssh, const char *host,
144 const char *host_arg, u_short port, const char *proxy_command)
145 {
146 char *command_string;
147 int sp[2], sock;
148 pid_t pid;
149 char *shell;
150
151 if ((shell = getenv("SHELL")) == NULL)
152 shell = _PATH_BSHELL;
153
154 if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) == -1)
155 fatal("Could not create socketpair to communicate with "
156 "proxy dialer: %.100s", strerror(errno));
157
158 command_string = expand_proxy_command(proxy_command, options.user,
159 host, host_arg, port);
160 debug("Executing proxy dialer command: %.500s", command_string);
161
162 /* Fork and execute the proxy command. */
163 if ((pid = fork()) == 0) {
164 char *argv[10];
165
166 close(sp[1]);
167 /* Redirect stdin and stdout. */
168 if (sp[0] != 0) {
169 if (dup2(sp[0], 0) == -1)
170 perror("dup2 stdin");
171 }
172 if (sp[0] != 1) {
173 if (dup2(sp[0], 1) == -1)
174 perror("dup2 stdout");
175 }
176 if (sp[0] >= 2)
177 close(sp[0]);
178
179 /*
180 * Stderr is left for non-ControlPersist connections is so
181 * error messages may be printed on the user's terminal.
182 */
183 if (!debug_flag && options.control_path != NULL &&
184 options.control_persist && stdfd_devnull(0, 0, 1) == -1)
185 error_f("stdfd_devnull failed");
186
187 argv[0] = shell;
188 argv[1] = "-c";
189 argv[2] = command_string;
190 argv[3] = NULL;
191
192 /*
193 * Execute the proxy command.
194 * Note that we gave up any extra privileges above.
195 */
196 execv(argv[0], argv);
197 perror(argv[0]);
198 exit(1);
199 }
200 /* Parent. */
201 if (pid == -1)
202 fatal("fork failed: %.100s", strerror(errno));
203 close(sp[0]);
204 free(command_string);
205
206 if ((sock = mm_receive_fd(sp[1])) == -1)
207 fatal("proxy dialer did not pass back a connection");
208 close(sp[1]);
209
210 while (waitpid(pid, NULL, 0) == -1)
211 if (errno != EINTR)
212 fatal("Couldn't wait for child: %s", strerror(errno));
213
214 /* Set the connection file descriptors. */
215 if (ssh_packet_set_connection(ssh, sock, sock) == NULL)
216 return -1; /* ssh_packet_set_connection logs error */
217
218 return 0;
219 }
220
221 /*
222 * Connect to the given ssh server using a proxy command.
223 */
224 static int
ssh_proxy_connect(struct ssh * ssh,const char * host,const char * host_arg,u_short port,const char * proxy_command)225 ssh_proxy_connect(struct ssh *ssh, const char *host, const char *host_arg,
226 u_short port, const char *proxy_command)
227 {
228 char *command_string;
229 int pin[2], pout[2];
230 pid_t pid;
231 char *shell;
232
233 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
234 shell = _PATH_BSHELL;
235
236 /* Create pipes for communicating with the proxy. */
237 if (pipe(pin) == -1 || pipe(pout) == -1)
238 fatal("Could not create pipes to communicate with the proxy: %.100s",
239 strerror(errno));
240
241 command_string = expand_proxy_command(proxy_command, options.user,
242 host, host_arg, port);
243 debug("Executing proxy command: %.500s", command_string);
244
245 /* Fork and execute the proxy command. */
246 if ((pid = fork()) == 0) {
247 char *argv[10];
248
249 /* Redirect stdin and stdout. */
250 close(pin[1]);
251 if (pin[0] != 0) {
252 if (dup2(pin[0], 0) == -1)
253 perror("dup2 stdin");
254 close(pin[0]);
255 }
256 close(pout[0]);
257 if (dup2(pout[1], 1) == -1)
258 perror("dup2 stdout");
259 /* Cannot be 1 because pin allocated two descriptors. */
260 close(pout[1]);
261
262 /*
263 * Stderr is left for non-ControlPersist connections is so
264 * error messages may be printed on the user's terminal.
265 */
266 if (!debug_flag && options.control_path != NULL &&
267 options.control_persist && stdfd_devnull(0, 0, 1) == -1)
268 error_f("stdfd_devnull failed");
269
270 argv[0] = shell;
271 argv[1] = "-c";
272 argv[2] = command_string;
273 argv[3] = NULL;
274
275 /*
276 * Execute the proxy command. Note that we gave up any
277 * extra privileges above.
278 */
279 ssh_signal(SIGPIPE, SIG_DFL);
280 execv(argv[0], argv);
281 perror(argv[0]);
282 exit(1);
283 }
284 /* Parent. */
285 if (pid == -1)
286 fatal("fork failed: %.100s", strerror(errno));
287 else
288 proxy_command_pid = pid; /* save pid to clean up later */
289
290 /* Close child side of the descriptors. */
291 close(pin[0]);
292 close(pout[1]);
293
294 /* Free the command name. */
295 free(command_string);
296
297 /* Set the connection file descriptors. */
298 if (ssh_packet_set_connection(ssh, pout[0], pin[1]) == NULL)
299 return -1; /* ssh_packet_set_connection logs error */
300
301 return 0;
302 }
303
304 void
ssh_kill_proxy_command(void)305 ssh_kill_proxy_command(void)
306 {
307 /*
308 * Send SIGHUP to proxy command if used. We don't wait() in
309 * case it hangs and instead rely on init to reap the child
310 */
311 if (proxy_command_pid > 1)
312 kill(proxy_command_pid, SIGHUP);
313 }
314
315 #ifdef HAVE_IFADDRS_H
316 /*
317 * Search a interface address list (returned from getifaddrs(3)) for an
318 * address that matches the desired address family on the specified interface.
319 * Returns 0 and fills in *resultp and *rlenp on success. Returns -1 on failure.
320 */
321 static int
check_ifaddrs(const char * ifname,int af,const struct ifaddrs * ifaddrs,struct sockaddr_storage * resultp,socklen_t * rlenp)322 check_ifaddrs(const char *ifname, int af, const struct ifaddrs *ifaddrs,
323 struct sockaddr_storage *resultp, socklen_t *rlenp)
324 {
325 struct sockaddr_in6 *sa6;
326 struct sockaddr_in *sa;
327 struct in6_addr *v6addr;
328 const struct ifaddrs *ifa;
329 int allow_local;
330
331 /*
332 * Prefer addresses that are not loopback or linklocal, but use them
333 * if nothing else matches.
334 */
335 for (allow_local = 0; allow_local < 2; allow_local++) {
336 for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) {
337 if (ifa->ifa_addr == NULL || ifa->ifa_name == NULL ||
338 (ifa->ifa_flags & IFF_UP) == 0 ||
339 ifa->ifa_addr->sa_family != af ||
340 strcmp(ifa->ifa_name, options.bind_interface) != 0)
341 continue;
342 switch (ifa->ifa_addr->sa_family) {
343 case AF_INET:
344 sa = (struct sockaddr_in *)ifa->ifa_addr;
345 if (!allow_local && sa->sin_addr.s_addr ==
346 htonl(INADDR_LOOPBACK))
347 continue;
348 if (*rlenp < sizeof(struct sockaddr_in)) {
349 error_f("v4 addr doesn't fit");
350 return -1;
351 }
352 *rlenp = sizeof(struct sockaddr_in);
353 memcpy(resultp, sa, *rlenp);
354 return 0;
355 case AF_INET6:
356 sa6 = (struct sockaddr_in6 *)ifa->ifa_addr;
357 v6addr = &sa6->sin6_addr;
358 if (!allow_local &&
359 (IN6_IS_ADDR_LINKLOCAL(v6addr) ||
360 IN6_IS_ADDR_LOOPBACK(v6addr)))
361 continue;
362 if (*rlenp < sizeof(struct sockaddr_in6)) {
363 error_f("v6 addr doesn't fit");
364 return -1;
365 }
366 *rlenp = sizeof(struct sockaddr_in6);
367 memcpy(resultp, sa6, *rlenp);
368 return 0;
369 }
370 }
371 }
372 return -1;
373 }
374 #endif
375
376 /*
377 * Creates a socket for use as the ssh connection.
378 */
379 static int
ssh_create_socket(struct addrinfo * ai)380 ssh_create_socket(struct addrinfo *ai)
381 {
382 int sock, r;
383 struct sockaddr_storage bindaddr;
384 socklen_t bindaddrlen = 0;
385 struct addrinfo hints, *res = NULL;
386 #ifdef HAVE_IFADDRS_H
387 struct ifaddrs *ifaddrs = NULL;
388 #endif
389 char ntop[NI_MAXHOST];
390
391 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
392 if (sock == -1) {
393 error("socket: %s", strerror(errno));
394 return -1;
395 }
396 (void)fcntl(sock, F_SETFD, FD_CLOEXEC);
397
398 /* Use interactive QOS (if specified) until authentication completed */
399 if (options.ip_qos_interactive != INT_MAX)
400 set_sock_tos(sock, options.ip_qos_interactive);
401
402 /* Bind the socket to an alternative local IP address */
403 if (options.bind_address == NULL && options.bind_interface == NULL)
404 return sock;
405
406 if (options.bind_address != NULL) {
407 memset(&hints, 0, sizeof(hints));
408 hints.ai_family = ai->ai_family;
409 hints.ai_socktype = ai->ai_socktype;
410 hints.ai_protocol = ai->ai_protocol;
411 hints.ai_flags = AI_PASSIVE;
412 if ((r = getaddrinfo(options.bind_address, NULL,
413 &hints, &res)) != 0) {
414 error("getaddrinfo: %s: %s", options.bind_address,
415 ssh_gai_strerror(r));
416 goto fail;
417 }
418 if (res == NULL) {
419 error("getaddrinfo: no addrs");
420 goto fail;
421 }
422 memcpy(&bindaddr, res->ai_addr, res->ai_addrlen);
423 bindaddrlen = res->ai_addrlen;
424 } else if (options.bind_interface != NULL) {
425 #ifdef HAVE_IFADDRS_H
426 if ((r = getifaddrs(&ifaddrs)) != 0) {
427 error("getifaddrs: %s: %s", options.bind_interface,
428 strerror(errno));
429 goto fail;
430 }
431 bindaddrlen = sizeof(bindaddr);
432 if (check_ifaddrs(options.bind_interface, ai->ai_family,
433 ifaddrs, &bindaddr, &bindaddrlen) != 0) {
434 logit("getifaddrs: %s: no suitable addresses",
435 options.bind_interface);
436 goto fail;
437 }
438 #else
439 error("BindInterface not supported on this platform.");
440 #endif
441 }
442 if ((r = getnameinfo((struct sockaddr *)&bindaddr, bindaddrlen,
443 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST)) != 0) {
444 error_f("getnameinfo failed: %s", ssh_gai_strerror(r));
445 goto fail;
446 }
447 if (bind(sock, (struct sockaddr *)&bindaddr, bindaddrlen) != 0) {
448 error("bind %s: %s", ntop, strerror(errno));
449 goto fail;
450 }
451 debug_f("bound to %s", ntop);
452 /* success */
453 goto out;
454 fail:
455 close(sock);
456 sock = -1;
457 out:
458 if (res != NULL)
459 freeaddrinfo(res);
460 #ifdef HAVE_IFADDRS_H
461 if (ifaddrs != NULL)
462 freeifaddrs(ifaddrs);
463 #endif
464 return sock;
465 }
466
467 /*
468 * Opens a TCP/IP connection to the remote server on the given host.
469 * The address of the remote host will be returned in hostaddr.
470 * If port is 0, the default port will be used.
471 * Connection_attempts specifies the maximum number of tries (one per
472 * second). If proxy_command is non-NULL, it specifies the command (with %h
473 * and %p substituted for host and port, respectively) to use to contact
474 * the daemon.
475 */
476 static int
ssh_connect_direct(struct ssh * ssh,const char * host,struct addrinfo * aitop,struct sockaddr_storage * hostaddr,u_short port,int connection_attempts,int * timeout_ms,int want_keepalive)477 ssh_connect_direct(struct ssh *ssh, const char *host, struct addrinfo *aitop,
478 struct sockaddr_storage *hostaddr, u_short port, int connection_attempts,
479 int *timeout_ms, int want_keepalive)
480 {
481 int on = 1, saved_timeout_ms = *timeout_ms;
482 int oerrno, sock = -1, attempt;
483 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
484 struct addrinfo *ai;
485
486 debug3_f("entering");
487 memset(ntop, 0, sizeof(ntop));
488 memset(strport, 0, sizeof(strport));
489
490 int inet_supported = feature_present("inet");
491 int inet6_supported = feature_present("inet6");
492 for (attempt = 0; attempt < connection_attempts; attempt++) {
493 if (attempt > 0) {
494 /* Sleep a moment before retrying. */
495 sleep(1);
496 debug("Trying again...");
497 }
498 /*
499 * Loop through addresses for this host, and try each one in
500 * sequence until the connection succeeds.
501 */
502 for (ai = aitop; ai; ai = ai->ai_next) {
503 if (ai->ai_family != AF_INET &&
504 ai->ai_family != AF_INET6) {
505 errno = EAFNOSUPPORT;
506 continue;
507 }
508 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
509 ntop, sizeof(ntop), strport, sizeof(strport),
510 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
511 oerrno = errno;
512 error_f("getnameinfo failed");
513 errno = oerrno;
514 continue;
515 }
516 if ((ai->ai_family == AF_INET && !inet_supported) ||
517 (ai->ai_family == AF_INET6 && !inet6_supported)) {
518 debug2_f("skipping address [%s]:%s: "
519 "unsupported address family", ntop, strport);
520 errno = EAFNOSUPPORT;
521 continue;
522 }
523 if (options.address_family != AF_UNSPEC &&
524 ai->ai_family != options.address_family) {
525 debug2_f("skipping address [%s]:%s: "
526 "wrong address family", ntop, strport);
527 errno = EAFNOSUPPORT;
528 continue;
529 }
530
531 debug("Connecting to %.200s [%.100s] port %s.",
532 host, ntop, strport);
533
534 /* Create a socket for connecting. */
535 sock = ssh_create_socket(ai);
536 if (sock < 0) {
537 /* Any error is already output */
538 errno = 0;
539 continue;
540 }
541
542 *timeout_ms = saved_timeout_ms;
543 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
544 timeout_ms) >= 0) {
545 /* Successful connection. */
546 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
547 break;
548 } else {
549 oerrno = errno;
550 debug("connect to address %s port %s: %s",
551 ntop, strport, strerror(errno));
552 close(sock);
553 sock = -1;
554 errno = oerrno;
555 }
556 }
557 if (sock != -1)
558 break; /* Successful connection. */
559 }
560
561 /* Return failure if we didn't get a successful connection. */
562 if (sock == -1) {
563 error("ssh: connect to host %s port %s: %s",
564 host, strport, errno == 0 ? "failure" : strerror(errno));
565 return -1;
566 }
567
568 debug("Connection established.");
569
570 /* Set SO_KEEPALIVE if requested. */
571 if (want_keepalive &&
572 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
573 sizeof(on)) == -1)
574 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
575
576 /* Set the connection. */
577 if (ssh_packet_set_connection(ssh, sock, sock) == NULL)
578 return -1; /* ssh_packet_set_connection logs error */
579
580 return 0;
581 }
582
583 int
ssh_connect(struct ssh * ssh,const char * host,const char * host_arg,struct addrinfo * addrs,struct sockaddr_storage * hostaddr,u_short port,int connection_attempts,int * timeout_ms,int want_keepalive)584 ssh_connect(struct ssh *ssh, const char *host, const char *host_arg,
585 struct addrinfo *addrs, struct sockaddr_storage *hostaddr, u_short port,
586 int connection_attempts, int *timeout_ms, int want_keepalive)
587 {
588 int in, out;
589
590 if (options.proxy_command == NULL) {
591 return ssh_connect_direct(ssh, host, addrs, hostaddr, port,
592 connection_attempts, timeout_ms, want_keepalive);
593 } else if (strcmp(options.proxy_command, "-") == 0) {
594 if ((in = dup(STDIN_FILENO)) == -1 ||
595 (out = dup(STDOUT_FILENO)) == -1) {
596 if (in >= 0)
597 close(in);
598 error_f("dup() in/out failed");
599 return -1; /* ssh_packet_set_connection logs error */
600 }
601 if ((ssh_packet_set_connection(ssh, in, out)) == NULL)
602 return -1; /* ssh_packet_set_connection logs error */
603 return 0;
604 } else if (options.proxy_use_fdpass) {
605 return ssh_proxy_fdpass_connect(ssh, host, host_arg, port,
606 options.proxy_command);
607 }
608 return ssh_proxy_connect(ssh, host, host_arg, port,
609 options.proxy_command);
610 }
611
612 /* defaults to 'no' */
613 static int
confirm(const char * prompt,const char * fingerprint)614 confirm(const char *prompt, const char *fingerprint)
615 {
616 const char *msg, *again = "Please type 'yes' or 'no': ";
617 const char *again_fp = "Please type 'yes', 'no' or the fingerprint: ";
618 char *p, *cp;
619 int ret = -1;
620
621 if (options.batch_mode)
622 return 0;
623 for (msg = prompt;;msg = fingerprint ? again_fp : again) {
624 cp = p = read_passphrase(msg, RP_ECHO);
625 if (p == NULL)
626 return 0;
627 p += strspn(p, " \t"); /* skip leading whitespace */
628 p[strcspn(p, " \t\n")] = '\0'; /* remove trailing whitespace */
629 if (p[0] == '\0' || strcasecmp(p, "no") == 0)
630 ret = 0;
631 else if (strcasecmp(p, "yes") == 0 || (fingerprint != NULL &&
632 strcmp(p, fingerprint) == 0))
633 ret = 1;
634 free(cp);
635 if (ret != -1)
636 return ret;
637 }
638 }
639
640 static int
sockaddr_is_local(struct sockaddr * hostaddr)641 sockaddr_is_local(struct sockaddr *hostaddr)
642 {
643 switch (hostaddr->sa_family) {
644 case AF_INET:
645 return (ntohl(((struct sockaddr_in *)hostaddr)->
646 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
647 case AF_INET6:
648 return IN6_IS_ADDR_LOOPBACK(
649 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
650 default:
651 return 0;
652 }
653 }
654
655 /*
656 * Prepare the hostname and ip address strings that are used to lookup
657 * host keys in known_hosts files. These may have a port number appended.
658 */
659 void
get_hostfile_hostname_ipaddr(char * hostname,struct sockaddr * hostaddr,u_short port,char ** hostfile_hostname,char ** hostfile_ipaddr)660 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr,
661 u_short port, char **hostfile_hostname, char **hostfile_ipaddr)
662 {
663 char ntop[NI_MAXHOST];
664 socklen_t addrlen;
665
666 switch (hostaddr == NULL ? -1 : hostaddr->sa_family) {
667 case -1:
668 addrlen = 0;
669 break;
670 case AF_INET:
671 addrlen = sizeof(struct sockaddr_in);
672 break;
673 case AF_INET6:
674 addrlen = sizeof(struct sockaddr_in6);
675 break;
676 default:
677 addrlen = sizeof(struct sockaddr);
678 break;
679 }
680
681 /*
682 * We don't have the remote ip-address for connections
683 * using a proxy command
684 */
685 if (hostfile_ipaddr != NULL) {
686 if (options.proxy_command == NULL) {
687 if (getnameinfo(hostaddr, addrlen,
688 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0)
689 fatal_f("getnameinfo failed");
690 *hostfile_ipaddr = put_host_port(ntop, port);
691 } else {
692 *hostfile_ipaddr = xstrdup("<no hostip for proxy "
693 "command>");
694 }
695 }
696
697 /*
698 * Allow the user to record the key under a different name or
699 * differentiate a non-standard port. This is useful for ssh
700 * tunneling over forwarded connections or if you run multiple
701 * sshd's on different ports on the same machine.
702 */
703 if (hostfile_hostname != NULL) {
704 if (options.host_key_alias != NULL) {
705 *hostfile_hostname = xstrdup(options.host_key_alias);
706 debug("using hostkeyalias: %s", *hostfile_hostname);
707 } else {
708 *hostfile_hostname = put_host_port(hostname, port);
709 }
710 }
711 }
712
713 /* returns non-zero if path appears in hostfiles, or 0 if not. */
714 static int
path_in_hostfiles(const char * path,char ** hostfiles,u_int num_hostfiles)715 path_in_hostfiles(const char *path, char **hostfiles, u_int num_hostfiles)
716 {
717 u_int i;
718
719 for (i = 0; i < num_hostfiles; i++) {
720 if (strcmp(path, hostfiles[i]) == 0)
721 return 1;
722 }
723 return 0;
724 }
725
726 struct find_by_key_ctx {
727 const char *host, *ip;
728 const struct sshkey *key;
729 char **names;
730 u_int nnames;
731 };
732
733 /* Try to replace home directory prefix (per $HOME) with a ~/ sequence */
734 static char *
try_tilde_unexpand(const char * path)735 try_tilde_unexpand(const char *path)
736 {
737 char *home, *ret = NULL;
738 size_t l;
739
740 if (*path != '/')
741 return xstrdup(path);
742 if ((home = getenv("HOME")) == NULL || (l = strlen(home)) == 0)
743 return xstrdup(path);
744 if (strncmp(path, home, l) != 0)
745 return xstrdup(path);
746 /*
747 * ensure we have matched on a path boundary: either the $HOME that
748 * we just compared ends with a '/' or the next character of the path
749 * must be a '/'.
750 */
751 if (home[l - 1] != '/' && path[l] != '/')
752 return xstrdup(path);
753 if (path[l] == '/')
754 l++;
755 xasprintf(&ret, "~/%s", path + l);
756 return ret;
757 }
758
759 /*
760 * Returns non-zero if the key is accepted by HostkeyAlgorithms.
761 * Made slightly less trivial by the multiple RSA signature algorithm names.
762 */
763 int
hostkey_accepted_by_hostkeyalgs(const struct sshkey * key)764 hostkey_accepted_by_hostkeyalgs(const struct sshkey *key)
765 {
766 const char *ktype = sshkey_ssh_name(key);
767 const char *hostkeyalgs = options.hostkeyalgorithms;
768
769 if (key->type == KEY_UNSPEC)
770 return 0;
771 if (key->type == KEY_RSA &&
772 (match_pattern_list("rsa-sha2-256", hostkeyalgs, 0) == 1 ||
773 match_pattern_list("rsa-sha2-512", hostkeyalgs, 0) == 1))
774 return 1;
775 if (key->type == KEY_RSA_CERT &&
776 (match_pattern_list("rsa-sha2-512-cert-v01@openssh.com", hostkeyalgs, 0) == 1 ||
777 match_pattern_list("rsa-sha2-256-cert-v01@openssh.com", hostkeyalgs, 0) == 1))
778 return 1;
779 return match_pattern_list(ktype, hostkeyalgs, 0) == 1;
780 }
781
782 static int
hostkeys_find_by_key_cb(struct hostkey_foreach_line * l,void * _ctx)783 hostkeys_find_by_key_cb(struct hostkey_foreach_line *l, void *_ctx)
784 {
785 struct find_by_key_ctx *ctx = (struct find_by_key_ctx *)_ctx;
786 char *path;
787
788 /* we are looking for keys with names that *do not* match */
789 if ((l->match & HKF_MATCH_HOST) != 0)
790 return 0;
791 /* not interested in marker lines */
792 if (l->marker != MRK_NONE)
793 return 0;
794 /* we are only interested in exact key matches */
795 if (l->key == NULL || !sshkey_equal(ctx->key, l->key))
796 return 0;
797 path = try_tilde_unexpand(l->path);
798 debug_f("found matching key in %s:%lu", path, l->linenum);
799 ctx->names = xrecallocarray(ctx->names,
800 ctx->nnames, ctx->nnames + 1, sizeof(*ctx->names));
801 xasprintf(&ctx->names[ctx->nnames], "%s:%lu: %s", path, l->linenum,
802 strncmp(l->hosts, HASH_MAGIC, strlen(HASH_MAGIC)) == 0 ?
803 "[hashed name]" : l->hosts);
804 ctx->nnames++;
805 free(path);
806 return 0;
807 }
808
809 static int
hostkeys_find_by_key_hostfile(const char * file,const char * which,struct find_by_key_ctx * ctx)810 hostkeys_find_by_key_hostfile(const char *file, const char *which,
811 struct find_by_key_ctx *ctx)
812 {
813 int r;
814
815 debug3_f("trying %s hostfile \"%s\"", which, file);
816 if ((r = hostkeys_foreach(file, hostkeys_find_by_key_cb, ctx,
817 ctx->host, ctx->ip, HKF_WANT_PARSE_KEY, 0)) != 0) {
818 if (r == SSH_ERR_SYSTEM_ERROR && errno == ENOENT) {
819 debug_f("hostkeys file %s does not exist", file);
820 return 0;
821 }
822 error_fr(r, "hostkeys_foreach failed for %s", file);
823 return r;
824 }
825 return 0;
826 }
827
828 /*
829 * Find 'key' in known hosts file(s) that do not match host/ip.
830 * Used to display also-known-as information for previously-unseen hostkeys.
831 */
832 static void
hostkeys_find_by_key(const char * host,const char * ip,const struct sshkey * key,char ** user_hostfiles,u_int num_user_hostfiles,char ** system_hostfiles,u_int num_system_hostfiles,char *** names,u_int * nnames)833 hostkeys_find_by_key(const char *host, const char *ip, const struct sshkey *key,
834 char **user_hostfiles, u_int num_user_hostfiles,
835 char **system_hostfiles, u_int num_system_hostfiles,
836 char ***names, u_int *nnames)
837 {
838 struct find_by_key_ctx ctx = {NULL, NULL, NULL, NULL, 0};
839 u_int i;
840
841 *names = NULL;
842 *nnames = 0;
843
844 if (key == NULL || sshkey_is_cert(key))
845 return;
846
847 ctx.host = host;
848 ctx.ip = ip;
849 ctx.key = key;
850
851 for (i = 0; i < num_user_hostfiles; i++) {
852 if (hostkeys_find_by_key_hostfile(user_hostfiles[i],
853 "user", &ctx) != 0)
854 goto fail;
855 }
856 for (i = 0; i < num_system_hostfiles; i++) {
857 if (hostkeys_find_by_key_hostfile(system_hostfiles[i],
858 "system", &ctx) != 0)
859 goto fail;
860 }
861 /* success */
862 *names = ctx.names;
863 *nnames = ctx.nnames;
864 ctx.names = NULL;
865 ctx.nnames = 0;
866 return;
867 fail:
868 for (i = 0; i < ctx.nnames; i++)
869 free(ctx.names[i]);
870 free(ctx.names);
871 }
872
873 #define MAX_OTHER_NAMES 8 /* Maximum number of names to list */
874 static char *
other_hostkeys_message(const char * host,const char * ip,const struct sshkey * key,char ** user_hostfiles,u_int num_user_hostfiles,char ** system_hostfiles,u_int num_system_hostfiles)875 other_hostkeys_message(const char *host, const char *ip,
876 const struct sshkey *key,
877 char **user_hostfiles, u_int num_user_hostfiles,
878 char **system_hostfiles, u_int num_system_hostfiles)
879 {
880 char *ret = NULL, **othernames = NULL;
881 u_int i, n, num_othernames = 0;
882
883 hostkeys_find_by_key(host, ip, key,
884 user_hostfiles, num_user_hostfiles,
885 system_hostfiles, num_system_hostfiles,
886 &othernames, &num_othernames);
887 if (num_othernames == 0)
888 return xstrdup("This key is not known by any other names.");
889
890 xasprintf(&ret, "This host key is known by the following other "
891 "names/addresses:");
892
893 n = num_othernames;
894 if (n > MAX_OTHER_NAMES)
895 n = MAX_OTHER_NAMES;
896 for (i = 0; i < n; i++) {
897 xextendf(&ret, "\n", " %s", othernames[i]);
898 }
899 if (n < num_othernames) {
900 xextendf(&ret, "\n", " (%d additional names omitted)",
901 num_othernames - n);
902 }
903 for (i = 0; i < num_othernames; i++)
904 free(othernames[i]);
905 free(othernames);
906 return ret;
907 }
908
909 void
load_hostkeys_command(struct hostkeys * hostkeys,const char * command_template,const char * invocation,const struct ssh_conn_info * cinfo,const struct sshkey * host_key,const char * hostfile_hostname)910 load_hostkeys_command(struct hostkeys *hostkeys, const char *command_template,
911 const char *invocation, const struct ssh_conn_info *cinfo,
912 const struct sshkey *host_key, const char *hostfile_hostname)
913 {
914 int r, i, ac = 0;
915 char *key_fp = NULL, *keytext = NULL, *tmp;
916 char *command = NULL, *tag = NULL, **av = NULL;
917 FILE *f = NULL;
918 pid_t pid;
919 void (*osigchld)(int);
920
921 xasprintf(&tag, "KnownHostsCommand-%s", invocation);
922
923 if (host_key != NULL) {
924 if ((key_fp = sshkey_fingerprint(host_key,
925 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
926 fatal_f("sshkey_fingerprint failed");
927 if ((r = sshkey_to_base64(host_key, &keytext)) != 0)
928 fatal_fr(r, "sshkey_to_base64 failed");
929 }
930 /*
931 * NB. all returns later this function should go via "out" to
932 * ensure the original SIGCHLD handler is restored properly.
933 */
934 osigchld = ssh_signal(SIGCHLD, SIG_DFL);
935
936 /* Turn the command into an argument vector */
937 if (argv_split(command_template, &ac, &av, 0) != 0) {
938 error("%s \"%s\" contains invalid quotes", tag,
939 command_template);
940 goto out;
941 }
942 if (ac == 0) {
943 error("%s \"%s\" yielded no arguments", tag,
944 command_template);
945 goto out;
946 }
947 for (i = 1; i < ac; i++) {
948 tmp = percent_dollar_expand(av[i],
949 DEFAULT_CLIENT_PERCENT_EXPAND_ARGS(cinfo),
950 "H", hostfile_hostname,
951 "I", invocation,
952 "t", host_key == NULL ? "NONE" : sshkey_ssh_name(host_key),
953 "f", key_fp == NULL ? "NONE" : key_fp,
954 "K", keytext == NULL ? "NONE" : keytext,
955 (char *)NULL);
956 if (tmp == NULL)
957 fatal_f("percent_expand failed");
958 free(av[i]);
959 av[i] = tmp;
960 }
961 /* Prepare a printable command for logs, etc. */
962 command = argv_assemble(ac, av);
963
964 if ((pid = subprocess(tag, command, ac, av, &f,
965 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_UNSAFE_PATH|
966 SSH_SUBPROCESS_PRESERVE_ENV, NULL, NULL, NULL)) == 0)
967 goto out;
968
969 load_hostkeys_file(hostkeys, hostfile_hostname, tag, f, 1);
970
971 if (exited_cleanly(pid, tag, command, 0) != 0)
972 fatal("KnownHostsCommand failed");
973
974 out:
975 if (f != NULL)
976 fclose(f);
977 ssh_signal(SIGCHLD, osigchld);
978 for (i = 0; i < ac; i++)
979 free(av[i]);
980 free(av);
981 free(tag);
982 free(command);
983 free(key_fp);
984 free(keytext);
985 }
986
987 /*
988 * check whether the supplied host key is valid, return -1 if the key
989 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true.
990 */
991 #define RDRW 0
992 #define RDONLY 1
993 #define ROQUIET 2
994 static int
check_host_key(char * hostname,const struct ssh_conn_info * cinfo,struct sockaddr * hostaddr,u_short port,struct sshkey * host_key,int readonly,int clobber_port,char ** user_hostfiles,u_int num_user_hostfiles,char ** system_hostfiles,u_int num_system_hostfiles,const char * hostfile_command)995 check_host_key(char *hostname, const struct ssh_conn_info *cinfo,
996 struct sockaddr *hostaddr, u_short port,
997 struct sshkey *host_key, int readonly, int clobber_port,
998 char **user_hostfiles, u_int num_user_hostfiles,
999 char **system_hostfiles, u_int num_system_hostfiles,
1000 const char *hostfile_command)
1001 {
1002 HostStatus host_status = -1, ip_status = -1;
1003 struct sshkey *raw_key = NULL;
1004 char *ip = NULL, *host = NULL;
1005 char hostline[1000], *hostp, *fp, *ra;
1006 char msg[1024];
1007 const char *type, *fail_reason = NULL;
1008 const struct hostkey_entry *host_found = NULL, *ip_found = NULL;
1009 int len, cancelled_forwarding = 0, confirmed;
1010 int local = sockaddr_is_local(hostaddr);
1011 int r, want_cert = sshkey_is_cert(host_key), host_ip_differ = 0;
1012 int hostkey_trusted = 0; /* Known or explicitly accepted by user */
1013 struct hostkeys *host_hostkeys, *ip_hostkeys;
1014 u_int i;
1015
1016 /*
1017 * Force accepting of the host key for loopback/localhost. The
1018 * problem is that if the home directory is NFS-mounted to multiple
1019 * machines, localhost will refer to a different machine in each of
1020 * them, and the user will get bogus HOST_CHANGED warnings. This
1021 * essentially disables host authentication for localhost; however,
1022 * this is probably not a real problem.
1023 */
1024 if (options.no_host_authentication_for_localhost == 1 && local &&
1025 options.host_key_alias == NULL) {
1026 debug("Forcing accepting of host key for "
1027 "loopback/localhost.");
1028 options.update_hostkeys = 0;
1029 return 0;
1030 }
1031
1032 /*
1033 * Don't ever try to write an invalid name to a known hosts file.
1034 * Note: do this before get_hostfile_hostname_ipaddr() to catch
1035 * '[' or ']' in the name before they are added.
1036 */
1037 if (strcspn(hostname, "@?*#[]|'\'\"\\") != strlen(hostname)) {
1038 debug_f("invalid hostname \"%s\"; will not record: %s",
1039 hostname, fail_reason);
1040 readonly = RDONLY;
1041 }
1042
1043 /*
1044 * Prepare the hostname and address strings used for hostkey lookup.
1045 * In some cases, these will have a port number appended.
1046 */
1047 get_hostfile_hostname_ipaddr(hostname, hostaddr,
1048 clobber_port ? 0 : port, &host, &ip);
1049
1050 /*
1051 * Turn off check_host_ip if the connection is to localhost, via proxy
1052 * command or if we don't have a hostname to compare with
1053 */
1054 if (options.check_host_ip && (local ||
1055 strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
1056 options.check_host_ip = 0;
1057
1058 host_hostkeys = init_hostkeys();
1059 for (i = 0; i < num_user_hostfiles; i++)
1060 load_hostkeys(host_hostkeys, host, user_hostfiles[i], 0);
1061 for (i = 0; i < num_system_hostfiles; i++)
1062 load_hostkeys(host_hostkeys, host, system_hostfiles[i], 0);
1063 if (hostfile_command != NULL && !clobber_port) {
1064 load_hostkeys_command(host_hostkeys, hostfile_command,
1065 "HOSTNAME", cinfo, host_key, host);
1066 }
1067
1068 ip_hostkeys = NULL;
1069 if (!want_cert && options.check_host_ip) {
1070 ip_hostkeys = init_hostkeys();
1071 for (i = 0; i < num_user_hostfiles; i++)
1072 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i], 0);
1073 for (i = 0; i < num_system_hostfiles; i++)
1074 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i], 0);
1075 if (hostfile_command != NULL && !clobber_port) {
1076 load_hostkeys_command(ip_hostkeys, hostfile_command,
1077 "ADDRESS", cinfo, host_key, ip);
1078 }
1079 }
1080
1081 retry:
1082 if (!hostkey_accepted_by_hostkeyalgs(host_key)) {
1083 error("host key %s not permitted by HostkeyAlgorithms",
1084 sshkey_ssh_name(host_key));
1085 goto fail;
1086 }
1087
1088 /* Reload these as they may have changed on cert->key downgrade */
1089 want_cert = sshkey_is_cert(host_key);
1090 type = sshkey_type(host_key);
1091
1092 /*
1093 * Check if the host key is present in the user's list of known
1094 * hosts or in the systemwide list.
1095 */
1096 host_status = check_key_in_hostkeys(host_hostkeys, host_key,
1097 &host_found);
1098
1099 /*
1100 * If there are no hostfiles, or if the hostkey was found via
1101 * KnownHostsCommand, then don't try to touch the disk.
1102 */
1103 if (!readonly && (num_user_hostfiles == 0 ||
1104 (host_found != NULL && host_found->note != 0)))
1105 readonly = RDONLY;
1106
1107 /*
1108 * Also perform check for the ip address, skip the check if we are
1109 * localhost, looking for a certificate, or the hostname was an ip
1110 * address to begin with.
1111 */
1112 if (!want_cert && ip_hostkeys != NULL) {
1113 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key,
1114 &ip_found);
1115 if (host_status == HOST_CHANGED &&
1116 (ip_status != HOST_CHANGED ||
1117 (ip_found != NULL &&
1118 !sshkey_equal(ip_found->key, host_found->key))))
1119 host_ip_differ = 1;
1120 } else
1121 ip_status = host_status;
1122
1123 switch (host_status) {
1124 case HOST_OK:
1125 /* The host is known and the key matches. */
1126 debug("Host '%.200s' is known and matches the %s host %s.",
1127 host, type, want_cert ? "certificate" : "key");
1128 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key",
1129 host_found->file, host_found->line);
1130 if (want_cert) {
1131 if (sshkey_cert_check_host(host_key,
1132 options.host_key_alias == NULL ?
1133 hostname : options.host_key_alias,
1134 options.ca_sign_algorithms, &fail_reason) != 0) {
1135 error("%s", fail_reason);
1136 goto fail;
1137 }
1138 /*
1139 * Do not attempt hostkey update if a certificate was
1140 * successfully matched.
1141 */
1142 if (options.update_hostkeys != 0) {
1143 options.update_hostkeys = 0;
1144 debug3_f("certificate host key in use; "
1145 "disabling UpdateHostkeys");
1146 }
1147 }
1148 /* Turn off UpdateHostkeys if key was in system known_hosts */
1149 if (options.update_hostkeys != 0 &&
1150 (path_in_hostfiles(host_found->file,
1151 system_hostfiles, num_system_hostfiles) ||
1152 (ip_status == HOST_OK && ip_found != NULL &&
1153 path_in_hostfiles(ip_found->file,
1154 system_hostfiles, num_system_hostfiles)))) {
1155 options.update_hostkeys = 0;
1156 debug3_f("host key found in GlobalKnownHostsFile; "
1157 "disabling UpdateHostkeys");
1158 }
1159 if (options.update_hostkeys != 0 && host_found->note) {
1160 options.update_hostkeys = 0;
1161 debug3_f("host key found via KnownHostsCommand; "
1162 "disabling UpdateHostkeys");
1163 }
1164 if (options.check_host_ip && ip_status == HOST_NEW) {
1165 if (readonly || want_cert)
1166 logit("%s host key for IP address "
1167 "'%.128s' not in list of known hosts.",
1168 type, ip);
1169 else if (!add_host_to_hostfile(user_hostfiles[0], ip,
1170 host_key, options.hash_known_hosts))
1171 logit("Failed to add the %s host key for IP "
1172 "address '%.128s' to the list of known "
1173 "hosts (%.500s).", type, ip,
1174 user_hostfiles[0]);
1175 else
1176 logit("Warning: Permanently added the %s host "
1177 "key for IP address '%.128s' to the list "
1178 "of known hosts.", type, ip);
1179 } else if (options.visual_host_key) {
1180 fp = sshkey_fingerprint(host_key,
1181 options.fingerprint_hash, SSH_FP_DEFAULT);
1182 ra = sshkey_fingerprint(host_key,
1183 options.fingerprint_hash, SSH_FP_RANDOMART);
1184 if (fp == NULL || ra == NULL)
1185 fatal_f("sshkey_fingerprint failed");
1186 logit("Host key fingerprint is: %s\n%s", fp, ra);
1187 free(ra);
1188 free(fp);
1189 }
1190 hostkey_trusted = 1;
1191 break;
1192 case HOST_NEW:
1193 if (options.host_key_alias == NULL && port != 0 &&
1194 port != SSH_DEFAULT_PORT && !clobber_port) {
1195 debug("checking without port identifier");
1196 if (check_host_key(hostname, cinfo, hostaddr, 0,
1197 host_key, ROQUIET, 1,
1198 user_hostfiles, num_user_hostfiles,
1199 system_hostfiles, num_system_hostfiles,
1200 hostfile_command) == 0) {
1201 debug("found matching key w/out port");
1202 break;
1203 }
1204 }
1205 if (readonly || want_cert)
1206 goto fail;
1207 /* The host is new. */
1208 if (options.strict_host_key_checking ==
1209 SSH_STRICT_HOSTKEY_YES) {
1210 /*
1211 * User has requested strict host key checking. We
1212 * will not add the host key automatically. The only
1213 * alternative left is to abort.
1214 */
1215 error("No %s host key is known for %.200s and you "
1216 "have requested strict checking.", type, host);
1217 goto fail;
1218 } else if (options.strict_host_key_checking ==
1219 SSH_STRICT_HOSTKEY_ASK) {
1220 char *msg1 = NULL, *msg2 = NULL;
1221
1222 xasprintf(&msg1, "The authenticity of host "
1223 "'%.200s (%s)' can't be established", host, ip);
1224
1225 if (show_other_keys(host_hostkeys, host_key)) {
1226 xextendf(&msg1, "\n", "but keys of different "
1227 "type are already known for this host.");
1228 } else
1229 xextendf(&msg1, "", ".");
1230
1231 fp = sshkey_fingerprint(host_key,
1232 options.fingerprint_hash, SSH_FP_DEFAULT);
1233 ra = sshkey_fingerprint(host_key,
1234 options.fingerprint_hash, SSH_FP_RANDOMART);
1235 if (fp == NULL || ra == NULL)
1236 fatal_f("sshkey_fingerprint failed");
1237 xextendf(&msg1, "\n", "%s key fingerprint is: %s",
1238 type, fp);
1239 if (options.visual_host_key)
1240 xextendf(&msg1, "\n", "%s", ra);
1241 if (options.verify_host_key_dns) {
1242 xextendf(&msg1, "\n",
1243 "%s host key fingerprint found in DNS.",
1244 matching_host_key_dns ?
1245 "Matching" : "No matching");
1246 }
1247 /* msg2 informs for other names matching this key */
1248 if ((msg2 = other_hostkeys_message(host, ip, host_key,
1249 user_hostfiles, num_user_hostfiles,
1250 system_hostfiles, num_system_hostfiles)) != NULL)
1251 xextendf(&msg1, "\n", "%s", msg2);
1252
1253 xextendf(&msg1, "\n",
1254 "Are you sure you want to continue connecting "
1255 "(yes/no/[fingerprint])? ");
1256
1257 confirmed = confirm(msg1, fp);
1258 free(ra);
1259 free(fp);
1260 free(msg1);
1261 free(msg2);
1262 if (!confirmed)
1263 goto fail;
1264 hostkey_trusted = 1; /* user explicitly confirmed */
1265 }
1266 /*
1267 * If in "new" or "off" strict mode, add the key automatically
1268 * to the local known_hosts file.
1269 */
1270 if (options.check_host_ip && ip_status == HOST_NEW) {
1271 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
1272 hostp = hostline;
1273 if (options.hash_known_hosts) {
1274 /* Add hash of host and IP separately */
1275 r = add_host_to_hostfile(user_hostfiles[0],
1276 host, host_key, options.hash_known_hosts) &&
1277 add_host_to_hostfile(user_hostfiles[0], ip,
1278 host_key, options.hash_known_hosts);
1279 } else {
1280 /* Add unhashed "host,ip" */
1281 r = add_host_to_hostfile(user_hostfiles[0],
1282 hostline, host_key,
1283 options.hash_known_hosts);
1284 }
1285 } else {
1286 r = add_host_to_hostfile(user_hostfiles[0], host,
1287 host_key, options.hash_known_hosts);
1288 hostp = host;
1289 }
1290
1291 if (!r)
1292 logit("Failed to add the host to the list of known "
1293 "hosts (%.500s).", user_hostfiles[0]);
1294 else
1295 logit("Warning: Permanently added '%.200s' (%s) to the "
1296 "list of known hosts.", hostp, type);
1297 break;
1298 case HOST_REVOKED:
1299 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1300 error("@ WARNING: REVOKED HOST KEY DETECTED! @");
1301 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1302 error("The %s host key for %s is marked as revoked.", type, host);
1303 error("This could mean that a stolen key is being used to");
1304 error("impersonate this host.");
1305
1306 /*
1307 * If strict host key checking is in use, the user will have
1308 * to edit the key manually and we can only abort.
1309 */
1310 if (options.strict_host_key_checking !=
1311 SSH_STRICT_HOSTKEY_OFF) {
1312 error("%s host key for %.200s was revoked and you have "
1313 "requested strict checking.", type, host);
1314 goto fail;
1315 }
1316 goto continue_unsafe;
1317
1318 case HOST_CHANGED:
1319 if (want_cert) {
1320 /*
1321 * This is only a debug() since it is valid to have
1322 * CAs with wildcard DNS matches that don't match
1323 * all hosts that one might visit.
1324 */
1325 debug("Host certificate authority does not "
1326 "match %s in %s:%lu", CA_MARKER,
1327 host_found->file, host_found->line);
1328 goto fail;
1329 }
1330 if (readonly == ROQUIET)
1331 goto fail;
1332 if (options.check_host_ip && host_ip_differ) {
1333 char *key_msg;
1334 if (ip_status == HOST_NEW)
1335 key_msg = "is unknown";
1336 else if (ip_status == HOST_OK)
1337 key_msg = "is unchanged";
1338 else
1339 key_msg = "has a different value";
1340 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1341 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
1342 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1343 error("The %s host key for %s has changed,", type, host);
1344 error("and the key for the corresponding IP address %s", ip);
1345 error("%s. This could either mean that", key_msg);
1346 error("DNS SPOOFING is happening or the IP address for the host");
1347 error("and its host key have changed at the same time.");
1348 if (ip_status != HOST_NEW)
1349 error("Offending key for IP in %s:%lu",
1350 ip_found->file, ip_found->line);
1351 }
1352 /* The host key has changed. */
1353 warn_changed_key(host_key);
1354 if (num_user_hostfiles > 0 || num_system_hostfiles > 0) {
1355 error("Add correct host key in %.100s to get rid "
1356 "of this message.", num_user_hostfiles > 0 ?
1357 user_hostfiles[0] : system_hostfiles[0]);
1358 }
1359 error("Offending %s key in %s:%lu",
1360 sshkey_type(host_found->key),
1361 host_found->file, host_found->line);
1362
1363 /*
1364 * If strict host key checking is in use, the user will have
1365 * to edit the key manually and we can only abort.
1366 */
1367 if (options.strict_host_key_checking !=
1368 SSH_STRICT_HOSTKEY_OFF) {
1369 error("Host key for %.200s has changed and you have "
1370 "requested strict checking.", host);
1371 goto fail;
1372 }
1373
1374 continue_unsafe:
1375 /*
1376 * If strict host key checking has not been requested, allow
1377 * the connection but without MITM-able authentication or
1378 * forwarding.
1379 */
1380 if (options.password_authentication) {
1381 error("Password authentication is disabled to avoid "
1382 "man-in-the-middle attacks.");
1383 options.password_authentication = 0;
1384 cancelled_forwarding = 1;
1385 }
1386 if (options.kbd_interactive_authentication) {
1387 error("Keyboard-interactive authentication is disabled"
1388 " to avoid man-in-the-middle attacks.");
1389 options.kbd_interactive_authentication = 0;
1390 cancelled_forwarding = 1;
1391 }
1392 if (options.forward_agent) {
1393 error("Agent forwarding is disabled to avoid "
1394 "man-in-the-middle attacks.");
1395 options.forward_agent = 0;
1396 cancelled_forwarding = 1;
1397 }
1398 if (options.forward_x11) {
1399 error("X11 forwarding is disabled to avoid "
1400 "man-in-the-middle attacks.");
1401 options.forward_x11 = 0;
1402 cancelled_forwarding = 1;
1403 }
1404 if (options.num_local_forwards > 0 ||
1405 options.num_remote_forwards > 0) {
1406 error("Port forwarding is disabled to avoid "
1407 "man-in-the-middle attacks.");
1408 options.num_local_forwards =
1409 options.num_remote_forwards = 0;
1410 cancelled_forwarding = 1;
1411 }
1412 if (options.tun_open != SSH_TUNMODE_NO) {
1413 error("Tunnel forwarding is disabled to avoid "
1414 "man-in-the-middle attacks.");
1415 options.tun_open = SSH_TUNMODE_NO;
1416 cancelled_forwarding = 1;
1417 }
1418 if (options.update_hostkeys != 0) {
1419 error("UpdateHostkeys is disabled because the host "
1420 "key is not trusted.");
1421 options.update_hostkeys = 0;
1422 }
1423 if (options.exit_on_forward_failure && cancelled_forwarding)
1424 fatal("Error: forwarding disabled due to host key "
1425 "check failure");
1426
1427 /*
1428 * XXX Should permit the user to change to use the new id.
1429 * This could be done by converting the host key to an
1430 * identifying sentence, tell that the host identifies itself
1431 * by that sentence, and ask the user if they wish to
1432 * accept the authentication.
1433 */
1434 break;
1435 case HOST_FOUND:
1436 fatal("internal error");
1437 break;
1438 }
1439
1440 if (options.check_host_ip && host_status != HOST_CHANGED &&
1441 ip_status == HOST_CHANGED) {
1442 snprintf(msg, sizeof(msg),
1443 "Warning: the %s host key for '%.200s' "
1444 "differs from the key for the IP address '%.128s'"
1445 "\nOffending key for IP in %s:%lu",
1446 type, host, ip, ip_found->file, ip_found->line);
1447 if (host_status == HOST_OK) {
1448 len = strlen(msg);
1449 snprintf(msg + len, sizeof(msg) - len,
1450 "\nMatching host key in %s:%lu",
1451 host_found->file, host_found->line);
1452 }
1453 if (options.strict_host_key_checking ==
1454 SSH_STRICT_HOSTKEY_ASK) {
1455 strlcat(msg, "\nAre you sure you want "
1456 "to continue connecting (yes/no)? ", sizeof(msg));
1457 if (!confirm(msg, NULL))
1458 goto fail;
1459 } else if (options.strict_host_key_checking !=
1460 SSH_STRICT_HOSTKEY_OFF) {
1461 logit("%s", msg);
1462 error("Exiting, you have requested strict checking.");
1463 goto fail;
1464 } else {
1465 logit("%s", msg);
1466 }
1467 }
1468
1469 if (!hostkey_trusted && options.update_hostkeys) {
1470 debug_f("hostkey not known or explicitly trusted: "
1471 "disabling UpdateHostkeys");
1472 options.update_hostkeys = 0;
1473 }
1474
1475 sshkey_free(raw_key);
1476 free(ip);
1477 free(host);
1478 if (host_hostkeys != NULL)
1479 free_hostkeys(host_hostkeys);
1480 if (ip_hostkeys != NULL)
1481 free_hostkeys(ip_hostkeys);
1482 return 0;
1483
1484 fail:
1485 if (want_cert && host_status != HOST_REVOKED) {
1486 /*
1487 * No matching certificate. Downgrade cert to raw key and
1488 * search normally.
1489 */
1490 debug("No matching CA found. Retry with plain key");
1491 if ((r = sshkey_from_private(host_key, &raw_key)) != 0)
1492 fatal_fr(r, "decode key");
1493 if ((r = sshkey_drop_cert(raw_key)) != 0)
1494 fatal_r(r, "Couldn't drop certificate");
1495 host_key = raw_key;
1496 goto retry;
1497 }
1498 sshkey_free(raw_key);
1499 free(ip);
1500 free(host);
1501 if (host_hostkeys != NULL)
1502 free_hostkeys(host_hostkeys);
1503 if (ip_hostkeys != NULL)
1504 free_hostkeys(ip_hostkeys);
1505 return -1;
1506 }
1507
1508 /* returns 0 if key verifies or -1 if key does NOT verify */
1509 int
verify_host_key(char * host,struct sockaddr * hostaddr,struct sshkey * host_key,const struct ssh_conn_info * cinfo)1510 verify_host_key(char *host, struct sockaddr *hostaddr, struct sshkey *host_key,
1511 const struct ssh_conn_info *cinfo)
1512 {
1513 u_int i;
1514 int r = -1, flags = 0;
1515 char valid[64], *fp = NULL, *cafp = NULL;
1516 struct sshkey *plain = NULL;
1517
1518 if ((fp = sshkey_fingerprint(host_key,
1519 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1520 error_fr(r, "fingerprint host key");
1521 r = -1;
1522 goto out;
1523 }
1524
1525 if (sshkey_is_cert(host_key)) {
1526 if ((cafp = sshkey_fingerprint(host_key->cert->signature_key,
1527 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1528 error_fr(r, "fingerprint CA key");
1529 r = -1;
1530 goto out;
1531 }
1532 sshkey_format_cert_validity(host_key->cert,
1533 valid, sizeof(valid));
1534 debug("Server host certificate: %s %s, serial %llu "
1535 "ID \"%s\" CA %s %s valid %s",
1536 sshkey_ssh_name(host_key), fp,
1537 (unsigned long long)host_key->cert->serial,
1538 host_key->cert->key_id,
1539 sshkey_ssh_name(host_key->cert->signature_key), cafp,
1540 valid);
1541 for (i = 0; i < host_key->cert->nprincipals; i++) {
1542 debug2("Server host certificate hostname: %s",
1543 host_key->cert->principals[i]);
1544 }
1545 } else {
1546 debug("Server host key: %s %s", sshkey_ssh_name(host_key), fp);
1547 }
1548
1549 if (sshkey_equal(previous_host_key, host_key)) {
1550 debug2_f("server host key %s %s matches cached key",
1551 sshkey_type(host_key), fp);
1552 r = 0;
1553 goto out;
1554 }
1555
1556 /* Check in RevokedHostKeys files if specified */
1557 for (i = 0; i < options.num_revoked_host_keys; i++) {
1558 r = sshkey_check_revoked(host_key,
1559 options.revoked_host_keys[i]);
1560 switch (r) {
1561 case 0:
1562 break; /* not revoked */
1563 case SSH_ERR_KEY_REVOKED:
1564 error("Host key %s %s revoked by file %s",
1565 sshkey_type(host_key), fp,
1566 options.revoked_host_keys[i]);
1567 r = -1;
1568 goto out;
1569 default:
1570 error_r(r, "Error checking host key %s %s in "
1571 "revoked keys file %s", sshkey_type(host_key),
1572 fp, options.revoked_host_keys[i]);
1573 r = -1;
1574 goto out;
1575 }
1576 }
1577
1578 if (options.verify_host_key_dns) {
1579 /*
1580 * XXX certs are not yet supported for DNS, so downgrade
1581 * them and try the plain key.
1582 */
1583 if ((r = sshkey_from_private(host_key, &plain)) != 0)
1584 goto out;
1585 if (sshkey_is_cert(plain))
1586 sshkey_drop_cert(plain);
1587 if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) {
1588 if (flags & DNS_VERIFY_FOUND) {
1589 if (options.verify_host_key_dns == 1 &&
1590 flags & DNS_VERIFY_MATCH &&
1591 flags & DNS_VERIFY_SECURE) {
1592 r = 0;
1593 goto out;
1594 }
1595 if (flags & DNS_VERIFY_MATCH) {
1596 matching_host_key_dns = 1;
1597 } else {
1598 warn_changed_key(plain);
1599 error("Update the SSHFP RR in DNS "
1600 "with the new host key to get rid "
1601 "of this message.");
1602 }
1603 }
1604 }
1605 }
1606 r = check_host_key(host, cinfo, hostaddr, options.port, host_key,
1607 RDRW, 0, options.user_hostfiles, options.num_user_hostfiles,
1608 options.system_hostfiles, options.num_system_hostfiles,
1609 options.known_hosts_command);
1610
1611 out:
1612 sshkey_free(plain);
1613 free(fp);
1614 free(cafp);
1615 if (r == 0 && host_key != NULL) {
1616 sshkey_free(previous_host_key);
1617 r = sshkey_from_private(host_key, &previous_host_key);
1618 }
1619
1620 return r;
1621 }
1622
1623 static void
warn_nonpq_kex(void)1624 warn_nonpq_kex(void)
1625 {
1626 logit("** WARNING: connection is not using a post-quantum key exchange algorithm.");
1627 logit("** This session may be vulnerable to \"store now, decrypt later\" attacks.");
1628 logit("** The server may need to be upgraded. See https://openssh.com/pq.html");
1629 }
1630
1631 /*
1632 * Starts a dialog with the server, and authenticates the current user on the
1633 * server. This does not need any extra privileges. The basic connection
1634 * to the server must already have been established before this is called.
1635 * If login fails, this function prints an error and never returns.
1636 * This function does not require super-user privileges.
1637 */
1638 void
ssh_login(struct ssh * ssh,Sensitive * sensitive,const char * orighost,struct sockaddr_storage * hostaddr,u_short port,struct passwd * pw,int timeout_ms,const struct ssh_conn_info * cinfo)1639 ssh_login(struct ssh *ssh, Sensitive *sensitive, const char *orighost,
1640 struct sockaddr_storage *hostaddr, u_short port, struct passwd *pw,
1641 int timeout_ms, const struct ssh_conn_info *cinfo)
1642 {
1643 char *host;
1644 char *server_user, *local_user;
1645 int r;
1646
1647 local_user = xstrdup(pw->pw_name);
1648 server_user = options.user ? options.user : local_user;
1649
1650 /* Convert the user-supplied hostname into all lowercase. */
1651 host = xstrdup(orighost);
1652 lowercase(host);
1653
1654 /* Exchange protocol version identification strings with the server. */
1655 if ((r = kex_exchange_identification(ssh, timeout_ms,
1656 options.version_addendum)) != 0)
1657 sshpkt_fatal(ssh, r, "banner exchange");
1658
1659 if ((ssh->compat & SSH_BUG_NOREKEY)) {
1660 logit("Warning: this server does not support rekeying.");
1661 logit("This session will eventually fail");
1662 }
1663
1664 /* Put the connection into non-blocking mode. */
1665 ssh_packet_set_nonblocking(ssh);
1666
1667 /* key exchange */
1668 /* authenticate user */
1669 debug("Authenticating to %s:%d as '%s'", host, port, server_user);
1670 ssh_kex2(ssh, host, hostaddr, port, cinfo);
1671 if (!options.kex_algorithms_set && ssh->kex != NULL &&
1672 ssh->kex->name != NULL && options.warn_weak_crypto &&
1673 !kex_is_pq_from_name(ssh->kex->name))
1674 warn_nonpq_kex();
1675 ssh_userauth2(ssh, local_user, server_user, host, sensitive);
1676 free(local_user);
1677 free(host);
1678 }
1679
1680 /* print all known host keys for a given host, but skip keys of given type */
1681 static int
show_other_keys(struct hostkeys * hostkeys,struct sshkey * key)1682 show_other_keys(struct hostkeys *hostkeys, struct sshkey *key)
1683 {
1684 int type[] = {
1685 KEY_RSA,
1686 KEY_ECDSA,
1687 KEY_ED25519,
1688 KEY_MLDSA44_ED25519,
1689 -1
1690 };
1691 int i, ret = 0;
1692 char *fp, *ra;
1693 const struct hostkey_entry *found;
1694
1695 for (i = 0; type[i] != -1; i++) {
1696 if (type[i] == key->type)
1697 continue;
1698 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i],
1699 -1, &found))
1700 continue;
1701 fp = sshkey_fingerprint(found->key,
1702 options.fingerprint_hash, SSH_FP_DEFAULT);
1703 ra = sshkey_fingerprint(found->key,
1704 options.fingerprint_hash, SSH_FP_RANDOMART);
1705 if (fp == NULL || ra == NULL)
1706 fatal_f("sshkey_fingerprint fail");
1707 logit("WARNING: %s key found for host %s\n"
1708 "in %s:%lu\n"
1709 "%s key fingerprint %s.",
1710 sshkey_type(found->key),
1711 found->host, found->file, found->line,
1712 sshkey_type(found->key), fp);
1713 if (options.visual_host_key)
1714 logit("%s", ra);
1715 free(ra);
1716 free(fp);
1717 ret = 1;
1718 }
1719 return ret;
1720 }
1721
1722 static void
warn_changed_key(struct sshkey * host_key)1723 warn_changed_key(struct sshkey *host_key)
1724 {
1725 char *fp;
1726
1727 fp = sshkey_fingerprint(host_key, options.fingerprint_hash,
1728 SSH_FP_DEFAULT);
1729 if (fp == NULL)
1730 fatal_f("sshkey_fingerprint fail");
1731
1732 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1733 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1734 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1735 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1736 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1737 error("It is also possible that a host key has just been changed.");
1738 error("The fingerprint for the %s key sent by the remote host is\n%s.",
1739 sshkey_type(host_key), fp);
1740 error("Please contact your system administrator.");
1741
1742 free(fp);
1743 }
1744
1745 /*
1746 * Execute a local command
1747 */
1748 int
ssh_local_cmd(const char * args)1749 ssh_local_cmd(const char *args)
1750 {
1751 char *shell;
1752 pid_t pid;
1753 int status;
1754 void (*osighand)(int);
1755
1756 if (!options.permit_local_command ||
1757 args == NULL || !*args)
1758 return (1);
1759
1760 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
1761 shell = _PATH_BSHELL;
1762
1763 osighand = ssh_signal(SIGCHLD, SIG_DFL);
1764 pid = fork();
1765 if (pid == 0) {
1766 ssh_signal(SIGPIPE, SIG_DFL);
1767 debug3("Executing %s -c \"%s\"", shell, args);
1768 execl(shell, shell, "-c", args, (char *)NULL);
1769 error("Couldn't execute %s -c \"%s\": %s",
1770 shell, args, strerror(errno));
1771 _exit(1);
1772 } else if (pid == -1)
1773 fatal("fork failed: %.100s", strerror(errno));
1774 while (waitpid(pid, &status, 0) == -1)
1775 if (errno != EINTR)
1776 fatal("Couldn't wait for child: %s", strerror(errno));
1777 ssh_signal(SIGCHLD, osighand);
1778
1779 if (!WIFEXITED(status))
1780 return (1);
1781
1782 return (WEXITSTATUS(status));
1783 }
1784
1785 void
maybe_add_key_to_agent(const char * authfile,struct sshkey * private,const char * comment,const char * passphrase)1786 maybe_add_key_to_agent(const char *authfile, struct sshkey *private,
1787 const char *comment, const char *passphrase)
1788 {
1789 int auth_sock = -1, r;
1790 const char *skprovider = NULL;
1791
1792 if (options.add_keys_to_agent == 0)
1793 return;
1794
1795 if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) {
1796 debug3("no authentication agent, not adding key");
1797 return;
1798 }
1799
1800 if (options.add_keys_to_agent == 2 &&
1801 !ask_permission("Add key %s (%s) to agent?", authfile, comment)) {
1802 debug3("user denied adding this key");
1803 close(auth_sock);
1804 return;
1805 }
1806 if (sshkey_is_sk(private))
1807 skprovider = options.sk_provider;
1808 if ((r = ssh_add_identity_constrained(auth_sock, private,
1809 comment == NULL ? authfile : comment,
1810 options.add_keys_to_agent_lifespan,
1811 (options.add_keys_to_agent == 3), skprovider, NULL, 0)) == 0)
1812 debug("identity added to agent: %s", authfile);
1813 else
1814 debug("could not add identity to agent: %s (%d)", authfile, r);
1815 close(auth_sock);
1816 }
1817