1 /* $OpenBSD: sshconnect.c,v 1.368 2024/04/30 02:10:49 djm Exp $ */
2 /*
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * All rights reserved
6 * Code to connect to a remote host, and to perform the client side of the
7 * login (authentication) dialog.
8 *
9 * As far as I am concerned, the code I have written for this software
10 * can be used freely for any purpose. Any derived versions of this
11 * software must be clearly marked as such, and if the derived work is
12 * incompatible with the protocol description in the RFC file, it must be
13 * called by a name other than "ssh" or "Secure Shell".
14 */
15
16 #include "includes.h"
17
18 #include <sys/types.h>
19 #include <sys/wait.h>
20 #include <sys/stat.h>
21 #include <sys/socket.h>
22 #ifdef HAVE_SYS_TIME_H
23 # include <sys/time.h>
24 #endif
25
26 #include <net/if.h>
27 #include <netinet/in.h>
28 #include <arpa/inet.h>
29
30 #include <ctype.h>
31 #include <errno.h>
32 #include <fcntl.h>
33 #include <limits.h>
34 #include <netdb.h>
35 #ifdef HAVE_PATHS_H
36 #include <paths.h>
37 #endif
38 #include <pwd.h>
39 #ifdef HAVE_POLL_H
40 #include <poll.h>
41 #endif
42 #include <signal.h>
43 #include <stdio.h>
44 #include <stdlib.h>
45 #include <stdarg.h>
46 #include <string.h>
47 #include <unistd.h>
48 #ifdef HAVE_IFADDRS_H
49 # include <ifaddrs.h>
50 #endif
51
52 #include "xmalloc.h"
53 #include "hostfile.h"
54 #include "ssh.h"
55 #include "sshbuf.h"
56 #include "packet.h"
57 #include "sshkey.h"
58 #include "sshconnect.h"
59 #include "log.h"
60 #include "match.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 *
expand_proxy_command(const char * proxy_command,const char * user,const char * host,const char * host_arg,int port)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
ssh_proxy_fdpass_connect(struct ssh * ssh,const char * host,const char * host_arg,u_short port,const char * proxy_command)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
ssh_proxy_connect(struct ssh * ssh,const char * host,const char * host_arg,u_short port,const char * proxy_command)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 /*
247 * Execute the proxy command. Note that we gave up any
248 * extra privileges above.
249 */
250 ssh_signal(SIGPIPE, SIG_DFL);
251 execv(argv[0], argv);
252 perror(argv[0]);
253 exit(1);
254 }
255 /* Parent. */
256 if (pid == -1)
257 fatal("fork failed: %.100s", strerror(errno));
258 else
259 proxy_command_pid = pid; /* save pid to clean up later */
260
261 /* Close child side of the descriptors. */
262 close(pin[0]);
263 close(pout[1]);
264
265 /* Free the command name. */
266 free(command_string);
267
268 /* Set the connection file descriptors. */
269 if (ssh_packet_set_connection(ssh, pout[0], pin[1]) == NULL)
270 return -1; /* ssh_packet_set_connection logs error */
271
272 return 0;
273 }
274
275 void
ssh_kill_proxy_command(void)276 ssh_kill_proxy_command(void)
277 {
278 /*
279 * Send SIGHUP to proxy command if used. We don't wait() in
280 * case it hangs and instead rely on init to reap the child
281 */
282 if (proxy_command_pid > 1)
283 kill(proxy_command_pid, SIGHUP);
284 }
285
286 #ifdef HAVE_IFADDRS_H
287 /*
288 * Search a interface address list (returned from getifaddrs(3)) for an
289 * address that matches the desired address family on the specified interface.
290 * Returns 0 and fills in *resultp and *rlenp on success. Returns -1 on failure.
291 */
292 static int
check_ifaddrs(const char * ifname,int af,const struct ifaddrs * ifaddrs,struct sockaddr_storage * resultp,socklen_t * rlenp)293 check_ifaddrs(const char *ifname, int af, const struct ifaddrs *ifaddrs,
294 struct sockaddr_storage *resultp, socklen_t *rlenp)
295 {
296 struct sockaddr_in6 *sa6;
297 struct sockaddr_in *sa;
298 struct in6_addr *v6addr;
299 const struct ifaddrs *ifa;
300 int allow_local;
301
302 /*
303 * Prefer addresses that are not loopback or linklocal, but use them
304 * if nothing else matches.
305 */
306 for (allow_local = 0; allow_local < 2; allow_local++) {
307 for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) {
308 if (ifa->ifa_addr == NULL || ifa->ifa_name == NULL ||
309 (ifa->ifa_flags & IFF_UP) == 0 ||
310 ifa->ifa_addr->sa_family != af ||
311 strcmp(ifa->ifa_name, options.bind_interface) != 0)
312 continue;
313 switch (ifa->ifa_addr->sa_family) {
314 case AF_INET:
315 sa = (struct sockaddr_in *)ifa->ifa_addr;
316 if (!allow_local && sa->sin_addr.s_addr ==
317 htonl(INADDR_LOOPBACK))
318 continue;
319 if (*rlenp < sizeof(struct sockaddr_in)) {
320 error_f("v4 addr doesn't fit");
321 return -1;
322 }
323 *rlenp = sizeof(struct sockaddr_in);
324 memcpy(resultp, sa, *rlenp);
325 return 0;
326 case AF_INET6:
327 sa6 = (struct sockaddr_in6 *)ifa->ifa_addr;
328 v6addr = &sa6->sin6_addr;
329 if (!allow_local &&
330 (IN6_IS_ADDR_LINKLOCAL(v6addr) ||
331 IN6_IS_ADDR_LOOPBACK(v6addr)))
332 continue;
333 if (*rlenp < sizeof(struct sockaddr_in6)) {
334 error_f("v6 addr doesn't fit");
335 return -1;
336 }
337 *rlenp = sizeof(struct sockaddr_in6);
338 memcpy(resultp, sa6, *rlenp);
339 return 0;
340 }
341 }
342 }
343 return -1;
344 }
345 #endif
346
347 /*
348 * Creates a socket for use as the ssh connection.
349 */
350 static int
ssh_create_socket(struct addrinfo * ai)351 ssh_create_socket(struct addrinfo *ai)
352 {
353 int sock, r;
354 struct sockaddr_storage bindaddr;
355 socklen_t bindaddrlen = 0;
356 struct addrinfo hints, *res = NULL;
357 #ifdef HAVE_IFADDRS_H
358 struct ifaddrs *ifaddrs = NULL;
359 #endif
360 char ntop[NI_MAXHOST];
361
362 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
363 if (sock == -1) {
364 error("socket: %s", strerror(errno));
365 return -1;
366 }
367 (void)fcntl(sock, F_SETFD, FD_CLOEXEC);
368
369 /* Use interactive QOS (if specified) until authentication completed */
370 if (options.ip_qos_interactive != INT_MAX)
371 set_sock_tos(sock, options.ip_qos_interactive);
372
373 /* Bind the socket to an alternative local IP address */
374 if (options.bind_address == NULL && options.bind_interface == NULL)
375 return sock;
376
377 if (options.bind_address != NULL) {
378 memset(&hints, 0, sizeof(hints));
379 hints.ai_family = ai->ai_family;
380 hints.ai_socktype = ai->ai_socktype;
381 hints.ai_protocol = ai->ai_protocol;
382 hints.ai_flags = AI_PASSIVE;
383 if ((r = getaddrinfo(options.bind_address, NULL,
384 &hints, &res)) != 0) {
385 error("getaddrinfo: %s: %s", options.bind_address,
386 ssh_gai_strerror(r));
387 goto fail;
388 }
389 if (res == NULL) {
390 error("getaddrinfo: no addrs");
391 goto fail;
392 }
393 memcpy(&bindaddr, res->ai_addr, res->ai_addrlen);
394 bindaddrlen = res->ai_addrlen;
395 } else if (options.bind_interface != NULL) {
396 #ifdef HAVE_IFADDRS_H
397 if ((r = getifaddrs(&ifaddrs)) != 0) {
398 error("getifaddrs: %s: %s", options.bind_interface,
399 strerror(errno));
400 goto fail;
401 }
402 bindaddrlen = sizeof(bindaddr);
403 if (check_ifaddrs(options.bind_interface, ai->ai_family,
404 ifaddrs, &bindaddr, &bindaddrlen) != 0) {
405 logit("getifaddrs: %s: no suitable addresses",
406 options.bind_interface);
407 goto fail;
408 }
409 #else
410 error("BindInterface not supported on this platform.");
411 #endif
412 }
413 if ((r = getnameinfo((struct sockaddr *)&bindaddr, bindaddrlen,
414 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST)) != 0) {
415 error_f("getnameinfo failed: %s", ssh_gai_strerror(r));
416 goto fail;
417 }
418 if (bind(sock, (struct sockaddr *)&bindaddr, bindaddrlen) != 0) {
419 error("bind %s: %s", ntop, strerror(errno));
420 goto fail;
421 }
422 debug_f("bound to %s", ntop);
423 /* success */
424 goto out;
425 fail:
426 close(sock);
427 sock = -1;
428 out:
429 if (res != NULL)
430 freeaddrinfo(res);
431 #ifdef HAVE_IFADDRS_H
432 if (ifaddrs != NULL)
433 freeifaddrs(ifaddrs);
434 #endif
435 return sock;
436 }
437
438 /*
439 * Opens a TCP/IP connection to the remote server on the given host.
440 * The address of the remote host will be returned in hostaddr.
441 * If port is 0, the default port will be used.
442 * Connection_attempts specifies the maximum number of tries (one per
443 * second). If proxy_command is non-NULL, it specifies the command (with %h
444 * and %p substituted for host and port, respectively) to use to contact
445 * the daemon.
446 */
447 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)448 ssh_connect_direct(struct ssh *ssh, const char *host, struct addrinfo *aitop,
449 struct sockaddr_storage *hostaddr, u_short port, int connection_attempts,
450 int *timeout_ms, int want_keepalive)
451 {
452 int on = 1, saved_timeout_ms = *timeout_ms;
453 int oerrno, sock = -1, attempt;
454 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
455 struct addrinfo *ai;
456
457 debug3_f("entering");
458 memset(ntop, 0, sizeof(ntop));
459 memset(strport, 0, sizeof(strport));
460
461 for (attempt = 0; attempt < connection_attempts; attempt++) {
462 if (attempt > 0) {
463 /* Sleep a moment before retrying. */
464 sleep(1);
465 debug("Trying again...");
466 }
467 /*
468 * Loop through addresses for this host, and try each one in
469 * sequence until the connection succeeds.
470 */
471 for (ai = aitop; ai; ai = ai->ai_next) {
472 if (ai->ai_family != AF_INET &&
473 ai->ai_family != AF_INET6) {
474 errno = EAFNOSUPPORT;
475 continue;
476 }
477 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
478 ntop, sizeof(ntop), strport, sizeof(strport),
479 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
480 oerrno = errno;
481 error_f("getnameinfo failed");
482 errno = oerrno;
483 continue;
484 }
485 if (options.address_family != AF_UNSPEC &&
486 ai->ai_family != options.address_family) {
487 debug2_f("skipping address [%s]:%s: "
488 "wrong address family", ntop, strport);
489 errno = EAFNOSUPPORT;
490 continue;
491 }
492
493 debug("Connecting to %.200s [%.100s] port %s.",
494 host, ntop, strport);
495
496 /* Create a socket for connecting. */
497 sock = ssh_create_socket(ai);
498 if (sock < 0) {
499 /* Any error is already output */
500 errno = 0;
501 continue;
502 }
503
504 *timeout_ms = saved_timeout_ms;
505 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
506 timeout_ms) >= 0) {
507 /* Successful connection. */
508 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
509 break;
510 } else {
511 oerrno = errno;
512 debug("connect to address %s port %s: %s",
513 ntop, strport, strerror(errno));
514 close(sock);
515 sock = -1;
516 errno = oerrno;
517 }
518 }
519 if (sock != -1)
520 break; /* Successful connection. */
521 }
522
523 /* Return failure if we didn't get a successful connection. */
524 if (sock == -1) {
525 error("ssh: connect to host %s port %s: %s",
526 host, strport, errno == 0 ? "failure" : strerror(errno));
527 return -1;
528 }
529
530 debug("Connection established.");
531
532 /* Set SO_KEEPALIVE if requested. */
533 if (want_keepalive &&
534 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
535 sizeof(on)) == -1)
536 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
537
538 /* Set the connection. */
539 if (ssh_packet_set_connection(ssh, sock, sock) == NULL)
540 return -1; /* ssh_packet_set_connection logs error */
541
542 return 0;
543 }
544
545 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)546 ssh_connect(struct ssh *ssh, const char *host, const char *host_arg,
547 struct addrinfo *addrs, struct sockaddr_storage *hostaddr, u_short port,
548 int connection_attempts, int *timeout_ms, int want_keepalive)
549 {
550 int in, out;
551
552 if (options.proxy_command == NULL) {
553 return ssh_connect_direct(ssh, host, addrs, hostaddr, port,
554 connection_attempts, timeout_ms, want_keepalive);
555 } else if (strcmp(options.proxy_command, "-") == 0) {
556 if ((in = dup(STDIN_FILENO)) == -1 ||
557 (out = dup(STDOUT_FILENO)) == -1) {
558 if (in >= 0)
559 close(in);
560 error_f("dup() in/out failed");
561 return -1; /* ssh_packet_set_connection logs error */
562 }
563 if ((ssh_packet_set_connection(ssh, in, out)) == NULL)
564 return -1; /* ssh_packet_set_connection logs error */
565 return 0;
566 } else if (options.proxy_use_fdpass) {
567 return ssh_proxy_fdpass_connect(ssh, host, host_arg, port,
568 options.proxy_command);
569 }
570 return ssh_proxy_connect(ssh, host, host_arg, port,
571 options.proxy_command);
572 }
573
574 /* defaults to 'no' */
575 static int
confirm(const char * prompt,const char * fingerprint)576 confirm(const char *prompt, const char *fingerprint)
577 {
578 const char *msg, *again = "Please type 'yes' or 'no': ";
579 const char *again_fp = "Please type 'yes', 'no' or the fingerprint: ";
580 char *p, *cp;
581 int ret = -1;
582
583 if (options.batch_mode)
584 return 0;
585 for (msg = prompt;;msg = fingerprint ? again_fp : again) {
586 cp = p = read_passphrase(msg, RP_ECHO);
587 if (p == NULL)
588 return 0;
589 p += strspn(p, " \t"); /* skip leading whitespace */
590 p[strcspn(p, " \t\n")] = '\0'; /* remove trailing whitespace */
591 if (p[0] == '\0' || strcasecmp(p, "no") == 0)
592 ret = 0;
593 else if (strcasecmp(p, "yes") == 0 || (fingerprint != NULL &&
594 strcmp(p, fingerprint) == 0))
595 ret = 1;
596 free(cp);
597 if (ret != -1)
598 return ret;
599 }
600 }
601
602 static int
sockaddr_is_local(struct sockaddr * hostaddr)603 sockaddr_is_local(struct sockaddr *hostaddr)
604 {
605 switch (hostaddr->sa_family) {
606 case AF_INET:
607 return (ntohl(((struct sockaddr_in *)hostaddr)->
608 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
609 case AF_INET6:
610 return IN6_IS_ADDR_LOOPBACK(
611 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
612 default:
613 return 0;
614 }
615 }
616
617 /*
618 * Prepare the hostname and ip address strings that are used to lookup
619 * host keys in known_hosts files. These may have a port number appended.
620 */
621 void
get_hostfile_hostname_ipaddr(char * hostname,struct sockaddr * hostaddr,u_short port,char ** hostfile_hostname,char ** hostfile_ipaddr)622 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr,
623 u_short port, char **hostfile_hostname, char **hostfile_ipaddr)
624 {
625 char ntop[NI_MAXHOST];
626 socklen_t addrlen;
627
628 switch (hostaddr == NULL ? -1 : hostaddr->sa_family) {
629 case -1:
630 addrlen = 0;
631 break;
632 case AF_INET:
633 addrlen = sizeof(struct sockaddr_in);
634 break;
635 case AF_INET6:
636 addrlen = sizeof(struct sockaddr_in6);
637 break;
638 default:
639 addrlen = sizeof(struct sockaddr);
640 break;
641 }
642
643 /*
644 * We don't have the remote ip-address for connections
645 * using a proxy command
646 */
647 if (hostfile_ipaddr != NULL) {
648 if (options.proxy_command == NULL) {
649 if (getnameinfo(hostaddr, addrlen,
650 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0)
651 fatal_f("getnameinfo failed");
652 *hostfile_ipaddr = put_host_port(ntop, port);
653 } else {
654 *hostfile_ipaddr = xstrdup("<no hostip for proxy "
655 "command>");
656 }
657 }
658
659 /*
660 * Allow the user to record the key under a different name or
661 * differentiate a non-standard port. This is useful for ssh
662 * tunneling over forwarded connections or if you run multiple
663 * sshd's on different ports on the same machine.
664 */
665 if (hostfile_hostname != NULL) {
666 if (options.host_key_alias != NULL) {
667 *hostfile_hostname = xstrdup(options.host_key_alias);
668 debug("using hostkeyalias: %s", *hostfile_hostname);
669 } else {
670 *hostfile_hostname = put_host_port(hostname, port);
671 }
672 }
673 }
674
675 /* returns non-zero if path appears in hostfiles, or 0 if not. */
676 static int
path_in_hostfiles(const char * path,char ** hostfiles,u_int num_hostfiles)677 path_in_hostfiles(const char *path, char **hostfiles, u_int num_hostfiles)
678 {
679 u_int i;
680
681 for (i = 0; i < num_hostfiles; i++) {
682 if (strcmp(path, hostfiles[i]) == 0)
683 return 1;
684 }
685 return 0;
686 }
687
688 struct find_by_key_ctx {
689 const char *host, *ip;
690 const struct sshkey *key;
691 char **names;
692 u_int nnames;
693 };
694
695 /* Try to replace home directory prefix (per $HOME) with a ~/ sequence */
696 static char *
try_tilde_unexpand(const char * path)697 try_tilde_unexpand(const char *path)
698 {
699 char *home, *ret = NULL;
700 size_t l;
701
702 if (*path != '/')
703 return xstrdup(path);
704 if ((home = getenv("HOME")) == NULL || (l = strlen(home)) == 0)
705 return xstrdup(path);
706 if (strncmp(path, home, l) != 0)
707 return xstrdup(path);
708 /*
709 * ensure we have matched on a path boundary: either the $HOME that
710 * we just compared ends with a '/' or the next character of the path
711 * must be a '/'.
712 */
713 if (home[l - 1] != '/' && path[l] != '/')
714 return xstrdup(path);
715 if (path[l] == '/')
716 l++;
717 xasprintf(&ret, "~/%s", path + l);
718 return ret;
719 }
720
721 /*
722 * Returns non-zero if the key is accepted by HostkeyAlgorithms.
723 * Made slightly less trivial by the multiple RSA signature algorithm names.
724 */
725 int
hostkey_accepted_by_hostkeyalgs(const struct sshkey * key)726 hostkey_accepted_by_hostkeyalgs(const struct sshkey *key)
727 {
728 const char *ktype = sshkey_ssh_name(key);
729 const char *hostkeyalgs = options.hostkeyalgorithms;
730
731 if (key->type == KEY_UNSPEC)
732 return 0;
733 if (key->type == KEY_RSA &&
734 (match_pattern_list("rsa-sha2-256", hostkeyalgs, 0) == 1 ||
735 match_pattern_list("rsa-sha2-512", hostkeyalgs, 0) == 1))
736 return 1;
737 if (key->type == KEY_RSA_CERT &&
738 (match_pattern_list("rsa-sha2-512-cert-v01@openssh.com", hostkeyalgs, 0) == 1 ||
739 match_pattern_list("rsa-sha2-256-cert-v01@openssh.com", hostkeyalgs, 0) == 1))
740 return 1;
741 return match_pattern_list(ktype, hostkeyalgs, 0) == 1;
742 }
743
744 static int
hostkeys_find_by_key_cb(struct hostkey_foreach_line * l,void * _ctx)745 hostkeys_find_by_key_cb(struct hostkey_foreach_line *l, void *_ctx)
746 {
747 struct find_by_key_ctx *ctx = (struct find_by_key_ctx *)_ctx;
748 char *path;
749
750 /* we are looking for keys with names that *do not* match */
751 if ((l->match & HKF_MATCH_HOST) != 0)
752 return 0;
753 /* not interested in marker lines */
754 if (l->marker != MRK_NONE)
755 return 0;
756 /* we are only interested in exact key matches */
757 if (l->key == NULL || !sshkey_equal(ctx->key, l->key))
758 return 0;
759 path = try_tilde_unexpand(l->path);
760 debug_f("found matching key in %s:%lu", path, l->linenum);
761 ctx->names = xrecallocarray(ctx->names,
762 ctx->nnames, ctx->nnames + 1, sizeof(*ctx->names));
763 xasprintf(&ctx->names[ctx->nnames], "%s:%lu: %s", path, l->linenum,
764 strncmp(l->hosts, HASH_MAGIC, strlen(HASH_MAGIC)) == 0 ?
765 "[hashed name]" : l->hosts);
766 ctx->nnames++;
767 free(path);
768 return 0;
769 }
770
771 static int
hostkeys_find_by_key_hostfile(const char * file,const char * which,struct find_by_key_ctx * ctx)772 hostkeys_find_by_key_hostfile(const char *file, const char *which,
773 struct find_by_key_ctx *ctx)
774 {
775 int r;
776
777 debug3_f("trying %s hostfile \"%s\"", which, file);
778 if ((r = hostkeys_foreach(file, hostkeys_find_by_key_cb, ctx,
779 ctx->host, ctx->ip, HKF_WANT_PARSE_KEY, 0)) != 0) {
780 if (r == SSH_ERR_SYSTEM_ERROR && errno == ENOENT) {
781 debug_f("hostkeys file %s does not exist", file);
782 return 0;
783 }
784 error_fr(r, "hostkeys_foreach failed for %s", file);
785 return r;
786 }
787 return 0;
788 }
789
790 /*
791 * Find 'key' in known hosts file(s) that do not match host/ip.
792 * Used to display also-known-as information for previously-unseen hostkeys.
793 */
794 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)795 hostkeys_find_by_key(const char *host, const char *ip, const struct sshkey *key,
796 char **user_hostfiles, u_int num_user_hostfiles,
797 char **system_hostfiles, u_int num_system_hostfiles,
798 char ***names, u_int *nnames)
799 {
800 struct find_by_key_ctx ctx = {0, 0, 0, 0, 0};
801 u_int i;
802
803 *names = NULL;
804 *nnames = 0;
805
806 if (key == NULL || sshkey_is_cert(key))
807 return;
808
809 ctx.host = host;
810 ctx.ip = ip;
811 ctx.key = key;
812
813 for (i = 0; i < num_user_hostfiles; i++) {
814 if (hostkeys_find_by_key_hostfile(user_hostfiles[i],
815 "user", &ctx) != 0)
816 goto fail;
817 }
818 for (i = 0; i < num_system_hostfiles; i++) {
819 if (hostkeys_find_by_key_hostfile(system_hostfiles[i],
820 "system", &ctx) != 0)
821 goto fail;
822 }
823 /* success */
824 *names = ctx.names;
825 *nnames = ctx.nnames;
826 ctx.names = NULL;
827 ctx.nnames = 0;
828 return;
829 fail:
830 for (i = 0; i < ctx.nnames; i++)
831 free(ctx.names[i]);
832 free(ctx.names);
833 }
834
835 #define MAX_OTHER_NAMES 8 /* Maximum number of names to list */
836 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)837 other_hostkeys_message(const char *host, const char *ip,
838 const struct sshkey *key,
839 char **user_hostfiles, u_int num_user_hostfiles,
840 char **system_hostfiles, u_int num_system_hostfiles)
841 {
842 char *ret = NULL, **othernames = NULL;
843 u_int i, n, num_othernames = 0;
844
845 hostkeys_find_by_key(host, ip, key,
846 user_hostfiles, num_user_hostfiles,
847 system_hostfiles, num_system_hostfiles,
848 &othernames, &num_othernames);
849 if (num_othernames == 0)
850 return xstrdup("This key is not known by any other names.");
851
852 xasprintf(&ret, "This host key is known by the following other "
853 "names/addresses:");
854
855 n = num_othernames;
856 if (n > MAX_OTHER_NAMES)
857 n = MAX_OTHER_NAMES;
858 for (i = 0; i < n; i++) {
859 xextendf(&ret, "\n", " %s", othernames[i]);
860 }
861 if (n < num_othernames) {
862 xextendf(&ret, "\n", " (%d additional names omitted)",
863 num_othernames - n);
864 }
865 for (i = 0; i < num_othernames; i++)
866 free(othernames[i]);
867 free(othernames);
868 return ret;
869 }
870
871 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)872 load_hostkeys_command(struct hostkeys *hostkeys, const char *command_template,
873 const char *invocation, const struct ssh_conn_info *cinfo,
874 const struct sshkey *host_key, const char *hostfile_hostname)
875 {
876 int r, i, ac = 0;
877 char *key_fp = NULL, *keytext = NULL, *tmp;
878 char *command = NULL, *tag = NULL, **av = NULL;
879 FILE *f = NULL;
880 pid_t pid;
881 void (*osigchld)(int);
882
883 xasprintf(&tag, "KnownHostsCommand-%s", invocation);
884
885 if (host_key != NULL) {
886 if ((key_fp = sshkey_fingerprint(host_key,
887 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
888 fatal_f("sshkey_fingerprint failed");
889 if ((r = sshkey_to_base64(host_key, &keytext)) != 0)
890 fatal_fr(r, "sshkey_to_base64 failed");
891 }
892 /*
893 * NB. all returns later this function should go via "out" to
894 * ensure the original SIGCHLD handler is restored properly.
895 */
896 osigchld = ssh_signal(SIGCHLD, SIG_DFL);
897
898 /* Turn the command into an argument vector */
899 if (argv_split(command_template, &ac, &av, 0) != 0) {
900 error("%s \"%s\" contains invalid quotes", tag,
901 command_template);
902 goto out;
903 }
904 if (ac == 0) {
905 error("%s \"%s\" yielded no arguments", tag,
906 command_template);
907 goto out;
908 }
909 for (i = 1; i < ac; i++) {
910 tmp = percent_dollar_expand(av[i],
911 DEFAULT_CLIENT_PERCENT_EXPAND_ARGS(cinfo),
912 "H", hostfile_hostname,
913 "I", invocation,
914 "t", host_key == NULL ? "NONE" : sshkey_ssh_name(host_key),
915 "f", key_fp == NULL ? "NONE" : key_fp,
916 "K", keytext == NULL ? "NONE" : keytext,
917 (char *)NULL);
918 if (tmp == NULL)
919 fatal_f("percent_expand failed");
920 free(av[i]);
921 av[i] = tmp;
922 }
923 /* Prepare a printable command for logs, etc. */
924 command = argv_assemble(ac, av);
925
926 if ((pid = subprocess(tag, command, ac, av, &f,
927 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_UNSAFE_PATH|
928 SSH_SUBPROCESS_PRESERVE_ENV, NULL, NULL, NULL)) == 0)
929 goto out;
930
931 load_hostkeys_file(hostkeys, hostfile_hostname, tag, f, 1);
932
933 if (exited_cleanly(pid, tag, command, 0) != 0)
934 fatal("KnownHostsCommand failed");
935
936 out:
937 if (f != NULL)
938 fclose(f);
939 ssh_signal(SIGCHLD, osigchld);
940 for (i = 0; i < ac; i++)
941 free(av[i]);
942 free(av);
943 free(tag);
944 free(command);
945 free(key_fp);
946 free(keytext);
947 }
948
949 /*
950 * check whether the supplied host key is valid, return -1 if the key
951 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true.
952 */
953 #define RDRW 0
954 #define RDONLY 1
955 #define ROQUIET 2
956 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)957 check_host_key(char *hostname, const struct ssh_conn_info *cinfo,
958 struct sockaddr *hostaddr, u_short port,
959 struct sshkey *host_key, int readonly, int clobber_port,
960 char **user_hostfiles, u_int num_user_hostfiles,
961 char **system_hostfiles, u_int num_system_hostfiles,
962 const char *hostfile_command)
963 {
964 HostStatus host_status = -1, ip_status = -1;
965 struct sshkey *raw_key = NULL;
966 char *ip = NULL, *host = NULL;
967 char hostline[1000], *hostp, *fp, *ra;
968 char msg[1024];
969 const char *type, *fail_reason = NULL;
970 const struct hostkey_entry *host_found = NULL, *ip_found = NULL;
971 int len, cancelled_forwarding = 0, confirmed;
972 int local = sockaddr_is_local(hostaddr);
973 int r, want_cert = sshkey_is_cert(host_key), host_ip_differ = 0;
974 int hostkey_trusted = 0; /* Known or explicitly accepted by user */
975 struct hostkeys *host_hostkeys, *ip_hostkeys;
976 u_int i;
977
978 /*
979 * Force accepting of the host key for loopback/localhost. The
980 * problem is that if the home directory is NFS-mounted to multiple
981 * machines, localhost will refer to a different machine in each of
982 * them, and the user will get bogus HOST_CHANGED warnings. This
983 * essentially disables host authentication for localhost; however,
984 * this is probably not a real problem.
985 */
986 if (options.no_host_authentication_for_localhost == 1 && local &&
987 options.host_key_alias == NULL) {
988 debug("Forcing accepting of host key for "
989 "loopback/localhost.");
990 options.update_hostkeys = 0;
991 return 0;
992 }
993
994 /*
995 * Don't ever try to write an invalid name to a known hosts file.
996 * Note: do this before get_hostfile_hostname_ipaddr() to catch
997 * '[' or ']' in the name before they are added.
998 */
999 if (strcspn(hostname, "@?*#[]|'\'\"\\") != strlen(hostname)) {
1000 debug_f("invalid hostname \"%s\"; will not record: %s",
1001 hostname, fail_reason);
1002 readonly = RDONLY;
1003 }
1004
1005 /*
1006 * Prepare the hostname and address strings used for hostkey lookup.
1007 * In some cases, these will have a port number appended.
1008 */
1009 get_hostfile_hostname_ipaddr(hostname, hostaddr,
1010 clobber_port ? 0 : port, &host, &ip);
1011
1012 /*
1013 * Turn off check_host_ip if the connection is to localhost, via proxy
1014 * command or if we don't have a hostname to compare with
1015 */
1016 if (options.check_host_ip && (local ||
1017 strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
1018 options.check_host_ip = 0;
1019
1020 host_hostkeys = init_hostkeys();
1021 for (i = 0; i < num_user_hostfiles; i++)
1022 load_hostkeys(host_hostkeys, host, user_hostfiles[i], 0);
1023 for (i = 0; i < num_system_hostfiles; i++)
1024 load_hostkeys(host_hostkeys, host, system_hostfiles[i], 0);
1025 if (hostfile_command != NULL && !clobber_port) {
1026 load_hostkeys_command(host_hostkeys, hostfile_command,
1027 "HOSTNAME", cinfo, host_key, host);
1028 }
1029
1030 ip_hostkeys = NULL;
1031 if (!want_cert && options.check_host_ip) {
1032 ip_hostkeys = init_hostkeys();
1033 for (i = 0; i < num_user_hostfiles; i++)
1034 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i], 0);
1035 for (i = 0; i < num_system_hostfiles; i++)
1036 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i], 0);
1037 if (hostfile_command != NULL && !clobber_port) {
1038 load_hostkeys_command(ip_hostkeys, hostfile_command,
1039 "ADDRESS", cinfo, host_key, ip);
1040 }
1041 }
1042
1043 retry:
1044 if (!hostkey_accepted_by_hostkeyalgs(host_key)) {
1045 error("host key %s not permitted by HostkeyAlgorithms",
1046 sshkey_ssh_name(host_key));
1047 goto fail;
1048 }
1049
1050 /* Reload these as they may have changed on cert->key downgrade */
1051 want_cert = sshkey_is_cert(host_key);
1052 type = sshkey_type(host_key);
1053
1054 /*
1055 * Check if the host key is present in the user's list of known
1056 * hosts or in the systemwide list.
1057 */
1058 host_status = check_key_in_hostkeys(host_hostkeys, host_key,
1059 &host_found);
1060
1061 /*
1062 * If there are no hostfiles, or if the hostkey was found via
1063 * KnownHostsCommand, then don't try to touch the disk.
1064 */
1065 if (!readonly && (num_user_hostfiles == 0 ||
1066 (host_found != NULL && host_found->note != 0)))
1067 readonly = RDONLY;
1068
1069 /*
1070 * Also perform check for the ip address, skip the check if we are
1071 * localhost, looking for a certificate, or the hostname was an ip
1072 * address to begin with.
1073 */
1074 if (!want_cert && ip_hostkeys != NULL) {
1075 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key,
1076 &ip_found);
1077 if (host_status == HOST_CHANGED &&
1078 (ip_status != HOST_CHANGED ||
1079 (ip_found != NULL &&
1080 !sshkey_equal(ip_found->key, host_found->key))))
1081 host_ip_differ = 1;
1082 } else
1083 ip_status = host_status;
1084
1085 switch (host_status) {
1086 case HOST_OK:
1087 /* The host is known and the key matches. */
1088 debug("Host '%.200s' is known and matches the %s host %s.",
1089 host, type, want_cert ? "certificate" : "key");
1090 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key",
1091 host_found->file, host_found->line);
1092 if (want_cert) {
1093 if (sshkey_cert_check_host(host_key,
1094 options.host_key_alias == NULL ?
1095 hostname : options.host_key_alias, 0,
1096 options.ca_sign_algorithms, &fail_reason) != 0) {
1097 error("%s", fail_reason);
1098 goto fail;
1099 }
1100 /*
1101 * Do not attempt hostkey update if a certificate was
1102 * successfully matched.
1103 */
1104 if (options.update_hostkeys != 0) {
1105 options.update_hostkeys = 0;
1106 debug3_f("certificate host key in use; "
1107 "disabling UpdateHostkeys");
1108 }
1109 }
1110 /* Turn off UpdateHostkeys if key was in system known_hosts */
1111 if (options.update_hostkeys != 0 &&
1112 (path_in_hostfiles(host_found->file,
1113 system_hostfiles, num_system_hostfiles) ||
1114 (ip_status == HOST_OK && ip_found != NULL &&
1115 path_in_hostfiles(ip_found->file,
1116 system_hostfiles, num_system_hostfiles)))) {
1117 options.update_hostkeys = 0;
1118 debug3_f("host key found in GlobalKnownHostsFile; "
1119 "disabling UpdateHostkeys");
1120 }
1121 if (options.update_hostkeys != 0 && host_found->note) {
1122 options.update_hostkeys = 0;
1123 debug3_f("host key found via KnownHostsCommand; "
1124 "disabling UpdateHostkeys");
1125 }
1126 if (options.check_host_ip && ip_status == HOST_NEW) {
1127 if (readonly || want_cert)
1128 logit("%s host key for IP address "
1129 "'%.128s' not in list of known hosts.",
1130 type, ip);
1131 else if (!add_host_to_hostfile(user_hostfiles[0], ip,
1132 host_key, options.hash_known_hosts))
1133 logit("Failed to add the %s host key for IP "
1134 "address '%.128s' to the list of known "
1135 "hosts (%.500s).", type, ip,
1136 user_hostfiles[0]);
1137 else
1138 logit("Warning: Permanently added the %s host "
1139 "key for IP address '%.128s' to the list "
1140 "of known hosts.", type, ip);
1141 } else if (options.visual_host_key) {
1142 fp = sshkey_fingerprint(host_key,
1143 options.fingerprint_hash, SSH_FP_DEFAULT);
1144 ra = sshkey_fingerprint(host_key,
1145 options.fingerprint_hash, SSH_FP_RANDOMART);
1146 if (fp == NULL || ra == NULL)
1147 fatal_f("sshkey_fingerprint failed");
1148 logit("Host key fingerprint is %s\n%s", fp, ra);
1149 free(ra);
1150 free(fp);
1151 }
1152 hostkey_trusted = 1;
1153 break;
1154 case HOST_NEW:
1155 if (options.host_key_alias == NULL && port != 0 &&
1156 port != SSH_DEFAULT_PORT && !clobber_port) {
1157 debug("checking without port identifier");
1158 if (check_host_key(hostname, cinfo, hostaddr, 0,
1159 host_key, ROQUIET, 1,
1160 user_hostfiles, num_user_hostfiles,
1161 system_hostfiles, num_system_hostfiles,
1162 hostfile_command) == 0) {
1163 debug("found matching key w/out port");
1164 break;
1165 }
1166 }
1167 if (readonly || want_cert)
1168 goto fail;
1169 /* The host is new. */
1170 if (options.strict_host_key_checking ==
1171 SSH_STRICT_HOSTKEY_YES) {
1172 /*
1173 * User has requested strict host key checking. We
1174 * will not add the host key automatically. The only
1175 * alternative left is to abort.
1176 */
1177 error("No %s host key is known for %.200s and you "
1178 "have requested strict checking.", type, host);
1179 goto fail;
1180 } else if (options.strict_host_key_checking ==
1181 SSH_STRICT_HOSTKEY_ASK) {
1182 char *msg1 = NULL, *msg2 = NULL;
1183
1184 xasprintf(&msg1, "The authenticity of host "
1185 "'%.200s (%s)' can't be established", host, ip);
1186
1187 if (show_other_keys(host_hostkeys, host_key)) {
1188 xextendf(&msg1, "\n", "but keys of different "
1189 "type are already known for this host.");
1190 } else
1191 xextendf(&msg1, "", ".");
1192
1193 fp = sshkey_fingerprint(host_key,
1194 options.fingerprint_hash, SSH_FP_DEFAULT);
1195 ra = sshkey_fingerprint(host_key,
1196 options.fingerprint_hash, SSH_FP_RANDOMART);
1197 if (fp == NULL || ra == NULL)
1198 fatal_f("sshkey_fingerprint failed");
1199 xextendf(&msg1, "\n", "%s key fingerprint is %s.",
1200 type, fp);
1201 if (options.visual_host_key)
1202 xextendf(&msg1, "\n", "%s", ra);
1203 if (options.verify_host_key_dns) {
1204 xextendf(&msg1, "\n",
1205 "%s host key fingerprint found in DNS.",
1206 matching_host_key_dns ?
1207 "Matching" : "No matching");
1208 }
1209 /* msg2 informs for other names matching this key */
1210 if ((msg2 = other_hostkeys_message(host, ip, host_key,
1211 user_hostfiles, num_user_hostfiles,
1212 system_hostfiles, num_system_hostfiles)) != NULL)
1213 xextendf(&msg1, "\n", "%s", msg2);
1214
1215 xextendf(&msg1, "\n",
1216 "Are you sure you want to continue connecting "
1217 "(yes/no/[fingerprint])? ");
1218
1219 confirmed = confirm(msg1, fp);
1220 free(ra);
1221 free(fp);
1222 free(msg1);
1223 free(msg2);
1224 if (!confirmed)
1225 goto fail;
1226 hostkey_trusted = 1; /* user explicitly confirmed */
1227 }
1228 /*
1229 * If in "new" or "off" strict mode, add the key automatically
1230 * to the local known_hosts file.
1231 */
1232 if (options.check_host_ip && ip_status == HOST_NEW) {
1233 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
1234 hostp = hostline;
1235 if (options.hash_known_hosts) {
1236 /* Add hash of host and IP separately */
1237 r = add_host_to_hostfile(user_hostfiles[0],
1238 host, host_key, options.hash_known_hosts) &&
1239 add_host_to_hostfile(user_hostfiles[0], ip,
1240 host_key, options.hash_known_hosts);
1241 } else {
1242 /* Add unhashed "host,ip" */
1243 r = add_host_to_hostfile(user_hostfiles[0],
1244 hostline, host_key,
1245 options.hash_known_hosts);
1246 }
1247 } else {
1248 r = add_host_to_hostfile(user_hostfiles[0], host,
1249 host_key, options.hash_known_hosts);
1250 hostp = host;
1251 }
1252
1253 if (!r)
1254 logit("Failed to add the host to the list of known "
1255 "hosts (%.500s).", user_hostfiles[0]);
1256 else
1257 logit("Warning: Permanently added '%.200s' (%s) to the "
1258 "list of known hosts.", hostp, type);
1259 break;
1260 case HOST_REVOKED:
1261 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1262 error("@ WARNING: REVOKED HOST KEY DETECTED! @");
1263 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1264 error("The %s host key for %s is marked as revoked.", type, host);
1265 error("This could mean that a stolen key is being used to");
1266 error("impersonate this host.");
1267
1268 /*
1269 * If strict host key checking is in use, the user will have
1270 * to edit the key manually and we can only abort.
1271 */
1272 if (options.strict_host_key_checking !=
1273 SSH_STRICT_HOSTKEY_OFF) {
1274 error("%s host key for %.200s was revoked and you have "
1275 "requested strict checking.", type, host);
1276 goto fail;
1277 }
1278 goto continue_unsafe;
1279
1280 case HOST_CHANGED:
1281 if (want_cert) {
1282 /*
1283 * This is only a debug() since it is valid to have
1284 * CAs with wildcard DNS matches that don't match
1285 * all hosts that one might visit.
1286 */
1287 debug("Host certificate authority does not "
1288 "match %s in %s:%lu", CA_MARKER,
1289 host_found->file, host_found->line);
1290 goto fail;
1291 }
1292 if (readonly == ROQUIET)
1293 goto fail;
1294 if (options.check_host_ip && host_ip_differ) {
1295 char *key_msg;
1296 if (ip_status == HOST_NEW)
1297 key_msg = "is unknown";
1298 else if (ip_status == HOST_OK)
1299 key_msg = "is unchanged";
1300 else
1301 key_msg = "has a different value";
1302 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1303 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
1304 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1305 error("The %s host key for %s has changed,", type, host);
1306 error("and the key for the corresponding IP address %s", ip);
1307 error("%s. This could either mean that", key_msg);
1308 error("DNS SPOOFING is happening or the IP address for the host");
1309 error("and its host key have changed at the same time.");
1310 if (ip_status != HOST_NEW)
1311 error("Offending key for IP in %s:%lu",
1312 ip_found->file, ip_found->line);
1313 }
1314 /* The host key has changed. */
1315 warn_changed_key(host_key);
1316 if (num_user_hostfiles > 0 || num_system_hostfiles > 0) {
1317 error("Add correct host key in %.100s to get rid "
1318 "of this message.", num_user_hostfiles > 0 ?
1319 user_hostfiles[0] : system_hostfiles[0]);
1320 }
1321 error("Offending %s key in %s:%lu",
1322 sshkey_type(host_found->key),
1323 host_found->file, host_found->line);
1324
1325 /*
1326 * If strict host key checking is in use, the user will have
1327 * to edit the key manually and we can only abort.
1328 */
1329 if (options.strict_host_key_checking !=
1330 SSH_STRICT_HOSTKEY_OFF) {
1331 error("Host key for %.200s has changed and you have "
1332 "requested strict checking.", host);
1333 goto fail;
1334 }
1335
1336 continue_unsafe:
1337 /*
1338 * If strict host key checking has not been requested, allow
1339 * the connection but without MITM-able authentication or
1340 * forwarding.
1341 */
1342 if (options.password_authentication) {
1343 error("Password authentication is disabled to avoid "
1344 "man-in-the-middle attacks.");
1345 options.password_authentication = 0;
1346 cancelled_forwarding = 1;
1347 }
1348 if (options.kbd_interactive_authentication) {
1349 error("Keyboard-interactive authentication is disabled"
1350 " to avoid man-in-the-middle attacks.");
1351 options.kbd_interactive_authentication = 0;
1352 cancelled_forwarding = 1;
1353 }
1354 if (options.forward_agent) {
1355 error("Agent forwarding is disabled to avoid "
1356 "man-in-the-middle attacks.");
1357 options.forward_agent = 0;
1358 cancelled_forwarding = 1;
1359 }
1360 if (options.forward_x11) {
1361 error("X11 forwarding is disabled to avoid "
1362 "man-in-the-middle attacks.");
1363 options.forward_x11 = 0;
1364 cancelled_forwarding = 1;
1365 }
1366 if (options.num_local_forwards > 0 ||
1367 options.num_remote_forwards > 0) {
1368 error("Port forwarding is disabled to avoid "
1369 "man-in-the-middle attacks.");
1370 options.num_local_forwards =
1371 options.num_remote_forwards = 0;
1372 cancelled_forwarding = 1;
1373 }
1374 if (options.tun_open != SSH_TUNMODE_NO) {
1375 error("Tunnel forwarding is disabled to avoid "
1376 "man-in-the-middle attacks.");
1377 options.tun_open = SSH_TUNMODE_NO;
1378 cancelled_forwarding = 1;
1379 }
1380 if (options.update_hostkeys != 0) {
1381 error("UpdateHostkeys is disabled because the host "
1382 "key is not trusted.");
1383 options.update_hostkeys = 0;
1384 }
1385 if (options.exit_on_forward_failure && cancelled_forwarding)
1386 fatal("Error: forwarding disabled due to host key "
1387 "check failure");
1388
1389 /*
1390 * XXX Should permit the user to change to use the new id.
1391 * This could be done by converting the host key to an
1392 * identifying sentence, tell that the host identifies itself
1393 * by that sentence, and ask the user if they wish to
1394 * accept the authentication.
1395 */
1396 break;
1397 case HOST_FOUND:
1398 fatal("internal error");
1399 break;
1400 }
1401
1402 if (options.check_host_ip && host_status != HOST_CHANGED &&
1403 ip_status == HOST_CHANGED) {
1404 snprintf(msg, sizeof(msg),
1405 "Warning: the %s host key for '%.200s' "
1406 "differs from the key for the IP address '%.128s'"
1407 "\nOffending key for IP in %s:%lu",
1408 type, host, ip, ip_found->file, ip_found->line);
1409 if (host_status == HOST_OK) {
1410 len = strlen(msg);
1411 snprintf(msg + len, sizeof(msg) - len,
1412 "\nMatching host key in %s:%lu",
1413 host_found->file, host_found->line);
1414 }
1415 if (options.strict_host_key_checking ==
1416 SSH_STRICT_HOSTKEY_ASK) {
1417 strlcat(msg, "\nAre you sure you want "
1418 "to continue connecting (yes/no)? ", sizeof(msg));
1419 if (!confirm(msg, NULL))
1420 goto fail;
1421 } else if (options.strict_host_key_checking !=
1422 SSH_STRICT_HOSTKEY_OFF) {
1423 logit("%s", msg);
1424 error("Exiting, you have requested strict checking.");
1425 goto fail;
1426 } else {
1427 logit("%s", msg);
1428 }
1429 }
1430
1431 if (!hostkey_trusted && options.update_hostkeys) {
1432 debug_f("hostkey not known or explicitly trusted: "
1433 "disabling UpdateHostkeys");
1434 options.update_hostkeys = 0;
1435 }
1436
1437 free(ip);
1438 free(host);
1439 if (host_hostkeys != NULL)
1440 free_hostkeys(host_hostkeys);
1441 if (ip_hostkeys != NULL)
1442 free_hostkeys(ip_hostkeys);
1443 return 0;
1444
1445 fail:
1446 if (want_cert && host_status != HOST_REVOKED) {
1447 /*
1448 * No matching certificate. Downgrade cert to raw key and
1449 * search normally.
1450 */
1451 debug("No matching CA found. Retry with plain key");
1452 if ((r = sshkey_from_private(host_key, &raw_key)) != 0)
1453 fatal_fr(r, "decode key");
1454 if ((r = sshkey_drop_cert(raw_key)) != 0)
1455 fatal_r(r, "Couldn't drop certificate");
1456 host_key = raw_key;
1457 goto retry;
1458 }
1459 sshkey_free(raw_key);
1460 free(ip);
1461 free(host);
1462 if (host_hostkeys != NULL)
1463 free_hostkeys(host_hostkeys);
1464 if (ip_hostkeys != NULL)
1465 free_hostkeys(ip_hostkeys);
1466 return -1;
1467 }
1468
1469 /* returns 0 if key verifies or -1 if key does NOT verify */
1470 int
verify_host_key(char * host,struct sockaddr * hostaddr,struct sshkey * host_key,const struct ssh_conn_info * cinfo)1471 verify_host_key(char *host, struct sockaddr *hostaddr, struct sshkey *host_key,
1472 const struct ssh_conn_info *cinfo)
1473 {
1474 u_int i;
1475 int r = -1, flags = 0;
1476 char valid[64], *fp = NULL, *cafp = NULL;
1477 struct sshkey *plain = NULL;
1478
1479 if ((fp = sshkey_fingerprint(host_key,
1480 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1481 error_fr(r, "fingerprint host key");
1482 r = -1;
1483 goto out;
1484 }
1485
1486 if (sshkey_is_cert(host_key)) {
1487 if ((cafp = sshkey_fingerprint(host_key->cert->signature_key,
1488 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1489 error_fr(r, "fingerprint CA key");
1490 r = -1;
1491 goto out;
1492 }
1493 sshkey_format_cert_validity(host_key->cert,
1494 valid, sizeof(valid));
1495 debug("Server host certificate: %s %s, serial %llu "
1496 "ID \"%s\" CA %s %s valid %s",
1497 sshkey_ssh_name(host_key), fp,
1498 (unsigned long long)host_key->cert->serial,
1499 host_key->cert->key_id,
1500 sshkey_ssh_name(host_key->cert->signature_key), cafp,
1501 valid);
1502 for (i = 0; i < host_key->cert->nprincipals; i++) {
1503 debug2("Server host certificate hostname: %s",
1504 host_key->cert->principals[i]);
1505 }
1506 } else {
1507 debug("Server host key: %s %s", sshkey_ssh_name(host_key), fp);
1508 }
1509
1510 if (sshkey_equal(previous_host_key, host_key)) {
1511 debug2_f("server host key %s %s matches cached key",
1512 sshkey_type(host_key), fp);
1513 r = 0;
1514 goto out;
1515 }
1516
1517 /* Check in RevokedHostKeys file if specified */
1518 if (options.revoked_host_keys != NULL) {
1519 r = sshkey_check_revoked(host_key, options.revoked_host_keys);
1520 switch (r) {
1521 case 0:
1522 break; /* not revoked */
1523 case SSH_ERR_KEY_REVOKED:
1524 error("Host key %s %s revoked by file %s",
1525 sshkey_type(host_key), fp,
1526 options.revoked_host_keys);
1527 r = -1;
1528 goto out;
1529 default:
1530 error_r(r, "Error checking host key %s %s in "
1531 "revoked keys file %s", sshkey_type(host_key),
1532 fp, options.revoked_host_keys);
1533 r = -1;
1534 goto out;
1535 }
1536 }
1537
1538 if (options.verify_host_key_dns) {
1539 /*
1540 * XXX certs are not yet supported for DNS, so downgrade
1541 * them and try the plain key.
1542 */
1543 if ((r = sshkey_from_private(host_key, &plain)) != 0)
1544 goto out;
1545 if (sshkey_is_cert(plain))
1546 sshkey_drop_cert(plain);
1547 if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) {
1548 if (flags & DNS_VERIFY_FOUND) {
1549 if (options.verify_host_key_dns == 1 &&
1550 flags & DNS_VERIFY_MATCH &&
1551 flags & DNS_VERIFY_SECURE) {
1552 r = 0;
1553 goto out;
1554 }
1555 if (flags & DNS_VERIFY_MATCH) {
1556 matching_host_key_dns = 1;
1557 } else {
1558 warn_changed_key(plain);
1559 error("Update the SSHFP RR in DNS "
1560 "with the new host key to get rid "
1561 "of this message.");
1562 }
1563 }
1564 }
1565 }
1566 r = check_host_key(host, cinfo, hostaddr, options.port, host_key,
1567 RDRW, 0, options.user_hostfiles, options.num_user_hostfiles,
1568 options.system_hostfiles, options.num_system_hostfiles,
1569 options.known_hosts_command);
1570
1571 out:
1572 sshkey_free(plain);
1573 free(fp);
1574 free(cafp);
1575 if (r == 0 && host_key != NULL) {
1576 sshkey_free(previous_host_key);
1577 r = sshkey_from_private(host_key, &previous_host_key);
1578 }
1579
1580 return r;
1581 }
1582
1583 /*
1584 * Starts a dialog with the server, and authenticates the current user on the
1585 * server. This does not need any extra privileges. The basic connection
1586 * to the server must already have been established before this is called.
1587 * If login fails, this function prints an error and never returns.
1588 * This function does not require super-user privileges.
1589 */
1590 void
ssh_login(struct ssh * ssh,Sensitive * sensitive,const char * orighost,struct sockaddr * hostaddr,u_short port,struct passwd * pw,int timeout_ms,const struct ssh_conn_info * cinfo)1591 ssh_login(struct ssh *ssh, Sensitive *sensitive, const char *orighost,
1592 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms,
1593 const struct ssh_conn_info *cinfo)
1594 {
1595 char *host;
1596 char *server_user, *local_user;
1597 int r;
1598
1599 local_user = xstrdup(pw->pw_name);
1600 server_user = options.user ? options.user : local_user;
1601
1602 /* Convert the user-supplied hostname into all lowercase. */
1603 host = xstrdup(orighost);
1604 lowercase(host);
1605
1606 /* Exchange protocol version identification strings with the server. */
1607 if ((r = kex_exchange_identification(ssh, timeout_ms, NULL)) != 0)
1608 sshpkt_fatal(ssh, r, "banner exchange");
1609
1610 /* Put the connection into non-blocking mode. */
1611 ssh_packet_set_nonblocking(ssh);
1612
1613 /* key exchange */
1614 /* authenticate user */
1615 debug("Authenticating to %s:%d as '%s'", host, port, server_user);
1616 ssh_kex2(ssh, host, hostaddr, port, cinfo);
1617 ssh_userauth2(ssh, local_user, server_user, host, sensitive);
1618 free(local_user);
1619 free(host);
1620 }
1621
1622 /* print all known host keys for a given host, but skip keys of given type */
1623 static int
show_other_keys(struct hostkeys * hostkeys,struct sshkey * key)1624 show_other_keys(struct hostkeys *hostkeys, struct sshkey *key)
1625 {
1626 int type[] = {
1627 KEY_RSA,
1628 #ifdef WITH_DSA
1629 KEY_DSA,
1630 #endif
1631 KEY_ECDSA,
1632 KEY_ED25519,
1633 KEY_XMSS,
1634 -1
1635 };
1636 int i, ret = 0;
1637 char *fp, *ra;
1638 const struct hostkey_entry *found;
1639
1640 for (i = 0; type[i] != -1; i++) {
1641 if (type[i] == key->type)
1642 continue;
1643 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i],
1644 -1, &found))
1645 continue;
1646 fp = sshkey_fingerprint(found->key,
1647 options.fingerprint_hash, SSH_FP_DEFAULT);
1648 ra = sshkey_fingerprint(found->key,
1649 options.fingerprint_hash, SSH_FP_RANDOMART);
1650 if (fp == NULL || ra == NULL)
1651 fatal_f("sshkey_fingerprint fail");
1652 logit("WARNING: %s key found for host %s\n"
1653 "in %s:%lu\n"
1654 "%s key fingerprint %s.",
1655 sshkey_type(found->key),
1656 found->host, found->file, found->line,
1657 sshkey_type(found->key), fp);
1658 if (options.visual_host_key)
1659 logit("%s", ra);
1660 free(ra);
1661 free(fp);
1662 ret = 1;
1663 }
1664 return ret;
1665 }
1666
1667 static void
warn_changed_key(struct sshkey * host_key)1668 warn_changed_key(struct sshkey *host_key)
1669 {
1670 char *fp;
1671
1672 fp = sshkey_fingerprint(host_key, options.fingerprint_hash,
1673 SSH_FP_DEFAULT);
1674 if (fp == NULL)
1675 fatal_f("sshkey_fingerprint fail");
1676
1677 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1678 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1679 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1680 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1681 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1682 error("It is also possible that a host key has just been changed.");
1683 error("The fingerprint for the %s key sent by the remote host is\n%s.",
1684 sshkey_type(host_key), fp);
1685 error("Please contact your system administrator.");
1686
1687 free(fp);
1688 }
1689
1690 /*
1691 * Execute a local command
1692 */
1693 int
ssh_local_cmd(const char * args)1694 ssh_local_cmd(const char *args)
1695 {
1696 char *shell;
1697 pid_t pid;
1698 int status;
1699 void (*osighand)(int);
1700
1701 if (!options.permit_local_command ||
1702 args == NULL || !*args)
1703 return (1);
1704
1705 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
1706 shell = _PATH_BSHELL;
1707
1708 osighand = ssh_signal(SIGCHLD, SIG_DFL);
1709 pid = fork();
1710 if (pid == 0) {
1711 ssh_signal(SIGPIPE, SIG_DFL);
1712 debug3("Executing %s -c \"%s\"", shell, args);
1713 execl(shell, shell, "-c", args, (char *)NULL);
1714 error("Couldn't execute %s -c \"%s\": %s",
1715 shell, args, strerror(errno));
1716 _exit(1);
1717 } else if (pid == -1)
1718 fatal("fork failed: %.100s", strerror(errno));
1719 while (waitpid(pid, &status, 0) == -1)
1720 if (errno != EINTR)
1721 fatal("Couldn't wait for child: %s", strerror(errno));
1722 ssh_signal(SIGCHLD, osighand);
1723
1724 if (!WIFEXITED(status))
1725 return (1);
1726
1727 return (WEXITSTATUS(status));
1728 }
1729
1730 void
maybe_add_key_to_agent(const char * authfile,struct sshkey * private,const char * comment,const char * passphrase)1731 maybe_add_key_to_agent(const char *authfile, struct sshkey *private,
1732 const char *comment, const char *passphrase)
1733 {
1734 int auth_sock = -1, r;
1735 const char *skprovider = NULL;
1736
1737 if (options.add_keys_to_agent == 0)
1738 return;
1739
1740 if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) {
1741 debug3("no authentication agent, not adding key");
1742 return;
1743 }
1744
1745 if (options.add_keys_to_agent == 2 &&
1746 !ask_permission("Add key %s (%s) to agent?", authfile, comment)) {
1747 debug3("user denied adding this key");
1748 close(auth_sock);
1749 return;
1750 }
1751 if (sshkey_is_sk(private))
1752 skprovider = options.sk_provider;
1753 if ((r = ssh_add_identity_constrained(auth_sock, private,
1754 comment == NULL ? authfile : comment,
1755 options.add_keys_to_agent_lifespan,
1756 (options.add_keys_to_agent == 3), 0, skprovider, NULL, 0)) == 0)
1757 debug("identity added to agent: %s", authfile);
1758 else
1759 debug("could not add identity to agent: %s (%d)", authfile, r);
1760 close(auth_sock);
1761 }
1762