1 /* $OpenBSD: sshconnect.c,v 1.314 2019/02/27 19:37:01 markus Exp $ */
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
6 * Code to connect to a remote host, and to perform the client side of the
7 * login (authentication) dialog.
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".
18 #include <sys/types.h>
21 #include <sys/socket.h>
22 #ifdef HAVE_SYS_TIME_H
23 # include <sys/time.h>
27 #include <netinet/in.h>
28 #include <arpa/inet.h>
58 #include "sshconnect.h"
65 #include "monitor_fdpass.h"
73 struct sshkey *previous_host_key = NULL;
75 static int matching_host_key_dns = 0;
77 static pid_t proxy_command_pid = 0;
80 extern int debug_flag;
81 extern Options options;
82 extern char *__progname;
84 static int show_other_keys(struct hostkeys *, struct sshkey *);
85 static void warn_changed_key(struct sshkey *);
87 /* Expand a proxy command */
89 expand_proxy_command(const char *proxy_command, const char *user,
90 const char *host, int port)
92 char *tmp, *ret, strport[NI_MAXSERV];
94 snprintf(strport, sizeof strport, "%d", port);
95 xasprintf(&tmp, "exec %s", proxy_command);
96 ret = percent_expand(tmp, "h", host, "p", strport,
97 "r", options.user, (char *)NULL);
107 if ((devnull = open(_PATH_DEVNULL, O_WRONLY)) == -1) {
108 error("Can't open %s for stderr redirection: %s",
109 _PATH_DEVNULL, strerror(errno));
112 if (devnull == STDERR_FILENO)
114 if (dup2(devnull, STDERR_FILENO) == -1)
115 error("Cannot redirect stderr to %s", _PATH_DEVNULL);
116 if (devnull > STDERR_FILENO)
121 * Connect to the given ssh server using a proxy command that passes a
122 * a connected fd back to us.
125 ssh_proxy_fdpass_connect(struct ssh *ssh, const char *host, u_short port,
126 const char *proxy_command)
128 char *command_string;
133 if ((shell = getenv("SHELL")) == NULL)
134 shell = _PATH_BSHELL;
136 if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) < 0)
137 fatal("Could not create socketpair to communicate with "
138 "proxy dialer: %.100s", strerror(errno));
140 command_string = expand_proxy_command(proxy_command, options.user,
142 debug("Executing proxy dialer command: %.500s", command_string);
144 /* Fork and execute the proxy command. */
145 if ((pid = fork()) == 0) {
149 /* Redirect stdin and stdout. */
151 if (dup2(sp[0], 0) < 0)
152 perror("dup2 stdin");
155 if (dup2(sp[0], 1) < 0)
156 perror("dup2 stdout");
162 * Stderr is left for non-ControlPersist connections is so
163 * error messages may be printed on the user's terminal.
165 if (!debug_flag && options.control_path != NULL &&
166 options.control_persist)
171 argv[2] = command_string;
175 * Execute the proxy command.
176 * Note that we gave up any extra privileges above.
178 execv(argv[0], argv);
184 fatal("fork failed: %.100s", strerror(errno));
186 free(command_string);
188 if ((sock = mm_receive_fd(sp[1])) == -1)
189 fatal("proxy dialer did not pass back a connection");
192 while (waitpid(pid, NULL, 0) == -1)
194 fatal("Couldn't wait for child: %s", strerror(errno));
196 /* Set the connection file descriptors. */
197 if (ssh_packet_set_connection(ssh, sock, sock) == NULL)
198 return -1; /* ssh_packet_set_connection logs error */
204 * Connect to the given ssh server using a proxy command.
207 ssh_proxy_connect(struct ssh *ssh, const char *host, u_short port,
208 const char *proxy_command)
210 char *command_string;
215 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
216 shell = _PATH_BSHELL;
218 /* Create pipes for communicating with the proxy. */
219 if (pipe(pin) < 0 || pipe(pout) < 0)
220 fatal("Could not create pipes to communicate with the proxy: %.100s",
223 command_string = expand_proxy_command(proxy_command, options.user,
225 debug("Executing proxy command: %.500s", command_string);
227 /* Fork and execute the proxy command. */
228 if ((pid = fork()) == 0) {
231 /* Redirect stdin and stdout. */
234 if (dup2(pin[0], 0) < 0)
235 perror("dup2 stdin");
239 if (dup2(pout[1], 1) < 0)
240 perror("dup2 stdout");
241 /* Cannot be 1 because pin allocated two descriptors. */
245 * Stderr is left for non-ControlPersist connections is so
246 * error messages may be printed on the user's terminal.
248 if (!debug_flag && options.control_path != NULL &&
249 options.control_persist)
254 argv[2] = command_string;
257 /* Execute the proxy command. Note that we gave up any
258 extra privileges above. */
259 signal(SIGPIPE, SIG_DFL);
260 execv(argv[0], argv);
266 fatal("fork failed: %.100s", strerror(errno));
268 proxy_command_pid = pid; /* save pid to clean up later */
270 /* Close child side of the descriptors. */
274 /* Free the command name. */
275 free(command_string);
277 /* Set the connection file descriptors. */
278 if (ssh_packet_set_connection(ssh, pout[0], pin[1]) == NULL)
279 return -1; /* ssh_packet_set_connection logs error */
285 ssh_kill_proxy_command(void)
288 * Send SIGHUP to proxy command if used. We don't wait() in
289 * case it hangs and instead rely on init to reap the child
291 if (proxy_command_pid > 1)
292 kill(proxy_command_pid, SIGHUP);
295 #ifdef HAVE_IFADDRS_H
297 * Search a interface address list (returned from getifaddrs(3)) for an
298 * address that matches the desired address family on the specified interface.
299 * Returns 0 and fills in *resultp and *rlenp on success. Returns -1 on failure.
302 check_ifaddrs(const char *ifname, int af, const struct ifaddrs *ifaddrs,
303 struct sockaddr_storage *resultp, socklen_t *rlenp)
305 struct sockaddr_in6 *sa6;
306 struct sockaddr_in *sa;
307 struct in6_addr *v6addr;
308 const struct ifaddrs *ifa;
312 * Prefer addresses that are not loopback or linklocal, but use them
313 * if nothing else matches.
315 for (allow_local = 0; allow_local < 2; allow_local++) {
316 for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) {
317 if (ifa->ifa_addr == NULL || ifa->ifa_name == NULL ||
318 (ifa->ifa_flags & IFF_UP) == 0 ||
319 ifa->ifa_addr->sa_family != af ||
320 strcmp(ifa->ifa_name, options.bind_interface) != 0)
322 switch (ifa->ifa_addr->sa_family) {
324 sa = (struct sockaddr_in *)ifa->ifa_addr;
325 if (!allow_local && sa->sin_addr.s_addr ==
326 htonl(INADDR_LOOPBACK))
328 if (*rlenp < sizeof(struct sockaddr_in)) {
329 error("%s: v4 addr doesn't fit",
333 *rlenp = sizeof(struct sockaddr_in);
334 memcpy(resultp, sa, *rlenp);
337 sa6 = (struct sockaddr_in6 *)ifa->ifa_addr;
338 v6addr = &sa6->sin6_addr;
340 (IN6_IS_ADDR_LINKLOCAL(v6addr) ||
341 IN6_IS_ADDR_LOOPBACK(v6addr)))
343 if (*rlenp < sizeof(struct sockaddr_in6)) {
344 error("%s: v6 addr doesn't fit",
348 *rlenp = sizeof(struct sockaddr_in6);
349 memcpy(resultp, sa6, *rlenp);
359 * Creates a socket for use as the ssh connection.
362 ssh_create_socket(struct addrinfo *ai)
365 struct sockaddr_storage bindaddr;
366 socklen_t bindaddrlen = 0;
367 struct addrinfo hints, *res = NULL;
368 #ifdef HAVE_IFADDRS_H
369 struct ifaddrs *ifaddrs = NULL;
371 char ntop[NI_MAXHOST];
373 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
375 error("socket: %s", strerror(errno));
378 fcntl(sock, F_SETFD, FD_CLOEXEC);
380 /* Bind the socket to an alternative local IP address */
381 if (options.bind_address == NULL && options.bind_interface == NULL)
384 if (options.bind_address != NULL) {
385 memset(&hints, 0, sizeof(hints));
386 hints.ai_family = ai->ai_family;
387 hints.ai_socktype = ai->ai_socktype;
388 hints.ai_protocol = ai->ai_protocol;
389 hints.ai_flags = AI_PASSIVE;
390 if ((r = getaddrinfo(options.bind_address, NULL,
391 &hints, &res)) != 0) {
392 error("getaddrinfo: %s: %s", options.bind_address,
393 ssh_gai_strerror(r));
397 error("getaddrinfo: no addrs");
400 memcpy(&bindaddr, res->ai_addr, res->ai_addrlen);
401 bindaddrlen = res->ai_addrlen;
402 } else if (options.bind_interface != NULL) {
403 #ifdef HAVE_IFADDRS_H
404 if ((r = getifaddrs(&ifaddrs)) != 0) {
405 error("getifaddrs: %s: %s", options.bind_interface,
409 bindaddrlen = sizeof(bindaddr);
410 if (check_ifaddrs(options.bind_interface, ai->ai_family,
411 ifaddrs, &bindaddr, &bindaddrlen) != 0) {
412 logit("getifaddrs: %s: no suitable addresses",
413 options.bind_interface);
417 error("BindInterface not supported on this platform.");
420 if ((r = getnameinfo((struct sockaddr *)&bindaddr, bindaddrlen,
421 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST)) != 0) {
422 error("%s: getnameinfo failed: %s", __func__,
423 ssh_gai_strerror(r));
426 if (bind(sock, (struct sockaddr *)&bindaddr, bindaddrlen) != 0) {
427 error("bind %s: %s", ntop, strerror(errno));
430 debug("%s: bound to %s", __func__, ntop);
439 #ifdef HAVE_IFADDRS_H
441 freeifaddrs(ifaddrs);
447 * Opens a TCP/IP connection to the remote server on the given host.
448 * The address of the remote host will be returned in hostaddr.
449 * If port is 0, the default port will be used.
450 * Connection_attempts specifies the maximum number of tries (one per
451 * second). If proxy_command is non-NULL, it specifies the command (with %h
452 * and %p substituted for host and port, respectively) to use to contact
456 ssh_connect_direct(struct ssh *ssh, const char *host, struct addrinfo *aitop,
457 struct sockaddr_storage *hostaddr, u_short port, int family,
458 int connection_attempts, int *timeout_ms, int want_keepalive)
460 int on = 1, saved_timeout_ms = *timeout_ms;
461 int oerrno, sock = -1, attempt;
462 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
465 debug2("%s", __func__);
466 memset(ntop, 0, sizeof(ntop));
467 memset(strport, 0, sizeof(strport));
469 for (attempt = 0; attempt < connection_attempts; attempt++) {
471 /* Sleep a moment before retrying. */
473 debug("Trying again...");
476 * Loop through addresses for this host, and try each one in
477 * sequence until the connection succeeds.
479 for (ai = aitop; ai; ai = ai->ai_next) {
480 if (ai->ai_family != AF_INET &&
481 ai->ai_family != AF_INET6) {
482 errno = EAFNOSUPPORT;
485 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
486 ntop, sizeof(ntop), strport, sizeof(strport),
487 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
489 error("%s: getnameinfo failed", __func__);
493 debug("Connecting to %.200s [%.100s] port %s.",
494 host, ntop, strport);
496 /* Create a socket for connecting. */
497 sock = ssh_create_socket(ai);
499 /* Any error is already output */
504 *timeout_ms = saved_timeout_ms;
505 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
507 /* Successful connection. */
508 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
512 debug("connect to address %s port %s: %s",
513 ntop, strport, strerror(errno));
520 break; /* Successful connection. */
523 /* Return failure if we didn't get a successful connection. */
525 error("ssh: connect to host %s port %s: %s",
526 host, strport, errno == 0 ? "failure" : strerror(errno));
530 debug("Connection established.");
532 /* Set SO_KEEPALIVE if requested. */
533 if (want_keepalive &&
534 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
536 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
538 /* Set the connection. */
539 if (ssh_packet_set_connection(ssh, sock, sock) == NULL)
540 return -1; /* ssh_packet_set_connection logs error */
546 ssh_connect(struct ssh *ssh, const char *host, struct addrinfo *addrs,
547 struct sockaddr_storage *hostaddr, u_short port, int family,
548 int connection_attempts, int *timeout_ms, int want_keepalive)
552 if (options.proxy_command == NULL) {
553 return ssh_connect_direct(ssh, host, addrs, hostaddr, port,
554 family, connection_attempts, timeout_ms, want_keepalive);
555 } else if (strcmp(options.proxy_command, "-") == 0) {
556 if ((in = dup(STDIN_FILENO)) < 0 ||
557 (out = dup(STDOUT_FILENO)) < 0) {
560 error("%s: dup() in/out failed", __func__);
561 return -1; /* ssh_packet_set_connection logs error */
563 if ((ssh_packet_set_connection(ssh, in, out)) == NULL)
564 return -1; /* ssh_packet_set_connection logs error */
566 } else if (options.proxy_use_fdpass) {
567 return ssh_proxy_fdpass_connect(ssh, host, port,
568 options.proxy_command);
570 return ssh_proxy_connect(ssh, host, port, options.proxy_command);
573 /* defaults to 'no' */
575 confirm(const char *prompt, const char *fingerprint)
577 const char *msg, *again = "Please type 'yes' or 'no': ";
578 const char *again_fp = "Please type 'yes', 'no' or the fingerprint: ";
582 if (options.batch_mode)
584 for (msg = prompt;;msg = fingerprint ? again_fp : again) {
585 p = read_passphrase(msg, RP_ECHO);
588 p[strcspn(p, "\n")] = '\0';
589 if (p[0] == '\0' || strcasecmp(p, "no") == 0)
591 else if (strcasecmp(p, "yes") == 0 || (fingerprint != NULL &&
592 strcasecmp(p, fingerprint) == 0))
601 check_host_cert(const char *host, const struct sshkey *key)
606 if (sshkey_cert_check_authority(key, 1, 0, host, &reason) != 0) {
610 if (sshbuf_len(key->cert->critical) != 0) {
611 error("Certificate for %s contains unsupported "
612 "critical options(s)", host);
615 if ((r = sshkey_check_cert_sigtype(key,
616 options.ca_sign_algorithms)) != 0) {
617 logit("%s: certificate signature algorithm %s: %s", __func__,
618 (key->cert == NULL || key->cert->signature_type == NULL) ?
619 "(null)" : key->cert->signature_type, ssh_err(r));
627 sockaddr_is_local(struct sockaddr *hostaddr)
629 switch (hostaddr->sa_family) {
631 return (ntohl(((struct sockaddr_in *)hostaddr)->
632 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
634 return IN6_IS_ADDR_LOOPBACK(
635 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
642 * Prepare the hostname and ip address strings that are used to lookup
643 * host keys in known_hosts files. These may have a port number appended.
646 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr,
647 u_short port, char **hostfile_hostname, char **hostfile_ipaddr)
649 char ntop[NI_MAXHOST];
652 switch (hostaddr == NULL ? -1 : hostaddr->sa_family) {
657 addrlen = sizeof(struct sockaddr_in);
660 addrlen = sizeof(struct sockaddr_in6);
663 addrlen = sizeof(struct sockaddr);
668 * We don't have the remote ip-address for connections
669 * using a proxy command
671 if (hostfile_ipaddr != NULL) {
672 if (options.proxy_command == NULL) {
673 if (getnameinfo(hostaddr, addrlen,
674 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0)
675 fatal("%s: getnameinfo failed", __func__);
676 *hostfile_ipaddr = put_host_port(ntop, port);
678 *hostfile_ipaddr = xstrdup("<no hostip for proxy "
684 * Allow the user to record the key under a different name or
685 * differentiate a non-standard port. This is useful for ssh
686 * tunneling over forwarded connections or if you run multiple
687 * sshd's on different ports on the same machine.
689 if (hostfile_hostname != NULL) {
690 if (options.host_key_alias != NULL) {
691 *hostfile_hostname = xstrdup(options.host_key_alias);
692 debug("using hostkeyalias: %s", *hostfile_hostname);
694 *hostfile_hostname = put_host_port(hostname, port);
700 * check whether the supplied host key is valid, return -1 if the key
701 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true.
707 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
708 struct sshkey *host_key, int readonly,
709 char **user_hostfiles, u_int num_user_hostfiles,
710 char **system_hostfiles, u_int num_system_hostfiles)
712 HostStatus host_status;
713 HostStatus ip_status;
714 struct sshkey *raw_key = NULL;
715 char *ip = NULL, *host = NULL;
716 char hostline[1000], *hostp, *fp, *ra;
719 const struct hostkey_entry *host_found, *ip_found;
720 int len, cancelled_forwarding = 0, confirmed;
721 int local = sockaddr_is_local(hostaddr);
722 int r, want_cert = sshkey_is_cert(host_key), host_ip_differ = 0;
723 int hostkey_trusted = 0; /* Known or explicitly accepted by user */
724 struct hostkeys *host_hostkeys, *ip_hostkeys;
728 * Force accepting of the host key for loopback/localhost. The
729 * problem is that if the home directory is NFS-mounted to multiple
730 * machines, localhost will refer to a different machine in each of
731 * them, and the user will get bogus HOST_CHANGED warnings. This
732 * essentially disables host authentication for localhost; however,
733 * this is probably not a real problem.
735 if (options.no_host_authentication_for_localhost == 1 && local &&
736 options.host_key_alias == NULL) {
737 debug("Forcing accepting of host key for "
738 "loopback/localhost.");
743 * Prepare the hostname and address strings used for hostkey lookup.
744 * In some cases, these will have a port number appended.
746 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip);
749 * Turn off check_host_ip if the connection is to localhost, via proxy
750 * command or if we don't have a hostname to compare with
752 if (options.check_host_ip && (local ||
753 strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
754 options.check_host_ip = 0;
756 host_hostkeys = init_hostkeys();
757 for (i = 0; i < num_user_hostfiles; i++)
758 load_hostkeys(host_hostkeys, host, user_hostfiles[i]);
759 for (i = 0; i < num_system_hostfiles; i++)
760 load_hostkeys(host_hostkeys, host, system_hostfiles[i]);
763 if (!want_cert && options.check_host_ip) {
764 ip_hostkeys = init_hostkeys();
765 for (i = 0; i < num_user_hostfiles; i++)
766 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]);
767 for (i = 0; i < num_system_hostfiles; i++)
768 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]);
772 /* Reload these as they may have changed on cert->key downgrade */
773 want_cert = sshkey_is_cert(host_key);
774 type = sshkey_type(host_key);
777 * Check if the host key is present in the user's list of known
778 * hosts or in the systemwide list.
780 host_status = check_key_in_hostkeys(host_hostkeys, host_key,
784 * Also perform check for the ip address, skip the check if we are
785 * localhost, looking for a certificate, or the hostname was an ip
786 * address to begin with.
788 if (!want_cert && ip_hostkeys != NULL) {
789 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key,
791 if (host_status == HOST_CHANGED &&
792 (ip_status != HOST_CHANGED ||
794 !sshkey_equal(ip_found->key, host_found->key))))
797 ip_status = host_status;
799 switch (host_status) {
801 /* The host is known and the key matches. */
802 debug("Host '%.200s' is known and matches the %s host %s.",
803 host, type, want_cert ? "certificate" : "key");
804 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key",
805 host_found->file, host_found->line);
807 !check_host_cert(options.host_key_alias == NULL ?
808 hostname : options.host_key_alias, host_key))
810 if (options.check_host_ip && ip_status == HOST_NEW) {
811 if (readonly || want_cert)
812 logit("%s host key for IP address "
813 "'%.128s' not in list of known hosts.",
815 else if (!add_host_to_hostfile(user_hostfiles[0], ip,
816 host_key, options.hash_known_hosts))
817 logit("Failed to add the %s host key for IP "
818 "address '%.128s' to the list of known "
819 "hosts (%.500s).", type, ip,
822 logit("Warning: Permanently added the %s host "
823 "key for IP address '%.128s' to the list "
824 "of known hosts.", type, ip);
825 } else if (options.visual_host_key) {
826 fp = sshkey_fingerprint(host_key,
827 options.fingerprint_hash, SSH_FP_DEFAULT);
828 ra = sshkey_fingerprint(host_key,
829 options.fingerprint_hash, SSH_FP_RANDOMART);
830 if (fp == NULL || ra == NULL)
831 fatal("%s: sshkey_fingerprint fail", __func__);
832 logit("Host key fingerprint is %s\n%s", fp, ra);
839 if (options.host_key_alias == NULL && port != 0 &&
840 port != SSH_DEFAULT_PORT) {
841 debug("checking without port identifier");
842 if (check_host_key(hostname, hostaddr, 0, host_key,
843 ROQUIET, user_hostfiles, num_user_hostfiles,
844 system_hostfiles, num_system_hostfiles) == 0) {
845 debug("found matching key w/out port");
849 if (readonly || want_cert)
851 /* The host is new. */
852 if (options.strict_host_key_checking ==
853 SSH_STRICT_HOSTKEY_YES) {
855 * User has requested strict host key checking. We
856 * will not add the host key automatically. The only
857 * alternative left is to abort.
859 error("No %s host key is known for %.200s and you "
860 "have requested strict checking.", type, host);
862 } else if (options.strict_host_key_checking ==
863 SSH_STRICT_HOSTKEY_ASK) {
864 char msg1[1024], msg2[1024];
866 if (show_other_keys(host_hostkeys, host_key))
867 snprintf(msg1, sizeof(msg1),
868 "\nbut keys of different type are already"
869 " known for this host.");
871 snprintf(msg1, sizeof(msg1), ".");
873 fp = sshkey_fingerprint(host_key,
874 options.fingerprint_hash, SSH_FP_DEFAULT);
875 ra = sshkey_fingerprint(host_key,
876 options.fingerprint_hash, SSH_FP_RANDOMART);
877 if (fp == NULL || ra == NULL)
878 fatal("%s: sshkey_fingerprint fail", __func__);
880 if (options.verify_host_key_dns) {
881 if (matching_host_key_dns)
882 snprintf(msg2, sizeof(msg2),
883 "Matching host key fingerprint"
886 snprintf(msg2, sizeof(msg2),
887 "No matching host key fingerprint"
890 snprintf(msg, sizeof(msg),
891 "The authenticity of host '%.200s (%s)' can't be "
893 "%s key fingerprint is %s.%s%s\n%s"
894 "Are you sure you want to continue connecting "
895 "(yes/no/[fingerprint])? ",
896 host, ip, msg1, type, fp,
897 options.visual_host_key ? "\n" : "",
898 options.visual_host_key ? ra : "",
901 confirmed = confirm(msg, fp);
905 hostkey_trusted = 1; /* user explicitly confirmed */
908 * If in "new" or "off" strict mode, add the key automatically
909 * to the local known_hosts file.
911 if (options.check_host_ip && ip_status == HOST_NEW) {
912 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
914 if (options.hash_known_hosts) {
915 /* Add hash of host and IP separately */
916 r = add_host_to_hostfile(user_hostfiles[0],
917 host, host_key, options.hash_known_hosts) &&
918 add_host_to_hostfile(user_hostfiles[0], ip,
919 host_key, options.hash_known_hosts);
921 /* Add unhashed "host,ip" */
922 r = add_host_to_hostfile(user_hostfiles[0],
924 options.hash_known_hosts);
927 r = add_host_to_hostfile(user_hostfiles[0], host,
928 host_key, options.hash_known_hosts);
933 logit("Failed to add the host to the list of known "
934 "hosts (%.500s).", user_hostfiles[0]);
936 logit("Warning: Permanently added '%.200s' (%s) to the "
937 "list of known hosts.", hostp, type);
940 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
941 error("@ WARNING: REVOKED HOST KEY DETECTED! @");
942 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
943 error("The %s host key for %s is marked as revoked.", type, host);
944 error("This could mean that a stolen key is being used to");
945 error("impersonate this host.");
948 * If strict host key checking is in use, the user will have
949 * to edit the key manually and we can only abort.
951 if (options.strict_host_key_checking !=
952 SSH_STRICT_HOSTKEY_OFF) {
953 error("%s host key for %.200s was revoked and you have "
954 "requested strict checking.", type, host);
957 goto continue_unsafe;
962 * This is only a debug() since it is valid to have
963 * CAs with wildcard DNS matches that don't match
964 * all hosts that one might visit.
966 debug("Host certificate authority does not "
967 "match %s in %s:%lu", CA_MARKER,
968 host_found->file, host_found->line);
971 if (readonly == ROQUIET)
973 if (options.check_host_ip && host_ip_differ) {
975 if (ip_status == HOST_NEW)
976 key_msg = "is unknown";
977 else if (ip_status == HOST_OK)
978 key_msg = "is unchanged";
980 key_msg = "has a different value";
981 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
982 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
983 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
984 error("The %s host key for %s has changed,", type, host);
985 error("and the key for the corresponding IP address %s", ip);
986 error("%s. This could either mean that", key_msg);
987 error("DNS SPOOFING is happening or the IP address for the host");
988 error("and its host key have changed at the same time.");
989 if (ip_status != HOST_NEW)
990 error("Offending key for IP in %s:%lu",
991 ip_found->file, ip_found->line);
993 /* The host key has changed. */
994 warn_changed_key(host_key);
995 error("Add correct host key in %.100s to get rid of this message.",
997 error("Offending %s key in %s:%lu",
998 sshkey_type(host_found->key),
999 host_found->file, host_found->line);
1002 * If strict host key checking is in use, the user will have
1003 * to edit the key manually and we can only abort.
1005 if (options.strict_host_key_checking !=
1006 SSH_STRICT_HOSTKEY_OFF) {
1007 error("%s host key for %.200s has changed and you have "
1008 "requested strict checking.", type, host);
1014 * If strict host key checking has not been requested, allow
1015 * the connection but without MITM-able authentication or
1018 if (options.password_authentication) {
1019 error("Password authentication is disabled to avoid "
1020 "man-in-the-middle attacks.");
1021 options.password_authentication = 0;
1022 cancelled_forwarding = 1;
1024 if (options.kbd_interactive_authentication) {
1025 error("Keyboard-interactive authentication is disabled"
1026 " to avoid man-in-the-middle attacks.");
1027 options.kbd_interactive_authentication = 0;
1028 options.challenge_response_authentication = 0;
1029 cancelled_forwarding = 1;
1031 if (options.challenge_response_authentication) {
1032 error("Challenge/response authentication is disabled"
1033 " to avoid man-in-the-middle attacks.");
1034 options.challenge_response_authentication = 0;
1035 cancelled_forwarding = 1;
1037 if (options.forward_agent) {
1038 error("Agent forwarding is disabled to avoid "
1039 "man-in-the-middle attacks.");
1040 options.forward_agent = 0;
1041 cancelled_forwarding = 1;
1043 if (options.forward_x11) {
1044 error("X11 forwarding is disabled to avoid "
1045 "man-in-the-middle attacks.");
1046 options.forward_x11 = 0;
1047 cancelled_forwarding = 1;
1049 if (options.num_local_forwards > 0 ||
1050 options.num_remote_forwards > 0) {
1051 error("Port forwarding is disabled to avoid "
1052 "man-in-the-middle attacks.");
1053 options.num_local_forwards =
1054 options.num_remote_forwards = 0;
1055 cancelled_forwarding = 1;
1057 if (options.tun_open != SSH_TUNMODE_NO) {
1058 error("Tunnel forwarding is disabled to avoid "
1059 "man-in-the-middle attacks.");
1060 options.tun_open = SSH_TUNMODE_NO;
1061 cancelled_forwarding = 1;
1063 if (options.exit_on_forward_failure && cancelled_forwarding)
1064 fatal("Error: forwarding disabled due to host key "
1068 * XXX Should permit the user to change to use the new id.
1069 * This could be done by converting the host key to an
1070 * identifying sentence, tell that the host identifies itself
1071 * by that sentence, and ask the user if he/she wishes to
1072 * accept the authentication.
1076 fatal("internal error");
1080 if (options.check_host_ip && host_status != HOST_CHANGED &&
1081 ip_status == HOST_CHANGED) {
1082 snprintf(msg, sizeof(msg),
1083 "Warning: the %s host key for '%.200s' "
1084 "differs from the key for the IP address '%.128s'"
1085 "\nOffending key for IP in %s:%lu",
1086 type, host, ip, ip_found->file, ip_found->line);
1087 if (host_status == HOST_OK) {
1089 snprintf(msg + len, sizeof(msg) - len,
1090 "\nMatching host key in %s:%lu",
1091 host_found->file, host_found->line);
1093 if (options.strict_host_key_checking ==
1094 SSH_STRICT_HOSTKEY_ASK) {
1095 strlcat(msg, "\nAre you sure you want "
1096 "to continue connecting (yes/no)? ", sizeof(msg));
1097 if (!confirm(msg, NULL))
1099 } else if (options.strict_host_key_checking !=
1100 SSH_STRICT_HOSTKEY_OFF) {
1102 error("Exiting, you have requested strict checking.");
1109 if (!hostkey_trusted && options.update_hostkeys) {
1110 debug("%s: hostkey not known or explicitly trusted: "
1111 "disabling UpdateHostkeys", __func__);
1112 options.update_hostkeys = 0;
1117 if (host_hostkeys != NULL)
1118 free_hostkeys(host_hostkeys);
1119 if (ip_hostkeys != NULL)
1120 free_hostkeys(ip_hostkeys);
1124 if (want_cert && host_status != HOST_REVOKED) {
1126 * No matching certificate. Downgrade cert to raw key and
1129 debug("No matching CA found. Retry with plain key");
1130 if ((r = sshkey_from_private(host_key, &raw_key)) != 0)
1131 fatal("%s: sshkey_from_private: %s",
1132 __func__, ssh_err(r));
1133 if ((r = sshkey_drop_cert(raw_key)) != 0)
1134 fatal("Couldn't drop certificate: %s", ssh_err(r));
1138 sshkey_free(raw_key);
1141 if (host_hostkeys != NULL)
1142 free_hostkeys(host_hostkeys);
1143 if (ip_hostkeys != NULL)
1144 free_hostkeys(ip_hostkeys);
1148 /* returns 0 if key verifies or -1 if key does NOT verify */
1150 verify_host_key(char *host, struct sockaddr *hostaddr, struct sshkey *host_key)
1153 int r = -1, flags = 0;
1154 char valid[64], *fp = NULL, *cafp = NULL;
1155 struct sshkey *plain = NULL;
1157 if ((fp = sshkey_fingerprint(host_key,
1158 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1159 error("%s: fingerprint host key: %s", __func__, ssh_err(r));
1164 if (sshkey_is_cert(host_key)) {
1165 if ((cafp = sshkey_fingerprint(host_key->cert->signature_key,
1166 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1167 error("%s: fingerprint CA key: %s",
1168 __func__, ssh_err(r));
1172 sshkey_format_cert_validity(host_key->cert,
1173 valid, sizeof(valid));
1174 debug("Server host certificate: %s %s, serial %llu "
1175 "ID \"%s\" CA %s %s valid %s",
1176 sshkey_ssh_name(host_key), fp,
1177 (unsigned long long)host_key->cert->serial,
1178 host_key->cert->key_id,
1179 sshkey_ssh_name(host_key->cert->signature_key), cafp,
1181 for (i = 0; i < host_key->cert->nprincipals; i++) {
1182 debug2("Server host certificate hostname: %s",
1183 host_key->cert->principals[i]);
1186 debug("Server host key: %s %s", sshkey_ssh_name(host_key), fp);
1189 if (sshkey_equal(previous_host_key, host_key)) {
1190 debug2("%s: server host key %s %s matches cached key",
1191 __func__, sshkey_type(host_key), fp);
1196 /* Check in RevokedHostKeys file if specified */
1197 if (options.revoked_host_keys != NULL) {
1198 r = sshkey_check_revoked(host_key, options.revoked_host_keys);
1201 break; /* not revoked */
1202 case SSH_ERR_KEY_REVOKED:
1203 error("Host key %s %s revoked by file %s",
1204 sshkey_type(host_key), fp,
1205 options.revoked_host_keys);
1209 error("Error checking host key %s %s in "
1210 "revoked keys file %s: %s", sshkey_type(host_key),
1211 fp, options.revoked_host_keys, ssh_err(r));
1217 if (options.verify_host_key_dns) {
1219 * XXX certs are not yet supported for DNS, so downgrade
1220 * them and try the plain key.
1222 if ((r = sshkey_from_private(host_key, &plain)) != 0)
1224 if (sshkey_is_cert(plain))
1225 sshkey_drop_cert(plain);
1226 if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) {
1227 if (flags & DNS_VERIFY_FOUND) {
1228 if (options.verify_host_key_dns == 1 &&
1229 flags & DNS_VERIFY_MATCH &&
1230 flags & DNS_VERIFY_SECURE) {
1234 if (flags & DNS_VERIFY_MATCH) {
1235 matching_host_key_dns = 1;
1237 warn_changed_key(plain);
1238 error("Update the SSHFP RR in DNS "
1239 "with the new host key to get rid "
1240 "of this message.");
1245 r = check_host_key(host, hostaddr, options.port, host_key, RDRW,
1246 options.user_hostfiles, options.num_user_hostfiles,
1247 options.system_hostfiles, options.num_system_hostfiles);
1253 if (r == 0 && host_key != NULL) {
1254 sshkey_free(previous_host_key);
1255 r = sshkey_from_private(host_key, &previous_host_key);
1262 * Starts a dialog with the server, and authenticates the current user on the
1263 * server. This does not need any extra privileges. The basic connection
1264 * to the server must already have been established before this is called.
1265 * If login fails, this function prints an error and never returns.
1266 * This function does not require super-user privileges.
1269 ssh_login(struct ssh *ssh, Sensitive *sensitive, const char *orighost,
1270 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms)
1273 char *server_user, *local_user;
1275 local_user = xstrdup(pw->pw_name);
1276 server_user = options.user ? options.user : local_user;
1278 /* Convert the user-supplied hostname into all lowercase. */
1279 host = xstrdup(orighost);
1282 /* Exchange protocol version identification strings with the server. */
1283 if (kex_exchange_identification(ssh, timeout_ms, NULL) != 0)
1284 cleanup_exit(255); /* error already logged */
1286 /* Put the connection into non-blocking mode. */
1287 ssh_packet_set_nonblocking(ssh);
1290 /* authenticate user */
1291 debug("Authenticating to %s:%d as '%s'", host, port, server_user);
1292 ssh_kex2(ssh, host, hostaddr, port);
1293 ssh_userauth2(ssh, local_user, server_user, host, sensitive);
1297 /* print all known host keys for a given host, but skip keys of given type */
1299 show_other_keys(struct hostkeys *hostkeys, struct sshkey *key)
1311 const struct hostkey_entry *found;
1313 for (i = 0; type[i] != -1; i++) {
1314 if (type[i] == key->type)
1316 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found))
1318 fp = sshkey_fingerprint(found->key,
1319 options.fingerprint_hash, SSH_FP_DEFAULT);
1320 ra = sshkey_fingerprint(found->key,
1321 options.fingerprint_hash, SSH_FP_RANDOMART);
1322 if (fp == NULL || ra == NULL)
1323 fatal("%s: sshkey_fingerprint fail", __func__);
1324 logit("WARNING: %s key found for host %s\n"
1326 "%s key fingerprint %s.",
1327 sshkey_type(found->key),
1328 found->host, found->file, found->line,
1329 sshkey_type(found->key), fp);
1330 if (options.visual_host_key)
1340 warn_changed_key(struct sshkey *host_key)
1344 fp = sshkey_fingerprint(host_key, options.fingerprint_hash,
1347 fatal("%s: sshkey_fingerprint fail", __func__);
1349 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1350 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1351 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1352 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1353 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1354 error("It is also possible that a host key has just been changed.");
1355 error("The fingerprint for the %s key sent by the remote host is\n%s.",
1356 sshkey_type(host_key), fp);
1357 error("Please contact your system administrator.");
1363 * Execute a local command
1366 ssh_local_cmd(const char *args)
1371 void (*osighand)(int);
1373 if (!options.permit_local_command ||
1374 args == NULL || !*args)
1377 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
1378 shell = _PATH_BSHELL;
1380 osighand = signal(SIGCHLD, SIG_DFL);
1383 signal(SIGPIPE, SIG_DFL);
1384 debug3("Executing %s -c \"%s\"", shell, args);
1385 execl(shell, shell, "-c", args, (char *)NULL);
1386 error("Couldn't execute %s -c \"%s\": %s",
1387 shell, args, strerror(errno));
1389 } else if (pid == -1)
1390 fatal("fork failed: %.100s", strerror(errno));
1391 while (waitpid(pid, &status, 0) == -1)
1393 fatal("Couldn't wait for child: %s", strerror(errno));
1394 signal(SIGCHLD, osighand);
1396 if (!WIFEXITED(status))
1399 return (WEXITSTATUS(status));
1403 maybe_add_key_to_agent(char *authfile, const struct sshkey *private,
1404 char *comment, char *passphrase)
1406 int auth_sock = -1, r;
1408 if (options.add_keys_to_agent == 0)
1411 if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) {
1412 debug3("no authentication agent, not adding key");
1416 if (options.add_keys_to_agent == 2 &&
1417 !ask_permission("Add key %s (%s) to agent?", authfile, comment)) {
1418 debug3("user denied adding this key");
1423 if ((r = ssh_add_identity_constrained(auth_sock, private, comment, 0,
1424 (options.add_keys_to_agent == 3), 0)) == 0)
1425 debug("identity added to agent: %s", authfile);
1427 debug("could not add identity to agent: %s (%d)", authfile, r);