1 /* $OpenBSD: sshconnect.c,v 1.232 2011/01/16 11:50:36 djm Exp $ */
4 * Author: Tatu Ylonen <ylo@cs.hut.fi>
5 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
7 * Code to connect to a remote host, and to perform the client side of the
8 * login (authentication) dialog.
10 * As far as I am concerned, the code I have written for this software
11 * can be used freely for any purpose. Any derived versions of this
12 * software must be clearly marked as such, and if the derived work is
13 * incompatible with the protocol description in the RFC file, it must be
14 * called by a name other than "ssh" or "Secure Shell".
19 #include <sys/types.h>
22 #include <sys/socket.h>
23 #ifdef HAVE_SYS_TIME_H
24 # include <sys/time.h>
27 #include <netinet/in.h>
28 #include <arpa/inet.h>
55 #include "sshconnect.h"
66 char *client_version_string = NULL;
67 char *server_version_string = NULL;
69 static int matching_host_key_dns = 0;
71 static pid_t proxy_command_pid = 0;
74 extern Options options;
75 extern char *__progname;
76 extern uid_t original_real_uid;
77 extern uid_t original_effective_uid;
79 static int show_other_keys(struct hostkeys *, Key *);
80 static void warn_changed_key(Key *);
83 * Connect to the given ssh server using a proxy command.
86 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
88 char *command_string, *tmp;
91 char *shell, strport[NI_MAXSERV];
93 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
96 /* Convert the port number into a string. */
97 snprintf(strport, sizeof strport, "%hu", port);
100 * Build the final command string in the buffer by making the
101 * appropriate substitutions to the given proxy command.
103 * Use "exec" to avoid "sh -c" processes on some platforms
106 xasprintf(&tmp, "exec %s", proxy_command);
107 command_string = percent_expand(tmp, "h", host, "p", strport,
108 "r", options.user, (char *)NULL);
111 /* Create pipes for communicating with the proxy. */
112 if (pipe(pin) < 0 || pipe(pout) < 0)
113 fatal("Could not create pipes to communicate with the proxy: %.100s",
116 debug("Executing proxy command: %.500s", command_string);
118 /* Fork and execute the proxy command. */
119 if ((pid = fork()) == 0) {
122 /* Child. Permanently give up superuser privileges. */
123 permanently_drop_suid(original_real_uid);
125 /* Redirect stdin and stdout. */
128 if (dup2(pin[0], 0) < 0)
129 perror("dup2 stdin");
133 if (dup2(pout[1], 1) < 0)
134 perror("dup2 stdout");
135 /* Cannot be 1 because pin allocated two descriptors. */
138 /* Stderr is left as it is so that error messages get
139 printed on the user's terminal. */
142 argv[2] = command_string;
145 /* Execute the proxy command. Note that we gave up any
146 extra privileges above. */
147 signal(SIGPIPE, SIG_DFL);
148 execv(argv[0], argv);
154 fatal("fork failed: %.100s", strerror(errno));
156 proxy_command_pid = pid; /* save pid to clean up later */
158 /* Close child side of the descriptors. */
162 /* Free the command name. */
163 xfree(command_string);
165 /* Set the connection file descriptors. */
166 packet_set_connection(pout[0], pin[1]);
167 packet_set_timeout(options.server_alive_interval,
168 options.server_alive_count_max);
170 /* Indicate OK return */
175 ssh_kill_proxy_command(void)
178 * Send SIGHUP to proxy command if used. We don't wait() in
179 * case it hangs and instead rely on init to reap the child
181 if (proxy_command_pid > 1)
182 kill(proxy_command_pid, SIGHUP);
186 * Creates a (possibly privileged) socket for use as the ssh connection.
189 ssh_create_socket(int privileged, struct addrinfo *ai)
192 struct addrinfo hints, *res;
195 * If we are running as root and want to connect to a privileged
196 * port, bind our own socket to a privileged port.
199 int p = IPPORT_RESERVED - 1;
201 sock = rresvport_af(&p, ai->ai_family);
204 error("rresvport: af=%d %.100s", ai->ai_family,
207 debug("Allocated local port %d.", p);
210 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
212 error("socket: %.100s", strerror(errno));
215 fcntl(sock, F_SETFD, FD_CLOEXEC);
217 /* Bind the socket to an alternative local IP address */
218 if (options.bind_address == NULL)
221 memset(&hints, 0, sizeof(hints));
222 hints.ai_family = ai->ai_family;
223 hints.ai_socktype = ai->ai_socktype;
224 hints.ai_protocol = ai->ai_protocol;
225 hints.ai_flags = AI_PASSIVE;
226 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res);
228 error("getaddrinfo: %s: %s", options.bind_address,
229 ssh_gai_strerror(gaierr));
233 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
234 error("bind: %s: %s", options.bind_address, strerror(errno));
244 timeout_connect(int sockfd, const struct sockaddr *serv_addr,
245 socklen_t addrlen, int *timeoutp)
248 struct timeval tv, t_start;
250 int optval, rc, result = -1;
252 gettimeofday(&t_start, NULL);
254 if (*timeoutp <= 0) {
255 result = connect(sockfd, serv_addr, addrlen);
259 set_nonblock(sockfd);
260 rc = connect(sockfd, serv_addr, addrlen);
262 unset_nonblock(sockfd);
266 if (errno != EINPROGRESS) {
271 fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS),
273 FD_SET(sockfd, fdset);
274 ms_to_timeval(&tv, *timeoutp);
277 rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
278 if (rc != -1 || errno != EINTR)
289 debug("select: %s", strerror(errno));
292 /* Completed or failed */
294 optlen = sizeof(optval);
295 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
297 debug("getsockopt: %s", strerror(errno));
305 unset_nonblock(sockfd);
308 /* Should not occur */
309 fatal("Bogus return (%d) from select()", rc);
315 if (result == 0 && *timeoutp > 0) {
316 ms_subtract_diff(&t_start, timeoutp);
317 if (*timeoutp <= 0) {
327 * Opens a TCP/IP connection to the remote server on the given host.
328 * The address of the remote host will be returned in hostaddr.
329 * If port is 0, the default port will be used. If needpriv is true,
330 * a privileged port will be allocated to make the connection.
331 * This requires super-user privileges if needpriv is true.
332 * Connection_attempts specifies the maximum number of tries (one per
333 * second). If proxy_command is non-NULL, it specifies the command (with %h
334 * and %p substituted for host and port, respectively) to use to contact
338 ssh_connect(const char *host, struct sockaddr_storage * hostaddr,
339 u_short port, int family, int connection_attempts, int *timeout_ms,
340 int want_keepalive, int needpriv, const char *proxy_command)
344 int sock = -1, attempt;
345 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
346 struct addrinfo hints, *ai, *aitop;
348 debug2("ssh_connect: needpriv %d", needpriv);
350 /* If a proxy command is given, connect using it. */
351 if (proxy_command != NULL)
352 return ssh_proxy_connect(host, port, proxy_command);
354 /* No proxy command. */
356 memset(&hints, 0, sizeof(hints));
357 hints.ai_family = family;
358 hints.ai_socktype = SOCK_STREAM;
359 snprintf(strport, sizeof strport, "%u", port);
360 if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0)
361 fatal("%s: Could not resolve hostname %.100s: %s", __progname,
362 host, ssh_gai_strerror(gaierr));
364 for (attempt = 0; attempt < connection_attempts; attempt++) {
366 /* Sleep a moment before retrying. */
368 debug("Trying again...");
371 * Loop through addresses for this host, and try each one in
372 * sequence until the connection succeeds.
374 for (ai = aitop; ai; ai = ai->ai_next) {
375 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
377 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
378 ntop, sizeof(ntop), strport, sizeof(strport),
379 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
380 error("ssh_connect: getnameinfo failed");
383 debug("Connecting to %.200s [%.100s] port %s.",
384 host, ntop, strport);
386 /* Create a socket for connecting. */
387 sock = ssh_create_socket(needpriv, ai);
389 /* Any error is already output */
392 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
394 /* Successful connection. */
395 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
398 debug("connect to address %s port %s: %s",
399 ntop, strport, strerror(errno));
405 break; /* Successful connection. */
410 /* Return failure if we didn't get a successful connection. */
412 error("ssh: connect to host %s port %s: %s",
413 host, strport, strerror(errno));
417 debug("Connection established.");
419 /* Set SO_KEEPALIVE if requested. */
420 if (want_keepalive &&
421 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
423 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
425 /* Set the connection. */
426 packet_set_connection(sock, sock);
427 packet_set_timeout(options.server_alive_interval,
428 options.server_alive_count_max);
434 * Waits for the server identification string, and sends our own
435 * identification string.
438 ssh_exchange_identification(int timeout_ms)
440 char buf[256], remote_version[256]; /* must be same size! */
441 int remote_major, remote_minor, mismatch;
442 int connection_in = packet_get_connection_in();
443 int connection_out = packet_get_connection_out();
444 int minor1 = PROTOCOL_MINOR_1;
447 int fdsetsz, remaining, rc;
448 struct timeval t_start, t_remaining;
451 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask);
452 fdset = xcalloc(1, fdsetsz);
454 /* Read other side's version identification. */
455 remaining = timeout_ms;
457 for (i = 0; i < sizeof(buf) - 1; i++) {
458 if (timeout_ms > 0) {
459 gettimeofday(&t_start, NULL);
460 ms_to_timeval(&t_remaining, remaining);
461 FD_SET(connection_in, fdset);
462 rc = select(connection_in + 1, fdset, NULL,
463 fdset, &t_remaining);
464 ms_subtract_diff(&t_start, &remaining);
465 if (rc == 0 || remaining <= 0)
466 fatal("Connection timed out during "
471 fatal("ssh_exchange_identification: "
472 "select: %s", strerror(errno));
476 len = roaming_atomicio(read, connection_in, &buf[i], 1);
478 if (len != 1 && errno == EPIPE)
479 fatal("ssh_exchange_identification: "
480 "Connection closed by remote host");
482 fatal("ssh_exchange_identification: "
483 "read: %.100s", strerror(errno));
484 if (buf[i] == '\r') {
487 continue; /**XXX wait for \n */
489 if (buf[i] == '\n') {
494 fatal("ssh_exchange_identification: "
495 "No banner received");
497 buf[sizeof(buf) - 1] = 0;
498 if (strncmp(buf, "SSH-", 4) == 0)
500 debug("ssh_exchange_identification: %s", buf);
502 server_version_string = xstrdup(buf);
506 * Check that the versions match. In future this might accept
507 * several versions and set appropriate flags to handle them.
509 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
510 &remote_major, &remote_minor, remote_version) != 3)
511 fatal("Bad remote protocol version identification: '%.100s'", buf);
512 debug("Remote protocol version %d.%d, remote software version %.100s",
513 remote_major, remote_minor, remote_version);
515 compat_datafellows(remote_version);
518 switch (remote_major) {
520 if (remote_minor == 99 &&
521 (options.protocol & SSH_PROTO_2) &&
522 !(options.protocol & SSH_PROTO_1_PREFERRED)) {
526 if (!(options.protocol & SSH_PROTO_1)) {
530 if (remote_minor < 3) {
531 fatal("Remote machine has too old SSH software version.");
532 } else if (remote_minor == 3 || remote_minor == 4) {
533 /* We speak 1.3, too. */
536 if (options.forward_agent) {
537 logit("Agent forwarding disabled for protocol 1.3");
538 options.forward_agent = 0;
543 if (options.protocol & SSH_PROTO_2) {
553 fatal("Protocol major versions differ: %d vs. %d",
554 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
556 /* Send our own protocol version identification. */
557 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s%s",
558 compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
559 compat20 ? PROTOCOL_MINOR_2 : minor1,
560 SSH_VERSION, compat20 ? "\r\n" : "\n");
561 if (roaming_atomicio(vwrite, connection_out, buf, strlen(buf))
563 fatal("write: %.100s", strerror(errno));
564 client_version_string = xstrdup(buf);
565 chop(client_version_string);
566 chop(server_version_string);
567 debug("Local version string %.100s", client_version_string);
570 /* defaults to 'no' */
572 confirm(const char *prompt)
574 const char *msg, *again = "Please type 'yes' or 'no': ";
578 if (options.batch_mode)
580 for (msg = prompt;;msg = again) {
581 p = read_passphrase(msg, RP_ECHO);
583 (p[0] == '\0') || (p[0] == '\n') ||
584 strncasecmp(p, "no", 2) == 0)
586 if (p && strncasecmp(p, "yes", 3) == 0)
596 check_host_cert(const char *host, const Key *host_key)
600 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) {
604 if (buffer_len(&host_key->cert->critical) != 0) {
605 error("Certificate for %s contains unsupported "
606 "critical options(s)", host);
613 sockaddr_is_local(struct sockaddr *hostaddr)
615 switch (hostaddr->sa_family) {
617 return (ntohl(((struct sockaddr_in *)hostaddr)->
618 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
620 return IN6_IS_ADDR_LOOPBACK(
621 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
628 * Prepare the hostname and ip address strings that are used to lookup
629 * host keys in known_hosts files. These may have a port number appended.
632 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr,
633 u_short port, char **hostfile_hostname, char **hostfile_ipaddr)
635 char ntop[NI_MAXHOST];
638 switch (hostaddr == NULL ? -1 : hostaddr->sa_family) {
643 addrlen = sizeof(struct sockaddr_in);
646 addrlen = sizeof(struct sockaddr_in6);
649 addrlen = sizeof(struct sockaddr);
654 * We don't have the remote ip-address for connections
655 * using a proxy command
657 if (hostfile_ipaddr != NULL) {
658 if (options.proxy_command == NULL) {
659 if (getnameinfo(hostaddr, addrlen,
660 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0)
661 fatal("check_host_key: getnameinfo failed");
662 *hostfile_ipaddr = put_host_port(ntop, port);
664 *hostfile_ipaddr = xstrdup("<no hostip for proxy "
670 * Allow the user to record the key under a different name or
671 * differentiate a non-standard port. This is useful for ssh
672 * tunneling over forwarded connections or if you run multiple
673 * sshd's on different ports on the same machine.
675 if (hostfile_hostname != NULL) {
676 if (options.host_key_alias != NULL) {
677 *hostfile_hostname = xstrdup(options.host_key_alias);
678 debug("using hostkeyalias: %s", *hostfile_hostname);
680 *hostfile_hostname = put_host_port(hostname, port);
686 * check whether the supplied host key is valid, return -1 if the key
687 * is not valid. the user_hostfile will not be updated if 'readonly' is true.
693 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
694 Key *host_key, int readonly, char *user_hostfile,
695 char *system_hostfile)
699 char *ip = NULL, *host = NULL;
700 char hostline[1000], *hostp, *fp, *ra;
701 HostStatus host_status;
702 HostStatus ip_status;
703 int r, want_cert = key_is_cert(host_key), host_ip_differ = 0;
704 int local = sockaddr_is_local(hostaddr);
706 int len, cancelled_forwarding = 0;
707 struct hostkeys *host_hostkeys, *ip_hostkeys;
708 const struct hostkey_entry *host_found, *ip_found;
711 * Force accepting of the host key for loopback/localhost. The
712 * problem is that if the home directory is NFS-mounted to multiple
713 * machines, localhost will refer to a different machine in each of
714 * them, and the user will get bogus HOST_CHANGED warnings. This
715 * essentially disables host authentication for localhost; however,
716 * this is probably not a real problem.
718 if (options.no_host_authentication_for_localhost == 1 && local &&
719 options.host_key_alias == NULL) {
720 debug("Forcing accepting of host key for "
721 "loopback/localhost.");
726 * Prepare the hostname and address strings used for hostkey lookup.
727 * In some cases, these will have a port number appended.
729 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip);
732 * Turn off check_host_ip if the connection is to localhost, via proxy
733 * command or if we don't have a hostname to compare with
735 if (options.check_host_ip && (local ||
736 strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
737 options.check_host_ip = 0;
739 host_hostkeys = init_hostkeys();
740 load_hostkeys(host_hostkeys, host, user_hostfile);
741 load_hostkeys(host_hostkeys, host, system_hostfile);
744 if (!want_cert && options.check_host_ip) {
745 ip_hostkeys = init_hostkeys();
746 load_hostkeys(ip_hostkeys, ip, user_hostfile);
747 load_hostkeys(ip_hostkeys, ip, system_hostfile);
751 /* Reload these as they may have changed on cert->key downgrade */
752 want_cert = key_is_cert(host_key);
753 type = key_type(host_key);
756 * Check if the host key is present in the user's list of known
757 * hosts or in the systemwide list.
759 host_status = check_key_in_hostkeys(host_hostkeys, host_key,
763 * Also perform check for the ip address, skip the check if we are
764 * localhost, looking for a certificate, or the hostname was an ip
765 * address to begin with.
767 if (!want_cert && ip_hostkeys != NULL) {
768 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key,
770 if (host_status == HOST_CHANGED &&
771 (ip_status != HOST_CHANGED ||
773 !key_equal(ip_found->key, host_found->key))))
776 ip_status = host_status;
778 switch (host_status) {
780 /* The host is known and the key matches. */
781 debug("Host '%.200s' is known and matches the %s host %s.",
782 host, type, want_cert ? "certificate" : "key");
783 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key",
784 host_found->file, host_found->line);
785 if (want_cert && !check_host_cert(hostname, host_key))
787 if (options.check_host_ip && ip_status == HOST_NEW) {
788 if (readonly || want_cert)
789 logit("%s host key for IP address "
790 "'%.128s' not in list of known hosts.",
792 else if (!add_host_to_hostfile(user_hostfile, ip,
793 host_key, options.hash_known_hosts))
794 logit("Failed to add the %s host key for IP "
795 "address '%.128s' to the list of known "
796 "hosts (%.30s).", type, ip, user_hostfile);
798 logit("Warning: Permanently added the %s host "
799 "key for IP address '%.128s' to the list "
800 "of known hosts.", type, ip);
801 } else if (options.visual_host_key) {
802 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
803 ra = key_fingerprint(host_key, SSH_FP_MD5,
805 logit("Host key fingerprint is %s\n%s\n", fp, ra);
811 if (options.host_key_alias == NULL && port != 0 &&
812 port != SSH_DEFAULT_PORT) {
813 debug("checking without port identifier");
814 if (check_host_key(hostname, hostaddr, 0, host_key,
815 ROQUIET, user_hostfile, system_hostfile) == 0) {
816 debug("found matching key w/out port");
820 if (readonly || want_cert)
822 /* The host is new. */
823 if (options.strict_host_key_checking == 1) {
825 * User has requested strict host key checking. We
826 * will not add the host key automatically. The only
827 * alternative left is to abort.
829 error("No %s host key is known for %.200s and you "
830 "have requested strict checking.", type, host);
832 } else if (options.strict_host_key_checking == 2) {
833 char msg1[1024], msg2[1024];
835 if (show_other_keys(host_hostkeys, host_key))
836 snprintf(msg1, sizeof(msg1),
837 "\nbut keys of different type are already"
838 " known for this host.");
840 snprintf(msg1, sizeof(msg1), ".");
842 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
843 ra = key_fingerprint(host_key, SSH_FP_MD5,
846 if (options.verify_host_key_dns) {
847 if (matching_host_key_dns)
848 snprintf(msg2, sizeof(msg2),
849 "Matching host key fingerprint"
852 snprintf(msg2, sizeof(msg2),
853 "No matching host key fingerprint"
856 snprintf(msg, sizeof(msg),
857 "The authenticity of host '%.200s (%s)' can't be "
859 "%s key fingerprint is %s.%s%s\n%s"
860 "Are you sure you want to continue connecting "
862 host, ip, msg1, type, fp,
863 options.visual_host_key ? "\n" : "",
864 options.visual_host_key ? ra : "",
872 * If not in strict mode, add the key automatically to the
873 * local known_hosts file.
875 if (options.check_host_ip && ip_status == HOST_NEW) {
876 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
878 if (options.hash_known_hosts) {
879 /* Add hash of host and IP separately */
880 r = add_host_to_hostfile(user_hostfile, host,
881 host_key, options.hash_known_hosts) &&
882 add_host_to_hostfile(user_hostfile, ip,
883 host_key, options.hash_known_hosts);
885 /* Add unhashed "host,ip" */
886 r = add_host_to_hostfile(user_hostfile,
888 options.hash_known_hosts);
891 r = add_host_to_hostfile(user_hostfile, host, host_key,
892 options.hash_known_hosts);
897 logit("Failed to add the host to the list of known "
898 "hosts (%.500s).", user_hostfile);
900 logit("Warning: Permanently added '%.200s' (%s) to the "
901 "list of known hosts.", hostp, type);
904 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
905 error("@ WARNING: REVOKED HOST KEY DETECTED! @");
906 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
907 error("The %s host key for %s is marked as revoked.", type, host);
908 error("This could mean that a stolen key is being used to");
909 error("impersonate this host.");
912 * If strict host key checking is in use, the user will have
913 * to edit the key manually and we can only abort.
915 if (options.strict_host_key_checking) {
916 error("%s host key for %.200s was revoked and you have "
917 "requested strict checking.", type, host);
920 goto continue_unsafe;
925 * This is only a debug() since it is valid to have
926 * CAs with wildcard DNS matches that don't match
927 * all hosts that one might visit.
929 debug("Host certificate authority does not "
930 "match %s in %s:%lu", CA_MARKER,
931 host_found->file, host_found->line);
934 if (readonly == ROQUIET)
936 if (options.check_host_ip && host_ip_differ) {
938 if (ip_status == HOST_NEW)
939 key_msg = "is unknown";
940 else if (ip_status == HOST_OK)
941 key_msg = "is unchanged";
943 key_msg = "has a different value";
944 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
945 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
946 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
947 error("The %s host key for %s has changed,", type, host);
948 error("and the key for the corresponding IP address %s", ip);
949 error("%s. This could either mean that", key_msg);
950 error("DNS SPOOFING is happening or the IP address for the host");
951 error("and its host key have changed at the same time.");
952 if (ip_status != HOST_NEW)
953 error("Offending key for IP in %s:%lu",
954 ip_found->file, ip_found->line);
956 /* The host key has changed. */
957 warn_changed_key(host_key);
958 error("Add correct host key in %.100s to get rid of this message.",
960 error("Offending %s key in %s:%lu", key_type(host_found->key),
961 host_found->file, host_found->line);
964 * If strict host key checking is in use, the user will have
965 * to edit the key manually and we can only abort.
967 if (options.strict_host_key_checking) {
968 error("%s host key for %.200s has changed and you have "
969 "requested strict checking.", type, host);
975 * If strict host key checking has not been requested, allow
976 * the connection but without MITM-able authentication or
979 if (options.password_authentication) {
980 error("Password authentication is disabled to avoid "
981 "man-in-the-middle attacks.");
982 options.password_authentication = 0;
983 cancelled_forwarding = 1;
985 if (options.kbd_interactive_authentication) {
986 error("Keyboard-interactive authentication is disabled"
987 " to avoid man-in-the-middle attacks.");
988 options.kbd_interactive_authentication = 0;
989 options.challenge_response_authentication = 0;
990 cancelled_forwarding = 1;
992 if (options.challenge_response_authentication) {
993 error("Challenge/response authentication is disabled"
994 " to avoid man-in-the-middle attacks.");
995 options.challenge_response_authentication = 0;
996 cancelled_forwarding = 1;
998 if (options.forward_agent) {
999 error("Agent forwarding is disabled to avoid "
1000 "man-in-the-middle attacks.");
1001 options.forward_agent = 0;
1002 cancelled_forwarding = 1;
1004 if (options.forward_x11) {
1005 error("X11 forwarding is disabled to avoid "
1006 "man-in-the-middle attacks.");
1007 options.forward_x11 = 0;
1008 cancelled_forwarding = 1;
1010 if (options.num_local_forwards > 0 ||
1011 options.num_remote_forwards > 0) {
1012 error("Port forwarding is disabled to avoid "
1013 "man-in-the-middle attacks.");
1014 options.num_local_forwards =
1015 options.num_remote_forwards = 0;
1016 cancelled_forwarding = 1;
1018 if (options.tun_open != SSH_TUNMODE_NO) {
1019 error("Tunnel forwarding is disabled to avoid "
1020 "man-in-the-middle attacks.");
1021 options.tun_open = SSH_TUNMODE_NO;
1022 cancelled_forwarding = 1;
1024 if (options.exit_on_forward_failure && cancelled_forwarding)
1025 fatal("Error: forwarding disabled due to host key "
1029 * XXX Should permit the user to change to use the new id.
1030 * This could be done by converting the host key to an
1031 * identifying sentence, tell that the host identifies itself
1032 * by that sentence, and ask the user if he/she wishes to
1033 * accept the authentication.
1037 fatal("internal error");
1041 if (options.check_host_ip && host_status != HOST_CHANGED &&
1042 ip_status == HOST_CHANGED) {
1043 snprintf(msg, sizeof(msg),
1044 "Warning: the %s host key for '%.200s' "
1045 "differs from the key for the IP address '%.128s'"
1046 "\nOffending key for IP in %s:%lu",
1047 type, host, ip, ip_found->file, ip_found->line);
1048 if (host_status == HOST_OK) {
1050 snprintf(msg + len, sizeof(msg) - len,
1051 "\nMatching host key in %s:%lu",
1052 host_found->file, host_found->line);
1054 if (options.strict_host_key_checking == 1) {
1056 error("Exiting, you have requested strict checking.");
1058 } else if (options.strict_host_key_checking == 2) {
1059 strlcat(msg, "\nAre you sure you want "
1060 "to continue connecting (yes/no)? ", sizeof(msg));
1070 if (host_hostkeys != NULL)
1071 free_hostkeys(host_hostkeys);
1072 if (ip_hostkeys != NULL)
1073 free_hostkeys(ip_hostkeys);
1077 if (want_cert && host_status != HOST_REVOKED) {
1079 * No matching certificate. Downgrade cert to raw key and
1082 debug("No matching CA found. Retry with plain key");
1083 raw_key = key_from_private(host_key);
1084 if (key_drop_cert(raw_key) != 0)
1085 fatal("Couldn't drop certificate");
1089 if (raw_key != NULL)
1093 if (host_hostkeys != NULL)
1094 free_hostkeys(host_hostkeys);
1095 if (ip_hostkeys != NULL)
1096 free_hostkeys(ip_hostkeys);
1100 /* returns 0 if key verifies or -1 if key does NOT verify */
1102 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
1108 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1109 debug("Server host key: %s %s", key_type(host_key), fp);
1112 /* XXX certs are not yet supported for DNS */
1113 if (!key_is_cert(host_key) && options.verify_host_key_dns &&
1114 verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) {
1116 if (flags & DNS_VERIFY_FOUND) {
1118 if (options.verify_host_key_dns == 1 &&
1119 flags & DNS_VERIFY_MATCH &&
1120 flags & DNS_VERIFY_SECURE)
1123 if (flags & DNS_VERIFY_MATCH) {
1124 matching_host_key_dns = 1;
1126 warn_changed_key(host_key);
1127 error("Update the SSHFP RR in DNS with the new "
1128 "host key to get rid of this message.");
1133 /* return ok if the key can be found in an old keyfile */
1134 if (stat(options.system_hostfile2, &st) == 0 ||
1135 stat(options.user_hostfile2, &st) == 0) {
1136 if (check_host_key(host, hostaddr, options.port, host_key,
1137 RDONLY, options.user_hostfile2,
1138 options.system_hostfile2) == 0)
1141 return check_host_key(host, hostaddr, options.port, host_key,
1142 RDRW, options.user_hostfile, options.system_hostfile);
1146 * Starts a dialog with the server, and authenticates the current user on the
1147 * server. This does not need any extra privileges. The basic connection
1148 * to the server must already have been established before this is called.
1149 * If login fails, this function prints an error and never returns.
1150 * This function does not require super-user privileges.
1153 ssh_login(Sensitive *sensitive, const char *orighost,
1154 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms)
1157 char *server_user, *local_user;
1159 local_user = xstrdup(pw->pw_name);
1160 server_user = options.user ? options.user : local_user;
1162 /* Convert the user-supplied hostname into all lowercase. */
1163 host = xstrdup(orighost);
1164 for (cp = host; *cp; cp++)
1166 *cp = (char)tolower(*cp);
1168 /* Exchange protocol version identification strings with the server. */
1169 ssh_exchange_identification(timeout_ms);
1171 /* Put the connection into non-blocking mode. */
1172 packet_set_nonblocking();
1175 /* authenticate user */
1177 ssh_kex2(host, hostaddr, port);
1178 ssh_userauth2(local_user, server_user, host, sensitive);
1180 ssh_kex(host, hostaddr);
1181 ssh_userauth1(local_user, server_user, host, sensitive);
1187 ssh_put_password(char *password)
1192 if (datafellows & SSH_BUG_PASSWORDPAD) {
1193 packet_put_cstring(password);
1196 size = roundup(strlen(password) + 1, 32);
1197 padded = xcalloc(1, size);
1198 strlcpy(padded, password, size);
1199 packet_put_string(padded, size);
1200 memset(padded, 0, size);
1204 /* print all known host keys for a given host, but skip keys of given type */
1206 show_other_keys(struct hostkeys *hostkeys, Key *key)
1208 int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, KEY_ECDSA, -1};
1211 const struct hostkey_entry *found;
1213 for (i = 0; type[i] != -1; i++) {
1214 if (type[i] == key->type)
1216 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found))
1218 fp = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_HEX);
1219 ra = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_RANDOMART);
1220 logit("WARNING: %s key found for host %s\n"
1222 "%s key fingerprint %s.",
1223 key_type(found->key),
1224 found->host, found->file, found->line,
1225 key_type(found->key), fp);
1226 if (options.visual_host_key)
1236 warn_changed_key(Key *host_key)
1240 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1242 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1243 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1244 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1245 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1246 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1247 error("It is also possible that a host key has just been changed.");
1248 error("The fingerprint for the %s key sent by the remote host is\n%s.",
1249 key_type(host_key), fp);
1250 error("Please contact your system administrator.");
1256 * Execute a local command
1259 ssh_local_cmd(const char *args)
1264 void (*osighand)(int);
1266 if (!options.permit_local_command ||
1267 args == NULL || !*args)
1270 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
1271 shell = _PATH_BSHELL;
1273 osighand = signal(SIGCHLD, SIG_DFL);
1276 signal(SIGPIPE, SIG_DFL);
1277 debug3("Executing %s -c \"%s\"", shell, args);
1278 execl(shell, shell, "-c", args, (char *)NULL);
1279 error("Couldn't execute %s -c \"%s\": %s",
1280 shell, args, strerror(errno));
1282 } else if (pid == -1)
1283 fatal("fork failed: %.100s", strerror(errno));
1284 while (waitpid(pid, &status, 0) == -1)
1286 fatal("Couldn't wait for child: %s", strerror(errno));
1287 signal(SIGCHLD, osighand);
1289 if (!WIFEXITED(status))
1292 return (WEXITSTATUS(status));