1 /* $OpenBSD: sshconnect.c,v 1.244 2014/01/09 23:26:48 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>
56 #include "sshconnect.h"
64 #include "monitor_fdpass.h"
68 char *client_version_string = NULL;
69 char *server_version_string = NULL;
71 static int matching_host_key_dns = 0;
73 static pid_t proxy_command_pid = 0;
76 extern Options options;
77 extern char *__progname;
78 extern uid_t original_real_uid;
79 extern uid_t original_effective_uid;
81 static int show_other_keys(struct hostkeys *, Key *);
82 static void warn_changed_key(Key *);
84 /* Expand a proxy command */
86 expand_proxy_command(const char *proxy_command, const char *user,
87 const char *host, int port)
89 char *tmp, *ret, strport[NI_MAXSERV];
91 snprintf(strport, sizeof strport, "%d", port);
92 xasprintf(&tmp, "exec %s", proxy_command);
93 ret = percent_expand(tmp, "h", host, "p", strport,
94 "r", options.user, (char *)NULL);
100 * Connect to the given ssh server using a proxy command that passes a
101 * a connected fd back to us.
104 ssh_proxy_fdpass_connect(const char *host, u_short port,
105 const char *proxy_command)
107 char *command_string;
112 if ((shell = getenv("SHELL")) == NULL)
113 shell = _PATH_BSHELL;
115 if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) < 0)
116 fatal("Could not create socketpair to communicate with "
117 "proxy dialer: %.100s", strerror(errno));
119 command_string = expand_proxy_command(proxy_command, options.user,
121 debug("Executing proxy dialer command: %.500s", command_string);
123 /* Fork and execute the proxy command. */
124 if ((pid = fork()) == 0) {
127 /* Child. Permanently give up superuser privileges. */
128 permanently_drop_suid(original_real_uid);
131 /* Redirect stdin and stdout. */
133 if (dup2(sp[0], 0) < 0)
134 perror("dup2 stdin");
137 if (dup2(sp[0], 1) < 0)
138 perror("dup2 stdout");
144 * Stderr is left as it is so that error messages get
145 * printed on the user's terminal.
149 argv[2] = command_string;
153 * Execute the proxy command.
154 * Note that we gave up any extra privileges above.
156 execv(argv[0], argv);
162 fatal("fork failed: %.100s", strerror(errno));
164 free(command_string);
166 if ((sock = mm_receive_fd(sp[1])) == -1)
167 fatal("proxy dialer did not pass back a connection");
169 while (waitpid(pid, NULL, 0) == -1)
171 fatal("Couldn't wait for child: %s", strerror(errno));
173 /* Set the connection file descriptors. */
174 packet_set_connection(sock, sock);
180 * Connect to the given ssh server using a proxy command.
183 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
185 char *command_string;
190 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
191 shell = _PATH_BSHELL;
193 /* Create pipes for communicating with the proxy. */
194 if (pipe(pin) < 0 || pipe(pout) < 0)
195 fatal("Could not create pipes to communicate with the proxy: %.100s",
198 command_string = expand_proxy_command(proxy_command, options.user,
200 debug("Executing proxy command: %.500s", command_string);
202 /* Fork and execute the proxy command. */
203 if ((pid = fork()) == 0) {
206 /* Child. Permanently give up superuser privileges. */
207 permanently_drop_suid(original_real_uid);
209 /* Redirect stdin and stdout. */
212 if (dup2(pin[0], 0) < 0)
213 perror("dup2 stdin");
217 if (dup2(pout[1], 1) < 0)
218 perror("dup2 stdout");
219 /* Cannot be 1 because pin allocated two descriptors. */
222 /* Stderr is left as it is so that error messages get
223 printed on the user's terminal. */
226 argv[2] = command_string;
229 /* Execute the proxy command. Note that we gave up any
230 extra privileges above. */
231 signal(SIGPIPE, SIG_DFL);
232 execv(argv[0], argv);
238 fatal("fork failed: %.100s", strerror(errno));
240 proxy_command_pid = pid; /* save pid to clean up later */
242 /* Close child side of the descriptors. */
246 /* Free the command name. */
247 free(command_string);
249 /* Set the connection file descriptors. */
250 packet_set_connection(pout[0], pin[1]);
252 /* Indicate OK return */
257 ssh_kill_proxy_command(void)
260 * Send SIGHUP to proxy command if used. We don't wait() in
261 * case it hangs and instead rely on init to reap the child
263 if (proxy_command_pid > 1)
264 kill(proxy_command_pid, SIGHUP);
268 * Set TCP receive buffer if requested.
269 * Note: tuning needs to happen after the socket is created but before the
270 * connection happens so winscale is negotiated properly.
273 ssh_set_socket_recvbuf(int sock)
275 void *buf = (void *)&options.tcp_rcv_buf;
276 int socksize, sz = sizeof(options.tcp_rcv_buf);
277 socklen_t len = sizeof(int);
279 debug("setsockopt attempting to set SO_RCVBUF to %d",
280 options.tcp_rcv_buf);
281 if (setsockopt(sock, SOL_SOCKET, SO_RCVBUF, buf, sz) >= 0) {
282 getsockopt(sock, SOL_SOCKET, SO_RCVBUF, &socksize, &len);
283 debug("setsockopt SO_RCVBUF: %.100s %d", strerror(errno),
286 error("Couldn't set socket receive buffer to %d: %.100s",
287 options.tcp_rcv_buf, strerror(errno));
291 * Creates a (possibly privileged) socket for use as the ssh connection.
294 ssh_create_socket(int privileged, struct addrinfo *ai)
297 struct addrinfo hints, *res;
299 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
301 error("socket: %s", strerror(errno));
304 fcntl(sock, F_SETFD, FD_CLOEXEC);
306 if (options.tcp_rcv_buf > 0)
307 ssh_set_socket_recvbuf(sock);
309 /* Bind the socket to an alternative local IP address */
310 if (options.bind_address == NULL && !privileged)
313 memset(&hints, 0, sizeof(hints));
314 hints.ai_family = ai->ai_family;
315 hints.ai_socktype = ai->ai_socktype;
316 hints.ai_protocol = ai->ai_protocol;
317 hints.ai_flags = AI_PASSIVE;
318 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res);
320 error("getaddrinfo: %s: %s", options.bind_address,
321 ssh_gai_strerror(gaierr));
326 * If we are running as root and want to connect to a privileged
327 * port, bind our own socket to a privileged port.
331 r = bindresvport_sa(sock, res->ai_addr);
334 error("bindresvport_sa: af=%d %s", ai->ai_family,
339 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
340 error("bind: %s: %s", options.bind_address,
353 timeout_connect(int sockfd, const struct sockaddr *serv_addr,
354 socklen_t addrlen, int *timeoutp)
357 struct timeval tv, t_start;
359 int optval, rc, result = -1;
361 gettimeofday(&t_start, NULL);
363 if (*timeoutp <= 0) {
364 result = connect(sockfd, serv_addr, addrlen);
368 set_nonblock(sockfd);
369 rc = connect(sockfd, serv_addr, addrlen);
371 unset_nonblock(sockfd);
375 if (errno != EINPROGRESS) {
380 fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS),
382 FD_SET(sockfd, fdset);
383 ms_to_timeval(&tv, *timeoutp);
386 rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
387 if (rc != -1 || errno != EINTR)
398 debug("select: %s", strerror(errno));
401 /* Completed or failed */
403 optlen = sizeof(optval);
404 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
406 debug("getsockopt: %s", strerror(errno));
414 unset_nonblock(sockfd);
417 /* Should not occur */
418 fatal("Bogus return (%d) from select()", rc);
424 if (result == 0 && *timeoutp > 0) {
425 ms_subtract_diff(&t_start, timeoutp);
426 if (*timeoutp <= 0) {
436 * Opens a TCP/IP connection to the remote server on the given host.
437 * The address of the remote host will be returned in hostaddr.
438 * If port is 0, the default port will be used. If needpriv is true,
439 * a privileged port will be allocated to make the connection.
440 * This requires super-user privileges if needpriv is true.
441 * Connection_attempts specifies the maximum number of tries (one per
442 * second). If proxy_command is non-NULL, it specifies the command (with %h
443 * and %p substituted for host and port, respectively) to use to contact
447 ssh_connect_direct(const char *host, struct addrinfo *aitop,
448 struct sockaddr_storage *hostaddr, u_short port, int family,
449 int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv)
452 int sock = -1, attempt;
453 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
456 debug2("ssh_connect: needpriv %d", needpriv);
458 for (attempt = 0; attempt < connection_attempts; attempt++) {
460 /* Sleep a moment before retrying. */
462 debug("Trying again...");
465 * Loop through addresses for this host, and try each one in
466 * sequence until the connection succeeds.
468 for (ai = aitop; ai; ai = ai->ai_next) {
469 if (ai->ai_family != AF_INET &&
470 ai->ai_family != AF_INET6)
472 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
473 ntop, sizeof(ntop), strport, sizeof(strport),
474 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
475 error("ssh_connect: getnameinfo failed");
478 debug("Connecting to %.200s [%.100s] port %s.",
479 host, ntop, strport);
481 /* Create a socket for connecting. */
482 sock = ssh_create_socket(needpriv, ai);
484 /* Any error is already output */
487 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
489 /* Successful connection. */
490 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
493 debug("connect to address %s port %s: %s",
494 ntop, strport, strerror(errno));
500 break; /* Successful connection. */
503 /* Return failure if we didn't get a successful connection. */
505 error("ssh: connect to host %s port %s: %s",
506 host, strport, strerror(errno));
510 debug("Connection established.");
512 /* Set SO_KEEPALIVE if requested. */
513 if (want_keepalive &&
514 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
516 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
518 /* Set the connection. */
519 packet_set_connection(sock, sock);
525 ssh_connect(const char *host, struct addrinfo *addrs,
526 struct sockaddr_storage *hostaddr, u_short port, int family,
527 int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv)
529 if (options.proxy_command == NULL) {
530 return ssh_connect_direct(host, addrs, hostaddr, port, family,
531 connection_attempts, timeout_ms, want_keepalive, needpriv);
532 } else if (strcmp(options.proxy_command, "-") == 0) {
533 packet_set_connection(STDIN_FILENO, STDOUT_FILENO);
534 return 0; /* Always succeeds */
535 } else if (options.proxy_use_fdpass) {
536 return ssh_proxy_fdpass_connect(host, port,
537 options.proxy_command);
539 return ssh_proxy_connect(host, port, options.proxy_command);
543 send_client_banner(int connection_out, int minor1)
545 /* Send our own protocol version identification. */
546 xasprintf(&client_version_string, "SSH-%d.%d-%.100s%s%s%s%s",
547 compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
548 compat20 ? PROTOCOL_MINOR_2 : minor1,
549 SSH_VERSION, options.hpn_disabled ? "" : SSH_VERSION_HPN,
550 *options.version_addendum == '\0' ? "" : " ",
551 options.version_addendum, compat20 ? "\r\n" : "\n");
552 if (roaming_atomicio(vwrite, connection_out, client_version_string,
553 strlen(client_version_string)) != strlen(client_version_string))
554 fatal("write: %.100s", strerror(errno));
555 chop(client_version_string);
556 debug("Local version string %.100s", client_version_string);
560 * Waits for the server identification string, and sends our own
561 * identification string.
564 ssh_exchange_identification(int timeout_ms)
566 char buf[256], remote_version[256]; /* must be same size! */
567 int remote_major, remote_minor, mismatch;
568 int connection_in = packet_get_connection_in();
569 int connection_out = packet_get_connection_out();
570 int minor1 = PROTOCOL_MINOR_1, client_banner_sent = 0;
573 int fdsetsz, remaining, rc;
574 struct timeval t_start, t_remaining;
577 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask);
578 fdset = xcalloc(1, fdsetsz);
581 * If we are SSH2-only then we can send the banner immediately and
584 if (options.protocol == SSH_PROTO_2) {
586 send_client_banner(connection_out, 0);
587 client_banner_sent = 1;
590 /* Read other side's version identification. */
591 remaining = timeout_ms;
593 for (i = 0; i < sizeof(buf) - 1; i++) {
594 if (timeout_ms > 0) {
595 gettimeofday(&t_start, NULL);
596 ms_to_timeval(&t_remaining, remaining);
597 FD_SET(connection_in, fdset);
598 rc = select(connection_in + 1, fdset, NULL,
599 fdset, &t_remaining);
600 ms_subtract_diff(&t_start, &remaining);
601 if (rc == 0 || remaining <= 0)
602 fatal("Connection timed out during "
607 fatal("ssh_exchange_identification: "
608 "select: %s", strerror(errno));
612 len = roaming_atomicio(read, connection_in, &buf[i], 1);
614 if (len != 1 && errno == EPIPE)
615 fatal("ssh_exchange_identification: "
616 "Connection closed by remote host");
618 fatal("ssh_exchange_identification: "
619 "read: %.100s", strerror(errno));
620 if (buf[i] == '\r') {
623 continue; /**XXX wait for \n */
625 if (buf[i] == '\n') {
630 fatal("ssh_exchange_identification: "
631 "No banner received");
633 buf[sizeof(buf) - 1] = 0;
634 if (strncmp(buf, "SSH-", 4) == 0)
636 debug("ssh_exchange_identification: %s", buf);
638 server_version_string = xstrdup(buf);
642 * Check that the versions match. In future this might accept
643 * several versions and set appropriate flags to handle them.
645 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
646 &remote_major, &remote_minor, remote_version) != 3)
647 fatal("Bad remote protocol version identification: '%.100s'", buf);
648 debug("Remote protocol version %d.%d, remote software version %.100s",
649 remote_major, remote_minor, remote_version);
651 compat_datafellows(remote_version);
654 switch (remote_major) {
656 if (remote_minor == 99 &&
657 (options.protocol & SSH_PROTO_2) &&
658 !(options.protocol & SSH_PROTO_1_PREFERRED)) {
662 if (!(options.protocol & SSH_PROTO_1)) {
666 if (remote_minor < 3) {
667 fatal("Remote machine has too old SSH software version.");
668 } else if (remote_minor == 3 || remote_minor == 4) {
669 /* We speak 1.3, too. */
672 if (options.forward_agent) {
673 logit("Agent forwarding disabled for protocol 1.3");
674 options.forward_agent = 0;
679 if (options.protocol & SSH_PROTO_2) {
689 fatal("Protocol major versions differ: %d vs. %d",
690 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
692 if ((datafellows & SSH_BUG_DERIVEKEY) != 0)
693 fatal("Server version \"%.100s\" uses unsafe key agreement; "
694 "refusing connection", remote_version);
695 if ((datafellows & SSH_BUG_RSASIGMD5) != 0)
696 logit("Server version \"%.100s\" uses unsafe RSA signature "
697 "scheme; disabling use of RSA keys", remote_version);
698 if (!client_banner_sent)
699 send_client_banner(connection_out, minor1);
700 chop(server_version_string);
703 /* defaults to 'no' */
705 confirm(const char *prompt)
707 const char *msg, *again = "Please type 'yes' or 'no': ";
711 if (options.batch_mode)
713 for (msg = prompt;;msg = again) {
714 p = read_passphrase(msg, RP_ECHO);
716 (p[0] == '\0') || (p[0] == '\n') ||
717 strncasecmp(p, "no", 2) == 0)
719 if (p && strncasecmp(p, "yes", 3) == 0)
728 check_host_cert(const char *host, const Key *host_key)
732 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) {
736 if (buffer_len(&host_key->cert->critical) != 0) {
737 error("Certificate for %s contains unsupported "
738 "critical options(s)", host);
745 sockaddr_is_local(struct sockaddr *hostaddr)
747 switch (hostaddr->sa_family) {
749 return (ntohl(((struct sockaddr_in *)hostaddr)->
750 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
752 return IN6_IS_ADDR_LOOPBACK(
753 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
760 * Prepare the hostname and ip address strings that are used to lookup
761 * host keys in known_hosts files. These may have a port number appended.
764 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr,
765 u_short port, char **hostfile_hostname, char **hostfile_ipaddr)
767 char ntop[NI_MAXHOST];
770 switch (hostaddr == NULL ? -1 : hostaddr->sa_family) {
775 addrlen = sizeof(struct sockaddr_in);
778 addrlen = sizeof(struct sockaddr_in6);
781 addrlen = sizeof(struct sockaddr);
786 * We don't have the remote ip-address for connections
787 * using a proxy command
789 if (hostfile_ipaddr != NULL) {
790 if (options.proxy_command == NULL) {
791 if (getnameinfo(hostaddr, addrlen,
792 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0)
793 fatal("check_host_key: getnameinfo failed");
794 *hostfile_ipaddr = put_host_port(ntop, port);
796 *hostfile_ipaddr = xstrdup("<no hostip for proxy "
802 * Allow the user to record the key under a different name or
803 * differentiate a non-standard port. This is useful for ssh
804 * tunneling over forwarded connections or if you run multiple
805 * sshd's on different ports on the same machine.
807 if (hostfile_hostname != NULL) {
808 if (options.host_key_alias != NULL) {
809 *hostfile_hostname = xstrdup(options.host_key_alias);
810 debug("using hostkeyalias: %s", *hostfile_hostname);
812 *hostfile_hostname = put_host_port(hostname, port);
818 * check whether the supplied host key is valid, return -1 if the key
819 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true.
825 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
826 Key *host_key, int readonly,
827 char **user_hostfiles, u_int num_user_hostfiles,
828 char **system_hostfiles, u_int num_system_hostfiles)
830 HostStatus host_status;
831 HostStatus ip_status;
833 char *ip = NULL, *host = NULL;
834 char hostline[1000], *hostp, *fp, *ra;
837 const struct hostkey_entry *host_found, *ip_found;
838 int len, cancelled_forwarding = 0;
839 int local = sockaddr_is_local(hostaddr);
840 int r, want_cert = key_is_cert(host_key), host_ip_differ = 0;
841 struct hostkeys *host_hostkeys, *ip_hostkeys;
845 * Force accepting of the host key for loopback/localhost. The
846 * problem is that if the home directory is NFS-mounted to multiple
847 * machines, localhost will refer to a different machine in each of
848 * them, and the user will get bogus HOST_CHANGED warnings. This
849 * essentially disables host authentication for localhost; however,
850 * this is probably not a real problem.
852 if (options.no_host_authentication_for_localhost == 1 && local &&
853 options.host_key_alias == NULL) {
854 debug("Forcing accepting of host key for "
855 "loopback/localhost.");
860 * Prepare the hostname and address strings used for hostkey lookup.
861 * In some cases, these will have a port number appended.
863 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip);
866 * Turn off check_host_ip if the connection is to localhost, via proxy
867 * command or if we don't have a hostname to compare with
869 if (options.check_host_ip && (local ||
870 strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
871 options.check_host_ip = 0;
873 host_hostkeys = init_hostkeys();
874 for (i = 0; i < num_user_hostfiles; i++)
875 load_hostkeys(host_hostkeys, host, user_hostfiles[i]);
876 for (i = 0; i < num_system_hostfiles; i++)
877 load_hostkeys(host_hostkeys, host, system_hostfiles[i]);
880 if (!want_cert && options.check_host_ip) {
881 ip_hostkeys = init_hostkeys();
882 for (i = 0; i < num_user_hostfiles; i++)
883 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]);
884 for (i = 0; i < num_system_hostfiles; i++)
885 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]);
889 /* Reload these as they may have changed on cert->key downgrade */
890 want_cert = key_is_cert(host_key);
891 type = key_type(host_key);
894 * Check if the host key is present in the user's list of known
895 * hosts or in the systemwide list.
897 host_status = check_key_in_hostkeys(host_hostkeys, host_key,
901 * Also perform check for the ip address, skip the check if we are
902 * localhost, looking for a certificate, or the hostname was an ip
903 * address to begin with.
905 if (!want_cert && ip_hostkeys != NULL) {
906 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key,
908 if (host_status == HOST_CHANGED &&
909 (ip_status != HOST_CHANGED ||
911 !key_equal(ip_found->key, host_found->key))))
914 ip_status = host_status;
916 switch (host_status) {
918 /* The host is known and the key matches. */
919 debug("Host '%.200s' is known and matches the %s host %s.",
920 host, type, want_cert ? "certificate" : "key");
921 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key",
922 host_found->file, host_found->line);
923 if (want_cert && !check_host_cert(hostname, host_key))
925 if (options.check_host_ip && ip_status == HOST_NEW) {
926 if (readonly || want_cert)
927 logit("%s host key for IP address "
928 "'%.128s' not in list of known hosts.",
930 else if (!add_host_to_hostfile(user_hostfiles[0], ip,
931 host_key, options.hash_known_hosts))
932 logit("Failed to add the %s host key for IP "
933 "address '%.128s' to the list of known "
934 "hosts (%.30s).", type, ip,
937 logit("Warning: Permanently added the %s host "
938 "key for IP address '%.128s' to the list "
939 "of known hosts.", type, ip);
940 } else if (options.visual_host_key) {
941 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
942 ra = key_fingerprint(host_key, SSH_FP_MD5,
944 logit("Host key fingerprint is %s\n%s\n", fp, ra);
950 if (options.host_key_alias == NULL && port != 0 &&
951 port != SSH_DEFAULT_PORT) {
952 debug("checking without port identifier");
953 if (check_host_key(hostname, hostaddr, 0, host_key,
954 ROQUIET, user_hostfiles, num_user_hostfiles,
955 system_hostfiles, num_system_hostfiles) == 0) {
956 debug("found matching key w/out port");
960 if (readonly || want_cert)
962 /* The host is new. */
963 if (options.strict_host_key_checking == 1) {
965 * User has requested strict host key checking. We
966 * will not add the host key automatically. The only
967 * alternative left is to abort.
969 error("No %s host key is known for %.200s and you "
970 "have requested strict checking.", type, host);
972 } else if (options.strict_host_key_checking == 2) {
973 char msg1[1024], msg2[1024];
975 if (show_other_keys(host_hostkeys, host_key))
976 snprintf(msg1, sizeof(msg1),
977 "\nbut keys of different type are already"
978 " known for this host.");
980 snprintf(msg1, sizeof(msg1), ".");
982 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
983 ra = key_fingerprint(host_key, SSH_FP_MD5,
986 if (options.verify_host_key_dns) {
987 if (matching_host_key_dns)
988 snprintf(msg2, sizeof(msg2),
989 "Matching host key fingerprint"
992 snprintf(msg2, sizeof(msg2),
993 "No matching host key fingerprint"
996 snprintf(msg, sizeof(msg),
997 "The authenticity of host '%.200s (%s)' can't be "
999 "%s key fingerprint is %s.%s%s\n%s"
1000 "Are you sure you want to continue connecting "
1002 host, ip, msg1, type, fp,
1003 options.visual_host_key ? "\n" : "",
1004 options.visual_host_key ? ra : "",
1012 * If not in strict mode, add the key automatically to the
1013 * local known_hosts file.
1015 if (options.check_host_ip && ip_status == HOST_NEW) {
1016 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
1018 if (options.hash_known_hosts) {
1019 /* Add hash of host and IP separately */
1020 r = add_host_to_hostfile(user_hostfiles[0],
1021 host, host_key, options.hash_known_hosts) &&
1022 add_host_to_hostfile(user_hostfiles[0], ip,
1023 host_key, options.hash_known_hosts);
1025 /* Add unhashed "host,ip" */
1026 r = add_host_to_hostfile(user_hostfiles[0],
1028 options.hash_known_hosts);
1031 r = add_host_to_hostfile(user_hostfiles[0], host,
1032 host_key, options.hash_known_hosts);
1037 logit("Failed to add the host to the list of known "
1038 "hosts (%.500s).", user_hostfiles[0]);
1040 logit("Warning: Permanently added '%.200s' (%s) to the "
1041 "list of known hosts.", hostp, type);
1044 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1045 error("@ WARNING: REVOKED HOST KEY DETECTED! @");
1046 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1047 error("The %s host key for %s is marked as revoked.", type, host);
1048 error("This could mean that a stolen key is being used to");
1049 error("impersonate this host.");
1052 * If strict host key checking is in use, the user will have
1053 * to edit the key manually and we can only abort.
1055 if (options.strict_host_key_checking) {
1056 error("%s host key for %.200s was revoked and you have "
1057 "requested strict checking.", type, host);
1060 goto continue_unsafe;
1065 * This is only a debug() since it is valid to have
1066 * CAs with wildcard DNS matches that don't match
1067 * all hosts that one might visit.
1069 debug("Host certificate authority does not "
1070 "match %s in %s:%lu", CA_MARKER,
1071 host_found->file, host_found->line);
1074 if (readonly == ROQUIET)
1076 if (options.check_host_ip && host_ip_differ) {
1078 if (ip_status == HOST_NEW)
1079 key_msg = "is unknown";
1080 else if (ip_status == HOST_OK)
1081 key_msg = "is unchanged";
1083 key_msg = "has a different value";
1084 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1085 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
1086 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1087 error("The %s host key for %s has changed,", type, host);
1088 error("and the key for the corresponding IP address %s", ip);
1089 error("%s. This could either mean that", key_msg);
1090 error("DNS SPOOFING is happening or the IP address for the host");
1091 error("and its host key have changed at the same time.");
1092 if (ip_status != HOST_NEW)
1093 error("Offending key for IP in %s:%lu",
1094 ip_found->file, ip_found->line);
1096 /* The host key has changed. */
1097 warn_changed_key(host_key);
1098 error("Add correct host key in %.100s to get rid of this message.",
1100 error("Offending %s key in %s:%lu", key_type(host_found->key),
1101 host_found->file, host_found->line);
1104 * If strict host key checking is in use, the user will have
1105 * to edit the key manually and we can only abort.
1107 if (options.strict_host_key_checking) {
1108 error("%s host key for %.200s has changed and you have "
1109 "requested strict checking.", type, host);
1115 * If strict host key checking has not been requested, allow
1116 * the connection but without MITM-able authentication or
1119 if (options.password_authentication) {
1120 error("Password authentication is disabled to avoid "
1121 "man-in-the-middle attacks.");
1122 options.password_authentication = 0;
1123 cancelled_forwarding = 1;
1125 if (options.kbd_interactive_authentication) {
1126 error("Keyboard-interactive authentication is disabled"
1127 " to avoid man-in-the-middle attacks.");
1128 options.kbd_interactive_authentication = 0;
1129 options.challenge_response_authentication = 0;
1130 cancelled_forwarding = 1;
1132 if (options.challenge_response_authentication) {
1133 error("Challenge/response authentication is disabled"
1134 " to avoid man-in-the-middle attacks.");
1135 options.challenge_response_authentication = 0;
1136 cancelled_forwarding = 1;
1138 if (options.forward_agent) {
1139 error("Agent forwarding is disabled to avoid "
1140 "man-in-the-middle attacks.");
1141 options.forward_agent = 0;
1142 cancelled_forwarding = 1;
1144 if (options.forward_x11) {
1145 error("X11 forwarding is disabled to avoid "
1146 "man-in-the-middle attacks.");
1147 options.forward_x11 = 0;
1148 cancelled_forwarding = 1;
1150 if (options.num_local_forwards > 0 ||
1151 options.num_remote_forwards > 0) {
1152 error("Port forwarding is disabled to avoid "
1153 "man-in-the-middle attacks.");
1154 options.num_local_forwards =
1155 options.num_remote_forwards = 0;
1156 cancelled_forwarding = 1;
1158 if (options.tun_open != SSH_TUNMODE_NO) {
1159 error("Tunnel forwarding is disabled to avoid "
1160 "man-in-the-middle attacks.");
1161 options.tun_open = SSH_TUNMODE_NO;
1162 cancelled_forwarding = 1;
1164 if (options.exit_on_forward_failure && cancelled_forwarding)
1165 fatal("Error: forwarding disabled due to host key "
1169 * XXX Should permit the user to change to use the new id.
1170 * This could be done by converting the host key to an
1171 * identifying sentence, tell that the host identifies itself
1172 * by that sentence, and ask the user if he/she wishes to
1173 * accept the authentication.
1177 fatal("internal error");
1181 if (options.check_host_ip && host_status != HOST_CHANGED &&
1182 ip_status == HOST_CHANGED) {
1183 snprintf(msg, sizeof(msg),
1184 "Warning: the %s host key for '%.200s' "
1185 "differs from the key for the IP address '%.128s'"
1186 "\nOffending key for IP in %s:%lu",
1187 type, host, ip, ip_found->file, ip_found->line);
1188 if (host_status == HOST_OK) {
1190 snprintf(msg + len, sizeof(msg) - len,
1191 "\nMatching host key in %s:%lu",
1192 host_found->file, host_found->line);
1194 if (options.strict_host_key_checking == 1) {
1196 error("Exiting, you have requested strict checking.");
1198 } else if (options.strict_host_key_checking == 2) {
1199 strlcat(msg, "\nAre you sure you want "
1200 "to continue connecting (yes/no)? ", sizeof(msg));
1210 if (host_hostkeys != NULL)
1211 free_hostkeys(host_hostkeys);
1212 if (ip_hostkeys != NULL)
1213 free_hostkeys(ip_hostkeys);
1217 if (want_cert && host_status != HOST_REVOKED) {
1219 * No matching certificate. Downgrade cert to raw key and
1222 debug("No matching CA found. Retry with plain key");
1223 raw_key = key_from_private(host_key);
1224 if (key_drop_cert(raw_key) != 0)
1225 fatal("Couldn't drop certificate");
1229 if (raw_key != NULL)
1233 if (host_hostkeys != NULL)
1234 free_hostkeys(host_hostkeys);
1235 if (ip_hostkeys != NULL)
1236 free_hostkeys(ip_hostkeys);
1240 /* returns 0 if key verifies or -1 if key does NOT verify */
1242 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
1247 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1248 debug("Server host key: %s %s", key_type(host_key), fp);
1251 /* XXX certs are not yet supported for DNS */
1252 if (!key_is_cert(host_key) && options.verify_host_key_dns &&
1253 verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) {
1254 if (flags & DNS_VERIFY_FOUND) {
1256 if (options.verify_host_key_dns == 1 &&
1257 flags & DNS_VERIFY_MATCH &&
1258 flags & DNS_VERIFY_SECURE)
1261 if (flags & DNS_VERIFY_MATCH) {
1262 matching_host_key_dns = 1;
1264 warn_changed_key(host_key);
1265 error("Update the SSHFP RR in DNS with the new "
1266 "host key to get rid of this message.");
1271 return check_host_key(host, hostaddr, options.port, host_key, RDRW,
1272 options.user_hostfiles, options.num_user_hostfiles,
1273 options.system_hostfiles, options.num_system_hostfiles);
1277 * Starts a dialog with the server, and authenticates the current user on the
1278 * server. This does not need any extra privileges. The basic connection
1279 * to the server must already have been established before this is called.
1280 * If login fails, this function prints an error and never returns.
1281 * This function does not require super-user privileges.
1284 ssh_login(Sensitive *sensitive, const char *orighost,
1285 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms)
1288 char *server_user, *local_user;
1290 local_user = xstrdup(pw->pw_name);
1291 server_user = options.user ? options.user : local_user;
1293 /* Convert the user-supplied hostname into all lowercase. */
1294 host = xstrdup(orighost);
1297 /* Exchange protocol version identification strings with the server. */
1298 ssh_exchange_identification(timeout_ms);
1300 /* Put the connection into non-blocking mode. */
1301 packet_set_nonblocking();
1304 /* authenticate user */
1306 ssh_kex2(host, hostaddr, port);
1307 ssh_userauth2(local_user, server_user, host, sensitive);
1309 ssh_kex(host, hostaddr);
1310 ssh_userauth1(local_user, server_user, host, sensitive);
1316 ssh_put_password(char *password)
1321 if (datafellows & SSH_BUG_PASSWORDPAD) {
1322 packet_put_cstring(password);
1325 size = roundup(strlen(password) + 1, 32);
1326 padded = xcalloc(1, size);
1327 strlcpy(padded, password, size);
1328 packet_put_string(padded, size);
1329 memset(padded, 0, size);
1333 /* print all known host keys for a given host, but skip keys of given type */
1335 show_other_keys(struct hostkeys *hostkeys, Key *key)
1347 const struct hostkey_entry *found;
1349 for (i = 0; type[i] != -1; i++) {
1350 if (type[i] == key->type)
1352 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found))
1354 fp = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_HEX);
1355 ra = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_RANDOMART);
1356 logit("WARNING: %s key found for host %s\n"
1358 "%s key fingerprint %s.",
1359 key_type(found->key),
1360 found->host, found->file, found->line,
1361 key_type(found->key), fp);
1362 if (options.visual_host_key)
1372 warn_changed_key(Key *host_key)
1376 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1378 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1379 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1380 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1381 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1382 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1383 error("It is also possible that a host key has just been changed.");
1384 error("The fingerprint for the %s key sent by the remote host is\n%s.",
1385 key_type(host_key), fp);
1386 error("Please contact your system administrator.");
1392 * Execute a local command
1395 ssh_local_cmd(const char *args)
1400 void (*osighand)(int);
1402 if (!options.permit_local_command ||
1403 args == NULL || !*args)
1406 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
1407 shell = _PATH_BSHELL;
1409 osighand = signal(SIGCHLD, SIG_DFL);
1412 signal(SIGPIPE, SIG_DFL);
1413 debug3("Executing %s -c \"%s\"", shell, args);
1414 execl(shell, shell, "-c", args, (char *)NULL);
1415 error("Couldn't execute %s -c \"%s\": %s",
1416 shell, args, strerror(errno));
1418 } else if (pid == -1)
1419 fatal("fork failed: %.100s", strerror(errno));
1420 while (waitpid(pid, &status, 0) == -1)
1422 fatal("Couldn't wait for child: %s", strerror(errno));
1423 signal(SIGCHLD, osighand);
1425 if (!WIFEXITED(status))
1428 return (WEXITSTATUS(status));