1 /* $OpenBSD: sshconnect.c,v 1.212 2008/10/14 18:11:33 stevesk 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>
26 #include <netinet/in.h>
27 #include <arpa/inet.h>
52 #include "sshconnect.h"
61 char *client_version_string = NULL;
62 char *server_version_string = NULL;
64 static int matching_host_key_dns = 0;
67 extern Options options;
68 extern char *__progname;
69 extern uid_t original_real_uid;
70 extern uid_t original_effective_uid;
71 extern pid_t proxy_command_pid;
73 static int show_other_keys(const char *, Key *);
74 static void warn_changed_key(Key *);
77 * Connect to the given ssh server using a proxy command.
80 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
82 char *command_string, *tmp;
85 char *shell, strport[NI_MAXSERV];
87 if ((shell = getenv("SHELL")) == NULL)
90 /* Convert the port number into a string. */
91 snprintf(strport, sizeof strport, "%hu", port);
94 * Build the final command string in the buffer by making the
95 * appropriate substitutions to the given proxy command.
97 * Use "exec" to avoid "sh -c" processes on some platforms
100 xasprintf(&tmp, "exec %s", proxy_command);
101 command_string = percent_expand(tmp, "h", host,
102 "p", strport, (char *)NULL);
105 /* Create pipes for communicating with the proxy. */
106 if (pipe(pin) < 0 || pipe(pout) < 0)
107 fatal("Could not create pipes to communicate with the proxy: %.100s",
110 debug("Executing proxy command: %.500s", command_string);
112 /* Fork and execute the proxy command. */
113 if ((pid = fork()) == 0) {
116 /* Child. Permanently give up superuser privileges. */
117 permanently_drop_suid(original_real_uid);
119 /* Redirect stdin and stdout. */
122 if (dup2(pin[0], 0) < 0)
123 perror("dup2 stdin");
127 if (dup2(pout[1], 1) < 0)
128 perror("dup2 stdout");
129 /* Cannot be 1 because pin allocated two descriptors. */
132 /* Stderr is left as it is so that error messages get
133 printed on the user's terminal. */
136 argv[2] = command_string;
139 /* Execute the proxy command. Note that we gave up any
140 extra privileges above. */
141 execv(argv[0], argv);
147 fatal("fork failed: %.100s", strerror(errno));
149 proxy_command_pid = pid; /* save pid to clean up later */
151 /* Close child side of the descriptors. */
155 /* Free the command name. */
156 xfree(command_string);
158 /* Set the connection file descriptors. */
159 packet_set_connection(pout[0], pin[1]);
160 packet_set_timeout(options.server_alive_interval,
161 options.server_alive_count_max);
163 /* Indicate OK return */
168 * Set TCP receive buffer if requested.
169 * Note: tuning needs to happen after the socket is
170 * created but before the connection happens
171 * so winscale is negotiated properly -cjr
174 ssh_set_socket_recvbuf(int sock)
176 void *buf = (void *)&options.tcp_rcv_buf;
177 int sz = sizeof(options.tcp_rcv_buf);
179 int socksizelen = sizeof(int);
181 debug("setsockopt Attempting to set SO_RCVBUF to %d", options.tcp_rcv_buf);
182 if (setsockopt(sock, SOL_SOCKET, SO_RCVBUF, buf, sz) >= 0) {
183 getsockopt(sock, SOL_SOCKET, SO_RCVBUF, &socksize, &socksizelen);
184 debug("setsockopt SO_RCVBUF: %.100s %d", strerror(errno), socksize);
187 error("Couldn't set socket receive buffer to %d: %.100s",
188 options.tcp_rcv_buf, strerror(errno));
193 * Creates a (possibly privileged) socket for use as the ssh connection.
196 ssh_create_socket(int privileged, struct addrinfo *ai)
199 struct addrinfo hints, *res;
202 * If we are running as root and want to connect to a privileged
203 * port, bind our own socket to a privileged port.
206 int p = IPPORT_RESERVED - 1;
208 sock = rresvport_af(&p, ai->ai_family);
211 error("rresvport: af=%d %.100s", ai->ai_family,
214 debug("Allocated local port %d.", p);
216 if (options.tcp_rcv_buf > 0)
217 ssh_set_socket_recvbuf(sock);
220 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
222 error("socket: %.100s", strerror(errno));
224 if (options.tcp_rcv_buf > 0)
225 ssh_set_socket_recvbuf(sock);
227 /* Bind the socket to an alternative local IP address */
228 if (options.bind_address == NULL)
231 memset(&hints, 0, sizeof(hints));
232 hints.ai_family = ai->ai_family;
233 hints.ai_socktype = ai->ai_socktype;
234 hints.ai_protocol = ai->ai_protocol;
235 hints.ai_flags = AI_PASSIVE;
236 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res);
238 error("getaddrinfo: %s: %s", options.bind_address,
239 ssh_gai_strerror(gaierr));
243 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
244 error("bind: %s: %s", options.bind_address, strerror(errno));
254 timeout_connect(int sockfd, const struct sockaddr *serv_addr,
255 socklen_t addrlen, int *timeoutp)
258 struct timeval tv, t_start;
260 int optval, rc, result = -1;
262 gettimeofday(&t_start, NULL);
264 if (*timeoutp <= 0) {
265 result = connect(sockfd, serv_addr, addrlen);
269 set_nonblock(sockfd);
270 rc = connect(sockfd, serv_addr, addrlen);
272 unset_nonblock(sockfd);
276 if (errno != EINPROGRESS) {
281 fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS),
283 FD_SET(sockfd, fdset);
284 ms_to_timeval(&tv, *timeoutp);
287 rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
288 if (rc != -1 || errno != EINTR)
299 debug("select: %s", strerror(errno));
302 /* Completed or failed */
304 optlen = sizeof(optval);
305 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
307 debug("getsockopt: %s", strerror(errno));
315 unset_nonblock(sockfd);
318 /* Should not occur */
319 fatal("Bogus return (%d) from select()", rc);
325 if (result == 0 && *timeoutp > 0) {
326 ms_subtract_diff(&t_start, timeoutp);
327 if (*timeoutp <= 0) {
337 * Opens a TCP/IP connection to the remote server on the given host.
338 * The address of the remote host will be returned in hostaddr.
339 * If port is 0, the default port will be used. If needpriv is true,
340 * a privileged port will be allocated to make the connection.
341 * This requires super-user privileges if needpriv is true.
342 * Connection_attempts specifies the maximum number of tries (one per
343 * second). If proxy_command is non-NULL, it specifies the command (with %h
344 * and %p substituted for host and port, respectively) to use to contact
348 ssh_connect(const char *host, struct sockaddr_storage * hostaddr,
349 u_short port, int family, int connection_attempts, int *timeout_ms,
350 int want_keepalive, int needpriv, const char *proxy_command)
354 int sock = -1, attempt;
355 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
356 struct addrinfo hints, *ai, *aitop;
358 debug2("ssh_connect: needpriv %d", needpriv);
360 /* If a proxy command is given, connect using it. */
361 if (proxy_command != NULL)
362 return ssh_proxy_connect(host, port, proxy_command);
364 /* No proxy command. */
366 memset(&hints, 0, sizeof(hints));
367 hints.ai_family = family;
368 hints.ai_socktype = SOCK_STREAM;
369 snprintf(strport, sizeof strport, "%u", port);
370 if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0)
371 fatal("%s: Could not resolve hostname %.100s: %s", __progname,
372 host, ssh_gai_strerror(gaierr));
374 for (attempt = 0; attempt < connection_attempts; attempt++) {
376 /* Sleep a moment before retrying. */
378 debug("Trying again...");
381 * Loop through addresses for this host, and try each one in
382 * sequence until the connection succeeds.
384 for (ai = aitop; ai; ai = ai->ai_next) {
385 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
387 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
388 ntop, sizeof(ntop), strport, sizeof(strport),
389 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
390 error("ssh_connect: getnameinfo failed");
393 debug("Connecting to %.200s [%.100s] port %s.",
394 host, ntop, strport);
396 /* Create a socket for connecting. */
397 sock = ssh_create_socket(needpriv, ai);
399 /* Any error is already output */
402 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
404 /* Successful connection. */
405 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
408 debug("connect to address %s port %s: %s",
409 ntop, strport, strerror(errno));
415 break; /* Successful connection. */
420 /* Return failure if we didn't get a successful connection. */
422 error("ssh: connect to host %s port %s: %s",
423 host, strport, strerror(errno));
427 debug("Connection established.");
429 /* Set SO_KEEPALIVE if requested. */
430 if (want_keepalive &&
431 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
433 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
435 /* Set the connection. */
436 packet_set_connection(sock, sock);
437 packet_set_timeout(options.server_alive_interval,
438 options.server_alive_count_max);
444 * Waits for the server identification string, and sends our own
445 * identification string.
448 ssh_exchange_identification(int timeout_ms)
450 char buf[256], remote_version[256]; /* must be same size! */
451 int remote_major, remote_minor, mismatch;
452 int connection_in = packet_get_connection_in();
453 int connection_out = packet_get_connection_out();
454 int minor1 = PROTOCOL_MINOR_1;
457 int fdsetsz, remaining, rc;
458 struct timeval t_start, t_remaining;
461 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask);
462 fdset = xcalloc(1, fdsetsz);
464 /* Read other side's version identification. */
465 remaining = timeout_ms;
467 for (i = 0; i < sizeof(buf) - 1; i++) {
468 if (timeout_ms > 0) {
469 gettimeofday(&t_start, NULL);
470 ms_to_timeval(&t_remaining, remaining);
471 FD_SET(connection_in, fdset);
472 rc = select(connection_in + 1, fdset, NULL,
473 fdset, &t_remaining);
474 ms_subtract_diff(&t_start, &remaining);
475 if (rc == 0 || remaining <= 0)
476 fatal("Connection timed out during "
481 fatal("ssh_exchange_identification: "
482 "select: %s", strerror(errno));
486 len = atomicio(read, connection_in, &buf[i], 1);
488 if (len != 1 && errno == EPIPE)
489 fatal("ssh_exchange_identification: "
490 "Connection closed by remote host");
492 fatal("ssh_exchange_identification: "
493 "read: %.100s", strerror(errno));
494 if (buf[i] == '\r') {
497 continue; /**XXX wait for \n */
499 if (buf[i] == '\n') {
504 fatal("ssh_exchange_identification: "
505 "No banner received");
507 buf[sizeof(buf) - 1] = 0;
508 if (strncmp(buf, "SSH-", 4) == 0)
510 debug("ssh_exchange_identification: %s", buf);
512 server_version_string = xstrdup(buf);
516 * Check that the versions match. In future this might accept
517 * several versions and set appropriate flags to handle them.
519 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
520 &remote_major, &remote_minor, remote_version) != 3)
521 fatal("Bad remote protocol version identification: '%.100s'", buf);
522 debug("Remote protocol version %d.%d, remote software version %.100s",
523 remote_major, remote_minor, remote_version);
525 compat_datafellows(remote_version);
528 switch (remote_major) {
530 if (remote_minor == 99 &&
531 (options.protocol & SSH_PROTO_2) &&
532 !(options.protocol & SSH_PROTO_1_PREFERRED)) {
536 if (!(options.protocol & SSH_PROTO_1)) {
540 if (remote_minor < 3) {
541 fatal("Remote machine has too old SSH software version.");
542 } else if (remote_minor == 3 || remote_minor == 4) {
543 /* We speak 1.3, too. */
546 if (options.forward_agent) {
547 logit("Agent forwarding disabled for protocol 1.3");
548 options.forward_agent = 0;
553 if (options.protocol & SSH_PROTO_2) {
563 fatal("Protocol major versions differ: %d vs. %d",
564 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
566 /* Send our own protocol version identification. */
567 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s%s",
568 compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
569 compat20 ? PROTOCOL_MINOR_2 : minor1,
570 SSH_RELEASE, compat20 ? "\r\n" : "\n");
571 if (atomicio(vwrite, connection_out, buf, strlen(buf)) != strlen(buf))
572 fatal("write: %.100s", strerror(errno));
573 client_version_string = xstrdup(buf);
574 chop(client_version_string);
575 chop(server_version_string);
576 debug("Local version string %.100s", client_version_string);
579 /* defaults to 'no' */
581 confirm(const char *prompt)
583 const char *msg, *again = "Please type 'yes' or 'no': ";
587 if (options.batch_mode)
589 for (msg = prompt;;msg = again) {
590 p = read_passphrase(msg, RP_ECHO);
592 (p[0] == '\0') || (p[0] == '\n') ||
593 strncasecmp(p, "no", 2) == 0)
595 if (p && strncasecmp(p, "yes", 3) == 0)
605 * check whether the supplied host key is valid, return -1 if the key
606 * is not valid. the user_hostfile will not be updated if 'readonly' is true.
612 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
613 Key *host_key, int readonly, const char *user_hostfile,
614 const char *system_hostfile)
617 const char *type = key_type(host_key);
618 char *ip = NULL, *host = NULL;
619 char hostline[1000], *hostp, *fp, *ra;
620 HostStatus host_status;
621 HostStatus ip_status;
622 int r, local = 0, host_ip_differ = 0;
624 char ntop[NI_MAXHOST];
626 int len, host_line, ip_line, cancelled_forwarding = 0;
627 const char *host_file = NULL, *ip_file = NULL;
630 * Force accepting of the host key for loopback/localhost. The
631 * problem is that if the home directory is NFS-mounted to multiple
632 * machines, localhost will refer to a different machine in each of
633 * them, and the user will get bogus HOST_CHANGED warnings. This
634 * essentially disables host authentication for localhost; however,
635 * this is probably not a real problem.
637 /** hostaddr == 0! */
638 switch (hostaddr->sa_family) {
640 local = (ntohl(((struct sockaddr_in *)hostaddr)->
641 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
642 salen = sizeof(struct sockaddr_in);
645 local = IN6_IS_ADDR_LOOPBACK(
646 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
647 salen = sizeof(struct sockaddr_in6);
651 salen = sizeof(struct sockaddr_storage);
654 if (options.no_host_authentication_for_localhost == 1 && local &&
655 options.host_key_alias == NULL) {
656 debug("Forcing accepting of host key for "
657 "loopback/localhost.");
662 * We don't have the remote ip-address for connections
663 * using a proxy command
665 if (options.proxy_command == NULL) {
666 if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop),
667 NULL, 0, NI_NUMERICHOST) != 0)
668 fatal("check_host_key: getnameinfo failed");
669 ip = put_host_port(ntop, port);
671 ip = xstrdup("<no hostip for proxy command>");
675 * Turn off check_host_ip if the connection is to localhost, via proxy
676 * command or if we don't have a hostname to compare with
678 if (options.check_host_ip && (local ||
679 strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
680 options.check_host_ip = 0;
683 * Allow the user to record the key under a different name or
684 * differentiate a non-standard port. This is useful for ssh
685 * tunneling over forwarded connections or if you run multiple
686 * sshd's on different ports on the same machine.
688 if (options.host_key_alias != NULL) {
689 host = xstrdup(options.host_key_alias);
690 debug("using hostkeyalias: %s", host);
692 host = put_host_port(hostname, port);
696 * Store the host key from the known host file in here so that we can
697 * compare it with the key for the IP address.
699 file_key = key_new(host_key->type);
702 * Check if the host key is present in the user's list of known
703 * hosts or in the systemwide list.
705 host_file = user_hostfile;
706 host_status = check_host_in_hostfile(host_file, host, host_key,
707 file_key, &host_line);
708 if (host_status == HOST_NEW) {
709 host_file = system_hostfile;
710 host_status = check_host_in_hostfile(host_file, host, host_key,
711 file_key, &host_line);
714 * Also perform check for the ip address, skip the check if we are
715 * localhost or the hostname was an ip address to begin with
717 if (options.check_host_ip) {
718 Key *ip_key = key_new(host_key->type);
720 ip_file = user_hostfile;
721 ip_status = check_host_in_hostfile(ip_file, ip, host_key,
723 if (ip_status == HOST_NEW) {
724 ip_file = system_hostfile;
725 ip_status = check_host_in_hostfile(ip_file, ip,
726 host_key, ip_key, &ip_line);
728 if (host_status == HOST_CHANGED &&
729 (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key)))
734 ip_status = host_status;
738 switch (host_status) {
740 /* The host is known and the key matches. */
741 debug("Host '%.200s' is known and matches the %s host key.",
743 debug("Found key in %s:%d", host_file, host_line);
744 if (options.check_host_ip && ip_status == HOST_NEW) {
746 logit("%s host key for IP address "
747 "'%.128s' not in list of known hosts.",
749 else if (!add_host_to_hostfile(user_hostfile, ip,
750 host_key, options.hash_known_hosts))
751 logit("Failed to add the %s host key for IP "
752 "address '%.128s' to the list of known "
753 "hosts (%.30s).", type, ip, user_hostfile);
755 logit("Warning: Permanently added the %s host "
756 "key for IP address '%.128s' to the list "
757 "of known hosts.", type, ip);
758 } else if (options.visual_host_key) {
759 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
760 ra = key_fingerprint(host_key, SSH_FP_MD5,
762 logit("Host key fingerprint is %s\n%s\n", fp, ra);
768 if (options.host_key_alias == NULL && port != 0 &&
769 port != SSH_DEFAULT_PORT) {
770 debug("checking without port identifier");
771 if (check_host_key(hostname, hostaddr, 0, host_key,
772 ROQUIET, user_hostfile, system_hostfile) == 0) {
773 debug("found matching key w/out port");
779 /* The host is new. */
780 if (options.strict_host_key_checking == 1) {
782 * User has requested strict host key checking. We
783 * will not add the host key automatically. The only
784 * alternative left is to abort.
786 error("No %s host key is known for %.200s and you "
787 "have requested strict checking.", type, host);
789 } else if (options.strict_host_key_checking == 2) {
790 char msg1[1024], msg2[1024];
792 if (show_other_keys(host, host_key))
793 snprintf(msg1, sizeof(msg1),
794 "\nbut keys of different type are already"
795 " known for this host.");
797 snprintf(msg1, sizeof(msg1), ".");
799 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
800 ra = key_fingerprint(host_key, SSH_FP_MD5,
803 if (options.verify_host_key_dns) {
804 if (matching_host_key_dns)
805 snprintf(msg2, sizeof(msg2),
806 "Matching host key fingerprint"
809 snprintf(msg2, sizeof(msg2),
810 "No matching host key fingerprint"
813 snprintf(msg, sizeof(msg),
814 "The authenticity of host '%.200s (%s)' can't be "
816 "%s key fingerprint is %s.%s%s\n%s"
817 "Are you sure you want to continue connecting "
819 host, ip, msg1, type, fp,
820 options.visual_host_key ? "\n" : "",
821 options.visual_host_key ? ra : "",
829 * If not in strict mode, add the key automatically to the
830 * local known_hosts file.
832 if (options.check_host_ip && ip_status == HOST_NEW) {
833 snprintf(hostline, sizeof(hostline), "%s,%s",
836 if (options.hash_known_hosts) {
837 /* Add hash of host and IP separately */
838 r = add_host_to_hostfile(user_hostfile, host,
839 host_key, options.hash_known_hosts) &&
840 add_host_to_hostfile(user_hostfile, ip,
841 host_key, options.hash_known_hosts);
843 /* Add unhashed "host,ip" */
844 r = add_host_to_hostfile(user_hostfile,
846 options.hash_known_hosts);
849 r = add_host_to_hostfile(user_hostfile, host, host_key,
850 options.hash_known_hosts);
855 logit("Failed to add the host to the list of known "
856 "hosts (%.500s).", user_hostfile);
858 logit("Warning: Permanently added '%.200s' (%s) to the "
859 "list of known hosts.", hostp, type);
862 if (readonly == ROQUIET)
864 if (options.check_host_ip && host_ip_differ) {
866 if (ip_status == HOST_NEW)
867 key_msg = "is unknown";
868 else if (ip_status == HOST_OK)
869 key_msg = "is unchanged";
871 key_msg = "has a different value";
872 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
873 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
874 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
875 error("The %s host key for %s has changed,", type, host);
876 error("and the key for the corresponding IP address %s", ip);
877 error("%s. This could either mean that", key_msg);
878 error("DNS SPOOFING is happening or the IP address for the host");
879 error("and its host key have changed at the same time.");
880 if (ip_status != HOST_NEW)
881 error("Offending key for IP in %s:%d", ip_file, ip_line);
883 /* The host key has changed. */
884 warn_changed_key(host_key);
885 error("Add correct host key in %.100s to get rid of this message.",
887 error("Offending key in %s:%d", host_file, host_line);
890 * If strict host key checking is in use, the user will have
891 * to edit the key manually and we can only abort.
893 if (options.strict_host_key_checking) {
894 error("%s host key for %.200s has changed and you have "
895 "requested strict checking.", type, host);
900 * If strict host key checking has not been requested, allow
901 * the connection but without MITM-able authentication or
904 if (options.password_authentication) {
905 error("Password authentication is disabled to avoid "
906 "man-in-the-middle attacks.");
907 options.password_authentication = 0;
908 cancelled_forwarding = 1;
910 if (options.kbd_interactive_authentication) {
911 error("Keyboard-interactive authentication is disabled"
912 " to avoid man-in-the-middle attacks.");
913 options.kbd_interactive_authentication = 0;
914 options.challenge_response_authentication = 0;
915 cancelled_forwarding = 1;
917 if (options.challenge_response_authentication) {
918 error("Challenge/response authentication is disabled"
919 " to avoid man-in-the-middle attacks.");
920 options.challenge_response_authentication = 0;
921 cancelled_forwarding = 1;
923 if (options.forward_agent) {
924 error("Agent forwarding is disabled to avoid "
925 "man-in-the-middle attacks.");
926 options.forward_agent = 0;
927 cancelled_forwarding = 1;
929 if (options.forward_x11) {
930 error("X11 forwarding is disabled to avoid "
931 "man-in-the-middle attacks.");
932 options.forward_x11 = 0;
933 cancelled_forwarding = 1;
935 if (options.num_local_forwards > 0 ||
936 options.num_remote_forwards > 0) {
937 error("Port forwarding is disabled to avoid "
938 "man-in-the-middle attacks.");
939 options.num_local_forwards =
940 options.num_remote_forwards = 0;
941 cancelled_forwarding = 1;
943 if (options.tun_open != SSH_TUNMODE_NO) {
944 error("Tunnel forwarding is disabled to avoid "
945 "man-in-the-middle attacks.");
946 options.tun_open = SSH_TUNMODE_NO;
947 cancelled_forwarding = 1;
949 if (options.exit_on_forward_failure && cancelled_forwarding)
950 fatal("Error: forwarding disabled due to host key "
954 * XXX Should permit the user to change to use the new id.
955 * This could be done by converting the host key to an
956 * identifying sentence, tell that the host identifies itself
957 * by that sentence, and ask the user if he/she whishes to
958 * accept the authentication.
962 fatal("internal error");
966 if (options.check_host_ip && host_status != HOST_CHANGED &&
967 ip_status == HOST_CHANGED) {
968 snprintf(msg, sizeof(msg),
969 "Warning: the %s host key for '%.200s' "
970 "differs from the key for the IP address '%.128s'"
971 "\nOffending key for IP in %s:%d",
972 type, host, ip, ip_file, ip_line);
973 if (host_status == HOST_OK) {
975 snprintf(msg + len, sizeof(msg) - len,
976 "\nMatching host key in %s:%d",
977 host_file, host_line);
979 if (options.strict_host_key_checking == 1) {
981 error("Exiting, you have requested strict checking.");
983 } else if (options.strict_host_key_checking == 2) {
984 strlcat(msg, "\nAre you sure you want "
985 "to continue connecting (yes/no)? ", sizeof(msg));
1003 /* returns 0 if key verifies or -1 if key does NOT verify */
1005 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
1010 if (options.verify_host_key_dns &&
1011 verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) {
1013 if (flags & DNS_VERIFY_FOUND) {
1015 if (options.verify_host_key_dns == 1 &&
1016 flags & DNS_VERIFY_MATCH &&
1017 flags & DNS_VERIFY_SECURE)
1020 if (flags & DNS_VERIFY_MATCH) {
1021 matching_host_key_dns = 1;
1023 warn_changed_key(host_key);
1024 error("Update the SSHFP RR in DNS with the new "
1025 "host key to get rid of this message.");
1030 /* return ok if the key can be found in an old keyfile */
1031 if (stat(options.system_hostfile2, &st) == 0 ||
1032 stat(options.user_hostfile2, &st) == 0) {
1033 if (check_host_key(host, hostaddr, options.port, host_key,
1034 RDONLY, options.user_hostfile2,
1035 options.system_hostfile2) == 0)
1038 return check_host_key(host, hostaddr, options.port, host_key,
1039 RDRW, options.user_hostfile, options.system_hostfile);
1043 * Starts a dialog with the server, and authenticates the current user on the
1044 * server. This does not need any extra privileges. The basic connection
1045 * to the server must already have been established before this is called.
1046 * If login fails, this function prints an error and never returns.
1047 * This function does not require super-user privileges.
1050 ssh_login(Sensitive *sensitive, const char *orighost,
1051 struct sockaddr *hostaddr, struct passwd *pw, int timeout_ms)
1054 char *server_user, *local_user;
1056 local_user = xstrdup(pw->pw_name);
1057 server_user = options.user ? options.user : local_user;
1059 /* Convert the user-supplied hostname into all lowercase. */
1060 host = xstrdup(orighost);
1061 for (cp = host; *cp; cp++)
1063 *cp = (char)tolower(*cp);
1065 /* Exchange protocol version identification strings with the server. */
1066 ssh_exchange_identification(timeout_ms);
1068 /* Put the connection into non-blocking mode. */
1069 packet_set_nonblocking();
1072 /* authenticate user */
1074 ssh_kex2(host, hostaddr);
1075 ssh_userauth2(local_user, server_user, host, sensitive);
1077 ssh_kex(host, hostaddr);
1078 ssh_userauth1(local_user, server_user, host, sensitive);
1084 ssh_put_password(char *password)
1089 if (datafellows & SSH_BUG_PASSWORDPAD) {
1090 packet_put_cstring(password);
1093 size = roundup(strlen(password) + 1, 32);
1094 padded = xcalloc(1, size);
1095 strlcpy(padded, password, size);
1096 packet_put_string(padded, size);
1097 memset(padded, 0, size);
1102 show_key_from_file(const char *file, const char *host, int keytype)
1108 found = key_new(keytype);
1109 if ((ret = lookup_key_in_hostfile_by_type(file, host,
1110 keytype, found, &line))) {
1111 fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
1112 ra = key_fingerprint(found, SSH_FP_MD5, SSH_FP_RANDOMART);
1113 logit("WARNING: %s key found for host %s\n"
1115 "%s key fingerprint %s.\n%s\n",
1116 key_type(found), host, file, line,
1117 key_type(found), fp, ra);
1125 /* print all known host keys for a given host, but skip keys of given type */
1127 show_other_keys(const char *host, Key *key)
1129 int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1};
1132 for (i = 0; type[i] != -1; i++) {
1133 if (type[i] == key->type)
1135 if (type[i] != KEY_RSA1 &&
1136 show_key_from_file(options.user_hostfile2, host, type[i])) {
1140 if (type[i] != KEY_RSA1 &&
1141 show_key_from_file(options.system_hostfile2, host, type[i])) {
1145 if (show_key_from_file(options.user_hostfile, host, type[i])) {
1149 if (show_key_from_file(options.system_hostfile, host, type[i])) {
1153 debug2("no key of type %d for host %s", type[i], host);
1159 warn_changed_key(Key *host_key)
1162 const char *type = key_type(host_key);
1164 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1166 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1167 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1168 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1169 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1170 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1171 error("It is also possible that the %s host key has just been changed.", type);
1172 error("The fingerprint for the %s key sent by the remote host is\n%s.",
1174 error("Please contact your system administrator.");
1180 * Execute a local command
1183 ssh_local_cmd(const char *args)
1189 if (!options.permit_local_command ||
1190 args == NULL || !*args)
1193 if ((shell = getenv("SHELL")) == NULL)
1194 shell = _PATH_BSHELL;
1198 debug3("Executing %s -c \"%s\"", shell, args);
1199 execl(shell, shell, "-c", args, (char *)NULL);
1200 error("Couldn't execute %s -c \"%s\": %s",
1201 shell, args, strerror(errno));
1203 } else if (pid == -1)
1204 fatal("fork failed: %.100s", strerror(errno));
1205 while (waitpid(pid, &status, 0) == -1)
1207 fatal("Couldn't wait for child: %s", strerror(errno));
1209 if (!WIFEXITED(status))
1212 return (WEXITSTATUS(status));