1 /* $OpenBSD: sshconnect.c,v 1.203 2007/12/27 14:22:08 dtucker 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 #ifndef INET6_ADDRSTRLEN /* for non IPv6 machines */
74 #define INET6_ADDRSTRLEN 46
77 static int show_other_keys(const char *, Key *);
78 static void warn_changed_key(Key *);
81 ms_subtract_diff(struct timeval *start, int *ms)
83 struct timeval diff, finish;
85 gettimeofday(&finish, NULL);
86 timersub(&finish, start, &diff);
87 *ms -= (diff.tv_sec * 1000) + (diff.tv_usec / 1000);
91 ms_to_timeval(struct timeval *tv, int ms)
93 tv->tv_sec = ms / 1000;
94 tv->tv_usec = (ms % 1000) * 1000;
98 * Connect to the given ssh server using a proxy command.
101 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
103 char *command_string, *tmp;
106 char *shell, strport[NI_MAXSERV];
108 if ((shell = getenv("SHELL")) == NULL)
109 shell = _PATH_BSHELL;
111 /* Convert the port number into a string. */
112 snprintf(strport, sizeof strport, "%hu", port);
115 * Build the final command string in the buffer by making the
116 * appropriate substitutions to the given proxy command.
118 * Use "exec" to avoid "sh -c" processes on some platforms
121 xasprintf(&tmp, "exec %s", proxy_command);
122 command_string = percent_expand(tmp, "h", host,
123 "p", strport, (char *)NULL);
126 /* Create pipes for communicating with the proxy. */
127 if (pipe(pin) < 0 || pipe(pout) < 0)
128 fatal("Could not create pipes to communicate with the proxy: %.100s",
131 debug("Executing proxy command: %.500s", command_string);
133 /* Fork and execute the proxy command. */
134 if ((pid = fork()) == 0) {
137 /* Child. Permanently give up superuser privileges. */
138 permanently_drop_suid(original_real_uid);
140 /* Redirect stdin and stdout. */
143 if (dup2(pin[0], 0) < 0)
144 perror("dup2 stdin");
148 if (dup2(pout[1], 1) < 0)
149 perror("dup2 stdout");
150 /* Cannot be 1 because pin allocated two descriptors. */
153 /* Stderr is left as it is so that error messages get
154 printed on the user's terminal. */
157 argv[2] = command_string;
160 /* Execute the proxy command. Note that we gave up any
161 extra privileges above. */
162 execv(argv[0], argv);
168 fatal("fork failed: %.100s", strerror(errno));
170 proxy_command_pid = pid; /* save pid to clean up later */
172 /* Close child side of the descriptors. */
176 /* Free the command name. */
177 xfree(command_string);
179 /* Set the connection file descriptors. */
180 packet_set_connection(pout[0], pin[1]);
182 /* Indicate OK return */
187 * Set TCP receive buffer if requested.
188 * Note: tuning needs to happen after the socket is
189 * created but before the connection happens
190 * so winscale is negotiated properly -cjr
193 ssh_set_socket_recvbuf(int sock)
195 void *buf = (void *)&options.tcp_rcv_buf;
196 int sz = sizeof(options.tcp_rcv_buf);
198 int socksizelen = sizeof(int);
200 debug("setsockopt Attempting to set SO_RCVBUF to %d", options.tcp_rcv_buf);
201 if (setsockopt(sock, SOL_SOCKET, SO_RCVBUF, buf, sz) >= 0) {
202 getsockopt(sock, SOL_SOCKET, SO_RCVBUF, &socksize, &socksizelen);
203 debug("setsockopt SO_RCVBUF: %.100s %d", strerror(errno), socksize);
206 error("Couldn't set socket receive buffer to %d: %.100s",
207 options.tcp_rcv_buf, strerror(errno));
212 * Creates a (possibly privileged) socket for use as the ssh connection.
215 ssh_create_socket(int privileged, struct addrinfo *ai)
218 struct addrinfo hints, *res;
221 * If we are running as root and want to connect to a privileged
222 * port, bind our own socket to a privileged port.
225 int p = IPPORT_RESERVED - 1;
227 sock = rresvport_af(&p, ai->ai_family);
230 error("rresvport: af=%d %.100s", ai->ai_family,
233 debug("Allocated local port %d.", p);
235 if (options.tcp_rcv_buf > 0)
236 ssh_set_socket_recvbuf(sock);
239 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
241 error("socket: %.100s", strerror(errno));
244 if (options.tcp_rcv_buf > 0)
245 ssh_set_socket_recvbuf(sock);
247 /* Bind the socket to an alternative local IP address */
248 if (options.bind_address == NULL)
251 memset(&hints, 0, sizeof(hints));
252 hints.ai_family = ai->ai_family;
253 hints.ai_socktype = ai->ai_socktype;
254 hints.ai_protocol = ai->ai_protocol;
255 hints.ai_flags = AI_PASSIVE;
256 gaierr = getaddrinfo(options.bind_address, "0", &hints, &res);
258 error("getaddrinfo: %s: %s", options.bind_address,
259 ssh_gai_strerror(gaierr));
263 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
264 error("bind: %s: %s", options.bind_address, strerror(errno));
274 timeout_connect(int sockfd, const struct sockaddr *serv_addr,
275 socklen_t addrlen, int *timeoutp)
278 struct timeval tv, t_start;
280 int optval, rc, result = -1;
282 gettimeofday(&t_start, NULL);
284 if (*timeoutp <= 0) {
285 result = connect(sockfd, serv_addr, addrlen);
289 set_nonblock(sockfd);
290 rc = connect(sockfd, serv_addr, addrlen);
292 unset_nonblock(sockfd);
296 if (errno != EINPROGRESS) {
301 fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS),
303 FD_SET(sockfd, fdset);
304 ms_to_timeval(&tv, *timeoutp);
307 rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
308 if (rc != -1 || errno != EINTR)
319 debug("select: %s", strerror(errno));
322 /* Completed or failed */
324 optlen = sizeof(optval);
325 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
327 debug("getsockopt: %s", strerror(errno));
335 unset_nonblock(sockfd);
338 /* Should not occur */
339 fatal("Bogus return (%d) from select()", rc);
345 if (result == 0 && *timeoutp > 0) {
346 ms_subtract_diff(&t_start, timeoutp);
347 if (*timeoutp <= 0) {
357 * Opens a TCP/IP connection to the remote server on the given host.
358 * The address of the remote host will be returned in hostaddr.
359 * If port is 0, the default port will be used. If needpriv is true,
360 * a privileged port will be allocated to make the connection.
361 * This requires super-user privileges if needpriv is true.
362 * Connection_attempts specifies the maximum number of tries (one per
363 * second). If proxy_command is non-NULL, it specifies the command (with %h
364 * and %p substituted for host and port, respectively) to use to contact
368 ssh_connect(const char *host, struct sockaddr_storage * hostaddr,
369 u_short port, int family, int connection_attempts, int *timeout_ms,
370 int want_keepalive, int needpriv, const char *proxy_command)
374 int sock = -1, attempt;
375 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
376 struct addrinfo hints, *ai, *aitop;
378 debug2("ssh_connect: needpriv %d", needpriv);
380 /* If a proxy command is given, connect using it. */
381 if (proxy_command != NULL)
382 return ssh_proxy_connect(host, port, proxy_command);
384 /* No proxy command. */
386 memset(&hints, 0, sizeof(hints));
387 hints.ai_family = family;
388 hints.ai_socktype = SOCK_STREAM;
389 snprintf(strport, sizeof strport, "%u", port);
390 if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0)
391 fatal("%s: Could not resolve hostname %.100s: %s", __progname,
392 host, ssh_gai_strerror(gaierr));
394 for (attempt = 0; attempt < connection_attempts; attempt++) {
396 /* Sleep a moment before retrying. */
398 debug("Trying again...");
401 * Loop through addresses for this host, and try each one in
402 * sequence until the connection succeeds.
404 for (ai = aitop; ai; ai = ai->ai_next) {
405 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
407 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
408 ntop, sizeof(ntop), strport, sizeof(strport),
409 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
410 error("ssh_connect: getnameinfo failed");
413 debug("Connecting to %.200s [%.100s] port %s.",
414 host, ntop, strport);
416 /* Create a socket for connecting. */
417 sock = ssh_create_socket(needpriv, ai);
419 /* Any error is already output */
422 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
424 /* Successful connection. */
425 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
428 debug("connect to address %s port %s: %s",
429 ntop, strport, strerror(errno));
435 break; /* Successful connection. */
440 /* Return failure if we didn't get a successful connection. */
442 error("ssh: connect to host %s port %s: %s",
443 host, strport, strerror(errno));
447 debug("Connection established.");
449 /* Set SO_KEEPALIVE if requested. */
450 if (want_keepalive &&
451 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
453 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
455 /* Set the connection. */
456 packet_set_connection(sock, sock);
462 * Waits for the server identification string, and sends our own
463 * identification string.
466 ssh_exchange_identification(int timeout_ms)
468 char buf[256], remote_version[256]; /* must be same size! */
469 int remote_major, remote_minor, mismatch;
470 int connection_in = packet_get_connection_in();
471 int connection_out = packet_get_connection_out();
472 int minor1 = PROTOCOL_MINOR_1;
475 int fdsetsz, remaining, rc;
476 struct timeval t_start, t_remaining;
479 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask);
480 fdset = xcalloc(1, fdsetsz);
482 /* Read other side's version identification. */
483 remaining = timeout_ms;
485 for (i = 0; i < sizeof(buf) - 1; i++) {
486 if (timeout_ms > 0) {
487 gettimeofday(&t_start, NULL);
488 ms_to_timeval(&t_remaining, remaining);
489 FD_SET(connection_in, fdset);
490 rc = select(connection_in + 1, fdset, NULL,
491 fdset, &t_remaining);
492 ms_subtract_diff(&t_start, &remaining);
493 if (rc == 0 || remaining <= 0)
494 fatal("Connection timed out during "
499 fatal("ssh_exchange_identification: "
500 "select: %s", strerror(errno));
504 len = atomicio(read, connection_in, &buf[i], 1);
506 if (len != 1 && errno == EPIPE)
507 fatal("ssh_exchange_identification: "
508 "Connection closed by remote host");
510 fatal("ssh_exchange_identification: "
511 "read: %.100s", strerror(errno));
512 if (buf[i] == '\r') {
515 continue; /**XXX wait for \n */
517 if (buf[i] == '\n') {
522 fatal("ssh_exchange_identification: "
523 "No banner received");
525 buf[sizeof(buf) - 1] = 0;
526 if (strncmp(buf, "SSH-", 4) == 0)
528 debug("ssh_exchange_identification: %s", buf);
530 server_version_string = xstrdup(buf);
534 * Check that the versions match. In future this might accept
535 * several versions and set appropriate flags to handle them.
537 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
538 &remote_major, &remote_minor, remote_version) != 3)
539 fatal("Bad remote protocol version identification: '%.100s'", buf);
540 debug("Remote protocol version %d.%d, remote software version %.100s",
541 remote_major, remote_minor, remote_version);
543 compat_datafellows(remote_version);
546 switch (remote_major) {
548 if (remote_minor == 99 &&
549 (options.protocol & SSH_PROTO_2) &&
550 !(options.protocol & SSH_PROTO_1_PREFERRED)) {
554 if (!(options.protocol & SSH_PROTO_1)) {
558 if (remote_minor < 3) {
559 fatal("Remote machine has too old SSH software version.");
560 } else if (remote_minor == 3 || remote_minor == 4) {
561 /* We speak 1.3, too. */
564 if (options.forward_agent) {
565 logit("Agent forwarding disabled for protocol 1.3");
566 options.forward_agent = 0;
571 if (options.protocol & SSH_PROTO_2) {
581 fatal("Protocol major versions differ: %d vs. %d",
582 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
584 /* Send our own protocol version identification. */
585 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n",
586 compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
587 compat20 ? PROTOCOL_MINOR_2 : minor1,
589 if (atomicio(vwrite, connection_out, buf, strlen(buf)) != strlen(buf))
590 fatal("write: %.100s", strerror(errno));
591 client_version_string = xstrdup(buf);
592 chop(client_version_string);
593 chop(server_version_string);
594 debug("Local version string %.100s", client_version_string);
597 /* defaults to 'no' */
599 confirm(const char *prompt)
601 const char *msg, *again = "Please type 'yes' or 'no': ";
605 if (options.batch_mode)
607 for (msg = prompt;;msg = again) {
608 p = read_passphrase(msg, RP_ECHO);
610 (p[0] == '\0') || (p[0] == '\n') ||
611 strncasecmp(p, "no", 2) == 0)
613 if (p && strncasecmp(p, "yes", 3) == 0)
623 * check whether the supplied host key is valid, return -1 if the key
624 * is not valid. the user_hostfile will not be updated if 'readonly' is true.
630 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
631 Key *host_key, int readonly, const char *user_hostfile,
632 const char *system_hostfile)
635 const char *type = key_type(host_key);
636 char *ip = NULL, *host = NULL;
637 char hostline[1000], *hostp, *fp;
638 HostStatus host_status;
639 HostStatus ip_status;
640 int r, local = 0, host_ip_differ = 0;
642 char ntop[NI_MAXHOST];
644 int len, host_line, ip_line;
645 const char *host_file = NULL, *ip_file = NULL;
648 * Force accepting of the host key for loopback/localhost. The
649 * problem is that if the home directory is NFS-mounted to multiple
650 * machines, localhost will refer to a different machine in each of
651 * them, and the user will get bogus HOST_CHANGED warnings. This
652 * essentially disables host authentication for localhost; however,
653 * this is probably not a real problem.
655 /** hostaddr == 0! */
656 switch (hostaddr->sa_family) {
658 local = (ntohl(((struct sockaddr_in *)hostaddr)->
659 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
660 salen = sizeof(struct sockaddr_in);
663 local = IN6_IS_ADDR_LOOPBACK(
664 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
665 salen = sizeof(struct sockaddr_in6);
669 salen = sizeof(struct sockaddr_storage);
672 if (options.no_host_authentication_for_localhost == 1 && local &&
673 options.host_key_alias == NULL) {
674 debug("Forcing accepting of host key for "
675 "loopback/localhost.");
680 * We don't have the remote ip-address for connections
681 * using a proxy command
683 if (options.proxy_command == NULL) {
684 if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop),
685 NULL, 0, NI_NUMERICHOST) != 0)
686 fatal("check_host_key: getnameinfo failed");
687 ip = put_host_port(ntop, port);
689 ip = xstrdup("<no hostip for proxy command>");
692 * Turn off check_host_ip if the connection is to localhost, via proxy
693 * command or if we don't have a hostname to compare with
695 if (options.check_host_ip && (local ||
696 strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
697 options.check_host_ip = 0;
700 * Allow the user to record the key under a different name or
701 * differentiate a non-standard port. This is useful for ssh
702 * tunneling over forwarded connections or if you run multiple
703 * sshd's on different ports on the same machine.
705 if (options.host_key_alias != NULL) {
706 host = xstrdup(options.host_key_alias);
707 debug("using hostkeyalias: %s", host);
709 host = put_host_port(hostname, port);
713 * Store the host key from the known host file in here so that we can
714 * compare it with the key for the IP address.
716 file_key = key_new(host_key->type);
719 * Check if the host key is present in the user's list of known
720 * hosts or in the systemwide list.
722 host_file = user_hostfile;
723 host_status = check_host_in_hostfile(host_file, host, host_key,
724 file_key, &host_line);
725 if (host_status == HOST_NEW) {
726 host_file = system_hostfile;
727 host_status = check_host_in_hostfile(host_file, host, host_key,
728 file_key, &host_line);
731 * Also perform check for the ip address, skip the check if we are
732 * localhost or the hostname was an ip address to begin with
734 if (options.check_host_ip) {
735 Key *ip_key = key_new(host_key->type);
737 ip_file = user_hostfile;
738 ip_status = check_host_in_hostfile(ip_file, ip, host_key,
740 if (ip_status == HOST_NEW) {
741 ip_file = system_hostfile;
742 ip_status = check_host_in_hostfile(ip_file, ip,
743 host_key, ip_key, &ip_line);
745 if (host_status == HOST_CHANGED &&
746 (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key)))
751 ip_status = host_status;
755 switch (host_status) {
757 /* The host is known and the key matches. */
758 debug("Host '%.200s' is known and matches the %s host key.",
760 debug("Found key in %s:%d", host_file, host_line);
761 if (options.check_host_ip && ip_status == HOST_NEW) {
763 logit("%s host key for IP address "
764 "'%.128s' not in list of known hosts.",
766 else if (!add_host_to_hostfile(user_hostfile, ip,
767 host_key, options.hash_known_hosts))
768 logit("Failed to add the %s host key for IP "
769 "address '%.128s' to the list of known "
770 "hosts (%.30s).", type, ip, user_hostfile);
772 logit("Warning: Permanently added the %s host "
773 "key for IP address '%.128s' to the list "
774 "of known hosts.", type, ip);
778 if (options.host_key_alias == NULL && port != 0 &&
779 port != SSH_DEFAULT_PORT) {
780 debug("checking without port identifier");
781 if (check_host_key(hostname, hostaddr, 0, host_key, 2,
782 user_hostfile, system_hostfile) == 0) {
783 debug("found matching key w/out port");
789 /* The host is new. */
790 if (options.strict_host_key_checking == 1) {
792 * User has requested strict host key checking. We
793 * will not add the host key automatically. The only
794 * alternative left is to abort.
796 error("No %s host key is known for %.200s and you "
797 "have requested strict checking.", type, host);
799 } else if (options.strict_host_key_checking == 2) {
800 char msg1[1024], msg2[1024];
802 if (show_other_keys(host, host_key))
803 snprintf(msg1, sizeof(msg1),
804 "\nbut keys of different type are already"
805 " known for this host.");
807 snprintf(msg1, sizeof(msg1), ".");
809 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
811 if (options.verify_host_key_dns) {
812 if (matching_host_key_dns)
813 snprintf(msg2, sizeof(msg2),
814 "Matching host key fingerprint"
817 snprintf(msg2, sizeof(msg2),
818 "No matching host key fingerprint"
821 snprintf(msg, sizeof(msg),
822 "The authenticity of host '%.200s (%s)' can't be "
824 "%s key fingerprint is %s.\n%s"
825 "Are you sure you want to continue connecting "
827 host, ip, msg1, type, fp, msg2);
833 * If not in strict mode, add the key automatically to the
834 * local known_hosts file.
836 if (options.check_host_ip && ip_status == HOST_NEW) {
837 snprintf(hostline, sizeof(hostline), "%s,%s",
840 if (options.hash_known_hosts) {
841 /* Add hash of host and IP separately */
842 r = add_host_to_hostfile(user_hostfile, host,
843 host_key, options.hash_known_hosts) &&
844 add_host_to_hostfile(user_hostfile, ip,
845 host_key, options.hash_known_hosts);
847 /* Add unhashed "host,ip" */
848 r = add_host_to_hostfile(user_hostfile,
850 options.hash_known_hosts);
853 r = add_host_to_hostfile(user_hostfile, host, host_key,
854 options.hash_known_hosts);
859 logit("Failed to add the host to the list of known "
860 "hosts (%.500s).", user_hostfile);
862 logit("Warning: Permanently added '%.200s' (%s) to the "
863 "list of known hosts.", hostp, type);
866 if (readonly == ROQUIET)
868 if (options.check_host_ip && host_ip_differ) {
870 if (ip_status == HOST_NEW)
871 key_msg = "is unknown";
872 else if (ip_status == HOST_OK)
873 key_msg = "is unchanged";
875 key_msg = "has a different value";
876 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
877 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
878 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
879 error("The %s host key for %s has changed,", type, host);
880 error("and the key for the according IP address %s", ip);
881 error("%s. This could either mean that", key_msg);
882 error("DNS SPOOFING is happening or the IP address for the host");
883 error("and its host key have changed at the same time.");
884 if (ip_status != HOST_NEW)
885 error("Offending key for IP in %s:%d", ip_file, ip_line);
887 /* The host key has changed. */
888 warn_changed_key(host_key);
889 error("Add correct host key in %.100s to get rid of this message.",
891 error("Offending key in %s:%d", host_file, host_line);
894 * If strict host key checking is in use, the user will have
895 * to edit the key manually and we can only abort.
897 if (options.strict_host_key_checking) {
898 error("%s host key for %.200s has changed and you have "
899 "requested strict checking.", type, host);
904 * If strict host key checking has not been requested, allow
905 * the connection but without MITM-able authentication or
908 if (options.password_authentication) {
909 error("Password authentication is disabled to avoid "
910 "man-in-the-middle attacks.");
911 options.password_authentication = 0;
913 if (options.kbd_interactive_authentication) {
914 error("Keyboard-interactive authentication is disabled"
915 " to avoid man-in-the-middle attacks.");
916 options.kbd_interactive_authentication = 0;
917 options.challenge_response_authentication = 0;
919 if (options.challenge_response_authentication) {
920 error("Challenge/response authentication is disabled"
921 " to avoid man-in-the-middle attacks.");
922 options.challenge_response_authentication = 0;
924 if (options.forward_agent) {
925 error("Agent forwarding is disabled to avoid "
926 "man-in-the-middle attacks.");
927 options.forward_agent = 0;
929 if (options.forward_x11) {
930 error("X11 forwarding is disabled to avoid "
931 "man-in-the-middle attacks.");
932 options.forward_x11 = 0;
934 if (options.num_local_forwards > 0 ||
935 options.num_remote_forwards > 0) {
936 error("Port forwarding is disabled to avoid "
937 "man-in-the-middle attacks.");
938 options.num_local_forwards =
939 options.num_remote_forwards = 0;
941 if (options.tun_open != SSH_TUNMODE_NO) {
942 error("Tunnel forwarding is disabled to avoid "
943 "man-in-the-middle attacks.");
944 options.tun_open = SSH_TUNMODE_NO;
947 * XXX Should permit the user to change to use the new id.
948 * This could be done by converting the host key to an
949 * identifying sentence, tell that the host identifies itself
950 * by that sentence, and ask the user if he/she whishes to
951 * accept the authentication.
955 fatal("internal error");
959 if (options.check_host_ip && host_status != HOST_CHANGED &&
960 ip_status == HOST_CHANGED) {
961 snprintf(msg, sizeof(msg),
962 "Warning: the %s host key for '%.200s' "
963 "differs from the key for the IP address '%.128s'"
964 "\nOffending key for IP in %s:%d",
965 type, host, ip, ip_file, ip_line);
966 if (host_status == HOST_OK) {
968 snprintf(msg + len, sizeof(msg) - len,
969 "\nMatching host key in %s:%d",
970 host_file, host_line);
972 if (options.strict_host_key_checking == 1) {
974 error("Exiting, you have requested strict checking.");
976 } else if (options.strict_host_key_checking == 2) {
977 strlcat(msg, "\nAre you sure you want "
978 "to continue connecting (yes/no)? ", sizeof(msg));
996 /* returns 0 if key verifies or -1 if key does NOT verify */
998 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
1003 if (options.verify_host_key_dns &&
1004 verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) {
1006 if (flags & DNS_VERIFY_FOUND) {
1008 if (options.verify_host_key_dns == 1 &&
1009 flags & DNS_VERIFY_MATCH &&
1010 flags & DNS_VERIFY_SECURE)
1013 if (flags & DNS_VERIFY_MATCH) {
1014 matching_host_key_dns = 1;
1016 warn_changed_key(host_key);
1017 error("Update the SSHFP RR in DNS with the new "
1018 "host key to get rid of this message.");
1023 /* return ok if the key can be found in an old keyfile */
1024 if (stat(options.system_hostfile2, &st) == 0 ||
1025 stat(options.user_hostfile2, &st) == 0) {
1026 if (check_host_key(host, hostaddr, options.port, host_key,
1027 RDONLY, options.user_hostfile2,
1028 options.system_hostfile2) == 0)
1031 return check_host_key(host, hostaddr, options.port, host_key,
1032 RDRW, options.user_hostfile, options.system_hostfile);
1036 * Starts a dialog with the server, and authenticates the current user on the
1037 * server. This does not need any extra privileges. The basic connection
1038 * to the server must already have been established before this is called.
1039 * If login fails, this function prints an error and never returns.
1040 * This function does not require super-user privileges.
1043 ssh_login(Sensitive *sensitive, const char *orighost,
1044 struct sockaddr *hostaddr, struct passwd *pw, int timeout_ms)
1047 char *server_user, *local_user;
1049 local_user = xstrdup(pw->pw_name);
1050 server_user = options.user ? options.user : local_user;
1052 /* Convert the user-supplied hostname into all lowercase. */
1053 host = xstrdup(orighost);
1054 for (cp = host; *cp; cp++)
1056 *cp = (char)tolower(*cp);
1058 /* Exchange protocol version identification strings with the server. */
1059 ssh_exchange_identification(timeout_ms);
1061 /* Put the connection into non-blocking mode. */
1062 packet_set_nonblocking();
1065 /* authenticate user */
1067 ssh_kex2(host, hostaddr);
1068 ssh_userauth2(local_user, server_user, host, sensitive);
1070 ssh_kex(host, hostaddr);
1071 ssh_userauth1(local_user, server_user, host, sensitive);
1077 ssh_put_password(char *password)
1082 if (datafellows & SSH_BUG_PASSWORDPAD) {
1083 packet_put_cstring(password);
1086 size = roundup(strlen(password) + 1, 32);
1087 padded = xcalloc(1, size);
1088 strlcpy(padded, password, size);
1089 packet_put_string(padded, size);
1090 memset(padded, 0, size);
1095 show_key_from_file(const char *file, const char *host, int keytype)
1101 found = key_new(keytype);
1102 if ((ret = lookup_key_in_hostfile_by_type(file, host,
1103 keytype, found, &line))) {
1104 fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
1105 logit("WARNING: %s key found for host %s\n"
1107 "%s key fingerprint %s.",
1108 key_type(found), host, file, line,
1109 key_type(found), fp);
1116 /* print all known host keys for a given host, but skip keys of given type */
1118 show_other_keys(const char *host, Key *key)
1120 int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1};
1123 for (i = 0; type[i] != -1; i++) {
1124 if (type[i] == key->type)
1126 if (type[i] != KEY_RSA1 &&
1127 show_key_from_file(options.user_hostfile2, host, type[i])) {
1131 if (type[i] != KEY_RSA1 &&
1132 show_key_from_file(options.system_hostfile2, host, type[i])) {
1136 if (show_key_from_file(options.user_hostfile, host, type[i])) {
1140 if (show_key_from_file(options.system_hostfile, host, type[i])) {
1144 debug2("no key of type %d for host %s", type[i], host);
1150 warn_changed_key(Key *host_key)
1153 const char *type = key_type(host_key);
1155 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1157 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1158 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1159 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1160 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1161 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1162 error("It is also possible that the %s host key has just been changed.", type);
1163 error("The fingerprint for the %s key sent by the remote host is\n%s.",
1165 error("Please contact your system administrator.");
1171 * Execute a local command
1174 ssh_local_cmd(const char *args)
1180 if (!options.permit_local_command ||
1181 args == NULL || !*args)
1184 if ((shell = getenv("SHELL")) == NULL)
1185 shell = _PATH_BSHELL;
1189 debug3("Executing %s -c \"%s\"", shell, args);
1190 execl(shell, shell, "-c", args, (char *)NULL);
1191 error("Couldn't execute %s -c \"%s\": %s",
1192 shell, args, strerror(errno));
1194 } else if (pid == -1)
1195 fatal("fork failed: %.100s", strerror(errno));
1196 while (waitpid(pid, &status, 0) == -1)
1198 fatal("Couldn't wait for child: %s", strerror(errno));
1200 if (!WIFEXITED(status))
1203 return (WEXITSTATUS(status));