1 /* $OpenBSD: sshconnect.c,v 1.224 2010/04/16 21:14:27 djm 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>
53 #include "sshconnect.h"
64 char *client_version_string = NULL;
65 char *server_version_string = NULL;
67 static int matching_host_key_dns = 0;
70 extern Options options;
71 extern char *__progname;
72 extern uid_t original_real_uid;
73 extern uid_t original_effective_uid;
74 extern pid_t proxy_command_pid;
76 static int show_other_keys(const char *, Key *);
77 static void warn_changed_key(Key *);
80 * Connect to the given ssh server using a proxy command.
83 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
85 char *command_string, *tmp;
88 char *shell, strport[NI_MAXSERV];
90 if ((shell = getenv("SHELL")) == NULL)
93 /* Convert the port number into a string. */
94 snprintf(strport, sizeof strport, "%hu", port);
97 * Build the final command string in the buffer by making the
98 * appropriate substitutions to the given proxy command.
100 * Use "exec" to avoid "sh -c" processes on some platforms
103 xasprintf(&tmp, "exec %s", proxy_command);
104 command_string = percent_expand(tmp, "h", host, "p", strport,
105 "r", options.user, (char *)NULL);
108 /* Create pipes for communicating with the proxy. */
109 if (pipe(pin) < 0 || pipe(pout) < 0)
110 fatal("Could not create pipes to communicate with the proxy: %.100s",
113 debug("Executing proxy command: %.500s", command_string);
115 /* Fork and execute the proxy command. */
116 if ((pid = fork()) == 0) {
119 /* Child. Permanently give up superuser privileges. */
120 permanently_drop_suid(original_real_uid);
122 /* Redirect stdin and stdout. */
125 if (dup2(pin[0], 0) < 0)
126 perror("dup2 stdin");
130 if (dup2(pout[1], 1) < 0)
131 perror("dup2 stdout");
132 /* Cannot be 1 because pin allocated two descriptors. */
135 /* Stderr is left as it is so that error messages get
136 printed on the user's terminal. */
139 argv[2] = command_string;
142 /* Execute the proxy command. Note that we gave up any
143 extra privileges above. */
144 execv(argv[0], argv);
150 fatal("fork failed: %.100s", strerror(errno));
152 proxy_command_pid = pid; /* save pid to clean up later */
154 /* Close child side of the descriptors. */
158 /* Free the command name. */
159 xfree(command_string);
161 /* Set the connection file descriptors. */
162 packet_set_connection(pout[0], pin[1]);
163 packet_set_timeout(options.server_alive_interval,
164 options.server_alive_count_max);
166 /* Indicate OK return */
171 * Creates a (possibly privileged) socket for use as the ssh connection.
174 ssh_create_socket(int privileged, struct addrinfo *ai)
177 struct addrinfo hints, *res;
180 * If we are running as root and want to connect to a privileged
181 * port, bind our own socket to a privileged port.
184 int p = IPPORT_RESERVED - 1;
186 sock = rresvport_af(&p, ai->ai_family);
189 error("rresvport: af=%d %.100s", ai->ai_family,
192 debug("Allocated local port %d.", p);
195 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
197 error("socket: %.100s", strerror(errno));
200 fcntl(sock, F_SETFD, FD_CLOEXEC);
202 /* Bind the socket to an alternative local IP address */
203 if (options.bind_address == NULL)
206 memset(&hints, 0, sizeof(hints));
207 hints.ai_family = ai->ai_family;
208 hints.ai_socktype = ai->ai_socktype;
209 hints.ai_protocol = ai->ai_protocol;
210 hints.ai_flags = AI_PASSIVE;
211 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res);
213 error("getaddrinfo: %s: %s", options.bind_address,
214 ssh_gai_strerror(gaierr));
218 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
219 error("bind: %s: %s", options.bind_address, strerror(errno));
229 timeout_connect(int sockfd, const struct sockaddr *serv_addr,
230 socklen_t addrlen, int *timeoutp)
233 struct timeval tv, t_start;
235 int optval, rc, result = -1;
237 gettimeofday(&t_start, NULL);
239 if (*timeoutp <= 0) {
240 result = connect(sockfd, serv_addr, addrlen);
244 set_nonblock(sockfd);
245 rc = connect(sockfd, serv_addr, addrlen);
247 unset_nonblock(sockfd);
251 if (errno != EINPROGRESS) {
256 fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS),
258 FD_SET(sockfd, fdset);
259 ms_to_timeval(&tv, *timeoutp);
262 rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
263 if (rc != -1 || errno != EINTR)
274 debug("select: %s", strerror(errno));
277 /* Completed or failed */
279 optlen = sizeof(optval);
280 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
282 debug("getsockopt: %s", strerror(errno));
290 unset_nonblock(sockfd);
293 /* Should not occur */
294 fatal("Bogus return (%d) from select()", rc);
300 if (result == 0 && *timeoutp > 0) {
301 ms_subtract_diff(&t_start, timeoutp);
302 if (*timeoutp <= 0) {
312 * Opens a TCP/IP connection to the remote server on the given host.
313 * The address of the remote host will be returned in hostaddr.
314 * If port is 0, the default port will be used. If needpriv is true,
315 * a privileged port will be allocated to make the connection.
316 * This requires super-user privileges if needpriv is true.
317 * Connection_attempts specifies the maximum number of tries (one per
318 * second). If proxy_command is non-NULL, it specifies the command (with %h
319 * and %p substituted for host and port, respectively) to use to contact
323 ssh_connect(const char *host, struct sockaddr_storage * hostaddr,
324 u_short port, int family, int connection_attempts, int *timeout_ms,
325 int want_keepalive, int needpriv, const char *proxy_command)
329 int sock = -1, attempt;
330 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
331 struct addrinfo hints, *ai, *aitop;
333 debug2("ssh_connect: needpriv %d", needpriv);
335 /* If a proxy command is given, connect using it. */
336 if (proxy_command != NULL)
337 return ssh_proxy_connect(host, port, proxy_command);
339 /* No proxy command. */
341 memset(&hints, 0, sizeof(hints));
342 hints.ai_family = family;
343 hints.ai_socktype = SOCK_STREAM;
344 snprintf(strport, sizeof strport, "%u", port);
345 if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0)
346 fatal("%s: Could not resolve hostname %.100s: %s", __progname,
347 host, ssh_gai_strerror(gaierr));
349 for (attempt = 0; attempt < connection_attempts; attempt++) {
351 /* Sleep a moment before retrying. */
353 debug("Trying again...");
356 * Loop through addresses for this host, and try each one in
357 * sequence until the connection succeeds.
359 for (ai = aitop; ai; ai = ai->ai_next) {
360 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
362 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
363 ntop, sizeof(ntop), strport, sizeof(strport),
364 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
365 error("ssh_connect: getnameinfo failed");
368 debug("Connecting to %.200s [%.100s] port %s.",
369 host, ntop, strport);
371 /* Create a socket for connecting. */
372 sock = ssh_create_socket(needpriv, ai);
374 /* Any error is already output */
377 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
379 /* Successful connection. */
380 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
383 debug("connect to address %s port %s: %s",
384 ntop, strport, strerror(errno));
390 break; /* Successful connection. */
395 /* Return failure if we didn't get a successful connection. */
397 error("ssh: connect to host %s port %s: %s",
398 host, strport, strerror(errno));
402 debug("Connection established.");
404 /* Set SO_KEEPALIVE if requested. */
405 if (want_keepalive &&
406 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
408 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
410 /* Set the connection. */
411 packet_set_connection(sock, sock);
412 packet_set_timeout(options.server_alive_interval,
413 options.server_alive_count_max);
419 * Waits for the server identification string, and sends our own
420 * identification string.
423 ssh_exchange_identification(int timeout_ms)
425 char buf[256], remote_version[256]; /* must be same size! */
426 int remote_major, remote_minor, mismatch;
427 int connection_in = packet_get_connection_in();
428 int connection_out = packet_get_connection_out();
429 int minor1 = PROTOCOL_MINOR_1;
432 int fdsetsz, remaining, rc;
433 struct timeval t_start, t_remaining;
436 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask);
437 fdset = xcalloc(1, fdsetsz);
439 /* Read other side's version identification. */
440 remaining = timeout_ms;
442 for (i = 0; i < sizeof(buf) - 1; i++) {
443 if (timeout_ms > 0) {
444 gettimeofday(&t_start, NULL);
445 ms_to_timeval(&t_remaining, remaining);
446 FD_SET(connection_in, fdset);
447 rc = select(connection_in + 1, fdset, NULL,
448 fdset, &t_remaining);
449 ms_subtract_diff(&t_start, &remaining);
450 if (rc == 0 || remaining <= 0)
451 fatal("Connection timed out during "
456 fatal("ssh_exchange_identification: "
457 "select: %s", strerror(errno));
461 len = roaming_atomicio(read, connection_in, &buf[i], 1);
463 if (len != 1 && errno == EPIPE)
464 fatal("ssh_exchange_identification: "
465 "Connection closed by remote host");
467 fatal("ssh_exchange_identification: "
468 "read: %.100s", strerror(errno));
469 if (buf[i] == '\r') {
472 continue; /**XXX wait for \n */
474 if (buf[i] == '\n') {
479 fatal("ssh_exchange_identification: "
480 "No banner received");
482 buf[sizeof(buf) - 1] = 0;
483 if (strncmp(buf, "SSH-", 4) == 0)
485 debug("ssh_exchange_identification: %s", buf);
487 server_version_string = xstrdup(buf);
491 * Check that the versions match. In future this might accept
492 * several versions and set appropriate flags to handle them.
494 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
495 &remote_major, &remote_minor, remote_version) != 3)
496 fatal("Bad remote protocol version identification: '%.100s'", buf);
497 debug("Remote protocol version %d.%d, remote software version %.100s",
498 remote_major, remote_minor, remote_version);
500 compat_datafellows(remote_version);
503 switch (remote_major) {
505 if (remote_minor == 99 &&
506 (options.protocol & SSH_PROTO_2) &&
507 !(options.protocol & SSH_PROTO_1_PREFERRED)) {
511 if (!(options.protocol & SSH_PROTO_1)) {
515 if (remote_minor < 3) {
516 fatal("Remote machine has too old SSH software version.");
517 } else if (remote_minor == 3 || remote_minor == 4) {
518 /* We speak 1.3, too. */
521 if (options.forward_agent) {
522 logit("Agent forwarding disabled for protocol 1.3");
523 options.forward_agent = 0;
528 if (options.protocol & SSH_PROTO_2) {
538 fatal("Protocol major versions differ: %d vs. %d",
539 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
541 /* Send our own protocol version identification. */
542 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s%s",
543 compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
544 compat20 ? PROTOCOL_MINOR_2 : minor1,
545 SSH_VERSION, compat20 ? "\r\n" : "\n");
546 if (roaming_atomicio(vwrite, connection_out, buf, strlen(buf))
548 fatal("write: %.100s", strerror(errno));
549 client_version_string = xstrdup(buf);
550 chop(client_version_string);
551 chop(server_version_string);
552 debug("Local version string %.100s", client_version_string);
555 /* defaults to 'no' */
557 confirm(const char *prompt)
559 const char *msg, *again = "Please type 'yes' or 'no': ";
563 if (options.batch_mode)
565 for (msg = prompt;;msg = again) {
566 p = read_passphrase(msg, RP_ECHO);
568 (p[0] == '\0') || (p[0] == '\n') ||
569 strncasecmp(p, "no", 2) == 0)
571 if (p && strncasecmp(p, "yes", 3) == 0)
581 check_host_cert(const char *host, const Key *host_key)
585 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) {
589 if (buffer_len(&host_key->cert->critical) != 0) {
590 error("Certificate for %s contains unsupported "
591 "critical options(s)", host);
598 * check whether the supplied host key is valid, return -1 if the key
599 * is not valid. the user_hostfile will not be updated if 'readonly' is true.
605 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
606 Key *host_key, int readonly, const char *user_hostfile,
607 const char *system_hostfile)
609 Key *file_key, *raw_key = NULL;
611 char *ip = NULL, *host = NULL;
612 char hostline[1000], *hostp, *fp, *ra;
613 HostStatus host_status;
614 HostStatus ip_status;
615 int r, want_cert, local = 0, host_ip_differ = 0;
617 char ntop[NI_MAXHOST];
619 int len, host_line, ip_line, cancelled_forwarding = 0;
620 const char *host_file = NULL, *ip_file = NULL;
623 * Force accepting of the host key for loopback/localhost. The
624 * problem is that if the home directory is NFS-mounted to multiple
625 * machines, localhost will refer to a different machine in each of
626 * them, and the user will get bogus HOST_CHANGED warnings. This
627 * essentially disables host authentication for localhost; however,
628 * this is probably not a real problem.
630 /** hostaddr == 0! */
631 switch (hostaddr->sa_family) {
633 local = (ntohl(((struct sockaddr_in *)hostaddr)->
634 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
635 salen = sizeof(struct sockaddr_in);
638 local = IN6_IS_ADDR_LOOPBACK(
639 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
640 salen = sizeof(struct sockaddr_in6);
644 salen = sizeof(struct sockaddr_storage);
647 if (options.no_host_authentication_for_localhost == 1 && local &&
648 options.host_key_alias == NULL) {
649 debug("Forcing accepting of host key for "
650 "loopback/localhost.");
655 * We don't have the remote ip-address for connections
656 * using a proxy command
658 if (options.proxy_command == NULL) {
659 if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop),
660 NULL, 0, NI_NUMERICHOST) != 0)
661 fatal("check_host_key: getnameinfo failed");
662 ip = put_host_port(ntop, port);
664 ip = xstrdup("<no hostip for proxy command>");
668 * Turn off check_host_ip if the connection is to localhost, via proxy
669 * command or if we don't have a hostname to compare with
671 if (options.check_host_ip && (local ||
672 strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
673 options.check_host_ip = 0;
676 * Allow the user to record the key under a different name or
677 * differentiate a non-standard port. This is useful for ssh
678 * tunneling over forwarded connections or if you run multiple
679 * sshd's on different ports on the same machine.
681 if (options.host_key_alias != NULL) {
682 host = xstrdup(options.host_key_alias);
683 debug("using hostkeyalias: %s", host);
685 host = put_host_port(hostname, port);
689 want_cert = key_is_cert(host_key);
690 type = key_type(host_key);
693 * Store the host key from the known host file in here so that we can
694 * compare it with the key for the IP address.
696 file_key = key_new(key_is_cert(host_key) ? KEY_UNSPEC : host_key->type);
699 * Check if the host key is present in the user's list of known
700 * hosts or in the systemwide list.
702 host_file = user_hostfile;
703 host_status = check_host_in_hostfile(host_file, host, host_key,
704 file_key, &host_line);
705 if (host_status == HOST_NEW) {
706 host_file = system_hostfile;
707 host_status = check_host_in_hostfile(host_file, host, host_key,
708 file_key, &host_line);
711 * Also perform check for the ip address, skip the check if we are
712 * localhost, looking for a certificate, or the hostname was an ip
713 * address to begin with.
715 if (!want_cert && options.check_host_ip) {
716 Key *ip_key = key_new(host_key->type);
718 ip_file = user_hostfile;
719 ip_status = check_host_in_hostfile(ip_file, ip, host_key,
721 if (ip_status == HOST_NEW) {
722 ip_file = system_hostfile;
723 ip_status = check_host_in_hostfile(ip_file, ip,
724 host_key, ip_key, &ip_line);
726 if (host_status == HOST_CHANGED &&
727 (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key)))
732 ip_status = host_status;
736 switch (host_status) {
738 /* The host is known and the key matches. */
739 debug("Host '%.200s' is known and matches the %s host %s.",
740 host, type, want_cert ? "certificate" : "key");
741 debug("Found %s in %s:%d",
742 want_cert ? "CA key" : "key", host_file, host_line);
743 if (want_cert && !check_host_cert(hostname, host_key))
745 if (options.check_host_ip && ip_status == HOST_NEW) {
746 if (readonly || want_cert)
747 logit("%s host key for IP address "
748 "'%.128s' not in list of known hosts.",
750 else if (!add_host_to_hostfile(user_hostfile, ip,
751 host_key, options.hash_known_hosts))
752 logit("Failed to add the %s host key for IP "
753 "address '%.128s' to the list of known "
754 "hosts (%.30s).", type, ip, user_hostfile);
756 logit("Warning: Permanently added the %s host "
757 "key for IP address '%.128s' to the list "
758 "of known hosts.", type, ip);
759 } else if (options.visual_host_key) {
760 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
761 ra = key_fingerprint(host_key, SSH_FP_MD5,
763 logit("Host key fingerprint is %s\n%s\n", fp, ra);
769 if (options.host_key_alias == NULL && port != 0 &&
770 port != SSH_DEFAULT_PORT) {
771 debug("checking without port identifier");
772 if (check_host_key(hostname, hostaddr, 0, host_key,
773 ROQUIET, user_hostfile, system_hostfile) == 0) {
774 debug("found matching key w/out port");
778 if (readonly || want_cert)
780 /* The host is new. */
781 if (options.strict_host_key_checking == 1) {
783 * User has requested strict host key checking. We
784 * will not add the host key automatically. The only
785 * alternative left is to abort.
787 error("No %s host key is known for %.200s and you "
788 "have requested strict checking.", type, host);
790 } else if (options.strict_host_key_checking == 2) {
791 char msg1[1024], msg2[1024];
793 if (show_other_keys(host, host_key))
794 snprintf(msg1, sizeof(msg1),
795 "\nbut keys of different type are already"
796 " known for this host.");
798 snprintf(msg1, sizeof(msg1), ".");
800 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
801 ra = key_fingerprint(host_key, SSH_FP_MD5,
804 if (options.verify_host_key_dns) {
805 if (matching_host_key_dns)
806 snprintf(msg2, sizeof(msg2),
807 "Matching host key fingerprint"
810 snprintf(msg2, sizeof(msg2),
811 "No matching host key fingerprint"
814 snprintf(msg, sizeof(msg),
815 "The authenticity of host '%.200s (%s)' can't be "
817 "%s key fingerprint is %s.%s%s\n%s"
818 "Are you sure you want to continue connecting "
820 host, ip, msg1, type, fp,
821 options.visual_host_key ? "\n" : "",
822 options.visual_host_key ? ra : "",
830 * If not in strict mode, add the key automatically to the
831 * local known_hosts file.
833 if (options.check_host_ip && ip_status == HOST_NEW) {
834 snprintf(hostline, sizeof(hostline), "%s,%s",
837 if (options.hash_known_hosts) {
838 /* Add hash of host and IP separately */
839 r = add_host_to_hostfile(user_hostfile, host,
840 host_key, options.hash_known_hosts) &&
841 add_host_to_hostfile(user_hostfile, ip,
842 host_key, options.hash_known_hosts);
844 /* Add unhashed "host,ip" */
845 r = add_host_to_hostfile(user_hostfile,
847 options.hash_known_hosts);
850 r = add_host_to_hostfile(user_hostfile, host, host_key,
851 options.hash_known_hosts);
856 logit("Failed to add the host to the list of known "
857 "hosts (%.500s).", user_hostfile);
859 logit("Warning: Permanently added '%.200s' (%s) to the "
860 "list of known hosts.", hostp, type);
863 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
864 error("@ WARNING: REVOKED HOST KEY DETECTED! @");
865 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
866 error("The %s host key for %s is marked as revoked.", type, host);
867 error("This could mean that a stolen key is being used to");
868 error("impersonate this host.");
871 * If strict host key checking is in use, the user will have
872 * to edit the key manually and we can only abort.
874 if (options.strict_host_key_checking) {
875 error("%s host key for %.200s was revoked and you have "
876 "requested strict checking.", type, host);
879 goto continue_unsafe;
884 * This is only a debug() since it is valid to have
885 * CAs with wildcard DNS matches that don't match
886 * all hosts that one might visit.
888 debug("Host certificate authority does not "
889 "match %s in %s:%d", CA_MARKER,
890 host_file, host_line);
893 if (readonly == ROQUIET)
895 if (options.check_host_ip && host_ip_differ) {
897 if (ip_status == HOST_NEW)
898 key_msg = "is unknown";
899 else if (ip_status == HOST_OK)
900 key_msg = "is unchanged";
902 key_msg = "has a different value";
903 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
904 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
905 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
906 error("The %s host key for %s has changed,", type, host);
907 error("and the key for the corresponding IP address %s", ip);
908 error("%s. This could either mean that", key_msg);
909 error("DNS SPOOFING is happening or the IP address for the host");
910 error("and its host key have changed at the same time.");
911 if (ip_status != HOST_NEW)
912 error("Offending key for IP in %s:%d", ip_file, ip_line);
914 /* The host key has changed. */
915 warn_changed_key(host_key);
916 error("Add correct host key in %.100s to get rid of this message.",
918 error("Offending key in %s:%d", host_file, host_line);
921 * If strict host key checking is in use, the user will have
922 * to edit the key manually and we can only abort.
924 if (options.strict_host_key_checking) {
925 error("%s host key for %.200s has changed and you have "
926 "requested strict checking.", type, host);
932 * If strict host key checking has not been requested, allow
933 * the connection but without MITM-able authentication or
936 if (options.password_authentication) {
937 error("Password authentication is disabled to avoid "
938 "man-in-the-middle attacks.");
939 options.password_authentication = 0;
940 cancelled_forwarding = 1;
942 if (options.kbd_interactive_authentication) {
943 error("Keyboard-interactive authentication is disabled"
944 " to avoid man-in-the-middle attacks.");
945 options.kbd_interactive_authentication = 0;
946 options.challenge_response_authentication = 0;
947 cancelled_forwarding = 1;
949 if (options.challenge_response_authentication) {
950 error("Challenge/response authentication is disabled"
951 " to avoid man-in-the-middle attacks.");
952 options.challenge_response_authentication = 0;
953 cancelled_forwarding = 1;
955 if (options.forward_agent) {
956 error("Agent forwarding is disabled to avoid "
957 "man-in-the-middle attacks.");
958 options.forward_agent = 0;
959 cancelled_forwarding = 1;
961 if (options.forward_x11) {
962 error("X11 forwarding is disabled to avoid "
963 "man-in-the-middle attacks.");
964 options.forward_x11 = 0;
965 cancelled_forwarding = 1;
967 if (options.num_local_forwards > 0 ||
968 options.num_remote_forwards > 0) {
969 error("Port forwarding is disabled to avoid "
970 "man-in-the-middle attacks.");
971 options.num_local_forwards =
972 options.num_remote_forwards = 0;
973 cancelled_forwarding = 1;
975 if (options.tun_open != SSH_TUNMODE_NO) {
976 error("Tunnel forwarding is disabled to avoid "
977 "man-in-the-middle attacks.");
978 options.tun_open = SSH_TUNMODE_NO;
979 cancelled_forwarding = 1;
981 if (options.exit_on_forward_failure && cancelled_forwarding)
982 fatal("Error: forwarding disabled due to host key "
986 * XXX Should permit the user to change to use the new id.
987 * This could be done by converting the host key to an
988 * identifying sentence, tell that the host identifies itself
989 * by that sentence, and ask the user if he/she wishes to
990 * accept the authentication.
994 fatal("internal error");
998 if (options.check_host_ip && host_status != HOST_CHANGED &&
999 ip_status == HOST_CHANGED) {
1000 snprintf(msg, sizeof(msg),
1001 "Warning: the %s host key for '%.200s' "
1002 "differs from the key for the IP address '%.128s'"
1003 "\nOffending key for IP in %s:%d",
1004 type, host, ip, ip_file, ip_line);
1005 if (host_status == HOST_OK) {
1007 snprintf(msg + len, sizeof(msg) - len,
1008 "\nMatching host key in %s:%d",
1009 host_file, host_line);
1011 if (options.strict_host_key_checking == 1) {
1013 error("Exiting, you have requested strict checking.");
1015 } else if (options.strict_host_key_checking == 2) {
1016 strlcat(msg, "\nAre you sure you want "
1017 "to continue connecting (yes/no)? ", sizeof(msg));
1030 if (want_cert && host_status != HOST_REVOKED) {
1032 * No matching certificate. Downgrade cert to raw key and
1035 debug("No matching CA found. Retry with plain key");
1036 raw_key = key_from_private(host_key);
1037 if (key_drop_cert(raw_key) != 0)
1038 fatal("Couldn't drop certificate");
1042 if (raw_key != NULL)
1049 /* returns 0 if key verifies or -1 if key does NOT verify */
1051 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
1056 /* XXX certs are not yet supported for DNS */
1057 if (!key_is_cert(host_key) && options.verify_host_key_dns &&
1058 verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) {
1060 if (flags & DNS_VERIFY_FOUND) {
1062 if (options.verify_host_key_dns == 1 &&
1063 flags & DNS_VERIFY_MATCH &&
1064 flags & DNS_VERIFY_SECURE)
1067 if (flags & DNS_VERIFY_MATCH) {
1068 matching_host_key_dns = 1;
1070 warn_changed_key(host_key);
1071 error("Update the SSHFP RR in DNS with the new "
1072 "host key to get rid of this message.");
1077 /* return ok if the key can be found in an old keyfile */
1078 if (stat(options.system_hostfile2, &st) == 0 ||
1079 stat(options.user_hostfile2, &st) == 0) {
1080 if (check_host_key(host, hostaddr, options.port, host_key,
1081 RDONLY, options.user_hostfile2,
1082 options.system_hostfile2) == 0)
1085 return check_host_key(host, hostaddr, options.port, host_key,
1086 RDRW, options.user_hostfile, options.system_hostfile);
1090 * Starts a dialog with the server, and authenticates the current user on the
1091 * server. This does not need any extra privileges. The basic connection
1092 * to the server must already have been established before this is called.
1093 * If login fails, this function prints an error and never returns.
1094 * This function does not require super-user privileges.
1097 ssh_login(Sensitive *sensitive, const char *orighost,
1098 struct sockaddr *hostaddr, struct passwd *pw, int timeout_ms)
1101 char *server_user, *local_user;
1103 local_user = xstrdup(pw->pw_name);
1104 server_user = options.user ? options.user : local_user;
1106 /* Convert the user-supplied hostname into all lowercase. */
1107 host = xstrdup(orighost);
1108 for (cp = host; *cp; cp++)
1110 *cp = (char)tolower(*cp);
1112 /* Exchange protocol version identification strings with the server. */
1113 ssh_exchange_identification(timeout_ms);
1115 /* Put the connection into non-blocking mode. */
1116 packet_set_nonblocking();
1119 /* authenticate user */
1121 ssh_kex2(host, hostaddr);
1122 ssh_userauth2(local_user, server_user, host, sensitive);
1124 ssh_kex(host, hostaddr);
1125 ssh_userauth1(local_user, server_user, host, sensitive);
1131 ssh_put_password(char *password)
1136 if (datafellows & SSH_BUG_PASSWORDPAD) {
1137 packet_put_cstring(password);
1140 size = roundup(strlen(password) + 1, 32);
1141 padded = xcalloc(1, size);
1142 strlcpy(padded, password, size);
1143 packet_put_string(padded, size);
1144 memset(padded, 0, size);
1149 show_key_from_file(const char *file, const char *host, int keytype)
1155 found = key_new(keytype);
1156 if ((ret = lookup_key_in_hostfile_by_type(file, host,
1157 keytype, found, &line))) {
1158 fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
1159 ra = key_fingerprint(found, SSH_FP_MD5, SSH_FP_RANDOMART);
1160 logit("WARNING: %s key found for host %s\n"
1162 "%s key fingerprint %s.\n%s\n",
1163 key_type(found), host, file, line,
1164 key_type(found), fp, ra);
1172 /* print all known host keys for a given host, but skip keys of given type */
1174 show_other_keys(const char *host, Key *key)
1176 int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1};
1179 for (i = 0; type[i] != -1; i++) {
1180 if (type[i] == key->type)
1182 if (type[i] != KEY_RSA1 &&
1183 show_key_from_file(options.user_hostfile2, host, type[i])) {
1187 if (type[i] != KEY_RSA1 &&
1188 show_key_from_file(options.system_hostfile2, host, type[i])) {
1192 if (show_key_from_file(options.user_hostfile, host, type[i])) {
1196 if (show_key_from_file(options.system_hostfile, host, type[i])) {
1200 debug2("no key of type %d for host %s", type[i], host);
1206 warn_changed_key(Key *host_key)
1209 const char *type = key_type(host_key);
1211 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1213 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1214 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1215 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1216 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1217 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1218 error("It is also possible that the %s host key has just been changed.", type);
1219 error("The fingerprint for the %s key sent by the remote host is\n%s.",
1221 error("Please contact your system administrator.");
1227 * Execute a local command
1230 ssh_local_cmd(const char *args)
1236 if (!options.permit_local_command ||
1237 args == NULL || !*args)
1240 if ((shell = getenv("SHELL")) == NULL)
1241 shell = _PATH_BSHELL;
1245 debug3("Executing %s -c \"%s\"", shell, args);
1246 execl(shell, shell, "-c", args, (char *)NULL);
1247 error("Couldn't execute %s -c \"%s\": %s",
1248 shell, args, strerror(errno));
1250 } else if (pid == -1)
1251 fatal("fork failed: %.100s", strerror(errno));
1252 while (waitpid(pid, &status, 0) == -1)
1254 fatal("Couldn't wait for child: %s", strerror(errno));
1256 if (!WIFEXITED(status))
1259 return (WEXITSTATUS(status));