1 /* $OpenBSD: sshconnect.c,v 1.232 2011/01/16 11:50:36 djm Exp $ */
4 * Author: Tatu Ylonen <ylo@cs.hut.fi>
5 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
7 * Code to connect to a remote host, and to perform the client side of the
8 * login (authentication) dialog.
10 * As far as I am concerned, the code I have written for this software
11 * can be used freely for any purpose. Any derived versions of this
12 * software must be clearly marked as such, and if the derived work is
13 * incompatible with the protocol description in the RFC file, it must be
14 * called by a name other than "ssh" or "Secure Shell".
19 #include <sys/types.h>
22 #include <sys/socket.h>
23 #ifdef HAVE_SYS_TIME_H
24 # include <sys/time.h>
27 #include <netinet/in.h>
28 #include <arpa/inet.h>
55 #include "sshconnect.h"
66 char *client_version_string = NULL;
67 char *server_version_string = NULL;
69 static int matching_host_key_dns = 0;
71 static pid_t proxy_command_pid = 0;
74 extern Options options;
75 extern char *__progname;
76 extern uid_t original_real_uid;
77 extern uid_t original_effective_uid;
79 static int show_other_keys(struct hostkeys *, Key *);
80 static void warn_changed_key(Key *);
83 * Connect to the given ssh server using a proxy command.
86 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
88 char *command_string, *tmp;
91 char *shell, strport[NI_MAXSERV];
93 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
96 /* Convert the port number into a string. */
97 snprintf(strport, sizeof strport, "%hu", port);
100 * Build the final command string in the buffer by making the
101 * appropriate substitutions to the given proxy command.
103 * Use "exec" to avoid "sh -c" processes on some platforms
106 xasprintf(&tmp, "exec %s", proxy_command);
107 command_string = percent_expand(tmp, "h", host, "p", strport,
108 "r", options.user, (char *)NULL);
111 /* Create pipes for communicating with the proxy. */
112 if (pipe(pin) < 0 || pipe(pout) < 0)
113 fatal("Could not create pipes to communicate with the proxy: %.100s",
116 debug("Executing proxy command: %.500s", command_string);
118 /* Fork and execute the proxy command. */
119 if ((pid = fork()) == 0) {
122 /* Child. Permanently give up superuser privileges. */
123 permanently_drop_suid(original_real_uid);
125 /* Redirect stdin and stdout. */
128 if (dup2(pin[0], 0) < 0)
129 perror("dup2 stdin");
133 if (dup2(pout[1], 1) < 0)
134 perror("dup2 stdout");
135 /* Cannot be 1 because pin allocated two descriptors. */
138 /* Stderr is left as it is so that error messages get
139 printed on the user's terminal. */
142 argv[2] = command_string;
145 /* Execute the proxy command. Note that we gave up any
146 extra privileges above. */
147 signal(SIGPIPE, SIG_DFL);
148 execv(argv[0], argv);
154 fatal("fork failed: %.100s", strerror(errno));
156 proxy_command_pid = pid; /* save pid to clean up later */
158 /* Close child side of the descriptors. */
162 /* Free the command name. */
163 xfree(command_string);
165 /* Set the connection file descriptors. */
166 packet_set_connection(pout[0], pin[1]);
167 packet_set_timeout(options.server_alive_interval,
168 options.server_alive_count_max);
170 /* Indicate OK return */
175 ssh_kill_proxy_command(void)
178 * Send SIGHUP to proxy command if used. We don't wait() in
179 * case it hangs and instead rely on init to reap the child
181 if (proxy_command_pid > 1)
182 kill(proxy_command_pid, SIGHUP);
186 * Set TCP receive buffer if requested.
187 * Note: tuning needs to happen after the socket is created but before the
188 * connection happens so winscale is negotiated properly.
191 ssh_set_socket_recvbuf(int sock)
193 void *buf = (void *)&options.tcp_rcv_buf;
194 int socksize, sz = sizeof(options.tcp_rcv_buf);
195 socklen_t len = sizeof(int);
197 debug("setsockopt attempting to set SO_RCVBUF to %d",
198 options.tcp_rcv_buf);
199 if (setsockopt(sock, SOL_SOCKET, SO_RCVBUF, buf, sz) >= 0) {
200 getsockopt(sock, SOL_SOCKET, SO_RCVBUF, &socksize, &len);
201 debug("setsockopt SO_RCVBUF: %.100s %d", strerror(errno),
204 error("Couldn't set socket receive buffer to %d: %.100s",
205 options.tcp_rcv_buf, strerror(errno));
209 * Creates a (possibly privileged) socket for use as the ssh connection.
212 ssh_create_socket(int privileged, struct addrinfo *ai)
215 struct addrinfo hints, *res;
218 * If we are running as root and want to connect to a privileged
219 * port, bind our own socket to a privileged port.
222 int p = IPPORT_RESERVED - 1;
224 sock = rresvport_af(&p, ai->ai_family);
227 error("rresvport: af=%d %.100s", ai->ai_family,
230 debug("Allocated local port %d.", p);
231 if (options.tcp_rcv_buf > 0)
232 ssh_set_socket_recvbuf(sock);
235 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
237 error("socket: %.100s", strerror(errno));
240 fcntl(sock, F_SETFD, FD_CLOEXEC);
242 if (options.tcp_rcv_buf > 0)
243 ssh_set_socket_recvbuf(sock);
245 /* Bind the socket to an alternative local IP address */
246 if (options.bind_address == NULL)
249 memset(&hints, 0, sizeof(hints));
250 hints.ai_family = ai->ai_family;
251 hints.ai_socktype = ai->ai_socktype;
252 hints.ai_protocol = ai->ai_protocol;
253 hints.ai_flags = AI_PASSIVE;
254 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res);
256 error("getaddrinfo: %s: %s", options.bind_address,
257 ssh_gai_strerror(gaierr));
261 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
262 error("bind: %s: %s", options.bind_address, strerror(errno));
272 timeout_connect(int sockfd, const struct sockaddr *serv_addr,
273 socklen_t addrlen, int *timeoutp)
276 struct timeval tv, t_start;
278 int optval, rc, result = -1;
280 gettimeofday(&t_start, NULL);
282 if (*timeoutp <= 0) {
283 result = connect(sockfd, serv_addr, addrlen);
287 set_nonblock(sockfd);
288 rc = connect(sockfd, serv_addr, addrlen);
290 unset_nonblock(sockfd);
294 if (errno != EINPROGRESS) {
299 fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS),
301 FD_SET(sockfd, fdset);
302 ms_to_timeval(&tv, *timeoutp);
305 rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
306 if (rc != -1 || errno != EINTR)
317 debug("select: %s", strerror(errno));
320 /* Completed or failed */
322 optlen = sizeof(optval);
323 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
325 debug("getsockopt: %s", strerror(errno));
333 unset_nonblock(sockfd);
336 /* Should not occur */
337 fatal("Bogus return (%d) from select()", rc);
343 if (result == 0 && *timeoutp > 0) {
344 ms_subtract_diff(&t_start, timeoutp);
345 if (*timeoutp <= 0) {
355 * Opens a TCP/IP connection to the remote server on the given host.
356 * The address of the remote host will be returned in hostaddr.
357 * If port is 0, the default port will be used. If needpriv is true,
358 * a privileged port will be allocated to make the connection.
359 * This requires super-user privileges if needpriv is true.
360 * Connection_attempts specifies the maximum number of tries (one per
361 * second). If proxy_command is non-NULL, it specifies the command (with %h
362 * and %p substituted for host and port, respectively) to use to contact
366 ssh_connect(const char *host, struct sockaddr_storage * hostaddr,
367 u_short port, int family, int connection_attempts, int *timeout_ms,
368 int want_keepalive, int needpriv, const char *proxy_command)
372 int sock = -1, attempt;
373 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
374 struct addrinfo hints, *ai, *aitop;
376 debug2("ssh_connect: needpriv %d", needpriv);
378 /* If a proxy command is given, connect using it. */
379 if (proxy_command != NULL)
380 return ssh_proxy_connect(host, port, proxy_command);
382 /* No proxy command. */
384 memset(&hints, 0, sizeof(hints));
385 hints.ai_family = family;
386 hints.ai_socktype = SOCK_STREAM;
387 snprintf(strport, sizeof strport, "%u", port);
388 if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0)
389 fatal("%s: Could not resolve hostname %.100s: %s", __progname,
390 host, ssh_gai_strerror(gaierr));
392 for (attempt = 0; attempt < connection_attempts; attempt++) {
394 /* Sleep a moment before retrying. */
396 debug("Trying again...");
399 * Loop through addresses for this host, and try each one in
400 * sequence until the connection succeeds.
402 for (ai = aitop; ai; ai = ai->ai_next) {
403 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
405 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
406 ntop, sizeof(ntop), strport, sizeof(strport),
407 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
408 error("ssh_connect: getnameinfo failed");
411 debug("Connecting to %.200s [%.100s] port %s.",
412 host, ntop, strport);
414 /* Create a socket for connecting. */
415 sock = ssh_create_socket(needpriv, ai);
417 /* Any error is already output */
420 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
422 /* Successful connection. */
423 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
426 debug("connect to address %s port %s: %s",
427 ntop, strport, strerror(errno));
433 break; /* Successful connection. */
438 /* Return failure if we didn't get a successful connection. */
440 error("ssh: connect to host %s port %s: %s",
441 host, strport, strerror(errno));
445 debug("Connection established.");
447 /* Set SO_KEEPALIVE if requested. */
448 if (want_keepalive &&
449 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
451 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
453 /* Set the connection. */
454 packet_set_connection(sock, sock);
455 packet_set_timeout(options.server_alive_interval,
456 options.server_alive_count_max);
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 = roaming_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%s",
586 compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
587 compat20 ? PROTOCOL_MINOR_2 : minor1,
588 SSH_RELEASE, compat20 ? "\r\n" : "\n");
589 if (roaming_atomicio(vwrite, connection_out, buf, strlen(buf))
591 fatal("write: %.100s", strerror(errno));
592 client_version_string = xstrdup(buf);
593 chop(client_version_string);
594 chop(server_version_string);
595 debug("Local version string %.100s", client_version_string);
598 /* defaults to 'no' */
600 confirm(const char *prompt)
602 const char *msg, *again = "Please type 'yes' or 'no': ";
606 if (options.batch_mode)
608 for (msg = prompt;;msg = again) {
609 p = read_passphrase(msg, RP_ECHO);
611 (p[0] == '\0') || (p[0] == '\n') ||
612 strncasecmp(p, "no", 2) == 0)
614 if (p && strncasecmp(p, "yes", 3) == 0)
624 check_host_cert(const char *host, const Key *host_key)
628 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) {
632 if (buffer_len(&host_key->cert->critical) != 0) {
633 error("Certificate for %s contains unsupported "
634 "critical options(s)", host);
641 sockaddr_is_local(struct sockaddr *hostaddr)
643 switch (hostaddr->sa_family) {
645 return (ntohl(((struct sockaddr_in *)hostaddr)->
646 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
648 return IN6_IS_ADDR_LOOPBACK(
649 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
656 * Prepare the hostname and ip address strings that are used to lookup
657 * host keys in known_hosts files. These may have a port number appended.
660 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr,
661 u_short port, char **hostfile_hostname, char **hostfile_ipaddr)
663 char ntop[NI_MAXHOST];
666 switch (hostaddr == NULL ? -1 : hostaddr->sa_family) {
671 addrlen = sizeof(struct sockaddr_in);
674 addrlen = sizeof(struct sockaddr_in6);
677 addrlen = sizeof(struct sockaddr);
682 * We don't have the remote ip-address for connections
683 * using a proxy command
685 if (hostfile_ipaddr != NULL) {
686 if (options.proxy_command == NULL) {
687 if (getnameinfo(hostaddr, addrlen,
688 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0)
689 fatal("check_host_key: getnameinfo failed");
690 *hostfile_ipaddr = put_host_port(ntop, port);
692 *hostfile_ipaddr = xstrdup("<no hostip for proxy "
698 * Allow the user to record the key under a different name or
699 * differentiate a non-standard port. This is useful for ssh
700 * tunneling over forwarded connections or if you run multiple
701 * sshd's on different ports on the same machine.
703 if (hostfile_hostname != NULL) {
704 if (options.host_key_alias != NULL) {
705 *hostfile_hostname = xstrdup(options.host_key_alias);
706 debug("using hostkeyalias: %s", *hostfile_hostname);
708 *hostfile_hostname = put_host_port(hostname, port);
714 * check whether the supplied host key is valid, return -1 if the key
715 * is not valid. the user_hostfile will not be updated if 'readonly' is true.
721 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
722 Key *host_key, int readonly, char *user_hostfile,
723 char *system_hostfile)
727 char *ip = NULL, *host = NULL;
728 char hostline[1000], *hostp, *fp, *ra;
729 HostStatus host_status;
730 HostStatus ip_status;
731 int r, want_cert = key_is_cert(host_key), host_ip_differ = 0;
732 int local = sockaddr_is_local(hostaddr);
734 int len, cancelled_forwarding = 0;
735 struct hostkeys *host_hostkeys, *ip_hostkeys;
736 const struct hostkey_entry *host_found, *ip_found;
739 * Force accepting of the host key for loopback/localhost. The
740 * problem is that if the home directory is NFS-mounted to multiple
741 * machines, localhost will refer to a different machine in each of
742 * them, and the user will get bogus HOST_CHANGED warnings. This
743 * essentially disables host authentication for localhost; however,
744 * this is probably not a real problem.
746 if (options.no_host_authentication_for_localhost == 1 && local &&
747 options.host_key_alias == NULL) {
748 debug("Forcing accepting of host key for "
749 "loopback/localhost.");
754 * Prepare the hostname and address strings used for hostkey lookup.
755 * In some cases, these will have a port number appended.
757 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip);
760 * Turn off check_host_ip if the connection is to localhost, via proxy
761 * command or if we don't have a hostname to compare with
763 if (options.check_host_ip && (local ||
764 strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
765 options.check_host_ip = 0;
767 host_hostkeys = init_hostkeys();
768 load_hostkeys(host_hostkeys, host, user_hostfile);
769 load_hostkeys(host_hostkeys, host, system_hostfile);
772 if (!want_cert && options.check_host_ip) {
773 ip_hostkeys = init_hostkeys();
774 load_hostkeys(ip_hostkeys, ip, user_hostfile);
775 load_hostkeys(ip_hostkeys, ip, system_hostfile);
779 /* Reload these as they may have changed on cert->key downgrade */
780 want_cert = key_is_cert(host_key);
781 type = key_type(host_key);
784 * Check if the host key is present in the user's list of known
785 * hosts or in the systemwide list.
787 host_status = check_key_in_hostkeys(host_hostkeys, host_key,
791 * Also perform check for the ip address, skip the check if we are
792 * localhost, looking for a certificate, or the hostname was an ip
793 * address to begin with.
795 if (!want_cert && ip_hostkeys != NULL) {
796 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key,
798 if (host_status == HOST_CHANGED &&
799 (ip_status != HOST_CHANGED ||
801 !key_equal(ip_found->key, host_found->key))))
804 ip_status = host_status;
806 switch (host_status) {
808 /* The host is known and the key matches. */
809 debug("Host '%.200s' is known and matches the %s host %s.",
810 host, type, want_cert ? "certificate" : "key");
811 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key",
812 host_found->file, host_found->line);
813 if (want_cert && !check_host_cert(hostname, host_key))
815 if (options.check_host_ip && ip_status == HOST_NEW) {
816 if (readonly || want_cert)
817 logit("%s host key for IP address "
818 "'%.128s' not in list of known hosts.",
820 else if (!add_host_to_hostfile(user_hostfile, ip,
821 host_key, options.hash_known_hosts))
822 logit("Failed to add the %s host key for IP "
823 "address '%.128s' to the list of known "
824 "hosts (%.30s).", type, ip, user_hostfile);
826 logit("Warning: Permanently added the %s host "
827 "key for IP address '%.128s' to the list "
828 "of known hosts.", type, ip);
829 } else if (options.visual_host_key) {
830 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
831 ra = key_fingerprint(host_key, SSH_FP_MD5,
833 logit("Host key fingerprint is %s\n%s\n", fp, ra);
839 if (options.host_key_alias == NULL && port != 0 &&
840 port != SSH_DEFAULT_PORT) {
841 debug("checking without port identifier");
842 if (check_host_key(hostname, hostaddr, 0, host_key,
843 ROQUIET, user_hostfile, system_hostfile) == 0) {
844 debug("found matching key w/out port");
848 if (readonly || want_cert)
850 /* The host is new. */
851 if (options.strict_host_key_checking == 1) {
853 * User has requested strict host key checking. We
854 * will not add the host key automatically. The only
855 * alternative left is to abort.
857 error("No %s host key is known for %.200s and you "
858 "have requested strict checking.", type, host);
860 } else if (options.strict_host_key_checking == 2) {
861 char msg1[1024], msg2[1024];
863 if (show_other_keys(host_hostkeys, host_key))
864 snprintf(msg1, sizeof(msg1),
865 "\nbut keys of different type are already"
866 " known for this host.");
868 snprintf(msg1, sizeof(msg1), ".");
870 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
871 ra = key_fingerprint(host_key, SSH_FP_MD5,
874 if (options.verify_host_key_dns) {
875 if (matching_host_key_dns)
876 snprintf(msg2, sizeof(msg2),
877 "Matching host key fingerprint"
880 snprintf(msg2, sizeof(msg2),
881 "No matching host key fingerprint"
884 snprintf(msg, sizeof(msg),
885 "The authenticity of host '%.200s (%s)' can't be "
887 "%s key fingerprint is %s.%s%s\n%s"
888 "Are you sure you want to continue connecting "
890 host, ip, msg1, type, fp,
891 options.visual_host_key ? "\n" : "",
892 options.visual_host_key ? ra : "",
900 * If not in strict mode, add the key automatically to the
901 * local known_hosts file.
903 if (options.check_host_ip && ip_status == HOST_NEW) {
904 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
906 if (options.hash_known_hosts) {
907 /* Add hash of host and IP separately */
908 r = add_host_to_hostfile(user_hostfile, host,
909 host_key, options.hash_known_hosts) &&
910 add_host_to_hostfile(user_hostfile, ip,
911 host_key, options.hash_known_hosts);
913 /* Add unhashed "host,ip" */
914 r = add_host_to_hostfile(user_hostfile,
916 options.hash_known_hosts);
919 r = add_host_to_hostfile(user_hostfile, host, host_key,
920 options.hash_known_hosts);
925 logit("Failed to add the host to the list of known "
926 "hosts (%.500s).", user_hostfile);
928 logit("Warning: Permanently added '%.200s' (%s) to the "
929 "list of known hosts.", hostp, type);
932 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
933 error("@ WARNING: REVOKED HOST KEY DETECTED! @");
934 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
935 error("The %s host key for %s is marked as revoked.", type, host);
936 error("This could mean that a stolen key is being used to");
937 error("impersonate this host.");
940 * If strict host key checking is in use, the user will have
941 * to edit the key manually and we can only abort.
943 if (options.strict_host_key_checking) {
944 error("%s host key for %.200s was revoked and you have "
945 "requested strict checking.", type, host);
948 goto continue_unsafe;
953 * This is only a debug() since it is valid to have
954 * CAs with wildcard DNS matches that don't match
955 * all hosts that one might visit.
957 debug("Host certificate authority does not "
958 "match %s in %s:%lu", CA_MARKER,
959 host_found->file, host_found->line);
962 if (readonly == ROQUIET)
964 if (options.check_host_ip && host_ip_differ) {
966 if (ip_status == HOST_NEW)
967 key_msg = "is unknown";
968 else if (ip_status == HOST_OK)
969 key_msg = "is unchanged";
971 key_msg = "has a different value";
972 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
973 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
974 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
975 error("The %s host key for %s has changed,", type, host);
976 error("and the key for the corresponding IP address %s", ip);
977 error("%s. This could either mean that", key_msg);
978 error("DNS SPOOFING is happening or the IP address for the host");
979 error("and its host key have changed at the same time.");
980 if (ip_status != HOST_NEW)
981 error("Offending key for IP in %s:%lu",
982 ip_found->file, ip_found->line);
984 /* The host key has changed. */
985 warn_changed_key(host_key);
986 error("Add correct host key in %.100s to get rid of this message.",
988 error("Offending %s key in %s:%lu", key_type(host_found->key),
989 host_found->file, host_found->line);
992 * If strict host key checking is in use, the user will have
993 * to edit the key manually and we can only abort.
995 if (options.strict_host_key_checking) {
996 error("%s host key for %.200s has changed and you have "
997 "requested strict checking.", type, host);
1003 * If strict host key checking has not been requested, allow
1004 * the connection but without MITM-able authentication or
1007 if (options.password_authentication) {
1008 error("Password authentication is disabled to avoid "
1009 "man-in-the-middle attacks.");
1010 options.password_authentication = 0;
1011 cancelled_forwarding = 1;
1013 if (options.kbd_interactive_authentication) {
1014 error("Keyboard-interactive authentication is disabled"
1015 " to avoid man-in-the-middle attacks.");
1016 options.kbd_interactive_authentication = 0;
1017 options.challenge_response_authentication = 0;
1018 cancelled_forwarding = 1;
1020 if (options.challenge_response_authentication) {
1021 error("Challenge/response authentication is disabled"
1022 " to avoid man-in-the-middle attacks.");
1023 options.challenge_response_authentication = 0;
1024 cancelled_forwarding = 1;
1026 if (options.forward_agent) {
1027 error("Agent forwarding is disabled to avoid "
1028 "man-in-the-middle attacks.");
1029 options.forward_agent = 0;
1030 cancelled_forwarding = 1;
1032 if (options.forward_x11) {
1033 error("X11 forwarding is disabled to avoid "
1034 "man-in-the-middle attacks.");
1035 options.forward_x11 = 0;
1036 cancelled_forwarding = 1;
1038 if (options.num_local_forwards > 0 ||
1039 options.num_remote_forwards > 0) {
1040 error("Port forwarding is disabled to avoid "
1041 "man-in-the-middle attacks.");
1042 options.num_local_forwards =
1043 options.num_remote_forwards = 0;
1044 cancelled_forwarding = 1;
1046 if (options.tun_open != SSH_TUNMODE_NO) {
1047 error("Tunnel forwarding is disabled to avoid "
1048 "man-in-the-middle attacks.");
1049 options.tun_open = SSH_TUNMODE_NO;
1050 cancelled_forwarding = 1;
1052 if (options.exit_on_forward_failure && cancelled_forwarding)
1053 fatal("Error: forwarding disabled due to host key "
1057 * XXX Should permit the user to change to use the new id.
1058 * This could be done by converting the host key to an
1059 * identifying sentence, tell that the host identifies itself
1060 * by that sentence, and ask the user if he/she wishes to
1061 * accept the authentication.
1065 fatal("internal error");
1069 if (options.check_host_ip && host_status != HOST_CHANGED &&
1070 ip_status == HOST_CHANGED) {
1071 snprintf(msg, sizeof(msg),
1072 "Warning: the %s host key for '%.200s' "
1073 "differs from the key for the IP address '%.128s'"
1074 "\nOffending key for IP in %s:%lu",
1075 type, host, ip, ip_found->file, ip_found->line);
1076 if (host_status == HOST_OK) {
1078 snprintf(msg + len, sizeof(msg) - len,
1079 "\nMatching host key in %s:%lu",
1080 host_found->file, host_found->line);
1082 if (options.strict_host_key_checking == 1) {
1084 error("Exiting, you have requested strict checking.");
1086 } else if (options.strict_host_key_checking == 2) {
1087 strlcat(msg, "\nAre you sure you want "
1088 "to continue connecting (yes/no)? ", sizeof(msg));
1098 if (host_hostkeys != NULL)
1099 free_hostkeys(host_hostkeys);
1100 if (ip_hostkeys != NULL)
1101 free_hostkeys(ip_hostkeys);
1105 if (want_cert && host_status != HOST_REVOKED) {
1107 * No matching certificate. Downgrade cert to raw key and
1110 debug("No matching CA found. Retry with plain key");
1111 raw_key = key_from_private(host_key);
1112 if (key_drop_cert(raw_key) != 0)
1113 fatal("Couldn't drop certificate");
1117 if (raw_key != NULL)
1121 if (host_hostkeys != NULL)
1122 free_hostkeys(host_hostkeys);
1123 if (ip_hostkeys != NULL)
1124 free_hostkeys(ip_hostkeys);
1128 /* returns 0 if key verifies or -1 if key does NOT verify */
1130 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
1136 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1137 debug("Server host key: %s %s", key_type(host_key), fp);
1140 /* XXX certs are not yet supported for DNS */
1141 if (!key_is_cert(host_key) && options.verify_host_key_dns &&
1142 verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) {
1144 if (flags & DNS_VERIFY_FOUND) {
1146 if (options.verify_host_key_dns == 1 &&
1147 flags & DNS_VERIFY_MATCH &&
1148 flags & DNS_VERIFY_SECURE)
1151 if (flags & DNS_VERIFY_MATCH) {
1152 matching_host_key_dns = 1;
1154 warn_changed_key(host_key);
1155 error("Update the SSHFP RR in DNS with the new "
1156 "host key to get rid of this message.");
1161 /* return ok if the key can be found in an old keyfile */
1162 if (stat(options.system_hostfile2, &st) == 0 ||
1163 stat(options.user_hostfile2, &st) == 0) {
1164 if (check_host_key(host, hostaddr, options.port, host_key,
1165 RDONLY, options.user_hostfile2,
1166 options.system_hostfile2) == 0)
1169 return check_host_key(host, hostaddr, options.port, host_key,
1170 RDRW, options.user_hostfile, options.system_hostfile);
1174 * Starts a dialog with the server, and authenticates the current user on the
1175 * server. This does not need any extra privileges. The basic connection
1176 * to the server must already have been established before this is called.
1177 * If login fails, this function prints an error and never returns.
1178 * This function does not require super-user privileges.
1181 ssh_login(Sensitive *sensitive, const char *orighost,
1182 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms)
1185 char *server_user, *local_user;
1187 local_user = xstrdup(pw->pw_name);
1188 server_user = options.user ? options.user : local_user;
1190 /* Convert the user-supplied hostname into all lowercase. */
1191 host = xstrdup(orighost);
1192 for (cp = host; *cp; cp++)
1194 *cp = (char)tolower(*cp);
1196 /* Exchange protocol version identification strings with the server. */
1197 ssh_exchange_identification(timeout_ms);
1199 /* Put the connection into non-blocking mode. */
1200 packet_set_nonblocking();
1203 /* authenticate user */
1205 ssh_kex2(host, hostaddr, port);
1206 ssh_userauth2(local_user, server_user, host, sensitive);
1208 ssh_kex(host, hostaddr);
1209 ssh_userauth1(local_user, server_user, host, sensitive);
1215 ssh_put_password(char *password)
1220 if (datafellows & SSH_BUG_PASSWORDPAD) {
1221 packet_put_cstring(password);
1224 size = roundup(strlen(password) + 1, 32);
1225 padded = xcalloc(1, size);
1226 strlcpy(padded, password, size);
1227 packet_put_string(padded, size);
1228 memset(padded, 0, size);
1232 /* print all known host keys for a given host, but skip keys of given type */
1234 show_other_keys(struct hostkeys *hostkeys, Key *key)
1236 int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, KEY_ECDSA, -1};
1239 const struct hostkey_entry *found;
1241 for (i = 0; type[i] != -1; i++) {
1242 if (type[i] == key->type)
1244 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found))
1246 fp = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_HEX);
1247 ra = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_RANDOMART);
1248 logit("WARNING: %s key found for host %s\n"
1250 "%s key fingerprint %s.",
1251 key_type(found->key),
1252 found->host, found->file, found->line,
1253 key_type(found->key), fp);
1254 if (options.visual_host_key)
1264 warn_changed_key(Key *host_key)
1268 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1270 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1271 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1272 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1273 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1274 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1275 error("It is also possible that a host key has just been changed.");
1276 error("The fingerprint for the %s key sent by the remote host is\n%s.",
1277 key_type(host_key), fp);
1278 error("Please contact your system administrator.");
1284 * Execute a local command
1287 ssh_local_cmd(const char *args)
1292 void (*osighand)(int);
1294 if (!options.permit_local_command ||
1295 args == NULL || !*args)
1298 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
1299 shell = _PATH_BSHELL;
1301 osighand = signal(SIGCHLD, SIG_DFL);
1304 signal(SIGPIPE, SIG_DFL);
1305 debug3("Executing %s -c \"%s\"", shell, args);
1306 execl(shell, shell, "-c", args, (char *)NULL);
1307 error("Couldn't execute %s -c \"%s\": %s",
1308 shell, args, strerror(errno));
1310 } else if (pid == -1)
1311 fatal("fork failed: %.100s", strerror(errno));
1312 while (waitpid(pid, &status, 0) == -1)
1314 fatal("Couldn't wait for child: %s", strerror(errno));
1315 signal(SIGCHLD, osighand);
1317 if (!WIFEXITED(status))
1320 return (WEXITSTATUS(status));