1 /* $OpenBSD: sshconnect.c,v 1.251 2014/07/15 15:54:14 millert 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>
54 #include "sshconnect.h"
62 #include "monitor_fdpass.h"
66 char *client_version_string = NULL;
67 char *server_version_string = NULL;
68 Key *previous_host_key = NULL;
70 static int matching_host_key_dns = 0;
72 static pid_t proxy_command_pid = 0;
75 extern Options options;
76 extern char *__progname;
77 extern uid_t original_real_uid;
78 extern uid_t original_effective_uid;
80 static int show_other_keys(struct hostkeys *, Key *);
81 static void warn_changed_key(Key *);
83 /* Expand a proxy command */
85 expand_proxy_command(const char *proxy_command, const char *user,
86 const char *host, int port)
88 char *tmp, *ret, strport[NI_MAXSERV];
90 snprintf(strport, sizeof strport, "%d", port);
91 xasprintf(&tmp, "exec %s", proxy_command);
92 ret = percent_expand(tmp, "h", host, "p", strport,
93 "r", options.user, (char *)NULL);
99 * Connect to the given ssh server using a proxy command that passes a
100 * a connected fd back to us.
103 ssh_proxy_fdpass_connect(const char *host, u_short port,
104 const char *proxy_command)
106 char *command_string;
111 if ((shell = getenv("SHELL")) == NULL)
112 shell = _PATH_BSHELL;
114 if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) < 0)
115 fatal("Could not create socketpair to communicate with "
116 "proxy dialer: %.100s", strerror(errno));
118 command_string = expand_proxy_command(proxy_command, options.user,
120 debug("Executing proxy dialer command: %.500s", command_string);
122 /* Fork and execute the proxy command. */
123 if ((pid = fork()) == 0) {
126 /* Child. Permanently give up superuser privileges. */
127 permanently_drop_suid(original_real_uid);
130 /* Redirect stdin and stdout. */
132 if (dup2(sp[0], 0) < 0)
133 perror("dup2 stdin");
136 if (dup2(sp[0], 1) < 0)
137 perror("dup2 stdout");
143 * Stderr is left as it is so that error messages get
144 * printed on the user's terminal.
148 argv[2] = command_string;
152 * Execute the proxy command.
153 * Note that we gave up any extra privileges above.
155 execv(argv[0], argv);
161 fatal("fork failed: %.100s", strerror(errno));
163 free(command_string);
165 if ((sock = mm_receive_fd(sp[1])) == -1)
166 fatal("proxy dialer did not pass back a connection");
168 while (waitpid(pid, NULL, 0) == -1)
170 fatal("Couldn't wait for child: %s", strerror(errno));
172 /* Set the connection file descriptors. */
173 packet_set_connection(sock, sock);
179 * Connect to the given ssh server using a proxy command.
182 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
184 char *command_string;
189 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
190 shell = _PATH_BSHELL;
192 /* Create pipes for communicating with the proxy. */
193 if (pipe(pin) < 0 || pipe(pout) < 0)
194 fatal("Could not create pipes to communicate with the proxy: %.100s",
197 command_string = expand_proxy_command(proxy_command, options.user,
199 debug("Executing proxy command: %.500s", command_string);
201 /* Fork and execute the proxy command. */
202 if ((pid = fork()) == 0) {
205 /* Child. Permanently give up superuser privileges. */
206 permanently_drop_suid(original_real_uid);
208 /* Redirect stdin and stdout. */
211 if (dup2(pin[0], 0) < 0)
212 perror("dup2 stdin");
216 if (dup2(pout[1], 1) < 0)
217 perror("dup2 stdout");
218 /* Cannot be 1 because pin allocated two descriptors. */
221 /* Stderr is left as it is so that error messages get
222 printed on the user's terminal. */
225 argv[2] = command_string;
228 /* Execute the proxy command. Note that we gave up any
229 extra privileges above. */
230 signal(SIGPIPE, SIG_DFL);
231 execv(argv[0], argv);
237 fatal("fork failed: %.100s", strerror(errno));
239 proxy_command_pid = pid; /* save pid to clean up later */
241 /* Close child side of the descriptors. */
245 /* Free the command name. */
246 free(command_string);
248 /* Set the connection file descriptors. */
249 packet_set_connection(pout[0], pin[1]);
251 /* Indicate OK return */
256 ssh_kill_proxy_command(void)
259 * Send SIGHUP to proxy command if used. We don't wait() in
260 * case it hangs and instead rely on init to reap the child
262 if (proxy_command_pid > 1)
263 kill(proxy_command_pid, SIGHUP);
267 * Creates a (possibly privileged) socket for use as the ssh connection.
270 ssh_create_socket(int privileged, struct addrinfo *ai)
273 struct addrinfo hints, *res = NULL;
275 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
277 error("socket: %s", strerror(errno));
280 fcntl(sock, F_SETFD, FD_CLOEXEC);
282 /* Bind the socket to an alternative local IP address */
283 if (options.bind_address == NULL && !privileged)
286 if (options.bind_address) {
287 memset(&hints, 0, sizeof(hints));
288 hints.ai_family = ai->ai_family;
289 hints.ai_socktype = ai->ai_socktype;
290 hints.ai_protocol = ai->ai_protocol;
291 hints.ai_flags = AI_PASSIVE;
292 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res);
294 error("getaddrinfo: %s: %s", options.bind_address,
295 ssh_gai_strerror(gaierr));
301 * If we are running as root and want to connect to a privileged
302 * port, bind our own socket to a privileged port.
306 r = bindresvport_sa(sock, res ? res->ai_addr : NULL);
309 error("bindresvport_sa: af=%d %s", ai->ai_family,
314 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
315 error("bind: %s: %s", options.bind_address,
329 timeout_connect(int sockfd, const struct sockaddr *serv_addr,
330 socklen_t addrlen, int *timeoutp)
333 struct timeval tv, t_start;
335 int optval, rc, result = -1;
337 gettimeofday(&t_start, NULL);
339 if (*timeoutp <= 0) {
340 result = connect(sockfd, serv_addr, addrlen);
344 set_nonblock(sockfd);
345 rc = connect(sockfd, serv_addr, addrlen);
347 unset_nonblock(sockfd);
351 if (errno != EINPROGRESS) {
356 fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS),
358 FD_SET(sockfd, fdset);
359 ms_to_timeval(&tv, *timeoutp);
362 rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
363 if (rc != -1 || errno != EINTR)
374 debug("select: %s", strerror(errno));
377 /* Completed or failed */
379 optlen = sizeof(optval);
380 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
382 debug("getsockopt: %s", strerror(errno));
390 unset_nonblock(sockfd);
393 /* Should not occur */
394 fatal("Bogus return (%d) from select()", rc);
400 if (result == 0 && *timeoutp > 0) {
401 ms_subtract_diff(&t_start, timeoutp);
402 if (*timeoutp <= 0) {
412 * Opens a TCP/IP connection to the remote server on the given host.
413 * The address of the remote host will be returned in hostaddr.
414 * If port is 0, the default port will be used. If needpriv is true,
415 * a privileged port will be allocated to make the connection.
416 * This requires super-user privileges if needpriv is true.
417 * Connection_attempts specifies the maximum number of tries (one per
418 * second). If proxy_command is non-NULL, it specifies the command (with %h
419 * and %p substituted for host and port, respectively) to use to contact
423 ssh_connect_direct(const char *host, struct addrinfo *aitop,
424 struct sockaddr_storage *hostaddr, u_short port, int family,
425 int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv)
428 int sock = -1, attempt;
429 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
432 debug2("ssh_connect: needpriv %d", needpriv);
434 for (attempt = 0; attempt < connection_attempts; attempt++) {
436 /* Sleep a moment before retrying. */
438 debug("Trying again...");
441 * Loop through addresses for this host, and try each one in
442 * sequence until the connection succeeds.
444 for (ai = aitop; ai; ai = ai->ai_next) {
445 if (ai->ai_family != AF_INET &&
446 ai->ai_family != AF_INET6)
448 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
449 ntop, sizeof(ntop), strport, sizeof(strport),
450 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
451 error("ssh_connect: getnameinfo failed");
454 debug("Connecting to %.200s [%.100s] port %s.",
455 host, ntop, strport);
457 /* Create a socket for connecting. */
458 sock = ssh_create_socket(needpriv, ai);
460 /* Any error is already output */
463 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
465 /* Successful connection. */
466 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
469 debug("connect to address %s port %s: %s",
470 ntop, strport, strerror(errno));
476 break; /* Successful connection. */
479 /* Return failure if we didn't get a successful connection. */
481 error("ssh: connect to host %s port %s: %s",
482 host, strport, strerror(errno));
486 debug("Connection established.");
488 /* Set SO_KEEPALIVE if requested. */
489 if (want_keepalive &&
490 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
492 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
494 /* Set the connection. */
495 packet_set_connection(sock, sock);
501 ssh_connect(const char *host, struct addrinfo *addrs,
502 struct sockaddr_storage *hostaddr, u_short port, int family,
503 int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv)
505 if (options.proxy_command == NULL) {
506 return ssh_connect_direct(host, addrs, hostaddr, port, family,
507 connection_attempts, timeout_ms, want_keepalive, needpriv);
508 } else if (strcmp(options.proxy_command, "-") == 0) {
509 packet_set_connection(STDIN_FILENO, STDOUT_FILENO);
510 return 0; /* Always succeeds */
511 } else if (options.proxy_use_fdpass) {
512 return ssh_proxy_fdpass_connect(host, port,
513 options.proxy_command);
515 return ssh_proxy_connect(host, port, options.proxy_command);
519 send_client_banner(int connection_out, int minor1)
521 /* Send our own protocol version identification. */
523 xasprintf(&client_version_string, "SSH-%d.%d-%.100s\r\n",
524 PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION);
526 xasprintf(&client_version_string, "SSH-%d.%d-%.100s\n",
527 PROTOCOL_MAJOR_1, minor1, SSH_VERSION);
529 if (roaming_atomicio(vwrite, connection_out, client_version_string,
530 strlen(client_version_string)) != strlen(client_version_string))
531 fatal("write: %.100s", strerror(errno));
532 chop(client_version_string);
533 debug("Local version string %.100s", client_version_string);
537 * Waits for the server identification string, and sends our own
538 * identification string.
541 ssh_exchange_identification(int timeout_ms)
543 char buf[256], remote_version[256]; /* must be same size! */
544 int remote_major, remote_minor, mismatch;
545 int connection_in = packet_get_connection_in();
546 int connection_out = packet_get_connection_out();
547 int minor1 = PROTOCOL_MINOR_1, client_banner_sent = 0;
550 int fdsetsz, remaining, rc;
551 struct timeval t_start, t_remaining;
554 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask);
555 fdset = xcalloc(1, fdsetsz);
558 * If we are SSH2-only then we can send the banner immediately and
561 if (options.protocol == SSH_PROTO_2) {
563 send_client_banner(connection_out, 0);
564 client_banner_sent = 1;
567 /* Read other side's version identification. */
568 remaining = timeout_ms;
570 for (i = 0; i < sizeof(buf) - 1; i++) {
571 if (timeout_ms > 0) {
572 gettimeofday(&t_start, NULL);
573 ms_to_timeval(&t_remaining, remaining);
574 FD_SET(connection_in, fdset);
575 rc = select(connection_in + 1, fdset, NULL,
576 fdset, &t_remaining);
577 ms_subtract_diff(&t_start, &remaining);
578 if (rc == 0 || remaining <= 0)
579 fatal("Connection timed out during "
584 fatal("ssh_exchange_identification: "
585 "select: %s", strerror(errno));
589 len = roaming_atomicio(read, connection_in, &buf[i], 1);
591 if (len != 1 && errno == EPIPE)
592 fatal("ssh_exchange_identification: "
593 "Connection closed by remote host");
595 fatal("ssh_exchange_identification: "
596 "read: %.100s", strerror(errno));
597 if (buf[i] == '\r') {
600 continue; /**XXX wait for \n */
602 if (buf[i] == '\n') {
607 fatal("ssh_exchange_identification: "
608 "No banner received");
610 buf[sizeof(buf) - 1] = 0;
611 if (strncmp(buf, "SSH-", 4) == 0)
613 debug("ssh_exchange_identification: %s", buf);
615 server_version_string = xstrdup(buf);
619 * Check that the versions match. In future this might accept
620 * several versions and set appropriate flags to handle them.
622 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
623 &remote_major, &remote_minor, remote_version) != 3)
624 fatal("Bad remote protocol version identification: '%.100s'", buf);
625 debug("Remote protocol version %d.%d, remote software version %.100s",
626 remote_major, remote_minor, remote_version);
628 compat_datafellows(remote_version);
631 switch (remote_major) {
633 if (remote_minor == 99 &&
634 (options.protocol & SSH_PROTO_2) &&
635 !(options.protocol & SSH_PROTO_1_PREFERRED)) {
639 if (!(options.protocol & SSH_PROTO_1)) {
643 if (remote_minor < 3) {
644 fatal("Remote machine has too old SSH software version.");
645 } else if (remote_minor == 3 || remote_minor == 4) {
646 /* We speak 1.3, too. */
649 if (options.forward_agent) {
650 logit("Agent forwarding disabled for protocol 1.3");
651 options.forward_agent = 0;
656 if (options.protocol & SSH_PROTO_2) {
666 fatal("Protocol major versions differ: %d vs. %d",
667 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
669 if ((datafellows & SSH_BUG_DERIVEKEY) != 0)
670 fatal("Server version \"%.100s\" uses unsafe key agreement; "
671 "refusing connection", remote_version);
672 if ((datafellows & SSH_BUG_RSASIGMD5) != 0)
673 logit("Server version \"%.100s\" uses unsafe RSA signature "
674 "scheme; disabling use of RSA keys", remote_version);
675 if (!client_banner_sent)
676 send_client_banner(connection_out, minor1);
677 chop(server_version_string);
680 /* defaults to 'no' */
682 confirm(const char *prompt)
684 const char *msg, *again = "Please type 'yes' or 'no': ";
688 if (options.batch_mode)
690 for (msg = prompt;;msg = again) {
691 p = read_passphrase(msg, RP_ECHO);
693 (p[0] == '\0') || (p[0] == '\n') ||
694 strncasecmp(p, "no", 2) == 0)
696 if (p && strncasecmp(p, "yes", 3) == 0)
705 check_host_cert(const char *host, const Key *host_key)
709 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) {
713 if (buffer_len(host_key->cert->critical) != 0) {
714 error("Certificate for %s contains unsupported "
715 "critical options(s)", host);
722 sockaddr_is_local(struct sockaddr *hostaddr)
724 switch (hostaddr->sa_family) {
726 return (ntohl(((struct sockaddr_in *)hostaddr)->
727 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
729 return IN6_IS_ADDR_LOOPBACK(
730 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
737 * Prepare the hostname and ip address strings that are used to lookup
738 * host keys in known_hosts files. These may have a port number appended.
741 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr,
742 u_short port, char **hostfile_hostname, char **hostfile_ipaddr)
744 char ntop[NI_MAXHOST];
747 switch (hostaddr == NULL ? -1 : hostaddr->sa_family) {
752 addrlen = sizeof(struct sockaddr_in);
755 addrlen = sizeof(struct sockaddr_in6);
758 addrlen = sizeof(struct sockaddr);
763 * We don't have the remote ip-address for connections
764 * using a proxy command
766 if (hostfile_ipaddr != NULL) {
767 if (options.proxy_command == NULL) {
768 if (getnameinfo(hostaddr, addrlen,
769 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0)
770 fatal("check_host_key: getnameinfo failed");
771 *hostfile_ipaddr = put_host_port(ntop, port);
773 *hostfile_ipaddr = xstrdup("<no hostip for proxy "
779 * Allow the user to record the key under a different name or
780 * differentiate a non-standard port. This is useful for ssh
781 * tunneling over forwarded connections or if you run multiple
782 * sshd's on different ports on the same machine.
784 if (hostfile_hostname != NULL) {
785 if (options.host_key_alias != NULL) {
786 *hostfile_hostname = xstrdup(options.host_key_alias);
787 debug("using hostkeyalias: %s", *hostfile_hostname);
789 *hostfile_hostname = put_host_port(hostname, port);
795 * check whether the supplied host key is valid, return -1 if the key
796 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true.
802 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
803 Key *host_key, int readonly,
804 char **user_hostfiles, u_int num_user_hostfiles,
805 char **system_hostfiles, u_int num_system_hostfiles)
807 HostStatus host_status;
808 HostStatus ip_status;
810 char *ip = NULL, *host = NULL;
811 char hostline[1000], *hostp, *fp, *ra;
814 const struct hostkey_entry *host_found, *ip_found;
815 int len, cancelled_forwarding = 0;
816 int local = sockaddr_is_local(hostaddr);
817 int r, want_cert = key_is_cert(host_key), host_ip_differ = 0;
818 struct hostkeys *host_hostkeys, *ip_hostkeys;
822 * Force accepting of the host key for loopback/localhost. The
823 * problem is that if the home directory is NFS-mounted to multiple
824 * machines, localhost will refer to a different machine in each of
825 * them, and the user will get bogus HOST_CHANGED warnings. This
826 * essentially disables host authentication for localhost; however,
827 * this is probably not a real problem.
829 if (options.no_host_authentication_for_localhost == 1 && local &&
830 options.host_key_alias == NULL) {
831 debug("Forcing accepting of host key for "
832 "loopback/localhost.");
837 * Prepare the hostname and address strings used for hostkey lookup.
838 * In some cases, these will have a port number appended.
840 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip);
843 * Turn off check_host_ip if the connection is to localhost, via proxy
844 * command or if we don't have a hostname to compare with
846 if (options.check_host_ip && (local ||
847 strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
848 options.check_host_ip = 0;
850 host_hostkeys = init_hostkeys();
851 for (i = 0; i < num_user_hostfiles; i++)
852 load_hostkeys(host_hostkeys, host, user_hostfiles[i]);
853 for (i = 0; i < num_system_hostfiles; i++)
854 load_hostkeys(host_hostkeys, host, system_hostfiles[i]);
857 if (!want_cert && options.check_host_ip) {
858 ip_hostkeys = init_hostkeys();
859 for (i = 0; i < num_user_hostfiles; i++)
860 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]);
861 for (i = 0; i < num_system_hostfiles; i++)
862 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]);
866 /* Reload these as they may have changed on cert->key downgrade */
867 want_cert = key_is_cert(host_key);
868 type = key_type(host_key);
871 * Check if the host key is present in the user's list of known
872 * hosts or in the systemwide list.
874 host_status = check_key_in_hostkeys(host_hostkeys, host_key,
878 * Also perform check for the ip address, skip the check if we are
879 * localhost, looking for a certificate, or the hostname was an ip
880 * address to begin with.
882 if (!want_cert && ip_hostkeys != NULL) {
883 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key,
885 if (host_status == HOST_CHANGED &&
886 (ip_status != HOST_CHANGED ||
888 !key_equal(ip_found->key, host_found->key))))
891 ip_status = host_status;
893 switch (host_status) {
895 /* The host is known and the key matches. */
896 debug("Host '%.200s' is known and matches the %s host %s.",
897 host, type, want_cert ? "certificate" : "key");
898 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key",
899 host_found->file, host_found->line);
900 if (want_cert && !check_host_cert(hostname, host_key))
902 if (options.check_host_ip && ip_status == HOST_NEW) {
903 if (readonly || want_cert)
904 logit("%s host key for IP address "
905 "'%.128s' not in list of known hosts.",
907 else if (!add_host_to_hostfile(user_hostfiles[0], ip,
908 host_key, options.hash_known_hosts))
909 logit("Failed to add the %s host key for IP "
910 "address '%.128s' to the list of known "
911 "hosts (%.30s).", type, ip,
914 logit("Warning: Permanently added the %s host "
915 "key for IP address '%.128s' to the list "
916 "of known hosts.", type, ip);
917 } else if (options.visual_host_key) {
918 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
919 ra = key_fingerprint(host_key, SSH_FP_MD5,
921 logit("Host key fingerprint is %s\n%s\n", fp, ra);
927 if (options.host_key_alias == NULL && port != 0 &&
928 port != SSH_DEFAULT_PORT) {
929 debug("checking without port identifier");
930 if (check_host_key(hostname, hostaddr, 0, host_key,
931 ROQUIET, user_hostfiles, num_user_hostfiles,
932 system_hostfiles, num_system_hostfiles) == 0) {
933 debug("found matching key w/out port");
937 if (readonly || want_cert)
939 /* The host is new. */
940 if (options.strict_host_key_checking == 1) {
942 * User has requested strict host key checking. We
943 * will not add the host key automatically. The only
944 * alternative left is to abort.
946 error("No %s host key is known for %.200s and you "
947 "have requested strict checking.", type, host);
949 } else if (options.strict_host_key_checking == 2) {
950 char msg1[1024], msg2[1024];
952 if (show_other_keys(host_hostkeys, host_key))
953 snprintf(msg1, sizeof(msg1),
954 "\nbut keys of different type are already"
955 " known for this host.");
957 snprintf(msg1, sizeof(msg1), ".");
959 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
960 ra = key_fingerprint(host_key, SSH_FP_MD5,
963 if (options.verify_host_key_dns) {
964 if (matching_host_key_dns)
965 snprintf(msg2, sizeof(msg2),
966 "Matching host key fingerprint"
969 snprintf(msg2, sizeof(msg2),
970 "No matching host key fingerprint"
973 snprintf(msg, sizeof(msg),
974 "The authenticity of host '%.200s (%s)' can't be "
976 "%s key fingerprint is %s.%s%s\n%s"
977 "Are you sure you want to continue connecting "
979 host, ip, msg1, type, fp,
980 options.visual_host_key ? "\n" : "",
981 options.visual_host_key ? ra : "",
989 * If not in strict mode, add the key automatically to the
990 * local known_hosts file.
992 if (options.check_host_ip && ip_status == HOST_NEW) {
993 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
995 if (options.hash_known_hosts) {
996 /* Add hash of host and IP separately */
997 r = add_host_to_hostfile(user_hostfiles[0],
998 host, host_key, options.hash_known_hosts) &&
999 add_host_to_hostfile(user_hostfiles[0], ip,
1000 host_key, options.hash_known_hosts);
1002 /* Add unhashed "host,ip" */
1003 r = add_host_to_hostfile(user_hostfiles[0],
1005 options.hash_known_hosts);
1008 r = add_host_to_hostfile(user_hostfiles[0], host,
1009 host_key, options.hash_known_hosts);
1014 logit("Failed to add the host to the list of known "
1015 "hosts (%.500s).", user_hostfiles[0]);
1017 logit("Warning: Permanently added '%.200s' (%s) to the "
1018 "list of known hosts.", hostp, type);
1021 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1022 error("@ WARNING: REVOKED HOST KEY DETECTED! @");
1023 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1024 error("The %s host key for %s is marked as revoked.", type, host);
1025 error("This could mean that a stolen key is being used to");
1026 error("impersonate this host.");
1029 * If strict host key checking is in use, the user will have
1030 * to edit the key manually and we can only abort.
1032 if (options.strict_host_key_checking) {
1033 error("%s host key for %.200s was revoked and you have "
1034 "requested strict checking.", type, host);
1037 goto continue_unsafe;
1042 * This is only a debug() since it is valid to have
1043 * CAs with wildcard DNS matches that don't match
1044 * all hosts that one might visit.
1046 debug("Host certificate authority does not "
1047 "match %s in %s:%lu", CA_MARKER,
1048 host_found->file, host_found->line);
1051 if (readonly == ROQUIET)
1053 if (options.check_host_ip && host_ip_differ) {
1055 if (ip_status == HOST_NEW)
1056 key_msg = "is unknown";
1057 else if (ip_status == HOST_OK)
1058 key_msg = "is unchanged";
1060 key_msg = "has a different value";
1061 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1062 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
1063 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1064 error("The %s host key for %s has changed,", type, host);
1065 error("and the key for the corresponding IP address %s", ip);
1066 error("%s. This could either mean that", key_msg);
1067 error("DNS SPOOFING is happening or the IP address for the host");
1068 error("and its host key have changed at the same time.");
1069 if (ip_status != HOST_NEW)
1070 error("Offending key for IP in %s:%lu",
1071 ip_found->file, ip_found->line);
1073 /* The host key has changed. */
1074 warn_changed_key(host_key);
1075 error("Add correct host key in %.100s to get rid of this message.",
1077 error("Offending %s key in %s:%lu", key_type(host_found->key),
1078 host_found->file, host_found->line);
1081 * If strict host key checking is in use, the user will have
1082 * to edit the key manually and we can only abort.
1084 if (options.strict_host_key_checking) {
1085 error("%s host key for %.200s has changed and you have "
1086 "requested strict checking.", type, host);
1092 * If strict host key checking has not been requested, allow
1093 * the connection but without MITM-able authentication or
1096 if (options.password_authentication) {
1097 error("Password authentication is disabled to avoid "
1098 "man-in-the-middle attacks.");
1099 options.password_authentication = 0;
1100 cancelled_forwarding = 1;
1102 if (options.kbd_interactive_authentication) {
1103 error("Keyboard-interactive authentication is disabled"
1104 " to avoid man-in-the-middle attacks.");
1105 options.kbd_interactive_authentication = 0;
1106 options.challenge_response_authentication = 0;
1107 cancelled_forwarding = 1;
1109 if (options.challenge_response_authentication) {
1110 error("Challenge/response authentication is disabled"
1111 " to avoid man-in-the-middle attacks.");
1112 options.challenge_response_authentication = 0;
1113 cancelled_forwarding = 1;
1115 if (options.forward_agent) {
1116 error("Agent forwarding is disabled to avoid "
1117 "man-in-the-middle attacks.");
1118 options.forward_agent = 0;
1119 cancelled_forwarding = 1;
1121 if (options.forward_x11) {
1122 error("X11 forwarding is disabled to avoid "
1123 "man-in-the-middle attacks.");
1124 options.forward_x11 = 0;
1125 cancelled_forwarding = 1;
1127 if (options.num_local_forwards > 0 ||
1128 options.num_remote_forwards > 0) {
1129 error("Port forwarding is disabled to avoid "
1130 "man-in-the-middle attacks.");
1131 options.num_local_forwards =
1132 options.num_remote_forwards = 0;
1133 cancelled_forwarding = 1;
1135 if (options.tun_open != SSH_TUNMODE_NO) {
1136 error("Tunnel forwarding is disabled to avoid "
1137 "man-in-the-middle attacks.");
1138 options.tun_open = SSH_TUNMODE_NO;
1139 cancelled_forwarding = 1;
1141 if (options.exit_on_forward_failure && cancelled_forwarding)
1142 fatal("Error: forwarding disabled due to host key "
1146 * XXX Should permit the user to change to use the new id.
1147 * This could be done by converting the host key to an
1148 * identifying sentence, tell that the host identifies itself
1149 * by that sentence, and ask the user if he/she wishes to
1150 * accept the authentication.
1154 fatal("internal error");
1158 if (options.check_host_ip && host_status != HOST_CHANGED &&
1159 ip_status == HOST_CHANGED) {
1160 snprintf(msg, sizeof(msg),
1161 "Warning: the %s host key for '%.200s' "
1162 "differs from the key for the IP address '%.128s'"
1163 "\nOffending key for IP in %s:%lu",
1164 type, host, ip, ip_found->file, ip_found->line);
1165 if (host_status == HOST_OK) {
1167 snprintf(msg + len, sizeof(msg) - len,
1168 "\nMatching host key in %s:%lu",
1169 host_found->file, host_found->line);
1171 if (options.strict_host_key_checking == 1) {
1173 error("Exiting, you have requested strict checking.");
1175 } else if (options.strict_host_key_checking == 2) {
1176 strlcat(msg, "\nAre you sure you want "
1177 "to continue connecting (yes/no)? ", sizeof(msg));
1187 if (host_hostkeys != NULL)
1188 free_hostkeys(host_hostkeys);
1189 if (ip_hostkeys != NULL)
1190 free_hostkeys(ip_hostkeys);
1194 if (want_cert && host_status != HOST_REVOKED) {
1196 * No matching certificate. Downgrade cert to raw key and
1199 debug("No matching CA found. Retry with plain key");
1200 raw_key = key_from_private(host_key);
1201 if (key_drop_cert(raw_key) != 0)
1202 fatal("Couldn't drop certificate");
1206 if (raw_key != NULL)
1210 if (host_hostkeys != NULL)
1211 free_hostkeys(host_hostkeys);
1212 if (ip_hostkeys != NULL)
1213 free_hostkeys(ip_hostkeys);
1217 /* returns 0 if key verifies or -1 if key does NOT verify */
1219 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
1221 int r = -1, flags = 0;
1225 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1226 debug("Server host key: %s %s", key_type(host_key), fp);
1229 if (key_equal(previous_host_key, host_key)) {
1230 debug("%s: server host key matches cached key", __func__);
1234 if (options.verify_host_key_dns) {
1236 * XXX certs are not yet supported for DNS, so downgrade
1237 * them and try the plain key.
1239 plain = key_from_private(host_key);
1240 if (key_is_cert(plain))
1241 key_drop_cert(plain);
1242 if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) {
1243 if (flags & DNS_VERIFY_FOUND) {
1244 if (options.verify_host_key_dns == 1 &&
1245 flags & DNS_VERIFY_MATCH &&
1246 flags & DNS_VERIFY_SECURE) {
1251 if (flags & DNS_VERIFY_MATCH) {
1252 matching_host_key_dns = 1;
1254 warn_changed_key(plain);
1255 error("Update the SSHFP RR in DNS "
1256 "with the new host key to get rid "
1257 "of this message.");
1264 r = check_host_key(host, hostaddr, options.port, host_key, RDRW,
1265 options.user_hostfiles, options.num_user_hostfiles,
1266 options.system_hostfiles, options.num_system_hostfiles);
1269 if (r == 0 && host_key != NULL) {
1270 key_free(previous_host_key);
1271 previous_host_key = key_from_private(host_key);
1278 * Starts a dialog with the server, and authenticates the current user on the
1279 * server. This does not need any extra privileges. The basic connection
1280 * to the server must already have been established before this is called.
1281 * If login fails, this function prints an error and never returns.
1282 * This function does not require super-user privileges.
1285 ssh_login(Sensitive *sensitive, const char *orighost,
1286 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms)
1289 char *server_user, *local_user;
1291 local_user = xstrdup(pw->pw_name);
1292 server_user = options.user ? options.user : local_user;
1294 /* Convert the user-supplied hostname into all lowercase. */
1295 host = xstrdup(orighost);
1298 /* Exchange protocol version identification strings with the server. */
1299 ssh_exchange_identification(timeout_ms);
1301 /* Put the connection into non-blocking mode. */
1302 packet_set_nonblocking();
1305 /* authenticate user */
1307 ssh_kex2(host, hostaddr, port);
1308 ssh_userauth2(local_user, server_user, host, sensitive);
1311 ssh_kex(host, hostaddr);
1312 ssh_userauth1(local_user, server_user, host, sensitive);
1314 fatal("ssh1 is not unsupported");
1321 ssh_put_password(char *password)
1326 if (datafellows & SSH_BUG_PASSWORDPAD) {
1327 packet_put_cstring(password);
1330 size = roundup(strlen(password) + 1, 32);
1331 padded = xcalloc(1, size);
1332 strlcpy(padded, password, size);
1333 packet_put_string(padded, size);
1334 explicit_bzero(padded, size);
1338 /* print all known host keys for a given host, but skip keys of given type */
1340 show_other_keys(struct hostkeys *hostkeys, Key *key)
1352 const struct hostkey_entry *found;
1354 for (i = 0; type[i] != -1; i++) {
1355 if (type[i] == key->type)
1357 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found))
1359 fp = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_HEX);
1360 ra = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_RANDOMART);
1361 logit("WARNING: %s key found for host %s\n"
1363 "%s key fingerprint %s.",
1364 key_type(found->key),
1365 found->host, found->file, found->line,
1366 key_type(found->key), fp);
1367 if (options.visual_host_key)
1377 warn_changed_key(Key *host_key)
1381 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1383 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1384 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1385 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1386 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1387 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1388 error("It is also possible that a host key has just been changed.");
1389 error("The fingerprint for the %s key sent by the remote host is\n%s.",
1390 key_type(host_key), fp);
1391 error("Please contact your system administrator.");
1397 * Execute a local command
1400 ssh_local_cmd(const char *args)
1405 void (*osighand)(int);
1407 if (!options.permit_local_command ||
1408 args == NULL || !*args)
1411 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
1412 shell = _PATH_BSHELL;
1414 osighand = signal(SIGCHLD, SIG_DFL);
1417 signal(SIGPIPE, SIG_DFL);
1418 debug3("Executing %s -c \"%s\"", shell, args);
1419 execl(shell, shell, "-c", args, (char *)NULL);
1420 error("Couldn't execute %s -c \"%s\": %s",
1421 shell, args, strerror(errno));
1423 } else if (pid == -1)
1424 fatal("fork failed: %.100s", strerror(errno));
1425 while (waitpid(pid, &status, 0) == -1)
1427 fatal("Couldn't wait for child: %s", strerror(errno));
1428 signal(SIGCHLD, osighand);
1430 if (!WIFEXITED(status))
1433 return (WEXITSTATUS(status));