1 /* $OpenBSD: sshconnect.c,v 1.263 2015/08/20 22:32:42 deraadt 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/param.h> /* roundup */
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"
63 #include "monitor_fdpass.h"
69 char *client_version_string = NULL;
70 char *server_version_string = NULL;
71 Key *previous_host_key = NULL;
73 static int matching_host_key_dns = 0;
75 static pid_t proxy_command_pid = 0;
78 extern Options options;
79 extern char *__progname;
80 extern uid_t original_real_uid;
81 extern uid_t original_effective_uid;
83 static int show_other_keys(struct hostkeys *, Key *);
84 static void warn_changed_key(Key *);
86 /* Expand a proxy command */
88 expand_proxy_command(const char *proxy_command, const char *user,
89 const char *host, int port)
91 char *tmp, *ret, strport[NI_MAXSERV];
93 snprintf(strport, sizeof strport, "%d", port);
94 xasprintf(&tmp, "exec %s", proxy_command);
95 ret = percent_expand(tmp, "h", host, "p", strport,
96 "r", options.user, (char *)NULL);
102 * Connect to the given ssh server using a proxy command that passes a
103 * a connected fd back to us.
106 ssh_proxy_fdpass_connect(const char *host, u_short port,
107 const char *proxy_command)
109 char *command_string;
114 if ((shell = getenv("SHELL")) == NULL)
115 shell = _PATH_BSHELL;
117 if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) < 0)
118 fatal("Could not create socketpair to communicate with "
119 "proxy dialer: %.100s", strerror(errno));
121 command_string = expand_proxy_command(proxy_command, options.user,
123 debug("Executing proxy dialer command: %.500s", command_string);
125 /* Fork and execute the proxy command. */
126 if ((pid = fork()) == 0) {
129 /* Child. Permanently give up superuser privileges. */
130 permanently_drop_suid(original_real_uid);
133 /* Redirect stdin and stdout. */
135 if (dup2(sp[0], 0) < 0)
136 perror("dup2 stdin");
139 if (dup2(sp[0], 1) < 0)
140 perror("dup2 stdout");
146 * Stderr is left as it is so that error messages get
147 * printed on the user's terminal.
151 argv[2] = command_string;
155 * Execute the proxy command.
156 * Note that we gave up any extra privileges above.
158 execv(argv[0], argv);
164 fatal("fork failed: %.100s", strerror(errno));
166 free(command_string);
168 if ((sock = mm_receive_fd(sp[1])) == -1)
169 fatal("proxy dialer did not pass back a connection");
171 while (waitpid(pid, NULL, 0) == -1)
173 fatal("Couldn't wait for child: %s", strerror(errno));
175 /* Set the connection file descriptors. */
176 packet_set_connection(sock, sock);
182 * Connect to the given ssh server using a proxy command.
185 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
187 char *command_string;
192 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
193 shell = _PATH_BSHELL;
195 /* Create pipes for communicating with the proxy. */
196 if (pipe(pin) < 0 || pipe(pout) < 0)
197 fatal("Could not create pipes to communicate with the proxy: %.100s",
200 command_string = expand_proxy_command(proxy_command, options.user,
202 debug("Executing proxy command: %.500s", command_string);
204 /* Fork and execute the proxy command. */
205 if ((pid = fork()) == 0) {
208 /* Child. Permanently give up superuser privileges. */
209 permanently_drop_suid(original_real_uid);
211 /* Redirect stdin and stdout. */
214 if (dup2(pin[0], 0) < 0)
215 perror("dup2 stdin");
219 if (dup2(pout[1], 1) < 0)
220 perror("dup2 stdout");
221 /* Cannot be 1 because pin allocated two descriptors. */
224 /* Stderr is left as it is so that error messages get
225 printed on the user's terminal. */
228 argv[2] = command_string;
231 /* Execute the proxy command. Note that we gave up any
232 extra privileges above. */
233 signal(SIGPIPE, SIG_DFL);
234 execv(argv[0], argv);
240 fatal("fork failed: %.100s", strerror(errno));
242 proxy_command_pid = pid; /* save pid to clean up later */
244 /* Close child side of the descriptors. */
248 /* Free the command name. */
249 free(command_string);
251 /* Set the connection file descriptors. */
252 packet_set_connection(pout[0], pin[1]);
254 /* Indicate OK return */
259 ssh_kill_proxy_command(void)
262 * Send SIGHUP to proxy command if used. We don't wait() in
263 * case it hangs and instead rely on init to reap the child
265 if (proxy_command_pid > 1)
266 kill(proxy_command_pid, SIGHUP);
270 * Creates a (possibly privileged) socket for use as the ssh connection.
273 ssh_create_socket(int privileged, struct addrinfo *ai)
276 struct addrinfo hints, *res = NULL;
278 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
280 error("socket: %s", strerror(errno));
283 fcntl(sock, F_SETFD, FD_CLOEXEC);
285 /* Bind the socket to an alternative local IP address */
286 if (options.bind_address == NULL && !privileged)
289 if (options.bind_address) {
290 memset(&hints, 0, sizeof(hints));
291 hints.ai_family = ai->ai_family;
292 hints.ai_socktype = ai->ai_socktype;
293 hints.ai_protocol = ai->ai_protocol;
294 hints.ai_flags = AI_PASSIVE;
295 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res);
297 error("getaddrinfo: %s: %s", options.bind_address,
298 ssh_gai_strerror(gaierr));
304 * If we are running as root and want to connect to a privileged
305 * port, bind our own socket to a privileged port.
309 r = bindresvport_sa(sock, res ? res->ai_addr : NULL);
312 error("bindresvport_sa: af=%d %s", ai->ai_family,
317 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
318 error("bind: %s: %s", options.bind_address,
332 timeout_connect(int sockfd, const struct sockaddr *serv_addr,
333 socklen_t addrlen, int *timeoutp)
336 struct timeval tv, t_start;
338 int optval, rc, result = -1;
340 gettimeofday(&t_start, NULL);
342 if (*timeoutp <= 0) {
343 result = connect(sockfd, serv_addr, addrlen);
347 set_nonblock(sockfd);
348 rc = connect(sockfd, serv_addr, addrlen);
350 unset_nonblock(sockfd);
354 if (errno != EINPROGRESS) {
359 fdset = xcalloc(howmany(sockfd + 1, NFDBITS),
361 FD_SET(sockfd, fdset);
362 ms_to_timeval(&tv, *timeoutp);
365 rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
366 if (rc != -1 || errno != EINTR)
377 debug("select: %s", strerror(errno));
380 /* Completed or failed */
382 optlen = sizeof(optval);
383 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
385 debug("getsockopt: %s", strerror(errno));
393 unset_nonblock(sockfd);
396 /* Should not occur */
397 fatal("Bogus return (%d) from select()", rc);
403 if (result == 0 && *timeoutp > 0) {
404 ms_subtract_diff(&t_start, timeoutp);
405 if (*timeoutp <= 0) {
415 * Opens a TCP/IP connection to the remote server on the given host.
416 * The address of the remote host will be returned in hostaddr.
417 * If port is 0, the default port will be used. If needpriv is true,
418 * a privileged port will be allocated to make the connection.
419 * This requires super-user privileges if needpriv is true.
420 * Connection_attempts specifies the maximum number of tries (one per
421 * second). If proxy_command is non-NULL, it specifies the command (with %h
422 * and %p substituted for host and port, respectively) to use to contact
426 ssh_connect_direct(const char *host, struct addrinfo *aitop,
427 struct sockaddr_storage *hostaddr, u_short port, int family,
428 int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv)
431 int sock = -1, attempt;
432 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
435 debug2("ssh_connect: needpriv %d", needpriv);
437 for (attempt = 0; attempt < connection_attempts; attempt++) {
439 /* Sleep a moment before retrying. */
441 debug("Trying again...");
444 * Loop through addresses for this host, and try each one in
445 * sequence until the connection succeeds.
447 for (ai = aitop; ai; ai = ai->ai_next) {
448 if (ai->ai_family != AF_INET &&
449 ai->ai_family != AF_INET6)
451 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
452 ntop, sizeof(ntop), strport, sizeof(strport),
453 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
454 error("ssh_connect: getnameinfo failed");
457 debug("Connecting to %.200s [%.100s] port %s.",
458 host, ntop, strport);
460 /* Create a socket for connecting. */
461 sock = ssh_create_socket(needpriv, ai);
463 /* Any error is already output */
466 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
468 /* Successful connection. */
469 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
472 debug("connect to address %s port %s: %s",
473 ntop, strport, strerror(errno));
479 break; /* Successful connection. */
482 /* Return failure if we didn't get a successful connection. */
484 error("ssh: connect to host %s port %s: %s",
485 host, strport, strerror(errno));
489 debug("Connection established.");
491 /* Set SO_KEEPALIVE if requested. */
492 if (want_keepalive &&
493 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
495 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
497 /* Set the connection. */
498 packet_set_connection(sock, sock);
504 ssh_connect(const char *host, struct addrinfo *addrs,
505 struct sockaddr_storage *hostaddr, u_short port, int family,
506 int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv)
508 if (options.proxy_command == NULL) {
509 return ssh_connect_direct(host, addrs, hostaddr, port, family,
510 connection_attempts, timeout_ms, want_keepalive, needpriv);
511 } else if (strcmp(options.proxy_command, "-") == 0) {
512 packet_set_connection(STDIN_FILENO, STDOUT_FILENO);
513 return 0; /* Always succeeds */
514 } else if (options.proxy_use_fdpass) {
515 return ssh_proxy_fdpass_connect(host, port,
516 options.proxy_command);
518 return ssh_proxy_connect(host, port, options.proxy_command);
522 send_client_banner(int connection_out, int minor1)
524 /* Send our own protocol version identification. */
526 xasprintf(&client_version_string, "SSH-%d.%d-%.100s\r\n",
527 PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION);
529 xasprintf(&client_version_string, "SSH-%d.%d-%.100s\n",
530 PROTOCOL_MAJOR_1, minor1, SSH_VERSION);
532 if (roaming_atomicio(vwrite, connection_out, client_version_string,
533 strlen(client_version_string)) != strlen(client_version_string))
534 fatal("write: %.100s", strerror(errno));
535 chop(client_version_string);
536 debug("Local version string %.100s", client_version_string);
540 * Waits for the server identification string, and sends our own
541 * identification string.
544 ssh_exchange_identification(int timeout_ms)
546 char buf[256], remote_version[256]; /* must be same size! */
547 int remote_major, remote_minor, mismatch;
548 int connection_in = packet_get_connection_in();
549 int connection_out = packet_get_connection_out();
550 int minor1 = PROTOCOL_MINOR_1, client_banner_sent = 0;
553 int fdsetsz, remaining, rc;
554 struct timeval t_start, t_remaining;
557 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask);
558 fdset = xcalloc(1, fdsetsz);
561 * If we are SSH2-only then we can send the banner immediately and
564 if (options.protocol == SSH_PROTO_2) {
566 send_client_banner(connection_out, 0);
567 client_banner_sent = 1;
570 /* Read other side's version identification. */
571 remaining = timeout_ms;
573 for (i = 0; i < sizeof(buf) - 1; i++) {
574 if (timeout_ms > 0) {
575 gettimeofday(&t_start, NULL);
576 ms_to_timeval(&t_remaining, remaining);
577 FD_SET(connection_in, fdset);
578 rc = select(connection_in + 1, fdset, NULL,
579 fdset, &t_remaining);
580 ms_subtract_diff(&t_start, &remaining);
581 if (rc == 0 || remaining <= 0)
582 fatal("Connection timed out during "
587 fatal("ssh_exchange_identification: "
588 "select: %s", strerror(errno));
592 len = roaming_atomicio(read, connection_in, &buf[i], 1);
594 if (len != 1 && errno == EPIPE)
595 fatal("ssh_exchange_identification: "
596 "Connection closed by remote host");
598 fatal("ssh_exchange_identification: "
599 "read: %.100s", strerror(errno));
600 if (buf[i] == '\r') {
603 continue; /**XXX wait for \n */
605 if (buf[i] == '\n') {
610 fatal("ssh_exchange_identification: "
611 "No banner received");
613 buf[sizeof(buf) - 1] = 0;
614 if (strncmp(buf, "SSH-", 4) == 0)
616 debug("ssh_exchange_identification: %s", buf);
618 server_version_string = xstrdup(buf);
622 * Check that the versions match. In future this might accept
623 * several versions and set appropriate flags to handle them.
625 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
626 &remote_major, &remote_minor, remote_version) != 3)
627 fatal("Bad remote protocol version identification: '%.100s'", buf);
628 debug("Remote protocol version %d.%d, remote software version %.100s",
629 remote_major, remote_minor, remote_version);
631 active_state->compat = compat_datafellows(remote_version);
634 switch (remote_major) {
636 if (remote_minor == 99 &&
637 (options.protocol & SSH_PROTO_2) &&
638 !(options.protocol & SSH_PROTO_1_PREFERRED)) {
642 if (!(options.protocol & SSH_PROTO_1)) {
646 if (remote_minor < 3) {
647 fatal("Remote machine has too old SSH software version.");
648 } else if (remote_minor == 3 || remote_minor == 4) {
649 /* We speak 1.3, too. */
652 if (options.forward_agent) {
653 logit("Agent forwarding disabled for protocol 1.3");
654 options.forward_agent = 0;
659 if (options.protocol & SSH_PROTO_2) {
669 fatal("Protocol major versions differ: %d vs. %d",
670 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
672 if ((datafellows & SSH_BUG_DERIVEKEY) != 0)
673 fatal("Server version \"%.100s\" uses unsafe key agreement; "
674 "refusing connection", remote_version);
675 if ((datafellows & SSH_BUG_RSASIGMD5) != 0)
676 logit("Server version \"%.100s\" uses unsafe RSA signature "
677 "scheme; disabling use of RSA keys", remote_version);
678 if (!client_banner_sent)
679 send_client_banner(connection_out, minor1);
680 chop(server_version_string);
683 /* defaults to 'no' */
685 confirm(const char *prompt)
687 const char *msg, *again = "Please type 'yes' or 'no': ";
691 if (options.batch_mode)
693 for (msg = prompt;;msg = again) {
694 p = read_passphrase(msg, RP_ECHO);
696 (p[0] == '\0') || (p[0] == '\n') ||
697 strncasecmp(p, "no", 2) == 0)
699 if (p && strncasecmp(p, "yes", 3) == 0)
708 check_host_cert(const char *host, const Key *host_key)
712 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) {
716 if (buffer_len(host_key->cert->critical) != 0) {
717 error("Certificate for %s contains unsupported "
718 "critical options(s)", host);
725 sockaddr_is_local(struct sockaddr *hostaddr)
727 switch (hostaddr->sa_family) {
729 return (ntohl(((struct sockaddr_in *)hostaddr)->
730 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
732 return IN6_IS_ADDR_LOOPBACK(
733 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
740 * Prepare the hostname and ip address strings that are used to lookup
741 * host keys in known_hosts files. These may have a port number appended.
744 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr,
745 u_short port, char **hostfile_hostname, char **hostfile_ipaddr)
747 char ntop[NI_MAXHOST];
750 switch (hostaddr == NULL ? -1 : hostaddr->sa_family) {
755 addrlen = sizeof(struct sockaddr_in);
758 addrlen = sizeof(struct sockaddr_in6);
761 addrlen = sizeof(struct sockaddr);
766 * We don't have the remote ip-address for connections
767 * using a proxy command
769 if (hostfile_ipaddr != NULL) {
770 if (options.proxy_command == NULL) {
771 if (getnameinfo(hostaddr, addrlen,
772 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0)
773 fatal("%s: getnameinfo failed", __func__);
774 *hostfile_ipaddr = put_host_port(ntop, port);
776 *hostfile_ipaddr = xstrdup("<no hostip for proxy "
782 * Allow the user to record the key under a different name or
783 * differentiate a non-standard port. This is useful for ssh
784 * tunneling over forwarded connections or if you run multiple
785 * sshd's on different ports on the same machine.
787 if (hostfile_hostname != NULL) {
788 if (options.host_key_alias != NULL) {
789 *hostfile_hostname = xstrdup(options.host_key_alias);
790 debug("using hostkeyalias: %s", *hostfile_hostname);
792 *hostfile_hostname = put_host_port(hostname, port);
798 * check whether the supplied host key is valid, return -1 if the key
799 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true.
805 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
806 Key *host_key, int readonly,
807 char **user_hostfiles, u_int num_user_hostfiles,
808 char **system_hostfiles, u_int num_system_hostfiles)
810 HostStatus host_status;
811 HostStatus ip_status;
813 char *ip = NULL, *host = NULL;
814 char hostline[1000], *hostp, *fp, *ra;
817 const struct hostkey_entry *host_found, *ip_found;
818 int len, cancelled_forwarding = 0;
819 int local = sockaddr_is_local(hostaddr);
820 int r, want_cert = key_is_cert(host_key), host_ip_differ = 0;
821 int hostkey_trusted = 0; /* Known or explicitly accepted by user */
822 struct hostkeys *host_hostkeys, *ip_hostkeys;
826 * Force accepting of the host key for loopback/localhost. The
827 * problem is that if the home directory is NFS-mounted to multiple
828 * machines, localhost will refer to a different machine in each of
829 * them, and the user will get bogus HOST_CHANGED warnings. This
830 * essentially disables host authentication for localhost; however,
831 * this is probably not a real problem.
833 if (options.no_host_authentication_for_localhost == 1 && local &&
834 options.host_key_alias == NULL) {
835 debug("Forcing accepting of host key for "
836 "loopback/localhost.");
841 * Prepare the hostname and address strings used for hostkey lookup.
842 * In some cases, these will have a port number appended.
844 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip);
847 * Turn off check_host_ip if the connection is to localhost, via proxy
848 * command or if we don't have a hostname to compare with
850 if (options.check_host_ip && (local ||
851 strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
852 options.check_host_ip = 0;
854 host_hostkeys = init_hostkeys();
855 for (i = 0; i < num_user_hostfiles; i++)
856 load_hostkeys(host_hostkeys, host, user_hostfiles[i]);
857 for (i = 0; i < num_system_hostfiles; i++)
858 load_hostkeys(host_hostkeys, host, system_hostfiles[i]);
861 if (!want_cert && options.check_host_ip) {
862 ip_hostkeys = init_hostkeys();
863 for (i = 0; i < num_user_hostfiles; i++)
864 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]);
865 for (i = 0; i < num_system_hostfiles; i++)
866 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]);
870 /* Reload these as they may have changed on cert->key downgrade */
871 want_cert = key_is_cert(host_key);
872 type = key_type(host_key);
875 * Check if the host key is present in the user's list of known
876 * hosts or in the systemwide list.
878 host_status = check_key_in_hostkeys(host_hostkeys, host_key,
882 * Also perform check for the ip address, skip the check if we are
883 * localhost, looking for a certificate, or the hostname was an ip
884 * address to begin with.
886 if (!want_cert && ip_hostkeys != NULL) {
887 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key,
889 if (host_status == HOST_CHANGED &&
890 (ip_status != HOST_CHANGED ||
892 !key_equal(ip_found->key, host_found->key))))
895 ip_status = host_status;
897 switch (host_status) {
899 /* The host is known and the key matches. */
900 debug("Host '%.200s' is known and matches the %s host %s.",
901 host, type, want_cert ? "certificate" : "key");
902 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key",
903 host_found->file, host_found->line);
904 if (want_cert && !check_host_cert(hostname, host_key))
906 if (options.check_host_ip && ip_status == HOST_NEW) {
907 if (readonly || want_cert)
908 logit("%s host key for IP address "
909 "'%.128s' not in list of known hosts.",
911 else if (!add_host_to_hostfile(user_hostfiles[0], ip,
912 host_key, options.hash_known_hosts))
913 logit("Failed to add the %s host key for IP "
914 "address '%.128s' to the list of known "
915 "hosts (%.500s).", type, ip,
918 logit("Warning: Permanently added the %s host "
919 "key for IP address '%.128s' to the list "
920 "of known hosts.", type, ip);
921 } else if (options.visual_host_key) {
922 fp = sshkey_fingerprint(host_key,
923 options.fingerprint_hash, SSH_FP_DEFAULT);
924 ra = sshkey_fingerprint(host_key,
925 options.fingerprint_hash, SSH_FP_RANDOMART);
926 if (fp == NULL || ra == NULL)
927 fatal("%s: sshkey_fingerprint fail", __func__);
928 logit("Host key fingerprint is %s\n%s\n", fp, ra);
935 if (options.host_key_alias == NULL && port != 0 &&
936 port != SSH_DEFAULT_PORT) {
937 debug("checking without port identifier");
938 if (check_host_key(hostname, hostaddr, 0, host_key,
939 ROQUIET, user_hostfiles, num_user_hostfiles,
940 system_hostfiles, num_system_hostfiles) == 0) {
941 debug("found matching key w/out port");
945 if (readonly || want_cert)
947 /* The host is new. */
948 if (options.strict_host_key_checking == 1) {
950 * User has requested strict host key checking. We
951 * will not add the host key automatically. The only
952 * alternative left is to abort.
954 error("No %s host key is known for %.200s and you "
955 "have requested strict checking.", type, host);
957 } else if (options.strict_host_key_checking == 2) {
958 char msg1[1024], msg2[1024];
960 if (show_other_keys(host_hostkeys, host_key))
961 snprintf(msg1, sizeof(msg1),
962 "\nbut keys of different type are already"
963 " known for this host.");
965 snprintf(msg1, sizeof(msg1), ".");
967 fp = sshkey_fingerprint(host_key,
968 options.fingerprint_hash, SSH_FP_DEFAULT);
969 ra = sshkey_fingerprint(host_key,
970 options.fingerprint_hash, SSH_FP_RANDOMART);
971 if (fp == NULL || ra == NULL)
972 fatal("%s: sshkey_fingerprint fail", __func__);
974 if (options.verify_host_key_dns) {
975 if (matching_host_key_dns)
976 snprintf(msg2, sizeof(msg2),
977 "Matching host key fingerprint"
980 snprintf(msg2, sizeof(msg2),
981 "No matching host key fingerprint"
984 snprintf(msg, sizeof(msg),
985 "The authenticity of host '%.200s (%s)' can't be "
987 "%s key fingerprint is %s.%s%s\n%s"
988 "Are you sure you want to continue connecting "
990 host, ip, msg1, type, fp,
991 options.visual_host_key ? "\n" : "",
992 options.visual_host_key ? ra : "",
998 hostkey_trusted = 1; /* user explicitly confirmed */
1001 * If not in strict mode, add the key automatically to the
1002 * local known_hosts file.
1004 if (options.check_host_ip && ip_status == HOST_NEW) {
1005 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
1007 if (options.hash_known_hosts) {
1008 /* Add hash of host and IP separately */
1009 r = add_host_to_hostfile(user_hostfiles[0],
1010 host, host_key, options.hash_known_hosts) &&
1011 add_host_to_hostfile(user_hostfiles[0], ip,
1012 host_key, options.hash_known_hosts);
1014 /* Add unhashed "host,ip" */
1015 r = add_host_to_hostfile(user_hostfiles[0],
1017 options.hash_known_hosts);
1020 r = add_host_to_hostfile(user_hostfiles[0], host,
1021 host_key, options.hash_known_hosts);
1026 logit("Failed to add the host to the list of known "
1027 "hosts (%.500s).", user_hostfiles[0]);
1029 logit("Warning: Permanently added '%.200s' (%s) to the "
1030 "list of known hosts.", hostp, type);
1033 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1034 error("@ WARNING: REVOKED HOST KEY DETECTED! @");
1035 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1036 error("The %s host key for %s is marked as revoked.", type, host);
1037 error("This could mean that a stolen key is being used to");
1038 error("impersonate this host.");
1041 * If strict host key checking is in use, the user will have
1042 * to edit the key manually and we can only abort.
1044 if (options.strict_host_key_checking) {
1045 error("%s host key for %.200s was revoked and you have "
1046 "requested strict checking.", type, host);
1049 goto continue_unsafe;
1054 * This is only a debug() since it is valid to have
1055 * CAs with wildcard DNS matches that don't match
1056 * all hosts that one might visit.
1058 debug("Host certificate authority does not "
1059 "match %s in %s:%lu", CA_MARKER,
1060 host_found->file, host_found->line);
1063 if (readonly == ROQUIET)
1065 if (options.check_host_ip && host_ip_differ) {
1067 if (ip_status == HOST_NEW)
1068 key_msg = "is unknown";
1069 else if (ip_status == HOST_OK)
1070 key_msg = "is unchanged";
1072 key_msg = "has a different value";
1073 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1074 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
1075 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1076 error("The %s host key for %s has changed,", type, host);
1077 error("and the key for the corresponding IP address %s", ip);
1078 error("%s. This could either mean that", key_msg);
1079 error("DNS SPOOFING is happening or the IP address for the host");
1080 error("and its host key have changed at the same time.");
1081 if (ip_status != HOST_NEW)
1082 error("Offending key for IP in %s:%lu",
1083 ip_found->file, ip_found->line);
1085 /* The host key has changed. */
1086 warn_changed_key(host_key);
1087 error("Add correct host key in %.100s to get rid of this message.",
1089 error("Offending %s key in %s:%lu", key_type(host_found->key),
1090 host_found->file, host_found->line);
1093 * If strict host key checking is in use, the user will have
1094 * to edit the key manually and we can only abort.
1096 if (options.strict_host_key_checking) {
1097 error("%s host key for %.200s has changed and you have "
1098 "requested strict checking.", type, host);
1104 * If strict host key checking has not been requested, allow
1105 * the connection but without MITM-able authentication or
1108 if (options.password_authentication) {
1109 error("Password authentication is disabled to avoid "
1110 "man-in-the-middle attacks.");
1111 options.password_authentication = 0;
1112 cancelled_forwarding = 1;
1114 if (options.kbd_interactive_authentication) {
1115 error("Keyboard-interactive authentication is disabled"
1116 " to avoid man-in-the-middle attacks.");
1117 options.kbd_interactive_authentication = 0;
1118 options.challenge_response_authentication = 0;
1119 cancelled_forwarding = 1;
1121 if (options.challenge_response_authentication) {
1122 error("Challenge/response authentication is disabled"
1123 " to avoid man-in-the-middle attacks.");
1124 options.challenge_response_authentication = 0;
1125 cancelled_forwarding = 1;
1127 if (options.forward_agent) {
1128 error("Agent forwarding is disabled to avoid "
1129 "man-in-the-middle attacks.");
1130 options.forward_agent = 0;
1131 cancelled_forwarding = 1;
1133 if (options.forward_x11) {
1134 error("X11 forwarding is disabled to avoid "
1135 "man-in-the-middle attacks.");
1136 options.forward_x11 = 0;
1137 cancelled_forwarding = 1;
1139 if (options.num_local_forwards > 0 ||
1140 options.num_remote_forwards > 0) {
1141 error("Port forwarding is disabled to avoid "
1142 "man-in-the-middle attacks.");
1143 options.num_local_forwards =
1144 options.num_remote_forwards = 0;
1145 cancelled_forwarding = 1;
1147 if (options.tun_open != SSH_TUNMODE_NO) {
1148 error("Tunnel forwarding is disabled to avoid "
1149 "man-in-the-middle attacks.");
1150 options.tun_open = SSH_TUNMODE_NO;
1151 cancelled_forwarding = 1;
1153 if (options.exit_on_forward_failure && cancelled_forwarding)
1154 fatal("Error: forwarding disabled due to host key "
1158 * XXX Should permit the user to change to use the new id.
1159 * This could be done by converting the host key to an
1160 * identifying sentence, tell that the host identifies itself
1161 * by that sentence, and ask the user if he/she wishes to
1162 * accept the authentication.
1166 fatal("internal error");
1170 if (options.check_host_ip && host_status != HOST_CHANGED &&
1171 ip_status == HOST_CHANGED) {
1172 snprintf(msg, sizeof(msg),
1173 "Warning: the %s host key for '%.200s' "
1174 "differs from the key for the IP address '%.128s'"
1175 "\nOffending key for IP in %s:%lu",
1176 type, host, ip, ip_found->file, ip_found->line);
1177 if (host_status == HOST_OK) {
1179 snprintf(msg + len, sizeof(msg) - len,
1180 "\nMatching host key in %s:%lu",
1181 host_found->file, host_found->line);
1183 if (options.strict_host_key_checking == 1) {
1185 error("Exiting, you have requested strict checking.");
1187 } else if (options.strict_host_key_checking == 2) {
1188 strlcat(msg, "\nAre you sure you want "
1189 "to continue connecting (yes/no)? ", sizeof(msg));
1197 if (!hostkey_trusted && options.update_hostkeys) {
1198 debug("%s: hostkey not known or explicitly trusted: "
1199 "disabling UpdateHostkeys", __func__);
1200 options.update_hostkeys = 0;
1205 if (host_hostkeys != NULL)
1206 free_hostkeys(host_hostkeys);
1207 if (ip_hostkeys != NULL)
1208 free_hostkeys(ip_hostkeys);
1212 if (want_cert && host_status != HOST_REVOKED) {
1214 * No matching certificate. Downgrade cert to raw key and
1217 debug("No matching CA found. Retry with plain key");
1218 raw_key = key_from_private(host_key);
1219 if (key_drop_cert(raw_key) != 0)
1220 fatal("Couldn't drop certificate");
1224 if (raw_key != NULL)
1228 if (host_hostkeys != NULL)
1229 free_hostkeys(host_hostkeys);
1230 if (ip_hostkeys != NULL)
1231 free_hostkeys(ip_hostkeys);
1235 /* returns 0 if key verifies or -1 if key does NOT verify */
1237 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
1239 int r = -1, flags = 0;
1241 struct sshkey *plain = NULL;
1243 if ((fp = sshkey_fingerprint(host_key,
1244 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1245 error("%s: fingerprint host key: %s", __func__, ssh_err(r));
1250 debug("Server host key: %s %s",
1251 compat20 ? sshkey_ssh_name(host_key) : sshkey_type(host_key), fp);
1253 if (sshkey_equal(previous_host_key, host_key)) {
1254 debug2("%s: server host key %s %s matches cached key",
1255 __func__, sshkey_type(host_key), fp);
1260 /* Check in RevokedHostKeys file if specified */
1261 if (options.revoked_host_keys != NULL) {
1262 r = sshkey_check_revoked(host_key, options.revoked_host_keys);
1265 break; /* not revoked */
1266 case SSH_ERR_KEY_REVOKED:
1267 error("Host key %s %s revoked by file %s",
1268 sshkey_type(host_key), fp,
1269 options.revoked_host_keys);
1273 error("Error checking host key %s %s in "
1274 "revoked keys file %s: %s", sshkey_type(host_key),
1275 fp, options.revoked_host_keys, ssh_err(r));
1281 if (options.verify_host_key_dns) {
1283 * XXX certs are not yet supported for DNS, so downgrade
1284 * them and try the plain key.
1286 if ((r = sshkey_from_private(host_key, &plain)) != 0)
1288 if (sshkey_is_cert(plain))
1289 sshkey_drop_cert(plain);
1290 if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) {
1291 if (flags & DNS_VERIFY_FOUND) {
1292 if (options.verify_host_key_dns == 1 &&
1293 flags & DNS_VERIFY_MATCH &&
1294 flags & DNS_VERIFY_SECURE) {
1298 if (flags & DNS_VERIFY_MATCH) {
1299 matching_host_key_dns = 1;
1301 warn_changed_key(plain);
1302 error("Update the SSHFP RR in DNS "
1303 "with the new host key to get rid "
1304 "of this message.");
1309 r = check_host_key(host, hostaddr, options.port, host_key, RDRW,
1310 options.user_hostfiles, options.num_user_hostfiles,
1311 options.system_hostfiles, options.num_system_hostfiles);
1316 if (r == 0 && host_key != NULL) {
1317 key_free(previous_host_key);
1318 previous_host_key = key_from_private(host_key);
1325 * Starts a dialog with the server, and authenticates the current user on the
1326 * server. This does not need any extra privileges. The basic connection
1327 * to the server must already have been established before this is called.
1328 * If login fails, this function prints an error and never returns.
1329 * This function does not require super-user privileges.
1332 ssh_login(Sensitive *sensitive, const char *orighost,
1333 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms)
1336 char *server_user, *local_user;
1338 local_user = xstrdup(pw->pw_name);
1339 server_user = options.user ? options.user : local_user;
1341 /* Convert the user-supplied hostname into all lowercase. */
1342 host = xstrdup(orighost);
1345 /* Exchange protocol version identification strings with the server. */
1346 ssh_exchange_identification(timeout_ms);
1348 /* Put the connection into non-blocking mode. */
1349 packet_set_nonblocking();
1352 /* authenticate user */
1353 debug("Authenticating to %s:%d as '%s'", host, port, server_user);
1355 ssh_kex2(host, hostaddr, port);
1356 ssh_userauth2(local_user, server_user, host, sensitive);
1359 ssh_kex(host, hostaddr);
1360 ssh_userauth1(local_user, server_user, host, sensitive);
1362 fatal("ssh1 is not supported");
1369 ssh_put_password(char *password)
1374 if (datafellows & SSH_BUG_PASSWORDPAD) {
1375 packet_put_cstring(password);
1378 size = roundup(strlen(password) + 1, 32);
1379 padded = xcalloc(1, size);
1380 strlcpy(padded, password, size);
1381 packet_put_string(padded, size);
1382 explicit_bzero(padded, size);
1386 /* print all known host keys for a given host, but skip keys of given type */
1388 show_other_keys(struct hostkeys *hostkeys, Key *key)
1400 const struct hostkey_entry *found;
1402 for (i = 0; type[i] != -1; i++) {
1403 if (type[i] == key->type)
1405 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found))
1407 fp = sshkey_fingerprint(found->key,
1408 options.fingerprint_hash, SSH_FP_DEFAULT);
1409 ra = sshkey_fingerprint(found->key,
1410 options.fingerprint_hash, SSH_FP_RANDOMART);
1411 if (fp == NULL || ra == NULL)
1412 fatal("%s: sshkey_fingerprint fail", __func__);
1413 logit("WARNING: %s key found for host %s\n"
1415 "%s key fingerprint %s.",
1416 key_type(found->key),
1417 found->host, found->file, found->line,
1418 key_type(found->key), fp);
1419 if (options.visual_host_key)
1429 warn_changed_key(Key *host_key)
1433 fp = sshkey_fingerprint(host_key, options.fingerprint_hash,
1436 fatal("%s: sshkey_fingerprint fail", __func__);
1438 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1439 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1440 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1441 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1442 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1443 error("It is also possible that a host key has just been changed.");
1444 error("The fingerprint for the %s key sent by the remote host is\n%s.",
1445 key_type(host_key), fp);
1446 error("Please contact your system administrator.");
1452 * Execute a local command
1455 ssh_local_cmd(const char *args)
1460 void (*osighand)(int);
1462 if (!options.permit_local_command ||
1463 args == NULL || !*args)
1466 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
1467 shell = _PATH_BSHELL;
1469 osighand = signal(SIGCHLD, SIG_DFL);
1472 signal(SIGPIPE, SIG_DFL);
1473 debug3("Executing %s -c \"%s\"", shell, args);
1474 execl(shell, shell, "-c", args, (char *)NULL);
1475 error("Couldn't execute %s -c \"%s\": %s",
1476 shell, args, strerror(errno));
1478 } else if (pid == -1)
1479 fatal("fork failed: %.100s", strerror(errno));
1480 while (waitpid(pid, &status, 0) == -1)
1482 fatal("Couldn't wait for child: %s", strerror(errno));
1483 signal(SIGCHLD, osighand);
1485 if (!WIFEXITED(status))
1488 return (WEXITSTATUS(status));