1 /* $OpenBSD: sshconnect.c,v 1.273 2017/03/10 03:22:40 dtucker Exp $ */
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
6 * Code to connect to a remote host, and to perform the client side of the
7 * login (authentication) dialog.
9 * As far as I am concerned, the code I have written for this software
10 * can be used freely for any purpose. Any derived versions of this
11 * software must be clearly marked as such, and if the derived work is
12 * incompatible with the protocol description in the RFC file, it must be
13 * called by a name other than "ssh" or "Secure Shell".
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>
56 #include "sshconnect.h"
63 #include "monitor_fdpass.h"
70 char *client_version_string = NULL;
71 char *server_version_string = NULL;
72 Key *previous_host_key = NULL;
74 static int matching_host_key_dns = 0;
76 static pid_t proxy_command_pid = 0;
79 extern Options options;
80 extern char *__progname;
81 extern uid_t original_real_uid;
82 extern uid_t original_effective_uid;
84 static int show_other_keys(struct hostkeys *, Key *);
85 static void warn_changed_key(Key *);
87 /* Expand a proxy command */
89 expand_proxy_command(const char *proxy_command, const char *user,
90 const char *host, int port)
92 char *tmp, *ret, strport[NI_MAXSERV];
94 snprintf(strport, sizeof strport, "%d", port);
95 xasprintf(&tmp, "exec %s", proxy_command);
96 ret = percent_expand(tmp, "h", host, "p", strport,
97 "r", options.user, (char *)NULL);
103 * Connect to the given ssh server using a proxy command that passes a
104 * a connected fd back to us.
107 ssh_proxy_fdpass_connect(const char *host, u_short port,
108 const char *proxy_command)
110 char *command_string;
115 if ((shell = getenv("SHELL")) == NULL)
116 shell = _PATH_BSHELL;
118 if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) < 0)
119 fatal("Could not create socketpair to communicate with "
120 "proxy dialer: %.100s", strerror(errno));
122 command_string = expand_proxy_command(proxy_command, options.user,
124 debug("Executing proxy dialer command: %.500s", command_string);
126 /* Fork and execute the proxy command. */
127 if ((pid = fork()) == 0) {
130 /* Child. Permanently give up superuser privileges. */
131 permanently_drop_suid(original_real_uid);
134 /* Redirect stdin and stdout. */
136 if (dup2(sp[0], 0) < 0)
137 perror("dup2 stdin");
140 if (dup2(sp[0], 1) < 0)
141 perror("dup2 stdout");
147 * Stderr is left as it is so that error messages get
148 * printed on the user's terminal.
152 argv[2] = command_string;
156 * Execute the proxy command.
157 * Note that we gave up any extra privileges above.
159 execv(argv[0], argv);
165 fatal("fork failed: %.100s", strerror(errno));
167 free(command_string);
169 if ((sock = mm_receive_fd(sp[1])) == -1)
170 fatal("proxy dialer did not pass back a connection");
173 while (waitpid(pid, NULL, 0) == -1)
175 fatal("Couldn't wait for child: %s", strerror(errno));
177 /* Set the connection file descriptors. */
178 packet_set_connection(sock, sock);
184 * Connect to the given ssh server using a proxy command.
187 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
189 char *command_string;
194 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
195 shell = _PATH_BSHELL;
197 /* Create pipes for communicating with the proxy. */
198 if (pipe(pin) < 0 || pipe(pout) < 0)
199 fatal("Could not create pipes to communicate with the proxy: %.100s",
202 command_string = expand_proxy_command(proxy_command, options.user,
204 debug("Executing proxy command: %.500s", command_string);
206 /* Fork and execute the proxy command. */
207 if ((pid = fork()) == 0) {
210 /* Child. Permanently give up superuser privileges. */
211 permanently_drop_suid(original_real_uid);
213 /* Redirect stdin and stdout. */
216 if (dup2(pin[0], 0) < 0)
217 perror("dup2 stdin");
221 if (dup2(pout[1], 1) < 0)
222 perror("dup2 stdout");
223 /* Cannot be 1 because pin allocated two descriptors. */
226 /* Stderr is left as it is so that error messages get
227 printed on the user's terminal. */
230 argv[2] = command_string;
233 /* Execute the proxy command. Note that we gave up any
234 extra privileges above. */
235 signal(SIGPIPE, SIG_DFL);
236 execv(argv[0], argv);
242 fatal("fork failed: %.100s", strerror(errno));
244 proxy_command_pid = pid; /* save pid to clean up later */
246 /* Close child side of the descriptors. */
250 /* Free the command name. */
251 free(command_string);
253 /* Set the connection file descriptors. */
254 packet_set_connection(pout[0], pin[1]);
256 /* Indicate OK return */
261 ssh_kill_proxy_command(void)
264 * Send SIGHUP to proxy command if used. We don't wait() in
265 * case it hangs and instead rely on init to reap the child
267 if (proxy_command_pid > 1)
268 kill(proxy_command_pid, SIGHUP);
272 * Creates a (possibly privileged) socket for use as the ssh connection.
275 ssh_create_socket(int privileged, struct addrinfo *ai)
278 struct addrinfo hints, *res = NULL;
280 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
282 error("socket: %s", strerror(errno));
285 fcntl(sock, F_SETFD, FD_CLOEXEC);
287 /* Bind the socket to an alternative local IP address */
288 if (options.bind_address == NULL && !privileged)
291 if (options.bind_address) {
292 memset(&hints, 0, sizeof(hints));
293 hints.ai_family = ai->ai_family;
294 hints.ai_socktype = ai->ai_socktype;
295 hints.ai_protocol = ai->ai_protocol;
296 hints.ai_flags = AI_PASSIVE;
297 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res);
299 error("getaddrinfo: %s: %s", options.bind_address,
300 ssh_gai_strerror(gaierr));
306 * If we are running as root and want to connect to a privileged
307 * port, bind our own socket to a privileged port.
311 r = bindresvport_sa(sock, res ? res->ai_addr : NULL);
314 error("bindresvport_sa: af=%d %s", ai->ai_family,
319 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
320 error("bind: %s: %s", options.bind_address,
334 timeout_connect(int sockfd, const struct sockaddr *serv_addr,
335 socklen_t addrlen, int *timeoutp)
338 struct timeval tv, t_start;
340 int optval, rc, result = -1;
342 gettimeofday(&t_start, NULL);
344 if (*timeoutp <= 0) {
345 result = connect(sockfd, serv_addr, addrlen);
349 set_nonblock(sockfd);
350 rc = connect(sockfd, serv_addr, addrlen);
352 unset_nonblock(sockfd);
356 if (errno != EINPROGRESS) {
361 fdset = xcalloc(howmany(sockfd + 1, NFDBITS),
363 FD_SET(sockfd, fdset);
364 ms_to_timeval(&tv, *timeoutp);
367 rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
368 if (rc != -1 || errno != EINTR)
379 debug("select: %s", strerror(errno));
382 /* Completed or failed */
384 optlen = sizeof(optval);
385 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
387 debug("getsockopt: %s", strerror(errno));
395 unset_nonblock(sockfd);
398 /* Should not occur */
399 fatal("Bogus return (%d) from select()", rc);
405 if (result == 0 && *timeoutp > 0) {
406 ms_subtract_diff(&t_start, timeoutp);
407 if (*timeoutp <= 0) {
417 * Opens a TCP/IP connection to the remote server on the given host.
418 * The address of the remote host will be returned in hostaddr.
419 * If port is 0, the default port will be used. If needpriv is true,
420 * a privileged port will be allocated to make the connection.
421 * This requires super-user privileges if needpriv is true.
422 * Connection_attempts specifies the maximum number of tries (one per
423 * second). If proxy_command is non-NULL, it specifies the command (with %h
424 * and %p substituted for host and port, respectively) to use to contact
428 ssh_connect_direct(const char *host, struct addrinfo *aitop,
429 struct sockaddr_storage *hostaddr, u_short port, int family,
430 int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv)
433 int sock = -1, attempt;
434 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
437 debug2("%s: needpriv %d", __func__, needpriv);
438 memset(ntop, 0, sizeof(ntop));
439 memset(strport, 0, sizeof(strport));
441 for (attempt = 0; attempt < connection_attempts; attempt++) {
443 /* Sleep a moment before retrying. */
445 debug("Trying again...");
448 * Loop through addresses for this host, and try each one in
449 * sequence until the connection succeeds.
451 for (ai = aitop; ai; ai = ai->ai_next) {
452 if (ai->ai_family != AF_INET &&
453 ai->ai_family != AF_INET6)
455 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
456 ntop, sizeof(ntop), strport, sizeof(strport),
457 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
458 error("%s: getnameinfo failed", __func__);
461 debug("Connecting to %.200s [%.100s] port %s.",
462 host, ntop, strport);
464 /* Create a socket for connecting. */
465 sock = ssh_create_socket(needpriv, ai);
467 /* Any error is already output */
470 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
472 /* Successful connection. */
473 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
476 debug("connect to address %s port %s: %s",
477 ntop, strport, strerror(errno));
483 break; /* Successful connection. */
486 /* Return failure if we didn't get a successful connection. */
488 error("ssh: connect to host %s port %s: %s",
489 host, strport, strerror(errno));
493 debug("Connection established.");
495 /* Set SO_KEEPALIVE if requested. */
496 if (want_keepalive &&
497 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
499 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
501 /* Set the connection. */
502 packet_set_connection(sock, sock);
508 ssh_connect(const char *host, struct addrinfo *addrs,
509 struct sockaddr_storage *hostaddr, u_short port, int family,
510 int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv)
512 if (options.proxy_command == NULL) {
513 return ssh_connect_direct(host, addrs, hostaddr, port, family,
514 connection_attempts, timeout_ms, want_keepalive, needpriv);
515 } else if (strcmp(options.proxy_command, "-") == 0) {
516 packet_set_connection(STDIN_FILENO, STDOUT_FILENO);
517 return 0; /* Always succeeds */
518 } else if (options.proxy_use_fdpass) {
519 return ssh_proxy_fdpass_connect(host, port,
520 options.proxy_command);
522 return ssh_proxy_connect(host, port, options.proxy_command);
526 send_client_banner(int connection_out, int minor1)
528 /* Send our own protocol version identification. */
529 xasprintf(&client_version_string, "SSH-%d.%d-%.100s%s%s%s",
530 compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
531 compat20 ? PROTOCOL_MINOR_2 : minor1,
533 *options.version_addendum == '\0' ? "" : " ",
534 options.version_addendum, compat20 ? "\r\n" : "\n");
535 if (atomicio(vwrite, connection_out, client_version_string,
536 strlen(client_version_string)) != strlen(client_version_string))
537 fatal("write: %.100s", strerror(errno));
538 chop(client_version_string);
539 debug("Local version string %.100s", client_version_string);
543 * Waits for the server identification string, and sends our own
544 * identification string.
547 ssh_exchange_identification(int timeout_ms)
549 char buf[256], remote_version[256]; /* must be same size! */
550 int remote_major, remote_minor, mismatch;
551 int connection_in = packet_get_connection_in();
552 int connection_out = packet_get_connection_out();
553 int minor1 = PROTOCOL_MINOR_1, client_banner_sent = 0;
556 int fdsetsz, remaining, rc;
557 struct timeval t_start, t_remaining;
560 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask);
561 fdset = xcalloc(1, fdsetsz);
564 * If we are SSH2-only then we can send the banner immediately and
567 if (options.protocol == SSH_PROTO_2) {
569 send_client_banner(connection_out, 0);
570 client_banner_sent = 1;
573 /* Read other side's version identification. */
574 remaining = timeout_ms;
576 for (i = 0; i < sizeof(buf) - 1; i++) {
577 if (timeout_ms > 0) {
578 gettimeofday(&t_start, NULL);
579 ms_to_timeval(&t_remaining, remaining);
580 FD_SET(connection_in, fdset);
581 rc = select(connection_in + 1, fdset, NULL,
582 fdset, &t_remaining);
583 ms_subtract_diff(&t_start, &remaining);
584 if (rc == 0 || remaining <= 0)
585 fatal("Connection timed out during "
590 fatal("ssh_exchange_identification: "
591 "select: %s", strerror(errno));
595 len = atomicio(read, connection_in, &buf[i], 1);
597 if (len != 1 && errno == EPIPE)
598 fatal("ssh_exchange_identification: "
599 "Connection closed by remote host");
601 fatal("ssh_exchange_identification: "
602 "read: %.100s", strerror(errno));
603 if (buf[i] == '\r') {
606 continue; /**XXX wait for \n */
608 if (buf[i] == '\n') {
613 fatal("ssh_exchange_identification: "
614 "No banner received");
616 buf[sizeof(buf) - 1] = 0;
617 if (strncmp(buf, "SSH-", 4) == 0)
619 debug("ssh_exchange_identification: %s", buf);
621 server_version_string = xstrdup(buf);
625 * Check that the versions match. In future this might accept
626 * several versions and set appropriate flags to handle them.
628 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
629 &remote_major, &remote_minor, remote_version) != 3)
630 fatal("Bad remote protocol version identification: '%.100s'", buf);
631 debug("Remote protocol version %d.%d, remote software version %.100s",
632 remote_major, remote_minor, remote_version);
634 active_state->compat = compat_datafellows(remote_version);
637 switch (remote_major) {
639 if (remote_minor == 99 &&
640 (options.protocol & SSH_PROTO_2) &&
641 !(options.protocol & SSH_PROTO_1_PREFERRED)) {
645 if (!(options.protocol & SSH_PROTO_1)) {
649 if (remote_minor < 3) {
650 fatal("Remote machine has too old SSH software version.");
651 } else if (remote_minor == 3 || remote_minor == 4) {
652 /* We speak 1.3, too. */
655 if (options.forward_agent) {
656 logit("Agent forwarding disabled for protocol 1.3");
657 options.forward_agent = 0;
662 if (options.protocol & SSH_PROTO_2) {
672 fatal("Protocol major versions differ: %d vs. %d",
673 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
675 if ((datafellows & SSH_BUG_DERIVEKEY) != 0)
676 fatal("Server version \"%.100s\" uses unsafe key agreement; "
677 "refusing connection", remote_version);
678 if ((datafellows & SSH_BUG_RSASIGMD5) != 0)
679 logit("Server version \"%.100s\" uses unsafe RSA signature "
680 "scheme; disabling use of RSA keys", remote_version);
681 if (!client_banner_sent)
682 send_client_banner(connection_out, minor1);
683 chop(server_version_string);
686 /* defaults to 'no' */
688 confirm(const char *prompt)
690 const char *msg, *again = "Please type 'yes' or 'no': ";
694 if (options.batch_mode)
696 for (msg = prompt;;msg = again) {
697 p = read_passphrase(msg, RP_ECHO);
699 (p[0] == '\0') || (p[0] == '\n') ||
700 strncasecmp(p, "no", 2) == 0)
702 if (p && strncasecmp(p, "yes", 3) == 0)
711 check_host_cert(const char *host, const Key *host_key)
715 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) {
719 if (buffer_len(host_key->cert->critical) != 0) {
720 error("Certificate for %s contains unsupported "
721 "critical options(s)", host);
728 sockaddr_is_local(struct sockaddr *hostaddr)
730 switch (hostaddr->sa_family) {
732 return (ntohl(((struct sockaddr_in *)hostaddr)->
733 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
735 return IN6_IS_ADDR_LOOPBACK(
736 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
743 * Prepare the hostname and ip address strings that are used to lookup
744 * host keys in known_hosts files. These may have a port number appended.
747 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr,
748 u_short port, char **hostfile_hostname, char **hostfile_ipaddr)
750 char ntop[NI_MAXHOST];
753 switch (hostaddr == NULL ? -1 : hostaddr->sa_family) {
758 addrlen = sizeof(struct sockaddr_in);
761 addrlen = sizeof(struct sockaddr_in6);
764 addrlen = sizeof(struct sockaddr);
769 * We don't have the remote ip-address for connections
770 * using a proxy command
772 if (hostfile_ipaddr != NULL) {
773 if (options.proxy_command == NULL) {
774 if (getnameinfo(hostaddr, addrlen,
775 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0)
776 fatal("%s: getnameinfo failed", __func__);
777 *hostfile_ipaddr = put_host_port(ntop, port);
779 *hostfile_ipaddr = xstrdup("<no hostip for proxy "
785 * Allow the user to record the key under a different name or
786 * differentiate a non-standard port. This is useful for ssh
787 * tunneling over forwarded connections or if you run multiple
788 * sshd's on different ports on the same machine.
790 if (hostfile_hostname != NULL) {
791 if (options.host_key_alias != NULL) {
792 *hostfile_hostname = xstrdup(options.host_key_alias);
793 debug("using hostkeyalias: %s", *hostfile_hostname);
795 *hostfile_hostname = put_host_port(hostname, port);
801 * check whether the supplied host key is valid, return -1 if the key
802 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true.
808 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
809 Key *host_key, int readonly,
810 char **user_hostfiles, u_int num_user_hostfiles,
811 char **system_hostfiles, u_int num_system_hostfiles)
813 HostStatus host_status;
814 HostStatus ip_status;
816 char *ip = NULL, *host = NULL;
817 char hostline[1000], *hostp, *fp, *ra;
820 const struct hostkey_entry *host_found, *ip_found;
821 int len, cancelled_forwarding = 0;
822 int local = sockaddr_is_local(hostaddr);
823 int r, want_cert = key_is_cert(host_key), host_ip_differ = 0;
824 int hostkey_trusted = 0; /* Known or explicitly accepted by user */
825 struct hostkeys *host_hostkeys, *ip_hostkeys;
829 * Force accepting of the host key for loopback/localhost. The
830 * problem is that if the home directory is NFS-mounted to multiple
831 * machines, localhost will refer to a different machine in each of
832 * them, and the user will get bogus HOST_CHANGED warnings. This
833 * essentially disables host authentication for localhost; however,
834 * this is probably not a real problem.
836 if (options.no_host_authentication_for_localhost == 1 && local &&
837 options.host_key_alias == NULL) {
838 debug("Forcing accepting of host key for "
839 "loopback/localhost.");
844 * Prepare the hostname and address strings used for hostkey lookup.
845 * In some cases, these will have a port number appended.
847 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip);
850 * Turn off check_host_ip if the connection is to localhost, via proxy
851 * command or if we don't have a hostname to compare with
853 if (options.check_host_ip && (local ||
854 strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
855 options.check_host_ip = 0;
857 host_hostkeys = init_hostkeys();
858 for (i = 0; i < num_user_hostfiles; i++)
859 load_hostkeys(host_hostkeys, host, user_hostfiles[i]);
860 for (i = 0; i < num_system_hostfiles; i++)
861 load_hostkeys(host_hostkeys, host, system_hostfiles[i]);
864 if (!want_cert && options.check_host_ip) {
865 ip_hostkeys = init_hostkeys();
866 for (i = 0; i < num_user_hostfiles; i++)
867 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]);
868 for (i = 0; i < num_system_hostfiles; i++)
869 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]);
873 /* Reload these as they may have changed on cert->key downgrade */
874 want_cert = key_is_cert(host_key);
875 type = key_type(host_key);
878 * Check if the host key is present in the user's list of known
879 * hosts or in the systemwide list.
881 host_status = check_key_in_hostkeys(host_hostkeys, host_key,
885 * Also perform check for the ip address, skip the check if we are
886 * localhost, looking for a certificate, or the hostname was an ip
887 * address to begin with.
889 if (!want_cert && ip_hostkeys != NULL) {
890 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key,
892 if (host_status == HOST_CHANGED &&
893 (ip_status != HOST_CHANGED ||
895 !key_equal(ip_found->key, host_found->key))))
898 ip_status = host_status;
900 switch (host_status) {
902 /* The host is known and the key matches. */
903 debug("Host '%.200s' is known and matches the %s host %s.",
904 host, type, want_cert ? "certificate" : "key");
905 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key",
906 host_found->file, host_found->line);
907 if (want_cert && !check_host_cert(hostname, host_key))
909 if (options.check_host_ip && ip_status == HOST_NEW) {
910 if (readonly || want_cert)
911 logit("%s host key for IP address "
912 "'%.128s' not in list of known hosts.",
914 else if (!add_host_to_hostfile(user_hostfiles[0], ip,
915 host_key, options.hash_known_hosts))
916 logit("Failed to add the %s host key for IP "
917 "address '%.128s' to the list of known "
918 "hosts (%.500s).", type, ip,
921 logit("Warning: Permanently added the %s host "
922 "key for IP address '%.128s' to the list "
923 "of known hosts.", type, ip);
924 } else if (options.visual_host_key) {
925 fp = sshkey_fingerprint(host_key,
926 options.fingerprint_hash, SSH_FP_DEFAULT);
927 ra = sshkey_fingerprint(host_key,
928 options.fingerprint_hash, SSH_FP_RANDOMART);
929 if (fp == NULL || ra == NULL)
930 fatal("%s: sshkey_fingerprint fail", __func__);
931 logit("Host key fingerprint is %s\n%s", fp, ra);
938 if (options.host_key_alias == NULL && port != 0 &&
939 port != SSH_DEFAULT_PORT) {
940 debug("checking without port identifier");
941 if (check_host_key(hostname, hostaddr, 0, host_key,
942 ROQUIET, user_hostfiles, num_user_hostfiles,
943 system_hostfiles, num_system_hostfiles) == 0) {
944 debug("found matching key w/out port");
948 if (readonly || want_cert)
950 /* The host is new. */
951 if (options.strict_host_key_checking == 1) {
953 * User has requested strict host key checking. We
954 * will not add the host key automatically. The only
955 * alternative left is to abort.
957 error("No %s host key is known for %.200s and you "
958 "have requested strict checking.", type, host);
960 } else if (options.strict_host_key_checking == 2) {
961 char msg1[1024], msg2[1024];
963 if (show_other_keys(host_hostkeys, host_key))
964 snprintf(msg1, sizeof(msg1),
965 "\nbut keys of different type are already"
966 " known for this host.");
968 snprintf(msg1, sizeof(msg1), ".");
970 fp = sshkey_fingerprint(host_key,
971 options.fingerprint_hash, SSH_FP_DEFAULT);
972 ra = sshkey_fingerprint(host_key,
973 options.fingerprint_hash, SSH_FP_RANDOMART);
974 if (fp == NULL || ra == NULL)
975 fatal("%s: sshkey_fingerprint fail", __func__);
977 if (options.verify_host_key_dns) {
978 if (matching_host_key_dns)
979 snprintf(msg2, sizeof(msg2),
980 "Matching host key fingerprint"
983 snprintf(msg2, sizeof(msg2),
984 "No matching host key fingerprint"
987 snprintf(msg, sizeof(msg),
988 "The authenticity of host '%.200s (%s)' can't be "
990 "%s key fingerprint is %s.%s%s\n%s"
991 "Are you sure you want to continue connecting "
993 host, ip, msg1, type, fp,
994 options.visual_host_key ? "\n" : "",
995 options.visual_host_key ? ra : "",
1001 hostkey_trusted = 1; /* user explicitly confirmed */
1004 * If not in strict mode, add the key automatically to the
1005 * local known_hosts file.
1007 if (options.check_host_ip && ip_status == HOST_NEW) {
1008 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
1010 if (options.hash_known_hosts) {
1011 /* Add hash of host and IP separately */
1012 r = add_host_to_hostfile(user_hostfiles[0],
1013 host, host_key, options.hash_known_hosts) &&
1014 add_host_to_hostfile(user_hostfiles[0], ip,
1015 host_key, options.hash_known_hosts);
1017 /* Add unhashed "host,ip" */
1018 r = add_host_to_hostfile(user_hostfiles[0],
1020 options.hash_known_hosts);
1023 r = add_host_to_hostfile(user_hostfiles[0], host,
1024 host_key, options.hash_known_hosts);
1029 logit("Failed to add the host to the list of known "
1030 "hosts (%.500s).", user_hostfiles[0]);
1032 logit("Warning: Permanently added '%.200s' (%s) to the "
1033 "list of known hosts.", hostp, type);
1036 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1037 error("@ WARNING: REVOKED HOST KEY DETECTED! @");
1038 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1039 error("The %s host key for %s is marked as revoked.", type, host);
1040 error("This could mean that a stolen key is being used to");
1041 error("impersonate this host.");
1044 * If strict host key checking is in use, the user will have
1045 * to edit the key manually and we can only abort.
1047 if (options.strict_host_key_checking) {
1048 error("%s host key for %.200s was revoked and you have "
1049 "requested strict checking.", type, host);
1052 goto continue_unsafe;
1057 * This is only a debug() since it is valid to have
1058 * CAs with wildcard DNS matches that don't match
1059 * all hosts that one might visit.
1061 debug("Host certificate authority does not "
1062 "match %s in %s:%lu", CA_MARKER,
1063 host_found->file, host_found->line);
1066 if (readonly == ROQUIET)
1068 if (options.check_host_ip && host_ip_differ) {
1070 if (ip_status == HOST_NEW)
1071 key_msg = "is unknown";
1072 else if (ip_status == HOST_OK)
1073 key_msg = "is unchanged";
1075 key_msg = "has a different value";
1076 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1077 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
1078 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1079 error("The %s host key for %s has changed,", type, host);
1080 error("and the key for the corresponding IP address %s", ip);
1081 error("%s. This could either mean that", key_msg);
1082 error("DNS SPOOFING is happening or the IP address for the host");
1083 error("and its host key have changed at the same time.");
1084 if (ip_status != HOST_NEW)
1085 error("Offending key for IP in %s:%lu",
1086 ip_found->file, ip_found->line);
1088 /* The host key has changed. */
1089 warn_changed_key(host_key);
1090 error("Add correct host key in %.100s to get rid of this message.",
1092 error("Offending %s key in %s:%lu", key_type(host_found->key),
1093 host_found->file, host_found->line);
1096 * If strict host key checking is in use, the user will have
1097 * to edit the key manually and we can only abort.
1099 if (options.strict_host_key_checking) {
1100 error("%s host key for %.200s has changed and you have "
1101 "requested strict checking.", type, host);
1107 * If strict host key checking has not been requested, allow
1108 * the connection but without MITM-able authentication or
1111 if (options.password_authentication) {
1112 error("Password authentication is disabled to avoid "
1113 "man-in-the-middle attacks.");
1114 options.password_authentication = 0;
1115 cancelled_forwarding = 1;
1117 if (options.kbd_interactive_authentication) {
1118 error("Keyboard-interactive authentication is disabled"
1119 " to avoid man-in-the-middle attacks.");
1120 options.kbd_interactive_authentication = 0;
1121 options.challenge_response_authentication = 0;
1122 cancelled_forwarding = 1;
1124 if (options.challenge_response_authentication) {
1125 error("Challenge/response authentication is disabled"
1126 " to avoid man-in-the-middle attacks.");
1127 options.challenge_response_authentication = 0;
1128 cancelled_forwarding = 1;
1130 if (options.forward_agent) {
1131 error("Agent forwarding is disabled to avoid "
1132 "man-in-the-middle attacks.");
1133 options.forward_agent = 0;
1134 cancelled_forwarding = 1;
1136 if (options.forward_x11) {
1137 error("X11 forwarding is disabled to avoid "
1138 "man-in-the-middle attacks.");
1139 options.forward_x11 = 0;
1140 cancelled_forwarding = 1;
1142 if (options.num_local_forwards > 0 ||
1143 options.num_remote_forwards > 0) {
1144 error("Port forwarding is disabled to avoid "
1145 "man-in-the-middle attacks.");
1146 options.num_local_forwards =
1147 options.num_remote_forwards = 0;
1148 cancelled_forwarding = 1;
1150 if (options.tun_open != SSH_TUNMODE_NO) {
1151 error("Tunnel forwarding is disabled to avoid "
1152 "man-in-the-middle attacks.");
1153 options.tun_open = SSH_TUNMODE_NO;
1154 cancelled_forwarding = 1;
1156 if (options.exit_on_forward_failure && cancelled_forwarding)
1157 fatal("Error: forwarding disabled due to host key "
1161 * XXX Should permit the user to change to use the new id.
1162 * This could be done by converting the host key to an
1163 * identifying sentence, tell that the host identifies itself
1164 * by that sentence, and ask the user if he/she wishes to
1165 * accept the authentication.
1169 fatal("internal error");
1173 if (options.check_host_ip && host_status != HOST_CHANGED &&
1174 ip_status == HOST_CHANGED) {
1175 snprintf(msg, sizeof(msg),
1176 "Warning: the %s host key for '%.200s' "
1177 "differs from the key for the IP address '%.128s'"
1178 "\nOffending key for IP in %s:%lu",
1179 type, host, ip, ip_found->file, ip_found->line);
1180 if (host_status == HOST_OK) {
1182 snprintf(msg + len, sizeof(msg) - len,
1183 "\nMatching host key in %s:%lu",
1184 host_found->file, host_found->line);
1186 if (options.strict_host_key_checking == 1) {
1188 error("Exiting, you have requested strict checking.");
1190 } else if (options.strict_host_key_checking == 2) {
1191 strlcat(msg, "\nAre you sure you want "
1192 "to continue connecting (yes/no)? ", sizeof(msg));
1200 if (!hostkey_trusted && options.update_hostkeys) {
1201 debug("%s: hostkey not known or explicitly trusted: "
1202 "disabling UpdateHostkeys", __func__);
1203 options.update_hostkeys = 0;
1208 if (host_hostkeys != NULL)
1209 free_hostkeys(host_hostkeys);
1210 if (ip_hostkeys != NULL)
1211 free_hostkeys(ip_hostkeys);
1215 if (want_cert && host_status != HOST_REVOKED) {
1217 * No matching certificate. Downgrade cert to raw key and
1220 debug("No matching CA found. Retry with plain key");
1221 raw_key = key_from_private(host_key);
1222 if (key_drop_cert(raw_key) != 0)
1223 fatal("Couldn't drop certificate");
1227 if (raw_key != NULL)
1231 if (host_hostkeys != NULL)
1232 free_hostkeys(host_hostkeys);
1233 if (ip_hostkeys != NULL)
1234 free_hostkeys(ip_hostkeys);
1238 /* returns 0 if key verifies or -1 if key does NOT verify */
1240 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
1243 int r = -1, flags = 0;
1244 char valid[64], *fp = NULL, *cafp = NULL;
1245 struct sshkey *plain = NULL;
1247 if ((fp = sshkey_fingerprint(host_key,
1248 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1249 error("%s: fingerprint host key: %s", __func__, ssh_err(r));
1254 if (sshkey_is_cert(host_key)) {
1255 if ((cafp = sshkey_fingerprint(host_key->cert->signature_key,
1256 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1257 error("%s: fingerprint CA key: %s",
1258 __func__, ssh_err(r));
1262 sshkey_format_cert_validity(host_key->cert,
1263 valid, sizeof(valid));
1264 debug("Server host certificate: %s %s, serial %llu "
1265 "ID \"%s\" CA %s %s valid %s",
1266 sshkey_ssh_name(host_key), fp,
1267 (unsigned long long)host_key->cert->serial,
1268 host_key->cert->key_id,
1269 sshkey_ssh_name(host_key->cert->signature_key), cafp,
1271 for (i = 0; i < host_key->cert->nprincipals; i++) {
1272 debug2("Server host certificate hostname: %s",
1273 host_key->cert->principals[i]);
1276 debug("Server host key: %s %s", compat20 ?
1277 sshkey_ssh_name(host_key) : sshkey_type(host_key), fp);
1280 if (sshkey_equal(previous_host_key, host_key)) {
1281 debug2("%s: server host key %s %s matches cached key",
1282 __func__, sshkey_type(host_key), fp);
1287 /* Check in RevokedHostKeys file if specified */
1288 if (options.revoked_host_keys != NULL) {
1289 r = sshkey_check_revoked(host_key, options.revoked_host_keys);
1292 break; /* not revoked */
1293 case SSH_ERR_KEY_REVOKED:
1294 error("Host key %s %s revoked by file %s",
1295 sshkey_type(host_key), fp,
1296 options.revoked_host_keys);
1300 error("Error checking host key %s %s in "
1301 "revoked keys file %s: %s", sshkey_type(host_key),
1302 fp, options.revoked_host_keys, ssh_err(r));
1308 if (options.verify_host_key_dns) {
1310 * XXX certs are not yet supported for DNS, so downgrade
1311 * them and try the plain key.
1313 if ((r = sshkey_from_private(host_key, &plain)) != 0)
1315 if (sshkey_is_cert(plain))
1316 sshkey_drop_cert(plain);
1317 if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) {
1318 if (flags & DNS_VERIFY_FOUND) {
1319 if (options.verify_host_key_dns == 1 &&
1320 flags & DNS_VERIFY_MATCH &&
1321 flags & DNS_VERIFY_SECURE) {
1325 if (flags & DNS_VERIFY_MATCH) {
1326 matching_host_key_dns = 1;
1328 warn_changed_key(plain);
1329 error("Update the SSHFP RR in DNS "
1330 "with the new host key to get rid "
1331 "of this message.");
1336 r = check_host_key(host, hostaddr, options.port, host_key, RDRW,
1337 options.user_hostfiles, options.num_user_hostfiles,
1338 options.system_hostfiles, options.num_system_hostfiles);
1344 if (r == 0 && host_key != NULL) {
1345 key_free(previous_host_key);
1346 previous_host_key = key_from_private(host_key);
1353 * Starts a dialog with the server, and authenticates the current user on the
1354 * server. This does not need any extra privileges. The basic connection
1355 * to the server must already have been established before this is called.
1356 * If login fails, this function prints an error and never returns.
1357 * This function does not require super-user privileges.
1360 ssh_login(Sensitive *sensitive, const char *orighost,
1361 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms)
1364 char *server_user, *local_user;
1366 local_user = xstrdup(pw->pw_name);
1367 server_user = options.user ? options.user : local_user;
1369 /* Convert the user-supplied hostname into all lowercase. */
1370 host = xstrdup(orighost);
1373 /* Exchange protocol version identification strings with the server. */
1374 ssh_exchange_identification(timeout_ms);
1376 /* Put the connection into non-blocking mode. */
1377 packet_set_nonblocking();
1380 /* authenticate user */
1381 debug("Authenticating to %s:%d as '%s'", host, port, server_user);
1383 ssh_kex2(host, hostaddr, port);
1384 ssh_userauth2(local_user, server_user, host, sensitive);
1387 ssh_kex(host, hostaddr);
1388 ssh_userauth1(local_user, server_user, host, sensitive);
1390 fatal("ssh1 is not supported");
1397 ssh_put_password(char *password)
1402 if (datafellows & SSH_BUG_PASSWORDPAD) {
1403 packet_put_cstring(password);
1406 size = ROUNDUP(strlen(password) + 1, 32);
1407 padded = xcalloc(1, size);
1408 strlcpy(padded, password, size);
1409 packet_put_string(padded, size);
1410 explicit_bzero(padded, size);
1414 /* print all known host keys for a given host, but skip keys of given type */
1416 show_other_keys(struct hostkeys *hostkeys, Key *key)
1428 const struct hostkey_entry *found;
1430 for (i = 0; type[i] != -1; i++) {
1431 if (type[i] == key->type)
1433 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found))
1435 fp = sshkey_fingerprint(found->key,
1436 options.fingerprint_hash, SSH_FP_DEFAULT);
1437 ra = sshkey_fingerprint(found->key,
1438 options.fingerprint_hash, SSH_FP_RANDOMART);
1439 if (fp == NULL || ra == NULL)
1440 fatal("%s: sshkey_fingerprint fail", __func__);
1441 logit("WARNING: %s key found for host %s\n"
1443 "%s key fingerprint %s.",
1444 key_type(found->key),
1445 found->host, found->file, found->line,
1446 key_type(found->key), fp);
1447 if (options.visual_host_key)
1457 warn_changed_key(Key *host_key)
1461 fp = sshkey_fingerprint(host_key, options.fingerprint_hash,
1464 fatal("%s: sshkey_fingerprint fail", __func__);
1466 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1467 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1468 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1469 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1470 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1471 error("It is also possible that a host key has just been changed.");
1472 error("The fingerprint for the %s key sent by the remote host is\n%s.",
1473 key_type(host_key), fp);
1474 error("Please contact your system administrator.");
1480 * Execute a local command
1483 ssh_local_cmd(const char *args)
1488 void (*osighand)(int);
1490 if (!options.permit_local_command ||
1491 args == NULL || !*args)
1494 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
1495 shell = _PATH_BSHELL;
1497 osighand = signal(SIGCHLD, SIG_DFL);
1500 signal(SIGPIPE, SIG_DFL);
1501 debug3("Executing %s -c \"%s\"", shell, args);
1502 execl(shell, shell, "-c", args, (char *)NULL);
1503 error("Couldn't execute %s -c \"%s\": %s",
1504 shell, args, strerror(errno));
1506 } else if (pid == -1)
1507 fatal("fork failed: %.100s", strerror(errno));
1508 while (waitpid(pid, &status, 0) == -1)
1510 fatal("Couldn't wait for child: %s", strerror(errno));
1511 signal(SIGCHLD, osighand);
1513 if (!WIFEXITED(status))
1516 return (WEXITSTATUS(status));
1520 maybe_add_key_to_agent(char *authfile, Key *private, char *comment,
1523 int auth_sock = -1, r;
1525 if (options.add_keys_to_agent == 0)
1528 if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) {
1529 debug3("no authentication agent, not adding key");
1533 if (options.add_keys_to_agent == 2 &&
1534 !ask_permission("Add key %s (%s) to agent?", authfile, comment)) {
1535 debug3("user denied adding this key");
1540 if ((r = ssh_add_identity_constrained(auth_sock, private, comment, 0,
1541 (options.add_keys_to_agent == 3))) == 0)
1542 debug("identity added to agent: %s", authfile);
1544 debug("could not add identity to agent: %s (%d)", authfile, r);