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>
55 #include "sshconnect.h"
63 #include "monitor_fdpass.h"
67 char *client_version_string = NULL;
68 char *server_version_string = NULL;
69 Key *previous_host_key = NULL;
71 static int matching_host_key_dns = 0;
73 static pid_t proxy_command_pid = 0;
76 extern Options options;
77 extern char *__progname;
78 extern uid_t original_real_uid;
79 extern uid_t original_effective_uid;
81 static int show_other_keys(struct hostkeys *, Key *);
82 static void warn_changed_key(Key *);
84 /* Expand a proxy command */
86 expand_proxy_command(const char *proxy_command, const char *user,
87 const char *host, int port)
89 char *tmp, *ret, strport[NI_MAXSERV];
91 snprintf(strport, sizeof strport, "%d", port);
92 xasprintf(&tmp, "exec %s", proxy_command);
93 ret = percent_expand(tmp, "h", host, "p", strport,
94 "r", options.user, (char *)NULL);
100 * Connect to the given ssh server using a proxy command that passes a
101 * a connected fd back to us.
104 ssh_proxy_fdpass_connect(const char *host, u_short port,
105 const char *proxy_command)
107 char *command_string;
112 if ((shell = getenv("SHELL")) == NULL)
113 shell = _PATH_BSHELL;
115 if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) < 0)
116 fatal("Could not create socketpair to communicate with "
117 "proxy dialer: %.100s", strerror(errno));
119 command_string = expand_proxy_command(proxy_command, options.user,
121 debug("Executing proxy dialer command: %.500s", command_string);
123 /* Fork and execute the proxy command. */
124 if ((pid = fork()) == 0) {
127 /* Child. Permanently give up superuser privileges. */
128 permanently_drop_suid(original_real_uid);
131 /* Redirect stdin and stdout. */
133 if (dup2(sp[0], 0) < 0)
134 perror("dup2 stdin");
137 if (dup2(sp[0], 1) < 0)
138 perror("dup2 stdout");
144 * Stderr is left as it is so that error messages get
145 * printed on the user's terminal.
149 argv[2] = command_string;
153 * Execute the proxy command.
154 * Note that we gave up any extra privileges above.
156 execv(argv[0], argv);
162 fatal("fork failed: %.100s", strerror(errno));
164 free(command_string);
166 if ((sock = mm_receive_fd(sp[1])) == -1)
167 fatal("proxy dialer did not pass back a connection");
169 while (waitpid(pid, NULL, 0) == -1)
171 fatal("Couldn't wait for child: %s", strerror(errno));
173 /* Set the connection file descriptors. */
174 packet_set_connection(sock, sock);
180 * Connect to the given ssh server using a proxy command.
183 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
185 char *command_string;
190 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
191 shell = _PATH_BSHELL;
193 /* Create pipes for communicating with the proxy. */
194 if (pipe(pin) < 0 || pipe(pout) < 0)
195 fatal("Could not create pipes to communicate with the proxy: %.100s",
198 command_string = expand_proxy_command(proxy_command, options.user,
200 debug("Executing proxy command: %.500s", command_string);
202 /* Fork and execute the proxy command. */
203 if ((pid = fork()) == 0) {
206 /* Child. Permanently give up superuser privileges. */
207 permanently_drop_suid(original_real_uid);
209 /* Redirect stdin and stdout. */
212 if (dup2(pin[0], 0) < 0)
213 perror("dup2 stdin");
217 if (dup2(pout[1], 1) < 0)
218 perror("dup2 stdout");
219 /* Cannot be 1 because pin allocated two descriptors. */
222 /* Stderr is left as it is so that error messages get
223 printed on the user's terminal. */
226 argv[2] = command_string;
229 /* Execute the proxy command. Note that we gave up any
230 extra privileges above. */
231 signal(SIGPIPE, SIG_DFL);
232 execv(argv[0], argv);
238 fatal("fork failed: %.100s", strerror(errno));
240 proxy_command_pid = pid; /* save pid to clean up later */
242 /* Close child side of the descriptors. */
246 /* Free the command name. */
247 free(command_string);
249 /* Set the connection file descriptors. */
250 packet_set_connection(pout[0], pin[1]);
252 /* Indicate OK return */
257 ssh_kill_proxy_command(void)
260 * Send SIGHUP to proxy command if used. We don't wait() in
261 * case it hangs and instead rely on init to reap the child
263 if (proxy_command_pid > 1)
264 kill(proxy_command_pid, SIGHUP);
268 * Set TCP receive buffer if requested.
269 * Note: tuning needs to happen after the socket is
270 * created but before the connection happens
271 * so winscale is negotiated properly -cjr
274 ssh_set_socket_recvbuf(int sock)
276 void *buf = (void *)&options.tcp_rcv_buf;
277 int sz = sizeof(options.tcp_rcv_buf);
279 int socksizelen = sizeof(int);
281 debug("setsockopt Attempting to set SO_RCVBUF to %d", options.tcp_rcv_buf);
282 if (setsockopt(sock, SOL_SOCKET, SO_RCVBUF, buf, sz) >= 0) {
283 getsockopt(sock, SOL_SOCKET, SO_RCVBUF, &socksize, &socksizelen);
284 debug("setsockopt SO_RCVBUF: %.100s %d", strerror(errno), socksize);
287 error("Couldn't set socket receive buffer to %d: %.100s",
288 options.tcp_rcv_buf, strerror(errno));
293 * Creates a (possibly privileged) socket for use as the ssh connection.
296 ssh_create_socket(int privileged, struct addrinfo *ai)
299 struct addrinfo hints, *res = NULL;
301 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
303 error("socket: %s", strerror(errno));
306 fcntl(sock, F_SETFD, FD_CLOEXEC);
308 if (options.tcp_rcv_buf > 0)
309 ssh_set_socket_recvbuf(sock);
311 /* Bind the socket to an alternative local IP address */
312 if (options.bind_address == NULL && !privileged)
315 if (options.bind_address) {
316 memset(&hints, 0, sizeof(hints));
317 hints.ai_family = ai->ai_family;
318 hints.ai_socktype = ai->ai_socktype;
319 hints.ai_protocol = ai->ai_protocol;
320 hints.ai_flags = AI_PASSIVE;
321 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res);
323 error("getaddrinfo: %s: %s", options.bind_address,
324 ssh_gai_strerror(gaierr));
330 * If we are running as root and want to connect to a privileged
331 * port, bind our own socket to a privileged port.
335 r = bindresvport_sa(sock, res ? res->ai_addr : NULL);
338 error("bindresvport_sa: af=%d %s", ai->ai_family,
343 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
344 error("bind: %s: %s", options.bind_address,
358 timeout_connect(int sockfd, const struct sockaddr *serv_addr,
359 socklen_t addrlen, int *timeoutp)
362 struct timeval tv, t_start;
364 int optval, rc, result = -1;
366 gettimeofday(&t_start, NULL);
368 if (*timeoutp <= 0) {
369 result = connect(sockfd, serv_addr, addrlen);
373 set_nonblock(sockfd);
374 rc = connect(sockfd, serv_addr, addrlen);
376 unset_nonblock(sockfd);
380 if (errno != EINPROGRESS) {
385 fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS),
387 FD_SET(sockfd, fdset);
388 ms_to_timeval(&tv, *timeoutp);
391 rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
392 if (rc != -1 || errno != EINTR)
403 debug("select: %s", strerror(errno));
406 /* Completed or failed */
408 optlen = sizeof(optval);
409 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
411 debug("getsockopt: %s", strerror(errno));
419 unset_nonblock(sockfd);
422 /* Should not occur */
423 fatal("Bogus return (%d) from select()", rc);
429 if (result == 0 && *timeoutp > 0) {
430 ms_subtract_diff(&t_start, timeoutp);
431 if (*timeoutp <= 0) {
441 * Opens a TCP/IP connection to the remote server on the given host.
442 * The address of the remote host will be returned in hostaddr.
443 * If port is 0, the default port will be used. If needpriv is true,
444 * a privileged port will be allocated to make the connection.
445 * This requires super-user privileges if needpriv is true.
446 * Connection_attempts specifies the maximum number of tries (one per
447 * second). If proxy_command is non-NULL, it specifies the command (with %h
448 * and %p substituted for host and port, respectively) to use to contact
452 ssh_connect_direct(const char *host, struct addrinfo *aitop,
453 struct sockaddr_storage *hostaddr, u_short port, int family,
454 int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv)
457 int sock = -1, attempt;
458 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
461 debug2("ssh_connect: needpriv %d", needpriv);
463 for (attempt = 0; attempt < connection_attempts; attempt++) {
465 /* Sleep a moment before retrying. */
467 debug("Trying again...");
470 * Loop through addresses for this host, and try each one in
471 * sequence until the connection succeeds.
473 for (ai = aitop; ai; ai = ai->ai_next) {
474 if (ai->ai_family != AF_INET &&
475 ai->ai_family != AF_INET6)
477 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
478 ntop, sizeof(ntop), strport, sizeof(strport),
479 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
480 error("ssh_connect: getnameinfo failed");
483 debug("Connecting to %.200s [%.100s] port %s.",
484 host, ntop, strport);
486 /* Create a socket for connecting. */
487 sock = ssh_create_socket(needpriv, ai);
489 /* Any error is already output */
492 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
494 /* Successful connection. */
495 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
498 debug("connect to address %s port %s: %s",
499 ntop, strport, strerror(errno));
505 break; /* Successful connection. */
508 /* Return failure if we didn't get a successful connection. */
510 error("ssh: connect to host %s port %s: %s",
511 host, strport, strerror(errno));
515 debug("Connection established.");
517 /* Set SO_KEEPALIVE if requested. */
518 if (want_keepalive &&
519 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
521 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
523 /* Set the connection. */
524 packet_set_connection(sock, sock);
530 ssh_connect(const char *host, struct addrinfo *addrs,
531 struct sockaddr_storage *hostaddr, u_short port, int family,
532 int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv)
534 if (options.proxy_command == NULL) {
535 return ssh_connect_direct(host, addrs, hostaddr, port, family,
536 connection_attempts, timeout_ms, want_keepalive, needpriv);
537 } else if (strcmp(options.proxy_command, "-") == 0) {
538 packet_set_connection(STDIN_FILENO, STDOUT_FILENO);
539 return 0; /* Always succeeds */
540 } else if (options.proxy_use_fdpass) {
541 return ssh_proxy_fdpass_connect(host, port,
542 options.proxy_command);
544 return ssh_proxy_connect(host, port, options.proxy_command);
548 send_client_banner(int connection_out, int minor1)
550 /* Send our own protocol version identification. */
552 xasprintf(&client_version_string, "SSH-%d.%d-%.100s\r\n",
553 PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_RELEASE);
555 xasprintf(&client_version_string, "SSH-%d.%d-%.100s\n",
556 PROTOCOL_MAJOR_1, minor1, SSH_RELEASE);
558 if (roaming_atomicio(vwrite, connection_out, client_version_string,
559 strlen(client_version_string)) != strlen(client_version_string))
560 fatal("write: %.100s", strerror(errno));
561 chop(client_version_string);
562 debug("Local version string %.100s", client_version_string);
566 * Waits for the server identification string, and sends our own
567 * identification string.
570 ssh_exchange_identification(int timeout_ms)
572 char buf[256], remote_version[256]; /* must be same size! */
573 int remote_major, remote_minor, mismatch;
574 int connection_in = packet_get_connection_in();
575 int connection_out = packet_get_connection_out();
576 int minor1 = PROTOCOL_MINOR_1, client_banner_sent = 0;
579 int fdsetsz, remaining, rc;
580 struct timeval t_start, t_remaining;
583 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask);
584 fdset = xcalloc(1, fdsetsz);
587 * If we are SSH2-only then we can send the banner immediately and
590 if (options.protocol == SSH_PROTO_2) {
592 send_client_banner(connection_out, 0);
593 client_banner_sent = 1;
596 /* Read other side's version identification. */
597 remaining = timeout_ms;
599 for (i = 0; i < sizeof(buf) - 1; i++) {
600 if (timeout_ms > 0) {
601 gettimeofday(&t_start, NULL);
602 ms_to_timeval(&t_remaining, remaining);
603 FD_SET(connection_in, fdset);
604 rc = select(connection_in + 1, fdset, NULL,
605 fdset, &t_remaining);
606 ms_subtract_diff(&t_start, &remaining);
607 if (rc == 0 || remaining <= 0)
608 fatal("Connection timed out during "
613 fatal("ssh_exchange_identification: "
614 "select: %s", strerror(errno));
618 len = roaming_atomicio(read, connection_in, &buf[i], 1);
620 if (len != 1 && errno == EPIPE)
621 fatal("ssh_exchange_identification: "
622 "Connection closed by remote host");
624 fatal("ssh_exchange_identification: "
625 "read: %.100s", strerror(errno));
626 if (buf[i] == '\r') {
629 continue; /**XXX wait for \n */
631 if (buf[i] == '\n') {
636 fatal("ssh_exchange_identification: "
637 "No banner received");
639 buf[sizeof(buf) - 1] = 0;
640 if (strncmp(buf, "SSH-", 4) == 0)
642 debug("ssh_exchange_identification: %s", buf);
644 server_version_string = xstrdup(buf);
648 * Check that the versions match. In future this might accept
649 * several versions and set appropriate flags to handle them.
651 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
652 &remote_major, &remote_minor, remote_version) != 3)
653 fatal("Bad remote protocol version identification: '%.100s'", buf);
654 debug("Remote protocol version %d.%d, remote software version %.100s",
655 remote_major, remote_minor, remote_version);
657 compat_datafellows(remote_version);
660 switch (remote_major) {
662 if (remote_minor == 99 &&
663 (options.protocol & SSH_PROTO_2) &&
664 !(options.protocol & SSH_PROTO_1_PREFERRED)) {
668 if (!(options.protocol & SSH_PROTO_1)) {
672 if (remote_minor < 3) {
673 fatal("Remote machine has too old SSH software version.");
674 } else if (remote_minor == 3 || remote_minor == 4) {
675 /* We speak 1.3, too. */
678 if (options.forward_agent) {
679 logit("Agent forwarding disabled for protocol 1.3");
680 options.forward_agent = 0;
685 if (options.protocol & SSH_PROTO_2) {
695 fatal("Protocol major versions differ: %d vs. %d",
696 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
698 if ((datafellows & SSH_BUG_DERIVEKEY) != 0)
699 fatal("Server version \"%.100s\" uses unsafe key agreement; "
700 "refusing connection", remote_version);
701 if ((datafellows & SSH_BUG_RSASIGMD5) != 0)
702 logit("Server version \"%.100s\" uses unsafe RSA signature "
703 "scheme; disabling use of RSA keys", remote_version);
704 if (!client_banner_sent)
705 send_client_banner(connection_out, minor1);
706 chop(server_version_string);
709 /* defaults to 'no' */
711 confirm(const char *prompt)
713 const char *msg, *again = "Please type 'yes' or 'no': ";
717 if (options.batch_mode)
719 for (msg = prompt;;msg = again) {
720 p = read_passphrase(msg, RP_ECHO);
722 (p[0] == '\0') || (p[0] == '\n') ||
723 strncasecmp(p, "no", 2) == 0)
725 if (p && strncasecmp(p, "yes", 3) == 0)
734 check_host_cert(const char *host, const Key *host_key)
738 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) {
742 if (buffer_len(host_key->cert->critical) != 0) {
743 error("Certificate for %s contains unsupported "
744 "critical options(s)", host);
751 sockaddr_is_local(struct sockaddr *hostaddr)
753 switch (hostaddr->sa_family) {
755 return (ntohl(((struct sockaddr_in *)hostaddr)->
756 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
758 return IN6_IS_ADDR_LOOPBACK(
759 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
766 * Prepare the hostname and ip address strings that are used to lookup
767 * host keys in known_hosts files. These may have a port number appended.
770 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr,
771 u_short port, char **hostfile_hostname, char **hostfile_ipaddr)
773 char ntop[NI_MAXHOST];
776 switch (hostaddr == NULL ? -1 : hostaddr->sa_family) {
781 addrlen = sizeof(struct sockaddr_in);
784 addrlen = sizeof(struct sockaddr_in6);
787 addrlen = sizeof(struct sockaddr);
792 * We don't have the remote ip-address for connections
793 * using a proxy command
795 if (hostfile_ipaddr != NULL) {
796 if (options.proxy_command == NULL) {
797 if (getnameinfo(hostaddr, addrlen,
798 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0)
799 fatal("check_host_key: getnameinfo failed");
800 *hostfile_ipaddr = put_host_port(ntop, port);
802 *hostfile_ipaddr = xstrdup("<no hostip for proxy "
808 * Allow the user to record the key under a different name or
809 * differentiate a non-standard port. This is useful for ssh
810 * tunneling over forwarded connections or if you run multiple
811 * sshd's on different ports on the same machine.
813 if (hostfile_hostname != NULL) {
814 if (options.host_key_alias != NULL) {
815 *hostfile_hostname = xstrdup(options.host_key_alias);
816 debug("using hostkeyalias: %s", *hostfile_hostname);
818 *hostfile_hostname = put_host_port(hostname, port);
824 * check whether the supplied host key is valid, return -1 if the key
825 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true.
831 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
832 Key *host_key, int readonly,
833 char **user_hostfiles, u_int num_user_hostfiles,
834 char **system_hostfiles, u_int num_system_hostfiles)
836 HostStatus host_status;
837 HostStatus ip_status;
839 char *ip = NULL, *host = NULL;
840 char hostline[1000], *hostp, *fp, *ra;
843 const struct hostkey_entry *host_found, *ip_found;
844 int len, cancelled_forwarding = 0;
845 int local = sockaddr_is_local(hostaddr);
846 int r, want_cert = key_is_cert(host_key), host_ip_differ = 0;
847 struct hostkeys *host_hostkeys, *ip_hostkeys;
851 * Force accepting of the host key for loopback/localhost. The
852 * problem is that if the home directory is NFS-mounted to multiple
853 * machines, localhost will refer to a different machine in each of
854 * them, and the user will get bogus HOST_CHANGED warnings. This
855 * essentially disables host authentication for localhost; however,
856 * this is probably not a real problem.
858 if (options.no_host_authentication_for_localhost == 1 && local &&
859 options.host_key_alias == NULL) {
860 debug("Forcing accepting of host key for "
861 "loopback/localhost.");
866 * Prepare the hostname and address strings used for hostkey lookup.
867 * In some cases, these will have a port number appended.
869 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip);
872 * Turn off check_host_ip if the connection is to localhost, via proxy
873 * command or if we don't have a hostname to compare with
875 if (options.check_host_ip && (local ||
876 strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
877 options.check_host_ip = 0;
879 host_hostkeys = init_hostkeys();
880 for (i = 0; i < num_user_hostfiles; i++)
881 load_hostkeys(host_hostkeys, host, user_hostfiles[i]);
882 for (i = 0; i < num_system_hostfiles; i++)
883 load_hostkeys(host_hostkeys, host, system_hostfiles[i]);
886 if (!want_cert && options.check_host_ip) {
887 ip_hostkeys = init_hostkeys();
888 for (i = 0; i < num_user_hostfiles; i++)
889 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]);
890 for (i = 0; i < num_system_hostfiles; i++)
891 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]);
895 /* Reload these as they may have changed on cert->key downgrade */
896 want_cert = key_is_cert(host_key);
897 type = key_type(host_key);
900 * Check if the host key is present in the user's list of known
901 * hosts or in the systemwide list.
903 host_status = check_key_in_hostkeys(host_hostkeys, host_key,
907 * Also perform check for the ip address, skip the check if we are
908 * localhost, looking for a certificate, or the hostname was an ip
909 * address to begin with.
911 if (!want_cert && ip_hostkeys != NULL) {
912 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key,
914 if (host_status == HOST_CHANGED &&
915 (ip_status != HOST_CHANGED ||
917 !key_equal(ip_found->key, host_found->key))))
920 ip_status = host_status;
922 switch (host_status) {
924 /* The host is known and the key matches. */
925 debug("Host '%.200s' is known and matches the %s host %s.",
926 host, type, want_cert ? "certificate" : "key");
927 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key",
928 host_found->file, host_found->line);
929 if (want_cert && !check_host_cert(hostname, host_key))
931 if (options.check_host_ip && ip_status == HOST_NEW) {
932 if (readonly || want_cert)
933 logit("%s host key for IP address "
934 "'%.128s' not in list of known hosts.",
936 else if (!add_host_to_hostfile(user_hostfiles[0], ip,
937 host_key, options.hash_known_hosts))
938 logit("Failed to add the %s host key for IP "
939 "address '%.128s' to the list of known "
940 "hosts (%.30s).", type, ip,
943 logit("Warning: Permanently added the %s host "
944 "key for IP address '%.128s' to the list "
945 "of known hosts.", type, ip);
946 } else if (options.visual_host_key) {
947 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
948 ra = key_fingerprint(host_key, SSH_FP_MD5,
950 logit("Host key fingerprint is %s\n%s\n", fp, ra);
956 if (options.host_key_alias == NULL && port != 0 &&
957 port != SSH_DEFAULT_PORT) {
958 debug("checking without port identifier");
959 if (check_host_key(hostname, hostaddr, 0, host_key,
960 ROQUIET, user_hostfiles, num_user_hostfiles,
961 system_hostfiles, num_system_hostfiles) == 0) {
962 debug("found matching key w/out port");
966 if (readonly || want_cert)
968 /* The host is new. */
969 if (options.strict_host_key_checking == 1) {
971 * User has requested strict host key checking. We
972 * will not add the host key automatically. The only
973 * alternative left is to abort.
975 error("No %s host key is known for %.200s and you "
976 "have requested strict checking.", type, host);
978 } else if (options.strict_host_key_checking == 2) {
979 char msg1[1024], msg2[1024];
981 if (show_other_keys(host_hostkeys, host_key))
982 snprintf(msg1, sizeof(msg1),
983 "\nbut keys of different type are already"
984 " known for this host.");
986 snprintf(msg1, sizeof(msg1), ".");
988 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
989 ra = key_fingerprint(host_key, SSH_FP_MD5,
992 if (options.verify_host_key_dns) {
993 if (matching_host_key_dns)
994 snprintf(msg2, sizeof(msg2),
995 "Matching host key fingerprint"
998 snprintf(msg2, sizeof(msg2),
999 "No matching host key fingerprint"
1000 " found in DNS.\n");
1002 snprintf(msg, sizeof(msg),
1003 "The authenticity of host '%.200s (%s)' can't be "
1005 "%s key fingerprint is %s.%s%s\n%s"
1006 "Are you sure you want to continue connecting "
1008 host, ip, msg1, type, fp,
1009 options.visual_host_key ? "\n" : "",
1010 options.visual_host_key ? ra : "",
1018 * If not in strict mode, add the key automatically to the
1019 * local known_hosts file.
1021 if (options.check_host_ip && ip_status == HOST_NEW) {
1022 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
1024 if (options.hash_known_hosts) {
1025 /* Add hash of host and IP separately */
1026 r = add_host_to_hostfile(user_hostfiles[0],
1027 host, host_key, options.hash_known_hosts) &&
1028 add_host_to_hostfile(user_hostfiles[0], ip,
1029 host_key, options.hash_known_hosts);
1031 /* Add unhashed "host,ip" */
1032 r = add_host_to_hostfile(user_hostfiles[0],
1034 options.hash_known_hosts);
1037 r = add_host_to_hostfile(user_hostfiles[0], host,
1038 host_key, options.hash_known_hosts);
1043 logit("Failed to add the host to the list of known "
1044 "hosts (%.500s).", user_hostfiles[0]);
1046 logit("Warning: Permanently added '%.200s' (%s) to the "
1047 "list of known hosts.", hostp, type);
1050 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1051 error("@ WARNING: REVOKED HOST KEY DETECTED! @");
1052 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1053 error("The %s host key for %s is marked as revoked.", type, host);
1054 error("This could mean that a stolen key is being used to");
1055 error("impersonate this host.");
1058 * If strict host key checking is in use, the user will have
1059 * to edit the key manually and we can only abort.
1061 if (options.strict_host_key_checking) {
1062 error("%s host key for %.200s was revoked and you have "
1063 "requested strict checking.", type, host);
1066 goto continue_unsafe;
1071 * This is only a debug() since it is valid to have
1072 * CAs with wildcard DNS matches that don't match
1073 * all hosts that one might visit.
1075 debug("Host certificate authority does not "
1076 "match %s in %s:%lu", CA_MARKER,
1077 host_found->file, host_found->line);
1080 if (readonly == ROQUIET)
1082 if (options.check_host_ip && host_ip_differ) {
1084 if (ip_status == HOST_NEW)
1085 key_msg = "is unknown";
1086 else if (ip_status == HOST_OK)
1087 key_msg = "is unchanged";
1089 key_msg = "has a different value";
1090 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1091 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
1092 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1093 error("The %s host key for %s has changed,", type, host);
1094 error("and the key for the corresponding IP address %s", ip);
1095 error("%s. This could either mean that", key_msg);
1096 error("DNS SPOOFING is happening or the IP address for the host");
1097 error("and its host key have changed at the same time.");
1098 if (ip_status != HOST_NEW)
1099 error("Offending key for IP in %s:%lu",
1100 ip_found->file, ip_found->line);
1102 /* The host key has changed. */
1103 warn_changed_key(host_key);
1104 error("Add correct host key in %.100s to get rid of this message.",
1106 error("Offending %s key in %s:%lu", key_type(host_found->key),
1107 host_found->file, host_found->line);
1110 * If strict host key checking is in use, the user will have
1111 * to edit the key manually and we can only abort.
1113 if (options.strict_host_key_checking) {
1114 error("%s host key for %.200s has changed and you have "
1115 "requested strict checking.", type, host);
1121 * If strict host key checking has not been requested, allow
1122 * the connection but without MITM-able authentication or
1125 if (options.password_authentication) {
1126 error("Password authentication is disabled to avoid "
1127 "man-in-the-middle attacks.");
1128 options.password_authentication = 0;
1129 cancelled_forwarding = 1;
1131 if (options.kbd_interactive_authentication) {
1132 error("Keyboard-interactive authentication is disabled"
1133 " to avoid man-in-the-middle attacks.");
1134 options.kbd_interactive_authentication = 0;
1135 options.challenge_response_authentication = 0;
1136 cancelled_forwarding = 1;
1138 if (options.challenge_response_authentication) {
1139 error("Challenge/response authentication is disabled"
1140 " to avoid man-in-the-middle attacks.");
1141 options.challenge_response_authentication = 0;
1142 cancelled_forwarding = 1;
1144 if (options.forward_agent) {
1145 error("Agent forwarding is disabled to avoid "
1146 "man-in-the-middle attacks.");
1147 options.forward_agent = 0;
1148 cancelled_forwarding = 1;
1150 if (options.forward_x11) {
1151 error("X11 forwarding is disabled to avoid "
1152 "man-in-the-middle attacks.");
1153 options.forward_x11 = 0;
1154 cancelled_forwarding = 1;
1156 if (options.num_local_forwards > 0 ||
1157 options.num_remote_forwards > 0) {
1158 error("Port forwarding is disabled to avoid "
1159 "man-in-the-middle attacks.");
1160 options.num_local_forwards =
1161 options.num_remote_forwards = 0;
1162 cancelled_forwarding = 1;
1164 if (options.tun_open != SSH_TUNMODE_NO) {
1165 error("Tunnel forwarding is disabled to avoid "
1166 "man-in-the-middle attacks.");
1167 options.tun_open = SSH_TUNMODE_NO;
1168 cancelled_forwarding = 1;
1170 if (options.exit_on_forward_failure && cancelled_forwarding)
1171 fatal("Error: forwarding disabled due to host key "
1175 * XXX Should permit the user to change to use the new id.
1176 * This could be done by converting the host key to an
1177 * identifying sentence, tell that the host identifies itself
1178 * by that sentence, and ask the user if he/she wishes to
1179 * accept the authentication.
1183 fatal("internal error");
1187 if (options.check_host_ip && host_status != HOST_CHANGED &&
1188 ip_status == HOST_CHANGED) {
1189 snprintf(msg, sizeof(msg),
1190 "Warning: the %s host key for '%.200s' "
1191 "differs from the key for the IP address '%.128s'"
1192 "\nOffending key for IP in %s:%lu",
1193 type, host, ip, ip_found->file, ip_found->line);
1194 if (host_status == HOST_OK) {
1196 snprintf(msg + len, sizeof(msg) - len,
1197 "\nMatching host key in %s:%lu",
1198 host_found->file, host_found->line);
1200 if (options.strict_host_key_checking == 1) {
1202 error("Exiting, you have requested strict checking.");
1204 } else if (options.strict_host_key_checking == 2) {
1205 strlcat(msg, "\nAre you sure you want "
1206 "to continue connecting (yes/no)? ", sizeof(msg));
1216 if (host_hostkeys != NULL)
1217 free_hostkeys(host_hostkeys);
1218 if (ip_hostkeys != NULL)
1219 free_hostkeys(ip_hostkeys);
1223 if (want_cert && host_status != HOST_REVOKED) {
1225 * No matching certificate. Downgrade cert to raw key and
1228 debug("No matching CA found. Retry with plain key");
1229 raw_key = key_from_private(host_key);
1230 if (key_drop_cert(raw_key) != 0)
1231 fatal("Couldn't drop certificate");
1235 if (raw_key != NULL)
1239 if (host_hostkeys != NULL)
1240 free_hostkeys(host_hostkeys);
1241 if (ip_hostkeys != NULL)
1242 free_hostkeys(ip_hostkeys);
1246 /* returns 0 if key verifies or -1 if key does NOT verify */
1248 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
1250 int r = -1, flags = 0;
1254 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1255 debug("Server host key: %s %s", key_type(host_key), fp);
1258 if (key_equal(previous_host_key, host_key)) {
1259 debug("%s: server host key matches cached key", __func__);
1263 if (options.verify_host_key_dns) {
1265 * XXX certs are not yet supported for DNS, so downgrade
1266 * them and try the plain key.
1268 plain = key_from_private(host_key);
1269 if (key_is_cert(plain))
1270 key_drop_cert(plain);
1271 if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) {
1272 if (flags & DNS_VERIFY_FOUND) {
1273 if (options.verify_host_key_dns == 1 &&
1274 flags & DNS_VERIFY_MATCH &&
1275 flags & DNS_VERIFY_SECURE) {
1280 if (flags & DNS_VERIFY_MATCH) {
1281 matching_host_key_dns = 1;
1283 warn_changed_key(plain);
1284 error("Update the SSHFP RR in DNS "
1285 "with the new host key to get rid "
1286 "of this message.");
1293 r = check_host_key(host, hostaddr, options.port, host_key, RDRW,
1294 options.user_hostfiles, options.num_user_hostfiles,
1295 options.system_hostfiles, options.num_system_hostfiles);
1298 if (r == 0 && host_key != NULL) {
1299 key_free(previous_host_key);
1300 previous_host_key = key_from_private(host_key);
1307 * Starts a dialog with the server, and authenticates the current user on the
1308 * server. This does not need any extra privileges. The basic connection
1309 * to the server must already have been established before this is called.
1310 * If login fails, this function prints an error and never returns.
1311 * This function does not require super-user privileges.
1314 ssh_login(Sensitive *sensitive, const char *orighost,
1315 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms)
1318 char *server_user, *local_user;
1320 local_user = xstrdup(pw->pw_name);
1321 server_user = options.user ? options.user : local_user;
1323 /* Convert the user-supplied hostname into all lowercase. */
1324 host = xstrdup(orighost);
1327 /* Exchange protocol version identification strings with the server. */
1328 ssh_exchange_identification(timeout_ms);
1330 /* Put the connection into non-blocking mode. */
1331 packet_set_nonblocking();
1334 /* authenticate user */
1336 ssh_kex2(host, hostaddr, port);
1337 ssh_userauth2(local_user, server_user, host, sensitive);
1340 ssh_kex(host, hostaddr);
1341 ssh_userauth1(local_user, server_user, host, sensitive);
1343 fatal("ssh1 is not unsupported");
1350 ssh_put_password(char *password)
1355 if (datafellows & SSH_BUG_PASSWORDPAD) {
1356 packet_put_cstring(password);
1359 size = roundup(strlen(password) + 1, 32);
1360 padded = xcalloc(1, size);
1361 strlcpy(padded, password, size);
1362 packet_put_string(padded, size);
1363 explicit_bzero(padded, size);
1367 /* print all known host keys for a given host, but skip keys of given type */
1369 show_other_keys(struct hostkeys *hostkeys, Key *key)
1381 const struct hostkey_entry *found;
1383 for (i = 0; type[i] != -1; i++) {
1384 if (type[i] == key->type)
1386 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found))
1388 fp = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_HEX);
1389 ra = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_RANDOMART);
1390 logit("WARNING: %s key found for host %s\n"
1392 "%s key fingerprint %s.",
1393 key_type(found->key),
1394 found->host, found->file, found->line,
1395 key_type(found->key), fp);
1396 if (options.visual_host_key)
1406 warn_changed_key(Key *host_key)
1410 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1412 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1413 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1414 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1415 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1416 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1417 error("It is also possible that a host key has just been changed.");
1418 error("The fingerprint for the %s key sent by the remote host is\n%s.",
1419 key_type(host_key), fp);
1420 error("Please contact your system administrator.");
1426 * Execute a local command
1429 ssh_local_cmd(const char *args)
1434 void (*osighand)(int);
1436 if (!options.permit_local_command ||
1437 args == NULL || !*args)
1440 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
1441 shell = _PATH_BSHELL;
1443 osighand = signal(SIGCHLD, SIG_DFL);
1446 signal(SIGPIPE, SIG_DFL);
1447 debug3("Executing %s -c \"%s\"", shell, args);
1448 execl(shell, shell, "-c", args, (char *)NULL);
1449 error("Couldn't execute %s -c \"%s\": %s",
1450 shell, args, strerror(errno));
1452 } else if (pid == -1)
1453 fatal("fork failed: %.100s", strerror(errno));
1454 while (waitpid(pid, &status, 0) == -1)
1456 fatal("Couldn't wait for child: %s", strerror(errno));
1457 signal(SIGCHLD, osighand);
1459 if (!WIFEXITED(status))
1462 return (WEXITSTATUS(status));