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 * Creates a (possibly privileged) socket for use as the ssh connection.
271 ssh_create_socket(int privileged, struct addrinfo *ai)
274 struct addrinfo hints, *res = NULL;
276 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
278 error("socket: %s", strerror(errno));
281 fcntl(sock, F_SETFD, FD_CLOEXEC);
283 /* Bind the socket to an alternative local IP address */
284 if (options.bind_address == NULL && !privileged)
287 if (options.bind_address) {
288 memset(&hints, 0, sizeof(hints));
289 hints.ai_family = ai->ai_family;
290 hints.ai_socktype = ai->ai_socktype;
291 hints.ai_protocol = ai->ai_protocol;
292 hints.ai_flags = AI_PASSIVE;
293 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res);
295 error("getaddrinfo: %s: %s", options.bind_address,
296 ssh_gai_strerror(gaierr));
302 * If we are running as root and want to connect to a privileged
303 * port, bind our own socket to a privileged port.
307 r = bindresvport_sa(sock, res ? res->ai_addr : NULL);
310 error("bindresvport_sa: af=%d %s", ai->ai_family,
315 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
316 error("bind: %s: %s", options.bind_address,
330 timeout_connect(int sockfd, const struct sockaddr *serv_addr,
331 socklen_t addrlen, int *timeoutp)
334 struct timeval tv, t_start;
336 int optval, rc, result = -1;
338 gettimeofday(&t_start, NULL);
340 if (*timeoutp <= 0) {
341 result = connect(sockfd, serv_addr, addrlen);
345 set_nonblock(sockfd);
346 rc = connect(sockfd, serv_addr, addrlen);
348 unset_nonblock(sockfd);
352 if (errno != EINPROGRESS) {
357 fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS),
359 FD_SET(sockfd, fdset);
360 ms_to_timeval(&tv, *timeoutp);
363 rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
364 if (rc != -1 || errno != EINTR)
375 debug("select: %s", strerror(errno));
378 /* Completed or failed */
380 optlen = sizeof(optval);
381 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
383 debug("getsockopt: %s", strerror(errno));
391 unset_nonblock(sockfd);
394 /* Should not occur */
395 fatal("Bogus return (%d) from select()", rc);
401 if (result == 0 && *timeoutp > 0) {
402 ms_subtract_diff(&t_start, timeoutp);
403 if (*timeoutp <= 0) {
413 * Opens a TCP/IP connection to the remote server on the given host.
414 * The address of the remote host will be returned in hostaddr.
415 * If port is 0, the default port will be used. If needpriv is true,
416 * a privileged port will be allocated to make the connection.
417 * This requires super-user privileges if needpriv is true.
418 * Connection_attempts specifies the maximum number of tries (one per
419 * second). If proxy_command is non-NULL, it specifies the command (with %h
420 * and %p substituted for host and port, respectively) to use to contact
424 ssh_connect_direct(const char *host, struct addrinfo *aitop,
425 struct sockaddr_storage *hostaddr, u_short port, int family,
426 int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv)
429 int sock = -1, attempt;
430 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
433 debug2("ssh_connect: needpriv %d", needpriv);
435 for (attempt = 0; attempt < connection_attempts; attempt++) {
437 /* Sleep a moment before retrying. */
439 debug("Trying again...");
442 * Loop through addresses for this host, and try each one in
443 * sequence until the connection succeeds.
445 for (ai = aitop; ai; ai = ai->ai_next) {
446 if (ai->ai_family != AF_INET &&
447 ai->ai_family != AF_INET6)
449 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
450 ntop, sizeof(ntop), strport, sizeof(strport),
451 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
452 error("ssh_connect: getnameinfo failed");
455 debug("Connecting to %.200s [%.100s] port %s.",
456 host, ntop, strport);
458 /* Create a socket for connecting. */
459 sock = ssh_create_socket(needpriv, ai);
461 /* Any error is already output */
464 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
466 /* Successful connection. */
467 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
470 debug("connect to address %s port %s: %s",
471 ntop, strport, strerror(errno));
477 break; /* Successful connection. */
480 /* Return failure if we didn't get a successful connection. */
482 error("ssh: connect to host %s port %s: %s",
483 host, strport, strerror(errno));
487 debug("Connection established.");
489 /* Set SO_KEEPALIVE if requested. */
490 if (want_keepalive &&
491 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
493 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
495 /* Set the connection. */
496 packet_set_connection(sock, sock);
502 ssh_connect(const char *host, struct addrinfo *addrs,
503 struct sockaddr_storage *hostaddr, u_short port, int family,
504 int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv)
506 if (options.proxy_command == NULL) {
507 return ssh_connect_direct(host, addrs, hostaddr, port, family,
508 connection_attempts, timeout_ms, want_keepalive, needpriv);
509 } else if (strcmp(options.proxy_command, "-") == 0) {
510 packet_set_connection(STDIN_FILENO, STDOUT_FILENO);
511 return 0; /* Always succeeds */
512 } else if (options.proxy_use_fdpass) {
513 return ssh_proxy_fdpass_connect(host, port,
514 options.proxy_command);
516 return ssh_proxy_connect(host, port, options.proxy_command);
520 send_client_banner(int connection_out, int minor1)
522 /* Send our own protocol version identification. */
524 xasprintf(&client_version_string, "SSH-%d.%d-%.100s\r\n",
525 PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION);
527 xasprintf(&client_version_string, "SSH-%d.%d-%.100s\n",
528 PROTOCOL_MAJOR_1, minor1, SSH_VERSION);
530 if (roaming_atomicio(vwrite, connection_out, client_version_string,
531 strlen(client_version_string)) != strlen(client_version_string))
532 fatal("write: %.100s", strerror(errno));
533 chop(client_version_string);
534 debug("Local version string %.100s", client_version_string);
538 * Waits for the server identification string, and sends our own
539 * identification string.
542 ssh_exchange_identification(int timeout_ms)
544 char buf[256], remote_version[256]; /* must be same size! */
545 int remote_major, remote_minor, mismatch;
546 int connection_in = packet_get_connection_in();
547 int connection_out = packet_get_connection_out();
548 int minor1 = PROTOCOL_MINOR_1, client_banner_sent = 0;
551 int fdsetsz, remaining, rc;
552 struct timeval t_start, t_remaining;
555 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask);
556 fdset = xcalloc(1, fdsetsz);
559 * If we are SSH2-only then we can send the banner immediately and
562 if (options.protocol == SSH_PROTO_2) {
564 send_client_banner(connection_out, 0);
565 client_banner_sent = 1;
568 /* Read other side's version identification. */
569 remaining = timeout_ms;
571 for (i = 0; i < sizeof(buf) - 1; i++) {
572 if (timeout_ms > 0) {
573 gettimeofday(&t_start, NULL);
574 ms_to_timeval(&t_remaining, remaining);
575 FD_SET(connection_in, fdset);
576 rc = select(connection_in + 1, fdset, NULL,
577 fdset, &t_remaining);
578 ms_subtract_diff(&t_start, &remaining);
579 if (rc == 0 || remaining <= 0)
580 fatal("Connection timed out during "
585 fatal("ssh_exchange_identification: "
586 "select: %s", strerror(errno));
590 len = roaming_atomicio(read, connection_in, &buf[i], 1);
592 if (len != 1 && errno == EPIPE)
593 fatal("ssh_exchange_identification: "
594 "Connection closed by remote host");
596 fatal("ssh_exchange_identification: "
597 "read: %.100s", strerror(errno));
598 if (buf[i] == '\r') {
601 continue; /**XXX wait for \n */
603 if (buf[i] == '\n') {
608 fatal("ssh_exchange_identification: "
609 "No banner received");
611 buf[sizeof(buf) - 1] = 0;
612 if (strncmp(buf, "SSH-", 4) == 0)
614 debug("ssh_exchange_identification: %s", buf);
616 server_version_string = xstrdup(buf);
620 * Check that the versions match. In future this might accept
621 * several versions and set appropriate flags to handle them.
623 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
624 &remote_major, &remote_minor, remote_version) != 3)
625 fatal("Bad remote protocol version identification: '%.100s'", buf);
626 debug("Remote protocol version %d.%d, remote software version %.100s",
627 remote_major, remote_minor, remote_version);
629 compat_datafellows(remote_version);
632 switch (remote_major) {
634 if (remote_minor == 99 &&
635 (options.protocol & SSH_PROTO_2) &&
636 !(options.protocol & SSH_PROTO_1_PREFERRED)) {
640 if (!(options.protocol & SSH_PROTO_1)) {
644 if (remote_minor < 3) {
645 fatal("Remote machine has too old SSH software version.");
646 } else if (remote_minor == 3 || remote_minor == 4) {
647 /* We speak 1.3, too. */
650 if (options.forward_agent) {
651 logit("Agent forwarding disabled for protocol 1.3");
652 options.forward_agent = 0;
657 if (options.protocol & SSH_PROTO_2) {
667 fatal("Protocol major versions differ: %d vs. %d",
668 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
670 if ((datafellows & SSH_BUG_DERIVEKEY) != 0)
671 fatal("Server version \"%.100s\" uses unsafe key agreement; "
672 "refusing connection", remote_version);
673 if ((datafellows & SSH_BUG_RSASIGMD5) != 0)
674 logit("Server version \"%.100s\" uses unsafe RSA signature "
675 "scheme; disabling use of RSA keys", remote_version);
676 if (!client_banner_sent)
677 send_client_banner(connection_out, minor1);
678 chop(server_version_string);
681 /* defaults to 'no' */
683 confirm(const char *prompt)
685 const char *msg, *again = "Please type 'yes' or 'no': ";
689 if (options.batch_mode)
691 for (msg = prompt;;msg = again) {
692 p = read_passphrase(msg, RP_ECHO);
694 (p[0] == '\0') || (p[0] == '\n') ||
695 strncasecmp(p, "no", 2) == 0)
697 if (p && strncasecmp(p, "yes", 3) == 0)
706 check_host_cert(const char *host, const Key *host_key)
710 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) {
714 if (buffer_len(host_key->cert->critical) != 0) {
715 error("Certificate for %s contains unsupported "
716 "critical options(s)", host);
723 sockaddr_is_local(struct sockaddr *hostaddr)
725 switch (hostaddr->sa_family) {
727 return (ntohl(((struct sockaddr_in *)hostaddr)->
728 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
730 return IN6_IS_ADDR_LOOPBACK(
731 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
738 * Prepare the hostname and ip address strings that are used to lookup
739 * host keys in known_hosts files. These may have a port number appended.
742 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr,
743 u_short port, char **hostfile_hostname, char **hostfile_ipaddr)
745 char ntop[NI_MAXHOST];
748 switch (hostaddr == NULL ? -1 : hostaddr->sa_family) {
753 addrlen = sizeof(struct sockaddr_in);
756 addrlen = sizeof(struct sockaddr_in6);
759 addrlen = sizeof(struct sockaddr);
764 * We don't have the remote ip-address for connections
765 * using a proxy command
767 if (hostfile_ipaddr != NULL) {
768 if (options.proxy_command == NULL) {
769 if (getnameinfo(hostaddr, addrlen,
770 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0)
771 fatal("check_host_key: getnameinfo failed");
772 *hostfile_ipaddr = put_host_port(ntop, port);
774 *hostfile_ipaddr = xstrdup("<no hostip for proxy "
780 * Allow the user to record the key under a different name or
781 * differentiate a non-standard port. This is useful for ssh
782 * tunneling over forwarded connections or if you run multiple
783 * sshd's on different ports on the same machine.
785 if (hostfile_hostname != NULL) {
786 if (options.host_key_alias != NULL) {
787 *hostfile_hostname = xstrdup(options.host_key_alias);
788 debug("using hostkeyalias: %s", *hostfile_hostname);
790 *hostfile_hostname = put_host_port(hostname, port);
796 * check whether the supplied host key is valid, return -1 if the key
797 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true.
803 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
804 Key *host_key, int readonly,
805 char **user_hostfiles, u_int num_user_hostfiles,
806 char **system_hostfiles, u_int num_system_hostfiles)
808 HostStatus host_status;
809 HostStatus ip_status;
811 char *ip = NULL, *host = NULL;
812 char hostline[1000], *hostp, *fp, *ra;
815 const struct hostkey_entry *host_found, *ip_found;
816 int len, cancelled_forwarding = 0;
817 int local = sockaddr_is_local(hostaddr);
818 int r, want_cert = key_is_cert(host_key), host_ip_differ = 0;
819 struct hostkeys *host_hostkeys, *ip_hostkeys;
823 * Force accepting of the host key for loopback/localhost. The
824 * problem is that if the home directory is NFS-mounted to multiple
825 * machines, localhost will refer to a different machine in each of
826 * them, and the user will get bogus HOST_CHANGED warnings. This
827 * essentially disables host authentication for localhost; however,
828 * this is probably not a real problem.
830 if (options.no_host_authentication_for_localhost == 1 && local &&
831 options.host_key_alias == NULL) {
832 debug("Forcing accepting of host key for "
833 "loopback/localhost.");
838 * Prepare the hostname and address strings used for hostkey lookup.
839 * In some cases, these will have a port number appended.
841 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip);
844 * Turn off check_host_ip if the connection is to localhost, via proxy
845 * command or if we don't have a hostname to compare with
847 if (options.check_host_ip && (local ||
848 strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
849 options.check_host_ip = 0;
851 host_hostkeys = init_hostkeys();
852 for (i = 0; i < num_user_hostfiles; i++)
853 load_hostkeys(host_hostkeys, host, user_hostfiles[i]);
854 for (i = 0; i < num_system_hostfiles; i++)
855 load_hostkeys(host_hostkeys, host, system_hostfiles[i]);
858 if (!want_cert && options.check_host_ip) {
859 ip_hostkeys = init_hostkeys();
860 for (i = 0; i < num_user_hostfiles; i++)
861 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]);
862 for (i = 0; i < num_system_hostfiles; i++)
863 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]);
867 /* Reload these as they may have changed on cert->key downgrade */
868 want_cert = key_is_cert(host_key);
869 type = key_type(host_key);
872 * Check if the host key is present in the user's list of known
873 * hosts or in the systemwide list.
875 host_status = check_key_in_hostkeys(host_hostkeys, host_key,
879 * Also perform check for the ip address, skip the check if we are
880 * localhost, looking for a certificate, or the hostname was an ip
881 * address to begin with.
883 if (!want_cert && ip_hostkeys != NULL) {
884 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key,
886 if (host_status == HOST_CHANGED &&
887 (ip_status != HOST_CHANGED ||
889 !key_equal(ip_found->key, host_found->key))))
892 ip_status = host_status;
894 switch (host_status) {
896 /* The host is known and the key matches. */
897 debug("Host '%.200s' is known and matches the %s host %s.",
898 host, type, want_cert ? "certificate" : "key");
899 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key",
900 host_found->file, host_found->line);
901 if (want_cert && !check_host_cert(hostname, host_key))
903 if (options.check_host_ip && ip_status == HOST_NEW) {
904 if (readonly || want_cert)
905 logit("%s host key for IP address "
906 "'%.128s' not in list of known hosts.",
908 else if (!add_host_to_hostfile(user_hostfiles[0], ip,
909 host_key, options.hash_known_hosts))
910 logit("Failed to add the %s host key for IP "
911 "address '%.128s' to the list of known "
912 "hosts (%.30s).", type, ip,
915 logit("Warning: Permanently added the %s host "
916 "key for IP address '%.128s' to the list "
917 "of known hosts.", type, ip);
918 } else if (options.visual_host_key) {
919 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
920 ra = key_fingerprint(host_key, SSH_FP_MD5,
922 logit("Host key fingerprint is %s\n%s\n", fp, ra);
928 if (options.host_key_alias == NULL && port != 0 &&
929 port != SSH_DEFAULT_PORT) {
930 debug("checking without port identifier");
931 if (check_host_key(hostname, hostaddr, 0, host_key,
932 ROQUIET, user_hostfiles, num_user_hostfiles,
933 system_hostfiles, num_system_hostfiles) == 0) {
934 debug("found matching key w/out port");
938 if (readonly || want_cert)
940 /* The host is new. */
941 if (options.strict_host_key_checking == 1) {
943 * User has requested strict host key checking. We
944 * will not add the host key automatically. The only
945 * alternative left is to abort.
947 error("No %s host key is known for %.200s and you "
948 "have requested strict checking.", type, host);
950 } else if (options.strict_host_key_checking == 2) {
951 char msg1[1024], msg2[1024];
953 if (show_other_keys(host_hostkeys, host_key))
954 snprintf(msg1, sizeof(msg1),
955 "\nbut keys of different type are already"
956 " known for this host.");
958 snprintf(msg1, sizeof(msg1), ".");
960 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
961 ra = key_fingerprint(host_key, SSH_FP_MD5,
964 if (options.verify_host_key_dns) {
965 if (matching_host_key_dns)
966 snprintf(msg2, sizeof(msg2),
967 "Matching host key fingerprint"
970 snprintf(msg2, sizeof(msg2),
971 "No matching host key fingerprint"
974 snprintf(msg, sizeof(msg),
975 "The authenticity of host '%.200s (%s)' can't be "
977 "%s key fingerprint is %s.%s%s\n%s"
978 "Are you sure you want to continue connecting "
980 host, ip, msg1, type, fp,
981 options.visual_host_key ? "\n" : "",
982 options.visual_host_key ? ra : "",
990 * If not in strict mode, add the key automatically to the
991 * local known_hosts file.
993 if (options.check_host_ip && ip_status == HOST_NEW) {
994 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
996 if (options.hash_known_hosts) {
997 /* Add hash of host and IP separately */
998 r = add_host_to_hostfile(user_hostfiles[0],
999 host, host_key, options.hash_known_hosts) &&
1000 add_host_to_hostfile(user_hostfiles[0], ip,
1001 host_key, options.hash_known_hosts);
1003 /* Add unhashed "host,ip" */
1004 r = add_host_to_hostfile(user_hostfiles[0],
1006 options.hash_known_hosts);
1009 r = add_host_to_hostfile(user_hostfiles[0], host,
1010 host_key, options.hash_known_hosts);
1015 logit("Failed to add the host to the list of known "
1016 "hosts (%.500s).", user_hostfiles[0]);
1018 logit("Warning: Permanently added '%.200s' (%s) to the "
1019 "list of known hosts.", hostp, type);
1022 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1023 error("@ WARNING: REVOKED HOST KEY DETECTED! @");
1024 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1025 error("The %s host key for %s is marked as revoked.", type, host);
1026 error("This could mean that a stolen key is being used to");
1027 error("impersonate this host.");
1030 * If strict host key checking is in use, the user will have
1031 * to edit the key manually and we can only abort.
1033 if (options.strict_host_key_checking) {
1034 error("%s host key for %.200s was revoked and you have "
1035 "requested strict checking.", type, host);
1038 goto continue_unsafe;
1043 * This is only a debug() since it is valid to have
1044 * CAs with wildcard DNS matches that don't match
1045 * all hosts that one might visit.
1047 debug("Host certificate authority does not "
1048 "match %s in %s:%lu", CA_MARKER,
1049 host_found->file, host_found->line);
1052 if (readonly == ROQUIET)
1054 if (options.check_host_ip && host_ip_differ) {
1056 if (ip_status == HOST_NEW)
1057 key_msg = "is unknown";
1058 else if (ip_status == HOST_OK)
1059 key_msg = "is unchanged";
1061 key_msg = "has a different value";
1062 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1063 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
1064 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1065 error("The %s host key for %s has changed,", type, host);
1066 error("and the key for the corresponding IP address %s", ip);
1067 error("%s. This could either mean that", key_msg);
1068 error("DNS SPOOFING is happening or the IP address for the host");
1069 error("and its host key have changed at the same time.");
1070 if (ip_status != HOST_NEW)
1071 error("Offending key for IP in %s:%lu",
1072 ip_found->file, ip_found->line);
1074 /* The host key has changed. */
1075 warn_changed_key(host_key);
1076 error("Add correct host key in %.100s to get rid of this message.",
1078 error("Offending %s key in %s:%lu", key_type(host_found->key),
1079 host_found->file, host_found->line);
1082 * If strict host key checking is in use, the user will have
1083 * to edit the key manually and we can only abort.
1085 if (options.strict_host_key_checking) {
1086 error("%s host key for %.200s has changed and you have "
1087 "requested strict checking.", type, host);
1093 * If strict host key checking has not been requested, allow
1094 * the connection but without MITM-able authentication or
1097 if (options.password_authentication) {
1098 error("Password authentication is disabled to avoid "
1099 "man-in-the-middle attacks.");
1100 options.password_authentication = 0;
1101 cancelled_forwarding = 1;
1103 if (options.kbd_interactive_authentication) {
1104 error("Keyboard-interactive authentication is disabled"
1105 " to avoid man-in-the-middle attacks.");
1106 options.kbd_interactive_authentication = 0;
1107 options.challenge_response_authentication = 0;
1108 cancelled_forwarding = 1;
1110 if (options.challenge_response_authentication) {
1111 error("Challenge/response authentication is disabled"
1112 " to avoid man-in-the-middle attacks.");
1113 options.challenge_response_authentication = 0;
1114 cancelled_forwarding = 1;
1116 if (options.forward_agent) {
1117 error("Agent forwarding is disabled to avoid "
1118 "man-in-the-middle attacks.");
1119 options.forward_agent = 0;
1120 cancelled_forwarding = 1;
1122 if (options.forward_x11) {
1123 error("X11 forwarding is disabled to avoid "
1124 "man-in-the-middle attacks.");
1125 options.forward_x11 = 0;
1126 cancelled_forwarding = 1;
1128 if (options.num_local_forwards > 0 ||
1129 options.num_remote_forwards > 0) {
1130 error("Port forwarding is disabled to avoid "
1131 "man-in-the-middle attacks.");
1132 options.num_local_forwards =
1133 options.num_remote_forwards = 0;
1134 cancelled_forwarding = 1;
1136 if (options.tun_open != SSH_TUNMODE_NO) {
1137 error("Tunnel forwarding is disabled to avoid "
1138 "man-in-the-middle attacks.");
1139 options.tun_open = SSH_TUNMODE_NO;
1140 cancelled_forwarding = 1;
1142 if (options.exit_on_forward_failure && cancelled_forwarding)
1143 fatal("Error: forwarding disabled due to host key "
1147 * XXX Should permit the user to change to use the new id.
1148 * This could be done by converting the host key to an
1149 * identifying sentence, tell that the host identifies itself
1150 * by that sentence, and ask the user if he/she wishes to
1151 * accept the authentication.
1155 fatal("internal error");
1159 if (options.check_host_ip && host_status != HOST_CHANGED &&
1160 ip_status == HOST_CHANGED) {
1161 snprintf(msg, sizeof(msg),
1162 "Warning: the %s host key for '%.200s' "
1163 "differs from the key for the IP address '%.128s'"
1164 "\nOffending key for IP in %s:%lu",
1165 type, host, ip, ip_found->file, ip_found->line);
1166 if (host_status == HOST_OK) {
1168 snprintf(msg + len, sizeof(msg) - len,
1169 "\nMatching host key in %s:%lu",
1170 host_found->file, host_found->line);
1172 if (options.strict_host_key_checking == 1) {
1174 error("Exiting, you have requested strict checking.");
1176 } else if (options.strict_host_key_checking == 2) {
1177 strlcat(msg, "\nAre you sure you want "
1178 "to continue connecting (yes/no)? ", sizeof(msg));
1188 if (host_hostkeys != NULL)
1189 free_hostkeys(host_hostkeys);
1190 if (ip_hostkeys != NULL)
1191 free_hostkeys(ip_hostkeys);
1195 if (want_cert && host_status != HOST_REVOKED) {
1197 * No matching certificate. Downgrade cert to raw key and
1200 debug("No matching CA found. Retry with plain key");
1201 raw_key = key_from_private(host_key);
1202 if (key_drop_cert(raw_key) != 0)
1203 fatal("Couldn't drop certificate");
1207 if (raw_key != NULL)
1211 if (host_hostkeys != NULL)
1212 free_hostkeys(host_hostkeys);
1213 if (ip_hostkeys != NULL)
1214 free_hostkeys(ip_hostkeys);
1218 /* returns 0 if key verifies or -1 if key does NOT verify */
1220 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
1222 int r = -1, flags = 0;
1226 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1227 debug("Server host key: %s %s", key_type(host_key), fp);
1230 if (key_equal(previous_host_key, host_key)) {
1231 debug("%s: server host key matches cached key", __func__);
1235 if (options.verify_host_key_dns) {
1237 * XXX certs are not yet supported for DNS, so downgrade
1238 * them and try the plain key.
1240 plain = key_from_private(host_key);
1241 if (key_is_cert(plain))
1242 key_drop_cert(plain);
1243 if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) {
1244 if (flags & DNS_VERIFY_FOUND) {
1245 if (options.verify_host_key_dns == 1 &&
1246 flags & DNS_VERIFY_MATCH &&
1247 flags & DNS_VERIFY_SECURE) {
1252 if (flags & DNS_VERIFY_MATCH) {
1253 matching_host_key_dns = 1;
1255 warn_changed_key(plain);
1256 error("Update the SSHFP RR in DNS "
1257 "with the new host key to get rid "
1258 "of this message.");
1265 r = check_host_key(host, hostaddr, options.port, host_key, RDRW,
1266 options.user_hostfiles, options.num_user_hostfiles,
1267 options.system_hostfiles, options.num_system_hostfiles);
1270 if (r == 0 && host_key != NULL) {
1271 key_free(previous_host_key);
1272 previous_host_key = key_from_private(host_key);
1279 * Starts a dialog with the server, and authenticates the current user on the
1280 * server. This does not need any extra privileges. The basic connection
1281 * to the server must already have been established before this is called.
1282 * If login fails, this function prints an error and never returns.
1283 * This function does not require super-user privileges.
1286 ssh_login(Sensitive *sensitive, const char *orighost,
1287 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms)
1290 char *server_user, *local_user;
1292 local_user = xstrdup(pw->pw_name);
1293 server_user = options.user ? options.user : local_user;
1295 /* Convert the user-supplied hostname into all lowercase. */
1296 host = xstrdup(orighost);
1299 /* Exchange protocol version identification strings with the server. */
1300 ssh_exchange_identification(timeout_ms);
1302 /* Put the connection into non-blocking mode. */
1303 packet_set_nonblocking();
1306 /* authenticate user */
1308 ssh_kex2(host, hostaddr, port);
1309 ssh_userauth2(local_user, server_user, host, sensitive);
1312 ssh_kex(host, hostaddr);
1313 ssh_userauth1(local_user, server_user, host, sensitive);
1315 fatal("ssh1 is not unsupported");
1322 ssh_put_password(char *password)
1327 if (datafellows & SSH_BUG_PASSWORDPAD) {
1328 packet_put_cstring(password);
1331 size = roundup(strlen(password) + 1, 32);
1332 padded = xcalloc(1, size);
1333 strlcpy(padded, password, size);
1334 packet_put_string(padded, size);
1335 explicit_bzero(padded, size);
1339 /* print all known host keys for a given host, but skip keys of given type */
1341 show_other_keys(struct hostkeys *hostkeys, Key *key)
1353 const struct hostkey_entry *found;
1355 for (i = 0; type[i] != -1; i++) {
1356 if (type[i] == key->type)
1358 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found))
1360 fp = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_HEX);
1361 ra = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_RANDOMART);
1362 logit("WARNING: %s key found for host %s\n"
1364 "%s key fingerprint %s.",
1365 key_type(found->key),
1366 found->host, found->file, found->line,
1367 key_type(found->key), fp);
1368 if (options.visual_host_key)
1378 warn_changed_key(Key *host_key)
1382 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1384 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1385 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1386 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1387 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1388 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1389 error("It is also possible that a host key has just been changed.");
1390 error("The fingerprint for the %s key sent by the remote host is\n%s.",
1391 key_type(host_key), fp);
1392 error("Please contact your system administrator.");
1398 * Execute a local command
1401 ssh_local_cmd(const char *args)
1406 void (*osighand)(int);
1408 if (!options.permit_local_command ||
1409 args == NULL || !*args)
1412 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
1413 shell = _PATH_BSHELL;
1415 osighand = signal(SIGCHLD, SIG_DFL);
1418 signal(SIGPIPE, SIG_DFL);
1419 debug3("Executing %s -c \"%s\"", shell, args);
1420 execl(shell, shell, "-c", args, (char *)NULL);
1421 error("Couldn't execute %s -c \"%s\": %s",
1422 shell, args, strerror(errno));
1424 } else if (pid == -1)
1425 fatal("fork failed: %.100s", strerror(errno));
1426 while (waitpid(pid, &status, 0) == -1)
1428 fatal("Couldn't wait for child: %s", strerror(errno));
1429 signal(SIGCHLD, osighand);
1431 if (!WIFEXITED(status))
1434 return (WEXITSTATUS(status));