1 /* $OpenBSD: sshconnect.c,v 1.237 2013/02/22 19:13:56 markus Exp $ */
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
6 * Code to connect to a remote host, and to perform the client side of the
7 * login (authentication) dialog.
9 * As far as I am concerned, the code I have written for this software
10 * can be used freely for any purpose. Any derived versions of this
11 * software must be clearly marked as such, and if the derived work is
12 * incompatible with the protocol description in the RFC file, it must be
13 * called by a name other than "ssh" or "Secure Shell".
18 #include <sys/types.h>
21 #include <sys/socket.h>
22 #ifdef HAVE_SYS_TIME_H
23 # include <sys/time.h>
26 #include <netinet/in.h>
27 #include <arpa/inet.h>
54 #include "sshconnect.h"
65 char *client_version_string = NULL;
66 char *server_version_string = NULL;
68 static int matching_host_key_dns = 0;
70 static pid_t proxy_command_pid = 0;
73 extern Options options;
74 extern char *__progname;
75 extern uid_t original_real_uid;
76 extern uid_t original_effective_uid;
78 static int show_other_keys(struct hostkeys *, Key *);
79 static void warn_changed_key(Key *);
82 * Connect to the given ssh server using a proxy command.
85 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
87 char *command_string, *tmp;
90 char *shell, strport[NI_MAXSERV];
92 if (!strcmp(proxy_command, "-")) {
93 packet_set_connection(STDIN_FILENO, STDOUT_FILENO);
94 packet_set_timeout(options.server_alive_interval,
95 options.server_alive_count_max);
99 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
100 shell = _PATH_BSHELL;
102 /* Convert the port number into a string. */
103 snprintf(strport, sizeof strport, "%hu", port);
106 * Build the final command string in the buffer by making the
107 * appropriate substitutions to the given proxy command.
109 * Use "exec" to avoid "sh -c" processes on some platforms
112 xasprintf(&tmp, "exec %s", proxy_command);
113 command_string = percent_expand(tmp, "h", host, "p", strport,
114 "r", options.user, (char *)NULL);
117 /* Create pipes for communicating with the proxy. */
118 if (pipe(pin) < 0 || pipe(pout) < 0)
119 fatal("Could not create pipes to communicate with the proxy: %.100s",
122 debug("Executing proxy command: %.500s", command_string);
124 /* Fork and execute the proxy command. */
125 if ((pid = fork()) == 0) {
128 /* Child. Permanently give up superuser privileges. */
129 permanently_drop_suid(original_real_uid);
131 /* Redirect stdin and stdout. */
134 if (dup2(pin[0], 0) < 0)
135 perror("dup2 stdin");
139 if (dup2(pout[1], 1) < 0)
140 perror("dup2 stdout");
141 /* Cannot be 1 because pin allocated two descriptors. */
144 /* Stderr is left as it is so that error messages get
145 printed on the user's terminal. */
148 argv[2] = command_string;
151 /* Execute the proxy command. Note that we gave up any
152 extra privileges above. */
153 signal(SIGPIPE, SIG_DFL);
154 execv(argv[0], argv);
160 fatal("fork failed: %.100s", strerror(errno));
162 proxy_command_pid = pid; /* save pid to clean up later */
164 /* Close child side of the descriptors. */
168 /* Free the command name. */
169 xfree(command_string);
171 /* Set the connection file descriptors. */
172 packet_set_connection(pout[0], pin[1]);
173 packet_set_timeout(options.server_alive_interval,
174 options.server_alive_count_max);
176 /* Indicate OK return */
181 ssh_kill_proxy_command(void)
184 * Send SIGHUP to proxy command if used. We don't wait() in
185 * case it hangs and instead rely on init to reap the child
187 if (proxy_command_pid > 1)
188 kill(proxy_command_pid, SIGHUP);
192 * Creates a (possibly privileged) socket for use as the ssh connection.
195 ssh_create_socket(int privileged, struct addrinfo *ai)
198 struct addrinfo hints, *res;
201 * If we are running as root and want to connect to a privileged
202 * port, bind our own socket to a privileged port.
205 int p = IPPORT_RESERVED - 1;
207 sock = rresvport_af(&p, ai->ai_family);
210 error("rresvport: af=%d %.100s", ai->ai_family,
213 debug("Allocated local port %d.", p);
216 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
218 error("socket: %.100s", strerror(errno));
221 fcntl(sock, F_SETFD, FD_CLOEXEC);
223 /* Bind the socket to an alternative local IP address */
224 if (options.bind_address == NULL)
227 memset(&hints, 0, sizeof(hints));
228 hints.ai_family = ai->ai_family;
229 hints.ai_socktype = ai->ai_socktype;
230 hints.ai_protocol = ai->ai_protocol;
231 hints.ai_flags = AI_PASSIVE;
232 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res);
234 error("getaddrinfo: %s: %s", options.bind_address,
235 ssh_gai_strerror(gaierr));
239 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
240 error("bind: %s: %s", options.bind_address, strerror(errno));
250 timeout_connect(int sockfd, const struct sockaddr *serv_addr,
251 socklen_t addrlen, int *timeoutp)
254 struct timeval tv, t_start;
256 int optval, rc, result = -1;
258 gettimeofday(&t_start, NULL);
260 if (*timeoutp <= 0) {
261 result = connect(sockfd, serv_addr, addrlen);
265 set_nonblock(sockfd);
266 rc = connect(sockfd, serv_addr, addrlen);
268 unset_nonblock(sockfd);
272 if (errno != EINPROGRESS) {
277 fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS),
279 FD_SET(sockfd, fdset);
280 ms_to_timeval(&tv, *timeoutp);
283 rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
284 if (rc != -1 || errno != EINTR)
295 debug("select: %s", strerror(errno));
298 /* Completed or failed */
300 optlen = sizeof(optval);
301 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
303 debug("getsockopt: %s", strerror(errno));
311 unset_nonblock(sockfd);
314 /* Should not occur */
315 fatal("Bogus return (%d) from select()", rc);
321 if (result == 0 && *timeoutp > 0) {
322 ms_subtract_diff(&t_start, timeoutp);
323 if (*timeoutp <= 0) {
333 * Opens a TCP/IP connection to the remote server on the given host.
334 * The address of the remote host will be returned in hostaddr.
335 * If port is 0, the default port will be used. If needpriv is true,
336 * a privileged port will be allocated to make the connection.
337 * This requires super-user privileges if needpriv is true.
338 * Connection_attempts specifies the maximum number of tries (one per
339 * second). If proxy_command is non-NULL, it specifies the command (with %h
340 * and %p substituted for host and port, respectively) to use to contact
344 ssh_connect(const char *host, struct sockaddr_storage * hostaddr,
345 u_short port, int family, int connection_attempts, int *timeout_ms,
346 int want_keepalive, int needpriv, const char *proxy_command)
350 int sock = -1, attempt;
351 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
352 struct addrinfo hints, *ai, *aitop;
354 debug2("ssh_connect: needpriv %d", needpriv);
356 /* If a proxy command is given, connect using it. */
357 if (proxy_command != NULL)
358 return ssh_proxy_connect(host, port, proxy_command);
360 /* No proxy command. */
362 memset(&hints, 0, sizeof(hints));
363 hints.ai_family = family;
364 hints.ai_socktype = SOCK_STREAM;
365 snprintf(strport, sizeof strport, "%u", port);
366 if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0)
367 fatal("%s: Could not resolve hostname %.100s: %s", __progname,
368 host, ssh_gai_strerror(gaierr));
370 for (attempt = 0; attempt < connection_attempts; attempt++) {
372 /* Sleep a moment before retrying. */
374 debug("Trying again...");
377 * Loop through addresses for this host, and try each one in
378 * sequence until the connection succeeds.
380 for (ai = aitop; ai; ai = ai->ai_next) {
381 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
383 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
384 ntop, sizeof(ntop), strport, sizeof(strport),
385 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
386 error("ssh_connect: getnameinfo failed");
389 debug("Connecting to %.200s [%.100s] port %s.",
390 host, ntop, strport);
392 /* Create a socket for connecting. */
393 sock = ssh_create_socket(needpriv, ai);
395 /* Any error is already output */
398 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
400 /* Successful connection. */
401 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
404 debug("connect to address %s port %s: %s",
405 ntop, strport, strerror(errno));
411 break; /* Successful connection. */
416 /* Return failure if we didn't get a successful connection. */
418 error("ssh: connect to host %s port %s: %s",
419 host, strport, strerror(errno));
423 debug("Connection established.");
425 /* Set SO_KEEPALIVE if requested. */
426 if (want_keepalive &&
427 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
429 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
431 /* Set the connection. */
432 packet_set_connection(sock, sock);
433 packet_set_timeout(options.server_alive_interval,
434 options.server_alive_count_max);
440 send_client_banner(int connection_out, int minor1)
442 /* Send our own protocol version identification. */
444 xasprintf(&client_version_string, "SSH-%d.%d-%.100s\r\n",
445 PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION);
447 xasprintf(&client_version_string, "SSH-%d.%d-%.100s\n",
448 PROTOCOL_MAJOR_1, minor1, SSH_VERSION);
450 if (roaming_atomicio(vwrite, connection_out, client_version_string,
451 strlen(client_version_string)) != strlen(client_version_string))
452 fatal("write: %.100s", strerror(errno));
453 chop(client_version_string);
454 debug("Local version string %.100s", client_version_string);
458 * Waits for the server identification string, and sends our own
459 * identification string.
462 ssh_exchange_identification(int timeout_ms)
464 char buf[256], remote_version[256]; /* must be same size! */
465 int remote_major, remote_minor, mismatch;
466 int connection_in = packet_get_connection_in();
467 int connection_out = packet_get_connection_out();
468 int minor1 = PROTOCOL_MINOR_1, client_banner_sent = 0;
471 int fdsetsz, remaining, rc;
472 struct timeval t_start, t_remaining;
475 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask);
476 fdset = xcalloc(1, fdsetsz);
479 * If we are SSH2-only then we can send the banner immediately and
482 if (options.protocol == SSH_PROTO_2) {
484 send_client_banner(connection_out, 0);
485 client_banner_sent = 1;
488 /* Read other side's version identification. */
489 remaining = timeout_ms;
491 for (i = 0; i < sizeof(buf) - 1; i++) {
492 if (timeout_ms > 0) {
493 gettimeofday(&t_start, NULL);
494 ms_to_timeval(&t_remaining, remaining);
495 FD_SET(connection_in, fdset);
496 rc = select(connection_in + 1, fdset, NULL,
497 fdset, &t_remaining);
498 ms_subtract_diff(&t_start, &remaining);
499 if (rc == 0 || remaining <= 0)
500 fatal("Connection timed out during "
505 fatal("ssh_exchange_identification: "
506 "select: %s", strerror(errno));
510 len = roaming_atomicio(read, connection_in, &buf[i], 1);
512 if (len != 1 && errno == EPIPE)
513 fatal("ssh_exchange_identification: "
514 "Connection closed by remote host");
516 fatal("ssh_exchange_identification: "
517 "read: %.100s", strerror(errno));
518 if (buf[i] == '\r') {
521 continue; /**XXX wait for \n */
523 if (buf[i] == '\n') {
528 fatal("ssh_exchange_identification: "
529 "No banner received");
531 buf[sizeof(buf) - 1] = 0;
532 if (strncmp(buf, "SSH-", 4) == 0)
534 debug("ssh_exchange_identification: %s", buf);
536 server_version_string = xstrdup(buf);
540 * Check that the versions match. In future this might accept
541 * several versions and set appropriate flags to handle them.
543 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
544 &remote_major, &remote_minor, remote_version) != 3)
545 fatal("Bad remote protocol version identification: '%.100s'", buf);
546 debug("Remote protocol version %d.%d, remote software version %.100s",
547 remote_major, remote_minor, remote_version);
549 compat_datafellows(remote_version);
552 switch (remote_major) {
554 if (remote_minor == 99 &&
555 (options.protocol & SSH_PROTO_2) &&
556 !(options.protocol & SSH_PROTO_1_PREFERRED)) {
560 if (!(options.protocol & SSH_PROTO_1)) {
564 if (remote_minor < 3) {
565 fatal("Remote machine has too old SSH software version.");
566 } else if (remote_minor == 3 || remote_minor == 4) {
567 /* We speak 1.3, too. */
570 if (options.forward_agent) {
571 logit("Agent forwarding disabled for protocol 1.3");
572 options.forward_agent = 0;
577 if (options.protocol & SSH_PROTO_2) {
587 fatal("Protocol major versions differ: %d vs. %d",
588 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
590 if (!client_banner_sent)
591 send_client_banner(connection_out, minor1);
592 chop(server_version_string);
595 /* defaults to 'no' */
597 confirm(const char *prompt)
599 const char *msg, *again = "Please type 'yes' or 'no': ";
603 if (options.batch_mode)
605 for (msg = prompt;;msg = again) {
606 p = read_passphrase(msg, RP_ECHO);
608 (p[0] == '\0') || (p[0] == '\n') ||
609 strncasecmp(p, "no", 2) == 0)
611 if (p && strncasecmp(p, "yes", 3) == 0)
621 check_host_cert(const char *host, const Key *host_key)
625 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) {
629 if (buffer_len(&host_key->cert->critical) != 0) {
630 error("Certificate for %s contains unsupported "
631 "critical options(s)", host);
638 sockaddr_is_local(struct sockaddr *hostaddr)
640 switch (hostaddr->sa_family) {
642 return (ntohl(((struct sockaddr_in *)hostaddr)->
643 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
645 return IN6_IS_ADDR_LOOPBACK(
646 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
653 * Prepare the hostname and ip address strings that are used to lookup
654 * host keys in known_hosts files. These may have a port number appended.
657 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr,
658 u_short port, char **hostfile_hostname, char **hostfile_ipaddr)
660 char ntop[NI_MAXHOST];
663 switch (hostaddr == NULL ? -1 : hostaddr->sa_family) {
668 addrlen = sizeof(struct sockaddr_in);
671 addrlen = sizeof(struct sockaddr_in6);
674 addrlen = sizeof(struct sockaddr);
679 * We don't have the remote ip-address for connections
680 * using a proxy command
682 if (hostfile_ipaddr != NULL) {
683 if (options.proxy_command == NULL) {
684 if (getnameinfo(hostaddr, addrlen,
685 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0)
686 fatal("check_host_key: getnameinfo failed");
687 *hostfile_ipaddr = put_host_port(ntop, port);
689 *hostfile_ipaddr = xstrdup("<no hostip for proxy "
695 * Allow the user to record the key under a different name or
696 * differentiate a non-standard port. This is useful for ssh
697 * tunneling over forwarded connections or if you run multiple
698 * sshd's on different ports on the same machine.
700 if (hostfile_hostname != NULL) {
701 if (options.host_key_alias != NULL) {
702 *hostfile_hostname = xstrdup(options.host_key_alias);
703 debug("using hostkeyalias: %s", *hostfile_hostname);
705 *hostfile_hostname = put_host_port(hostname, port);
711 * check whether the supplied host key is valid, return -1 if the key
712 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true.
718 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
719 Key *host_key, int readonly,
720 char **user_hostfiles, u_int num_user_hostfiles,
721 char **system_hostfiles, u_int num_system_hostfiles)
723 HostStatus host_status;
724 HostStatus ip_status;
726 char *ip = NULL, *host = NULL;
727 char hostline[1000], *hostp, *fp, *ra;
730 const struct hostkey_entry *host_found, *ip_found;
731 int len, cancelled_forwarding = 0;
732 int local = sockaddr_is_local(hostaddr);
733 int r, want_cert = key_is_cert(host_key), host_ip_differ = 0;
734 struct hostkeys *host_hostkeys, *ip_hostkeys;
738 * Force accepting of the host key for loopback/localhost. The
739 * problem is that if the home directory is NFS-mounted to multiple
740 * machines, localhost will refer to a different machine in each of
741 * them, and the user will get bogus HOST_CHANGED warnings. This
742 * essentially disables host authentication for localhost; however,
743 * this is probably not a real problem.
745 if (options.no_host_authentication_for_localhost == 1 && local &&
746 options.host_key_alias == NULL) {
747 debug("Forcing accepting of host key for "
748 "loopback/localhost.");
753 * Prepare the hostname and address strings used for hostkey lookup.
754 * In some cases, these will have a port number appended.
756 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip);
759 * Turn off check_host_ip if the connection is to localhost, via proxy
760 * command or if we don't have a hostname to compare with
762 if (options.check_host_ip && (local ||
763 strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
764 options.check_host_ip = 0;
766 host_hostkeys = init_hostkeys();
767 for (i = 0; i < num_user_hostfiles; i++)
768 load_hostkeys(host_hostkeys, host, user_hostfiles[i]);
769 for (i = 0; i < num_system_hostfiles; i++)
770 load_hostkeys(host_hostkeys, host, system_hostfiles[i]);
773 if (!want_cert && options.check_host_ip) {
774 ip_hostkeys = init_hostkeys();
775 for (i = 0; i < num_user_hostfiles; i++)
776 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]);
777 for (i = 0; i < num_system_hostfiles; i++)
778 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]);
782 /* Reload these as they may have changed on cert->key downgrade */
783 want_cert = key_is_cert(host_key);
784 type = key_type(host_key);
787 * Check if the host key is present in the user's list of known
788 * hosts or in the systemwide list.
790 host_status = check_key_in_hostkeys(host_hostkeys, host_key,
794 * Also perform check for the ip address, skip the check if we are
795 * localhost, looking for a certificate, or the hostname was an ip
796 * address to begin with.
798 if (!want_cert && ip_hostkeys != NULL) {
799 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key,
801 if (host_status == HOST_CHANGED &&
802 (ip_status != HOST_CHANGED ||
804 !key_equal(ip_found->key, host_found->key))))
807 ip_status = host_status;
809 switch (host_status) {
811 /* The host is known and the key matches. */
812 debug("Host '%.200s' is known and matches the %s host %s.",
813 host, type, want_cert ? "certificate" : "key");
814 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key",
815 host_found->file, host_found->line);
816 if (want_cert && !check_host_cert(hostname, host_key))
818 if (options.check_host_ip && ip_status == HOST_NEW) {
819 if (readonly || want_cert)
820 logit("%s host key for IP address "
821 "'%.128s' not in list of known hosts.",
823 else if (!add_host_to_hostfile(user_hostfiles[0], ip,
824 host_key, options.hash_known_hosts))
825 logit("Failed to add the %s host key for IP "
826 "address '%.128s' to the list of known "
827 "hosts (%.30s).", type, ip,
830 logit("Warning: Permanently added the %s host "
831 "key for IP address '%.128s' to the list "
832 "of known hosts.", type, ip);
833 } else if (options.visual_host_key) {
834 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
835 ra = key_fingerprint(host_key, SSH_FP_MD5,
837 logit("Host key fingerprint is %s\n%s\n", fp, ra);
843 if (options.host_key_alias == NULL && port != 0 &&
844 port != SSH_DEFAULT_PORT) {
845 debug("checking without port identifier");
846 if (check_host_key(hostname, hostaddr, 0, host_key,
847 ROQUIET, user_hostfiles, num_user_hostfiles,
848 system_hostfiles, num_system_hostfiles) == 0) {
849 debug("found matching key w/out port");
853 if (readonly || want_cert)
855 /* The host is new. */
856 if (options.strict_host_key_checking == 1) {
858 * User has requested strict host key checking. We
859 * will not add the host key automatically. The only
860 * alternative left is to abort.
862 error("No %s host key is known for %.200s and you "
863 "have requested strict checking.", type, host);
865 } else if (options.strict_host_key_checking == 2) {
866 char msg1[1024], msg2[1024];
868 if (show_other_keys(host_hostkeys, host_key))
869 snprintf(msg1, sizeof(msg1),
870 "\nbut keys of different type are already"
871 " known for this host.");
873 snprintf(msg1, sizeof(msg1), ".");
875 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
876 ra = key_fingerprint(host_key, SSH_FP_MD5,
879 if (options.verify_host_key_dns) {
880 if (matching_host_key_dns)
881 snprintf(msg2, sizeof(msg2),
882 "Matching host key fingerprint"
885 snprintf(msg2, sizeof(msg2),
886 "No matching host key fingerprint"
889 snprintf(msg, sizeof(msg),
890 "The authenticity of host '%.200s (%s)' can't be "
892 "%s key fingerprint is %s.%s%s\n%s"
893 "Are you sure you want to continue connecting "
895 host, ip, msg1, type, fp,
896 options.visual_host_key ? "\n" : "",
897 options.visual_host_key ? ra : "",
905 * If not in strict mode, add the key automatically to the
906 * local known_hosts file.
908 if (options.check_host_ip && ip_status == HOST_NEW) {
909 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
911 if (options.hash_known_hosts) {
912 /* Add hash of host and IP separately */
913 r = add_host_to_hostfile(user_hostfiles[0],
914 host, host_key, options.hash_known_hosts) &&
915 add_host_to_hostfile(user_hostfiles[0], ip,
916 host_key, options.hash_known_hosts);
918 /* Add unhashed "host,ip" */
919 r = add_host_to_hostfile(user_hostfiles[0],
921 options.hash_known_hosts);
924 r = add_host_to_hostfile(user_hostfiles[0], host,
925 host_key, options.hash_known_hosts);
930 logit("Failed to add the host to the list of known "
931 "hosts (%.500s).", user_hostfiles[0]);
933 logit("Warning: Permanently added '%.200s' (%s) to the "
934 "list of known hosts.", hostp, type);
937 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
938 error("@ WARNING: REVOKED HOST KEY DETECTED! @");
939 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
940 error("The %s host key for %s is marked as revoked.", type, host);
941 error("This could mean that a stolen key is being used to");
942 error("impersonate this host.");
945 * If strict host key checking is in use, the user will have
946 * to edit the key manually and we can only abort.
948 if (options.strict_host_key_checking) {
949 error("%s host key for %.200s was revoked and you have "
950 "requested strict checking.", type, host);
953 goto continue_unsafe;
958 * This is only a debug() since it is valid to have
959 * CAs with wildcard DNS matches that don't match
960 * all hosts that one might visit.
962 debug("Host certificate authority does not "
963 "match %s in %s:%lu", CA_MARKER,
964 host_found->file, host_found->line);
967 if (readonly == ROQUIET)
969 if (options.check_host_ip && host_ip_differ) {
971 if (ip_status == HOST_NEW)
972 key_msg = "is unknown";
973 else if (ip_status == HOST_OK)
974 key_msg = "is unchanged";
976 key_msg = "has a different value";
977 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
978 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
979 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
980 error("The %s host key for %s has changed,", type, host);
981 error("and the key for the corresponding IP address %s", ip);
982 error("%s. This could either mean that", key_msg);
983 error("DNS SPOOFING is happening or the IP address for the host");
984 error("and its host key have changed at the same time.");
985 if (ip_status != HOST_NEW)
986 error("Offending key for IP in %s:%lu",
987 ip_found->file, ip_found->line);
989 /* The host key has changed. */
990 warn_changed_key(host_key);
991 error("Add correct host key in %.100s to get rid of this message.",
993 error("Offending %s key in %s:%lu", key_type(host_found->key),
994 host_found->file, host_found->line);
997 * If strict host key checking is in use, the user will have
998 * to edit the key manually and we can only abort.
1000 if (options.strict_host_key_checking) {
1001 error("%s host key for %.200s has changed and you have "
1002 "requested strict checking.", type, host);
1008 * If strict host key checking has not been requested, allow
1009 * the connection but without MITM-able authentication or
1012 if (options.password_authentication) {
1013 error("Password authentication is disabled to avoid "
1014 "man-in-the-middle attacks.");
1015 options.password_authentication = 0;
1016 cancelled_forwarding = 1;
1018 if (options.kbd_interactive_authentication) {
1019 error("Keyboard-interactive authentication is disabled"
1020 " to avoid man-in-the-middle attacks.");
1021 options.kbd_interactive_authentication = 0;
1022 options.challenge_response_authentication = 0;
1023 cancelled_forwarding = 1;
1025 if (options.challenge_response_authentication) {
1026 error("Challenge/response authentication is disabled"
1027 " to avoid man-in-the-middle attacks.");
1028 options.challenge_response_authentication = 0;
1029 cancelled_forwarding = 1;
1031 if (options.forward_agent) {
1032 error("Agent forwarding is disabled to avoid "
1033 "man-in-the-middle attacks.");
1034 options.forward_agent = 0;
1035 cancelled_forwarding = 1;
1037 if (options.forward_x11) {
1038 error("X11 forwarding is disabled to avoid "
1039 "man-in-the-middle attacks.");
1040 options.forward_x11 = 0;
1041 cancelled_forwarding = 1;
1043 if (options.num_local_forwards > 0 ||
1044 options.num_remote_forwards > 0) {
1045 error("Port forwarding is disabled to avoid "
1046 "man-in-the-middle attacks.");
1047 options.num_local_forwards =
1048 options.num_remote_forwards = 0;
1049 cancelled_forwarding = 1;
1051 if (options.tun_open != SSH_TUNMODE_NO) {
1052 error("Tunnel forwarding is disabled to avoid "
1053 "man-in-the-middle attacks.");
1054 options.tun_open = SSH_TUNMODE_NO;
1055 cancelled_forwarding = 1;
1057 if (options.exit_on_forward_failure && cancelled_forwarding)
1058 fatal("Error: forwarding disabled due to host key "
1062 * XXX Should permit the user to change to use the new id.
1063 * This could be done by converting the host key to an
1064 * identifying sentence, tell that the host identifies itself
1065 * by that sentence, and ask the user if he/she wishes to
1066 * accept the authentication.
1070 fatal("internal error");
1074 if (options.check_host_ip && host_status != HOST_CHANGED &&
1075 ip_status == HOST_CHANGED) {
1076 snprintf(msg, sizeof(msg),
1077 "Warning: the %s host key for '%.200s' "
1078 "differs from the key for the IP address '%.128s'"
1079 "\nOffending key for IP in %s:%lu",
1080 type, host, ip, ip_found->file, ip_found->line);
1081 if (host_status == HOST_OK) {
1083 snprintf(msg + len, sizeof(msg) - len,
1084 "\nMatching host key in %s:%lu",
1085 host_found->file, host_found->line);
1087 if (options.strict_host_key_checking == 1) {
1089 error("Exiting, you have requested strict checking.");
1091 } else if (options.strict_host_key_checking == 2) {
1092 strlcat(msg, "\nAre you sure you want "
1093 "to continue connecting (yes/no)? ", sizeof(msg));
1103 if (host_hostkeys != NULL)
1104 free_hostkeys(host_hostkeys);
1105 if (ip_hostkeys != NULL)
1106 free_hostkeys(ip_hostkeys);
1110 if (want_cert && host_status != HOST_REVOKED) {
1112 * No matching certificate. Downgrade cert to raw key and
1115 debug("No matching CA found. Retry with plain key");
1116 raw_key = key_from_private(host_key);
1117 if (key_drop_cert(raw_key) != 0)
1118 fatal("Couldn't drop certificate");
1122 if (raw_key != NULL)
1126 if (host_hostkeys != NULL)
1127 free_hostkeys(host_hostkeys);
1128 if (ip_hostkeys != NULL)
1129 free_hostkeys(ip_hostkeys);
1133 /* returns 0 if key verifies or -1 if key does NOT verify */
1135 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
1140 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1141 debug("Server host key: %s %s", key_type(host_key), fp);
1144 /* XXX certs are not yet supported for DNS */
1145 if (!key_is_cert(host_key) && options.verify_host_key_dns &&
1146 verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) {
1147 if (flags & DNS_VERIFY_FOUND) {
1149 if (options.verify_host_key_dns == 1 &&
1150 flags & DNS_VERIFY_MATCH &&
1151 flags & DNS_VERIFY_SECURE)
1154 if (flags & DNS_VERIFY_MATCH) {
1155 matching_host_key_dns = 1;
1157 warn_changed_key(host_key);
1158 error("Update the SSHFP RR in DNS with the new "
1159 "host key to get rid of this message.");
1164 return check_host_key(host, hostaddr, options.port, host_key, RDRW,
1165 options.user_hostfiles, options.num_user_hostfiles,
1166 options.system_hostfiles, options.num_system_hostfiles);
1170 * Starts a dialog with the server, and authenticates the current user on the
1171 * server. This does not need any extra privileges. The basic connection
1172 * to the server must already have been established before this is called.
1173 * If login fails, this function prints an error and never returns.
1174 * This function does not require super-user privileges.
1177 ssh_login(Sensitive *sensitive, const char *orighost,
1178 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms)
1181 char *server_user, *local_user;
1183 local_user = xstrdup(pw->pw_name);
1184 server_user = options.user ? options.user : local_user;
1186 /* Convert the user-supplied hostname into all lowercase. */
1187 host = xstrdup(orighost);
1188 for (cp = host; *cp; cp++)
1190 *cp = (char)tolower(*cp);
1192 /* Exchange protocol version identification strings with the server. */
1193 ssh_exchange_identification(timeout_ms);
1195 /* Put the connection into non-blocking mode. */
1196 packet_set_nonblocking();
1199 /* authenticate user */
1201 ssh_kex2(host, hostaddr, port);
1202 ssh_userauth2(local_user, server_user, host, sensitive);
1204 ssh_kex(host, hostaddr);
1205 ssh_userauth1(local_user, server_user, host, sensitive);
1211 ssh_put_password(char *password)
1216 if (datafellows & SSH_BUG_PASSWORDPAD) {
1217 packet_put_cstring(password);
1220 size = roundup(strlen(password) + 1, 32);
1221 padded = xcalloc(1, size);
1222 strlcpy(padded, password, size);
1223 packet_put_string(padded, size);
1224 memset(padded, 0, size);
1228 /* print all known host keys for a given host, but skip keys of given type */
1230 show_other_keys(struct hostkeys *hostkeys, Key *key)
1232 int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, KEY_ECDSA, -1};
1235 const struct hostkey_entry *found;
1237 for (i = 0; type[i] != -1; i++) {
1238 if (type[i] == key->type)
1240 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found))
1242 fp = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_HEX);
1243 ra = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_RANDOMART);
1244 logit("WARNING: %s key found for host %s\n"
1246 "%s key fingerprint %s.",
1247 key_type(found->key),
1248 found->host, found->file, found->line,
1249 key_type(found->key), fp);
1250 if (options.visual_host_key)
1260 warn_changed_key(Key *host_key)
1264 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1266 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1267 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1268 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1269 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1270 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1271 error("It is also possible that a host key has just been changed.");
1272 error("The fingerprint for the %s key sent by the remote host is\n%s.",
1273 key_type(host_key), fp);
1274 error("Please contact your system administrator.");
1280 * Execute a local command
1283 ssh_local_cmd(const char *args)
1288 void (*osighand)(int);
1290 if (!options.permit_local_command ||
1291 args == NULL || !*args)
1294 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
1295 shell = _PATH_BSHELL;
1297 osighand = signal(SIGCHLD, SIG_DFL);
1300 signal(SIGPIPE, SIG_DFL);
1301 debug3("Executing %s -c \"%s\"", shell, args);
1302 execl(shell, shell, "-c", args, (char *)NULL);
1303 error("Couldn't execute %s -c \"%s\": %s",
1304 shell, args, strerror(errno));
1306 } else if (pid == -1)
1307 fatal("fork failed: %.100s", strerror(errno));
1308 while (waitpid(pid, &status, 0) == -1)
1310 fatal("Couldn't wait for child: %s", strerror(errno));
1311 signal(SIGCHLD, osighand);
1313 if (!WIFEXITED(status))
1316 return (WEXITSTATUS(status));