1 /* $OpenBSD: sshconnect.c,v 1.297 2018/02/23 15:58:38 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".
19 #include <sys/types.h>
22 #include <sys/socket.h>
23 #ifdef HAVE_SYS_TIME_H
24 # include <sys/time.h>
28 #include <netinet/in.h>
29 #include <arpa/inet.h>
62 #include "sshconnect.h"
69 #include "monitor_fdpass.h"
76 char *client_version_string = NULL;
77 char *server_version_string = NULL;
78 struct sshkey *previous_host_key = NULL;
80 static int matching_host_key_dns = 0;
82 static pid_t proxy_command_pid = 0;
85 extern Options options;
86 extern char *__progname;
87 extern uid_t original_real_uid;
88 extern uid_t original_effective_uid;
90 static int show_other_keys(struct hostkeys *, struct sshkey *);
91 static void warn_changed_key(struct sshkey *);
93 /* Expand a proxy command */
95 expand_proxy_command(const char *proxy_command, const char *user,
96 const char *host, int port)
98 char *tmp, *ret, strport[NI_MAXSERV];
100 snprintf(strport, sizeof strport, "%d", port);
101 xasprintf(&tmp, "exec %s", proxy_command);
102 ret = percent_expand(tmp, "h", host, "p", strport,
103 "r", options.user, (char *)NULL);
109 * Connect to the given ssh server using a proxy command that passes a
110 * a connected fd back to us.
113 ssh_proxy_fdpass_connect(struct ssh *ssh, const char *host, u_short port,
114 const char *proxy_command)
116 char *command_string;
121 if ((shell = getenv("SHELL")) == NULL)
122 shell = _PATH_BSHELL;
124 if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) < 0)
125 fatal("Could not create socketpair to communicate with "
126 "proxy dialer: %.100s", strerror(errno));
128 command_string = expand_proxy_command(proxy_command, options.user,
130 debug("Executing proxy dialer command: %.500s", command_string);
132 /* Fork and execute the proxy command. */
133 if ((pid = fork()) == 0) {
136 /* Child. Permanently give up superuser privileges. */
137 permanently_drop_suid(original_real_uid);
140 /* Redirect stdin and stdout. */
142 if (dup2(sp[0], 0) < 0)
143 perror("dup2 stdin");
146 if (dup2(sp[0], 1) < 0)
147 perror("dup2 stdout");
153 * Stderr is left as it is so that error messages get
154 * printed on the user's terminal.
158 argv[2] = command_string;
162 * Execute the proxy command.
163 * Note that we gave up any extra privileges above.
165 execv(argv[0], argv);
171 fatal("fork failed: %.100s", strerror(errno));
173 free(command_string);
175 if ((sock = mm_receive_fd(sp[1])) == -1)
176 fatal("proxy dialer did not pass back a connection");
179 while (waitpid(pid, NULL, 0) == -1)
181 fatal("Couldn't wait for child: %s", strerror(errno));
183 /* Set the connection file descriptors. */
184 if (ssh_packet_set_connection(ssh, sock, sock) == NULL)
185 return -1; /* ssh_packet_set_connection logs error */
191 * Connect to the given ssh server using a proxy command.
194 ssh_proxy_connect(struct ssh *ssh, const char *host, u_short port,
195 const char *proxy_command)
197 char *command_string;
202 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
203 shell = _PATH_BSHELL;
205 /* Create pipes for communicating with the proxy. */
206 if (pipe(pin) < 0 || pipe(pout) < 0)
207 fatal("Could not create pipes to communicate with the proxy: %.100s",
210 command_string = expand_proxy_command(proxy_command, options.user,
212 debug("Executing proxy command: %.500s", command_string);
214 /* Fork and execute the proxy command. */
215 if ((pid = fork()) == 0) {
218 /* Child. Permanently give up superuser privileges. */
219 permanently_drop_suid(original_real_uid);
221 /* Redirect stdin and stdout. */
224 if (dup2(pin[0], 0) < 0)
225 perror("dup2 stdin");
229 if (dup2(pout[1], 1) < 0)
230 perror("dup2 stdout");
231 /* Cannot be 1 because pin allocated two descriptors. */
234 /* Stderr is left as it is so that error messages get
235 printed on the user's terminal. */
238 argv[2] = command_string;
241 /* Execute the proxy command. Note that we gave up any
242 extra privileges above. */
243 signal(SIGPIPE, SIG_DFL);
244 execv(argv[0], argv);
250 fatal("fork failed: %.100s", strerror(errno));
252 proxy_command_pid = pid; /* save pid to clean up later */
254 /* Close child side of the descriptors. */
258 /* Free the command name. */
259 free(command_string);
261 /* Set the connection file descriptors. */
262 if (ssh_packet_set_connection(ssh, pout[0], pin[1]) == NULL)
263 return -1; /* ssh_packet_set_connection logs error */
269 ssh_kill_proxy_command(void)
272 * Send SIGHUP to proxy command if used. We don't wait() in
273 * case it hangs and instead rely on init to reap the child
275 if (proxy_command_pid > 1)
276 kill(proxy_command_pid, SIGHUP);
279 #ifdef HAVE_IFADDRS_H
281 * Search a interface address list (returned from getifaddrs(3)) for an
282 * address that matches the desired address family on the specifed interface.
283 * Returns 0 and fills in *resultp and *rlenp on success. Returns -1 on failure.
286 check_ifaddrs(const char *ifname, int af, const struct ifaddrs *ifaddrs,
287 struct sockaddr_storage *resultp, socklen_t *rlenp)
289 struct sockaddr_in6 *sa6;
290 struct sockaddr_in *sa;
291 struct in6_addr *v6addr;
292 const struct ifaddrs *ifa;
296 * Prefer addresses that are not loopback or linklocal, but use them
297 * if nothing else matches.
299 for (allow_local = 0; allow_local < 2; allow_local++) {
300 for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) {
301 if (ifa->ifa_addr == NULL || ifa->ifa_name == NULL ||
302 (ifa->ifa_flags & IFF_UP) == 0 ||
303 ifa->ifa_addr->sa_family != af ||
304 strcmp(ifa->ifa_name, options.bind_interface) != 0)
306 switch (ifa->ifa_addr->sa_family) {
308 sa = (struct sockaddr_in *)ifa->ifa_addr;
309 if (!allow_local && sa->sin_addr.s_addr ==
310 htonl(INADDR_LOOPBACK))
312 if (*rlenp < sizeof(struct sockaddr_in)) {
313 error("%s: v4 addr doesn't fit",
317 *rlenp = sizeof(struct sockaddr_in);
318 memcpy(resultp, sa, *rlenp);
321 sa6 = (struct sockaddr_in6 *)ifa->ifa_addr;
322 v6addr = &sa6->sin6_addr;
324 (IN6_IS_ADDR_LINKLOCAL(v6addr) ||
325 IN6_IS_ADDR_LOOPBACK(v6addr)))
327 if (*rlenp < sizeof(struct sockaddr_in6)) {
328 error("%s: v6 addr doesn't fit",
332 *rlenp = sizeof(struct sockaddr_in6);
333 memcpy(resultp, sa6, *rlenp);
343 * Creates a (possibly privileged) socket for use as the ssh connection.
346 ssh_create_socket(int privileged, struct addrinfo *ai)
349 struct sockaddr_storage bindaddr;
350 socklen_t bindaddrlen = 0;
351 struct addrinfo hints, *res = NULL;
352 #ifdef HAVE_IFADDRS_H
353 struct ifaddrs *ifaddrs = NULL;
355 char ntop[NI_MAXHOST];
357 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
359 error("socket: %s", strerror(errno));
362 fcntl(sock, F_SETFD, FD_CLOEXEC);
364 /* Bind the socket to an alternative local IP address */
365 if (options.bind_address == NULL && options.bind_interface == NULL &&
369 if (options.bind_address != NULL) {
370 memset(&hints, 0, sizeof(hints));
371 hints.ai_family = ai->ai_family;
372 hints.ai_socktype = ai->ai_socktype;
373 hints.ai_protocol = ai->ai_protocol;
374 hints.ai_flags = AI_PASSIVE;
375 if ((r = getaddrinfo(options.bind_address, NULL,
376 &hints, &res)) != 0) {
377 error("getaddrinfo: %s: %s", options.bind_address,
378 ssh_gai_strerror(r));
382 error("getaddrinfo: no addrs");
385 if (res->ai_addrlen > sizeof(bindaddr)) {
386 error("%s: addr doesn't fit", __func__);
389 memcpy(&bindaddr, res->ai_addr, res->ai_addrlen);
390 bindaddrlen = res->ai_addrlen;
391 } else if (options.bind_interface != NULL) {
392 #ifdef HAVE_IFADDRS_H
393 if ((r = getifaddrs(&ifaddrs)) != 0) {
394 error("getifaddrs: %s: %s", options.bind_interface,
398 bindaddrlen = sizeof(bindaddr);
399 if (check_ifaddrs(options.bind_interface, ai->ai_family,
400 ifaddrs, &bindaddr, &bindaddrlen) != 0) {
401 logit("getifaddrs: %s: no suitable addresses",
402 options.bind_interface);
406 error("BindInterface not supported on this platform.");
409 if ((r = getnameinfo((struct sockaddr *)&bindaddr, bindaddrlen,
410 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST)) != 0) {
411 error("%s: getnameinfo failed: %s", __func__,
412 ssh_gai_strerror(r));
416 * If we are running as root and want to connect to a privileged
417 * port, bind our own socket to a privileged port.
421 r = bindresvport_sa(sock,
422 bindaddrlen == 0 ? NULL : (struct sockaddr *)&bindaddr);
426 error("bindresvport_sa %s: %s", ntop,
430 } else if (bind(sock, (struct sockaddr *)&bindaddr, bindaddrlen) != 0) {
431 error("bind %s: %s", ntop, strerror(errno));
434 debug("%s: bound to %s", __func__, ntop);
443 #ifdef HAVE_IFADDRS_H
445 freeifaddrs(ifaddrs);
451 * Wait up to *timeoutp milliseconds for fd to be readable. Updates
452 * *timeoutp with time remaining.
453 * Returns 0 if fd ready or -1 on timeout or error (see errno).
456 waitrfd(int fd, int *timeoutp)
459 struct timeval t_start;
462 monotime_tv(&t_start);
465 for (; *timeoutp >= 0;) {
466 r = poll(&pfd, 1, *timeoutp);
468 ms_subtract_diff(&t_start, timeoutp);
472 else if (r == -1 && errno != EAGAIN)
483 timeout_connect(int sockfd, const struct sockaddr *serv_addr,
484 socklen_t addrlen, int *timeoutp)
487 socklen_t optlen = sizeof(optval);
489 /* No timeout: just do a blocking connect() */
491 return connect(sockfd, serv_addr, addrlen);
493 set_nonblock(sockfd);
494 if (connect(sockfd, serv_addr, addrlen) == 0) {
495 /* Succeeded already? */
496 unset_nonblock(sockfd);
498 } else if (errno != EINPROGRESS)
501 if (waitrfd(sockfd, timeoutp) == -1)
504 /* Completed or failed */
505 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, &optlen) == -1) {
506 debug("getsockopt: %s", strerror(errno));
513 unset_nonblock(sockfd);
518 * Opens a TCP/IP connection to the remote server on the given host.
519 * The address of the remote host will be returned in hostaddr.
520 * If port is 0, the default port will be used. If needpriv is true,
521 * a privileged port will be allocated to make the connection.
522 * This requires super-user privileges if needpriv is true.
523 * Connection_attempts specifies the maximum number of tries (one per
524 * second). If proxy_command is non-NULL, it specifies the command (with %h
525 * and %p substituted for host and port, respectively) to use to contact
529 ssh_connect_direct(struct ssh *ssh, const char *host, struct addrinfo *aitop,
530 struct sockaddr_storage *hostaddr, u_short port, int family,
531 int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv)
534 int oerrno, sock = -1, attempt;
535 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
538 debug2("%s: needpriv %d", __func__, needpriv);
539 memset(ntop, 0, sizeof(ntop));
540 memset(strport, 0, sizeof(strport));
542 for (attempt = 0; attempt < connection_attempts; attempt++) {
544 /* Sleep a moment before retrying. */
546 debug("Trying again...");
549 * Loop through addresses for this host, and try each one in
550 * sequence until the connection succeeds.
552 for (ai = aitop; ai; ai = ai->ai_next) {
553 if (ai->ai_family != AF_INET &&
554 ai->ai_family != AF_INET6) {
555 errno = EAFNOSUPPORT;
558 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
559 ntop, sizeof(ntop), strport, sizeof(strport),
560 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
562 error("%s: getnameinfo failed", __func__);
566 debug("Connecting to %.200s [%.100s] port %s.",
567 host, ntop, strport);
569 /* Create a socket for connecting. */
570 sock = ssh_create_socket(needpriv, ai);
572 /* Any error is already output */
577 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
579 /* Successful connection. */
580 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
584 debug("connect to address %s port %s: %s",
585 ntop, strport, strerror(errno));
592 break; /* Successful connection. */
595 /* Return failure if we didn't get a successful connection. */
597 error("ssh: connect to host %s port %s: %s",
598 host, strport, errno == 0 ? "failure" : strerror(errno));
602 debug("Connection established.");
604 /* Set SO_KEEPALIVE if requested. */
605 if (want_keepalive &&
606 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
608 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
610 /* Set the connection. */
611 if (ssh_packet_set_connection(ssh, sock, sock) == NULL)
612 return -1; /* ssh_packet_set_connection logs error */
618 ssh_connect(struct ssh *ssh, const char *host, struct addrinfo *addrs,
619 struct sockaddr_storage *hostaddr, u_short port, int family,
620 int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv)
622 if (options.proxy_command == NULL) {
623 return ssh_connect_direct(ssh, host, addrs, hostaddr, port,
624 family, connection_attempts, timeout_ms, want_keepalive,
626 } else if (strcmp(options.proxy_command, "-") == 0) {
627 if ((ssh_packet_set_connection(ssh,
628 STDIN_FILENO, STDOUT_FILENO)) == NULL)
629 return -1; /* ssh_packet_set_connection logs error */
631 } else if (options.proxy_use_fdpass) {
632 return ssh_proxy_fdpass_connect(ssh, host, port,
633 options.proxy_command);
635 return ssh_proxy_connect(ssh, host, port, options.proxy_command);
639 send_client_banner(int connection_out, int minor1)
641 /* Send our own protocol version identification. */
642 xasprintf(&client_version_string, "SSH-%d.%d-%.100s%s%s\n",
643 PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION,
644 *options.version_addendum == '\0' ? "" : " ",
645 options.version_addendum);
646 if (atomicio(vwrite, connection_out, client_version_string,
647 strlen(client_version_string)) != strlen(client_version_string))
648 fatal("write: %.100s", strerror(errno));
649 chop(client_version_string);
650 debug("Local version string %.100s", client_version_string);
654 * Waits for the server identification string, and sends our own
655 * identification string.
658 ssh_exchange_identification(int timeout_ms)
660 char buf[256], remote_version[256]; /* must be same size! */
661 int remote_major, remote_minor, mismatch;
662 int connection_in = packet_get_connection_in();
663 int connection_out = packet_get_connection_out();
668 send_client_banner(connection_out, 0);
670 /* Read other side's version identification. */
672 for (i = 0; i < sizeof(buf) - 1; i++) {
673 if (timeout_ms > 0) {
674 rc = waitrfd(connection_in, &timeout_ms);
675 if (rc == -1 && errno == ETIMEDOUT) {
676 fatal("Connection timed out during "
678 } else if (rc == -1) {
680 __func__, strerror(errno));
684 len = atomicio(read, connection_in, &buf[i], 1);
685 if (len != 1 && errno == EPIPE)
686 fatal("ssh_exchange_identification: "
687 "Connection closed by remote host");
689 fatal("ssh_exchange_identification: "
690 "read: %.100s", strerror(errno));
691 if (buf[i] == '\r') {
694 continue; /**XXX wait for \n */
696 if (buf[i] == '\n') {
701 fatal("ssh_exchange_identification: "
702 "No banner received");
704 buf[sizeof(buf) - 1] = 0;
705 if (strncmp(buf, "SSH-", 4) == 0)
707 debug("ssh_exchange_identification: %s", buf);
709 server_version_string = xstrdup(buf);
712 * Check that the versions match. In future this might accept
713 * several versions and set appropriate flags to handle them.
715 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
716 &remote_major, &remote_minor, remote_version) != 3)
717 fatal("Bad remote protocol version identification: '%.100s'", buf);
718 debug("Remote protocol version %d.%d, remote software version %.100s",
719 remote_major, remote_minor, remote_version);
721 active_state->compat = compat_datafellows(remote_version);
724 switch (remote_major) {
728 if (remote_minor != 99)
736 fatal("Protocol major versions differ: %d vs. %d",
737 PROTOCOL_MAJOR_2, remote_major);
738 if ((datafellows & SSH_BUG_RSASIGMD5) != 0)
739 logit("Server version \"%.100s\" uses unsafe RSA signature "
740 "scheme; disabling use of RSA keys", remote_version);
741 chop(server_version_string);
744 /* defaults to 'no' */
746 confirm(const char *prompt)
748 const char *msg, *again = "Please type 'yes' or 'no': ";
752 if (options.batch_mode)
754 for (msg = prompt;;msg = again) {
755 p = read_passphrase(msg, RP_ECHO);
758 p[strcspn(p, "\n")] = '\0';
759 if (p[0] == '\0' || strcasecmp(p, "no") == 0)
761 else if (strcasecmp(p, "yes") == 0)
770 check_host_cert(const char *host, const struct sshkey *host_key)
774 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) {
778 if (buffer_len(host_key->cert->critical) != 0) {
779 error("Certificate for %s contains unsupported "
780 "critical options(s)", host);
787 sockaddr_is_local(struct sockaddr *hostaddr)
789 switch (hostaddr->sa_family) {
791 return (ntohl(((struct sockaddr_in *)hostaddr)->
792 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
794 return IN6_IS_ADDR_LOOPBACK(
795 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
802 * Prepare the hostname and ip address strings that are used to lookup
803 * host keys in known_hosts files. These may have a port number appended.
806 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr,
807 u_short port, char **hostfile_hostname, char **hostfile_ipaddr)
809 char ntop[NI_MAXHOST];
812 switch (hostaddr == NULL ? -1 : hostaddr->sa_family) {
817 addrlen = sizeof(struct sockaddr_in);
820 addrlen = sizeof(struct sockaddr_in6);
823 addrlen = sizeof(struct sockaddr);
828 * We don't have the remote ip-address for connections
829 * using a proxy command
831 if (hostfile_ipaddr != NULL) {
832 if (options.proxy_command == NULL) {
833 if (getnameinfo(hostaddr, addrlen,
834 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0)
835 fatal("%s: getnameinfo failed", __func__);
836 *hostfile_ipaddr = put_host_port(ntop, port);
838 *hostfile_ipaddr = xstrdup("<no hostip for proxy "
844 * Allow the user to record the key under a different name or
845 * differentiate a non-standard port. This is useful for ssh
846 * tunneling over forwarded connections or if you run multiple
847 * sshd's on different ports on the same machine.
849 if (hostfile_hostname != NULL) {
850 if (options.host_key_alias != NULL) {
851 *hostfile_hostname = xstrdup(options.host_key_alias);
852 debug("using hostkeyalias: %s", *hostfile_hostname);
854 *hostfile_hostname = put_host_port(hostname, port);
860 * check whether the supplied host key is valid, return -1 if the key
861 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true.
867 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
868 struct sshkey *host_key, int readonly,
869 char **user_hostfiles, u_int num_user_hostfiles,
870 char **system_hostfiles, u_int num_system_hostfiles)
872 HostStatus host_status;
873 HostStatus ip_status;
874 struct sshkey *raw_key = NULL;
875 char *ip = NULL, *host = NULL;
876 char hostline[1000], *hostp, *fp, *ra;
879 const struct hostkey_entry *host_found, *ip_found;
880 int len, cancelled_forwarding = 0;
881 int local = sockaddr_is_local(hostaddr);
882 int r, want_cert = sshkey_is_cert(host_key), host_ip_differ = 0;
883 int hostkey_trusted = 0; /* Known or explicitly accepted by user */
884 struct hostkeys *host_hostkeys, *ip_hostkeys;
888 * Force accepting of the host key for loopback/localhost. The
889 * problem is that if the home directory is NFS-mounted to multiple
890 * machines, localhost will refer to a different machine in each of
891 * them, and the user will get bogus HOST_CHANGED warnings. This
892 * essentially disables host authentication for localhost; however,
893 * this is probably not a real problem.
895 if (options.no_host_authentication_for_localhost == 1 && local &&
896 options.host_key_alias == NULL) {
897 debug("Forcing accepting of host key for "
898 "loopback/localhost.");
903 * Prepare the hostname and address strings used for hostkey lookup.
904 * In some cases, these will have a port number appended.
906 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip);
909 * Turn off check_host_ip if the connection is to localhost, via proxy
910 * command or if we don't have a hostname to compare with
912 if (options.check_host_ip && (local ||
913 strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
914 options.check_host_ip = 0;
916 host_hostkeys = init_hostkeys();
917 for (i = 0; i < num_user_hostfiles; i++)
918 load_hostkeys(host_hostkeys, host, user_hostfiles[i]);
919 for (i = 0; i < num_system_hostfiles; i++)
920 load_hostkeys(host_hostkeys, host, system_hostfiles[i]);
923 if (!want_cert && options.check_host_ip) {
924 ip_hostkeys = init_hostkeys();
925 for (i = 0; i < num_user_hostfiles; i++)
926 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]);
927 for (i = 0; i < num_system_hostfiles; i++)
928 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]);
932 /* Reload these as they may have changed on cert->key downgrade */
933 want_cert = sshkey_is_cert(host_key);
934 type = sshkey_type(host_key);
937 * Check if the host key is present in the user's list of known
938 * hosts or in the systemwide list.
940 host_status = check_key_in_hostkeys(host_hostkeys, host_key,
944 * Also perform check for the ip address, skip the check if we are
945 * localhost, looking for a certificate, or the hostname was an ip
946 * address to begin with.
948 if (!want_cert && ip_hostkeys != NULL) {
949 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key,
951 if (host_status == HOST_CHANGED &&
952 (ip_status != HOST_CHANGED ||
954 !sshkey_equal(ip_found->key, host_found->key))))
957 ip_status = host_status;
959 switch (host_status) {
961 /* The host is known and the key matches. */
962 debug("Host '%.200s' is known and matches the %s host %s.",
963 host, type, want_cert ? "certificate" : "key");
964 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key",
965 host_found->file, host_found->line);
967 !check_host_cert(options.host_key_alias == NULL ?
968 hostname : options.host_key_alias, host_key))
970 if (options.check_host_ip && ip_status == HOST_NEW) {
971 if (readonly || want_cert)
972 logit("%s host key for IP address "
973 "'%.128s' not in list of known hosts.",
975 else if (!add_host_to_hostfile(user_hostfiles[0], ip,
976 host_key, options.hash_known_hosts))
977 logit("Failed to add the %s host key for IP "
978 "address '%.128s' to the list of known "
979 "hosts (%.500s).", type, ip,
982 logit("Warning: Permanently added the %s host "
983 "key for IP address '%.128s' to the list "
984 "of known hosts.", type, ip);
985 } else if (options.visual_host_key) {
986 fp = sshkey_fingerprint(host_key,
987 options.fingerprint_hash, SSH_FP_DEFAULT);
988 ra = sshkey_fingerprint(host_key,
989 options.fingerprint_hash, SSH_FP_RANDOMART);
990 if (fp == NULL || ra == NULL)
991 fatal("%s: sshkey_fingerprint fail", __func__);
992 logit("Host key fingerprint is %s\n%s", fp, ra);
999 if (options.host_key_alias == NULL && port != 0 &&
1000 port != SSH_DEFAULT_PORT) {
1001 debug("checking without port identifier");
1002 if (check_host_key(hostname, hostaddr, 0, host_key,
1003 ROQUIET, user_hostfiles, num_user_hostfiles,
1004 system_hostfiles, num_system_hostfiles) == 0) {
1005 debug("found matching key w/out port");
1009 if (readonly || want_cert)
1011 /* The host is new. */
1012 if (options.strict_host_key_checking ==
1013 SSH_STRICT_HOSTKEY_YES) {
1015 * User has requested strict host key checking. We
1016 * will not add the host key automatically. The only
1017 * alternative left is to abort.
1019 error("No %s host key is known for %.200s and you "
1020 "have requested strict checking.", type, host);
1022 } else if (options.strict_host_key_checking ==
1023 SSH_STRICT_HOSTKEY_ASK) {
1024 char msg1[1024], msg2[1024];
1026 if (show_other_keys(host_hostkeys, host_key))
1027 snprintf(msg1, sizeof(msg1),
1028 "\nbut keys of different type are already"
1029 " known for this host.");
1031 snprintf(msg1, sizeof(msg1), ".");
1033 fp = sshkey_fingerprint(host_key,
1034 options.fingerprint_hash, SSH_FP_DEFAULT);
1035 ra = sshkey_fingerprint(host_key,
1036 options.fingerprint_hash, SSH_FP_RANDOMART);
1037 if (fp == NULL || ra == NULL)
1038 fatal("%s: sshkey_fingerprint fail", __func__);
1040 if (options.verify_host_key_dns) {
1041 if (matching_host_key_dns)
1042 snprintf(msg2, sizeof(msg2),
1043 "Matching host key fingerprint"
1044 " found in DNS.\n");
1046 snprintf(msg2, sizeof(msg2),
1047 "No matching host key fingerprint"
1048 " found in DNS.\n");
1050 snprintf(msg, sizeof(msg),
1051 "The authenticity of host '%.200s (%s)' can't be "
1053 "%s key fingerprint is %s.%s%s\n%s"
1054 "Are you sure you want to continue connecting "
1056 host, ip, msg1, type, fp,
1057 options.visual_host_key ? "\n" : "",
1058 options.visual_host_key ? ra : "",
1064 hostkey_trusted = 1; /* user explicitly confirmed */
1067 * If in "new" or "off" strict mode, add the key automatically
1068 * to the local known_hosts file.
1070 if (options.check_host_ip && ip_status == HOST_NEW) {
1071 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
1073 if (options.hash_known_hosts) {
1074 /* Add hash of host and IP separately */
1075 r = add_host_to_hostfile(user_hostfiles[0],
1076 host, host_key, options.hash_known_hosts) &&
1077 add_host_to_hostfile(user_hostfiles[0], ip,
1078 host_key, options.hash_known_hosts);
1080 /* Add unhashed "host,ip" */
1081 r = add_host_to_hostfile(user_hostfiles[0],
1083 options.hash_known_hosts);
1086 r = add_host_to_hostfile(user_hostfiles[0], host,
1087 host_key, options.hash_known_hosts);
1092 logit("Failed to add the host to the list of known "
1093 "hosts (%.500s).", user_hostfiles[0]);
1095 logit("Warning: Permanently added '%.200s' (%s) to the "
1096 "list of known hosts.", hostp, type);
1099 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1100 error("@ WARNING: REVOKED HOST KEY DETECTED! @");
1101 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1102 error("The %s host key for %s is marked as revoked.", type, host);
1103 error("This could mean that a stolen key is being used to");
1104 error("impersonate this host.");
1107 * If strict host key checking is in use, the user will have
1108 * to edit the key manually and we can only abort.
1110 if (options.strict_host_key_checking !=
1111 SSH_STRICT_HOSTKEY_OFF) {
1112 error("%s host key for %.200s was revoked and you have "
1113 "requested strict checking.", type, host);
1116 goto continue_unsafe;
1121 * This is only a debug() since it is valid to have
1122 * CAs with wildcard DNS matches that don't match
1123 * all hosts that one might visit.
1125 debug("Host certificate authority does not "
1126 "match %s in %s:%lu", CA_MARKER,
1127 host_found->file, host_found->line);
1130 if (readonly == ROQUIET)
1132 if (options.check_host_ip && host_ip_differ) {
1134 if (ip_status == HOST_NEW)
1135 key_msg = "is unknown";
1136 else if (ip_status == HOST_OK)
1137 key_msg = "is unchanged";
1139 key_msg = "has a different value";
1140 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1141 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
1142 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1143 error("The %s host key for %s has changed,", type, host);
1144 error("and the key for the corresponding IP address %s", ip);
1145 error("%s. This could either mean that", key_msg);
1146 error("DNS SPOOFING is happening or the IP address for the host");
1147 error("and its host key have changed at the same time.");
1148 if (ip_status != HOST_NEW)
1149 error("Offending key for IP in %s:%lu",
1150 ip_found->file, ip_found->line);
1152 /* The host key has changed. */
1153 warn_changed_key(host_key);
1154 error("Add correct host key in %.100s to get rid of this message.",
1156 error("Offending %s key in %s:%lu",
1157 sshkey_type(host_found->key),
1158 host_found->file, host_found->line);
1161 * If strict host key checking is in use, the user will have
1162 * to edit the key manually and we can only abort.
1164 if (options.strict_host_key_checking !=
1165 SSH_STRICT_HOSTKEY_OFF) {
1166 error("%s host key for %.200s has changed and you have "
1167 "requested strict checking.", type, host);
1173 * If strict host key checking has not been requested, allow
1174 * the connection but without MITM-able authentication or
1177 if (options.password_authentication) {
1178 error("Password authentication is disabled to avoid "
1179 "man-in-the-middle attacks.");
1180 options.password_authentication = 0;
1181 cancelled_forwarding = 1;
1183 if (options.kbd_interactive_authentication) {
1184 error("Keyboard-interactive authentication is disabled"
1185 " to avoid man-in-the-middle attacks.");
1186 options.kbd_interactive_authentication = 0;
1187 options.challenge_response_authentication = 0;
1188 cancelled_forwarding = 1;
1190 if (options.challenge_response_authentication) {
1191 error("Challenge/response authentication is disabled"
1192 " to avoid man-in-the-middle attacks.");
1193 options.challenge_response_authentication = 0;
1194 cancelled_forwarding = 1;
1196 if (options.forward_agent) {
1197 error("Agent forwarding is disabled to avoid "
1198 "man-in-the-middle attacks.");
1199 options.forward_agent = 0;
1200 cancelled_forwarding = 1;
1202 if (options.forward_x11) {
1203 error("X11 forwarding is disabled to avoid "
1204 "man-in-the-middle attacks.");
1205 options.forward_x11 = 0;
1206 cancelled_forwarding = 1;
1208 if (options.num_local_forwards > 0 ||
1209 options.num_remote_forwards > 0) {
1210 error("Port forwarding is disabled to avoid "
1211 "man-in-the-middle attacks.");
1212 options.num_local_forwards =
1213 options.num_remote_forwards = 0;
1214 cancelled_forwarding = 1;
1216 if (options.tun_open != SSH_TUNMODE_NO) {
1217 error("Tunnel forwarding is disabled to avoid "
1218 "man-in-the-middle attacks.");
1219 options.tun_open = SSH_TUNMODE_NO;
1220 cancelled_forwarding = 1;
1222 if (options.exit_on_forward_failure && cancelled_forwarding)
1223 fatal("Error: forwarding disabled due to host key "
1227 * XXX Should permit the user to change to use the new id.
1228 * This could be done by converting the host key to an
1229 * identifying sentence, tell that the host identifies itself
1230 * by that sentence, and ask the user if he/she wishes to
1231 * accept the authentication.
1235 fatal("internal error");
1239 if (options.check_host_ip && host_status != HOST_CHANGED &&
1240 ip_status == HOST_CHANGED) {
1241 snprintf(msg, sizeof(msg),
1242 "Warning: the %s host key for '%.200s' "
1243 "differs from the key for the IP address '%.128s'"
1244 "\nOffending key for IP in %s:%lu",
1245 type, host, ip, ip_found->file, ip_found->line);
1246 if (host_status == HOST_OK) {
1248 snprintf(msg + len, sizeof(msg) - len,
1249 "\nMatching host key in %s:%lu",
1250 host_found->file, host_found->line);
1252 if (options.strict_host_key_checking ==
1253 SSH_STRICT_HOSTKEY_ASK) {
1254 strlcat(msg, "\nAre you sure you want "
1255 "to continue connecting (yes/no)? ", sizeof(msg));
1258 } else if (options.strict_host_key_checking !=
1259 SSH_STRICT_HOSTKEY_OFF) {
1261 error("Exiting, you have requested strict checking.");
1268 if (!hostkey_trusted && options.update_hostkeys) {
1269 debug("%s: hostkey not known or explicitly trusted: "
1270 "disabling UpdateHostkeys", __func__);
1271 options.update_hostkeys = 0;
1276 if (host_hostkeys != NULL)
1277 free_hostkeys(host_hostkeys);
1278 if (ip_hostkeys != NULL)
1279 free_hostkeys(ip_hostkeys);
1283 if (want_cert && host_status != HOST_REVOKED) {
1285 * No matching certificate. Downgrade cert to raw key and
1288 debug("No matching CA found. Retry with plain key");
1289 if ((r = sshkey_from_private(host_key, &raw_key)) != 0)
1290 fatal("%s: sshkey_from_private: %s",
1291 __func__, ssh_err(r));
1292 if ((r = sshkey_drop_cert(raw_key)) != 0)
1293 fatal("Couldn't drop certificate: %s", ssh_err(r));
1297 sshkey_free(raw_key);
1300 if (host_hostkeys != NULL)
1301 free_hostkeys(host_hostkeys);
1302 if (ip_hostkeys != NULL)
1303 free_hostkeys(ip_hostkeys);
1307 /* returns 0 if key verifies or -1 if key does NOT verify */
1309 verify_host_key(char *host, struct sockaddr *hostaddr, struct sshkey *host_key)
1312 int r = -1, flags = 0;
1313 char valid[64], *fp = NULL, *cafp = NULL;
1314 struct sshkey *plain = NULL;
1316 if ((fp = sshkey_fingerprint(host_key,
1317 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1318 error("%s: fingerprint host key: %s", __func__, ssh_err(r));
1323 if (sshkey_is_cert(host_key)) {
1324 if ((cafp = sshkey_fingerprint(host_key->cert->signature_key,
1325 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1326 error("%s: fingerprint CA key: %s",
1327 __func__, ssh_err(r));
1331 sshkey_format_cert_validity(host_key->cert,
1332 valid, sizeof(valid));
1333 debug("Server host certificate: %s %s, serial %llu "
1334 "ID \"%s\" CA %s %s valid %s",
1335 sshkey_ssh_name(host_key), fp,
1336 (unsigned long long)host_key->cert->serial,
1337 host_key->cert->key_id,
1338 sshkey_ssh_name(host_key->cert->signature_key), cafp,
1340 for (i = 0; i < host_key->cert->nprincipals; i++) {
1341 debug2("Server host certificate hostname: %s",
1342 host_key->cert->principals[i]);
1345 debug("Server host key: %s %s", sshkey_ssh_name(host_key), fp);
1348 if (sshkey_equal(previous_host_key, host_key)) {
1349 debug2("%s: server host key %s %s matches cached key",
1350 __func__, sshkey_type(host_key), fp);
1355 /* Check in RevokedHostKeys file if specified */
1356 if (options.revoked_host_keys != NULL) {
1357 r = sshkey_check_revoked(host_key, options.revoked_host_keys);
1360 break; /* not revoked */
1361 case SSH_ERR_KEY_REVOKED:
1362 error("Host key %s %s revoked by file %s",
1363 sshkey_type(host_key), fp,
1364 options.revoked_host_keys);
1368 error("Error checking host key %s %s in "
1369 "revoked keys file %s: %s", sshkey_type(host_key),
1370 fp, options.revoked_host_keys, ssh_err(r));
1376 if (options.verify_host_key_dns) {
1378 * XXX certs are not yet supported for DNS, so downgrade
1379 * them and try the plain key.
1381 if ((r = sshkey_from_private(host_key, &plain)) != 0)
1383 if (sshkey_is_cert(plain))
1384 sshkey_drop_cert(plain);
1385 if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) {
1386 if (flags & DNS_VERIFY_FOUND) {
1387 if (options.verify_host_key_dns == 1 &&
1388 flags & DNS_VERIFY_MATCH &&
1389 flags & DNS_VERIFY_SECURE) {
1393 if (flags & DNS_VERIFY_MATCH) {
1394 matching_host_key_dns = 1;
1396 warn_changed_key(plain);
1397 error("Update the SSHFP RR in DNS "
1398 "with the new host key to get rid "
1399 "of this message.");
1404 r = check_host_key(host, hostaddr, options.port, host_key, RDRW,
1405 options.user_hostfiles, options.num_user_hostfiles,
1406 options.system_hostfiles, options.num_system_hostfiles);
1412 if (r == 0 && host_key != NULL) {
1413 sshkey_free(previous_host_key);
1414 r = sshkey_from_private(host_key, &previous_host_key);
1421 * Starts a dialog with the server, and authenticates the current user on the
1422 * server. This does not need any extra privileges. The basic connection
1423 * to the server must already have been established before this is called.
1424 * If login fails, this function prints an error and never returns.
1425 * This function does not require super-user privileges.
1428 ssh_login(Sensitive *sensitive, const char *orighost,
1429 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms)
1432 char *server_user, *local_user;
1434 local_user = xstrdup(pw->pw_name);
1435 server_user = options.user ? options.user : local_user;
1437 /* Convert the user-supplied hostname into all lowercase. */
1438 host = xstrdup(orighost);
1441 /* Exchange protocol version identification strings with the server. */
1442 ssh_exchange_identification(timeout_ms);
1444 /* Put the connection into non-blocking mode. */
1445 packet_set_nonblocking();
1448 /* authenticate user */
1449 debug("Authenticating to %s:%d as '%s'", host, port, server_user);
1450 ssh_kex2(host, hostaddr, port);
1451 ssh_userauth2(local_user, server_user, host, sensitive);
1456 ssh_put_password(char *password)
1461 if (datafellows & SSH_BUG_PASSWORDPAD) {
1462 packet_put_cstring(password);
1465 size = ROUNDUP(strlen(password) + 1, 32);
1466 padded = xcalloc(1, size);
1467 strlcpy(padded, password, size);
1468 packet_put_string(padded, size);
1469 explicit_bzero(padded, size);
1473 /* print all known host keys for a given host, but skip keys of given type */
1475 show_other_keys(struct hostkeys *hostkeys, struct sshkey *key)
1487 const struct hostkey_entry *found;
1489 for (i = 0; type[i] != -1; i++) {
1490 if (type[i] == key->type)
1492 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found))
1494 fp = sshkey_fingerprint(found->key,
1495 options.fingerprint_hash, SSH_FP_DEFAULT);
1496 ra = sshkey_fingerprint(found->key,
1497 options.fingerprint_hash, SSH_FP_RANDOMART);
1498 if (fp == NULL || ra == NULL)
1499 fatal("%s: sshkey_fingerprint fail", __func__);
1500 logit("WARNING: %s key found for host %s\n"
1502 "%s key fingerprint %s.",
1503 key_type(found->key),
1504 found->host, found->file, found->line,
1505 key_type(found->key), fp);
1506 if (options.visual_host_key)
1516 warn_changed_key(struct sshkey *host_key)
1520 fp = sshkey_fingerprint(host_key, options.fingerprint_hash,
1523 fatal("%s: sshkey_fingerprint fail", __func__);
1525 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1526 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1527 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1528 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1529 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1530 error("It is also possible that a host key has just been changed.");
1531 error("The fingerprint for the %s key sent by the remote host is\n%s.",
1532 key_type(host_key), fp);
1533 error("Please contact your system administrator.");
1539 * Execute a local command
1542 ssh_local_cmd(const char *args)
1547 void (*osighand)(int);
1549 if (!options.permit_local_command ||
1550 args == NULL || !*args)
1553 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
1554 shell = _PATH_BSHELL;
1556 osighand = signal(SIGCHLD, SIG_DFL);
1559 signal(SIGPIPE, SIG_DFL);
1560 debug3("Executing %s -c \"%s\"", shell, args);
1561 execl(shell, shell, "-c", args, (char *)NULL);
1562 error("Couldn't execute %s -c \"%s\": %s",
1563 shell, args, strerror(errno));
1565 } else if (pid == -1)
1566 fatal("fork failed: %.100s", strerror(errno));
1567 while (waitpid(pid, &status, 0) == -1)
1569 fatal("Couldn't wait for child: %s", strerror(errno));
1570 signal(SIGCHLD, osighand);
1572 if (!WIFEXITED(status))
1575 return (WEXITSTATUS(status));
1579 maybe_add_key_to_agent(char *authfile, const struct sshkey *private,
1580 char *comment, char *passphrase)
1582 int auth_sock = -1, r;
1584 if (options.add_keys_to_agent == 0)
1587 if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) {
1588 debug3("no authentication agent, not adding key");
1592 if (options.add_keys_to_agent == 2 &&
1593 !ask_permission("Add key %s (%s) to agent?", authfile, comment)) {
1594 debug3("user denied adding this key");
1599 if ((r = ssh_add_identity_constrained(auth_sock, private, comment, 0,
1600 (options.add_keys_to_agent == 3), 0)) == 0)
1601 debug("identity added to agent: %s", authfile);
1603 debug("could not add identity to agent: %s (%d)", authfile, r);