1 /* $OpenBSD: sshconnect.c,v 1.273 2017/03/10 03:22:40 dtucker Exp $ */
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
6 * Code to connect to a remote host, and to perform the client side of the
7 * login (authentication) dialog.
9 * As far as I am concerned, the code I have written for this software
10 * can be used freely for any purpose. Any derived versions of this
11 * software must be clearly marked as such, and if the derived work is
12 * incompatible with the protocol description in the RFC file, it must be
13 * called by a name other than "ssh" or "Secure Shell".
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"
61 #include "monitor_fdpass.h"
68 char *client_version_string = NULL;
69 char *server_version_string = NULL;
70 Key *previous_host_key = NULL;
72 static int matching_host_key_dns = 0;
74 static pid_t proxy_command_pid = 0;
77 extern Options options;
78 extern char *__progname;
79 extern uid_t original_real_uid;
80 extern uid_t original_effective_uid;
82 static int show_other_keys(struct hostkeys *, Key *);
83 static void warn_changed_key(Key *);
85 /* Expand a proxy command */
87 expand_proxy_command(const char *proxy_command, const char *user,
88 const char *host, int port)
90 char *tmp, *ret, strport[NI_MAXSERV];
92 snprintf(strport, sizeof strport, "%d", port);
93 xasprintf(&tmp, "exec %s", proxy_command);
94 ret = percent_expand(tmp, "h", host, "p", strport,
95 "r", options.user, (char *)NULL);
101 * Connect to the given ssh server using a proxy command that passes a
102 * a connected fd back to us.
105 ssh_proxy_fdpass_connect(const char *host, u_short port,
106 const char *proxy_command)
108 char *command_string;
113 if ((shell = getenv("SHELL")) == NULL)
114 shell = _PATH_BSHELL;
116 if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) < 0)
117 fatal("Could not create socketpair to communicate with "
118 "proxy dialer: %.100s", strerror(errno));
120 command_string = expand_proxy_command(proxy_command, options.user,
122 debug("Executing proxy dialer 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);
132 /* Redirect stdin and stdout. */
134 if (dup2(sp[0], 0) < 0)
135 perror("dup2 stdin");
138 if (dup2(sp[0], 1) < 0)
139 perror("dup2 stdout");
145 * Stderr is left as it is so that error messages get
146 * printed on the user's terminal.
150 argv[2] = command_string;
154 * Execute the proxy command.
155 * Note that we gave up any extra privileges above.
157 execv(argv[0], argv);
163 fatal("fork failed: %.100s", strerror(errno));
165 free(command_string);
167 if ((sock = mm_receive_fd(sp[1])) == -1)
168 fatal("proxy dialer did not pass back a connection");
171 while (waitpid(pid, NULL, 0) == -1)
173 fatal("Couldn't wait for child: %s", strerror(errno));
175 /* Set the connection file descriptors. */
176 packet_set_connection(sock, sock);
182 * Connect to the given ssh server using a proxy command.
185 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
187 char *command_string;
192 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
193 shell = _PATH_BSHELL;
195 /* Create pipes for communicating with the proxy. */
196 if (pipe(pin) < 0 || pipe(pout) < 0)
197 fatal("Could not create pipes to communicate with the proxy: %.100s",
200 command_string = expand_proxy_command(proxy_command, options.user,
202 debug("Executing proxy command: %.500s", command_string);
204 /* Fork and execute the proxy command. */
205 if ((pid = fork()) == 0) {
208 /* Child. Permanently give up superuser privileges. */
209 permanently_drop_suid(original_real_uid);
211 /* Redirect stdin and stdout. */
214 if (dup2(pin[0], 0) < 0)
215 perror("dup2 stdin");
219 if (dup2(pout[1], 1) < 0)
220 perror("dup2 stdout");
221 /* Cannot be 1 because pin allocated two descriptors. */
224 /* Stderr is left as it is so that error messages get
225 printed on the user's terminal. */
228 argv[2] = command_string;
231 /* Execute the proxy command. Note that we gave up any
232 extra privileges above. */
233 signal(SIGPIPE, SIG_DFL);
234 execv(argv[0], argv);
240 fatal("fork failed: %.100s", strerror(errno));
242 proxy_command_pid = pid; /* save pid to clean up later */
244 /* Close child side of the descriptors. */
248 /* Free the command name. */
249 free(command_string);
251 /* Set the connection file descriptors. */
252 packet_set_connection(pout[0], pin[1]);
254 /* Indicate OK return */
259 ssh_kill_proxy_command(void)
262 * Send SIGHUP to proxy command if used. We don't wait() in
263 * case it hangs and instead rely on init to reap the child
265 if (proxy_command_pid > 1)
266 kill(proxy_command_pid, SIGHUP);
270 * Creates a (possibly privileged) socket for use as the ssh connection.
273 ssh_create_socket(int privileged, struct addrinfo *ai)
276 struct addrinfo hints, *res = NULL;
278 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
280 error("socket: %s", strerror(errno));
283 fcntl(sock, F_SETFD, FD_CLOEXEC);
285 /* Bind the socket to an alternative local IP address */
286 if (options.bind_address == NULL && !privileged)
289 if (options.bind_address) {
290 memset(&hints, 0, sizeof(hints));
291 hints.ai_family = ai->ai_family;
292 hints.ai_socktype = ai->ai_socktype;
293 hints.ai_protocol = ai->ai_protocol;
294 hints.ai_flags = AI_PASSIVE;
295 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res);
297 error("getaddrinfo: %s: %s", options.bind_address,
298 ssh_gai_strerror(gaierr));
304 * If we are running as root and want to connect to a privileged
305 * port, bind our own socket to a privileged port.
309 r = bindresvport_sa(sock, res ? res->ai_addr : NULL);
312 error("bindresvport_sa: af=%d %s", ai->ai_family,
317 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
318 error("bind: %s: %s", options.bind_address,
332 timeout_connect(int sockfd, const struct sockaddr *serv_addr,
333 socklen_t addrlen, int *timeoutp)
336 struct timeval tv, t_start;
338 int optval, rc, result = -1;
340 gettimeofday(&t_start, NULL);
342 if (*timeoutp <= 0) {
343 result = connect(sockfd, serv_addr, addrlen);
347 set_nonblock(sockfd);
348 rc = connect(sockfd, serv_addr, addrlen);
350 unset_nonblock(sockfd);
354 if (errno != EINPROGRESS) {
359 fdset = xcalloc(howmany(sockfd + 1, NFDBITS),
361 FD_SET(sockfd, fdset);
362 ms_to_timeval(&tv, *timeoutp);
365 rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
366 if (rc != -1 || errno != EINTR)
377 debug("select: %s", strerror(errno));
380 /* Completed or failed */
382 optlen = sizeof(optval);
383 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
385 debug("getsockopt: %s", strerror(errno));
393 unset_nonblock(sockfd);
396 /* Should not occur */
397 fatal("Bogus return (%d) from select()", rc);
403 if (result == 0 && *timeoutp > 0) {
404 ms_subtract_diff(&t_start, timeoutp);
405 if (*timeoutp <= 0) {
415 * Opens a TCP/IP connection to the remote server on the given host.
416 * The address of the remote host will be returned in hostaddr.
417 * If port is 0, the default port will be used. If needpriv is true,
418 * a privileged port will be allocated to make the connection.
419 * This requires super-user privileges if needpriv is true.
420 * Connection_attempts specifies the maximum number of tries (one per
421 * second). If proxy_command is non-NULL, it specifies the command (with %h
422 * and %p substituted for host and port, respectively) to use to contact
426 ssh_connect_direct(const char *host, struct addrinfo *aitop,
427 struct sockaddr_storage *hostaddr, u_short port, int family,
428 int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv)
431 int sock = -1, attempt;
432 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
435 debug2("%s: needpriv %d", __func__, needpriv);
436 memset(ntop, 0, sizeof(ntop));
437 memset(strport, 0, sizeof(strport));
439 for (attempt = 0; attempt < connection_attempts; attempt++) {
441 /* Sleep a moment before retrying. */
443 debug("Trying again...");
446 * Loop through addresses for this host, and try each one in
447 * sequence until the connection succeeds.
449 for (ai = aitop; ai; ai = ai->ai_next) {
450 if (ai->ai_family != AF_INET &&
451 ai->ai_family != AF_INET6)
453 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
454 ntop, sizeof(ntop), strport, sizeof(strport),
455 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
456 error("%s: getnameinfo failed", __func__);
459 debug("Connecting to %.200s [%.100s] port %s.",
460 host, ntop, strport);
462 /* Create a socket for connecting. */
463 sock = ssh_create_socket(needpriv, ai);
465 /* Any error is already output */
468 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
470 /* Successful connection. */
471 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
474 debug("connect to address %s port %s: %s",
475 ntop, strport, strerror(errno));
481 break; /* Successful connection. */
484 /* Return failure if we didn't get a successful connection. */
486 error("ssh: connect to host %s port %s: %s",
487 host, strport, strerror(errno));
491 debug("Connection established.");
493 /* Set SO_KEEPALIVE if requested. */
494 if (want_keepalive &&
495 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
497 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
499 /* Set the connection. */
500 packet_set_connection(sock, sock);
506 ssh_connect(const char *host, struct addrinfo *addrs,
507 struct sockaddr_storage *hostaddr, u_short port, int family,
508 int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv)
510 if (options.proxy_command == NULL) {
511 return ssh_connect_direct(host, addrs, hostaddr, port, family,
512 connection_attempts, timeout_ms, want_keepalive, needpriv);
513 } else if (strcmp(options.proxy_command, "-") == 0) {
514 packet_set_connection(STDIN_FILENO, STDOUT_FILENO);
515 return 0; /* Always succeeds */
516 } else if (options.proxy_use_fdpass) {
517 return ssh_proxy_fdpass_connect(host, port,
518 options.proxy_command);
520 return ssh_proxy_connect(host, port, options.proxy_command);
524 send_client_banner(int connection_out, int minor1)
526 /* Send our own protocol version identification. */
528 xasprintf(&client_version_string, "SSH-%d.%d-%.100s\r\n",
529 PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION);
531 xasprintf(&client_version_string, "SSH-%d.%d-%.100s\n",
532 PROTOCOL_MAJOR_1, minor1, SSH_VERSION);
534 if (atomicio(vwrite, connection_out, client_version_string,
535 strlen(client_version_string)) != strlen(client_version_string))
536 fatal("write: %.100s", strerror(errno));
537 chop(client_version_string);
538 debug("Local version string %.100s", client_version_string);
542 * Waits for the server identification string, and sends our own
543 * identification string.
546 ssh_exchange_identification(int timeout_ms)
548 char buf[256], remote_version[256]; /* must be same size! */
549 int remote_major, remote_minor, mismatch;
550 int connection_in = packet_get_connection_in();
551 int connection_out = packet_get_connection_out();
552 int minor1 = PROTOCOL_MINOR_1, client_banner_sent = 0;
555 int fdsetsz, remaining, rc;
556 struct timeval t_start, t_remaining;
559 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask);
560 fdset = xcalloc(1, fdsetsz);
563 * If we are SSH2-only then we can send the banner immediately and
566 if (options.protocol == SSH_PROTO_2) {
568 send_client_banner(connection_out, 0);
569 client_banner_sent = 1;
572 /* Read other side's version identification. */
573 remaining = timeout_ms;
575 for (i = 0; i < sizeof(buf) - 1; i++) {
576 if (timeout_ms > 0) {
577 gettimeofday(&t_start, NULL);
578 ms_to_timeval(&t_remaining, remaining);
579 FD_SET(connection_in, fdset);
580 rc = select(connection_in + 1, fdset, NULL,
581 fdset, &t_remaining);
582 ms_subtract_diff(&t_start, &remaining);
583 if (rc == 0 || remaining <= 0)
584 fatal("Connection timed out during "
589 fatal("ssh_exchange_identification: "
590 "select: %s", strerror(errno));
594 len = atomicio(read, connection_in, &buf[i], 1);
596 if (len != 1 && errno == EPIPE)
597 fatal("ssh_exchange_identification: "
598 "Connection closed by remote host");
600 fatal("ssh_exchange_identification: "
601 "read: %.100s", strerror(errno));
602 if (buf[i] == '\r') {
605 continue; /**XXX wait for \n */
607 if (buf[i] == '\n') {
612 fatal("ssh_exchange_identification: "
613 "No banner received");
615 buf[sizeof(buf) - 1] = 0;
616 if (strncmp(buf, "SSH-", 4) == 0)
618 debug("ssh_exchange_identification: %s", buf);
620 server_version_string = xstrdup(buf);
624 * Check that the versions match. In future this might accept
625 * several versions and set appropriate flags to handle them.
627 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
628 &remote_major, &remote_minor, remote_version) != 3)
629 fatal("Bad remote protocol version identification: '%.100s'", buf);
630 debug("Remote protocol version %d.%d, remote software version %.100s",
631 remote_major, remote_minor, remote_version);
633 active_state->compat = compat_datafellows(remote_version);
636 switch (remote_major) {
638 if (remote_minor == 99 &&
639 (options.protocol & SSH_PROTO_2) &&
640 !(options.protocol & SSH_PROTO_1_PREFERRED)) {
644 if (!(options.protocol & SSH_PROTO_1)) {
648 if (remote_minor < 3) {
649 fatal("Remote machine has too old SSH software version.");
650 } else if (remote_minor == 3 || remote_minor == 4) {
651 /* We speak 1.3, too. */
654 if (options.forward_agent) {
655 logit("Agent forwarding disabled for protocol 1.3");
656 options.forward_agent = 0;
661 if (options.protocol & SSH_PROTO_2) {
671 fatal("Protocol major versions differ: %d vs. %d",
672 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
674 if ((datafellows & SSH_BUG_DERIVEKEY) != 0)
675 fatal("Server version \"%.100s\" uses unsafe key agreement; "
676 "refusing connection", remote_version);
677 if ((datafellows & SSH_BUG_RSASIGMD5) != 0)
678 logit("Server version \"%.100s\" uses unsafe RSA signature "
679 "scheme; disabling use of RSA keys", remote_version);
680 if (!client_banner_sent)
681 send_client_banner(connection_out, minor1);
682 chop(server_version_string);
685 /* defaults to 'no' */
687 confirm(const char *prompt)
689 const char *msg, *again = "Please type 'yes' or 'no': ";
693 if (options.batch_mode)
695 for (msg = prompt;;msg = again) {
696 p = read_passphrase(msg, RP_ECHO);
698 (p[0] == '\0') || (p[0] == '\n') ||
699 strncasecmp(p, "no", 2) == 0)
701 if (p && strncasecmp(p, "yes", 3) == 0)
710 check_host_cert(const char *host, const Key *host_key)
714 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) {
718 if (buffer_len(host_key->cert->critical) != 0) {
719 error("Certificate for %s contains unsupported "
720 "critical options(s)", host);
727 sockaddr_is_local(struct sockaddr *hostaddr)
729 switch (hostaddr->sa_family) {
731 return (ntohl(((struct sockaddr_in *)hostaddr)->
732 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
734 return IN6_IS_ADDR_LOOPBACK(
735 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
742 * Prepare the hostname and ip address strings that are used to lookup
743 * host keys in known_hosts files. These may have a port number appended.
746 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr,
747 u_short port, char **hostfile_hostname, char **hostfile_ipaddr)
749 char ntop[NI_MAXHOST];
752 switch (hostaddr == NULL ? -1 : hostaddr->sa_family) {
757 addrlen = sizeof(struct sockaddr_in);
760 addrlen = sizeof(struct sockaddr_in6);
763 addrlen = sizeof(struct sockaddr);
768 * We don't have the remote ip-address for connections
769 * using a proxy command
771 if (hostfile_ipaddr != NULL) {
772 if (options.proxy_command == NULL) {
773 if (getnameinfo(hostaddr, addrlen,
774 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0)
775 fatal("%s: getnameinfo failed", __func__);
776 *hostfile_ipaddr = put_host_port(ntop, port);
778 *hostfile_ipaddr = xstrdup("<no hostip for proxy "
784 * Allow the user to record the key under a different name or
785 * differentiate a non-standard port. This is useful for ssh
786 * tunneling over forwarded connections or if you run multiple
787 * sshd's on different ports on the same machine.
789 if (hostfile_hostname != NULL) {
790 if (options.host_key_alias != NULL) {
791 *hostfile_hostname = xstrdup(options.host_key_alias);
792 debug("using hostkeyalias: %s", *hostfile_hostname);
794 *hostfile_hostname = put_host_port(hostname, port);
800 * check whether the supplied host key is valid, return -1 if the key
801 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true.
807 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
808 Key *host_key, int readonly,
809 char **user_hostfiles, u_int num_user_hostfiles,
810 char **system_hostfiles, u_int num_system_hostfiles)
812 HostStatus host_status;
813 HostStatus ip_status;
815 char *ip = NULL, *host = NULL;
816 char hostline[1000], *hostp, *fp, *ra;
819 const struct hostkey_entry *host_found, *ip_found;
820 int len, cancelled_forwarding = 0;
821 int local = sockaddr_is_local(hostaddr);
822 int r, want_cert = key_is_cert(host_key), host_ip_differ = 0;
823 int hostkey_trusted = 0; /* Known or explicitly accepted by user */
824 struct hostkeys *host_hostkeys, *ip_hostkeys;
828 * Force accepting of the host key for loopback/localhost. The
829 * problem is that if the home directory is NFS-mounted to multiple
830 * machines, localhost will refer to a different machine in each of
831 * them, and the user will get bogus HOST_CHANGED warnings. This
832 * essentially disables host authentication for localhost; however,
833 * this is probably not a real problem.
835 if (options.no_host_authentication_for_localhost == 1 && local &&
836 options.host_key_alias == NULL) {
837 debug("Forcing accepting of host key for "
838 "loopback/localhost.");
843 * Prepare the hostname and address strings used for hostkey lookup.
844 * In some cases, these will have a port number appended.
846 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip);
849 * Turn off check_host_ip if the connection is to localhost, via proxy
850 * command or if we don't have a hostname to compare with
852 if (options.check_host_ip && (local ||
853 strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
854 options.check_host_ip = 0;
856 host_hostkeys = init_hostkeys();
857 for (i = 0; i < num_user_hostfiles; i++)
858 load_hostkeys(host_hostkeys, host, user_hostfiles[i]);
859 for (i = 0; i < num_system_hostfiles; i++)
860 load_hostkeys(host_hostkeys, host, system_hostfiles[i]);
863 if (!want_cert && options.check_host_ip) {
864 ip_hostkeys = init_hostkeys();
865 for (i = 0; i < num_user_hostfiles; i++)
866 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]);
867 for (i = 0; i < num_system_hostfiles; i++)
868 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]);
872 /* Reload these as they may have changed on cert->key downgrade */
873 want_cert = key_is_cert(host_key);
874 type = key_type(host_key);
877 * Check if the host key is present in the user's list of known
878 * hosts or in the systemwide list.
880 host_status = check_key_in_hostkeys(host_hostkeys, host_key,
884 * Also perform check for the ip address, skip the check if we are
885 * localhost, looking for a certificate, or the hostname was an ip
886 * address to begin with.
888 if (!want_cert && ip_hostkeys != NULL) {
889 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key,
891 if (host_status == HOST_CHANGED &&
892 (ip_status != HOST_CHANGED ||
894 !key_equal(ip_found->key, host_found->key))))
897 ip_status = host_status;
899 switch (host_status) {
901 /* The host is known and the key matches. */
902 debug("Host '%.200s' is known and matches the %s host %s.",
903 host, type, want_cert ? "certificate" : "key");
904 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key",
905 host_found->file, host_found->line);
906 if (want_cert && !check_host_cert(hostname, host_key))
908 if (options.check_host_ip && ip_status == HOST_NEW) {
909 if (readonly || want_cert)
910 logit("%s host key for IP address "
911 "'%.128s' not in list of known hosts.",
913 else if (!add_host_to_hostfile(user_hostfiles[0], ip,
914 host_key, options.hash_known_hosts))
915 logit("Failed to add the %s host key for IP "
916 "address '%.128s' to the list of known "
917 "hosts (%.500s).", type, ip,
920 logit("Warning: Permanently added the %s host "
921 "key for IP address '%.128s' to the list "
922 "of known hosts.", type, ip);
923 } else if (options.visual_host_key) {
924 fp = sshkey_fingerprint(host_key,
925 options.fingerprint_hash, SSH_FP_DEFAULT);
926 ra = sshkey_fingerprint(host_key,
927 options.fingerprint_hash, SSH_FP_RANDOMART);
928 if (fp == NULL || ra == NULL)
929 fatal("%s: sshkey_fingerprint fail", __func__);
930 logit("Host key fingerprint is %s\n%s", fp, ra);
937 if (options.host_key_alias == NULL && port != 0 &&
938 port != SSH_DEFAULT_PORT) {
939 debug("checking without port identifier");
940 if (check_host_key(hostname, hostaddr, 0, host_key,
941 ROQUIET, user_hostfiles, num_user_hostfiles,
942 system_hostfiles, num_system_hostfiles) == 0) {
943 debug("found matching key w/out port");
947 if (readonly || want_cert)
949 /* The host is new. */
950 if (options.strict_host_key_checking == 1) {
952 * User has requested strict host key checking. We
953 * will not add the host key automatically. The only
954 * alternative left is to abort.
956 error("No %s host key is known for %.200s and you "
957 "have requested strict checking.", type, host);
959 } else if (options.strict_host_key_checking == 2) {
960 char msg1[1024], msg2[1024];
962 if (show_other_keys(host_hostkeys, host_key))
963 snprintf(msg1, sizeof(msg1),
964 "\nbut keys of different type are already"
965 " known for this host.");
967 snprintf(msg1, sizeof(msg1), ".");
969 fp = sshkey_fingerprint(host_key,
970 options.fingerprint_hash, SSH_FP_DEFAULT);
971 ra = sshkey_fingerprint(host_key,
972 options.fingerprint_hash, SSH_FP_RANDOMART);
973 if (fp == NULL || ra == NULL)
974 fatal("%s: sshkey_fingerprint fail", __func__);
976 if (options.verify_host_key_dns) {
977 if (matching_host_key_dns)
978 snprintf(msg2, sizeof(msg2),
979 "Matching host key fingerprint"
982 snprintf(msg2, sizeof(msg2),
983 "No matching host key fingerprint"
986 snprintf(msg, sizeof(msg),
987 "The authenticity of host '%.200s (%s)' can't be "
989 "%s key fingerprint is %s.%s%s\n%s"
990 "Are you sure you want to continue connecting "
992 host, ip, msg1, type, fp,
993 options.visual_host_key ? "\n" : "",
994 options.visual_host_key ? ra : "",
1000 hostkey_trusted = 1; /* user explicitly confirmed */
1003 * If not in strict mode, add the key automatically to the
1004 * local known_hosts file.
1006 if (options.check_host_ip && ip_status == HOST_NEW) {
1007 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
1009 if (options.hash_known_hosts) {
1010 /* Add hash of host and IP separately */
1011 r = add_host_to_hostfile(user_hostfiles[0],
1012 host, host_key, options.hash_known_hosts) &&
1013 add_host_to_hostfile(user_hostfiles[0], ip,
1014 host_key, options.hash_known_hosts);
1016 /* Add unhashed "host,ip" */
1017 r = add_host_to_hostfile(user_hostfiles[0],
1019 options.hash_known_hosts);
1022 r = add_host_to_hostfile(user_hostfiles[0], host,
1023 host_key, options.hash_known_hosts);
1028 logit("Failed to add the host to the list of known "
1029 "hosts (%.500s).", user_hostfiles[0]);
1031 logit("Warning: Permanently added '%.200s' (%s) to the "
1032 "list of known hosts.", hostp, type);
1035 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1036 error("@ WARNING: REVOKED HOST KEY DETECTED! @");
1037 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1038 error("The %s host key for %s is marked as revoked.", type, host);
1039 error("This could mean that a stolen key is being used to");
1040 error("impersonate this host.");
1043 * If strict host key checking is in use, the user will have
1044 * to edit the key manually and we can only abort.
1046 if (options.strict_host_key_checking) {
1047 error("%s host key for %.200s was revoked and you have "
1048 "requested strict checking.", type, host);
1051 goto continue_unsafe;
1056 * This is only a debug() since it is valid to have
1057 * CAs with wildcard DNS matches that don't match
1058 * all hosts that one might visit.
1060 debug("Host certificate authority does not "
1061 "match %s in %s:%lu", CA_MARKER,
1062 host_found->file, host_found->line);
1065 if (readonly == ROQUIET)
1067 if (options.check_host_ip && host_ip_differ) {
1069 if (ip_status == HOST_NEW)
1070 key_msg = "is unknown";
1071 else if (ip_status == HOST_OK)
1072 key_msg = "is unchanged";
1074 key_msg = "has a different value";
1075 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1076 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
1077 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1078 error("The %s host key for %s has changed,", type, host);
1079 error("and the key for the corresponding IP address %s", ip);
1080 error("%s. This could either mean that", key_msg);
1081 error("DNS SPOOFING is happening or the IP address for the host");
1082 error("and its host key have changed at the same time.");
1083 if (ip_status != HOST_NEW)
1084 error("Offending key for IP in %s:%lu",
1085 ip_found->file, ip_found->line);
1087 /* The host key has changed. */
1088 warn_changed_key(host_key);
1089 error("Add correct host key in %.100s to get rid of this message.",
1091 error("Offending %s key in %s:%lu", key_type(host_found->key),
1092 host_found->file, host_found->line);
1095 * If strict host key checking is in use, the user will have
1096 * to edit the key manually and we can only abort.
1098 if (options.strict_host_key_checking) {
1099 error("%s host key for %.200s has changed and you have "
1100 "requested strict checking.", type, host);
1106 * If strict host key checking has not been requested, allow
1107 * the connection but without MITM-able authentication or
1110 if (options.password_authentication) {
1111 error("Password authentication is disabled to avoid "
1112 "man-in-the-middle attacks.");
1113 options.password_authentication = 0;
1114 cancelled_forwarding = 1;
1116 if (options.kbd_interactive_authentication) {
1117 error("Keyboard-interactive authentication is disabled"
1118 " to avoid man-in-the-middle attacks.");
1119 options.kbd_interactive_authentication = 0;
1120 options.challenge_response_authentication = 0;
1121 cancelled_forwarding = 1;
1123 if (options.challenge_response_authentication) {
1124 error("Challenge/response authentication is disabled"
1125 " to avoid man-in-the-middle attacks.");
1126 options.challenge_response_authentication = 0;
1127 cancelled_forwarding = 1;
1129 if (options.forward_agent) {
1130 error("Agent forwarding is disabled to avoid "
1131 "man-in-the-middle attacks.");
1132 options.forward_agent = 0;
1133 cancelled_forwarding = 1;
1135 if (options.forward_x11) {
1136 error("X11 forwarding is disabled to avoid "
1137 "man-in-the-middle attacks.");
1138 options.forward_x11 = 0;
1139 cancelled_forwarding = 1;
1141 if (options.num_local_forwards > 0 ||
1142 options.num_remote_forwards > 0) {
1143 error("Port forwarding is disabled to avoid "
1144 "man-in-the-middle attacks.");
1145 options.num_local_forwards =
1146 options.num_remote_forwards = 0;
1147 cancelled_forwarding = 1;
1149 if (options.tun_open != SSH_TUNMODE_NO) {
1150 error("Tunnel forwarding is disabled to avoid "
1151 "man-in-the-middle attacks.");
1152 options.tun_open = SSH_TUNMODE_NO;
1153 cancelled_forwarding = 1;
1155 if (options.exit_on_forward_failure && cancelled_forwarding)
1156 fatal("Error: forwarding disabled due to host key "
1160 * XXX Should permit the user to change to use the new id.
1161 * This could be done by converting the host key to an
1162 * identifying sentence, tell that the host identifies itself
1163 * by that sentence, and ask the user if he/she wishes to
1164 * accept the authentication.
1168 fatal("internal error");
1172 if (options.check_host_ip && host_status != HOST_CHANGED &&
1173 ip_status == HOST_CHANGED) {
1174 snprintf(msg, sizeof(msg),
1175 "Warning: the %s host key for '%.200s' "
1176 "differs from the key for the IP address '%.128s'"
1177 "\nOffending key for IP in %s:%lu",
1178 type, host, ip, ip_found->file, ip_found->line);
1179 if (host_status == HOST_OK) {
1181 snprintf(msg + len, sizeof(msg) - len,
1182 "\nMatching host key in %s:%lu",
1183 host_found->file, host_found->line);
1185 if (options.strict_host_key_checking == 1) {
1187 error("Exiting, you have requested strict checking.");
1189 } else if (options.strict_host_key_checking == 2) {
1190 strlcat(msg, "\nAre you sure you want "
1191 "to continue connecting (yes/no)? ", sizeof(msg));
1199 if (!hostkey_trusted && options.update_hostkeys) {
1200 debug("%s: hostkey not known or explicitly trusted: "
1201 "disabling UpdateHostkeys", __func__);
1202 options.update_hostkeys = 0;
1207 if (host_hostkeys != NULL)
1208 free_hostkeys(host_hostkeys);
1209 if (ip_hostkeys != NULL)
1210 free_hostkeys(ip_hostkeys);
1214 if (want_cert && host_status != HOST_REVOKED) {
1216 * No matching certificate. Downgrade cert to raw key and
1219 debug("No matching CA found. Retry with plain key");
1220 raw_key = key_from_private(host_key);
1221 if (key_drop_cert(raw_key) != 0)
1222 fatal("Couldn't drop certificate");
1226 if (raw_key != NULL)
1230 if (host_hostkeys != NULL)
1231 free_hostkeys(host_hostkeys);
1232 if (ip_hostkeys != NULL)
1233 free_hostkeys(ip_hostkeys);
1237 /* returns 0 if key verifies or -1 if key does NOT verify */
1239 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
1242 int r = -1, flags = 0;
1243 char valid[64], *fp = NULL, *cafp = NULL;
1244 struct sshkey *plain = NULL;
1246 if ((fp = sshkey_fingerprint(host_key,
1247 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1248 error("%s: fingerprint host key: %s", __func__, ssh_err(r));
1253 if (sshkey_is_cert(host_key)) {
1254 if ((cafp = sshkey_fingerprint(host_key->cert->signature_key,
1255 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1256 error("%s: fingerprint CA key: %s",
1257 __func__, ssh_err(r));
1261 sshkey_format_cert_validity(host_key->cert,
1262 valid, sizeof(valid));
1263 debug("Server host certificate: %s %s, serial %llu "
1264 "ID \"%s\" CA %s %s valid %s",
1265 sshkey_ssh_name(host_key), fp,
1266 (unsigned long long)host_key->cert->serial,
1267 host_key->cert->key_id,
1268 sshkey_ssh_name(host_key->cert->signature_key), cafp,
1270 for (i = 0; i < host_key->cert->nprincipals; i++) {
1271 debug2("Server host certificate hostname: %s",
1272 host_key->cert->principals[i]);
1275 debug("Server host key: %s %s", compat20 ?
1276 sshkey_ssh_name(host_key) : sshkey_type(host_key), fp);
1279 if (sshkey_equal(previous_host_key, host_key)) {
1280 debug2("%s: server host key %s %s matches cached key",
1281 __func__, sshkey_type(host_key), fp);
1286 /* Check in RevokedHostKeys file if specified */
1287 if (options.revoked_host_keys != NULL) {
1288 r = sshkey_check_revoked(host_key, options.revoked_host_keys);
1291 break; /* not revoked */
1292 case SSH_ERR_KEY_REVOKED:
1293 error("Host key %s %s revoked by file %s",
1294 sshkey_type(host_key), fp,
1295 options.revoked_host_keys);
1299 error("Error checking host key %s %s in "
1300 "revoked keys file %s: %s", sshkey_type(host_key),
1301 fp, options.revoked_host_keys, ssh_err(r));
1307 if (options.verify_host_key_dns) {
1309 * XXX certs are not yet supported for DNS, so downgrade
1310 * them and try the plain key.
1312 if ((r = sshkey_from_private(host_key, &plain)) != 0)
1314 if (sshkey_is_cert(plain))
1315 sshkey_drop_cert(plain);
1316 if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) {
1317 if (flags & DNS_VERIFY_FOUND) {
1318 if (options.verify_host_key_dns == 1 &&
1319 flags & DNS_VERIFY_MATCH &&
1320 flags & DNS_VERIFY_SECURE) {
1324 if (flags & DNS_VERIFY_MATCH) {
1325 matching_host_key_dns = 1;
1327 warn_changed_key(plain);
1328 error("Update the SSHFP RR in DNS "
1329 "with the new host key to get rid "
1330 "of this message.");
1335 r = check_host_key(host, hostaddr, options.port, host_key, RDRW,
1336 options.user_hostfiles, options.num_user_hostfiles,
1337 options.system_hostfiles, options.num_system_hostfiles);
1343 if (r == 0 && host_key != NULL) {
1344 key_free(previous_host_key);
1345 previous_host_key = key_from_private(host_key);
1352 * Starts a dialog with the server, and authenticates the current user on the
1353 * server. This does not need any extra privileges. The basic connection
1354 * to the server must already have been established before this is called.
1355 * If login fails, this function prints an error and never returns.
1356 * This function does not require super-user privileges.
1359 ssh_login(Sensitive *sensitive, const char *orighost,
1360 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms)
1363 char *server_user, *local_user;
1365 local_user = xstrdup(pw->pw_name);
1366 server_user = options.user ? options.user : local_user;
1368 /* Convert the user-supplied hostname into all lowercase. */
1369 host = xstrdup(orighost);
1372 /* Exchange protocol version identification strings with the server. */
1373 ssh_exchange_identification(timeout_ms);
1375 /* Put the connection into non-blocking mode. */
1376 packet_set_nonblocking();
1379 /* authenticate user */
1380 debug("Authenticating to %s:%d as '%s'", host, port, server_user);
1382 ssh_kex2(host, hostaddr, port);
1383 ssh_userauth2(local_user, server_user, host, sensitive);
1386 ssh_kex(host, hostaddr);
1387 ssh_userauth1(local_user, server_user, host, sensitive);
1389 fatal("ssh1 is not supported");
1396 ssh_put_password(char *password)
1401 if (datafellows & SSH_BUG_PASSWORDPAD) {
1402 packet_put_cstring(password);
1405 size = ROUNDUP(strlen(password) + 1, 32);
1406 padded = xcalloc(1, size);
1407 strlcpy(padded, password, size);
1408 packet_put_string(padded, size);
1409 explicit_bzero(padded, size);
1413 /* print all known host keys for a given host, but skip keys of given type */
1415 show_other_keys(struct hostkeys *hostkeys, Key *key)
1427 const struct hostkey_entry *found;
1429 for (i = 0; type[i] != -1; i++) {
1430 if (type[i] == key->type)
1432 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found))
1434 fp = sshkey_fingerprint(found->key,
1435 options.fingerprint_hash, SSH_FP_DEFAULT);
1436 ra = sshkey_fingerprint(found->key,
1437 options.fingerprint_hash, SSH_FP_RANDOMART);
1438 if (fp == NULL || ra == NULL)
1439 fatal("%s: sshkey_fingerprint fail", __func__);
1440 logit("WARNING: %s key found for host %s\n"
1442 "%s key fingerprint %s.",
1443 key_type(found->key),
1444 found->host, found->file, found->line,
1445 key_type(found->key), fp);
1446 if (options.visual_host_key)
1456 warn_changed_key(Key *host_key)
1460 fp = sshkey_fingerprint(host_key, options.fingerprint_hash,
1463 fatal("%s: sshkey_fingerprint fail", __func__);
1465 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1466 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1467 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1468 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1469 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1470 error("It is also possible that a host key has just been changed.");
1471 error("The fingerprint for the %s key sent by the remote host is\n%s.",
1472 key_type(host_key), fp);
1473 error("Please contact your system administrator.");
1479 * Execute a local command
1482 ssh_local_cmd(const char *args)
1487 void (*osighand)(int);
1489 if (!options.permit_local_command ||
1490 args == NULL || !*args)
1493 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
1494 shell = _PATH_BSHELL;
1496 osighand = signal(SIGCHLD, SIG_DFL);
1499 signal(SIGPIPE, SIG_DFL);
1500 debug3("Executing %s -c \"%s\"", shell, args);
1501 execl(shell, shell, "-c", args, (char *)NULL);
1502 error("Couldn't execute %s -c \"%s\": %s",
1503 shell, args, strerror(errno));
1505 } else if (pid == -1)
1506 fatal("fork failed: %.100s", strerror(errno));
1507 while (waitpid(pid, &status, 0) == -1)
1509 fatal("Couldn't wait for child: %s", strerror(errno));
1510 signal(SIGCHLD, osighand);
1512 if (!WIFEXITED(status))
1515 return (WEXITSTATUS(status));
1519 maybe_add_key_to_agent(char *authfile, Key *private, char *comment,
1522 int auth_sock = -1, r;
1524 if (options.add_keys_to_agent == 0)
1527 if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) {
1528 debug3("no authentication agent, not adding key");
1532 if (options.add_keys_to_agent == 2 &&
1533 !ask_permission("Add key %s (%s) to agent?", authfile, comment)) {
1534 debug3("user denied adding this key");
1539 if ((r = ssh_add_identity_constrained(auth_sock, private, comment, 0,
1540 (options.add_keys_to_agent == 3))) == 0)
1541 debug("identity added to agent: %s", authfile);
1543 debug("could not add identity to agent: %s (%d)", authfile, r);