1 /* $OpenBSD: sshconnect.c,v 1.271 2016/01/14 22:56:56 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".
19 #include <sys/param.h> /* roundup */
20 #include <sys/types.h>
23 #include <sys/socket.h>
24 #ifdef HAVE_SYS_TIME_H
25 # include <sys/time.h>
28 #include <netinet/in.h>
29 #include <arpa/inet.h>
57 #include "sshconnect.h"
64 #include "monitor_fdpass.h"
71 char *client_version_string = NULL;
72 char *server_version_string = NULL;
73 Key *previous_host_key = NULL;
75 static int matching_host_key_dns = 0;
77 static pid_t proxy_command_pid = 0;
80 extern Options options;
81 extern char *__progname;
82 extern uid_t original_real_uid;
83 extern uid_t original_effective_uid;
85 static int show_other_keys(struct hostkeys *, Key *);
86 static void warn_changed_key(Key *);
88 /* Expand a proxy command */
90 expand_proxy_command(const char *proxy_command, const char *user,
91 const char *host, int port)
93 char *tmp, *ret, strport[NI_MAXSERV];
95 snprintf(strport, sizeof strport, "%d", port);
96 xasprintf(&tmp, "exec %s", proxy_command);
97 ret = percent_expand(tmp, "h", host, "p", strport,
98 "r", options.user, (char *)NULL);
104 * Connect to the given ssh server using a proxy command that passes a
105 * a connected fd back to us.
108 ssh_proxy_fdpass_connect(const char *host, u_short port,
109 const char *proxy_command)
111 char *command_string;
116 if ((shell = getenv("SHELL")) == NULL)
117 shell = _PATH_BSHELL;
119 if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) < 0)
120 fatal("Could not create socketpair to communicate with "
121 "proxy dialer: %.100s", strerror(errno));
123 command_string = expand_proxy_command(proxy_command, options.user,
125 debug("Executing proxy dialer command: %.500s", command_string);
127 /* Fork and execute the proxy command. */
128 if ((pid = fork()) == 0) {
131 /* Child. Permanently give up superuser privileges. */
132 permanently_drop_suid(original_real_uid);
135 /* Redirect stdin and stdout. */
137 if (dup2(sp[0], 0) < 0)
138 perror("dup2 stdin");
141 if (dup2(sp[0], 1) < 0)
142 perror("dup2 stdout");
148 * Stderr is left as it is so that error messages get
149 * printed on the user's terminal.
153 argv[2] = command_string;
157 * Execute the proxy command.
158 * Note that we gave up any extra privileges above.
160 execv(argv[0], argv);
166 fatal("fork failed: %.100s", strerror(errno));
168 free(command_string);
170 if ((sock = mm_receive_fd(sp[1])) == -1)
171 fatal("proxy dialer did not pass back a connection");
174 while (waitpid(pid, NULL, 0) == -1)
176 fatal("Couldn't wait for child: %s", strerror(errno));
178 /* Set the connection file descriptors. */
179 packet_set_connection(sock, sock);
185 * Connect to the given ssh server using a proxy command.
188 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
190 char *command_string;
195 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
196 shell = _PATH_BSHELL;
198 /* Create pipes for communicating with the proxy. */
199 if (pipe(pin) < 0 || pipe(pout) < 0)
200 fatal("Could not create pipes to communicate with the proxy: %.100s",
203 command_string = expand_proxy_command(proxy_command, options.user,
205 debug("Executing proxy command: %.500s", command_string);
207 /* Fork and execute the proxy command. */
208 if ((pid = fork()) == 0) {
211 /* Child. Permanently give up superuser privileges. */
212 permanently_drop_suid(original_real_uid);
214 /* Redirect stdin and stdout. */
217 if (dup2(pin[0], 0) < 0)
218 perror("dup2 stdin");
222 if (dup2(pout[1], 1) < 0)
223 perror("dup2 stdout");
224 /* Cannot be 1 because pin allocated two descriptors. */
227 /* Stderr is left as it is so that error messages get
228 printed on the user's terminal. */
231 argv[2] = command_string;
234 /* Execute the proxy command. Note that we gave up any
235 extra privileges above. */
236 signal(SIGPIPE, SIG_DFL);
237 execv(argv[0], argv);
243 fatal("fork failed: %.100s", strerror(errno));
245 proxy_command_pid = pid; /* save pid to clean up later */
247 /* Close child side of the descriptors. */
251 /* Free the command name. */
252 free(command_string);
254 /* Set the connection file descriptors. */
255 packet_set_connection(pout[0], pin[1]);
257 /* Indicate OK return */
262 ssh_kill_proxy_command(void)
265 * Send SIGHUP to proxy command if used. We don't wait() in
266 * case it hangs and instead rely on init to reap the child
268 if (proxy_command_pid > 1)
269 kill(proxy_command_pid, SIGHUP);
273 * Creates a (possibly privileged) socket for use as the ssh connection.
276 ssh_create_socket(int privileged, struct addrinfo *ai)
279 struct addrinfo hints, *res = NULL;
281 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
283 error("socket: %s", strerror(errno));
286 fcntl(sock, F_SETFD, FD_CLOEXEC);
288 /* Bind the socket to an alternative local IP address */
289 if (options.bind_address == NULL && !privileged)
292 if (options.bind_address) {
293 memset(&hints, 0, sizeof(hints));
294 hints.ai_family = ai->ai_family;
295 hints.ai_socktype = ai->ai_socktype;
296 hints.ai_protocol = ai->ai_protocol;
297 hints.ai_flags = AI_PASSIVE;
298 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res);
300 error("getaddrinfo: %s: %s", options.bind_address,
301 ssh_gai_strerror(gaierr));
307 * If we are running as root and want to connect to a privileged
308 * port, bind our own socket to a privileged port.
312 r = bindresvport_sa(sock, res ? res->ai_addr : NULL);
315 error("bindresvport_sa: af=%d %s", ai->ai_family,
320 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
321 error("bind: %s: %s", options.bind_address,
335 timeout_connect(int sockfd, const struct sockaddr *serv_addr,
336 socklen_t addrlen, int *timeoutp)
339 struct timeval tv, t_start;
341 int optval, rc, result = -1;
343 gettimeofday(&t_start, NULL);
345 if (*timeoutp <= 0) {
346 result = connect(sockfd, serv_addr, addrlen);
350 set_nonblock(sockfd);
351 rc = connect(sockfd, serv_addr, addrlen);
353 unset_nonblock(sockfd);
357 if (errno != EINPROGRESS) {
362 fdset = xcalloc(howmany(sockfd + 1, NFDBITS),
364 FD_SET(sockfd, fdset);
365 ms_to_timeval(&tv, *timeoutp);
368 rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
369 if (rc != -1 || errno != EINTR)
380 debug("select: %s", strerror(errno));
383 /* Completed or failed */
385 optlen = sizeof(optval);
386 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
388 debug("getsockopt: %s", strerror(errno));
396 unset_nonblock(sockfd);
399 /* Should not occur */
400 fatal("Bogus return (%d) from select()", rc);
406 if (result == 0 && *timeoutp > 0) {
407 ms_subtract_diff(&t_start, timeoutp);
408 if (*timeoutp <= 0) {
418 * Opens a TCP/IP connection to the remote server on the given host.
419 * The address of the remote host will be returned in hostaddr.
420 * If port is 0, the default port will be used. If needpriv is true,
421 * a privileged port will be allocated to make the connection.
422 * This requires super-user privileges if needpriv is true.
423 * Connection_attempts specifies the maximum number of tries (one per
424 * second). If proxy_command is non-NULL, it specifies the command (with %h
425 * and %p substituted for host and port, respectively) to use to contact
429 ssh_connect_direct(const char *host, struct addrinfo *aitop,
430 struct sockaddr_storage *hostaddr, u_short port, int family,
431 int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv)
434 int sock = -1, attempt;
435 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
438 debug2("%s: needpriv %d", __func__, needpriv);
439 memset(ntop, 0, sizeof(ntop));
440 memset(strport, 0, sizeof(strport));
442 for (attempt = 0; attempt < connection_attempts; attempt++) {
444 /* Sleep a moment before retrying. */
446 debug("Trying again...");
449 * Loop through addresses for this host, and try each one in
450 * sequence until the connection succeeds.
452 for (ai = aitop; ai; ai = ai->ai_next) {
453 if (ai->ai_family != AF_INET &&
454 ai->ai_family != AF_INET6)
456 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
457 ntop, sizeof(ntop), strport, sizeof(strport),
458 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
459 error("%s: getnameinfo failed", __func__);
462 debug("Connecting to %.200s [%.100s] port %s.",
463 host, ntop, strport);
465 /* Create a socket for connecting. */
466 sock = ssh_create_socket(needpriv, ai);
468 /* Any error is already output */
471 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
473 /* Successful connection. */
474 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
477 debug("connect to address %s port %s: %s",
478 ntop, strport, strerror(errno));
484 break; /* Successful connection. */
487 /* Return failure if we didn't get a successful connection. */
489 error("ssh: connect to host %s port %s: %s",
490 host, strport, strerror(errno));
494 debug("Connection established.");
496 /* Set SO_KEEPALIVE if requested. */
497 if (want_keepalive &&
498 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
500 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
502 /* Set the connection. */
503 packet_set_connection(sock, sock);
509 ssh_connect(const char *host, struct addrinfo *addrs,
510 struct sockaddr_storage *hostaddr, u_short port, int family,
511 int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv)
513 if (options.proxy_command == NULL) {
514 return ssh_connect_direct(host, addrs, hostaddr, port, family,
515 connection_attempts, timeout_ms, want_keepalive, needpriv);
516 } else if (strcmp(options.proxy_command, "-") == 0) {
517 packet_set_connection(STDIN_FILENO, STDOUT_FILENO);
518 return 0; /* Always succeeds */
519 } else if (options.proxy_use_fdpass) {
520 return ssh_proxy_fdpass_connect(host, port,
521 options.proxy_command);
523 return ssh_proxy_connect(host, port, options.proxy_command);
527 send_client_banner(int connection_out, int minor1)
529 /* Send our own protocol version identification. */
530 xasprintf(&client_version_string, "SSH-%d.%d-%.100s%s%s%s",
531 compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
532 compat20 ? PROTOCOL_MINOR_2 : minor1,
534 *options.version_addendum == '\0' ? "" : " ",
535 options.version_addendum, compat20 ? "\r\n" : "\n");
536 if (atomicio(vwrite, connection_out, client_version_string,
537 strlen(client_version_string)) != strlen(client_version_string))
538 fatal("write: %.100s", strerror(errno));
539 chop(client_version_string);
540 debug("Local version string %.100s", client_version_string);
544 * Waits for the server identification string, and sends our own
545 * identification string.
548 ssh_exchange_identification(int timeout_ms)
550 char buf[256], remote_version[256]; /* must be same size! */
551 int remote_major, remote_minor, mismatch;
552 int connection_in = packet_get_connection_in();
553 int connection_out = packet_get_connection_out();
554 int minor1 = PROTOCOL_MINOR_1, client_banner_sent = 0;
557 int fdsetsz, remaining, rc;
558 struct timeval t_start, t_remaining;
561 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask);
562 fdset = xcalloc(1, fdsetsz);
565 * If we are SSH2-only then we can send the banner immediately and
568 if (options.protocol == SSH_PROTO_2) {
570 send_client_banner(connection_out, 0);
571 client_banner_sent = 1;
574 /* Read other side's version identification. */
575 remaining = timeout_ms;
577 for (i = 0; i < sizeof(buf) - 1; i++) {
578 if (timeout_ms > 0) {
579 gettimeofday(&t_start, NULL);
580 ms_to_timeval(&t_remaining, remaining);
581 FD_SET(connection_in, fdset);
582 rc = select(connection_in + 1, fdset, NULL,
583 fdset, &t_remaining);
584 ms_subtract_diff(&t_start, &remaining);
585 if (rc == 0 || remaining <= 0)
586 fatal("Connection timed out during "
591 fatal("ssh_exchange_identification: "
592 "select: %s", strerror(errno));
596 len = atomicio(read, connection_in, &buf[i], 1);
598 if (len != 1 && errno == EPIPE)
599 fatal("ssh_exchange_identification: "
600 "Connection closed by remote host");
602 fatal("ssh_exchange_identification: "
603 "read: %.100s", strerror(errno));
604 if (buf[i] == '\r') {
607 continue; /**XXX wait for \n */
609 if (buf[i] == '\n') {
614 fatal("ssh_exchange_identification: "
615 "No banner received");
617 buf[sizeof(buf) - 1] = 0;
618 if (strncmp(buf, "SSH-", 4) == 0)
620 debug("ssh_exchange_identification: %s", buf);
622 server_version_string = xstrdup(buf);
626 * Check that the versions match. In future this might accept
627 * several versions and set appropriate flags to handle them.
629 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
630 &remote_major, &remote_minor, remote_version) != 3)
631 fatal("Bad remote protocol version identification: '%.100s'", buf);
632 debug("Remote protocol version %d.%d, remote software version %.100s",
633 remote_major, remote_minor, remote_version);
635 active_state->compat = compat_datafellows(remote_version);
638 switch (remote_major) {
640 if (remote_minor == 99 &&
641 (options.protocol & SSH_PROTO_2) &&
642 !(options.protocol & SSH_PROTO_1_PREFERRED)) {
646 if (!(options.protocol & SSH_PROTO_1)) {
650 if (remote_minor < 3) {
651 fatal("Remote machine has too old SSH software version.");
652 } else if (remote_minor == 3 || remote_minor == 4) {
653 /* We speak 1.3, too. */
656 if (options.forward_agent) {
657 logit("Agent forwarding disabled for protocol 1.3");
658 options.forward_agent = 0;
663 if (options.protocol & SSH_PROTO_2) {
673 fatal("Protocol major versions differ: %d vs. %d",
674 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
676 if ((datafellows & SSH_BUG_DERIVEKEY) != 0)
677 fatal("Server version \"%.100s\" uses unsafe key agreement; "
678 "refusing connection", remote_version);
679 if ((datafellows & SSH_BUG_RSASIGMD5) != 0)
680 logit("Server version \"%.100s\" uses unsafe RSA signature "
681 "scheme; disabling use of RSA keys", remote_version);
682 if (!client_banner_sent)
683 send_client_banner(connection_out, minor1);
684 chop(server_version_string);
687 /* defaults to 'no' */
689 confirm(const char *prompt)
691 const char *msg, *again = "Please type 'yes' or 'no': ";
695 if (options.batch_mode)
697 for (msg = prompt;;msg = again) {
698 p = read_passphrase(msg, RP_ECHO);
700 (p[0] == '\0') || (p[0] == '\n') ||
701 strncasecmp(p, "no", 2) == 0)
703 if (p && strncasecmp(p, "yes", 3) == 0)
712 check_host_cert(const char *host, const Key *host_key)
716 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) {
720 if (buffer_len(host_key->cert->critical) != 0) {
721 error("Certificate for %s contains unsupported "
722 "critical options(s)", host);
729 sockaddr_is_local(struct sockaddr *hostaddr)
731 switch (hostaddr->sa_family) {
733 return (ntohl(((struct sockaddr_in *)hostaddr)->
734 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
736 return IN6_IS_ADDR_LOOPBACK(
737 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
744 * Prepare the hostname and ip address strings that are used to lookup
745 * host keys in known_hosts files. These may have a port number appended.
748 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr,
749 u_short port, char **hostfile_hostname, char **hostfile_ipaddr)
751 char ntop[NI_MAXHOST];
754 switch (hostaddr == NULL ? -1 : hostaddr->sa_family) {
759 addrlen = sizeof(struct sockaddr_in);
762 addrlen = sizeof(struct sockaddr_in6);
765 addrlen = sizeof(struct sockaddr);
770 * We don't have the remote ip-address for connections
771 * using a proxy command
773 if (hostfile_ipaddr != NULL) {
774 if (options.proxy_command == NULL) {
775 if (getnameinfo(hostaddr, addrlen,
776 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0)
777 fatal("%s: getnameinfo failed", __func__);
778 *hostfile_ipaddr = put_host_port(ntop, port);
780 *hostfile_ipaddr = xstrdup("<no hostip for proxy "
786 * Allow the user to record the key under a different name or
787 * differentiate a non-standard port. This is useful for ssh
788 * tunneling over forwarded connections or if you run multiple
789 * sshd's on different ports on the same machine.
791 if (hostfile_hostname != NULL) {
792 if (options.host_key_alias != NULL) {
793 *hostfile_hostname = xstrdup(options.host_key_alias);
794 debug("using hostkeyalias: %s", *hostfile_hostname);
796 *hostfile_hostname = put_host_port(hostname, port);
802 * check whether the supplied host key is valid, return -1 if the key
803 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true.
809 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
810 Key *host_key, int readonly,
811 char **user_hostfiles, u_int num_user_hostfiles,
812 char **system_hostfiles, u_int num_system_hostfiles)
814 HostStatus host_status;
815 HostStatus ip_status;
817 char *ip = NULL, *host = NULL;
818 char hostline[1000], *hostp, *fp, *ra;
821 const struct hostkey_entry *host_found, *ip_found;
822 int len, cancelled_forwarding = 0;
823 int local = sockaddr_is_local(hostaddr);
824 int r, want_cert = key_is_cert(host_key), host_ip_differ = 0;
825 int hostkey_trusted = 0; /* Known or explicitly accepted by user */
826 struct hostkeys *host_hostkeys, *ip_hostkeys;
830 * Force accepting of the host key for loopback/localhost. The
831 * problem is that if the home directory is NFS-mounted to multiple
832 * machines, localhost will refer to a different machine in each of
833 * them, and the user will get bogus HOST_CHANGED warnings. This
834 * essentially disables host authentication for localhost; however,
835 * this is probably not a real problem.
837 if (options.no_host_authentication_for_localhost == 1 && local &&
838 options.host_key_alias == NULL) {
839 debug("Forcing accepting of host key for "
840 "loopback/localhost.");
845 * Prepare the hostname and address strings used for hostkey lookup.
846 * In some cases, these will have a port number appended.
848 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip);
851 * Turn off check_host_ip if the connection is to localhost, via proxy
852 * command or if we don't have a hostname to compare with
854 if (options.check_host_ip && (local ||
855 strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
856 options.check_host_ip = 0;
858 host_hostkeys = init_hostkeys();
859 for (i = 0; i < num_user_hostfiles; i++)
860 load_hostkeys(host_hostkeys, host, user_hostfiles[i]);
861 for (i = 0; i < num_system_hostfiles; i++)
862 load_hostkeys(host_hostkeys, host, system_hostfiles[i]);
865 if (!want_cert && options.check_host_ip) {
866 ip_hostkeys = init_hostkeys();
867 for (i = 0; i < num_user_hostfiles; i++)
868 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]);
869 for (i = 0; i < num_system_hostfiles; i++)
870 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]);
874 /* Reload these as they may have changed on cert->key downgrade */
875 want_cert = key_is_cert(host_key);
876 type = key_type(host_key);
879 * Check if the host key is present in the user's list of known
880 * hosts or in the systemwide list.
882 host_status = check_key_in_hostkeys(host_hostkeys, host_key,
886 * Also perform check for the ip address, skip the check if we are
887 * localhost, looking for a certificate, or the hostname was an ip
888 * address to begin with.
890 if (!want_cert && ip_hostkeys != NULL) {
891 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key,
893 if (host_status == HOST_CHANGED &&
894 (ip_status != HOST_CHANGED ||
896 !key_equal(ip_found->key, host_found->key))))
899 ip_status = host_status;
901 switch (host_status) {
903 /* The host is known and the key matches. */
904 debug("Host '%.200s' is known and matches the %s host %s.",
905 host, type, want_cert ? "certificate" : "key");
906 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key",
907 host_found->file, host_found->line);
908 if (want_cert && !check_host_cert(hostname, host_key))
910 if (options.check_host_ip && ip_status == HOST_NEW) {
911 if (readonly || want_cert)
912 logit("%s host key for IP address "
913 "'%.128s' not in list of known hosts.",
915 else if (!add_host_to_hostfile(user_hostfiles[0], ip,
916 host_key, options.hash_known_hosts))
917 logit("Failed to add the %s host key for IP "
918 "address '%.128s' to the list of known "
919 "hosts (%.500s).", type, ip,
922 logit("Warning: Permanently added the %s host "
923 "key for IP address '%.128s' to the list "
924 "of known hosts.", type, ip);
925 } else if (options.visual_host_key) {
926 fp = sshkey_fingerprint(host_key,
927 options.fingerprint_hash, SSH_FP_DEFAULT);
928 ra = sshkey_fingerprint(host_key,
929 options.fingerprint_hash, SSH_FP_RANDOMART);
930 if (fp == NULL || ra == NULL)
931 fatal("%s: sshkey_fingerprint fail", __func__);
932 logit("Host key fingerprint is %s\n%s", fp, ra);
939 if (options.host_key_alias == NULL && port != 0 &&
940 port != SSH_DEFAULT_PORT) {
941 debug("checking without port identifier");
942 if (check_host_key(hostname, hostaddr, 0, host_key,
943 ROQUIET, user_hostfiles, num_user_hostfiles,
944 system_hostfiles, num_system_hostfiles) == 0) {
945 debug("found matching key w/out port");
949 if (readonly || want_cert)
951 /* The host is new. */
952 if (options.strict_host_key_checking == 1) {
954 * User has requested strict host key checking. We
955 * will not add the host key automatically. The only
956 * alternative left is to abort.
958 error("No %s host key is known for %.200s and you "
959 "have requested strict checking.", type, host);
961 } else if (options.strict_host_key_checking == 2) {
962 char msg1[1024], msg2[1024];
964 if (show_other_keys(host_hostkeys, host_key))
965 snprintf(msg1, sizeof(msg1),
966 "\nbut keys of different type are already"
967 " known for this host.");
969 snprintf(msg1, sizeof(msg1), ".");
971 fp = sshkey_fingerprint(host_key,
972 options.fingerprint_hash, SSH_FP_DEFAULT);
973 ra = sshkey_fingerprint(host_key,
974 options.fingerprint_hash, SSH_FP_RANDOMART);
975 if (fp == NULL || ra == NULL)
976 fatal("%s: sshkey_fingerprint fail", __func__);
978 if (options.verify_host_key_dns) {
979 if (matching_host_key_dns)
980 snprintf(msg2, sizeof(msg2),
981 "Matching host key fingerprint"
984 snprintf(msg2, sizeof(msg2),
985 "No matching host key fingerprint"
988 snprintf(msg, sizeof(msg),
989 "The authenticity of host '%.200s (%s)' can't be "
991 "%s key fingerprint is %s.%s%s\n%s"
992 "Are you sure you want to continue connecting "
994 host, ip, msg1, type, fp,
995 options.visual_host_key ? "\n" : "",
996 options.visual_host_key ? ra : "",
1002 hostkey_trusted = 1; /* user explicitly confirmed */
1005 * If not in strict mode, add the key automatically to the
1006 * local known_hosts file.
1008 if (options.check_host_ip && ip_status == HOST_NEW) {
1009 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
1011 if (options.hash_known_hosts) {
1012 /* Add hash of host and IP separately */
1013 r = add_host_to_hostfile(user_hostfiles[0],
1014 host, host_key, options.hash_known_hosts) &&
1015 add_host_to_hostfile(user_hostfiles[0], ip,
1016 host_key, options.hash_known_hosts);
1018 /* Add unhashed "host,ip" */
1019 r = add_host_to_hostfile(user_hostfiles[0],
1021 options.hash_known_hosts);
1024 r = add_host_to_hostfile(user_hostfiles[0], host,
1025 host_key, options.hash_known_hosts);
1030 logit("Failed to add the host to the list of known "
1031 "hosts (%.500s).", user_hostfiles[0]);
1033 logit("Warning: Permanently added '%.200s' (%s) to the "
1034 "list of known hosts.", hostp, type);
1037 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1038 error("@ WARNING: REVOKED HOST KEY DETECTED! @");
1039 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1040 error("The %s host key for %s is marked as revoked.", type, host);
1041 error("This could mean that a stolen key is being used to");
1042 error("impersonate this host.");
1045 * If strict host key checking is in use, the user will have
1046 * to edit the key manually and we can only abort.
1048 if (options.strict_host_key_checking) {
1049 error("%s host key for %.200s was revoked and you have "
1050 "requested strict checking.", type, host);
1053 goto continue_unsafe;
1058 * This is only a debug() since it is valid to have
1059 * CAs with wildcard DNS matches that don't match
1060 * all hosts that one might visit.
1062 debug("Host certificate authority does not "
1063 "match %s in %s:%lu", CA_MARKER,
1064 host_found->file, host_found->line);
1067 if (readonly == ROQUIET)
1069 if (options.check_host_ip && host_ip_differ) {
1071 if (ip_status == HOST_NEW)
1072 key_msg = "is unknown";
1073 else if (ip_status == HOST_OK)
1074 key_msg = "is unchanged";
1076 key_msg = "has a different value";
1077 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1078 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
1079 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1080 error("The %s host key for %s has changed,", type, host);
1081 error("and the key for the corresponding IP address %s", ip);
1082 error("%s. This could either mean that", key_msg);
1083 error("DNS SPOOFING is happening or the IP address for the host");
1084 error("and its host key have changed at the same time.");
1085 if (ip_status != HOST_NEW)
1086 error("Offending key for IP in %s:%lu",
1087 ip_found->file, ip_found->line);
1089 /* The host key has changed. */
1090 warn_changed_key(host_key);
1091 error("Add correct host key in %.100s to get rid of this message.",
1093 error("Offending %s key in %s:%lu", key_type(host_found->key),
1094 host_found->file, host_found->line);
1097 * If strict host key checking is in use, the user will have
1098 * to edit the key manually and we can only abort.
1100 if (options.strict_host_key_checking) {
1101 error("%s host key for %.200s has changed and you have "
1102 "requested strict checking.", type, host);
1108 * If strict host key checking has not been requested, allow
1109 * the connection but without MITM-able authentication or
1112 if (options.password_authentication) {
1113 error("Password authentication is disabled to avoid "
1114 "man-in-the-middle attacks.");
1115 options.password_authentication = 0;
1116 cancelled_forwarding = 1;
1118 if (options.kbd_interactive_authentication) {
1119 error("Keyboard-interactive authentication is disabled"
1120 " to avoid man-in-the-middle attacks.");
1121 options.kbd_interactive_authentication = 0;
1122 options.challenge_response_authentication = 0;
1123 cancelled_forwarding = 1;
1125 if (options.challenge_response_authentication) {
1126 error("Challenge/response authentication is disabled"
1127 " to avoid man-in-the-middle attacks.");
1128 options.challenge_response_authentication = 0;
1129 cancelled_forwarding = 1;
1131 if (options.forward_agent) {
1132 error("Agent forwarding is disabled to avoid "
1133 "man-in-the-middle attacks.");
1134 options.forward_agent = 0;
1135 cancelled_forwarding = 1;
1137 if (options.forward_x11) {
1138 error("X11 forwarding is disabled to avoid "
1139 "man-in-the-middle attacks.");
1140 options.forward_x11 = 0;
1141 cancelled_forwarding = 1;
1143 if (options.num_local_forwards > 0 ||
1144 options.num_remote_forwards > 0) {
1145 error("Port forwarding is disabled to avoid "
1146 "man-in-the-middle attacks.");
1147 options.num_local_forwards =
1148 options.num_remote_forwards = 0;
1149 cancelled_forwarding = 1;
1151 if (options.tun_open != SSH_TUNMODE_NO) {
1152 error("Tunnel forwarding is disabled to avoid "
1153 "man-in-the-middle attacks.");
1154 options.tun_open = SSH_TUNMODE_NO;
1155 cancelled_forwarding = 1;
1157 if (options.exit_on_forward_failure && cancelled_forwarding)
1158 fatal("Error: forwarding disabled due to host key "
1162 * XXX Should permit the user to change to use the new id.
1163 * This could be done by converting the host key to an
1164 * identifying sentence, tell that the host identifies itself
1165 * by that sentence, and ask the user if he/she wishes to
1166 * accept the authentication.
1170 fatal("internal error");
1174 if (options.check_host_ip && host_status != HOST_CHANGED &&
1175 ip_status == HOST_CHANGED) {
1176 snprintf(msg, sizeof(msg),
1177 "Warning: the %s host key for '%.200s' "
1178 "differs from the key for the IP address '%.128s'"
1179 "\nOffending key for IP in %s:%lu",
1180 type, host, ip, ip_found->file, ip_found->line);
1181 if (host_status == HOST_OK) {
1183 snprintf(msg + len, sizeof(msg) - len,
1184 "\nMatching host key in %s:%lu",
1185 host_found->file, host_found->line);
1187 if (options.strict_host_key_checking == 1) {
1189 error("Exiting, you have requested strict checking.");
1191 } else if (options.strict_host_key_checking == 2) {
1192 strlcat(msg, "\nAre you sure you want "
1193 "to continue connecting (yes/no)? ", sizeof(msg));
1201 if (!hostkey_trusted && options.update_hostkeys) {
1202 debug("%s: hostkey not known or explicitly trusted: "
1203 "disabling UpdateHostkeys", __func__);
1204 options.update_hostkeys = 0;
1209 if (host_hostkeys != NULL)
1210 free_hostkeys(host_hostkeys);
1211 if (ip_hostkeys != NULL)
1212 free_hostkeys(ip_hostkeys);
1216 if (want_cert && host_status != HOST_REVOKED) {
1218 * No matching certificate. Downgrade cert to raw key and
1221 debug("No matching CA found. Retry with plain key");
1222 raw_key = key_from_private(host_key);
1223 if (key_drop_cert(raw_key) != 0)
1224 fatal("Couldn't drop certificate");
1228 if (raw_key != NULL)
1232 if (host_hostkeys != NULL)
1233 free_hostkeys(host_hostkeys);
1234 if (ip_hostkeys != NULL)
1235 free_hostkeys(ip_hostkeys);
1239 /* returns 0 if key verifies or -1 if key does NOT verify */
1241 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
1244 int r = -1, flags = 0;
1245 char valid[64], *fp = NULL, *cafp = NULL;
1246 struct sshkey *plain = NULL;
1248 if ((fp = sshkey_fingerprint(host_key,
1249 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1250 error("%s: fingerprint host key: %s", __func__, ssh_err(r));
1255 if (sshkey_is_cert(host_key)) {
1256 if ((cafp = sshkey_fingerprint(host_key->cert->signature_key,
1257 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1258 error("%s: fingerprint CA key: %s",
1259 __func__, ssh_err(r));
1263 sshkey_format_cert_validity(host_key->cert,
1264 valid, sizeof(valid));
1265 debug("Server host certificate: %s %s, serial %llu "
1266 "ID \"%s\" CA %s %s valid %s",
1267 sshkey_ssh_name(host_key), fp,
1268 (unsigned long long)host_key->cert->serial,
1269 host_key->cert->key_id,
1270 sshkey_ssh_name(host_key->cert->signature_key), cafp,
1272 for (i = 0; i < host_key->cert->nprincipals; i++) {
1273 debug2("Server host certificate hostname: %s",
1274 host_key->cert->principals[i]);
1277 debug("Server host key: %s %s", compat20 ?
1278 sshkey_ssh_name(host_key) : sshkey_type(host_key), fp);
1281 if (sshkey_equal(previous_host_key, host_key)) {
1282 debug2("%s: server host key %s %s matches cached key",
1283 __func__, sshkey_type(host_key), fp);
1288 /* Check in RevokedHostKeys file if specified */
1289 if (options.revoked_host_keys != NULL) {
1290 r = sshkey_check_revoked(host_key, options.revoked_host_keys);
1293 break; /* not revoked */
1294 case SSH_ERR_KEY_REVOKED:
1295 error("Host key %s %s revoked by file %s",
1296 sshkey_type(host_key), fp,
1297 options.revoked_host_keys);
1301 error("Error checking host key %s %s in "
1302 "revoked keys file %s: %s", sshkey_type(host_key),
1303 fp, options.revoked_host_keys, ssh_err(r));
1309 if (options.verify_host_key_dns) {
1311 * XXX certs are not yet supported for DNS, so downgrade
1312 * them and try the plain key.
1314 if ((r = sshkey_from_private(host_key, &plain)) != 0)
1316 if (sshkey_is_cert(plain))
1317 sshkey_drop_cert(plain);
1318 if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) {
1319 if (flags & DNS_VERIFY_FOUND) {
1320 if (options.verify_host_key_dns == 1 &&
1321 flags & DNS_VERIFY_MATCH &&
1322 flags & DNS_VERIFY_SECURE) {
1326 if (flags & DNS_VERIFY_MATCH) {
1327 matching_host_key_dns = 1;
1329 warn_changed_key(plain);
1330 error("Update the SSHFP RR in DNS "
1331 "with the new host key to get rid "
1332 "of this message.");
1337 r = check_host_key(host, hostaddr, options.port, host_key, RDRW,
1338 options.user_hostfiles, options.num_user_hostfiles,
1339 options.system_hostfiles, options.num_system_hostfiles);
1345 if (r == 0 && host_key != NULL) {
1346 key_free(previous_host_key);
1347 previous_host_key = key_from_private(host_key);
1354 * Starts a dialog with the server, and authenticates the current user on the
1355 * server. This does not need any extra privileges. The basic connection
1356 * to the server must already have been established before this is called.
1357 * If login fails, this function prints an error and never returns.
1358 * This function does not require super-user privileges.
1361 ssh_login(Sensitive *sensitive, const char *orighost,
1362 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms)
1365 char *server_user, *local_user;
1367 local_user = xstrdup(pw->pw_name);
1368 server_user = options.user ? options.user : local_user;
1370 /* Convert the user-supplied hostname into all lowercase. */
1371 host = xstrdup(orighost);
1374 /* Exchange protocol version identification strings with the server. */
1375 ssh_exchange_identification(timeout_ms);
1377 /* Put the connection into non-blocking mode. */
1378 packet_set_nonblocking();
1381 /* authenticate user */
1382 debug("Authenticating to %s:%d as '%s'", host, port, server_user);
1384 ssh_kex2(host, hostaddr, port);
1385 ssh_userauth2(local_user, server_user, host, sensitive);
1388 ssh_kex(host, hostaddr);
1389 ssh_userauth1(local_user, server_user, host, sensitive);
1391 fatal("ssh1 is not supported");
1398 ssh_put_password(char *password)
1403 if (datafellows & SSH_BUG_PASSWORDPAD) {
1404 packet_put_cstring(password);
1407 size = roundup(strlen(password) + 1, 32);
1408 padded = xcalloc(1, size);
1409 strlcpy(padded, password, size);
1410 packet_put_string(padded, size);
1411 explicit_bzero(padded, size);
1415 /* print all known host keys for a given host, but skip keys of given type */
1417 show_other_keys(struct hostkeys *hostkeys, Key *key)
1429 const struct hostkey_entry *found;
1431 for (i = 0; type[i] != -1; i++) {
1432 if (type[i] == key->type)
1434 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found))
1436 fp = sshkey_fingerprint(found->key,
1437 options.fingerprint_hash, SSH_FP_DEFAULT);
1438 ra = sshkey_fingerprint(found->key,
1439 options.fingerprint_hash, SSH_FP_RANDOMART);
1440 if (fp == NULL || ra == NULL)
1441 fatal("%s: sshkey_fingerprint fail", __func__);
1442 logit("WARNING: %s key found for host %s\n"
1444 "%s key fingerprint %s.",
1445 key_type(found->key),
1446 found->host, found->file, found->line,
1447 key_type(found->key), fp);
1448 if (options.visual_host_key)
1458 warn_changed_key(Key *host_key)
1462 fp = sshkey_fingerprint(host_key, options.fingerprint_hash,
1465 fatal("%s: sshkey_fingerprint fail", __func__);
1467 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1468 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1469 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1470 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1471 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1472 error("It is also possible that a host key has just been changed.");
1473 error("The fingerprint for the %s key sent by the remote host is\n%s.",
1474 key_type(host_key), fp);
1475 error("Please contact your system administrator.");
1481 * Execute a local command
1484 ssh_local_cmd(const char *args)
1489 void (*osighand)(int);
1491 if (!options.permit_local_command ||
1492 args == NULL || !*args)
1495 if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
1496 shell = _PATH_BSHELL;
1498 osighand = signal(SIGCHLD, SIG_DFL);
1501 signal(SIGPIPE, SIG_DFL);
1502 debug3("Executing %s -c \"%s\"", shell, args);
1503 execl(shell, shell, "-c", args, (char *)NULL);
1504 error("Couldn't execute %s -c \"%s\": %s",
1505 shell, args, strerror(errno));
1507 } else if (pid == -1)
1508 fatal("fork failed: %.100s", strerror(errno));
1509 while (waitpid(pid, &status, 0) == -1)
1511 fatal("Couldn't wait for child: %s", strerror(errno));
1512 signal(SIGCHLD, osighand);
1514 if (!WIFEXITED(status))
1517 return (WEXITSTATUS(status));
1521 maybe_add_key_to_agent(char *authfile, Key *private, char *comment,
1524 int auth_sock = -1, r;
1526 if (options.add_keys_to_agent == 0)
1529 if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) {
1530 debug3("no authentication agent, not adding key");
1534 if (options.add_keys_to_agent == 2 &&
1535 !ask_permission("Add key %s (%s) to agent?", authfile, comment)) {
1536 debug3("user denied adding this key");
1540 if ((r = ssh_add_identity_constrained(auth_sock, private, comment, 0,
1541 (options.add_keys_to_agent == 3))) == 0)
1542 debug("identity added to agent: %s", authfile);
1544 debug("could not add identity to agent: %s (%d)", authfile, r);