2 * Author: Tatu Ylonen <ylo@cs.hut.fi>
3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * Created: Sat Mar 18 16:36:11 1995 ylo
6 * Ssh client program. This program can be used to log into a remote machine.
7 * The software supports strong authentication, encryption, and forwarding
8 * of X11, TCP/IP, and authentication connections.
10 * Modified to work with SSL by Niels Provos <provos@citi.umich.edu> in Canada.
24 #ifdef HAVE___PROGNAME
25 extern char *__progname;
26 #else /* HAVE___PROGNAME */
27 const char *__progname = "ssh";
28 #endif /* HAVE___PROGNAME */
30 /* Flag indicating whether IPv4 or IPv6. This can be set on the command line.
31 Default value is AF_UNSPEC means both IPv4 and IPv6. */
33 int IPv4or6 = AF_INET;
35 int IPv4or6 = AF_UNSPEC;
38 /* Flag indicating whether debug mode is on. This can be set on the command line. */
44 * Flag indicating that nothing should be read from stdin. This can be set
45 * on the command line.
47 int stdin_null_flag = 0;
50 * Flag indicating that ssh should fork after authentication. This is useful
51 * so that the pasphrase can be entered manually, and then ssh goes to the
54 int fork_after_authentication_flag = 0;
57 * General data structure for command line options and options configurable
58 * in configuration files. See readconf.h.
63 * Name of the host we are connecting to. This is the name given on the
64 * command line, or the HostName specified for the user-supplied name in a
69 /* socket address the host resolves to */
70 struct sockaddr_storage hostaddr;
73 * Flag to indicate that we have received a window change signal which has
74 * not yet been processed. This will cause a message indicating the new
75 * window size to be sent to the server a little later. This is volatile
76 * because this is updated in a signal handler.
78 volatile int received_window_change_signal = 0;
80 /* Value of argv[0] (set in the main program). */
83 /* Flag indicating whether we have a valid host private key loaded. */
84 int host_private_key_loaded = 0;
86 /* Host private key. */
87 RSA *host_private_key = NULL;
89 /* Original real UID. */
90 uid_t original_real_uid;
92 /* Prints a help message to the user. This function never returns. */
97 fprintf(stderr, "Usage: %s [options] host [command]\n", av0);
98 fprintf(stderr, "Options:\n");
99 fprintf(stderr, " -l user Log in using this user name.\n");
100 fprintf(stderr, " -n Redirect input from /dev/null.\n");
101 fprintf(stderr, " -a Disable authentication agent forwarding.\n");
103 fprintf(stderr, " -k Disable Kerberos ticket and AFS token forwarding.\n");
105 fprintf(stderr, " -x Disable X11 connection forwarding.\n");
106 fprintf(stderr, " -X Enable X11 connection forwarding.\n");
107 fprintf(stderr, " -i file Identity for RSA authentication (default: ~/.ssh/identity).\n");
108 fprintf(stderr, " -t Tty; allocate a tty even if command is given.\n");
109 fprintf(stderr, " -v Verbose; display verbose debugging messages.\n");
110 fprintf(stderr, " -V Display version number only.\n");
111 fprintf(stderr, " -P Don't allocate a privileged port.\n");
112 fprintf(stderr, " -q Quiet; don't display any warning messages.\n");
113 fprintf(stderr, " -f Fork into background after authentication.\n");
114 fprintf(stderr, " -e char Set escape character; ``none'' = disable (default: ~).\n");
116 fprintf(stderr, " -c cipher Select encryption algorithm: "
119 fprintf(stderr, " -p port Connect to this port. Server must be on the same port.\n");
120 fprintf(stderr, " -L listen-port:host:port Forward local port to remote address\n");
121 fprintf(stderr, " -R listen-port:host:port Forward remote port to local address\n");
122 fprintf(stderr, " These cause %s to listen for connections on a port, and\n", av0);
123 fprintf(stderr, " forward them to the other side by connecting to host:port.\n");
124 fprintf(stderr, " -C Enable compression.\n");
125 fprintf(stderr, " -g Allow remote hosts to connect to forwarded ports.\n");
126 fprintf(stderr, " -4 Use IPv4 only.\n");
127 fprintf(stderr, " -6 Use IPv6 only.\n");
128 fprintf(stderr, " -o 'option' Process the option as if it was read from a configuration file.\n");
133 * Connects to the given host using rsh (or prints an error message and exits
134 * if rsh is not available). This function never returns.
137 rsh_connect(char *host, char *user, Buffer * command)
142 log("Using rsh. WARNING: Connection will not be encrypted.");
143 /* Build argument list for rsh. */
145 args[i++] = _PATH_RSH;
146 /* host may have to come after user on some systems */
152 if (buffer_len(command) > 0) {
153 buffer_append(command, "\0", 1);
154 args[i++] = buffer_ptr(command);
158 for (i = 0; args[i]; i++) {
160 fprintf(stderr, " ");
161 fprintf(stderr, "%s", args[i]);
163 fprintf(stderr, "\n");
165 execv(_PATH_RSH, args);
171 * Main program for the ssh client.
174 main(int ac, char **av)
176 int i, opt, optind, type, exit_status, ok, authfd;
177 u_short fwd_port, fwd_host_port;
178 char *optarg, *cp, buf[256];
182 struct passwd *pw, pwcopy;
183 int interactive = 0, dummy;
185 uid_t original_effective_uid;
189 * Save the original real uid. It will be needed later (uid-swapping
190 * may clobber the real uid).
192 original_real_uid = getuid();
193 original_effective_uid = geteuid();
195 /* If we are installed setuid root be careful to not drop core. */
196 if (original_real_uid != original_effective_uid) {
198 rlim.rlim_cur = rlim.rlim_max = 0;
199 if (setrlimit(RLIMIT_CORE, &rlim) < 0)
200 fatal("setrlimit failed: %.100s", strerror(errno));
203 * Use uid-swapping to give up root privileges for the duration of
204 * option processing. We will re-instantiate the rights when we are
205 * ready to create the privileged port, and will permanently drop
206 * them when the port has been created (actually, when the connection
207 * has been made, as we may need to create the port several times).
209 temporarily_use_uid(original_real_uid);
212 * Set our umask to something reasonable, as some files are created
213 * with the default umask. This will make them world-readable but
214 * writable only by the owner, which is ok for all files for which we
215 * don't set the modes explicitly.
219 /* Save our own name. */
222 /* Initialize option structure to indicate that no values have been set. */
223 initialize_options(&options);
225 /* Parse command-line arguments. */
228 /* If program name is not one of the standard names, use it as host name. */
229 if (strchr(av0, '/'))
230 cp = strrchr(av0, '/') + 1;
233 if (strcmp(cp, "rsh") != 0 && strcmp(cp, "ssh") != 0 &&
234 strcmp(cp, "rlogin") != 0 && strcmp(cp, "slogin") != 0)
237 for (optind = 1; optind < ac; optind++) {
238 if (av[optind][0] != '-') {
241 if ((cp = strchr(av[optind], '@'))) {
244 options.user = av[optind];
254 if (strchr("eilcpLRo", opt)) { /* options with arguments */
255 optarg = av[optind] + 2;
256 if (strcmp(optarg, "") == 0) {
257 if (optind >= ac - 1)
259 optarg = av[++optind];
280 fork_after_authentication_flag = 1;
285 options.forward_x11 = 0;
289 options.forward_x11 = 1;
293 options.gateway_ports = 1;
297 options.use_privileged_port = 0;
301 options.forward_agent = 0;
305 options.kerberos_tgt_passing = 0;
306 options.afs_token_passing = 0;
310 if (stat(optarg, &st) < 0) {
311 fprintf(stderr, "Warning: Identity file %s does not exist.\n",
315 if (options.num_identity_files >= SSH_MAX_IDENTITY_FILES)
316 fatal("Too many identity files specified (max %d)",
317 SSH_MAX_IDENTITY_FILES);
318 options.identity_files[options.num_identity_files++] =
328 fprintf(stderr, "SSH Version %s, protocol version %d.%d.\n",
329 SSH_VERSION, PROTOCOL_MAJOR, PROTOCOL_MINOR);
330 fprintf(stderr, "Compiled with SSL.\n");
334 options.log_level = SYSLOG_LEVEL_DEBUG;
338 options.log_level = SYSLOG_LEVEL_QUIET;
342 if (optarg[0] == '^' && optarg[2] == 0 &&
343 (unsigned char) optarg[1] >= 64 && (unsigned char) optarg[1] < 128)
344 options.escape_char = (unsigned char) optarg[1] & 31;
345 else if (strlen(optarg) == 1)
346 options.escape_char = (unsigned char) optarg[0];
347 else if (strcmp(optarg, "none") == 0)
348 options.escape_char = -2;
350 fprintf(stderr, "Bad escape character '%s'.\n", optarg);
356 options.cipher = cipher_number(optarg);
357 if (options.cipher == -1) {
358 fprintf(stderr, "Unknown cipher type '%s'\n", optarg);
364 options.port = atoi(optarg);
368 options.user = optarg;
372 if (sscanf(optarg, "%hu/%255[^/]/%hu", &fwd_port, buf,
373 &fwd_host_port) != 3 &&
374 sscanf(optarg, "%hu:%255[^:]:%hu", &fwd_port, buf,
375 &fwd_host_port) != 3) {
376 fprintf(stderr, "Bad forwarding specification '%s'.\n", optarg);
380 add_remote_forward(&options, fwd_port, buf, fwd_host_port);
384 if (sscanf(optarg, "%hu/%255[^/]/%hu", &fwd_port, buf,
385 &fwd_host_port) != 3 &&
386 sscanf(optarg, "%hu:%255[^:]:%hu", &fwd_port, buf,
387 &fwd_host_port) != 3) {
388 fprintf(stderr, "Bad forwarding specification '%s'.\n", optarg);
392 add_local_forward(&options, fwd_port, buf, fwd_host_port);
396 options.compression = 1;
401 if (process_config_line(&options, host ? host : "", optarg,
402 "command-line", 0, &dummy) != 0)
411 /* Check that we got a host name. */
415 /* check if RSA support exists */
416 if (rsa_alive() == 0) {
418 "%s: no RSA support in libssl and libcrypto. See ssl(8).\n",
422 /* Initialize the command to execute on remote host. */
423 buffer_init(&command);
426 * Save the command to execute on the remote host in a buffer. There
427 * is no limit on the length of the command, except by the maximum
428 * packet size. Also sets the tty flag if there is no command.
431 /* No command specified - execute shell on a tty. */
434 /* A command has been specified. Store it into the
436 for (i = optind; i < ac; i++) {
438 buffer_append(&command, " ", 1);
439 buffer_append(&command, av[i], strlen(av[i]));
443 /* Cannot fork to background if no command. */
444 if (fork_after_authentication_flag && buffer_len(&command) == 0)
445 fatal("Cannot fork into background without a command to execute.");
447 /* Allocate a tty by default if no command specified. */
448 if (buffer_len(&command) == 0)
451 /* Do not allocate a tty if stdin is not a tty. */
452 if (!isatty(fileno(stdin))) {
454 fprintf(stderr, "Pseudo-terminal will not be allocated because stdin is not a terminal.\n");
458 pw = getpwuid(original_real_uid);
460 fprintf(stderr, "You don't exist, go away!\n");
463 /* Take a copy of the returned structure. */
464 memset(&pwcopy, 0, sizeof(pwcopy));
465 pwcopy.pw_name = xstrdup(pw->pw_name);
466 pwcopy.pw_passwd = xstrdup(pw->pw_passwd);
467 pwcopy.pw_uid = pw->pw_uid;
468 pwcopy.pw_gid = pw->pw_gid;
469 pwcopy.pw_dir = xstrdup(pw->pw_dir);
470 pwcopy.pw_shell = xstrdup(pw->pw_shell);
473 /* Initialize "log" output. Since we are the client all output
474 actually goes to the terminal. */
475 log_init(av[0], options.log_level, SYSLOG_FACILITY_USER, 0);
477 /* Read per-user configuration file. */
478 snprintf(buf, sizeof buf, "%.100s/%.100s", pw->pw_dir, SSH_USER_CONFFILE);
479 read_config_file(buf, host, &options);
481 /* Read systemwide configuration file. */
482 read_config_file(HOST_CONFIG_FILE, host, &options);
484 /* Fill configuration defaults. */
485 fill_default_options(&options);
488 log_init(av[0], options.log_level, SYSLOG_FACILITY_USER, 0);
490 if (options.user == NULL)
491 options.user = xstrdup(pw->pw_name);
493 if (options.hostname != NULL)
494 host = options.hostname;
496 /* Find canonic host name. */
497 if (strchr(host, '.') == 0) {
498 struct addrinfo hints;
499 struct addrinfo *ai = NULL;
501 memset(&hints, 0, sizeof(hints));
502 hints.ai_family = IPv4or6;
503 hints.ai_flags = AI_CANONNAME;
504 hints.ai_socktype = SOCK_STREAM;
505 errgai = getaddrinfo(host, NULL, &hints, &ai);
507 if (ai->ai_canonname != NULL)
508 host = xstrdup(ai->ai_canonname);
512 /* Disable rhosts authentication if not running as root. */
513 if (original_effective_uid != 0 || !options.use_privileged_port) {
514 options.rhosts_authentication = 0;
515 options.rhosts_rsa_authentication = 0;
518 * If using rsh has been selected, exec it now (without trying
519 * anything else). Note that we must release privileges first.
521 if (options.use_rsh) {
523 * Restore our superuser privileges. This must be done
524 * before permanently setting the uid.
528 /* Switch to the original uid permanently. */
529 permanently_set_uid(original_real_uid);
532 rsh_connect(host, options.user, &command);
533 fatal("rsh_connect returned");
535 /* Restore our superuser privileges. */
539 * Open a connection to the remote host. This needs root privileges
540 * if rhosts_{rsa_}authentication is enabled.
543 ok = ssh_connect(host, &hostaddr, options.port,
544 options.connection_attempts,
545 !options.rhosts_authentication &&
546 !options.rhosts_rsa_authentication,
548 options.proxy_command);
551 * If we successfully made the connection, load the host private key
552 * in case we will need it later for combined rsa-rhosts
553 * authentication. This must be done before releasing extra
554 * privileges, because the file is only readable by root.
557 host_private_key = RSA_new();
558 if (load_private_key(HOST_KEY_FILE, "", host_private_key, NULL))
559 host_private_key_loaded = 1;
562 * Get rid of any extra privileges that we may have. We will no
563 * longer need them. Also, extra privileges could make it very hard
564 * to read identity files and other non-world-readable files from the
565 * user's home directory if it happens to be on a NFS volume where
566 * root is mapped to nobody.
570 * Note that some legacy systems need to postpone the following call
571 * to permanently_set_uid() until the private hostkey is destroyed
572 * with RSA_free(). Otherwise the calling user could ptrace() the
573 * process, read the private hostkey and impersonate the host.
574 * OpenBSD does not allow ptracing of setuid processes.
576 permanently_set_uid(original_real_uid);
579 * Now that we are back to our own permissions, create ~/.ssh
580 * directory if it doesn\'t already exist.
582 snprintf(buf, sizeof buf, "%.100s/%.100s", pw->pw_dir, SSH_USER_DIR);
583 if (stat(buf, &st) < 0)
584 if (mkdir(buf, 0755) < 0)
585 error("Could not create directory '%.200s'.", buf);
587 /* Check if the connection failed, and try "rsh" if appropriate. */
589 if (options.port != 0)
590 log("Secure connection to %.100s on port %hu refused%.100s.",
592 options.fallback_to_rsh ? "; reverting to insecure method" : "");
594 log("Secure connection to %.100s refused%.100s.", host,
595 options.fallback_to_rsh ? "; reverting to insecure method" : "");
597 if (options.fallback_to_rsh) {
598 rsh_connect(host, options.user, &command);
599 fatal("rsh_connect returned");
603 /* Expand ~ in options.identity_files. */
604 for (i = 0; i < options.num_identity_files; i++)
605 options.identity_files[i] =
606 tilde_expand_filename(options.identity_files[i], original_real_uid);
608 /* Expand ~ in known host file names. */
609 options.system_hostfile = tilde_expand_filename(options.system_hostfile,
611 options.user_hostfile = tilde_expand_filename(options.user_hostfile,
614 /* Log into the remote system. This never returns if the login fails. */
615 ssh_login(host_private_key_loaded, host_private_key,
616 host, (struct sockaddr *)&hostaddr, original_real_uid);
618 /* We no longer need the host private key. Clear it now. */
619 if (host_private_key_loaded)
620 RSA_free(host_private_key); /* Destroys contents safely */
622 /* Enable compression if requested. */
623 if (options.compression) {
624 debug("Requesting compression at level %d.", options.compression_level);
626 if (options.compression_level < 1 || options.compression_level > 9)
627 fatal("Compression level must be from 1 (fast) to 9 (slow, best).");
629 /* Send the request. */
630 packet_start(SSH_CMSG_REQUEST_COMPRESSION);
631 packet_put_int(options.compression_level);
634 type = packet_read(&plen);
635 if (type == SSH_SMSG_SUCCESS)
636 packet_start_compression(options.compression_level);
637 else if (type == SSH_SMSG_FAILURE)
638 log("Warning: Remote host refused compression.");
640 packet_disconnect("Protocol error waiting for compression response.");
642 /* Allocate a pseudo tty if appropriate. */
644 debug("Requesting pty.");
646 /* Start the packet. */
647 packet_start(SSH_CMSG_REQUEST_PTY);
649 /* Store TERM in the packet. There is no limit on the
650 length of the string. */
654 packet_put_string(cp, strlen(cp));
656 /* Store window size in the packet. */
657 if (ioctl(fileno(stdin), TIOCGWINSZ, &ws) < 0)
658 memset(&ws, 0, sizeof(ws));
659 packet_put_int(ws.ws_row);
660 packet_put_int(ws.ws_col);
661 packet_put_int(ws.ws_xpixel);
662 packet_put_int(ws.ws_ypixel);
664 /* Store tty modes in the packet. */
665 tty_make_modes(fileno(stdin));
667 /* Send the packet, and wait for it to leave. */
671 /* Read response from the server. */
672 type = packet_read(&plen);
673 if (type == SSH_SMSG_SUCCESS) {
676 } else if (type == SSH_SMSG_FAILURE)
677 log("Warning: Remote host failed or refused to allocate a pseudo tty.");
679 packet_disconnect("Protocol error waiting for pty request response.");
681 /* Request X11 forwarding if enabled and DISPLAY is set. */
682 if (options.forward_x11 && getenv("DISPLAY") != NULL) {
683 char line[512], proto[512], data[512];
685 int forwarded = 0, got_data = 0, i;
688 /* Try to get Xauthority information for the display. */
689 snprintf(line, sizeof line, "%.100s list %.200s 2>/dev/null",
690 XAUTH_PATH, getenv("DISPLAY"));
691 f = popen(line, "r");
692 if (f && fgets(line, sizeof(line), f) &&
693 sscanf(line, "%*s %s %s", proto, data) == 2)
697 #endif /* XAUTH_PATH */
699 * If we didn't get authentication data, just make up some
700 * data. The forwarding code will check the validity of the
701 * response anyway, and substitute this data. The X11
702 * server, however, will ignore this fake data and use
703 * whatever authentication mechanisms it was using otherwise
704 * for the local connection.
709 strlcpy(proto, "MIT-MAGIC-COOKIE-1", sizeof proto);
710 for (i = 0; i < 16; i++) {
713 snprintf(data + 2 * i, sizeof data - 2 * i, "%02x", rand & 0xff);
718 * Got local authentication reasonable information. Request
719 * forwarding with authentication spoofing.
721 debug("Requesting X11 forwarding with authentication spoofing.");
722 x11_request_forwarding_with_spoofing(proto, data);
724 /* Read response from the server. */
725 type = packet_read(&plen);
726 if (type == SSH_SMSG_SUCCESS) {
729 } else if (type == SSH_SMSG_FAILURE)
730 log("Warning: Remote host denied X11 forwarding.");
732 packet_disconnect("Protocol error waiting for X11 forwarding");
734 /* Tell the packet module whether this is an interactive session. */
735 packet_set_interactive(interactive, options.keepalives);
737 /* Clear agent forwarding if we don\'t have an agent. */
738 authfd = ssh_get_authentication_socket();
740 options.forward_agent = 0;
742 ssh_close_authentication_socket(authfd);
744 /* Request authentication agent forwarding if appropriate. */
745 if (options.forward_agent) {
746 debug("Requesting authentication agent forwarding.");
747 auth_request_forwarding();
749 /* Read response from the server. */
750 type = packet_read(&plen);
751 packet_integrity_check(plen, 0, type);
752 if (type != SSH_SMSG_SUCCESS)
753 log("Warning: Remote host denied authentication agent forwarding.");
755 /* Initiate local TCP/IP port forwardings. */
756 for (i = 0; i < options.num_local_forwards; i++) {
757 debug("Connections to local port %d forwarded to remote address %.200s:%d",
758 options.local_forwards[i].port,
759 options.local_forwards[i].host,
760 options.local_forwards[i].host_port);
761 channel_request_local_forwarding(options.local_forwards[i].port,
762 options.local_forwards[i].host,
763 options.local_forwards[i].host_port,
764 options.gateway_ports);
767 /* Initiate remote TCP/IP port forwardings. */
768 for (i = 0; i < options.num_remote_forwards; i++) {
769 debug("Connections to remote port %d forwarded to local address %.200s:%d",
770 options.remote_forwards[i].port,
771 options.remote_forwards[i].host,
772 options.remote_forwards[i].host_port);
773 channel_request_remote_forwarding(options.remote_forwards[i].port,
774 options.remote_forwards[i].host,
775 options.remote_forwards[i].host_port);
778 /* If requested, let ssh continue in the background. */
779 if (fork_after_authentication_flag)
780 if (daemon(1, 1) < 0)
781 fatal("daemon() failed: %.200s", strerror(errno));
784 * If a command was specified on the command line, execute the
785 * command now. Otherwise request the server to start a shell.
787 if (buffer_len(&command) > 0) {
788 int len = buffer_len(&command);
791 debug("Sending command: %.*s", len, buffer_ptr(&command));
792 packet_start(SSH_CMSG_EXEC_CMD);
793 packet_put_string(buffer_ptr(&command), buffer_len(&command));
797 debug("Requesting shell.");
798 packet_start(SSH_CMSG_EXEC_SHELL);
803 /* Enter the interactive session. */
804 exit_status = client_loop(have_pty, tty_flag ? options.escape_char : -1);
806 /* Close the connection to the remote host. */
809 /* Exit with the status returned by the program on the remote side. */