5 Author: Tatu Ylonen <ylo@cs.hut.fi>
7 Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
10 Created: Sat Mar 18 16:36:11 1995 ylo
12 Ssh client program. This program can be used to log into a remote machine.
13 The software supports strong authentication, encryption, and forwarding
14 of X11, TCP/IP, and authentication connections.
16 Modified to work with SSL by Niels Provos <provos@citi.umich.edu> in Canada.
31 #ifdef HAVE___PROGNAME
32 extern char *__progname;
33 #else /* HAVE___PROGNAME */
34 const char *__progname = "ssh";
35 #endif /* HAVE___PROGNAME */
37 /* Flag indicating whether debug mode is on. This can be set on the
41 /* Flag indicating whether to allocate a pseudo tty. This can be set on the
42 command line, and is automatically set if no command is given on the command
46 /* Flag indicating that nothing should be read from stdin. This can be set
47 on the command line. */
48 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
53 int fork_after_authentication_flag = 0;
55 /* General data structure for command line options and options configurable
56 in configuration files. See readconf.h. */
59 /* Name of the host we are connecting to. This is the name given on the
60 command line, or the HostName specified for the user-supplied name
61 in a configuration file. */
64 /* socket address the host resolves to */
65 struct sockaddr_in hostaddr;
67 /* Flag to indicate that we have received a window change signal which has
68 not yet been processed. This will cause a message indicating the new
69 window size to be sent to the server a little later. This is volatile
70 because this is updated in a signal handler. */
71 volatile int received_window_change_signal = 0;
73 /* Value of argv[0] (set in the main program). */
76 /* Flag indicating whether we have a valid host private key loaded. */
77 int host_private_key_loaded = 0;
79 /* Host private key. */
80 RSA *host_private_key = NULL;
82 /* Original real UID. */
83 uid_t original_real_uid;
85 /* Prints a help message to the user. This function never returns. */
90 fprintf(stderr, "Usage: %s [options] host [command]\n", av0);
91 fprintf(stderr, "Options:\n");
92 fprintf(stderr, " -l user Log in using this user name.\n");
93 fprintf(stderr, " -n Redirect input from /dev/null.\n");
94 fprintf(stderr, " -a Disable authentication agent forwarding.\n");
96 fprintf(stderr, " -k Disable Kerberos ticket and AFS token forwarding.\n");
98 fprintf(stderr, " -x Disable X11 connection forwarding.\n");
99 fprintf(stderr, " -i file Identity for RSA authentication (default: ~/.ssh/identity).\n");
100 fprintf(stderr, " -t Tty; allocate a tty even if command is given.\n");
101 fprintf(stderr, " -v Verbose; display verbose debugging messages.\n");
102 fprintf(stderr, " -V Display version number only.\n");
103 fprintf(stderr, " -P Don't allocate a privileged port.\n");
104 fprintf(stderr, " -q Quiet; don't display any warning messages.\n");
105 fprintf(stderr, " -f Fork into background after authentication.\n");
106 fprintf(stderr, " -e char Set escape character; ``none'' = disable (default: ~).\n");
108 fprintf(stderr, " -c cipher Select encryption algorithm: "
111 fprintf(stderr, " -p port Connect to this port. Server must be on the same port.\n");
112 fprintf(stderr, " -L listen-port:host:port Forward local port to remote address\n");
113 fprintf(stderr, " -R listen-port:host:port Forward remote port to local address\n");
114 fprintf(stderr, " These cause %s to listen for connections on a port, and\n", av0);
115 fprintf(stderr, " forward them to the other side by connecting to host:port.\n");
116 fprintf(stderr, " -C Enable compression.\n");
117 fprintf(stderr, " -g Allow remote hosts to connect to forwarded ports.\n");
118 fprintf(stderr, " -o 'option' Process the option as if it was read from a configuration file.\n");
122 /* Connects to the given host using rsh (or prints an error message and exits
123 if rsh is not available). This function never returns. */
126 rsh_connect(char *host, char *user, Buffer *command)
131 log("Using rsh. WARNING: Connection will not be encrypted.");
132 /* Build argument list for rsh. */
134 args[i++] = _PATH_RSH;
135 args[i++] = host; /* may have to come after user on some systems */
141 if (buffer_len(command) > 0)
143 buffer_append(command, "\0", 1);
144 args[i++] = buffer_ptr(command);
149 for (i = 0; args[i]; i++)
152 fprintf(stderr, " ");
153 fprintf(stderr, "%s", args[i]);
155 fprintf(stderr, "\n");
157 execv(_PATH_RSH, args);
162 /* Main program for the ssh client. */
165 main(int ac, char **av)
167 int i, opt, optind, type, exit_status, ok, fwd_port, fwd_host_port, authfd;
168 char *optarg, *cp, buf[256];
172 struct passwd *pw, pwcopy;
173 int interactive = 0, dummy;
174 uid_t original_effective_uid;
177 /* Save the original real uid. It will be needed later (uid-swapping may
178 clobber the real uid). */
179 original_real_uid = getuid();
180 original_effective_uid = geteuid();
182 /* If we are installed setuid root be careful to not drop core. */
183 if (original_real_uid != original_effective_uid)
186 rlim.rlim_cur = rlim.rlim_max = 0;
187 if (setrlimit(RLIMIT_CORE, &rlim) < 0)
188 fatal("setrlimit failed: %.100s", strerror(errno));
191 /* Use uid-swapping to give up root privileges for the duration of option
192 processing. We will re-instantiate the rights when we are ready to
193 create the privileged port, and will permanently drop them when the
194 port has been created (actually, when the connection has been made, as
195 we may need to create the port several times). */
196 temporarily_use_uid(original_real_uid);
198 /* Set our umask to something reasonable, as some files are created with
199 the default umask. This will make them world-readable but writable
200 only by the owner, which is ok for all files for which we don't set
201 the modes explicitly. */
204 /* Save our own name. */
207 /* Initialize option structure to indicate that no values have been set. */
208 initialize_options(&options);
210 /* Parse command-line arguments. */
213 /* If program name is not one of the standard names, use it as host name. */
214 if (strchr(av0, '/'))
215 cp = strrchr(av0, '/') + 1;
218 if (strcmp(cp, "rsh") != 0 && strcmp(cp, "ssh") != 0 &&
219 strcmp(cp, "rlogin") != 0 && strcmp(cp, "slogin") != 0)
222 for (optind = 1; optind < ac; optind++)
224 if (av[optind][0] != '-')
228 if ((cp = strchr(av[optind], '@'))) {
229 options.user = av[optind];
240 if (strchr("eilcpLRo", opt)) /* options with arguments */
242 optarg = av[optind] + 2;
243 if (strcmp(optarg, "") == 0)
245 if (optind >= ac - 1)
247 optarg = av[++optind];
263 fork_after_authentication_flag = 1;
268 options.forward_x11 = 0;
272 options.forward_x11 = 1;
276 options.gateway_ports = 1;
280 options.use_privileged_port = 0;
284 options.forward_agent = 0;
288 options.kerberos_tgt_passing = 0;
289 options.afs_token_passing = 0;
293 if (stat(optarg, &st) < 0)
295 fprintf(stderr, "Warning: Identity file %s does not exist.\n",
299 if (options.num_identity_files >= SSH_MAX_IDENTITY_FILES)
300 fatal("Too many identity files specified (max %d)",
301 SSH_MAX_IDENTITY_FILES);
302 options.identity_files[options.num_identity_files++] =
312 fprintf(stderr, "SSH Version %s, protocol version %d.%d.\n",
313 SSH_VERSION, PROTOCOL_MAJOR, PROTOCOL_MINOR);
314 fprintf(stderr, "Compiled with SSL.\n");
318 options.log_level = SYSLOG_LEVEL_DEBUG;
322 options.log_level = SYSLOG_LEVEL_QUIET;
326 if (optarg[0] == '^' && optarg[2] == 0 &&
327 (unsigned char)optarg[1] >= 64 && (unsigned char)optarg[1] < 128)
328 options.escape_char = (unsigned char)optarg[1] & 31;
330 if (strlen(optarg) == 1)
331 options.escape_char = (unsigned char)optarg[0];
333 if (strcmp(optarg, "none") == 0)
334 options.escape_char = -2;
337 fprintf(stderr, "Bad escape character '%s'.\n", optarg);
343 options.cipher = cipher_number(optarg);
344 if (options.cipher == -1)
346 fprintf(stderr, "Unknown cipher type '%s'\n", optarg);
352 options.port = atoi(optarg);
353 if (options.port < 1 || options.port > 65535)
355 fprintf(stderr, "Bad port %s.\n", optarg);
361 options.user = optarg;
365 if (sscanf(optarg, "%d:%255[^:]:%d", &fwd_port, buf,
366 &fwd_host_port) != 3)
368 fprintf(stderr, "Bad forwarding specification '%s'.\n", optarg);
372 add_remote_forward(&options, fwd_port, buf, fwd_host_port);
376 if (sscanf(optarg, "%d:%255[^:]:%d", &fwd_port, buf,
377 &fwd_host_port) != 3)
379 fprintf(stderr, "Bad forwarding specification '%s'.\n", optarg);
383 add_local_forward(&options, fwd_port, buf, fwd_host_port);
387 options.compression = 1;
392 if (process_config_line(&options, host ? host : "", optarg,
393 "command-line", 0, &dummy) != 0)
402 /* Check that we got a host name. */
406 /* check if RSA support exists */
407 if (rsa_alive() == 0) {
410 "%s: no RSA support in libssl and libcrypto. See ssl(8).\n",
415 /* Initialize the command to execute on remote host. */
416 buffer_init(&command);
418 /* Save the command to execute on the remote host in a buffer. There is
419 no limit on the length of the command, except by the maximum packet
420 size. Also sets the tty flag if there is no command. */
423 /* No command specified - execute shell on a tty. */
428 /* A command has been specified. Store it into the buffer. */
429 for (i = optind; i < ac; i++)
432 buffer_append(&command, " ", 1);
433 buffer_append(&command, av[i], strlen(av[i]));
437 /* Cannot fork to background if no command. */
438 if (fork_after_authentication_flag && buffer_len(&command) == 0)
439 fatal("Cannot fork into background without a command to execute.");
441 /* Allocate a tty by default if no command specified. */
442 if (buffer_len(&command) == 0)
445 /* Do not allocate a tty if stdin is not a tty. */
446 if (!isatty(fileno(stdin)))
449 fprintf(stderr, "Pseudo-terminal will not be allocated because stdin is not a terminal.\n");
454 pw = getpwuid(original_real_uid);
457 fprintf(stderr, "You don't exist, go away!\n");
461 /* Take a copy of the returned structure. */
462 memset(&pwcopy, 0, sizeof(pwcopy));
463 pwcopy.pw_name = xstrdup(pw->pw_name);
464 pwcopy.pw_passwd = xstrdup(pw->pw_passwd);
465 pwcopy.pw_uid = pw->pw_uid;
466 pwcopy.pw_gid = pw->pw_gid;
467 pwcopy.pw_dir = xstrdup(pw->pw_dir);
468 pwcopy.pw_shell = xstrdup(pw->pw_shell);
471 /* Initialize "log" output. Since we are the client all output actually
472 goes to the terminal. */
473 log_init(av[0], options.log_level, SYSLOG_FACILITY_USER, 0);
475 /* Read per-user configuration file. */
476 snprintf(buf, sizeof buf, "%.100s/%.100s", pw->pw_dir, SSH_USER_CONFFILE);
477 read_config_file(buf, host, &options);
479 /* Read systemwide configuration file. */
480 read_config_file(HOST_CONFIG_FILE, host, &options);
482 /* Fill configuration defaults. */
483 fill_default_options(&options);
486 log_init(av[0], options.log_level, SYSLOG_FACILITY_USER, 0);
488 if (options.user == NULL)
489 options.user = xstrdup(pw->pw_name);
491 if (options.hostname != NULL)
492 host = options.hostname;
494 /* Find canonic host name. */
495 if (strchr(host, '.') == 0)
497 struct hostent *hp = gethostbyname(host);
500 if (strchr(hp->h_name, '.') != 0)
501 host = xstrdup(hp->h_name);
502 else if (hp->h_aliases != 0
503 && hp->h_aliases[0] != 0
504 && strchr(hp->h_aliases[0], '.') != 0)
505 host = xstrdup(hp->h_aliases[0]);
509 /* Disable rhosts authentication if not running as root. */
510 if (original_effective_uid != 0 || !options.use_privileged_port)
512 options.rhosts_authentication = 0;
513 options.rhosts_rsa_authentication = 0;
516 /* If using rsh has been selected, exec it now (without trying anything
517 else). Note that we must release privileges first. */
520 /* Restore our superuser privileges. This must be done before
521 permanently setting the uid. */
524 /* Switch to the original uid permanently. */
525 permanently_set_uid(original_real_uid);
528 rsh_connect(host, options.user, &command);
529 fatal("rsh_connect returned");
532 /* Restore our superuser privileges. */
535 /* Open a connection to the remote host. This needs root privileges if
536 rhosts_{rsa_}authentication is enabled. */
538 ok = ssh_connect(host, &hostaddr, options.port, options.connection_attempts,
539 !options.rhosts_authentication &&
540 !options.rhosts_rsa_authentication,
541 original_real_uid, options.proxy_command);
543 /* If we successfully made the connection, load the host private key in
544 case we will need it later for combined rsa-rhosts authentication.
545 This must be done before releasing extra privileges, because the file
546 is only readable by root. */
549 host_private_key = RSA_new();
550 if (load_private_key(HOST_KEY_FILE, "", host_private_key, NULL))
551 host_private_key_loaded = 1;
554 /* Get rid of any extra privileges that we may have. We will no longer need
555 them. Also, extra privileges could make it very hard to read identity
556 files and other non-world-readable files from the user's home directory
557 if it happens to be on a NFS volume where root is mapped to nobody. */
559 /* Note that some legacy systems need to postpone the following call to
560 permanently_set_uid() until the private hostkey is destroyed with
561 RSA_free(). Otherwise the calling user could ptrace() the process,
562 read the private hostkey and impersonate the host. OpenBSD does not
563 allow ptracing of setuid processes. */
565 permanently_set_uid(original_real_uid);
567 /* Now that we are back to our own permissions, create ~/.ssh directory
568 if it doesn\'t already exist. */
569 snprintf(buf, sizeof buf, "%.100s/%.100s", pw->pw_dir, SSH_USER_DIR);
570 if (stat(buf, &st) < 0)
571 if (mkdir(buf, 0755) < 0)
572 error("Could not create directory '%.200s'.", buf);
574 /* Check if the connection failed, and try "rsh" if appropriate. */
577 if (options.port != 0)
578 log("Secure connection to %.100s on port %d refused%.100s.",
580 options.fallback_to_rsh ? "; reverting to insecure method" : "");
582 log("Secure connection to %.100s refused%.100s.", host,
583 options.fallback_to_rsh ? "; reverting to insecure method" : "");
585 if (options.fallback_to_rsh)
587 rsh_connect(host, options.user, &command);
588 fatal("rsh_connect returned");
593 /* Expand ~ in options.identity_files. */
594 for (i = 0; i < options.num_identity_files; i++)
595 options.identity_files[i] =
596 tilde_expand_filename(options.identity_files[i], original_real_uid);
598 /* Expand ~ in known host file names. */
599 options.system_hostfile = tilde_expand_filename(options.system_hostfile,
601 options.user_hostfile = tilde_expand_filename(options.user_hostfile,
604 /* Log into the remote system. This never returns if the login fails. */
605 ssh_login(host_private_key_loaded, host_private_key,
606 host, &hostaddr, original_real_uid);
608 /* We no longer need the host private key. Clear it now. */
609 if (host_private_key_loaded)
610 RSA_free(host_private_key); /* Destroys contents safely */
612 /* Close connection cleanly after attack. */
613 cipher_attack_detected = packet_disconnect;
615 /* Enable compression if requested. */
616 if (options.compression)
618 debug("Requesting compression at level %d.", options.compression_level);
620 if (options.compression_level < 1 || options.compression_level > 9)
621 fatal("Compression level must be from 1 (fast) to 9 (slow, best).");
623 /* Send the request. */
624 packet_start(SSH_CMSG_REQUEST_COMPRESSION);
625 packet_put_int(options.compression_level);
628 type = packet_read(&plen);
629 if (type == SSH_SMSG_SUCCESS)
630 packet_start_compression(options.compression_level);
631 else if (type == SSH_SMSG_FAILURE)
632 log("Warning: Remote host refused compression.");
634 packet_disconnect("Protocol error waiting for compression response.");
637 /* Allocate a pseudo tty if appropriate. */
640 debug("Requesting pty.");
642 /* Start the packet. */
643 packet_start(SSH_CMSG_REQUEST_PTY);
645 /* Store TERM in the packet. There is no limit on the length of the
650 packet_put_string(cp, strlen(cp));
652 /* Store window size in the packet. */
653 if (ioctl(fileno(stdin), TIOCGWINSZ, &ws) < 0)
654 memset(&ws, 0, sizeof(ws));
655 packet_put_int(ws.ws_row);
656 packet_put_int(ws.ws_col);
657 packet_put_int(ws.ws_xpixel);
658 packet_put_int(ws.ws_ypixel);
660 /* Store tty modes in the packet. */
661 tty_make_modes(fileno(stdin));
663 /* Send the packet, and wait for it to leave. */
667 /* Read response from the server. */
668 type = packet_read(&plen);
669 if (type == SSH_SMSG_SUCCESS)
671 else if (type == SSH_SMSG_FAILURE)
672 log("Warning: Remote host failed or refused to allocate a pseudo tty.");
674 packet_disconnect("Protocol error waiting for pty request response.");
677 /* Request X11 forwarding if enabled and DISPLAY is set. */
678 if (options.forward_x11 && getenv("DISPLAY") != NULL)
680 char line[512], proto[512], data[512];
682 int forwarded = 0, got_data = 0, i;
685 /* Try to get Xauthority information for the display. */
686 snprintf(line, sizeof line, "%.100s list %.200s 2>/dev/null",
687 XAUTH_PATH, getenv("DISPLAY"));
688 f = popen(line, "r");
689 if (f && fgets(line, sizeof(line), f) &&
690 sscanf(line, "%*s %s %s", proto, data) == 2)
694 #endif /* XAUTH_PATH */
695 /* If we didn't get authentication data, just make up some data. The
696 forwarding code will check the validity of the response anyway, and
697 substitute this data. The X11 server, however, will ignore this
698 fake data and use whatever authentication mechanisms it was using
699 otherwise for the local connection. */
704 strlcpy(proto, "MIT-MAGIC-COOKIE-1", sizeof proto);
705 for (i = 0; i < 16; i++) {
708 snprintf(data + 2 * i, sizeof data - 2 * i, "%02x", rand & 0xff);
713 /* Got local authentication reasonable information. Request forwarding
714 with authentication spoofing. */
715 debug("Requesting X11 forwarding with authentication spoofing.");
716 x11_request_forwarding_with_spoofing(proto, data);
718 /* Read response from the server. */
719 type = packet_read(&plen);
720 if (type == SSH_SMSG_SUCCESS)
725 else if (type == SSH_SMSG_FAILURE)
726 log("Warning: Remote host denied X11 forwarding.");
728 packet_disconnect("Protocol error waiting for X11 forwarding");
731 /* Tell the packet module whether this is an interactive session. */
732 packet_set_interactive(interactive, options.keepalives);
734 /* Clear agent forwarding if we don\'t have an agent. */
735 authfd = ssh_get_authentication_socket();
737 options.forward_agent = 0;
739 ssh_close_authentication_socket(authfd);
741 /* Request authentication agent forwarding if appropriate. */
742 if (options.forward_agent)
744 debug("Requesting authentication agent forwarding.");
745 auth_request_forwarding();
747 /* Read response from the server. */
748 type = packet_read(&plen);
749 packet_integrity_check(plen, 0, type);
750 if (type != SSH_SMSG_SUCCESS)
751 log("Warning: Remote host denied authentication agent forwarding.");
754 /* Initiate local TCP/IP port forwardings. */
755 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, options.local_forwards[i].host,
759 options.local_forwards[i].host_port);
760 channel_request_local_forwarding(options.local_forwards[i].port,
761 options.local_forwards[i].host,
762 options.local_forwards[i].host_port);
765 /* Initiate remote TCP/IP port forwardings. */
766 for (i = 0; i < options.num_remote_forwards; i++)
768 debug("Connections to remote port %d forwarded to local address %.200s:%d",
769 options.remote_forwards[i].port, options.remote_forwards[i].host,
770 options.remote_forwards[i].host_port);
771 channel_request_remote_forwarding(options.remote_forwards[i].port,
772 options.remote_forwards[i].host,
773 options.remote_forwards[i].host_port);
776 /* If requested, fork and let ssh continue in the background. */
777 if (fork_after_authentication_flag)
781 fatal("fork failed: %.100s", strerror(errno));
787 /* If a command was specified on the command line, execute the command now.
788 Otherwise request the server to start a shell. */
789 if (buffer_len(&command) > 0)
791 int len = buffer_len(&command);
794 debug("Sending command: %.*s", len, buffer_ptr(&command));
795 packet_start(SSH_CMSG_EXEC_CMD);
796 packet_put_string(buffer_ptr(&command), buffer_len(&command));
802 debug("Requesting shell.");
803 packet_start(SSH_CMSG_EXEC_SHELL);
808 /* Enter the interactive session. */
809 exit_status = client_loop(tty_flag, tty_flag ? options.escape_char : -1);
811 /* Close the connection to the remote host. */
814 /* Exit with the status returned by the program on the remote side. */