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 /* Flag indicating whether debug mode is on. This can be set on the
35 /* Flag indicating whether to allocate a pseudo tty. This can be set on the
36 command line, and is automatically set if no command is given on the command
40 /* Flag indicating that nothing should be read from stdin. This can be set
41 on the command line. */
42 int stdin_null_flag = 0;
44 /* Flag indicating that ssh should fork after authentication. This is useful
45 so that the pasphrase can be entered manually, and then ssh goes to the
47 int fork_after_authentication_flag = 0;
49 /* General data structure for command line options and options configurable
50 in configuration files. See readconf.h. */
53 /* Name of the host we are connecting to. This is the name given on the
54 command line, or the HostName specified for the user-supplied name
55 in a configuration file. */
58 /* socket address the host resolves to */
59 struct sockaddr_in hostaddr;
61 /* Flag to indicate that we have received a window change signal which has
62 not yet been processed. This will cause a message indicating the new
63 window size to be sent to the server a little later. This is volatile
64 because this is updated in a signal handler. */
65 volatile int received_window_change_signal = 0;
67 /* Value of argv[0] (set in the main program). */
70 /* Flag indicating whether we have a valid host private key loaded. */
71 int host_private_key_loaded = 0;
73 /* Host private key. */
74 RSA *host_private_key = NULL;
76 /* Original real UID. */
77 uid_t original_real_uid;
79 /* Prints a help message to the user. This function never returns. */
84 fprintf(stderr, "Usage: %s [options] host [command]\n", av0);
85 fprintf(stderr, "Options:\n");
86 fprintf(stderr, " -l user Log in using this user name.\n");
87 fprintf(stderr, " -n Redirect input from /dev/null.\n");
88 fprintf(stderr, " -a Disable authentication agent forwarding.\n");
90 fprintf(stderr, " -k Disable Kerberos ticket and AFS token forwarding.\n");
92 fprintf(stderr, " -x Disable X11 connection forwarding.\n");
93 fprintf(stderr, " -i file Identity for RSA authentication (default: ~/.ssh/identity).\n");
94 fprintf(stderr, " -t Tty; allocate a tty even if command is given.\n");
95 fprintf(stderr, " -v Verbose; display verbose debugging messages.\n");
96 fprintf(stderr, " -V Display version number only.\n");
97 fprintf(stderr, " -P Don't allocate a privileged port.\n");
98 fprintf(stderr, " -q Quiet; don't display any warning messages.\n");
99 fprintf(stderr, " -f Fork into background after authentication.\n");
100 fprintf(stderr, " -e char Set escape character; ``none'' = disable (default: ~).\n");
102 fprintf(stderr, " -c cipher Select encryption algorithm: "
105 fprintf(stderr, " -p port Connect to this port. Server must be on the same port.\n");
106 fprintf(stderr, " -L listen-port:host:port Forward local port to remote address\n");
107 fprintf(stderr, " -R listen-port:host:port Forward remote port to local address\n");
108 fprintf(stderr, " These cause %s to listen for connections on a port, and\n", av0);
109 fprintf(stderr, " forward them to the other side by connecting to host:port.\n");
110 fprintf(stderr, " -C Enable compression.\n");
111 fprintf(stderr, " -g Allow remote hosts to connect to forwarded ports.\n");
112 fprintf(stderr, " -o 'option' Process the option as if it was read from a configuration file.\n");
116 /* Connects to the given host using rsh (or prints an error message and exits
117 if rsh is not available). This function never returns. */
120 rsh_connect(char *host, char *user, Buffer *command)
125 log("Using rsh. WARNING: Connection will not be encrypted.");
126 /* Build argument list for rsh. */
128 args[i++] = _PATH_RSH;
129 args[i++] = host; /* may have to come after user on some systems */
135 if (buffer_len(command) > 0)
137 buffer_append(command, "\0", 1);
138 args[i++] = buffer_ptr(command);
143 for (i = 0; args[i]; i++)
146 fprintf(stderr, " ");
147 fprintf(stderr, "%s", args[i]);
149 fprintf(stderr, "\n");
151 execv(_PATH_RSH, args);
156 /* Main program for the ssh client. */
159 main(int ac, char **av)
161 int i, opt, optind, type, exit_status, ok, fwd_port, fwd_host_port, authfd;
162 char *optarg, *cp, buf[256];
166 struct passwd *pw, pwcopy;
167 int interactive = 0, dummy;
168 uid_t original_effective_uid;
171 /* Save the original real uid. It will be needed later (uid-swapping may
172 clobber the real uid). */
173 original_real_uid = getuid();
174 original_effective_uid = geteuid();
176 /* If we are installed setuid root be careful to not drop core. */
177 if (original_real_uid != original_effective_uid)
180 rlim.rlim_cur = rlim.rlim_max = 0;
181 if (setrlimit(RLIMIT_CORE, &rlim) < 0)
182 fatal("setrlimit failed: %.100s", strerror(errno));
185 /* Use uid-swapping to give up root privileges for the duration of option
186 processing. We will re-instantiate the rights when we are ready to
187 create the privileged port, and will permanently drop them when the
188 port has been created (actually, when the connection has been made, as
189 we may need to create the port several times). */
190 temporarily_use_uid(original_real_uid);
192 /* Set our umask to something reasonable, as some files are created with
193 the default umask. This will make them world-readable but writable
194 only by the owner, which is ok for all files for which we don't set
195 the modes explicitly. */
198 /* Save our own name. */
201 /* Initialize option structure to indicate that no values have been set. */
202 initialize_options(&options);
204 /* Parse command-line arguments. */
207 /* If program name is not one of the standard names, use it as host name. */
208 if (strchr(av0, '/'))
209 cp = strrchr(av0, '/') + 1;
212 if (strcmp(cp, "rsh") != 0 && strcmp(cp, "ssh") != 0 &&
213 strcmp(cp, "rlogin") != 0 && strcmp(cp, "slogin") != 0)
216 for (optind = 1; optind < ac; optind++)
218 if (av[optind][0] != '-')
222 if ((cp = strchr(av[optind], '@'))) {
223 options.user = av[optind];
234 if (strchr("eilcpLRo", opt)) /* options with arguments */
236 optarg = av[optind] + 2;
237 if (strcmp(optarg, "") == 0)
239 if (optind >= ac - 1)
241 optarg = av[++optind];
257 fork_after_authentication_flag = 1;
262 options.forward_x11 = 0;
266 options.forward_x11 = 1;
270 options.gateway_ports = 1;
274 options.use_privileged_port = 0;
278 options.forward_agent = 0;
282 options.kerberos_tgt_passing = 0;
283 options.afs_token_passing = 0;
287 if (stat(optarg, &st) < 0)
289 fprintf(stderr, "Warning: Identity file %s does not exist.\n",
293 if (options.num_identity_files >= SSH_MAX_IDENTITY_FILES)
294 fatal("Too many identity files specified (max %d)",
295 SSH_MAX_IDENTITY_FILES);
296 options.identity_files[options.num_identity_files++] =
306 fprintf(stderr, "SSH Version %s, protocol version %d.%d.\n",
307 SSH_VERSION, PROTOCOL_MAJOR, PROTOCOL_MINOR);
308 fprintf(stderr, "Compiled with SSL.\n");
312 options.log_level = SYSLOG_LEVEL_DEBUG;
316 options.log_level = SYSLOG_LEVEL_QUIET;
320 if (optarg[0] == '^' && optarg[2] == 0 &&
321 (unsigned char)optarg[1] >= 64 && (unsigned char)optarg[1] < 128)
322 options.escape_char = (unsigned char)optarg[1] & 31;
324 if (strlen(optarg) == 1)
325 options.escape_char = (unsigned char)optarg[0];
327 if (strcmp(optarg, "none") == 0)
328 options.escape_char = -2;
331 fprintf(stderr, "Bad escape character '%s'.\n", optarg);
337 options.cipher = cipher_number(optarg);
338 if (options.cipher == -1)
340 fprintf(stderr, "Unknown cipher type '%s'\n", optarg);
346 options.port = atoi(optarg);
347 if (options.port < 1 || options.port > 65535)
349 fprintf(stderr, "Bad port %s.\n", optarg);
355 options.user = optarg;
359 if (sscanf(optarg, "%d:%255[^:]:%d", &fwd_port, buf,
360 &fwd_host_port) != 3)
362 fprintf(stderr, "Bad forwarding specification '%s'.\n", optarg);
366 add_remote_forward(&options, fwd_port, buf, fwd_host_port);
370 if (sscanf(optarg, "%d:%255[^:]:%d", &fwd_port, buf,
371 &fwd_host_port) != 3)
373 fprintf(stderr, "Bad forwarding specification '%s'.\n", optarg);
377 add_local_forward(&options, fwd_port, buf, fwd_host_port);
381 options.compression = 1;
386 if (process_config_line(&options, host ? host : "", optarg,
387 "command-line", 0, &dummy) != 0)
396 /* Check that we got a host name. */
400 /* check if RSA support exists */
401 if (rsa_alive() == 0) {
402 extern char *__progname;
405 "%s: no RSA support in libssl and libcrypto. See ssl(8).\n",
410 /* Initialize the command to execute on remote host. */
411 buffer_init(&command);
413 /* Save the command to execute on the remote host in a buffer. There is
414 no limit on the length of the command, except by the maximum packet
415 size. Also sets the tty flag if there is no command. */
418 /* No command specified - execute shell on a tty. */
423 /* A command has been specified. Store it into the buffer. */
424 for (i = optind; i < ac; i++)
427 buffer_append(&command, " ", 1);
428 buffer_append(&command, av[i], strlen(av[i]));
432 /* Cannot fork to background if no command. */
433 if (fork_after_authentication_flag && buffer_len(&command) == 0)
434 fatal("Cannot fork into background without a command to execute.");
436 /* Allocate a tty by default if no command specified. */
437 if (buffer_len(&command) == 0)
440 /* Do not allocate a tty if stdin is not a tty. */
441 if (!isatty(fileno(stdin)))
444 fprintf(stderr, "Pseudo-terminal will not be allocated because stdin is not a terminal.\n");
449 pw = getpwuid(original_real_uid);
452 fprintf(stderr, "You don't exist, go away!\n");
456 /* Take a copy of the returned structure. */
457 memset(&pwcopy, 0, sizeof(pwcopy));
458 pwcopy.pw_name = xstrdup(pw->pw_name);
459 pwcopy.pw_passwd = xstrdup(pw->pw_passwd);
460 pwcopy.pw_uid = pw->pw_uid;
461 pwcopy.pw_gid = pw->pw_gid;
462 pwcopy.pw_dir = xstrdup(pw->pw_dir);
463 pwcopy.pw_shell = xstrdup(pw->pw_shell);
466 /* Initialize "log" output. Since we are the client all output actually
467 goes to the terminal. */
468 log_init(av[0], options.log_level, SYSLOG_FACILITY_USER, 0);
470 /* Read per-user configuration file. */
471 snprintf(buf, sizeof buf, "%.100s/%.100s", pw->pw_dir, SSH_USER_CONFFILE);
472 read_config_file(buf, host, &options);
474 /* Read systemwide configuration file. */
475 read_config_file(HOST_CONFIG_FILE, host, &options);
477 /* Fill configuration defaults. */
478 fill_default_options(&options);
481 log_init(av[0], options.log_level, SYSLOG_FACILITY_USER, 0);
483 if (options.user == NULL)
484 options.user = xstrdup(pw->pw_name);
486 if (options.hostname != NULL)
487 host = options.hostname;
489 /* Find canonic host name. */
490 if (strchr(host, '.') == 0)
492 struct hostent *hp = gethostbyname(host);
495 if (strchr(hp->h_name, '.') != 0)
496 host = xstrdup(hp->h_name);
497 else if (hp->h_aliases != 0
498 && hp->h_aliases[0] != 0
499 && strchr(hp->h_aliases[0], '.') != 0)
500 host = xstrdup(hp->h_aliases[0]);
504 /* Disable rhosts authentication if not running as root. */
505 if (original_effective_uid != 0 || !options.use_privileged_port)
507 options.rhosts_authentication = 0;
508 options.rhosts_rsa_authentication = 0;
511 /* If using rsh has been selected, exec it now (without trying anything
512 else). Note that we must release privileges first. */
515 /* Restore our superuser privileges. This must be done before
516 permanently setting the uid. */
519 /* Switch to the original uid permanently. */
520 permanently_set_uid(original_real_uid);
523 rsh_connect(host, options.user, &command);
524 fatal("rsh_connect returned");
527 /* Restore our superuser privileges. */
530 /* Open a connection to the remote host. This needs root privileges if
531 rhosts_{rsa_}authentication is enabled. */
533 ok = ssh_connect(host, &hostaddr, options.port, options.connection_attempts,
534 !options.rhosts_authentication &&
535 !options.rhosts_rsa_authentication,
536 original_real_uid, options.proxy_command);
538 /* If we successfully made the connection, load the host private key in
539 case we will need it later for combined rsa-rhosts authentication.
540 This must be done before releasing extra privileges, because the file
541 is only readable by root. */
544 host_private_key = RSA_new();
545 if (load_private_key(HOST_KEY_FILE, "", host_private_key, NULL))
546 host_private_key_loaded = 1;
549 /* Get rid of any extra privileges that we may have. We will no longer need
550 them. Also, extra privileges could make it very hard to read identity
551 files and other non-world-readable files from the user's home directory
552 if it happens to be on a NFS volume where root is mapped to nobody. */
553 permanently_set_uid(original_real_uid);
555 /* Now that we are back to our own permissions, create ~/.ssh directory
556 if it doesn\'t already exist. */
557 snprintf(buf, sizeof buf, "%.100s/%.100s", pw->pw_dir, SSH_USER_DIR);
558 if (stat(buf, &st) < 0)
559 if (mkdir(buf, 0755) < 0)
560 error("Could not create directory '%.200s'.", buf);
562 /* Check if the connection failed, and try "rsh" if appropriate. */
565 if (options.port != 0)
566 log("Secure connection to %.100s on port %d refused%.100s.",
568 options.fallback_to_rsh ? "; reverting to insecure method" : "");
570 log("Secure connection to %.100s refused%.100s.", host,
571 options.fallback_to_rsh ? "; reverting to insecure method" : "");
573 if (options.fallback_to_rsh)
575 rsh_connect(host, options.user, &command);
576 fatal("rsh_connect returned");
581 /* Expand ~ in options.identity_files. */
582 for (i = 0; i < options.num_identity_files; i++)
583 options.identity_files[i] =
584 tilde_expand_filename(options.identity_files[i], original_real_uid);
586 /* Expand ~ in known host file names. */
587 options.system_hostfile = tilde_expand_filename(options.system_hostfile,
589 options.user_hostfile = tilde_expand_filename(options.user_hostfile,
592 /* Log into the remote system. This never returns if the login fails. */
593 ssh_login(host_private_key_loaded, host_private_key,
594 host, &hostaddr, original_real_uid);
596 /* We no longer need the host private key. Clear it now. */
597 if (host_private_key_loaded)
598 RSA_free(host_private_key); /* Destroys contents safely */
600 /* Close connection cleanly after attack. */
601 cipher_attack_detected = packet_disconnect;
603 /* Enable compression if requested. */
604 if (options.compression)
606 debug("Requesting compression at level %d.", options.compression_level);
608 if (options.compression_level < 1 || options.compression_level > 9)
609 fatal("Compression level must be from 1 (fast) to 9 (slow, best).");
611 /* Send the request. */
612 packet_start(SSH_CMSG_REQUEST_COMPRESSION);
613 packet_put_int(options.compression_level);
616 type = packet_read(&plen);
617 if (type == SSH_SMSG_SUCCESS)
618 packet_start_compression(options.compression_level);
619 else if (type == SSH_SMSG_FAILURE)
620 log("Warning: Remote host refused compression.");
622 packet_disconnect("Protocol error waiting for compression response.");
625 /* Allocate a pseudo tty if appropriate. */
628 debug("Requesting pty.");
630 /* Start the packet. */
631 packet_start(SSH_CMSG_REQUEST_PTY);
633 /* Store TERM in the packet. There is no limit on the length of the
638 packet_put_string(cp, strlen(cp));
640 /* Store window size in the packet. */
641 if (ioctl(fileno(stdin), TIOCGWINSZ, &ws) < 0)
642 memset(&ws, 0, sizeof(ws));
643 packet_put_int(ws.ws_row);
644 packet_put_int(ws.ws_col);
645 packet_put_int(ws.ws_xpixel);
646 packet_put_int(ws.ws_ypixel);
648 /* Store tty modes in the packet. */
649 tty_make_modes(fileno(stdin));
651 /* Send the packet, and wait for it to leave. */
655 /* Read response from the server. */
656 type = packet_read(&plen);
657 if (type == SSH_SMSG_SUCCESS)
659 else if (type == SSH_SMSG_FAILURE)
660 log("Warning: Remote host failed or refused to allocate a pseudo tty.");
662 packet_disconnect("Protocol error waiting for pty request response.");
665 /* Request X11 forwarding if enabled and DISPLAY is set. */
666 if (options.forward_x11 && getenv("DISPLAY") != NULL)
668 char line[512], proto[512], data[512];
670 int forwarded = 0, got_data = 0, i;
673 /* Try to get Xauthority information for the display. */
674 snprintf(line, sizeof line, "%.100s list %.200s 2>/dev/null",
675 XAUTH_PATH, getenv("DISPLAY"));
676 f = popen(line, "r");
677 if (f && fgets(line, sizeof(line), f) &&
678 sscanf(line, "%*s %s %s", proto, data) == 2)
682 #endif /* XAUTH_PATH */
683 /* If we didn't get authentication data, just make up some data. The
684 forwarding code will check the validity of the response anyway, and
685 substitute this data. The X11 server, however, will ignore this
686 fake data and use whatever authentication mechanisms it was using
687 otherwise for the local connection. */
692 strlcpy(proto, "MIT-MAGIC-COOKIE-1", sizeof proto);
693 for (i = 0; i < 16; i++) {
696 snprintf(data + 2 * i, sizeof data - 2 * i, "%02x", rand & 0xff);
701 /* Got local authentication reasonable information. Request forwarding
702 with authentication spoofing. */
703 debug("Requesting X11 forwarding with authentication spoofing.");
704 x11_request_forwarding_with_spoofing(proto, data);
706 /* Read response from the server. */
707 type = packet_read(&plen);
708 if (type == SSH_SMSG_SUCCESS)
713 else if (type == SSH_SMSG_FAILURE)
714 log("Warning: Remote host denied X11 forwarding.");
716 packet_disconnect("Protocol error waiting for X11 forwarding");
719 /* Tell the packet module whether this is an interactive session. */
720 packet_set_interactive(interactive, options.keepalives);
722 /* Clear agent forwarding if we don\'t have an agent. */
723 authfd = ssh_get_authentication_socket();
725 options.forward_agent = 0;
727 ssh_close_authentication_socket(authfd);
729 /* Request authentication agent forwarding if appropriate. */
730 if (options.forward_agent)
732 debug("Requesting authentication agent forwarding.");
733 auth_request_forwarding();
735 /* Read response from the server. */
736 type = packet_read(&plen);
737 packet_integrity_check(plen, 0, type);
738 if (type != SSH_SMSG_SUCCESS)
739 log("Warning: Remote host denied authentication agent forwarding.");
742 /* Initiate local TCP/IP port forwardings. */
743 for (i = 0; i < options.num_local_forwards; i++)
745 debug("Connections to local port %d forwarded to remote address %.200s:%d",
746 options.local_forwards[i].port, options.local_forwards[i].host,
747 options.local_forwards[i].host_port);
748 channel_request_local_forwarding(options.local_forwards[i].port,
749 options.local_forwards[i].host,
750 options.local_forwards[i].host_port);
753 /* Initiate remote TCP/IP port forwardings. */
754 for (i = 0; i < options.num_remote_forwards; i++)
756 debug("Connections to remote port %d forwarded to local address %.200s:%d",
757 options.remote_forwards[i].port, options.remote_forwards[i].host,
758 options.remote_forwards[i].host_port);
759 channel_request_remote_forwarding(options.remote_forwards[i].port,
760 options.remote_forwards[i].host,
761 options.remote_forwards[i].host_port);
764 /* If requested, fork and let ssh continue in the background. */
765 if (fork_after_authentication_flag)
769 fatal("fork failed: %.100s", strerror(errno));
775 /* If a command was specified on the command line, execute the command now.
776 Otherwise request the server to start a shell. */
777 if (buffer_len(&command) > 0)
779 int len = buffer_len(&command);
782 debug("Sending command: %.*s", len, buffer_ptr(&command));
783 packet_start(SSH_CMSG_EXEC_CMD);
784 packet_put_string(buffer_ptr(&command), buffer_len(&command));
790 debug("Requesting shell.");
791 packet_start(SSH_CMSG_EXEC_SHELL);
796 /* Enter the interactive session. */
797 exit_status = client_loop(tty_flag, tty_flag ? options.escape_char : -1);
799 /* Close the connection to the remote host. */
802 /* Exit with the status returned by the program on the remote side. */