示例#1
0
/*
 * Main program for the ssh client.
 */
int
main(int ac, char **av)
{
	int i, r, opt, exit_status, use_syslog;
	char *p, *cp, *line, *argv0, buf[MAXPATHLEN], *host_arg;
	char thishost[NI_MAXHOST], shorthost[NI_MAXHOST], portstr[NI_MAXSERV];
	struct stat st;
	struct passwd *pw;
	int dummy, timeout_ms;
	extern int optind, optreset;
	extern char *optarg;

	struct servent *sp;
	Forward fwd;

	/* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
	sanitise_stdfd();

	__progname = ssh_get_progname(av[0]);

#ifndef HAVE_SETPROCTITLE
	/* Prepare for later setproctitle emulation */
	/* Save argv so it isn't clobbered by setproctitle() emulation */
	saved_av = xcalloc(ac + 1, sizeof(*saved_av));
	for (i = 0; i < ac; i++)
		saved_av[i] = xstrdup(av[i]);
	saved_av[i] = NULL;
	compat_init_setproctitle(ac, av);
	av = saved_av;
#endif

	/*
	 * Discard other fds that are hanging around. These can cause problem
	 * with backgrounded ssh processes started by ControlPersist.
	 */
	closefrom(STDERR_FILENO + 1);

	/*
	 * Save the original real uid.  It will be needed later (uid-swapping
	 * may clobber the real uid).
	 */
	original_real_uid = getuid();
	original_effective_uid = geteuid();

	/*
	 * Use uid-swapping to give up root privileges for the duration of
	 * option processing.  We will re-instantiate the rights when we are
	 * ready to create the privileged port, and will permanently drop
	 * them when the port has been created (actually, when the connection
	 * has been made, as we may need to create the port several times).
	 */
	PRIV_END;

#ifdef HAVE_SETRLIMIT
	/* If we are installed setuid root be careful to not drop core. */
	if (original_real_uid != original_effective_uid) {
		struct rlimit rlim;
		rlim.rlim_cur = rlim.rlim_max = 0;
		if (setrlimit(RLIMIT_CORE, &rlim) < 0)
			fatal("setrlimit failed: %.100s", strerror(errno));
	}
#endif
	/* Get user data. */
	pw = getpwuid(original_real_uid);
	if (!pw) {
		logit("You don't exist, go away!");
		exit(255);
	}
	/* Take a copy of the returned structure. */
	pw = pwcopy(pw);

	/*
	 * Set our umask to something reasonable, as some files are created
	 * with the default umask.  This will make them world-readable but
	 * writable only by the owner, which is ok for all files for which we
	 * don't set the modes explicitly.
	 */
	umask(022);

	/*
	 * Initialize option structure to indicate that no values have been
	 * set.
	 */
	initialize_options(&options);

	/* Parse command-line arguments. */
	host = NULL;
	use_syslog = 0;
	argv0 = av[0];

 again:
	while ((opt = getopt(ac, av, "1246ab:c:e:fgi:kl:m:no:p:qstvx"
	    "ACD:F:I:KL:MNO:PR:S:TVw:W:XYy")) != -1) {
		switch (opt) {
		case '1':
			options.protocol = SSH_PROTO_1;
			break;
		case '2':
			options.protocol = SSH_PROTO_2;
			break;
		case '4':
			options.address_family = AF_INET;
			break;
		case '6':
			options.address_family = AF_INET6;
			break;
		case 'n':
			stdin_null_flag = 1;
			break;
		case 'f':
			fork_after_authentication_flag = 1;
			stdin_null_flag = 1;
			break;
		case 'x':
			options.forward_x11 = 0;
			break;
		case 'X':
			options.forward_x11 = 1;
			break;
		case 'y':
			use_syslog = 1;
			break;
		case 'Y':
			options.forward_x11 = 1;
			options.forward_x11_trusted = 1;
			break;
		case 'g':
			options.gateway_ports = 1;
			break;
		case 'O':
			if (stdio_forward_host != NULL)
				fatal("Cannot specify multiplexing "
				    "command with -W");
			else if (muxclient_command != 0)
				fatal("Multiplexing command already specified");
			if (strcmp(optarg, "check") == 0)
				muxclient_command = SSHMUX_COMMAND_ALIVE_CHECK;
			else if (strcmp(optarg, "forward") == 0)
				muxclient_command = SSHMUX_COMMAND_FORWARD;
			else if (strcmp(optarg, "exit") == 0)
				muxclient_command = SSHMUX_COMMAND_TERMINATE;
			else if (strcmp(optarg, "stop") == 0)
				muxclient_command = SSHMUX_COMMAND_STOP;
			else if (strcmp(optarg, "cancel") == 0)
				muxclient_command = SSHMUX_COMMAND_CANCEL_FWD;
			else
				fatal("Invalid multiplex command.");
			break;
		case 'P':	/* deprecated */
			options.use_privileged_port = 0;
			break;
		case 'a':
			options.forward_agent = 0;
			break;
		case 'A':
			options.forward_agent = 1;
			break;
		case 'k':
			options.gss_deleg_creds = 0;
			break;
		case 'K':
			options.gss_authentication = 1;
			options.gss_deleg_creds = 1;
			break;
		case 'i':
			if (stat(optarg, &st) < 0) {
				fprintf(stderr, "Warning: Identity file %s "
				    "not accessible: %s.\n", optarg,
				    strerror(errno));
				break;
			}
			if (options.num_identity_files >=
			    SSH_MAX_IDENTITY_FILES)
				fatal("Too many identity files specified "
				    "(max %d)", SSH_MAX_IDENTITY_FILES);
			options.identity_files[options.num_identity_files++] =
			    xstrdup(optarg);
			break;
		case 'I':
#ifdef ENABLE_PKCS11
			options.pkcs11_provider = xstrdup(optarg);
#else
			fprintf(stderr, "no support for PKCS#11.\n");
#endif
			break;
		case 't':
			if (options.request_tty == REQUEST_TTY_YES)
				options.request_tty = REQUEST_TTY_FORCE;
			else
				options.request_tty = REQUEST_TTY_YES;
			break;
		case 'v':
			if (debug_flag == 0) {
				debug_flag = 1;
				options.log_level = SYSLOG_LEVEL_DEBUG1;
			} else {
				if (options.log_level < SYSLOG_LEVEL_DEBUG3)
					options.log_level++;
				break;
			}
			/* FALLTHROUGH */
		case 'V':
			fprintf(stderr, "%s, %s\n",
			    SSH_RELEASE, SSLeay_version(SSLEAY_VERSION));
			if (opt == 'V')
				exit(0);
			break;
		case 'w':
			if (options.tun_open == -1)
				options.tun_open = SSH_TUNMODE_DEFAULT;
			options.tun_local = a2tun(optarg, &options.tun_remote);
			if (options.tun_local == SSH_TUNID_ERR) {
				fprintf(stderr,
				    "Bad tun device '%s'\n", optarg);
				exit(255);
			}
			break;
		case 'W':
			if (stdio_forward_host != NULL)
				fatal("stdio forward already specified");
			if (muxclient_command != 0)
				fatal("Cannot specify stdio forward with -O");
			if (parse_forward(&fwd, optarg, 1, 0)) {
				stdio_forward_host = fwd.listen_host;
				stdio_forward_port = fwd.listen_port;
				xfree(fwd.connect_host);
			} else {
				fprintf(stderr,
				    "Bad stdio forwarding specification '%s'\n",
				    optarg);
				exit(255);
			}
			options.request_tty = REQUEST_TTY_NO;
			no_shell_flag = 1;
			options.clear_forwardings = 1;
			options.exit_on_forward_failure = 1;
			break;
		case 'q':
			options.log_level = SYSLOG_LEVEL_QUIET;
			break;
		case 'e':
			if (optarg[0] == '^' && optarg[2] == 0 &&
			    (u_char) optarg[1] >= 64 &&
			    (u_char) optarg[1] < 128)
				options.escape_char = (u_char) optarg[1] & 31;
			else if (strlen(optarg) == 1)
				options.escape_char = (u_char) optarg[0];
			else if (strcmp(optarg, "none") == 0)
				options.escape_char = SSH_ESCAPECHAR_NONE;
			else {
				fprintf(stderr, "Bad escape character '%s'.\n",
				    optarg);
				exit(255);
			}
			break;
		case 'c':
			if (ciphers_valid(optarg)) {
				/* SSH2 only */
				options.ciphers = xstrdup(optarg);
				options.cipher = SSH_CIPHER_INVALID;
			} else {
				/* SSH1 only */
				options.cipher = cipher_number(optarg);
				if (options.cipher == -1) {
					fprintf(stderr,
					    "Unknown cipher type '%s'\n",
					    optarg);
					exit(255);
				}
				if (options.cipher == SSH_CIPHER_3DES)
					options.ciphers = "3des-cbc";
				else if (options.cipher == SSH_CIPHER_BLOWFISH)
					options.ciphers = "blowfish-cbc";
				else
					options.ciphers = (char *)-1;
			}
			break;
		case 'm':
			if (mac_valid(optarg))
				options.macs = xstrdup(optarg);
			else {
				fprintf(stderr, "Unknown mac type '%s'\n",
				    optarg);
				exit(255);
			}
			break;
		case 'M':
			if (options.control_master == SSHCTL_MASTER_YES)
				options.control_master = SSHCTL_MASTER_ASK;
			else
				options.control_master = SSHCTL_MASTER_YES;
			break;
		case 'p':
			options.port = a2port(optarg);
			if (options.port <= 0) {
				fprintf(stderr, "Bad port '%s'\n", optarg);
				exit(255);
			}
			break;
		case 'l':
			options.user = optarg;
			break;

		case 'L':
			if (parse_forward(&fwd, optarg, 0, 0))
				add_local_forward(&options, &fwd);
			else {
				fprintf(stderr,
				    "Bad local forwarding specification '%s'\n",
				    optarg);
				exit(255);
			}
			break;

		case 'R':
			if (parse_forward(&fwd, optarg, 0, 1)) {
				add_remote_forward(&options, &fwd);
			} else {
				fprintf(stderr,
				    "Bad remote forwarding specification "
				    "'%s'\n", optarg);
				exit(255);
			}
			break;

		case 'D':
			if (parse_forward(&fwd, optarg, 1, 0)) {
				add_local_forward(&options, &fwd);
			} else {
				fprintf(stderr,
				    "Bad dynamic forwarding specification "
				    "'%s'\n", optarg);
				exit(255);
			}
			break;

		case 'C':
			options.compression = 1;
			break;
		case 'N':
			no_shell_flag = 1;
			options.request_tty = REQUEST_TTY_NO;
			break;
		case 'T':
			options.request_tty = REQUEST_TTY_NO;
			break;
		case 'o':
			dummy = 1;
			line = xstrdup(optarg);
			if (process_config_line(&options, host ? host : "",
			    line, "command-line", 0, &dummy) != 0)
				exit(255);
			xfree(line);
			break;
		case 's':
			subsystem_flag = 1;
			break;
		case 'S':
			if (options.control_path != NULL)
				free(options.control_path);
			options.control_path = xstrdup(optarg);
			break;
		case 'b':
			options.bind_address = optarg;
			break;
		case 'F':
			config = optarg;
			break;
		default:
			usage();
		}
	}

	ac -= optind;
	av += optind;

	if (ac > 0 && !host) {
		if (strrchr(*av, '@')) {
			p = xstrdup(*av);
			cp = strrchr(p, '@');
			if (cp == NULL || cp == p)
				usage();
			options.user = p;
			*cp = '\0';
			host = ++cp;
		} else
			host = *av;
		if (ac > 1) {
			optind = optreset = 1;
			goto again;
		}
		ac--, av++;
	}

	/* Check that we got a host name. */
	if (!host)
		usage();

	OpenSSL_add_all_algorithms();
	ERR_load_crypto_strings();

	/* Initialize the command to execute on remote host. */
	buffer_init(&command);

	if (options.request_tty == REQUEST_TTY_YES ||
	    options.request_tty == REQUEST_TTY_FORCE)
		tty_flag = 1;

	/*
	 * Save the command to execute on the remote host in a buffer. There
	 * is no limit on the length of the command, except by the maximum
	 * packet size.  Also sets the tty flag if there is no command.
	 */
	if (!ac) {
		/* No command specified - execute shell on a tty. */
		tty_flag = options.request_tty != REQUEST_TTY_NO;
		if (subsystem_flag) {
			fprintf(stderr,
			    "You must specify a subsystem to invoke.\n");
			usage();
		}
	} else {
		/* A command has been specified.  Store it into the buffer. */
		for (i = 0; i < ac; i++) {
			if (i)
				buffer_append(&command, " ", 1);
			buffer_append(&command, av[i], strlen(av[i]));
		}
	}

	/* Cannot fork to background if no command. */
	if (fork_after_authentication_flag && buffer_len(&command) == 0 &&
	    !no_shell_flag)
		fatal("Cannot fork into background without a command "
		    "to execute.");

	/* Allocate a tty by default if no command specified. */
	if (buffer_len(&command) == 0)
		tty_flag = options.request_tty != REQUEST_TTY_NO;

	/* Force no tty */
	if (options.request_tty == REQUEST_TTY_NO || muxclient_command != 0)
		tty_flag = 0;
	/* Do not allocate a tty if stdin is not a tty. */
	if ((!isatty(fileno(stdin)) || stdin_null_flag) &&
	    options.request_tty != REQUEST_TTY_FORCE) {
		if (tty_flag)
			logit("Pseudo-terminal will not be allocated because "
			    "stdin is not a terminal.");
		tty_flag = 0;
	}

	/*
	 * Initialize "log" output.  Since we are the client all output
	 * actually goes to stderr.
	 */
	log_init(argv0,
	    options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
	    SYSLOG_FACILITY_USER, !use_syslog);

	/*
	 * Read per-user configuration file.  Ignore the system wide config
	 * file if the user specifies a config file on the command line.
	 */
	if (config != NULL) {
		if (!read_config_file(config, host, &options, 0))
			fatal("Can't open user config file %.100s: "
			    "%.100s", config, strerror(errno));
	} else {
		r = snprintf(buf, sizeof buf, "%s/%s", pw->pw_dir,
		    _PATH_SSH_USER_CONFFILE);
		if (r > 0 && (size_t)r < sizeof(buf))
			(void)read_config_file(buf, host, &options, 1);

		/* Read systemwide configuration file after user config. */
		(void)read_config_file(_PATH_HOST_CONFIG_FILE, host,
		    &options, 0);
	}

	/* Fill configuration defaults. */
	fill_default_options(&options);

	channel_set_af(options.address_family);

	/* reinit */
	log_init(argv0, options.log_level, SYSLOG_FACILITY_USER, !use_syslog);

	seed_rng();

	if (options.user == NULL)
		options.user = xstrdup(pw->pw_name);

	/* Get default port if port has not been set. */
	if (options.port == 0) {
		sp = getservbyname(SSH_SERVICE_NAME, "tcp");
		options.port = sp ? ntohs(sp->s_port) : SSH_DEFAULT_PORT;
	}

	/* preserve host name given on command line for %n expansion */
	host_arg = host;
	if (options.hostname != NULL) {
		host = percent_expand(options.hostname,
		    "h", host, (char *)NULL);
	}

	if (gethostname(thishost, sizeof(thishost)) == -1)
		fatal("gethostname: %s", strerror(errno));
	strlcpy(shorthost, thishost, sizeof(shorthost));
	shorthost[strcspn(thishost, ".")] = '\0';
	snprintf(portstr, sizeof(portstr), "%d", options.port);

	if (options.local_command != NULL) {
		debug3("expanding LocalCommand: %s", options.local_command);
		cp = options.local_command;
		options.local_command = percent_expand(cp, "d", pw->pw_dir,
		    "h", host, "l", thishost, "n", host_arg, "r", options.user,
		    "p", portstr, "u", pw->pw_name, "L", shorthost,
		    (char *)NULL);
		debug3("expanded LocalCommand: %s", options.local_command);
		xfree(cp);
	}

	/* force lowercase for hostkey matching */
	if (options.host_key_alias != NULL) {
		for (p = options.host_key_alias; *p; p++)
			if (isupper(*p))
				*p = (char)tolower(*p);
	}

	if (options.proxy_command != NULL &&
	    strcmp(options.proxy_command, "none") == 0) {
		xfree(options.proxy_command);
		options.proxy_command = NULL;
	}
	if (options.control_path != NULL &&
	    strcmp(options.control_path, "none") == 0) {
		xfree(options.control_path);
		options.control_path = NULL;
	}

	if (options.control_path != NULL) {
		cp = tilde_expand_filename(options.control_path,
		    original_real_uid);
		xfree(options.control_path);
		options.control_path = percent_expand(cp, "h", host,
		    "l", thishost, "n", host_arg, "r", options.user,
		    "p", portstr, "u", pw->pw_name, "L", shorthost,
		    (char *)NULL);
		xfree(cp);
	}
	if (muxclient_command != 0 && options.control_path == NULL)
		fatal("No ControlPath specified for \"-O\" command");
	if (options.control_path != NULL)
		muxclient(options.control_path);

	timeout_ms = options.connection_timeout * 1000;

	/* Open a connection to the remote host. */
	if (ssh_connect(host, &hostaddr, options.port,
	    options.address_family, options.connection_attempts, &timeout_ms,
	    options.tcp_keep_alive, 
#ifdef HAVE_CYGWIN
	    options.use_privileged_port,
#else
	    original_effective_uid == 0 && options.use_privileged_port,
#endif
	    options.proxy_command) != 0)
		exit(255);

	if (timeout_ms > 0)
		debug3("timeout: %d ms remain after connect", timeout_ms);

	/*
	 * If we successfully made the connection, load the host private key
	 * in case we will need it later for combined rsa-rhosts
	 * authentication. This must be done before releasing extra
	 * privileges, because the file is only readable by root.
	 * If we cannot access the private keys, load the public keys
	 * instead and try to execute the ssh-keysign helper instead.
	 */
	sensitive_data.nkeys = 0;
	sensitive_data.keys = NULL;
	sensitive_data.external_keysign = 0;
	if (options.rhosts_rsa_authentication ||
	    options.hostbased_authentication) {
		sensitive_data.nkeys = 7;
		sensitive_data.keys = xcalloc(sensitive_data.nkeys,
		    sizeof(Key));
		for (i = 0; i < sensitive_data.nkeys; i++)
			sensitive_data.keys[i] = NULL;

		PRIV_START;
		sensitive_data.keys[0] = key_load_private_type(KEY_RSA1,
		    _PATH_HOST_KEY_FILE, "", NULL, NULL);
		sensitive_data.keys[1] = key_load_private_cert(KEY_DSA,
		    _PATH_HOST_DSA_KEY_FILE, "", NULL);
#ifdef OPENSSL_HAS_ECC
		sensitive_data.keys[2] = key_load_private_cert(KEY_ECDSA,
		    _PATH_HOST_ECDSA_KEY_FILE, "", NULL);
#endif
		sensitive_data.keys[3] = key_load_private_cert(KEY_RSA,
		    _PATH_HOST_RSA_KEY_FILE, "", NULL);
		sensitive_data.keys[4] = key_load_private_type(KEY_DSA,
		    _PATH_HOST_DSA_KEY_FILE, "", NULL, NULL);
#ifdef OPENSSL_HAS_ECC
		sensitive_data.keys[5] = key_load_private_type(KEY_ECDSA,
		    _PATH_HOST_ECDSA_KEY_FILE, "", NULL, NULL);
#endif
		sensitive_data.keys[6] = key_load_private_type(KEY_RSA,
		    _PATH_HOST_RSA_KEY_FILE, "", NULL, NULL);
		PRIV_END;

		if (options.hostbased_authentication == 1 &&
		    sensitive_data.keys[0] == NULL &&
		    sensitive_data.keys[4] == NULL &&
		    sensitive_data.keys[5] == NULL &&
		    sensitive_data.keys[6] == NULL) {
			sensitive_data.keys[1] = key_load_cert(
			    _PATH_HOST_DSA_KEY_FILE);
#ifdef OPENSSL_HAS_ECC
			sensitive_data.keys[2] = key_load_cert(
			    _PATH_HOST_ECDSA_KEY_FILE);
#endif
			sensitive_data.keys[3] = key_load_cert(
			    _PATH_HOST_RSA_KEY_FILE);
			sensitive_data.keys[4] = key_load_public(
			    _PATH_HOST_DSA_KEY_FILE, NULL);
#ifdef OPENSSL_HAS_ECC
			sensitive_data.keys[5] = key_load_public(
			    _PATH_HOST_ECDSA_KEY_FILE, NULL);
#endif
			sensitive_data.keys[6] = key_load_public(
			    _PATH_HOST_RSA_KEY_FILE, NULL);
			sensitive_data.external_keysign = 1;
		}
	}
	/*
	 * Get rid of any extra privileges that we may have.  We will no
	 * longer need them.  Also, extra privileges could make it very hard
	 * to read identity files and other non-world-readable files from the
	 * user's home directory if it happens to be on a NFS volume where
	 * root is mapped to nobody.
	 */
	if (original_effective_uid == 0) {
		PRIV_START;
		permanently_set_uid(pw);
	}

	/*
	 * Now that we are back to our own permissions, create ~/.ssh
	 * directory if it doesn't already exist.
	 */
	if (config == NULL) {
		r = snprintf(buf, sizeof buf, "%s%s%s", pw->pw_dir,
		    strcmp(pw->pw_dir, "/") ? "/" : "", _PATH_SSH_USER_DIR);
		if (r > 0 && (size_t)r < sizeof(buf) && stat(buf, &st) < 0) {
#ifdef WITH_SELINUX
			ssh_selinux_setfscreatecon(buf);
#endif
			if (mkdir(buf, 0700) < 0)
				error("Could not create directory '%.200s'.",
				    buf);
#ifdef WITH_SELINUX
			ssh_selinux_setfscreatecon(NULL);
#endif
		}
	}
	/* load options.identity_files */
	load_public_identity_files();

	/* Expand ~ in known host file names. */
	tilde_expand_paths(options.system_hostfiles,
	    options.num_system_hostfiles);
	tilde_expand_paths(options.user_hostfiles, options.num_user_hostfiles);

	signal(SIGPIPE, SIG_IGN); /* ignore SIGPIPE early */
	signal(SIGCHLD, main_sigchld_handler);

	/* Log into the remote system.  Never returns if the login fails. */
	ssh_login(&sensitive_data, host, (struct sockaddr *)&hostaddr,
	    options.port, pw, timeout_ms);

	if (packet_connection_is_on_socket()) {
		verbose("Authenticated to %s ([%s]:%d).", host,
		    get_remote_ipaddr(), get_remote_port());
	} else {
		verbose("Authenticated to %s (via proxy).", host);
	}

	/* We no longer need the private host keys.  Clear them now. */
	if (sensitive_data.nkeys != 0) {
		for (i = 0; i < sensitive_data.nkeys; i++) {
			if (sensitive_data.keys[i] != NULL) {
				/* Destroys contents safely */
				debug3("clear hostkey %d", i);
				key_free(sensitive_data.keys[i]);
				sensitive_data.keys[i] = NULL;
			}
		}
		xfree(sensitive_data.keys);
	}
	for (i = 0; i < options.num_identity_files; i++) {
		if (options.identity_files[i]) {
			xfree(options.identity_files[i]);
			options.identity_files[i] = NULL;
		}
		if (options.identity_keys[i]) {
			key_free(options.identity_keys[i]);
			options.identity_keys[i] = NULL;
		}
	}

	exit_status = compat20 ? ssh_session2() : ssh_session();
	packet_close();

	if (options.control_path != NULL && muxserver_sock != -1)
		unlink(options.control_path);

	/* Kill ProxyCommand if it is running. */
	ssh_kill_proxy_command();

	return exit_status;
}
示例#2
0
/*
 * Main program for the ssh client.
 */
int
main(int ac, char **av)
{
	int i, opt, exit_status;
	u_short fwd_port, fwd_host_port;
	char sfwd_port[6], sfwd_host_port[6];
	char *p, *cp, buf[256];
	struct stat st;
	struct passwd *pw;
	int dummy;
	extern int optind, optreset;
	extern char *optarg;

	__progname = get_progname(av[0]);
	init_rng();

	/*
	 * Save the original real uid.  It will be needed later (uid-swapping
	 * may clobber the real uid).
	 */
	original_real_uid = getuid();
	original_effective_uid = geteuid();
 
	/*
	 * Use uid-swapping to give up root privileges for the duration of
	 * option processing.  We will re-instantiate the rights when we are
	 * ready to create the privileged port, and will permanently drop
	 * them when the port has been created (actually, when the connection
	 * has been made, as we may need to create the port several times).
	 */
	PRIV_END;

#ifdef HAVE_SETRLIMIT
	/* If we are installed setuid root be careful to not drop core. */
	if (original_real_uid != original_effective_uid) {
		struct rlimit rlim;
		rlim.rlim_cur = rlim.rlim_max = 0;
		if (setrlimit(RLIMIT_CORE, &rlim) < 0)
			fatal("setrlimit failed: %.100s", strerror(errno));
	}
#endif
	/* Get user data. */
	pw = getpwuid(original_real_uid);
	if (!pw) {
		log("You don't exist, go away!");
		exit(1);
	}
	/* Take a copy of the returned structure. */
	pw = pwcopy(pw);

	/*
	 * Set our umask to something reasonable, as some files are created
	 * with the default umask.  This will make them world-readable but
	 * writable only by the owner, which is ok for all files for which we
	 * don't set the modes explicitly.
	 */
	umask(022);

	/* Initialize option structure to indicate that no values have been set. */
	initialize_options(&options);

	/* Parse command-line arguments. */
	host = NULL;

again:
	while ((opt = getopt(ac, av,
	    "1246ab:c:e:fgi:kl:m:no:p:qstvxACD:F:I:L:NPR:TVX")) != -1) {
		switch (opt) {
		case '1':
			options.protocol = SSH_PROTO_1;
			break;
		case '2':
			options.protocol = SSH_PROTO_2;
			break;
		case '4':
			IPv4or6 = AF_INET;
			break;
		case '6':
			IPv4or6 = AF_INET6;
			break;
		case 'n':
			stdin_null_flag = 1;
			break;
		case 'f':
			fork_after_authentication_flag = 1;
			stdin_null_flag = 1;
			break;
		case 'x':
			options.forward_x11 = 0;
			break;
		case 'X':
			options.forward_x11 = 1;
			break;
		case 'g':
			options.gateway_ports = 1;
			break;
		case 'P':	/* deprecated */
			options.use_privileged_port = 0;
			break;
		case 'a':
			options.forward_agent = 0;
			break;
		case 'A':
			options.forward_agent = 1;
			break;
#ifdef AFS
		case 'k':
			options.kerberos_tgt_passing = 0;
			options.afs_token_passing = 0;
			break;
#endif
		case 'i':
			if (stat(optarg, &st) < 0) {
				fprintf(stderr, "Warning: Identity file %s "
				    "does not exist.\n", optarg);
				break;
			}
			if (options.num_identity_files >=
			    SSH_MAX_IDENTITY_FILES)
				fatal("Too many identity files specified "
				    "(max %d)", SSH_MAX_IDENTITY_FILES);
			options.identity_files[options.num_identity_files++] =
			    xstrdup(optarg);
			break;
		case 'I':
#ifdef SMARTCARD
			options.smartcard_device = xstrdup(optarg);
#else
			fprintf(stderr, "no support for smartcards.\n");
#endif
			break;
		case 't':
			if (tty_flag)
				force_tty_flag = 1;
			tty_flag = 1;
			break;
		case 'v':
			if (0 == debug_flag) {
				debug_flag = 1;
				options.log_level = SYSLOG_LEVEL_DEBUG1;
			} else if (options.log_level < SYSLOG_LEVEL_DEBUG3) {
				options.log_level++;
				break;
			} else
				fatal("Too high debugging level.");
			/* fallthrough */
		case 'V':
			fprintf(stderr,
			    "%s, SSH protocols %d.%d/%d.%d, OpenSSL 0x%8.8lx\n",
			    SSH_VERSION,
			    PROTOCOL_MAJOR_1, PROTOCOL_MINOR_1,
			    PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2,
			    SSLeay());
			if (opt == 'V')
				exit(0);
			break;
		case 'q':
			options.log_level = SYSLOG_LEVEL_QUIET;
			break;
		case 'e':
			if (optarg[0] == '^' && optarg[2] == 0 &&
			    (u_char) optarg[1] >= 64 &&
			    (u_char) optarg[1] < 128)
				options.escape_char = (u_char) optarg[1] & 31;
			else if (strlen(optarg) == 1)
				options.escape_char = (u_char) optarg[0];
			else if (strcmp(optarg, "none") == 0)
				options.escape_char = SSH_ESCAPECHAR_NONE;
			else {
				fprintf(stderr, "Bad escape character '%s'.\n",
				    optarg);
				exit(1);
			}
			break;
		case 'c':
			if (ciphers_valid(optarg)) {
				/* SSH2 only */
				options.ciphers = xstrdup(optarg);
				options.cipher = SSH_CIPHER_ILLEGAL;
			} else {
				/* SSH1 only */
				options.cipher = cipher_number(optarg);
				if (options.cipher == -1) {
					fprintf(stderr,
					    "Unknown cipher type '%s'\n",
					    optarg);
					exit(1);
				}
				if (options.cipher == SSH_CIPHER_3DES)
					options.ciphers = "3des-cbc";
				else if (options.cipher == SSH_CIPHER_BLOWFISH)
					options.ciphers = "blowfish-cbc";
				else
					options.ciphers = (char *)-1;
			}
			break;
		case 'm':
			if (mac_valid(optarg))
				options.macs = xstrdup(optarg);
			else {
				fprintf(stderr, "Unknown mac type '%s'\n",
				    optarg);
				exit(1);
			}
			break;
		case 'p':
			options.port = a2port(optarg);
			if (options.port == 0) {
				fprintf(stderr, "Bad port '%s'\n", optarg);
				exit(1);
			}
			break;
		case 'l':
			options.user = optarg;
			break;

		case 'L':
		case 'R':
			if (sscanf(optarg, "%5[0-9]:%255[^:]:%5[0-9]",
			    sfwd_port, buf, sfwd_host_port) != 3 &&
			    sscanf(optarg, "%5[0-9]/%255[^/]/%5[0-9]",
			    sfwd_port, buf, sfwd_host_port) != 3) {
				fprintf(stderr,
				    "Bad forwarding specification '%s'\n",
				    optarg);
				usage();
				/* NOTREACHED */
			}
			if ((fwd_port = a2port(sfwd_port)) == 0 ||
			    (fwd_host_port = a2port(sfwd_host_port)) == 0) {
				fprintf(stderr,
				    "Bad forwarding port(s) '%s'\n", optarg);
				exit(1);
			}
			if (opt == 'L')
				add_local_forward(&options, fwd_port, buf,
				    fwd_host_port);
			else if (opt == 'R')
				add_remote_forward(&options, fwd_port, buf,
				    fwd_host_port);
			break;

		case 'D':
			fwd_port = a2port(optarg);
			if (fwd_port == 0) {
				fprintf(stderr, "Bad dynamic port '%s'\n",
				    optarg);
				exit(1);
			}
			add_local_forward(&options, fwd_port, "socks4", 0);
			break;

		case 'C':
			options.compression = 1;
			break;
		case 'N':
			no_shell_flag = 1;
			no_tty_flag = 1;
			break;
		case 'T':
			no_tty_flag = 1;
			break;
		case 'o':
			dummy = 1;
			if (process_config_line(&options, host ? host : "",
			    optarg, "command-line", 0, &dummy) != 0)
				exit(1);
			break;
		case 's':
			subsystem_flag = 1;
			break;
		case 'b':
			options.bind_address = optarg;
			break;
		case 'F':
			config = optarg;
			break;
		default:
			usage();
		}
	}

	ac -= optind;
	av += optind;

	if (ac > 0 && !host && **av != '-') {
		if (strrchr(*av, '@')) {
			p = xstrdup(*av);
			cp = strrchr(p, '@');
			if (cp == NULL || cp == p)
				usage();
			options.user = p;
			*cp = '\0';
			host = ++cp;
		} else
			host = *av;
		if (ac > 1) {
			optind = optreset = 1;
			goto again;
		}
		ac--, av++;
	}

	/* Check that we got a host name. */
	if (!host)
		usage();

	SSLeay_add_all_algorithms();
	ERR_load_crypto_strings();
	channel_set_af(IPv4or6);

	/* Initialize the command to execute on remote host. */
	buffer_init(&command);

	/*
	 * Save the command to execute on the remote host in a buffer. There
	 * is no limit on the length of the command, except by the maximum
	 * packet size.  Also sets the tty flag if there is no command.
	 */
	if (!ac) {
		/* No command specified - execute shell on a tty. */
		tty_flag = 1;
		if (subsystem_flag) {
			fprintf(stderr,
			    "You must specify a subsystem to invoke.\n");
			usage();
		}
	} else {
		/* A command has been specified.  Store it into the buffer. */
		for (i = 0; i < ac; i++) {
			if (i)
				buffer_append(&command, " ", 1);
			buffer_append(&command, av[i], strlen(av[i]));
		}
	}

	/* Cannot fork to background if no command. */
	if (fork_after_authentication_flag && buffer_len(&command) == 0 && !no_shell_flag)
		fatal("Cannot fork into background without a command to execute.");

	/* Allocate a tty by default if no command specified. */
	if (buffer_len(&command) == 0)
		tty_flag = 1;

	/* Force no tty */
	if (no_tty_flag)
		tty_flag = 0;
	/* Do not allocate a tty if stdin is not a tty. */
	if (!isatty(fileno(stdin)) && !force_tty_flag) {
		if (tty_flag)
			log("Pseudo-terminal will not be allocated because stdin is not a terminal.");
		tty_flag = 0;
	}

	/*
	 * Initialize "log" output.  Since we are the client all output
	 * actually goes to stderr.
	 */
	log_init(av[0], options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
	    SYSLOG_FACILITY_USER, 1);

	/*
	 * Read per-user configuration file.  Ignore the system wide config
	 * file if the user specifies a config file on the command line.
	 */
	if (config != NULL) {
		if (!read_config_file(config, host, &options))
			fatal("Can't open user config file %.100s: "
			    "%.100s", config, strerror(errno));
	} else  {
		snprintf(buf, sizeof buf, "%.100s/%.100s", pw->pw_dir,
		    _PATH_SSH_USER_CONFFILE);
		(void)read_config_file(buf, host, &options);

		/* Read systemwide configuration file after use config. */
		(void)read_config_file(_PATH_HOST_CONFIG_FILE, host, &options);
	}

	/* Fill configuration defaults. */
	fill_default_options(&options);

	/* reinit */
	log_init(av[0], options.log_level, SYSLOG_FACILITY_USER, 1);

	seed_rng();

	if (options.user == NULL)
		options.user = xstrdup(pw->pw_name);

	if (options.hostname != NULL)
		host = options.hostname;

	if (options.proxy_command != NULL &&
	    strcmp(options.proxy_command, "none") == 0)
		options.proxy_command = NULL;

	/* Disable rhosts authentication if not running as root. */
#ifdef HAVE_CYGWIN
	/* Ignore uid if running under Windows */
	if (!options.use_privileged_port) {
#else
	if (original_effective_uid != 0 || !options.use_privileged_port) {
#endif
		debug("Rhosts Authentication disabled, "
		    "originating port will not be trusted.");
		options.rhosts_authentication = 0;
	}
	/* Open a connection to the remote host. */

	if (ssh_connect(host, &hostaddr, options.port, IPv4or6,
	    options.connection_attempts,
#ifdef HAVE_CYGWIN
	    options.use_privileged_port,
#else
	    original_effective_uid == 0 && options.use_privileged_port,
#endif
	    options.proxy_command) != 0)
		exit(1);

	/*
	 * If we successfully made the connection, load the host private key
	 * in case we will need it later for combined rsa-rhosts
	 * authentication. This must be done before releasing extra
	 * privileges, because the file is only readable by root.
	 * If we cannot access the private keys, load the public keys
	 * instead and try to execute the ssh-keysign helper instead.
	 */
	sensitive_data.nkeys = 0;
	sensitive_data.keys = NULL;
	sensitive_data.external_keysign = 0;
	if (options.rhosts_rsa_authentication ||
	    options.hostbased_authentication) {
		sensitive_data.nkeys = 3;
		sensitive_data.keys = xmalloc(sensitive_data.nkeys *
		    sizeof(Key));

		PRIV_START;
		sensitive_data.keys[0] = key_load_private_type(KEY_RSA1,
		    _PATH_HOST_KEY_FILE, "", NULL);
		sensitive_data.keys[1] = key_load_private_type(KEY_DSA,
		    _PATH_HOST_DSA_KEY_FILE, "", NULL);
		sensitive_data.keys[2] = key_load_private_type(KEY_RSA,
		    _PATH_HOST_RSA_KEY_FILE, "", NULL);
		PRIV_END;

		if (options.hostbased_authentication == 1 &&
		    sensitive_data.keys[0] == NULL &&
		    sensitive_data.keys[1] == NULL &&
		    sensitive_data.keys[2] == NULL) {
			sensitive_data.keys[1] = key_load_public(
			    _PATH_HOST_DSA_KEY_FILE, NULL);
			sensitive_data.keys[2] = key_load_public(
			    _PATH_HOST_RSA_KEY_FILE, NULL);
			sensitive_data.external_keysign = 1;
		}
	}
	/*
	 * Get rid of any extra privileges that we may have.  We will no
	 * longer need them.  Also, extra privileges could make it very hard
	 * to read identity files and other non-world-readable files from the
	 * user's home directory if it happens to be on a NFS volume where
	 * root is mapped to nobody.
	 */
	seteuid(original_real_uid);
	setuid(original_real_uid);

	/*
	 * Now that we are back to our own permissions, create ~/.ssh
	 * directory if it doesn\'t already exist.
	 */
	snprintf(buf, sizeof buf, "%.100s%s%.100s", pw->pw_dir, strcmp(pw->pw_dir, "/") ? "/" : "", _PATH_SSH_USER_DIR);
	if (stat(buf, &st) < 0)
		if (mkdir(buf, 0700) < 0)
			error("Could not create directory '%.200s'.", buf);

	/* load options.identity_files */
	load_public_identity_files();

	/* Expand ~ in known host file names. */
	/* XXX mem-leaks: */
	options.system_hostfile =
	    tilde_expand_filename(options.system_hostfile, original_real_uid);
	options.user_hostfile =
	    tilde_expand_filename(options.user_hostfile, original_real_uid);
	options.system_hostfile2 =
	    tilde_expand_filename(options.system_hostfile2, original_real_uid);
	options.user_hostfile2 =
	    tilde_expand_filename(options.user_hostfile2, original_real_uid);

	signal(SIGPIPE, SIG_IGN); /* ignore SIGPIPE early */

	/* Log into the remote system.  This never returns if the login fails. */
	ssh_login(&sensitive_data, host, (struct sockaddr *)&hostaddr, pw);

	/* We no longer need the private host keys.  Clear them now. */
	if (sensitive_data.nkeys != 0) {
		for (i = 0; i < sensitive_data.nkeys; i++) {
			if (sensitive_data.keys[i] != NULL) {
				/* Destroys contents safely */
				debug3("clear hostkey %d", i);
				key_free(sensitive_data.keys[i]);
				sensitive_data.keys[i] = NULL;
			}
		}
		xfree(sensitive_data.keys);
	}
	for (i = 0; i < options.num_identity_files; i++) {
		if (options.identity_files[i]) {
			xfree(options.identity_files[i]);
			options.identity_files[i] = NULL;
		}
		if (options.identity_keys[i]) {
			key_free(options.identity_keys[i]);
			options.identity_keys[i] = NULL;
		}
	}

	exit_status = compat20 ? ssh_session2() : ssh_session();
	packet_close();

	/*
	 * Send SIGHUP to proxy command if used. We don't wait() in 
	 * case it hangs and instead rely on init to reap the child
	 */
	if (proxy_command_pid > 1)
		kill(proxy_command_pid, SIGHUP);

	return exit_status;
}

static void
x11_get_proto(char **_proto, char **_data)
{
	char line[512];
	static char proto[512], data[512];
	FILE *f;
	int got_data = 0, i;
	char *display;
	struct stat st;

	*_proto = proto;
	*_data = data;
	proto[0] = data[0] = '\0';
	if (!options.xauth_location ||
	    (stat(options.xauth_location, &st) == -1)) {
		debug("No xauth program.");
	} else {
		if ((display = getenv("DISPLAY")) == NULL) {
			debug("x11_get_proto: DISPLAY not set");
			return;
		}
		/* Try to get Xauthority information for the display. */
		if (strncmp(display, "localhost:", 10) == 0)
			/*
			 * Handle FamilyLocal case where $DISPLAY does
			 * not match an authorization entry.  For this we
			 * just try "xauth list unix:displaynum.screennum".
			 * XXX: "localhost" match to determine FamilyLocal
			 *      is not perfect.
			 */
			snprintf(line, sizeof line, "%s list unix:%s 2>"
			    _PATH_DEVNULL, options.xauth_location, display+10);
		else
			snprintf(line, sizeof line, "%s list %.200s 2>"
			    _PATH_DEVNULL, options.xauth_location, display);
		debug2("x11_get_proto: %s", line);
		f = popen(line, "r");
		if (f && fgets(line, sizeof(line), f) &&
		    sscanf(line, "%*s %511s %511s", proto, data) == 2)
			got_data = 1;
		if (f)
			pclose(f);
	}
	/*
	 * If we didn't get authentication data, just make up some
	 * data.  The forwarding code will check the validity of the
	 * response anyway, and substitute this data.  The X11
	 * server, however, will ignore this fake data and use
	 * whatever authentication mechanisms it was using otherwise
	 * for the local connection.
	 */
	if (!got_data) {
		u_int32_t rand = 0;

		log("Warning: No xauth data; using fake authentication data for X11 forwarding.");
		strlcpy(proto, "MIT-MAGIC-COOKIE-1", sizeof proto);
		for (i = 0; i < 16; i++) {
			if (i % 4 == 0)
				rand = arc4random();
			snprintf(data + 2 * i, sizeof data - 2 * i, "%02x", rand & 0xff);
			rand >>= 8;
		}
	}