ssh.c

C＋＋编写

		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);

	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. */
	if (original_effective_uid != 0 || !options.use_privileged_port) {
		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,
	    original_effective_uid == 0 && options.use_privileged_port,
	    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;
		}
	}
}

static void
ssh_init_forwarding(void)
{
	int success = 0;
	int i;