sshd.c

C＋＋编写

			break;
		case 't':
			test_flag = 1;
			break;
		case 'u':
			utmp_len = atoi(optarg);
			if (utmp_len > MAXHOSTNAMELEN) {
				fprintf(stderr, "Invalid utmp length.\n");
				exit(1);
			}
			break;
		case 'o':
			if (process_server_config_line(&options, optarg,
			    "command-line", 0) != 0)
				exit(1);
			break;
		case '?':
		default:
			usage();
			break;
		}
	}
	SSLeay_add_all_algorithms();
	channel_set_af(IPv4or6);

	/*
	 * Force logging to stderr until we have loaded the private host
	 * key (unless started from inetd)
	 */
	log_init(__progname,
	    options.log_level == SYSLOG_LEVEL_NOT_SET ?
	    SYSLOG_LEVEL_INFO : options.log_level,
	    options.log_facility == SYSLOG_FACILITY_NOT_SET ?
	    SYSLOG_FACILITY_AUTH : options.log_facility,
	    log_stderr || !inetd_flag);

	/* Read server configuration options from the configuration file. */
	read_server_config(&options, config_file_name);

	/* Fill in default values for those options not explicitly set. */
	fill_default_server_options(&options);

	/* Check that there are no remaining arguments. */
	if (optind < ac) {
		fprintf(stderr, "Extra argument %s.\n", av[optind]);
		exit(1);
	}

	debug("sshd version %.100s", SSH_VERSION);

	/* load private host keys */
	sensitive_data.host_keys = xmalloc(options.num_host_key_files *
	    sizeof(Key *));
	for (i = 0; i < options.num_host_key_files; i++)
		sensitive_data.host_keys[i] = NULL;
	sensitive_data.server_key = NULL;
	sensitive_data.ssh1_host_key = NULL;
	sensitive_data.have_ssh1_key = 0;
	sensitive_data.have_ssh2_key = 0;

	for (i = 0; i < options.num_host_key_files; i++) {
		key = key_load_private(options.host_key_files[i], "", NULL);
		sensitive_data.host_keys[i] = key;
		if (key == NULL) {
			error("Could not load host key: %s",
			    options.host_key_files[i]);
			sensitive_data.host_keys[i] = NULL;
			continue;
		}
		switch (key->type) {
		case KEY_RSA1:
			sensitive_data.ssh1_host_key = key;
			sensitive_data.have_ssh1_key = 1;
			break;
		case KEY_RSA:
		case KEY_DSA:
			sensitive_data.have_ssh2_key = 1;
			break;
		}
		debug("private host key: #%d type %d %s", i, key->type,
		    key_type(key));
	}
	if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
		log("Disabling protocol version 1. Could not load host key");
		options.protocol &= ~SSH_PROTO_1;
	}
	if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
		log("Disabling protocol version 2. Could not load host key");
		options.protocol &= ~SSH_PROTO_2;
	}
	if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
		log("sshd: no hostkeys available -- exiting.");
		exit(1);
	}

	/* Check certain values for sanity. */
	if (options.protocol & SSH_PROTO_1) {
		if (options.server_key_bits < 512 ||
		    options.server_key_bits > 32768) {
			fprintf(stderr, "Bad server key size.\n");
			exit(1);
		}
		/*
		 * Check that server and host key lengths differ sufficiently. This
		 * is necessary to make double encryption work with rsaref. Oh, I
		 * hate software patents. I dont know if this can go? Niels
		 */
		if (options.server_key_bits >
		    BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) -
		    SSH_KEY_BITS_RESERVED && options.server_key_bits <
		    BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
		    SSH_KEY_BITS_RESERVED) {
			options.server_key_bits =
			    BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
			    SSH_KEY_BITS_RESERVED;
			debug("Forcing server key to %d bits to make it differ from host key.",
			    options.server_key_bits);
		}
	}

	if (use_privsep) {
		struct passwd *pw;
		struct stat st;

		if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL)
			fatal("Privilege separation user %s does not exist",
			    SSH_PRIVSEP_USER);
		if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) ||
		    (S_ISDIR(st.st_mode) == 0))
			fatal("Missing privilege separation directory: %s",
			    _PATH_PRIVSEP_CHROOT_DIR);
		if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)
			fatal("%s must be owned by root and not group or "
			    "world-writable.", _PATH_PRIVSEP_CHROOT_DIR);
	}

	/* Configuration looks good, so exit if in test mode. */
	if (test_flag)
		exit(0);

	/* Initialize the log (it is reinitialized below in case we forked). */
	if (debug_flag && !inetd_flag)
		log_stderr = 1;
	log_init(__progname, options.log_level, options.log_facility, log_stderr);

	/*
	 * If not in debugging mode, and not started from inetd, disconnect
	 * from the controlling terminal, and fork.  The original process
	 * exits.
	 */
	if (!(debug_flag || inetd_flag || no_daemon_flag)) {
#ifdef TIOCNOTTY
		int fd;
#endif /* TIOCNOTTY */
		if (daemon(0, 0) < 0)
			fatal("daemon() failed: %.200s", strerror(errno));

		/* Disconnect from the controlling tty. */
#ifdef TIOCNOTTY
		fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
		if (fd >= 0) {
			(void) ioctl(fd, TIOCNOTTY, NULL);
			close(fd);
		}
#endif /* TIOCNOTTY */
	}
	/* Reinitialize the log (because of the fork above). */
	log_init(__progname, options.log_level, options.log_facility, log_stderr);

	/* Initialize the random number generator. */
	arc4random_stir();

	/* Chdir to the root directory so that the current disk can be
	   unmounted if desired. */
	chdir("/");

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

	/* Start listening for a socket, unless started from inetd. */
	if (inetd_flag) {
		int s1;
		s1 = dup(0);	/* Make sure descriptors 0, 1, and 2 are in use. */
		dup(s1);
		sock_in = dup(0);
		sock_out = dup(1);
		startup_pipe = -1;
		/*
		 * We intentionally do not close the descriptors 0, 1, and 2
		 * as our code for setting the descriptors won\'t work if
		 * ttyfd happens to be one of those.
		 */
		debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
		if (options.protocol & SSH_PROTO_1)
			generate_ephemeral_server_key();
	} else {
		for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
			if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
				continue;
			if (num_listen_socks >= MAX_LISTEN_SOCKS)
				fatal("Too many listen sockets. "
				    "Enlarge MAX_LISTEN_SOCKS");
			if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
			    ntop, sizeof(ntop), strport, sizeof(strport),
			    NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
				error("getnameinfo failed");
				continue;
			}
			/* Create socket for listening. */
			listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
			if (listen_sock < 0) {
				/* kernel may not support ipv6 */
				verbose("socket: %.100s", strerror(errno));
				continue;
			}
			if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
				error("listen_sock O_NONBLOCK: %s", strerror(errno));
				close(listen_sock);
				continue;
			}
			/*
			 * Set socket options.
			 * Allow local port reuse in TIME_WAIT.
			 */
			if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
			    &on, sizeof(on)) == -1)
				error("setsockopt SO_REUSEADDR: %s", strerror(errno));

			debug("Bind to port %s on %s.", strport, ntop);

			/* Bind the socket to the desired port. */
			if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
				error("Bind to port %s on %s failed: %.200s.",
				    strport, ntop, strerror(errno));
				close(listen_sock);
				continue;
			}
			listen_socks[num_listen_socks] = listen_sock;
			num_listen_socks++;

			/* Start listening on the port. */
			log("Server listening on %s port %s.", ntop, strport);
			if (listen(listen_sock, 5) < 0)
				fatal("listen: %.100s", strerror(errno));

		}
		freeaddrinfo(options.listen_addrs);

		if (!num_listen_socks)
			fatal("Cannot bind any address.");

		if (options.protocol & SSH_PROTO_1)
			generate_ephemeral_server_key();

		/*
		 * Arrange to restart on SIGHUP.  The handler needs
		 * listen_sock.
		 */
		signal(SIGHUP, sighup_handler);

		signal(SIGTERM, sigterm_handler);
		signal(SIGQUIT, sigterm_handler);

		/* Arrange SIGCHLD to be caught. */
		signal(SIGCHLD, main_sigchld_handler);

		/* Write out the pid file after the sigterm handler is setup */
		if (!debug_flag) {
			/*
			 * Record our pid in /var/run/sshd.pid to make it
			 * easier to kill the correct sshd.  We don't want to
			 * do this before the bind above because the bind will
			 * fail if there already is a daemon, and this will
			 * overwrite any old pid in the file.
			 */
			f = fopen(options.pid_file, "w");
			if (f) {
				fprintf(f, "%ld\n", (long) getpid());
				fclose(f);
			}
		}

		/* setup fd set for listen */
		fdset = NULL;
		maxfd = 0;
		for (i = 0; i < num_listen_socks; i++)
			if (listen_socks[i] > maxfd)
				maxfd = listen_socks[i];
		/* pipes connected to unauthenticated childs */
		startup_pipes = xmalloc(options.max_startups * sizeof(int));
		for (i = 0; i < options.max_startups; i++)
			startup_pipes[i] = -1;

		/*
		 * Stay listening for connections until the system crashes or
		 * the daemon is killed with a signal.
		 */
		for (;;) {
			if (received_sighup)
				sighup_restart();
			if (fdset != NULL)
				xfree(fdset);
			fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask);
			fdset = (fd_set *)xmalloc(fdsetsz);
			memset(fdset, 0, fdsetsz);

			for (i = 0; i < num_listen_socks; i++)
				FD_SET(listen_socks[i], fdset);
			for (i = 0; i < options.max_startups; i++)
				if (startup_pipes[i] != -1)
					FD_SET(startup_pipes[i], fdset);

			/* Wait in select until there is a connection. */
			ret = select(maxfd+1, fdset, NULL, NULL, NULL);
			if (ret < 0 && errno != EINTR)
				error("select: %.100s", strerror(errno));
			if (received_sigterm) {
				log("Received signal %d; terminating.",
				    (int) received_sigterm);
				close_listen_socks();
				unlink(options.pid_file);
				exit(255);
			}
			if (key_used && key_do_regen) {
				generate_ephemeral_server_key();
				key_used = 0;
				key_do_regen = 0;
			}
			if (ret < 0)
				continue;

			for (i = 0; i < options.max_startups; i++)
				if (startup_pipes[i] != -1 &&
				    FD_ISSET(startup_pipes[i], fdset)) {
					/*
					 * the read end of the pipe is ready
					 * if the child has closed the pipe
					 * after successful authentication
					 * or if the child has died
					 */
					close(startup_pipes[i]);
					startup_pipes[i] = -1;
					startups--;
				}
			for (i = 0; i < num_listen_socks; i++) {
				if (!FD_ISSET(listen_socks[i], fdset))
					continue;
				fromlen = sizeof(from);
				newsock = accept(listen_socks[i], (struct sockaddr *)&from,
				    &fromlen);
				if (newsock < 0) {
					if (errno != EINTR && errno != EWOULDBLOCK)
						error("accept: %.100s", strerror(errno));
					continue;
				}
				if (fcntl(newsock, F_SETFL, 0) < 0) {
					error("newsock del O_NONBLOCK: %s", strerror(errno));
					close(newsock);
					continue;
				}
				if (drop_connection(startups) == 1) {
					debug("drop connection #%d", startups);
					close(newsock);
					continue;
				}
				if (pipe(startup_p) == -1) {
					close(newsock);
					continue;
				}

				for (j = 0; j < options.max_startups; j++)
					if (startup_pipes[j] == -1) {
						startup_pipes[j] = startup_p[0];
						if (maxfd < startup_p[0])
							maxfd = startup_p[0];
						startups++;
						break;
					}

				/*
				 * Got connection.  Fork a child to handle it, unless
				 * we are in debugging mode.
				 */
				if (debug_flag) {
					/*
					 * In debugging mode.  Close the listening
					 * socket, and start processing the
					 * connection without forking.
					 */
					debug("Server will not fork when running in debugging mode.");
					close_listen_socks();
					sock_in = newsock;
					sock_out = newsock;
					startup_pipe = -1;
					pid = getpid();
					break;
				} else {
					/*
					 * Normal production daemon.  Fork, and have
					 * the child process the connection. The
					 * parent continues listening.
					 */
					if ((pid = fork()) == 0) {
						/*
						 * Child.  Close the listening and max_startup
						 * sockets.  Start using the accepted socket.
						 * Reinitialize logging (since our pid has
						 * changed).  We break out of the loop to handle
						 * the connection.
						 */
						startup_pipe = startup_p[1];
						close_startup_pipes();
						close_listen_socks();
						sock_in = newsock;
						sock_out = newsock;
						log_init(__progname, options.log_level, options.log_facility, log_stderr);
						break;
					}
				}

				/* Parent.  Stay in the loop. */
				if (pid < 0)
					error("fork: %.100s", strerror(errno));
				else
					debug("Forked child %ld.", (long)pid);

				close(startup_p[1]);

				/* Mark that the key has been used (it was "given" to the child). */
				if ((options.protocol & SSH_PROTO_1) &&
				    key_used == 0) {
					/* Schedule server key regeneration alarm. */
					signal(SIGALRM, key_regeneration_alarm);
					alarm(options.key_regeneration_time);
					key_used = 1;
				}

				arc4random_stir();

				/* Close the new socket (the child is now taking care of it). */
				close(newsock);
			}
			/* child process check (or debug mode) */
			if (num_listen_socks < 0)