This commit was generated by cvs2svn to compensate for changes in r57429,

which included commits to RCS files with non-trunk default branches.

1 files changed, 2541 insertions, 0 deletions

diff --git a/crypto/openssh/sshd.c b/crypto/openssh/sshd.c
new file mode 100644
index 0000000..6cea307
--- /dev/null
+++ b/crypto/openssh/sshd.c
@@ -0,0 +1,2541 @@
+/*
+ * Author: Tatu Ylonen <ylo@cs.hut.fi>
+ * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
+ *                    All rights reserved
+ * Created: Fri Mar 17 17:09:28 1995 ylo
+ * This program is the ssh daemon.  It listens for connections from clients, and
+ * performs authentication, executes use commands or shell, and forwards
+ * information to/from the application to the user client over an encrypted
+ * connection.  This can also handle forwarding of X11, TCP/IP, and authentication
+ * agent connections.
+ */
+
+#include "includes.h"
+RCSID("$OpenBSD: sshd.c,v 1.88 2000/02/15 16:52:57 markus Exp $");
+
+#include "xmalloc.h"
+#include "rsa.h"
+#include "ssh.h"
+#include "pty.h"
+#include "packet.h"
+#include "buffer.h"
+#include "cipher.h"
+#include "mpaux.h"
+#include "servconf.h"
+#include "uidswap.h"
+#include "compat.h"
+
+#ifdef LIBWRAP
+#include <tcpd.h>
+#include <syslog.h>
+int allow_severity = LOG_INFO;
+int deny_severity = LOG_WARNING;
+#endif /* LIBWRAP */
+
+#ifndef O_NOCTTY
+#define O_NOCTTY	0
+#endif
+
+/* Local Xauthority file. */
+static char *xauthfile = NULL;
+
+/* Server configuration options. */
+ServerOptions options;
+
+/* Name of the server configuration file. */
+char *config_file_name = SERVER_CONFIG_FILE;
+
+/* 
+ * Flag indicating whether IPv4 or IPv6.  This can be set on the command line.
+ * Default value is AF_UNSPEC means both IPv4 and IPv6.
+ */
+int IPv4or6 = AF_UNSPEC;
+
+/*
+ * Debug mode flag.  This can be set on the command line.  If debug
+ * mode is enabled, extra debugging output will be sent to the system
+ * log, the daemon will not go to background, and will exit after processing
+ * the first connection.
+ */
+int debug_flag = 0;
+
+/* Flag indicating that the daemon is being started from inetd. */
+int inetd_flag = 0;
+
+/* debug goes to stderr unless inetd_flag is set */
+int log_stderr = 0;
+
+/* argv[0] without path. */
+char *av0;
+
+/* Saved arguments to main(). */
+char **saved_argv;
+
+/*
+ * The sockets that the server is listening; this is used in the SIGHUP
+ * signal handler.
+ */
+#define	MAX_LISTEN_SOCKS	16
+int listen_socks[MAX_LISTEN_SOCKS];
+int num_listen_socks = 0;
+
+/*
+ * the client's version string, passed by sshd2 in compat mode. if != NULL,
+ * sshd will skip the version-number exchange
+ */
+char *client_version_string = NULL;
+
+/* Flags set in auth-rsa from authorized_keys flags.  These are set in auth-rsa.c. */
+int no_port_forwarding_flag = 0;
+int no_agent_forwarding_flag = 0;
+int no_x11_forwarding_flag = 0;
+int no_pty_flag = 0;
+
+/* RSA authentication "command=" option. */
+char *forced_command = NULL;
+
+/* RSA authentication "environment=" options. */
+struct envstring *custom_environment = NULL;
+
+/* Session id for the current session. */
+unsigned char session_id[16];
+
+/*
+ * Any really sensitive data in the application is contained in this
+ * structure. The idea is that this structure could be locked into memory so
+ * that the pages do not get written into swap.  However, there are some
+ * problems. The private key contains BIGNUMs, and we do not (in principle)
+ * have access to the internals of them, and locking just the structure is
+ * not very useful.  Currently, memory locking is not implemented.
+ */
+struct {
+	RSA *private_key;	 /* Private part of server key. */
+	RSA *host_key;		 /* Private part of host key. */
+} sensitive_data;
+
+/*
+ * Flag indicating whether the current session key has been used.  This flag
+ * is set whenever the key is used, and cleared when the key is regenerated.
+ */
+int key_used = 0;
+
+/* This is set to true when SIGHUP is received. */
+int received_sighup = 0;
+
+/* Public side of the server key.  This value is regenerated regularly with
+   the private key. */
+RSA *public_key;
+
+/* Prototypes for various functions defined later in this file. */
+void do_ssh_kex();
+void do_authentication();
+void do_authloop(struct passwd * pw);
+void do_fake_authloop(char *user);
+void do_authenticated(struct passwd * pw);
+void do_exec_pty(const char *command, int ptyfd, int ttyfd,
+	         const char *ttyname, struct passwd * pw, const char *term,
+	         const char *display, const char *auth_proto,
+	         const char *auth_data);
+void do_exec_no_pty(const char *command, struct passwd * pw,
+	            const char *display, const char *auth_proto,
+	            const char *auth_data);
+void do_child(const char *command, struct passwd * pw, const char *term,
+	      const char *display, const char *auth_proto,
+	      const char *auth_data, const char *ttyname);
+
+/*
+ * Remove local Xauthority file.
+ */
+void
+xauthfile_cleanup_proc(void *ignore)
+{
+	debug("xauthfile_cleanup_proc called");
+
+	if (xauthfile != NULL) {
+		char *p;
+		unlink(xauthfile);
+		p = strrchr(xauthfile, '/');
+		if (p != NULL) {
+			*p = '\0';
+			rmdir(xauthfile);
+		}
+		xfree(xauthfile);
+		xauthfile = NULL;
+	}
+}
+
+/*
+ * Close all listening sockets
+ */
+void
+close_listen_socks(void)
+{
+	int i;
+	for (i = 0; i < num_listen_socks; i++)
+		close(listen_socks[i]);
+	num_listen_socks = -1;
+}
+
+/*
+ * Signal handler for SIGHUP.  Sshd execs itself when it receives SIGHUP;
+ * the effect is to reread the configuration file (and to regenerate
+ * the server key).
+ */
+void 
+sighup_handler(int sig)
+{
+	received_sighup = 1;
+	signal(SIGHUP, sighup_handler);
+}
+
+/*
+ * Called from the main program after receiving SIGHUP.
+ * Restarts the server.
+ */
+void 
+sighup_restart()
+{
+	log("Received SIGHUP; restarting.");
+	close_listen_socks();
+	execv(saved_argv[0], saved_argv);
+	log("RESTART FAILED: av0='%s', error: %s.", av0, strerror(errno));
+	exit(1);
+}
+
+/*
+ * Generic signal handler for terminating signals in the master daemon.
+ * These close the listen socket; not closing it seems to cause "Address
+ * already in use" problems on some machines, which is inconvenient.
+ */
+void 
+sigterm_handler(int sig)
+{
+	log("Received signal %d; terminating.", sig);
+	close_listen_socks();
+	exit(255);
+}
+
+/*
+ * SIGCHLD handler.  This is called whenever a child dies.  This will then
+ * reap any zombies left by exited c.
+ */
+void 
+main_sigchld_handler(int sig)
+{
+	int save_errno = errno;
+	int status;
+
+	while (waitpid(-1, &status, WNOHANG) > 0)
+		;
+
+	signal(SIGCHLD, main_sigchld_handler);
+	errno = save_errno;
+}
+
+/*
+ * Signal handler for the alarm after the login grace period has expired.
+ */
+void 
+grace_alarm_handler(int sig)
+{
+	/* Close the connection. */
+	packet_close();
+
+	/* Log error and exit. */
+	fatal("Timeout before authentication for %s.", get_remote_ipaddr());
+}
+
+/*
+ * convert ssh auth msg type into description
+ */
+char *
+get_authname(int type)
+{
+	static char buf[1024];
+	switch (type) {
+	case SSH_CMSG_AUTH_PASSWORD:
+		return "password";
+	case SSH_CMSG_AUTH_RSA:
+		return "rsa";
+	case SSH_CMSG_AUTH_RHOSTS_RSA:
+		return "rhosts-rsa";
+	case SSH_CMSG_AUTH_RHOSTS:
+		return "rhosts";
+#ifdef KRB4
+	case SSH_CMSG_AUTH_KERBEROS:
+		return "kerberos";
+#endif
+#ifdef SKEY
+	case SSH_CMSG_AUTH_TIS_RESPONSE:
+		return "s/key";
+#endif
+	}
+	snprintf(buf, sizeof buf, "bad-auth-msg-%d", type);
+	return buf;
+}
+
+/*
+ * Signal handler for the key regeneration alarm.  Note that this
+ * alarm only occurs in the daemon waiting for connections, and it does not
+ * do anything with the private key or random state before forking.
+ * Thus there should be no concurrency control/asynchronous execution
+ * problems.
+ */
+void 
+key_regeneration_alarm(int sig)
+{
+	int save_errno = errno;
+
+	/* Check if we should generate a new key. */
+	if (key_used) {
+		/* This should really be done in the background. */
+		log("Generating new %d bit RSA key.", options.server_key_bits);
+
+		if (sensitive_data.private_key != NULL)
+			RSA_free(sensitive_data.private_key);
+		sensitive_data.private_key = RSA_new();
+
+		if (public_key != NULL)
+			RSA_free(public_key);
+		public_key = RSA_new();
+
+		rsa_generate_key(sensitive_data.private_key, public_key,
+				 options.server_key_bits);
+		arc4random_stir();
+		key_used = 0;
+		log("RSA key generation complete.");
+	}
+	/* Reschedule the alarm. */
+	signal(SIGALRM, key_regeneration_alarm);
+	alarm(options.key_regeneration_time);
+	errno = save_errno;
+}
+
+/*
+ * Main program for the daemon.
+ */
+int
+main(int ac, char **av)
+{
+	extern char *optarg;
+	extern int optind;
+	int opt, sock_in = 0, sock_out = 0, newsock, i, fdsetsz, pid, on = 1;
+	socklen_t fromlen;
+	int remote_major, remote_minor;
+	int silentrsa = 0;
+	fd_set *fdset;
+	struct sockaddr_storage from;
+	char buf[100];			/* Must not be larger than remote_version. */
+	char remote_version[100];	/* Must be at least as big as buf. */
+	const char *remote_ip;
+	int remote_port;
+	char *comment;
+	FILE *f;
+	struct linger linger;
+	struct addrinfo *ai;
+	char ntop[NI_MAXHOST], strport[NI_MAXSERV];
+	int listen_sock, maxfd;
+
+	/* Save argv[0]. */
+	saved_argv = av;
+	if (strchr(av[0], '/'))
+		av0 = strrchr(av[0], '/') + 1;
+	else
+		av0 = av[0];
+
+	/* Initialize configuration options to their default values. */
+	initialize_server_options(&options);
+
+	/* Parse command-line arguments. */
+	while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:diqQ46")) != EOF) {
+		switch (opt) {
+		case '4':
+			IPv4or6 = AF_INET;
+			break;
+		case '6':
+			IPv4or6 = AF_INET6;
+			break;
+		case 'f':
+			config_file_name = optarg;
+			break;
+		case 'd':
+			debug_flag = 1;
+			options.log_level = SYSLOG_LEVEL_DEBUG;
+			break;
+		case 'i':
+			inetd_flag = 1;
+			break;
+		case 'Q':
+			silentrsa = 1;
+			break;
+		case 'q':
+			options.log_level = SYSLOG_LEVEL_QUIET;
+			break;
+		case 'b':
+			options.server_key_bits = atoi(optarg);
+			break;
+		case 'p':
+			options.ports_from_cmdline = 1;
+			if (options.num_ports >= MAX_PORTS)
+				fatal("too many ports.\n");
+			options.ports[options.num_ports++] = atoi(optarg);
+			break;
+		case 'g':
+			options.login_grace_time = atoi(optarg);
+			break;
+		case 'k':
+			options.key_regeneration_time = atoi(optarg);
+			break;
+		case 'h':
+			options.host_key_file = optarg;
+			break;
+		case 'V':
+			client_version_string = optarg;
+			/* only makes sense with inetd_flag, i.e. no listen() */
+			inetd_flag = 1;
+			break;
+		case '?':
+		default:
+			fprintf(stderr, "sshd version %s\n", SSH_VERSION);
+			fprintf(stderr, "Usage: %s [options]\n", av0);
+			fprintf(stderr, "Options:\n");
+			fprintf(stderr, "  -f file    Configuration file (default %s)\n", SERVER_CONFIG_FILE);
+			fprintf(stderr, "  -d         Debugging mode\n");
+			fprintf(stderr, "  -i         Started from inetd\n");
+			fprintf(stderr, "  -q         Quiet (no logging)\n");
+			fprintf(stderr, "  -p port    Listen on the specified port (default: 22)\n");
+			fprintf(stderr, "  -k seconds Regenerate server key every this many seconds (default: 3600)\n");
+			fprintf(stderr, "  -g seconds Grace period for authentication (default: 300)\n");
+			fprintf(stderr, "  -b bits    Size of server RSA key (default: 768 bits)\n");
+			fprintf(stderr, "  -h file    File from which to read host key (default: %s)\n",
+			    HOST_KEY_FILE);
+			fprintf(stderr, "  -4         Use IPv4 only\n");
+			fprintf(stderr, "  -6         Use IPv6 only\n");
+			exit(1);
+		}
+	}
+
+	/*
+	 * Force logging to stderr until we have loaded the private host
+	 * key (unless started from inetd)
+	 */
+	log_init(av0,
+	    options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
+	    options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility,
+	    !inetd_flag);
+
+	/* check if RSA support exists */
+	if (rsa_alive() == 0) {
+		if (silentrsa == 0)
+			printf("sshd: no RSA support in libssl and libcrypto -- exiting.  See ssl(8)\n");
+		log("no RSA support in libssl and libcrypto -- exiting.  See ssl(8)");
+		exit(1);
+	}
+	/* 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 certain values for sanity. */
+	if (options.server_key_bits < 512 ||
+	    options.server_key_bits > 32768) {
+		fprintf(stderr, "Bad server key size.\n");
+		exit(1);
+	}
+	/* 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);
+
+	sensitive_data.host_key = RSA_new();
+	errno = 0;
+	/* Load the host key.  It must have empty passphrase. */
+	if (!load_private_key(options.host_key_file, "",
+			      sensitive_data.host_key, &comment)) {
+		error("Could not load host key: %.200s: %.100s",
+		      options.host_key_file, strerror(errno));
+		exit(1);
+	}
+	xfree(comment);
+
+	/* Initialize the log (it is reinitialized below in case we
+	   forked). */
+	if (debug_flag && !inetd_flag)
+		log_stderr = 1;
+	log_init(av0, 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) {
+#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("/dev/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(av0, options.log_level, options.log_facility, log_stderr);
+
+	/* 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.host_key->n) - SSH_KEY_BITS_RESERVED &&
+	    options.server_key_bits <
+	BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) {
+		options.server_key_bits =
+			BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED;
+		debug("Forcing server key to %d bits to make it differ from host key.",
+		      options.server_key_bits);
+	}
+	/* Do not display messages to stdout in RSA code. */
+	rsa_set_verbose(0);
+
+	/* Initialize the random number generator. */
+	arc4random_stir();
+
+	/* Chdir to the root directory so that the current disk can be
+	   unmounted if desired. */
+	chdir("/");
+
+	/* Close connection cleanly after attack. */
+	cipher_attack_detected = packet_disconnect;
+
+	/* Start listening for a socket, unless started from inetd. */
+	if (inetd_flag) {
+		int s1, s2;
+		s1 = dup(0);	/* Make sure descriptors 0, 1, and 2 are in use. */
+		s2 = dup(s1);
+		sock_in = dup(0);
+		sock_out = dup(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);
+
+		public_key = RSA_new();
+		sensitive_data.private_key = RSA_new();
+
+		log("Generating %d bit RSA key.", options.server_key_bits);
+		rsa_generate_key(sensitive_data.private_key, public_key,
+				 options.server_key_bits);
+		arc4random_stir();
+		log("RSA key generation complete.");
+	} 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.  We try to make the port
+			 * reusable and have it close as fast as possible
+			 * without waiting in unnecessary wait states on
+			 * close.
+			 */
+			setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
+			    (void *) &on, sizeof(on));
+			linger.l_onoff = 1;
+			linger.l_linger = 5;
+			setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
+			    (void *) &linger, sizeof(linger));
+
+			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 (!debug_flag) {
+			/*
+			 * Record our pid in /etc/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(SSH_DAEMON_PID_FILE, "w");
+			if (f) {
+				fprintf(f, "%u\n", (unsigned int) getpid());
+				fclose(f);
+			}
+		}
+
+		public_key = RSA_new();
+		sensitive_data.private_key = RSA_new();
+
+		log("Generating %d bit RSA key.", options.server_key_bits);
+		rsa_generate_key(sensitive_data.private_key, public_key,
+				 options.server_key_bits);
+		arc4random_stir();
+		log("RSA key generation complete.");
+
+		/* Schedule server key regeneration alarm. */
+		signal(SIGALRM, key_regeneration_alarm);
+		alarm(options.key_regeneration_time);
+
+		/* 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);
+
+		/* setup fd set for listen */
+		maxfd = 0;
+		for (i = 0; i < num_listen_socks; i++)
+			if (listen_socks[i] > maxfd)
+				maxfd = listen_socks[i];
+		fdsetsz = howmany(maxfd, NFDBITS) * sizeof(fd_mask);         
+		fdset = (fd_set *)xmalloc(fdsetsz);                                  
+
+		/*
+		 * Stay listening for connections until the system crashes or
+		 * the daemon is killed with a signal.
+		 */
+		for (;;) {
+			if (received_sighup)
+				sighup_restart();
+			/* Wait in select until there is a connection. */
+			memset(fdset, 0, fdsetsz);
+			for (i = 0; i < num_listen_socks; i++)
+				FD_SET(listen_socks[i], fdset);
+			if (select(maxfd + 1, fdset, NULL, NULL, NULL) < 0) {
+				if (errno != EINTR)
+					error("select: %.100s", strerror(errno));
+				continue;
+			}
+			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));
+				continue;
+			}
+			/*
+			 * 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;
+				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 socket, and start using the
+					 * accepted socket.  Reinitialize logging (since our pid has
+					 * changed).  We break out of the loop to handle the connection.
+					 */
+					close_listen_socks();
+					sock_in = newsock;
+					sock_out = newsock;
+					log_init(av0, 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 %d.", pid);
+
+			/* Mark that the key has been used (it was "given" to the child). */
+			key_used = 1;
+
+			arc4random_stir();
+
+			/* Close the new socket (the child is now taking care of it). */
+			close(newsock);
+			} /* for (i = 0; i < num_listen_socks; i++) */
+			/* child process check (or debug mode) */
+			if (num_listen_socks < 0)
+				break;
+		}
+	}
+
+	/* This is the child processing a new connection. */
+
+	/*
+	 * Disable the key regeneration alarm.  We will not regenerate the
+	 * key since we are no longer in a position to give it to anyone. We
+	 * will not restart on SIGHUP since it no longer makes sense.
+	 */
+	alarm(0);
+	signal(SIGALRM, SIG_DFL);
+	signal(SIGHUP, SIG_DFL);
+	signal(SIGTERM, SIG_DFL);
+	signal(SIGQUIT, SIG_DFL);
+	signal(SIGCHLD, SIG_DFL);
+
+	/*
+	 * Set socket options for the connection.  We want the socket to
+	 * close as fast as possible without waiting for anything.  If the
+	 * connection is not a socket, these will do nothing.
+	 */
+	/* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
+	linger.l_onoff = 1;
+	linger.l_linger = 5;
+	setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
+
+	/*
+	 * Register our connection.  This turns encryption off because we do
+	 * not have a key.
+	 */
+	packet_set_connection(sock_in, sock_out);
+
+	remote_port = get_remote_port();
+	remote_ip = get_remote_ipaddr();
+
+	/* Check whether logins are denied from this host. */
+#ifdef LIBWRAP
+	/* XXX LIBWRAP noes not know about IPv6 */
+	{
+		struct request_info req;
+
+		request_init(&req, RQ_DAEMON, av0, RQ_FILE, sock_in, NULL);
+		fromhost(&req);
+
+		if (!hosts_access(&req)) {
+			close(sock_in);
+			close(sock_out);
+			refuse(&req);
+		}
+/*XXX IPv6 verbose("Connection from %.500s port %d", eval_client(&req), remote_port); */
+	}
+#endif /* LIBWRAP */
+	/* Log the connection. */
+	verbose("Connection from %.500s port %d", remote_ip, remote_port);
+
+	/*
+	 * We don\'t want to listen forever unless the other side
+	 * successfully authenticates itself.  So we set up an alarm which is
+	 * cleared after successful authentication.  A limit of zero
+	 * indicates no limit. Note that we don\'t set the alarm in debugging
+	 * mode; it is just annoying to have the server exit just when you
+	 * are about to discover the bug.
+	 */
+	signal(SIGALRM, grace_alarm_handler);
+	if (!debug_flag)
+		alarm(options.login_grace_time);
+
+	if (client_version_string != NULL) {
+		/* we are exec'ed by sshd2, so skip exchange of protocol version */
+		strlcpy(buf, client_version_string, sizeof(buf));
+	} else {
+		/* Send our protocol version identification. */
+		snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n",
+			 PROTOCOL_MAJOR, PROTOCOL_MINOR, SSH_VERSION);
+		if (atomicio(write, sock_out, buf, strlen(buf)) != strlen(buf)) {
+			log("Could not write ident string to %s.", remote_ip);
+			fatal_cleanup();
+		}
+
+		/* Read other side\'s version identification. */
+		for (i = 0; i < sizeof(buf) - 1; i++) {
+			if (read(sock_in, &buf[i], 1) != 1) {
+				log("Did not receive ident string from %s.", remote_ip);
+				fatal_cleanup();
+			}
+			if (buf[i] == '\r') {
+				buf[i] = '\n';
+				buf[i + 1] = 0;
+				break;
+			}
+			if (buf[i] == '\n') {
+				/* buf[i] == '\n' */
+				buf[i + 1] = 0;
+				break;
+			}
+		}
+		buf[sizeof(buf) - 1] = 0;
+	}
+
+	/*
+	 * Check that the versions match.  In future this might accept
+	 * several versions and set appropriate flags to handle them.
+	 */
+	if (sscanf(buf, "SSH-%d.%d-%[^\n]\n", &remote_major, &remote_minor,
+	    remote_version) != 3) {
+		char *s = "Protocol mismatch.\n";
+
+		(void) atomicio(write, sock_out, s, strlen(s));
+		close(sock_in);
+		close(sock_out);
+		log("Bad protocol version identification '%.100s' from %s",
+		    buf, remote_ip);
+		fatal_cleanup();
+	}
+	debug("Client protocol version %d.%d; client software version %.100s",
+	      remote_major, remote_minor, remote_version);
+	if (remote_major != PROTOCOL_MAJOR) {
+		char *s = "Protocol major versions differ.\n";
+
+		(void) atomicio(write, sock_out, s, strlen(s));
+		close(sock_in);
+		close(sock_out);
+		log("Protocol major versions differ for %s: %d vs. %d",
+		    remote_ip, PROTOCOL_MAJOR, remote_major);
+		fatal_cleanup();
+	}
+	/* Check that the client has sufficiently high software version. */
+	if (remote_major == 1 && remote_minor < 3)
+		packet_disconnect("Your ssh version is too old and is no longer supported.  Please install a newer version.");
+
+	if (remote_major == 1 && remote_minor == 3) {
+		/* note that this disables agent-forwarding */
+		enable_compat13();
+	}
+	/*
+	 * Check that the connection comes from a privileged port.  Rhosts-
+	 * and Rhosts-RSA-Authentication only make sense from priviledged
+	 * programs.  Of course, if the intruder has root access on his local
+	 * machine, he can connect from any port.  So do not use these
+	 * authentication methods from machines that you do not trust.
+	 */
+	if (remote_port >= IPPORT_RESERVED ||
+	    remote_port < IPPORT_RESERVED / 2) {
+		options.rhosts_authentication = 0;
+		options.rhosts_rsa_authentication = 0;
+	}
+#ifdef KRB4
+	if (!packet_connection_is_ipv4() &&
+	    options.kerberos_authentication) {
+		debug("Kerberos Authentication disabled, only available for IPv4.");
+		options.kerberos_authentication = 0;
+	}
+#endif /* KRB4 */
+
+	packet_set_nonblocking();
+
+	/* perform the key exchange */
+	do_ssh_kex();
+
+	/* authenticate user and start session */
+	do_authentication();
+
+#ifdef KRB4
+	/* Cleanup user's ticket cache file. */
+	if (options.kerberos_ticket_cleanup)
+		(void) dest_tkt();
+#endif /* KRB4 */
+
+	/* Cleanup user's local Xauthority file. */
+	if (xauthfile)
+		xauthfile_cleanup_proc(NULL);
+
+	/* The connection has been terminated. */
+	verbose("Closing connection to %.100s", remote_ip);
+	packet_close();
+	exit(0);
+}
+
+/*
+ * SSH1 key exchange
+ */
+void
+do_ssh_kex()
+{
+	int i, len;
+	int plen, slen;
+	BIGNUM *session_key_int;
+	unsigned char session_key[SSH_SESSION_KEY_LENGTH];
+	unsigned char cookie[8];
+	unsigned int cipher_type, auth_mask, protocol_flags;
+	u_int32_t rand = 0;
+
+	/*
+	 * Generate check bytes that the client must send back in the user
+	 * packet in order for it to be accepted; this is used to defy ip
+	 * spoofing attacks.  Note that this only works against somebody
+	 * doing IP spoofing from a remote machine; any machine on the local
+	 * network can still see outgoing packets and catch the random
+	 * cookie.  This only affects rhosts authentication, and this is one
+	 * of the reasons why it is inherently insecure.
+	 */
+	for (i = 0; i < 8; i++) {
+		if (i % 4 == 0)
+			rand = arc4random();
+		cookie[i] = rand & 0xff;
+		rand >>= 8;
+	}
+
+	/*
+	 * Send our public key.  We include in the packet 64 bits of random
+	 * data that must be matched in the reply in order to prevent IP
+	 * spoofing.
+	 */
+	packet_start(SSH_SMSG_PUBLIC_KEY);
+	for (i = 0; i < 8; i++)
+		packet_put_char(cookie[i]);
+
+	/* Store our public server RSA key. */
+	packet_put_int(BN_num_bits(public_key->n));
+	packet_put_bignum(public_key->e);
+	packet_put_bignum(public_key->n);
+
+	/* Store our public host RSA key. */
+	packet_put_int(BN_num_bits(sensitive_data.host_key->n));
+	packet_put_bignum(sensitive_data.host_key->e);
+	packet_put_bignum(sensitive_data.host_key->n);
+
+	/* Put protocol flags. */
+	packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
+
+	/* Declare which ciphers we support. */
+	packet_put_int(cipher_mask());
+
+	/* Declare supported authentication types. */
+	auth_mask = 0;
+	if (options.rhosts_authentication)
+		auth_mask |= 1 << SSH_AUTH_RHOSTS;
+	if (options.rhosts_rsa_authentication)
+		auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
+	if (options.rsa_authentication)
+		auth_mask |= 1 << SSH_AUTH_RSA;
+#ifdef KRB4
+	if (options.kerberos_authentication)
+		auth_mask |= 1 << SSH_AUTH_KERBEROS;
+#endif
+#ifdef AFS
+	if (options.kerberos_tgt_passing)
+		auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
+	if (options.afs_token_passing)
+		auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
+#endif
+#ifdef SKEY
+	if (options.skey_authentication == 1)
+		auth_mask |= 1 << SSH_AUTH_TIS;
+#endif
+	if (options.password_authentication)
+		auth_mask |= 1 << SSH_AUTH_PASSWORD;
+	packet_put_int(auth_mask);
+
+	/* Send the packet and wait for it to be sent. */
+	packet_send();
+	packet_write_wait();
+
+	debug("Sent %d bit public key and %d bit host key.",
+	      BN_num_bits(public_key->n), BN_num_bits(sensitive_data.host_key->n));
+
+	/* Read clients reply (cipher type and session key). */
+	packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
+
+	/* Get cipher type and check whether we accept this. */
+	cipher_type = packet_get_char();
+
+        if (!(cipher_mask() & (1 << cipher_type)))
+		packet_disconnect("Warning: client selects unsupported cipher.");
+
+	/* Get check bytes from the packet.  These must match those we
+	   sent earlier with the public key packet. */
+	for (i = 0; i < 8; i++)
+		if (cookie[i] != packet_get_char())
+			packet_disconnect("IP Spoofing check bytes do not match.");
+
+	debug("Encryption type: %.200s", cipher_name(cipher_type));
+
+	/* Get the encrypted integer. */
+	session_key_int = BN_new();
+	packet_get_bignum(session_key_int, &slen);
+
+	protocol_flags = packet_get_int();
+	packet_set_protocol_flags(protocol_flags);
+
+	packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
+
+	/*
+	 * Decrypt it using our private server key and private host key (key
+	 * with larger modulus first).
+	 */
+	if (BN_cmp(sensitive_data.private_key->n, sensitive_data.host_key->n) > 0) {
+		/* Private key has bigger modulus. */
+		if (BN_num_bits(sensitive_data.private_key->n) <
+		    BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) {
+			fatal("do_connection: %s: private_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
+			      get_remote_ipaddr(),
+			      BN_num_bits(sensitive_data.private_key->n),
+			      BN_num_bits(sensitive_data.host_key->n),
+			      SSH_KEY_BITS_RESERVED);
+		}
+		rsa_private_decrypt(session_key_int, session_key_int,
+				    sensitive_data.private_key);
+		rsa_private_decrypt(session_key_int, session_key_int,
+				    sensitive_data.host_key);
+	} else {
+		/* Host key has bigger modulus (or they are equal). */
+		if (BN_num_bits(sensitive_data.host_key->n) <
+		    BN_num_bits(sensitive_data.private_key->n) + SSH_KEY_BITS_RESERVED) {
+			fatal("do_connection: %s: host_key %d < private_key %d + SSH_KEY_BITS_RESERVED %d",
+			      get_remote_ipaddr(),
+			      BN_num_bits(sensitive_data.host_key->n),
+			      BN_num_bits(sensitive_data.private_key->n),
+			      SSH_KEY_BITS_RESERVED);
+		}
+		rsa_private_decrypt(session_key_int, session_key_int,
+				    sensitive_data.host_key);
+		rsa_private_decrypt(session_key_int, session_key_int,
+				    sensitive_data.private_key);
+	}
+
+	compute_session_id(session_id, cookie,
+			   sensitive_data.host_key->n,
+			   sensitive_data.private_key->n);
+
+	/* Destroy the private and public keys.  They will no longer be needed. */
+	RSA_free(public_key);
+	RSA_free(sensitive_data.private_key);
+	RSA_free(sensitive_data.host_key);
+
+	/*
+	 * Extract session key from the decrypted integer.  The key is in the
+	 * least significant 256 bits of the integer; the first byte of the
+	 * key is in the highest bits.
+	 */
+	BN_mask_bits(session_key_int, sizeof(session_key) * 8);
+	len = BN_num_bytes(session_key_int);
+	if (len < 0 || len > sizeof(session_key))
+		fatal("do_connection: bad len from %s: session_key_int %d > sizeof(session_key) %d",
+		      get_remote_ipaddr(),
+		      len, sizeof(session_key));
+	memset(session_key, 0, sizeof(session_key));
+	BN_bn2bin(session_key_int, session_key + sizeof(session_key) - len);
+
+	/* Destroy the decrypted integer.  It is no longer needed. */
+	BN_clear_free(session_key_int);
+
+	/* Xor the first 16 bytes of the session key with the session id. */
+	for (i = 0; i < 16; i++)
+		session_key[i] ^= session_id[i];
+
+	/* Set the session key.  From this on all communications will be encrypted. */
+	packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
+
+	/* Destroy our copy of the session key.  It is no longer needed. */
+	memset(session_key, 0, sizeof(session_key));
+
+	debug("Received session key; encryption turned on.");
+
+	/* Send an acknowledgement packet.  Note that this packet is sent encrypted. */
+	packet_start(SSH_SMSG_SUCCESS);
+	packet_send();
+	packet_write_wait();
+}
+
+
+/*
+ * Check if the user is allowed to log in via ssh. If user is listed in
+ * DenyUsers or user's primary group is listed in DenyGroups, false will
+ * be returned. If AllowUsers isn't empty and user isn't listed there, or
+ * if AllowGroups isn't empty and user isn't listed there, false will be
+ * returned. 
+ * If the user's shell is not executable, false will be returned.
+ * Otherwise true is returned. 
+ */
+static int
+allowed_user(struct passwd * pw)
+{
+	struct stat st;
+	struct group *grp;
+	int i;
+
+	/* Shouldn't be called if pw is NULL, but better safe than sorry... */
+	if (!pw)
+		return 0;
+
+	/* deny if shell does not exists or is not executable */
+	if (stat(pw->pw_shell, &st) != 0)
+		return 0;
+	if (!((st.st_mode & S_IFREG) && (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP))))
+		return 0;
+
+	/* Return false if user is listed in DenyUsers */
+	if (options.num_deny_users > 0) {
+		if (!pw->pw_name)
+			return 0;
+		for (i = 0; i < options.num_deny_users; i++)
+			if (match_pattern(pw->pw_name, options.deny_users[i]))
+				return 0;
+	}
+	/* Return false if AllowUsers isn't empty and user isn't listed there */
+	if (options.num_allow_users > 0) {
+		if (!pw->pw_name)
+			return 0;
+		for (i = 0; i < options.num_allow_users; i++)
+			if (match_pattern(pw->pw_name, options.allow_users[i]))
+				break;
+		/* i < options.num_allow_users iff we break for loop */
+		if (i >= options.num_allow_users)
+			return 0;
+	}
+	/* Get the primary group name if we need it. Return false if it fails */
+	if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
+		grp = getgrgid(pw->pw_gid);
+		if (!grp)
+			return 0;
+
+		/* Return false if user's group is listed in DenyGroups */
+		if (options.num_deny_groups > 0) {
+			if (!grp->gr_name)
+				return 0;
+			for (i = 0; i < options.num_deny_groups; i++)
+				if (match_pattern(grp->gr_name, options.deny_groups[i]))
+					return 0;
+		}
+		/*
+		 * Return false if AllowGroups isn't empty and user's group
+		 * isn't listed there
+		 */
+		if (options.num_allow_groups > 0) {
+			if (!grp->gr_name)
+				return 0;
+			for (i = 0; i < options.num_allow_groups; i++)
+				if (match_pattern(grp->gr_name, options.allow_groups[i]))
+					break;
+			/* i < options.num_allow_groups iff we break for
+			   loop */
+			if (i >= options.num_allow_groups)
+				return 0;
+		}
+	}
+	/* We found no reason not to let this user try to log on... */
+	return 1;
+}
+
+/*
+ * Performs authentication of an incoming connection.  Session key has already
+ * been exchanged and encryption is enabled.
+ */
+void
+do_authentication()
+{
+	struct passwd *pw, pwcopy;
+	int plen, ulen;
+	char *user;
+
+	/* Get the name of the user that we wish to log in as. */
+	packet_read_expect(&plen, SSH_CMSG_USER);
+
+	/* Get the user name. */
+	user = packet_get_string(&ulen);
+	packet_integrity_check(plen, (4 + ulen), SSH_CMSG_USER);
+
+	setproctitle("%s", user);
+
+#ifdef AFS
+	/* If machine has AFS, set process authentication group. */
+	if (k_hasafs()) {
+		k_setpag();
+		k_unlog();
+	}
+#endif /* AFS */
+
+	/* Verify that the user is a valid user. */
+	pw = getpwnam(user);
+	if (!pw || !allowed_user(pw))
+		do_fake_authloop(user);
+	xfree(user);
+
+	/* Take a copy of the returned structure. */
+	memset(&pwcopy, 0, sizeof(pwcopy));
+	pwcopy.pw_name = xstrdup(pw->pw_name);
+	pwcopy.pw_passwd = xstrdup(pw->pw_passwd);
+	pwcopy.pw_uid = pw->pw_uid;
+	pwcopy.pw_gid = pw->pw_gid;
+	pwcopy.pw_dir = xstrdup(pw->pw_dir);
+	pwcopy.pw_shell = xstrdup(pw->pw_shell);
+	pw = &pwcopy;
+
+	/*
+	 * If we are not running as root, the user must have the same uid as
+	 * the server.
+	 */
+	if (getuid() != 0 && pw->pw_uid != getuid())
+		packet_disconnect("Cannot change user when server not running as root.");
+
+	debug("Attempting authentication for %.100s.", pw->pw_name);
+
+	/* If the user has no password, accept authentication immediately. */
+	if (options.password_authentication &&
+#ifdef KRB4
+	    (!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
+#endif /* KRB4 */
+	    auth_password(pw, "")) {
+		/* Authentication with empty password succeeded. */
+		log("Login for user %s from %.100s, accepted without authentication.",
+		    pw->pw_name, get_remote_ipaddr());
+	} else {
+		/* Loop until the user has been authenticated or the
+		   connection is closed, do_authloop() returns only if
+		   authentication is successfull */
+		do_authloop(pw);
+	}
+
+	/* Check if the user is logging in as root and root logins are disallowed. */
+	if (pw->pw_uid == 0 && !options.permit_root_login) {
+		if (forced_command)
+			log("Root login accepted for forced command.");
+		else
+			packet_disconnect("ROOT LOGIN REFUSED FROM %.200s",
+					  get_canonical_hostname());
+	}
+	/* The user has been authenticated and accepted. */
+	packet_start(SSH_SMSG_SUCCESS);
+	packet_send();
+	packet_write_wait();
+
+	/* Perform session preparation. */
+	do_authenticated(pw);
+}
+
+#define AUTH_FAIL_MAX 6
+#define AUTH_FAIL_LOG (AUTH_FAIL_MAX/2)
+#define AUTH_FAIL_MSG "Too many authentication failures for %.100s"
+
+/*
+ * read packets and try to authenticate local user *pw.
+ * return if authentication is successfull
+ */
+void
+do_authloop(struct passwd * pw)
+{
+	int attempt = 0;
+	unsigned int bits;
+	BIGNUM *client_host_key_e, *client_host_key_n;
+	BIGNUM *n;
+	char *client_user, *password;
+	char user[1024];
+	int plen, dlen, nlen, ulen, elen;
+	int type = 0;
+	void (*authlog) (const char *fmt,...) = verbose;
+
+	/* Indicate that authentication is needed. */
+	packet_start(SSH_SMSG_FAILURE);
+	packet_send();
+	packet_write_wait();
+
+	for (attempt = 1;; attempt++) {
+		int authenticated = 0;
+		strlcpy(user, "", sizeof user);
+
+		/* Get a packet from the client. */
+		type = packet_read(&plen);
+
+		/* Process the packet. */
+		switch (type) {
+#ifdef AFS
+		case SSH_CMSG_HAVE_KERBEROS_TGT:
+			if (!options.kerberos_tgt_passing) {
+				/* packet_get_all(); */
+				verbose("Kerberos tgt passing disabled.");
+				break;
+			} else {
+				/* Accept Kerberos tgt. */
+				char *tgt = packet_get_string(&dlen);
+				packet_integrity_check(plen, 4 + dlen, type);
+				if (!auth_kerberos_tgt(pw, tgt))
+					verbose("Kerberos tgt REFUSED for %s", pw->pw_name);
+				xfree(tgt);
+			}
+			continue;
+
+		case SSH_CMSG_HAVE_AFS_TOKEN:
+			if (!options.afs_token_passing || !k_hasafs()) {
+				/* packet_get_all(); */
+				verbose("AFS token passing disabled.");
+				break;
+			} else {
+				/* Accept AFS token. */
+				char *token_string = packet_get_string(&dlen);
+				packet_integrity_check(plen, 4 + dlen, type);
+				if (!auth_afs_token(pw, token_string))
+					verbose("AFS token REFUSED for %s", pw->pw_name);
+				xfree(token_string);
+			}
+			continue;
+#endif /* AFS */
+#ifdef KRB4
+		case SSH_CMSG_AUTH_KERBEROS:
+			if (!options.kerberos_authentication) {
+				/* packet_get_all(); */
+				verbose("Kerberos authentication disabled.");
+				break;
+			} else {
+				/* Try Kerberos v4 authentication. */
+				KTEXT_ST auth;
+				char *tkt_user = NULL;
+				char *kdata = packet_get_string((unsigned int *) &auth.length);
+				packet_integrity_check(plen, 4 + auth.length, type);
+
+				if (auth.length < MAX_KTXT_LEN)
+					memcpy(auth.dat, kdata, auth.length);
+				xfree(kdata);
+
+				authenticated = auth_krb4(pw->pw_name, &auth, &tkt_user);
+
+				if (authenticated) {
+					snprintf(user, sizeof user, " tktuser %s", tkt_user);
+					xfree(tkt_user);
+				}
+			}
+			break;
+#endif /* KRB4 */
+
+		case SSH_CMSG_AUTH_RHOSTS:
+			if (!options.rhosts_authentication) {
+				verbose("Rhosts authentication disabled.");
+				break;
+			}
+			/*
+			 * Get client user name.  Note that we just have to
+			 * trust the client; this is one reason why rhosts
+			 * authentication is insecure. (Another is
+			 * IP-spoofing on a local network.)
+			 */
+			client_user = packet_get_string(&ulen);
+			packet_integrity_check(plen, 4 + ulen, type);
+
+			/* Try to authenticate using /etc/hosts.equiv and
+			   .rhosts. */
+			authenticated = auth_rhosts(pw, client_user);
+
+			snprintf(user, sizeof user, " ruser %s", client_user);
+			xfree(client_user);
+			break;
+
+		case SSH_CMSG_AUTH_RHOSTS_RSA:
+			if (!options.rhosts_rsa_authentication) {
+				verbose("Rhosts with RSA authentication disabled.");
+				break;
+			}
+			/*
+			 * Get client user name.  Note that we just have to
+			 * trust the client; root on the client machine can
+			 * claim to be any user.
+			 */
+			client_user = packet_get_string(&ulen);
+
+			/* Get the client host key. */
+			client_host_key_e = BN_new();
+			client_host_key_n = BN_new();
+			bits = packet_get_int();
+			packet_get_bignum(client_host_key_e, &elen);
+			packet_get_bignum(client_host_key_n, &nlen);
+
+			if (bits != BN_num_bits(client_host_key_n))
+				error("Warning: keysize mismatch for client_host_key: "
+				      "actual %d, announced %d", BN_num_bits(client_host_key_n), bits);
+			packet_integrity_check(plen, (4 + ulen) + 4 + elen + nlen, type);
+
+			authenticated = auth_rhosts_rsa(pw, client_user,
+				   client_host_key_e, client_host_key_n);
+			BN_clear_free(client_host_key_e);
+			BN_clear_free(client_host_key_n);
+
+			snprintf(user, sizeof user, " ruser %s", client_user);
+			xfree(client_user);
+			break;
+
+		case SSH_CMSG_AUTH_RSA:
+			if (!options.rsa_authentication) {
+				verbose("RSA authentication disabled.");
+				break;
+			}
+			/* RSA authentication requested. */
+			n = BN_new();
+			packet_get_bignum(n, &nlen);
+			packet_integrity_check(plen, nlen, type);
+			authenticated = auth_rsa(pw, n);
+			BN_clear_free(n);
+			break;
+
+		case SSH_CMSG_AUTH_PASSWORD:
+			if (!options.password_authentication) {
+				verbose("Password authentication disabled.");
+				break;
+			}
+			/*
+			 * Read user password.  It is in plain text, but was
+			 * transmitted over the encrypted channel so it is
+			 * not visible to an outside observer.
+			 */
+			password = packet_get_string(&dlen);
+			packet_integrity_check(plen, 4 + dlen, type);
+
+			/* Try authentication with the password. */
+			authenticated = auth_password(pw, password);
+
+			memset(password, 0, strlen(password));
+			xfree(password);
+			break;
+
+#ifdef SKEY
+		case SSH_CMSG_AUTH_TIS:
+			debug("rcvd SSH_CMSG_AUTH_TIS");
+			if (options.skey_authentication == 1) {
+				char *skeyinfo = skey_keyinfo(pw->pw_name);
+				if (skeyinfo == NULL) {
+					debug("generating fake skeyinfo for %.100s.", pw->pw_name);
+					skeyinfo = skey_fake_keyinfo(pw->pw_name);
+				}
+				if (skeyinfo != NULL) {
+					/* we send our s/key- in tis-challenge messages */
+					debug("sending challenge '%s'", skeyinfo);
+					packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
+					packet_put_string(skeyinfo, strlen(skeyinfo));
+					packet_send();
+					packet_write_wait();
+					continue;
+				}
+			}
+			break;
+		case SSH_CMSG_AUTH_TIS_RESPONSE:
+			debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
+			if (options.skey_authentication == 1) {
+				char *response = packet_get_string(&dlen);
+				debug("skey response == '%s'", response);
+				packet_integrity_check(plen, 4 + dlen, type);
+				authenticated = (skey_haskey(pw->pw_name) == 0 &&
+						 skey_passcheck(pw->pw_name, response) != -1);
+				xfree(response);
+			}
+			break;
+#else
+		case SSH_CMSG_AUTH_TIS:
+			/* TIS Authentication is unsupported */
+			log("TIS authentication unsupported.");
+			break;
+#endif
+
+		default:
+			/*
+			 * Any unknown messages will be ignored (and failure
+			 * returned) during authentication.
+			 */
+			log("Unknown message during authentication: type %d", type);
+			break;
+		}
+
+		/* Raise logging level */
+		if (authenticated ||
+		    attempt == AUTH_FAIL_LOG ||
+		    type == SSH_CMSG_AUTH_PASSWORD)
+			authlog = log;
+
+		authlog("%s %s for %.200s from %.200s port %d%s",
+			authenticated ? "Accepted" : "Failed",
+			get_authname(type),
+			pw->pw_uid == 0 ? "ROOT" : pw->pw_name,
+			get_remote_ipaddr(),
+			get_remote_port(),
+			user);
+
+		if (authenticated)
+			return;
+
+		if (attempt > AUTH_FAIL_MAX)
+			packet_disconnect(AUTH_FAIL_MSG, pw->pw_name);
+
+		/* Send a message indicating that the authentication attempt failed. */
+		packet_start(SSH_SMSG_FAILURE);
+		packet_send();
+		packet_write_wait();
+	}
+}
+
+/*
+ * The user does not exist or access is denied,
+ * but fake indication that authentication is needed.
+ */
+void
+do_fake_authloop(char *user)
+{
+	int attempt = 0;
+
+	log("Faking authloop for illegal user %.200s from %.200s port %d",
+	    user,
+	    get_remote_ipaddr(),
+	    get_remote_port());
+
+	/* Indicate that authentication is needed. */
+	packet_start(SSH_SMSG_FAILURE);
+	packet_send();
+	packet_write_wait();
+
+	/*
+	 * Keep reading packets, and always respond with a failure.  This is
+	 * to avoid disclosing whether such a user really exists.
+	 */
+	for (attempt = 1;; attempt++) {
+		/* Read a packet.  This will not return if the client disconnects. */
+		int plen;
+		int type = packet_read(&plen);
+#ifdef SKEY
+		int dlen;
+		char *password, *skeyinfo;
+		/* Try to send a fake s/key challenge. */
+		if (options.skey_authentication == 1 &&
+		    (skeyinfo = skey_fake_keyinfo(user)) != NULL) {
+			password = NULL;
+			if (type == SSH_CMSG_AUTH_TIS) {
+				packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
+				packet_put_string(skeyinfo, strlen(skeyinfo));
+				packet_send();
+				packet_write_wait();
+				continue;
+			} else if (type == SSH_CMSG_AUTH_PASSWORD &&
+			           options.password_authentication &&
+			           (password = packet_get_string(&dlen)) != NULL &&
+			           dlen == 5 &&
+			           strncasecmp(password, "s/key", 5) == 0 ) {
+				packet_send_debug(skeyinfo);
+			}
+			if (password != NULL)
+				xfree(password);
+		}
+#endif
+		if (attempt > AUTH_FAIL_MAX)
+			packet_disconnect(AUTH_FAIL_MSG, user);
+
+		/*
+		 * Send failure.  This should be indistinguishable from a
+		 * failed authentication.
+		 */
+		packet_start(SSH_SMSG_FAILURE);
+		packet_send();
+		packet_write_wait();
+	}
+	/* NOTREACHED */
+	abort();
+}
+
+struct pty_cleanup_context {
+	const char *ttyname;
+	int pid;
+};
+
+/*
+ * Function to perform cleanup if we get aborted abnormally (e.g., due to a
+ * dropped connection).
+ */
+void 
+pty_cleanup_proc(void *context)
+{
+	struct pty_cleanup_context *cu = context;
+
+	debug("pty_cleanup_proc called");
+
+	/* Record that the user has logged out. */
+	record_logout(cu->pid, cu->ttyname);
+
+	/* Release the pseudo-tty. */
+	pty_release(cu->ttyname);
+}
+
+/* simple cleanup: chown tty slave back to root */
+static void
+pty_release_proc(void *tty)
+{
+	char *ttyname = tty;
+	pty_release(ttyname);
+}
+
+/*
+ * Prepares for an interactive session.  This is called after the user has
+ * been successfully authenticated.  During this message exchange, pseudo
+ * terminals are allocated, X11, TCP/IP, and authentication agent forwardings
+ * are requested, etc.
+ */
+void 
+do_authenticated(struct passwd * pw)
+{
+	int type;
+	int compression_level = 0, enable_compression_after_reply = 0;
+	int have_pty = 0, ptyfd = -1, ttyfd = -1;
+	int row, col, xpixel, ypixel, screen;
+	char ttyname[64];
+	char *command, *term = NULL, *display = NULL, *proto = NULL, *data = NULL;
+	int n_bytes;
+
+	/*
+	 * Cancel the alarm we set to limit the time taken for
+	 * authentication.
+	 */
+	alarm(0);
+
+	/*
+	 * Inform the channel mechanism that we are the server side and that
+	 * the client may request to connect to any port at all. (The user
+	 * could do it anyway, and we wouldn\'t know what is permitted except
+	 * by the client telling us, so we can equally well trust the client
+	 * not to request anything bogus.)
+	 */
+	if (!no_port_forwarding_flag)
+		channel_permit_all_opens();
+
+	/*
+	 * We stay in this loop until the client requests to execute a shell
+	 * or a command.
+	 */
+	while (1) {
+		int plen, dlen;
+
+		/* Get a packet from the client. */
+		type = packet_read(&plen);
+
+		/* Process the packet. */
+		switch (type) {
+		case SSH_CMSG_REQUEST_COMPRESSION:
+			packet_integrity_check(plen, 4, type);
+			compression_level = packet_get_int();
+			if (compression_level < 1 || compression_level > 9) {
+				packet_send_debug("Received illegal compression level %d.",
+						  compression_level);
+				goto fail;
+			}
+			/* Enable compression after we have responded with SUCCESS. */
+			enable_compression_after_reply = 1;
+			break;
+
+		case SSH_CMSG_REQUEST_PTY:
+			if (no_pty_flag) {
+				debug("Allocating a pty not permitted for this authentication.");
+				goto fail;
+			}
+			if (have_pty)
+				packet_disconnect("Protocol error: you already have a pty.");
+
+			debug("Allocating pty.");
+
+			/* Allocate a pty and open it. */
+			if (!pty_allocate(&ptyfd, &ttyfd, ttyname,
+			    sizeof(ttyname))) {
+				error("Failed to allocate pty.");
+				goto fail;
+			}
+			fatal_add_cleanup(pty_release_proc, (void *)ttyname);
+			pty_setowner(pw, ttyname);
+
+			/* Get TERM from the packet.  Note that the value may be of arbitrary length. */
+			term = packet_get_string(&dlen);
+			packet_integrity_check(dlen, strlen(term), type);
+
+			/* Remaining bytes */
+			n_bytes = plen - (4 + dlen + 4 * 4);
+
+			if (strcmp(term, "") == 0) {
+				xfree(term);
+				term = NULL;
+			}
+
+			/* Get window size from the packet. */
+			row = packet_get_int();
+			col = packet_get_int();
+			xpixel = packet_get_int();
+			ypixel = packet_get_int();
+			pty_change_window_size(ptyfd, row, col, xpixel, ypixel);
+
+			/* Get tty modes from the packet. */
+			tty_parse_modes(ttyfd, &n_bytes);
+			packet_integrity_check(plen, 4 + dlen + 4 * 4 + n_bytes, type);
+
+			/* Indicate that we now have a pty. */
+			have_pty = 1;
+			break;
+
+		case SSH_CMSG_X11_REQUEST_FORWARDING:
+			if (!options.x11_forwarding) {
+				packet_send_debug("X11 forwarding disabled in server configuration file.");
+				goto fail;
+			}
+#ifdef XAUTH_PATH
+			if (no_x11_forwarding_flag) {
+				packet_send_debug("X11 forwarding not permitted for this authentication.");
+				goto fail;
+			}
+			debug("Received request for X11 forwarding with auth spoofing.");
+			if (display)
+				packet_disconnect("Protocol error: X11 display already set.");
+			{
+				int proto_len, data_len;
+				proto = packet_get_string(&proto_len);
+				data = packet_get_string(&data_len);
+				packet_integrity_check(plen, 4 + proto_len + 4 + data_len + 4, type);
+			}
+			if (packet_get_protocol_flags() & SSH_PROTOFLAG_SCREEN_NUMBER)
+				screen = packet_get_int();
+			else
+				screen = 0;
+			display = x11_create_display_inet(screen, options.x11_display_offset);
+			if (!display)
+				goto fail;
+
+			/* Setup to always have a local .Xauthority. */
+			xauthfile = xmalloc(MAXPATHLEN);
+			strlcpy(xauthfile, "/tmp/ssh-XXXXXXXX", MAXPATHLEN);
+			temporarily_use_uid(pw->pw_uid);
+			if (mkdtemp(xauthfile) == NULL) {
+				restore_uid();
+				error("private X11 dir: mkdtemp %s failed: %s",
+				    xauthfile, strerror(errno));
+				xfree(xauthfile);
+				xauthfile = NULL;
+				goto fail;
+			}
+			restore_uid();
+			strlcat(xauthfile, "/cookies", MAXPATHLEN);
+			fatal_add_cleanup(xauthfile_cleanup_proc, NULL);
+			break;
+#else /* XAUTH_PATH */
+			packet_send_debug("No xauth program; cannot forward with spoofing.");
+			goto fail;
+#endif /* XAUTH_PATH */
+
+		case SSH_CMSG_AGENT_REQUEST_FORWARDING:
+			if (no_agent_forwarding_flag || compat13) {
+				debug("Authentication agent forwarding not permitted for this authentication.");
+				goto fail;
+			}
+			debug("Received authentication agent forwarding request.");
+			auth_input_request_forwarding(pw);
+			break;
+
+		case SSH_CMSG_PORT_FORWARD_REQUEST:
+			if (no_port_forwarding_flag) {
+				debug("Port forwarding not permitted for this authentication.");
+				goto fail;
+			}
+			debug("Received TCP/IP port forwarding request.");
+			channel_input_port_forward_request(pw->pw_uid == 0);
+			break;
+
+		case SSH_CMSG_MAX_PACKET_SIZE:
+			if (packet_set_maxsize(packet_get_int()) < 0)
+				goto fail;
+			break;
+
+		case SSH_CMSG_EXEC_SHELL:
+			/* Set interactive/non-interactive mode. */
+			packet_set_interactive(have_pty || display != NULL,
+					       options.keepalives);
+
+			if (forced_command != NULL)
+				goto do_forced_command;
+			debug("Forking shell.");
+			packet_integrity_check(plen, 0, type);
+			if (have_pty)
+				do_exec_pty(NULL, ptyfd, ttyfd, ttyname, pw, term, display, proto, data);
+			else
+				do_exec_no_pty(NULL, pw, display, proto, data);
+			return;
+
+		case SSH_CMSG_EXEC_CMD:
+			/* Set interactive/non-interactive mode. */
+			packet_set_interactive(have_pty || display != NULL,
+					       options.keepalives);
+
+			if (forced_command != NULL)
+				goto do_forced_command;
+			/* Get command from the packet. */
+			{
+				int dlen;
+				command = packet_get_string(&dlen);
+				debug("Executing command '%.500s'", command);
+				packet_integrity_check(plen, 4 + dlen, type);
+			}
+			if (have_pty)
+				do_exec_pty(command, ptyfd, ttyfd, ttyname, pw, term, display, proto, data);
+			else
+				do_exec_no_pty(command, pw, display, proto, data);
+			xfree(command);
+			return;
+
+		default:
+			/*
+			 * Any unknown messages in this phase are ignored,
+			 * and a failure message is returned.
+			 */
+			log("Unknown packet type received after authentication: %d", type);
+			goto fail;
+		}
+
+		/* The request was successfully processed. */
+		packet_start(SSH_SMSG_SUCCESS);
+		packet_send();
+		packet_write_wait();
+
+		/* Enable compression now that we have replied if appropriate. */
+		if (enable_compression_after_reply) {
+			enable_compression_after_reply = 0;
+			packet_start_compression(compression_level);
+		}
+		continue;
+
+fail:
+		/* The request failed. */
+		packet_start(SSH_SMSG_FAILURE);
+		packet_send();
+		packet_write_wait();
+		continue;
+
+do_forced_command:
+		/*
+		 * There is a forced command specified for this login.
+		 * Execute it.
+		 */
+		debug("Executing forced command: %.900s", forced_command);
+		if (have_pty)
+			do_exec_pty(forced_command, ptyfd, ttyfd, ttyname, pw, term, display, proto, data);
+		else
+			do_exec_no_pty(forced_command, pw, display, proto, data);
+		return;
+	}
+}
+
+/*
+ * This is called to fork and execute a command when we have no tty.  This
+ * will call do_child from the child, and server_loop from the parent after
+ * setting up file descriptors and such.
+ */
+void 
+do_exec_no_pty(const char *command, struct passwd * pw,
+	       const char *display, const char *auth_proto,
+	       const char *auth_data)
+{
+	int pid;
+
+#ifdef USE_PIPES
+	int pin[2], pout[2], perr[2];
+	/* Allocate pipes for communicating with the program. */
+	if (pipe(pin) < 0 || pipe(pout) < 0 || pipe(perr) < 0)
+		packet_disconnect("Could not create pipes: %.100s",
+				  strerror(errno));
+#else /* USE_PIPES */
+	int inout[2], err[2];
+	/* Uses socket pairs to communicate with the program. */
+	if (socketpair(AF_UNIX, SOCK_STREAM, 0, inout) < 0 ||
+	    socketpair(AF_UNIX, SOCK_STREAM, 0, err) < 0)
+		packet_disconnect("Could not create socket pairs: %.100s",
+				  strerror(errno));
+#endif /* USE_PIPES */
+
+	setproctitle("%s@notty", pw->pw_name);
+
+	/* Fork the child. */
+	if ((pid = fork()) == 0) {
+		/* Child.  Reinitialize the log since the pid has changed. */
+		log_init(av0, options.log_level, options.log_facility, log_stderr);
+
+		/*
+		 * Create a new session and process group since the 4.4BSD
+		 * setlogin() affects the entire process group.
+		 */
+		if (setsid() < 0)
+			error("setsid failed: %.100s", strerror(errno));
+
+#ifdef USE_PIPES
+		/*
+		 * Redirect stdin.  We close the parent side of the socket
+		 * pair, and make the child side the standard input.
+		 */
+		close(pin[1]);
+		if (dup2(pin[0], 0) < 0)
+			perror("dup2 stdin");
+		close(pin[0]);
+
+		/* Redirect stdout. */
+		close(pout[0]);
+		if (dup2(pout[1], 1) < 0)
+			perror("dup2 stdout");
+		close(pout[1]);
+
+		/* Redirect stderr. */
+		close(perr[0]);
+		if (dup2(perr[1], 2) < 0)
+			perror("dup2 stderr");
+		close(perr[1]);
+#else /* USE_PIPES */
+		/*
+		 * Redirect stdin, stdout, and stderr.  Stdin and stdout will
+		 * use the same socket, as some programs (particularly rdist)
+		 * seem to depend on it.
+		 */
+		close(inout[1]);
+		close(err[1]);
+		if (dup2(inout[0], 0) < 0)	/* stdin */
+			perror("dup2 stdin");
+		if (dup2(inout[0], 1) < 0)	/* stdout.  Note: same socket as stdin. */
+			perror("dup2 stdout");
+		if (dup2(err[0], 2) < 0)	/* stderr */
+			perror("dup2 stderr");
+#endif /* USE_PIPES */
+
+		/* Do processing for the child (exec command etc). */
+		do_child(command, pw, NULL, display, auth_proto, auth_data, NULL);
+		/* NOTREACHED */
+	}
+	if (pid < 0)
+		packet_disconnect("fork failed: %.100s", strerror(errno));
+#ifdef USE_PIPES
+	/* We are the parent.  Close the child sides of the pipes. */
+	close(pin[0]);
+	close(pout[1]);
+	close(perr[1]);
+
+	/* Enter the interactive session. */
+	server_loop(pid, pin[1], pout[0], perr[0]);
+	/* server_loop has closed pin[1], pout[1], and perr[1]. */
+#else /* USE_PIPES */
+	/* We are the parent.  Close the child sides of the socket pairs. */
+	close(inout[0]);
+	close(err[0]);
+
+	/*
+	 * Enter the interactive session.  Note: server_loop must be able to
+	 * handle the case that fdin and fdout are the same.
+	 */
+	server_loop(pid, inout[1], inout[1], err[1]);
+	/* server_loop has closed inout[1] and err[1]. */
+#endif /* USE_PIPES */
+}
+
+/*
+ * This is called to fork and execute a command when we have a tty.  This
+ * will call do_child from the child, and server_loop from the parent after
+ * setting up file descriptors, controlling tty, updating wtmp, utmp,
+ * lastlog, and other such operations.
+ */
+void 
+do_exec_pty(const char *command, int ptyfd, int ttyfd,
+	    const char *ttyname, struct passwd * pw, const char *term,
+	    const char *display, const char *auth_proto,
+	    const char *auth_data)
+{
+	int pid, fdout;
+	int ptymaster;
+	const char *hostname;
+	time_t last_login_time;
+	char buf[100], *time_string;
+	FILE *f;
+	char line[256];
+	struct stat st;
+	int quiet_login;
+	struct sockaddr_storage from;
+	socklen_t fromlen;
+	struct pty_cleanup_context cleanup_context;
+
+	/* Get remote host name. */
+	hostname = get_canonical_hostname();
+
+	/*
+	 * Get the time when the user last logged in.  Buf will be set to
+	 * contain the hostname the last login was from.
+	 */
+	if (!options.use_login) {
+		last_login_time = get_last_login_time(pw->pw_uid, pw->pw_name,
+						      buf, sizeof(buf));
+	}
+	setproctitle("%s@%s", pw->pw_name, strrchr(ttyname, '/') + 1);
+
+	/* Fork the child. */
+	if ((pid = fork()) == 0) {
+		pid = getpid();
+
+		/* Child.  Reinitialize the log because the pid has
+		   changed. */
+		log_init(av0, options.log_level, options.log_facility, log_stderr);
+
+		/* Close the master side of the pseudo tty. */
+		close(ptyfd);
+
+		/* Make the pseudo tty our controlling tty. */
+		pty_make_controlling_tty(&ttyfd, ttyname);
+
+		/* Redirect stdin from the pseudo tty. */
+		if (dup2(ttyfd, fileno(stdin)) < 0)
+			error("dup2 stdin failed: %.100s", strerror(errno));
+
+		/* Redirect stdout to the pseudo tty. */
+		if (dup2(ttyfd, fileno(stdout)) < 0)
+			error("dup2 stdin failed: %.100s", strerror(errno));
+
+		/* Redirect stderr to the pseudo tty. */
+		if (dup2(ttyfd, fileno(stderr)) < 0)
+			error("dup2 stdin failed: %.100s", strerror(errno));
+
+		/* Close the extra descriptor for the pseudo tty. */
+		close(ttyfd);
+
+		/*
+		 * Get IP address of client.  This is needed because we want
+		 * to record where the user logged in from.  If the
+		 * connection is not a socket, let the ip address be 0.0.0.0.
+		 */
+		memset(&from, 0, sizeof(from));
+		if (packet_get_connection_in() == packet_get_connection_out()) {
+			fromlen = sizeof(from);
+			if (getpeername(packet_get_connection_in(),
+			     (struct sockaddr *) & from, &fromlen) < 0) {
+				debug("getpeername: %.100s", strerror(errno));
+				fatal_cleanup();
+			}
+		}
+		/* Record that there was a login on that terminal. */
+		record_login(pid, ttyname, pw->pw_name, pw->pw_uid, hostname,
+			     (struct sockaddr *)&from);
+
+		/* Check if .hushlogin exists. */
+		snprintf(line, sizeof line, "%.200s/.hushlogin", pw->pw_dir);
+		quiet_login = stat(line, &st) >= 0;
+
+		/*
+		 * If the user has logged in before, display the time of last
+		 * login. However, don't display anything extra if a command
+		 * has been specified (so that ssh can be used to execute
+		 * commands on a remote machine without users knowing they
+		 * are going to another machine). Login(1) will do this for
+		 * us as well, so check if login(1) is used
+		 */
+		if (command == NULL && last_login_time != 0 && !quiet_login &&
+		    !options.use_login) {
+			/* Convert the date to a string. */
+			time_string = ctime(&last_login_time);
+			/* Remove the trailing newline. */
+			if (strchr(time_string, '\n'))
+				*strchr(time_string, '\n') = 0;
+			/* Display the last login time.  Host if displayed
+			   if known. */
+			if (strcmp(buf, "") == 0)
+				printf("Last login: %s\r\n", time_string);
+			else
+				printf("Last login: %s from %s\r\n", time_string, buf);
+		}
+		/*
+		 * Print /etc/motd unless a command was specified or printing
+		 * it was disabled in server options or login(1) will be
+		 * used.  Note that some machines appear to print it in
+		 * /etc/profile or similar.
+		 */
+		if (command == NULL && options.print_motd && !quiet_login &&
+		    !options.use_login) {
+			/* Print /etc/motd if it exists. */
+			f = fopen("/etc/motd", "r");
+			if (f) {
+				while (fgets(line, sizeof(line), f))
+					fputs(line, stdout);
+				fclose(f);
+			}
+		}
+		/* Do common processing for the child, such as execing the command. */
+		do_child(command, pw, term, display, auth_proto, auth_data, ttyname);
+		/* NOTREACHED */
+	}
+	if (pid < 0)
+		packet_disconnect("fork failed: %.100s", strerror(errno));
+	/* Parent.  Close the slave side of the pseudo tty. */
+	close(ttyfd);
+
+	/*
+	 * Add a cleanup function to clear the utmp entry and record logout
+	 * time in case we call fatal() (e.g., the connection gets closed).
+	 */
+	cleanup_context.pid = pid;
+	cleanup_context.ttyname = ttyname;
+	fatal_add_cleanup(pty_cleanup_proc, (void *) &cleanup_context);
+	fatal_remove_cleanup(pty_release_proc, (void *) ttyname);
+
+	/*
+	 * Create another descriptor of the pty master side for use as the
+	 * standard input.  We could use the original descriptor, but this
+	 * simplifies code in server_loop.  The descriptor is bidirectional.
+	 */
+	fdout = dup(ptyfd);
+	if (fdout < 0)
+		packet_disconnect("dup #1 failed: %.100s", strerror(errno));
+
+	/* we keep a reference to the pty master */
+	ptymaster = dup(ptyfd);
+	if (ptymaster < 0)
+		packet_disconnect("dup #2 failed: %.100s", strerror(errno));
+
+	/* Enter interactive session. */
+	server_loop(pid, ptyfd, fdout, -1);
+	/* server_loop _has_ closed ptyfd and fdout. */
+
+	/* Cancel the cleanup function. */
+	fatal_remove_cleanup(pty_cleanup_proc, (void *) &cleanup_context);
+
+	/* Record that the user has logged out. */
+	record_logout(pid, ttyname);
+
+	/* Release the pseudo-tty. */
+	pty_release(ttyname);
+
+	/*
+	 * Close the server side of the socket pairs.  We must do this after
+	 * the pty cleanup, so that another process doesn't get this pty
+	 * while we're still cleaning up.
+	 */
+	if (close(ptymaster) < 0)
+		error("close(ptymaster): %s", strerror(errno));
+}
+
+/*
+ * Sets the value of the given variable in the environment.  If the variable
+ * already exists, its value is overriden.
+ */
+void 
+child_set_env(char ***envp, unsigned int *envsizep, const char *name,
+	      const char *value)
+{
+	unsigned int i, namelen;
+	char **env;
+
+	/*
+	 * Find the slot where the value should be stored.  If the variable
+	 * already exists, we reuse the slot; otherwise we append a new slot
+	 * at the end of the array, expanding if necessary.
+	 */
+	env = *envp;
+	namelen = strlen(name);
+	for (i = 0; env[i]; i++)
+		if (strncmp(env[i], name, namelen) == 0 && env[i][namelen] == '=')
+			break;
+	if (env[i]) {
+		/* Reuse the slot. */
+		xfree(env[i]);
+	} else {
+		/* New variable.  Expand if necessary. */
+		if (i >= (*envsizep) - 1) {
+			(*envsizep) += 50;
+			env = (*envp) = xrealloc(env, (*envsizep) * sizeof(char *));
+		}
+		/* Need to set the NULL pointer at end of array beyond the new slot. */
+		env[i + 1] = NULL;
+	}
+
+	/* Allocate space and format the variable in the appropriate slot. */
+	env[i] = xmalloc(strlen(name) + 1 + strlen(value) + 1);
+	snprintf(env[i], strlen(name) + 1 + strlen(value) + 1, "%s=%s", name, value);
+}
+
+/*
+ * Reads environment variables from the given file and adds/overrides them
+ * into the environment.  If the file does not exist, this does nothing.
+ * Otherwise, it must consist of empty lines, comments (line starts with '#')
+ * and assignments of the form name=value.  No other forms are allowed.
+ */
+void 
+read_environment_file(char ***env, unsigned int *envsize,
+		      const char *filename)
+{
+	FILE *f;
+	char buf[4096];
+	char *cp, *value;
+
+	f = fopen(filename, "r");
+	if (!f)
+		return;
+
+	while (fgets(buf, sizeof(buf), f)) {
+		for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
+			;
+		if (!*cp || *cp == '#' || *cp == '\n')
+			continue;
+		if (strchr(cp, '\n'))
+			*strchr(cp, '\n') = '\0';
+		value = strchr(cp, '=');
+		if (value == NULL) {
+			fprintf(stderr, "Bad line in %.100s: %.200s\n", filename, buf);
+			continue;
+		}
+		/* Replace the equals sign by nul, and advance value to the value string. */
+		*value = '\0';
+		value++;
+		child_set_env(env, envsize, cp, value);
+	}
+	fclose(f);
+}
+
+/*
+ * Performs common processing for the child, such as setting up the
+ * environment, closing extra file descriptors, setting the user and group
+ * ids, and executing the command or shell.
+ */
+void 
+do_child(const char *command, struct passwd * pw, const char *term,
+	 const char *display, const char *auth_proto,
+	 const char *auth_data, const char *ttyname)
+{
+	const char *shell, *cp = NULL;
+	char buf[256];
+	FILE *f;
+	unsigned int envsize, i;
+	char **env;
+	extern char **environ;
+	struct stat st;
+	char *argv[10];
+
+	f = fopen("/etc/nologin", "r");
+	if (f) {
+		/* /etc/nologin exists.  Print its contents and exit. */
+		while (fgets(buf, sizeof(buf), f))
+			fputs(buf, stderr);
+		fclose(f);
+		if (pw->pw_uid != 0)
+			exit(254);
+	}
+	/* Set login name in the kernel. */
+	if (setlogin(pw->pw_name) < 0)
+		error("setlogin failed: %s", strerror(errno));
+
+	/* Set uid, gid, and groups. */
+	/* Login(1) does this as well, and it needs uid 0 for the "-h"
+	   switch, so we let login(1) to this for us. */
+	if (!options.use_login) {
+		if (getuid() == 0 || geteuid() == 0) {
+			if (setgid(pw->pw_gid) < 0) {
+				perror("setgid");
+				exit(1);
+			}
+			/* Initialize the group list. */
+			if (initgroups(pw->pw_name, pw->pw_gid) < 0) {
+				perror("initgroups");
+				exit(1);
+			}
+			endgrent();
+
+			/* Permanently switch to the desired uid. */
+			permanently_set_uid(pw->pw_uid);
+		}
+		if (getuid() != pw->pw_uid || geteuid() != pw->pw_uid)
+			fatal("Failed to set uids to %d.", (int) pw->pw_uid);
+	}
+	/*
+	 * Get the shell from the password data.  An empty shell field is
+	 * legal, and means /bin/sh.
+	 */
+	shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell;
+
+#ifdef AFS
+	/* Try to get AFS tokens for the local cell. */
+	if (k_hasafs()) {
+		char cell[64];
+
+		if (k_afs_cell_of_file(pw->pw_dir, cell, sizeof(cell)) == 0)
+			krb_afslog(cell, 0);
+
+		krb_afslog(0, 0);
+	}
+#endif /* AFS */
+
+	/* Initialize the environment. */
+	envsize = 100;
+	env = xmalloc(envsize * sizeof(char *));
+	env[0] = NULL;
+
+	if (!options.use_login) {
+		/* Set basic environment. */
+		child_set_env(&env, &envsize, "USER", pw->pw_name);
+		child_set_env(&env, &envsize, "LOGNAME", pw->pw_name);
+		child_set_env(&env, &envsize, "HOME", pw->pw_dir);
+		child_set_env(&env, &envsize, "PATH", _PATH_STDPATH);
+
+		snprintf(buf, sizeof buf, "%.200s/%.50s",
+			 _PATH_MAILDIR, pw->pw_name);
+		child_set_env(&env, &envsize, "MAIL", buf);
+
+		/* Normal systems set SHELL by default. */
+		child_set_env(&env, &envsize, "SHELL", shell);
+	}
+	if (getenv("TZ"))
+		child_set_env(&env, &envsize, "TZ", getenv("TZ"));
+
+	/* Set custom environment options from RSA authentication. */
+	while (custom_environment) {
+		struct envstring *ce = custom_environment;
+		char *s = ce->s;
+		int i;
+		for (i = 0; s[i] != '=' && s[i]; i++);
+		if (s[i] == '=') {
+			s[i] = 0;
+			child_set_env(&env, &envsize, s, s + i + 1);
+		}
+		custom_environment = ce->next;
+		xfree(ce->s);
+		xfree(ce);
+	}
+
+	snprintf(buf, sizeof buf, "%.50s %d %d",
+		 get_remote_ipaddr(), get_remote_port(), get_local_port());
+	child_set_env(&env, &envsize, "SSH_CLIENT", buf);
+
+	if (ttyname)
+		child_set_env(&env, &envsize, "SSH_TTY", ttyname);
+	if (term)
+		child_set_env(&env, &envsize, "TERM", term);
+	if (display)
+		child_set_env(&env, &envsize, "DISPLAY", display);
+
+#ifdef KRB4
+	{
+		extern char *ticket;
+
+		if (ticket)
+			child_set_env(&env, &envsize, "KRBTKFILE", ticket);
+	}
+#endif /* KRB4 */
+
+	if (xauthfile)
+		child_set_env(&env, &envsize, "XAUTHORITY", xauthfile);
+	if (auth_get_socket_name() != NULL)
+		child_set_env(&env, &envsize, SSH_AUTHSOCKET_ENV_NAME,
+			      auth_get_socket_name());
+
+	/* read $HOME/.ssh/environment. */
+	if (!options.use_login) {
+		snprintf(buf, sizeof buf, "%.200s/.ssh/environment", pw->pw_dir);
+		read_environment_file(&env, &envsize, buf);
+	}
+	if (debug_flag) {
+		/* dump the environment */
+		fprintf(stderr, "Environment:\n");
+		for (i = 0; env[i]; i++)
+			fprintf(stderr, "  %.200s\n", env[i]);
+	}
+	/*
+	 * Close the connection descriptors; note that this is the child, and
+	 * the server will still have the socket open, and it is important
+	 * that we do not shutdown it.  Note that the descriptors cannot be
+	 * closed before building the environment, as we call
+	 * get_remote_ipaddr there.
+	 */
+	if (packet_get_connection_in() == packet_get_connection_out())
+		close(packet_get_connection_in());
+	else {
+		close(packet_get_connection_in());
+		close(packet_get_connection_out());
+	}
+	/*
+	 * Close all descriptors related to channels.  They will still remain
+	 * open in the parent.
+	 */
+	/* XXX better use close-on-exec? -markus */
+	channel_close_all();
+
+	/*
+	 * Close any extra file descriptors.  Note that there may still be
+	 * descriptors left by system functions.  They will be closed later.
+	 */
+	endpwent();
+
+	/*
+	 * Close any extra open file descriptors so that we don\'t have them
+	 * hanging around in clients.  Note that we want to do this after
+	 * initgroups, because at least on Solaris 2.3 it leaves file
+	 * descriptors open.
+	 */
+	for (i = 3; i < 64; i++)
+		close(i);
+
+	/* Change current directory to the user\'s home directory. */
+	if (chdir(pw->pw_dir) < 0)
+		fprintf(stderr, "Could not chdir to home directory %s: %s\n",
+			pw->pw_dir, strerror(errno));
+
+	/*
+	 * Must take new environment into use so that .ssh/rc, /etc/sshrc and
+	 * xauth are run in the proper environment.
+	 */
+	environ = env;
+
+	/*
+	 * Run $HOME/.ssh/rc, /etc/sshrc, or xauth (whichever is found first
+	 * in this order).
+	 */
+	if (!options.use_login) {
+		if (stat(SSH_USER_RC, &st) >= 0) {
+			if (debug_flag)
+				fprintf(stderr, "Running /bin/sh %s\n", SSH_USER_RC);
+
+			f = popen("/bin/sh " SSH_USER_RC, "w");
+			if (f) {
+				if (auth_proto != NULL && auth_data != NULL)
+					fprintf(f, "%s %s\n", auth_proto, auth_data);
+				pclose(f);
+			} else
+				fprintf(stderr, "Could not run %s\n", SSH_USER_RC);
+		} else if (stat(SSH_SYSTEM_RC, &st) >= 0) {
+			if (debug_flag)
+				fprintf(stderr, "Running /bin/sh %s\n", SSH_SYSTEM_RC);
+
+			f = popen("/bin/sh " SSH_SYSTEM_RC, "w");
+			if (f) {
+				if (auth_proto != NULL && auth_data != NULL)
+					fprintf(f, "%s %s\n", auth_proto, auth_data);
+				pclose(f);
+			} else
+				fprintf(stderr, "Could not run %s\n", SSH_SYSTEM_RC);
+		}
+#ifdef XAUTH_PATH
+		else {
+			/* Add authority data to .Xauthority if appropriate. */
+			if (auth_proto != NULL && auth_data != NULL) {
+				if (debug_flag)
+					fprintf(stderr, "Running %.100s add %.100s %.100s %.100s\n",
+						XAUTH_PATH, display, auth_proto, auth_data);
+
+				f = popen(XAUTH_PATH " -q -", "w");
+				if (f) {
+					fprintf(f, "add %s %s %s\n", display, auth_proto, auth_data);
+					fclose(f);
+				} else
+					fprintf(stderr, "Could not run %s -q -\n", XAUTH_PATH);
+			}
+		}
+#endif /* XAUTH_PATH */
+
+		/* Get the last component of the shell name. */
+		cp = strrchr(shell, '/');
+		if (cp)
+			cp++;
+		else
+			cp = shell;
+	}
+	/*
+	 * If we have no command, execute the shell.  In this case, the shell
+	 * name to be passed in argv[0] is preceded by '-' to indicate that
+	 * this is a login shell.
+	 */
+	if (!command) {
+		if (!options.use_login) {
+			char buf[256];
+
+			/*
+			 * Check for mail if we have a tty and it was enabled
+			 * in server options.
+			 */
+			if (ttyname && options.check_mail) {
+				char *mailbox;
+				struct stat mailstat;
+				mailbox = getenv("MAIL");
+				if (mailbox != NULL) {
+					if (stat(mailbox, &mailstat) != 0 || mailstat.st_size == 0)
+						printf("No mail.\n");
+					else if (mailstat.st_mtime < mailstat.st_atime)
+						printf("You have mail.\n");
+					else
+						printf("You have new mail.\n");
+				}
+			}
+			/* Start the shell.  Set initial character to '-'. */
+			buf[0] = '-';
+			strncpy(buf + 1, cp, sizeof(buf) - 1);
+			buf[sizeof(buf) - 1] = 0;
+
+			/* Execute the shell. */
+			argv[0] = buf;
+			argv[1] = NULL;
+			execve(shell, argv, env);
+
+			/* Executing the shell failed. */
+			perror(shell);
+			exit(1);
+
+		} else {
+			/* Launch login(1). */
+
+			execl("/usr/bin/login", "login", "-h", get_remote_ipaddr(),
+			      "-p", "-f", "--", pw->pw_name, NULL);
+
+			/* Login couldn't be executed, die. */
+
+			perror("login");
+			exit(1);
+		}
+	}
+	/*
+	 * Execute the command using the user's shell.  This uses the -c
+	 * option to execute the command.
+	 */
+	argv[0] = (char *) cp;
+	argv[1] = "-c";
+	argv[2] = (char *) command;
+	argv[3] = NULL;
+	execve(shell, argv, env);
+	perror(shell);
+	exit(1);
+}