text: /* $OpenBSD: session.c,v 1.315 2019/02/22 03:37:11 djm Exp $ */
  /*
   * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   *                    All rights reserved
   *
   * 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 support by Markus Friedl.
   * Copyright (c) 2000, 2001 Markus Friedl.  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.
   */
  
  #include "includes.h"
  
  #include <sys/types.h>
  #include <sys/param.h>
  #ifdef HAVE_SYS_STAT_H
  # include <sys/stat.h>
  #endif
  #include <sys/socket.h>
  #include <sys/un.h>
  #include <sys/wait.h>
  
  #include <arpa/inet.h>
  
  #include <ctype.h>
  #include <errno.h>
  #include <fcntl.h>
  #include <grp.h>
  #include <netdb.h>
  #ifdef HAVE_PATHS_H
  #include <paths.h>
  #endif
  #include <pwd.h>
  #include <signal.h>
  #include <stdarg.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <unistd.h>
  #include <limits.h>
  
  #include "openbsd-compat/sys-queue.h"
  #include "xmalloc.h"
  #include "ssh.h"
  #include "ssh2.h"
  #include "sshpty.h"
  #include "packet.h"
  #include "sshbuf.h"
  #include "ssherr.h"
  #include "match.h"
  #include "uidswap.h"
  #include "compat.h"
  #include "channels.h"
  #include "sshkey.h"
  #include "cipher.h"
  #ifdef GSSAPI
  #include "ssh-gss.h"
  #endif
  #include "hostfile.h"
  #include "auth.h"
  #include "auth-options.h"
  #include "authfd.h"
  #include "pathnames.h"
  #include "log.h"
  #include "misc.h"
  #include "servconf.h"
  #include "sshlogin.h"
  #include "serverloop.h"
  #include "canohost.h"
  #include "session.h"
  #include "kex.h"
  #include "monitor_wrap.h"
  #include "sftp.h"
  #include "atomicio.h"
  
  #if defined(KRB5) && defined(USE_AFS)
  #include <kafs.h>
  #endif
  
  #ifdef WITH_SELINUX
  #include <selinux/selinux.h>
  #endif
  
  #define IS_INTERNAL_SFTP(c) \
  	(!strncmp(c, INTERNAL_SFTP_NAME, sizeof(INTERNAL_SFTP_NAME) - 1) && \
  	 (c[sizeof(INTERNAL_SFTP_NAME) - 1] == '\0' || \
  	  c[sizeof(INTERNAL_SFTP_NAME) - 1] == ' ' || \
  	  c[sizeof(INTERNAL_SFTP_NAME) - 1] == '\t'))
  
  /* func */
  
  Session *session_new(void);
  void	session_set_fds(struct ssh *, Session *, int, int, int, int, int);
  void	session_pty_cleanup(Session *);
  void	session_proctitle(Session *);
  int	session_setup_x11fwd(struct ssh *, Session *);
  int	do_exec_pty(struct ssh *, Session *, const char *);
  int	do_exec_no_pty(struct ssh *, Session *, const char *);
  int	do_exec(struct ssh *, Session *, const char *);
  void	do_login(struct ssh *, Session *, const char *);
  void	do_child(struct ssh *, Session *, const char *);
  void	do_motd(void);
  int	check_quietlogin(Session *, const char *);
  
  static void do_authenticated2(struct ssh *, Authctxt *);
  
  static int session_pty_req(struct ssh *, Session *);
  
  /* import */
  extern ServerOptions options;
  extern char *__progname;
  extern int debug_flag;
  extern u_int utmp_len;
  extern int startup_pipe;
  extern void destroy_sensitive_data(void);
  extern struct sshbuf *loginmsg;
  extern struct sshauthopt *auth_opts;
  extern char *tun_fwd_ifnames; /* serverloop.c */
  
  /* original command from peer. */
  const char *original_command = NULL;
  
  /* data */
  static int sessions_first_unused = -1;
  static int sessions_nalloc = 0;
  static Session *sessions = NULL;
  
  #define SUBSYSTEM_NONE			0
  #define SUBSYSTEM_EXT			1
  #define SUBSYSTEM_INT_SFTP		2
  #define SUBSYSTEM_INT_SFTP_ERROR	3
  
  #ifdef HAVE_LOGIN_CAP
  login_cap_t *lc;
  #endif
  
  static int is_child = 0;
  static int in_chroot = 0;
  
  /* File containing userauth info, if ExposeAuthInfo set */
  static char *auth_info_file = NULL;
  
  /* Name and directory of socket for authentication agent forwarding. */
  static char *auth_sock_name = NULL;
  static char *auth_sock_dir = NULL;
  
  /* removes the agent forwarding socket */
  
  static void
  auth_sock_cleanup_proc(struct passwd *pw)
  {
  	if (auth_sock_name != NULL) {
  		temporarily_use_uid(pw);
  		unlink(auth_sock_name);
  		rmdir(auth_sock_dir);
  		auth_sock_name = NULL;
  		restore_uid();
  	}
  }
  
  static int
  auth_input_request_forwarding(struct ssh *ssh, struct passwd * pw)
  {
  	Channel *nc;
  	int sock = -1;
  
  	if (auth_sock_name != NULL) {
  		error("authentication forwarding requested twice.");
  		return 0;
  	}
  
  	/* Temporarily drop privileged uid for mkdir/bind. */
  	temporarily_use_uid(pw);
  
  	/* Allocate a buffer for the socket name, and format the name. */
  	auth_sock_dir = xstrdup("/tmp/ssh-XXXXXXXXXX");
  
  	/* Create private directory for socket */
  	if (mkdtemp(auth_sock_dir) == NULL) {
  		ssh_packet_send_debug(ssh, "Agent forwarding disabled: "
  		    "mkdtemp() failed: %.100s", strerror(errno));
  		restore_uid();
  		free(auth_sock_dir);
  		auth_sock_dir = NULL;
  		goto authsock_err;
  	}
  
  	xasprintf(&auth_sock_name, "%s/agent.%ld",
  	    auth_sock_dir, (long) getpid());
  
  	/* Start a Unix listener on auth_sock_name. */
  	sock = unix_listener(auth_sock_name, SSH_LISTEN_BACKLOG, 0);
  
  	/* Restore the privileged uid. */
  	restore_uid();
  
  	/* Check for socket/bind/listen failure. */
  	if (sock < 0)
  		goto authsock_err;
  
  	/* Allocate a channel for the authentication agent socket. */
  	nc = channel_new(ssh, "auth socket",
  	    SSH_CHANNEL_AUTH_SOCKET, sock, sock, -1,
  	    CHAN_X11_WINDOW_DEFAULT, CHAN_X11_PACKET_DEFAULT,
  	    0, "auth socket", 1);
  	nc->path = xstrdup(auth_sock_name);
  	return 1;
  
   authsock_err:
  	free(auth_sock_name);
  	if (auth_sock_dir != NULL) {
  		temporarily_use_uid(pw);
  		rmdir(auth_sock_dir);
  		restore_uid();
  		free(auth_sock_dir);
  	}
  	if (sock != -1)
  		close(sock);
  	auth_sock_name = NULL;
  	auth_sock_dir = NULL;
  	return 0;
  }
  
  static void
  display_loginmsg(void)
  {
  	int r;
  
  	if (sshbuf_len(loginmsg) == 0)
  		return;
  	if ((r = sshbuf_put_u8(loginmsg, 0)) != 0)
  		fatal("%s: buffer error: %s", __func__, ssh_err(r));
  	printf("%s", (char *)sshbuf_ptr(loginmsg));
  	sshbuf_reset(loginmsg);
  }
  
  static void
  prepare_auth_info_file(struct passwd *pw, struct sshbuf *info)
  {
  	int fd = -1, success = 0;
  
  	if (!options.expose_userauth_info || info == NULL)
  		return;
  
  	temporarily_use_uid(pw);
  	auth_info_file = xstrdup("/tmp/sshauth.XXXXXXXXXXXXXXX");
  	if ((fd = mkstemp(auth_info_file)) == -1) {
  		error("%s: mkstemp: %s", __func__, strerror(errno));
  		goto out;
  	}
  	if (atomicio(vwrite, fd, sshbuf_mutable_ptr(info),
  	    sshbuf_len(info)) != sshbuf_len(info)) {
  		error("%s: write: %s", __func__, strerror(errno));
  		goto out;
  	}
  	if (close(fd) != 0) {
  		error("%s: close: %s", __func__, strerror(errno));
  		goto out;
  	}
  	success = 1;
   out:
  	if (!success) {
  		if (fd != -1)
  			close(fd);
  		free(auth_info_file);
  		auth_info_file = NULL;
  	}
  	restore_uid();
  }
  
  static void
  set_fwdpermit_from_authopts(struct ssh *ssh, const struct sshauthopt *opts)
  {
  	char *tmp, *cp, *host;
  	int port;
  	size_t i;
  
  	if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0) {
  		channel_clear_permission(ssh, FORWARD_USER, FORWARD_LOCAL);
  		for (i = 0; i < auth_opts->npermitopen; i++) {
  			tmp = cp = xstrdup(auth_opts->permitopen[i]);
  			/* This shouldn't fail as it has already been checked */
  			if ((host = hpdelim(&cp)) == NULL)
  				fatal("%s: internal error: hpdelim", __func__);
  			host = cleanhostname(host);
  			if (cp == NULL || (port = permitopen_port(cp)) < 0)
  				fatal("%s: internal error: permitopen port",
  				    __func__);
  			channel_add_permission(ssh,
  			    FORWARD_USER, FORWARD_LOCAL, host, port);
  			free(tmp);
  		}
  	}
  	if ((options.allow_tcp_forwarding & FORWARD_REMOTE) != 0) {
  		channel_clear_permission(ssh, FORWARD_USER, FORWARD_REMOTE);
  		for (i = 0; i < auth_opts->npermitlisten; i++) {
  			tmp = cp = xstrdup(auth_opts->permitlisten[i]);
  			/* This shouldn't fail as it has already been checked */
  			if ((host = hpdelim(&cp)) == NULL)
  				fatal("%s: internal error: hpdelim", __func__);
  			host = cleanhostname(host);
  			if (cp == NULL || (port = permitopen_port(cp)) < 0)
  				fatal("%s: internal error: permitlisten port",
  				    __func__);
  			channel_add_permission(ssh,
  			    FORWARD_USER, FORWARD_REMOTE, host, port);
  			free(tmp);
  		}
  	}
  }
  
  void
  do_authenticated(struct ssh *ssh, Authctxt *authctxt)
  {
  	setproctitle("%s", authctxt->pw->pw_name);
  
  	auth_log_authopts("active", auth_opts, 0);
  
  	/* setup the channel layer */
  	/* XXX - streamlocal? */
  	set_fwdpermit_from_authopts(ssh, auth_opts);
  
  	if (!auth_opts->permit_port_forwarding_flag ||
  	    options.disable_forwarding) {
  		channel_disable_admin(ssh, FORWARD_LOCAL);
  		channel_disable_admin(ssh, FORWARD_REMOTE);
  	} else {
  		if ((options.allow_tcp_forwarding & FORWARD_LOCAL) == 0)
  			channel_disable_admin(ssh, FORWARD_LOCAL);
  		else
  			channel_permit_all(ssh, FORWARD_LOCAL);
  		if ((options.allow_tcp_forwarding & FORWARD_REMOTE) == 0)
  			channel_disable_admin(ssh, FORWARD_REMOTE);
  		else
  			channel_permit_all(ssh, FORWARD_REMOTE);
  	}
  	auth_debug_send(ssh);
  
  	prepare_auth_info_file(authctxt->pw, authctxt->session_info);
  
  	do_authenticated2(ssh, authctxt);
  
  	do_cleanup(ssh, authctxt);
  }
  
  /* Check untrusted xauth strings for metacharacters */
  static int
  xauth_valid_string(const char *s)
  {
  	size_t i;
  
  	for (i = 0; s[i] != '\0'; i++) {
  		if (!isalnum((u_char)s[i]) &&
  		    s[i] != '.' && s[i] != ':' && s[i] != '/' &&
  		    s[i] != '-' && s[i] != '_')
  			return 0;
  	}
  	return 1;
  }
  
  #define USE_PIPES 1
  /*
   * 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.
   */
  int
  do_exec_no_pty(struct ssh *ssh, Session *s, const char *command)
  {
  	pid_t pid;
  #ifdef USE_PIPES
  	int pin[2], pout[2], perr[2];
  
  	if (s == NULL)
  		fatal("do_exec_no_pty: no session");
  
  	/* Allocate pipes for communicating with the program. */
  	if (pipe(pin) < 0) {
  		error("%s: pipe in: %.100s", __func__, strerror(errno));
  		return -1;
  	}
  	if (pipe(pout) < 0) {
  		error("%s: pipe out: %.100s", __func__, strerror(errno));
  		close(pin[0]);
  		close(pin[1]);
  		return -1;
  	}
  	if (pipe(perr) < 0) {
  		error("%s: pipe err: %.100s", __func__,
  		    strerror(errno));
  		close(pin[0]);
  		close(pin[1]);
  		close(pout[0]);
  		close(pout[1]);
  		return -1;
  	}
  #else
  	int inout[2], err[2];
  
  	if (s == NULL)
  		fatal("do_exec_no_pty: no session");
  
  	/* Uses socket pairs to communicate with the program. */
  	if (socketpair(AF_UNIX, SOCK_STREAM, 0, inout) < 0) {
  		error("%s: socketpair #1: %.100s", __func__, strerror(errno));
  		return -1;
  	}
  	if (socketpair(AF_UNIX, SOCK_STREAM, 0, err) < 0) {
  		error("%s: socketpair #2: %.100s", __func__,
  		    strerror(errno));
  		close(inout[0]);
  		close(inout[1]);
  		return -1;
  	}
  #endif
  
  	session_proctitle(s);
  
  	/* Fork the child. */
  	switch ((pid = fork())) {
  	case -1:
  		error("%s: fork: %.100s", __func__, strerror(errno));
  #ifdef USE_PIPES
  		close(pin[0]);
  		close(pin[1]);
  		close(pout[0]);
  		close(pout[1]);
  		close(perr[0]);
  		close(perr[1]);
  #else
  		close(inout[0]);
  		close(inout[1]);
  		close(err[0]);
  		close(err[1]);
  #endif
  		return -1;
  	case 0:
  		is_child = 1;
  
  		/*
  		 * 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
  		/*
  		 * 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 (same as stdin) */
  			perror("dup2 stdout");
  		close(inout[0]);
  		if (dup2(err[0], 2) < 0)	/* stderr */
  			perror("dup2 stderr");
  		close(err[0]);
  #endif
  
  		/* Do processing for the child (exec command etc). */
  		do_child(ssh, s, command);
  		/* NOTREACHED */
  	default:
  		break;
  	}
  
  #ifdef HAVE_CYGWIN
  	cygwin_set_impersonation_token(INVALID_HANDLE_VALUE);
  #endif
  
  	s->pid = pid;
  	/* Set interactive/non-interactive mode. */
  	ssh_packet_set_interactive(ssh, s->display != NULL,
  	    options.ip_qos_interactive, options.ip_qos_bulk);
  
  	/*
  	 * Clear loginmsg, since it's the child's responsibility to display
  	 * it to the user, otherwise multiple sessions may accumulate
  	 * multiple copies of the login messages.
  	 */
  	sshbuf_reset(loginmsg);
  
  #ifdef USE_PIPES
  	/* We are the parent.  Close the child sides of the pipes. */
  	close(pin[0]);
  	close(pout[1]);
  	close(perr[1]);
  
  	session_set_fds(ssh, s, pin[1], pout[0], perr[0],
  	    s->is_subsystem, 0);
  #else
  	/* 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.
  	 */
  	session_set_fds(ssh, s, inout[1], inout[1], err[1],
  	    s->is_subsystem, 0);
  #endif
  	return 0;
  }
  
  /*
   * 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.
   */
  int
  do_exec_pty(struct ssh *ssh, Session *s, const char *command)
  {
  	int fdout, ptyfd, ttyfd, ptymaster;
  	pid_t pid;
  
  	if (s == NULL)
  		fatal("do_exec_pty: no session");
  	ptyfd = s->ptyfd;
  	ttyfd = s->ttyfd;
  
  	/*
  	 * 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.
  	 * Do this before forking (and cleanup in the child) so as to
  	 * detect and gracefully fail out-of-fd conditions.
  	 */
  	if ((fdout = dup(ptyfd)) < 0) {
  		error("%s: dup #1: %s", __func__, strerror(errno));
  		close(ttyfd);
  		close(ptyfd);
  		return -1;
  	}
  	/* we keep a reference to the pty master */
  	if ((ptymaster = dup(ptyfd)) < 0) {
  		error("%s: dup #2: %s", __func__, strerror(errno));
  		close(ttyfd);
  		close(ptyfd);
  		close(fdout);
  		return -1;
  	}
  
  	/* Fork the child. */
  	switch ((pid = fork())) {
  	case -1:
  		error("%s: fork: %.100s", __func__, strerror(errno));
  		close(fdout);
  		close(ptymaster);
  		close(ttyfd);
  		close(ptyfd);
  		return -1;
  	case 0:
  		is_child = 1;
  
  		close(fdout);
  		close(ptymaster);
  
  		/* Close the master side of the pseudo tty. */
  		close(ptyfd);
  
  		/* Make the pseudo tty our controlling tty. */
  		pty_make_controlling_tty(&ttyfd, s->tty);
  
  		/* Redirect stdin/stdout/stderr from the pseudo tty. */
  		if (dup2(ttyfd, 0) < 0)
  			error("dup2 stdin: %s", strerror(errno));
  		if (dup2(ttyfd, 1) < 0)
  			error("dup2 stdout: %s", strerror(errno));
  		if (dup2(ttyfd, 2) < 0)
  			error("dup2 stderr: %s", strerror(errno));
  
  		/* Close the extra descriptor for the pseudo tty. */
  		close(ttyfd);
  
  		/* record login, etc. similar to login(1) */
  #ifndef HAVE_OSF_SIA
  		do_login(ssh, s, command);
  #endif
  		/*
  		 * Do common processing for the child, such as execing
  		 * the command.
  		 */
  		do_child(ssh, s, command);
  		/* NOTREACHED */
  	default:
  		break;
  	}
  
  #ifdef HAVE_CYGWIN
  	cygwin_set_impersonation_token(INVALID_HANDLE_VALUE);
  #endif
  
  	s->pid = pid;
  
  	/* Parent.  Close the slave side of the pseudo tty. */
  	close(ttyfd);
  
  	/* Enter interactive session. */
  	s->ptymaster = ptymaster;
  	ssh_packet_set_interactive(ssh, 1,
  	    options.ip_qos_interactive, options.ip_qos_bulk);
  	session_set_fds(ssh, s, ptyfd, fdout, -1, 1, 1);
  	return 0;
  }
  
  /*
   * This is called to fork and execute a command.  If another command is
   * to be forced, execute that instead.
   */
  int
  do_exec(struct ssh *ssh, Session *s, const char *command)
  {
  	int ret;
  	const char *forced = NULL, *tty = NULL;
  	char session_type[1024];
  
  	if (options.adm_forced_command) {
  		original_command = command;
  		command = options.adm_forced_command;
  		forced = "(config)";
  	} else if (auth_opts->force_command != NULL) {
  		original_command = command;
  		command = auth_opts->force_command;
  		forced = "(key-option)";
  	}
  	s->forced = 0;
  	if (forced != NULL) {
  		s->forced = 1;
  		if (IS_INTERNAL_SFTP(command)) {
  			s->is_subsystem = s->is_subsystem ?
  			    SUBSYSTEM_INT_SFTP : SUBSYSTEM_INT_SFTP_ERROR;
  		} else if (s->is_subsystem)
  			s->is_subsystem = SUBSYSTEM_EXT;
  		snprintf(session_type, sizeof(session_type),
  		    "forced-command %s '%.900s'", forced, command);
  	} else if (s->is_subsystem) {
  		snprintf(session_type, sizeof(session_type),
  		    "subsystem '%.900s'", s->subsys);
  	} else if (command == NULL) {
  		snprintf(session_type, sizeof(session_type), "shell");
  	} else {
  		/* NB. we don't log unforced commands to preserve privacy */
  		snprintf(session_type, sizeof(session_type), "command");
  	}
  
  	if (s->ttyfd != -1) {
  		tty = s->tty;
  		if (strncmp(tty, "/dev/", 5) == 0)
  			tty += 5;
  	}
  
  	verbose("Starting session: %s%s%s for %s from %.200s port %d id %d",
  	    session_type,
  	    tty == NULL ? "" : " on ",
  	    tty == NULL ? "" : tty,
  	    s->pw->pw_name,
  	    ssh_remote_ipaddr(ssh),
  	    ssh_remote_port(ssh),
  	    s->self);
  
  #ifdef SSH_AUDIT_EVENTS
  	if (command != NULL)
  		PRIVSEP(audit_run_command(command));
  	else if (s->ttyfd == -1) {
  		char *shell = s->pw->pw_shell;
  
  		if (shell[0] == '\0')	/* empty shell means /bin/sh */
  			shell =_PATH_BSHELL;
  		PRIVSEP(audit_run_command(shell));
  	}
  #endif
  	if (s->ttyfd != -1)
  		ret = do_exec_pty(ssh, s, command);
  	else
  		ret = do_exec_no_pty(ssh, s, command);
  
  	original_command = NULL;
  
  	/*
  	 * Clear loginmsg: it's the child's responsibility to display
  	 * it to the user, otherwise multiple sessions may accumulate
  	 * multiple copies of the login messages.
  	 */
  	sshbuf_reset(loginmsg);
  
  	return ret;
  }
  
  /* administrative, login(1)-like work */
  void
  do_login(struct ssh *ssh, Session *s, const char *command)
  {
  	socklen_t fromlen;
  	struct sockaddr_storage from;
  	struct passwd * pw = s->pw;
  	pid_t pid = getpid();
  
  	/*
  	 * Get IP address of client. If the connection is not a socket, let
  	 * the address be 0.0.0.0.
  	 */
  	memset(&from, 0, sizeof(from));
  	fromlen = sizeof(from);
  	if (ssh_packet_connection_is_on_socket(ssh)) {
  		if (getpeername(ssh_packet_get_connection_in(ssh),
  		    (struct sockaddr *)&from, &fromlen) < 0) {
  			debug("getpeername: %.100s", strerror(errno));
  			cleanup_exit(255);
  		}
  	}
  
  	/* Record that there was a login on that tty from the remote host. */
  	if (!use_privsep)
  		record_login(pid, s->tty, pw->pw_name, pw->pw_uid,
  		    session_get_remote_name_or_ip(ssh, utmp_len,
  		    options.use_dns),
  		    (struct sockaddr *)&from, fromlen);
  
  #ifdef USE_PAM
  	/*
  	 * If password change is needed, do it now.
  	 * This needs to occur before the ~/.hushlogin check.
  	 */
  	if (options.use_pam && !use_privsep && s->authctxt->force_pwchange) {
  		display_loginmsg();
  		do_pam_chauthtok();
  		s->authctxt->force_pwchange = 0;
  		/* XXX - signal [net] parent to enable forwardings */
  	}
  #endif
  
  	if (check_quietlogin(s, command))
  		return;
  
  	display_loginmsg();
  
  	do_motd();
  }
  
  /*
   * Display the message of the day.
   */
  void
  do_motd(void)
  {
  	FILE *f;
  	char buf[256];
  
  	if (options.print_motd) {
  #ifdef HAVE_LOGIN_CAP
  		f = fopen(login_getcapstr(lc, "welcome", "/etc/motd",
  		    "/etc/motd"), "r");
  #else
  		f = fopen("/etc/motd", "r");
  #endif
  		if (f) {
  			while (fgets(buf, sizeof(buf), f))
  				fputs(buf, stdout);
  			fclose(f);
  		}
  	}
  }
  
  
  /*
   * Check for quiet login, either .hushlogin or command given.
   */
  int
  check_quietlogin(Session *s, const char *command)
  {
  	char buf[256];
  	struct passwd *pw = s->pw;
  	struct stat st;
  
  	/* Return 1 if .hushlogin exists or a command given. */
  	if (command != NULL)
  		return 1;
  	snprintf(buf, sizeof(buf), "%.200s/.hushlogin", pw->pw_dir);
  #ifdef HAVE_LOGIN_CAP
  	if (login_getcapbool(lc, "hushlogin", 0) || stat(buf, &st) >= 0)
  		return 1;
  #else
  	if (stat(buf, &st) >= 0)
  		return 1;
  #endif
  	return 0;
  }
  
  /*
   * 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.
   * If whitelist is not NULL, then it is interpreted as a pattern list and
   * only variable names that match it will be accepted.
   */
  static void
  read_environment_file(char ***env, u_int *envsize,
  	const char *filename, const char *whitelist)
  {
  	FILE *f;
  	char *line = NULL, *cp, *value;
  	size_t linesize = 0;
  	u_int lineno = 0;
  
  	f = fopen(filename, "r");
  	if (!f)
  		return;
  
  	while (getline(&line, &linesize, f) != -1) {
  		if (++lineno > 1000)
  			fatal("Too many lines in environment file %s", filename);
  		for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
  			;
  		if (!*cp || *cp == '#' || *cp == '\n')
  			continue;
  
  		cp[strcspn(cp, "\n")] = '\0';
  
  		value = strchr(cp, '=');
  		if (value == NULL) {
  			fprintf(stderr, "Bad line %u in %.100s\n", lineno,
  			    filename);
  			continue;
  		}
  		/*
  		 * Replace the equals sign by nul, and advance value to
  		 * the value string.
  		 */
  		*value = '\0';
  		value++;
  		if (whitelist != NULL &&
  		    match_pattern_list(cp, whitelist, 0) != 1)
  			continue;
  		child_set_env(env, envsize, cp, value);
  	}
  	free(line);
  	fclose(f);
  }
  
  #ifdef HAVE_ETC_DEFAULT_LOGIN
  /*
   * Return named variable from specified environment, or NULL if not present.
   */
  static char *
  child_get_env(char **env, const char *name)
  {
  	int i;
  	size_t len;
  
  	len = strlen(name);
  	for (i=0; env[i] != NULL; i++)
  		if (strncmp(name, env[i], len) == 0 && env[i][len] == '=')
  			return(env[i] + len + 1);
  	return NULL;
  }
  
  /*
   * Read /etc/default/login.
   * We pick up the PATH (or SUPATH for root) and UMASK.
   */
  static void
  read_etc_default_login(char ***env, u_int *envsize, uid_t uid)
  {
  	char **tmpenv = NULL, *var;
  	u_int i, tmpenvsize = 0;
  	u_long mask;
  
  	/*
  	 * We don't want to copy the whole file to the child's environment,
  	 * so we use a temporary environment and copy the variables we're
  	 * interested in.
  	 */
  	read_environment_file(&tmpenv, &tmpenvsize, "/etc/default/login",
  	    options.permit_user_env_whitelist);
  
  	if (tmpenv == NULL)
  		return;
  
  	if (uid == 0)
  		var = child_get_env(tmpenv, "SUPATH");
  	else
  		var = child_get_env(tmpenv, "PATH");
  	if (var != NULL)
  		child_set_env(env, envsize, "PATH", var);
  
  	if ((var = child_get_env(tmpenv, "UMASK")) != NULL)
  		if (sscanf(var, "%5lo", &mask) == 1)
  			umask((mode_t)mask);
  
  	for (i = 0; tmpenv[i] != NULL; i++)
  		free(tmpenv[i]);
  	free(tmpenv);
  }
  #endif /* HAVE_ETC_DEFAULT_LOGIN */
  
  static void
  copy_environment_blacklist(char **source, char ***env, u_int *envsize,
      const char *blacklist)
  {
  	char *var_name, *var_val;
  	int i;
  
  	if (source == NULL)
  		return;
  
  	for(i = 0; source[i] != NULL; i++) {
  		var_name = xstrdup(source[i]);
  		if ((var_val = strstr(var_name, "=")) == NULL) {
  			free(var_name);
  			continue;
  		}
  		*var_val++ = '\0';
  
  		if (blacklist == NULL ||
  		    match_pattern_list(var_name, blacklist, 0) != 1) {
  			debug3("Copy environment: %s=%s", var_name, var_val);
  			child_set_env(env, envsize, var_name, var_val);
  		}
  
  		free(var_name);
  	}
  }
  
  #ifdef HAVE_CYGWIN
  
  static void
  copy_environment(char **source, char ***env, u_int *envsize)
  {
  	copy_environment_blacklist(source, env, envsize, NULL);
  }
  
  #endif
  
  static char **
  do_setup_env(struct ssh *ssh, Session *s, const char *shell)
  {
  	char buf[256];
  	size_t n;
  	u_int i, envsize;
  	char *ocp, *cp, *value, **env, *laddr;
  	struct passwd *pw = s->pw;
  #if !defined (HAVE_LOGIN_CAP) && !defined (HAVE_CYGWIN)
  	char *path = NULL;
  #endif
  
  	/* Initialize the environment. */
  	envsize = 100;
  	env = xcalloc(envsize, sizeof(char *));
  	env[0] = NULL;
  
  #ifdef HAVE_CYGWIN
  	/*
  	 * The Windows environment contains some setting which are
  	 * important for a running system. They must not be dropped.
  	 */
  	{
  		char **p;
  
  		p = fetch_windows_environment();
  		copy_environment(p, &env, &envsize);
  		free_windows_environment(p);
  	}
  #endif
  
  #ifdef GSSAPI
  	/* Allow any GSSAPI methods that we've used to alter
  	 * the childs environment as they see fit
  	 */
  	ssh_gssapi_do_child(&env, &envsize);
  #endif
  
  	/* Set basic environment. */
  	for (i = 0; i < s->num_env; i++)
  		child_set_env(&env, &envsize, s->env[i].name, s->env[i].val);
  
  	child_set_env(&env, &envsize, "USER", pw->pw_name);
  	child_set_env(&env, &envsize, "LOGNAME", pw->pw_name);
  #ifdef _AIX
  	child_set_env(&env, &envsize, "LOGIN", pw->pw_name);
  #endif
  	child_set_env(&env, &envsize, "HOME", pw->pw_dir);
  #ifdef HAVE_LOGIN_CAP
  	if (setusercontext(lc, pw, pw->pw_uid, LOGIN_SETPATH) < 0)
  		child_set_env(&env, &envsize, "PATH", _PATH_STDPATH);
  	else
  		child_set_env(&env, &envsize, "PATH", getenv("PATH"));
  #else /* HAVE_LOGIN_CAP */
  # ifndef HAVE_CYGWIN
  	/*
  	 * There's no standard path on Windows. The path contains
  	 * important components pointing to the system directories,
  	 * needed for loading shared libraries. So the path better
  	 * remains intact here.
  	 */
  #  ifdef HAVE_ETC_DEFAULT_LOGIN
  	read_etc_default_login(&env, &envsize, pw->pw_uid);
  	path = child_get_env(env, "PATH");
  #  endif /* HAVE_ETC_DEFAULT_LOGIN */
  	if (path == NULL || *path == '\0') {
  		child_set_env(&env, &envsize, "PATH",
  		    s->pw->pw_uid == 0 ?  SUPERUSER_PATH : _PATH_STDPATH);
  	}
  # endif /* HAVE_CYGWIN */
  #endif /* HAVE_LOGIN_CAP */
  
  	if (!options.use_pam) {
  		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"));
  	if (s->term)
  		child_set_env(&env, &envsize, "TERM", s->term);
  	if (s->display)
  		child_set_env(&env, &envsize, "DISPLAY", s->display);
  
  	/*
  	 * Since we clear KRB5CCNAME at startup, if it's set now then it
  	 * must have been set by a native authentication method (eg AIX or
  	 * SIA), so copy it to the child.
  	 */
  	{
  		char *cp;
  
  		if ((cp = getenv("KRB5CCNAME")) != NULL)
  			child_set_env(&env, &envsize, "KRB5CCNAME", cp);
  	}
  
  #ifdef _AIX
  	{
  		char *cp;
  
  		if ((cp = getenv("AUTHSTATE")) != NULL)
  			child_set_env(&env, &envsize, "AUTHSTATE", cp);
  		read_environment_file(&env, &envsize, "/etc/environment",
  		    options.permit_user_env_whitelist);
  	}
  #endif
  #ifdef KRB5
  	if (s->authctxt->krb5_ccname)
  		child_set_env(&env, &envsize, "KRB5CCNAME",
  		    s->authctxt->krb5_ccname);
  #endif
  	if (auth_sock_name != NULL)
  		child_set_env(&env, &envsize, SSH_AUTHSOCKET_ENV_NAME,
  		    auth_sock_name);
  
  
  	/* Set custom environment options from pubkey authentication. */
  	if (options.permit_user_env) {
  		for (n = 0 ; n < auth_opts->nenv; n++) {
  			ocp = xstrdup(auth_opts->env[n]);
  			cp = strchr(ocp, '=');
  			if (*cp == '=') {
  				*cp = '\0';
  				/* Apply PermitUserEnvironment whitelist */
  				if (options.permit_user_env_whitelist == NULL ||
  				    match_pattern_list(ocp,
  				    options.permit_user_env_whitelist, 0) == 1)
  					child_set_env(&env, &envsize,
  					    ocp, cp + 1);
  			}
  			free(ocp);
  		}
  	}
  
  	/* read $HOME/.ssh/environment. */
  	if (options.permit_user_env) {
  		snprintf(buf, sizeof buf, "%.200s/.ssh/environment",
  		    pw->pw_dir);
  		read_environment_file(&env, &envsize, buf,
  		    options.permit_user_env_whitelist);
  	}
  
  #ifdef USE_PAM
  	/*
  	 * Pull in any environment variables that may have
  	 * been set by PAM.
  	 */
  	if (options.use_pam) {
  		char **p;
  
  		/*
  		 * Don't allow PAM-internal env vars to leak
  		 * back into the session environment.
  		 */
  #define PAM_ENV_BLACKLIST  "SSH_AUTH_INFO*,SSH_CONNECTION*"
  		p = fetch_pam_child_environment();
  		copy_environment_blacklist(p, &env, &envsize,
  		    PAM_ENV_BLACKLIST);
  		free_pam_environment(p);
  
  		p = fetch_pam_environment();
  		copy_environment_blacklist(p, &env, &envsize,
  		    PAM_ENV_BLACKLIST);
  		free_pam_environment(p);
  	}
  #endif /* USE_PAM */
  
  	/* Environment specified by admin */
  	for (i = 0; i < options.num_setenv; i++) {
  		cp = xstrdup(options.setenv[i]);
  		if ((value = strchr(cp, '=')) == NULL) {
  			/* shouldn't happen; vars are checked in servconf.c */
  			fatal("Invalid config SetEnv: %s", options.setenv[i]);
  		}
  		*value++ = '\0';
  		child_set_env(&env, &envsize, cp, value);
  	}
  
  	/* SSH_CLIENT deprecated */
  	snprintf(buf, sizeof buf, "%.50s %d %d",
  	    ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
  	    ssh_local_port(ssh));
  	child_set_env(&env, &envsize, "SSH_CLIENT", buf);
  
  	laddr = get_local_ipaddr(ssh_packet_get_connection_in(ssh));
  	snprintf(buf, sizeof buf, "%.50s %d %.50s %d",
  	    ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
  	    laddr, ssh_local_port(ssh));
  	free(laddr);
  	child_set_env(&env, &envsize, "SSH_CONNECTION", buf);
  
  	if (tun_fwd_ifnames != NULL)
  		child_set_env(&env, &envsize, "SSH_TUNNEL", tun_fwd_ifnames);
  	if (auth_info_file != NULL)
  		child_set_env(&env, &envsize, "SSH_USER_AUTH", auth_info_file);
  	if (s->ttyfd != -1)
  		child_set_env(&env, &envsize, "SSH_TTY", s->tty);
  	if (original_command)
  		child_set_env(&env, &envsize, "SSH_ORIGINAL_COMMAND",
  		    original_command);
  
  	if (debug_flag) {
  		/* dump the environment */
  		fprintf(stderr, "Environment:\n");
  		for (i = 0; env[i]; i++)
  			fprintf(stderr, "  %.200s\n", env[i]);
  	}
  	return env;
  }
  
  /*
   * Run $HOME/.ssh/rc, /etc/ssh/sshrc, or xauth (whichever is found
   * first in this order).
   */
  static void
  do_rc_files(struct ssh *ssh, Session *s, const char *shell)
  {
  	FILE *f = NULL;
  	char cmd[1024];
  	int do_xauth;
  	struct stat st;
  
  	do_xauth =
  	    s->display != NULL && s->auth_proto != NULL && s->auth_data != NULL;
  
  	/* ignore _PATH_SSH_USER_RC for subsystems and admin forced commands */
  	if (!s->is_subsystem && options.adm_forced_command == NULL &&
  	    auth_opts->permit_user_rc && options.permit_user_rc &&
  	    stat(_PATH_SSH_USER_RC, &st) >= 0) {
  		snprintf(cmd, sizeof cmd, "%s -c '%s %s'",
  		    shell, _PATH_BSHELL, _PATH_SSH_USER_RC);
  		if (debug_flag)
  			fprintf(stderr, "Running %s\n", cmd);
  		f = popen(cmd, "w");
  		if (f) {
  			if (do_xauth)
  				fprintf(f, "%s %s\n", s->auth_proto,
  				    s->auth_data);
  			pclose(f);
  		} else
  			fprintf(stderr, "Could not run %s\n",
  			    _PATH_SSH_USER_RC);
  	} else if (stat(_PATH_SSH_SYSTEM_RC, &st) >= 0) {
  		if (debug_flag)
  			fprintf(stderr, "Running %s %s\n", _PATH_BSHELL,
  			    _PATH_SSH_SYSTEM_RC);
  		f = popen(_PATH_BSHELL " " _PATH_SSH_SYSTEM_RC, "w");
  		if (f) {
  			if (do_xauth)
  				fprintf(f, "%s %s\n", s->auth_proto,
  				    s->auth_data);
  			pclose(f);
  		} else
  			fprintf(stderr, "Could not run %s\n",
  			    _PATH_SSH_SYSTEM_RC);
  	} else if (do_xauth && options.xauth_location != NULL) {
  		/* Add authority data to .Xauthority if appropriate. */
  		if (debug_flag) {
  			fprintf(stderr,
  			    "Running %.500s remove %.100s\n",
  			    options.xauth_location, s->auth_display);
  			fprintf(stderr,
  			    "%.500s add %.100s %.100s %.100s\n",
  			    options.xauth_location, s->auth_display,
  			    s->auth_proto, s->auth_data);
  		}
  		snprintf(cmd, sizeof cmd, "%s -q -",
  		    options.xauth_location);
  		f = popen(cmd, "w");
  		if (f) {
  			fprintf(f, "remove %s\n",
  			    s->auth_display);
  			fprintf(f, "add %s %s %s\n",
  			    s->auth_display, s->auth_proto,
  			    s->auth_data);
  			pclose(f);
  		} else {
  			fprintf(stderr, "Could not run %s\n",
  			    cmd);
  		}
  	}
  }
  
  static void
  do_nologin(struct passwd *pw)
  {
  	FILE *f = NULL;
  	char buf[1024], *nl, *def_nl = _PATH_NOLOGIN;
  	struct stat sb;
  
  #ifdef HAVE_LOGIN_CAP
  	if (login_getcapbool(lc, "ignorenologin", 0) || pw->pw_uid == 0)
  		return;
  	nl = strdup(login_getcapstr(lc, "nologin", def_nl, def_nl));
  #else
  	if (pw->pw_uid == 0)
  		return;
  	nl = def_nl;
  #endif
  	if (stat(nl, &sb) == -1) {
  		if (nl != def_nl)
  			free(nl);
  		return;
  	}
  
  	/* /etc/nologin exists.  Print its contents if we can and exit. */
  	logit("User %.100s not allowed because %s exists", pw->pw_name, nl);
  	if ((f = fopen(nl, "r")) != NULL) {
  		while (fgets(buf, sizeof(buf), f))
  			fputs(buf, stderr);
  		fclose(f);
  	}
  	exit(254);
  }
  
  /*
   * Chroot into a directory after checking it for safety: all path components
   * must be root-owned directories with strict permissions.
   */
  static void
  safely_chroot(const char *path, uid_t uid)
  {
  	const char *cp;
  	char component[PATH_MAX];
  	struct stat st;
  
  	if (!path_absolute(path))
  		fatal("chroot path does not begin at root");
  	if (strlen(path) >= sizeof(component))
  		fatal("chroot path too long");
  
  	/*
  	 * Descend the path, checking that each component is a
  	 * root-owned directory with strict permissions.
  	 */
  	for (cp = path; cp != NULL;) {
  		if ((cp = strchr(cp, '/')) == NULL)
  			strlcpy(component, path, sizeof(component));
  		else {
  			cp++;
  			memcpy(component, path, cp - path);
  			component[cp - path] = '\0';
  		}
  	
  		debug3("%s: checking '%s'", __func__, component);
  
  		if (stat(component, &st) != 0)
  			fatal("%s: stat(\"%s\"): %s", __func__,
  			    component, strerror(errno));
  		if (st.st_uid != 0 || (st.st_mode & 022) != 0)
  			fatal("bad ownership or modes for chroot "
  			    "directory %s\"%s\"",
  			    cp == NULL ? "" : "component ", component);
  		if (!S_ISDIR(st.st_mode))
  			fatal("chroot path %s\"%s\" is not a directory",
  			    cp == NULL ? "" : "component ", component);
  
  	}
  
  	if (chdir(path) == -1)
  		fatal("Unable to chdir to chroot path \"%s\": "
  		    "%s", path, strerror(errno));
  	if (chroot(path) == -1)
  		fatal("chroot(\"%s\"): %s", path, strerror(errno));
  	if (chdir("/") == -1)
  		fatal("%s: chdir(/) after chroot: %s",
  		    __func__, strerror(errno));
  	verbose("Changed root directory to \"%s\"", path);
  }
  
  /* Set login name, uid, gid, and groups. */
  void
  do_setusercontext(struct passwd *pw)
  {
  	char uidstr[32], *chroot_path, *tmp;
  
  	platform_setusercontext(pw);
  
  	if (platform_privileged_uidswap()) {
  #ifdef HAVE_LOGIN_CAP
  		if (setusercontext(lc, pw, pw->pw_uid,
  		    (LOGIN_SETALL & ~(LOGIN_SETPATH|LOGIN_SETUSER))) < 0) {
  			perror("unable to set user context");
  			exit(1);
  		}
  #else
  		if (setlogin(pw->pw_name) < 0)
  			error("setlogin failed: %s", strerror(errno));
  		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();
  #endif
  
  		platform_setusercontext_post_groups(pw);
  
  		if (!in_chroot && options.chroot_directory != NULL &&
  		    strcasecmp(options.chroot_directory, "none") != 0) {
                          tmp = tilde_expand_filename(options.chroot_directory,
  			    pw->pw_uid);
  			snprintf(uidstr, sizeof(uidstr), "%llu",
  			    (unsigned long long)pw->pw_uid);
  			chroot_path = percent_expand(tmp, "h", pw->pw_dir,
  			    "u", pw->pw_name, "U", uidstr, (char *)NULL);
  			safely_chroot(chroot_path, pw->pw_uid);
  			free(tmp);
  			free(chroot_path);
  			/* Make sure we don't attempt to chroot again */
  			free(options.chroot_directory);
  			options.chroot_directory = NULL;
  			in_chroot = 1;
  		}
  
  #ifdef HAVE_LOGIN_CAP
  		if (setusercontext(lc, pw, pw->pw_uid, LOGIN_SETUSER) < 0) {
  			perror("unable to set user context (setuser)");
  			exit(1);
  		}
  		/* 
  		 * FreeBSD's setusercontext() will not apply the user's
  		 * own umask setting unless running with the user's UID.
  		 */
  		(void) setusercontext(lc, pw, pw->pw_uid, LOGIN_SETUMASK);
  #else
  # ifdef USE_LIBIAF
  		/*
  		 * In a chroot environment, the set_id() will always fail;
  		 * typically because of the lack of necessary authentication
  		 * services and runtime such as ./usr/lib/libiaf.so,
  		 * ./usr/lib/libpam.so.1, and ./etc/passwd We skip it in the
  		 * internal sftp chroot case.  We'll lose auditing and ACLs but
  		 * permanently_set_uid will take care of the rest.
  		 */
  		if (!in_chroot && set_id(pw->pw_name) != 0)
  			fatal("set_id(%s) Failed", pw->pw_name);
  # endif /* USE_LIBIAF */
  		/* Permanently switch to the desired uid. */
  		permanently_set_uid(pw);
  #endif
  	} else if (options.chroot_directory != NULL &&
  	    strcasecmp(options.chroot_directory, "none") != 0) {
  		fatal("server lacks privileges to chroot to ChrootDirectory");
  	}
  
  	if (getuid() != pw->pw_uid || geteuid() != pw->pw_uid)
  		fatal("Failed to set uids to %u.", (u_int) pw->pw_uid);
  }
  
  static void
  do_pwchange(Session *s)
  {
  	fflush(NULL);
  	fprintf(stderr, "WARNING: Your password has expired.\n");
  	if (s->ttyfd != -1) {
  		fprintf(stderr,
  		    "You must change your password now and login again!\n");
  #ifdef WITH_SELINUX
  		setexeccon(NULL);
  #endif
  #ifdef PASSWD_NEEDS_USERNAME
  		execl(_PATH_PASSWD_PROG, "passwd", s->pw->pw_name,
  		    (char *)NULL);
  #else
  		execl(_PATH_PASSWD_PROG, "passwd", (char *)NULL);
  #endif
  		perror("passwd");
  	} else {
  		fprintf(stderr,
  		    "Password change required but no TTY available.\n");
  	}
  	exit(1);
  }
  
  static void
  child_close_fds(struct ssh *ssh)
  {
  	extern int auth_sock;
  
  	if (auth_sock != -1) {
  		close(auth_sock);
  		auth_sock = -1;
  	}
  
  	if (ssh_packet_get_connection_in(ssh) ==
  	    ssh_packet_get_connection_out(ssh))
  		close(ssh_packet_get_connection_in(ssh));
  	else {
  		close(ssh_packet_get_connection_in(ssh));
  		close(ssh_packet_get_connection_out(ssh));
  	}
  	/*
  	 * Close all descriptors related to channels.  They will still remain
  	 * open in the parent.
  	 */
  	/* XXX better use close-on-exec? -markus */
  	channel_close_all(ssh);
  
  	/*
  	 * 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.
  	 */
  	closefrom(STDERR_FILENO + 1);
  }
  
  /*
   * 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.
   */
  #define ARGV_MAX 10
  void
  do_child(struct ssh *ssh, Session *s, const char *command)
  {
  	extern char **environ;
  	char **env, *argv[ARGV_MAX], remote_id[512];
  	const char *shell, *shell0;
  	struct passwd *pw = s->pw;
  	int r = 0;
  
  	sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id));
  
  	/* remove hostkey from the child's memory */
  	destroy_sensitive_data();
  	ssh_packet_clear_keys(ssh);
  
  	/* Force a password change */
  	if (s->authctxt->force_pwchange) {
  		do_setusercontext(pw);
  		child_close_fds(ssh);
  		do_pwchange(s);
  		exit(1);
  	}
  
  	/*
  	 * Login(1) does this as well, and it needs uid 0 for the "-h"
  	 * switch, so we let login(1) to this for us.
  	 */
  #ifdef HAVE_OSF_SIA
  	session_setup_sia(pw, s->ttyfd == -1 ? NULL : s->tty);
  	if (!check_quietlogin(s, command))
  		do_motd();
  #else /* HAVE_OSF_SIA */
  	/* When PAM is enabled we rely on it to do the nologin check */
  	if (!options.use_pam)
  		do_nologin(pw);
  	do_setusercontext(pw);
  	/*
  	 * PAM session modules in do_setusercontext may have
  	 * generated messages, so if this in an interactive
  	 * login then display them too.
  	 */
  	if (!check_quietlogin(s, command))
  		display_loginmsg();
  #endif /* HAVE_OSF_SIA */
  
  #ifdef USE_PAM
  	if (options.use_pam && !is_pam_session_open()) {
  		debug3("PAM session not opened, exiting");
  		display_loginmsg();
  		exit(254);
  	}
  #endif
  
  	/*
  	 * 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;
  
  	/*
  	 * Make sure $SHELL points to the shell from the password file,
  	 * even if shell is overridden from login.conf
  	 */
  	env = do_setup_env(ssh, s, shell);
  
  #ifdef HAVE_LOGIN_CAP
  	shell = login_getcapstr(lc, "shell", (char *)shell, (char *)shell);
  #endif
  
  	/*
  	 * 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
  	 * ssh_remote_ipaddr there.
  	 */
  	child_close_fds(ssh);
  
  	/*
  	 * Must take new environment into use so that .ssh/rc,
  	 * /etc/ssh/sshrc and xauth are run in the proper environment.
  	 */
  	environ = env;
  
  #if defined(KRB5) && defined(USE_AFS)
  	/*
  	 * At this point, we check to see if AFS is active and if we have
  	 * a valid Kerberos 5 TGT. If so, it seems like a good idea to see
  	 * if we can (and need to) extend the ticket into an AFS token. If
  	 * we don't do this, we run into potential problems if the user's
  	 * home directory is in AFS and it's not world-readable.
  	 */
  
  	if (options.kerberos_get_afs_token && k_hasafs() &&
  	    (s->authctxt->krb5_ctx != NULL)) {
  		char cell[64];
  
  		debug("Getting AFS token");
  
  		k_setpag();
  
  		if (k_afs_cell_of_file(pw->pw_dir, cell, sizeof(cell)) == 0)
  			krb5_afslog(s->authctxt->krb5_ctx,
  			    s->authctxt->krb5_fwd_ccache, cell, NULL);
  
  		krb5_afslog_home(s->authctxt->krb5_ctx,
  		    s->authctxt->krb5_fwd_ccache, NULL, NULL, pw->pw_dir);
  	}
  #endif
  
  	/* Change current directory to the user's home directory. */
  	if (chdir(pw->pw_dir) < 0) {
  		/* Suppress missing homedir warning for chroot case */
  #ifdef HAVE_LOGIN_CAP
  		r = login_getcapbool(lc, "requirehome", 0);
  #endif
  		if (r || !in_chroot) {
  			fprintf(stderr, "Could not chdir to home "
  			    "directory %s: %s\n", pw->pw_dir,
  			    strerror(errno));
  		}
  		if (r)
  			exit(1);
  	}
  
  	closefrom(STDERR_FILENO + 1);
  
  	do_rc_files(ssh, s, shell);
  
  	/* restore SIGPIPE for child */
  	signal(SIGPIPE, SIG_DFL);
  
  	if (s->is_subsystem == SUBSYSTEM_INT_SFTP_ERROR) {
  		error("Connection from %s: refusing non-sftp session",
  		    remote_id);
  		printf("This service allows sftp connections only.\n");
  		fflush(NULL);
  		exit(1);
  	} else if (s->is_subsystem == SUBSYSTEM_INT_SFTP) {
  		extern int optind, optreset;
  		int i;
  		char *p, *args;
  
  		setproctitle("%s@%s", s->pw->pw_name, INTERNAL_SFTP_NAME);
  		args = xstrdup(command ? command : "sftp-server");
  		for (i = 0, (p = strtok(args, " ")); p; (p = strtok(NULL, " ")))
  			if (i < ARGV_MAX - 1)
  				argv[i++] = p;
  		argv[i] = NULL;
  		optind = optreset = 1;
  		__progname = argv[0];
  #ifdef WITH_SELINUX
  		ssh_selinux_change_context("sftpd_t");
  #endif
  		exit(sftp_server_main(i, argv, s->pw));
  	}
  
  	fflush(NULL);
  
  	/* Get the last component of the shell name. */
  	if ((shell0 = strrchr(shell, '/')) != NULL)
  		shell0++;
  	else
  		shell0 = 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) {
  		char argv0[256];
  
  		/* Start the shell.  Set initial character to '-'. */
  		argv0[0] = '-';
  
  		if (strlcpy(argv0 + 1, shell0, sizeof(argv0) - 1)
  		    >= sizeof(argv0) - 1) {
  			errno = EINVAL;
  			perror(shell);
  			exit(1);
  		}
  
  		/* Execute the shell. */
  		argv[0] = argv0;
  		argv[1] = NULL;
  		execve(shell, argv, env);
  
  		/* Executing the shell failed. */
  		perror(shell);
  		exit(1);
  	}
  	/*
  	 * Execute the command using the user's shell.  This uses the -c
  	 * option to execute the command.
  	 */
  	argv[0] = (char *) shell0;
  	argv[1] = "-c";
  	argv[2] = (char *) command;
  	argv[3] = NULL;
  	execve(shell, argv, env);
  	perror(shell);
  	exit(1);
  }
  
  void
  session_unused(int id)
  {
  	debug3("%s: session id %d unused", __func__, id);
  	if (id >= options.max_sessions ||
  	    id >= sessions_nalloc) {
  		fatal("%s: insane session id %d (max %d nalloc %d)",
  		    __func__, id, options.max_sessions, sessions_nalloc);
  	}
  	memset(&sessions[id], 0, sizeof(*sessions));
  	sessions[id].self = id;
  	sessions[id].used = 0;
  	sessions[id].chanid = -1;
  	sessions[id].ptyfd = -1;
  	sessions[id].ttyfd = -1;
  	sessions[id].ptymaster = -1;
  	sessions[id].x11_chanids = NULL;
  	sessions[id].next_unused = sessions_first_unused;
  	sessions_first_unused = id;
  }
  
  Session *
  session_new(void)
  {
  	Session *s, *tmp;
  
  	if (sessions_first_unused == -1) {
  		if (sessions_nalloc >= options.max_sessions)
  			return NULL;
  		debug2("%s: allocate (allocated %d max %d)",
  		    __func__, sessions_nalloc, options.max_sessions);
  		tmp = xrecallocarray(sessions, sessions_nalloc,
  		    sessions_nalloc + 1, sizeof(*sessions));
  		if (tmp == NULL) {
  			error("%s: cannot allocate %d sessions",
  			    __func__, sessions_nalloc + 1);
  			return NULL;
  		}
  		sessions = tmp;
  		session_unused(sessions_nalloc++);
  	}
  
  	if (sessions_first_unused >= sessions_nalloc ||
  	    sessions_first_unused < 0) {
  		fatal("%s: insane first_unused %d max %d nalloc %d",
  		    __func__, sessions_first_unused, options.max_sessions,
  		    sessions_nalloc);
  	}
  
  	s = &sessions[sessions_first_unused];
  	if (s->used) {
  		fatal("%s: session %d already used",
  		    __func__, sessions_first_unused);
  	}
  	sessions_first_unused = s->next_unused;
  	s->used = 1;
  	s->next_unused = -1;
  	debug("session_new: session %d", s->self);
  
  	return s;
  }
  
  static void
  session_dump(void)
  {
  	int i;
  	for (i = 0; i < sessions_nalloc; i++) {
  		Session *s = &sessions[i];
  
  		debug("dump: used %d next_unused %d session %d %p "
  		    "channel %d pid %ld",
  		    s->used,
  		    s->next_unused,
  		    s->self,
  		    s,
  		    s->chanid,
  		    (long)s->pid);
  	}
  }
  
  int
  session_open(Authctxt *authctxt, int chanid)
  {
  	Session *s = session_new();
  	debug("session_open: channel %d", chanid);
  	if (s == NULL) {
  		error("no more sessions");
  		return 0;
  	}
  	s->authctxt = authctxt;
  	s->pw = authctxt->pw;
  	if (s->pw == NULL || !authctxt->valid)
  		fatal("no user for session %d", s->self);
  	debug("session_open: session %d: link with channel %d", s->self, chanid);
  	s->chanid = chanid;
  	return 1;
  }
  
  Session *
  session_by_tty(char *tty)
  {
  	int i;
  	for (i = 0; i < sessions_nalloc; i++) {
  		Session *s = &sessions[i];
  		if (s->used && s->ttyfd != -1 && strcmp(s->tty, tty) == 0) {
  			debug("session_by_tty: session %d tty %s", i, tty);
  			return s;
  		}
  	}
  	debug("session_by_tty: unknown tty %.100s", tty);
  	session_dump();
  	return NULL;
  }
  
  static Session *
  session_by_channel(int id)
  {
  	int i;
  	for (i = 0; i < sessions_nalloc; i++) {
  		Session *s = &sessions[i];
  		if (s->used && s->chanid == id) {
  			debug("session_by_channel: session %d channel %d",
  			    i, id);
  			return s;
  		}
  	}
  	debug("session_by_channel: unknown channel %d", id);
  	session_dump();
  	return NULL;
  }
  
  static Session *
  session_by_x11_channel(int id)
  {
  	int i, j;
  
  	for (i = 0; i < sessions_nalloc; i++) {
  		Session *s = &sessions[i];
  
  		if (s->x11_chanids == NULL || !s->used)
  			continue;
  		for (j = 0; s->x11_chanids[j] != -1; j++) {
  			if (s->x11_chanids[j] == id) {
  				debug("session_by_x11_channel: session %d "
  				    "channel %d", s->self, id);
  				return s;
  			}
  		}
  	}
  	debug("session_by_x11_channel: unknown channel %d", id);
  	session_dump();
  	return NULL;
  }
  
  static Session *
  session_by_pid(pid_t pid)
  {
  	int i;
  	debug("session_by_pid: pid %ld", (long)pid);
  	for (i = 0; i < sessions_nalloc; i++) {
  		Session *s = &sessions[i];
  		if (s->used && s->pid == pid)
  			return s;
  	}
  	error("session_by_pid: unknown pid %ld", (long)pid);
  	session_dump();
  	return NULL;
  }
  
  static int
  session_window_change_req(struct ssh *ssh, Session *s)
  {
  	int r;
  
  	if ((r = sshpkt_get_u32(ssh, &s->col)) != 0 ||
  	    (r = sshpkt_get_u32(ssh, &s->row)) != 0 ||
  	    (r = sshpkt_get_u32(ssh, &s->xpixel)) != 0 ||
  	    (r = sshpkt_get_u32(ssh, &s->ypixel)) != 0 ||
  	    (r = sshpkt_get_end(ssh)) != 0)
  		sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
  	pty_change_window_size(s->ptyfd, s->row, s->col, s->xpixel, s->ypixel);
  	return 1;
  }
  
  static int
  session_pty_req(struct ssh *ssh, Session *s)
  {
  	int r;
  
  	if (!auth_opts->permit_pty_flag || !options.permit_tty) {
  		debug("Allocating a pty not permitted for this connection.");
  		return 0;
  	}
  	if (s->ttyfd != -1) {
  		ssh_packet_disconnect(ssh, "Protocol error: you already have a pty.");
  		return 0;
  	}
  
  	if ((r = sshpkt_get_cstring(ssh, &s->term, NULL)) != 0 ||
  	    (r = sshpkt_get_u32(ssh, &s->col)) != 0 ||
  	    (r = sshpkt_get_u32(ssh, &s->row)) != 0 ||
  	    (r = sshpkt_get_u32(ssh, &s->xpixel)) != 0 ||
  	    (r = sshpkt_get_u32(ssh, &s->ypixel)) != 0)
  		sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
  
  	if (strcmp(s->term, "") == 0) {
  		free(s->term);
  		s->term = NULL;
  	}
  
  	/* Allocate a pty and open it. */
  	debug("Allocating pty.");
  	if (!PRIVSEP(pty_allocate(&s->ptyfd, &s->ttyfd, s->tty,
  	    sizeof(s->tty)))) {
  		free(s->term);
  		s->term = NULL;
  		s->ptyfd = -1;
  		s->ttyfd = -1;
  		error("session_pty_req: session %d alloc failed", s->self);
  		return 0;
  	}
  	debug("session_pty_req: session %d alloc %s", s->self, s->tty);
  
  	ssh_tty_parse_modes(ssh, s->ttyfd);
  
  	if ((r = sshpkt_get_end(ssh)) != 0)
  		sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
  
  	if (!use_privsep)
  		pty_setowner(s->pw, s->tty);
  
  	/* Set window size from the packet. */
  	pty_change_window_size(s->ptyfd, s->row, s->col, s->xpixel, s->ypixel);
  
  	session_proctitle(s);
  	return 1;
  }
  
  static int
  session_subsystem_req(struct ssh *ssh, Session *s)
  {
  	struct stat st;
  	int r, success = 0;
  	char *prog, *cmd;
  	u_int i;
  
  	if ((r = sshpkt_get_cstring(ssh, &s->subsys, NULL)) != 0 ||
  	    (r = sshpkt_get_end(ssh)) != 0)
  		sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
  	debug2("subsystem request for %.100s by user %s", s->subsys,
  	    s->pw->pw_name);
  
  	for (i = 0; i < options.num_subsystems; i++) {
  		if (strcmp(s->subsys, options.subsystem_name[i]) == 0) {
  			prog = options.subsystem_command[i];
  			cmd = options.subsystem_args[i];
  			if (strcmp(INTERNAL_SFTP_NAME, prog) == 0) {
  				s->is_subsystem = SUBSYSTEM_INT_SFTP;
  				debug("subsystem: %s", prog);
  			} else {
  				if (stat(prog, &st) < 0)
  					debug("subsystem: cannot stat %s: %s",
  					    prog, strerror(errno));
  				s->is_subsystem = SUBSYSTEM_EXT;
  				debug("subsystem: exec() %s", cmd);
  			}
  			success = do_exec(ssh, s, cmd) == 0;
  			break;
  		}
  	}
  
  	if (!success)
  		logit("subsystem request for %.100s by user %s failed, "
  		    "subsystem not found", s->subsys, s->pw->pw_name);
  
  	return success;
  }
  
  static int
  session_x11_req(struct ssh *ssh, Session *s)
  {
  	int r, success;
  	u_char single_connection = 0;
  
  	if (s->auth_proto != NULL || s->auth_data != NULL) {
  		error("session_x11_req: session %d: "
  		    "x11 forwarding already active", s->self);
  		return 0;
  	}
  	if ((r = sshpkt_get_u8(ssh, &single_connection)) != 0 ||
  	    (r = sshpkt_get_cstring(ssh, &s->auth_proto, NULL)) != 0 ||
  	    (r = sshpkt_get_cstring(ssh, &s->auth_data, NULL)) != 0 ||
  	    (r = sshpkt_get_u32(ssh, &s->screen)) != 0 ||
  	    (r = sshpkt_get_end(ssh)) != 0)
  		sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
  
  	s->single_connection = single_connection;
  
  	if (xauth_valid_string(s->auth_proto) &&
  	    xauth_valid_string(s->auth_data))
  		success = session_setup_x11fwd(ssh, s);
  	else {
  		success = 0;
  		error("Invalid X11 forwarding data");
  	}
  	if (!success) {
  		free(s->auth_proto);
  		free(s->auth_data);
  		s->auth_proto = NULL;
  		s->auth_data = NULL;
  	}
  	return success;
  }
  
  static int
  session_shell_req(struct ssh *ssh, Session *s)
  {
  	int r;
  
  	if ((r = sshpkt_get_end(ssh)) != 0)
  		sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
  	return do_exec(ssh, s, NULL) == 0;
  }
  
  static int
  session_exec_req(struct ssh *ssh, Session *s)
  {
  	u_int success;
  	int r;
  	char *command = NULL;
  
  	if ((r = sshpkt_get_cstring(ssh, &command, NULL)) != 0 ||
  	    (r = sshpkt_get_end(ssh)) != 0)
  		sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
  
  	success = do_exec(ssh, s, command) == 0;
  	free(command);
  	return success;
  }
  
  static int
  session_break_req(struct ssh *ssh, Session *s)
  {
  	int r;
  
  	if ((r = sshpkt_get_u32(ssh, NULL)) != 0 || /* ignore */
  	    (r = sshpkt_get_end(ssh)) != 0)
  		sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
  
  	if (s->ptymaster == -1 || tcsendbreak(s->ptymaster, 0) < 0)
  		return 0;
  	return 1;
  }
  
  static int
  session_env_req(struct ssh *ssh, Session *s)
  {
  	char *name, *val;
  	u_int i;
  	int r;
  
  	if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0 ||
  	    (r = sshpkt_get_cstring(ssh, &val, NULL)) != 0 ||
  	    (r = sshpkt_get_end(ssh)) != 0)
  		sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
  
  	/* Don't set too many environment variables */
  	if (s->num_env > 128) {
  		debug2("Ignoring env request %s: too many env vars", name);
  		goto fail;
  	}
  
  	for (i = 0; i < options.num_accept_env; i++) {
  		if (match_pattern(name, options.accept_env[i])) {
  			debug2("Setting env %d: %s=%s", s->num_env, name, val);
  			s->env = xrecallocarray(s->env, s->num_env,
  			    s->num_env + 1, sizeof(*s->env));
  			s->env[s->num_env].name = name;
  			s->env[s->num_env].val = val;
  			s->num_env++;
  			return (1);
  		}
  	}
  	debug2("Ignoring env request %s: disallowed name", name);
  
   fail:
  	free(name);
  	free(val);
  	return (0);
  }
  
  /*
   * Conversion of signals from ssh channel request names.
   * Subset of signals from RFC 4254 section 6.10C, with SIGINFO as
   * local extension.
   */
  static int
  name2sig(char *name)
  {
  #define SSH_SIG(x) if (strcmp(name, #x) == 0) return SIG ## x
  	SSH_SIG(HUP);
  	SSH_SIG(INT);
  	SSH_SIG(KILL);
  	SSH_SIG(QUIT);
  	SSH_SIG(TERM);
  	SSH_SIG(USR1);
  	SSH_SIG(USR2);
  #undef	SSH_SIG
  #ifdef SIGINFO
  	if (strcmp(name, "INFO@openssh.com") == 0)
  		return SIGINFO;
  #endif
  	return -1;
  }
  
  static int
  session_signal_req(struct ssh *ssh, Session *s)
  {
  	char *signame = NULL;
  	int r, sig, success = 0;
  
  	if ((r = sshpkt_get_cstring(ssh, &signame, NULL)) != 0 ||
  	    (r = sshpkt_get_end(ssh)) != 0) {
  		error("%s: parse packet: %s", __func__, ssh_err(r));
  		goto out;
  	}
  	if ((sig = name2sig(signame)) == -1) {
  		error("%s: unsupported signal \"%s\"", __func__, signame);
  		goto out;
  	}
  	if (s->pid <= 0) {
  		error("%s: no pid for session %d", __func__, s->self);
  		goto out;
  	}
  	if (s->forced || s->is_subsystem) {
  		error("%s: refusing to send signal %s to %s session", __func__,
  		    signame, s->forced ? "forced-command" : "subsystem");
  		goto out;
  	}
  	if (!use_privsep || mm_is_monitor()) {
  		error("%s: session signalling requires privilege separation",
  		    __func__);
  		goto out;
  	}
  
  	debug("%s: signal %s, killpg(%ld, %d)", __func__, signame,
  	    (long)s->pid, sig);
  	temporarily_use_uid(s->pw);
  	r = killpg(s->pid, sig);
  	restore_uid();
  	if (r != 0) {
  		error("%s: killpg(%ld, %d): %s", __func__, (long)s->pid,
  		    sig, strerror(errno));
  		goto out;
  	}
  
  	/* success */
  	success = 1;
   out:
  	free(signame);
  	return success;
  }
  
  static int
  session_auth_agent_req(struct ssh *ssh, Session *s)
  {
  	static int called = 0;
  	int r;
  
  	if ((r = sshpkt_get_end(ssh)) != 0)
  		sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
  	if (!auth_opts->permit_agent_forwarding_flag ||
  	    !options.allow_agent_forwarding) {
  		debug("%s: agent forwarding disabled", __func__);
  		return 0;
  	}
  	if (called) {
  		return 0;
  	} else {
  		called = 1;
  		return auth_input_request_forwarding(ssh, s->pw);
  	}
  }
  
  int
  session_input_channel_req(struct ssh *ssh, Channel *c, const char *rtype)
  {
  	int success = 0;
  	Session *s;
  
  	if ((s = session_by_channel(c->self)) == NULL) {
  		logit("%s: no session %d req %.100s", __func__, c->self, rtype);
  		return 0;
  	}
  	debug("%s: session %d req %s", __func__, s->self, rtype);
  
  	/*
  	 * a session is in LARVAL state until a shell, a command
  	 * or a subsystem is executed
  	 */
  	if (c->type == SSH_CHANNEL_LARVAL) {
  		if (strcmp(rtype, "shell") == 0) {
  			success = session_shell_req(ssh, s);
  		} else if (strcmp(rtype, "exec") == 0) {
  			success = session_exec_req(ssh, s);
  		} else if (strcmp(rtype, "pty-req") == 0) {
  			success = session_pty_req(ssh, s);
  		} else if (strcmp(rtype, "x11-req") == 0) {
  			success = session_x11_req(ssh, s);
  		} else if (strcmp(rtype, "auth-agent-req@openssh.com") == 0) {
  			success = session_auth_agent_req(ssh, s);
  		} else if (strcmp(rtype, "subsystem") == 0) {
  			success = session_subsystem_req(ssh, s);
  		} else if (strcmp(rtype, "env") == 0) {
  			success = session_env_req(ssh, s);
  		}
  	}
  	if (strcmp(rtype, "window-change") == 0) {
  		success = session_window_change_req(ssh, s);
  	} else if (strcmp(rtype, "break") == 0) {
  		success = session_break_req(ssh, s);
  	} else if (strcmp(rtype, "signal") == 0) {
  		success = session_signal_req(ssh, s);
  	}
  
  	return success;
  }
  
  void
  session_set_fds(struct ssh *ssh, Session *s,
      int fdin, int fdout, int fderr, int ignore_fderr, int is_tty)
  {
  	/*
  	 * now that have a child and a pipe to the child,
  	 * we can activate our channel and register the fd's
  	 */
  	if (s->chanid == -1)
  		fatal("no channel for session %d", s->self);
  	channel_set_fds(ssh, s->chanid,
  	    fdout, fdin, fderr,
  	    ignore_fderr ? CHAN_EXTENDED_IGNORE : CHAN_EXTENDED_READ,
  	    1, is_tty, CHAN_SES_WINDOW_DEFAULT);
  }
  
  /*
   * Function to perform pty cleanup. Also called if we get aborted abnormally
   * (e.g., due to a dropped connection).
   */
  void
  session_pty_cleanup2(Session *s)
  {
  	if (s == NULL) {
  		error("%s: no session", __func__);
  		return;
  	}
  	if (s->ttyfd == -1)
  		return;
  
  	debug("%s: session %d release %s", __func__, s->self, s->tty);
  
  	/* Record that the user has logged out. */
  	if (s->pid != 0)
  		record_logout(s->pid, s->tty, s->pw->pw_name);
  
  	/* Release the pseudo-tty. */
  	if (getuid() == 0)
  		pty_release(s->tty);
  
  	/*
  	 * 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 (s->ptymaster != -1 && close(s->ptymaster) < 0)
  		error("close(s->ptymaster/%d): %s",
  		    s->ptymaster, strerror(errno));
  
  	/* unlink pty from session */
  	s->ttyfd = -1;
  }
  
  void
  session_pty_cleanup(Session *s)
  {
  	PRIVSEP(session_pty_cleanup2(s));
  }
  
  static char *
  sig2name(int sig)
  {
  #define SSH_SIG(x) if (sig == SIG ## x) return #x
  	SSH_SIG(ABRT);
  	SSH_SIG(ALRM);
  	SSH_SIG(FPE);
  	SSH_SIG(HUP);
  	SSH_SIG(ILL);
  	SSH_SIG(INT);
  	SSH_SIG(KILL);
  	SSH_SIG(PIPE);
  	SSH_SIG(QUIT);
  	SSH_SIG(SEGV);
  	SSH_SIG(TERM);
  	SSH_SIG(USR1);
  	SSH_SIG(USR2);
  #undef	SSH_SIG
  	return "SIG@openssh.com";
  }
  
  static void
  session_close_x11(struct ssh *ssh, int id)
  {
  	Channel *c;
  
  	if ((c = channel_by_id(ssh, id)) == NULL) {
  		debug("%s: x11 channel %d missing", __func__, id);
  	} else {
  		/* Detach X11 listener */
  		debug("%s: detach x11 channel %d", __func__, id);
  		channel_cancel_cleanup(ssh, id);
  		if (c->ostate != CHAN_OUTPUT_CLOSED)
  			chan_mark_dead(ssh, c);
  	}
  }
  
  static void
  session_close_single_x11(struct ssh *ssh, int id, void *arg)
  {
  	Session *s;
  	u_int i;
  
  	debug3("%s: channel %d", __func__, id);
  	channel_cancel_cleanup(ssh, id);
  	if ((s = session_by_x11_channel(id)) == NULL)
  		fatal("%s: no x11 channel %d", __func__, id);
  	for (i = 0; s->x11_chanids[i] != -1; i++) {
  		debug("%s: session %d: closing channel %d",
  		    __func__, s->self, s->x11_chanids[i]);
  		/*
  		 * The channel "id" is already closing, but make sure we
  		 * close all of its siblings.
  		 */
  		if (s->x11_chanids[i] != id)
  			session_close_x11(ssh, s->x11_chanids[i]);
  	}
  	free(s->x11_chanids);
  	s->x11_chanids = NULL;
  	free(s->display);
  	s->display = NULL;
  	free(s->auth_proto);
  	s->auth_proto = NULL;
  	free(s->auth_data);
  	s->auth_data = NULL;
  	free(s->auth_display);
  	s->auth_display = NULL;
  }
  
  static void
  session_exit_message(struct ssh *ssh, Session *s, int status)
  {
  	Channel *c;
  	int r;
  
  	if ((c = channel_lookup(ssh, s->chanid)) == NULL)
  		fatal("%s: session %d: no channel %d",
  		    __func__, s->self, s->chanid);
  	debug("%s: session %d channel %d pid %ld",
  	    __func__, s->self, s->chanid, (long)s->pid);
  
  	if (WIFEXITED(status)) {
  		channel_request_start(ssh, s->chanid, "exit-status", 0);
  		if ((r = sshpkt_put_u32(ssh, WEXITSTATUS(status))) != 0 ||
  		    (r = sshpkt_send(ssh)) != 0)
  			sshpkt_fatal(ssh, r, "%s: exit reply", __func__);
  	} else if (WIFSIGNALED(status)) {
  		channel_request_start(ssh, s->chanid, "exit-signal", 0);
  #ifndef WCOREDUMP
  # define WCOREDUMP(x) (0)
  #endif
  		if ((r = sshpkt_put_cstring(ssh, sig2name(WTERMSIG(status)))) != 0 ||
  		    (r = sshpkt_put_u8(ssh, WCOREDUMP(status)? 1 : 0)) != 0 ||
  		    (r = sshpkt_put_cstring(ssh, "")) != 0 ||
  		    (r = sshpkt_put_cstring(ssh, "")) != 0 ||
  		    (r = sshpkt_send(ssh)) != 0)
  			sshpkt_fatal(ssh, r, "%s: exit reply", __func__);
  	} else {
  		/* Some weird exit cause.  Just exit. */
  		ssh_packet_disconnect(ssh, "wait returned status %04x.", status);
  	}
  
  	/* disconnect channel */
  	debug("%s: release channel %d", __func__, s->chanid);
  
  	/*
  	 * Adjust cleanup callback attachment to send close messages when
  	 * the channel gets EOF. The session will be then be closed
  	 * by session_close_by_channel when the childs close their fds.
  	 */
  	channel_register_cleanup(ssh, c->self, session_close_by_channel, 1);
  
  	/*
  	 * emulate a write failure with 'chan_write_failed', nobody will be
  	 * interested in data we write.
  	 * Note that we must not call 'chan_read_failed', since there could
  	 * be some more data waiting in the pipe.
  	 */
  	if (c->ostate != CHAN_OUTPUT_CLOSED)
  		chan_write_failed(ssh, c);
  }
  
  void
  session_close(struct ssh *ssh, Session *s)
  {
  	u_int i;
  
  	verbose("Close session: user %s from %.200s port %d id %d",
  	    s->pw->pw_name,
  	    ssh_remote_ipaddr(ssh),
  	    ssh_remote_port(ssh),
  	    s->self);
  
  	if (s->ttyfd != -1)
  		session_pty_cleanup(s);
  	free(s->term);
  	free(s->display);
  	free(s->x11_chanids);
  	free(s->auth_display);
  	free(s->auth_data);
  	free(s->auth_proto);
  	free(s->subsys);
  	if (s->env != NULL) {
  		for (i = 0; i < s->num_env; i++) {
  			free(s->env[i].name);
  			free(s->env[i].val);
  		}
  		free(s->env);
  	}
  	session_proctitle(s);
  	session_unused(s->self);
  }
  
  void
  session_close_by_pid(struct ssh *ssh, pid_t pid, int status)
  {
  	Session *s = session_by_pid(pid);
  	if (s == NULL) {
  		debug("%s: no session for pid %ld", __func__, (long)pid);
  		return;
  	}
  	if (s->chanid != -1)
  		session_exit_message(ssh, s, status);
  	if (s->ttyfd != -1)
  		session_pty_cleanup(s);
  	s->pid = 0;
  }
  
  /*
   * this is called when a channel dies before
   * the session 'child' itself dies
   */
  void
  session_close_by_channel(struct ssh *ssh, int id, void *arg)
  {
  	Session *s = session_by_channel(id);
  	u_int i;
  
  	if (s == NULL) {
  		debug("%s: no session for id %d", __func__, id);
  		return;
  	}
  	debug("%s: channel %d child %ld", __func__, id, (long)s->pid);
  	if (s->pid != 0) {
  		debug("%s: channel %d: has child, ttyfd %d",
  		    __func__, id, s->ttyfd);
  		/*
  		 * delay detach of session, but release pty, since
  		 * the fd's to the child are already closed
  		 */
  		if (s->ttyfd != -1)
  			session_pty_cleanup(s);
  		return;
  	}
  	/* detach by removing callback */
  	channel_cancel_cleanup(ssh, s->chanid);
  
  	/* Close any X11 listeners associated with this session */
  	if (s->x11_chanids != NULL) {
  		for (i = 0; s->x11_chanids[i] != -1; i++) {
  			session_close_x11(ssh, s->x11_chanids[i]);
  			s->x11_chanids[i] = -1;
  		}
  	}
  
  	s->chanid = -1;
  	session_close(ssh, s);
  }
  
  void
  session_destroy_all(struct ssh *ssh, void (*closefunc)(Session *))
  {
  	int i;
  	for (i = 0; i < sessions_nalloc; i++) {
  		Session *s = &sessions[i];
  		if (s->used) {
  			if (closefunc != NULL)
  				closefunc(s);
  			else
  				session_close(ssh, s);
  		}
  	}
  }
  
  static char *
  session_tty_list(void)
  {
  	static char buf[1024];
  	int i;
  	char *cp;
  
  	buf[0] = '\0';
  	for (i = 0; i < sessions_nalloc; i++) {
  		Session *s = &sessions[i];
  		if (s->used && s->ttyfd != -1) {
  
  			if (strncmp(s->tty, "/dev/", 5) != 0) {
  				cp = strrchr(s->tty, '/');
  				cp = (cp == NULL) ? s->tty : cp + 1;
  			} else
  				cp = s->tty + 5;
  
  			if (buf[0] != '\0')
  				strlcat(buf, ",", sizeof buf);
  			strlcat(buf, cp, sizeof buf);
  		}
  	}
  	if (buf[0] == '\0')
  		strlcpy(buf, "notty", sizeof buf);
  	return buf;
  }
  
  void
  session_proctitle(Session *s)
  {
  	if (s->pw == NULL)
  		error("no user for session %d", s->self);
  	else
  		setproctitle("%s@%s", s->pw->pw_name, session_tty_list());
  }
  
  int
  session_setup_x11fwd(struct ssh *ssh, Session *s)
  {
  	struct stat st;
  	char display[512], auth_display[512];
  	char hostname[NI_MAXHOST];
  	u_int i;
  
  	if (!auth_opts->permit_x11_forwarding_flag) {
  		ssh_packet_send_debug(ssh, "X11 forwarding disabled by key options.");
  		return 0;
  	}
  	if (!options.x11_forwarding) {
  		debug("X11 forwarding disabled in server configuration file.");
  		return 0;
  	}
  	if (options.xauth_location == NULL ||
  	    (stat(options.xauth_location, &st) == -1)) {
  		ssh_packet_send_debug(ssh, "No xauth program; cannot forward X11.");
  		return 0;
  	}
  	if (s->display != NULL) {
  		debug("X11 display already set.");
  		return 0;
  	}
  	if (x11_create_display_inet(ssh, options.x11_display_offset,
  	    options.x11_use_localhost, s->single_connection,
  	    &s->display_number, &s->x11_chanids) == -1) {
  		debug("x11_create_display_inet failed.");
  		return 0;
  	}
  	for (i = 0; s->x11_chanids[i] != -1; i++) {
  		channel_register_cleanup(ssh, s->x11_chanids[i],
  		    session_close_single_x11, 0);
  	}
  
  	/* Set up a suitable value for the DISPLAY variable. */
  	if (gethostname(hostname, sizeof(hostname)) < 0)
  		fatal("gethostname: %.100s", strerror(errno));
  	/*
  	 * auth_display must be used as the displayname when the
  	 * authorization entry is added with xauth(1).  This will be
  	 * different than the DISPLAY string for localhost displays.
  	 */
  	if (options.x11_use_localhost) {
  		snprintf(display, sizeof display, "localhost:%u.%u",
  		    s->display_number, s->screen);
  		snprintf(auth_display, sizeof auth_display, "unix:%u.%u",
  		    s->display_number, s->screen);
  		s->display = xstrdup(display);
  		s->auth_display = xstrdup(auth_display);
  	} else {
  #ifdef IPADDR_IN_DISPLAY
  		struct hostent *he;
  		struct in_addr my_addr;
  
  		he = gethostbyname(hostname);
  		if (he == NULL) {
  			error("Can't get IP address for X11 DISPLAY.");
  			ssh_packet_send_debug(ssh, "Can't get IP address for X11 DISPLAY.");
  			return 0;
  		}
  		memcpy(&my_addr, he->h_addr_list[0], sizeof(struct in_addr));
  		snprintf(display, sizeof display, "%.50s:%u.%u", inet_ntoa(my_addr),
  		    s->display_number, s->screen);
  #else
  		snprintf(display, sizeof display, "%.400s:%u.%u", hostname,
  		    s->display_number, s->screen);
  #endif
  		s->display = xstrdup(display);
  		s->auth_display = xstrdup(display);
  	}
  
  	return 1;
  }
  
  static void
  do_authenticated2(struct ssh *ssh, Authctxt *authctxt)
  {
  	server_loop2(ssh, authctxt);
  }
  
  void
  do_cleanup(struct ssh *ssh, Authctxt *authctxt)
  {
  	static int called = 0;
  
  	debug("do_cleanup");
  
  	/* no cleanup if we're in the child for login shell */
  	if (is_child)
  		return;
  
  	/* avoid double cleanup */
  	if (called)
  		return;
  	called = 1;
  
  	if (authctxt == NULL)
  		return;
  
  #ifdef USE_PAM
  	if (options.use_pam) {
  		sshpam_cleanup();
  		sshpam_thread_cleanup();
  	}
  #endif
  
  	if (!authctxt->authenticated)
  		return;
  
  #ifdef KRB5
  	if (options.kerberos_ticket_cleanup &&
  	    authctxt->krb5_ctx)
  		krb5_cleanup_proc(authctxt);
  #endif
  
  #ifdef GSSAPI
  	if (options.gss_cleanup_creds)
  		ssh_gssapi_cleanup_creds();
  #endif
  
  	/* remove agent socket */
  	auth_sock_cleanup_proc(authctxt->pw);
  
  	/* remove userauth info */
  	if (auth_info_file != NULL) {
  		temporarily_use_uid(authctxt->pw);
  		unlink(auth_info_file);
  		restore_uid();
  		free(auth_info_file);
  		auth_info_file = NULL;
  	}
  
  	/*
  	 * Cleanup ptys/utmp only if privsep is disabled,
  	 * or if running in monitor.
  	 */
  	if (!use_privsep || mm_is_monitor())
  		session_destroy_all(ssh, session_pty_cleanup2);
  }
  
  /* Return a name for the remote host that fits inside utmp_size */
  
  const char *
  session_get_remote_name_or_ip(struct ssh *ssh, u_int utmp_size, int use_dns)
  {
  	const char *remote = "";
  
  	if (utmp_size > 0)
  		remote = auth_get_canonical_hostname(ssh, use_dns);
  	if (utmp_size == 0 || strlen(remote) > utmp_size)
  		remote = ssh_remote_ipaddr(ssh);
  	return remote;
  }
  
  