/* $OpenBSD: session.c,v 1.341 2025/04/09 07:00:03 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>
#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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.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 "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

/*
 * Hack for systems that do not support FD passing: allocate PTYs directly
 * without calling into the monitor. This requires either the post-auth
 * privsep process retain root privileges (see the comment in
 * sshd-session.c:privsep_postauth) or that PTY allocation doesn't require
 * privileges to begin with (e.g. Cygwin).
 */
#ifdef DISABLE_FD_PASSING
#define mm_pty_allocate pty_allocate
#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-listener",
            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_fr(r, "sshbuf_put_u8");
        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_f("mkstemp: %s", strerror(errno));
                goto out;
        }
        if (atomicio(vwrite, fd, sshbuf_mutable_ptr(info),
            sshbuf_len(info)) != sshbuf_len(info)) {
                error_f("write: %s", strerror(errno));
                goto out;
        }
        if (close(fd) != 0) {
                error_f("close: %s", 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 = hpdelim2(&cp, NULL)) == NULL)
                                fatal_f("internal error: hpdelim");
                        host = cleanhostname(host);
                        if (cp == NULL || (port = permitopen_port(cp)) < 0)
                                fatal_f("internal error: permitopen port");
                        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_f("internal error: hpdelim");
                        host = cleanhostname(host);
                        if (cp == NULL || (port = permitopen_port(cp)) < 0)
                                fatal_f("internal error: permitlisten port");
                        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) == -1) {
                error_f("pipe in: %.100s", strerror(errno));
                return -1;
        }
        if (pipe(pout) == -1) {
                error_f("pipe out: %.100s", strerror(errno));
                close(pin[0]);
                close(pin[1]);
                return -1;
        }
        if (pipe(perr) == -1) {
                error_f("pipe err: %.100s", 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) == -1) {
                error_f("socketpair #1: %.100s", strerror(errno));
                return -1;
        }
        if (socketpair(AF_UNIX, SOCK_STREAM, 0, err) == -1) {
                error_f("socketpair #2: %.100s", strerror(errno));
                close(inout[0]);
                close(inout[1]);
                return -1;
        }
#endif

        session_proctitle(s);

        /* Fork the child. */
        switch ((pid = fork())) {
        case -1:
                error_f("fork: %.100s", 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() == -1)
                        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) == -1)
                        perror("dup2 stdin");
                close(pin[0]);

                /* Redirect stdout. */
                close(pout[0]);
                if (dup2(pout[1], 1) == -1)
                        perror("dup2 stdout");
                close(pout[1]);

                /* Redirect stderr. */
                close(perr[0]);
                if (dup2(perr[1], 2) == -1)
                        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) == -1)    /* stdin */
                        perror("dup2 stdin");
                if (dup2(inout[0], 1) == -1)    /* stdout (same as stdin) */
                        perror("dup2 stdout");
                close(inout[0]);
                if (dup2(err[0], 2) == -1)      /* 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)) == -1) {
                error_f("dup #1: %s", strerror(errno));
                close(ttyfd);
                close(ptyfd);
                return -1;
        }
        /* we keep a reference to the pty master */
        if ((ptymaster = dup(ptyfd)) == -1) {
                error_f("dup #2: %s", strerror(errno));
                close(ttyfd);
                close(ptyfd);
                close(fdout);
                return -1;
        }

        /* Fork the child. */
        switch ((pid = fork())) {
        case -1:
                error_f("fork: %.100s", 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) == -1)
                        error("dup2 stdin: %s", strerror(errno));
                if (dup2(ttyfd, 1) == -1)
                        error("dup2 stdout: %s", strerror(errno));
                if (dup2(ttyfd, 2) == -1)
                        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)
                mm_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;
                mm_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;

        /*
         * 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) == -1) {
                        debug("getpeername: %.100s", strerror(errno));
                        cleanup_exit(255);
                }
        }

        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 allowlist 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 *allowlist)
{
        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 (allowlist != NULL &&
                    match_pattern_list(cp, allowlist, 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_allowlist);

        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 */

#if defined(USE_PAM) || defined(HAVE_CYGWIN)
static void
copy_environment_denylist(char **source, char ***env, u_int *envsize,
    const char *denylist)
{
        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 (denylist == NULL ||
                    match_pattern_list(var_name, denylist, 0) != 1) {
                        debug3("Copy environment: %s=%s", var_name, var_val);
                        child_set_env(env, envsize, var_name, var_val);
                }

                free(var_name);
        }
}
#endif /* defined(USE_PAM) || defined(HAVE_CYGWIN) */

#ifdef HAVE_CYGWIN
static void
copy_environment(char **source, char ***env, u_int *envsize)
{
        copy_environment_denylist(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;
#else
        extern char **environ;
        char **senv, **var, *val;
#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

        if (getenv("TZ"))
                child_set_env(&env, &envsize, "TZ", getenv("TZ"));

#ifdef GSSAPI
        /* Allow any GSSAPI methods that we've used to alter
         * the child's 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);
        snprintf(buf, sizeof buf, "%.200s/%.50s", _PATH_MAILDIR, pw->pw_name);
        child_set_env(&env, &envsize, "MAIL", buf);
#ifdef HAVE_LOGIN_CAP
        child_set_env(&env, &envsize, "PATH", _PATH_STDPATH);
        child_set_env(&env, &envsize, "TERM", "su");
        /*
         * Temporarily swap out our real environment with an empty one,
         * let setusercontext() apply any environment variables defined
         * for the user's login class, copy those variables to the child,
         * free the temporary environment, and restore the original.
         */
        senv = environ;
        environ = xmalloc(sizeof(*environ));
        *environ = NULL;
        (void)setusercontext(lc, pw, pw->pw_uid, LOGIN_SETENV|LOGIN_SETPATH);
        for (var = environ; *var != NULL; ++var) {
                if ((val = strchr(*var, '=')) != NULL) {
                        *val++ = '\0';
                        child_set_env(&env, &envsize, *var, val);
                }
                free(*var);
        }
        free(environ);
        environ = senv;
#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 */

        /* Normal systems set SHELL by default. */
        child_set_env(&env, &envsize, "SHELL", shell);

        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_allowlist);
        }
#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 != NULL) {
                                *cp = '\0';
                                /* Apply PermitUserEnvironment allowlist */
                                if (options.permit_user_env_allowlist == NULL ||
                                    match_pattern_list(ocp,
                                    options.permit_user_env_allowlist, 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/%s/environment",
                    pw->pw_dir, _PATH_SSH_USER_DIR);
                read_environment_file(&env, &envsize, buf,
                    options.permit_user_env_allowlist);
        }

#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_DENYLIST  "SSH_AUTH_INFO*,SSH_CONNECTION*"
                p = fetch_pam_child_environment();
                copy_environment_denylist(p, &env, &envsize,
                    PAM_ENV_DENYLIST);
                free_pam_environment(p);

                p = fetch_pam_environment();
                copy_environment_denylist(p, &env, &envsize,
                    PAM_ENV_DENYLIST);
                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);
                free(cp);
        }

        /* 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 = NULL, *user_rc = NULL;
        int do_xauth;
        struct stat st;

        do_xauth =
            s->display != NULL && s->auth_proto != NULL && s->auth_data != NULL;
        xasprintf(&user_rc, "%s/%s", s->pw->pw_dir, _PATH_SSH_USER_RC);

        /* 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(user_rc, &st) >= 0) {
                if (xasprintf(&cmd, "%s -c '%s %s'", shell, _PATH_BSHELL,
                    user_rc) == -1)
                        fatal_f("xasprintf: %s", strerror(errno));
                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",
                            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);
                }
                if (xasprintf(&cmd, "%s -q -", options.xauth_location) == -1)
                        fatal_f("xasprintf: %s", strerror(errno));
                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);
                }
        }
        free(cmd);
        free(user_rc);
}

static void
do_nologin(struct passwd *pw)
{
        FILE *f = NULL;
        const char *nl;
        char buf[1024], *def_nl = _PATH_NOLOGIN;
        struct stat sb;

#ifdef HAVE_LOGIN_CAP
        if (login_getcapbool(lc, "ignorenologin", 0) || pw->pw_uid == 0)
                return;
        nl = login_getcapstr(lc, "nologin", def_nl, def_nl);
#else
        if (pw->pw_uid == 0)
                return;
        nl = def_nl;
#endif
        if (stat(nl, &sb) == -1)
                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_f("checking '%s'", component);

                if (stat(component, &st) != 0)
                        fatal_f("stat(\"%s\"): %s",
                            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_f("chdir(/) after chroot: %s", 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_SETENV|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 log in 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();

        /* Stop directing logs to a high-numbered fd before we close it */
        log_redirect_stderr_to(NULL);

        /*
         * 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 keys from memory */
        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) == -1) {
                /* 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 */
        ssh_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_f("session id %d unused", id);
        if (id >= options.max_sessions ||
            id >= sessions_nalloc) {
                fatal_f("insane session id %d (max %d nalloc %d)",
                    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_f("allocate (allocated %d max %d)",
                    sessions_nalloc, options.max_sessions);
                tmp = xrecallocarray(sessions, sessions_nalloc,
                    sessions_nalloc + 1, sizeof(*sessions));
                if (tmp == NULL) {
                        error_f("cannot allocate %d sessions",
                            sessions_nalloc + 1);
                        return NULL;
                }
                sessions = tmp;
                session_unused(sessions_nalloc++);
        }

        if (sessions_first_unused >= sessions_nalloc ||
            sessions_first_unused < 0) {
                fatal_f("insane first_unused %d max %d nalloc %d",
                    sessions_first_unused, options.max_sessions,
                    sessions_nalloc);
        }

        s = &sessions[sessions_first_unused];
        if (s->used)
                fatal_f("session %d already used", 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 "
                    "channel %d pid %ld",
                    s->used,
                    s->next_unused,
                    s->self,
                    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 (!mm_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__);

        /* 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, *type;
        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) == -1)
                                        debug("subsystem: cannot stat %s: %s",
                                            prog, strerror(errno));
                                s->is_subsystem = SUBSYSTEM_EXT;
                                debug("subsystem: exec() %s", cmd);
                        }
                        xasprintf(&type, "session:subsystem:%s",
                            options.subsystem_name[i]);
                        channel_set_xtype(ssh, s->chanid, type);
                        free(type);
                        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__);

        channel_set_xtype(ssh, s->chanid, "session:shell");

        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__);

        channel_set_xtype(ssh, s->chanid, "session:command");

        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) == -1)
                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_fr(r, "parse");
                goto out;
        }
        if ((sig = name2sig(signame)) == -1) {
                error_f("unsupported signal \"%s\"", signame);
                goto out;
        }
        if (s->pid <= 0) {
                error_f("no pid for session %d", s->self);
                goto out;
        }
        if (s->forced || s->is_subsystem) {
                error_f("refusing to send signal %s to %s session",
                    signame, s->forced ? "forced-command" : "subsystem");
                goto out;
        }

        debug_f("signal %s, killpg(%ld, %d)", signame, (long)s->pid, sig);
        temporarily_use_uid(s->pw);
        r = killpg(s->pid, sig);
        restore_uid();
        if (r != 0) {
                error_f("killpg(%ld, %d): %s", (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 ||
            options.disable_forwarding) {
                debug_f("agent forwarding disabled");
                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_f("no session %d req %.100s", c->self, rtype);
                return 0;
        }
        debug_f("session %d req %s", 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_f("no session");
                return;
        }
        if (s->ttyfd == -1)
                return;

        debug_f("session %d release %s", 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) == -1)
                error("close(s->ptymaster/%d): %s",
                    s->ptymaster, strerror(errno));

        /* unlink pty from session */
        s->ttyfd = -1;
}

void
session_pty_cleanup(Session *s)
{
        mm_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_f("x11 channel %d missing", id);
        } else {
                /* Detach X11 listener */
                debug_f("detach x11 channel %d", 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, int force, void *arg)
{
        Session *s;
        u_int i;

        debug3_f("channel %d", id);
        channel_cancel_cleanup(ssh, id);
        if ((s = session_by_x11_channel(id)) == NULL)
                fatal_f("no x11 channel %d", id);
        for (i = 0; s->x11_chanids[i] != -1; i++) {
                debug_f("session %d: closing channel %d",
                    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;
        char *note = NULL;

        if ((c = channel_lookup(ssh, s->chanid)) == NULL)
                fatal_f("session %d: no channel %d", s->self, s->chanid);

        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__);
                xasprintf(&note, "exit %d", WEXITSTATUS(status));
        } 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__);
                xasprintf(&note, "signal %d%s", WTERMSIG(status),
                    WCOREDUMP(status) ? " core dumped" : "");
        } else {
                /* Some weird exit cause.  Just exit. */
                ssh_packet_disconnect(ssh, "wait returned status %04x.",
                    status);
        }

        debug_f("session %d channel %d pid %ld %s", s->self, s->chanid,
            (long)s->pid, note == NULL ? "UNKNOWN" : note);
        free(note);

        /* disconnect channel */
        debug_f("release channel %d", 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 child sessions 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_f("no session for pid %ld", (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, int force, void *arg)
{
        Session *s = session_by_channel(id);
        u_int i;

        if (s == NULL) {
                debug_f("no session for id %d", id);
                return;
        }
        debug_f("channel %d child %ld", id, (long)s->pid);
        if (s->pid != 0) {
                debug_f("channel %d: has child, ttyfd %d", id, s->ttyfd);
                /*
                 * delay detach of session (unless this is a forced close),
                 * but release pty, since the fd's to the child are already
                 * closed
                 */
                if (s->ttyfd != -1)
                        session_pty_cleanup(s);
                if (!force)
                        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 || options.disable_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)) == -1)
                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 (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;
}