* data dynamically allocated: instead, the backend handle is just
 * a null pointer and ignored everywhere.
 */

#define _XOPEN_SOURCE
#define _XOPEN_SOURCE_EXTENDED
#define _GNU_SOURCE
#include <features.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <fcntl.h>
#include <termios.h>
#include <grp.h>
#include <utmp.h>
#include <pwd.h>
#include <time.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/ioctl.h>
#include <errno.h>

#include "putty.h"

#ifndef FALSE

#endif

static Config pty_cfg;
static int pty_master_fd;
static void *pty_frontend;
static char pty_name[FILENAME_MAX];
static int pty_signal_pipe[2];
static int pty_stamped_utmp = 0;
static int pty_child_pid;
static int pty_utmp_helper_pid, pty_utmp_helper_pipe;
static int pty_term_width, pty_term_height;
static int pty_child_dead, pty_finished;
static int pty_exit_code;
#ifndef OMIT_UTMP
static struct utmp utmp_entry;
#endif
char **pty_argv;
int use_pty_argv = TRUE;

static void pty_close(void);

#ifndef OMIT_UTMP
static int pty_utmp_helper_pid, pty_utmp_helper_pipe;
static int pty_stamped_utmp = 0;
static struct utmp utmp_entry;

static void setup_utmp(char *ttyname, char *location)
{
#ifndef OMIT_UTMP
#ifdef HAVE_LASTLOG
    struct lastlog lastlog_entry;
    FILE *lastlog;
#endif
    struct passwd *pw;
    FILE *wtmp;
    time_t uttime;

	fwrite(&lastlog_entry, 1, sizeof(lastlog_entry), lastlog);
	fclose(lastlog);
    }
#endif

    pty_stamped_utmp = 1;

#endif
}

static void cleanup_utmp(void)
{
#ifndef OMIT_UTMP
    FILE *wtmp;
    time_t uttime;

    if (!pty_stamped_utmp)
	return;

    utmp_entry.ut_type = DEAD_PROCESS;

    utmpname(UTMP_FILE);
    setutent();
    pututline(&utmp_entry);
    endutent();
#endif

    pty_stamped_utmp = 0;	       /* ensure we never double-cleanup */
#endif
}
#endif

static void sigchld_handler(int signum)
{
    write(pty_signal_pipe[1], "x", 1);
}

#ifndef OMIT_UTMP
static void fatal_sig_handler(int signum)
{
    putty_signal(signum, SIG_DFL);
    cleanup_utmp();
    setuid(getuid());
    raise(signum);
}
#endif

static void pty_open_master(void)
{
#ifdef BSD_PTYS
    const char chars1[] = "pqrstuvwxyz";
    const char chars2[] = "0123456789abcdef";
    const char *p1, *p2;

 * also fork off a utmp helper process and communicate with it by
 * means of a pipe; the utmp helper will keep privileges in order
 * to clean up utmp when we exit (i.e. when its end of our pipe
 * closes).
 */
void pty_pre_init(void)
{
#ifndef OMIT_UTMP
    pid_t pid;
    int pipefd[2];
#endif

    /* set the child signal handler straight away; it needs to be set
     * before we ever fork. */
    putty_signal(SIGCHLD, sigchld_handler);
    pty_master_fd = -1;

    if (geteuid() != getuid() || getegid() != getgid()) {

	pty_utmp_helper_pid = pid;
	pty_utmp_helper_pipe = pipefd[1];
    }
#endif

    /* Drop privs. */
    {
	int gid = getgid(), uid = getuid();
#ifndef HAVE_NO_SETRESUID
	int gid = getgid(), uid = getuid();
	int setresgid(gid_t, gid_t, gid_t);
	int setresuid(uid_t, uid_t, uid_t);
	setresgid(gid, gid, gid);
	setresuid(uid, uid, uid);
#else
	setgid(getgid());
	setuid(getuid());

    {
	struct termios attrs;
	tcgetattr(pty_master_fd, &attrs);
	attrs.c_cc[VERASE] = cfg->bksp_is_delete ? '\177' : '\010';
	tcsetattr(pty_master_fd, TCSANOW, &attrs);
    }

#ifndef OMIT_UTMP
    /*
     * Stamp utmp (that is, tell the utmp helper process to do so),
     * or not.
     */
    if (!cfg->stamp_utmp) {
	close(pty_utmp_helper_pipe);   /* just let the child process die */
	pty_utmp_helper_pipe = -1;

		close(pty_utmp_helper_pipe);   /* arrgh, just give up */
		pty_utmp_helper_pipe = -1;
		break;
	    }
	    pos += ret;
	}
    }
#endif

    windowid = get_windowid(pty_frontend);

    /*
     * Fork and execute the command.
     */
    pid = fork();

	dup2(slavefd, 0);
	dup2(slavefd, 1);
	dup2(slavefd, 2);
	setsid();
	ioctl(slavefd, TIOCSCTTY, 1);
	pgrp = getpid();
	tcsetpgrp(slavefd, pgrp);
	setpgrp();
	setpgrp(pgrp, pgrp);
	close(open(pty_name, O_WRONLY, 0));
	setpgrp();
	setpgrp(pgrp, pgrp);
	/* Close everything _else_, for tidiness. */
	for (i = 3; i < 1024; i++)
	    close(i);
	{
	    char term_env_var[10 + sizeof(cfg->termtype)];
	    sprintf(term_env_var, "TERM=%s", cfg->termtype);
	    putenv(term_env_var);

static void pty_close(void)
{
    if (pty_master_fd >= 0) {
	close(pty_master_fd);
	pty_master_fd = -1;
    }
#ifndef OMIT_UTMP
    if (pty_utmp_helper_pipe >= 0) {
	close(pty_utmp_helper_pipe);   /* this causes utmp to be cleaned up */
	pty_utmp_helper_pipe = -1;
    }
#endif
}

/*
 * Called to query the current socket sendability status.
 */
static int pty_sendbuffer(void *handle)
{