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script is two processes.  the main io-loop process can be locked down with
tame "stdio" since all it does is move data back and forth, while the master
process needs "stdio ioctl" to use TCSAFLUSH at the very end.  TCSAFLUSH is
included in the kernel's rather restrictive ioctl feature lists made
available with the "ioctl" ability.

/*	$OpenBSD: script.c,v 1.28 2015/10/03 02:14:51 deraadt Exp $	*/
/*	$NetBSD: script.c,v 1.3 1994/12/21 08:55:43 jtc Exp $	*/

/*
 * Copyright (c) 2001 Theo de Raadt
 * 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.
 */

/*
 * Copyright (c) 1980, 1992, 1993
 *	The Regents of the University of California.  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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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 <sys/types.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/time.h>

#include <errno.h>
#include <fcntl.h>
#include <paths.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <termios.h>
#include <unistd.h>

#include <util.h>
#include <err.h>

FILE	*fscript;
int	master, slave;
volatile sig_atomic_t child;
pid_t	subchild;
char	*fname;

volatile sig_atomic_t dead;
volatile sig_atomic_t sigdeadstatus;
volatile sig_atomic_t flush;

struct	termios tt;

__dead void done(int);
void dooutput(void);
void doshell(void);
void fail(void);
void finish(int);
void scriptflush(int);
void handlesigwinch(int);

int
main(int argc, char *argv[])
{
	extern char *__progname;
	struct sigaction sa;
	struct termios rtt;
	struct winsize win;
	char ibuf[BUFSIZ];
	ssize_t cc, off;
	int aflg, ch;

	aflg = 0;
	while ((ch = getopt(argc, argv, "a")) != -1)
		switch(ch) {
		case 'a':
			aflg = 1;
			break;
		default:
			fprintf(stderr, "usage: %s [-a] [file]\n", __progname);
			exit(1);
		}
	argc -= optind;
	argv += optind;

	if (argc > 0)
		fname = argv[0];
	else
		fname = "typescript";

	if ((fscript = fopen(fname, aflg ? "a" : "w")) == NULL)
		err(1, "%s", fname);

	(void)tcgetattr(STDIN_FILENO, &tt);
	(void)ioctl(STDIN_FILENO, TIOCGWINSZ, &win);
	if (openpty(&master, &slave, NULL, &tt, &win) == -1)
		err(1, "openpty");

	(void)printf("Script started, output file is %s\n", fname);
	rtt = tt;
	cfmakeraw(&rtt);
	rtt.c_lflag &= ~ECHO;
	(void)tcsetattr(STDIN_FILENO, TCSAFLUSH, &rtt);

	bzero(&sa, sizeof sa);
	sigemptyset(&sa.sa_mask);
	sa.sa_handler = handlesigwinch;
	sa.sa_flags = SA_RESTART;
	(void)sigaction(SIGWINCH, &sa, NULL);

	child = fork();
	if (child < 0) {
		warn("fork");
		fail();
	}
	if (child == 0) {
		subchild = child = fork();
		if (child < 0) {
			warn("fork");
			fail();
		}
		if (child)
			dooutput();
		else
			doshell();
	}

	bzero(&sa, sizeof sa);
	sigemptyset(&sa.sa_mask);
	sa.sa_handler = finish;
	(void)sigaction(SIGCHLD, &sa, NULL);

	if (tame("stdio ioctl", NULL) == -1)
		err(1, "tame");

	(void)fclose(fscript);
	while (1) {
		if (dead)
			break;
		cc = read(STDIN_FILENO, ibuf, BUFSIZ);
		if (cc == -1 && errno == EINTR)
			continue;
		if (cc <= 0)
			break;
		for (off = 0; off < cc; ) {
			ssize_t n = write(master, ibuf + off, cc - off);
			if (n == -1 && errno != EAGAIN)
				break;
			if (n == 0)
				break;	/* skip writing */
			if (n > 0)
				off += n;
		}
	}
	done(sigdeadstatus);
}

/* ARGSUSED */
void
finish(int signo)
{
	int save_errno = errno;
	int status, e = 1;
	pid_t pid;

	while ((pid = wait3(&status, WNOHANG, 0)) > 0) {
		if (pid == (pid_t)child) {
			if (WIFEXITED(status))
				e = WEXITSTATUS(status);
		}
	}
	dead = 1;
	sigdeadstatus = e;
	errno = save_errno;
}

/* ARGSUSED */
void
handlesigwinch(int signo)
{
	int save_errno = errno;
	struct winsize win;
	pid_t pgrp;

	if (ioctl(STDIN_FILENO, TIOCGWINSZ, &win) != -1) {
		ioctl(slave, TIOCSWINSZ, &win);
		if (ioctl(slave, TIOCGPGRP, &pgrp) != -1)
			killpg(pgrp, SIGWINCH);
	}
	errno = save_errno;
}

void
dooutput(void)
{
	struct sigaction sa;
	struct itimerval value;
	sigset_t blkalrm;
	char obuf[BUFSIZ];
	time_t tvec;
	ssize_t outcc = 0, cc, off;

	(void)close(STDIN_FILENO);
	tvec = time(NULL);
	(void)fprintf(fscript, "Script started on %s", ctime(&tvec));

	sigemptyset(&blkalrm);
	sigaddset(&blkalrm, SIGALRM);
	bzero(&sa, sizeof sa);
	sigemptyset(&sa.sa_mask);
	sa.sa_handler = scriptflush;
	(void)sigaction(SIGALRM, &sa, NULL);

	bzero(&sa, sizeof sa);
	sigemptyset(&sa.sa_mask);
	sa.sa_handler = SIG_IGN;
	(void)sigaction(SIGCHLD, &sa, NULL);

	if (tame("stdio", NULL) != 0)
		err(1, "tame");

	value.it_interval.tv_sec = 30;
	value.it_interval.tv_usec = 0;
	value.it_value = value.it_interval;
	(void)setitimer(ITIMER_REAL, &value, NULL);
	for (;;) {
		if (flush) {
			if (outcc) {
				(void)fflush(fscript);
				outcc = 0;
			}
			flush = 0;
		}
		cc = read(master, obuf, sizeof (obuf));
		if (cc == -1 && errno == EINTR)
			continue;
		if (cc <= 0)
			break;
		sigprocmask(SIG_BLOCK, &blkalrm, NULL);
		for (off = 0; off < cc; ) {
			ssize_t n = write(STDOUT_FILENO, obuf + off, cc - off);
			if (n == -1 && errno != EAGAIN)
				break;
			if (n == 0)
				break;	/* skip writing */
			if (n > 0)
				off += n;
		}
		(void)fwrite(obuf, 1, cc, fscript);
		outcc += cc;
		sigprocmask(SIG_UNBLOCK, &blkalrm, NULL);
	}
	done(0);
}

/* ARGSUSED */
void
scriptflush(int signo)
{
	flush = 1;
}

void
doshell(void)
{
	char *shell;

	shell = getenv("SHELL");
	if (shell == NULL)
		shell = _PATH_BSHELL;

	(void)close(master);
	(void)fclose(fscript);
	login_tty(slave);
	execl(shell, shell, "-i", (char *)NULL);
	warn("%s", shell);
	fail();
}

void
fail(void)
{

	(void)kill(0, SIGTERM);
	done(1);
}

void
done(int eval)
{
	time_t tvec;

	if (subchild) {
		tvec = time(NULL);
		(void)fprintf(fscript,"\nScript done on %s", ctime(&tvec));
		(void)fclose(fscript);
		(void)close(master);
	} else {
		(void)tcsetattr(STDIN_FILENO, TCSAFLUSH, &tt);
		(void)printf("Script done, output file is %s\n", fname);
	}
	exit(eval);
}