/*	$NetBSD: system.c,v 1.28 2022/03/14 22:14:19 riastradh Exp $	*/

/*
 * Copyright (c) 1988, 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/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
#if 0
static char sccsid[] = "@(#)system.c	8.1 (Berkeley) 6/4/93";
#else
__RCSID("$NetBSD: system.c,v 1.28 2022/03/14 22:14:19 riastradh Exp $");
#endif
#endif /* LIBC_SCCS and not lint */

#include "namespace.h"
#include <sys/types.h>
#include <sys/wait.h>
#include <errno.h>
#include <signal.h>
#include <stdlib.h>
#include <unistd.h>
#include <paths.h>
#include <spawn.h>

#include "env.h"

int
system(const char *command)
{
	pid_t pid;
	struct sigaction intsa, quitsa, sa;
	sigset_t nmask, omask, sigdefault;
	int pstat;
	const char *argp[] = {"sh", "-c", "--", command, NULL};
	posix_spawnattr_t attr;
	int error;

	/*
	 * ISO/IEC 9899:1999 in 7.20.4.6 describes this special case.
	 * We need to check availability of a command interpreter.
	 */
	if (command == NULL) {
		if (access(_PATH_BSHELL, X_OK) == 0)
			return 1;
		return 0;
	}

	sa.sa_handler = SIG_IGN;
	sigemptyset(&sa.sa_mask);
	sa.sa_flags = 0;

	if (sigaction(SIGINT, &sa, &intsa) == -1)
		return -1;
	if (sigaction(SIGQUIT, &sa, &quitsa) == -1) {
		sigaction(SIGINT, &intsa, NULL);
		return -1;
	}

	sigemptyset(&nmask);
	sigaddset(&nmask, SIGCHLD);
	if (sigprocmask(SIG_BLOCK, &nmask, &omask) == -1) {
		sigaction(SIGINT, &intsa, NULL);
		sigaction(SIGQUIT, &quitsa, NULL);
		return -1;
	}

	/*
	 * We arrange to inherit all signal handlers from the caller by
	 * default, except possibly SIGINT and SIGQUIT.  These we have
	 * overridden internally for system(3) to be SIG_IGN.
	 *
	 * - If the caller had SIGINT or SIGQUIT at SIG_IGN, then we
	 *   inherit them as is -- caller had SIG_IGN, child will too.
	 *
	 * - Otherwise, they are SIG_DFL or a signal handler, and we
	 *   must reset them to SIG_DFL in the child, rather than
	 *   SIG_IGN in system(3) in the parent, by including them in
	 *   the sigdefault set.
	 */
	sigemptyset(&sigdefault);
	if (intsa.sa_handler != SIG_IGN)
		sigaddset(&sigdefault, SIGINT);
	if (quitsa.sa_handler != SIG_IGN)
		sigaddset(&sigdefault, SIGQUIT);

	posix_spawnattr_init(&attr);
	posix_spawnattr_setsigdefault(&attr, &sigdefault);
	posix_spawnattr_setsigmask(&attr, &omask);
	posix_spawnattr_setflags(&attr,
	    POSIX_SPAWN_SETSIGDEF|POSIX_SPAWN_SETSIGMASK);
	(void)__readlockenv();
	error = posix_spawn(&pid, _PATH_BSHELL, NULL, &attr, __UNCONST(argp),
	    environ);
	(void)__unlockenv();
	posix_spawnattr_destroy(&attr);

	if (error) {
		errno = error;
		pstat = -1;
		goto out;
	}

	while (waitpid(pid, &pstat, 0) == -1) {
		if (errno != EINTR) {
			pstat = -1;
			break;
		}
	}

out:	sigaction(SIGINT, &intsa, NULL);
	sigaction(SIGQUIT, &quitsa, NULL);
	(void)sigprocmask(SIG_SETMASK, &omask, NULL);

	return (pstat);
}