/*      $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);
}