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      1 /*	$NetBSD: system.c,v 1.28 2022/03/14 22:14:19 riastradh Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1988, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. Neither the name of the University nor the names of its contributors
     16  *    may be used to endorse or promote products derived from this software
     17  *    without specific prior written permission.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     29  * SUCH DAMAGE.
     30  */
     31 
     32 #include <sys/cdefs.h>
     33 #if defined(LIBC_SCCS) && !defined(lint)
     34 #if 0
     35 static char sccsid[] = "@(#)system.c	8.1 (Berkeley) 6/4/93";
     36 #else
     37 __RCSID("$NetBSD: system.c,v 1.28 2022/03/14 22:14:19 riastradh Exp $");
     38 #endif
     39 #endif /* LIBC_SCCS and not lint */
     40 
     41 #include "namespace.h"
     42 #include <sys/types.h>
     43 #include <sys/wait.h>
     44 #include <errno.h>
     45 #include <signal.h>
     46 #include <stdlib.h>
     47 #include <unistd.h>
     48 #include <paths.h>
     49 #include <spawn.h>
     50 
     51 #include "env.h"
     52 
     53 int
     54 system(const char *command)
     55 {
     56 	pid_t pid;
     57 	struct sigaction intsa, quitsa, sa;
     58 	sigset_t nmask, omask, sigdefault;
     59 	int pstat;
     60 	const char *argp[] = {"sh", "-c", "--", command, NULL};
     61 	posix_spawnattr_t attr;
     62 	int error;
     63 
     64 	/*
     65 	 * ISO/IEC 9899:1999 in 7.20.4.6 describes this special case.
     66 	 * We need to check availability of a command interpreter.
     67 	 */
     68 	if (command == NULL) {
     69 		if (access(_PATH_BSHELL, X_OK) == 0)
     70 			return 1;
     71 		return 0;
     72 	}
     73 
     74 	sa.sa_handler = SIG_IGN;
     75 	sigemptyset(&sa.sa_mask);
     76 	sa.sa_flags = 0;
     77 
     78 	if (sigaction(SIGINT, &sa, &intsa) == -1)
     79 		return -1;
     80 	if (sigaction(SIGQUIT, &sa, &quitsa) == -1) {
     81 		sigaction(SIGINT, &intsa, NULL);
     82 		return -1;
     83 	}
     84 
     85 	sigemptyset(&nmask);
     86 	sigaddset(&nmask, SIGCHLD);
     87 	if (sigprocmask(SIG_BLOCK, &nmask, &omask) == -1) {
     88 		sigaction(SIGINT, &intsa, NULL);
     89 		sigaction(SIGQUIT, &quitsa, NULL);
     90 		return -1;
     91 	}
     92 
     93 	/*
     94 	 * We arrange to inherit all signal handlers from the caller by
     95 	 * default, except possibly SIGINT and SIGQUIT.  These we have
     96 	 * overridden internally for system(3) to be SIG_IGN.
     97 	 *
     98 	 * - If the caller had SIGINT or SIGQUIT at SIG_IGN, then we
     99 	 *   inherit them as is -- caller had SIG_IGN, child will too.
    100 	 *
    101 	 * - Otherwise, they are SIG_DFL or a signal handler, and we
    102 	 *   must reset them to SIG_DFL in the child, rather than
    103 	 *   SIG_IGN in system(3) in the parent, by including them in
    104 	 *   the sigdefault set.
    105 	 */
    106 	sigemptyset(&sigdefault);
    107 	if (intsa.sa_handler != SIG_IGN)
    108 		sigaddset(&sigdefault, SIGINT);
    109 	if (quitsa.sa_handler != SIG_IGN)
    110 		sigaddset(&sigdefault, SIGQUIT);
    111 
    112 	posix_spawnattr_init(&attr);
    113 	posix_spawnattr_setsigdefault(&attr, &sigdefault);
    114 	posix_spawnattr_setsigmask(&attr, &omask);
    115 	posix_spawnattr_setflags(&attr,
    116 	    POSIX_SPAWN_SETSIGDEF|POSIX_SPAWN_SETSIGMASK);
    117 	(void)__readlockenv();
    118 	error = posix_spawn(&pid, _PATH_BSHELL, NULL, &attr, __UNCONST(argp),
    119 	    environ);
    120 	(void)__unlockenv();
    121 	posix_spawnattr_destroy(&attr);
    122 
    123 	if (error) {
    124 		errno = error;
    125 		pstat = -1;
    126 		goto out;
    127 	}
    128 
    129 	while (waitpid(pid, &pstat, 0) == -1) {
    130 		if (errno != EINTR) {
    131 			pstat = -1;
    132 			break;
    133 		}
    134 	}
    135 
    136 out:	sigaction(SIGINT, &intsa, NULL);
    137 	sigaction(SIGQUIT, &quitsa, NULL);
    138 	(void)sigprocmask(SIG_SETMASK, &omask, NULL);
    139 
    140 	return (pstat);
    141 }
    142