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/* $OpenBSD: shell_cmd.c,v 1.2 2002/01/02 20:18:33 deraadt Exp $ */
/*
* shell_cmd() takes a shell command after %<character> substitutions. The
* command is executed by a /bin/sh child process, with standard input,
* standard output and standard error connected to /dev/null.
*
* Diagnostics are reported through syslog(3).
*
* Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
*/
#ifndef lint
#if 0
static char sccsid[] = "@(#) shell_cmd.c 1.5 94/12/28 17:42:44";
#else
static char rcsid[] = "$OpenBSD: shell_cmd.c,v 1.2 2002/01/02 20:18:33 deraadt Exp $";
#endif
#endif
/* System libraries. */
#include <sys/types.h>
#include <sys/param.h>
#include <sys/wait.h>
#include <signal.h>
#include <stdio.h>
#include <syslog.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
/* Local stuff. */
#include "tcpd.h"
/* Forward declarations. */
static void do_child();
/* shell_cmd - execute shell command */
void shell_cmd(command)
char *command;
{
pid_t child_pid;
pid_t wait_pid;
/*
* Most of the work is done within the child process, to minimize the
* risk of damage to the parent.
*/
switch (child_pid = fork()) {
case -1: /* error */
tcpd_warn("cannot fork: %m");
break;
case 00: /* child */
do_child(command);
/* NOTREACHED */
default: /* parent */
while ((wait_pid = wait((int *) 0)) != -1 && wait_pid != child_pid)
/* void */ ;
}
}
/* do_child - exec command with { stdin, stdout, stderr } to /dev/null */
static void do_child(command)
char *command;
{
char *error;
int tmp_fd;
/*
* Systems with POSIX sessions may send a SIGHUP to grandchildren if the
* child exits first. This is sick, sessions were invented for terminals.
*/
signal(SIGHUP, SIG_IGN);
/* Set up new stdin, stdout, stderr, and exec the shell command. */
for (tmp_fd = 0; tmp_fd < 3; tmp_fd++)
(void) close(tmp_fd);
if (open("/dev/null", O_RDWR) != 0) {
error = "open /dev/null: %m";
} else if (dup(0) != 1 || dup(0) != 2) {
error = "dup: %m";
} else {
(void) execl("/bin/sh", "sh", "-c", command, (char *) 0);
error = "execl /bin/sh: %m";
}
/* Something went wrong. We MUST terminate the child process. */
tcpd_warn(error);
_exit(0);
}
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