shell_cmd.c revision 1.2 
1/*	$NetBSD: shell_cmd.c,v 1.2 1997/10/09 21:20:48 christos Exp $	*/
2
3 /*
4  * shell_cmd() takes a shell command after %<character> substitutions. The
5  * command is executed by a /bin/sh child process, with standard input,
6  * standard output and standard error connected to /dev/null.
7  *
8  * Diagnostics are reported through syslog(3).
9  *
10  * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
11  */
12
13#include <sys/cdefs.h>
14#ifndef lint
15#if 0
16static char sccsid[] = "@(#) shell_cmd.c 1.5 94/12/28 17:42:44";
17#else
18__RCSID("$NetBSD: shell_cmd.c,v 1.2 1997/10/09 21:20:48 christos Exp $");
19#endif
20#endif
21
22/* System libraries. */
23
24#include <sys/types.h>
25#include <sys/param.h>
26#include <sys/wait.h>
27#include <signal.h>
28#include <stdio.h>
29#include <stdlib.h>
30#include <unistd.h>
31#include <fcntl.h>
32#include <syslog.h>
33#include <string.h>
34
35/* Local stuff. */
36
37#include "tcpd.h"
38
39/* Forward declarations. */
40
41static void do_child __P((char *));
42
43/* shell_cmd - execute shell command */
44
45void    shell_cmd(command)
46char   *command;
47{
48    int     child_pid;
49    int     wait_pid;
50
51    /*
52     * Most of the work is done within the child process, to minimize the
53     * risk of damage to the parent.
54     */
55
56    switch (child_pid = fork()) {
57    case -1:					/* error */
58	tcpd_warn("cannot fork: %m");
59	break;
60    case 00:					/* child */
61	do_child(command);
62	/* NOTREACHED */
63    default:					/* parent */
64	while ((wait_pid = wait((int *) 0)) != -1 && wait_pid != child_pid)
65	     /* void */ ;
66    }
67}
68
69/* do_child - exec command with { stdin, stdout, stderr } to /dev/null */
70
71static void do_child(command)
72char   *command;
73{
74    char   *error;
75    int     tmp_fd;
76
77    /*
78     * Systems with POSIX sessions may send a SIGHUP to grandchildren if the
79     * child exits first. This is sick, sessions were invented for terminals.
80     */
81
82    signal(SIGHUP, SIG_IGN);
83
84    /* Set up new stdin, stdout, stderr, and exec the shell command. */
85
86    for (tmp_fd = 0; tmp_fd < 3; tmp_fd++)
87	(void) close(tmp_fd);
88    if (open("/dev/null", 2) != 0) {
89	error = "open /dev/null: %m";
90    } else if (dup(0) != 1 || dup(0) != 2) {
91	error = "dup: %m";
92    } else {
93	(void) execl("/bin/sh", "sh", "-c", command, (char *) 0);
94	error = "execl /bin/sh: %m";
95    }
96
97    /* Something went wrong. We MUST terminate the child process. */
98
99    tcpd_warn(error);
100    _exit(0);
101}
102