1 /* $NetBSD: shell_cmd.c,v 1.7 2012/03/22 22:59:43 joerg 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
16 static char sccsid[] = "@(#) shell_cmd.c 1.5 94/12/28 17:42:44";
17 #else
18 __RCSID("$NetBSD: shell_cmd.c,v 1.7 2012/03/22 22:59:43 joerg 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
41 static void do_child(char *) __dead;
42
43 /* shell_cmd - execute shell command */
44
45 void
shell_cmd(char * command)46 shell_cmd(char *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
71 static void
do_child(char * command)72 do_child(char *command)
73 {
74 int tmp_fd;
75
76 /*
77 * Systems with POSIX sessions may send a SIGHUP to grandchildren if the
78 * child exits first. This is sick, sessions were invented for terminals.
79 */
80
81 signal(SIGHUP, SIG_IGN);
82
83 /* Set up new stdin, stdout, stderr, and exec the shell command. */
84
85 for (tmp_fd = 0; tmp_fd < 3; tmp_fd++)
86 (void) close(tmp_fd);
87 if (open("/dev/null", 2) != 0) {
88 tcpd_warn("open /dev/null: %m");
89 } else if (dup(0) != 1 || dup(0) != 2) {
90 tcpd_warn("dup: %m");
91 } else {
92 (void) execl("/bin/sh", "sh", "-c", command, (char *) 0);
93 tcpd_warn("execl /bin/sh: %m");
94 }
95
96 /* Something went wrong. We MUST terminate the child process. */
97 _exit(0);
98 }
99