1 /*
2 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
3 * Use is subject to license terms.
4 */
5
6 /*
7 * shell_cmd() takes a shell command after %<character> substitutions. The
8 * command is executed by a /bin/sh child process, with standard input,
9 * standard output and standard error connected to /dev/null.
10 *
11 * Diagnostics are reported through syslog(3).
12 *
13 * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
14 */
15
16 #ifndef lint
17 static char sccsid[] = "@(#) shell_cmd.c 1.5 94/12/28 17:42:44";
18 #endif
19
20 /* System libraries. */
21
22 #include <sys/types.h>
23 #include <sys/param.h>
24 #include <signal.h>
25 #include <stdio.h>
26 #include <stdlib.h>
27 #include <unistd.h>
28 #include <wait.h>
29 #include <fcntl.h>
30 #include <syslog.h>
31 #include <string.h>
32
33 extern void exit();
34
35 /* Local stuff. */
36
37 #include "tcpd.h"
38
39 /* Forward declarations. */
40
41 static void do_child();
42
43 /* shell_cmd - execute shell command */
44
shell_cmd(command)45 void shell_cmd(command)
46 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
do_child(command)71 static void do_child(command)
72 char *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