1 /*
2 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
3 * Use is subject to license terms.
4 */
5
6 #pragma ident "%Z%%M% %I% %E% SMI"
7
8 /*
9 * shell_cmd() takes a shell command after %<character> substitutions. The
10 * command is executed by a /bin/sh child process, with standard input,
11 * standard output and standard error connected to /dev/null.
12 *
13 * Diagnostics are reported through syslog(3).
14 *
15 * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
16 */
17
18 #ifndef lint
19 static char sccsid[] = "@(#) shell_cmd.c 1.5 94/12/28 17:42:44";
20 #endif
21
22 /* System libraries. */
23
24 #include <sys/types.h>
25 #include <sys/param.h>
26 #include <signal.h>
27 #include <stdio.h>
28 #include <stdlib.h>
29 #include <unistd.h>
30 #include <wait.h>
31 #include <fcntl.h>
32 #include <syslog.h>
33 #include <string.h>
34
35 extern void exit();
36
37 /* Local stuff. */
38
39 #include "tcpd.h"
40
41 /* Forward declarations. */
42
43 static void do_child();
44
45 /* shell_cmd - execute shell command */
46
shell_cmd(command)47 void shell_cmd(command)
48 char *command;
49 {
50 int child_pid;
51 int wait_pid;
52
53 /*
54 * Most of the work is done within the child process, to minimize the
55 * risk of damage to the parent.
56 */
57
58 switch (child_pid = fork()) {
59 case -1: /* error */
60 tcpd_warn("cannot fork: %m");
61 break;
62 case 00: /* child */
63 do_child(command);
64 /* NOTREACHED */
65 default: /* parent */
66 while ((wait_pid = wait((int *) 0)) != -1 && wait_pid != child_pid)
67 /* void */ ;
68 }
69 }
70
71 /* do_child - exec command with { stdin, stdout, stderr } to /dev/null */
72
do_child(command)73 static void do_child(command)
74 char *command;
75 {
76 char *error;
77 int tmp_fd;
78
79 /*
80 * Systems with POSIX sessions may send a SIGHUP to grandchildren if the
81 * child exits first. This is sick, sessions were invented for terminals.
82 */
83
84 signal(SIGHUP, SIG_IGN);
85
86 /* Set up new stdin, stdout, stderr, and exec the shell command. */
87
88 for (tmp_fd = 0; tmp_fd < 3; tmp_fd++)
89 (void) close(tmp_fd);
90 if (open("/dev/null", 2) != 0) {
91 error = "open /dev/null: %m";
92 } else if (dup(0) != 1 || dup(0) != 2) {
93 error = "dup: %m";
94 } else {
95 (void) execl("/bin/sh", "sh", "-c", command, (char *) 0);
96 error = "execl /bin/sh: %m";
97 }
98
99 /* Something went wrong. We MUST terminate the child process. */
100
101 tcpd_warn(error);
102 _exit(0);
103 }
104