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