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 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 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