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 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 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