1 /* $NetBSD: shell_cmd.c,v 1.2 1997/10/09 21:20:48 christos 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 1.2 1997/10/09 21:20:48 christos 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 __P((char *)); 42 43 /* shell_cmd - execute shell command */ 44 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 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