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