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 <signal.h> 20 #include <stdio.h> 21 #include <unistd.h> 22 #include <syslog.h> 23 #include <string.h> 24 25 extern void exit(); 26 27 /* Local stuff. */ 28 29 #include "tcpd.h" 30 31 /* Forward declarations. */ 32 33 static void do_child(); 34 35 /* shell_cmd - execute shell command */ 36 37 void shell_cmd(command) 38 char *command; 39 { 40 int child_pid; 41 int wait_pid; 42 43 /* 44 * Most of the work is done within the child process, to minimize the 45 * risk of damage to the parent. 46 */ 47 48 switch (child_pid = fork()) { 49 case -1: /* error */ 50 tcpd_warn("cannot fork: %m"); 51 break; 52 case 00: /* child */ 53 do_child(command); 54 /* NOTREACHED */ 55 default: /* parent */ 56 while ((wait_pid = wait((int *) 0)) != -1 && wait_pid != child_pid) 57 /* void */ ; 58 } 59 } 60 61 /* do_child - exec command with { stdin, stdout, stderr } to /dev/null */ 62 63 static void do_child(command) 64 char *command; 65 { 66 char *error; 67 int tmp_fd; 68 69 /* 70 * Systems with POSIX sessions may send a SIGHUP to grandchildren if the 71 * child exits first. This is sick, sessions were invented for terminals. 72 */ 73 74 signal(SIGHUP, SIG_IGN); 75 76 /* Set up new stdin, stdout, stderr, and exec the shell command. */ 77 78 for (tmp_fd = 0; tmp_fd < 3; tmp_fd++) 79 (void) close(tmp_fd); 80 if (open("/dev/null", 2) != 0) { 81 error = "open /dev/null: %m"; 82 } else if (dup(0) != 1 || dup(0) != 2) { 83 error = "dup: %m"; 84 } else { 85 (void) execl("/bin/sh", "sh", "-c", command, (char *) 0); 86 error = "execl /bin/sh: %m"; 87 } 88 89 /* Something went wrong. We MUST terminate the child process. */ 90 91 tcpd_warn(error); 92 _exit(0); 93 } 94