2.11BSD#431 - /usr/src/libexec/tcpd/shell_cmd.c

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

Defined functions

Defined variables