#!/bin/bash

usage()

{

  echo

  echo 'This script setups chroot environment for BIND'

  echo 'Usage: setup-named-chroot.sh ROOTDIR <on|off> <config.files>'

}

if ! [ "$#" -eq 3 ]; then

  echo 'Wrong number of arguments'

  usage

  exit 1

fi

ROOTDIR="$1"

CONFIG_FILES="$3"

# Exit if ROOTDIR doesn't exist

if ! [ -d "$ROOTDIR" ]; then

  echo "Root directory $ROOTDIR doesn't exist"

  usage

  exit 1

fi

dev_create()

{

  DEVNAME="$ROOTDIR/dev/$1"

  shift

  if ! [ -e "$DEVNAME" ]; then

    /bin/mknod -m 0664 "$DEVNAME" $@

    /bin/chgrp named "$DEVNAME"

    if [ -x /usr/sbin/selinuxenabled -a -x /sbin/restorecon ]; then

      /usr/sbin/selinuxenabled && /sbin/restorecon "$DEVNAME" > /dev/null || :

    fi

  fi

}

dev_chroot_prep()

{

  dev_create random c 1 8

  dev_create zero   c 1 5

  dev_create null   c 1 3

}

files_comment_filter()

{

  if [ -d "$1" ]; then

    grep -v '^[[:space:]]*#' "$1"/*.files

  else

    grep -v '^[[:space:]]*#' "$1"

  fi

}

mount_chroot_conf()

{

  if [ -n "$ROOTDIR" ]; then

    # Check devices are prepared

    dev_chroot_prep

    files_comment_filter "$CONFIG_FILES" | while read -r all; do

      # Skip nonexistant files

      [ -e "$all" ] || continue

      # If mount source is a file

      if ! [ -d "$all" ]; then

        # mount it only if it is not present in chroot or it is empty

        if ! [ -e "$ROOTDIR$all" ] || [ `stat -c'%s' "$ROOTDIR$all"` -eq 0 ]; then

          touch "$ROOTDIR$all"

          mount --bind "$all" "$ROOTDIR$all"

        fi

      else

        # Mount source is a directory. Mount it only if directory in chroot is

        # empty.

        if [ -e "$all" ] && [ `ls -1A $ROOTDIR$all | wc -l` -eq 0 ]; then

          mount --bind --make-private "$all" "$ROOTDIR$all"

        fi

      fi

    done

  fi

}

umount_chroot_conf()

{

  if [ -n "$ROOTDIR" ]; then

    files_comment_filter "$CONFIG_FILES" | while read -r all; do

      # Check if file is mount target. Do not use /proc/mounts because detecting

      # of modified mounted files can fail.

      if mount | grep -q '.* on '"$ROOTDIR$all"' .*'; then

        umount "$ROOTDIR$all"

        # Remove temporary created files

        [ -f "$all" ] && rm -f "$ROOTDIR$all"

      fi

    done

  fi

}

case "$2" in

  on)

    mount_chroot_conf

    ;;

  off)

    umount_chroot_conf

    ;;

  *)

    echo 'Second argument has to be "on" or "off"'

    usage

    exit 1

esac

exit 0