Encrypted Filespace with EncFS

From NAS-Central Buffalo - The Linkstation Wiki
Revision as of 17:50, 21 August 2006 by 209.94.50.66 (Talk)

Jump to: navigation, search

This article based on work done by Ramuk and Andre on Linkstationwiki.org

PowerPC Only : This method only works for the powerpc-hdhlan and powerpc-hdhglan LinkStations.

Contents

Abstract

This article is for people that want to add an encrypted filespace to their Link Station. We will use the powerpc-hdhglan Link Station for our example. EncFS is used to do this. This probably will work on any PPC link station. It may work on a MIPS Link station but you'll have to compile the FUSE module yourself somehow.

Encryption Type : EncFS was chosen because of it's relative ease and speed of use. Loop-AES could be used as well, a good comparison is here: Encrypt filesystems with EncFS and Loop-AES , A client side encryption system like Truecrypt could be used from a windows client. The TeraStation people have a nice tutorial on using TrueCrypt

Prerequisites

This article assumes that you have installed FreeLink or OpenLink. You also will need to upgrade to a 2.6 Kernel. Use these instructions: Upgrade to the 2.6-kernel (ppc only)

Method

Install the FUSE module

  • I used the binaries from André's site:
wget  http://hvkls.dyndns.org/downloads/fuse_2.5.3-binaries-ppc.tar.gz 
tar -C / -xvzf fuse_2.5.3-binaries-ppc.tar.gz

Install EncFS

FreeLink

apt-get install encfs

OpenLink

wget http://downloads.linkstationwiki.net/packages/ppc/rlog-1.3.7_ppc.tar.gz
tar -C / xzvf rlog-1.3.7_ppc.tar.gz
wget http://downloads.linkstationwiki.net/packages/ppc/encfs-1.3.1_ppc.tar.gz
tar -C / xzvf encfs-1.3.1_ppc.tar.gz

Create an encrypted partition

  • place it in a shared directory if you want to access it as a file share using Samba.
encfs --public /mnt/locked /mnt/share/locked

/mnt/share here is a shared directory. /mnt/locked is where the encrypted bits will be stored and /mnt/share/locked is where the (de)crypted space will be mounted to. You will be prompted for the type of encryption that you want and for password creation. Look here for more details on using EncFS.

Access Permissions

  • You will have to chmod the created directory so everyone can access it
chmod og+rwx /mnt/share/locked/

Just beware that it takes a long time for files to be encrypted when you copy or move them into this directory, however you can use this directory like any other shared space with Samba. After files are placed in there they can be accessed pretty fast.

Unmount

  • You can unmount the partition at any time in which case the encrypted directory will end up appearing blank.
fusermount -u /mnt/share/locked

Remount

  • And remount it when you need it the same way you created it, this time you will just be prompted for the password you used when you created it.
encfs --public /mnt/locked /mnt/share/locked

What's the point?

Slow to Write
Bar.png
I've been using this solution for awhile now, it's slow to ENcode data but faster to DEcode data. So that saving (ENcoding) a file over 50MB to an encrypted share over samba can be somewhat buggy. So I save files to an unencrypted share and then move them over to the encrypted filespace from the command line. Reading (DEcoding) the files works fine for me for files that are even 1-2GB in size - Ramuk 22:44, 15 August 2006 (EDT)


What's the point of all this? Well you can create an encrypted file space that once mounted functions completely transparently as a shared directory. Once it is unmounted, either manually or automatically (when the system is shut down) the data will only exist in an encrypted form in the encrypted directory you specified. In this example in /mnt/locked , if your linkstation is stolen or lost, as soon as it is unplugged the data will no longer be accessible without the password. Even if someone cracks open the device and takes the hard drive out all they will be able to get is encrypted gibberish in that directory. However they would be able to figure out how MANY files you had in that directory and the SIZE of each file, as EncFS encypts each file individually, not the block device.

Keyfile and Security

The keyfile is stored in the encrypted directory /mnt/locked/.encfs5 you could store it externally (on a USB Key Drive for example) and move it to the proper location if you wanted even more security.


Shell Scripts

#!/bin/bash
# mountcrypt.sh
# You can change these lines to reflect the locations on your system
# or add whatever user comments you want

   usage(){
   echo "mountcrypt [m|mount|u|unmount]"
   echo " either mounts or unmounts our encrypted shared file space to /mnt/share/locked"
   }

   if [ -z $1 ]
   then
           usage
           exit
   fi

# You will have to change the directories to reflect what is on your
# system here

   case "$1" in
           "m" | "mount" )
                   /usr/bin/encfs --public /mnt/locked /mnt/share/locked
                   echo "Encrypted filesystem now mounted"
                   ;;
           "u" | "unmount" )
                   /usr/bin/fusermount -u /mnt/share/locked
                   echo "Encrypted filesystem has been unmounted"
                   ;;
           * )
                   usage
                   ;;
   esac

Bonnie++ I/O Speeds

Here is a speed comparision using Bonnie++ as a diagnostic tool

Linkstation Hard Drive (/dev/hda3)  UNENCRYPTED

Version  1.03       ------Sequential Output------ --Sequential Input- --Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
linkstation    300M  1946  95 18425  85 14093  63  2166  98 37001  57 154.2   3

                    ------Sequential Create------ --------Random Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
                 16   163  97 +++++ +++  7736  97   165  97 +++++ +++   850  96

EncFS mounted partition (encfs) ENCRYPTED

Version  1.03       ------Sequential Output------ --Sequential Input- --Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
encfs          300M  1042  49  2088   5  1430   5  1388  63  3619   5  74.0   1

                    ------Sequential Create------ --------Random Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
                 16   112   2  1311   9   704   8   112   2  1568  11   355   4

References