Difference between revisions of "EncFS"

Revision as of 05:25, 10 June 2011

EncFS is a userspace stackable cryptographic file-system similar to eCryptFS, and aims to secure data with the minimum hassle. It uses FUSE to mount an encrypted directory onto another directory specified by the user. It does not use a loopback system like some other comparable systems such as TrueCrypt and dm-crypt.

EncFS is definetely the simplest software if you want to try disk encryption on Linux.

This has a number of advantages and disadvantages compared to these systems. Firstly, it does not require any root privileges to implement; any user can create a repository of encrypted files. Secondly, one does not need to create a single file and create a file-system within that; it works on existing file-system without modifications.

This does create a few disadvantages, though; because the encrypted files are not stored in their own file, someone who obtains access to the system can still see the underlying directory structure, the number of files, their sizes and when they were modified. They cannot see the contents, however.

This particular method of securing data is obviously not perfect, but there are situations in which it is useful.

Comparison to eCryptFS

eCryptFS is implemented in kernelspace and therefore little bit harder to configure. You have to remember various encryption options (used cyphers, key type, etc...), in EncFS this is not the case, because EncFS is storing these informations in it's signature so you don't have to remember anything (except the passphrase :-). But it's authors claims that eCryptFS is faster because there's no overhead caused by context switching (between kernel and userspace).

Installation

Install the Template:Package Official package using pacman:

# pacman -S encfs

Usage

To create a secured repository, type:

$ encfs ~/.DIRNAME ~/DIRNAME

This will be followed by a prompt about whether you want to go with the default (paranoid options) or expert configuration. The latter allows specifying algorithms and other options. The former is a fairly secure default setup. After entering a key for the encryption, the encoded file-system will be created and mounted. The encoded files are stored, in this example, at Template:Filename, and their unencrypted versions in Template:Filename.

To unmount the file-system, type:

$ fusermount -u ~/DIRNAME

To remount the file-system, issue the first command, and enter the key used to encode it. Once this has been entered, the file-system will be mounted again.

User friendly mounting

Mount using CryptKeeper trayicon

Quite simple app, just install from AUR and add to your X session:

• http://aur.archlinux.org/packages.php?ID=12743

Mount at login using pam_encfs

Pam module

• http://aur.archlinux.org/packages.php?ID=2759
• http://pam-encfs.googlecode.com/svn/trunk/README
• http://pam-encfs.googlecode.com/svn/trunk/pam_encfs.conf
• https://wiki.edubuntu.org/EncryptedHomeFolder
• http://code.google.com/p/pam-encfs/

Single password

Note that if you will use same password (eg.: using try_first_pass or use_first_pass) for login and encfs (so encfs will mount during your login) then you should use SHA password hashes (Preferably SHA512 with some huge numer of rounds) and (which is most important) SECURE PASSWORD! because hash of your password is probably stored in unencrypted form in /etc/shadow and it can be cracked in order to get your encfs password (because it's same as your regular unix login password).

/etc/pam.d/

Note that when you are using try_first_pass parameter to pam_unix.so then you'll have to set EncFS to use same password as you are using to login (or vice-versa) and you'll be entering just single password. Without this parameter you'll need to enter two passwords.

login

I am personally not using pam_encfs in login, but only in GDM because i don't expect VC to be user friendly. Anyway you will probably need to debug configuration for login and then migrate it to gdm, because it's faster and easier to debug on console.

#%PAM-1.0

auth		required	pam_securetty.so
auth		requisite	pam_nologin.so
auth		sufficient	pam_encfs.so
auth		required	pam_unix.so nullok try_first_pass
#auth		required	pam_unix.so nullok
auth		required	pam_tally.so onerr=succeed file=/var/log/faillog
# use this to lockout accounts for 10 minutes after 3 failed attempts
#auth		required	pam_tally.so deny=2 unlock_time=600 onerr=succeed file=/var/log/faillog
account		required	pam_access.so
account		required	pam_time.so
account		required	pam_unix.so
#password	required	pam_cracklib.so difok=2 minlen=8 dcredit=2 ocredit=2 retry=3
#password	required	pam_unix.so md5 shadow use_authtok
session		required	pam_unix.so
session		required	pam_env.so
session		required	pam_motd.so
session		required	pam_limits.so
session		optional	pam_mail.so dir=/var/spool/mail standard
session		optional	pam_lastlog.so
session		optional	pam_loginuid.so
-session	optional	pam_ck_connector.so nox11
#Automatic unmount (optional):
#session	required	pam_encfs.so

Note that automatic unmout will process even when there is another session. eg.: logout on VC can unmout encfs mounted by GDM session that is still active (that's why i don't use pam_encfs on console).

gdm

#%PAM-1.0
auth            requisite       pam_nologin.so
auth            required        pam_env.so
auth            sufficient      pam_encfs.so
auth            required        pam_unix.so try_first_pass
auth            optional        pam_gnome_keyring.so
account         required        pam_unix.so
session         required        pam_limits.so
session         required        pam_unix.so
session         optional        pam_gnome_keyring.so auto_start
password        required        pam_unix.so
session         required        pam_encfs.so

Mount at Gnome startup using gnome-encfs

• http://aur.archlinux.org/packages.php?ID=37097

Mount when USB drive with EncFS folders is inserted using fsniper

Simple method to automount (asking for password) encfs when USB drive with EncFS one or more folders in root is inserted. We'll use fsniper (filesystem watching daemon using inotify) and git (for askpass binary).

• http://aur.archlinux.org/packages.php?ID=16677
• https://github.com/Harvie/Programs/tree/master/bash/encfs/automount (latest version of files used in following HOWTO)

HOWTO

1. (you need USB automount working for this - like thunar or nautilus does)
2. make encrypted folder on your drive, eg.: encfs /media/USB/somename /media/USB/somename.plain (and then unmount everything)
3. install fsniper and git from aur
4. configure fsniper:

# ~/.config/fsniper/config
# You can get fsniper at http://code.l3ib.org/?p=fsniper.git

watch {
	/etc/ {
		mtab {
			# %% is replaced with the filename of the new file
			handler = encfs-automount.sh %%;
		}
	}
}

1. install helper script:

#!/bin/sh
#	~/.config/fsniper/scripts/encfs-automount.sh
# Quick & dirty script for automounting EncFS USB drives
# TODO:
#  - Unmounting!!!
#
ASKPASS="/usr/lib/git-core/git-gui--askpass"

lock=/tmp/fsniper_encfs.lock
lpid=$(cat "$lock" 2>/dev/null) &&
ps "$lpid" | grep "$lpid" >/dev/null && {
	echo "Another instance of fsniper_encfs is running"
	exit;
}
echo $BASHPID > "$lock";
sleep 2;

echo
echo ==== EncFS automount script for fsniper ====

list_mounts() {
	cat /proc/mounts | cut -d ' ' -f 2
}

list_mounts | while read mount; do
	config="$mount"'/*/.encfs*';
	echo Looking for "$config"
	config="$(echo $config)"
	[ -r "$config" ] && {
		cyphertext="$(dirname "$config")";
		plaintext="$cyphertext".plain
		echo Found config: "$config";
		echo Trying to mount: "$cyphertext to $plaintext";
		list_mounts | grep "$plaintext" >/dev/null && {
			echo Already mounted: "$plaintext"
		} || {
			echo WOOHOO Will mount "$cyphertext to $plaintext"
			"$ASKPASS" "EncFS $cyphertext to $plaintext" | encfs --stdinpass "$cyphertext" "$plaintext"
		}
	}
done
echo

rm "$lock" 2>/dev/null

1. Make sure that /usr/lib/git-core/git-gui--askpass is working for you (that's why you need git package - but you can adjust the helper script)
2. try fsniper --log-to-stdout in terminal (askpass should appear when USB drive is inserted)
3. add fsniper --daemon to your session
4. don't forget to unmount encfs before removing drive