Difference between revisions of "TrueCrypt"

Revision as of 20:39, 8 March 2013

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TrueCrypt is a free open source on-the-fly encryption (OTFE) program. Some of its features are:

• Virtual encrypted disks within files that can be mounted as real disks.
• Encryption of an entire hard disk partition or a storage device/medium.
• All encryption algorithms use the LRW mode of operation, which is more secure than CBC mode with predictable initialization vectors for storage encryption.
• "Hidden volumes" within a normal "outer" encrypted volume. A hidden volume can not be distinguished from random data without access to a passphrase and/or keyfile.

For more details on how TrueCrypt compares to other disk encryption solution, see Disk Encryption#Comparison table.

Installation

Type as root in a terminal:

# pacman -S truecrypt

If you use any kernel other than linux install the corresponding kernel module.

If you are using truecrypt to encrypt a virtual filesystem (e.g. a file), the module will be automatically loaded whenever you run the truecrypt command. Add it to the MODULES array in /etc/rc.conf.

If you are using truecrypt to encrypt a physical device (e.g. a hard disk or usb drive), you will likely want to load the module during the boot sequence:

Add the module to /etc/modules-load.d/:

# tee /etc/modules-load.d/truecrypt.conf <<< "truecrypt"

Encrypting a file as a virtual volume

The following instructions will create a file that will act as a virtual filesystem, allowing you to mount it and store files within the encrypted file. This is a convenient way to store sensitive information, such as financial data or passwords, in a single file that can be accessed from Linux, Windows, or Macs.

To create a new truecrypt file interactively, type the following in a terminal:

$ truecrypt -c

Template:Box Note

Follow the instructions, choosing the default values unless you know what you are doing:

Volume type:
 1) Normal
 2) Hidden
Select [1]: 1

Enter file or device path for new volume: /home/user/myEncryptedFile.tc

Enter volume size (bytes - size/sizeK/sizeM/sizeG): 32M

Encryption algorithm:
 1) AES
 2) Blowfish
 3) CAST5
 4) Serpent
 5) Triple DES
 6) Twofish
 7) AES-Twofish
 8) AES-Twofish-Serpent
 9) Serpent-AES
10) Serpent-Twofish-AES
11) Twofish-Serpent
Select [1]: 1

Hash algorithm:
 1) RIPEMD-160
 2) SHA-1
 3) Whirlpool
Select [1]: 1  

Filesystem:
 1) FAT
 2) None
Select [1]: 1

Enter password for new volume '/home/user/myEncryptedFile.tc': *****************************
Re-enter password: *****************************

Enter keyfile path [none]: 

TrueCrypt will now collect random data.
Is your mouse connected directly to computer where TrueCrypt is running? [Y/n]: 
Please move the mouse randomly until the required amount of data is captured...
Mouse data captured: 100%  

Done: 32.00 MB  Speed: 10.76 MB/s  Left: 0:00:00  
Volume created.

[user@host:~] $

You can now mount the new encrypted file to a previously-created directory:

$ truecrypt /home/user/myEncryptedFile.tc /home/user/myEncryptedFileFolder

Note: Truecrypt requires root privileges and as such, running the above command as a user will attempt to use sudo for authentication. To work with files as a regular user, please see the appropriate section below.

Once mounted, you can copy or create new files within the encrypted directory as if it was any normal directory. When you are you ready to re-encrypt the contents and unmount the directory, run:

$ truecrypt -d

Again, this will require administrator privileges through the use of sudo. After running it check if the files that are to be encrypted are indeed no longer in the directory. (might want to try unimportant data first) If they are still there, note that rm doesn't make the data unrecoverable.

For more information about truecrypt in general, run:

$ man truecrypt #Note: as of 1:7.1a-1 dont see a man or info page

Several options can be passed at the command line, making automated access and creation a simple task. The man page is highly recommended reading.

Encrypting a physical volume

If you want to use a keyfile, create one with this command:

 truecrypt --create-keyfile /etc/disk.key

By default both passphrase and key will be needed to unlock the volume.

Create a new volume in the device /dev/sda1:

 truecrypt --volume-type normal -c /dev/sda1

Map the volume to /dev/mapper/truecrypt1:

 truecrypt -N 1 /dev/sda1

If this command does not for you try this to map the volume:

 truecrypt --filesystem=none --slot=1 /dev/sda1

If you want to use another file system than ext3 simply format the disk like you normally would, except use the path /dev/mapper/truecrypt1.

 mkfs.ext3 /dev/mapper/truecrypt1

Mount the volume:

 mount /dev/mapper/truecrypt1 /media/disk

Map and mount a volume:

 truecrypt /dev/sda1 /media/disk

Unmount and unmap a volume:

 truecrypt -d /dev/sda1

Creating a hidden volume

First, create a normal outer volume as described above.

Map the outer volume to /dev/mapper/truecrypt1:

 truecrypt -N 1 /dev/sda1

Create a hidden truecrypt volume in the free space of the outer volume:

 truecrypt --type hidden -c /dev/sda1

You need to use another passphrase and/or keyfile here than the one you used for the outer volume.

Unmap the outer truecrypt volume and map the hidden one:

 truecrypt -d /dev/sda1
 truecrypt -N 1 /dev/sda1

Just use the passphrase you chose for the hidden volume and TrueCrypt will automatically choose it before the outer.

Create a file system on it (if you have not already) and mount it:

 mkfs.ext3 /dev/mapper/truecrypt1
 mount /dev/mapper/truecrypt1 /media/disk

Map and mount the outer volume with the hidden write-protected:

 truecrypt -P /dev/sda1 /media/disk

Mount a special filesystem

Template:Box Note

In my example I want to mount a ntfs-volume, but truecrypt does not use ntfs-3g by default (so there is no write access; checked in version 6.1). The following command works for me:

truecrypt --filesystem=ntfs-3g --mount /file/you/want/to/mount

You may also want to mount ntfs volume without execute flag on all files

truecrypt --filesystem=ntfs-3g --fs-options=users,uid=$(id -u),gid=$(id -g),fmask=0113,dmask=0002

Mount volumes via fstab

First of all, we need to write a script which will handle the way mounting via fstab is done. Place the following in /sbin/mount.truecrypt:

#!/usr/bin/env sh 
DEV="$1"
MNTPT="$2"
OPTIONS=""
TCOPTIONS=""
shift 3
IFS=','
for arg in $*; do
    if [ "${arg}" == "system" ]; then
        TCOPTIONS="${TCOPTIONS}-m=system "
    elif [[ "${arg}" == fs=* ]]; then
        FS=${arg#*=}
        TCOPTIONS="${TCOPTIONS}--filesystem=${FS} "
    else
         OPTIONS="${OPTIONS}${arg},"
    fi
done
truecrypt ${DEV} ${MNTPT} ${TCOPTIONS% *} --fs-options="${OPTIONS%,*}"

Also do not forget to make the file executable:

chmod +x /sbin/mount.truecrypt

Finally, add the device to fstab somewhat like this:

/dev/sdb3 /mnt truecrypt fs=vfat,defaults 0 0

Mount volumes using a systemd service

To use Truecrypt with systemd, it is advised to use truecrypt as decryptor and mapper and fstab to do the mounting of encrypted volumes.

First, create this service Systemd/Services#truecrypt_volume_setup in /usr/lib/systemd/system. Enable it with (assuming your encrypted volume is /dev/sda2):

# systemctl enable truecrypt@dev-sda2.service

Secondly, create a line similar to that one in your fstab (the 2 means your fs will be fscked regularly):

/etc/fstab

/dev/mapper/truecrypt1  /home/          ext4 defaults        0       2

And you should be set.

Mount volumes as a normal user

TrueCrypt needs root privileges to work: this procedure will allow normal users to use it, also giving writing permissions to mounted volumes.

Both methods below require Sudo. Make sure it is configured before proceeding.

Method 1 (Add a truecrypt group)

Create a new group called truecrypt and give it the necessary permissions. Any users that belongs to that group, will be able to use TrueCrypt.

# groupadd truecrypt

Edit the sudo configuration:

# visudo

Append the following lines at the bottom of the sudo configuration file:

# Users in the truecrypt group are allowed to run TrueCrypt as root.
%truecrypt ALL=(root) NOPASSWD:/usr/bin/truecrypt

You can now add your users to the truecrypt group:

# gpasswd -a USER_1 truecrypt
# gpasswd -a USER_2 truecrypt
...

Note: In order to make these changes active, any user that has been added to the truecrypt group have to logout.

After that, you can mount your device by

# truecrypt --mount /PATH/TO/DEVICE /PATH/TO/MOUNTPOINT

Default mountpoint is /media/truecrypt1. Normally, it is not necessary to explicitly specify the filesystem of your device using the --filesystem flag.

It is definitely reasonable to give truecrypt some permission masks. Otherwise, every file on your mounted device will be executable. So instead of the above, you can use

# truecrypt --fs-options=users,uid=$(id -u),gid=$(id -g),fmask=0113,dmask=0002 --mount /PATH/TO/DEVICE /PATH/TO/MOUNTPOINT

and add this line to your bash configuration file, ~/.bashrc as an alias:

alias tc1='truecrypt --fs-options=users,uid=$(id -u),gid=$(id -g),fmask=0113,dmask=0002 --mount /PATH/TO/DEVICE /PATH/TO/MOUNTPOINT'

To mount this specific device, use

# tc1

as a normal user.

Method 2 (sudo simplified)

Simply enable desired user to run truecrypt without a password:

# visudo

Append the following:

USERNAME ALL = (root) NOPASSWD:/usr/bin/truecrypt

alternatively, if you make use of the wheel group:

%wheel ALL = (root) NOPASSWD:/usr/bin/truecrypt

If you have any difficulties with permissions as a normal user, just add the '-u' flag to the truecrypt mount command, for example:

$ truecrypt -u /home/user/myEncryptedFile.tc /home/user/myEncryptedFileFolder

Automatic mount on login

Simply add

$ truecrypt /home/user/myEncryptedFile.tc /home/user/myEncryptedFileFolder <<EOF
password
EOF

to your startup procedure. Do not use the -p switch, this method is more secure. Otherwise everyone can just look up the password via ps and similar tools, as it is in the process name! source

Safely unmount and unmap volumes (on shutdown)

You can unmount a specific device by

# truecrypt -d /PATH/TO/MOUNTPOINT

or leave away the path to unmount all truecrypt volumes.

If you want your truecrypt device to be unmounted automatically at shutdown, add the following to the file /etc/rc.local.shutdown:

if (/usr/bin/truecrypt --text --list)
then {
/usr/bin/truecrypt -d
sleep 3
}
fi

You can also leave away the sleep command, it is just to give the unmounting some time to complete before the actual shutdown.

If you're using systemd, there is a service trying to unmount truecrypt-encrypted filesystems at shutdown automatically on the Systemd/Services page.

Errors

TrueCrypt is already running

If a messagebox TrueCrypt is already running appears when starting TrueCrypt, check for a hidden file in the home directory of the concerned user called .TrueCrypt-lock-username. Substitute username with the individual username. Delete the file and start TrueCrypt again.

Deleted stale lockfile

If you always get a message "Delete stale lockfile [....]" after starting Truecrypt, the Truecrypt process with the lowest ID has to be killed during Gnome log out. A user in the Ubuntuforum provided the following solution: edit

/etc/gdm/PostSession/Default 

and add the following line before exit 0:

kill `ps -ef | grep truecrypt | tr -s ' ' | cut -d ' ' -f 2`

Issues with Unicode file / folder names

NTFS

Should files resp. folders containing Unicode characters in their names be incorrectly or not at all displayed on TrueCrypt NTFS volumes (while e. g. being correctly handled on non-encrypted NTFS partitions), first verify that you have the NTFS-3G driver installed and then create the following symlink as root:

ln -s /sbin/mount.ntfs-3g /sbin/mount.ntfs

That will cause TrueCrypt to automatically use this driver for NTFS volumes, having the same effect as the explicit use of

truecrypt --filesystem=ntfs-3g /path/to/volume

via the console.

One may also consider setting e. g.

rw,noatime

amongst other options in the TrueCrypt GUI (Settings → Preferences → Mount Options).

FAT

Similarly, FAT32 volumes created using Windows may use Unicode rather than ISO 8859-1. In order to use UTF-8, set the mount option

iocharset=utf8

when mounting such volumes, or globally as described above.

Unmount error (device mapper)

If you always get a message "device-mapper: remove ioctl failed: Device or resource busy" when attempting to dismount your truecrypt volume, the solution is to goto: Setting > Preferences > System Integration > Kernel Service and check the box

Do not use kernel cryptographic services

Failed to set up a loop device

If you get a message "Failed to set up a loop device" when trying to create/mount a TrueCrypt volume, it may be because you updated your kernel recently without rebooting. Rebooting should fix this error.

Otherwise, check if loop has been loaded as kernel module:

lsmod | grep loop

If not listed, retry the TrueCrypt command after modprobe loop. Should it work, consider to add loop to the MODULES array in /etc/modules-load.d:

# tee /etc/modules-load.d/truecrypt.conf <<< "loop"

Related links

• TrueCrypt Homepage
• HOWTO: Truecrypt Gentoo wiki
• Truecrypt Tutorial on HowToForge
• There is a good chance the CIA has a backdoor? (via wp)