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TrueCrypt: Linux
Содержание
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.
Contents
Installation
Note: For opening and accessing an existing TrueCrypt container cryptsetup is the preferred way, since it is well integrated with the rest of the system. Creating a new TrueCrypt container can be done using truecrypt, after which it can be opened using cryptsetup.
Install truecrypt from the official repositories. 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.
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"
Note:
- This didn't work for me (module truecrypt seems to be non-existent now), but adding «loop» module worked
# tee /etc/modules-load.d/truecrypt.conf <<< "loop" # modprobe loop
- It does not appear that loading a module applies with TrueCrypt 7.1a, the current version in Arch as of 4/19/2013. The above advice may be outdated with respect to the module, however it is still important to enable FUSE, loop and your encryption algorithm (e.g. AES, XTS, SHA512) in custom kernels.
If you only want to open and access an existing truecrypt container, this can also be done with cryptsetup i.e. without installing Truecrypt.
Accessing a TrueCrypt container using cryptsetup
Since version 1.6, cryptsetup supports opening TrueCrypt containers natively, without the need of the truecrypt package. To do so, execute the following command:
$ cryptsetup --type tcrypt open container-to-mount container-name
Replace container-to-mount with the device file under /dev or the path to the file you wish to open. Upon successful opening, the plaintext device will appear as /dev/mapper/container-name, which you can mount like any normal device.
If you are using key files, supply them using the –key-file option, to open a hidden volume, supply the –tcrypt-hidden option and for a partition or whole drive that is encrypted in system mode use the –tcrypt-system option.
See man cryptsetup for more details and all supported options.
Automounting using /etc/crypttab
Since version 206, systemd supports (auto)mounting TrueCrypt containers at boot or runtime using /etc/crypttab.
The following example setup will mount /dev/sda2 in system encryption mode as soon as /mnt/truecrypt-volume is accessed using systemd's automounting logic. The passphrase to open the volume is given in /etc/volume.password. Note that the device file given in /etc/fstab needs to be the one from /dev/mapper/ and not, for example, from /dev/disk/by-uuid/ for automounting logic to kick in. Other than that you can still reliably identify the encrypted volume itself inside of /etc/crypttab using device file names from /dev/disk/.
/etc/crypttab truecrypt-volume /dev/sda2 /etc/volume.password tcrypt-system,noauto /etc/fstab /dev/mapper/truecrypt-volume /mnt/truecrypt-volume auto noauto,x-systemd.automount 0 0
See man crypttab for more details and options supported.
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 -t -c
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/EncryptedFile.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) None 2) FAT 3) Linux Ext2 4) Linux Ext3 5) Linux Ext4
Select [2]:
Enter password for new volume '/home/user/EncryptedFile.tc': ***************************** Re-enter password: ***************************** Enter keyfile path [none]: Please type at least 320 randomly chosen characters and then press Enter: Done: 32.00 MB Speed: 10.76 MB/s Left: 0:00:00 Volume created.
You can now mount the new encrypted file to a previously-created directory:
$ truecrypt -t /home/user/EncryptedFile.tc /home/user/EncryptedFileFolder
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 seeMount volumes as a normal user.
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 -t -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
Note: If you are having problems with the graphical interface, you can run in CLI mode with the -t flag.
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
Simply format the disk like you normally would choosing your favourite file system, except use the path /dev/mapper/truecrypt1. E.g. for ext4 use:
# mkfs.ext4 /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 in #Encrypting a physical volume.
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.ext4 /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
Note: Current Versions of truecrypt seem to support NTFS write support by default so the –filesystem flag no longer seems to be necessary.
In the following 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 /usr/bin/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 /usr/bin/mount.truecrypt
Finally, add the device to fstab somewhat like this:
/dev/sdb3 /mnt truecrypt fs=vfat,defaults 0 0
Tip: This script is also provided by the truecrypt-mount package.
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 -M first_user,second_user,etc 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/EncryptedFile.tc /home/user/EncryptedFileFolder
Automatic mount on login
Simply add:
$ truecrypt /home/user/Encrypted File.tc /home/user/Encrypted File Folder <<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
The most recent truecrypt has a couple of followup questions. If you have expect installed, this will work (assuming no keyfile and no desire to protect hidden volume), saved to a file with root-only perms called from /etc/rc.local:
#! /bin/bash expect << EOF spawn /usr/bin/truecrypt ''/path/to/EncryptedFile'' ''/mount/point'' expect "Enter password" send "volume password\n" expect "Enter keyfile" send "\n" expect "Protect hidden volume" send "\n" expect eof; EOF
Of course, this isn't as secure as entering your password manually. But for some use cases, such as when your TrueCrypt filesystem is in a file on shared storage, it's better than being unencrypted.
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. 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
Mount error (device mapper, truecrypt partition)
When attempting to mount your truecrypt volume, a message like this one may appear:
Error: device-mapper: create ioctl failed: Device or resource busy Command failed
If so, run:
# cryptsetup remove /dev/mapper/truecrypt1
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 in /etc/modules-load.d:
# tee /etc/modules-load.d/truecrypt.conf <<< "loop"
Note: As of udev 181-5, the loop device module is no longer auto-loaded, and the procedure described here is necessary.
System partition passwords need en_US keymap
If you are using Xorg (which you most likely are, should you not know what that is), use the following command to use US keymap until restart:
# setxkbmap us
See also
Retrieved from «https://wiki.archlinux.org/index.php?title=TrueCrypt&oldid=296527»
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- This page was last modified on 8 February 2014, at 02:21.
- Content is available under GNU Free Documentation License 1.3 or later unless otherwise noted.
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