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Additional mount scripts for DM-Crypt containers

Script for comfortable create / mount DM-Crypt containers over sudo, make Crypted SWAP.

Use one command instead three command. Mount your containers under LiveCD with one easy step. With many safety checks.

0). Programs cryptsetup, sed, basename, realpath, losetup, dd, mkfs*, shred, touch and bash must be installed (usually default) On some system cryptsetup must be installed manually (ex Ubuntu 18 minimal): apt-get install cryptsetup-bin

Optionally you can install sudo and tools for support other filesystems (ex btrfs, xfs, ntfs, exfat, reiserfs).

1). download scripts to local system, for example to /opt (you can run script from any fs)

cd /opt

wget https://github.com/Aminuxer/DM-Crypt-Helper-Scripts/raw/master/_dmc.sh

chmod +x _dmc.sh

Tools curl or fetch can be used instead of wget.

2). Optional step. Usage dm-crypt require high permissions. Create sudo rules for start scripts under non-privileged users:

# vi /etc/sudoers.d/myscripts-example

user1 ALL=(root) NOPASSWD: /opt/_dmc.sh

Without this step (ex. livecd like knoppix) manage cryptocontainers will require root permissions.

3). Run script with sudo : $ sudo /opt/_dmc.sh

Start without parameters will show mini-help:

Usage: ./_dmc.sh <Path to Dm-Crypt container> [start|stop|create|make_loops] [Mount point] [cipher]
    Example: ./_dmc.sh ~/mysecrets.bin create    - make new in file
             ./_dmc.sh /dev/md0 create           - on RAID
             ./_dmc.sh ~/mysecrets.bin           - switch
             ./_dmc.sh ~/mysecrets.bin stop      - force stop
    create - make new container. Existing file don't touch for safety
    make_loops - create new loop-devices in /dev

You can create containers in new files or unused block devices (like raw drives, partitions, LVM-slices or RAIDs). Script don't touch existing files or mounted/used devices when create method called. Also many safety checks added - for block devices like /dev/(md*|sd*|mapper|lvm*) make many checks for mounted state or contain RAID / LVM / ZFS used structures.

In this case you see messages like "file /var/tmp/fs1.bin exist, usage existing files denied.", "Device mounted" or "Device in RAID / LVM / ZFS".

Run script with full path to new containers and use cli dialogs for create new container:

In usual file : $ sudo /opt/_dmc.sh /var/tmp/fs1.bin create

In partition #9 on physical drive sdg: $ sudo /opt/_dmc.sh /dev/sdg9 create

in free LVM-LV (logical volume) $ sudo /opt/_dmc.sh /dev/mapper/free-LVM-LogicalVolume create

----- CREATE NEW CryptoContainer ---------------------
You start to CREATE dm-crypt container. Continue (Yes/No)? Yes
OK, continue...
Enter internal volume label for new container: MyNewContainer1
Enter volume size (1048576, 1024K, 100M, 2G): 42M
Supported filesystems on your machine:
------------------------------------------
btrfs     ext2      ext3     ext4     fat
msdos     ntfs      vfat     xfs
------------------------------------------
Enter filesystem type (from list above): ext4
Fast fill container
0+0 records in
0+0 records out
0 bytes copied, 7.7594e-05 s, 0.0 kB/s
Enter passphrase for /dev/loop2: EnterYouStrongUberMegaPaSsW0rD~PhRAZe+Here
Shreding [42M] space on [/var/tmp/fs1.bin] ...   (please wait)
Formatting cryptocontainer...
mke2fs 1.44.6 (5-Mar-2019)
Creating filesystem with 43008 1k blocks and 10752 inodes
Filesystem UUID: 340138b4-b630-47c2-852c-bf57d3d7ca99
Superblock backups stored on blocks:
        8193, 24577, 40961

Allocating group tables: done
Writing inode tables: done
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done

Label :: [fs1.bin] ; /var/tmp/fs1.bin --> /run/media/MyNewContainer1 ; [on /dev/loop2], SIZE: [42M]
----- New CryptoContainer mounted succesfully ! ---------

For physical devices don't need input size - autodetect present. After this your container will already mounted and ready for usage.

Run script with full path to container and method start:

$ sudo /opt/_dmc.sh /var/tmp/fs1.bin start

Normal mount will show this output:

----- Mount CryptoContainer [/var/tmp/fs1.bin] ---------------------
Cipher options: aes-xts-essiv:sha256 --hash sha512 --key-size 512
Enter passphrase for /dev/loop3: EnterYouStrongUberMegaPaSsW0rD~PhRAZe+Here
Command successful.
FS in container: ext4
Label :: [fs1.bin] ; /var/tmp/fs1.bin --> /run/media/MyNewContainer1 ; [on /dev/loop3]
----- Mount CryptoContainer Complete ! ---------

You must input passphrase "as one string", without misprints, errors or try editing. Inputed symbols don't displayed. Any error in passphrase will cause mount errors.

Run script with full path to container and method stop:

$ sudo /opt/_dmc.sh /var/tmp/fs1.bin stop

Normal shutdown will show this output:

----- Unmount CryptoContainer [/var/tmp/fs1.bin] --------------------
losetup: /dev/loop1
Check mount-point [/run/media/MyNewContainer1] and try remove empty dir
!! Remove mount-point /run/media/MyNewContainer1 !!
removed directory '/run/media/MyNewContainer1'
----- Unmount CryptoContainer Complete ! ---------

If any file from internal fs will be opened in external program, script stopped with umount error message. Close all files opened from container and try again.

• What happens if i run $ sudo /opt/_dmc.sh /var/tmp/fs1.bin - command with only path to existing file ?

  • Script will try detect current status and propose mount / umount action. Mounted containr will try umount, unmounted - mount with passphrase request.

• Can i use raw devices or partitions like /dev/sdh or /dev/sdg2 instead of file ?

  • Yes. But script allow this only for unmounted partitions, not included in active RAID / LVM / ZFS structures; Work with mounted partitions so destructive and denied by safety checks in script. At your own risk anyway; I tested this on Fedora and Ubuntu and this work normally.

• What is method make_loops ?

  • This method for some old or livecd systems, where loopback devices not created at boot. Use mknod util. Can be useful , if you try mount too many containers.

• Can script damage my trivial file if i try mount this as container ? ex _dmc.sh dsc0001.jpg ?

  • No. You cannot create passphrase for convert jpeg-file to FS-image by AES =) It's fantastic. Script can't found internal FS and rollback all changes. File will not changed. But you must have backups in any case =].

• How to mount container in another mount point, for example, in path under /tmp, /home or other path ?

  • Use third parameter: $ sudo /opt/_dmc.sh /var/tmp/fs1.bin start /tmp/mountpoint

• What filesystems can be used ?

  • On external storage for place encrypted container - any type. Check maximal size and characters in filename (actually only for old MS products like FAT).
  • For FS inside container - all standard with labels support and present in your system - ext*, fat*, ntfs, btrfs, xfs, reiser
  • Another FS can be added in future, depends of many factors.

• I have container without volume label. How it important ?

  • Not important. Containers with unlabeled fs will mount to path like /run/media/Disk_NoLABEL__fs1.bin and only with parameter start. Mount container, see device name by df and change label for /dev/mapper/fs1.bin by e2label or similar tool. Some FS must be unmount first. Use mount, change label, _dmc.sh ... stop Label will applied at next _dmc.sh ... start

• Can i mount different copies of same container ?

  • Be careful; Use different mount-points: ./_dmc.sh /tmp/copy1/disk.dmc start /tmp/mounpoint1 ./_dmc.sh /tmp/copy2/disk.dmc start /tmp/mounpoint2 Since 2021-10-26 script prevent multiple start-binding to loop-devices for same file. Since 2021-11-12 support mounting copies of same container. In case of simple mounting without specified mountpount data directories will be substituted (not recommended).

• Can i make fsck or another service works for fs in container ?

  • Yes. Mount container with correct passphrase by script _dmc.sh. See device name by df command or command mount. umount this filesystem with umount system command (NOT by script !!). Start fsck for /dev/mapper/<virtual.device.name> Force stop cryptodevice by call script with stop parameter.

• What is Cipher option - parameter 4 ?

  • If you have another or older dm-crypt container with other ciphers you can use this options for manual mount this. Syntax of this same as -c parameter for cryptsetup.

• Can i update file by new version ?

  • Yes. Make backup copy and simple download over. If you don't change default cipher-method - all must work. In other case, use fourth parametr for CIPHER specification.

• Why used aes-xts-essiv:sha256 --hash sha512 --key-size 512 ?

  • This methods suitable for full-disk encryption, prevent many attacks against crypted partitions and supported in almost all linux distribs. Also AES ciphers have hardware-acceleration on modern CPU - this important for big containers (ex virtual machines storages
  • More deep understand will require learn more about cryptography:

  https://wikipedia.org/wiki/Disk_encryption_theory

  Disk encryption is one of hardest cryptograhy task - too many crypto-issues must be solved.

• How to view list of supported ciphers ?

  • Use commands cryptsetup benchmark and cryptsetup --help
  • More detailed info here: https://unix.stackexchange.com/questions/354787/list-available-methods-of-encryption-for-luks

• Can i resize container, change passphrase or encryption method ?

  • By this script - No. You can create new container and copy files by cp / mc / rsync. Container resizing can be make manually by dd / cryptsetup resize / resizefs.

  For make this convert on existing container you must strong understand how work dm-crypt, loopback devices and linux block devices / filesystems. This work required accuracy; Make backups BEFORE start work; Read this:

  • https://wiki.gentoo.org/wiki/Dm-crypt
  • https://geekpeek.net/resize-filesystem-fdisk-resize2fs/
  • https://wiki.archlinux.org/index.php/Dm-crypt/Device_encryption

  Test result and make backups again;

• What about crypto swap ?

  • Same as containers, but use script _swap.sh, passphrase generated random at each start, mountpoint not need, first 512 bytes not used.
  • This script so old and don't have many safety checks. Be careful.

• Can i use multi-keys / multi-user scenario ?

  • No. This raw dm-crypt related code. Use LUKS for more compex tasks.

• Can i embed containers in containers ? Is it deniable encryption ?

  • Your can place container in another container (container is usual file), but this tested slightly; You must use different filenames and FS labels at least; This not deniable; Deniable encryption required more complex software like TrueCrypt or use steganograhy like steghide utility.

• Can i place scripts or containers on removable media ?

  • No problem. But your possible will need root permissions (sudo rules danger apply to removable), start script as bash parameter (fs without +x attr) or speed of removable media can be lower. This script work in Knoppix-Live environment when running from KNOPPIX-DATA storage.

• How to move my PGP-keys / Bitcoin wallet / SSH-keys / TOTP apps / private documents inside crypto-container ?

  • Be sure that you strongly remember your passphrase. Check this twice; Check that you have BACKUPS. If your forget passphrase, almost no way to recover it; Bruteforce of dm-crypt so difficult.
  • Create subdirs in container and copy sensitive data in container FS.
  • shred sensitive data on non-encrypted disks; Simple rm or delete by Del/F8 buttons vulnerable to forensics / data-recovery tools. For SSD drives, remove shreded files and run trim procedure by fstrim command.
  • make symlinks like this ln -s /media/MyNewContainer1/SSH/id_rsa ~/.ssh/id_rsa (~/.ssh/id_rsa -> /media/MyNewContainer1/SSH/id_rsa)
  • Move your highly-private apps like micro totp-generator (https://github.com/Aminuxer/Other-nix-Scripts/blob/master/totp.py) to subdir inside container-FS.

• How big/small size can have dm-crypt cryptocontainer ?

  • Almost any, but depends of filesystems. I create small containers with fat / ext2 system inside with 100 Kb size; Big 200-300 Gb containers i create too - if your hard disk work properly, no problem taking place;
  • Since 2021-10-30 added big dimensions in create dialog - KMGTPEZY =)
  • I recommend store only high-critical data inside containers with comfortable size for transfer / backups / restore / archiving; P.S. Archiving can be bad idea in terms of cryptography; But in most cases accessibility and integrity must be prefer.

• Can i use this script on Mac with MacOS ?

  • No. MacOS use another tools like hdiutil and older versions of coreutils. Theoretically it is possible, but i don't has interest do this. Your can make fork.