This Blog Is Not For Reading

A blog, just like any blog, only more so

  • Subscribe

  • Categories

  • RSS Bob Jonkman’s Microblog

    • Favorite 22 September 2018
      bobjonkman favorited something by djsundog: 'I am not the Dread Cryptographer Zimmerman', he said. 'My name is Ryan; I inherited the pad from the previous Dread Cryptographer Zimmerman, just as you will inherit it from me. The man I inherited it from is not the real Dread Cryptographer Zimmerman either. His name was Cummerbund. The […]
    • Favorite 22 September 2018
      bobjonkman favorited something by codeawayhaley: The person who keeps stealing from the Herb garden please get a hobby, and stop wasting our thyme.
    • New note by bobjonkman 22 September 2018
      That's very sage advice.
    • Favorite 22 September 2018
      bobjonkman favorited something by storm: !joke There once was a man from Racine, who invented a fucking machine. concave and convex, it fucked either sex, and jerked off itself in between.
    • Favorite 22 September 2018
      bobjonkman favorited something by moondoggy: @hairylarry listening to today's Something Blue now, because I couldn't turn it on at work. Awesome show! @bobjonkman is listening too.
    • bobjonkman repeated a notice by moondoggy 22 September 2018
      RT @moondoggy @hairylarry listening to today's Something Blue now, because I couldn't turn it on at work. Awesome show! @bobjonkman is listening too.
    • bobjonkman repeated a notice by cypnk 21 September 2018
      RT @cypnk Ever-growing list of websites that don’t work at all or show a plain white page without #JavaScript is a testament to the cesspool that is modern web developmentI browse without JS on mobile to save my meager bandwidth (8mb for JS libs from 10 different sources), to save battery life, and to avoid […]
    • Favorite 21 September 2018
      bobjonkman favorited something by cypnk: Ever-growing list of websites that don’t work at all or show a plain white page without #JavaScript is a testament to the cesspool that is modern web developmentI browse without JS on mobile to save my meager bandwidth (8mb for JS libs from 10 different sources), to save battery life, […]
    • bobjonkman repeated a notice by strypey 20 September 2018
      RT @strypey @danyspin97 this is why I don't trust Signal. Why is Moxie so opposed to F-Droid (or even Debian) compiling #Signal clients from source rather than using his binaries? If he does all the compiling, it doesn't matter that both the client and server source code are on public repos, because we only have […]
    • Favorite 20 September 2018
      bobjonkman favorited something by strypey: @danyspin97 this is why I don't trust Signal. Why is Moxie so opposed to F-Droid (or even Debian) compiling #Signal clients from source rather than using his binaries? If he does all the compiling, it doesn't matter that both the client and server source code are on public repos, because […]

How To Create an Encrypted Drive in a File Container

Posted by Bob Jonkman on 9th October 2017

Inspired by The Linux Experiment, I want to create an encrypted drive in a file container using only the command line.

Creating an encrypted file container

Create the container file. We’ll call it containerfile.img:


laptop:~/temp$ fallocate -l 250MB containerfile.img

laptop:~/temp$ ls -l
total 244148
-rw-rw-r-- 1 bjonkman bjonkman 250000000 Oct  8 22:45 containerfile.img

laptop:~/temp$

Create the encrypted LUKS volume. Note that creating volumes and file systems requires elevated privileges, so we use the sudo command:


laptop:~/temp$ sudo cryptsetup luksFormat containerfile.img 
[sudo] password for bjonkman: 

WARNING!
========
This will overwrite data on containerfile.img irrevocably.

Are you sure? (Type uppercase yes): YES
Enter passphrase: 
Verify passphrase: 
Command successful.

laptop:~/temp$

Of course, the passphrase doesn’t show on the screen, not even as asterisks. That would give a shouldersurfer an idea of how long the passphrase is. It is a long passphrase, right?

Open the encrypted LUKS volume, which we’ll call cryptvolume:


laptop:~/temp$ sudo cryptsetup luksOpen containerfile.img cryptvolume
Enter passphrase for containerfile.img: 

laptop:~/temp$

Let’s see if the encrypted LUKS volume exists:


laptop:~/temp$ lsblk
NAME                                          MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
sda                                             8:0    0 465.8G  0 disk  
├─sda1                                          8:1    0   243M  0 part  
├─sda2                                          8:2    0    14G  0 part  /
└─sda3                                          8:3    0     1K  0 part  
loop4                                           7:4    0 238.4M  0 loop  
└─cryptvolume                                 252:11   0 236.4M  0 crypt 

laptop:~/temp$

Yay!

Now we create a filesystem inside the encrypted LUKS volume. We’ll give it the label cryptdrive:


laptop:~/temp$ sudo mkfs -L cryptdrive -t ext4 /dev/mapper/cryptvolume 
mke2fs 1.42.13 (17-May-2015)
Creating filesystem with 253952 1k blocks and 63488 inodes
Filesystem UUID: 040765be-eddb-4ea6-b8d8-594b81233465
Superblock backups stored on blocks: 
	8193, 24577, 40961, 57345, 73729, 204801, 221185

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

laptop:~/temp$

Create a mount point, which we’ll call mountpoint, then mount the encrypted drive:


laptop:~/temp$ mkdir mountpoint

laptop:~/temp$ sudo mount /dev/mapper/cryptvolume mountpoint

laptop:~/temp$ lsblk
NAME                                          MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
sda                                             8:0    0 465.8G  0 disk  
├─sda1                                          8:1    0   243M  0 part  
├─sda2                                          8:2    0    14G  0 part  /
└─sda3                                          8:3    0     1K  0 part  
loop4                                           7:4    0 238.4M  0 loop  
└─cryptvolume                                 252:11   0 236.4M  0 crypt /home/bjonkman/temp/mountpoint

laptop:~/temp$ ls -l
total 244149
-rw-rw-r-- 1 bjonkman bjonkman 250000000 Oct  8 23:19 containerfile.img
drwxr-xr-x 3 root     root          1024 Oct  8 23:14 mountpoint

laptop:~/temp$

Note that the encrypted file system still belongs to root:root because we used the sudo command.

Change file ownership to bjonkman:bjonkman so I can read/write to it without elevated permissions:


laptop:~/temp$ sudo chown bjonkman: mountpoint/

laptop:~/temp$ ls -l
total 244149
-rw-rw-r-- 1 bjonkman bjonkman 250000000 Oct  8 23:19 containerfile.img
drwxr-xr-x 3 bjonkman bjonkman      1024 Oct  8 23:14 mountpoint

laptop:~/temp$

Since an encrypted container file is probably secret, it shouldn’t be visible to groups or others, so remove those file permissions:


laptop:~/temp$ chmod go-rwx containerfile.img 

laptop:~/temp$ ls -l
total 244149
-rw------- 1 bjonkman bjonkman 250000000 Oct  8 23:34 containerfile.img
drwxr-xr-x 3 bjonkman bjonkman      1024 Oct  8 23:14 mountpoint

laptop:~/temp$

Do some work in the encrypted drive:


laptop:~/temp$ echo "Hello World" > mountpoint/hello.txt

laptop:~/temp$ ls -l mountpoint/
total 13
-rw-rw-r-- 1 bjonkman bjonkman    12 Oct  8 23:53 hello.txt
drwx------ 2 root     root     12288 Oct  8 23:14 lost+found

laptop:~/temp$

And finally, unmount the encrypted filesystem and close the encrypted volume:


laptop:~/temp$ sudo umount mountpoint/

laptop:~/temp$ sudo cryptsetup luksClose cryptvolume 

laptop:~/temp$

Using an encrypted file container

Next time you want to do some work:


laptop:~/temp$ sudo cryptsetup luksOpen containerfile.img cryptvolume
Enter passphrase for containerfile.img: 

laptop:~/temp$ sudo mount /dev/mapper/cryptvolume mountpoint

laptop:~/temp$ echo "Hello again" > mountpoint/again.txt

laptop:~/temp$ ls -l mountpoint/
total 14
-rw-rw-r-- 1 bjonkman bjonkman    12 Oct  9 00:12 again.txt
-rw-rw-r-- 1 bjonkman bjonkman    12 Oct  8 23:53 hello.txt
drwx------ 2 root     root     12288 Oct  8 23:14 lost+found

laptop:~/temp$ sudo umount mountpoint/

laptop:~/temp$ sudo cryptsetup luksClose cryptvolume 

laptop:~/temp$

Using an encrypted file container from the GUI

Once the encrypted file container has been created you can open it from the graphical file manager just by double-clicking:
File manager window

Enter the passphrase to unlock the volume:
A file manager window and a password prompt window

A file manager window for the encrypted volume opens:
Two file manager windows

Note that the mountpoint is /media/bjonkman/cryptdrive/, chosen by the Gnome Disk Mounter application that runs when you doubleclick the container:


laptop:~/temp$ lsblk
NAME                                          MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
sda                                             8:0    0 465.8G  0 disk  
├─sda1                                          8:1    0   243M  0 part  
├─sda2                                          8:2    0    14G  0 part  /
└─sda3                                          8:3    0     1K  0 part  
loop5                                           7:5    0 238.4M  1 loop  
└─luks-54f8e41b-73bf-4adf-aa29-a147733c5202   252:11   0 236.4M  1 crypt /media/bjonkman/cryptdrive

laptop:~/temp$

Also, note that the encrypted drive is mounted read-only:


laptop:~/temp$ mount | grep cryptdrive
/dev/mapper/luks-54f8e41b-73bf-4adf-aa29-a147733c5202 on /media/bjonkman/cryptdrive type ext4 (ro,nosuid,nodev,relatime,data=ordered,uhelper=udisks2)

laptop:~/temp$

Gnome Disk Mounter can be launched from the command line with a --writeable or -w parameter:
Command line window and Enter Passphrase window

Happily, this all works without elevated privileges; no sudo required. I don’t know how to open an encrypted file container using only command line tools without using sudo, nor how to launch Gnome Disk Manager in writeable mode just by doubleclicking — if you know, leave a comment or send me e-mail!

TL;DR:


fallocate -l 250MB containerfile.img

sudo cryptsetup luksFormat containerfile.img

sudo cryptsetup luksOpen containerfile.img cryptvolume

sudo mkfs -L cryptdrive -t ext4 /dev/mapper/cryptvolume

mkdir mountpoint

sudo mount /dev/mapper/cryptvolume mountpoint

sudo chown bjonkman: mountpoint/

chmod go-rwx containerfile.img

(do some work)

sudo umount mountpoint/

sudo cryptsetup luksClose cryptvolume

-----

sudo cryptsetup luksOpen containerfile.img cryptvolume
sudo mount /dev/mapper/cryptvolume mountpoint
(do some work)
sudo umount mountpoint/
sudo cryptsetup luksClose cryptvolume

Tags: , , ,
Posted in Crypto, GNU/Linux | 1 Comment »

 
Better Tag Cloud