This Blog Is Not For Reading

A blog, just like any blog, only more so

  • Subscribe

  • Categories

  • RSS Bob Jonkman’s Microblog

    • New note by bobjonkman 9 July 2022
      New Zealand #ProportionalRepresentation
    • Favorite 9 July 2022
      bobjonkman favorited something by blacksam: What country do Canadians threaten to move to when they don't like election outcomes? #politics #canada
    • bobjonkman repeated a notice by blacksam 9 July 2022
      RT @blacksam What country do Canadians threaten to move to when they don't like election outcomes? #politics #canada
    • New note by bobjonkman 5 July 2022
      Congratulations to Dr. Cooley, and to you! And welcome to Canada!https://twitter.com/SNOLABscience/status/1542562373193633793 I saw the news on Twitter, and said to myself "Hey, I know that person!" It's amazing how familiar we humans feel with each other using only social media...
    • bobjonkman repeated a notice by steve 5 July 2022
      RT @steve Spring Cleaning, Except its Packing to Move to Canada https://steve.cooleysekula.net/blog/2022/07/02/spring-cleaning-except-its-packing-to-move-to-canada/
    • Favorite 5 July 2022
      bobjonkman favorited something by steve: Spring Cleaning, Except its Packing to Move to Canada https://steve.cooleysekula.net/blog/2022/07/02/spring-cleaning-except-its-packing-to-move-to-canada/
    • New note by bobjonkman 26 June 2022
      I've never played #Minecraft - Is this #Federated software? Is it #FreeSoftware? If so, how can Microsoft control what's happening on someone's private server? Even if such code existed in a #FreeSoftware application, I would have thought there'd be a fork that eliminates that external control. It's time for that now. But if #Minecraft isn't […]
    • bobjonkman repeated a notice by lnxw48a1 26 June 2022
      RT @lnxw48a1 Seen via @sullybiker https://freeradical.zone/@thenewoil/108539077382008407 Microsoft bans in #Minecraft will soon carry over to privately run servers as well. One commenter said "Seems like there is a really simple solution here: Don't be a toxic asshole on a public server." But once $CORPORATION starts interfering with privately hosted servers in any way, those servers' […]
    • New note by bobjonkman 27 May 2022
      Mind you, there's something charming and soporific about listening to a professional baseball game with an old-fashioned, laid-back announcer. But most of those have retired... #ASMR
    • New note by bobjonkman 27 May 2022
      Applies to all professional #Sportsball: begging to see overpaid drug-users doing something that the rest of us would gladly do for free. When I walked our dog we'd pass the local baseball field, and we'd stop and watch the game for hours. But the one time I went to a professional baseball match (Toronto Blue […]

How To Create an Encrypted Drive in a File Container

Posted by Bob Jonkman on October 9th, 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
 
Better Tag Cloud