FreeBSD USB Disk and ZVOL Encryption with GELI

Disk encryption is becoming more important in our day to day life, specially when you have access to some corporate servers or “top secret” files.

I love FreeBSD, it’s simple, rock-solid, easy to use, the handbook is amazing! It also has the option to encrypt the disks during installation. I use FreeBSD everywhere (and TrueOS on my laptop), but disk encryption takes a lot of power, so I chose instead of doing full disk encryption in my laptop, I’ll just have a small media like a USB drive or ZFS ZVOL and encrypt that.

Here’s how to do so πŸ™‚

If you compiled your own kernel ensure it contains these options

options GEOM_ELI
device crypto

Now, make sure crypto and geom_eli is loaded and add these lines to /boot/loader.conf:


Let’s move on.

Now, we need the partition that we are going to encrypt it.
In case it’s a USB drive that you want to encrypt, here’s what to do. First, plug-in the USB drive into your computer. Now, let’s check it’s GEOM class name.

# geom disk list
Geom name: ada0
1. Name: ada0
   Mediasize: 480103981056 (447G)
   Sectorsize: 512
   Mode: r1w1e2
   descr: SanDisk Ultra II 480GB
   lunid: 5001b444a4a40542
   ident: 162265428493
   rotationrate: 0
   fwsectors: 63
   fwheads: 16

Geom name: da0
1. Name: da0
   Mediasize: 4004511744 (3.7G)
   Sectorsize: 512
   Mode: r0w0e0
   descr: SanDisk Cruzer Fit
   lunname: SanDisk Cruzer Fit      4C532000030211123165
   lunid: SanDisk Cruzer Fit      4C532000030211123165
   ident: 4C532000030211123165
   rotationrate: unknown
   fwsectors: 63
   fwheads: 255

Destroy and Create New Partitions

Okay, as we can see it’s da0. First, let’s destroy it and make a new partition on it! (Make sure you backup your data in case you have any important files).

# gpart destroy -F da0
da0 destroyed
# gpart create -s GPT da0
da0 created
# gpart add -t freebsd-ufs -i 1 da0
da0p1 added

In my case, I didn’t want to use a USB drive, I wanted to have an encrypted ZVOL, here’s how to do that as well.
First, create a ZVOL

# zfs create -V 1G zroot/private

Okay, so, in case of a USB drive, we have a partition waiting for us, in case of ZVOL, we have 1GB volume.

Let’s encrypt those!

Initiating Encryption

There are multiple ways to encrypt a disk, check geli(8) for detailed info. Here I’ll show you two options.

  • Encrypting with a master key that is protected with a passphrase.
  • Encrypting with a passphrase only.

For the first option first, generate a key!

# dd if=/dev/random of=/root/master.key bs=64 count=1

Now we initialize the provider which needs to be encrypted.

# geli init -s 4096 -K /root/master.key /dev/da0p1

or in case of ZVOL

# geli init -s 4096 -K /root/master.key /dev/zvol/zroot/private

You’ll be asked to enter your passphrase, twice.

For the second option, it’s exactly the same command without -K /root/master.key. So for the ZVOL it would be

# geli init -s 4096 /dev/zvol/zroot/private

Attaching Encrypted Disks

Now we can attach the provider with the generated key or without it, here’s an example.

# geli attach -k /root/master.key /dev/da0p1

You will be asked for your passphrase.
Or without the key, only the passphrase, here’s an example.

# geli attach /dev/zvol/zroot/private

This creates a new device with .eli extention:

# ls /dev/zvol/zroot/private
private.eli%    private%

Create New File System

First, let’s randomize whatever is on the device and then format it with UFS file system.

# dd if=/dev/random of=/dev/zvol/zroot/private.eli bs=1m
# newfs /dev/zvol/zroot/private.eli

Mount and Use

# mount /dev/zvol/zroot/private.eli /mnt/private
# echo 'some data' > /mnt/private/mytopsecretdata

Detaching Encrypted Volume

# umount /mnt/private
# geli detach /dev/zvol/zroot/private.eli

That’s all folks! πŸ™‚

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