A secure solution for unattended booting a Debian/Ubuntu (or any other GNU/Linux) distro that uses full disk encryption via Initramfs utilizing Enceeper.

Warning: Before starting we recommend to have a working full disk encrypted system that is unlocked via a passphrase to avoid misconfigurations and locking yourself out of your system. Also taking a full backup of your system or testing everything in a VM are also good approaches!

The Enceeper app (https://github.com/enceeper/enceeper) and the Enceeper service (https://www.enceeper.com/) can be used to securely store and retrieve credentials (usernames, passwords, API keys etc). We wanted to provide a solution that will allow a GNU/Linux distro to securely boot utilizing Enceeper. To this end we created the following:

• An AES256-CCM decryptor (utilizing a stripped-down version of Nettle or via the OpenSSL library)
• Scripts and configs to allow Initramfs to connect to the Internet (either via wired or wireless interface)
• Scripts and configs to connect to the Enceeper service and retrieve a single key for unlocking the LUKS encrypted partition(s)

Before continuing make sure that you have installed the latest software:

sudo apt update
sudo apt dist-upgrade

and once completed you have rebooted the system:

sudo reboot

git clone https://github.com/enceeper/enceeper-boot
cd enceeper-boot
sudo make install

Now edit the file /etc/enceeper.conf and provide the slot ID and the decryption password.

Then add the Enceeper password to an additional slot of your encrypted disk (where /dev/sda5 is the name of your disk):

sudo ./enceeper.sh > /dev/shm/enceeper_key
sudo cryptsetup luksAddKey /dev/sda5 /dev/shm/enceeper_key
sudo shred -z -u /dev/shm/enceeper_key

In case you are utilizing a wireless interface for networking you will need to edit the following files:

• /etc/initramfs-tools/wpa_supplicant.conf
• /etc/initramfs-tools/hooks/enceeper

In the wpa_supplicant.conf you will have to provide the correct wireless name (ssid) and the WPA/WPA2 key (psk: Pre Shared Key). In the enceeper script you will need to uncomment the lines for utilizing the wireless interface and update the line: manual_add_modules ath9k_htc and provide the modules required by your wireless interface. To find out the required modules execute:

ethtool -i wlXXX | grep driver

Regardless of wired or wireless connection you will need to edit the file /etc/default/grub and add/edit the following line:

GRUB_CMDLINE_LINUX="ip=:::::enp0s3:on panic=10"

Where enp0s3 is the name of your network interface and panic is the number of seconds to wait before rebooting the system in case something goes wrong.

Backup your current Initramfs and update:

sudo cp /boot/initrd.img-`uname -r` /boot/initrd.img-`uname -r`.back
sudo update-initramfs -k `uname -r` -u
sudo update-grub

You can now enjoy your unattended boot 😉.