Native Encryption

ZFSBootMenu can import pools or filesystems with native encryption enabled. If your boot environments are not encrypted but, for example, /home is, you will not receive a decryption prompt during boot. To ensure that you can decrypt your pool to load the kernel and initramfs, you'll need to you have the filesystem parameters configured correctly.

It's critical that keyformat is set to passphrase, otherwise you'll be unable to enter the correct value in the bootloader. OpenZFS currently supports only one key, but in a way which ZFSBootMenu can exploit: if you configure the keylocation value to a file on disk, put your passphrase in that, and then include that file into the FINAL initramfs (the one in the /boot subdirectory of your encrypted root), you won't receive a second password prompt on boot. When ZFSBootMenu attempts to unlock root filesystems, it will override any file:// URI it encounters as a keylocation if that file is not accessible from within the bootloader image. This allows ZFSBootMenu to prompt for passphrases when necessary.

Note

Never place encryption keys inside a custom ZFSBootMenu image! The ZFSBootMenu image will typically be installed on an unencrypted partition with minimal or no access restrictions. If an encryption key is placed in such a location, anybody with access to the system will be able to read your passphrase.

As an example, Consider a filesystem layout such as:

zfs get all zroot | egrep '(encryption|keylocation|keyformat)'
zroot  encryption            aes-256-gcm                -
zroot  keylocation           file:///etc/zfs/zroot.key  local
zroot  keyformat             passphrase                 -
zroot  encryptionroot        zroot                      -

On systems that use dracut, the key for zroot can be added to initramfs images by running:

echo 'install_items+=" /etc/zfs/zroot.key "' > /etc/dracut.conf.d/zfs-keys.conf

For mkinitcpio, add the key to the FILES array in mkinitcpio.conf:

echo 'FILES+=(/etc/zfs/zroot.key)' >> /etc/mkinitcpio.conf

Note

When adding encryption keys to initramfs images, always ensure that the resulting images are not readable by any user other than root. Recent versions of dracut and mkinitcpio ensure this by default with umask of 0077. Users with read access to your initramfs image will be able to read your ZFS key file even if it has mode 000 in the image; always confirm for your self that the initramfs is protected!

For convenience, ZFSBootMenu recognizes the ZFS property org.zfsbootmenu:keysource as the name of a filesystem that should be searched for ZFS key files. When a boot environment specifies a file:// URI as its keylocation, ZFSBootMenu will attempt to mount a filesystem indicated by the org.zfsbootmenu:keysource property (if it exists) and search for the named keylocation therein. If found, ZFSBootMenu will copy the key into a cache within the in-memory root filesystem so that subsequent operations that require reloading the key (for example, changing the default boot environment or cloning a snapshot) will not prompt the user for passphrases.

When searching for a keylocation relative to the filesystem named by org.zfsbootmenu:keysource, ZFSBootMenu will first try to strip the mountpoint of the keysource filesystem from any keylocation URI that references the keys to map the keylocation that would be observed on a running system to the proper location in the keysource. For example, if the running system is set up so that zroot is the encryptionroot for all filesystems on a pool, running the commands:

zfs create -o mountpoint=/etc/zfs/keys zroot/keystore
echo "MySecretPassphrase" > /etc/zfs/keys/zroot.key
chmod 000 /etc/zfs/keys/zroot.key
zfs set keylocation=file:///etc/zfs/keys/zroot.key zroot
zfs set org.zfsbootmenu:keysource=zroot/keystore zroot
echo install_optional_items+=" /etc/zfs/keys/zroot.key " >> /etc/dracut.conf.d/zol.conf

will cause ZFSBootMenu to attempt to cache the key file:///etc/zfs/keys/zroot.key from zroot/keystore when unlocking the zroot pool. Because zroot/keystore specifies mountpoint=/etc/zfs/keys, ZFSBootMenu will first try to strip /etc/zfs/keys from the keylocation URI, looking for the file zroot.key at the root of the filesystem zroot/keystore. If this fails, ZFSBootMenu will fall back to the full path, looking for etc/zfs/keys/zroot.key within the keysource filesystem. If either location is found, ZFSBootMenu will retain a cache of the key should it be needed to unlock the pool again.