Script to extend LUKS-encrypted LVM-volume with a key stored on a remote server

luks_encrypted_extend_lvm_volume.sh

#!/bin/bash

# For disk-encryption & key-creation see: https://gist.github.com/NiceRath/7fc47f0b6f9e73af01f686eb34e0d4fb
# This is meant to be used for a LVM volume

if [ $# -lt 3 ]
then
  cat << EOF
You must provide:
1. -> the vg-name
2. -> the lv-name and
3. -> size to increase by (p.e. '100GB')

Available volumes:"
EOF
  lvscan
  exit 1
fi

set -euo pipefail

VG_NAME=$1
LV_NAME=$2
RESIZE_AMOUNT=$3

# CONFIGURE YOUR REMOTE KEY-STORE-SERVER
KEY_HOST='<SERVER-IP-DNS>'
GPG_FILE='<PATH-TO-GPG-PASSPHRASE-FILE>'  # gpg_passphrase as created on creation: https://gist.github.com/NiceRath/7fc47f0b6f9e73af01f686eb34e0d4fb
KEY_SSH_USER='<SSH-USER>'
KEY_SSH_PORT='<SSH-PORT>'
KEY_SSH_KEY='<SSH-KEY>'
KEY_HOST_KEY_DIR='<REMOTE-KEY-DIR>'

MAPPER_DIR='/dev/mapper'
LV_DEV="${MAPPER_DIR}/${VG_NAME}-${LV_NAME}"
ENC_LV_NAME="crypt-${VG_NAME}-${LV_NAME}"
LV_DEV_ENC="${MAPPER_DIR}/${ENC_LV_NAME}"

# resize lvm lv
lvresize "/dev/${VG_NAME}/${LV_NAME}" --size "+${RESIZE_AMOUNT}"

# resize crypto container
UUID=$(cryptsetup luksUUID "$LV_DEV")

KEY_FILE="${KEY_HOST_KEY_DIR}/${UUID}.key.asc"
KEY=$(ssh -p "$KEY_SSH_PORT" "${KEY_SSH_USER}@${KEY_HOST}" -i "${KEY_SSH_KEY}"  "cat ${KEY_FILE}" | gpg --batch --yes --ignore-mdc-error --no-mdc-warning --no-tty --passphrase-file "$GPG_FILE" --quiet --decrypt)
echo "$KEY" | tr -d '\n' | cryptsetup resize "$LV_DEV_ENC" --key-file=-

# resize file system
resize2fs "$LV_DEV_ENC"

# output current lv's
echo "Resizing of volume ${LV_DEV_ENC} finished; Current size:"
lvscan