#!/bin/bash
set -euo pipefail

# Needs to run as root to get all hashes
[ $(id -u) -eq 0 ] || exec sudo $0 "$@"

# Read command from CLI
cmd=${1:-verify}
KEY=${KEY:-6A64A47A}
signature_file=/boot/files.sig

case "${cmd}" in

# Create a new signature file
sign)
	find /boot -type f -! -name 'files.sig' -! -name 'files.sha512' -exec sha512sum '{}' \; >/boot/files.sha512
	gpg --output ${signature_file} --detach-sign /boot/files.sha512
	;;

# Verify signature file
verify)
	[ -f ${signature_file} ] || {
		echo "Signature file not yet initialized. Use '$0 sign'"
		exit 1
	}

	find /boot -type f -! -name 'files.sig' -! -name 'files.sha512' -exec sha512sum '{}' \; >/tmp/files.sha512
	gpg --verify ${signature_file} /tmp/files.sha512 || {
		echo
		echo '/!\ ATTENTION: SIGNATURE MISMATCH! /!\'
		echo
		diff -wu /boot/files.sha512 /tmp/files.sha512

		exit 1
	}
	;;

*)
	echo "Unsupported command '${cmd}': $0 <sign|verify>"
	exit 1
	;;

esac