#!/bin/bash

# Try to get LUKS info and master key from active mapping and prepare parameters for cryptsetup.
#
# Copyright (C) 2010,2011 Milan Broz <asi@ucw.cz>
#
# This copyrighted material is made available to anyone wishing to use,
# modify, copy, or redistribute it subject to the terms and conditions
# of the GNU General Public License v.2.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software Foundation,
# Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
#

fail() { echo -e $1 ; exit 1 ; }
field() { echo $(dmsetup table --target crypt --showkeys $DEVICE | sed 's/.*: //' | cut -d' ' -f$1) ; }
field_cryptsetup() { echo $(cryptsetup status $DEVICE | grep $1 | sed "s/.*$1:\s*//;s/\ .*//") ; }

which xxd >/dev/null || fail "You need xxd (part of vim package) installed to convert key."

[ -z "$2" ] && fail "Recover LUKS header from active mapping, use:\n $0 crypt_mapped_device mk_file_name"

DEVICE=$1
MK_FILE=$2

[ -z "$(field 4)" ] && fail "Mapping $1 not active or it is not crypt target."

# FIXME:
# - add UUID
# - check for CRYPT-LUKS1-* DM-UUID

CIPHER=$(field_cryptsetup cipher)
OFFSET=$(field_cryptsetup offset)
REAL_DEVICE=$(field_cryptsetup device)
KEY_SIZE=$(field_cryptsetup keysize)
KEY=$(field 5)

[ -z "$CIPHER" -o -z "$OFFSET" -o "$OFFSET" -le 383 -o -z "$KEY" ] && fail "Incompatible device, sorry."

echo "Generating master key to file $MK_FILE."
echo -E -n $KEY| xxd -r -p >$MK_FILE

echo "You can now try to reformat LUKS device using:"
echo "  cryptsetup luksFormat -c $CIPHER -s $KEY_SIZE --align-payload=$OFFSET --master-key-file=$MK_FILE $REAL_DEVICE"