#!/bin/bash

# Try to get LUKS info and master key from active mapping and prepare parameters for cryptsetup.
#
# Copyright (C) 2010,2011,2012 Milan Broz <gmazyland@gmail.com>
#
# 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.
#
umask 0077

fail() { echo -e $1 ; exit 1 ; }
field() { echo $(dmsetup table --target crypt --showkeys $DEVICE | sed 's/.*: //' | cut -d' ' -f$1) ; }
field_uuid() { echo $(dmsetup info $1 --noheadings -c -o uuid) ; }
field_device() {
	TEMP=$(readlink /sys/dev/block/$1 | sed -e 's/.*\///')
	if [  ${TEMP:0:3} = "dm-" -a -e /sys/block/$TEMP/dm/name ] ; then
		TEMP=/dev/mapper/$(cat /sys/block/$TEMP/dm/name)
	else
		TEMP=/dev/$TEMP
	fi
	echo $TEMP
}

which readlink >/dev/null || fail "You need readlink (part of coreutils package)."
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."

CIPHER=$(field 4)
OFFSET=$(field 8)
SYS_DEVICE=$(field 7)
REAL_DEVICE=$(field_device $SYS_DEVICE)
KEY=$(field 5)
KEY_SIZE=$(( ${#KEY} / 2 * 8 ))
SYS_UUID=$(field_uuid $DEVICE)
UUID="${SYS_UUID:12:8}-${SYS_UUID:20:4}-${SYS_UUID:24:4}-${SYS_UUID:28:4}-${SYS_UUID:32:12}"

#echo "CIPHER=$CIPHER OFFSET=$OFFSET SYS_DEVICE=$SYS_DEVICE REAL_DEVICE=$REAL_DEVICE KEY_SIZE=$KEY_SIZE KEY=$KEY UUID=$UUID SYS_UUID=$SYS_UUID"

[ -z "$CIPHER" -o -z "$OFFSET" -o "$OFFSET" -le 383 -o \
-z "$KEY" -o -z "$UUID" -o -z "$REAL_DEVICE" -o "${SYS_UUID:0:12}" != "CRYPT-LUKS1-" ] && \
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=$MK_FILE --uuid=$UUID $REAL_DEVICE"