#!/bin/bash -e
# vim: set tabstop=8 shiftwidth=4 softtabstop=4 expandtab smarttab colorcolumn=80:
#
# Copyright (c) 2016 Red Hat, Inc.
# Author: Harald Hoyer <harald@redhat.com>
# Author: Nathaniel McCallum <npmccallum@redhat.com>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#

SUMMARY="Binds a LUKSv1 device using the specified policy"
UUID=cb6e8904-81ff-40da-a84a-07ab9ab5715e

function onerr() {
    if [ -n "$DEV" -a -n "$SLT" ]; then
        luksmeta wipe -f -d "$DEV" -u "$UUID" -s "$SLT"
        SLT=
    fi
    stty echo
    exit 1
}

trap 'onerr' ERR HUP INT QUIT PIPE TERM

function usage() {
    echo >&2
    echo "Usage: clevis luks bind [-f] [-s SLT] [-k KEY] -d DEV PIN CFG" >&2
    echo >&2
    echo "$SUMMARY": >&2
    echo >&2
    echo "  -f      Do not prompt for LUKSMeta initialization" >&2
    echo >&2
    echo "  -d DEV  The LUKS device on which to perform binding" >&2
    echo >&2
    echo "  -s SLT  The LUKSMeta slot to use for metadata storage" >&2
    echo >&2
    echo "  -k KEY  Non-interactively read LUKS password from KEY file" >&2
    echo "  -k -    Non-interactively read LUKS password from standard input" >&2
    echo >&2
    exit 1
}

if [ $# -eq 1 -a "$1" == "--summary" ]; then
    echo "$SUMMARY"
    exit 0
fi

while getopts ":hfd:s:k:" o; do
    case "$o" in
    f) FRC=-f;;
    d) DEV=$OPTARG;;
    s) SLT=$OPTARG;;
    k) KEY=$OPTARG;;
    *) usage;;
    esac
done

if [ -z "$DEV" ]; then
    echo "Did not specify a device!" >&2
    usage
fi

if ! PIN=${@:$((OPTIND++)):1} || [ -z "$PIN" ]; then
    echo "Did not specify a pin!" >&2
    usage
fi

if ! CFG=${@:$((OPTIND++)):1} || [ -z "$CFG" ]; then
    echo "Did not specify a pin config!" >&2
    usage
fi

if [ -n "$KEY" ]; then
    if [ "$KEY" == "-" ]; then
        if ! luksmeta test -d $DEV && [ -z "$FRC" ]; then
            echo "Cannot use '-k-' without '-f' unless already initialized!" >&2
            usage
        fi
    elif ! [ -f "$KEY" ]; then
        echo "Key file '$KEY' not found!" >&2
        exit 1
    fi
fi

# Generate a key with the same entropy as the LUKS Master Key
dump=`cryptsetup luksDump $DEV`
bits=`sed -r -n 's|MK bits:[ \t]*([0-9]+)|\1|p' <<< "$dump"`
key=`pwmake $bits`

# Encrypt the new key
jwe=`echo -n "$key" | clevis encrypt "$PIN" "$CFG"`

# If necessary, initialize the LUKS volume
if ! luksmeta test -d $DEV; then
    luksmeta init -d $DEV $FRC
fi

# Write the JWE into the specified slot. Or, if no slot is given, ...
if [ -n "$SLT" ]; then
    if ! echo -n $jwe | luksmeta save -d "$DEV" -u "$UUID" -s $SLT 2>/dev/null; then
        echo "Error while saving Clevis metadata in LUKS header!" >&2
        false
    fi

# ... write the JWE to the first slot unused by both LUKS and LUKSMeta
elif ! SLT=`echo -n $jwe | luksmeta save -d "$DEV" -u "$UUID" 2>/dev/null`; then
    echo "Error while saving Clevis metadata in LUKS header!" >&2
    false
fi

export DEV
export SLT

# Add the new key to the LUKS slot that matches the LUKSMeta slot
case "$KEY" in
"") read -s -p "Enter existing LUKS password: " old; echo;;
 -) old=`cat`;;
 *) old=`cat "$KEY"`;;
esac

echo -e "$old\n$key" | cryptsetup luksAddKey -S $SLT $DEV