yubikey-luks-open

#!/bin/sh
DISK="/dev/sda3"
NAME="yubikey-luks"
DBG=0

set -e
. /etc/ykluks.cfg

while getopts ":d:n:hv" opt; do
  case $opt in
	d)
		DISK=$OPTARG
		echo "setting disk to $OPTARG."
		;;
	n)
		NAME=$OPTARG
		echo "setting name to $OPTARG."
		;;
	v)
		DBG=1
		echo "debugging enabled"
		;;
	h)
		echo
		echo " -d <partition>: select existing partition"
		echo " -n <name>     : set the new container name"
		echo " -v            : show input/output in cleartext"
		echo
		exit 1
		;;
	\?)
		echo "Invalid option: -$OPTARG" >&2
		;;
  esac
done

echo "This script will try opening $NAME LUKS container on drive $DISK . If this is not what you intended, exit now!"

while true ; do
	if lsusb | grep -iq 'yubico'; then break; fi
	printf "Please insert a yubikey and press enter."
	read -r _ <&1
done

P1=$(/lib/cryptsetup/askpass "Enter password created with yubikey-luks-enroll:")
	if [ "$DBG" = "1" ]; then echo "Password: $P1"; fi

if [ "$HASH" = "1" ]; then
	P1=$(printf %s "$P1" | sha256sum | awk '{print $1}')
		if [ "$DBG" = "1" ]; then echo "Password hash: $P1"; fi
fi

R="$(ykchalresp "-$YUBIKEY_SLOT" "$P1" 2>/dev/null || true)"
	if [ "$DBG" = "1" ]; then echo "Yubikey response: $R"; fi

if [ -z "$R" ]; then
	echo "Yubikey not available or timed out waiting for button press"
	exit 1
fi

_passphrase=''
if [ "$CONCATENATE" = "1" ]; then
	_passphrase=$(printf '%s' "$P1$R")
else
	_passphrase=$(printf '%s' "$R")
fi
	if [ "$DBG" = "1" ]; then echo "LUKS key: ${_passphrase}"; fi

if [ "$(id -u)" -eq 0 ]; then
	printf %s "${_passphrase}" | cryptsetup luksOpen "$DISK" "$NAME" 2>&1;
else
	# c-style escapes are not available in sh, so instead of doing symply
	# $'\n' we have to put a newline in a variable, see:
	#   https://github.com/koalaman/shellcheck/wiki/SC2039
	_n="$(printf '%b_' '\n')"
	_n="${_n%_}"

	# reading a HEREDOC to a variable in a POSIX-compliant shell, see:
	#   https://unix.stackexchange.com/a/340907/162158
	# basically, the while loop reads the HEREDOC line-by-line (IFS set to
	# newline) and concatenates everything in a variable and adds a newline.
	expect_script=''
	OLDIFS="$IFS"
	while IFS="${_n}" read -r line; do
		expect_script="$expect_script$line${_n}"
	done <<EXPECTSCRIPT
		set timeout -1;
		spawn udisksctl unlock -b "$DISK";
		match_max 100000;
		expect -exact "Passphrase: ";
		send -- "${_passphrase}\\r";
		expect eof
EXPECTSCRIPT
	# get rid of all tabs and convert newlines to spaces in the expect script,
	# otherwise it will break when it is piped to expect
	expect_script=$(echo "$expect_script" | tr -d '\t' | tr '\n' ' ')
	IFS="$OLDIFS"

	echo "$expect_script" | expect -f -
fi

exit 0