yubikey-luks-enroll

#!/bin/bash

set -euo pipefail

#Instead of assuming /dev/sda3, this function reads /etc/crypttab for the first non-cryptswap entry and then
#queries cryptsetup to determine the actual device. More reliable, especially for computers using NVMe SSDs.
function getLUKSRootDisk() {
	luksDevice=$(grep -v cryptswap /etc/crypttab | awk '{print $1}');
	DISK=$(cryptsetup status "$luksDevice" | grep 'device: ' | awk '{print $2}')
}


SLOT=7;
DISK='';
CLEAR_SLOT=0;
DBG=0;

. /etc/ykluks.cfg

getLUKSRootDisk;

if [ "$(id -u)" -ne 0 ]; then
  echo "You must be root." 1>&2;
  exit 1;
fi

while getopts ":s:d:hcv" opt; do
  case $opt in
	s)
		if [ "$OPTARG" -gt -1 ] && [ "$OPTARG" -lt 8 ]; then
			SLOT=$OPTARG
			echo "Setting slot to $OPTARG."
		else
			echo "Invalid slot specified, choose one slot between 0 and 7 or omit this option to choose the default ($SLOT)";
			exit 3;
		fi;
		;;
	d)
		if [ -b "$OPTARG" ]; then #Check it's a block device
			DISK=$OPTARG
			echo "Setting disk to $OPTARG."
		else
			echo "$OPTARG is not a block device!"
			exit 4;
		fi
		;;
	c)  CLEAR_SLOT=1
		echo "clearing slot"
		;;
	v)  DBG=1
		echo "debugging enabled"
		;;
	h)
		echo;
		echo " -d <partition>: set the partition";
		echo " -s <slot>     : set the slot";
		echo " -c            : clear the slot prior to writing";
		echo " -v            : show input/output in cleartext";
		echo
		exit 1;
		;;
	\?)
		echo "Invalid option: -$OPTARG" >&2;
		;;
  esac
done

echo "This script will utilize slot $SLOT on drive $DISK.  If this is not what you intended, exit now!";

if [ "$CLEAR_SLOT" = "1" ]; then
	echo "Killing LUKS slot $SLOT"
	cryptsetup luksKillSlot "$DISK" "$SLOT"
fi

echo "Adding yubikey to initrd"

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

P1=$(/lib/cryptsetup/askpass "Please enter the yubikey challenge password. This is the password that will only work while your yubikey is installed in your computer:")
	if [ "$DBG" = "1" ]; then echo "Password: $P1"; fi

P2=$(/lib/cryptsetup/askpass "Please enter the yubikey challenge password again:")
	if [ "$DBG" = "1" ]; then echo "Password: $P2"; fi

if [ "x$P1" != "x$P2" ]; then
	echo "Passwords do not match";
	exit 1;
fi

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

#Run the password through the Yubikey. We probably want to know if this fails!
R=$(ykchalresp -2 "$P1");
	if [ $DBG -eq 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

OLD=$(/lib/cryptsetup/askpass "Please provide an existing passphrase. This is NOT the passphrase you just entered, this is the passphrase that you currently use to unlock your LUKS encrypted drive:")
	if [ "$DBG" = "1" ]; then echo "Old passphrase: $OLD"; fi

if [ "$CONCATENATE" -eq 1 ]; then
	printf '%s\n' "$OLD" "$P1$R" "$P1$R" | cryptsetup --key-slot="$SLOT" luksAddKey "$DISK" 2>&1;
		if [ $DBG -eq 1 ]; then echo "LUKS key: $P1$R"; fi
else
	printf '%s\n' "$OLD" "$R" "$R" | cryptsetup --key-slot="$SLOT" luksAddKey "$DISK" 2>&1;
		if [ $DBG -eq 1 ]; then echo "LUKS key: $R"; fi
fi

exit 0;