:

# This uses the public/private keys on a Yubikey, and requires a
# use-entered PIN.

[ "$#" -ne 2 ] && echo "cluster_passphrase_command usage: $0 \"%d\" %R" 1>&2 && exit 1

DIR="$1"
FD="$2"

# PIV slot 3 is the "Key Management" slot
PIV_SLOT='0:3'

# File containing the passphrased encrypted with the PIV_SLOT's public key
KEY_FILE="$DIR/yubipass.key"


MSG='Enter Yubikey PIN:'

stty -echo <&"$FD"

# Create a passphrased encrypted with the PIV_SLOT's public key?
if [ ! -e "$KEY_FILE" ]
then	echo 1>&"$FD"
	echo -n "$MSG" 1>&"$FD"

	# The 'postgres' operating system user must have permission to
	# access the Yubikey device.

	openssl rand -hex 32 |
	xxd -plain -cols 999 |
	openssl rsautl -engine pkcs11 -keyform engine -encrypt \
		-inkey "$PIV_SLOT" -passin fd:"$FD" -out "$KEY_FILE" 2>&1 |
	grep -v '^engine "pkcs11" set\.$'

	echo 1>&"$FD"

	# Warn the user to save the passphrase in a safe place
	cat 1>&"$FD" <<END

WARNING:  The Yubikey can be locked and require a reset if too many PIN
attempts fail.  It is recommended to run this command manually and save
the passphrase in a secure location for possible recovery.
END

fi

echo 1>&"$FD"
echo -n "$MSG" 1>&"$FD"

# Decrypt the passphrased encrypted with the PIV_SLOT's public key
openssl rsautl -engine pkcs11 -keyform engine -decrypt \
		-inkey "$PIV_SLOT" -passin fd:"$FD" -in "$KEY_FILE" 2>&1 |
grep -v '^engine "pkcs11" set\.$'

echo 1>&"$FD"

stty echo <&"$FD"

exit 0