#!/bin/sh -eu

HOST=${1%:*}
PORT=${1#*:}
[ "${HOST}" != "${PORT}" ] || PORT=443

echo QUIT |
openssl s_client -connect ${HOST}:${PORT:-443} 2>/dev/null |
openssl x509 -noout -text |
sed -nre '/^\s+DNS:/s/ +DNS://; s/, DNS:/\n/gp'