Check SSL certificate expires days

ssl_cert_expire.sh

#!/usr/bin/env bash

#
# Program: Check SSL certificate expires days <ssl_cert_expire.sh>
#
# Author: Mikhail Grigorev <sleuthhound at gmail dot com>
#
# Current Version: 1.0.2
#
# License:
#  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.
#

DEBUG=0

SOURCE="${BASH_SOURCE[0]}"
while [ -h "$SOURCE" ]; do
    DIR="$( cd -P "$( dirname "$SOURCE" )" && pwd )"
    SOURCE="$(readlink "$SOURCE")"
    [[ $SOURCE != /* ]] && SOURCE="$DIR/$SOURCE"
done
SCRIPT_DIR="$( cd -P "$( dirname "$SOURCE" )" && pwd )"
SCRIPT_NAME=$(basename "$0")

if [ ${DEBUG} -gt 0 ]; then
	exec 2>> /var/log/${SCRIPT_NAME%.*}.log
	set -x
fi

_usage() {
	echo ""
	echo "usage: $0 [-i|-d] HOST PORT SNI"
	echo "    -i Show Issuer"
	echo "    -d Show valid days remaining"
	echo ""
	exit 1
}

[ $# -lt 2 ] && _usage

OPT=$1
HOST=$2
PORT=$3
SNI=$4
PROTO=$5

if [ -z "${SNI}" ]; then
	SERVER_NAME=${HOST}
else
	SERVER_NAME=${SNI}
fi

if [ -z "${PORT}" ]; then
	PORT=443
fi

if [ -n "${PROTO}" ]; then
	START_TLS="-starttls ${PROTO}"
fi

case ${OPT} in
	-d)
			END_DATE=$(echo -e "quit\n" | openssl s_client -servername ${SERVER_NAME} -host ${HOST} -port ${PORT} -showcerts ${START_TLS} -prexit 2>&1 | sed -n '/BEGIN CERTIFICATE/,/END CERT/p' | openssl x509 -text 2>/dev/null | sed -n 's/ *Not After : *//p')
			if [ -n "${END_DATE}" ]; then
					END_DATE_SECOND=$(date '+%s' --date "${END_DATE}")
					NOW_SECONDS=$(date '+%s')
					END_DAY=$(echo "(${END_DATE_SECOND}-${NOW_SECONDS})/86400" | bc)
					echo -n "${END_DAY}"
			else
					echo -n "0"
			fi
	;;
	-i)
			ISSUE_DN=$(echo -e "quit\n" | openssl s_client -servername ${SERVER_NAME} -host ${HOST} -port ${PORT} -showcerts ${START_TLS} -prexit 2>&1 | sed -n '/BEGIN CERTIFICATE/,/END CERT/p' | openssl x509 -text 2>/dev/null | sed -n 's/ *Issuer: *//p')
			if [ -n "${ISSUE_DN}" ]; then
				ISSUER=$(echo -n "${ISSUE_DN}" | sed -n 's/.*CN=*//p' | sed 's/^[ \t]*//;s/[ ]*$//' | sed 's/^[= ]*//')
				echo -n "${ISSUER}"
			else
				echo -n "Not found"
			fi
	;;
	*)
		_usage
	;;
esac

exit 0