Check certificate expiration date using timeout, openssl and date cli tools

check_cert_data.sh

#!/usr/bin/env bash

HOST=$1
PORT=$2
DAYS=${3:-10}

CERT_FILE=$(mktemp)

### Read Site Certificate and save as File ###
timeout --preserve-status 3 openssl s_client -servername $HOST -connect $HOST:$PORT 2>/dev/null | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' > "$CERT_FILE"

if [ ! -s "$CERT_FILE" ]; then
    echo "$HOST:$PORT was not up!"
    exit 1
fi

### Get Full Expiration Date ###
date=$(openssl x509 -in $CERT_FILE -enddate -noout | sed "s/.*=\(.*\)/\1/" | awk -F " " '{print $1,$2,$3,$4}')

rm "$CERT_FILE"

### Convert Expiration Date in Epoch Format ###
date_s=$(date -j -f "%b %d %T %Y" "$date" "+%s")

### Get Curent Date in Epoch Format ###
now_s=$(date +%s)

### Calculate Time Difference ###
date_diff=$(( (date_s - now_s) / 86400 ))

echo "Cert for $HOST:$PORT will expire in $date_diff days"

if [ "${date_diff}" -lt "${DAYS}" ]; then
    exit 1
else
    exit 0
fi