Letsencrypt: Send E-Mail if certificate validity is less than 10 days

renew-letsencrypt.sh

#! /bin/bash

LOG=/tmp/letsencrypt-renewal-attempt

/usr/local/sbin/certbot-auto renew >$LOG 2>&1
service nginx reload >>$LOG 2>&1


#
# Check SSL Certificate is valid for at least $DAYS
#

DAYS=10
HOST=werkzeugkasten.dpa-newslab.com
 

openssl s_client -showcerts -connect $HOST:443 </dev/null 2>/dev/null|openssl x509 -noout -checkend $(echo $((24*60*60*$DAYS)) ) || \
cat <<__END__ | msmtp mvirtel@wherever_this_shoud_go
Subject: Certificate Check for $HOST failed
From: ubuntu@werkzeugkasten.dpa-newslab.com

$HOST SSL Certificate check failed. Certificate valitiy could be less than $DAYS days.

Message generated by $0. 

Certificate Renewal Logfile:

$(cat $LOG)

__END__