certificate_file_expiry

#!/bin/sh
: << =cut
=head1 NAME

certificate_file_expiry - check the certificate validity of your certificates

= head1 CONFIGURATION

Installing: Add list of your certificates prefixed by the type in munin plugin-conf.d

For openvpn ca.crt and crl.pem

 [certificate_file_expiry]
 user root
 env.CERTS crl:/etc/openvpn/easy-rsa/keys/crl.pem x509:/etc/openvpn/easy-rsa/keys/ca.crt
 env.LOGARITHMIC yes

For letsencrypt certificates

 [certificate_file_expiry]
 user root
 env.CERTS x509:/etc/letsencrypt/live/*/cert.pem

Warning and Critical levels can also be configured with env variables like this:

 [certificate_file_expiry]
 ...
 # warn when certificate will be invalid within 5 days
 env.warning 5:
 # for this certificate warn us 10 days before because it takes longer to renew
 env._etc_letsencrypt_live_example_com_cert_pem_warning 10:
 # critical when certificate will be invalid within 1 day
 env.critical 1:

env.CERTS should be a space separated list of patterns prefixed by the type of certificate to check and a colon. All types of
certificates that openssl supports as standard commands and have a validity output are supported (e.g. x509, crl).
File patterns can be a single file (e.g. /etc/openvpn/easy-rsa/keys/crl.pem) or a pattern that matches multiple files
(e.g. /etc/letsencrypt/live/*/cert.pem).

env.warning and env.critical are configurable values for the warning and critical levels according to
http://guide.munin-monitoring.org/en/latest/tutorial/alert.html?highlight=warning#syntax-of-warning-and-critical

env.LOGARITHMIC "yes" enables the logarithmic display of values which is useful if some of your certs are relatively
long lived in respect to the warning level. e.g. a ca.crt that is valid for 10 years together with a crl.pem that is
valid for only a few months combined with warning levels of 5 days. default is "yes" to disable set it to "no".

=head1 Dependencies

Dependencies: openssl

=head1 AUTHOR

andreas perhab - andreas.perhab@wt-io-it.at (https://www.wt-io-it.at/)

=head1 LICENSE

GPLv2

=cut

. "$MUNIN_LIBDIR/plugins/plugin.sh"

LOGARITHMIC=${LOGARITHMIC:-yes}

if [ "$1" = "config" ] ; then
  echo "graph_title Certificate validity"
  if [ "$LOGARITHMIC" = "yes" ] ; then
    graph_args="--logarithmic --units=si"
  fi
  echo "graph_args --base 1000 $graph_args"
  echo "graph_vlabel days"
  echo "graph_category security"
fi

now=$(date +%s)
for cert in ${CERTS}; do
  cert_type=${cert%:*}
  cert_pattern=${cert#*:}
  for cert_file in $cert_pattern; do
    cert_name=$(clean_fieldname "$cert_file")
    if [ "$1" = "config" ] ; then
      echo "${cert_name}.label ${cert_file}"
      print_warning "$cert_name"
      print_critical "$cert_name"
    elif [ "$1" = "" ] ; then
      validity=$(/usr/bin/openssl "$cert_type" -text -noout -in "$cert_file" | grep -E '(Next Update|Not After)')
      validity=${validity#*:}
      validity=$(date --date="$validity" +%s)
      validity=$((validity - now))
      validity=$(echo "$validity" | awk '{ print ($1 / 86400) }')
      echo "${cert_name}.value $validity"
    fi
  done
done