check_certificate_file.sh

#!/bin/sh
PROGNAME=`basename $0`
REVISION="1.0.0"
PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin"
export PATH

# Nagios Status Code
STATE_OK=0
STATE_WARNING=1
STATE_CRITICAL=2
STATE_UNKNOWN=3
STATE_DEPENDENT=4

print_usage() {
    echo "Check expiration date of ssl certification file plugin for Nagios"
    echo "Usage: ${PROGNAME} --crt-file crtfile.crt -w WARNING_DAYS -c CRITICAL_DAYS"
    echo "Usage: ${PROGNAME} --crt-file crtfile.crt -w WARNING_DAYS"
    echo "Usage: ${PROGNAME} --help"
    echo "Usage: ${PROGNAME} --version"
}

if [ $# -lt 4 ]; then
    print_usage
    exit ${STATE_UNKNOWN}
fi

while test -n "$1"; do
    case "$1" in
        -h)
            print_usage
            exit ${STATE_OK}
            ;;
        --crt-file)
            crt_file=$2
            shift
            ;;
        -w)
            warning_days=$2
            shift
            ;;
        -c)
            critical_days=$2
            shift
            ;;
        -v)
            print_revision ${PROGNAME} ${REVISION}
            exit ${STATE_OK}
            ;;
        *)
            echo "Unknown argument: $1"
            print_usage
            exit ${STATE_UNKNOWN}
            ;;
    esac
    shift
done

if [ ! -e ${crt_file} ];then
  echo "Crt file ${crt_file} does not exist."
  exit ${STATE_UNKNOWN}
fi
if [ ! -z ${warning_days} ];then
  if ! expr ${warning_days} + 1 &> /dev/null;then
    echo "the warning days should be an integer."
    exit ${STATE_UNKNOWN}
  else
    has_warning_days=true
  fi
fi
if [ ! -z ${critical_days} ];then
  if ! expr ${critical_days} + 1 &> /dev/null;then
    echo "the critical days should be an integer."
    exit ${STATE_UNKNOWN}
  else
    has_critical_days=true
  fi
fi

date_string=$(openssl x509 -noout -dates -in ${crt_file} | grep notAfter | sed -e 's/notAfter=//')
ssl_date=$(date -d "${date_string}" '+%s')
now_date=$(date '+%s')
diff="$((${ssl_date}-${now_date}))"

if [ "${diff}" -lt "0" ];then
   echo "The certificate file ${crt_file} has already expired."
   exit ${STATE_CRITICAL}
else
   echo "The certificate file ${crt_file} will expire in $((${diff}/3600/24)) days."
   if [ ${has_critical_days} ];then
     if [ "${diff}" -lt "$((${critical_days}*24*3600))" ];then
       exit ${STATE_CRITICAL}
     fi
   fi
   if [ ${has_warning_days} ];then
     if [ "${diff}" -lt "$((${warning_days}*24*3600))" ];then
       exit ${STATE_WARNING}
     fi
   fi
fi