#!/usr/bin/python

from __future__ import print_function
from optparse import OptionParser
from ssl import SSLContext, PROTOCOL_TLSv1_2, CERT_REQUIRED, cert_time_to_seconds, SSLError, CertificateError
from socket import socket, AF_INET6
from datetime import datetime, timedelta
from smtplib import SMTP
import yaml

VERBOSE=False

class Verifier:
    def __init__(self, cafile, warn, crit):
        self.cafile = cafile
        self.crit = crit
        self.warn = warn

    def check(self, proto, host, port):
        context = SSLContext(PROTOCOL_TLSv1_2)
        context.verify_mode = CERT_REQUIRED
        context.load_verify_locations(self.cafile)
        if hasattr(self, 'remote_check_%s' % proto):
            getattr(self, 'remote_check_%s' % proto)(context, host, port)

    def remote_check_smtp(self, context, host, port):
        smtp = SMTP(host, port)
        try:
            smtp.starttls(context=context)
        except SSLError:
            print("CRIT (invalid certificate) %s:%d" % (host, port))
            return 2

        cert = smtp.sock.getpeercert()
        return self.check_cert(cert, host, port)

    def remote_check_ssl(self, context, host, port):
        connection = context.wrap_socket(socket(AF_INET6),
                                     server_hostname=host)
        try:
            connection.connect((host, port))
        except SSLError:
            print("CRIT (invalid certificate) %s:%d" % (host, port))
            return 2

        cert = connection.getpeercert()
        return self.check_cert(cert, host, port)

    def check_cert(self, data, host, port):
        expiretimestamp = cert_time_to_seconds(data['notAfter'])
        delta = datetime.utcfromtimestamp(expiretimestamp) - datetime.utcnow()

        if delta < self.crit:
            print("CRIT (expires in %s) %s:%d" % (delta, host, port))
            return 2
        elif delta < self.warn:
            print("WARN (expires in %s) %s:%d" % (delta, host, port))
            return 1

def main():
    global VERBOSE
    parser = OptionParser()
    parser.add_option("--config", action="store", type="string", dest="config",
                      help="configuration file to use")
    parser.add_option("-n", "--name",
                      action="append", type="string", dest="names",
                      help="hostname:port to check for expired certificates")
    parser.add_option("-w", "--warning-days",
                      action="store", type=int, dest="warn",
                      help="minimum remaining validity in days before a warning is issued")
    parser.add_option("-c", "--critical-days",
                      action="store", type=int, dest="crit",
                      help="minimum remaining validity in days before a warning is issued")
    parser.add_option("-v", action="store_true", dest="verbose", default=False)
    parser.add_option("-q", action="store_false", dest="verbose")
    parser.add_option("--ca", action="store", type="string", dest="ca",
                      help="ca certificate bundle")

        
    opts, _args = parser.parse_args()

    if opts.config:
        configuration = yaml.load(open(opts.config))
    else:
        configuration = dict()

    if opts.names:
        configuration['names'] = opts.names
    if opts.warn:
        configuration['warn_days'] = opts.warn
    if opts.crit:
        configuration['crit_days'] = opts.crit
    if opts.ca:
        configuration['cacertificates'] = opts.ca
    if opts.verbose:
        configuration['verbose'] = opts.verbose

    if 'verbose' in configuration:
        VERBOSE = configuration['verbose']

    if not 'names' in configuration:
        parser.error("needs at least one host")

    verifier = Verifier(configuration['cacertificates'] if 'cacertificates' in configuration else '/etc/ssl/certs/ca-certificates.crt',
                        timedelta(configuration['warn_days'] if 'warn_days' in configuration else 15),
                        timedelta(configuration['crit_days'] if 'crit_days' in configuration else 5))

    try:
        hosts = [ (i[0], i[1], int(i[2])) for i in [ j.split(':', 2) for j in configuration['names'] ] ]
    except (ValueError, IndexError):
        parser.error("names need to be in PROTO:DNSNAME:PORT format")
        
    for proto, host, port in hosts:
        verifier.check(proto, host, port)
                      
if __name__ == "__main__":
    main()