Returns the expiration date of the SSL certificate in the number of days remaining, useful for Zabbix external scripts.

checksslcert.py

#!/usr/bin/env python3

import socket, ssl, sys, time, re

if len(sys.argv) < 2:
    print('Usage: %s {HOST|URL} [PORT]' % sys.argv[0])
    exit(1)

host = sys.argv[1]
if '://' in host:
    protocol, host, _ = re.search(r'(.*?)://(.*?)(/|$)', host).groups()
    if protocol == 'http':
        print('99999999')
        exit()

if len(sys.argv) >= 3:
    port = int(sys.argv[2])
else:
    port = 443

ctx = ssl.create_default_context()

rawsock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sslsock = ctx.wrap_socket(rawsock, server_hostname=host)
try:
    sslsock.connect((host, port))
except ssl.SSLError as e:
    print(e, file=sys.stderr)
    exit(1)
cert = sslsock.getpeercert()
expire = ssl.cert_time_to_seconds(cert['notAfter'])
seconds = expire - time.time()
print(seconds / (60 * 60 * 24))