X509 certificate tester

test_cert.py

from cryptography import x509
from cryptography.hazmat.backends import default_backend

import datetime


def cert_is_valid(cert_file, min_lifetime=0):
    """
    Returns boolean - True if the certificate is in date.
    Optional argument min_lifetime is the number of seconds
    which must remain.
    """
    try:
        with open(cert_file) as f:
            crt_data = f.read()
    except IOError:
        return False

    try:
        cert = x509.load_pem_x509_certificate(crt_data, default_backend())
    except ValueError:
        return False

    now = datetime.datetime.now()

    return (cert.not_valid_before <= now
            and cert.not_valid_after > now + datetime.timedelta(0, min_lifetime))

Requires pip install cryptography