Python script to check on SSL certificates

ssl-check.py

# -*- encoding: utf-8 -*-
# requires a recent enough python with idna support in socket
# pyopenssl, cryptography and idna

from OpenSSL import SSL
from cryptography import x509
from cryptography.x509.oid import NameOID
import idna

from socket import socket
from collections import namedtuple

HostInfo = namedtuple(field_names='cert hostname peername', typename='HostInfo')

HOSTS = [
    ('damjan.softver.org.mk', 443),
    ('expired.badssl.com', 443),
    ('wrong.host.badssl.com', 443),
    ('ca.ocsr.nl', 443),
    ('faß.de', 443),
    ('самодеј.мкд', 443),
]

def verify_cert(cert, hostname):
    # verify notAfter/notBefore, CA trusted, servername/sni/hostname
    cert.has_expired()
    # service_identity.pyopenssl.verify_hostname(client_ssl, hostname)
    # issuer

def get_certificate(hostname, port):
    hostname_idna = idna.encode(hostname)
    sock = socket()

    sock.connect((hostname, port))
    peername = sock.getpeername()
    ctx = SSL.Context(SSL.SSLv23_METHOD) # most compatible
    ctx.check_hostname = False
    ctx.verify_mode = SSL.VERIFY_NONE

    sock_ssl = SSL.Connection(ctx, sock)
    sock_ssl.set_connect_state()
    sock_ssl.set_tlsext_host_name(hostname_idna)
    sock_ssl.do_handshake()
    cert = sock_ssl.get_peer_certificate()
    crypto_cert = cert.to_cryptography()
    sock_ssl.close()
    sock.close()

    return HostInfo(cert=crypto_cert, peername=peername, hostname=hostname)

def get_alt_names(cert):
    try:
        ext = cert.extensions.get_extension_for_class(x509.SubjectAlternativeName)
        return ext.value.get_values_for_type(x509.DNSName)
    except x509.ExtensionNotFound:
        return None

def get_common_name(cert):
    try:
        names = cert.subject.get_attributes_for_oid(NameOID.COMMON_NAME)
        return names[0].value
    except x509.ExtensionNotFound:
        return None

def get_issuer(cert):
    try:
        names = cert.issuer.get_attributes_for_oid(NameOID.COMMON_NAME)
        return names[0].value
    except x509.ExtensionNotFound:
        return None


def print_basic_info(hostinfo):
    s = '''» {hostname} « … {peername}
    \tcommonName: {commonname}
    \tSAN: {SAN}
    \tissuer: {issuer}
    \tnotBefore: {notbefore}
    \tnotAfter:  {notafter}
    '''.format(
            hostname=hostinfo.hostname,
            peername=hostinfo.peername,
            commonname=get_common_name(hostinfo.cert),
            SAN=get_alt_names(hostinfo.cert),
            issuer=get_issuer(hostinfo.cert),
            notbefore=hostinfo.cert.not_valid_before,
            notafter=hostinfo.cert.not_valid_after
    )
    print(s)

def check_it_out(hostname, port):
    hostinfo = get_certificate(hostname, port)
    print_basic_info(hostinfo)


import concurrent.futures
if __name__ == '__main__':
    with concurrent.futures.ThreadPoolExecutor(max_workers=4) as e:
        for hostinfo in e.map(lambda x: get_certificate(x[0], x[1]), HOSTS):
            print_basic_info(hostinfo)

How to add the output of the organization that issued the certificate to the script. For example
(O) Let's Encrypt

Everything. Figured it out
names_o = cert.issuer.get_attributes_for_oid(NameOID.ORGANIZATION_NAME)

when I get a list of sites and one of them does not have a TLS certificate configured, it generates an error:
sock.connect((hostname, port))
BlockingIOError: [Errno 11] Resource temporarily unavailable

Would it be possible to convert the cert to a byte string or an instance of asn1crypto.x509.Certificate please?

Hi, the script is useful, but it's possible put these values: ('damjan.softver.org.mk', 443), ('expired.badssl.com', 443), ('wrong.host.badssl.com', 443), ('ca.ocsr.nl', 443), ('faß.de', 443), ('самодеј.мкд', 443), inside a text file? I mean exist an elegant way to read lines of file into list?

you can change HOSTS into this:

HOSTS = []

for line in hosts_file:
host, port = line.strip().split(':')
HOSTS.append((host, int(port)))

I really appreciate that you took the time to share this with the world... super useful !!! Thank you.

Thank you so much for being so helpful.