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)

Are you able to distinguish the certificate type from this info e.g. ('OV SSL', 'EV SSL', 'DV SSL') ?

Are you able to distinguish the certificate type from this info e.g. ('OV SSL', 'EV SSL', 'DV SSL') ?

afaik yes, if you give me an example site with those attributes I can take a look how to extract those from the cert info

For example PayPal.com has an expensive EV(Extended Validation) SSL cert but the only indication I've been able to find is occasionally sites have 'Extended Validation Server' in their CN field.

This isn't standard either, some just have a name like 'Google Trust Services' like for Google.com.

Edit - I just found this post clearing some of this up for me, https://security.stackexchange.com/questions/88721/how-to-detect-whether-a-ca-used-ev-for-a-certificate-using-openssl

https://en.wikipedia.org/wiki/Extended_Validation_Certificate

EV certificates are different from domain-validated certificates and organization-validation certificates in that they can be issued only by a subset of certificate authorities (CAs) and require verification of the requesting entity's legal identity before certificate issuance.

so you'll need to have a list of the CAs

Hi gdamjan,

I am trying to get the following information from a certificate through python:

• Issuer Name

• Valid From

• Valid To

• Site Name

And I was trying your script only to get the following error:

AttributeError: 'X509' object has no attribute 'issuer'

Please Help
Thanks and Regards.

those are all in the script above

Can you help regarding this issue also:
AttributeError: 'X509' object has no attribute 'issuer'
Thanks

Are you able to distinguish the certificate type from this info e.g. ('OV SSL', 'EV SSL', 'DV SSL') ?

You may go through the extensions (certificate.get_extension(i)) and search for the EV policy id:

2.23.140.1.2.1 DV
2.23.140.1.2.2 OV
2.23.140.1.1   EV

@simon-wessel cool.

So, def get_certificate(hostname, port): returns the HostInfo object. Its .cert field has the .extensions list.

An example:

def cert_type(cert):
    for ext in cert.extensions:
        if ext.oid.dotted_string == '2.23.140.1.2.1':
            return 'DV type'
        if ext.oid.dotted_string == '2.23.140.1.2.2':
            return 'OV type'
        if ext.oid.dotted_string == '2.23.140.1.1':
            return 'EV' type
    return 'Normal certificate type'

host = get_certificate('example.net')
cert_type(host.cert)

This works great at a basic level, I'm new with python, I struggled a bit figuring out where to run PIP from to get pyopenssl and the other dependencies installed to run it , but it was easy if when you install python, you get pip installed from the beginning , obviously you set the path variable, then you just use pip from the windows CMD and it works. I would like this code to have a separate alerts field in the output for certs expiring in 60 days I would also like to figure out getting email built into it.

How do we get the results in json format?

How do we get the results in json format?

json.dumps(host._as_dict())

How do we get the results in json format?

json.dumps(host._as_dict())

Thanks - but this is what I get

Code:
host = get_certificate('google.co.nz', 443)
print(host)
json.dumps(host._as_dict())

Error:
HostInfo(cert=<Certificate(subject=<Name(C=US,ST=California,L=Mountain View,O=Google LLC,CN=*.google.co.nz)>, ...)>, hostname='google.co.nz', peername=('142.250.66.195', 443))
Traceback (most recent call last):
File ".\ssl-check.py", line 110, in
print_basic_info(hostinfo)
File ".\ssl-check.py", line 91, in print_basic_info
json.dumps(host._as_dict())
AttributeError: 'HostInfo' object has no attribute '_as_dict'

I am able to build the json manually but am thinking of a cooler option. :)

._asdict()

I'm running into a suspected firewall issue when I attempt to access few hosts, and the script is failing and erroring out with:

Traceback (most recent call last):
  File "/usr/local/adm/checkcerts.py", line 53, in get_certificate
    sock.connect((hostname, port))
TimeoutError: [Errno 110] Connection timed out

For the specific hosts in my issue, I intend to address the issue with my networking team, but does anyone have a good suggestion for handling that error in the script?

Insanely dope script. namedtuple just blew my mind.
Any idea on how to verify the chain?

I am having problems with the verify_cert option is this working correctly and is there a way to check a self signed certificate?

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.

cert.has_expired() doesn't work for this version. Is there a workaround?
Error
'cryptography.hazmat.bindings._rust.x509.Certificat' object has no attribute 'has_expired'

cert.has_expired() doesn't work for this version.

and what is "this" version !?!

Is there a workaround?

install "another" version?!