Parse a certificates and print data as csv

crt2csv.py

import argparse
import OpenSSL
from dateutil.parser import parse


if __name__ == '__main__':
    parser = argparse.ArgumentParser(description='Process some certs')
    parser.add_argument('CERT', help="Cert file to parse")
    args = parser.parse_args()
    with open(args.CERT, 'r') as f:
        data = f.read()

    cert = OpenSSL.crypto.load_certificate(OpenSSL.crypto.FILETYPE_PEM, data)
    subject = dict(cert.get_subject().get_components())
    issuer = dict(cert.get_issuer().get_components())
    not_before = parse(cert.get_notBefore().decode('utf-8'))
    not_after = parse(cert.get_notAfter().decode('utf-8'))
    serial = cert.get_serial_number()
    sha1 = cert.digest("sha1").decode('utf-8').replace(":", "")
    basic_constraints = False
    alt_names = []
    for c in range(cert.get_extension_count()):
        ext = cert.get_extension(c)
        if ext.get_short_name() == b'basicConstraints':
            if ext.get_data() == b'0\x00':
                basic_constraints = False
            else:
                basic_constraints = True
        if ext.get_short_name() == b'subjectAltName':
            dat = ext.get_data()
            # Ugly ASN1 decoder
            i = 3
            while i < len(dat):
                alt_names.append(dat[i+1:dat[i]+i+1].decode('utf-8'))
                i += dat[i] + 2

    print("%s|%s|%s|%s|%s|%s|%s|%s|%s" % (
        "", # id
        hex(serial)[2:], # serial
        sha1, #sha1
        subject[b'CN'].decode('utf-8'), # Common Name
        issuer[b'CN'].decode('utf-8'), #Issuer
        not_before.isoformat(), # Not Before
        not_after.isoformat(), # Not After
        str(basic_constraints), # Basic Constraints
        ", ".join(alt_names) # Alt names
        )
    )