Create a self signed X509 certificate in Python

Question

I followed this url to create a X509 certificate. And the code is:

from OpenSSL import crypto, SSL
from socket import gethostname
from pprint import pprint
from time import gmtime, mktime

CERT_FILE = "selfsigned.crt"
KEY_FILE = "private.key"

def create_self_signed_cert():

    # create a key pair
    k = crypto.PKey()
    k.generate_key(crypto.TYPE_<wbr>RSA, 1024)

    # create a self-signed cert
    cert = crypto.X509()
    cert.get_subject().C = "UK"
    cert.get_subject().ST = "London"
    cert.get_subject().L = "London"
    cert.get_subject().O = "Dummy Company Ltd"
    cert.get_subject().OU = "Dummy Company Ltd"
    cert.get_subject().CN = gethostname()
    cert.set_serial_number(1000)
    cert.gmtime_adj_notBefore(0)
    cert.gmtime_adj_notAfter(10*<wbr>365*24*60*60)
    cert.set_issuer(cert.get_<wbr>subject())
    cert.set_pubkey(k)
    cert.sign(k, 'sha1')

    open(CERT_FILE, "wt").write(
        crypto.dump_certificate(<wbr>crypto.FILETYPE_PEM, cert))
    open(KEY_FILE, "wt").write(
        crypto.dump_privatekey(crypto.<wbr>FILETYPE_PEM, k))

create_self_signed_cert()

But there is something wrong with the code when I run it. Could someone tell me what the meaning of <wbr> ? There is a SyntaxError in cert.gmtime_adj_notAfter(10*<wbr>365*24*60*60) . Thx.

Answer 1

A version which works with python3

from OpenSSL import crypto, SSL

def cert_gen(
    emailAddress="emailAddress",
    commonName="commonName",
    countryName="NT",
    localityName="localityName",
    stateOrProvinceName="stateOrProvinceName",
    organizationName="organizationName",
    organizationUnitName="organizationUnitName",
    serialNumber=0,
    validityStartInSeconds=0,
    validityEndInSeconds=10*365*24*60*60,
    KEY_FILE = "private.key",
    CERT_FILE="selfsigned.crt"):
    #can look at generated file using openssl:
    #openssl x509 -inform pem -in selfsigned.crt -noout -text
    # create a key pair
    k = crypto.PKey()
    k.generate_key(crypto.TYPE_RSA, 4096)
    # create a self-signed cert
    cert = crypto.X509()
    cert.get_subject().C = countryName
    cert.get_subject().ST = stateOrProvinceName
    cert.get_subject().L = localityName
    cert.get_subject().O = organizationName
    cert.get_subject().OU = organizationUnitName
    cert.get_subject().CN = commonName
    cert.get_subject().emailAddress = emailAddress
    cert.set_serial_number(serialNumber)
    cert.gmtime_adj_notBefore(0)
    cert.gmtime_adj_notAfter(validityEndInSeconds)
    cert.set_issuer(cert.get_subject())
    cert.set_pubkey(k)
    cert.sign(k, 'sha512')
    with open(CERT_FILE, "wt") as f:
        f.write(crypto.dump_certificate(crypto.FILETYPE_PEM, cert).decode("utf-8"))
    with open(KEY_FILE, "wt") as f:
        f.write(crypto.dump_privatekey(crypto.FILETYPE_PEM, k).decode("utf-8"))

cert_gen()

Answer 2

Just remove <wbr> . So stupid I am.

Answer 3

This is a really useful question; as the referenced link is now dead; and this is one of the first results for searching for "python create ssl certificate".

I would add to it though, that "open(xxx, "wt").write()" is asking for problems later. By not explicitly closing the file, you may find that the garbage collector hasn't run when you try to actually use the file - resulting in a failure.

it's better to use:

with open(xxx, "w") as f:
    f.write()

which will ensure that the file is closed when you're done.