Error while creating a self signed certificate using pyopenssl

Question

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_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*365*24*60*60)
    cert.set_issuer(cert.get_subject())
    cert.set_pubkey(k)
    cert.sign(k, 'sha1')

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

create_self_signed_cert()

I am trying to create self certificate but its displaying error :

crypto.dump_certificate(crypto.FILETYPE_PEM, cert))
TypeError: write() argument must be str, not bytes

please help me.

Answer 1

I think os.write() will be able to write the buffer returned by crypto.dump_certificate :

import os

f = os.open(CERT_FILE)
os.write(f, crypto.dump_certificate(crypto.FILETYPE_PEM, cert))
os.close(f)

Answer 2

In python 3 I used decode

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

Answer 3

You may use "write binary" file open mode
by replacing the value "wt" with "wb" in open(FILE, "wt").