import datetime

from cryptography import x509
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import hashes, serialization
from cryptography.hazmat.primitives.asymmetric import rsa
from cryptography.x509.oid import NameOID

one_day = datetime.timedelta(days=1)
ten_day = datetime.timedelta(days=3650)
today = datetime.datetime.today()
yesterday = today - one_day
tomorrow = today + ten_day

private_key = rsa.generate_private_key(
    public_exponent=65537,
    key_size=4096,
    backend=default_backend()
)
public_key = private_key.public_key()
builder = x509.CertificateBuilder()

builder = builder.subject_name(x509.Name([
    x509.NameAttribute(NameOID.COMMON_NAME, 'Novice'),
]))
builder = builder.issuer_name(x509.Name([
    x509.NameAttribute(NameOID.COMMON_NAME, 'JetProfile CA'),
]))
builder = builder.not_valid_before(yesterday)
builder = builder.not_valid_after(tomorrow)
builder = builder.serial_number(x509.random_serial_number())
builder = builder.public_key(public_key)

certificate = builder.sign(
    private_key=private_key, algorithm=hashes.SHA256(),
    backend=default_backend()
)

private_bytes = private_key.private_bytes(
    encoding=serialization.Encoding.PEM,
    format=serialization.PrivateFormat.TraditionalOpenSSL,
    encryption_algorithm=serialization.NoEncryption())
public_bytes = certificate.public_bytes(
    encoding=serialization.Encoding.PEM)
with open("ca.key", "wb") as fout:
    fout.write(private_bytes)
with open("ca.crt", "wb") as fout:
    fout.write(public_bytes)