csr_with_exsiting_key.py

from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import serialization
from cryptography import x509
from cryptography.x509.oid import NameOID
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.serialization import load_pem_private_key

# The sample code is extracted from the book Python Cryptography
# The book can be downloaded from https://leanpub.com/cryptop
# Online Crypto Playgroud https://8gwifi.org
# Author Anish Nath

encryptedpass = "myverystrongpassword "
key = load_pem_private_key(open('/tmp/rsakey.pem', 'rb').read(),encryptedpass,default_backend())

# Generate CSR
csr = x509.CertificateSigningRequestBuilder().subject_name(x509.Name([
        x509.NameAttribute(NameOID.COUNTRY_NAME, u"US"),
        x509.NameAttribute(NameOID.STATE_OR_PROVINCE_NAME, u"CA"),
        x509.NameAttribute(NameOID.LOCALITY_NAME, u"San Francisco"),
        x509.NameAttribute(NameOID.ORGANIZATION_NAME, u"Python Cryptography"),
        x509.NameAttribute(NameOID.COMMON_NAME, u"8gwifi.org"),
])).add_extension(
        x509.SubjectAlternativeName([
    x509.DNSName(u"mysite.com"),
]),
critical=False,

# Sign the CSR with our private key.
).sign(key, hashes.SHA256(), default_backend())
with open("/tmp/csr.pem", "wb") as f:
    f.write(csr.public_bytes(serialization.Encoding.PEM))