Skip to content

Instantly share code, notes, and snippets.

Embed
What would you like to do?
Sample acme code to get a certificate from Let's Encrypt
# There's a lack of sample code for acme/Let's Encrypt out there, and
# this is an attempt to at least slightly remedy that. It's the result
# of my first day's hacking on this stuff, so almost certainly contains
# errors and oversights.
#
# It's not designed to be specifically useful if what you want is
# just a cert -- certbot or dehydrated are better for that. It is sample
# code for people who are building automated systems to deal with large
# numbers of Let's Encrypt certificates to play with.
#
# request_cert will create a new user on Let's Encrypt's staging server,
# then apply for a certificate for the given domain. Production systems
# would more probably have a persistent private key for the user; the
# reason this code doesn't is just to make it self-contained.
#
# It only handles HTTP-based verification; when it is ready for you
# to do so, it will present you with a URL where you'll need to serve
# a particular bit of text.
#
# The code is Python 2.7, and needs you to "pip install acme".
#
# See http://www.gilesthomas.com/2018/11/python-code-to-generate-lets-encrypt-certificates/
# for a code walkthrough.
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives.asymmetric import rsa
from OpenSSL import crypto
from OpenSSL.SSL import FILETYPE_PEM
import time
from acme import client
from acme import messages
import josepy
DIRECTORY_URL = 'https://acme-staging.api.letsencrypt.org/directory'
KEY_SIZE = 2048
def get_http_challenge(authzr):
for challenge in authzr.body.challenges:
if challenge.chall.typ == 'http-01':
return challenge
else:
raise Exception("Could not find an HTTP challenge!")
def request_cert(domain):
domain = domain.lower()
print("Generating user key")
user_key = josepy.JWKRSA(
key=rsa.generate_private_key(
public_exponent=65537,
key_size=KEY_SIZE,
backend=default_backend()
)
)
print("Connecting to Let's Encrypt on {}".format(DIRECTORY_URL))
acme = client.Client(DIRECTORY_URL, user_key)
print("Registering")
regr = acme.register()
print("Agreeing to ToS")
acme.agree_to_tos(regr)
print("Requesting challenges")
authzr = acme.request_challenges(
identifier=messages.Identifier(typ=messages.IDENTIFIER_FQDN, value=domain)
)
print("Looking for HTTP challenge")
challenge = get_http_challenge(authzr)
print("You need to set up the challenge response.")
print("URL: http://{}{}".format(domain, challenge.chall.path))
print("Content: {}".format(challenge.chall.validation(user_key)))
response = challenge.chall.response(user_key)
while not response.simple_verify(challenge.chall, domain, user_key.public_key()):
raw_input("It doesn't look like it's set up yet; press return when it is.")
print("Authorizing -- here goes...")
auth_response = acme.answer_challenge(challenge, challenge.chall.response(user_key))
print("Response was {}".format(auth_response))
print("Waiting for authorization to become valid")
while True:
print("Polling")
authzr, authzr_response = acme.poll(authzr)
challenge = get_http_challenge(authzr)
if challenge.status.name == "valid":
break
print("HTTP challenge is currently {}".format(challenge))
time.sleep(1)
print("Auth valid")
print("Generating CSR")
certificate_key = crypto.PKey()
certificate_key.generate_key(crypto.TYPE_RSA, 2048)
csr = crypto.X509Req()
csr.get_subject().CN = domain
csr.set_pubkey(certificate_key)
csr.sign(certificate_key, "sha256")
print("Requesting certificate")
certificate_response = acme.request_issuance(josepy.util.ComparableX509(csr), [authzr])
print("Got it!")
print("Fetching chain")
chain = acme.fetch_chain(certificate_response)
print("Done!")
print("Here are the details:")
print("Private key:")
print(crypto.dump_privatekey(FILETYPE_PEM, certificate_key))
print("Combined cert:")
print(crypto.dump_certificate(FILETYPE_PEM, certificate_response.body.wrapped))
for cert in chain:
print(crypto.dump_certificate(FILETYPE_PEM, cert.wrapped))
@ChenHarold
Copy link

ChenHarold commented Aug 23, 2021

Can you teach me how to use this function ??

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment