199 lines
8.5 KiB
Python
199 lines
8.5 KiB
Python
#!/usr/bin/env python
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import argparse, subprocess, json, os, os.path, urllib2, sys, base64, binascii, time, \
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hashlib, re, copy, textwrap
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#CA = "https://acme-staging.api.letsencrypt.org"
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CA = "https://acme-v01.api.letsencrypt.org"
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def get_crt(account_key, csr, acme_dir):
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# helper function base64 encode for jose spec
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def _b64(b):
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return base64.urlsafe_b64encode(b).replace("=", "")
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# parse account key to get public key
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sys.stderr.write("Parsing account key...")
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proc = subprocess.Popen(["openssl", "rsa", "-in", account_key, "-noout", "-text"],
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stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
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out, err = proc.communicate()
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if proc.returncode != 0:
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raise IOError("OpenSSL Error: {0}".format(err))
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pub_hex, pub_exp = re.search(
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r"modulus:\n\s+00:([a-f0-9\:\s]+?)\npublicExponent: ([0-9]+)",
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out, re.MULTILINE|re.DOTALL).groups()
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pub_mod = binascii.unhexlify(re.sub(r"(\s|:)", "", pub_hex))
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pub_mod64 = _b64(pub_mod)
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pub_exp = "{0:x}".format(int(pub_exp))
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pub_exp = "0{0}".format(pub_exp) if len(pub_exp) % 2 else pub_exp
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pub_exp64 = _b64(binascii.unhexlify(pub_exp))
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header = {
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"alg": "RS256",
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"jwk": {
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"e": pub_exp64,
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"kty": "RSA",
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"n": pub_mod64,
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},
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}
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accountkey_json = json.dumps(header['jwk'], sort_keys=True, separators=(',', ':'))
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thumbprint = _b64(hashlib.sha256(accountkey_json).digest())
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sys.stderr.write("parsed!\n")
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# helper function make signed requests
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def _send_signed_request(url, payload):
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nonce = urllib2.urlopen(CA + "/directory").headers['Replay-Nonce']
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payload64 = _b64(json.dumps(payload))
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protected = copy.deepcopy(header)
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protected.update({"nonce": nonce})
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protected64 = _b64(json.dumps(protected))
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proc = subprocess.Popen(["openssl", "dgst", "-sha256", "-sign", account_key],
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stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
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out, err = proc.communicate("{0}.{1}".format(protected64, payload64))
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if proc.returncode != 0:
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raise IOError("OpenSSL Error: {0}".format(err))
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data = json.dumps({
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"header": header,
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"protected": protected64,
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"payload": payload64,
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"signature": _b64(out),
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})
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try:
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resp = urllib2.urlopen(url, data)
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return resp.getcode(), resp.read()
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except urllib2.HTTPError as e:
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return e.code, e.read()
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# find domains
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sys.stderr.write("Parsing CSR...")
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proc = subprocess.Popen(["openssl", "req", "-in", csr, "-noout", "-text"],
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stdout=subprocess.PIPE, stderr=subprocess.PIPE)
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out, err = proc.communicate()
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if proc.returncode != 0:
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raise IOError("Error loading {0}: {1}".format(csr, err))
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domains = set([])
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common_name = re.search(r"Subject:.*? CN=([^\s,;/]+)", out)
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if common_name is not None:
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domains.add(common_name.group(1))
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subject_alt_names = re.search(r"X509v3 Subject Alternative Name: \n +([^\n]+)\n", out, re.MULTILINE|re.DOTALL)
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if subject_alt_names is not None:
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for san in subject_alt_names.group(1).split(", "):
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if san.startswith("DNS:"):
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domains.add(san[4:])
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sys.stderr.write("parsed!\n")
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# get the certificate domains and expiration
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sys.stderr.write("Registering account...")
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code, result = _send_signed_request(CA + "/acme/new-reg", {
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"resource": "new-reg",
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"agreement": "https://letsencrypt.org/documents/LE-SA-v1.0.1-July-27-2015.pdf",
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})
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if code == 201:
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sys.stderr.write("registered!\n")
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elif code == 409:
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sys.stderr.write("already registered!\n")
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else:
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raise ValueError("Error registering: {0} {1}".format(code, result))
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# verify each domain
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for domain in domains:
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sys.stderr.write("Verifying {0}...".format(domain))
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# get new challenge
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code, result = _send_signed_request(CA + "/acme/new-authz", {
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"resource": "new-authz",
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"identifier": {
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"type": "dns",
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"value": domain,
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},
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})
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if code != 201:
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raise ValueError("Error registering: {0} {1}".format(code, result))
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# make the challenge file
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challenge = [c for c in json.loads(result)['challenges'] if c['type'] == "http-01"][0]
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challenge['token'] = re.sub(r"[^A-Za-z0-9_\-]", "_", challenge['token'])
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keyauthorization = "{0}.{1}".format(challenge['token'], thumbprint)
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wellknown_path = os.path.join(acme_dir, challenge['token'])
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wellknown_file = open(wellknown_path, "w")
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wellknown_file.write(keyauthorization)
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wellknown_file.close()
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# check that the file is in place
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wellknown_url = "http://{0}/.well-known/acme-challenge/{1}".format(
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domain, challenge['token'])
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try:
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resp = urllib2.urlopen(wellknown_url)
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assert resp.read().strip() == keyauthorization
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except (urllib2.HTTPError, urllib2.URLError, AssertionError):
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os.remove(wellknown_path)
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raise ValueError("Wrote file to {0}, but couldn't download {1}".format(
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wellknown_path, wellknown_url))
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# notify challenge are met
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code, result = _send_signed_request(challenge['uri'], {
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"resource": "challenge",
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"keyAuthorization": keyauthorization,
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})
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if code != 202:
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raise ValueError("Error triggering challenge: {0} {1}".format(code, result))
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# wait for challenge to be verified
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while True:
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try:
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resp = urllib2.urlopen(challenge['uri'])
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challenge_status = json.loads(resp.read())
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except urllib2.HTTPError as e:
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raise ValueError("Error checking challenge: {0} {1}".format(
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e.code, json.loads(e.read())))
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if challenge_status['status'] == "pending":
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time.sleep(2)
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elif challenge_status['status'] == "valid":
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sys.stderr.write("verified!\n")
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os.remove(wellknown_path)
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break
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else:
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raise ValueError("{0} challenge did not pass: {1}".format(
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domain, challenge_status))
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# get the new certificate
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sys.stderr.write("Signing certificate...")
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proc = subprocess.Popen(["openssl", "req", "-in", csr, "-outform", "DER"],
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stdout=subprocess.PIPE, stderr=subprocess.PIPE)
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csr_der, err = proc.communicate()
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code, result = _send_signed_request(CA + "/acme/new-cert", {
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"resource": "new-cert",
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"csr": _b64(csr_der),
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})
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if code != 201:
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raise ValueError("Error signing certificate: {0} {1}".format(code, result))
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# return signed certificate!
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sys.stderr.write("signed!\n")
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return """-----BEGIN CERTIFICATE-----\n{0}\n-----END CERTIFICATE-----\n""".format(
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"\n".join(textwrap.wrap(base64.b64encode(result), 64)))
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if __name__ == "__main__":
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parser = argparse.ArgumentParser(
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formatter_class=argparse.RawDescriptionHelpFormatter,
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description=textwrap.dedent("""\
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This script automates the process of getting a signed TLS certificate from
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Let's Encrypt using the ACME protocol. It will need to be run on your server
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and have access to your private account key, so PLEASE READ THROUGH IT! It's
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only ~200 lines, so it won't take long.
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===Example Usage===
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python acme_tiny.py --account-key ./account.key --csr ./domain.csr --acme-dir /usr/share/nginx/html/.well-known/acme-challenge/ > signed.crt
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===================
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===Example Crontab Renewal (once per month)===
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0 0 1 * * python /path/to/acme_tiny.py --account-key /path/to/account.key --csr /path/to/domain.csr --acme-dir /usr/share/nginx/html/.well-known/acme-challenge/ > /path/to/signed.crt 2>> /var/log/acme_tiny.log
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==============================================
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""")
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)
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parser.add_argument("--account-key", required=True, help="path to your Let's Encrypt account private key")
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parser.add_argument("--csr", required=True, help="path to your certificate signing request")
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parser.add_argument("--acme-dir", required=True, help="path to the .well-known/acme-challenge/ directory")
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args = parser.parse_args()
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signed_crt = get_crt(args.account_key, args.csr, args.acme_dir)
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sys.stdout.write(signed_crt)
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