added basic script

acme_tiny.py

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