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383 lines
15 KiB
Python
383 lines
15 KiB
Python
# Utilities for installing and selecting SSL certificates.
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import os, os.path, re, shutil
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from utils import shell, safe_domain_name
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def get_ssl_certificates(env):
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# Scan all of the installed SSL certificates and map every domain
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# that the certificates are good for to the best certificate for
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# the domain.
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from cryptography.hazmat.primitives.asymmetric.rsa import RSAPrivateKey
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from cryptography.x509 import Certificate
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# The certificates are all stored here:
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ssl_root = os.path.join(env["STORAGE_ROOT"], 'ssl')
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# List all of the files in the SSL directory and one level deep.
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def get_file_list():
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for fn in os.listdir(ssl_root):
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fn = os.path.join(ssl_root, fn)
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if os.path.isfile(fn):
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yield fn
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elif os.path.isdir(fn):
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for fn1 in os.listdir(fn):
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fn1 = os.path.join(fn, fn1)
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if os.path.isfile(fn1):
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yield fn1
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# Remember stuff.
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private_keys = { }
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certificates = [ ]
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# Scan each of the files to find private keys and certificates.
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# We must load all of the private keys first before processing
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# certificates so that we can check that we have a private key
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# available before using a certificate.
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for fn in get_file_list():
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try:
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pem = load_pem(load_cert_chain(fn)[0])
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except ValueError:
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# Not a valid PEM format for a PEM type we care about.
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continue
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# Remember where we got this object.
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pem._filename = fn
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# Is it a private key?
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if isinstance(pem, RSAPrivateKey):
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private_keys[pem.public_key().public_numbers()] = pem
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# Is it a certificate?
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if isinstance(pem, Certificate):
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certificates.append(pem)
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# Process the certificates.
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domains = { }
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for cert in certificates:
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# What domains is this certificate good for?
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cert_domains, primary_domain = get_certificate_domains(cert)
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cert._primary_domain = primary_domain
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# Is there a private key file for this certificate?
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private_key = private_keys.get(cert.public_key().public_numbers())
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if not private_key:
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continue
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cert._private_key = private_key
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# Add this cert to the list of certs usable for the domains.
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for domain in cert_domains:
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domains.setdefault(domain, []).append(cert)
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# Sort the certificates to prefer good ones.
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import datetime
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now = datetime.datetime.utcnow()
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ret = { }
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for domain, cert_list in domains.items():
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cert_list.sort(key = lambda cert : (
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# must be valid NOW
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cert.not_valid_before <= now <= cert.not_valid_after,
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# prefer one that is not self-signed
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cert.issuer != cert.subject,
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# prefer one with the expiration furthest into the future so
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# that we can easily rotate to new certs as we get them
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cert.not_valid_after,
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# in case a certificate is installed in multiple paths,
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# prefer the... lexicographically last one?
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cert._filename,
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), reverse=True)
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cert = cert_list.pop(0)
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ret[domain] = {
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"private-key": cert._private_key._filename,
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"certificate": cert._filename,
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"primary-domain": cert._primary_domain,
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}
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return ret
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def get_domain_ssl_files(domain, ssl_certificates, env, allow_missing_cert=False):
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# Get the default paths.
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ssl_private_key = os.path.join(os.path.join(env["STORAGE_ROOT"], 'ssl', 'ssl_private_key.pem'))
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ssl_certificate = os.path.join(os.path.join(env["STORAGE_ROOT"], 'ssl', 'ssl_certificate.pem'))
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if domain == env['PRIMARY_HOSTNAME']:
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# The primary domain must use the server certificate because
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# it is hard-coded in some service configuration files.
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return ssl_private_key, ssl_certificate, None
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wildcard_domain = re.sub("^[^\.]+", "*", domain)
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if domain in ssl_certificates:
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cert_info = ssl_certificates[domain]
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cert_type = "multi-domain"
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elif wildcard_domain in ssl_certificates:
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cert_info = ssl_certificates[wildcard_domain]
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cert_type = "wildcard"
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elif not allow_missing_cert:
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# No certificate is available for this domain! Return default files.
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ssl_via = "Using certificate for %s." % env['PRIMARY_HOSTNAME']
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return ssl_private_key, ssl_certificate, ssl_via
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else:
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# No certificate is available - and warn appropriately.
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return None
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# 'via' is a hint to the user about which certificate is in use for the domain
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if cert_info['certificate'] == os.path.join(env["STORAGE_ROOT"], 'ssl', 'ssl_certificate.pem'):
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# Using the server certificate.
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via = "Using same %s certificate as for %s." % (cert_type, env['PRIMARY_HOSTNAME'])
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elif cert_info['primary-domain'] != domain and cert_info['primary-domain'] in ssl_certificates and cert_info == ssl_certificates[cert_info['primary-domain']]:
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via = "Using same %s certificate as for %s." % (cert_type, cert_info['primary-domain'])
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else:
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via = None # don't show a hint - show expiration info instead
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return cert_info['private-key'], cert_info['certificate'], via
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def create_csr(domain, ssl_key, env):
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return shell("check_output", [
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"openssl", "req", "-new",
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"-key", ssl_key,
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"-sha256",
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"-subj", "/C=%s/ST=/L=/O=/CN=%s" % (env["CSR_COUNTRY"], domain)])
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def install_cert(domain, ssl_cert, ssl_chain, env):
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# Write the combined cert+chain to a temporary path and validate that it is OK.
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# The certificate always goes above the chain.
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import tempfile
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fd, fn = tempfile.mkstemp('.pem')
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os.write(fd, (ssl_cert + '\n' + ssl_chain).encode("ascii"))
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os.close(fd)
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# Do validation on the certificate before installing it.
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ssl_private_key = os.path.join(os.path.join(env["STORAGE_ROOT"], 'ssl', 'ssl_private_key.pem'))
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cert_status, cert_status_details = check_certificate(domain, fn, ssl_private_key)
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if cert_status != "OK":
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if cert_status == "SELF-SIGNED":
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cert_status = "This is a self-signed certificate. I can't install that."
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os.unlink(fn)
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if cert_status_details is not None:
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cert_status += " " + cert_status_details
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return cert_status
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# Where to put it?
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# Make a unique path for the certificate.
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from cryptography.hazmat.primitives import hashes
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from binascii import hexlify
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cert = load_pem(load_cert_chain(fn)[0])
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all_domains, cn = get_certificate_domains(cert)
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path = "%s-%s-%s.pem" % (
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safe_domain_name(cn), # common name, which should be filename safe because it is IDNA-encoded, but in case of a malformed cert make sure it's ok to use as a filename
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cert.not_valid_after.date().isoformat().replace("-", ""), # expiration date
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hexlify(cert.fingerprint(hashes.SHA256())).decode("ascii")[0:8], # fingerprint prefix
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)
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ssl_certificate = os.path.join(os.path.join(env["STORAGE_ROOT"], 'ssl', path))
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# Install the certificate.
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os.makedirs(os.path.dirname(ssl_certificate), exist_ok=True)
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shutil.move(fn, ssl_certificate)
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ret = ["OK"]
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# When updating the cert for PRIMARY_HOSTNAME, symlink it from the system
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# certificate path, which is hard-coded for various purposes, and then
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# update DNS (because of the DANE TLSA record), postfix, and dovecot,
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# which all use the file.
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if domain == env['PRIMARY_HOSTNAME']:
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# Update symlink.
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system_ssl_certificate = os.path.join(os.path.join(env["STORAGE_ROOT"], 'ssl', 'ssl_certificate.pem'))
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os.unlink(system_ssl_certificate)
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os.symlink(ssl_certificate, system_ssl_certificate)
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# Update DNS & restart postfix and dovecot so they pick up the new file.
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from dns_update import do_dns_update
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ret.append( do_dns_update(env) )
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shell('check_call', ["/usr/sbin/service", "postfix", "restart"])
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shell('check_call', ["/usr/sbin/service", "dovecot", "restart"])
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ret.append("mail services restarted")
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# Update the web configuration so nginx picks up the new certificate file.
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from web_update import do_web_update
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ret.append( do_web_update(env) )
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return "\n".join(ret)
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def check_certificate(domain, ssl_certificate, ssl_private_key, warn_if_expiring_soon=True, rounded_time=False, just_check_domain=False):
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# Check that the ssl_certificate & ssl_private_key files are good
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# for the provided domain.
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from cryptography.hazmat.primitives.asymmetric.rsa import RSAPrivateKey
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from cryptography.x509 import Certificate
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# The ssl_certificate file may contain a chain of certificates. We'll
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# need to split that up before we can pass anything to openssl or
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# parse them in Python. Parse it with the cryptography library.
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try:
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ssl_cert_chain = load_cert_chain(ssl_certificate)
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cert = load_pem(ssl_cert_chain[0])
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if not isinstance(cert, Certificate): raise ValueError("This is not a certificate file.")
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except ValueError as e:
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return ("There is a problem with the certificate file: %s" % str(e), None)
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# First check that the domain name is one of the names allowed by
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# the certificate.
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if domain is not None:
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certificate_names, cert_primary_name = get_certificate_domains(cert)
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# Check that the domain appears among the acceptable names, or a wildcard
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# form of the domain name (which is a stricter check than the specs but
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# should work in normal cases).
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wildcard_domain = re.sub("^[^\.]+", "*", domain)
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if domain not in certificate_names and wildcard_domain not in certificate_names:
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return ("The certificate is for the wrong domain name. It is for %s."
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% ", ".join(sorted(certificate_names)), None)
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# Second, check that the certificate matches the private key.
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if ssl_private_key is not None:
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try:
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priv_key = load_pem(open(ssl_private_key, 'rb').read())
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except ValueError as e:
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return ("The private key file %s is not a private key file: %s" % (ssl_private_key, str(e)), None)
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if not isinstance(priv_key, RSAPrivateKey):
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return ("The private key file %s is not a private key file." % ssl_private_key, None)
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if priv_key.public_key().public_numbers() != cert.public_key().public_numbers():
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return ("The certificate does not correspond to the private key at %s." % ssl_private_key, None)
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# We could also use the openssl command line tool to get the modulus
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# listed in each file. The output of each command below looks like "Modulus=XXXXX".
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# $ openssl rsa -inform PEM -noout -modulus -in ssl_private_key
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# $ openssl x509 -in ssl_certificate -noout -modulus
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# Third, check if the certificate is self-signed. Return a special flag string.
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if cert.issuer == cert.subject:
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return ("SELF-SIGNED", None)
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# When selecting which certificate to use for non-primary domains, we check if the primary
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# certificate or a www-parent-domain certificate is good for the domain. There's no need
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# to run extra checks beyond this point.
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if just_check_domain:
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return ("OK", None)
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# Check that the certificate hasn't expired. The datetimes returned by the
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# certificate are 'naive' and in UTC. We need to get the current time in UTC.
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import datetime
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now = datetime.datetime.utcnow()
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if not(cert.not_valid_before <= now <= cert.not_valid_after):
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return ("The certificate has expired or is not yet valid. It is valid from %s to %s." % (cert.not_valid_before, cert.not_valid_after), None)
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# Next validate that the certificate is valid. This checks whether the certificate
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# is self-signed, that the chain of trust makes sense, that it is signed by a CA
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# that Ubuntu has installed on this machine's list of CAs, and I think that it hasn't
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# expired.
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# The certificate chain has to be passed separately and is given via STDIN.
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# This command returns a non-zero exit status in most cases, so trap errors.
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retcode, verifyoutput = shell('check_output', [
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"openssl",
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"verify", "-verbose",
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"-purpose", "sslserver", "-policy_check",]
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+ ([] if len(ssl_cert_chain) == 1 else ["-untrusted", "/proc/self/fd/0"])
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+ [ssl_certificate],
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input=b"\n\n".join(ssl_cert_chain[1:]),
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trap=True)
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if "self signed" in verifyoutput:
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# Certificate is self-signed. Probably we detected this above.
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return ("SELF-SIGNED", None)
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elif retcode != 0:
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if "unable to get local issuer certificate" in verifyoutput:
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return ("The certificate is missing an intermediate chain or the intermediate chain is incorrect or incomplete. (%s)" % verifyoutput, None)
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# There is some unknown problem. Return the `openssl verify` raw output.
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return ("There is a problem with the SSL certificate.", verifyoutput.strip())
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else:
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# `openssl verify` returned a zero exit status so the cert is currently
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# good.
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# But is it expiring soon?
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cert_expiration_date = cert.not_valid_after
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ndays = (cert_expiration_date-now).days
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if not rounded_time or ndays < 7:
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expiry_info = "The certificate expires in %d days on %s." % (ndays, cert_expiration_date.strftime("%x"))
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elif ndays <= 14:
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expiry_info = "The certificate expires in less than two weeks, on %s." % cert_expiration_date.strftime("%x")
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elif ndays <= 31:
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expiry_info = "The certificate expires in less than a month, on %s." % cert_expiration_date.strftime("%x")
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else:
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expiry_info = "The certificate expires on %s." % cert_expiration_date.strftime("%x")
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if ndays <= 31 and warn_if_expiring_soon:
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return ("The certificate is expiring soon: " + expiry_info, None)
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# Return the special OK code.
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return ("OK", expiry_info)
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def load_cert_chain(pemfile):
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# A certificate .pem file may contain a chain of certificates.
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# Load the file and split them apart.
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re_pem = rb"(-+BEGIN (?:.+)-+[\r\n]+(?:[A-Za-z0-9+/=]{1,64}[\r\n]+)+-+END (?:.+)-+[\r\n]+)"
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with open(pemfile, "rb") as f:
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pem = f.read() + b"\n" # ensure trailing newline
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pemblocks = re.findall(re_pem, pem)
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if len(pemblocks) == 0:
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raise ValueError("File does not contain valid PEM data.")
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return pemblocks
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def load_pem(pem):
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# Parse a "---BEGIN .... END---" PEM string and return a Python object for it
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# using classes from the cryptography package.
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from cryptography.x509 import load_pem_x509_certificate
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from cryptography.hazmat.primitives import serialization
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from cryptography.hazmat.backends import default_backend
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pem_type = re.match(b"-+BEGIN (.*?)-+[\r\n]", pem)
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if pem_type is None:
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raise ValueError("File is not a valid PEM-formatted file.")
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pem_type = pem_type.group(1)
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if pem_type in (b"RSA PRIVATE KEY", b"PRIVATE KEY"):
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return serialization.load_pem_private_key(pem, password=None, backend=default_backend())
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if pem_type == b"CERTIFICATE":
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return load_pem_x509_certificate(pem, default_backend())
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raise ValueError("Unsupported PEM object type: " + pem_type.decode("ascii", "replace"))
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def get_certificate_domains(cert):
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from cryptography.x509 import DNSName, ExtensionNotFound, OID_COMMON_NAME, OID_SUBJECT_ALTERNATIVE_NAME
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import idna
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names = set()
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cn = None
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# The domain may be found in the Subject Common Name (CN). This comes back as an IDNA (ASCII)
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# string, which is the format we store domains in - so good.
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try:
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cn = cert.subject.get_attributes_for_oid(OID_COMMON_NAME)[0].value
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names.add(cn)
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except IndexError:
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# No common name? Certificate is probably generated incorrectly.
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# But we'll let it error-out when it doesn't find the domain.
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pass
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# ... or be one of the Subject Alternative Names. The cryptography library handily IDNA-decodes
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# the names for us. We must encode back to ASCII, but wildcard certificates can't pass through
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# IDNA encoding/decoding so we must special-case. See https://github.com/pyca/cryptography/pull/2071.
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def idna_decode_dns_name(dns_name):
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if dns_name.startswith("*."):
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return "*." + idna.encode(dns_name[2:]).decode('ascii')
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else:
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return idna.encode(dns_name).decode('ascii')
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try:
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sans = cert.extensions.get_extension_for_oid(OID_SUBJECT_ALTERNATIVE_NAME).value.get_values_for_type(DNSName)
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for san in sans:
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names.add(idna_decode_dns_name(san))
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except ExtensionNotFound:
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pass
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return names, cn
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