"""ACME Identifier Validation Challenges."""
import abc
import functools
import hashlib
import logging
import socket
import warnings
from cryptography.hazmat.primitives import hashes # type: ignore
import josepy as jose
import OpenSSL
import requests
import six
from acme import errors
from acme import crypto_util
from acme import fields
logger = logging.getLogger(__name__)
# pylint: disable=too-few-public-methods
class Challenge(jose.TypedJSONObjectWithFields):
# _fields_to_partial_json | pylint: disable=abstract-method
"""ACME challenge."""
TYPES = {} # type: dict
@classmethod
def from_json(cls, jobj):
try:
return super(Challenge, cls).from_json(jobj)
except jose.UnrecognizedTypeError as error:
logger.debug(error)
return UnrecognizedChallenge.from_json(jobj)
class ChallengeResponse(jose.TypedJSONObjectWithFields):
# _fields_to_partial_json | pylint: disable=abstract-method
"""ACME challenge response."""
TYPES = {} # type: dict
resource_type = 'challenge'
resource = fields.Resource(resource_type)
class UnrecognizedChallenge(Challenge):
"""Unrecognized challenge.
ACME specification defines a generic framework for challenges and
defines some standard challenges that are implemented in this
module. However, other implementations (including peers) might
define additional challenge types, which should be ignored if
unrecognized.
:ivar jobj: Original JSON decoded object.
"""
def __init__(self, jobj):
super(UnrecognizedChallenge, self).__init__()
object.__setattr__(self, "jobj", jobj)
def to_partial_json(self):
# pylint: disable=no-member
return self.jobj
@classmethod
def from_json(cls, jobj):
return cls(jobj)
class _TokenChallenge(Challenge):
"""Challenge with token.
:ivar bytes token:
"""
TOKEN_SIZE = 128 / 8 # Based on the entropy value from the spec
"""Minimum size of the :attr:`token` in bytes."""
# TODO: acme-spec doesn't specify token as base64-encoded value
token = jose.Field(
"token", encoder=jose.encode_b64jose, decoder=functools.partial(
jose.decode_b64jose, size=TOKEN_SIZE, minimum=True))
# XXX: rename to ~token_good_for_url
@property
def good_token(self): # XXX: @token.decoder
"""Is `token` good?
.. todo:: acme-spec wants "It MUST NOT contain any non-ASCII
characters", but it should also warrant that it doesn't
contain ".." or "/"...
"""
# TODO: check that path combined with uri does not go above
# URI_ROOT_PATH!
return b'..' not in self.token and b'/' not in self.token
class KeyAuthorizationChallengeResponse(ChallengeResponse):
"""Response to Challenges based on Key Authorization.
:param unicode key_authorization:
"""
key_authorization = jose.Field("keyAuthorization")
thumbprint_hash_function = hashes.SHA256
def __init__(self, *args, **kwargs):
super(KeyAuthorizationChallengeResponse, self).__init__(*args, **kwargs)
self._dump_authorization_key(False)
def verify(self, chall, account_public_key):
"""Verify the key authorization.
:param KeyAuthorization chall: Challenge that corresponds to
this response.
:param JWK account_public_key:
:return: ``True`` iff verification of the key authorization was
successful.
:rtype: bool
"""
parts = self.key_authorization.split('.') # pylint: disable=no-member
if len(parts) != 2:
logger.debug("Key authorization (%r) is not well formed",
self.key_authorization)
return False
if parts[0] != chall.encode("token"):
logger.debug("Mismatching token in key authorization: "
"%r instead of %r", parts[0], chall.encode("token"))
return False
thumbprint = jose.b64encode(account_public_key.thumbprint(
hash_function=self.thumbprint_hash_function)).decode()
if parts[1] != thumbprint:
logger.debug("Mismatching thumbprint in key authorization: "
"%r instead of %r", parts[0], thumbprint)
return False
return True
def _dump_authorization_key(self, dump):
# type: (bool) -> None
"""
Set if keyAuthorization is dumped in the JSON representation of this ChallengeResponse.
NB: This method is declared as private because it will eventually be removed.
:param bool dump: True to dump the keyAuthorization, False otherwise
"""
object.__setattr__(self, '_dump_auth_key', dump)
def to_partial_json(self):
jobj = super(KeyAuthorizationChallengeResponse, self).to_partial_json()
if not self._dump_auth_key: # pylint: disable=no-member
jobj.pop('keyAuthorization', None)
return jobj
@six.add_metaclass(abc.ABCMeta)
class KeyAuthorizationChallenge(_TokenChallenge):
# pylint: disable=abstract-class-little-used,too-many-ancestors
"""Challenge based on Key Authorization.
:param response_cls: Subclass of `KeyAuthorizationChallengeResponse`
that will be used to generate `response`.
:param str typ: type of the challenge
"""
typ = NotImplemented
response_cls = NotImplemented
thumbprint_hash_function = (
KeyAuthorizationChallengeResponse.thumbprint_hash_function)
def key_authorization(self, account_key):
"""Generate Key Authorization.
:param JWK account_key:
:rtype unicode:
"""
return self.encode("token") + "." + jose.b64encode(
account_key.thumbprint(
hash_function=self.thumbprint_hash_function)).decode()
def response(self, account_key):
"""Generate response to the challenge.
:param JWK account_key:
:returns: Response (initialized `response_cls`) to the challenge.
:rtype: KeyAuthorizationChallengeResponse
"""
return self.response_cls(
key_authorization=self.key_authorization(account_key))
@abc.abstractmethod
def validation(self, account_key, **kwargs):
"""Generate validation for the challenge.
Subclasses must implement this method, but they are likely to
return completely different data structures, depending on what's
necessary to complete the challenge. Interpretation of that
return value must be known to the caller.
:param JWK account_key:
:returns: Challenge-specific validation.
"""
raise NotImplementedError() # pragma: no cover
def response_and_validation(self, account_key, *args, **kwargs):
"""Generate response and validation.
Convenience function that return results of `response` and
`validation`.
:param JWK account_key:
:rtype: tuple
"""
return (self.response(account_key),
self.validation(account_key, *args, **kwargs))
@ChallengeResponse.register
class DNS01Response(KeyAuthorizationChallengeResponse):
"""ACME dns-01 challenge response."""
typ = "dns-01"
def simple_verify(self, chall, domain, account_public_key):
"""Simple verify.
This method no longer checks DNS records and is a simple wrapper
around `KeyAuthorizationChallengeResponse.verify`.
:param challenges.DNS01 chall: Corresponding challenge.
:param unicode domain: Domain name being verified.
:param JWK account_public_key: Public key for the key pair
being authorized.
:return: ``True`` iff verification of the key authorization was
successful.
:rtype: bool
"""
# pylint: disable=unused-argument
verified = self.verify(chall, account_public_key)
if not verified:
logger.debug("Verification of key authorization in response failed")
return verified
@Challenge.register # pylint: disable=too-many-ancestors
class DNS01(KeyAuthorizationChallenge):
"""ACME dns-01 challenge."""
response_cls = DNS01Response
typ = response_cls.typ
LABEL = "_acme-challenge"
"""Label clients prepend to the domain name being validated."""
def validation(self, account_key, **unused_kwargs):
"""Generate validation.
:param JWK account_key:
:rtype: unicode
"""
return jose.b64encode(hashlib.sha256(self.key_authorization(
account_key).encode("utf-8")).digest()).decode()
def validation_domain_name(self, name):
"""Domain name for TXT validation record.
:param unicode name: Domain name being validated.
"""
return "{0}.{1}".format(self.LABEL, name)
@ChallengeResponse.register
class HTTP01Response(KeyAuthorizationChallengeResponse):
"""ACME http-01 challenge response."""
typ = "http-01"
PORT = 80
"""Verification port as defined by the protocol.
You can override it (e.g. for testing) by passing ``port`` to
`simple_verify`.
"""
WHITESPACE_CUTSET = "\n\r\t "
"""Whitespace characters which should be ignored at the end of the body."""
def simple_verify(self, chall, domain, account_public_key, port=None):
"""Simple verify.
:param challenges.SimpleHTTP chall: Corresponding challenge.
:param unicode domain: Domain name being verified.
:param JWK account_public_key: Public key for the key pair
being authorized.
:param int port: Port used in the validation.
:returns: ``True`` iff validation with the files currently served by the
HTTP server is successful.
:rtype: bool
"""
if not self.verify(chall, account_public_key):
logger.debug("Verification of key authorization in response failed")
return False
# TODO: ACME specification defines URI template that doesn't
# allow to use a custom port... Make sure port is not in the
# request URI, if it's standard.
if port is not None and port != self.PORT:
logger.warning(
"Using non-standard port for http-01 verification: %s", port)
domain += ":{0}".format(port)
uri = chall.uri(domain)
logger.debug("Verifying %s at %s...", chall.typ, uri)
try:
http_response = requests.get(uri)
except requests.exceptions.RequestException as error:
logger.error("Unable to reach %s: %s", uri, error)
return False
logger.debug("Received %s: %s. Headers: %s", http_response,
http_response.text, http_response.headers)
challenge_response = http_response.text.rstrip(self.WHITESPACE_CUTSET)
if self.key_authorization != challenge_response:
logger.debug("Key authorization from response (%r) doesn't match "
"HTTP response (%r)", self.key_authorization,
challenge_response)
return False
return True
@Challenge.register # pylint: disable=too-many-ancestors
class HTTP01(KeyAuthorizationChallenge):
"""ACME http-01 challenge."""
response_cls = HTTP01Response
typ = response_cls.typ
URI_ROOT_PATH = ".well-known/acme-challenge"
"""URI root path for the server provisioned resource."""
@property
def path(self):
"""Path (starting with '/') for provisioned resource.
:rtype: string
"""
return '/' + self.URI_ROOT_PATH + '/' + self.encode('token')
def uri(self, domain):
"""Create an URI to the provisioned resource.
Forms an URI to the HTTPS server provisioned resource
(containing :attr:`~SimpleHTTP.token`).
:param unicode domain: Domain name being verified.
:rtype: string
"""
return "http://" + domain + self.path
def validation(self, account_key, **unused_kwargs):
"""Generate validation.
:param JWK account_key:
:rtype: unicode
"""
return self.key_authorization(account_key)
@ChallengeResponse.register
class TLSSNI01Response(KeyAuthorizationChallengeResponse):
"""ACME tls-sni-01 challenge response."""
typ = "tls-sni-01"
DOMAIN_SUFFIX = b".acme.invalid"
"""Domain name suffix."""
PORT = 443
"""Verification port as defined by the protocol.
You can override it (e.g. for testing) by passing ``port`` to
`simple_verify`.
"""
@property
def z(self): # pylint: disable=invalid-name
"""``z`` value used for verification.
:rtype bytes:
"""
return hashlib.sha256(
self.key_authorization.encode("utf-8")).hexdigest().lower().encode()
@property
def z_domain(self):
"""Domain name used for verification, generated from `z`.
:rtype bytes:
"""
return self.z[:32] + b'.' + self.z[32:] + self.DOMAIN_SUFFIX
def gen_cert(self, key=None, bits=2048):
"""Generate tls-sni-01 certificate.
:param OpenSSL.crypto.PKey key: Optional private key used in
certificate generation. If not provided (``None``), then
fresh key will be generated.
:param int bits: Number of bits for newly generated key.
:rtype: `tuple` of `OpenSSL.crypto.X509` and `OpenSSL.crypto.PKey`
"""
if key is None:
key = OpenSSL.crypto.PKey()
key.generate_key(OpenSSL.crypto.TYPE_RSA, bits)
return crypto_util.gen_ss_cert(key, [
# z_domain is too big to fit into CN, hence first dummy domain
'dummy', self.z_domain.decode()], force_san=True), key
def probe_cert(self, domain, **kwargs):
"""Probe tls-sni-01 challenge certificate.
:param unicode domain:
"""
# TODO: domain is not necessary if host is provided
if "host" not in kwargs:
host = socket.gethostbyname(domain)
logger.debug('%s resolved to %s', domain, host)
kwargs["host"] = host
kwargs.setdefault("port", self.PORT)
kwargs["name"] = self.z_domain
# TODO: try different methods?
# pylint: disable=protected-access
return crypto_util.probe_sni(**kwargs)
def verify_cert(self, cert):
"""Verify tls-sni-01 challenge certificate.
:param OpensSSL.crypto.X509 cert: Challenge certificate.
:returns: Whether the certificate was successfully verified.
:rtype: bool
"""
# pylint: disable=protected-access
sans = crypto_util._pyopenssl_cert_or_req_san(cert)
logger.debug('Certificate %s. SANs: %s', cert.digest('sha256'), sans)
return self.z_domain.decode() in sans
def simple_verify(self, chall, domain, account_public_key,
cert=None, **kwargs):
"""Simple verify.
Verify ``validation`` using ``account_public_key``, optionally
probe tls-sni-01 certificate and check using `verify_cert`.
:param .challenges.TLSSNI01 chall: Corresponding challenge.
:param str domain: Domain name being validated.
:param JWK account_public_key:
:param OpenSSL.crypto.X509 cert: Optional certificate. If not
provided (``None``) certificate will be retrieved using
`probe_cert`.
:param int port: Port used to probe the certificate.
:returns: ``True`` iff client's control of the domain has been
verified.
:rtype: bool
"""
if not self.verify(chall, account_public_key):
logger.debug("Verification of key authorization in response failed")
return False
if cert is None:
try:
cert = self.probe_cert(domain=domain, **kwargs)
except errors.Error as error:
logger.debug(str(error), exc_info=True)
return False
return self.verify_cert(cert)
@Challenge.register # pylint: disable=too-many-ancestors
class TLSSNI01(KeyAuthorizationChallenge):
"""ACME tls-sni-01 challenge."""
response_cls = TLSSNI01Response
typ = response_cls.typ
# boulder#962, ietf-wg-acme#22
#n = jose.Field("n", encoder=int, decoder=int)
def __init__(self, *args, **kwargs):
warnings.warn("TLS-SNI-01 is deprecated, and will stop working soon.",
DeprecationWarning, stacklevel=2)
super(TLSSNI01, self).__init__(*args, **kwargs)
def validation(self, account_key, **kwargs):
"""Generate validation.
:param JWK account_key:
:param OpenSSL.crypto.PKey cert_key: Optional private key used
in certificate generation. If not provided (``None``), then
fresh key will be generated.
:rtype: `tuple` of `OpenSSL.crypto.X509` and `OpenSSL.crypto.PKey`
"""
return self.response(account_key).gen_cert(key=kwargs.get('cert_key'))
@ChallengeResponse.register
class TLSALPN01Response(KeyAuthorizationChallengeResponse):
"""ACME TLS-ALPN-01 challenge response.
This class only allows initiating a TLS-ALPN-01 challenge returned from the
CA. Full support for responding to TLS-ALPN-01 challenges by generating and
serving the expected response certificate is not currently provided.
"""
typ = "tls-alpn-01"
@Challenge.register # pylint: disable=too-many-ancestors
class TLSALPN01(KeyAuthorizationChallenge):
"""ACME tls-alpn-01 challenge.
This class simply allows parsing the TLS-ALPN-01 challenge returned from
the CA. Full TLS-ALPN-01 support is not currently provided.
"""
typ = "tls-alpn-01"
response_cls = TLSALPN01Response
def validation(self, account_key, **kwargs):
"""Generate validation for the challenge."""
raise NotImplementedError()
@Challenge.register # pylint: disable=too-many-ancestors
class DNS(_TokenChallenge):
"""ACME "dns" challenge."""
typ = "dns"
LABEL = "_acme-challenge"
"""Label clients prepend to the domain name being validated."""
def gen_validation(self, account_key, alg=jose.RS256, **kwargs):
"""Generate validation.
:param .JWK account_key: Private account key.
:param .JWA alg:
:returns: This challenge wrapped in `.JWS`
:rtype: .JWS
"""
return jose.JWS.sign(
payload=self.json_dumps(sort_keys=True).encode('utf-8'),
key=account_key, alg=alg, **kwargs)
def check_validation(self, validation, account_public_key):
"""Check validation.
:param JWS validation:
:param JWK account_public_key:
:rtype: bool
"""
if not validation.verify(key=account_public_key):
return False
try:
return self == self.json_loads(
validation.payload.decode('utf-8'))
except jose.DeserializationError as error:
logger.debug("Checking validation for DNS failed: %s", error)
return False
def gen_response(self, account_key, **kwargs):
"""Generate response.
:param .JWK account_key: Private account key.
:param .JWA alg:
:rtype: DNSResponse
"""
return DNSResponse(validation=self.gen_validation(
account_key, **kwargs))
def validation_domain_name(self, name):
"""Domain name for TXT validation record.
:param unicode name: Domain name being validated.
"""
return "{0}.{1}".format(self.LABEL, name)
@ChallengeResponse.register
class DNSResponse(ChallengeResponse):
"""ACME "dns" challenge response.
:param JWS validation:
"""
typ = "dns"
validation = jose.Field("validation", decoder=jose.JWS.from_json)
def check_validation(self, chall, account_public_key):
"""Check validation.
:param challenges.DNS chall:
:param JWK account_public_key:
:rtype: bool
"""
return chall.check_validation(self.validation, account_public_key)