Fix acme compliance to RFC 8555 (#7176)

This PR is an alternative to #7125.

Instead of disabling the strict mode on Pebble, this PR fixes the JWS payloads regarding RFC 8555 to be compliant, and allow certbot to work with Pebble v2.1.0+.

* Fix acme compliance to RFC 8555.

* Working mixin

* Activate back pebble strict mode

* Use mixin for type

* Update dependencies

* Fix also in fields_to_partial_json

* Update pebble

* Add changelog

acme/acme/challenges.py

@@ -16,6 +16,7 @@ from OpenSSL import crypto
 from acme import crypto_util
 from acme import errors
 from acme import fields
+from acme.mixins import ResourceMixin, TypeMixin
 
 logger = logging.getLogger(__name__)
 
@@ -34,7 +35,7 @@ class Challenge(jose.TypedJSONObjectWithFields):
             return UnrecognizedChallenge.from_json(jobj)
 
 
-class ChallengeResponse(jose.TypedJSONObjectWithFields):
+class ChallengeResponse(ResourceMixin, TypeMixin, jose.TypedJSONObjectWithFields):
     # _fields_to_partial_json
     """ACME challenge response."""
     TYPES = {}  # type: dict

acme/acme/client.py

@@ -25,6 +25,7 @@ from acme.magic_typing import Dict
 from acme.magic_typing import List
 from acme.magic_typing import Set
 from acme.magic_typing import Text
+from acme.mixins import VersionedLEACMEMixin
 
 logger = logging.getLogger(__name__)
 
@@ -987,6 +988,8 @@ class ClientNetwork(object):
         :rtype: `josepy.JWS`
 
         """
+        if isinstance(obj, VersionedLEACMEMixin):
+            obj.le_acme_version = acme_version
         jobj = obj.json_dumps(indent=2).encode() if obj else b''
         logger.debug('JWS payload:\n%s', jobj)
         kwargs = {

acme/acme/messages.py

@@ -9,6 +9,7 @@ from acme import errors
 from acme import fields
 from acme import jws
 from acme import util
+from acme.mixins import ResourceMixin
 
 try:
     from collections.abc import Hashable
@@ -356,13 +357,13 @@ class Registration(ResourceBody):
 
 
 @Directory.register
-class NewRegistration(Registration):
+class NewRegistration(ResourceMixin, Registration):
     """New registration."""
     resource_type = 'new-reg'
     resource = fields.Resource(resource_type)
 
 
-class UpdateRegistration(Registration):
+class UpdateRegistration(ResourceMixin, Registration):
     """Update registration."""
     resource_type = 'reg'
     resource = fields.Resource(resource_type)
@@ -498,13 +499,13 @@ class Authorization(ResourceBody):
 
 
 @Directory.register
-class NewAuthorization(Authorization):
+class NewAuthorization(ResourceMixin, Authorization):
     """New authorization."""
     resource_type = 'new-authz'
     resource = fields.Resource(resource_type)
 
 
-class UpdateAuthorization(Authorization):
+class UpdateAuthorization(ResourceMixin, Authorization):
     """Update authorization."""
     resource_type = 'authz'
     resource = fields.Resource(resource_type)
@@ -522,7 +523,7 @@ class AuthorizationResource(ResourceWithURI):
 
 
 @Directory.register
-class CertificateRequest(jose.JSONObjectWithFields):
+class CertificateRequest(ResourceMixin, jose.JSONObjectWithFields):
     """ACME new-cert request.
 
     :ivar josepy.util.ComparableX509 csr:
@@ -548,7 +549,7 @@ class CertificateResource(ResourceWithURI):
 
 
 @Directory.register
-class Revocation(jose.JSONObjectWithFields):
+class Revocation(ResourceMixin, jose.JSONObjectWithFields):
     """Revocation message.
 
     :ivar .ComparableX509 certificate: `OpenSSL.crypto.X509` wrapped in

acme/acme/mixins.py

@@ -0,0 +1,65 @@
+"""Useful mixins for Challenge and Resource objects"""
+
+
+class VersionedLEACMEMixin(object):
+    """This mixin stores the version of Let's Encrypt's endpoint being used."""
+    @property
+    def le_acme_version(self):
+        """Define the version of ACME protocol to use"""
+        return getattr(self, '_le_acme_version', 1)
+
+    @le_acme_version.setter
+    def le_acme_version(self, version):
+        # We need to use object.__setattr__ to not depend on the specific implementation of
+        # __setattr__  in current class (eg. jose.TypedJSONObjectWithFields raises AttributeError
+        # for any attempt to set an attribute to make objects immutable).
+        object.__setattr__(self, '_le_acme_version', version)
+
+    def __setattr__(self, key, value):
+        if key == 'le_acme_version':
+            # Required for @property to operate properly. See comment above.
+            object.__setattr__(self, key, value)
+        else:
+            super(VersionedLEACMEMixin, self).__setattr__(key, value)  # pragma: no cover
+
+
+class ResourceMixin(VersionedLEACMEMixin):
+    """
+    This mixin generates a RFC8555 compliant JWS payload
+    by removing the `resource` field if needed (eg. ACME v2 protocol).
+    """
+    def to_partial_json(self):
+        """See josepy.JSONDeserializable.to_partial_json()"""
+        return _safe_jobj_compliance(super(ResourceMixin, self),
+                                     'to_partial_json', 'resource')
+
+    def fields_to_partial_json(self):
+        """See josepy.JSONObjectWithFields.fields_to_partial_json()"""
+        return _safe_jobj_compliance(super(ResourceMixin, self),
+                                     'fields_to_partial_json', 'resource')
+
+
+class TypeMixin(VersionedLEACMEMixin):
+    """
+    This mixin allows generation of a RFC8555 compliant JWS payload
+    by removing the `type` field if needed (eg. ACME v2 protocol).
+    """
+    def to_partial_json(self):
+        """See josepy.JSONDeserializable.to_partial_json()"""
+        return _safe_jobj_compliance(super(TypeMixin, self),
+                                     'to_partial_json', 'type')
+
+    def fields_to_partial_json(self):
+        """See josepy.JSONObjectWithFields.fields_to_partial_json()"""
+        return _safe_jobj_compliance(super(TypeMixin, self),
+                                     'fields_to_partial_json', 'type')
+
+
+def _safe_jobj_compliance(instance, jobj_method, uncompliant_field):
+    if hasattr(instance, jobj_method):
+        jobj = getattr(instance, jobj_method)()
+        if instance.le_acme_version == 2:
+            jobj.pop(uncompliant_field, None)
+        return jobj
+
+    raise AttributeError('Method {0}() is not implemented.'.format(jobj_method))  # pragma: no cover

acme/tests/challenges_test.py

@@ -478,5 +478,18 @@ class DNSResponseTest(unittest.TestCase):
             self.msg.check_validation(self.chall, KEY.public_key()))
 
 
+class JWSPayloadRFC8555Compliant(unittest.TestCase):
+    """Test for RFC8555 compliance of JWS generated from resources/challenges"""
+    def test_challenge_payload(self):
+        from acme.challenges import HTTP01Response
+
+        challenge_body = HTTP01Response()
+        challenge_body.le_acme_version = 2
+
+        jobj = challenge_body.json_dumps(indent=2).encode()
+        # RFC8555 states that challenge responses must have an empty payload.
+        self.assertEqual(jobj, b'{}')
+
+
 if __name__ == '__main__':
     unittest.main()  # pragma: no cover

acme/tests/client_test.py

@@ -16,6 +16,7 @@ from acme import errors
 from acme import jws as acme_jws
 from acme import messages
 from acme.magic_typing import Dict  # pylint: disable=unused-import, no-name-in-module
+from acme.mixins import VersionedLEACMEMixin
 import messages_test
 import test_util
 
@@ -886,7 +887,7 @@ class ClientV2Test(ClientTestBase):
             self.client.net.get.assert_not_called()
 
 
-class MockJSONDeSerializable(jose.JSONDeSerializable):
+class MockJSONDeSerializable(VersionedLEACMEMixin, jose.JSONDeSerializable):
     # pylint: disable=missing-docstring
     def __init__(self, value):
         self.value = value

acme/tests/messages_test.py

@@ -453,6 +453,7 @@ class OrderResourceTest(unittest.TestCase):
             'authorizations': None,
         })
 
+
 class NewOrderTest(unittest.TestCase):
     """Tests for acme.messages.NewOrder."""
 
@@ -467,5 +468,18 @@ class NewOrderTest(unittest.TestCase):
         })
 
 
+class JWSPayloadRFC8555Compliant(unittest.TestCase):
+    """Test for RFC8555 compliance of JWS generated from resources/challenges"""
+    def test_message_payload(self):
+        from acme.messages import NewAuthorization
+
+        new_order = NewAuthorization()
+        new_order.le_acme_version = 2
+
+        jobj = new_order.json_dumps(indent=2).encode()
+        # RFC8555 states that JWS bodies must not have a resource field.
+        self.assertEqual(jobj, b'{}')
+
+
 if __name__ == '__main__':
     unittest.main()  # pragma: no cover