Raise ConflictError on attempts to create an existing account (#6251)

* Raise ConflictError on attempts to create an existing account in ACME V2.

Fixes issue #6246

* Allow querying an account without calling new_account in ACMEv2

Fixed issue #6258

acme/acme/client.py

@@ -577,16 +577,33 @@ class ClientV2(ClientBase):
 
         :param .NewRegistration new_account:
 
+        :raises .ConflictError: in case the account already exists
+
         :returns: Registration Resource.
         :rtype: `.RegistrationResource`
         """
         response = self._post(self.directory['newAccount'], new_account)
+        # if account already exists
+        if response.status_code == 200 and 'Location' in response.headers:
+            raise errors.ConflictError(response.headers.get('Location'))
         # "Instance of 'Field' has no key/contact member" bug:
         # pylint: disable=no-member
         regr = self._regr_from_response(response)
         self.net.account = regr
         return regr
 
+    def query_registration(self, regr):
+        """Query server about registration.
+
+        :param messages.RegistrationResource: Existing Registration
+            Resource.
+
+        """
+        self.net.account = regr
+        updated_regr = super(ClientV2, self).query_registration(regr)
+        self.net.account = updated_regr
+        return updated_regr
+
     def update_registration(self, regr, update=None):
         """Update registration.
 

acme/acme/client_test.py

@@ -134,6 +134,12 @@ class BackwardsCompatibleClientV2Test(ClientTestBase):
         client = self._init()
         self.assertEqual(client.acme_version, 2)
 
+    def test_query_registration_client_v2(self):
+        self.response.json.return_value = DIRECTORY_V2.to_json()
+        client = self._init()
+        self.response.json.return_value = self.regr.body.to_json()
+        self.assertEqual(self.regr, client.query_registration(self.regr))
+
     def test_forwarding(self):
         self.response.json.return_value = DIRECTORY_V1.to_json()
         client = self._init()
@@ -706,6 +712,11 @@ class ClientV2Test(ClientTestBase):
 
         self.assertEqual(self.regr, self.client.new_account(self.new_reg))
 
+    def test_new_account_conflict(self):
+        self.response.status_code = http_client.OK
+        self.response.headers['Location'] = self.regr.uri
+        self.assertRaises(errors.ConflictError, self.client.new_account, self.new_reg)
+
     def test_new_order(self):
         order_response = copy.deepcopy(self.response)
         order_response.status_code = http_client.CREATED

acme/acme/errors.py

@@ -110,6 +110,8 @@ class ConflictError(ClientError):
 
     In the version of ACME implemented by Boulder, this is used to find an
     account if you only have the private key, but don't know the account URL.
+
+    Also used in V2 of the ACME client for the same purpose.
     """
     def __init__(self, location):
         self.location = location