Dh parameters serialization (#3504)

* Support DH parameter serizalization - no X9.42

* Support X9.42 serialization - DER not working

* Fix dhp_rfc5114_2.der

Changing the DER parameters serialization after the
fix in openssl commit a292c9f1b835

* DH parameters X9.42 DER serialization fixed

* fix _skip_dhx_unsupported

* document DH parameter_bytes

* PEP8 fixes

* Document load_pem_parameters

* Document load_der_parameters

* document ParameterFormat

* Increase test coverage

* Increase test covrage

* Remove unneeded check

* Fix typo

* Fix error in load_der_parameters

* Add load_pem_parameters and load_der_parameters to interfaces

* CR fixes

* Removed unverified phrase

* Update version to 2.0

* Fix pep8

* Rename ParameterFormat.ASN1 to ParameterFormat.DHParameter

* link pkcs3

* Add new line at end of file to serialization.rst

* Rename DHparameters to PKCS3

* doc CR fix

1 files changed, 17 insertions, 2 deletions

diff --git a/tests/hazmat/primitives/test_serialization.py b/tests/hazmat/primitives/test_serialization.py
index f4b953e6..a7355221 100644
--- a/tests/hazmat/primitives/test_serialization.py
+++ b/tests/hazmat/primitives/test_serialization.py
@@ -18,8 +18,9 @@ from cryptography.hazmat.backends.interfaces import (
 )
 from cryptography.hazmat.primitives.asymmetric import dsa, ec, rsa
 from cryptography.hazmat.primitives.serialization import (
-    BestAvailableEncryption, load_der_private_key, load_der_public_key,
-    load_pem_private_key, load_pem_public_key, load_ssh_public_key
+    BestAvailableEncryption, load_der_parameters, load_der_private_key,
+    load_der_public_key, load_pem_parameters, load_pem_private_key,
+    load_pem_public_key, load_ssh_public_key
 )
 
 
@@ -310,6 +311,14 @@ class TestDERSerialization(object):
         assert key.curve.name == "secp256r1"
         assert key.curve.key_size == 256
 
+    def test_wrong_parameters_format(self, backend):
+        param_data = b"---- NOT A KEY ----\n"
+
+        with pytest.raises(ValueError):
+            load_der_parameters(
+                param_data, backend
+            )
+
 
 @pytest.mark.requires_backend_interface(interface=PEMSerializationBackend)
 class TestPEMSerialization(object):
@@ -591,6 +600,12 @@ class TestPEMSerialization(object):
         with pytest.raises(ValueError):
             load_pem_public_key(key_data, backend)
 
+    def test_wrong_parameters_format(self, backend):
+        param_data = b"---- NOT A KEY ----\n"
+
+        with pytest.raises(ValueError):
+            load_pem_parameters(param_data, backend)
+
     def test_corrupt_traditional_format(self, backend):
         # privkey.pem with a bunch of data missing.
         key_data = textwrap.dedent("""\