[WIP] add support for the TLSFeature extension in x509 (#3899)

* add support for the TLSFeature extension in x509

This extension is used for OCSP Must-Staple.

* fix changelog link

* pep8

* refactor to support the sequence properly and add status_request_v2

* update some language

* add test vector, implement eq/ne/hash on TLSFeature

* address review comments

1 files changed, 63 insertions, 0 deletions

diff --git a/tests/x509/test_x509_ext.py b/tests/x509/test_x509_ext.py
index fc8651c8..5b9fb347 100644
--- a/tests/x509/test_x509_ext.py
+++ b/tests/x509/test_x509_ext.py
@@ -92,6 +92,69 @@ class TestExtension(object):
         assert ext1 != object()
 
 
+class TestTLSFeature(object):
+    def test_not_enum_type(self):
+        with pytest.raises(TypeError):
+            x509.TLSFeature([3])
+
+    def test_empty_list(self):
+        with pytest.raises(TypeError):
+            x509.TLSFeature([])
+
+    def test_repr(self):
+        ext1 = x509.TLSFeature([x509.TLSFeatureType.status_request])
+        assert repr(ext1) == (
+            "<TLSFeature(features=[<TLSFeatureType.status_request: 5>])>"
+        )
+
+    def test_eq(self):
+        ext1 = x509.TLSFeature([x509.TLSFeatureType.status_request])
+        ext2 = x509.TLSFeature([x509.TLSFeatureType.status_request])
+        assert ext1 == ext2
+
+    def test_ne(self):
+        ext1 = x509.TLSFeature([x509.TLSFeatureType.status_request])
+        ext2 = x509.TLSFeature([x509.TLSFeatureType.status_request_v2])
+        ext3 = x509.TLSFeature([
+            x509.TLSFeatureType.status_request,
+            x509.TLSFeatureType.status_request_v2
+        ])
+        assert ext1 != ext2
+        assert ext1 != ext3
+        assert ext1 != object()
+
+    def test_hash(self):
+        ext1 = x509.TLSFeature([x509.TLSFeatureType.status_request])
+        ext2 = x509.TLSFeature([x509.TLSFeatureType.status_request])
+        ext3 = x509.TLSFeature([
+            x509.TLSFeatureType.status_request,
+            x509.TLSFeatureType.status_request_v2
+        ])
+        assert hash(ext1) == hash(ext2)
+        assert hash(ext1) != hash(ext3)
+
+    def test_iter(self):
+        ext1_features = [x509.TLSFeatureType.status_request]
+        ext1 = x509.TLSFeature(ext1_features)
+        assert len(ext1) == 1
+        assert list(ext1) == ext1_features
+        ext2_features = [
+            x509.TLSFeatureType.status_request,
+            x509.TLSFeatureType.status_request_v2,
+        ]
+        ext2 = x509.TLSFeature(ext2_features)
+        assert len(ext2) == 2
+        assert list(ext2) == ext2_features
+
+    def test_indexing(self):
+        ext = x509.TLSFeature([
+            x509.TLSFeatureType.status_request,
+            x509.TLSFeatureType.status_request_v2,
+        ])
+        assert ext[-1] == ext[1]
+        assert ext[0] == x509.TLSFeatureType.status_request
+
+
 class TestUnrecognizedExtension(object):
     def test_invalid_oid(self):
         with pytest.raises(TypeError):