Typed but unhandled extensions preserve DER via public_bytes()

server/packages/kca-core/src/kca/core/extensions.py

@@ -793,11 +793,11 @@ def _netscape_to_spec(ext: x509.Extension) -> Optional[Dict[str, Any]]:
     return spec
 
 
-def _raw_value(ext: x509.Extension) -> Optional[bytes]:
+def _raw_value(ext: x509.Extension) -> bytes:
     value = ext.value
     if isinstance(value, x509.UnrecognizedExtension):
         return value.value
-    return None
+    return value.public_bytes()
 
 
 def extension_specs(extensions: Iterable[x509.Extension]) -> Dict[str, Any]:
@@ -892,7 +892,7 @@ def extension_specs(extensions: Iterable[x509.Extension]) -> Dict[str, Any]:
                     {
                         "oid": oid,
                         "critical": ext.critical,
-                        "der_hex": (value.value if isinstance(value, x509.UnrecognizedExtension) else b"").hex(),
+                        "der_hex": _raw_value(ext).hex(),
                     }
                 )
     if netscape:

server/packages/kca-core/tests/test_core.py

@@ -82,6 +82,37 @@ class ExtensionTest(unittest.TestCase):
         self.assertEqual(exts[0].oid.dotted_string, "1.2.3.4")
         self.assertTrue(exts[0].critical)
 
+    def test_unhandled_typed_extension_roundtrip(self) -> None:
+        value = x509.SubjectInformationAccess(
+            [
+                x509.AccessDescription(
+                    x509.oid.AuthorityInformationAccessOID.OCSP,
+                    x509.UniformResourceIdentifier("http://ocsp.example.com"),
+                )
+            ]
+        )
+        ext = x509.Extension(
+            oid=x509.oid.ExtensionOID.SUBJECT_INFORMATION_ACCESS,
+            critical=True,
+            value=value,
+        )
+
+        spec = extension_specs([ext])
+
+        self.assertEqual(
+            spec["raw"],
+            [
+                {
+                    "oid": ext.oid.dotted_string,
+                    "critical": True,
+                    "der_hex": value.public_bytes().hex(),
+                }
+            ],
+        )
+        rebuilt = build_extensions(spec, public_key=None)
+        self.assertEqual(len(rebuilt), 1)
+        self.assertEqual(rebuilt[0].value.public_bytes(), value.public_bytes())
+
 
 class KeyTest(unittest.TestCase):
     def test_all_types(self) -> None: