chg: Use default category from template

Fix #477

pymisp/mispevent.py

@@ -1070,6 +1070,9 @@ class MISPObjectAttribute(MISPAttribute):
         self.type = kwargs.pop('type', None)
         if self.type is None:
             self.type = self._definition.get('misp-attribute')
+        if 'category' not in kwargs and 'categories' in self._definition:
+            # Get first category in the list from the object template as default
+            self.category = self._definition['categories'][0]
         self.disable_correlation = kwargs.pop('disable_correlation', None)
         if self.disable_correlation is None:
             # The correlation can be disabled by default in the object definition.
@@ -1331,7 +1334,7 @@ class MISPObject(AbstractMISP):
             logger.warning("The value of the attribute you're trying to add is None or empty string, skipping it. Object relation: {}".format(object_relation))
             return None
         if self._known_template:
-            if self._definition['attributes'].get(object_relation):
+            if object_relation in self._definition['attributes']:
                 attribute = MISPObjectAttribute(self._definition['attributes'][object_relation])
             else:
                 # Woopsie, this object_relation is unknown, no sane defaults for you.

tests/mispevent_testfiles/event_obj_def_param.json

@@ -14,6 +14,14 @@
           "to_ids": true,
           "type": "filename",
           "value": "bar"
+        },
+        {
+          "category": "Artifacts dropped",
+          "disable_correlation": false,
+          "object_relation": "pattern-in-file",
+          "to_ids": true,
+          "type": "pattern-in-file",
+          "value": "baz"
         }
       ],
       "description": "File object describing a file with meta-information",

tests/test_mispevent.py

@@ -159,6 +159,9 @@ class TestMISPEvent(unittest.TestCase):
         self.mispevent.add_object(name='file', strict=True)
         a = self.mispevent.objects[0].add_attribute('filename', value='bar', Tag=[{'name': 'blah'}])
         del a.uuid
+        a = self.mispevent.objects[0].add_attribute('pattern-in-file', value='baz')
+        self.assertEqual(a.category, 'Artifacts dropped')
+        del a.uuid
         self.mispevent.add_object(name='file', strict=False, default_attributes_parameters=self.mispevent.objects[0].attributes[0])
         a = self.mispevent.objects[1].add_attribute('filename', value='baz')
         del a.uuid