Disallow missing 'type' property with allow_custom

There was a bug where if you allowed custom content the library would parse an
object without the required 'type' property.

stix2/base.py

@@ -6,11 +6,11 @@ import datetime as dt
 
 import simplejson as json
 
-from .exceptions import (AtLeastOnePropertyError, DependentPropertiesError,
-                         ExtraPropertiesError, ImmutableError,
-                         InvalidObjRefError, InvalidValueError,
+from .exceptions import (AtLeastOnePropertyError, CustomContentError,
+                         DependentPropertiesError, ExtraPropertiesError,
+                         ImmutableError, InvalidObjRefError, InvalidValueError,
                          MissingPropertiesError,
-                         MutuallyExclusivePropertiesError, ParseError)
+                         MutuallyExclusivePropertiesError)
 from .markings.utils import validate
 from .utils import NOW, find_property_index, format_datetime, get_timestamp
 from .utils import new_version as _new_version
@@ -61,7 +61,7 @@ class _STIXBase(collections.Mapping):
             try:
                 kwargs[prop_name] = prop.clean(kwargs[prop_name])
             except ValueError as exc:
-                if self.__allow_custom and isinstance(exc, ParseError):
+                if self.__allow_custom and isinstance(exc, CustomContentError):
                     return
                 raise InvalidValueError(self.__class__, prop_name, reason=str(exc))
 

stix2/exceptions.py

@@ -163,6 +163,13 @@ class ParseError(STIXError, ValueError):
         super(ParseError, self).__init__(msg)
 
 
+class CustomContentError(STIXError, ValueError):
+    """Custom STIX Content (SDO, Observable, Extension, etc.) detected."""
+
+    def __init__(self, msg):
+        super(CustomContentError, self).__init__(msg)
+
+
 class InvalidSelectorError(STIXError, AssertionError):
     """Granular Marking selector violation. The selector must resolve into an existing STIX object property."""
 

stix2/test/test_custom.py

@@ -373,7 +373,7 @@ def test_parse_unregistered_custom_observable_object():
         "property1": "something"
     }"""
 
-    with pytest.raises(stix2.exceptions.ParseError) as excinfo:
+    with pytest.raises(stix2.exceptions.CustomContentError) as excinfo:
         stix2.parse_observable(nt_string)
     assert "Can't parse unknown observable type" in str(excinfo.value)
 
@@ -384,6 +384,16 @@ def test_parse_unregistered_custom_observable_object():
     assert not isinstance(parsed_custom, stix2.core._STIXBase)
 
 
+def test_parse_unregistered_custom_observable_object_with_no_type():
+    nt_string = """{
+        "property1": "something"
+    }"""
+
+    with pytest.raises(stix2.exceptions.ParseError) as excinfo:
+        stix2.parse_observable(nt_string, allow_custom=True)
+    assert "Can't parse observable with no 'type' property" in str(excinfo.value)
+
+
 def test_parse_observed_data_with_custom_observable():
     input_str = """{
         "type": "observed-data",

stix2/v20/observables.py

@@ -8,8 +8,8 @@ Observable and do not have a ``_type`` attribute.
 from collections import OrderedDict
 
 from ..base import _Extension, _Observable, _STIXBase
-from ..exceptions import (AtLeastOnePropertyError, DependentPropertiesError,
-                          ParseError)
+from ..exceptions import (AtLeastOnePropertyError, CustomContentError,
+                          DependentPropertiesError, ParseError)
 from ..properties import (BinaryProperty, BooleanProperty, DictionaryProperty,
                           EmbeddedObjectProperty, EnumProperty, FloatProperty,
                           HashesProperty, HexProperty, IntegerProperty,
@@ -67,7 +67,7 @@ class ExtensionsProperty(DictionaryProperty):
                     else:
                         raise ValueError("Cannot determine extension type.")
                 else:
-                    raise ParseError("Can't parse unknown extension type: {}".format(key))
+                    raise CustomContentError("Can't parse unknown extension type: {}".format(key))
         else:
             raise ValueError("The enclosing type '%s' has no extensions defined" % self.enclosing_type)
         return dictified
@@ -927,7 +927,7 @@ def parse_observable(data, _valid_refs=None, allow_custom=False):
             # flag allows for unknown custom objects too, but will not
             # be parsed into STIX observable object, just returned as is
             return obj
-        raise ParseError("Can't parse unknown observable type '%s'! For custom observables, "
+        raise CustomContentError("Can't parse unknown observable type '%s'! For custom observables, "
                                  "use the CustomObservable decorator." % obj['type'])
 
     if 'extensions' in obj and obj['type'] in EXT_MAP:
@@ -936,7 +936,8 @@ def parse_observable(data, _valid_refs=None, allow_custom=False):
                 ext_class = EXT_MAP[obj['type']][name]
             except KeyError:
                 if not allow_custom:
-                    raise ParseError("Can't parse unknown extension type '%s' for observable type '%s'!" % (name, obj['type']))
+                    raise CustomContentError("Can't parse unknown extension type '%s'"
+                                             "for observable type '%s'!" % (name, obj['type']))
             else:  # extension was found
                 obj['extensions'][name] = ext_class(allow_custom=allow_custom, **obj['extensions'][name])