Add enforcement of a new STIX 2.1 SCO extension name requirement:

that it must end with "-ext".

stix2/core.py

@@ -7,10 +7,10 @@ import re
 
 import stix2
 
-from .base import _STIXBase
+from .base import _Observable, _STIXBase
 from .exceptions import ParseError
 from .markings import _MarkingsMixin
-from .utils import _get_dict
+from .utils import SCO21_EXT_REGEX, TYPE_REGEX, _get_dict
 
 STIX2_OBJ_MAPS = {}
 
@@ -258,22 +258,54 @@ def _register_observable(new_observable, version=None):
     OBJ_MAP_OBSERVABLE[new_observable._type] = new_observable
 
 
-def _register_observable_extension(observable, new_extension, version=None):
+def _register_observable_extension(
+    observable, new_extension, version=stix2.DEFAULT_VERSION
+):
     """Register a custom extension to a STIX Cyber Observable type.
 
     Args:
-        observable: An observable object
+        observable: An observable class or instance
         new_extension (class): A class to register in the Observables
             Extensions map.
-        version (str): Which STIX2 version to use. (e.g. "2.0", "2.1"). If
+        version (str): Which STIX2 version to use. (e.g. "2.0", "2.1").
-            None, use latest version.
+            Defaults to the latest supported version.
 
     """
-    if version:
+    obs_class = observable if isinstance(observable, type) else \
-        v = 'v' + version.replace('.', '')
+        type(observable)
-    else:
+    ext_type = new_extension._type
-        # Use default version (latest) if no version was provided.
+
-        v = 'v' + stix2.DEFAULT_VERSION.replace('.', '')
+    if not issubclass(obs_class, _Observable):
+        raise ValueError("'observable' must be a valid Observable class!")
+
+    if version == "2.0":
+        if not re.match(TYPE_REGEX, ext_type):
+            raise ValueError(
+                "Invalid extension type name '%s': must only contain the "
+                "characters a-z (lowercase ASCII), 0-9, and hyphen (-)." %
+                ext_type,
+            )
+    else:  # 2.1+
+        if not re.match(SCO21_EXT_REGEX, ext_type):
+            raise ValueError(
+                "Invalid extension type name '%s': must only contain the "
+                "characters a-z (lowercase ASCII), 0-9, hyphen (-), and end "
+                "with '-ext'." % ext_type,
+            )
+
+    if len(ext_type) < 3 or len(ext_type) > 250:
+        raise ValueError(
+            "Invalid extension type name '%s': must be between 3 and 250"
+            " characters." % ext_type,
+        )
+
+    if not new_extension._properties:
+        raise ValueError(
+            "Invalid extension: must define at least one property: " +
+            ext_type,
+        )
+
+    v = 'v' + version.replace('.', '')
 
     try:
         observable_type = observable._type
@@ -287,7 +319,7 @@ def _register_observable_extension(observable, new_extension, version=None):
     EXT_MAP = STIX2_OBJ_MAPS[v]['observable-extensions']
 
     try:
-        EXT_MAP[observable_type][new_extension._type] = new_extension
+        EXT_MAP[observable_type][ext_type] = new_extension
     except KeyError:
         if observable_type not in OBJ_MAP_OBSERVABLE:
             raise ValueError(
@@ -296,7 +328,7 @@ def _register_observable_extension(observable, new_extension, version=None):
                 % observable_type,
             )
         else:
-            EXT_MAP[observable_type] = {new_extension._type: new_extension}
+            EXT_MAP[observable_type] = {ext_type: new_extension}
 
 
 def _collect_stix2_mappings():

stix2/custom.py

@@ -1,6 +1,8 @@
 from collections import OrderedDict
 import re
 
+import six
+
 from .base import _cls_init, _Extension, _Observable, _STIXBase
 from .core import (
     STIXDomainObject, _register_marking, _register_object,
@@ -113,24 +115,23 @@ def _custom_observable_builder(cls, type, properties, version, id_contrib_props=
 
 
 def _custom_extension_builder(cls, observable, type, properties, version):
-    if not observable or not issubclass(observable, _Observable):
+
-        raise ValueError("'observable' must be a valid Observable class!")
+    try:
+        prop_dict = OrderedDict(properties)
+    except TypeError as e:
+        six.raise_from(
+            ValueError(
+                "Extension properties must be dict-like, e.g. a list "
+                "containing tuples.  For example, "
+                "[('property1', IntegerProperty())]",
+            ),
+            e,
+        )
 
     class _CustomExtension(cls, _Extension):
 
-        if not re.match(TYPE_REGEX, type):
-            raise ValueError(
-                "Invalid extension type name '%s': must only contain the "
-                "characters a-z (lowercase ASCII), 0-9, and hyphen (-)." % type,
-            )
-        elif len(type) < 3 or len(type) > 250:
-            raise ValueError("Invalid extension type name '%s': must be between 3 and 250 characters." % type)
-
-        if not properties or not isinstance(properties, list):
-            raise ValueError("Must supply a list, containing tuples. For example, [('property1', IntegerProperty())]")
-
         _type = type
-        _properties = OrderedDict(properties)
+        _properties = prop_dict
 
         def __init__(self, **kwargs):
             _Extension.__init__(self, **kwargs)

stix2/test/v20/test_custom.py

@@ -821,27 +821,24 @@ def test_custom_extension_invalid_type_name():
 
 
 def test_custom_extension_no_properties():
-    with pytest.raises(ValueError) as excinfo:
+    with pytest.raises(ValueError):
         @stix2.v20.CustomExtension(stix2.v20.DomainName, 'x-new-ext2', None)
         class BarExtension():
             pass
-    assert "Must supply a list, containing tuples." in str(excinfo.value)
 
 
 def test_custom_extension_empty_properties():
-    with pytest.raises(ValueError) as excinfo:
+    with pytest.raises(ValueError):
         @stix2.v20.CustomExtension(stix2.v20.DomainName, 'x-new-ext2', [])
         class BarExtension():
             pass
-    assert "Must supply a list, containing tuples." in str(excinfo.value)
 
 
 def test_custom_extension_dict_properties():
-    with pytest.raises(ValueError) as excinfo:
+    with pytest.raises(ValueError):
         @stix2.v20.CustomExtension(stix2.v20.DomainName, 'x-new-ext2', {})
         class BarExtension():
             pass
-    assert "Must supply a list, containing tuples." in str(excinfo.value)
 
 
 def test_custom_extension_no_init_1():

stix2/test/v21/test_custom.py

@@ -800,7 +800,7 @@ def test_custom_extension_wrong_observable_type():
 )
 def test_custom_extension_with_list_and_dict_properties_observable_type(data):
     @stix2.v21.CustomExtension(
-        stix2.v21.UserAccount, 'some-extension', [
+        stix2.v21.UserAccount, 'some-extension-ext', [
             ('keys', stix2.properties.ListProperty(stix2.properties.DictionaryProperty, required=True)),
         ],
     )
@@ -876,32 +876,29 @@ def test_custom_extension_invalid_type_name():
 
 
 def test_custom_extension_no_properties():
-    with pytest.raises(ValueError) as excinfo:
+    with pytest.raises(ValueError):
-        @stix2.v21.CustomExtension(stix2.v21.DomainName, 'x-new-ext2', None)
+        @stix2.v21.CustomExtension(stix2.v21.DomainName, 'x-new2-ext', None)
         class BarExtension():
             pass
-    assert "Must supply a list, containing tuples." in str(excinfo.value)
 
 
 def test_custom_extension_empty_properties():
-    with pytest.raises(ValueError) as excinfo:
+    with pytest.raises(ValueError):
-        @stix2.v21.CustomExtension(stix2.v21.DomainName, 'x-new-ext2', [])
+        @stix2.v21.CustomExtension(stix2.v21.DomainName, 'x-new2-ext', [])
         class BarExtension():
             pass
-    assert "Must supply a list, containing tuples." in str(excinfo.value)
 
 
 def test_custom_extension_dict_properties():
-    with pytest.raises(ValueError) as excinfo:
+    with pytest.raises(ValueError):
-        @stix2.v21.CustomExtension(stix2.v21.DomainName, 'x-new-ext2', {})
+        @stix2.v21.CustomExtension(stix2.v21.DomainName, 'x-new2-ext', {})
         class BarExtension():
             pass
-    assert "Must supply a list, containing tuples." in str(excinfo.value)
 
 
 def test_custom_extension_no_init_1():
     @stix2.v21.CustomExtension(
-        stix2.v21.DomainName, 'x-new-extension', [
+        stix2.v21.DomainName, 'x-new-extension-ext', [
             ('property1', stix2.properties.StringProperty(required=True)),
         ],
     )
@@ -914,7 +911,7 @@ def test_custom_extension_no_init_1():
 
 def test_custom_extension_no_init_2():
     @stix2.v21.CustomExtension(
-        stix2.v21.DomainName, 'x-new-ext2', [
+        stix2.v21.DomainName, 'x-new2-ext', [
             ('property1', stix2.properties.StringProperty(required=True)),
         ],
     )
@@ -949,14 +946,14 @@ def test_custom_and_spec_extension_mix():
     file_obs = stix2.v21.File(
         name="my_file.dat",
         extensions={
-            "x-custom1": {
+            "custom1-ext": {
                 "a": 1,
                 "b": 2,
             },
             "ntfs-ext": {
                 "sid": "S-1-whatever",
             },
-            "x-custom2": {
+            "custom2-ext": {
                 "z": 99.9,
                 "y": False,
             },
@@ -969,8 +966,8 @@ def test_custom_and_spec_extension_mix():
         allow_custom=True,
     )
 
-    assert file_obs.extensions["x-custom1"] == {"a": 1, "b": 2}
+    assert file_obs.extensions["custom1-ext"] == {"a": 1, "b": 2}
-    assert file_obs.extensions["x-custom2"] == {"y": False, "z": 99.9}
+    assert file_obs.extensions["custom2-ext"] == {"y": False, "z": 99.9}
     assert file_obs.extensions["ntfs-ext"].sid == "S-1-whatever"
     assert file_obs.extensions["raster-image-ext"].image_height == 1024
 

stix2/utils.py

@@ -26,6 +26,7 @@ NOW = object()
 STIX_UNMOD_PROPERTIES = ['created', 'created_by_ref', 'id', 'type']
 
 TYPE_REGEX = r'^\-?[a-z0-9]+(-[a-z0-9]+)*\-?$'
+SCO21_EXT_REGEX = r'^\-?[a-z0-9]+(-[a-z0-9]+)*\-ext$'
 
 
 class STIXdatetime(dt.datetime):