203 lines
8.1 KiB
Python
203 lines
8.1 KiB
Python
"""Base class for type definitions in the stix2 library."""
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import collections
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import copy
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import datetime as dt
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import json
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from .exceptions import (AtLeastOnePropertyError, DependentPropertiestError, ExtraFieldsError, ImmutableError,
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InvalidObjRefError, InvalidValueError, MissingFieldsError, MutuallyExclusivePropertiesError,
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RevokeError, UnmodifiablePropertyError)
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from .utils import NOW, format_datetime, get_timestamp, parse_into_datetime
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__all__ = ['STIXJSONEncoder', '_STIXBase']
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DEFAULT_ERROR = "{type} must have {field}='{expected}'."
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class STIXJSONEncoder(json.JSONEncoder):
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def default(self, obj):
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if isinstance(obj, (dt.date, dt.datetime)):
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return format_datetime(obj)
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elif isinstance(obj, _STIXBase):
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return dict(obj)
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else:
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return super(STIXJSONEncoder, self).default(obj)
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def get_required_properties(properties):
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return (k for k, v in properties.items() if v.required)
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class _STIXBase(collections.Mapping):
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"""Base class for STIX object types"""
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def _check_property(self, prop_name, prop, kwargs):
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if prop_name not in kwargs:
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if hasattr(prop, 'default'):
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value = prop.default()
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if value == NOW:
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value = self.__now
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kwargs[prop_name] = value
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if prop_name in kwargs:
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try:
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kwargs[prop_name] = prop.clean(kwargs[prop_name])
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except ValueError as exc:
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raise InvalidValueError(self.__class__, prop_name, reason=str(exc))
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# interproperty constraint methods
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def _check_mutually_exclusive_properties(self, list_of_properties, at_least_one=True):
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current_properties = self.properties_populated()
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count = len(set(list_of_properties).intersection(current_properties))
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# at_least_one allows for xor to be checked
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if count > 1 or (at_least_one and count == 0):
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raise MutuallyExclusivePropertiesError(self.__class__, list_of_properties)
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def _check_at_least_one_property(self, list_of_properties=None):
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if not list_of_properties:
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list_of_properties = sorted(list(self.__class__._properties.keys()))
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if "type" in list_of_properties:
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list_of_properties.remove("type")
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current_properties = self.properties_populated()
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list_of_properties_populated = set(list_of_properties).intersection(current_properties)
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if list_of_properties and (not list_of_properties_populated or list_of_properties_populated == {"extensions"}):
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raise AtLeastOnePropertyError(self.__class__, list_of_properties)
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def _check_properties_dependency(self, list_of_properties, list_of_dependent_properties, values=[]):
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failed_dependency_pairs = []
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current_properties = self.properties_populated()
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for p in list_of_properties:
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v = values.pop() if values else None
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for dp in list_of_dependent_properties:
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if dp in current_properties and (p not in current_properties or (v and not current_properties(p) == v)):
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failed_dependency_pairs.append((p, dp))
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if failed_dependency_pairs:
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raise DependentPropertiestError(self.__class__, failed_dependency_pairs)
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def _check_object_constaints(self):
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if self.granular_markings:
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for m in self.granular_markings:
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# TODO: check selectors
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pass
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def __init__(self, **kwargs):
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cls = self.__class__
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# Use the same timestamp for any auto-generated datetimes
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self.__now = get_timestamp()
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# Detect any keyword arguments not allowed for a specific type
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extra_kwargs = list(set(kwargs) - set(cls._properties))
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if extra_kwargs:
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raise ExtraFieldsError(cls, extra_kwargs)
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# Remove any keyword arguments whose value is None
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setting_kwargs = {}
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for prop_name, prop_value in kwargs.items():
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if prop_value:
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setting_kwargs[prop_name] = prop_value
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# Detect any missing required fields
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required_fields = get_required_properties(cls._properties)
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missing_kwargs = set(required_fields) - set(setting_kwargs)
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if missing_kwargs:
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raise MissingFieldsError(cls, missing_kwargs)
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for prop_name, prop_metadata in cls._properties.items():
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self._check_property(prop_name, prop_metadata, setting_kwargs)
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self._inner = setting_kwargs
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self._check_object_constaints()
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def __getitem__(self, key):
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return self._inner[key]
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def __iter__(self):
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return iter(self._inner)
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def __len__(self):
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return len(self._inner)
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# Handle attribute access just like key access
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def __getattr__(self, name):
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return self.get(name)
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def __setattr__(self, name, value):
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if name != '_inner' and not name.startswith("_STIXBase__"):
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raise ImmutableError
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super(_STIXBase, self).__setattr__(name, value)
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def __str__(self):
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# TODO: put keys in specific order. Probably need custom JSON encoder.
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return json.dumps(self, indent=4, sort_keys=True, cls=STIXJSONEncoder,
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separators=(",", ": ")) # Don't include spaces after commas.
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def __repr__(self):
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props = [(k, self[k]) for k in sorted(self._properties) if self.get(k)]
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return "{0}({1})".format(self.__class__.__name__,
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", ".join(["{0!s}={1!r}".format(k, v) for k, v in props]))
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def __deepcopy__(self, memo):
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# Assumption: we can ignore the memo argument, because no object will ever contain the same sub-object multiple times.
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new_inner = copy.deepcopy(self._inner, memo)
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cls = type(self)
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return cls(**new_inner)
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def properties_populated(self):
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return list(self._inner.keys())
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# Versioning API
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def new_version(self, **kwargs):
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unchangable_properties = []
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if self.revoked:
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raise RevokeError("new_version")
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new_obj_inner = copy.deepcopy(self._inner)
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properties_to_change = kwargs.keys()
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for prop in ["created", "created_by_ref", "id", "type"]:
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if prop in properties_to_change:
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unchangable_properties.append(prop)
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if unchangable_properties:
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raise UnmodifiablePropertyError(unchangable_properties)
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cls = type(self)
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if 'modified' not in kwargs:
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kwargs['modified'] = get_timestamp()
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else:
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new_modified_property = parse_into_datetime(kwargs['modified'])
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if new_modified_property < self.modified:
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raise InvalidValueError(cls, 'modified', "The new modified datetime cannot be before the current modified datatime.")
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new_obj_inner.update(kwargs)
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return cls(**new_obj_inner)
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def revoke(self):
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if self.revoked:
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raise RevokeError("revoke")
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return self.new_version(revoked=True)
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class _Observable(_STIXBase):
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def __init__(self, **kwargs):
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# the constructor might be called independently of an observed data object
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if '_valid_refs' in kwargs:
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self._STIXBase__valid_refs = kwargs.pop('_valid_refs')
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else:
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self._STIXBase__valid_refs = []
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super(_Observable, self).__init__(**kwargs)
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def _check_property(self, prop_name, prop, kwargs):
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super(_Observable, self)._check_property(prop_name, prop, kwargs)
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if prop_name.endswith('_ref') and prop_name in kwargs:
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ref = kwargs[prop_name]
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if ref not in self._STIXBase__valid_refs:
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raise InvalidObjRefError(self.__class__, prop_name, "'%s' is not a valid object in local scope" % ref)
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elif prop_name.endswith('_refs') and prop_name in kwargs:
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for ref in kwargs[prop_name]:
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if ref not in self._STIXBase__valid_refs:
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raise InvalidObjRefError(self.__class__, prop_name, "'%s' is not a valid object in local scope" % ref)
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# TODO also check the type of the object referenced, not just that the key exists
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