cti-python-stix2/stix2/base.py

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