716 lines
25 KiB
Python
716 lines
25 KiB
Python
"""Classes for representing properties of STIX Objects and Cyber Observables."""
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import base64
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import binascii
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import copy
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import inspect
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import re
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import uuid
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from six import string_types, text_type
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import stix2
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from .base import _STIXBase
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from .exceptions import (
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CustomContentError, DictionaryKeyError, MissingPropertiesError,
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MutuallyExclusivePropertiesError,
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)
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from .parsing import STIX2_OBJ_MAPS, parse, parse_observable
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from .utils import (
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TYPE_21_REGEX, TYPE_REGEX, _get_dict, get_class_hierarchy_names,
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parse_into_datetime,
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)
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try:
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from collections.abc import Mapping
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except ImportError:
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from collections import Mapping
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ERROR_INVALID_ID = (
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"not a valid STIX identifier, must match <object-type>--<UUID>: {}"
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)
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def _check_uuid(uuid_str, spec_version):
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"""
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Check whether the given UUID string is valid with respect to the given STIX
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spec version. STIX 2.0 requires UUIDv4; 2.1 only requires the RFC 4122
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variant.
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:param uuid_str: A UUID as a string
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:param spec_version: The STIX spec version
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:return: True if the UUID is valid, False if not
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:raises ValueError: If uuid_str is malformed
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"""
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uuid_obj = uuid.UUID(uuid_str)
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ok = uuid_obj.variant == uuid.RFC_4122
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if ok and spec_version == "2.0":
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ok = uuid_obj.version == 4
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return ok
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def _validate_id(id_, spec_version, required_prefix):
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"""
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Check the STIX identifier for correctness, raise an exception if there are
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errors.
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:param id_: The STIX identifier
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:param spec_version: The STIX specification version to use
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:param required_prefix: The required prefix on the identifier, if any.
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This function doesn't add a "--" suffix to the prefix, so callers must
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add it if it is important. Pass None to skip the prefix check.
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:raises ValueError: If there are any errors with the identifier
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"""
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if required_prefix:
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if not id_.startswith(required_prefix):
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raise ValueError("must start with '{}'.".format(required_prefix))
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try:
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if required_prefix:
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uuid_part = id_[len(required_prefix):]
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else:
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idx = id_.index("--")
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uuid_part = id_[idx+2:]
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result = _check_uuid(uuid_part, spec_version)
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except ValueError:
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# replace their ValueError with ours
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raise ValueError(ERROR_INVALID_ID.format(id_))
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if not result:
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raise ValueError(ERROR_INVALID_ID.format(id_))
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def _validate_type(type_, spec_version):
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"""
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Check the STIX type name for correctness, raise an exception if there are
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errors.
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:param type_: The STIX type name
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:param spec_version: The STIX specification version to use
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:raises ValueError: If there are any errors with the identifier
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"""
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if spec_version == "2.0":
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if not re.match(TYPE_REGEX, type_):
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raise ValueError(
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"Invalid type name '%s': must only contain the "
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"characters a-z (lowercase ASCII), 0-9, and hyphen (-)." %
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type_,
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)
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else: # 2.1+
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if not re.match(TYPE_21_REGEX, type_):
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raise ValueError(
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"Invalid type name '%s': must only contain the "
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"characters a-z (lowercase ASCII), 0-9, and hyphen (-) "
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"and must begin with an a-z character" % type_,
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)
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if len(type_) < 3 or len(type_) > 250:
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raise ValueError(
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"Invalid type name '%s': must be between 3 and 250 characters." % type_,
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)
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class Property(object):
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"""Represent a property of STIX data type.
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Subclasses can define the following attributes as keyword arguments to
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``__init__()``.
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Args:
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required (bool): If ``True``, the property must be provided when
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creating an object with that property. No default value exists for
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these properties. (Default: ``False``)
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fixed: This provides a constant default value. Users are free to
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provide this value explicity when constructing an object (which
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allows you to copy **all** values from an existing object to a new
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object), but if the user provides a value other than the ``fixed``
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value, it will raise an error. This is semantically equivalent to
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defining both:
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- a ``clean()`` function that checks if the value matches the fixed
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value, and
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- a ``default()`` function that returns the fixed value.
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Subclasses can also define the following functions:
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- ``def clean(self, value) -> any:``
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- Return a value that is valid for this property. If ``value`` is not
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valid for this property, this will attempt to transform it first. If
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``value`` is not valid and no such transformation is possible, it
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should raise an exception.
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- ``def default(self):``
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- provide a default value for this property.
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- ``default()`` can return the special value ``NOW`` to use the current
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time. This is useful when several timestamps in the same object
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need to use the same default value, so calling now() for each
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property-- likely several microseconds apart-- does not work.
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Subclasses can instead provide a lambda function for ``default`` as a
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keyword argument. ``clean`` should not be provided as a lambda since
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lambdas cannot raise their own exceptions.
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When instantiating Properties, ``required`` and ``default`` should not be
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used together. ``default`` implies that the property is required in the
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specification so this function will be used to supply a value if none is
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provided. ``required`` means that the user must provide this; it is
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required in the specification and we can't or don't want to create a
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default value.
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"""
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def _default_clean(self, value):
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if value != self._fixed_value:
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raise ValueError("must equal '{}'.".format(self._fixed_value))
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return value
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def __init__(self, required=False, fixed=None, default=None):
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self.required = required
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if fixed:
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self._fixed_value = fixed
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self.clean = self._default_clean
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self.default = lambda: fixed
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if default:
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self.default = default
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def clean(self, value):
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return value
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def __call__(self, value=None):
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"""Used by ListProperty to handle lists that have been defined with
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either a class or an instance.
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"""
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return value
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class ListProperty(Property):
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def __init__(self, contained, **kwargs):
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"""
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``contained`` should be a function which returns an object from the value.
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"""
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if inspect.isclass(contained) and issubclass(contained, Property):
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# If it's a class and not an instance, instantiate it so that
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# clean() can be called on it, and ListProperty.clean() will
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# use __call__ when it appends the item.
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self.contained = contained()
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else:
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self.contained = contained
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super(ListProperty, self).__init__(**kwargs)
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def clean(self, value):
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try:
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iter(value)
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except TypeError:
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raise ValueError("must be an iterable.")
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if isinstance(value, (_STIXBase, string_types)):
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value = [value]
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result = []
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for item in value:
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try:
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valid = self.contained.clean(item)
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except ValueError:
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raise
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except AttributeError:
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# type of list has no clean() function (eg. built in Python types)
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# TODO Should we raise an error here?
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valid = item
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if type(self.contained) is EmbeddedObjectProperty:
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obj_type = self.contained.type
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elif type(self.contained).__name__ == "STIXObjectProperty":
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# ^ this way of checking doesn't require a circular import
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# valid is already an instance of a python-stix2 class; no need
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# to turn it into a dictionary and then pass it to the class
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# constructor again
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result.append(valid)
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continue
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elif type(self.contained) is DictionaryProperty:
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obj_type = dict
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else:
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obj_type = self.contained
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if isinstance(valid, Mapping):
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try:
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valid._allow_custom
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except AttributeError:
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result.append(obj_type(**valid))
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else:
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result.append(obj_type(allow_custom=True, **valid))
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else:
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result.append(obj_type(valid))
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# STIX spec forbids empty lists
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if len(result) < 1:
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raise ValueError("must not be empty.")
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return result
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class StringProperty(Property):
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def __init__(self, **kwargs):
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super(StringProperty, self).__init__(**kwargs)
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def clean(self, value):
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if not isinstance(value, string_types):
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return text_type(value)
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return value
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class TypeProperty(Property):
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def __init__(self, type, spec_version=stix2.DEFAULT_VERSION):
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_validate_type(type, spec_version)
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self.spec_version = spec_version
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super(TypeProperty, self).__init__(fixed=type)
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class IDProperty(Property):
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def __init__(self, type, spec_version=stix2.DEFAULT_VERSION):
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self.required_prefix = type + "--"
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self.spec_version = spec_version
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super(IDProperty, self).__init__()
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def clean(self, value):
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_validate_id(value, self.spec_version, self.required_prefix)
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return value
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def default(self):
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return self.required_prefix + str(uuid.uuid4())
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class IntegerProperty(Property):
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def __init__(self, min=None, max=None, **kwargs):
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self.min = min
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self.max = max
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super(IntegerProperty, self).__init__(**kwargs)
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def clean(self, value):
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try:
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value = int(value)
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except Exception:
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raise ValueError("must be an integer.")
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if self.min is not None and value < self.min:
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msg = "minimum value is {}. received {}".format(self.min, value)
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raise ValueError(msg)
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if self.max is not None and value > self.max:
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msg = "maximum value is {}. received {}".format(self.max, value)
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raise ValueError(msg)
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return value
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class FloatProperty(Property):
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def __init__(self, min=None, max=None, **kwargs):
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self.min = min
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self.max = max
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super(FloatProperty, self).__init__(**kwargs)
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def clean(self, value):
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try:
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value = float(value)
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except Exception:
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raise ValueError("must be a float.")
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if self.min is not None and value < self.min:
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msg = "minimum value is {}. received {}".format(self.min, value)
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raise ValueError(msg)
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if self.max is not None and value > self.max:
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msg = "maximum value is {}. received {}".format(self.max, value)
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raise ValueError(msg)
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return value
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class BooleanProperty(Property):
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def clean(self, value):
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if isinstance(value, bool):
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return value
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trues = ['true', 't', '1']
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falses = ['false', 'f', '0']
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try:
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if value.lower() in trues:
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return True
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if value.lower() in falses:
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return False
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except AttributeError:
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if value == 1:
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return True
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if value == 0:
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return False
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raise ValueError("must be a boolean value.")
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class TimestampProperty(Property):
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def __init__(self, precision="any", precision_constraint="exact", **kwargs):
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self.precision = precision
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self.precision_constraint = precision_constraint
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super(TimestampProperty, self).__init__(**kwargs)
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def clean(self, value):
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return parse_into_datetime(
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value, self.precision, self.precision_constraint,
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)
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class DictionaryProperty(Property):
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def __init__(self, spec_version=stix2.DEFAULT_VERSION, **kwargs):
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self.spec_version = spec_version
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super(DictionaryProperty, self).__init__(**kwargs)
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def clean(self, value):
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try:
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dictified = _get_dict(value)
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except ValueError:
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raise ValueError("The dictionary property must contain a dictionary")
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for k in dictified.keys():
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if self.spec_version == '2.0':
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if len(k) < 3:
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raise DictionaryKeyError(k, "shorter than 3 characters")
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elif len(k) > 256:
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raise DictionaryKeyError(k, "longer than 256 characters")
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elif self.spec_version == '2.1':
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if len(k) > 250:
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raise DictionaryKeyError(k, "longer than 250 characters")
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if not re.match(r"^[a-zA-Z0-9_-]+$", k):
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msg = (
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"contains characters other than lowercase a-z, "
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"uppercase A-Z, numerals 0-9, hyphen (-), or "
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"underscore (_)"
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)
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raise DictionaryKeyError(k, msg)
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if len(dictified) < 1:
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raise ValueError("must not be empty.")
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return dictified
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HASHES_REGEX = {
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"MD5": (r"^[a-fA-F0-9]{32}$", "MD5"),
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"MD6": (r"^[a-fA-F0-9]{32}|[a-fA-F0-9]{40}|[a-fA-F0-9]{56}|[a-fA-F0-9]{64}|[a-fA-F0-9]{96}|[a-fA-F0-9]{128}$", "MD6"),
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"RIPEMD160": (r"^[a-fA-F0-9]{40}$", "RIPEMD-160"),
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"SHA1": (r"^[a-fA-F0-9]{40}$", "SHA-1"),
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"SHA224": (r"^[a-fA-F0-9]{56}$", "SHA-224"),
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"SHA256": (r"^[a-fA-F0-9]{64}$", "SHA-256"),
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"SHA384": (r"^[a-fA-F0-9]{96}$", "SHA-384"),
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"SHA512": (r"^[a-fA-F0-9]{128}$", "SHA-512"),
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"SHA3224": (r"^[a-fA-F0-9]{56}$", "SHA3-224"),
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"SHA3256": (r"^[a-fA-F0-9]{64}$", "SHA3-256"),
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"SHA3384": (r"^[a-fA-F0-9]{96}$", "SHA3-384"),
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"SHA3512": (r"^[a-fA-F0-9]{128}$", "SHA3-512"),
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"SSDEEP": (r"^[a-zA-Z0-9/+:.]{1,128}$", "SSDEEP"),
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"WHIRLPOOL": (r"^[a-fA-F0-9]{128}$", "WHIRLPOOL"),
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"TLSH": (r"^[a-fA-F0-9]{70}$", "TLSH"),
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}
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class HashesProperty(DictionaryProperty):
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def clean(self, value):
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clean_dict = super(HashesProperty, self).clean(value)
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for k, v in copy.deepcopy(clean_dict).items():
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key = k.upper().replace('-', '')
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if key in HASHES_REGEX:
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vocab_key = HASHES_REGEX[key][1]
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if vocab_key == "SSDEEP" and self.spec_version == "2.0":
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vocab_key = vocab_key.lower()
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if not re.match(HASHES_REGEX[key][0], v):
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raise ValueError("'{0}' is not a valid {1} hash".format(v, vocab_key))
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if k != vocab_key:
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clean_dict[vocab_key] = clean_dict[k]
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del clean_dict[k]
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return clean_dict
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class BinaryProperty(Property):
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def clean(self, value):
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try:
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base64.b64decode(value)
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except (binascii.Error, TypeError):
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raise ValueError("must contain a base64 encoded string")
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return value
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class HexProperty(Property):
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def clean(self, value):
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if not re.match(r"^([a-fA-F0-9]{2})+$", value):
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raise ValueError("must contain an even number of hexadecimal characters")
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return value
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class ReferenceProperty(Property):
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def __init__(self, valid_types=None, invalid_types=None, spec_version=stix2.DEFAULT_VERSION, **kwargs):
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"""
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references sometimes must be to a specific object type
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"""
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self.spec_version = spec_version
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# These checks need to be done prior to the STIX object finishing construction
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# and thus we can't use base.py's _check_mutually_exclusive_properties()
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# in the typical location of _check_object_constraints() in sdo.py
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if valid_types and invalid_types:
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raise MutuallyExclusivePropertiesError(self.__class__, ['invalid_types', 'valid_types'])
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elif valid_types is None and invalid_types is None:
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raise MissingPropertiesError(self.__class__, ['invalid_types', 'valid_types'])
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if valid_types and type(valid_types) is not list:
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valid_types = [valid_types]
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elif invalid_types and type(invalid_types) is not list:
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invalid_types = [invalid_types]
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self.valid_types = valid_types
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self.invalid_types = invalid_types
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super(ReferenceProperty, self).__init__(**kwargs)
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def clean(self, value):
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if isinstance(value, _STIXBase):
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value = value.id
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value = str(value)
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possible_prefix = value[:value.index('--')]
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if self.valid_types:
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ref_valid_types = enumerate_types(self.valid_types, 'v' + self.spec_version.replace(".", ""))
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if possible_prefix in ref_valid_types:
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required_prefix = possible_prefix
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else:
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raise ValueError("The type-specifying prefix '%s' for this property is not valid" % (possible_prefix))
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elif self.invalid_types:
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ref_invalid_types = enumerate_types(self.invalid_types, 'v' + self.spec_version.replace(".", ""))
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if possible_prefix not in ref_invalid_types:
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required_prefix = possible_prefix
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else:
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raise ValueError("An invalid type-specifying prefix '%s' was specified for this property" % (possible_prefix))
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_validate_id(value, self.spec_version, required_prefix)
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return value
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def enumerate_types(types, spec_version):
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"""
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`types` is meant to be a list; it may contain specific object types and/or
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the any of the words "SCO", "SDO", or "SRO"
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Since "SCO", "SDO", and "SRO" are general types that encompass various specific object types,
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once each of those words is being processed, that word will be removed from `return_types`,
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so as not to mistakenly allow objects to be created of types "SCO", "SDO", or "SRO"
|
|
"""
|
|
return_types = []
|
|
return_types += types
|
|
|
|
if "SDO" in types:
|
|
return_types.remove("SDO")
|
|
return_types += STIX2_OBJ_MAPS[spec_version]['objects'].keys()
|
|
if "SCO" in types:
|
|
return_types.remove("SCO")
|
|
return_types += STIX2_OBJ_MAPS[spec_version]['observables'].keys()
|
|
if "SRO" in types:
|
|
return_types.remove("SRO")
|
|
return_types += ['relationship', 'sighting']
|
|
|
|
return return_types
|
|
|
|
|
|
SELECTOR_REGEX = re.compile(r"^[a-z0-9_-]{3,250}(\.(\[\d+\]|[a-z0-9_-]{1,250}))*$")
|
|
|
|
|
|
class SelectorProperty(Property):
|
|
|
|
def clean(self, value):
|
|
if not SELECTOR_REGEX.match(value):
|
|
raise ValueError("must adhere to selector syntax.")
|
|
return value
|
|
|
|
|
|
class ObjectReferenceProperty(StringProperty):
|
|
|
|
def __init__(self, valid_types=None, **kwargs):
|
|
if valid_types and type(valid_types) is not list:
|
|
valid_types = [valid_types]
|
|
self.valid_types = valid_types
|
|
super(ObjectReferenceProperty, self).__init__(**kwargs)
|
|
|
|
|
|
class EmbeddedObjectProperty(Property):
|
|
|
|
def __init__(self, type, **kwargs):
|
|
self.type = type
|
|
super(EmbeddedObjectProperty, self).__init__(**kwargs)
|
|
|
|
def clean(self, value):
|
|
if type(value) is dict:
|
|
value = self.type(**value)
|
|
elif not isinstance(value, self.type):
|
|
raise ValueError("must be of type {}.".format(self.type.__name__))
|
|
return value
|
|
|
|
|
|
class EnumProperty(StringProperty):
|
|
|
|
def __init__(self, allowed, **kwargs):
|
|
if type(allowed) is not list:
|
|
allowed = list(allowed)
|
|
self.allowed = allowed
|
|
super(EnumProperty, self).__init__(**kwargs)
|
|
|
|
def clean(self, value):
|
|
cleaned_value = super(EnumProperty, self).clean(value)
|
|
if cleaned_value not in self.allowed:
|
|
raise ValueError("value '{}' is not valid for this enumeration.".format(cleaned_value))
|
|
|
|
return cleaned_value
|
|
|
|
|
|
class PatternProperty(StringProperty):
|
|
pass
|
|
|
|
|
|
class ObservableProperty(Property):
|
|
"""Property for holding Cyber Observable Objects.
|
|
"""
|
|
|
|
def __init__(self, spec_version=stix2.DEFAULT_VERSION, allow_custom=False, *args, **kwargs):
|
|
self.allow_custom = allow_custom
|
|
self.spec_version = spec_version
|
|
super(ObservableProperty, self).__init__(*args, **kwargs)
|
|
|
|
def clean(self, value):
|
|
try:
|
|
dictified = _get_dict(value)
|
|
# get deep copy since we are going modify the dict and might
|
|
# modify the original dict as _get_dict() does not return new
|
|
# dict when passed a dict
|
|
dictified = copy.deepcopy(dictified)
|
|
except ValueError:
|
|
raise ValueError("The observable property must contain a dictionary")
|
|
if dictified == {}:
|
|
raise ValueError("The observable property must contain a non-empty dictionary")
|
|
|
|
valid_refs = dict((k, v['type']) for (k, v) in dictified.items())
|
|
|
|
for key, obj in dictified.items():
|
|
parsed_obj = parse_observable(
|
|
obj,
|
|
valid_refs,
|
|
allow_custom=self.allow_custom,
|
|
version=self.spec_version,
|
|
)
|
|
dictified[key] = parsed_obj
|
|
|
|
return dictified
|
|
|
|
|
|
class ExtensionsProperty(DictionaryProperty):
|
|
"""Property for representing extensions on Observable objects.
|
|
"""
|
|
|
|
def __init__(self, spec_version=stix2.DEFAULT_VERSION, allow_custom=False, enclosing_type=None, required=False):
|
|
self.allow_custom = allow_custom
|
|
self.enclosing_type = enclosing_type
|
|
super(ExtensionsProperty, self).__init__(spec_version=spec_version, required=required)
|
|
|
|
def clean(self, value):
|
|
try:
|
|
dictified = _get_dict(value)
|
|
# get deep copy since we are going modify the dict and might
|
|
# modify the original dict as _get_dict() does not return new
|
|
# dict when passed a dict
|
|
dictified = copy.deepcopy(dictified)
|
|
except ValueError:
|
|
raise ValueError("The extensions property must contain a dictionary")
|
|
|
|
v = 'v' + self.spec_version.replace('.', '')
|
|
|
|
specific_type_map = STIX2_OBJ_MAPS[v]['observable-extensions'].get(self.enclosing_type, {})
|
|
for key, subvalue in dictified.items():
|
|
if key in specific_type_map:
|
|
cls = specific_type_map[key]
|
|
if type(subvalue) is dict:
|
|
if self.allow_custom:
|
|
subvalue['allow_custom'] = True
|
|
dictified[key] = cls(**subvalue)
|
|
else:
|
|
dictified[key] = cls(**subvalue)
|
|
elif type(subvalue) is cls:
|
|
# If already an instance of an _Extension class, assume it's valid
|
|
dictified[key] = subvalue
|
|
else:
|
|
raise ValueError("Cannot determine extension type.")
|
|
else:
|
|
if self.allow_custom:
|
|
dictified[key] = subvalue
|
|
else:
|
|
raise CustomContentError("Can't parse unknown extension type: {}".format(key))
|
|
return dictified
|
|
|
|
|
|
class STIXObjectProperty(Property):
|
|
|
|
def __init__(self, spec_version=stix2.DEFAULT_VERSION, allow_custom=False, *args, **kwargs):
|
|
self.allow_custom = allow_custom
|
|
self.spec_version = spec_version
|
|
super(STIXObjectProperty, self).__init__(*args, **kwargs)
|
|
|
|
def clean(self, value):
|
|
# Any STIX Object (SDO, SRO, or Marking Definition) can be added to
|
|
# a bundle with no further checks.
|
|
if any(x in ('_DomainObject', '_RelationshipObject', 'MarkingDefinition')
|
|
for x in get_class_hierarchy_names(value)):
|
|
# A simple "is this a spec version 2.1+ object" test. For now,
|
|
# limit 2.0 bundles to 2.0 objects. It's not possible yet to
|
|
# have validation co-constraints among properties, e.g. have
|
|
# validation here depend on the value of another property
|
|
# (spec_version). So this is a hack, and not technically spec-
|
|
# compliant.
|
|
if 'spec_version' in value and self.spec_version == '2.0':
|
|
raise ValueError(
|
|
"Spec version 2.0 bundles don't yet support "
|
|
"containing objects of a different spec "
|
|
"version.",
|
|
)
|
|
return value
|
|
try:
|
|
dictified = _get_dict(value)
|
|
except ValueError:
|
|
raise ValueError("This property may only contain a dictionary or object")
|
|
if dictified == {}:
|
|
raise ValueError("This property may only contain a non-empty dictionary or object")
|
|
if 'type' in dictified and dictified['type'] == 'bundle':
|
|
raise ValueError("This property may not contain a Bundle object")
|
|
if 'spec_version' in dictified and self.spec_version == '2.0':
|
|
# See above comment regarding spec_version.
|
|
raise ValueError(
|
|
"Spec version 2.0 bundles don't yet support "
|
|
"containing objects of a different spec version.",
|
|
)
|
|
|
|
parsed_obj = parse(dictified, allow_custom=self.allow_custom)
|
|
|
|
return parsed_obj
|