247 lines
8.4 KiB
Python
247 lines
8.4 KiB
Python
"""Utility functions and classes for the stix2 library."""
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from collections import Mapping
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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 dateutil import parser
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import pytz
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from .exceptions import (InvalidValueError, RevokeError,
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UnmodifiablePropertyError)
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# Sentinel value for properties that should be set to the current time.
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# We can't use the standard 'default' approach, since if there are multiple
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# timestamps in a single object, the timestamps will vary by a few microseconds.
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NOW = object()
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class STIXdatetime(dt.datetime):
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def __new__(cls, *args, **kwargs):
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precision = kwargs.pop('precision', None)
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if isinstance(args[0], dt.datetime): # Allow passing in a datetime object
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dttm = args[0]
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args = (dttm.year, dttm.month, dttm.day, dttm.hour, dttm.minute,
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dttm.second, dttm.microsecond, dttm.tzinfo)
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# self will be an instance of STIXdatetime, not dt.datetime
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self = dt.datetime.__new__(cls, *args, **kwargs)
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self.precision = precision
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return self
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def __repr__(self):
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return "'%s'" % format_datetime(self)
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def deduplicate(stix_obj_list):
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"""Deduplicate a list of STIX objects to a unique set
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Reduces a set of STIX objects to unique set by looking
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at 'id' and 'modified' fields - as a unique object version
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is determined by the combination of those fields
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Note: Be aware, as can be seen in the implementation
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of deduplicate(),that if the "stix_obj_list" argument has
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multiple STIX objects of the same version, the last object
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version found in the list will be the one that is returned.
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()
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Args:
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stix_obj_list (list): list of STIX objects (dicts)
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Returns:
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A list with a unique set of the passed list of STIX objects.
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"""
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unique_objs = {}
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for obj in stix_obj_list:
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unique_objs[(obj['id'], obj['modified'])] = obj
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return list(unique_objs.values())
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def get_timestamp():
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"""Return a STIX timestamp of the current date and time."""
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return STIXdatetime.now(tz=pytz.UTC)
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def format_datetime(dttm):
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"""Convert a datetime object into a valid STIX timestamp string.
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1. Convert to timezone-aware
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2. Convert to UTC
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3. Format in ISO format
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4. Ensure correct precision
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a. Add subsecond value if non-zero and precision not defined
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5. Add "Z"
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"""
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if dttm.tzinfo is None or dttm.tzinfo.utcoffset(dttm) is None:
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# dttm is timezone-naive; assume UTC
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zoned = pytz.utc.localize(dttm)
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else:
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zoned = dttm.astimezone(pytz.utc)
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ts = zoned.strftime("%Y-%m-%dT%H:%M:%S")
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ms = zoned.strftime("%f")
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precision = getattr(dttm, "precision", None)
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if precision == 'second':
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pass # Alredy precise to the second
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elif precision == "millisecond":
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ts = ts + '.' + ms[:3]
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elif zoned.microsecond > 0:
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ts = ts + '.' + ms.rstrip("0")
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return ts + "Z"
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def parse_into_datetime(value, precision=None):
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"""Parse a value into a valid STIX timestamp object.
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"""
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if isinstance(value, dt.date):
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if hasattr(value, 'hour'):
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ts = value
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else:
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# Add a time component
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ts = dt.datetime.combine(value, dt.time(0, 0, tzinfo=pytz.utc))
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else:
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# value isn't a date or datetime object so assume it's a string
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try:
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parsed = parser.parse(value)
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except (TypeError, ValueError):
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# Unknown format
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raise ValueError("must be a datetime object, date object, or "
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"timestamp string in a recognizable format.")
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if parsed.tzinfo:
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ts = parsed.astimezone(pytz.utc)
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else:
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# Doesn't have timezone info in the string; assume UTC
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ts = pytz.utc.localize(parsed)
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# Ensure correct precision
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if not precision:
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return STIXdatetime(ts, precision=precision)
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ms = ts.microsecond
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if precision == 'second':
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ts = ts.replace(microsecond=0)
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elif precision == 'millisecond':
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ms_len = len(str(ms))
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if ms_len > 3:
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# Truncate to millisecond precision
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factor = 10 ** (ms_len - 3)
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ts = ts.replace(microsecond=(ts.microsecond // factor) * factor)
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else:
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ts = ts.replace(microsecond=0)
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return STIXdatetime(ts, precision=precision)
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def get_dict(data):
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"""Return data as a dictionary.
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Input can be a dictionary, string, or file-like object.
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"""
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if type(data) is dict:
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return data
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else:
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try:
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return json.loads(data)
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except TypeError:
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pass
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try:
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return json.load(data)
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except AttributeError:
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pass
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try:
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return dict(data)
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except (ValueError, TypeError):
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raise ValueError("Cannot convert '%s' to dictionary." % str(data))
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def find_property_index(obj, properties, tuple_to_find):
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"""Recursively find the property in the object model, return the index
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according to the _properties OrderedDict. If it's a list look for
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individual objects.
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"""
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from .base import _STIXBase
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try:
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if tuple_to_find[1] in obj._inner.values():
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return properties.index(tuple_to_find[0])
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raise ValueError
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except ValueError:
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for pv in obj._inner.values():
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if isinstance(pv, list):
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for item in pv:
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if isinstance(item, _STIXBase):
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val = find_property_index(item,
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item.object_properties(),
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tuple_to_find)
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if val is not None:
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return val
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elif isinstance(pv, dict):
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if pv.get(tuple_to_find[0]) is not None:
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try:
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return int(tuple_to_find[0])
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except ValueError:
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return len(tuple_to_find[0])
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for item in pv.values():
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if isinstance(item, _STIXBase):
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val = find_property_index(item,
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item.object_properties(),
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tuple_to_find)
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if val is not None:
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return val
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def new_version(data, **kwargs):
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"""Create a new version of a STIX object, by modifying properties and
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updating the ``modified`` property.
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"""
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if not isinstance(data, Mapping):
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raise ValueError('cannot create new version of object of this type! '
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'Try a dictionary or instance of an SDO or SRO class.')
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unchangable_properties = []
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if data.get("revoked"):
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raise RevokeError("new_version")
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try:
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new_obj_inner = copy.deepcopy(data._inner)
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except AttributeError:
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new_obj_inner = copy.deepcopy(data)
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properties_to_change = kwargs.keys()
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# Make sure certain properties aren't trying to change
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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(data)
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if 'modified' not in kwargs:
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kwargs['modified'] = get_timestamp()
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elif 'modified' in data:
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old_modified_property = parse_into_datetime(data.get('modified'), precision='millisecond')
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new_modified_property = parse_into_datetime(kwargs['modified'], precision='millisecond')
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if new_modified_property < old_modified_property:
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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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# Exclude properties with a value of 'None' in case data is not an instance of a _STIXBase subclass
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return cls(**{k: v for k, v in new_obj_inner.items() if v is not None})
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def revoke(data):
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"""Revoke a STIX object.
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Returns:
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A new version of the object with ``revoked`` set to ``True``.
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"""
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if not isinstance(data, Mapping):
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raise ValueError('cannot revoke object of this type! Try a dictionary '
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'or instance of an SDO or SRO class.')
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if data.get("revoked"):
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raise RevokeError("revoke")
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return new_version(data, revoked=True)
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