cti-python-stix2/stix2/properties.py

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2018-11-28 22:51:00 +01:00
"""Classes for representing properties of STIX Objects and Cyber Observables."""
import base64
import binascii
import collections
import copy
import inspect
import re
import uuid
from six import string_types, text_type
from stix2patterns.validator import run_validator
import stix2
from .base import _Observable, _STIXBase
from .core import STIX2_OBJ_MAPS, parse, parse_observable
from .exceptions import CustomContentError, DictionaryKeyError
from .utils import _get_dict, get_class_hierarchy_names, parse_into_datetime
ERROR_INVALID_ID = (
"not a valid STIX identifier, must match <object-type>--<UUID>: {}"
)
def _check_uuid(uuid_str, spec_version):
"""
Check whether the given UUID string is valid with respect to the given STIX
spec version. STIX 2.0 requires UUIDv4; 2.1 only requires the RFC 4122
variant.
:param uuid_str: A UUID as a string
:param spec_version: The STIX spec version
:return: True if the UUID is valid, False if not
:raises ValueError: If uuid_str is malformed
"""
uuid_obj = uuid.UUID(uuid_str)
ok = uuid_obj.variant == uuid.RFC_4122
if ok and spec_version == "2.0":
ok = uuid_obj.version == 4
return ok
def _validate_id(id_, spec_version, required_prefix):
"""
Check the STIX identifier for correctness, raise an exception if there are
errors.
:param id_: The STIX identifier
:param spec_version: The STIX specification version to use
:param required_prefix: The required prefix on the identifier, if any.
This function doesn't add a "--" suffix to the prefix, so callers must
add it if it is important. Pass None to skip the prefix check.
:raises ValueError: If there are any errors with the identifier
"""
if required_prefix:
if not id_.startswith(required_prefix):
raise ValueError("must start with '{}'.".format(required_prefix))
try:
if required_prefix:
uuid_part = id_[len(required_prefix):]
else:
idx = id_.index("--")
uuid_part = id_[idx+2:]
result = _check_uuid(uuid_part, spec_version)
except ValueError:
# replace their ValueError with ours
raise ValueError(ERROR_INVALID_ID.format(id_))
if not result:
raise ValueError(ERROR_INVALID_ID.format(id_))
class Property(object):
"""Represent a property of STIX data type.
Subclasses can define the following attributes as keyword arguments to
``__init__()``.
Args:
required (bool): If ``True``, the property must be provided when
creating an object with that property. No default value exists for
these properties. (Default: ``False``)
fixed: This provides a constant default value. Users are free to
provide this value explicity when constructing an object (which
allows you to copy **all** values from an existing object to a new
object), but if the user provides a value other than the ``fixed``
value, it will raise an error. This is semantically equivalent to
defining both:
- a ``clean()`` function that checks if the value matches the fixed
value, and
- a ``default()`` function that returns the fixed value.
Subclasses can also define the following functions:
- ``def clean(self, value) -> any:``
- Return a value that is valid for this property. If ``value`` is not
valid for this property, this will attempt to transform it first. If
``value`` is not valid and no such transformation is possible, it
should raise a ValueError.
- ``def default(self):``
- provide a default value for this property.
- ``default()`` can return the special value ``NOW`` to use the current
time. This is useful when several timestamps in the same object
need to use the same default value, so calling now() for each
property-- likely several microseconds apart-- does not work.
Subclasses can instead provide a lambda function for ``default`` as a
keyword argument. ``clean`` should not be provided as a lambda since
lambdas cannot raise their own exceptions.
When instantiating Properties, ``required`` and ``default`` should not be
used together. ``default`` implies that the property is required in the
specification so this function will be used to supply a value if none is
provided. ``required`` means that the user must provide this; it is
required in the specification and we can't or don't want to create a
default value.
"""
def _default_clean(self, value):
if value != self._fixed_value:
raise ValueError("must equal '{}'.".format(self._fixed_value))
return value
def __init__(self, required=False, fixed=None, default=None):
self.required = required
if fixed:
self._fixed_value = fixed
self.clean = self._default_clean
self.default = lambda: fixed
if default:
self.default = default
def clean(self, value):
return value
def __call__(self, value=None):
"""Used by ListProperty to handle lists that have been defined with
either a class or an instance.
"""
return value
class ListProperty(Property):
def __init__(self, contained, **kwargs):
"""
``contained`` should be a function which returns an object from the value.
"""
if inspect.isclass(contained) and issubclass(contained, Property):
# If it's a class and not an instance, instantiate it so that
# clean() can be called on it, and ListProperty.clean() will
# use __call__ when it appends the item.
self.contained = contained()
else:
self.contained = contained
super(ListProperty, self).__init__(**kwargs)
def clean(self, value):
try:
iter(value)
except TypeError:
raise ValueError("must be an iterable.")
if isinstance(value, (_STIXBase, string_types)):
value = [value]
result = []
for item in value:
try:
valid = self.contained.clean(item)
except ValueError:
raise
except AttributeError:
# type of list has no clean() function (eg. built in Python types)
# TODO Should we raise an error here?
valid = item
if type(self.contained) is EmbeddedObjectProperty:
obj_type = self.contained.type
elif type(self.contained).__name__ == "STIXObjectProperty":
# ^ this way of checking doesn't require a circular import
# valid is already an instance of a python-stix2 class; no need
# to turn it into a dictionary and then pass it to the class
# constructor again
result.append(valid)
continue
elif type(self.contained) is DictionaryProperty:
obj_type = dict
else:
obj_type = self.contained
if isinstance(valid, collections.Mapping):
result.append(obj_type(**valid))
else:
result.append(obj_type(valid))
# STIX spec forbids empty lists
if len(result) < 1:
raise ValueError("must not be empty.")
return result
class CallableValues(list):
"""Wrapper to allow `values()` method on WindowsRegistryKey objects.
Needed because `values` is also a property.
"""
def __init__(self, parent_instance, *args, **kwargs):
self.parent_instance = parent_instance
super(CallableValues, self).__init__(*args, **kwargs)
def __call__(self):
return _Observable.values(self.parent_instance)
class StringProperty(Property):
def __init__(self, **kwargs):
super(StringProperty, self).__init__(**kwargs)
def clean(self, value):
if not isinstance(value, string_types):
return text_type(value)
return value
class TypeProperty(Property):
def __init__(self, type):
super(TypeProperty, self).__init__(fixed=type)
class IDProperty(Property):
def __init__(self, type, spec_version=stix2.DEFAULT_VERSION):
self.required_prefix = type + "--"
self.spec_version = spec_version
super(IDProperty, self).__init__()
def clean(self, value):
_validate_id(value, self.spec_version, self.required_prefix)
return value
def default(self):
return self.required_prefix + str(uuid.uuid4())
class IntegerProperty(Property):
def __init__(self, min=None, max=None, **kwargs):
self.min = min
self.max = max
super(IntegerProperty, self).__init__(**kwargs)
def clean(self, value):
try:
value = int(value)
except Exception:
raise ValueError("must be an integer.")
if self.min is not None and value < self.min:
msg = "minimum value is {}. received {}".format(self.min, value)
raise ValueError(msg)
if self.max is not None and value > self.max:
msg = "maximum value is {}. received {}".format(self.max, value)
raise ValueError(msg)
return value
class FloatProperty(Property):
def __init__(self, min=None, max=None, **kwargs):
self.min = min
self.max = max
super(FloatProperty, self).__init__(**kwargs)
def clean(self, value):
try:
value = float(value)
except Exception:
raise ValueError("must be a float.")
if self.min is not None and value < self.min:
msg = "minimum value is {}. received {}".format(self.min, value)
raise ValueError(msg)
if self.max is not None and value > self.max:
msg = "maximum value is {}. received {}".format(self.max, value)
raise ValueError(msg)
return value
class BooleanProperty(Property):
def clean(self, value):
if isinstance(value, bool):
return value
trues = ['true', 't', '1']
falses = ['false', 'f', '0']
try:
if value.lower() in trues:
return True
if value.lower() in falses:
return False
except AttributeError:
if value == 1:
return True
if value == 0:
return False
raise ValueError("must be a boolean value.")
class TimestampProperty(Property):
def __init__(self, precision=None, **kwargs):
self.precision = precision
super(TimestampProperty, self).__init__(**kwargs)
def clean(self, value):
return parse_into_datetime(value, self.precision)
class DictionaryProperty(Property):
def __init__(self, spec_version=stix2.DEFAULT_VERSION, **kwargs):
self.spec_version = spec_version
super(DictionaryProperty, self).__init__(**kwargs)
def clean(self, value):
try:
dictified = _get_dict(value)
except ValueError:
raise ValueError("The dictionary property must contain a dictionary")
for k in dictified.keys():
if self.spec_version == '2.0':
if len(k) < 3:
raise DictionaryKeyError(k, "shorter than 3 characters")
elif len(k) > 256:
raise DictionaryKeyError(k, "longer than 256 characters")
elif self.spec_version == '2.1':
if len(k) > 250:
raise DictionaryKeyError(k, "longer than 250 characters")
if not re.match(r"^[a-zA-Z0-9_-]+$", k):
msg = (
"contains characters other than lowercase a-z, "
"uppercase A-Z, numerals 0-9, hyphen (-), or "
"underscore (_)"
)
raise DictionaryKeyError(k, msg)
return dictified
HASHES_REGEX = {
"MD5": (r"^[a-fA-F0-9]{32}$", "MD5"),
"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}$", "MD6"),
"RIPEMD160": (r"^[a-fA-F0-9]{40}$", "RIPEMD-160"),
"SHA1": (r"^[a-fA-F0-9]{40}$", "SHA-1"),
"SHA224": (r"^[a-fA-F0-9]{56}$", "SHA-224"),
"SHA256": (r"^[a-fA-F0-9]{64}$", "SHA-256"),
"SHA384": (r"^[a-fA-F0-9]{96}$", "SHA-384"),
"SHA512": (r"^[a-fA-F0-9]{128}$", "SHA-512"),
"SHA3224": (r"^[a-fA-F0-9]{56}$", "SHA3-224"),
"SHA3256": (r"^[a-fA-F0-9]{64}$", "SHA3-256"),
"SHA3384": (r"^[a-fA-F0-9]{96}$", "SHA3-384"),
"SHA3512": (r"^[a-fA-F0-9]{128}$", "SHA3-512"),
"SSDEEP": (r"^[a-zA-Z0-9/+:.]{1,128}$", "ssdeep"),
"WHIRLPOOL": (r"^[a-fA-F0-9]{128}$", "WHIRLPOOL"),
}
class HashesProperty(DictionaryProperty):
def clean(self, value):
clean_dict = super(HashesProperty, self).clean(value)
for k, v in clean_dict.items():
key = k.upper().replace('-', '')
if key in HASHES_REGEX:
vocab_key = HASHES_REGEX[key][1]
if not re.match(HASHES_REGEX[key][0], v):
raise ValueError("'{0}' is not a valid {1} hash".format(v, vocab_key))
if k != vocab_key:
clean_dict[vocab_key] = clean_dict[k]
del clean_dict[k]
return clean_dict
class BinaryProperty(Property):
def clean(self, value):
try:
base64.b64decode(value)
except (binascii.Error, TypeError):
raise ValueError("must contain a base64 encoded string")
return value
class HexProperty(Property):
def clean(self, value):
if not re.match(r"^([a-fA-F0-9]{2})+$", value):
raise ValueError("must contain an even number of hexadecimal characters")
return value
class ReferenceProperty(Property):
def __init__(self, type=None, spec_version=stix2.DEFAULT_VERSION, **kwargs):
"""
references sometimes must be to a specific object type
"""
self.required_prefix = type + "--" if type else None
self.spec_version = spec_version
super(ReferenceProperty, self).__init__(**kwargs)
def clean(self, value):
if isinstance(value, _STIXBase):
value = value.id
value = str(value)
_validate_id(value, self.spec_version, self.required_prefix)
return value
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):
def clean(self, value):
cleaned_value = super(PatternProperty, self).clean(value)
errors = run_validator(cleaned_value)
if errors:
raise ValueError(str(errors[0]))
return cleaned_value
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:
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 ('STIXDomainObject', 'STIXRelationshipObject', '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