cti-python-stix2/stix2/properties.py

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"""Classes for representing properties of STIX Objects and Cyber Observables.
"""
import base64
import binascii
import collections
import inspect
import re
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import uuid
from six import string_types, text_type
from stix2patterns.validator import run_validator
from .base import _STIXBase
from .exceptions import DictionaryKeyError
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from .utils import _get_dict, parse_into_datetime
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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
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valid for this property, this will attempt to transform it first. If
``value`` is not valid and no such transformation is possible, it should
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raise a ValueError.
- ``def default(self):``
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- provide a default value for this property.
- ``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 need
to use the same default value, so calling now() for each property--
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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
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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.
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"""
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def _default_clean(self, value):
if value != self._fixed_value:
raise ValueError("must equal '{0}'.".format(self._fixed_value))
return value
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def __init__(self, required=False, fixed=None, default=None, type=None):
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self.required = required
self.type = type
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if fixed:
self._fixed_value = fixed
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self.clean = self._default_clean
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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
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class ListProperty(Property):
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def __init__(self, contained, **kwargs):
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"""
``contained`` should be a function which returns an object from the value.
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"""
if inspect.isclass(contained) and issubclass(contained, Property):
# 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
# use __call__ when it appends the item.
self.contained = contained()
else:
self.contained = contained
super(ListProperty, self).__init__(**kwargs)
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def clean(self, value):
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try:
iter(value)
except TypeError:
raise ValueError("must be an iterable.")
if isinstance(value, (_STIXBase, string_types)):
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)
except ValueError:
raise
except AttributeError:
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# 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__ is '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 StringProperty(Property):
def __init__(self, **kwargs):
self.string_type = text_type
super(StringProperty, self).__init__(**kwargs)
def clean(self, value):
return self.string_type(value)
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class TypeProperty(Property):
def __init__(self, type):
super(TypeProperty, self).__init__(fixed=type)
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class IDProperty(Property):
def __init__(self, type):
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self.required_prefix = type + "--"
super(IDProperty, self).__init__()
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def clean(self, value):
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if not value.startswith(self.required_prefix):
raise ValueError("must start with '{0}'.".format(self.required_prefix))
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try:
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uuid.UUID(value.split('--', 1)[1])
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except Exception:
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raise ValueError("must have a valid UUID after the 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):
def clean(self, value):
try:
return int(value)
except Exception:
raise ValueError("must be an integer.")
class FloatProperty(Property):
def clean(self, value):
try:
return float(value)
except Exception:
raise ValueError("must be a float.")
class BooleanProperty(Property):
def clean(self, value):
if isinstance(value, bool):
return value
trues = ['true', 't']
falses = ['false', 'f']
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
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raise ValueError("must be a boolean value.")
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class TimestampProperty(Property):
def __init__(self, precision=None, **kwargs):
self.precision = precision
super(TimestampProperty, self).__init__(**kwargs)
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def clean(self, value):
return parse_into_datetime(value, self.precision)
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class DictionaryProperty(Property):
def clean(self, value):
try:
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dictified = _get_dict(value)
except ValueError:
raise ValueError("The dictionary property must contain a dictionary")
if dictified == {}:
raise ValueError("The dictionary property must contain a non-empty dictionary")
for k in dictified.keys():
if len(k) < 3:
raise DictionaryKeyError(k, "shorter than 3 characters")
elif len(k) > 256:
raise DictionaryKeyError(k, "longer than 256 characters")
if not re.match('^[a-zA-Z0-9_-]+$', k):
raise DictionaryKeyError(k, "contains characters other than"
"lowercase a-z, uppercase A-Z, "
"numerals 0-9, hyphen (-), or "
"underscore (_)")
return dictified
HASHES_REGEX = {
"MD5": ("^[a-fA-F0-9]{32}$", "MD5"),
"MD6": ("^[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}$", "MD6"),
"RIPEMD160": ("^[a-fA-F0-9]{40}$", "RIPEMD-160"),
"SHA1": ("^[a-fA-F0-9]{40}$", "SHA-1"),
"SHA224": ("^[a-fA-F0-9]{56}$", "SHA-224"),
"SHA256": ("^[a-fA-F0-9]{64}$", "SHA-256"),
"SHA384": ("^[a-fA-F0-9]{96}$", "SHA-384"),
"SHA512": ("^[a-fA-F0-9]{128}$", "SHA-512"),
"SHA3224": ("^[a-fA-F0-9]{56}$", "SHA3-224"),
"SHA3256": ("^[a-fA-F0-9]{64}$", "SHA3-256"),
"SHA3384": ("^[a-fA-F0-9]{96}$", "SHA3-384"),
"SHA3512": ("^[a-fA-F0-9]{128}$", "SHA3-512"),
"SSDEEP": ("^[a-zA-Z0-9/+:.]{1,128}$", "ssdeep"),
"WHIRLPOOL": ("^[a-fA-F0-9]{128}$", "WHIRLPOOL"),
}
class HashesProperty(DictionaryProperty):
def clean(self, value):
clean_dict = super(HashesProperty, self).clean(value)
for k, v in clean_dict.items():
key = k.upper().replace('-', '')
if key in HASHES_REGEX:
vocab_key = HASHES_REGEX[key][1]
if not re.match(HASHES_REGEX[key][0], v):
raise ValueError("'%s' is not a valid %s hash" % (v, vocab_key))
if k != vocab_key:
clean_dict[vocab_key] = clean_dict[k]
del clean_dict[k]
return clean_dict
class BinaryProperty(Property):
def clean(self, value):
try:
base64.b64decode(value)
except (binascii.Error, TypeError):
raise ValueError("must contain a base64 encoded string")
return value
class HexProperty(Property):
def clean(self, value):
if not re.match('^([a-fA-F0-9]{2})+$', value):
raise ValueError("must contain an even number of hexadecimal characters")
return value
REF_REGEX = re.compile("^[a-z][a-z-]+[a-z]--[0-9a-fA-F]{8}-[0-9a-fA-F]{4}"
"-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}$")
class ReferenceProperty(Property):
def __init__(self, required=False, type=None):
"""
references sometimes must be to a specific object type
"""
self.type = type
super(ReferenceProperty, self).__init__(required, type=type)
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def clean(self, value):
if isinstance(value, _STIXBase):
value = value.id
value = str(value)
if self.type:
if not value.startswith(self.type):
raise ValueError("must start with '{0}'.".format(self.type))
if not REF_REGEX.match(value):
raise ValueError("must match <object-type>--<guid>.")
return value
SELECTOR_REGEX = re.compile("^[a-z0-9_-]{3,250}(\\.(\\[\\d+\\]|[a-z0-9_-]{1,250}))*$")
class SelectorProperty(Property):
def __init__(self, type=None):
# ignore type
super(SelectorProperty, self).__init__()
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def clean(self, value):
if not SELECTOR_REGEX.match(value):
raise ValueError("must adhere to selector syntax.")
return value
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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, required=False):
self.type = type
super(EmbeddedObjectProperty, self).__init__(required, type=type)
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 %s." % 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):
value = super(EnumProperty, self).clean(value)
if value not in self.allowed:
raise ValueError("value '%s' is not valid for this enumeration." % value)
return self.string_type(value)
class PatternProperty(StringProperty):
def __init__(self, **kwargs):
super(PatternProperty, self).__init__(**kwargs)
def clean(self, value):
str_value = super(PatternProperty, self).clean(value)
errors = run_validator(str_value)
if errors:
raise ValueError(str(errors[0]))
return self.string_type(value)