cti-python-stix2/stix2/markings/utils.py

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2018-11-28 22:51:00 +01:00
"""Utility functions for STIX2 data markings."""
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import collections
import six
from stix2 import exceptions
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def _evaluate_expression(obj, selector):
"""Walk an SDO or SRO generating selectors to match against ``selector``.
If a match is found and the the value of this property is present in the
objects. Matching value of the property will be returned.
Args:
obj: An SDO or SRO object.
selector (str): A string following the selector syntax.
Returns:
list: Values contained in matching property. Otherwise empty list.
"""
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for items, value in iterpath(obj):
path = '.'.join(items)
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if path == selector and value:
return [value]
return []
def _validate_selector(obj, selector):
"""Evaluate each selector against an object."""
results = list(_evaluate_expression(obj, selector))
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if len(results) >= 1:
return True
def _get_marking_id(marking):
if type(marking).__name__ is 'MarkingDefinition': # avoid circular import
return marking.id
return marking
def validate(obj, selectors):
"""Given an SDO or SRO, check that each selector is valid."""
if selectors:
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for s in selectors:
if not _validate_selector(obj, s):
raise exceptions.InvalidSelectorError(obj, s)
return
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raise exceptions.InvalidSelectorError(obj, selectors)
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def convert_to_list(data):
"""Convert input into a list for further processing."""
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if data is not None:
if isinstance(data, list):
return data
else:
return [data]
def convert_to_marking_list(data):
"""Convert input into a list of marking identifiers."""
if data is not None:
if isinstance(data, list):
return [_get_marking_id(x) for x in data]
else:
return [_get_marking_id(data)]
def compress_markings(granular_markings):
"""Compress granular markings list.
If there is more than one marking identifier matches. It will collapse into
a single granular marking.
Example:
>>> compress_markings([
... {
... "selectors": [
... "description"
... ],
... "marking_ref": "marking-definition--613f2e26-407d-48c7-9eca-b8e91df99dc9"
... },
... {
... "selectors": [
... "name"
... ],
... "marking_ref": "marking-definition--613f2e26-407d-48c7-9eca-b8e91df99dc9"
... }
... ])
[
{
"selectors": [
"description",
"name"
],
"marking_ref": "marking-definition--613f2e26-407d-48c7-9eca-b8e91df99dc9"
}
]
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Args:
granular_markings: The granular markings list property present in a
SDO or SRO.
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Returns:
list: A list with all markings collapsed.
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"""
if not granular_markings:
return
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map_ = collections.defaultdict(set)
for granular_marking in granular_markings:
if granular_marking.get('marking_ref'):
map_[granular_marking.get('marking_ref')].update(granular_marking.get('selectors'))
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compressed = \
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[
{'marking_ref': marking_ref, 'selectors': sorted(selectors)}
for marking_ref, selectors in six.iteritems(map_)
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]
return compressed
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def expand_markings(granular_markings):
"""Expand granular markings list.
If there is more than one selector per granular marking. It will be
expanded using the same marking_ref.
Example:
>>> expand_markings([
... {
... "selectors": [
... "description",
... "name"
... ],
... "marking_ref": "marking-definition--613f2e26-407d-48c7-9eca-b8e91df99dc9"
... }
... ])
[
{
"selectors": [
"description"
],
"marking_ref": "marking-definition--613f2e26-407d-48c7-9eca-b8e91df99dc9"
},
{
"selectors": [
"name"
],
"marking_ref": "marking-definition--613f2e26-407d-48c7-9eca-b8e91df99dc9"
}
]
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Args:
granular_markings: The granular markings list property present in a
SDO or SRO.
Returns:
list: A list with all markings expanded.
"""
expanded = []
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for marking in granular_markings:
selectors = marking.get('selectors')
marking_ref = marking.get('marking_ref')
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expanded.extend(
[
{'marking_ref': marking_ref, 'selectors': [selector]}
for selector in selectors
],
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)
return expanded
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def build_granular_marking(granular_marking):
"""Return a dictionary with the required structure for a granular marking.
"""
return {'granular_markings': expand_markings(granular_marking)}
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def iterpath(obj, path=None):
"""Generator which walks the input ``obj`` model.
Each iteration yields a tuple containing a list of ancestors and the
property value.
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Args:
obj: An SDO or SRO object.
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path: None, used recursively to store ancestors.
Example:
>>> for item in iterpath(obj):
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>>> print(item)
(['type'], 'campaign')
...
(['cybox', 'objects', '[0]', 'hashes', 'sha1'], 'cac35ec206d868b7d7cb0b55f31d9425b075082b')
Returns:
tuple: Containing two items: a list of ancestors and the
property value.
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"""
if path is None:
path = []
for varname, varobj in iter(sorted(six.iteritems(obj))):
path.append(varname)
yield (path, varobj)
if isinstance(varobj, dict):
for item in iterpath(varobj, path):
yield item
elif isinstance(varobj, list):
for item in varobj:
index = '[{0}]'.format(varobj.index(item))
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path.append(index)
yield (path, item)
if isinstance(item, dict):
for descendant in iterpath(item, path):
yield descendant
path.pop()
path.pop()