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

"""Utility functions for STIX 2.0 data markings.
"""

import collections

import six

from stix2 import exceptions


def _evaluate_expression(obj, selector):
    """Walks 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.

    """
    for items, value in iterpath(obj):
        path = ".".join(items)

        if path == selector and value:
            return [value]

    return []


def _validate_selector(obj, selector):
    """Internal method to evaluate each selector."""
    results = list(_evaluate_expression(obj, selector))

    if len(results) >= 1:
        return True


def validate(obj, selectors):
    """Given an SDO or SRO, check that each selector is valid."""
    if selectors:
        for s in selectors:
            if not _validate_selector(obj, s):
                raise exceptions.InvalidSelectorError(obj, s)
        return

    raise exceptions.InvalidSelectorError(obj, selectors)


def convert_to_list(data):
    """Convert input into a list for further processing."""
    if data is not None:
        if isinstance(data, list):
            return data
        else:
            return [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"
            }
        ]

    Args:
        granular_markings: The granular markings list property present in a
            SDO or SRO.

    Returns:
        list: A list with all markings collapsed.

    """
    if not granular_markings:
        return

    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"))

    compressed = \
        [
            {"marking_ref": marking_ref, "selectors": sorted(selectors)}
            for marking_ref, selectors in six.iteritems(map_)
        ]

    return compressed


def expand_markings(granular_markings):
    """Expands 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"
            }
        ]

    Args:
        granular_markings: The granular markings list property present in a
            SDO or SRO.

    Returns:
        list: A list with all markings expanded.

    """
    expanded = []

    for marking in granular_markings:
        selectors = marking.get("selectors")
        marking_ref = marking.get("marking_ref")

        expanded.extend(
            [
                {"marking_ref": marking_ref, "selectors": [selector]}
                for selector in selectors
            ]
        )

    return expanded


def build_granular_marking(granular_marking):
    """Returns a dictionary with the required structure for a granular marking.
    """
    return {"granular_markings": expand_markings(granular_marking)}


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.

    Args:
        obj: An SDO or SRO object.
        path: None, used recursively to store ancestors.

    Example:
        >>> for item in iterpath(obj):
        >>>     print(item)
        (['type'], 'campaign')
        ...
        (['cybox', 'objects', '[0]', 'hashes', 'sha1'], 'cac35ec206d868b7d7cb0b55f31d9425b075082b')

    Returns:
        tuple: Containing two items: a list of ancestors and the
            property value.

    """
    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))
                path.append(index)

                yield (path, item)

                if isinstance(item, dict):
                    for descendant in iterpath(item, path):
                        yield descendant

                path.pop()

        path.pop()