# Copyright 2015-2016, Tresys Technology, LLC
# Copyright 2018, Chris PeBenito <pebenito@ieee.org>
#
# SPDX-License-Identifier: LGPL-2.1-only
#
import logging
from abc import ABC, abstractmethod
from typing import Generic, Iterable, TypeVar
from ..policyrep import PolicyObject, PolicySymbol, SELinuxPolicy
class Difference:
"""Base class for all policy differences."""
def __init__(self, left_policy: SELinuxPolicy, right_policy: SELinuxPolicy) -> None:
self.log = logging.getLogger(__name__)
self.left_policy = left_policy
self.right_policy = right_policy
#
# Policies to compare
#
@property
def left_policy(self):
return self._left_policy
@left_policy.setter
def left_policy(self, policy):
self.log.info("Policy diff left policy set to {0}".format(policy))
self._left_policy = policy
self._reset_diff()
@property
def right_policy(self):
return self._right_policy
@right_policy.setter
def right_policy(self, policy):
self.log.info("Policy diff right policy set to {0}".format(policy))
self._right_policy = policy
self._reset_diff()
#
# Internal functions
#
def _reset_diff(self) -> None:
"""Reset diff results on policy changes."""
raise NotImplementedError
@staticmethod
def _expand_generator(rule_list: Iterable, wrapper_class) -> Iterable:
"""Generator that yields a wrapped, expanded rule list."""
# this is to delay creating any containers
# as long as possible, since rule lists
# are typically massive.
for unexpanded_rule in rule_list:
for expanded_rule in unexpanded_rule.expand():
yield wrapper_class(expanded_rule)
@staticmethod
def _set_diff(left, right, key=None, unwrap=True):
"""
Standard diff of two sets.
Parameters:
left An iterable
right An iterable
Return:
tuple (added, removed, matched)
added Set of items in right but not left
removed Set of items in left but not right
matched Set of items in both left and right. This is
in the form of tuples with the matching item
from left and right
"""
left_items = set(left)
right_items = set(right)
added_items = right_items - left_items
removed_items = left_items - right_items
# The problem here is the symbol from both policies are
# needed to build each tuple in the matched items set.
# Using the standard Python set intersection code will only result
# in one object.
#
# This tuple-generating code creates lists from the sets, to sort them.
# This should result in all of the symbols lining up. If they don't,
# this will break the caller. This should work since there is no remapping.
#
# This has extra checking to make sure this assertion holds, to fail
# instead of giving wrong results. If there is a better way to,
# ensure the items match up, please let me know how or submit a patch.
matched_items = set()
left_matched_items = sorted((left_items - removed_items), key=key)
right_matched_items = sorted((right_items - added_items), key=key)
assert len(left_matched_items) == len(right_matched_items), \
"Matched items assertion failure (this is an SETools bug), {0} != {1}". \
format(len(left_matched_items), len(right_matched_items))
for left, right in zip(left_matched_items, right_matched_items):
assert left == right, \
"Matched items assertion failure (this is an SETools bug), {0} != {1}".format(
left, right)
matched_items.add((left, right))
if unwrap:
return set(i.origin for i in added_items), \
set(i.origin for i in removed_items), \
set((left.origin, right.origin) for (left, right) in matched_items)
else:
return added_items, removed_items, matched_items
T = TypeVar("T", bound=PolicyObject)
class Wrapper(ABC, Generic[T]):
"""Abstract base class for policy object wrappers."""
origin: T
key: int
__slots__ = ("origin", "key")
def __init__(self, origin: T, key: int) -> None:
self.origin = origin
self.key = key
def __repr__(self):
# pylint: disable=no-member
return "<{0.__class__.__name__}(Wrapping {1})>".format(self, repr(self.origin))
@abstractmethod
def __hash__(self):
pass
@abstractmethod
def __eq__(self, other):
pass
@abstractmethod
def __lt__(self, other):
pass
def __ne__(self, other):
return not self == other
S = TypeVar("S", bound=PolicySymbol)
class SymbolWrapper(Wrapper[S]):
"""
General wrapper for policy symbols, e.g. types, roles
to provide a diff-specific equality operation based
on its name.
"""
name: str
__slots__ = ("name",)
def __init__(self, symbol: S) -> None:
super().__init__(symbol, hash(symbol.name))
self.name = symbol.name
def __hash__(self):
return self.key
def __lt__(self, other):
return self.name < other.name
def __eq__(self, other):
return self.name == other.name
