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# Copyright 2016, Tresys Technology, LLC
#
# This file is part of SETools.
#
# SETools is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as
# published by the Free Software Foundation, either version 2.1 of
# the License, or (at your option) any later version.
#
# SETools is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with SETools. If not, see
# <http://www.gnu.org/licenses/>.
#
from collections import namedtuple
from .descriptors import DiffResultDescriptor
from .difference import Difference, SymbolWrapper, Wrapper
from .mls import RangeWrapper
modified_mlsrule_record = namedtuple("modified_mlsrule", ["rule",
"added_default",
"removed_default"])
class MLSRulesDifference(Difference):
"""Determine the difference in MLS rules between two policies."""
added_range_transitions = DiffResultDescriptor("diff_range_transitions")
removed_range_transitions = DiffResultDescriptor("diff_range_transitions")
modified_range_transitions = DiffResultDescriptor("diff_range_transitions")
# Lists of rules for each policy
_left_range_transitions = None
_right_range_transitions = None
def diff_range_transitions(self):
"""Generate the difference in range_transition rules between the policies."""
self.log.info(
"Generating range_transition differences from {0.left_policy} to {0.right_policy}".
format(self))
if self._left_range_transitions is None or self._right_range_transitions is None:
self._create_mls_rule_lists()
self.added_range_transitions, \
self.removed_range_transitions, \
self.modified_range_transitions = self._diff_mls_rules(
self._expand_generator(self._left_range_transitions, MLSRuleWrapper),
self._expand_generator(self._right_range_transitions, MLSRuleWrapper))
#
# Internal functions
#
def _create_mls_rule_lists(self):
"""Create rule lists for both policies."""
self._left_range_transitions = []
for rule in self.left_policy.mlsrules():
# do not expand yet, to keep memory
# use down as long as possible
if rule.ruletype == "range_transition":
self._left_range_transitions.append(rule)
else:
self.log.error("Unknown rule type: {0} (This is an SETools bug)".
format(rule.ruletype))
self._right_range_transitions = []
for rule in self.right_policy.mlsrules():
# do not expand yet, to keep memory
# use down as long as possible
if rule.ruletype == "range_transition":
self._right_range_transitions.append(rule)
else:
self.log.error("Unknown rule type: {0} (This is an SETools bug)".
format(rule.ruletype))
def _diff_mls_rules(self, left_list, right_list):
"""Common method for comparing type_* rules."""
added, removed, matched = self._set_diff(left_list, right_list)
modified = []
for left_rule, right_rule in matched:
# Criteria for modified rules
# 1. change to default range
if RangeWrapper(left_rule.default) != RangeWrapper(right_rule.default):
modified.append(modified_mlsrule_record(left_rule,
right_rule.default,
left_rule.default))
return added, removed, modified
def _reset_diff(self):
"""Reset diff results on policy changes."""
self.log.debug("Resetting MLS rule differences")
self.added_range_transitions = None
self.removed_range_transitions = None
self.modified_range_transitions = None
# Sets of rules for each policy
self._left_range_transitions = None
self._right_range_transitions = None
class MLSRuleWrapper(Wrapper):
"""Wrap MLS rules to allow set operations."""
def __init__(self, rule):
self.origin = rule
self.ruletype = rule.ruletype
self.source = SymbolWrapper(rule.source)
self.target = SymbolWrapper(rule.target)
self.tclass = SymbolWrapper(rule.tclass)
self.key = hash(rule)
def __hash__(self):
return self.key
def __lt__(self, other):
return self.key < other.key
def __eq__(self, other):
# because MLSRuleDifference groups rules by ruletype,
# the ruletype always matches.
return self.source == other.source and \
self.target == other.target and \
self.tclass == other.tclass
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