# Copyright 2016, Tresys Technology, LLC
# Copyright 2018, Chris PeBenito <pebenito@ieee.org>
#
# SPDX-License-Identifier: LGPL-2.1-only
#
from collections import defaultdict
from typing import FrozenSet, List, Optional, Union
from ..policyrep import AnyConstraint, ConstraintRuletype, Role, Type, User
from .descriptors import DiffResultDescriptor
from .difference import Difference, SymbolWrapper, Wrapper
from .objclass import class_wrapper_factory
from .typing import RuleList
class ConstraintsDifference(Difference):
"""
Determine the difference in constraints between two policies.
Since the compiler does not union constraints, there may be multiple
constraints with the same ruletype, object class, and permission
set, so constraints can only be added or removed, not modified.
The constraint expressions are compared only on a basic level.
Expressions that are logically equivalent but are structurally
different, for example, by associativity, will be considered
different. Type and role attributes are also not expanded,
so if there are changes to attribute members, it will not
be reflected as a difference.
"""
added_constrains = DiffResultDescriptor("diff_constrains")
removed_constrains = DiffResultDescriptor("diff_constrains")
added_mlsconstrains = DiffResultDescriptor("diff_mlsconstrains")
removed_mlsconstrains = DiffResultDescriptor("diff_mlsconstrains")
added_validatetrans = DiffResultDescriptor("diff_validatetrans")
removed_validatetrans = DiffResultDescriptor("diff_validatetrans")
added_mlsvalidatetrans = DiffResultDescriptor("diff_mlsvalidatetrans")
removed_mlsvalidatetrans = DiffResultDescriptor("diff_mlsvalidatetrans")
# Lists of rules for each policy
_left_constraints: RuleList[ConstraintRuletype, AnyConstraint] = None
_right_constraints: RuleList[ConstraintRuletype, AnyConstraint] = None
def diff_constrains(self) -> None:
"""Generate the difference in constraint rules between the policies."""
self.log.info("Generating constraint differences from {0.left_policy} to {0.right_policy}".
format(self))
if self._left_constraints is None or self._right_constraints is None:
self._create_constrain_lists()
assert self._left_constraints is not None, "Left constraints didn't load, this a bug."
assert self._right_constraints is not None, "Right constraints didn't load, this a bug."
self.added_constrains, self.removed_constrains, _ = self._set_diff(
(ConstraintWrapper(c) for c in self._left_constraints[ConstraintRuletype.constrain]),
(ConstraintWrapper(c) for c in self._right_constraints[ConstraintRuletype.constrain]))
def diff_mlsconstrains(self) -> None:
"""Generate the difference in MLS constraint rules between the policies."""
self.log.info(
"Generating MLS constraint differences from {0.left_policy} to {0.right_policy}".
format(self))
if self._left_constraints is None or self._right_constraints is None:
self._create_constrain_lists()
assert self._left_constraints is not None, "Left constraints didn't load, this a bug."
assert self._right_constraints is not None, "Right constraints didn't load, this a bug."
self.added_mlsconstrains, self.removed_mlsconstrains, _ = self._set_diff(
(ConstraintWrapper(c) for c in self._left_constraints[
ConstraintRuletype.mlsconstrain]),
(ConstraintWrapper(c) for c in self._right_constraints[
ConstraintRuletype.mlsconstrain]))
def diff_validatetrans(self) -> None:
"""Generate the difference in validatetrans rules between the policies."""
self.log.info(
"Generating validatetrans differences from {0.left_policy} to {0.right_policy}".
format(self))
if self._left_constraints is None or self._right_constraints is None:
self._create_constrain_lists()
assert self._left_constraints is not None, "Left constraints didn't load, this a bug."
assert self._right_constraints is not None, "Right constraints didn't load, this a bug."
self.added_validatetrans, self.removed_validatetrans, _ = self._set_diff(
(ConstraintWrapper(c) for c in self._left_constraints[
ConstraintRuletype.validatetrans]),
(ConstraintWrapper(c) for c in self._right_constraints[
ConstraintRuletype.validatetrans]))
def diff_mlsvalidatetrans(self) -> None:
"""Generate the difference in MLS validatetrans rules between the policies."""
self.log.info(
"Generating mlsvalidatetrans differences from {0.left_policy} to {0.right_policy}".
format(self))
if self._left_constraints is None or self._right_constraints is None:
self._create_constrain_lists()
assert self._left_constraints is not None, "Left constraints didn't load, this a bug."
assert self._right_constraints is not None, "Right constraints didn't load, this a bug."
self.added_mlsvalidatetrans, self.removed_mlsvalidatetrans, _ = self._set_diff(
(ConstraintWrapper(c) for c in self._left_constraints[
ConstraintRuletype.mlsvalidatetrans]),
(ConstraintWrapper(c) for c in self._right_constraints[
ConstraintRuletype.mlsvalidatetrans]))
#
# Internal functions
#
def _create_constrain_lists(self) -> None:
"""Create rule lists for both policies."""
self._left_constraints = defaultdict(list)
self.log.debug("Building constraint lists from {0.left_policy}".format(self))
for rule in self.left_policy.constraints():
self._left_constraints[rule.ruletype].append(rule)
for ruletype, rules in self._left_constraints.items():
self.log.debug("Loaded {0} {1} rules.".format(len(rules), ruletype))
self._right_constraints = defaultdict(list)
self.log.debug("Building constraint lists from {0.right_policy}".format(self))
for rule in self.right_policy.constraints():
self._right_constraints[rule.ruletype].append(rule)
for ruletype, rules in self._right_constraints.items():
self.log.debug("Loaded {0} {1} rules.".format(len(rules), ruletype))
self.log.debug("Completed building constraint rule lists.")
def _reset_diff(self) -> None:
"""Reset diff results on policy changes."""
self.log.debug("Resetting all constraints differences")
self.added_constrains = None
self.removed_constrains = None
self.added_mlsconstrains = None
self.removed_mlsconstrains = None
self.added_validatetrans = None
self.removed_validatetrans = None
self.added_mlsvalidatetrans = None
self.removed_mlsvalidatetrans = None
# Sets of rules for each policy
self._left_constraints = None
self._right_constraints = None
class ConstraintWrapper(Wrapper[AnyConstraint]):
"""Wrap constraints for diff purposes."""
__slots__ = ("ruletype", "tclass", "perms", "expr")
def __init__(self, rule: AnyConstraint) -> None:
self.origin = rule
self.ruletype = rule.ruletype
self.tclass = class_wrapper_factory(rule.tclass)
try:
self.perms: Optional[FrozenSet[str]] = rule.perms
except AttributeError:
# (mls)validatetrans
self.perms = None
self.key = hash(rule)
self.expr: List[Union[FrozenSet[SymbolWrapper[Union[Role, Type, User]]], str]] = []
for op in rule.expression:
if isinstance(op, frozenset):
# lists of types/users/roles
self.expr.append(frozenset(SymbolWrapper(item) for item in op))
else:
# strings in the expression such as u1/r1/t1 or "=="
self.expr.append(op)
def __hash__(self):
return self.key
def __lt__(self, other):
return self.key < other.key
def __eq__(self, other):
return self.ruletype == other.ruletype and \
self.tclass == other.tclass and \
self.perms == other.perms and \
self.expr == other.expr
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