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terules.py
# Copyright 2015-2016, Tresys Technology, LLC # Copyright 2016, 2018, Chris PeBenito <pebenito@ieee.org> # # SPDX-License-Identifier: LGPL-2.1-only # import logging from collections import defaultdict from sys import intern from enum import Enum from typing import Any, Callable, Dict, Iterable, List, NamedTuple, Optional, Set, Tuple, Union from ..exception import RuleNotConditional, RuleUseError, TERuleNoFilename from ..policyrep import AnyTERule, AVRule, AVRuleXperm, Conditional, IoctlSet, TERuletype, Type from .conditional import conditional_wrapper_factory from .descriptors import DiffResultDescriptor from .difference import Difference, Wrapper from .types import type_wrapper_factory, type_or_attr_wrapper_factory from .typing import RuleList from .objclass import class_wrapper_factory TERULES_UNCONDITIONAL = intern("<<unconditional>>") TERULES_UNCONDITIONAL_BLOCK = intern("True") class ModifiedAVRule(NamedTuple): """Difference details for a modified access vector rule.""" rule: AVRule added_perms: Union[Set[str], IoctlSet] removed_perms: Union[Set[str], IoctlSet] matched_perms: Union[Set[str], IoctlSet] class ModifiedTERule(NamedTuple): """Difference details for a modified type_* rule.""" rule: AVRule added_default: Type removed_default: Type # # Internal datastructure types # class Side(Enum): left = 0 right = 1 class RuleDBSideDataRecord(NamedTuple): perms: Set[str] orig_rule: AVRule class RuleDBSidesRecord(NamedTuple): left: Optional[RuleDBSideDataRecord] right: Optional[RuleDBSideDataRecord] class TypeDBRecord(NamedTuple): left: Dict[str, Type] right: Dict[str, Type] # These conditional items are unioned with str to handle unconditional rules CondExp = Union[Conditional, str] CondBlock = Union[bool, str] RuleDB = Dict[CondExp, Dict[CondBlock, Dict[str, Dict[str, Dict[str, RuleDBSidesRecord]]]]] def _avrule_expand_generator(rule_list: List[AVRule], rule_db: RuleDB, type_db: TypeDBRecord, side: Side) -> None: """ Using rule_list, build up rule_db which is a data structure which consists of nested dicts that store BOTH the left and the right policies. All of the keys are interned strings. The permissions are stored as a set. The basic structure is rule_db[cond_exp][block_bool][src][tgt][tclass] = sides where: cond_exp is a boolean expression block_bool is either true or false src is the source type tgt is the target type tclass is the target class sides is a named tuple with attributes "left" and "right" referring to the left or right policy. Each attribute in the sides named tuple refers to a named tuple with attributes "perms" and "orig_rule" which refer to a permission set and the original unexpanded rule. sides = ((left_perms, left_orig_rule),(right_perms, right_orig_rule)) There are a few advantages to this structure. First, it takes up way less memory. Second, it allows redundant rules to be easily eliminated. And, third, it makes it easy to create the added, removed, and modified rules. """ if side == Side.left: types = type_db.left else: types = type_db.right for unexpanded_rule in rule_list: try: cond_exp = intern(str(unexpanded_rule.conditional)) block_bool = intern(str(unexpanded_rule.conditional_block)) except RuleNotConditional: cond_exp = TERULES_UNCONDITIONAL block_bool = TERULES_UNCONDITIONAL_BLOCK if cond_exp not in rule_db: rule_db[cond_exp] = dict() rule_db[cond_exp][block_bool] = dict() elif block_bool not in rule_db[cond_exp]: rule_db[cond_exp][block_bool] = dict() tclass = unexpanded_rule.tclass.name perms = set(unexpanded_rule.perms) side_data = RuleDBSideDataRecord(perms, unexpanded_rule) block = rule_db[cond_exp][block_bool] for src in unexpanded_rule.source.expand(): src_str = src.name if src_str not in types: types[src_str] = src if src_str not in block: block[src_str] = dict() for tgt in unexpanded_rule.target.expand(): tgt_str = tgt.name if tgt_str not in types: types[tgt_str] = tgt if tgt_str not in block[src_str]: block[src_str][tgt_str] = dict() left_side = None right_side = None if tclass in block[src_str][tgt_str]: sides = block[src_str][tgt_str][tclass] left_side = sides.left right_side = sides.right if side == Side.left: if not left_side: left_side = side_data else: """ The original tuple and perm set might be shared with many expanded rules so a new ones must created. Using "|=" would cause the old perm set to be modified instead of creating a new one. """ p = left_side.perms | perms orig = left_side.orig_rule left_side = RuleDBSideDataRecord(p, orig) else: if not right_side: right_side = side_data else: """ Must create new tuple and perm set as explained above. """ p = right_side.perms | perms orig = right_side.orig_rule right_side = RuleDBSideDataRecord(p, orig) block[src_str][tgt_str][tclass] = RuleDBSidesRecord(left_side, right_side) def _av_remove_redundant_rules(rule_db: RuleDB) -> None: uncond_block = rule_db[TERULES_UNCONDITIONAL][TERULES_UNCONDITIONAL_BLOCK] for cond_exp, cond_blocks in rule_db.items(): if cond_exp == TERULES_UNCONDITIONAL: continue for block in cond_blocks.values(): for src, src_data in block.items(): if src not in uncond_block: continue for tgt, tgt_data in src_data.items(): if tgt not in uncond_block[src]: continue for tclass, side_data in tgt_data.items(): if tclass not in uncond_block[src][tgt]: continue uncond_side_data = uncond_block[src][tgt][tclass] left_side = side_data.left right_side = side_data.right if uncond_side_data.left and left_side: c = left_side.perms & uncond_side_data.left.perms if c: p = left_side.perms - c if p: left_side = RuleDBSideDataRecord(p, left_side.orig_rule) else: left_side = None tgt_data[tclass] = RuleDBSidesRecord(left_side, right_side) if uncond_side_data.right and right_side: c = right_side.perms & uncond_side_data.right.perms if c: p = right_side.perms - c if p: right_side = RuleDBSideDataRecord(p, right_side.orig_rule) else: right_side = None tgt_data[tclass] = RuleDBSidesRecord(left_side, right_side) def _av_generate_diffs(rule_db: RuleDB, type_db: TypeDBRecord) -> \ Tuple[List[AVRule], List[AVRule], List[ModifiedAVRule]]: added: List[AVRule] = [] removed: List[AVRule] = [] modified: List[ModifiedAVRule] = [] for cond_blocks in rule_db.values(): for block in cond_blocks.values(): for src, src_data in block.items(): for tgt, tgt_data in src_data.items(): for side_data in tgt_data.values(): if side_data.left and side_data.right: common_perms = side_data.left.perms & side_data.right.perms left_perms = side_data.left.perms - common_perms right_perms = side_data.right.perms - common_perms if left_perms or right_perms: original_rule = side_data.left.orig_rule rule = original_rule.derive_expanded( type_db.left[src], type_db.left[tgt], side_data.left.perms) modified.append(ModifiedAVRule(rule, right_perms, left_perms, common_perms)) elif side_data.left: original_rule = side_data.left.orig_rule rule = original_rule.derive_expanded( type_db.left[src], type_db.left[tgt], side_data.left.perms) removed.append(rule) elif side_data.right: original_rule = side_data.right.orig_rule rule = original_rule.derive_expanded( type_db.right[src], type_db.right[tgt], side_data.right.perms) added.append(rule) return added, removed, modified def av_diff_template(ruletype: str) -> Callable[["TERulesDifference"], None]: """ This is a template for the access vector diff functions. Parameters: ruletype The rule type, e.g. "allow". """ ruletype = TERuletype.lookup(ruletype) def diff(self) -> None: """Generate the difference in rules between the policies.""" self.log.info( "Generating {0} differences from {1.left_policy} to {1.right_policy}". format(ruletype, self)) if self._left_te_rules is None or self._right_te_rules is None: self._create_te_rule_lists() type_db = TypeDBRecord(dict(), dict()) rule_db: RuleDB = dict() rule_db[TERULES_UNCONDITIONAL] = dict() rule_db[TERULES_UNCONDITIONAL][TERULES_UNCONDITIONAL_BLOCK] = dict() self.log.info("Expanding AV rules from {0.left_policy}.".format(self)) _avrule_expand_generator(self._left_te_rules[ruletype], rule_db, type_db, Side.left) self.log.info("Expanding AV rules from {0.right_policy}.".format(self)) _avrule_expand_generator(self._right_te_rules[ruletype], rule_db, type_db, Side.right) self.log.info("Removing redundant AV rules.") _av_remove_redundant_rules(rule_db) self.log.info("Generating AV rule diff.") added, removed, modified = _av_generate_diffs(rule_db, type_db) type_db.left.clear() type_db.right.clear() rule_db.clear() setattr(self, "added_{0}s".format(ruletype), added) setattr(self, "removed_{0}s".format(ruletype), removed) setattr(self, "modified_{0}s".format(ruletype), modified) return diff def _avxrule_expand_generator(rule_list: Iterable[AVRuleXperm]) -> Iterable["AVRuleXpermWrapper"]: """ Generator that yields wrapped, expanded, av(x) rules with unioned permission sets. """ items: Dict["AVRuleXpermWrapper", "AVRuleXpermWrapper"] = dict() for unexpanded_rule in rule_list: for expanded_rule in unexpanded_rule.expand(): expanded_wrapped_rule = AVRuleXpermWrapper(expanded_rule) # create a hash table (dict) with the first rule # as the key and value. Rules where permission sets should # be unioned together have the same hash, so this will union # the permissions together. try: items[expanded_wrapped_rule].perms |= expanded_wrapped_rule.perms except KeyError: items[expanded_wrapped_rule] = expanded_wrapped_rule if items: logging.getLogger(__name__).debug( "Expanded {0.ruletype} rules for {0.policy}: {1}".format( unexpanded_rule, len(items))) return items.keys() def avx_diff_template(ruletype: str) -> Callable[["TERulesDifference"], None]: """ This is a template for the extended permission access vector diff functions. Parameters: ruletype The rule type, e.g. "allowxperm". """ ruletype = TERuletype.lookup(ruletype) def diff(self) -> None: """Generate the difference in rules between the policies.""" self.log.info( "Generating {0} differences from {1.left_policy} to {1.right_policy}". format(ruletype, self)) if not self._left_te_rules or not self._right_te_rules: self._create_te_rule_lists() added, removed, matched = self._set_diff( _avxrule_expand_generator(self._left_te_rules[ruletype]), _avxrule_expand_generator(self._right_te_rules[ruletype]), unwrap=False) modified = [] for left_rule, right_rule in matched: # Criteria for modified rules # 1. change to permissions added_perms, removed_perms, matched_perms = self._set_diff(left_rule.perms, right_rule.perms, unwrap=False) # the final set comprehension is to avoid having lists # like [("perm1", "perm1"), ("perm2", "perm2")], as the # matched_perms return from _set_diff is a set of tuples if added_perms or removed_perms: modified.append(ModifiedAVRule(left_rule.origin, IoctlSet(added_perms), IoctlSet(removed_perms), IoctlSet(p[0] for p in matched_perms))) setattr(self, "added_{0}s".format(ruletype), set(a.origin for a in added)) setattr(self, "removed_{0}s".format(ruletype), set(r.origin for r in removed)) setattr(self, "modified_{0}s".format(ruletype), modified) return diff def te_diff_template(ruletype: str) -> Callable[[Any], None]: """ This is a template for the type_* diff functions. Parameters: ruletype The rule type, e.g. "type_transition". """ ruletype = TERuletype.lookup(ruletype) def diff(self) -> None: """Generate the difference in rules between the policies.""" self.log.info( "Generating {0} differences from {1.left_policy} to {1.right_policy}". format(ruletype, self)) if self._left_te_rules is None or self._right_te_rules is None: self._create_te_rule_lists() added, removed, matched = self._set_diff( self._expand_generator(self._left_te_rules[ruletype], TERuleWrapper), self._expand_generator(self._right_te_rules[ruletype], TERuleWrapper)) modified = [] for left_rule, right_rule in matched: # Criteria for modified rules # 1. change to default type if type_wrapper_factory(left_rule.default) != type_wrapper_factory(right_rule.default): modified.append(ModifiedTERule(left_rule, right_rule.default, left_rule.default)) setattr(self, "added_{0}s".format(ruletype), added) setattr(self, "removed_{0}s".format(ruletype), removed) setattr(self, "modified_{0}s".format(ruletype), modified) return diff class TERulesDifference(Difference): """ Determine the difference in type enforcement rules between two policies. """ diff_allows = av_diff_template("allow") added_allows = DiffResultDescriptor("diff_allows") removed_allows = DiffResultDescriptor("diff_allows") modified_allows = DiffResultDescriptor("diff_allows") diff_auditallows = av_diff_template("auditallow") added_auditallows = DiffResultDescriptor("diff_auditallows") removed_auditallows = DiffResultDescriptor("diff_auditallows") modified_auditallows = DiffResultDescriptor("diff_auditallows") diff_neverallows = av_diff_template("neverallow") added_neverallows = DiffResultDescriptor("diff_neverallows") removed_neverallows = DiffResultDescriptor("diff_neverallows") modified_neverallows = DiffResultDescriptor("diff_neverallows") diff_dontaudits = av_diff_template("dontaudit") added_dontaudits = DiffResultDescriptor("diff_dontaudits") removed_dontaudits = DiffResultDescriptor("diff_dontaudits") modified_dontaudits = DiffResultDescriptor("diff_dontaudits") diff_allowxperms = avx_diff_template("allowxperm") added_allowxperms = DiffResultDescriptor("diff_allowxperms") removed_allowxperms = DiffResultDescriptor("diff_allowxperms") modified_allowxperms = DiffResultDescriptor("diff_allowxperms") diff_auditallowxperms = avx_diff_template("auditallowxperm") added_auditallowxperms = DiffResultDescriptor("diff_auditallowxperms") removed_auditallowxperms = DiffResultDescriptor("diff_auditallowxperms") modified_auditallowxperms = DiffResultDescriptor("diff_auditallowxperms") diff_neverallowxperms = avx_diff_template("neverallowxperm") added_neverallowxperms = DiffResultDescriptor("diff_neverallowxperms") removed_neverallowxperms = DiffResultDescriptor("diff_neverallowxperms") modified_neverallowxperms = DiffResultDescriptor("diff_neverallowxperms") diff_dontauditxperms = avx_diff_template("dontauditxperm") added_dontauditxperms = DiffResultDescriptor("diff_dontauditxperms") removed_dontauditxperms = DiffResultDescriptor("diff_dontauditxperms") modified_dontauditxperms = DiffResultDescriptor("diff_dontauditxperms") diff_type_transitions = te_diff_template("type_transition") added_type_transitions = DiffResultDescriptor("diff_type_transitions") removed_type_transitions = DiffResultDescriptor("diff_type_transitions") modified_type_transitions = DiffResultDescriptor("diff_type_transitions") diff_type_changes = te_diff_template("type_change") added_type_changes = DiffResultDescriptor("diff_type_changes") removed_type_changes = DiffResultDescriptor("diff_type_changes") modified_type_changes = DiffResultDescriptor("diff_type_changes") diff_type_members = te_diff_template("type_member") added_type_members = DiffResultDescriptor("diff_type_members") removed_type_members = DiffResultDescriptor("diff_type_members") modified_type_members = DiffResultDescriptor("diff_type_members") _left_te_rules: RuleList[TERuletype, AnyTERule] = None _right_te_rules: RuleList[TERuletype, AnyTERule] = None # # Internal functions # def _create_te_rule_lists(self) -> None: """Create rule lists for both policies.""" # do not expand yet, to keep memory # use down as long as possible self.log.debug("Building TE rule lists from {0.left_policy}".format(self)) self._left_te_rules = defaultdict(list) for rule in self.left_policy.terules(): self._left_te_rules[rule.ruletype].append(rule) for ruletype, rules in self._left_te_rules.items(): self.log.debug("Loaded {0} {1} rules.".format(len(rules), ruletype)) self.log.debug("Building TE rule lists from {0.right_policy}".format(self)) self._right_te_rules = defaultdict(list) for rule in self.right_policy.terules(): self._right_te_rules[rule.ruletype].append(rule) for ruletype, rules in self._right_te_rules.items(): self.log.debug("Loaded {0} {1} rules.".format(len(rules), ruletype)) self.log.debug("Completed building TE rule lists.") def _reset_diff(self) -> None: """Reset diff results on policy changes.""" self.log.debug("Resetting TE rule differences") self.added_allows = None self.removed_allows = None self.modified_allows = None self.added_auditallows = None self.removed_auditallows = None self.modified_auditallows = None self.added_neverallows = None self.removed_neverallows = None self.modified_neverallows = None self.added_dontaudits = None self.removed_dontaudits = None self.modified_dontaudits = None self.added_allowxperms = None self.removed_allowxperms = None self.modified_allowxperms = None self.added_auditallowxperms = None self.removed_auditallowxperms = None self.modified_auditallowxperms = None self.added_neverallowxperms = None self.removed_neverallowxperms = None self.modified_neverallowxperms = None self.added_dontauditxperms = None self.removed_dontauditxperms = None self.modified_dontauditxperms = None self.added_type_transitions = None self.removed_type_transitions = None self.modified_type_transitions = None self.added_type_changes = None self.removed_type_changes = None self.modified_type_changes = None self.added_type_members = None self.removed_type_members = None self.modified_type_members = None # Lists of rules for each policy self._left_te_rules = None self._right_te_rules = None class AVRuleXpermWrapper(Wrapper[AVRuleXperm]): """Wrap extended permission access vector rules to allow set operations.""" __slots__ = ("source", "target", "tclass", "xperm_type", "perms") def __init__(self, rule: AVRuleXperm) -> None: self.origin = rule self.source = type_or_attr_wrapper_factory(rule.source) self.target = type_or_attr_wrapper_factory(rule.target) self.tclass = class_wrapper_factory(rule.tclass) self.xperm_type = rule.xperm_type self.perms = set(rule.perms) self.key = hash(rule) def __hash__(self): return self.key def __lt__(self, other): return self.key < other.key def __eq__(self, other): # because TERuleDifference groups rules by ruletype, # the ruletype always matches. return self.source == other.source and \ self.target == other.target and \ self.tclass == other.tclass and \ self.xperm_type == other.xperm_type class TERuleWrapper(Wrapper): """Wrap type_* rules to allow set operations.""" __slots__ = ("source", "target", "tclass", "conditional", "conditional_block", "filename") def __init__(self, rule): self.origin = rule self.source = type_or_attr_wrapper_factory(rule.source) self.target = type_or_attr_wrapper_factory(rule.target) self.tclass = class_wrapper_factory(rule.tclass) self.key = hash(rule) try: self.conditional = conditional_wrapper_factory(rule.conditional) self.conditional_block = rule.conditional_block except RuleNotConditional: self.conditional = None self.conditional_block = None try: self.filename = rule.filename except (RuleUseError, TERuleNoFilename): self.filename = None def __hash__(self): return self.key def __lt__(self, other): return self.key < other.key def __eq__(self, other): # because TERuleDifference groups rules by ruletype, # the ruletype always matches. return self.source == other.source and \ self.target == other.target and \ self.tclass == other.tclass and \ self.conditional == other.conditional and \ self.conditional_block == other.conditional_block and \ self.filename == other.filename
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