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Editing: rokmod.py
# Copyright 2020, 2025, Microsoft Corporation # # SPDX-License-Identifier: LGPL-2.1-only # from collections import defaultdict import typing from .. import policyrep from ..terulequery import TERuleQuery from .checkermodule import CheckerModule from .descriptors import ConfigSetDescriptor EXEMPT_WRITE: typing.Final[str] = "exempt_write_domain" EXEMPT_LOAD: typing.Final[str] = "exempt_load_domain" EXEMPT_FILE: typing.Final[str] = "exempt_file" __all__: typing.Final[tuple[str, ...]] = ("ReadOnlyKernelModules",) class ReadOnlyKernelModules(CheckerModule): """Checker module for asserting all kernel modules are read-only.""" check_type = "ro_kmods" check_config = frozenset((EXEMPT_WRITE, EXEMPT_LOAD, EXEMPT_FILE)) exempt_write_domain = ConfigSetDescriptor[policyrep.Type]( "lookup_type_or_attr", strict=False, expand=True) exempt_file = ConfigSetDescriptor[policyrep.Type]( "lookup_type_or_attr", strict=False, expand=True) exempt_load_domain = ConfigSetDescriptor[policyrep.Type]( "lookup_type_or_attr", strict=False, expand=True) def __init__(self, policy: policyrep.SELinuxPolicy, checkname: str, config: dict[str, str]) -> None: super().__init__(policy, checkname, config) self.exempt_write_domain = config.get(EXEMPT_WRITE) self.exempt_file = config.get(EXEMPT_FILE) self.exempt_load_domain = config.get(EXEMPT_LOAD) def _collect_kernel_mods(self) -> defaultdict[policyrep.Type, set[policyrep.AVRule]]: self.log.debug("Collecting list of kernel module types.") self.log.debug(f"{self.exempt_load_domain=}") query = TERuleQuery(self.policy, ruletype=("allow",), tclass=("system",), perms=("module_load",)) collected = defaultdict[policyrep.Type, set[policyrep.AVRule]](set) for rule in query.results(): sources = set(rule.source.expand()) - self.exempt_load_domain targets = set(rule.target.expand()) - self.exempt_file # remove self rules targets -= sources # ignore rule if source or target is an empty attr if not sources or not targets: self.log.debug(f"Ignoring empty module_load rule: {rule}") continue for t in targets: self.log.debug(f"Determined {t} is a kernel module by: {rule}") assert isinstance(rule, policyrep.AVRule), \ f"Expected AVRule, got {type(rule)}, this is an SETools bug." collected[t].add(rule) return collected def run(self) -> list[policyrep.Type]: self.log.info("Checking kernel modules are read-only.") query = TERuleQuery(self.policy, ruletype=("allow",), tclass=("file",), perms=("write", "append")) kmods = self._collect_kernel_mods() failures = defaultdict(set) for kmod_type in kmods.keys(): self.log.debug(f"Checking if kernel module type {kmod_type} is writable.") query.target = kmod_type for rule in sorted(query.results()): if set(rule.source.expand()) - self.exempt_write_domain: failures[kmod_type].add(rule) for kmod_type in sorted(failures.keys()): self.output.write("\n------------\n\n") self.output.write(f"Kernel module type {kmod_type} is writable.\n\n") self.output.write("Module load rules:\n") for rule in sorted(kmods[kmod_type]): self.output.write(f" * {rule}\n") self.output.write("\nWrite rules:\n") for rule in sorted(failures[kmod_type]): self.log_fail(str(rule)) self.log.debug(f"{len(failures)} failure(s)") return sorted(failures.keys())
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