#!/usr/bin/env python3
# -*- coding:UTF-8 -*-
# Copyright (C) 2019 Nicolas Iooss
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, version 2.
#
# This program 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 General Public License for more
# details.
"""Check the .fc files for some common errors
@author: Nicolas Iooss
@license: GPLv2
"""
import argparse
from pathlib import Path
import re
# Common patterns for ending a file pattern, associated with something to
# replace the pattern with, during the checks.
# Order matters as the first ones are tried before the last ones
#
# Use the infinity symbol to replace "any character", in order to keep a meaning
# of any possible character in the pattern after the reduction operations.
COMMON_FILE_END_PATTERNS = (
('/.+', ''), # Match the children of a directory
('/.*', ''), # Like /.+, but it could be empty
('(/.*)', ''), # Like /.*, but with useless parentheses
('/[^/]+', ''), # Match any filename
('/[^/]*', ''), # Match any filename, but it could be empty
('(/[^/]*)', ''), # Like /[^/]*, but with useless parentheses
('(/[^/]*)?', ''), # Match a directory and its direct children
('(/.+)?', ''), # Match a directory and its children
('(/.*)?', ''), # Match a directory and its children
('/(sbin/)?.*', ''), # Weird pattern for postfix, which would better be (/sbin)?(/.*)?
('\\.so(\\.[^/]*)*', '\\.so'), # Match a .so extension, which is really weird because [^/] matches a dot too, so the final star can be replaced with '?' # noqa
('\\.db(\\.[^/]*)*', '\\.db'), # Match a .db extension, which is really weird because [^/] matches a dot too, so the final star can be replaced with '?' # noqa
('(\\.[^/]+)?', ''), # Match a possible file extension
('(\\..+)', '\\.∞'), # Match a dot and anything after
('(\\..*)?', '\\.∞'), # Match a dot and anything after or nothing, or nothing at all
('\\..*', '\\.'), # Match a dot and anything after or nothing
('.*', ''), # Match anything after
('.+', '∞'), # Match anything after, but at least one character
('[^/]+', '∞'), # Match anything after which does not create a new directory level
('[^/]*', ''), # Like [^/]+, but may be empty
('[^/-]*', ''), # Like [^/]*, but do not match files with dashes in their names
('[a-z]?', ''), # Match a possible letter
('[a-z]*', ''), # Match some letters
('[0-9]?', ''), # Match a possible digit
('[0-9]*', ''), # Match some digits
('[0-9]+', '0'), # Match at least one digit
('(\\.bin)?', ''), # Match an optional extension
('(-.*)?', ''), # Match an optional suffix with a minus sign
)
# File types in a .fc file
FILE_TYPES = (None, '--', '-b', '-c', '-d', '-l', '-p', '-s')
NONE_CONTEXT = '<<none>>'
MLS_LEVELS = ('s0', 'mls_systemhigh', 's0-mls_systemhigh')
def analyze_fc_file(fc_path):
"""Analyze a .fc file
Return False if a warning has been generated
"""
retval = True
with fc_path.open('r') as fd:
for lineno, line in enumerate(fd, start=1):
line = line.strip()
# Ignore lines that cannot contain a file context
if not line or line.startswith(('#', "'", 'ifdef(', 'ifndef(')):
continue
prefix = f"{fc_path}:{lineno}: "
matches = re.match(r'^(?P<path>\S+)\s+(?P<ftype>-.)?\s*(?P<context>.+)$', line)
if matches is None:
print(f"{prefix}unable to parse a file context file: {repr(line)}")
retval = False
continue
path, ftype, context = matches.group('path', 'ftype', 'context')
# Check the file type of the pattern
if ftype not in FILE_TYPES:
print(f"{prefix}unexpected file type for {path}: {repr(ftype)}")
retval = False
# Check the SELinux context
if context != NONE_CONTEXT:
matches = re.match(r'^gen_context\((\S*), ?(\S*)\)$', context)
if not matches:
print(f"{prefix}unknown SELinux context format for {path}: {context}")
retval = False
else:
context_label, context_mls = matches.groups()
if not context_label.startswith('system_u:object_r:'):
print(f"{prefix}SELinux context does not begin with 'system_u:object_r:' for {path}: {context}") # noqa
retval = False
elif not re.match(r'^system_u:object_r:[0-9A-Za-z_]+$', context_label):
print(f"{prefix}SELinux context type uses unexpected characters for {path}: {context}") # noqa
retval = False
elif context_mls not in MLS_LEVELS:
print(f"{prefix}SELinux context uses an unexpected MLS label for {path}: {context_mls} (in {context})") # noqa
retval = False
# Find obviously-wrong patterns
if '(.*)?' in path:
# As (.*) can match the empty string, the question mark is redundant
print(f"{prefix}pattern (.*)? is very likely to be a misspelling for .* or (/.*)?, for {path}")
retval = False
if '\\d' in path:
# In the past, "resource.\d" has already been introduced instead of "resource\.d".
# Detect such bugs by forbidding the use of \d
print(f"{prefix}escaping d could be a bug in {path}, please use [0-9] instead")
retval = False
if re.search(r'[^/]\(\.\*/\)\?', path):
print(f"{prefix}using (.*/)? without a previous slash could be a bug in {path} as it can match the empty string, please use /(.*/)? instead") # noqa
retval = False
if re.search(r'[^/]\(\[\^/\]\+/\)\?', path):
print(f"{prefix}using ([^/]+/)? without a previous slash could be a bug in {path} as it can match the empty string, please use /([^/]+/)? instead") # noqa
retval = False
if re.search(r'[^/]\(\.\*/\)\*', path):
print(f"{prefix}using (.*/)* without a previous slash could be a bug in {path} as it can match the empty string, please use /(.*/)* instead") # noqa
retval = False
if re.search(r'\(\.\*/\)[^?*+]', path):
print(f"{prefix}using (.*/) without a ?, * or + symbol could be a bug in {path} as it misleads readers into thinking that this part is optional, please use .*/ instead") # noqa
retval = False
reduced_path = path
# Using "index`'(...)" is a way to prevent an error message from m4:
# https://github.com/SELinuxProject/refpolicy/commit/cc1eee120263523c7b79ac16acc698c537a4d25e
# Let's replace the symbols in the path, for the checks,
# while keeping "path" untouched in the warning messages
reduced_path = reduced_path.replace("index`'(", 'index(')
reduced_path = reduced_path.replace("inde(x)(", 'index(')
reduced_path = reduced_path.replace("include`'(", 'include(')
# Check the character set of the path
invalid_characters = set(re.findall(r'[^-0-9A-Za-z_./()?+*%{}\[\]^|:~\\]', reduced_path))
if invalid_characters:
print(f"{prefix}unexpected characters {' '.join(sorted(invalid_characters))} in {path}")
retval = False
# Check the start of the path
if not path.startswith(('/', 'HOME_DIR/', 'HOME_ROOT/')) and path not in ('HOME_DIR', 'HOME_ROOT'):
print(f"{prefix}unexpected start of file pattern for {path}")
retval = False
# Reduce the path in order to check its sanity (like using a non-buggy end pattern):
# * Truncating common endings
while True:
has_truncated = False
for (common_end, substitute) in COMMON_FILE_END_PATTERNS:
if reduced_path.endswith(common_end):
reduced_path = f"{reduced_path[:-len(common_end)]}{substitute}"
has_truncated = True
break
if not has_truncated:
break
# * Replace back-slashed characters with special ones
while '\\' in reduced_path:
backslash_index = reduced_path.index('\\')
esc_sequence = reduced_path[backslash_index:backslash_index + 2]
if esc_sequence == '\\.':
# Replace \. with U+00B7 middle dot
reduced_path = f"{reduced_path[:backslash_index]}\u00b7{reduced_path[backslash_index + 2:]}"
elif esc_sequence == '\\+':
# Replace \+ with U+2020 dagger
reduced_path = f"{reduced_path[:backslash_index]}\u2020{reduced_path[backslash_index + 2:]}"
elif esc_sequence == '\\d':
# Replace \d with U+03B4 delta
reduced_path = f"{reduced_path[:backslash_index]}\u03b4{reduced_path[backslash_index + 2:]}"
else:
print(f"{prefix}unexpected escape sequence {esc_sequence} in {path} (reduced to {reduced_path})")
retval = False
break
# * Replace variables with place-holders
if '%' in reduced_path:
reduced_path = reduced_path.replace('%{USERID}', '_USERID_')
reduced_path = reduced_path.replace('%{USERNAME}', '_USERNAME_')
if '%{' in reduced_path:
print(f"{prefix}unexpected '%{{' in {path} after reduction to {reduced_path}")
retval = False
# * Detect "??", "**", etc. before more reductions occur
for bad_pattern in sorted(set(re.findall(r'[?*+][?*+]', reduced_path))):
print(f"{prefix}unexpected pattern {repr(bad_pattern)} in {path} after reduction to {reduced_path}")
retval = False
# Remove optional directories and filename parts
reduced_path = reduced_path.replace('/([^/]+/)?', '/')
reduced_path = reduced_path.replace('(/[^/]+)?/', '/')
reduced_path = reduced_path.replace('[^/]*', '')
reduced_path = reduced_path.replace('[^/]+', '∞')
reduced_path = reduced_path.replace('[^/-]+', '∞')
reduced_path = reduced_path.replace('/(.*/)?', '/')
reduced_path = reduced_path.replace('(/.*)?', '')
reduced_path = reduced_path.replace('/.*/', '/')
# * Remove parenthesese around choices options: ((www)|(web)|(public_html)) -> (www|web|public_html)
while True:
new_reduced_path = re.sub(r'([|(])\(([-0-9A-Za-z_]+)\)([|)])', r'\1\2\3', reduced_path)
if new_reduced_path == reduced_path:
break
reduced_path = new_reduced_path
# * Detect a pipe directly inside a parenthesis, which is wrong (use symbol ? instead)
if '|)' in reduced_path or '(|' in reduced_path:
print(f"{prefix}unexpected pipe-parenthesis pattern in {path} after reduction to {reduced_path}")
retval = False
# * Remove optional choices (...|...)?
while True:
new_reduced_path = re.sub(r'\([-0-9A-Za-z_|/·]+\)\?', '', reduced_path)
if new_reduced_path == reduced_path:
break
reduced_path = new_reduced_path
# * Replace mandatory choices (...|...) with the first option
while True:
new_reduced_path = re.sub(r'\(([-0-9A-Za-z_/]+)\|[-0-9A-Za-z_|/]+\)', r'\1', reduced_path)
if new_reduced_path == reduced_path:
break
reduced_path = new_reduced_path
# * Remove optional characters like c?
reduced_path = re.sub(r'[-0-9A-Za-z_·]\?', '', reduced_path)
# If the reduced path still ends with a special character, something went wrong.
# Instead of guessing the possible buggy characters, list the allowed ones.
if reduced_path and not re.match(r'[-0-9A-Za-z_\]~ᠰ]', reduced_path[-1]):
if path != '/':
if reduced_path == path:
print(f"{prefix}unexpected end of file pattern for {path}")
else:
print(f"{prefix}unexpected end of file pattern for {path} after being reduced to {reduced_path}") # noqa
retval = False
# Now remove and replace some matching patterns from the path, in order to catch invalid characters
reduced_path = reduced_path.replace('(-.*)?', '')
reduced_path = reduced_path.replace('(.*-)?', '')
reduced_path = reduced_path.replace('(-[0-9])?', '')
reduced_path = reduced_path.replace('(.*)', '')
reduced_path = reduced_path.replace('.*', '')
reduced_path = reduced_path.replace('.+', '∞')
reduced_path = re.sub(r'\[[-0-9A-Za-z_.^]+\][?*]', '', reduced_path)
reduced_path = re.sub(r'\[[-0-9A-Za-z_.^]+\](\+)?', '∞', reduced_path)
reduced_path = reduced_path.replace('/[^/]+/', '/∞/')
if '.' in reduced_path:
print(f"{prefix}unescaped dot still present {path} after being reduced to {reduced_path} (suggestion: use \\. to match a dot, or a charset like [^/])") # noqa
retval = False
# Check the remaining symbols in the reduced path.
# Only show a warning if no other ones were reported, in order to reduce the probability of false-positive.
invalid_symbols = set(re.findall(r'[^-0-9A-Za-z_~:ᠰ/]', reduced_path))
if retval and invalid_symbols:
print(f"{prefix}unexpected symbols {' '.join(sorted(invalid_symbols))} in {path} after being reduced to {reduced_path}. This could be due to an error in the pattern or a missing reduction rule in the checker") # noqa
retval = False
return retval
def analyze_all_fc(policy_dirpath):
"""Analyze all .fc files in the specified directory"""
retval = True
for file_path in sorted(policy_dirpath.glob('**/*.fc')):
if not analyze_fc_file(file_path):
retval = False
return retval
def main(argv=None):
policy_dir = (Path(__file__).parent / '..' / 'policy').resolve()
parser = argparse.ArgumentParser(description="Find missing file contexts")
parser.add_argument('fc_files', metavar='FC_FILES', nargs='*', type=Path,
help=".fc files to analyze (by default: all in the policy)")
parser.add_argument('-p', '--policy', metavar='POLICY_DIR', type=Path, default=policy_dir,
help="path to the policy directory [{0}]".format(policy_dir))
args = parser.parse_args(argv)
if args.fc_files:
retval = True
for file_path in args.fc_files:
if not analyze_fc_file(file_path):
retval = False
return retval
return 0 if analyze_all_fc(args.policy) else 1
if __name__ == '__main__':
import sys
sys.exit(main())