4 This tool is for checking the security hardening options of the Linux kernel.
6 Author: Alexander Popov <alex.popov@linux.com>
8 This module performs input/output.
11 # pylint: disable=missing-function-docstring,line-too-long,invalid-name,too-many-branches,too-many-statements
15 from argparse import ArgumentParser
16 from collections import OrderedDict
17 from typing import List, Tuple
20 from .__about__ import __version__
21 from .checks import add_kconfig_checks, add_cmdline_checks, normalize_cmdline_options, add_sysctl_checks
22 from .engine import populate_with_data, perform_checks, override_expected_value
25 def _open(file: str, *args, **kwargs):
27 if file.endswith('.gz'):
28 open_method = gzip.open
30 return open_method(file, *args, **kwargs)
33 def detect_arch(fname: str, archs: List[str]) -> Tuple:
34 with _open(fname, 'rt', encoding='utf-8') as f:
35 arch_pattern = re.compile(r"CONFIG_[a-zA-Z0-9_]+=y$")
37 for line in f.readlines():
38 if arch_pattern.match(line):
39 option, _ = line[7:].split('=', 1)
44 return None, 'detected more than one microarchitecture'
46 return None, 'failed to detect microarchitecture'
50 def detect_kernel_version(fname: str) -> Tuple:
51 with _open(fname, 'rt', encoding='utf-8') as f:
52 ver_pattern = re.compile(r"^# Linux/.+ Kernel Configuration$|^Linux version .+")
53 for line in f.readlines():
54 if ver_pattern.match(line):
57 ver_str = parts[2].split('-', 1)[0]
58 ver_numbers = ver_str.split('.')
59 if len(ver_numbers) >= 3:
60 if all(map(lambda x: x.isdigit(), ver_numbers)):
61 return tuple(map(int, ver_numbers)), None
62 msg = f'failed to parse the version "{parts[2]}"'
64 return None, 'no kernel version detected'
67 def detect_compiler(fname: str):
70 with _open(fname, 'rt', encoding='utf-8') as f:
71 for line in f.readlines():
72 if line.startswith('CONFIG_GCC_VERSION='):
73 gcc_version = line[19:-1]
74 if line.startswith('CONFIG_CLANG_VERSION='):
75 clang_version = line[21:-1]
76 if gcc_version is None or clang_version is None:
77 return None, 'no CONFIG_GCC_VERSION or CONFIG_CLANG_VERSION'
78 if gcc_version == '0' and clang_version != '0':
79 return f'CLANG {clang_version}', 'OK'
80 if gcc_version != '0' and clang_version == '0':
81 return f'GCC {gcc_version}', 'OK'
82 sys.exit(f'[!] ERROR: invalid GCC_VERSION and CLANG_VERSION: {gcc_version} {clang_version}')
85 def print_unknown_options(checklist, parsed_options, opt_type):
89 if o1.opt_type != 'complex':
90 known_options.append(o1.name)
93 if o2.opt_type != 'complex':
94 if hasattr(o2, 'name'):
95 known_options.append(o2.name)
98 assert(o3.opt_type != 'complex'), \
99 f'unexpected ComplexOptCheck inside {o2.name}'
100 if hasattr(o3, 'name'):
101 known_options.append(o3.name)
103 for option, value in parsed_options.items():
104 if option not in known_options:
105 print(f'[?] No check for {opt_type} option {option} ({value})')
108 def print_checklist(mode: str, checklist, with_results: bool):
111 for opt in checklist:
112 output.append(opt.json_dump(with_results))
113 print(json.dumps(output))
120 print('=' * sep_line_len)
121 print(f'{"option_name":^40}|{"type":^7}|{"desired_val":^12}|{"decision":^10}|{"reason":^18}', end='')
123 print('| check_result', end='')
125 print('=' * sep_line_len)
128 for opt in checklist:
130 if mode == 'show_ok':
131 if not opt.result.startswith('OK'):
133 if mode == 'show_fail':
134 if not opt.result.startswith('FAIL'):
136 opt.table_print(mode, with_results)
138 if mode == 'verbose':
139 print('-' * sep_line_len)
144 fail_count = len(list(filter(lambda opt: opt.result.startswith('FAIL'), checklist)))
146 ok_count = len(list(filter(lambda opt: opt.result.startswith('OK'), checklist)))
148 if mode == 'show_ok':
149 fail_suppressed = ' (suppressed in output)'
150 if mode == 'show_fail':
151 ok_suppressed = ' (suppressed in output)'
152 print(f'[+] Config check is finished: \'OK\' - {ok_count}{ok_suppressed} / \'FAIL\' - {fail_count}{fail_suppressed}')
155 def parse_kconfig_file(_mode, parsed_options, fname: str):
156 with _open(fname, 'rt', encoding='utf-8') as f:
157 opt_is_on = re.compile(r"CONFIG_[a-zA-Z0-9_]+=.+$")
158 opt_is_off = re.compile(r"# CONFIG_[a-zA-Z0-9_]+ is not set$")
160 for line in f.readlines():
165 if opt_is_on.match(line):
166 option, value = line.split('=', 1)
167 if value == 'is not set':
168 sys.exit(f'[!] ERROR: bad enabled Kconfig option "{line}"')
169 elif opt_is_off.match(line):
170 option, value = line[2:].split(' ', 1)
171 assert(value == 'is not set'), \
172 f'unexpected value of disabled Kconfig option "{line}"'
173 elif line != '' and not line.startswith('#'):
174 sys.exit(f'[!] ERROR: unexpected line in Kconfig file: "{line}"')
176 if option in parsed_options:
177 sys.exit(f'[!] ERROR: Kconfig option "{line}" is found multiple times')
180 parsed_options[option] = value
183 def parse_cmdline_file(mode, parsed_options, fname):
184 with open(fname, 'r', encoding='utf-8') as f:
190 sys.exit(f'[!] ERROR: more than one line in "{fname}"')
194 name, value = opt.split('=', 1)
197 value = '' # '' is not None
198 if name in parsed_options and mode != 'json':
199 print(f'[!] WARNING: cmdline option "{name}" is found multiple times')
200 value = normalize_cmdline_options(name, value)
201 parsed_options[name] = value
204 def parse_sysctl_file(mode, parsed_options, fname):
205 with open(fname, 'r', encoding='utf-8') as f:
206 sysctl_pattern = re.compile(r"[a-zA-Z0-9/\._-]+ =.*$")
207 for line in f.readlines():
209 if not sysctl_pattern.match(line):
210 sys.exit(f'[!] ERROR: unexpected line in sysctl file: "{line}"')
211 option, value = line.split('=', 1)
212 option = option.strip()
213 value = value.strip()
214 # sysctl options may be found multiple times, let's save the last value:
215 parsed_options[option] = value
217 # let's check the presence of some ancient sysctl option
218 # to ensure that we are parsing the output of `sudo sysctl -a > file`
219 if 'kernel.printk' not in parsed_options:
220 sys.exit(f'[!] ERROR: {fname} doesn\'t look like a sysctl output file, please try `sudo sysctl -a > {fname}`')
222 # let's check the presence of a sysctl option available for root
223 if 'kernel.cad_pid' not in parsed_options and mode != 'json':
224 print(f'[!] WARNING: sysctl option "kernel.cad_pid" available for root is not found in {fname}, please try `sudo sysctl -a > {fname}`')
230 # - reporting about unknown kernel options in the Kconfig
231 # - verbose printing of ComplexOptCheck items
232 # * json mode for printing the results in JSON format
233 report_modes = ['verbose', 'json', 'show_ok', 'show_fail']
234 supported_archs = ['X86_64', 'X86_32', 'ARM64', 'ARM']
235 parser = ArgumentParser(prog='kernel-hardening-checker',
236 description='A tool for checking the security hardening options of the Linux kernel')
237 parser.add_argument('--version', action='version', version=f'%(prog)s {__version__}')
238 parser.add_argument('-m', '--mode', choices=report_modes,
239 help='choose the report mode')
240 parser.add_argument('-c', '--config',
241 help='check the security hardening options in the kernel Kconfig file (also supports *.gz files)')
242 parser.add_argument('-l', '--cmdline',
243 help='check the security hardening options in the kernel cmdline file (contents of /proc/cmdline)')
244 parser.add_argument('-s', '--sysctl',
245 help='check the security hardening options in the sysctl output file (`sudo sysctl -a > file`)')
246 parser.add_argument('-v', '--kernel-version',
247 help='extract the version from the kernel version file (contents of /proc/version)')
248 parser.add_argument('-p', '--print', choices=supported_archs,
249 help='print the security hardening recommendations for the selected microarchitecture')
250 parser.add_argument('-g', '--generate', choices=supported_archs,
251 help='generate a Kconfig fragment with the security hardening options for the selected microarchitecture')
252 args = parser.parse_args()
258 print(f'[+] Special report mode: {mode}')
260 config_checklist = []
264 sys.exit('[!] ERROR: --config and --print can\'t be used together')
266 sys.exit('[!] ERROR: --config and --generate can\'t be used together')
269 print(f'[+] Kconfig file to check: {args.config}')
271 print(f'[+] Kernel cmdline file to check: {args.cmdline}')
273 print(f'[+] Sysctl output file to check: {args.sysctl}')
275 arch, msg = detect_arch(args.config, supported_archs)
277 sys.exit(f'[!] ERROR: {msg}')
279 print(f'[+] Detected microarchitecture: {arch}')
281 if args.kernel_version:
282 kernel_version, msg = detect_kernel_version(args.kernel_version)
284 kernel_version, msg = detect_kernel_version(args.config)
285 if kernel_version is None:
286 if args.kernel_version is None:
287 print('[!] Hint: provide the kernel version file through --kernel-version option')
288 sys.exit(f'[!] ERROR: {msg}')
290 print(f'[+] Detected kernel version: {kernel_version}')
292 compiler, msg = detect_compiler(args.config)
295 print(f'[+] Detected compiler: {compiler}')
297 print(f'[-] Can\'t detect the compiler: {msg}')
299 # add relevant Kconfig checks to the checklist
300 add_kconfig_checks(config_checklist, arch)
303 # add relevant cmdline checks to the checklist
304 add_cmdline_checks(config_checklist, arch)
307 # add relevant sysctl checks to the checklist
308 add_sysctl_checks(config_checklist, arch)
310 # populate the checklist with the parsed Kconfig data
311 parsed_kconfig_options = OrderedDict()
312 parse_kconfig_file(mode, parsed_kconfig_options, args.config)
313 populate_with_data(config_checklist, parsed_kconfig_options, 'kconfig')
315 # populate the checklist with the kernel version data
316 populate_with_data(config_checklist, kernel_version, 'version')
319 # populate the checklist with the parsed cmdline data
320 parsed_cmdline_options = OrderedDict()
321 parse_cmdline_file(mode, parsed_cmdline_options, args.cmdline)
322 populate_with_data(config_checklist, parsed_cmdline_options, 'cmdline')
325 # populate the checklist with the parsed sysctl data
326 parsed_sysctl_options = OrderedDict()
327 parse_sysctl_file(mode, parsed_sysctl_options, args.sysctl)
328 populate_with_data(config_checklist, parsed_sysctl_options, 'sysctl')
330 # hackish refinement of the CONFIG_ARCH_MMAP_RND_BITS check
331 mmap_rnd_bits_max = parsed_kconfig_options.get('CONFIG_ARCH_MMAP_RND_BITS_MAX', None)
332 if mmap_rnd_bits_max:
333 override_expected_value(config_checklist, 'CONFIG_ARCH_MMAP_RND_BITS', mmap_rnd_bits_max)
335 # remove the CONFIG_ARCH_MMAP_RND_BITS check to avoid false results
337 print('[-] Can\'t check CONFIG_ARCH_MMAP_RND_BITS without CONFIG_ARCH_MMAP_RND_BITS_MAX')
338 config_checklist[:] = [o for o in config_checklist if o.name != 'CONFIG_ARCH_MMAP_RND_BITS']
340 # now everything is ready, perform the checks
341 perform_checks(config_checklist)
343 if mode == 'verbose':
344 # print the parsed options without the checks (for debugging)
345 print_unknown_options(config_checklist, parsed_kconfig_options, 'kconfig')
347 print_unknown_options(config_checklist, parsed_cmdline_options, 'cmdline')
349 print_unknown_options(config_checklist, parsed_sysctl_options, 'sysctl')
351 # finally print the results
352 print_checklist(mode, config_checklist, True)
355 sys.exit('[!] ERROR: checking cmdline depends on checking Kconfig')
357 # separate sysctl checking (without kconfig)
358 assert(args.config is None and args.cmdline is None), 'unexpected args'
360 sys.exit('[!] ERROR: --sysctl and --print can\'t be used together')
362 sys.exit('[!] ERROR: --sysctl and --generate can\'t be used together')
365 print(f'[+] Sysctl output file to check: {args.sysctl}')
367 # add relevant sysctl checks to the checklist
368 add_sysctl_checks(config_checklist, None)
370 # populate the checklist with the parsed sysctl data
371 parsed_sysctl_options = OrderedDict()
372 parse_sysctl_file(mode, parsed_sysctl_options, args.sysctl)
373 populate_with_data(config_checklist, parsed_sysctl_options, 'sysctl')
375 # now everything is ready, perform the checks
376 perform_checks(config_checklist)
378 if mode == 'verbose':
379 # print the parsed options without the checks (for debugging)
380 print_unknown_options(config_checklist, parsed_sysctl_options, 'sysctl')
382 # finally print the results
383 print_checklist(mode, config_checklist, True)
387 assert(args.config is None and args.cmdline is None and args.sysctl is None), 'unexpected args'
389 sys.exit('[!] ERROR: --print and --generate can\'t be used together')
390 if mode and mode not in ('verbose', 'json'):
391 sys.exit(f'[!] ERROR: wrong mode "{mode}" for --print')
393 add_kconfig_checks(config_checklist, arch)
394 add_cmdline_checks(config_checklist, arch)
395 add_sysctl_checks(config_checklist, arch)
397 print(f'[+] Printing kernel security hardening options for {arch}...')
398 print_checklist(mode, config_checklist, False)
402 assert(args.config is None and args.cmdline is None and args.sysctl is None and args.print is None), 'unexpected args'
404 sys.exit(f'[!] ERROR: wrong mode "{mode}" for --generate')
406 add_kconfig_checks(config_checklist, arch)
407 print(f'CONFIG_{arch}=y') # the Kconfig fragment should describe the microarchitecture
408 for opt in config_checklist:
409 if opt.name == 'CONFIG_ARCH_MMAP_RND_BITS':
410 continue # don't add CONFIG_ARCH_MMAP_RND_BITS because its value needs refinement
411 if opt.expected == 'is not off':
412 continue # don't add Kconfig options without explicitly recommended values
413 if opt.expected == 'is not set':
414 print(f'# {opt.name} is not set')
416 print(f'{opt.name}={opt.expected}')