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,too-many-branches,too-many-statements
16 from argparse import ArgumentParser
17 from typing import List, Tuple, Dict, TextIO
20 from .checks import add_kconfig_checks, add_cmdline_checks, normalize_cmdline_options, add_sysctl_checks
21 from .engine import StrOrNone, TupleOrNone, ChecklistObjType
22 from .engine import print_unknown_options, populate_with_data, perform_checks, override_expected_value
25 # kernel-hardening-checker version
29 def _open(file: str) -> TextIO:
31 if file.endswith('.gz'):
32 return gzip.open(file, 'rt', encoding='utf-8')
33 return open(file, 'rt', encoding='utf-8')
34 except FileNotFoundError:
35 sys.exit(f'[!] ERROR: unable to open {file}, are you sure it exists?')
38 def detect_arch(fname: str, archs: List[str]) -> Tuple[StrOrNone, str]:
39 with _open(fname) as f:
40 arch_pattern = re.compile(r"CONFIG_[a-zA-Z0-9_]+=y$")
42 for line in f.readlines():
43 if arch_pattern.match(line):
44 option, _ = line[7:].split('=', 1)
49 return None, 'detected more than one microarchitecture'
51 return None, 'failed to detect microarchitecture'
55 def detect_kernel_version(fname: str) -> Tuple[TupleOrNone, str]:
56 with _open(fname) as f:
57 ver_pattern = re.compile(r"^# Linux/.+ Kernel Configuration$|^Linux version .+")
58 for line in f.readlines():
59 if ver_pattern.match(line):
62 ver_str = parts[2].split('-', 1)[0]
63 ver_numbers = ver_str.split('.')
64 if len(ver_numbers) >= 3:
65 if all(map(lambda x: x.isdecimal(), ver_numbers)):
66 return tuple(map(int, ver_numbers)), 'OK'
67 msg = f'failed to parse the version "{parts[2]}"'
69 return None, 'no kernel version detected'
72 def detect_compiler(fname: str) -> Tuple[StrOrNone, str]:
75 with _open(fname) as f:
76 for line in f.readlines():
77 if line.startswith('CONFIG_GCC_VERSION='):
78 gcc_version = line[19:-1]
79 if line.startswith('CONFIG_CLANG_VERSION='):
80 clang_version = line[21:-1]
81 if gcc_version is None or clang_version is None:
82 return None, 'no CONFIG_GCC_VERSION or CONFIG_CLANG_VERSION'
83 if gcc_version == '0' and clang_version != '0':
84 return f'CLANG {clang_version}', 'OK'
85 if gcc_version != '0' and clang_version == '0':
86 return f'GCC {gcc_version}', 'OK'
87 sys.exit(f'[!] ERROR: invalid GCC_VERSION and CLANG_VERSION: {gcc_version} {clang_version}')
90 def print_checklist(mode: StrOrNone, checklist: List[ChecklistObjType], with_results: bool) -> None:
94 output.append(opt.json_dump(with_results))
95 print(json.dumps(output))
102 print('=' * sep_line_len)
103 print(f'{"option_name":^40}|{"type":^7}|{"desired_val":^12}|{"decision":^10}|{"reason":^18}', end='')
105 print('| check_result', end='')
107 print('=' * sep_line_len)
112 for opt in checklist:
114 assert(opt.result), f'unexpected empty result of {opt.name} check'
115 if opt.result.startswith('OK'):
117 if mode == 'show_fail':
119 elif opt.result.startswith('FAIL'):
121 if mode == 'show_ok':
124 assert(False), f'unexpected result "{opt.result}" of {opt.name} check'
125 opt.table_print(mode, with_results)
127 if mode == 'verbose':
128 print('-' * sep_line_len)
135 if mode == 'show_ok':
136 fail_suppressed = ' (suppressed in output)'
137 if mode == 'show_fail':
138 ok_suppressed = ' (suppressed in output)'
139 print(f'[+] Config check is finished: \'OK\' - {ok_count}{ok_suppressed} / \'FAIL\' - {fail_count}{fail_suppressed}')
142 def parse_kconfig_file(_mode: StrOrNone, parsed_options: Dict[str, str], fname: str) -> None:
143 with _open(fname) as f:
144 opt_is_on = re.compile(r"CONFIG_[a-zA-Z0-9_]+=.+$")
145 opt_is_off = re.compile(r"# CONFIG_[a-zA-Z0-9_]+ is not set$")
147 for line in f.readlines():
152 if opt_is_on.match(line):
153 option, value = line.split('=', 1)
154 if value == 'is not set':
155 sys.exit(f'[!] ERROR: bad enabled Kconfig option "{line}"')
156 elif opt_is_off.match(line):
157 option, value = line[2:].split(' ', 1)
158 assert(value == 'is not set'), \
159 f'unexpected value of disabled Kconfig option "{line}"'
160 elif line != '' and not line.startswith('#'):
161 sys.exit(f'[!] ERROR: unexpected line in Kconfig file: "{line}"')
163 if option in parsed_options:
164 sys.exit(f'[!] ERROR: Kconfig option "{line}" is found multiple times')
167 assert(value), f'unexpected empty value for {option}'
168 parsed_options[option] = value
171 def parse_cmdline_file(mode: StrOrNone, parsed_options: Dict[str, str], fname: str) -> None:
172 if not os.path.isfile(fname):
173 sys.exit(f'[!] ERROR: unable to open {fname}, are you sure it exists?')
175 with open(fname, 'r', encoding='utf-8') as f:
181 sys.exit(f'[!] ERROR: more than one line in "{fname}"')
185 name, value = opt.split('=', 1)
188 value = '' # '' is not None
189 if name in parsed_options and mode != 'json':
190 print(f'[!] WARNING: cmdline option "{name}" is found multiple times')
191 value = normalize_cmdline_options(name, value)
192 assert(value is not None), f'unexpected None value for {name}'
193 parsed_options[name] = value
196 def parse_sysctl_file(mode: StrOrNone, parsed_options: Dict[str, str], fname: str) -> None:
197 if not os.path.isfile(fname):
198 sys.exit(f'[!] ERROR: unable to open {fname}, are you sure it exists?')
200 with open(fname, 'r', encoding='utf-8') as f:
201 sysctl_pattern = re.compile(r"[a-zA-Z0-9/\._-]+ =.*$")
202 for line in f.readlines():
204 if not sysctl_pattern.match(line):
205 sys.exit(f'[!] ERROR: unexpected line in sysctl file: "{line}"')
206 option, value = line.split('=', 1)
207 option = option.strip()
208 value = value.strip()
209 # sysctl options may be found multiple times, let's save the last value:
210 parsed_options[option] = value
212 # let's check the presence of some ancient sysctl option
213 # to ensure that we are parsing the output of `sudo sysctl -a > file`
214 if 'kernel.printk' not in parsed_options:
215 sys.exit(f'[!] ERROR: {fname} doesn\'t look like a sysctl output file, please try `sudo sysctl -a > {fname}`')
217 # let's check the presence of a sysctl option available for root
218 if 'kernel.cad_pid' not in parsed_options and mode != 'json':
219 print(f'[!] WARNING: sysctl option "kernel.cad_pid" available for root is not found in {fname}, please try `sudo sysctl -a > {fname}`')
225 # - reporting about unknown kernel options in the Kconfig
226 # - verbose printing of ComplexOptCheck items
227 # * json mode for printing the results in JSON format
228 report_modes = ['verbose', 'json', 'show_ok', 'show_fail']
229 supported_archs = ['X86_64', 'X86_32', 'ARM64', 'ARM']
230 parser = ArgumentParser(prog='kernel-hardening-checker',
231 description='A tool for checking the security hardening options of the Linux kernel')
232 parser.add_argument('--version', action='version', version=f'%(prog)s {__version__}')
233 parser.add_argument('-m', '--mode', choices=report_modes,
234 help='choose the report mode')
235 parser.add_argument('-c', '--config',
236 help='check the security hardening options in the kernel Kconfig file (also supports *.gz files)')
237 parser.add_argument('-l', '--cmdline',
238 help='check the security hardening options in the kernel cmdline file (contents of /proc/cmdline)')
239 parser.add_argument('-s', '--sysctl',
240 help='check the security hardening options in the sysctl output file (`sudo sysctl -a > file`)')
241 parser.add_argument('-v', '--kernel-version',
242 help='extract the version from the kernel version file (contents of /proc/version)')
243 parser.add_argument('-p', '--print', choices=supported_archs,
244 help='print the security hardening recommendations for the selected microarchitecture')
245 parser.add_argument('-g', '--generate', choices=supported_archs,
246 help='generate a Kconfig fragment with the security hardening options for the selected microarchitecture')
247 args = parser.parse_args()
253 print(f'[+] Special report mode: {mode}')
255 config_checklist = [] # type: List[ChecklistObjType]
259 sys.exit('[!] ERROR: --config and --print can\'t be used together')
261 sys.exit('[!] ERROR: --config and --generate can\'t be used together')
264 print(f'[+] Kconfig file to check: {args.config}')
266 print(f'[+] Kernel cmdline file to check: {args.cmdline}')
268 print(f'[+] Sysctl output file to check: {args.sysctl}')
270 arch, msg = detect_arch(args.config, supported_archs)
272 sys.exit(f'[!] ERROR: {msg}')
274 print(f'[+] Detected microarchitecture: {arch}')
276 if args.kernel_version:
277 kernel_version, msg = detect_kernel_version(args.kernel_version)
279 kernel_version, msg = detect_kernel_version(args.config)
280 if kernel_version is None:
281 if args.kernel_version is None:
282 print('[!] Hint: provide the kernel version file through --kernel-version option')
283 sys.exit(f'[!] ERROR: {msg}')
285 print(f'[+] Detected kernel version: {kernel_version}')
287 compiler, msg = detect_compiler(args.config)
290 print(f'[+] Detected compiler: {compiler}')
292 print(f'[-] Can\'t detect the compiler: {msg}')
294 # add relevant Kconfig checks to the checklist
295 add_kconfig_checks(config_checklist, arch)
298 # add relevant cmdline checks to the checklist
299 add_cmdline_checks(config_checklist, arch)
302 # add relevant sysctl checks to the checklist
303 add_sysctl_checks(config_checklist, arch)
305 # populate the checklist with the parsed Kconfig data
306 parsed_kconfig_options = {} # type: Dict[str, str]
307 parse_kconfig_file(mode, parsed_kconfig_options, args.config)
308 populate_with_data(config_checklist, parsed_kconfig_options, 'kconfig')
310 # populate the checklist with the kernel version data
311 populate_with_data(config_checklist, kernel_version, 'version')
314 # populate the checklist with the parsed cmdline data
315 parsed_cmdline_options = {} # type: Dict[str, str]
316 parse_cmdline_file(mode, parsed_cmdline_options, args.cmdline)
317 populate_with_data(config_checklist, parsed_cmdline_options, 'cmdline')
320 # populate the checklist with the parsed sysctl data
321 parsed_sysctl_options = {} # type: Dict[str, str]
322 parse_sysctl_file(mode, parsed_sysctl_options, args.sysctl)
323 populate_with_data(config_checklist, parsed_sysctl_options, 'sysctl')
325 # hackish refinement of the CONFIG_ARCH_MMAP_RND_BITS check
326 mmap_rnd_bits_max = parsed_kconfig_options.get('CONFIG_ARCH_MMAP_RND_BITS_MAX', None)
327 if mmap_rnd_bits_max:
328 override_expected_value(config_checklist, 'CONFIG_ARCH_MMAP_RND_BITS', mmap_rnd_bits_max)
330 # remove the CONFIG_ARCH_MMAP_RND_BITS check to avoid false results
332 print('[-] Can\'t check CONFIG_ARCH_MMAP_RND_BITS without CONFIG_ARCH_MMAP_RND_BITS_MAX')
333 config_checklist[:] = [o for o in config_checklist if o.name != 'CONFIG_ARCH_MMAP_RND_BITS']
335 # now everything is ready, perform the checks
336 perform_checks(config_checklist)
338 if mode == 'verbose':
339 # print the parsed options without the checks (for debugging)
340 print_unknown_options(config_checklist, parsed_kconfig_options, 'kconfig')
342 print_unknown_options(config_checklist, parsed_cmdline_options, 'cmdline')
344 print_unknown_options(config_checklist, parsed_sysctl_options, 'sysctl')
346 # finally print the results
347 print_checklist(mode, config_checklist, True)
350 sys.exit('[!] ERROR: checking cmdline depends on checking Kconfig')
352 # separate sysctl checking (without kconfig)
353 assert(args.config is None and args.cmdline is None), 'unexpected args'
355 sys.exit('[!] ERROR: --sysctl and --print can\'t be used together')
357 sys.exit('[!] ERROR: --sysctl and --generate can\'t be used together')
360 print(f'[+] Sysctl output file to check: {args.sysctl}')
362 # add relevant sysctl checks to the checklist
363 add_sysctl_checks(config_checklist, None)
365 # populate the checklist with the parsed sysctl data
366 parsed_sysctl_options = {}
367 parse_sysctl_file(mode, parsed_sysctl_options, args.sysctl)
368 populate_with_data(config_checklist, parsed_sysctl_options, 'sysctl')
370 # now everything is ready, perform the checks
371 perform_checks(config_checklist)
373 if mode == 'verbose':
374 # print the parsed options without the checks (for debugging)
375 print_unknown_options(config_checklist, parsed_sysctl_options, 'sysctl')
377 # finally print the results
378 print_checklist(mode, config_checklist, True)
382 assert(args.config is None and args.cmdline is None and args.sysctl is None), 'unexpected args'
384 sys.exit('[!] ERROR: --print and --generate can\'t be used together')
385 if mode and mode not in ('verbose', 'json'):
386 sys.exit(f'[!] ERROR: wrong mode "{mode}" for --print')
388 assert(arch), 'unexpected empty arch from ArgumentParser'
389 add_kconfig_checks(config_checklist, arch)
390 add_cmdline_checks(config_checklist, arch)
391 add_sysctl_checks(config_checklist, arch)
393 print(f'[+] Printing kernel security hardening options for {arch}...')
394 print_checklist(mode, config_checklist, False)
398 assert(args.config is None and
399 args.cmdline is None and
400 args.sysctl is None and
401 args.print is None), \
404 sys.exit(f'[!] ERROR: wrong mode "{mode}" for --generate')
406 assert(arch), 'unexpected empty arch from ArgumentParser'
407 add_kconfig_checks(config_checklist, arch)
408 print(f'CONFIG_{arch}=y') # the Kconfig fragment should describe the microarchitecture
409 for opt in config_checklist:
410 if opt.name == 'CONFIG_ARCH_MMAP_RND_BITS':
411 continue # don't add CONFIG_ARCH_MMAP_RND_BITS because its value needs refinement
412 if opt.expected == 'is not off':
413 continue # don't add Kconfig options without explicitly recommended values
414 if opt.expected == 'is not set':
415 print(f'# {opt.name} is not set')
417 print(f'{opt.name}={opt.expected}')