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, OrderedDict, TextIO
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 StrOrNone, TupleOrNone, print_unknown_options, populate_with_data, perform_checks, override_expected_value
25 def _open(file: str, *args, **kwargs) -> TextIO:
26 if file.endswith('.gz'):
27 return gzip.open(file, *args, **kwargs)
28 return open(file, *args, **kwargs)
31 def detect_arch(fname: str, archs: List[str]) -> Tuple[StrOrNone, str]:
32 with _open(fname, 'rt', encoding='utf-8') as f:
33 arch_pattern = re.compile(r"CONFIG_[a-zA-Z0-9_]+=y$")
35 for line in f.readlines():
36 if arch_pattern.match(line):
37 option, _ = line[7:].split('=', 1)
42 return None, 'detected more than one microarchitecture'
44 return None, 'failed to detect microarchitecture'
48 def detect_kernel_version(fname: str) -> Tuple[TupleOrNone, str]:
49 with _open(fname, 'rt', encoding='utf-8') as f:
50 ver_pattern = re.compile(r"^# Linux/.+ Kernel Configuration$|^Linux version .+")
51 for line in f.readlines():
52 if ver_pattern.match(line):
55 ver_str = parts[2].split('-', 1)[0]
56 ver_numbers = ver_str.split('.')
57 if len(ver_numbers) >= 3:
58 if all(map(lambda x: x.isdigit(), ver_numbers)):
59 return tuple(map(int, ver_numbers)), 'OK'
60 msg = f'failed to parse the version "{parts[2]}"'
62 return None, 'no kernel version detected'
65 def detect_compiler(fname: str) -> Tuple[StrOrNone, str]:
68 with _open(fname, 'rt', encoding='utf-8') as f:
69 for line in f.readlines():
70 if line.startswith('CONFIG_GCC_VERSION='):
71 gcc_version = line[19:-1]
72 if line.startswith('CONFIG_CLANG_VERSION='):
73 clang_version = line[21:-1]
74 if gcc_version is None or clang_version is None:
75 return None, 'no CONFIG_GCC_VERSION or CONFIG_CLANG_VERSION'
76 if gcc_version == '0' and clang_version != '0':
77 return f'CLANG {clang_version}', 'OK'
78 if gcc_version != '0' and clang_version == '0':
79 return f'GCC {gcc_version}', 'OK'
80 sys.exit(f'[!] ERROR: invalid GCC_VERSION and CLANG_VERSION: {gcc_version} {clang_version}')
83 def print_checklist(mode: StrOrNone, checklist: List, with_results: bool) -> None:
87 output.append(opt.json_dump(with_results))
88 print(json.dumps(output))
95 print('=' * sep_line_len)
96 print(f'{"option_name":^40}|{"type":^7}|{"desired_val":^12}|{"decision":^10}|{"reason":^18}', end='')
98 print('| check_result', end='')
100 print('=' * sep_line_len)
103 for opt in checklist:
105 if mode == 'show_ok':
106 if not opt.result.startswith('OK'):
108 if mode == 'show_fail':
109 if not opt.result.startswith('FAIL'):
111 opt.table_print(mode, with_results)
113 if mode == 'verbose':
114 print('-' * sep_line_len)
119 fail_count = len(list(filter(lambda opt: opt.result.startswith('FAIL'), checklist)))
121 ok_count = len(list(filter(lambda opt: opt.result.startswith('OK'), checklist)))
123 if mode == 'show_ok':
124 fail_suppressed = ' (suppressed in output)'
125 if mode == 'show_fail':
126 ok_suppressed = ' (suppressed in output)'
127 print(f'[+] Config check is finished: \'OK\' - {ok_count}{ok_suppressed} / \'FAIL\' - {fail_count}{fail_suppressed}')
130 def parse_kconfig_file(_mode: StrOrNone, parsed_options: OrderedDict[str, str], fname: str) -> None:
131 with _open(fname, 'rt', encoding='utf-8') as f:
132 opt_is_on = re.compile(r"CONFIG_[a-zA-Z0-9_]+=.+$")
133 opt_is_off = re.compile(r"# CONFIG_[a-zA-Z0-9_]+ is not set$")
135 for line in f.readlines():
140 if opt_is_on.match(line):
141 option, value = line.split('=', 1)
142 if value == 'is not set':
143 sys.exit(f'[!] ERROR: bad enabled Kconfig option "{line}"')
144 elif opt_is_off.match(line):
145 option, value = line[2:].split(' ', 1)
146 assert(value == 'is not set'), \
147 f'unexpected value of disabled Kconfig option "{line}"'
148 elif line != '' and not line.startswith('#'):
149 sys.exit(f'[!] ERROR: unexpected line in Kconfig file: "{line}"')
151 if option in parsed_options:
152 sys.exit(f'[!] ERROR: Kconfig option "{line}" is found multiple times')
155 assert(value), f'unexpected empty value for {option}'
156 parsed_options[option] = value
159 def parse_cmdline_file(mode: StrOrNone, parsed_options: OrderedDict[str, str], fname: str) -> None:
160 with open(fname, 'r', encoding='utf-8') as f:
166 sys.exit(f'[!] ERROR: more than one line in "{fname}"')
170 name, value = opt.split('=', 1)
173 value = '' # '' is not None
174 if name in parsed_options and mode != 'json':
175 print(f'[!] WARNING: cmdline option "{name}" is found multiple times')
176 value = normalize_cmdline_options(name, value)
177 assert(value is not None), f'unexpected None value for {name}'
178 parsed_options[name] = value
181 def parse_sysctl_file(mode: StrOrNone, parsed_options: OrderedDict[str, str], fname: str) -> None:
182 with open(fname, 'r', encoding='utf-8') as f:
183 sysctl_pattern = re.compile(r"[a-zA-Z0-9/\._-]+ =.*$")
184 for line in f.readlines():
186 if not sysctl_pattern.match(line):
187 sys.exit(f'[!] ERROR: unexpected line in sysctl file: "{line}"')
188 option, value = line.split('=', 1)
189 option = option.strip()
190 value = value.strip()
191 # sysctl options may be found multiple times, let's save the last value:
192 parsed_options[option] = value
194 # let's check the presence of some ancient sysctl option
195 # to ensure that we are parsing the output of `sudo sysctl -a > file`
196 if 'kernel.printk' not in parsed_options:
197 sys.exit(f'[!] ERROR: {fname} doesn\'t look like a sysctl output file, please try `sudo sysctl -a > {fname}`')
199 # let's check the presence of a sysctl option available for root
200 if 'kernel.cad_pid' not in parsed_options and mode != 'json':
201 print(f'[!] WARNING: sysctl option "kernel.cad_pid" available for root is not found in {fname}, please try `sudo sysctl -a > {fname}`')
207 # - reporting about unknown kernel options in the Kconfig
208 # - verbose printing of ComplexOptCheck items
209 # * json mode for printing the results in JSON format
210 report_modes = ['verbose', 'json', 'show_ok', 'show_fail']
211 supported_archs = ['X86_64', 'X86_32', 'ARM64', 'ARM']
212 parser = ArgumentParser(prog='kernel-hardening-checker',
213 description='A tool for checking the security hardening options of the Linux kernel')
214 parser.add_argument('--version', action='version', version=f'%(prog)s {__version__}')
215 parser.add_argument('-m', '--mode', choices=report_modes,
216 help='choose the report mode')
217 parser.add_argument('-c', '--config',
218 help='check the security hardening options in the kernel Kconfig file (also supports *.gz files)')
219 parser.add_argument('-l', '--cmdline',
220 help='check the security hardening options in the kernel cmdline file (contents of /proc/cmdline)')
221 parser.add_argument('-s', '--sysctl',
222 help='check the security hardening options in the sysctl output file (`sudo sysctl -a > file`)')
223 parser.add_argument('-v', '--kernel-version',
224 help='extract the version from the kernel version file (contents of /proc/version)')
225 parser.add_argument('-p', '--print', choices=supported_archs,
226 help='print the security hardening recommendations for the selected microarchitecture')
227 parser.add_argument('-g', '--generate', choices=supported_archs,
228 help='generate a Kconfig fragment with the security hardening options for the selected microarchitecture')
229 args = parser.parse_args()
235 print(f'[+] Special report mode: {mode}')
237 config_checklist = [] # type: List
241 sys.exit('[!] ERROR: --config and --print can\'t be used together')
243 sys.exit('[!] ERROR: --config and --generate can\'t be used together')
246 print(f'[+] Kconfig file to check: {args.config}')
248 print(f'[+] Kernel cmdline file to check: {args.cmdline}')
250 print(f'[+] Sysctl output file to check: {args.sysctl}')
252 arch, msg = detect_arch(args.config, supported_archs)
254 sys.exit(f'[!] ERROR: {msg}')
256 print(f'[+] Detected microarchitecture: {arch}')
258 if args.kernel_version:
259 kernel_version, msg = detect_kernel_version(args.kernel_version)
261 kernel_version, msg = detect_kernel_version(args.config)
262 if kernel_version is None:
263 if args.kernel_version is None:
264 print('[!] Hint: provide the kernel version file through --kernel-version option')
265 sys.exit(f'[!] ERROR: {msg}')
267 print(f'[+] Detected kernel version: {kernel_version}')
269 compiler, msg = detect_compiler(args.config)
272 print(f'[+] Detected compiler: {compiler}')
274 print(f'[-] Can\'t detect the compiler: {msg}')
276 # add relevant Kconfig checks to the checklist
277 add_kconfig_checks(config_checklist, arch)
280 # add relevant cmdline checks to the checklist
281 add_cmdline_checks(config_checklist, arch)
284 # add relevant sysctl checks to the checklist
285 add_sysctl_checks(config_checklist, arch)
287 # populate the checklist with the parsed Kconfig data
288 parsed_kconfig_options = OrderedDict() # type: OrderedDict[str, str]
289 parse_kconfig_file(mode, parsed_kconfig_options, args.config)
290 populate_with_data(config_checklist, parsed_kconfig_options, 'kconfig')
292 # populate the checklist with the kernel version data
293 populate_with_data(config_checklist, kernel_version, 'version')
296 # populate the checklist with the parsed cmdline data
297 parsed_cmdline_options = OrderedDict() # type: OrderedDict[str, str]
298 parse_cmdline_file(mode, parsed_cmdline_options, args.cmdline)
299 populate_with_data(config_checklist, parsed_cmdline_options, 'cmdline')
302 # populate the checklist with the parsed sysctl data
303 parsed_sysctl_options = OrderedDict() # type: OrderedDict[str, str]
304 parse_sysctl_file(mode, parsed_sysctl_options, args.sysctl)
305 populate_with_data(config_checklist, parsed_sysctl_options, 'sysctl')
307 # hackish refinement of the CONFIG_ARCH_MMAP_RND_BITS check
308 mmap_rnd_bits_max = parsed_kconfig_options.get('CONFIG_ARCH_MMAP_RND_BITS_MAX', None)
309 if mmap_rnd_bits_max:
310 override_expected_value(config_checklist, 'CONFIG_ARCH_MMAP_RND_BITS', mmap_rnd_bits_max)
312 # remove the CONFIG_ARCH_MMAP_RND_BITS check to avoid false results
314 print('[-] Can\'t check CONFIG_ARCH_MMAP_RND_BITS without CONFIG_ARCH_MMAP_RND_BITS_MAX')
315 config_checklist[:] = [o for o in config_checklist if o.name != 'CONFIG_ARCH_MMAP_RND_BITS']
317 # now everything is ready, perform the checks
318 perform_checks(config_checklist)
320 if mode == 'verbose':
321 # print the parsed options without the checks (for debugging)
322 print_unknown_options(config_checklist, parsed_kconfig_options, 'kconfig')
324 print_unknown_options(config_checklist, parsed_cmdline_options, 'cmdline')
326 print_unknown_options(config_checklist, parsed_sysctl_options, 'sysctl')
328 # finally print the results
329 print_checklist(mode, config_checklist, True)
332 sys.exit('[!] ERROR: checking cmdline depends on checking Kconfig')
334 # separate sysctl checking (without kconfig)
335 assert(args.config is None and args.cmdline is None), 'unexpected args'
337 sys.exit('[!] ERROR: --sysctl and --print can\'t be used together')
339 sys.exit('[!] ERROR: --sysctl and --generate can\'t be used together')
342 print(f'[+] Sysctl output file to check: {args.sysctl}')
344 # add relevant sysctl checks to the checklist
345 add_sysctl_checks(config_checklist, None)
347 # populate the checklist with the parsed sysctl data
348 parsed_sysctl_options = OrderedDict()
349 parse_sysctl_file(mode, parsed_sysctl_options, args.sysctl)
350 populate_with_data(config_checklist, parsed_sysctl_options, 'sysctl')
352 # now everything is ready, perform the checks
353 perform_checks(config_checklist)
355 if mode == 'verbose':
356 # print the parsed options without the checks (for debugging)
357 print_unknown_options(config_checklist, parsed_sysctl_options, 'sysctl')
359 # finally print the results
360 print_checklist(mode, config_checklist, True)
364 assert(args.config is None and args.cmdline is None and args.sysctl is None), 'unexpected args'
366 sys.exit('[!] ERROR: --print and --generate can\'t be used together')
367 if mode and mode not in ('verbose', 'json'):
368 sys.exit(f'[!] ERROR: wrong mode "{mode}" for --print')
370 assert arch, 'unexpected empty arch from ArgumentParser'
371 add_kconfig_checks(config_checklist, arch)
372 add_cmdline_checks(config_checklist, arch)
373 add_sysctl_checks(config_checklist, arch)
375 print(f'[+] Printing kernel security hardening options for {arch}...')
376 print_checklist(mode, config_checklist, False)
380 assert(args.config is None and args.cmdline is None and args.sysctl is None and args.print is None), 'unexpected args'
382 sys.exit(f'[!] ERROR: wrong mode "{mode}" for --generate')
384 assert arch, 'unexpected empty arch from ArgumentParser'
385 add_kconfig_checks(config_checklist, arch)
386 print(f'CONFIG_{arch}=y') # the Kconfig fragment should describe the microarchitecture
387 for opt in config_checklist:
388 if opt.name == 'CONFIG_ARCH_MMAP_RND_BITS':
389 continue # don't add CONFIG_ARCH_MMAP_RND_BITS because its value needs refinement
390 if opt.expected == 'is not off':
391 continue # don't add Kconfig options without explicitly recommended values
392 if opt.expected == 'is not set':
393 print(f'# {opt.name} is not set')
395 print(f'{opt.name}={opt.expected}')