#
# This tool helps me to check the Linux kernel Kconfig option list
-# against my hardening preferences for X86_64, ARM64, X86_32, and ARM.
+# against my security hardening preferences for X86_64, ARM64, X86_32, and ARM.
# Let the computers do their job!
#
# Author: Alexander Popov <alex.popov@linux.com>
#
#
# N.B Hardening command line parameters:
-# slub_debug=FZP
# slab_nomerge
# page_alloc.shuffle=1
# iommu=force (does it help against DMA attacks?)
-# page_poison=1 (if enabled)
-# init_on_alloc=1
-# init_on_free=1
+# slub_debug=FZ (slow)
+# init_on_alloc=1 (since v5.3)
+# init_on_free=1 (since v5.3, otherwise slub_debug=P and page_poison=1)
# loadpin.enforce=1
+# debugfs=no-mount (or off if possible)
+# randomize_kstack_offset=1
#
# Mitigations of CPU vulnerabilities:
# Аrch-independent:
-# mitigations=auto,nosmt
+# mitigations=auto,nosmt (nosmt is slow)
# X86:
# spectre_v2=on
# pti=on
# kpti=on
# ssbd=force-on
#
+# Should NOT be set:
+# nokaslr
+# arm64.nobti
+# arm64.nopauth
+#
+# Hardware tag-based KASAN with arm64 Memory Tagging Extension (MTE):
+# kasan=on
+# kasan.stacktrace=off
+# kasan.fault=panic
+#
# N.B. Hardening sysctls:
-# kernel.kptr_restrict=2
-# kernel.dmesg_restrict=1
+# kernel.kptr_restrict=2 (or 1?)
+# kernel.dmesg_restrict=1 (also see the kconfig option)
# kernel.perf_event_paranoid=3
# kernel.kexec_load_disabled=1
# kernel.yama.ptrace_scope=3
# user.max_user_namespaces=0
+# what about bpf_jit_enable?
# kernel.unprivileged_bpf_disabled=1
# net.core.bpf_jit_harden=2
#
# vm.unprivileged_userfaultfd=0
+# (at first, it disabled unprivileged userfaultfd,
+# and since v5.11 it enables unprivileged userfaultfd for user-mode only)
#
# dev.tty.ldisc_autoload=0
# fs.protected_symlinks=1
# fs.suid_dumpable=0
# kernel.modules_disabled=1
+
+# pylint: disable=missing-module-docstring,missing-class-docstring,missing-function-docstring
+# pylint: disable=line-too-long,invalid-name,too-many-branches,too-many-statements
+
+
import sys
from argparse import ArgumentParser
from collections import OrderedDict
import json
from .__about__ import __version__
-# pylint: disable=line-too-long,bad-whitespace,too-many-branches
-# pylint: disable=too-many-statements,global-statement
-
class OptCheck:
def __init__(self, reason, decision, name, expected):
return True
return False
- def table_print(self, mode, with_results):
+ def table_print(self, _mode, with_results):
print('CONFIG_{:<38}|{:^13}|{:^10}|{:^20}'.format(self.name, self.expected, self.decision, self.reason), end='')
if with_results:
print('| {}'.format(self.result), end='')
class VerCheck:
def __init__(self, ver_expected):
self.ver_expected = ver_expected
- self.ver = None
+ self.ver = ()
self.result = None
def check(self):
self.result = 'FAIL: version < ' + str(self.ver_expected[0]) + '.' + str(self.ver_expected[1])
return False
- def table_print(self, mode, with_results):
+ def table_print(self, _mode, with_results):
ver_req = 'kernel version >= ' + str(self.ver_expected[0]) + '.' + str(self.ver_expected[1])
print('{:<91}'.format(ver_req), end='')
if with_results:
self.result = 'OK: is present'
return True
- def table_print(self, mode, with_results):
+ def table_print(self, _mode, with_results):
print('CONFIG_{:<84}'.format(self.name + ' is present'), end='')
if with_results:
print('| {}'.format(self.result), end='')
class ComplexOptCheck:
def __init__(self, *opts):
self.opts = opts
+ if not self.opts:
+ sys.exit('[!] ERROR: empty {} check'.format(self.__class__.__name__))
+ if not isinstance(opts[0], OptCheck):
+ sys.exit('[!] ERROR: invalid {} check: {}'.format(self.__class__.__name__, opts))
self.result = None
@property
for i, opt in enumerate(self.opts):
ret = opt.check()
if ret:
- if i == 0 or not hasattr(opt, 'expected'):
+ if opt.result != 'OK' or i == 0:
+ # Preserve additional explanation of this OK result.
+ # Simple OK is enough only for the main option that
+ # this OR-check is about.
self.result = opt.result
else:
+ # Simple OK is not enough for additional checks.
self.result = 'OK: CONFIG_{} "{}"'.format(opt.name, opt.expected)
return True
self.result = self.opts[0].result
self.result = opt.result
return ret
if not ret:
- if hasattr(opt, 'expected'):
+ # This FAIL is caused by additional checks,
+ # and not by the main option that this AND-check is about.
+ # Describe the reason of the FAIL.
+ if opt.result.startswith('FAIL: \"') or opt.result == 'FAIL: not found':
self.result = 'FAIL: CONFIG_{} not "{}"'.format(opt.name, opt.expected)
+ elif opt.result == 'FAIL: not present':
+ self.result = 'FAIL: CONFIG_{} not present'.format(opt.name)
else:
+ # This FAIL message is self-explaining.
self.result = opt.result
return False
VerCheck((5, 5)))] # REFCOUNT_FULL is enabled by default since v5.5
iommu_support_is_set = OptCheck('self_protection', 'defconfig', 'IOMMU_SUPPORT', 'y')
l += [iommu_support_is_set] # is needed for mitigating DMA attacks
+ if arch in ('X86_64', 'ARM64', 'X86_32'):
+ l += [OptCheck('self_protection', 'defconfig', 'RANDOMIZE_BASE', 'y')]
+ l += [OptCheck('self_protection', 'defconfig', 'THREAD_INFO_IN_TASK', 'y')]
+ if arch in ('X86_64', 'ARM64'):
+ l += [OptCheck('self_protection', 'defconfig', 'VMAP_STACK', 'y')]
if arch in ('X86_64', 'X86_32'):
l += [OptCheck('self_protection', 'defconfig', 'MICROCODE', 'y')] # is needed for mitigating CPU bugs
l += [OptCheck('self_protection', 'defconfig', 'RETPOLINE', 'y')]
l += [OptCheck('self_protection', 'defconfig', 'SYN_COOKIES', 'y')] # another reason?
l += [OR(OptCheck('self_protection', 'defconfig', 'X86_UMIP', 'y'),
OptCheck('self_protection', 'defconfig', 'X86_INTEL_UMIP', 'y'))]
+ if arch in ('ARM64', 'ARM'):
+ l += [OptCheck('self_protection', 'defconfig', 'STACKPROTECTOR_PER_TASK', 'y')]
if arch == 'X86_64':
l += [OptCheck('self_protection', 'defconfig', 'PAGE_TABLE_ISOLATION', 'y')]
l += [OptCheck('self_protection', 'defconfig', 'RANDOMIZE_MEMORY', 'y')]
iommu_support_is_set)]
if arch == 'ARM64':
l += [OptCheck('self_protection', 'defconfig', 'ARM64_PAN', 'y')]
+ l += [OptCheck('self_protection', 'defconfig', 'ARM64_EPAN', 'y')]
l += [OptCheck('self_protection', 'defconfig', 'UNMAP_KERNEL_AT_EL0', 'y')]
- l += [OptCheck('self_protection', 'defconfig', 'HARDEN_EL2_VECTORS', 'y')]
+ l += [OR(OptCheck('self_protection', 'defconfig', 'HARDEN_EL2_VECTORS', 'y'),
+ AND(OptCheck('self_protection', 'defconfig', 'RANDOMIZE_BASE', 'y'),
+ VerCheck((5, 9))))] # HARDEN_EL2_VECTORS was included in RANDOMIZE_BASE in v5.9
l += [OptCheck('self_protection', 'defconfig', 'RODATA_FULL_DEFAULT_ENABLED', 'y')]
l += [OptCheck('self_protection', 'defconfig', 'ARM64_PTR_AUTH', 'y')]
- if arch in ('X86_64', 'ARM64'):
- l += [OptCheck('self_protection', 'defconfig', 'VMAP_STACK', 'y')]
- if arch in ('X86_64', 'ARM64', 'X86_32'):
- l += [OptCheck('self_protection', 'defconfig', 'RANDOMIZE_BASE', 'y')]
- l += [OptCheck('self_protection', 'defconfig', 'THREAD_INFO_IN_TASK', 'y')]
+ l += [OptCheck('self_protection', 'defconfig', 'ARM64_BTI_KERNEL', 'y')]
+ l += [OR(OptCheck('self_protection', 'defconfig', 'HARDEN_BRANCH_PREDICTOR', 'y'),
+ VerCheck((5, 10)))] # HARDEN_BRANCH_PREDICTOR is enabled by default since v5.10
+ l += [OptCheck('self_protection', 'defconfig', 'ARM64_MTE', 'y')]
if arch == 'ARM':
l += [OptCheck('self_protection', 'defconfig', 'CPU_SW_DOMAIN_PAN', 'y')]
- l += [OptCheck('self_protection', 'defconfig', 'STACKPROTECTOR_PER_TASK', 'y')]
- if arch in ('ARM64', 'ARM'):
l += [OptCheck('self_protection', 'defconfig', 'HARDEN_BRANCH_PREDICTOR', 'y')]
# 'self_protection', 'kspp'
+ l += [OptCheck('self_protection', 'kspp', 'SECURITY_DMESG_RESTRICT', 'y')]
l += [OptCheck('self_protection', 'kspp', 'BUG_ON_DATA_CORRUPTION', 'y')]
l += [OptCheck('self_protection', 'kspp', 'DEBUG_WX', 'y')]
l += [OptCheck('self_protection', 'kspp', 'SCHED_STACK_END_CHECK', 'y')]
modules_not_set)]
l += [OR(OptCheck('self_protection', 'kspp', 'MODULE_SIG_FORCE', 'y'),
modules_not_set)] # refers to LOCKDOWN
- l += [OR(OptCheck('self_protection', 'kspp', 'INIT_STACK_ALL', 'y'),
+ l += [OR(OptCheck('self_protection', 'kspp', 'INIT_STACK_ALL_ZERO', 'y'),
OptCheck('self_protection', 'kspp', 'GCC_PLUGIN_STRUCTLEAK_BYREF_ALL', 'y'))]
l += [OR(OptCheck('self_protection', 'kspp', 'INIT_ON_FREE_DEFAULT_ON', 'y'),
- OptCheck('self_protection', 'kspp', 'PAGE_POISONING', 'y'))] # before v5.3
+ OptCheck('self_protection', 'kspp', 'PAGE_POISONING_ZERO', 'y'))]
+ # CONFIG_INIT_ON_FREE_DEFAULT_ON was added in v5.3.
+ # CONFIG_PAGE_POISONING_ZERO was removed in v5.11.
+ # Starting from v5.11 CONFIG_PAGE_POISONING unconditionally checks
+ # the 0xAA poison pattern on allocation.
+ # That brings higher performance penalty.
if arch in ('X86_64', 'ARM64', 'X86_32'):
stackleak_is_set = OptCheck('self_protection', 'kspp', 'GCC_PLUGIN_STACKLEAK', 'y')
l += [stackleak_is_set]
if arch in ('X86_64', 'X86_32'):
l += [OptCheck('self_protection', 'kspp', 'DEFAULT_MMAP_MIN_ADDR', '65536')]
+ if arch in ('ARM64', 'ARM'):
+ l += [OptCheck('self_protection', 'kspp', 'DEFAULT_MMAP_MIN_ADDR', '32768')]
+ l += [OptCheck('self_protection', 'kspp', 'SYN_COOKIES', 'y')] # another reason?
+ if arch == 'ARM64':
+ l += [OptCheck('self_protection', 'kspp', 'ARM64_SW_TTBR0_PAN', 'y')]
if arch == 'X86_32':
l += [OptCheck('self_protection', 'kspp', 'PAGE_TABLE_ISOLATION', 'y')]
l += [OptCheck('self_protection', 'kspp', 'HIGHMEM64G', 'y')]
l += [OptCheck('self_protection', 'kspp', 'X86_PAE', 'y')]
- if arch == 'ARM64':
- l += [OptCheck('self_protection', 'kspp', 'ARM64_SW_TTBR0_PAN', 'y')]
- if arch in ('ARM64', 'ARM'):
- l += [OptCheck('self_protection', 'kspp', 'SYN_COOKIES', 'y')] # another reason?
- l += [OptCheck('self_protection', 'kspp', 'DEFAULT_MMAP_MIN_ADDR', '32768')]
# 'self_protection', 'clipos'
- l += [OptCheck('self_protection', 'clipos', 'SECURITY_DMESG_RESTRICT', 'y')]
l += [OptCheck('self_protection', 'clipos', 'DEBUG_VIRTUAL', 'y')]
l += [OptCheck('self_protection', 'clipos', 'STATIC_USERMODEHELPER', 'y')] # needs userspace support
+ l += [OptCheck('self_protection', 'clipos', 'EFI_DISABLE_PCI_DMA', 'y')]
l += [OptCheck('self_protection', 'clipos', 'SLAB_MERGE_DEFAULT', 'is not set')] # slab_nomerge
l += [OptCheck('self_protection', 'clipos', 'RANDOM_TRUST_BOOTLOADER', 'is not set')]
l += [OptCheck('self_protection', 'clipos', 'RANDOM_TRUST_CPU', 'is not set')]
l += [AND(OptCheck('self_protection', 'clipos', 'STACKLEAK_RUNTIME_DISABLE', 'is not set'),
stackleak_is_set)]
if arch in ('X86_64', 'X86_32'):
- l += [AND(OptCheck('self_protection', 'clipos', 'INTEL_IOMMU_SVM', 'y'),
- iommu_support_is_set)]
l += [AND(OptCheck('self_protection', 'clipos', 'INTEL_IOMMU_DEFAULT_ON', 'y'),
iommu_support_is_set)]
+ if arch == 'X86_64':
+ l += [AND(OptCheck('self_protection', 'clipos', 'INTEL_IOMMU_SVM', 'y'),
+ iommu_support_is_set)]
if arch == 'X86_32':
l += [AND(OptCheck('self_protection', 'clipos', 'INTEL_IOMMU', 'y'),
iommu_support_is_set)]
# 'self_protection', 'my'
- l += [OptCheck('self_protection', 'my', 'SLUB_DEBUG_ON', 'y')]
+ l += [AND(OptCheck('self_protection', 'my', 'UBSAN_BOUNDS', 'y'),
+ OptCheck('self_protection', 'my', 'UBSAN_MISC', 'is not set'),
+ OptCheck('self_protection', 'my', 'UBSAN_TRAP', 'y'))]
l += [OptCheck('self_protection', 'my', 'RESET_ATTACK_MITIGATION', 'y')] # needs userspace support (systemd)
+ if arch in ('X86_64', 'ARM64', 'X86_32'):
+ l += [OptCheck('self_protection', 'my', 'RANDOMIZE_KSTACK_OFFSET_DEFAULT', 'y')]
if arch == 'X86_64':
l += [AND(OptCheck('self_protection', 'my', 'AMD_IOMMU_V2', 'y'),
iommu_support_is_set)]
+ if arch == 'ARM64':
+ l += [OptCheck('self_protection', 'my', 'SHADOW_CALL_STACK', 'y')] # depends on clang, maybe it's alternative to STACKPROTECTOR_STRONG
+ l += [OptCheck('self_protection', 'my', 'KASAN_HW_TAGS', 'y')]
+ cfi_clang_is_set = OptCheck('self_protection', 'my', 'CFI_CLANG', 'y')
+ l += [cfi_clang_is_set]
+ l += [AND(OptCheck('self_protection', 'my', 'CFI_PERMISSIVE', 'is not set'),
+ cfi_clang_is_set)]
# 'security_policy'
if arch in ('X86_64', 'ARM64', 'X86_32'):
l += [OptCheck('cut_attack_surface', 'grsecurity', 'MEM_SOFT_DIRTY', 'is not set')]
l += [OptCheck('cut_attack_surface', 'grsecurity', 'DEVPORT', 'is not set')] # refers to LOCKDOWN
l += [OptCheck('cut_attack_surface', 'grsecurity', 'DEBUG_FS', 'is not set')] # refers to LOCKDOWN
- l += [OptCheck('cut_attack_surface', 'grsecurity', 'NOTIFIER_ERROR_INJECTION','is not set')]
+ l += [OptCheck('cut_attack_surface', 'grsecurity', 'NOTIFIER_ERROR_INJECTION', 'is not set')]
l += [AND(OptCheck('cut_attack_surface', 'grsecurity', 'X86_PTDUMP', 'is not set'),
OptCheck('cut_attack_surface', 'my', 'PTDUMP_DEBUGFS', 'is not set'))]
l += [OptCheck('cut_attack_surface', 'maintainer', 'DRM_LEGACY', 'is not set')]
l += [OptCheck('cut_attack_surface', 'maintainer', 'FB', 'is not set')]
l += [OptCheck('cut_attack_surface', 'maintainer', 'VT', 'is not set')]
+ l += [OptCheck('cut_attack_surface', 'maintainer', 'BLK_DEV_FD', 'is not set')]
- # 'cut_attack_surface', 'lockdown'
- l += [OptCheck('cut_attack_surface', 'lockdown', 'ACPI_TABLE_UPGRADE', 'is not set')] # refers to LOCKDOWN
- l += [OptCheck('cut_attack_surface', 'lockdown', 'X86_IOPL_IOPERM', 'is not set')] # refers to LOCKDOWN
- l += [OptCheck('cut_attack_surface', 'lockdown', 'EFI_TEST', 'is not set')] # refers to LOCKDOWN
- l += [OptCheck('cut_attack_surface', 'lockdown', 'BPF_SYSCALL', 'is not set')] # refers to LOCKDOWN
- l += [OptCheck('cut_attack_surface', 'lockdown', 'MMIOTRACE_TEST', 'is not set')] # refers to LOCKDOWN
+ # 'cut_attack_surface', 'grapheneos'
+ l += [OptCheck('cut_attack_surface', 'grapheneos', 'AIO', 'is not set')]
# 'cut_attack_surface', 'clipos'
l += [OptCheck('cut_attack_surface', 'clipos', 'STAGING', 'is not set')]
l += [OptCheck('cut_attack_surface', 'clipos', 'USER_NS', 'is not set')] # user.max_user_namespaces=0
l += [OptCheck('cut_attack_surface', 'clipos', 'X86_MSR', 'is not set')] # refers to LOCKDOWN
l += [OptCheck('cut_attack_surface', 'clipos', 'X86_CPUID', 'is not set')]
+ l += [OptCheck('cut_attack_surface', 'clipos', 'IO_URING', 'is not set')]
+ l += [OptCheck('cut_attack_surface', 'clipos', 'X86_IOPL_IOPERM', 'is not set')] # refers to LOCKDOWN
+ l += [OptCheck('cut_attack_surface', 'clipos', 'ACPI_TABLE_UPGRADE', 'is not set')] # refers to LOCKDOWN
+ l += [OptCheck('cut_attack_surface', 'clipos', 'EFI_CUSTOM_SSDT_OVERLAYS', 'is not set')]
l += [AND(OptCheck('cut_attack_surface', 'clipos', 'LDISC_AUTOLOAD', 'is not set'),
PresenceCheck('LDISC_AUTOLOAD'))]
if arch in ('X86_64', 'X86_32'):
l += [OptCheck('cut_attack_surface', 'clipos', 'X86_INTEL_TSX_MODE_OFF', 'y')] # tsx=off
- # 'cut_attack_surface', 'grapheneos'
- l += [OptCheck('cut_attack_surface', 'grapheneos', 'AIO', 'is not set')]
+ # 'cut_attack_surface', 'lockdown'
+ l += [OptCheck('cut_attack_surface', 'lockdown', 'EFI_TEST', 'is not set')] # refers to LOCKDOWN
+ l += [OptCheck('cut_attack_surface', 'lockdown', 'BPF_SYSCALL', 'is not set')] # refers to LOCKDOWN
+ l += [OptCheck('cut_attack_surface', 'lockdown', 'MMIOTRACE_TEST', 'is not set')] # refers to LOCKDOWN
# 'cut_attack_surface', 'my'
+ l += [OptCheck('cut_attack_surface', 'my', 'TRIM_UNUSED_KSYMS', 'y')]
l += [OptCheck('cut_attack_surface', 'my', 'MMIOTRACE', 'is not set')] # refers to LOCKDOWN (permissive)
l += [OptCheck('cut_attack_surface', 'my', 'LIVEPATCH', 'is not set')]
l += [OptCheck('cut_attack_surface', 'my', 'IP_DCCP', 'is not set')]
l += [OptCheck('cut_attack_surface', 'my', 'IP_SCTP', 'is not set')]
l += [OptCheck('cut_attack_surface', 'my', 'FTRACE', 'is not set')] # refers to LOCKDOWN
- l += [OptCheck('cut_attack_surface', 'my', 'BPF_JIT', 'is not set')]
l += [OptCheck('cut_attack_surface', 'my', 'VIDEO_VIVID', 'is not set')]
l += [OptCheck('cut_attack_surface', 'my', 'INPUT_EVBUG', 'is not set')] # Can be used as a keylogger
l += [OptCheck('userspace_hardening', 'defconfig', 'INTEGRITY', 'y')]
if arch == 'ARM':
l += [OptCheck('userspace_hardening', 'my', 'INTEGRITY', 'y')]
+ if arch == 'ARM64':
+ l += [OptCheck('userspace_hardening', 'defconfig', 'ARM64_MTE', 'y')]
if arch in ('ARM', 'X86_32'):
l += [OptCheck('userspace_hardening', 'defconfig', 'VMSPLIT_3G', 'y')]
if arch in ('X86_64', 'ARM64'):
print('[+] Config check is finished: \'OK\' - {}{} / \'FAIL\' - {}{}'.format(ok_count, ok_suppressed, fail_count, fail_suppressed))
+def perform_check(opt, parsed_options, kernel_version):
+ if hasattr(opt, 'opts'):
+ # prepare ComplexOptCheck
+ for o in opt.opts:
+ if hasattr(o, 'opts'):
+ # Recursion for nested ComplexOptChecks
+ perform_check(o, parsed_options, kernel_version)
+ if hasattr(o, 'state'):
+ o.state = parsed_options.get(o.name, None)
+ if hasattr(o, 'ver'):
+ o.ver = kernel_version
+ else:
+ # prepare simple check, opt.state is mandatory
+ if not hasattr(opt, 'state'):
+ sys.exit('[!] ERROR: bad simple check {}'.format(vars(opt)))
+ opt.state = parsed_options.get(opt.name, None)
+ opt.check()
+
+
def perform_checks(checklist, parsed_options, kernel_version):
for opt in checklist:
- if hasattr(opt, 'opts'):
- # prepare ComplexOptCheck
- for o in opt.opts:
- if hasattr(o, 'state'):
- o.state = parsed_options.get(o.name, None)
- if hasattr(o, 'ver'):
- o.ver = kernel_version
- else:
- # prepare simple check
- if not hasattr(opt, 'state'):
- sys.exit('[!] ERROR: bad simple check {}'.format(vars(opt)))
- opt.state = parsed_options.get(opt.name, None)
- opt.check()
+ perform_check(opt, parsed_options, kernel_version)
def parse_config_file(parsed_options, fname):
report_modes = ['verbose', 'json', 'show_ok', 'show_fail']
supported_archs = ['X86_64', 'X86_32', 'ARM64', 'ARM']
parser = ArgumentParser(prog='kconfig-hardened-check',
- description='Checks the hardening options in the Linux kernel config')
+ description='A tool for checking the security hardening options of the Linux kernel')
parser.add_argument('--version', action='version', version='%(prog)s ' + __version__)
parser.add_argument('-p', '--print', choices=supported_archs,
- help='print hardening preferences for selected architecture')
+ help='print security hardening preferences for the selected architecture')
parser.add_argument('-c', '--config',
help='check the kernel config file against these preferences')
parser.add_argument('-m', '--mode', choices=report_modes,
arch = args.print
construct_checklist(config_checklist, arch)
if mode != 'json':
- print('[+] Printing kernel hardening preferences for {}...'.format(arch))
+ print('[+] Printing kernel security hardening preferences for {}...'.format(arch))
print_checklist(mode, config_checklist, False)
sys.exit(0)
projects / kconfig-hardened-check.git / blobdiff