Kconfig : Hardened-Check – A Tool For Checking The Hardening Options In The Linux Kernel Config

Kconfig is a tool For Checking The Hardening Options In The Linux Kernel Config

There are plenty of Linux kernel hardening config options. A lot of them are not enabled by the major distros. We have to enable these options ourselves to make our systems more secure.

But nobody likes checking configs manually. So let the computers do their job!

kconfig-hardened-check.py helps me to check the Linux kernel Kconfig option list against my hardening preferences, which are based on the

• KSPP recommended settings,
• CLIP OS kernel configuration,
• last public grsecurity patch (options which they disable),
• SECURITY_LOCKDOWN_LSM patchset,
• direct feedback from Linux kernel maintainers (Daniel Vetter in issue #38).

I also created Linux Kernel Defence Map that is a graphical representation of the relationships between these hardening features and the corresponding vulnerability classes or exploitation techniques.

Supported Microarchitectures

• X86_64
• X86_32
• ARM64
• ARM

Installation

You can install the package:

pip install git+https://github.com/a13xp0p0v/kconfig-hardened-check

or simply run ./bin/kconfig-hardened-check from the cloned repository.

Usage

usage: kconfig-hardened-check [-h] [–version] [-p {X86_64,X86_32,ARM64,ARM}]
[-c CONFIG]
[-m {verbose,json,show_ok,show_fail}]
Checks the hardening options in the Linux kernel config
optional arguments:
-h, –help show this help message and exit
–version show program’s version number and exit
-p {X86_64,X86_32,ARM64,ARM}, –print {X86_64,X86_32,ARM64,ARM}
print hardening preferences for selected architecture
-c CONFIG, –config CONFIG
check the kernel config file against these preferences
-m {verbose,json,show_ok,show_fail}, –mode {verbose,json,show_ok,show_fail}
choose the report mode

Output for Ubuntu 20.04 LTS (Focal Fossa) kernel config

$ ./bin/kconfig-hardened-check -c kconfig_hardened_check/config_files/distros/ubuntu-focal.config
[+] Config file to check: kconfig_hardened_check/config_files/distros/ubuntu-focal.config
[+] Detected architecture: X86_64
[+] Detected kernel version: 5.4
option name | desired val | decision | reason | check resultCONFIG_BUG | y |defconfig | self_protection | OK
CONFIG_SLUB_DEBUG | y |defconfig | self_protection | OK
CONFIG_GCC_PLUGINS | y |defconfig | self_protection | FAIL: not found
CONFIG_STACKPROTECTOR_STRONG | y |defconfig | self_protection | OK
CONFIG_STRICT_KERNEL_RWX | y |defconfig | self_protection | OK
CONFIG_STRICT_MODULE_RWX | y |defconfig | self_protection | OK
CONFIG_REFCOUNT_FULL | y |defconfig | self_protection | FAIL: “is not set”
CONFIG_IOMMU_SUPPORT | y |defconfig | self_protection | OK
CONFIG_RANDOMIZE_BASE | y |defconfig | self_protection | OK
CONFIG_THREAD_INFO_IN_TASK | y |defconfig | self_protection | OK
CONFIG_VMAP_STACK | y |defconfig | self_protection | OK
CONFIG_MICROCODE | y |defconfig | self_protection | OK
CONFIG_RETPOLINE | y |defconfig | self_protection | OK
CONFIG_X86_SMAP | y |defconfig | self_protection | OK
CONFIG_SYN_COOKIES | y |defconfig | self_protection | OK
CONFIG_X86_UMIP | y |defconfig | self_protection | OK: CONFIG_X86_INTEL_UMIP “y”
CONFIG_PAGE_TABLE_ISOLATION | y |defconfig | self_protection | OK
CONFIG_RANDOMIZE_MEMORY | y |defconfig | self_protection | OK
CONFIG_INTEL_IOMMU | y |defconfig | self_protection | OK
CONFIG_AMD_IOMMU | y |defconfig | self_protection | OK
CONFIG_SECURITY_DMESG_RESTRICT | y | kspp | self_protection | FAIL: “is not set”
CONFIG_BUG_ON_DATA_CORRUPTION | y | kspp | self_protection | FAIL: “is not set”
CONFIG_DEBUG_WX | y | kspp | self_protection | OK
CONFIG_SCHED_STACK_END_CHECK | y | kspp | self_protection | OK
CONFIG_SLAB_FREELIST_HARDENED | y | kspp | self_protection | OK
CONFIG_SLAB_FREELIST_RANDOM | y | kspp | self_protection | OK
CONFIG_SHUFFLE_PAGE_ALLOCATOR | y | kspp | self_protection | OK
CONFIG_FORTIFY_SOURCE | y | kspp | self_protection | OK
CONFIG_DEBUG_LIST | y | kspp | self_protection | FAIL: “is not set”
CONFIG_DEBUG_SG | y | kspp | self_protection | FAIL: “is not set”
CONFIG_DEBUG_CREDENTIALS | y | kspp | self_protection | FAIL: “is not set”
CONFIG_DEBUG_NOTIFIERS | y | kspp | self_protection | FAIL: “is not set”
CONFIG_INIT_ON_ALLOC_DEFAULT_ON | y | kspp | self_protection | OK
CONFIG_GCC_PLUGIN_LATENT_ENTROPY | y | kspp | self_protection | FAIL: not found
CONFIG_GCC_PLUGIN_RANDSTRUCT | y | kspp | self_protection | FAIL: not found
CONFIG_HARDENED_USERCOPY | y | kspp | self_protection | OK
CONFIG_HARDENED_USERCOPY_FALLBACK | is not set | kspp | self_protection | FAIL: “y”
CONFIG_MODULE_SIG | y | kspp | self_protection | OK
CONFIG_MODULE_SIG_ALL | y | kspp | self_protection | OK
CONFIG_MODULE_SIG_SHA512 | y | kspp | self_protection | OK
CONFIG_MODULE_SIG_FORCE | y | kspp | self_protection | FAIL: “is not set”
CONFIG_INIT_STACK_ALL_ZERO | y | kspp | self_protection | FAIL: not found
CONFIG_INIT_ON_FREE_DEFAULT_ON | y | kspp | self_protection | OK: CONFIG_PAGE_POISONING_ZERO “y”
CONFIG_GCC_PLUGIN_STACKLEAK | y | kspp | self_protection | FAIL: not found
CONFIG_DEFAULT_MMAP_MIN_ADDR | 65536 | kspp | self_protection | OK
CONFIG_DEBUG_VIRTUAL | y | clipos | self_protection | FAIL: “is not set”
CONFIG_STATIC_USERMODEHELPER | y | clipos | self_protection | FAIL: “is not set”
CONFIG_EFI_DISABLE_PCI_DMA | y | clipos | self_protection | FAIL: not found
CONFIG_SLAB_MERGE_DEFAULT | is not set | clipos | self_protection | FAIL: “y”
CONFIG_RANDOM_TRUST_BOOTLOADER | is not set | clipos | self_protection | FAIL: “y”
CONFIG_RANDOM_TRUST_CPU | is not set | clipos | self_protection | FAIL: “y”
CONFIG_GCC_PLUGIN_RANDSTRUCT_PERFORMANCE | is not set | clipos | self_protection | FAIL: CONFIG_GCC_PLUGIN_RANDSTRUCT not “y”
CONFIG_STACKLEAK_METRICS | is not set | clipos | self_protection | FAIL: CONFIG_GCC_PLUGIN_STACKLEAK not “y”
CONFIG_STACKLEAK_RUNTIME_DISABLE | is not set | clipos | self_protection | FAIL: CONFIG_GCC_PLUGIN_STACKLEAK not “y”
CONFIG_INTEL_IOMMU_DEFAULT_ON | y | clipos | self_protection | FAIL: “is not set”
CONFIG_INTEL_IOMMU_SVM | y | clipos | self_protection | OK
CONFIG_UBSAN_BOUNDS | y | my | self_protection | FAIL: CONFIG_UBSAN_TRAP not “y”
CONFIG_RESET_ATTACK_MITIGATION | y | my | self_protection | OK
CONFIG_AMD_IOMMU_V2 | y | my | self_protection | FAIL: “m”
CONFIG_SECURITY | y |defconfig | security_policy | OK
CONFIG_SECURITY_YAMA | y | kspp | security_policy | OK
CONFIG_SECURITY_WRITABLE_HOOKS | is not set | my | security_policy | OK: not found
CONFIG_SECURITY_LOCKDOWN_LSM | y | clipos | security_policy | OK
CONFIG_SECURITY_LOCKDOWN_LSM_EARLY | y | clipos | security_policy | OK
CONFIG_LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY| y | clipos | security_policy | FAIL: “is not set”
CONFIG_SECURITY_SAFESETID | y | my | security_policy | OK
CONFIG_SECURITY_LOADPIN | y | my | security_policy | FAIL: “is not set”
CONFIG_SECURITY_LOADPIN_ENFORCE | y | my | security_policy | FAIL: CONFIG_SECURITY_LOADPIN not “y”
CONFIG_SECCOMP | y |defconfig | cut_attack_surface | OK
CONFIG_SECCOMP_FILTER | y |defconfig | cut_attack_surface | OK
CONFIG_STRICT_DEVMEM | y |defconfig | cut_attack_surface | OK
CONFIG_ACPI_CUSTOM_METHOD | is not set | kspp | cut_attack_surface | OK
CONFIG_COMPAT_BRK | is not set | kspp | cut_attack_surface | OK
CONFIG_DEVKMEM | is not set | kspp | cut_attack_surface | OK
CONFIG_COMPAT_VDSO | is not set | kspp | cut_attack_surface | OK
CONFIG_BINFMT_MISC | is not set | kspp | cut_attack_surface | FAIL: “m”
CONFIG_INET_DIAG | is not set | kspp | cut_attack_surface | FAIL: “m”
CONFIG_KEXEC | is not set | kspp | cut_attack_surface | FAIL: “y”
CONFIG_PROC_KCORE | is not set | kspp | cut_attack_surface | FAIL: “y”
CONFIG_LEGACY_PTYS | is not set | kspp | cut_attack_surface | FAIL: “y”
CONFIG_HIBERNATION | is not set | kspp | cut_attack_surface | FAIL: “y”
CONFIG_IA32_EMULATION | is not set | kspp | cut_attack_surface | FAIL: “y”
CONFIG_X86_X32 | is not set | kspp | cut_attack_surface | FAIL: “y”
CONFIG_MODIFY_LDT_SYSCALL | is not set | kspp | cut_attack_surface | FAIL: “y”
CONFIG_OABI_COMPAT | is not set | kspp | cut_attack_surface | OK: not found
CONFIG_MODULES | is not set | kspp | cut_attack_surface | FAIL: “y”
CONFIG_DEVMEM | is not set | kspp | cut_attack_surface | FAIL: “y”
CONFIG_IO_STRICT_DEVMEM | y | kspp | cut_attack_surface | FAIL: “is not set”
CONFIG_LEGACY_VSYSCALL_NONE | y | kspp | cut_attack_surface | FAIL: “is not set”
CONFIG_ZSMALLOC_STAT | is not set |grsecurity| cut_attack_surface | OK
CONFIG_PAGE_OWNER | is not set |grsecurity| cut_attack_surface | OK
CONFIG_DEBUG_KMEMLEAK | is not set |grsecurity| cut_attack_surface | OK
CONFIG_BINFMT_AOUT | is not set |grsecurity| cut_attack_surface | OK: not found
CONFIG_KPROBES | is not set |grsecurity| cut_attack_surface | FAIL: “y”
CONFIG_UPROBES | is not set |grsecurity| cut_attack_surface | FAIL: “y”
CONFIG_GENERIC_TRACER | is not set |grsecurity| cut_attack_surface | FAIL: “y”
CONFIG_PROC_VMCORE | is not set |grsecurity| cut_attack_surface | FAIL: “y”
CONFIG_PROC_PAGE_MONITOR | is not set |grsecurity| cut_attack_surface | FAIL: “y”
CONFIG_USELIB | is not set |grsecurity| cut_attack_surface | FAIL: “y”
CONFIG_CHECKPOINT_RESTORE | is not set |grsecurity| cut_attack_surface | FAIL: “y”
CONFIG_USERFAULTFD | is not set |grsecurity| cut_attack_surface | FAIL: “y”
CONFIG_HWPOISON_INJECT | is not set |grsecurity| cut_attack_surface | FAIL: “m”
CONFIG_MEM_SOFT_DIRTY | is not set |grsecurity| cut_attack_surface | FAIL: “y”
CONFIG_DEVPORT | is not set |grsecurity| cut_attack_surface | FAIL: “y”
CONFIG_DEBUG_FS | is not set |grsecurity| cut_attack_surface | FAIL: “y”
CONFIG_NOTIFIER_ERROR_INJECTION | is not set |grsecurity| cut_attack_surface | FAIL: “m”
CONFIG_X86_PTDUMP | is not set |grsecurity| cut_attack_surface | OK
CONFIG_DRM_LEGACY | is not set |maintainer| cut_attack_surface | OK
CONFIG_FB | is not set |maintainer| cut_attack_surface | FAIL: “y”
CONFIG_VT | is not set |maintainer| cut_attack_surface | FAIL: “y”
CONFIG_AIO | is not set |grapheneos| cut_attack_surface | FAIL: “y”
CONFIG_STAGING | is not set | clipos | cut_attack_surface | FAIL: “y”
CONFIG_KSM | is not set | clipos | cut_attack_surface | FAIL: “y”
CONFIG_KALLSYMS | is not set | clipos | cut_attack_surface | FAIL: “y”
CONFIG_X86_VSYSCALL_EMULATION | is not set | clipos | cut_attack_surface | FAIL: “y”
CONFIG_MAGIC_SYSRQ | is not set | clipos | cut_attack_surface | FAIL: “y”
CONFIG_KEXEC_FILE | is not set | clipos | cut_attack_surface | FAIL: “y”
CONFIG_USER_NS | is not set | clipos | cut_attack_surface | FAIL: “y”
CONFIG_X86_MSR | is not set | clipos | cut_attack_surface | FAIL: “m”
CONFIG_X86_CPUID | is not set | clipos | cut_attack_surface | FAIL: “m”
CONFIG_IO_URING | is not set | clipos | cut_attack_surface | FAIL: “y”
CONFIG_X86_IOPL_IOPERM | is not set | clipos | cut_attack_surface | OK: not found
CONFIG_ACPI_TABLE_UPGRADE | is not set | clipos | cut_attack_surface | FAIL: “y”
CONFIG_EFI_CUSTOM_SSDT_OVERLAYS | is not set | clipos | cut_attack_surface | OK: not found
CONFIG_LDISC_AUTOLOAD | is not set | clipos | cut_attack_surface | FAIL: “y”
CONFIG_X86_INTEL_TSX_MODE_OFF | y | clipos | cut_attack_surface | OK
CONFIG_EFI_TEST | is not set | lockdown | cut_attack_surface | FAIL: “m”
CONFIG_BPF_SYSCALL | is not set | lockdown | cut_attack_surface | FAIL: “y”
CONFIG_MMIOTRACE_TEST | is not set | lockdown | cut_attack_surface | OK
CONFIG_TRIM_UNUSED_KSYMS | y | my | cut_attack_surface | FAIL: not found
CONFIG_MMIOTRACE | is not set | my | cut_attack_surface | FAIL: “y”
CONFIG_LIVEPATCH | is not set | my | cut_attack_surface | FAIL: “y”
CONFIG_IP_DCCP | is not set | my | cut_attack_surface | FAIL: “m”
CONFIG_IP_SCTP | is not set | my | cut_attack_surface | FAIL: “m”
CONFIG_FTRACE | is not set | my | cut_attack_surface | FAIL: “y”
CONFIG_VIDEO_VIVID | is not set | my | cut_attack_surface | FAIL: “m”
CONFIG_INPUT_EVBUG | is not set | my | cut_attack_surface | FAIL: “m”
CONFIG_INTEGRITY | y |defconfig |userspace_hardening | OK
CONFIG_ARCH_MMAP_RND_BITS | 32 | clipos |userspace_hardening | FAIL: “28”
[+] Config check is finished: ‘OK’ – 58 / ‘FAIL’ – 81

kconfig-hardened-check versioning

I usually update the kernel hardening recommendations after each Linux kernel release.

So the version of kconfig-hardened-check is associated with the corresponding version of the kernel.

The version format is: [major_number].[kernel_version].[kernel_patchlevel]