(formerly kconfig-hardened-check)
There are plenty of security hardening options for the Linux kernel. 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!
kernel-hardening-checker (formerly kconfig-hardened-check) is a tool for checking the security hardening options of the Linux kernel.
License: GPL-3.0.
- At GitHub https://github.com/a13xp0p0v/kernel-hardening-checker
- At Codeberg: https://codeberg.org/a13xp0p0v/kernel-hardening-checker (go there if something goes wrong with GitHub)
- At GitFlic: https://gitflic.ru/project/a13xp0p0v/kernel-hardening-checker
kernel-hardening-checker supports checking:
- Kconfig options (compile-time)
- Kernel cmdline arguments (boot-time)
- Sysctl parameters (runtime)
Supported microarchitectures:
- X86_64
- X86_32
- ARM64
- ARM
The security hardening recommendations are based on:
- KSPP recommended settings
- Direct feedback from the Linux kernel maintainers
- Kernel options disabled by grsecurity to cut attack surface
- CLIP OS kernel configuration
- GrapheneOS recommendations
- SECURITY_LOCKDOWN_LSM patchset
I also created the Linux Kernel Defence Map, which is a graphical representation of the relationships between security hardening features and the corresponding vulnerability classes or exploitation techniques.
Changing Linux kernel security parameters may also affect system performance and functionality of userspace software. So for choosing these parameters, consider the threat model of your Linux-based information system and perform thorough testing of its typical workload.
You can install the package:
pip install git+https://github.com/a13xp0p0v/kernel-hardening-checker
or simply run ./bin/kernel-hardening-checker from the cloned repository.
Some Linux distributions also provide kernel-hardening-checker as a package.
usage: kernel-hardening-checker [-h] [--version] [-m {verbose,json,show_ok,show_fail}]
[-c CONFIG] [-l CMDLINE] [-s SYSCTL] [-v KERNEL_VERSION]
[-p {X86_64,X86_32,ARM64,ARM}]
[-g {X86_64,X86_32,ARM64,ARM}]
A tool for checking the security hardening options of the Linux kernel
options:
-h, --help show this help message and exit
--version show program's version number and exit
-m {verbose,json,show_ok,show_fail}, --mode {verbose,json,show_ok,show_fail}
choose the report mode
-c CONFIG, --config CONFIG
check the security hardening options in the kernel Kconfig file
(also supports *.gz files)
-l CMDLINE, --cmdline CMDLINE
check the security hardening options in the kernel cmdline file
(contents of /proc/cmdline)
-s SYSCTL, --sysctl SYSCTL
check the security hardening options in the sysctl output file
(`sudo sysctl -a > file`)
-v KERNEL_VERSION, --kernel-version KERNEL_VERSION
extract the version from the kernel version file (contents of
/proc/version)
-p {X86_64,X86_32,ARM64,ARM}, --print {X86_64,X86_32,ARM64,ARM}
print the security hardening recommendations for the selected
microarchitecture
-g {X86_64,X86_32,ARM64,ARM}, --generate {X86_64,X86_32,ARM64,ARM}
generate a Kconfig fragment with the security hardening options
for the selected microarchitecture
- no
-margument for the default output mode (see the example below) -m verbosefor printing additional info:- config options without a corresponding check
- internals of complex checks with AND/OR, like this:
-------------------------------------------------------------------------------------------
<<< OR >>>
CONFIG_STRICT_DEVMEM |kconfig| y |defconfig |cut_attack_surface
CONFIG_DEVMEM |kconfig| is not set | kspp |cut_attack_surface
-------------------------------------------------------------------------------------------
-m show_failfor showing only the failed checks-m show_okfor showing only the successful checks-m jsonfor printing the results in JSON format (for combiningkernel-hardening-checkerwith other tools)
$ ./bin/kernel-hardening-checker -c kernel_hardening_checker/config_files/distros/ubuntu-22.04.config -l /proc/cmdline -s kernel_hardening_checker/config_files/distros/example_sysctls.txt
[+] Kconfig file to check: kernel_hardening_checker/config_files/distros/ubuntu-22.04.config
[+] Kernel cmdline file to check: /proc/cmdline
[+] Sysctl output file to check: kernel_hardening_checker/config_files/distros/example_sysctls.txt
[+] Detected microarchitecture: X86_64
[+] Detected kernel version: (5, 15, 0)
[+] Detected compiler: GCC 110200
=========================================================================================================================
option_name | type |desired_val | decision | reason | check_result
=========================================================================================================================
CONFIG_BUG |kconfig| y |defconfig | self_protection | OK
CONFIG_SLUB_DEBUG |kconfig| y |defconfig | self_protection | OK
CONFIG_THREAD_INFO_IN_TASK |kconfig| y |defconfig | self_protection | OK
CONFIG_IOMMU_SUPPORT |kconfig| y |defconfig | self_protection | OK
CONFIG_STACKPROTECTOR |kconfig| y |defconfig | self_protection | OK
CONFIG_STACKPROTECTOR_STRONG |kconfig| y |defconfig | self_protection | OK
CONFIG_STRICT_KERNEL_RWX |kconfig| y |defconfig | self_protection | OK
CONFIG_STRICT_MODULE_RWX |kconfig| y |defconfig | self_protection | OK
CONFIG_REFCOUNT_FULL |kconfig| y |defconfig | self_protection | OK: version >= (5, 4, 208)
CONFIG_INIT_STACK_ALL_ZERO |kconfig| y |defconfig | self_protection | FAIL: is not found
CONFIG_CPU_MITIGATIONS |kconfig| y |defconfig | self_protection | FAIL: is not found
CONFIG_RANDOMIZE_BASE |kconfig| y |defconfig | self_protection | OK
CONFIG_VMAP_STACK |kconfig| y |defconfig | self_protection | OK
CONFIG_DEBUG_WX |kconfig| y |defconfig | self_protection | OK
CONFIG_WERROR |kconfig| y |defconfig | self_protection | FAIL: "is not set"
CONFIG_X86_MCE |kconfig| y |defconfig | self_protection | OK
CONFIG_SYN_COOKIES |kconfig| y |defconfig | self_protection | OK
CONFIG_MICROCODE |kconfig| y |defconfig | self_protection | OK
CONFIG_MICROCODE_INTEL |kconfig| y |defconfig | self_protection | OK
CONFIG_MICROCODE_AMD |kconfig| y |defconfig | self_protection | OK
CONFIG_X86_SMAP |kconfig| y |defconfig | self_protection | OK
CONFIG_X86_UMIP |kconfig| y |defconfig | self_protection | OK
CONFIG_X86_MCE_INTEL |kconfig| y |defconfig | self_protection | OK
CONFIG_X86_MCE_AMD |kconfig| y |defconfig | self_protection | OK
CONFIG_MITIGATION_RETPOLINE |kconfig| y |defconfig | self_protection | OK: CONFIG_RETPOLINE is "y"
CONFIG_MITIGATION_RFDS |kconfig| y |defconfig | self_protection | FAIL: is not found
CONFIG_MITIGATION_SPECTRE_BHI |kconfig| y |defconfig | self_protection | FAIL: is not found
CONFIG_RANDOMIZE_MEMORY |kconfig| y |defconfig | self_protection | OK
CONFIG_X86_KERNEL_IBT |kconfig| y |defconfig | self_protection | FAIL: is not found
CONFIG_MITIGATION_PAGE_TABLE_ISOLATION |kconfig| y |defconfig | self_protection | OK: CONFIG_PAGE_TABLE_ISOLATION is "y"
CONFIG_MITIGATION_SRSO |kconfig| y |defconfig | self_protection | FAIL: is not found
CONFIG_INTEL_IOMMU |kconfig| y |defconfig | self_protection | OK
CONFIG_AMD_IOMMU |kconfig| y |defconfig | self_protection | OK
CONFIG_LIST_HARDENED |kconfig| y | kspp | self_protection | FAIL: is not found
CONFIG_RANDOM_KMALLOC_CACHES |kconfig| y | kspp | self_protection | FAIL: is not found
CONFIG_SLAB_MERGE_DEFAULT |kconfig| is not set | kspp | self_protection | FAIL: "y"
CONFIG_BUG_ON_DATA_CORRUPTION |kconfig| y | kspp | self_protection | FAIL: "is not set"
CONFIG_SLAB_FREELIST_HARDENED |kconfig| y | kspp | self_protection | OK
CONFIG_SLAB_FREELIST_RANDOM |kconfig| y | kspp | self_protection | OK
CONFIG_SHUFFLE_PAGE_ALLOCATOR |kconfig| y | kspp | self_protection | OK
CONFIG_FORTIFY_SOURCE |kconfig| y | kspp | self_protection | OK
CONFIG_DEBUG_LIST |kconfig| y | kspp | self_protection | FAIL: "is not set"
CONFIG_DEBUG_VIRTUAL |kconfig| y | kspp | self_protection | FAIL: "is not set"
CONFIG_DEBUG_SG |kconfig| y | kspp | self_protection | FAIL: "is not set"
CONFIG_INIT_ON_ALLOC_DEFAULT_ON |kconfig| y | kspp | self_protection | OK
CONFIG_STATIC_USERMODEHELPER |kconfig| y | kspp | self_protection | FAIL: "is not set"
CONFIG_SCHED_CORE |kconfig| y | kspp | self_protection | OK
CONFIG_SECURITY_LOCKDOWN_LSM |kconfig| y | kspp | self_protection | OK
CONFIG_SECURITY_LOCKDOWN_LSM_EARLY |kconfig| y | kspp | self_protection | OK
CONFIG_LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY|kconfig| y | kspp | self_protection | FAIL: "is not set"
CONFIG_DEBUG_CREDENTIALS |kconfig| y | kspp | self_protection | FAIL: "is not set"
CONFIG_DEBUG_NOTIFIERS |kconfig| y | kspp | self_protection | FAIL: "is not set"
CONFIG_SCHED_STACK_END_CHECK |kconfig| y | kspp | self_protection | OK
CONFIG_KFENCE |kconfig| y | kspp | self_protection | OK
CONFIG_KFENCE_SAMPLE_INTERVAL |kconfig| 100 | kspp | self_protection | FAIL: "0"
CONFIG_RANDSTRUCT_FULL |kconfig| y | kspp | self_protection | FAIL: is not found
CONFIG_HARDENED_USERCOPY |kconfig| y | kspp | self_protection | OK
CONFIG_HARDENED_USERCOPY_FALLBACK |kconfig| is not set | kspp | self_protection | OK
CONFIG_HARDENED_USERCOPY_PAGESPAN |kconfig| is not set | kspp | self_protection | OK
CONFIG_GCC_PLUGIN_LATENT_ENTROPY |kconfig| y | kspp | self_protection | FAIL: is not found
CONFIG_MODULE_SIG |kconfig| y | kspp | self_protection | OK
CONFIG_MODULE_SIG_ALL |kconfig| y | kspp | self_protection | OK
CONFIG_MODULE_SIG_SHA512 |kconfig| y | kspp | self_protection | OK
CONFIG_MODULE_SIG_FORCE |kconfig| y | kspp | self_protection | FAIL: "is not set"
CONFIG_INIT_ON_FREE_DEFAULT_ON |kconfig| y | kspp | self_protection | FAIL: "is not set"
CONFIG_EFI_DISABLE_PCI_DMA |kconfig| y | kspp | self_protection | FAIL: "is not set"
CONFIG_RESET_ATTACK_MITIGATION |kconfig| y | kspp | self_protection | OK
CONFIG_UBSAN_BOUNDS |kconfig| y | kspp | self_protection | OK
CONFIG_UBSAN_LOCAL_BOUNDS |kconfig| y | kspp | self_protection | OK: CONFIG_UBSAN_BOUNDS is "y"
CONFIG_UBSAN_TRAP |kconfig| y | kspp | self_protection | FAIL: CONFIG_UBSAN_ENUM is not "is not set"
CONFIG_UBSAN_SANITIZE_ALL |kconfig| y | kspp | self_protection | OK
CONFIG_GCC_PLUGIN_STACKLEAK |kconfig| y | kspp | self_protection | FAIL: is not found
CONFIG_STACKLEAK_METRICS |kconfig| is not set | kspp | self_protection | FAIL: CONFIG_GCC_PLUGIN_STACKLEAK is not "y"
CONFIG_STACKLEAK_RUNTIME_DISABLE |kconfig| is not set | kspp | self_protection | FAIL: CONFIG_GCC_PLUGIN_STACKLEAK is not "y"
CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT |kconfig| y | kspp | self_protection | OK
CONFIG_PAGE_TABLE_CHECK |kconfig| y | kspp | self_protection | FAIL: is not found
CONFIG_PAGE_TABLE_CHECK_ENFORCED |kconfig| y | kspp | self_protection | FAIL: is not found
CONFIG_CFI_CLANG |kconfig| y | kspp | self_protection | FAIL: CONFIG_CC_IS_CLANG is not "y"
CONFIG_CFI_PERMISSIVE |kconfig| is not set | kspp | self_protection | FAIL: CONFIG_CC_IS_CLANG is not "y"
CONFIG_HW_RANDOM_TPM |kconfig| y | kspp | self_protection | OK
CONFIG_DEFAULT_MMAP_MIN_ADDR |kconfig| 65536 | kspp | self_protection | OK
CONFIG_IOMMU_DEFAULT_DMA_STRICT |kconfig| y | kspp | self_protection | FAIL: "is not set"
CONFIG_IOMMU_DEFAULT_PASSTHROUGH |kconfig| is not set | kspp | self_protection | OK
CONFIG_INTEL_IOMMU_DEFAULT_ON |kconfig| y | kspp | self_protection | OK
CONFIG_MITIGATION_SLS |kconfig| y | kspp | self_protection | FAIL: is not found
CONFIG_INTEL_IOMMU_SVM |kconfig| y | kspp | self_protection | OK
CONFIG_AMD_IOMMU_V2 |kconfig| y | kspp | self_protection | FAIL: "m"
CONFIG_SECURITY |kconfig| y |defconfig | security_policy | OK
CONFIG_SECURITY_YAMA |kconfig| y | kspp | security_policy | OK
CONFIG_SECURITY_LANDLOCK |kconfig| y | kspp | security_policy | OK
CONFIG_SECURITY_SELINUX_DISABLE |kconfig| is not set | kspp | security_policy | OK
CONFIG_SECURITY_SELINUX_BOOTPARAM |kconfig| is not set | kspp | security_policy | FAIL: "y"
CONFIG_SECURITY_SELINUX_DEVELOP |kconfig| is not set | kspp | security_policy | FAIL: "y"
CONFIG_SECURITY_WRITABLE_HOOKS |kconfig| is not set | kspp | security_policy | OK: is not found
CONFIG_SECURITY_SELINUX_DEBUG |kconfig| is not set | kspp | security_policy | OK: is not found
CONFIG_SECURITY_SELINUX |kconfig| y |a13xp0p0v | security_policy | OK
CONFIG_SECCOMP |kconfig| y |defconfig |cut_attack_surface| OK
CONFIG_SECCOMP_FILTER |kconfig| y |defconfig |cut_attack_surface| OK
CONFIG_BPF_UNPRIV_DEFAULT_OFF |kconfig| y |defconfig |cut_attack_surface| OK
CONFIG_STRICT_DEVMEM |kconfig| y |defconfig |cut_attack_surface| OK
CONFIG_X86_INTEL_TSX_MODE_OFF |kconfig| y |defconfig |cut_attack_surface| OK
CONFIG_SECURITY_DMESG_RESTRICT |kconfig| y | kspp |cut_attack_surface| OK
CONFIG_ACPI_CUSTOM_METHOD |kconfig| is not set | kspp |cut_attack_surface| OK
CONFIG_COMPAT_BRK |kconfig| is not set | kspp |cut_attack_surface| OK
CONFIG_DEVKMEM |kconfig| is not set | kspp |cut_attack_surface| OK: is not found
CONFIG_BINFMT_MISC |kconfig| is not set | kspp |cut_attack_surface| FAIL: "m"
CONFIG_INET_DIAG |kconfig| is not set | kspp |cut_attack_surface| FAIL: "m"
CONFIG_KEXEC |kconfig| is not set | kspp |cut_attack_surface| FAIL: "y"
CONFIG_PROC_KCORE |kconfig| is not set | kspp |cut_attack_surface| FAIL: "y"
CONFIG_LEGACY_PTYS |kconfig| is not set | kspp |cut_attack_surface| FAIL: "y"
CONFIG_HIBERNATION |kconfig| is not set | kspp |cut_attack_surface| FAIL: "y"
CONFIG_COMPAT |kconfig| is not set | kspp |cut_attack_surface| FAIL: "y"
CONFIG_IA32_EMULATION |kconfig| is not set | kspp |cut_attack_surface| FAIL: "y"
CONFIG_X86_X32 |kconfig| is not set | kspp |cut_attack_surface| FAIL: "y"
CONFIG_X86_X32_ABI |kconfig| is not set | kspp |cut_attack_surface| OK: is not found
CONFIG_MODIFY_LDT_SYSCALL |kconfig| is not set | kspp |cut_attack_surface| FAIL: "y"
CONFIG_OABI_COMPAT |kconfig| is not set | kspp |cut_attack_surface| OK: is not found
CONFIG_X86_MSR |kconfig| is not set | kspp |cut_attack_surface| FAIL: "m"
CONFIG_LEGACY_TIOCSTI |kconfig| is not set | kspp |cut_attack_surface| OK: is not found
CONFIG_MODULE_FORCE_LOAD |kconfig| is not set | kspp |cut_attack_surface| OK
CONFIG_MODULES |kconfig| is not set | kspp |cut_attack_surface| FAIL: "y"
CONFIG_DEVMEM |kconfig| is not set | kspp |cut_attack_surface| FAIL: "y"
CONFIG_IO_STRICT_DEVMEM |kconfig| y | kspp |cut_attack_surface| FAIL: "is not set"
CONFIG_LDISC_AUTOLOAD |kconfig| is not set | kspp |cut_attack_surface| FAIL: "y"
CONFIG_X86_VSYSCALL_EMULATION |kconfig| is not set | kspp |cut_attack_surface| FAIL: "y"
CONFIG_COMPAT_VDSO |kconfig| is not set | kspp |cut_attack_surface| OK
CONFIG_DRM_LEGACY |kconfig| is not set |maintainer|cut_attack_surface| OK
CONFIG_FB |kconfig| is not set |maintainer|cut_attack_surface| FAIL: "y"
CONFIG_VT |kconfig| is not set |maintainer|cut_attack_surface| FAIL: "y"
CONFIG_BLK_DEV_FD |kconfig| is not set |maintainer|cut_attack_surface| FAIL: "m"
CONFIG_BLK_DEV_FD_RAWCMD |kconfig| is not set |maintainer|cut_attack_surface| OK: is not found
CONFIG_NOUVEAU_LEGACY_CTX_SUPPORT |kconfig| is not set |maintainer|cut_attack_surface| OK
CONFIG_N_GSM |kconfig| is not set |maintainer|cut_attack_surface| FAIL: "m"
CONFIG_ZSMALLOC_STAT |kconfig| is not set | grsec |cut_attack_surface| OK
CONFIG_DEBUG_KMEMLEAK |kconfig| is not set | grsec |cut_attack_surface| OK
CONFIG_BINFMT_AOUT |kconfig| is not set | grsec |cut_attack_surface| OK: is not found
CONFIG_KPROBE_EVENTS |kconfig| is not set | grsec |cut_attack_surface| FAIL: "y"
CONFIG_UPROBE_EVENTS |kconfig| is not set | grsec |cut_attack_surface| FAIL: "y"
CONFIG_GENERIC_TRACER |kconfig| is not set | grsec |cut_attack_surface| FAIL: "y"
CONFIG_FUNCTION_TRACER |kconfig| is not set | grsec |cut_attack_surface| FAIL: "y"
CONFIG_STACK_TRACER |kconfig| is not set | grsec |cut_attack_surface| FAIL: "y"
CONFIG_HIST_TRIGGERS |kconfig| is not set | grsec |cut_attack_surface| FAIL: "y"
CONFIG_BLK_DEV_IO_TRACE |kconfig| is not set | grsec |cut_attack_surface| FAIL: "y"
CONFIG_PROC_VMCORE |kconfig| is not set | grsec |cut_attack_surface| FAIL: "y"
CONFIG_PROC_PAGE_MONITOR |kconfig| is not set | grsec |cut_attack_surface| FAIL: "y"
CONFIG_USELIB |kconfig| is not set | grsec |cut_attack_surface| FAIL: "y"
CONFIG_CHECKPOINT_RESTORE |kconfig| is not set | grsec |cut_attack_surface| FAIL: "y"
CONFIG_USERFAULTFD |kconfig| is not set | grsec |cut_attack_surface| FAIL: "y"
CONFIG_HWPOISON_INJECT |kconfig| is not set | grsec |cut_attack_surface| FAIL: "m"
CONFIG_MEM_SOFT_DIRTY |kconfig| is not set | grsec |cut_attack_surface| FAIL: "y"
CONFIG_DEVPORT |kconfig| is not set | grsec |cut_attack_surface| FAIL: "y"
CONFIG_DEBUG_FS |kconfig| is not set | grsec |cut_attack_surface| FAIL: "y"
CONFIG_NOTIFIER_ERROR_INJECTION |kconfig| is not set | grsec |cut_attack_surface| FAIL: "m"
CONFIG_FAIL_FUTEX |kconfig| is not set | grsec |cut_attack_surface| OK: is not found
CONFIG_PUNIT_ATOM_DEBUG |kconfig| is not set | grsec |cut_attack_surface| FAIL: "m"
CONFIG_ACPI_CONFIGFS |kconfig| is not set | grsec |cut_attack_surface| FAIL: "m"
CONFIG_EDAC_DEBUG |kconfig| is not set | grsec |cut_attack_surface| OK
CONFIG_DRM_I915_DEBUG |kconfig| is not set | grsec |cut_attack_surface| OK
CONFIG_DVB_C8SECTPFE |kconfig| is not set | grsec |cut_attack_surface| OK: is not found
CONFIG_MTD_SLRAM |kconfig| is not set | grsec |cut_attack_surface| FAIL: "m"
CONFIG_MTD_PHRAM |kconfig| is not set | grsec |cut_attack_surface| FAIL: "m"
CONFIG_IO_URING |kconfig| is not set | grsec |cut_attack_surface| FAIL: "y"
CONFIG_KCMP |kconfig| is not set | grsec |cut_attack_surface| FAIL: "y"
CONFIG_RSEQ |kconfig| is not set | grsec |cut_attack_surface| FAIL: "y"
CONFIG_LATENCYTOP |kconfig| is not set | grsec |cut_attack_surface| OK
CONFIG_KCOV |kconfig| is not set | grsec |cut_attack_surface| OK
CONFIG_PROVIDE_OHCI1394_DMA_INIT |kconfig| is not set | grsec |cut_attack_surface| OK
CONFIG_SUNRPC_DEBUG |kconfig| is not set | grsec |cut_attack_surface| FAIL: "y"
CONFIG_X86_16BIT |kconfig| is not set | grsec |cut_attack_surface| FAIL: "y"
CONFIG_BLK_DEV_UBLK |kconfig| is not set | grsec |cut_attack_surface| OK: is not found
CONFIG_SMB_SERVER |kconfig| is not set | grsec |cut_attack_surface| FAIL: "m"
CONFIG_XFS_ONLINE_SCRUB_STATS |kconfig| is not set | grsec |cut_attack_surface| OK: is not found
CONFIG_CACHESTAT_SYSCALL |kconfig| is not set | grsec |cut_attack_surface| OK: is not found
CONFIG_PREEMPTIRQ_TRACEPOINTS |kconfig| is not set | grsec |cut_attack_surface| OK: is not found
CONFIG_ENABLE_DEFAULT_TRACERS |kconfig| is not set | grsec |cut_attack_surface| OK: is not found
CONFIG_PROVE_LOCKING |kconfig| is not set | grsec |cut_attack_surface| OK
CONFIG_TEST_DEBUG_VIRTUAL |kconfig| is not set | grsec |cut_attack_surface| OK: is not found
CONFIG_MPTCP |kconfig| is not set | grsec |cut_attack_surface| FAIL: "y"
CONFIG_TLS |kconfig| is not set | grsec |cut_attack_surface| FAIL: "m"
CONFIG_TIPC |kconfig| is not set | grsec |cut_attack_surface| FAIL: "m"
CONFIG_IP_SCTP |kconfig| is not set | grsec |cut_attack_surface| FAIL: "m"
CONFIG_KGDB |kconfig| is not set | grsec |cut_attack_surface| FAIL: "y"
CONFIG_PTDUMP_DEBUGFS |kconfig| is not set | grsec |cut_attack_surface| OK
CONFIG_X86_PTDUMP |kconfig| is not set | grsec |cut_attack_surface| OK: is not found
CONFIG_DEBUG_CLOSURES |kconfig| is not set | grsec |cut_attack_surface| OK: is not found
CONFIG_BCACHE_CLOSURES_DEBUG |kconfig| is not set | grsec |cut_attack_surface| OK
CONFIG_STAGING |kconfig| is not set | clipos |cut_attack_surface| FAIL: "y"
CONFIG_KSM |kconfig| is not set | clipos |cut_attack_surface| FAIL: "y"
CONFIG_KALLSYMS |kconfig| is not set | clipos |cut_attack_surface| FAIL: "y"
CONFIG_KEXEC_FILE |kconfig| is not set | clipos |cut_attack_surface| FAIL: "y"
CONFIG_CRASH_DUMP |kconfig| is not set | clipos |cut_attack_surface| FAIL: "y"
CONFIG_USER_NS |kconfig| is not set | clipos |cut_attack_surface| FAIL: "y"
CONFIG_X86_CPUID |kconfig| is not set | clipos |cut_attack_surface| FAIL: "m"
CONFIG_X86_IOPL_IOPERM |kconfig| is not set | clipos |cut_attack_surface| FAIL: "y"
CONFIG_ACPI_TABLE_UPGRADE |kconfig| is not set | clipos |cut_attack_surface| FAIL: "y"
CONFIG_EFI_CUSTOM_SSDT_OVERLAYS |kconfig| is not set | clipos |cut_attack_surface| FAIL: "y"
CONFIG_AIO |kconfig| is not set | clipos |cut_attack_surface| FAIL: "y"
CONFIG_MAGIC_SYSRQ |kconfig| is not set | clipos |cut_attack_surface| FAIL: "y"
CONFIG_MAGIC_SYSRQ_SERIAL |kconfig| is not set |grapheneos|cut_attack_surface| FAIL: "y"
CONFIG_EFI_TEST |kconfig| is not set | lockdown |cut_attack_surface| FAIL: "m"
CONFIG_MMIOTRACE_TEST |kconfig| is not set | lockdown |cut_attack_surface| OK
CONFIG_KPROBES |kconfig| is not set | lockdown |cut_attack_surface| FAIL: "y"
CONFIG_BPF_SYSCALL |kconfig| is not set | lockdown |cut_attack_surface| FAIL: "y"
CONFIG_MMIOTRACE |kconfig| is not set |a13xp0p0v |cut_attack_surface| FAIL: "y"
CONFIG_LIVEPATCH |kconfig| is not set |a13xp0p0v |cut_attack_surface| FAIL: "y"
CONFIG_IP_DCCP |kconfig| is not set |a13xp0p0v |cut_attack_surface| FAIL: "m"
CONFIG_FTRACE |kconfig| is not set |a13xp0p0v |cut_attack_surface| FAIL: "y"
CONFIG_VIDEO_VIVID |kconfig| is not set |a13xp0p0v |cut_attack_surface| FAIL: "m"
CONFIG_INPUT_EVBUG |kconfig| is not set |a13xp0p0v |cut_attack_surface| FAIL: "m"
CONFIG_CORESIGHT |kconfig| is not set |a13xp0p0v |cut_attack_surface| OK: is not found
CONFIG_XFS_SUPPORT_V4 |kconfig| is not set |a13xp0p0v |cut_attack_surface| FAIL: "y"
CONFIG_BLK_DEV_WRITE_MOUNTED |kconfig| is not set |a13xp0p0v |cut_attack_surface| OK: is not found
CONFIG_FAULT_INJECTION |kconfig| is not set |a13xp0p0v |cut_attack_surface| OK
CONFIG_ARM_PTDUMP_DEBUGFS |kconfig| is not set |a13xp0p0v |cut_attack_surface| OK: is not found
CONFIG_ARM_PTDUMP |kconfig| is not set |a13xp0p0v |cut_attack_surface| OK: is not found
CONFIG_LKDTM |kconfig| is not set |a13xp0p0v |cut_attack_surface| OK
CONFIG_TRIM_UNUSED_KSYMS |kconfig| y |a13xp0p0v |cut_attack_surface| FAIL: "is not set"
CONFIG_COREDUMP |kconfig| is not set | clipos | harden_userspace | FAIL: "y"
CONFIG_ARCH_MMAP_RND_BITS |kconfig| 32 |a13xp0p0v | harden_userspace | FAIL: "28"
CONFIG_X86_USER_SHADOW_STACK |kconfig| y | kspp | harden_userspace | FAIL: is not found
nosmep |cmdline| is not set |defconfig | self_protection | OK: is not found
nosmap |cmdline| is not set |defconfig | self_protection | OK: is not found
nokaslr |cmdline| is not set |defconfig | self_protection | OK: is not found
nopti |cmdline| is not set |defconfig | self_protection | OK: is not found
nospectre_v1 |cmdline| is not set |defconfig | self_protection | OK: is not found
nospectre_v2 |cmdline| is not set |defconfig | self_protection | OK: is not found
nospectre_bhb |cmdline| is not set |defconfig | self_protection | OK: is not found
nospec_store_bypass_disable |cmdline| is not set |defconfig | self_protection | OK: is not found
dis_ucode_ldr |cmdline| is not set |defconfig | self_protection | OK: is not found
arm64.nobti |cmdline| is not set |defconfig | self_protection | OK: is not found
arm64.nopauth |cmdline| is not set |defconfig | self_protection | OK: is not found
arm64.nomte |cmdline| is not set |defconfig | self_protection | OK: is not found
spectre_v2 |cmdline| is not off |defconfig | self_protection | FAIL: is off, not found
spectre_v2_user |cmdline| is not off |defconfig | self_protection | FAIL: is off, not found
spectre_bhi |cmdline| is not off |defconfig | self_protection | FAIL: is off, not found
spec_store_bypass_disable |cmdline| is not off |defconfig | self_protection | FAIL: is off, not found
l1tf |cmdline| is not off |defconfig | self_protection | FAIL: is off, not found
mds |cmdline| is not off |defconfig | self_protection | FAIL: is off, not found
tsx_async_abort |cmdline| is not off |defconfig | self_protection | FAIL: is off, not found
srbds |cmdline| is not off |defconfig | self_protection | FAIL: is off, not found
mmio_stale_data |cmdline| is not off |defconfig | self_protection | FAIL: is off, not found
retbleed |cmdline| is not off |defconfig | self_protection | FAIL: is off, not found
spec_rstack_overflow |cmdline| is not off |defconfig | self_protection | FAIL: is off, not found
gather_data_sampling |cmdline| is not off |defconfig | self_protection | FAIL: is off, not found
reg_file_data_sampling |cmdline| is not off |defconfig | self_protection | FAIL: is off, not found
rodata |cmdline| on |defconfig | self_protection | OK: rodata is not found
slab_merge |cmdline| is not set | kspp | self_protection | OK: is not found
slub_merge |cmdline| is not set | kspp | self_protection | OK: is not found
page_alloc.shuffle |cmdline| 1 | kspp | self_protection | FAIL: is not found
cfi |cmdline| kcfi | kspp | self_protection | FAIL: is not found
slab_nomerge |cmdline| is present | kspp | self_protection | FAIL: is not present
init_on_alloc |cmdline| 1 | kspp | self_protection | OK: CONFIG_INIT_ON_ALLOC_DEFAULT_ON is "y"
init_on_free |cmdline| 1 | kspp | self_protection | FAIL: is not found
hardened_usercopy |cmdline| 1 | kspp | self_protection | OK: CONFIG_HARDENED_USERCOPY is "y"
slab_common.usercopy_fallback |cmdline| is not set | kspp | self_protection | OK: is not found
kfence.sample_interval |cmdline| 100 | kspp | self_protection | FAIL: is not found
iommu.strict |cmdline| 1 | kspp | self_protection | FAIL: is not found
iommu.passthrough |cmdline| 0 | kspp | self_protection | OK: CONFIG_IOMMU_DEFAULT_PASSTHROUGH is "is not set"
randomize_kstack_offset |cmdline| 1 | kspp | self_protection | OK: CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT is "y"
mitigations |cmdline| auto,nosmt | kspp | self_protection | FAIL: is not found
pti |cmdline| on | kspp | self_protection | FAIL: is not found
iommu |cmdline| force | clipos | self_protection | FAIL: is not found
tsx |cmdline| off |defconfig |cut_attack_surface| OK: CONFIG_X86_INTEL_TSX_MODE_OFF is "y"
nosmt |cmdline| is present | kspp |cut_attack_surface| FAIL: is not present
vsyscall |cmdline| none | kspp |cut_attack_surface| FAIL: is not found
vdso32 |cmdline| 0 | kspp |cut_attack_surface| OK: CONFIG_COMPAT_VDSO is "is not set"
debugfs |cmdline| off | grsec |cut_attack_surface| FAIL: is not found
sysrq_always_enabled |cmdline| is not set |grapheneos|cut_attack_surface| OK: is not found
bdev_allow_write_mounted |cmdline| 0 |a13xp0p0v |cut_attack_surface| OK: CONFIG_BLK_DEV_WRITE_MOUNTED is not found
ia32_emulation |cmdline| 0 |a13xp0p0v |cut_attack_surface| FAIL: is not found
norandmaps |cmdline| is not set |defconfig | harden_userspace | OK: is not found
net.core.bpf_jit_harden |sysctl | 2 | kspp | self_protection | FAIL: "0"
kernel.oops_limit |sysctl | 100 |a13xp0p0v | self_protection | FAIL: is not found
kernel.warn_limit |sysctl | 100 |a13xp0p0v | self_protection | FAIL: is not found
kernel.dmesg_restrict |sysctl | 1 | kspp |cut_attack_surface| OK
kernel.perf_event_paranoid |sysctl | 3 | kspp |cut_attack_surface| FAIL: "4"
user.max_user_namespaces |sysctl | 0 | kspp |cut_attack_surface| FAIL: "31231"
dev.tty.ldisc_autoload |sysctl | 0 | kspp |cut_attack_surface| FAIL: "1"
kernel.kptr_restrict |sysctl | 2 | kspp |cut_attack_surface| FAIL: "1"
dev.tty.legacy_tiocsti |sysctl | 0 | kspp |cut_attack_surface| FAIL: is not found
kernel.kexec_load_disabled |sysctl | 1 | kspp |cut_attack_surface| FAIL: "0"
kernel.unprivileged_bpf_disabled |sysctl | 1 | kspp |cut_attack_surface| FAIL: "2"
vm.unprivileged_userfaultfd |sysctl | 0 | kspp |cut_attack_surface| OK
kernel.modules_disabled |sysctl | 1 | kspp |cut_attack_surface| FAIL: "0"
kernel.io_uring_disabled |sysctl | 2 | grsec |cut_attack_surface| FAIL: is not found
kernel.sysrq |sysctl | 0 |a13xp0p0v |cut_attack_surface| FAIL: "176"
fs.protected_symlinks |sysctl | 1 | kspp | harden_userspace | OK
fs.protected_hardlinks |sysctl | 1 | kspp | harden_userspace | OK
fs.protected_fifos |sysctl | 2 | kspp | harden_userspace | FAIL: "1"
fs.protected_regular |sysctl | 2 | kspp | harden_userspace | OK
fs.suid_dumpable |sysctl | 0 | kspp | harden_userspace | FAIL: "2"
kernel.randomize_va_space |sysctl | 2 | kspp | harden_userspace | OK
kernel.yama.ptrace_scope |sysctl | 3 | kspp | harden_userspace | FAIL: "1"
[+] Config check is finished: 'OK' - 135 / 'FAIL' - 158
With the -g argument, the tool generates a Kconfig fragment with the security hardening options for the selected microarchitecture.
This Kconfig fragment can be merged with the existing Linux kernel config:
$ ./bin/kernel-hardening-checker -g X86_64 > /tmp/fragment
$ cd ~/linux-src/
$ ./scripts/kconfig/merge_config.sh .config /tmp/fragment
Using .config as base
Merging /tmp/fragment
Value of CONFIG_BUG_ON_DATA_CORRUPTION is redefined by fragment /tmp/fragment:
Previous value: # CONFIG_BUG_ON_DATA_CORRUPTION is not set
New value: CONFIG_BUG_ON_DATA_CORRUPTION=y
...
Q: How all these kernel parameters influence the Linux kernel security?
A: To answer this question, you can use the kernel-hardening-checker sources of recommendations
and the Linux Kernel Defence Map with its references.
Q: How disabling CONFIG_USER_NS cuts the attack surface? It's needed for containers!
A: Yes, the CONFIG_USER_NS option provides some isolation between the userspace programs,
but the tool recommends disabling it to cut the attack surface of the kernel.
The rationale:
-
An LWN article about the corresponding LKML discussion: https://lwn.net/Articles/673597/
-
A twitter thread about
CONFIG_USER_NSand security: https://twitter.com/robertswiecki/status/1095447678949953541 -
A good overview of the trade-off between having user namespaces enabled, disabled and available only for root: NixOS/nixpkgs#84522 (comment)
Q: KSPP and CLIP OS recommend CONFIG_PANIC_ON_OOPS=y. Why doesn't this tool do the same?
A: I can't support this recommendation because:
- It decreases system robustness (kernel oops is still not a rare situation even on production systems)
- It allows easier denial-of-service attacks for the whole system
You should enable CONFIG_PANIC_ON_OOPS if:
- Your kernel doesn't encounter oopses during a typical workload
- Occasional system reboot is not a problem in your use case
I see a good compromise, which kernel-hardening-checker recommends:
- Enable the
CONFIG_BUGkconfig option. If a kernel oops happens in the process context, the offending/attacking process is killed. In other cases, the kernel panics, which is similar toCONFIG_PANIC_ON_OOPS=y. - Set the sysctl options
kernel.oops_limitandkernel.warn_limitto100, for example. On the one hand, this value doesn't allow easy DoS. On the other hand, it is not too large to miss the vulnerability exploitation attempts generating a lot of kernel warnings or oopses.
Q: Why enabling CONFIG_STATIC_USERMODEHELPER breaks various things in my GNU/Linux system?
Do I really need that feature?
A: Linux kernel usermode helpers can be used for privilege escalation in kernel exploits
(example 1, example 2). CONFIG_STATIC_USERMODEHELPER prevents that method. But it
requires the corresponding support in the userspace: see the example implementation by
Tycho Andersen @tych0.
Q: What about performance impact of these security hardening options?
A: Ike Devolder @BlackIkeEagle made some performance tests and described the results in this article. A more detailed evaluation is in the TODO list (the issue #66).
Q: Can I easily check which kernel versions support some Kconfig option?
A: Yes. See the LKDDb project (Linux Kernel Driver Database) by Giacomo Catenazzi @cateee.
You can use it for the mainline or stable tree from kernel.org or for your custom kernel sources.
Q: Does my kernel have all those mitigations of Transient Execution Vulnerabilities in my hardware?
A: Checking the kernel config is not enough to answer this question. I highly recommend using spectre-meltdown-checker tool maintained by Stéphane Lesimple @speed47.
Q: Why the CONFIG_GCC_PLUGINS option is automatically disabled during the kernel compilation?
A: It means that your gcc doesn't support plugins. For example, if you have gcc-14 on Ubuntu,
try to install gcc-14-plugin-dev package, it should help.