# kernel-hardening-checker __(formerly kconfig-hardened-check)__

[![functional test](https://github.com/a13xp0p0v/kernel-hardening-checker/workflows/functional%20test/badge.svg)](https://github.com/a13xp0p0v/kernel-hardening-checker/actions/workflows/functional_test.yml) [![functional test coverage](https://codecov.io/gh/a13xp0p0v/kernel-hardening-checker/graph/badge.svg?flag=functional_test)](https://app.codecov.io/gh/a13xp0p0v/kernel-hardening-checker?flags%5B0%5D=functional_test)
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[![GitHub tag (latest by date)](https://img.shields.io/github/v/tag/a13xp0p0v/kernel-hardening-checker?label=release)](https://github.com/a13xp0p0v/kernel-hardening-checker/tags) ## Motivation 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. It supports checking: - Kconfig options (compile-time) - Kernel cmdline arguments (boot-time) - Sysctl parameters (runtime) The security hardening recommendations are based on: - [KSPP recommended settings][1] - [CLIP OS kernel configuration][2] - Last public [grsecurity][3] patch (options which they disable) - [SECURITY_LOCKDOWN_LSM][5] patchset - [Direct feedback from the Linux kernel maintainers][23] I also created the [__Linux Kernel Defence Map__][4], which is a graphical representation of the relationships between security hardening features and the corresponding vulnerability classes or exploitation techniques. __Attention!__ 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. ## Repositories - Main at GitHub - Mirror at Codeberg: - Mirror at GitFlic: ## Supported microarchitectures - X86_64 - X86_32 - ARM64 - ARM TODO: RISC-V (issue [#56][22]) ## Installation 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 ``` 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 ``` ## Output modes - no `-m` argument for the default output mode (see the example below) - `-m verbose` for 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_fail` for showing only the failed checks - `-m show_ok` for showing only the successful checks - `-m json` for printing the results in JSON format (for combining `kernel-hardening-checker` with other tools) ## Example output for `Ubuntu 22.04` kernel configuration ``` $ ./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_RANDOMIZE_BASE |kconfig| y |defconfig | self_protection | OK CONFIG_VMAP_STACK |kconfig| y |defconfig | self_protection | OK CONFIG_SPECULATION_MITIGATIONS |kconfig| y |defconfig | self_protection | FAIL: is not found 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_X86_MCE_INTEL |kconfig| y |defconfig | self_protection | OK CONFIG_X86_MCE_AMD |kconfig| y |defconfig | self_protection | OK CONFIG_RETPOLINE |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_PAGE_TABLE_ISOLATION |kconfig| y |defconfig | self_protection | OK CONFIG_RANDOMIZE_MEMORY |kconfig| y |defconfig | self_protection | OK CONFIG_X86_KERNEL_IBT |kconfig| y |defconfig | self_protection | FAIL: is not found CONFIG_CPU_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_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| is not off |a13xp0p0v | self_protection | FAIL: is off, "0" CONFIG_RANDSTRUCT_FULL |kconfig| y | kspp | self_protection | FAIL: is not found CONFIG_RANDSTRUCT_PERFORMANCE |kconfig| is not set | kspp | self_protection | FAIL: CONFIG_RANDSTRUCT_FULL is not "y" 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_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_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_SLAB_MERGE_DEFAULT |kconfig| is not set | clipos | self_protection | FAIL: "y" CONFIG_LIST_HARDENED |kconfig| y |a13xp0p0v | self_protection | FAIL: is not found CONFIG_RANDOM_KMALLOC_CACHES |kconfig| y |a13xp0p0v | self_protection | FAIL: is not found 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 |a13xp0p0v | 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_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_COMPAT_VDSO |kconfig| is not set | kspp |cut_attack_surface| OK CONFIG_X86_VSYSCALL_EMULATION |kconfig| is not set | kspp |cut_attack_surface| FAIL: "y" CONFIG_ZSMALLOC_STAT |kconfig| is not set | grsec |cut_attack_surface| OK CONFIG_PAGE_OWNER |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_BCACHE_CLOSURES_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_PTDUMP_DEBUGFS |kconfig| is not set | grsec |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_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_MAGIC_SYSRQ |kconfig| is not set | clipos |cut_attack_surface| FAIL: "y" CONFIG_KEXEC_FILE |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_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_IP_SCTP |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_KGDB |kconfig| is not set |a13xp0p0v |cut_attack_surface| FAIL: "y" 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_TRIM_UNUSED_KSYMS |kconfig| y |a13xp0p0v |cut_attack_surface| FAIL: "is not set" CONFIG_MODULE_FORCE_LOAD |kconfig| is not set |a13xp0p0v |cut_attack_surface| OK CONFIG_COREDUMP |kconfig| is not set | clipos | harden_userspace | FAIL: "y" CONFIG_ARCH_MMAP_RND_BITS |kconfig| 32 |a13xp0p0v | harden_userspace | FAIL: "28" 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 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 rodata |cmdline| on |defconfig | self_protection | OK: rodata is not found mitigations |cmdline| auto,nosmt | kspp | self_protection | FAIL: 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 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 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" pti |cmdline| on | kspp | self_protection | FAIL: is not found iommu |cmdline| force | clipos | self_protection | FAIL: is not found kfence.sample_interval |cmdline| is not off |a13xp0p0v | self_protection | FAIL: is off, 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 |a13xp0p0v |cut_attack_surface| OK: 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.dmesg_restrict |sysctl | 1 | kspp |cut_attack_surface| OK kernel.perf_event_paranoid |sysctl | 3 | kspp |cut_attack_surface| FAIL: "4" kernel.kexec_load_disabled |sysctl | 1 | kspp |cut_attack_surface| FAIL: "0" 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.unprivileged_bpf_disabled |sysctl | 1 | kspp |cut_attack_surface| FAIL: "2" 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 vm.unprivileged_userfaultfd |sysctl | 0 | kspp |cut_attack_surface| OK kernel.modules_disabled |sysctl | 1 | clipos |cut_attack_surface| FAIL: "0" 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' - 121 / 'FAIL' - 139 ``` ## Generating a Kconfig fragment with the security hardening options 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 ... ``` ## Questions and answers __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][24] and the [Linux Kernel Defence Map][4] 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_NS` and 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: https://github.com/NixOS/nixpkgs/pull/84522#issuecomment-614640601
__Q:__ KSPP and CLIP OS recommend `CONFIG_PANIC_ON_OOPS=y`. Why doesn't this tool do the same? __A:__ I personally don't support this recommendation because: - It decreases system safety (kernel oops is still not a rare situation) - It allows easier denial-of-service attacks for the whole system I think having `CONFIG_BUG` is enough here. If a kernel oops happens in the process context, the offending/attacking process is killed. In other cases, the kernel panics, which is similar to `CONFIG_PANIC_ON_OOPS=y`.
__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][9], [example 2][10]). `CONFIG_STATIC_USERMODEHELPER` prevents that method. But it requires the corresponding support in the userspace: see the [example implementation][11] by Tycho Andersen [@tych0][12].
__Q:__ What about performance impact of these security hardening options? __A:__ Ike Devolder [@BlackIkeEagle][7] made some performance tests and described the results in [this article][8]. A more detailed evaluation is in the TODO list (the issue [#66][21]).
__Q:__ Can I easily check which kernel versions support some Kconfig option? __A:__ Yes. See the [LKDDb][18] project (Linux Kernel Driver Database) by Giacomo Catenazzi [@cateee][19]. You can use it for the `mainline` or `stable` tree from [kernel.org][20] 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][13] tool maintained by Stéphane Lesimple [@speed47][14].
__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-7` on Ubuntu, try to install `gcc-7-plugin-dev` package, it should help. [1]: http://kernsec.org/wiki/index.php/Kernel_Self_Protection_Project/Recommended_Settings [2]: https://docs.clip-os.org/clipos/kernel.html#configuration [3]: https://grsecurity.net/ [4]: https://github.com/a13xp0p0v/linux-kernel-defence-map [5]: https://lwn.net/Articles/791863/ [6]: https://github.com/a13xp0p0v/kernel-hardening-checker/issues/38 [7]: https://github.com/BlackIkeEagle [8]: https://blog.herecura.eu/blog/2020-05-30-kconfig-hardening-tests/ [9]: https://googleprojectzero.blogspot.com/2018/09/a-cache-invalidation-bug-in-linux.html [10]: https://a13xp0p0v.github.io/2020/02/15/CVE-2019-18683.html [11]: https://github.com/tych0/huldufolk [12]: https://github.com/tych0 [13]: https://github.com/speed47/spectre-meltdown-checker [14]: https://github.com/speed47 [15]: https://github.com/a13xp0p0v/kernel-hardening-checker/issues/53 [16]: https://github.com/a13xp0p0v/kernel-hardening-checker/pull/54 [17]: https://github.com/a13xp0p0v/kernel-hardening-checker/pull/62 [18]: https://cateee.net/lkddb/web-lkddb/ [19]: https://github.com/cateee/lkddb [20]: https://kernel.org/ [21]: https://github.com/a13xp0p0v/kernel-hardening-checker/issues/66 [22]: https://github.com/a13xp0p0v/kernel-hardening-checker/issues/56 [23]: https://github.com/a13xp0p0v/kernel-hardening-checker/issues?q=label%3Akernel_maintainer_feedback [24]: https://github.com/a13xp0p0v/kernel-hardening-checker#motivation