kconfig-hardened-check
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!
kconfig-hardened-check is a tool for checking the security hardening options of the Linux kernel. The recommendations are based on
- KSPP recommended settings
- CLIP OS kernel configuration
- Last public grsecurity patch (options which they disable)
- SECURITY_LOCKDOWN_LSM patchset
- Direct feedback from the Linux kernel maintainers
This tool supports checking Kconfig options and kernel cmdline parameters.
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.
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 https://github.com/a13xp0p0v/kconfig-hardened-check
- Mirror at Codeberg: https://codeberg.org/a13xp0p0v/kconfig-hardened-check
- Mirror at GitFlic: https://gitflic.ru/project/a13xp0p0v/kconfig-hardened-check
Supported microarchitectures
- X86_64
- X86_32
- ARM64
- ARM
TODO: RISC-V (issue #56)
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.
Some Linux distributions also provide kconfig-hardened-check as a package.
Usage
usage: kconfig-hardened-check [-h] [--version] [-m {verbose,json,show_ok,show_fail}]
[-c CONFIG] [-l CMDLINE] [-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)
-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
-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 | y |defconfig | cut_attack_surface
CONFIG_DEVMEM | 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 combiningkconfig-hardened-checkwith other tools)
Example output for Fedora 36 kernel configuration
$ ./bin/kconfig-hardened-check -c /boot/config-6.0.18-200.fc36.x86_64 -l /proc/cmdline
[+] Kconfig file to check: /boot/config-6.0.18-200.fc36.x86_64
[+] Kernel cmdline file to check: /proc/cmdline
[+] Detected architecture: X86_64
[+] Detected kernel version: 6.0
[+] Detected compiler: GCC 120201
=========================================================================================================================
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_GCC_PLUGINS |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 | FAIL: "is not set"
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 >= 5.5
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_X86_MCE_INTEL |kconfig| y |defconfig | self_protection | OK
CONFIG_X86_MCE_AMD |kconfig| y |defconfig | self_protection | OK
CONFIG_MICROCODE |kconfig| y |defconfig | self_protection | OK
CONFIG_RETPOLINE |kconfig| y |defconfig | self_protection | OK
CONFIG_SYN_COOKIES |kconfig| y |defconfig | self_protection | OK
CONFIG_X86_SMAP |kconfig| y |defconfig | self_protection | OK: version >= 5.19
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_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 | OK
CONFIG_SCHED_STACK_END_CHECK |kconfig| y | kspp | self_protection | OK
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 | OK
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_DEBUG_CREDENTIALS |kconfig| y | kspp | self_protection | FAIL: "is not set"
CONFIG_DEBUG_NOTIFIERS |kconfig| y | kspp | self_protection | FAIL: "is not set"
CONFIG_INIT_ON_ALLOC_DEFAULT_ON |kconfig| y | kspp | self_protection | FAIL: "is not set"
CONFIG_KFENCE |kconfig| y | kspp | self_protection | OK
CONFIG_ZERO_CALL_USED_REGS |kconfig| y | kspp | self_protection | FAIL: "is not set"
CONFIG_HW_RANDOM_TPM |kconfig| y | kspp | self_protection | OK
CONFIG_STATIC_USERMODEHELPER |kconfig| y | kspp | self_protection | FAIL: "is not set"
CONFIG_RANDSTRUCT_FULL |kconfig| y | kspp | self_protection | FAIL: "is not set"
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: is not found
CONFIG_HARDENED_USERCOPY_PAGESPAN |kconfig| is not set | kspp | self_protection | OK: is not found
CONFIG_GCC_PLUGIN_LATENT_ENTROPY |kconfig| y | kspp | self_protection | FAIL: "is not set"
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_STACK_ALL_ZERO |kconfig| y | kspp | self_protection | OK
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 | FAIL: "is not set"
CONFIG_UBSAN_BOUNDS |kconfig| y | kspp | self_protection | FAIL: is not found
CONFIG_UBSAN_LOCAL_BOUNDS |kconfig| y | kspp | self_protection | FAIL: is not found
CONFIG_UBSAN_TRAP |kconfig| y | kspp | self_protection | FAIL: CONFIG_UBSAN_BOUNDS is not "y"
CONFIG_UBSAN_SANITIZE_ALL |kconfig| y | kspp | self_protection | FAIL: CONFIG_UBSAN_BOUNDS is not "y"
CONFIG_GCC_PLUGIN_STACKLEAK |kconfig| y | kspp | self_protection | FAIL: "is not set"
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: is not found
CONFIG_CFI_PERMISSIVE |kconfig| is not set | kspp | self_protection | FAIL: CONFIG_CFI_CLANG is not "y"
CONFIG_SCHED_CORE |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 | FAIL: "is not set"
CONFIG_SLS |kconfig| y | kspp | self_protection | OK
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 | OK
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_LOCKDOWN_LSM |kconfig| y | kspp | security_policy | OK
CONFIG_SECURITY_LOCKDOWN_LSM_EARLY |kconfig| y | kspp | security_policy | OK
CONFIG_LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY|kconfig| y | kspp | security_policy | FAIL: "is not set"
CONFIG_SECURITY_WRITABLE_HOOKS |kconfig| is not set | kspp | security_policy | OK: is not found
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| FAIL: "is not set"
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_COMPAT_VDSO |kconfig| is not set | kspp |cut_attack_surface| OK
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: "y"
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| OK
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| OK: is not found
CONFIG_X86_X32_ABI |kconfig| is not set | kspp |cut_attack_surface| OK
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: "y"
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| OK
CONFIG_LDISC_AUTOLOAD |kconfig| is not set | kspp |cut_attack_surface| FAIL: "y"
CONFIG_LEGACY_VSYSCALL_NONE |kconfig| y | kspp |cut_attack_surface| FAIL: "is not set"
CONFIG_ZSMALLOC_STAT |kconfig| is not set | grsec |cut_attack_surface| OK
CONFIG_PAGE_OWNER |kconfig| is not set | grsec |cut_attack_surface| FAIL: "y"
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| OK
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| OK
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| OK
CONFIG_ACPI_CONFIGFS |kconfig| is not set | grsec |cut_attack_surface| OK
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: is not found
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| OK
CONFIG_MTD_PHRAM |kconfig| is not set | grsec |cut_attack_surface| OK
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| FAIL: "y"
CONFIG_KCOV |kconfig| is not set | grsec |cut_attack_surface| OK
CONFIG_PROVIDE_OHCI1394_DMA_INIT |kconfig| is not set | grsec |cut_attack_surface| FAIL: "y"
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
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_X86_VSYSCALL_EMULATION |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: "y"
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_COREDUMP |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 | my |cut_attack_surface| FAIL: "y"
CONFIG_LIVEPATCH |kconfig| is not set | my |cut_attack_surface| FAIL: "y"
CONFIG_IP_DCCP |kconfig| is not set | my |cut_attack_surface| OK
CONFIG_IP_SCTP |kconfig| is not set | my |cut_attack_surface| FAIL: "m"
CONFIG_FTRACE |kconfig| is not set | my |cut_attack_surface| FAIL: "y"
CONFIG_VIDEO_VIVID |kconfig| is not set | my |cut_attack_surface| OK: is not found
CONFIG_INPUT_EVBUG |kconfig| is not set | my |cut_attack_surface| OK
CONFIG_KGDB |kconfig| is not set | my |cut_attack_surface| FAIL: "y"
CONFIG_TRIM_UNUSED_KSYMS |kconfig| y | my |cut_attack_surface| FAIL: is not found
CONFIG_INTEGRITY |kconfig| y |defconfig | harden_userspace | OK
CONFIG_ARCH_MMAP_RND_BITS |kconfig| 32 | clipos | 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
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
mitigations |cmdline| is not off |defconfig | self_protection | OK: mitigations is not found
spectre_v2 |cmdline| is not off |defconfig | self_protection | OK: spectre_v2 is not found
spectre_v2_user |cmdline| is not off |defconfig | self_protection | OK: spectre_v2_user is not found
spec_store_bypass_disable |cmdline| is not off |defconfig | self_protection | OK: spec_store_bypass_disable is not found
l1tf |cmdline| is not off |defconfig | self_protection | OK: l1tf is not found
mds |cmdline| is not off |defconfig | self_protection | OK: mds is not found
tsx_async_abort |cmdline| is not off |defconfig | self_protection | OK: tsx_async_abort is not found
srbds |cmdline| is not off |defconfig | self_protection | OK: srbds is not found
mmio_stale_data |cmdline| is not off |defconfig | self_protection | OK: mmio_stale_data is not found
retbleed |cmdline| is not off |defconfig | self_protection | OK: retbleed is not found
kpti |cmdline| is not off |defconfig | self_protection | OK: kpti is not found
kvm.nx_huge_pages |cmdline| is not off |defconfig | self_protection | OK: kvm.nx_huge_pages is not found
rodata |cmdline| 1 |defconfig | self_protection | OK: rodata is not found
nosmt |cmdline| is present | kspp | self_protection | FAIL: is not present
init_on_alloc |cmdline| 1 | kspp | self_protection | FAIL: is not found
init_on_free |cmdline| 1 | kspp | self_protection | FAIL: is not found
slab_nomerge |cmdline| is present | kspp | self_protection | OK: CONFIG_SLAB_MERGE_DEFAULT is "is not set"
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"
hardened_usercopy |cmdline| 1 | kspp | self_protection | OK: CONFIG_HARDENED_USERCOPY is "y"
slab_common.usercopy_fallback |cmdline| 0 | kspp | self_protection | OK: CONFIG_HARDENED_USERCOPY_FALLBACK is not found
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
page_alloc.shuffle |cmdline| 1 | clipos | 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"
vsyscall |cmdline| none | kspp |cut_attack_surface| FAIL: is not found
debugfs |cmdline| off | grsec |cut_attack_surface| FAIL: is not found
sysrq_always_enabled |cmdline| is not set | my |cut_attack_surface| OK: is not found
[+] Config check is finished: 'OK' - 122 / 'FAIL' - 101
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/kconfig-hardened-check -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 kconfig-hardened-check 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 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, 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 Stรฉphane 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-7 on Ubuntu,
try to install gcc-7-plugin-dev package, it should help.