1 # kconfig-hardened-check
3 
4 [](https://codecov.io/gh/a13xp0p0v/kconfig-hardened-check)
8 There are plenty of security hardening options in the Linux kernel. A lot of them are
9 not enabled by the major distros. We have to enable these options ourselves to
10 make our systems more secure.
12 But nobody likes checking configs manually. So let the computers do their job!
14 __kconfig-hardened-check.py__ helps me to check the Linux kernel Kconfig option list
15 against my security hardening preferences, which are based on the
17 - [KSPP recommended settings][1],
18 - [CLIP OS kernel configuration][2],
19 - Last public [grsecurity][3] patch (options which they disable),
20 - [SECURITY_LOCKDOWN_LSM][5] patchset,
21 - Direct feedback from Linux kernel maintainers (see [#38][6], [#53][15], [#54][16]).
23 I also created [__Linux Kernel Defence Map__][4] that is a graphical representation of the
24 relationships between security hardening features and the corresponding vulnerability classes
25 or exploitation techniques.
27 ## Supported microarchitectures
38 You can install the package:
41 pip install git+https://github.com/a13xp0p0v/kconfig-hardened-check
44 or simply run `./bin/kconfig-hardened-check` from the cloned repository.
46 Some Linux distributions also provide `kconfig-hardened-check` as a package.
50 usage: kconfig-hardened-check [-h] [--version] [-p {X86_64,X86_32,ARM64,ARM}]
52 [-m {verbose,json,show_ok,show_fail}]
54 A tool for checking the security hardening options of the Linux kernel
57 -h, --help show this help message and exit
58 --version show program's version number and exit
59 -p {X86_64,X86_32,ARM64,ARM}, --print {X86_64,X86_32,ARM64,ARM}
60 print security hardening preferences for the selected architecture
61 -c CONFIG, --config CONFIG
62 check the kernel config file against these preferences
63 -m {verbose,json,show_ok,show_fail}, --mode {verbose,json,show_ok,show_fail}
64 choose the report mode
69 - no `-m` argument for the default output mode (see the example below)
70 - `-m verbose` for printing additional info:
71 - config options without a corresponding check
72 - internals of complex checks with AND/OR, like this:
74 -------------------------------------------------------------------------------------------
76 CONFIG_STRICT_DEVMEM | y |defconfig | cut_attack_surface
77 CONFIG_DEVMEM | is not set | kspp | cut_attack_surface
78 -------------------------------------------------------------------------------------------
80 - `-m show_fail` for showing only the failed checks
81 - `-m show_ok` for showing only the successful checks
82 - `-m json` for printing the results in JSON format (for combining `kconfig-hardened-check` with other tools)
84 ## Example output for `Ubuntu 20.04 LTS (Focal Fossa)` kernel config
86 $ ./bin/kconfig-hardened-check -c kconfig_hardened_check/config_files/distros/ubuntu-focal.config
87 [+] Config file to check: kconfig_hardened_check/config_files/distros/ubuntu-focal.config
88 [+] Detected architecture: X86_64
89 [+] Detected kernel version: 5.4
90 =========================================================================================================================
91 kconfig option name |desired val| decision | reason | check result
92 =========================================================================================================================
93 CONFIG_BUG | y |defconfig | self_protection | OK
94 CONFIG_SLUB_DEBUG | y |defconfig | self_protection | OK
95 CONFIG_GCC_PLUGINS | y |defconfig | self_protection | FAIL: not found
96 CONFIG_STACKPROTECTOR_STRONG | y |defconfig | self_protection | OK
97 CONFIG_STRICT_KERNEL_RWX | y |defconfig | self_protection | OK
98 CONFIG_STRICT_MODULE_RWX | y |defconfig | self_protection | OK
99 CONFIG_REFCOUNT_FULL | y |defconfig | self_protection | FAIL: "is not set"
100 CONFIG_IOMMU_SUPPORT | y |defconfig | self_protection | OK
101 CONFIG_RANDOMIZE_BASE | y |defconfig | self_protection | OK
102 CONFIG_THREAD_INFO_IN_TASK | y |defconfig | self_protection | OK
103 CONFIG_VMAP_STACK | y |defconfig | self_protection | OK
104 CONFIG_MICROCODE | y |defconfig | self_protection | OK
105 CONFIG_RETPOLINE | y |defconfig | self_protection | OK
106 CONFIG_X86_SMAP | y |defconfig | self_protection | OK
107 CONFIG_SYN_COOKIES | y |defconfig | self_protection | OK
108 CONFIG_X86_UMIP | y |defconfig | self_protection | OK: CONFIG_X86_INTEL_UMIP "y"
109 CONFIG_PAGE_TABLE_ISOLATION | y |defconfig | self_protection | OK
110 CONFIG_RANDOMIZE_MEMORY | y |defconfig | self_protection | OK
111 CONFIG_INTEL_IOMMU | y |defconfig | self_protection | OK
112 CONFIG_AMD_IOMMU | y |defconfig | self_protection | OK
113 CONFIG_SECURITY_DMESG_RESTRICT | y | kspp | self_protection | FAIL: "is not set"
114 CONFIG_BUG_ON_DATA_CORRUPTION | y | kspp | self_protection | FAIL: "is not set"
115 CONFIG_DEBUG_WX | y | kspp | self_protection | OK
116 CONFIG_SCHED_STACK_END_CHECK | y | kspp | self_protection | OK
117 CONFIG_SLAB_FREELIST_HARDENED | y | kspp | self_protection | OK
118 CONFIG_SLAB_FREELIST_RANDOM | y | kspp | self_protection | OK
119 CONFIG_SHUFFLE_PAGE_ALLOCATOR | y | kspp | self_protection | OK
120 CONFIG_FORTIFY_SOURCE | y | kspp | self_protection | OK
121 CONFIG_DEBUG_LIST | y | kspp | self_protection | FAIL: "is not set"
122 CONFIG_DEBUG_SG | y | kspp | self_protection | FAIL: "is not set"
123 CONFIG_DEBUG_CREDENTIALS | y | kspp | self_protection | FAIL: "is not set"
124 CONFIG_DEBUG_NOTIFIERS | y | kspp | self_protection | FAIL: "is not set"
125 CONFIG_INIT_ON_ALLOC_DEFAULT_ON | y | kspp | self_protection | OK
126 CONFIG_GCC_PLUGIN_LATENT_ENTROPY | y | kspp | self_protection | FAIL: not found
127 CONFIG_GCC_PLUGIN_RANDSTRUCT | y | kspp | self_protection | FAIL: not found
128 CONFIG_HARDENED_USERCOPY | y | kspp | self_protection | OK
129 CONFIG_HARDENED_USERCOPY_FALLBACK |is not set | kspp | self_protection | FAIL: "y"
130 CONFIG_HARDENED_USERCOPY_PAGESPAN |is not set | kspp | self_protection | OK
131 CONFIG_MODULE_SIG | y | kspp | self_protection | OK
132 CONFIG_MODULE_SIG_ALL | y | kspp | self_protection | OK
133 CONFIG_MODULE_SIG_SHA512 | y | kspp | self_protection | OK
134 CONFIG_MODULE_SIG_FORCE | y | kspp | self_protection | FAIL: "is not set"
135 CONFIG_INIT_STACK_ALL_ZERO | y | kspp | self_protection | FAIL: not found
136 CONFIG_INIT_ON_FREE_DEFAULT_ON | y | kspp | self_protection | OK: CONFIG_PAGE_POISONING_ZERO "y"
137 CONFIG_GCC_PLUGIN_STACKLEAK | y | kspp | self_protection | FAIL: not found
138 CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT | y | kspp | self_protection | FAIL: not found
139 CONFIG_DEFAULT_MMAP_MIN_ADDR | 65536 | kspp | self_protection | OK
140 CONFIG_UBSAN_BOUNDS | y |maintainer| self_protection | FAIL: not found
141 CONFIG_UBSAN_SANITIZE_ALL | y |maintainer| self_protection | FAIL: CONFIG_UBSAN_BOUNDS not "y"
142 CONFIG_UBSAN_TRAP | y |maintainer| self_protection | FAIL: CONFIG_UBSAN_BOUNDS not "y"
143 CONFIG_DEBUG_VIRTUAL | y | clipos | self_protection | FAIL: "is not set"
144 CONFIG_STATIC_USERMODEHELPER | y | clipos | self_protection | FAIL: "is not set"
145 CONFIG_EFI_DISABLE_PCI_DMA | y | clipos | self_protection | FAIL: not found
146 CONFIG_SLAB_MERGE_DEFAULT |is not set | clipos | self_protection | FAIL: "y"
147 CONFIG_RANDOM_TRUST_BOOTLOADER |is not set | clipos | self_protection | FAIL: "y"
148 CONFIG_RANDOM_TRUST_CPU |is not set | clipos | self_protection | FAIL: "y"
149 CONFIG_GCC_PLUGIN_RANDSTRUCT_PERFORMANCE|is not set | clipos | self_protection | FAIL: CONFIG_GCC_PLUGIN_RANDSTRUCT not "y"
150 CONFIG_STACKLEAK_METRICS |is not set | clipos | self_protection | FAIL: CONFIG_GCC_PLUGIN_STACKLEAK not "y"
151 CONFIG_STACKLEAK_RUNTIME_DISABLE |is not set | clipos | self_protection | FAIL: CONFIG_GCC_PLUGIN_STACKLEAK not "y"
152 CONFIG_INTEL_IOMMU_DEFAULT_ON | y | clipos | self_protection | FAIL: "is not set"
153 CONFIG_INTEL_IOMMU_SVM | y | clipos | self_protection | OK
154 CONFIG_RESET_ATTACK_MITIGATION | y | my | self_protection | OK
155 CONFIG_AMD_IOMMU_V2 | y | my | self_protection | FAIL: "m"
156 CONFIG_SECURITY | y |defconfig | security_policy | OK
157 CONFIG_SECURITY_YAMA | y | kspp | security_policy | OK
158 CONFIG_SECURITY_WRITABLE_HOOKS |is not set | my | security_policy | OK: not found
159 CONFIG_SECURITY_LOCKDOWN_LSM | y | clipos | security_policy | OK
160 CONFIG_SECURITY_LOCKDOWN_LSM_EARLY | y | clipos | security_policy | OK
161 CONFIG_LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY| y | clipos | security_policy | FAIL: "is not set"
162 CONFIG_SECURITY_SAFESETID | y | my | security_policy | OK
163 CONFIG_SECURITY_LOADPIN | y | my | security_policy | FAIL: "is not set"
164 CONFIG_SECURITY_LOADPIN_ENFORCE | y | my | security_policy | FAIL: CONFIG_SECURITY_LOADPIN not "y"
165 CONFIG_SECCOMP | y |defconfig |cut_attack_surface| OK
166 CONFIG_SECCOMP_FILTER | y |defconfig |cut_attack_surface| OK
167 CONFIG_STRICT_DEVMEM | y |defconfig |cut_attack_surface| OK
168 CONFIG_ACPI_CUSTOM_METHOD |is not set | kspp |cut_attack_surface| OK
169 CONFIG_COMPAT_BRK |is not set | kspp |cut_attack_surface| OK
170 CONFIG_DEVKMEM |is not set | kspp |cut_attack_surface| OK
171 CONFIG_COMPAT_VDSO |is not set | kspp |cut_attack_surface| OK
172 CONFIG_BINFMT_MISC |is not set | kspp |cut_attack_surface| FAIL: "m"
173 CONFIG_INET_DIAG |is not set | kspp |cut_attack_surface| FAIL: "m"
174 CONFIG_KEXEC |is not set | kspp |cut_attack_surface| FAIL: "y"
175 CONFIG_PROC_KCORE |is not set | kspp |cut_attack_surface| FAIL: "y"
176 CONFIG_LEGACY_PTYS |is not set | kspp |cut_attack_surface| FAIL: "y"
177 CONFIG_HIBERNATION |is not set | kspp |cut_attack_surface| FAIL: "y"
178 CONFIG_IA32_EMULATION |is not set | kspp |cut_attack_surface| FAIL: "y"
179 CONFIG_X86_X32 |is not set | kspp |cut_attack_surface| FAIL: "y"
180 CONFIG_MODIFY_LDT_SYSCALL |is not set | kspp |cut_attack_surface| FAIL: "y"
181 CONFIG_OABI_COMPAT |is not set | kspp |cut_attack_surface| OK: not found
182 CONFIG_MODULES |is not set | kspp |cut_attack_surface| FAIL: "y"
183 CONFIG_DEVMEM |is not set | kspp |cut_attack_surface| FAIL: "y"
184 CONFIG_IO_STRICT_DEVMEM | y | kspp |cut_attack_surface| FAIL: "is not set"
185 CONFIG_LEGACY_VSYSCALL_NONE | y | kspp |cut_attack_surface| FAIL: "is not set"
186 CONFIG_ZSMALLOC_STAT |is not set |grsecurity|cut_attack_surface| OK
187 CONFIG_PAGE_OWNER |is not set |grsecurity|cut_attack_surface| OK
188 CONFIG_DEBUG_KMEMLEAK |is not set |grsecurity|cut_attack_surface| OK
189 CONFIG_BINFMT_AOUT |is not set |grsecurity|cut_attack_surface| OK: not found
190 CONFIG_KPROBE_EVENTS |is not set |grsecurity|cut_attack_surface| FAIL: "y"
191 CONFIG_UPROBE_EVENTS |is not set |grsecurity|cut_attack_surface| FAIL: "y"
192 CONFIG_GENERIC_TRACER |is not set |grsecurity|cut_attack_surface| FAIL: "y"
193 CONFIG_FUNCTION_TRACER |is not set |grsecurity|cut_attack_surface| FAIL: "y"
194 CONFIG_STACK_TRACER |is not set |grsecurity|cut_attack_surface| FAIL: "y"
195 CONFIG_HIST_TRIGGERS |is not set |grsecurity|cut_attack_surface| FAIL: "y"
196 CONFIG_BLK_DEV_IO_TRACE |is not set |grsecurity|cut_attack_surface| FAIL: "y"
197 CONFIG_PROC_VMCORE |is not set |grsecurity|cut_attack_surface| FAIL: "y"
198 CONFIG_PROC_PAGE_MONITOR |is not set |grsecurity|cut_attack_surface| FAIL: "y"
199 CONFIG_USELIB |is not set |grsecurity|cut_attack_surface| FAIL: "y"
200 CONFIG_CHECKPOINT_RESTORE |is not set |grsecurity|cut_attack_surface| FAIL: "y"
201 CONFIG_USERFAULTFD |is not set |grsecurity|cut_attack_surface| FAIL: "y"
202 CONFIG_HWPOISON_INJECT |is not set |grsecurity|cut_attack_surface| FAIL: "m"
203 CONFIG_MEM_SOFT_DIRTY |is not set |grsecurity|cut_attack_surface| FAIL: "y"
204 CONFIG_DEVPORT |is not set |grsecurity|cut_attack_surface| FAIL: "y"
205 CONFIG_DEBUG_FS |is not set |grsecurity|cut_attack_surface| FAIL: "y"
206 CONFIG_NOTIFIER_ERROR_INJECTION |is not set |grsecurity|cut_attack_surface| FAIL: "m"
207 CONFIG_FAIL_FUTEX |is not set |grsecurity|cut_attack_surface| OK: not found
208 CONFIG_PUNIT_ATOM_DEBUG |is not set |grsecurity|cut_attack_surface| FAIL: "m"
209 CONFIG_ACPI_CONFIGFS |is not set |grsecurity|cut_attack_surface| FAIL: "m"
210 CONFIG_EDAC_DEBUG |is not set |grsecurity|cut_attack_surface| OK
211 CONFIG_DRM_I915_DEBUG |is not set |grsecurity|cut_attack_surface| OK
212 CONFIG_BCACHE_CLOSURES_DEBUG |is not set |grsecurity|cut_attack_surface| OK
213 CONFIG_DVB_C8SECTPFE |is not set |grsecurity|cut_attack_surface| OK: not found
214 CONFIG_MTD_SLRAM |is not set |grsecurity|cut_attack_surface| FAIL: "m"
215 CONFIG_MTD_PHRAM |is not set |grsecurity|cut_attack_surface| FAIL: "m"
216 CONFIG_IO_URING |is not set |grsecurity|cut_attack_surface| FAIL: "y"
217 CONFIG_KCMP |is not set |grsecurity|cut_attack_surface| OK: not found
218 CONFIG_RSEQ |is not set |grsecurity|cut_attack_surface| FAIL: "y"
219 CONFIG_LATENCYTOP |is not set |grsecurity|cut_attack_surface| OK
220 CONFIG_KCOV |is not set |grsecurity|cut_attack_surface| OK
221 CONFIG_PROVIDE_OHCI1394_DMA_INIT |is not set |grsecurity|cut_attack_surface| OK
222 CONFIG_SUNRPC_DEBUG |is not set |grsecurity|cut_attack_surface| FAIL: "y"
223 CONFIG_PTDUMP_DEBUGFS |is not set |grsecurity|cut_attack_surface| OK: not found
224 CONFIG_DRM_LEGACY |is not set |maintainer|cut_attack_surface| OK
225 CONFIG_FB |is not set |maintainer|cut_attack_surface| FAIL: "y"
226 CONFIG_VT |is not set |maintainer|cut_attack_surface| FAIL: "y"
227 CONFIG_BLK_DEV_FD |is not set |maintainer|cut_attack_surface| FAIL: "m"
228 CONFIG_AIO |is not set |grapheneos|cut_attack_surface| FAIL: "y"
229 CONFIG_STAGING |is not set | clipos |cut_attack_surface| FAIL: "y"
230 CONFIG_KSM |is not set | clipos |cut_attack_surface| FAIL: "y"
231 CONFIG_KALLSYMS |is not set | clipos |cut_attack_surface| FAIL: "y"
232 CONFIG_X86_VSYSCALL_EMULATION |is not set | clipos |cut_attack_surface| FAIL: "y"
233 CONFIG_MAGIC_SYSRQ |is not set | clipos |cut_attack_surface| FAIL: "y"
234 CONFIG_KEXEC_FILE |is not set | clipos |cut_attack_surface| FAIL: "y"
235 CONFIG_USER_NS |is not set | clipos |cut_attack_surface| FAIL: "y"
236 CONFIG_X86_MSR |is not set | clipos |cut_attack_surface| FAIL: "m"
237 CONFIG_X86_CPUID |is not set | clipos |cut_attack_surface| FAIL: "m"
238 CONFIG_X86_IOPL_IOPERM |is not set | clipos |cut_attack_surface| OK: not found
239 CONFIG_ACPI_TABLE_UPGRADE |is not set | clipos |cut_attack_surface| FAIL: "y"
240 CONFIG_EFI_CUSTOM_SSDT_OVERLAYS |is not set | clipos |cut_attack_surface| OK: not found
241 CONFIG_LDISC_AUTOLOAD |is not set | clipos |cut_attack_surface| FAIL: "y"
242 CONFIG_X86_INTEL_TSX_MODE_OFF | y | clipos |cut_attack_surface| OK
243 CONFIG_EFI_TEST |is not set | lockdown |cut_attack_surface| FAIL: "m"
244 CONFIG_BPF_SYSCALL |is not set | lockdown |cut_attack_surface| FAIL: "y"
245 CONFIG_MMIOTRACE_TEST |is not set | lockdown |cut_attack_surface| OK
246 CONFIG_KPROBES |is not set | lockdown |cut_attack_surface| FAIL: "y"
247 CONFIG_TRIM_UNUSED_KSYMS | y | my |cut_attack_surface| FAIL: not found
248 CONFIG_MMIOTRACE |is not set | my |cut_attack_surface| FAIL: "y"
249 CONFIG_LIVEPATCH |is not set | my |cut_attack_surface| FAIL: "y"
250 CONFIG_IP_DCCP |is not set | my |cut_attack_surface| FAIL: "m"
251 CONFIG_IP_SCTP |is not set | my |cut_attack_surface| FAIL: "m"
252 CONFIG_FTRACE |is not set | my |cut_attack_surface| FAIL: "y"
253 CONFIG_VIDEO_VIVID |is not set | my |cut_attack_surface| FAIL: "m"
254 CONFIG_INPUT_EVBUG |is not set | my |cut_attack_surface| FAIL: "m"
255 CONFIG_INTEGRITY | y |defconfig | harden_userspace | OK
256 CONFIG_ARCH_MMAP_RND_BITS | 32 | clipos | harden_userspace | FAIL: "28"
258 [+] Config check is finished: 'OK' - 68 / 'FAIL' - 96
261 ## kconfig-hardened-check versioning
263 I usually update the kernel security hardening recommendations after each Linux kernel release.
265 So the version of `kconfig-hardened-check` is associated with the corresponding version of the kernel.
267 The version format is: __[major_number].[kernel_version].[kernel_patchlevel]__
270 ## Questions and answers
272 __Q:__ How disabling `CONFIG_USER_NS` cuts the attack surface? It's needed for containers!
274 __A:__ Yes, the `CONFIG_USER_NS` option provides some isolation between the userspace programs,
275 but the tool recommends disabling it to cut the attack surface __of the kernel__.
279 - A nice LWN article about the corresponding LKML discussion: https://lwn.net/Articles/673597/
281 - A twitter thread about `CONFIG_USER_NS` and security: https://twitter.com/robertswiecki/status/1095447678949953541
283 - 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
287 __Q:__ Why `CONFIG_GCC_PLUGINS` is automatically disabled during the kernel compilation?
289 __A:__ It means that your gcc doesn't support plugins. For example, if you have `gcc-7` on Ubuntu,
290 try to install `gcc-7-plugin-dev` package, it should help.
294 __Q:__ KSPP and CLIP OS recommend `CONFIG_PANIC_ON_OOPS=y`. Why doesn't this tool do the same?
296 __A:__ I personally don't support this recommendation because it provides easy denial-of-service
297 attacks for the whole system (kernel oops is not a rare situation). I think having `CONFIG_BUG` is enough here --
298 if we have a kernel oops in the process context, the offending/attacking process is killed.
302 __Q:__ What about performance impact of these security hardening options?
304 __A:__ Ike Devolder [@BlackIkeEagle][7] made some performance tests and described the results in [this article][8].
308 __Q:__ Why enabling `CONFIG_STATIC_USERMODEHELPER` breaks various things in my GNU/Linux system?
309 Do I really need that feature?
311 __A:__ Linux kernel usermode helpers can be used for privilege escalation in kernel exploits
312 ([example 1][9], [example 2][10]). `CONFIG_STATIC_USERMODEHELPER` prevents that method. But it
313 requires the corresponding support in the userspace: see the [example implementation][11] by
314 Tycho Andersen [@tych0][12].
318 __Q:__ Does my kernel have all those mitigations of Transient Execution Vulnerabilities in my hardware?
320 __A:__ Checking the kernel config is not enough to answer this question.
321 I highly recommend using [spectre-meltdown-checker][13] tool maintained by Stéphane Lesimple [@speed47][14].
324 [1]: http://kernsec.org/wiki/index.php/Kernel_Self_Protection_Project/Recommended_Settings
325 [2]: https://docs.clip-os.org/clipos/kernel.html#configuration
326 [3]: https://grsecurity.net/
327 [4]: https://github.com/a13xp0p0v/linux-kernel-defence-map
328 [5]: https://lwn.net/Articles/791863/
329 [6]: https://github.com/a13xp0p0v/kconfig-hardened-check/issues/38
330 [7]: https://github.com/BlackIkeEagle
331 [8]: https://blog.herecura.eu/blog/2020-05-30-kconfig-hardening-tests/
332 [9]: https://googleprojectzero.blogspot.com/2018/09/a-cache-invalidation-bug-in-linux.html
333 [10]: https://a13xp0p0v.github.io/2020/02/15/CVE-2019-18683.html
334 [11]: https://github.com/tych0/huldufolk
335 [12]: https://github.com/tych0
336 [13]: https://github.com/speed47/spectre-meltdown-checker
337 [14]: https://github.com/speed47
338 [15]: https://github.com/a13xp0p0v/kconfig-hardened-check/issues/53
339 [16]: https://github.com/a13xp0p0v/kconfig-hardened-check/pull/54
projects / kconfig-hardened-check.git / blob