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.
48 usage: kconfig-hardened-check [-h] [--version] [-p {X86_64,X86_32,ARM64,ARM}]
50 [-m {verbose,json,show_ok,show_fail}]
52 A tool for checking the security hardening options of the Linux kernel
55 -h, --help show this help message and exit
56 --version show program's version number and exit
57 -p {X86_64,X86_32,ARM64,ARM}, --print {X86_64,X86_32,ARM64,ARM}
58 print security hardening preferences for the selected architecture
59 -c CONFIG, --config CONFIG
60 check the kernel config file against these preferences
61 -m {verbose,json,show_ok,show_fail}, --mode {verbose,json,show_ok,show_fail}
62 choose the report mode
65 ## Output for `Ubuntu 20.04 LTS (Focal Fossa)` kernel config
67 $ ./bin/kconfig-hardened-check -c kconfig_hardened_check/config_files/distros/ubuntu-focal.config
68 [+] Config file to check: kconfig_hardened_check/config_files/distros/ubuntu-focal.config
69 [+] Detected architecture: X86_64
70 [+] Detected kernel version: 5.4
71 =========================================================================================================================
72 option name | desired val | decision | reason | check result
73 =========================================================================================================================
74 CONFIG_BUG | y |defconfig | self_protection | OK
75 CONFIG_SLUB_DEBUG | y |defconfig | self_protection | OK
76 CONFIG_GCC_PLUGINS | y |defconfig | self_protection | FAIL: not found
77 CONFIG_STACKPROTECTOR_STRONG | y |defconfig | self_protection | OK
78 CONFIG_STRICT_KERNEL_RWX | y |defconfig | self_protection | OK
79 CONFIG_STRICT_MODULE_RWX | y |defconfig | self_protection | OK
80 CONFIG_REFCOUNT_FULL | y |defconfig | self_protection | FAIL: "is not set"
81 CONFIG_IOMMU_SUPPORT | y |defconfig | self_protection | OK
82 CONFIG_RANDOMIZE_BASE | y |defconfig | self_protection | OK
83 CONFIG_THREAD_INFO_IN_TASK | y |defconfig | self_protection | OK
84 CONFIG_VMAP_STACK | y |defconfig | self_protection | OK
85 CONFIG_MICROCODE | y |defconfig | self_protection | OK
86 CONFIG_RETPOLINE | y |defconfig | self_protection | OK
87 CONFIG_X86_SMAP | y |defconfig | self_protection | OK
88 CONFIG_SYN_COOKIES | y |defconfig | self_protection | OK
89 CONFIG_X86_UMIP | y |defconfig | self_protection | OK: CONFIG_X86_INTEL_UMIP "y"
90 CONFIG_PAGE_TABLE_ISOLATION | y |defconfig | self_protection | OK
91 CONFIG_RANDOMIZE_MEMORY | y |defconfig | self_protection | OK
92 CONFIG_INTEL_IOMMU | y |defconfig | self_protection | OK
93 CONFIG_AMD_IOMMU | y |defconfig | self_protection | OK
94 CONFIG_SECURITY_DMESG_RESTRICT | y | kspp | self_protection | FAIL: "is not set"
95 CONFIG_BUG_ON_DATA_CORRUPTION | y | kspp | self_protection | FAIL: "is not set"
96 CONFIG_DEBUG_WX | y | kspp | self_protection | OK
97 CONFIG_SCHED_STACK_END_CHECK | y | kspp | self_protection | OK
98 CONFIG_SLAB_FREELIST_HARDENED | y | kspp | self_protection | OK
99 CONFIG_SLAB_FREELIST_RANDOM | y | kspp | self_protection | OK
100 CONFIG_SHUFFLE_PAGE_ALLOCATOR | y | kspp | self_protection | OK
101 CONFIG_FORTIFY_SOURCE | y | kspp | self_protection | OK
102 CONFIG_DEBUG_LIST | y | kspp | self_protection | FAIL: "is not set"
103 CONFIG_DEBUG_SG | y | kspp | self_protection | FAIL: "is not set"
104 CONFIG_DEBUG_CREDENTIALS | y | kspp | self_protection | FAIL: "is not set"
105 CONFIG_DEBUG_NOTIFIERS | y | kspp | self_protection | FAIL: "is not set"
106 CONFIG_INIT_ON_ALLOC_DEFAULT_ON | y | kspp | self_protection | OK
107 CONFIG_GCC_PLUGIN_LATENT_ENTROPY | y | kspp | self_protection | FAIL: not found
108 CONFIG_GCC_PLUGIN_RANDSTRUCT | y | kspp | self_protection | FAIL: not found
109 CONFIG_HARDENED_USERCOPY | y | kspp | self_protection | OK
110 CONFIG_HARDENED_USERCOPY_FALLBACK | is not set | kspp | self_protection | FAIL: "y"
111 CONFIG_HARDENED_USERCOPY_PAGESPAN | is not set | kspp | self_protection | OK
112 CONFIG_MODULE_SIG | y | kspp | self_protection | OK
113 CONFIG_MODULE_SIG_ALL | y | kspp | self_protection | OK
114 CONFIG_MODULE_SIG_SHA512 | y | kspp | self_protection | OK
115 CONFIG_MODULE_SIG_FORCE | y | kspp | self_protection | FAIL: "is not set"
116 CONFIG_INIT_STACK_ALL_ZERO | y | kspp | self_protection | FAIL: not found
117 CONFIG_INIT_ON_FREE_DEFAULT_ON | y | kspp | self_protection | OK: CONFIG_PAGE_POISONING_ZERO "y"
118 CONFIG_GCC_PLUGIN_STACKLEAK | y | kspp | self_protection | FAIL: not found
119 CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT | y | kspp | self_protection | FAIL: not found
120 CONFIG_DEFAULT_MMAP_MIN_ADDR | 65536 | kspp | self_protection | OK
121 CONFIG_UBSAN_BOUNDS | y |maintainer| self_protection | FAIL: not found
122 CONFIG_UBSAN_SANITIZE_ALL | y |maintainer| self_protection | FAIL: CONFIG_UBSAN_BOUNDS not "y"
123 CONFIG_UBSAN_TRAP | y |maintainer| self_protection | FAIL: CONFIG_UBSAN_BOUNDS not "y"
124 CONFIG_DEBUG_VIRTUAL | y | clipos | self_protection | FAIL: "is not set"
125 CONFIG_STATIC_USERMODEHELPER | y | clipos | self_protection | FAIL: "is not set"
126 CONFIG_EFI_DISABLE_PCI_DMA | y | clipos | self_protection | FAIL: not found
127 CONFIG_SLAB_MERGE_DEFAULT | is not set | clipos | self_protection | FAIL: "y"
128 CONFIG_RANDOM_TRUST_BOOTLOADER | is not set | clipos | self_protection | FAIL: "y"
129 CONFIG_RANDOM_TRUST_CPU | is not set | clipos | self_protection | FAIL: "y"
130 CONFIG_GCC_PLUGIN_RANDSTRUCT_PERFORMANCE | is not set | clipos | self_protection | FAIL: CONFIG_GCC_PLUGIN_RANDSTRUCT not "y"
131 CONFIG_STACKLEAK_METRICS | is not set | clipos | self_protection | FAIL: CONFIG_GCC_PLUGIN_STACKLEAK not "y"
132 CONFIG_STACKLEAK_RUNTIME_DISABLE | is not set | clipos | self_protection | FAIL: CONFIG_GCC_PLUGIN_STACKLEAK not "y"
133 CONFIG_INTEL_IOMMU_DEFAULT_ON | y | clipos | self_protection | FAIL: "is not set"
134 CONFIG_INTEL_IOMMU_SVM | y | clipos | self_protection | OK
135 CONFIG_RESET_ATTACK_MITIGATION | y | my | self_protection | OK
136 CONFIG_AMD_IOMMU_V2 | y | my | self_protection | FAIL: "m"
137 CONFIG_SECURITY | y |defconfig | security_policy | OK
138 CONFIG_SECURITY_YAMA | y | kspp | security_policy | OK
139 CONFIG_SECURITY_WRITABLE_HOOKS | is not set | my | security_policy | OK: not found
140 CONFIG_SECURITY_LOCKDOWN_LSM | y | clipos | security_policy | OK
141 CONFIG_SECURITY_LOCKDOWN_LSM_EARLY | y | clipos | security_policy | OK
142 CONFIG_LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY| y | clipos | security_policy | FAIL: "is not set"
143 CONFIG_SECURITY_SAFESETID | y | my | security_policy | OK
144 CONFIG_SECURITY_LOADPIN | y | my | security_policy | FAIL: "is not set"
145 CONFIG_SECURITY_LOADPIN_ENFORCE | y | my | security_policy | FAIL: CONFIG_SECURITY_LOADPIN not "y"
146 CONFIG_SECCOMP | y |defconfig | cut_attack_surface | OK
147 CONFIG_SECCOMP_FILTER | y |defconfig | cut_attack_surface | OK
148 CONFIG_STRICT_DEVMEM | y |defconfig | cut_attack_surface | OK
149 CONFIG_ACPI_CUSTOM_METHOD | is not set | kspp | cut_attack_surface | OK
150 CONFIG_COMPAT_BRK | is not set | kspp | cut_attack_surface | OK
151 CONFIG_DEVKMEM | is not set | kspp | cut_attack_surface | OK
152 CONFIG_COMPAT_VDSO | is not set | kspp | cut_attack_surface | OK
153 CONFIG_BINFMT_MISC | is not set | kspp | cut_attack_surface | FAIL: "m"
154 CONFIG_INET_DIAG | is not set | kspp | cut_attack_surface | FAIL: "m"
155 CONFIG_KEXEC | is not set | kspp | cut_attack_surface | FAIL: "y"
156 CONFIG_PROC_KCORE | is not set | kspp | cut_attack_surface | FAIL: "y"
157 CONFIG_LEGACY_PTYS | is not set | kspp | cut_attack_surface | FAIL: "y"
158 CONFIG_HIBERNATION | is not set | kspp | cut_attack_surface | FAIL: "y"
159 CONFIG_IA32_EMULATION | is not set | kspp | cut_attack_surface | FAIL: "y"
160 CONFIG_X86_X32 | is not set | kspp | cut_attack_surface | FAIL: "y"
161 CONFIG_MODIFY_LDT_SYSCALL | is not set | kspp | cut_attack_surface | FAIL: "y"
162 CONFIG_OABI_COMPAT | is not set | kspp | cut_attack_surface | OK: not found
163 CONFIG_MODULES | is not set | kspp | cut_attack_surface | FAIL: "y"
164 CONFIG_DEVMEM | is not set | kspp | cut_attack_surface | FAIL: "y"
165 CONFIG_IO_STRICT_DEVMEM | y | kspp | cut_attack_surface | FAIL: "is not set"
166 CONFIG_LEGACY_VSYSCALL_NONE | y | kspp | cut_attack_surface | FAIL: "is not set"
167 CONFIG_ZSMALLOC_STAT | is not set |grsecurity| cut_attack_surface | OK
168 CONFIG_PAGE_OWNER | is not set |grsecurity| cut_attack_surface | OK
169 CONFIG_DEBUG_KMEMLEAK | is not set |grsecurity| cut_attack_surface | OK
170 CONFIG_BINFMT_AOUT | is not set |grsecurity| cut_attack_surface | OK: not found
171 CONFIG_KPROBE_EVENTS | is not set |grsecurity| cut_attack_surface | FAIL: "y"
172 CONFIG_UPROBE_EVENTS | is not set |grsecurity| cut_attack_surface | FAIL: "y"
173 CONFIG_GENERIC_TRACER | is not set |grsecurity| cut_attack_surface | FAIL: "y"
174 CONFIG_FUNCTION_TRACER | is not set |grsecurity| cut_attack_surface | FAIL: "y"
175 CONFIG_STACK_TRACER | is not set |grsecurity| cut_attack_surface | FAIL: "y"
176 CONFIG_HIST_TRIGGERS | is not set |grsecurity| cut_attack_surface | FAIL: "y"
177 CONFIG_BLK_DEV_IO_TRACE | is not set |grsecurity| cut_attack_surface | FAIL: "y"
178 CONFIG_PROC_VMCORE | is not set |grsecurity| cut_attack_surface | FAIL: "y"
179 CONFIG_PROC_PAGE_MONITOR | is not set |grsecurity| cut_attack_surface | FAIL: "y"
180 CONFIG_USELIB | is not set |grsecurity| cut_attack_surface | FAIL: "y"
181 CONFIG_CHECKPOINT_RESTORE | is not set |grsecurity| cut_attack_surface | FAIL: "y"
182 CONFIG_USERFAULTFD | is not set |grsecurity| cut_attack_surface | FAIL: "y"
183 CONFIG_HWPOISON_INJECT | is not set |grsecurity| cut_attack_surface | FAIL: "m"
184 CONFIG_MEM_SOFT_DIRTY | is not set |grsecurity| cut_attack_surface | FAIL: "y"
185 CONFIG_DEVPORT | is not set |grsecurity| cut_attack_surface | FAIL: "y"
186 CONFIG_DEBUG_FS | is not set |grsecurity| cut_attack_surface | FAIL: "y"
187 CONFIG_NOTIFIER_ERROR_INJECTION | is not set |grsecurity| cut_attack_surface | FAIL: "m"
188 CONFIG_FAIL_FUTEX | is not set |grsecurity| cut_attack_surface | OK: not found
189 CONFIG_PUNIT_ATOM_DEBUG | is not set |grsecurity| cut_attack_surface | FAIL: "m"
190 CONFIG_ACPI_CONFIGFS | is not set |grsecurity| cut_attack_surface | FAIL: "m"
191 CONFIG_EDAC_DEBUG | is not set |grsecurity| cut_attack_surface | OK
192 CONFIG_DRM_I915_DEBUG | is not set |grsecurity| cut_attack_surface | OK
193 CONFIG_BCACHE_CLOSURES_DEBUG | is not set |grsecurity| cut_attack_surface | OK
194 CONFIG_DVB_C8SECTPFE | is not set |grsecurity| cut_attack_surface | OK: not found
195 CONFIG_MTD_SLRAM | is not set |grsecurity| cut_attack_surface | FAIL: "m"
196 CONFIG_MTD_PHRAM | is not set |grsecurity| cut_attack_surface | FAIL: "m"
197 CONFIG_IO_URING | is not set |grsecurity| cut_attack_surface | FAIL: "y"
198 CONFIG_KCMP | is not set |grsecurity| cut_attack_surface | OK: not found
199 CONFIG_RSEQ | is not set |grsecurity| cut_attack_surface | FAIL: "y"
200 CONFIG_LATENCYTOP | is not set |grsecurity| cut_attack_surface | OK
201 CONFIG_KCOV | is not set |grsecurity| cut_attack_surface | OK
202 CONFIG_PROVIDE_OHCI1394_DMA_INIT | is not set |grsecurity| cut_attack_surface | OK
203 CONFIG_SUNRPC_DEBUG | is not set |grsecurity| cut_attack_surface | FAIL: "y"
204 CONFIG_PTDUMP_DEBUGFS | is not set |grsecurity| cut_attack_surface | OK: not found
205 CONFIG_DRM_LEGACY | is not set |maintainer| cut_attack_surface | OK
206 CONFIG_FB | is not set |maintainer| cut_attack_surface | FAIL: "y"
207 CONFIG_VT | is not set |maintainer| cut_attack_surface | FAIL: "y"
208 CONFIG_BLK_DEV_FD | is not set |maintainer| cut_attack_surface | FAIL: "m"
209 CONFIG_AIO | is not set |grapheneos| cut_attack_surface | FAIL: "y"
210 CONFIG_STAGING | is not set | clipos | cut_attack_surface | FAIL: "y"
211 CONFIG_KSM | is not set | clipos | cut_attack_surface | FAIL: "y"
212 CONFIG_KALLSYMS | is not set | clipos | cut_attack_surface | FAIL: "y"
213 CONFIG_X86_VSYSCALL_EMULATION | is not set | clipos | cut_attack_surface | FAIL: "y"
214 CONFIG_MAGIC_SYSRQ | is not set | clipos | cut_attack_surface | FAIL: "y"
215 CONFIG_KEXEC_FILE | is not set | clipos | cut_attack_surface | FAIL: "y"
216 CONFIG_USER_NS | is not set | clipos | cut_attack_surface | FAIL: "y"
217 CONFIG_X86_MSR | is not set | clipos | cut_attack_surface | FAIL: "m"
218 CONFIG_X86_CPUID | is not set | clipos | cut_attack_surface | FAIL: "m"
219 CONFIG_X86_IOPL_IOPERM | is not set | clipos | cut_attack_surface | OK: not found
220 CONFIG_ACPI_TABLE_UPGRADE | is not set | clipos | cut_attack_surface | FAIL: "y"
221 CONFIG_EFI_CUSTOM_SSDT_OVERLAYS | is not set | clipos | cut_attack_surface | OK: not found
222 CONFIG_LDISC_AUTOLOAD | is not set | clipos | cut_attack_surface | FAIL: "y"
223 CONFIG_X86_INTEL_TSX_MODE_OFF | y | clipos | cut_attack_surface | OK
224 CONFIG_EFI_TEST | is not set | lockdown | cut_attack_surface | FAIL: "m"
225 CONFIG_BPF_SYSCALL | is not set | lockdown | cut_attack_surface | FAIL: "y"
226 CONFIG_MMIOTRACE_TEST | is not set | lockdown | cut_attack_surface | OK
227 CONFIG_KPROBES | is not set | lockdown | cut_attack_surface | FAIL: "y"
228 CONFIG_TRIM_UNUSED_KSYMS | y | my | cut_attack_surface | FAIL: not found
229 CONFIG_MMIOTRACE | is not set | my | cut_attack_surface | FAIL: "y"
230 CONFIG_LIVEPATCH | is not set | my | cut_attack_surface | FAIL: "y"
231 CONFIG_IP_DCCP | is not set | my | cut_attack_surface | FAIL: "m"
232 CONFIG_IP_SCTP | is not set | my | cut_attack_surface | FAIL: "m"
233 CONFIG_FTRACE | is not set | my | cut_attack_surface | FAIL: "y"
234 CONFIG_VIDEO_VIVID | is not set | my | cut_attack_surface | FAIL: "m"
235 CONFIG_INPUT_EVBUG | is not set | my | cut_attack_surface | FAIL: "m"
236 CONFIG_INTEGRITY | y |defconfig |userspace_hardening | OK
237 CONFIG_ARCH_MMAP_RND_BITS | 32 | clipos |userspace_hardening | FAIL: "28"
239 [+] Config check is finished: 'OK' - 68 / 'FAIL' - 96
242 ## kconfig-hardened-check versioning
244 I usually update the kernel security hardening recommendations after each Linux kernel release.
246 So the version of `kconfig-hardened-check` is associated with the corresponding version of the kernel.
248 The version format is: __[major_number].[kernel_version].[kernel_patchlevel]__
251 ## Questions and answers
253 __Q:__ How disabling `CONFIG_USER_NS` cuts the attack surface? It's needed for containers!
255 __A:__ Yes, the `CONFIG_USER_NS` option provides some isolation between the userspace programs,
256 but the tool recommends disabling it to cut the attack surface __of the kernel__.
260 - A nice LWN article about the corresponding LKML discussion: https://lwn.net/Articles/673597/
262 - A twitter thread about `CONFIG_USER_NS` and security: https://twitter.com/robertswiecki/status/1095447678949953541
264 - 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
268 __Q:__ Why `CONFIG_GCC_PLUGINS` is automatically disabled during the kernel compilation?
270 __A:__ It means that your gcc doesn't support plugins. For example, if you have `gcc-7` on Ubuntu,
271 try to install `gcc-7-plugin-dev` package, it should help.
275 __Q:__ KSPP and CLIP OS recommend `CONFIG_PANIC_ON_OOPS=y`. Why doesn't this tool do the same?
277 __A:__ I personally don't support this recommendation because it provides easy denial-of-service
278 attacks for the whole system (kernel oops is not a rare situation). I think having `CONFIG_BUG` is enough here --
279 if we have a kernel oops in the process context, the offending/attacking process is killed.
283 __Q:__ What about performance impact of these security hardening options?
285 __A:__ Ike Devolder [@BlackIkeEagle][7] made some performance tests and described the results in [this article][8].
289 __Q:__ Why enabling `CONFIG_STATIC_USERMODEHELPER` breaks various things in my GNU/Linux system?
290 Do I really need that feature?
292 __A:__ Linux kernel usermode helpers can be used for privilege escalation in kernel exploits
293 ([example 1][9], [example 2][10]). `CONFIG_STATIC_USERMODEHELPER` prevents that method. But it
294 requires the corresponding support in the userspace: see the [example implementation][11] by
295 Tycho Andersen [@tych0][12].
299 __Q:__ Does my kernel have all those mitigations of Transient Execution Vulnerabilities in my hardware?
301 __A:__ Checking the kernel config is not enough to answer this question.
302 I highly recommend using [spectre-meltdown-checker][13] tool maintained by Stéphane Lesimple [@speed47][14].
305 [1]: http://kernsec.org/wiki/index.php/Kernel_Self_Protection_Project/Recommended_Settings
306 [2]: https://docs.clip-os.org/clipos/kernel.html#configuration
307 [3]: https://grsecurity.net/
308 [4]: https://github.com/a13xp0p0v/linux-kernel-defence-map
309 [5]: https://lwn.net/Articles/791863/
310 [6]: https://github.com/a13xp0p0v/kconfig-hardened-check/issues/38
311 [7]: https://github.com/BlackIkeEagle
312 [8]: https://blog.herecura.eu/blog/2020-05-30-kconfig-hardening-tests/
313 [9]: https://googleprojectzero.blogspot.com/2018/09/a-cache-invalidation-bug-in-linux.html
314 [10]: https://a13xp0p0v.github.io/2020/02/15/CVE-2019-18683.html
315 [11]: https://github.com/tych0/huldufolk
316 [12]: https://github.com/tych0
317 [13]: https://github.com/speed47/spectre-meltdown-checker
318 [14]: https://github.com/speed47
319 [15]: https://github.com/a13xp0p0v/kconfig-hardened-check/issues/53
320 [16]: https://github.com/a13xp0p0v/kconfig-hardened-check/pull/54
projects / kconfig-hardened-check.git / blob