X-Git-Url: https://jxself.org/git/?a=blobdiff_plain;f=README.md;h=3ae9147ac0ba3a5f454a17c5c3d37e45546c5116;hb=d361925ba8e7c1f712615e12d4eff678f1f4d59b;hp=846988528435c45fc09cc3f36717744d15bc9215;hpb=333af0092a7da2471f30689aac8c52ff2f5d2e4c;p=kconfig-hardened-check.git diff --git a/README.md b/README.md index 8469885..3ae9147 100644 --- a/README.md +++ b/README.md @@ -12,21 +12,26 @@ make our systems more secure. But nobody likes checking configs manually. So let the computers do their job! -__kconfig-hardened-check.py__ helps me to check the Linux kernel options +__kconfig-hardened-check__ helps me to check the Linux kernel options against my security hardening preferences, which are based on the - - [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 Linux kernel maintainers (see [#38][6], [#53][15], [#54][16], [#62][17]). + - [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] This tool supports checking __Kconfig__ options and __kernel cmdline__ parameters. -I also created [__Linux Kernel Defence Map__][4] that is a graphical representation of the +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. + ## Supported microarchitectures - X86_64 @@ -34,7 +39,7 @@ or exploitation techniques. - ARM64 - ARM -TODO: RISC-V +TODO: RISC-V (issue [#56][22]) ## Installation @@ -87,10 +92,10 @@ CONFIG_DEVMEM | is not set | kspp | cut_atta - `-m show_ok` for showing only the successful checks - `-m json` for printing the results in JSON format (for combining `kconfig-hardened-check` with other tools) -## Example output for `Fedora 34` kernel config +## Example output for `Fedora 34` kernel configuration ``` -$ ./bin/kconfig-hardened-check -c /boot/config-5.19.4-200.fc36.x86_64 -l /proc/cmdline -[+] Kconfig file to check: /boot/config-5.19.4-200.fc36.x86_64 +$ ./bin/kconfig-hardened-check -c /boot/config-5.19.14-200.fc36.x86_64 -l /proc/cmdline +[+] Kconfig file to check: /boot/config-5.19.14-200.fc36.x86_64 [+] Kernel cmdline file to check: /proc/cmdline [+] Detected architecture: X86_64 [+] Detected kernel version: 5.19 @@ -110,6 +115,9 @@ CONFIG_THREAD_INFO_IN_TASK |kconfig| y |defconfig | self_p CONFIG_IOMMU_SUPPORT |kconfig| y |defconfig | self_protection | OK CONFIG_RANDOMIZE_BASE |kconfig| y |defconfig | self_protection | OK CONFIG_VMAP_STACK |kconfig| y |defconfig | self_protection | OK +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_X86_SMAP |kconfig| y |defconfig | self_protection | OK: version >= 5.19 @@ -127,6 +135,7 @@ CONFIG_SLAB_FREELIST_RANDOM |kconfig| y | kspp | self_p 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" @@ -137,7 +146,11 @@ CONFIG_WERROR |kconfig| y | kspp | self_p 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_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_SCHED_CORE |kconfig| y | kspp | self_protection | OK 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 not "y" CONFIG_HARDENED_USERCOPY |kconfig| y | kspp | self_protection | OK CONFIG_HARDENED_USERCOPY_FALLBACK |kconfig| is not set | kspp | self_protection | OK: not found CONFIG_HARDENED_USERCOPY_PAGESPAN |kconfig| is not set | kspp | self_protection | OK: not found @@ -147,38 +160,34 @@ CONFIG_MODULE_SIG_SHA512 |kconfig| y | kspp | self_p CONFIG_MODULE_SIG_FORCE |kconfig| y | kspp | self_protection | FAIL: "is not set" CONFIG_INIT_STACK_ALL_ZERO |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 | FAIL: "is not set" +CONFIG_UBSAN_BOUNDS |kconfig| y | kspp | self_protection | FAIL: not found +CONFIG_UBSAN_LOCAL_BOUNDS |kconfig| y | kspp | self_protection | FAIL: not found +CONFIG_UBSAN_TRAP |kconfig| y | kspp | self_protection | FAIL: CONFIG_UBSAN_BOUNDS not "y" +CONFIG_UBSAN_SANITIZE_ALL |kconfig| y | kspp | self_protection | FAIL: CONFIG_UBSAN_BOUNDS 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 not "y" +CONFIG_STACKLEAK_RUNTIME_DISABLE |kconfig| is not set | kspp | self_protection | FAIL: CONFIG_GCC_PLUGIN_STACKLEAK not "y" CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT |kconfig| y | kspp | self_protection | OK -CONFIG_SCHED_CORE |kconfig| y | kspp | self_protection | OK +CONFIG_CFI_CLANG |kconfig| y | kspp | self_protection | FAIL: not found +CONFIG_CFI_PERMISSIVE |kconfig| is not set | kspp | self_protection | FAIL: CONFIG_CFI_CLANG not "y" CONFIG_DEFAULT_MMAP_MIN_ADDR |kconfig| 65536 | kspp | self_protection | OK -CONFIG_UBSAN_BOUNDS |kconfig| y |maintainer| self_protection | FAIL: not found -CONFIG_UBSAN_SANITIZE_ALL |kconfig| y |maintainer| self_protection | FAIL: CONFIG_UBSAN_BOUNDS not "y" -CONFIG_UBSAN_TRAP |kconfig| y |maintainer| self_protection | FAIL: CONFIG_UBSAN_BOUNDS not "y" -CONFIG_DEBUG_VIRTUAL |kconfig| y | clipos | self_protection | FAIL: "is not set" -CONFIG_STATIC_USERMODEHELPER |kconfig| y | clipos | self_protection | FAIL: "is not set" -CONFIG_EFI_DISABLE_PCI_DMA |kconfig| y | clipos | self_protection | FAIL: "is not set" +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_RANDOM_TRUST_BOOTLOADER |kconfig| is not set | clipos | self_protection | FAIL: "y" -CONFIG_RANDOM_TRUST_CPU |kconfig| is not set | clipos | self_protection | FAIL: "y" -CONFIG_RANDSTRUCT_PERFORMANCE |kconfig| is not set | clipos | self_protection | FAIL: CONFIG_RANDSTRUCT_FULL not "y" -CONFIG_STACKLEAK_METRICS |kconfig| is not set | clipos | self_protection | FAIL: CONFIG_GCC_PLUGIN_STACKLEAK not "y" -CONFIG_STACKLEAK_RUNTIME_DISABLE |kconfig| is not set | clipos | self_protection | FAIL: CONFIG_GCC_PLUGIN_STACKLEAK not "y" -CONFIG_INTEL_IOMMU_DEFAULT_ON |kconfig| y | clipos | self_protection | FAIL: "is not set" -CONFIG_INTEL_IOMMU_SVM |kconfig| y | clipos | self_protection | OK -CONFIG_RESET_ATTACK_MITIGATION |kconfig| y | my | self_protection | FAIL: "is not set" -CONFIG_SLS |kconfig| y | my | self_protection | OK -CONFIG_AMD_IOMMU_V2 |kconfig| y | my | self_protection | FAIL: "m" CONFIG_SECURITY |kconfig| y |defconfig | security_policy | OK CONFIG_SECURITY_YAMA |kconfig| y | kspp | security_policy | OK CONFIG_SECURITY_LANDLOCK |kconfig| y | kspp | security_policy | OK CONFIG_SECURITY_SELINUX_DISABLE |kconfig| is not set | kspp | security_policy | OK -CONFIG_SECURITY_LOCKDOWN_LSM |kconfig| y | clipos | security_policy | OK -CONFIG_SECURITY_LOCKDOWN_LSM_EARLY |kconfig| y | clipos | security_policy | OK -CONFIG_LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY|kconfig| y | clipos | security_policy | FAIL: "is not set" -CONFIG_SECURITY_WRITABLE_HOOKS |kconfig| is not set | my | security_policy | OK: not found -CONFIG_SECURITY_SAFESETID |kconfig| y | my | security_policy | FAIL: "is not set" -CONFIG_SECURITY_LOADPIN |kconfig| y | my | security_policy | FAIL: "is not set" -CONFIG_SECURITY_LOADPIN_ENFORCE |kconfig| y | my | security_policy | FAIL: CONFIG_SECURITY_LOADPIN not "y" +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: not found CONFIG_BPF_UNPRIV_DEFAULT_OFF |kconfig| y |defconfig |cut_attack_surface| OK CONFIG_SECCOMP |kconfig| y |defconfig |cut_attack_surface| OK CONFIG_SECCOMP_FILTER |kconfig| y |defconfig |cut_attack_surface| OK @@ -202,6 +211,7 @@ CONFIG_X86_MSR |kconfig| is not set | kspp |cut_att 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" @@ -258,7 +268,7 @@ CONFIG_X86_CPUID |kconfig| is not set | clipos |cut_att 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_LDISC_AUTOLOAD |kconfig| is not set | clipos |cut_attack_surface| FAIL: "y" +CONFIG_COREDUMP |kconfig| is not set | clipos |cut_attack_surface| FAIL: "y" CONFIG_X86_INTEL_TSX_MODE_OFF |kconfig| y | clipos |cut_attack_surface| OK CONFIG_BPF_SYSCALL |kconfig| is not set | lockdown |cut_attack_surface| FAIL: "y" CONFIG_EFI_TEST |kconfig| is not set | lockdown |cut_attack_surface| FAIL: "m" @@ -275,29 +285,33 @@ CONFIG_INPUT_EVBUG |kconfig| is not set | my |cut_att CONFIG_KGDB |kconfig| is not set | my |cut_attack_surface| FAIL: "y" 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: not found +nosmap |cmdline| is not set |defconfig | self_protection | OK: not found +nokaslr |cmdline| is not set |defconfig | self_protection | OK: not found +nopti |cmdline| is not set |defconfig | self_protection | OK: not found +nospectre_v1 |cmdline| is not set |defconfig | self_protection | OK: not found +nospectre_v2 |cmdline| is not set |defconfig | self_protection | OK: not found rodata |cmdline| 1 |defconfig | self_protection | OK: rodata not found init_on_alloc |cmdline| 1 | kspp | self_protection | FAIL: not found init_on_free |cmdline| 1 | kspp | self_protection | FAIL: not found slab_nomerge |cmdline| | kspp | self_protection | OK: CONFIG_SLAB_MERGE_DEFAULT "is not set" iommu.strict |cmdline| 1 | kspp | self_protection | FAIL: not found iommu.passthrough |cmdline| 0 | kspp | self_protection | OK: CONFIG_IOMMU_DEFAULT_PASSTHROUGH "is not set" -nokaslr |cmdline| is not set | kspp | self_protection | OK: not found hardened_usercopy |cmdline| 1 | kspp | self_protection | OK: CONFIG_HARDENED_USERCOPY "y" slab_common.usercopy_fallback |cmdline| 0 | kspp | self_protection | OK: CONFIG_HARDENED_USERCOPY_FALLBACK not found randomize_kstack_offset |cmdline| 1 | kspp | self_protection | OK: CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT "y" pti |cmdline| on | kspp | self_protection | FAIL: not found page_alloc.shuffle |cmdline| 1 | clipos | self_protection | FAIL: not found -nosmep |cmdline| is not set | my | self_protection | OK: not found -nosmap |cmdline| is not set | my | self_protection | OK: not found +spectre_v2 |cmdline| on | clipos | self_protection | FAIL: not found vsyscall |cmdline| none | kspp |cut_attack_surface| FAIL: not found debugfs |cmdline| off | grsec |cut_attack_surface| FAIL: not found -[+] Config check is finished: 'OK' - 94 / 'FAIL' - 99 +[+] Config check is finished: 'OK' - 101 / 'FAIL' - 101 ``` ## kconfig-hardened-check versioning -I usually update the kernel security hardening recommendations after each Linux kernel release. +I usually update the kernel security hardening recommendations every few kernel releases. So the version of `kconfig-hardened-check` is associated with the corresponding version of the kernel. @@ -306,6 +320,13 @@ The version format is: __[major_number].[kernel_version].[kernel_patchlevel]__ ## 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][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, @@ -313,7 +334,7 @@ but the tool recommends disabling it to cut the attack surface __of the kernel__ The rationale: - - A nice LWN article about the corresponding LKML discussion: https://lwn.net/Articles/673597/ + - 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 @@ -321,48 +342,53 @@ The rationale:
-__Q:__ Why `CONFIG_GCC_PLUGINS` is automatically disabled during the kernel compilation? +__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 -__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. +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:__ KSPP and CLIP OS recommend `CONFIG_PANIC_ON_OOPS=y`. Why doesn't this tool do the same? +__Q:__ Why enabling `CONFIG_STATIC_USERMODEHELPER` breaks various things in my GNU/Linux system? +Do I really need that feature? -__A:__ I personally don't support this recommendation because it provides easy denial-of-service -attacks for the whole system (kernel oops is not a rare situation). I think having `CONFIG_BUG` is enough here -- -if we have a kernel oops in the process context, the offending/attacking process is killed. +__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]. +__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:__ Why enabling `CONFIG_STATIC_USERMODEHELPER` breaks various things in my GNU/Linux system? -Do I really need that feature? +__Q:__ Does my kernel have all those mitigations of Transient Execution Vulnerabilities in my hardware? -__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]. +__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:__ Does my kernel have all those mitigations of Transient Execution Vulnerabilities in my hardware? +__Q:__ Why the `CONFIG_GCC_PLUGINS` option is automatically disabled during the kernel compilation? -__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]. +__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 @@ -385,3 +411,7 @@ I highly recommend using [spectre-meltdown-checker][13] tool maintained by Stép [18]: https://cateee.net/lkddb/web-lkddb/ [19]: https://github.com/cateee/lkddb [20]: https://kernel.org/ +[21]: https://github.com/a13xp0p0v/kconfig-hardened-check/issues/66 +[22]: https://github.com/a13xp0p0v/kconfig-hardened-check/issues/56 +[23]: https://github.com/a13xp0p0v/kconfig-hardened-check/issues?q=label%3Akernel_maintainer_feedback +[24]: https://github.com/a13xp0p0v/kconfig-hardened-check#motivation