Guide to the Secure Configuration of Fedora
Rules, Groups, and Values defined within the XCCDF Benchmark
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Disable kernel debugfs
<code>debugfs</code> is a virtual file system that kernel developers use to put debugging files into. Enable this option to be able to read and wri...Rule Low Severity -
Enable checks on linked list manipulation
Enable this to turn on extended checks in the linked-list walking routines. The configuration that was used to build kernel is available at <code>...Rule Low Severity -
Enable checks on notifier call chains
Enable this to turn on sanity checking for notifier call chains. This is most useful for kernel developers to make sure that modules properly unreg...Rule Low Severity -
Enable checks on scatter-gather (SG) table operations
Scatter-gather tables are mechanism used for high performance I/O on DMA devices. Enable this to turn on checks on scatter-gather tables. The conf...Rule Low Severity -
Warn on W+X mappings found at boot
Generate a warning if any W+X mappings are found at boot. This configuration is available from kernel 5.8. The configuration that was used to buil...Rule Medium Severity -
Configure low address space to protect from user allocation
This is the portion of low virtual memory which should be protected from userspace allocation. This configuration is available from kernel 3.14, bu...Rule Medium Severity -
Disable /dev/kmem virtual device support
Disable support for the /dev/kmem device. The configuration that was used to build kernel is available at <code>/boot/config-*</code>. To chec...Rule Low Severity -
Harden common str/mem functions against buffer overflows
Detect overflows of buffers in common string and memory functions where the compiler can determine and validate the buffer sizes. This configuratio...Rule Medium Severity -
Harden memory copies between kernel and userspace
This option checks for obviously wrong memory regions when copying memory to/from the kernel (via copy_to_user() and copy_from_user() functions) by...Rule High Severity -
Do not allow usercopy whitelist violations to fallback to object size
This is a temporary option that allows missing usercopy whitelists to be discovered via a WARN() to the kernel log, instead of rejecting the copy, ...Rule High Severity -
Disable hibernation
Enable the suspend to disk (STD) functionality, which is usually called "hibernation" in user interfaces. STD checkpoints the system and powers it ...Rule Medium Severity -
Disable IA32 emulation
Disables support for legacy 32-bit programs under a 64-bit kernel. The configuration that was used to build kernel is available at <code>/boot/con...Rule Medium Severity -
Disable the IPv6 protocol
Disable support for IP version 6 (IPv6). The configuration that was used to build kernel is available at <code>/boot/config-*</code>. To check...Rule Medium Severity -
Disable kexec system call
<code>kexec</code> is a system call that implements the ability to shutdown your current kernel, and to start another kernel. It is like a reboot b...Rule Low Severity -
Disable legacy (BSD) PTY support
Disable the Linux traditional BSD-like terminal names /dev/ptyxx for masters and /dev/ttyxx for slaves of pseudo terminals, and use only the modern...Rule Medium Severity -
Disable vsyscall emulation
The kernel traps and emulates calls into the fixed vsyscall address mapping. This configuration is available from kernel 5.3, but may be available ...Rule Medium Severity -
Disable vsyscall mapping
This config disables the vsyscall mapping at all. Attempts to use the vsyscalls will be reported to dmesg, so that either old or malicious userspac...Rule Medium Severity -
Disable vsyscall emulate execution only
The kernel traps and emulates calls into the fixed vsyscall address mapping and does not allow reads. This configuration is available from kernel 5...Rule Medium Severity -
authlogin_nsswitch_use_ldap SELinux Boolean
default - Default SELinux boolean setting.
on - SELinux boolean is enabled.
off - SELinux boolean is disabled.Value -
Disable the LDT (local descriptor table)
Linux can allow user programs to install a per-process x86 Local Descriptor Table (LDT) using the modify_ldt(2) system call. This is required to ru...Rule Medium Severity -
Enable module signature verification
Check modules for valid signatures upon load. Note that this option adds the OpenSSL development packages as a kernel build dependency so that the ...Rule Medium Severity -
Enable automatic signing of all modules
Sign all modules during make modules_install. Without this option, modules must be signed manually, using the scripts/sign-file tool. The configur...Rule Medium Severity -
Require modules to be validly signed
Reject unsigned modules or signed modules with an unknown key. The configuration that was used to build kernel is available at <code>/boot/config-...Rule Medium Severity -
Specify the hash to use when signing modules
This configures the kernel to build and sign modules using <xccdf-1.2:sub idref="xccdf_org.ssgproject.content_value_var_kernel_config_module_sig_ha...Rule Medium Severity -
Specify module signing key to use
Setting this option to something other than its default of <code>certs/signing_key.pem</code> will disable the autogeneration of signing keys and a...Rule Medium Severity -
Sign kernel modules with SHA-512
This configures the kernel to build and sign modules using SHA512 as the hash function. The configuration that was used to build kernel is availab...Rule Medium Severity -
Enable poison of pages after freeing
Fill the pages with poison patterns after free_pages() and verify the patterns before alloc_pages. This does have a potential performance impact if...Rule Medium Severity -
Enable poison without sanity check
Skip the sanity checking on alloc, only fill the pages with poison on free. This reduces some of the overhead of the poisoning feature. This config...Rule Medium Severity -
Use zero for poisoning instead of debugging value
Instead of using the existing poison value, fill the pages with zeros. This makes it harder to detect when errors are occurring due to sanitization...Rule Medium Severity -
Remove the kernel mapping in user mode
This feature reduces the number of hardware side channels by ensuring that the majority of kernel addresses are not mapped into userspace. This con...Rule High Severity -
Kernel panic oops
Enable the kernel to panic when it oopses. This has the same effect as setting oops=panic on the kernel command line. The configuration that was u...Rule Medium Severity -
Kernel panic timeout
Set the timeout value (in seconds) until a reboot occurs when the kernel panics. A timeout of 0 configures the system to wait forever. With a timeo...Rule Medium Severity -
Disable support for /proc/kkcore
Provides a virtual ELF core file of the live kernel. The configuration that was used to build kernel is available at <code>/boot/config-*</code>. ...Rule Low Severity -
Randomize the address of the kernel image (KASLR)
In support of Kernel Address Space Layout Randomization (KASLR), this randomizes the physical address at which the kernel image is decompressed and...Rule Medium Severity -
Randomize the kernel memory sections
Randomizes the base virtual address of kernel memory sections (physical memory mapping, vmalloc & vmemmap). This configuration is available fro...Rule Medium Severity -
Perform full reference count validation
Enabling this switches the refcounting infrastructure from a fast unchecked atomic_t implementation to a fully state checked implementation, which ...Rule Medium Severity -
Avoid speculative indirect branches in kernel
Compile kernel with the retpoline compiler options to guard against kernel-to-user data leaks by avoiding speculative indirect branches. Requires a...Rule Medium Severity -
Detect stack corruption on calls to schedule()
This option checks for a stack overrun on calls to schedule(). If the stack end location is found to be overwritten always panic as the content of ...Rule Medium Severity -
Enable seccomp to safely compute untrusted bytecode
This kernel feature is useful for number crunching applications that may need to compute untrusted bytecode during their execution. By using pipes ...Rule Medium Severity -
Enable use of Berkeley Packet Filter with seccomp
Enable tasks to build secure computing environments defined in terms of Berkeley Packet Filter programs which implement task-defined system call fi...Rule Medium Severity -
Enable different security models
This allows you to choose different security modules to be configured into your kernel. The configuration that was used to build kernel is availab...Rule Medium Severity -
Enable Yama support
This enables support for LSM module Yama, which extends DAC support with additional system-wide security settings beyond regular Linux discretionar...Rule Medium Severity -
Harden slab freelist metadata
This feature protects integrity of the allocator's metadata. This configuration is available from kernel 4.14. The configuration that was used to ...Rule Medium Severity -
Randomize slab freelist
Randomizes the freelist order used on creating new pages. This configuration is available from kernel 5.9, but may be available if backported by di...Rule Medium Severity -
authlogin_radius SELinux Boolean
default - Default SELinux boolean setting.
on - SELinux boolean is enabled.
off - SELinux boolean is disabled.Value -
Disallow merge of slab caches
For reduced kernel memory fragmentation, slab caches can be merged when they share the same size and other characteristics. This carries a risk of ...Rule Medium Severity -
Enable SLUB debugging support
SLUB has extensive debug support features and this allows the allocator validation checking to be enabled. The configuration that was used to buil...Rule Medium Severity -
Stack Protector buffer overlow detection
This feature puts, at the beginning of functions, a canary value on the stack just before the return address, and validates the value just before a...Rule Medium Severity -
Strong Stack Protector
This features adds canary logic protection to more kinds of vulnerable functions than CONFIG_STACKPROTECTOR, but not to all functions so that perfo...Rule Medium Severity -
Make the kernel text and rodata read-only
When set, kernel text and rodata memory will be made read-only, and non-text memory will be made non-executable. This configuration is available fr...Rule Medium Severity
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