Guide to the Secure Configuration of Red Hat Enterprise Linux 8
Rules, Groups, and Values defined within the XCCDF Benchmark
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Enforce Spectre v2 mitigation
Spectre V2 is an indirect branch poisoning attack that can lead to data leakage. An exploit for Spectre V2 tricks the indirect branch predictor into executing code from a future indirect branch cho...Rule High Severity -
Ensure debug-shell service is not enabled during boot
systemd's <code>debug-shell</code> service is intended to diagnose systemd related boot issues with various <code>systemctl</code> commands. Once enabled and following a system reboot, the root she...Rule Medium Severity -
Disable vsyscalls
To disable use of virtual syscalls, add the argument <code>vsyscall=none</code> to the default GRUB 2 command line for the Linux operating system. To ensure that <code>vsyscall=none</code> is added...Rule Medium Severity -
Non-UEFI GRUB2 bootloader configuration
Non-UEFI GRUB2 bootloader configurationGroup -
Verify /boot/grub2/grub.cfg Group Ownership
The file <code>/boot/grub2/grub.cfg</code> should be group-owned by the <code>root</code> group to prevent destruction or modification of the file. To properly set the group owner of <code>/boot/g...Rule Medium Severity -
Verify /boot/grub2/grub.cfg Permissions
File permissions for <code>/boot/grub2/grub.cfg</code> should be set to 600. To properly set the permissions of <code>/boot/grub2/grub.cfg</code>, run the command: <pre>$ sudo chmod 600 /boot/grub...Rule Medium Severity -
Key and certificate for kernel module signing
The private key and certificate to use when signing modules during kernel build process. On systems where the OpenSSL ENGINE_pkcs11 is functional — a PKCS#11 URI as defined by RFC7512 In the latter...Value -
Boot Loader Is Not Installed On Removeable Media
The system must not allow removable media to be used as the boot loader. Remove alternate methods of booting the system from removable media. <code>usb0</code>, <code>cd</code>, <code>fd0</code>, e...Rule Medium Severity -
Set Boot Loader Password in grub2
The grub2 boot loader should have a superuser account and password protection enabled to protect boot-time settings. <br> <br> Since plaintext passwords are a security risk, generate a hash...Rule High Severity -
UEFI GRUB2 bootloader configuration
UEFI GRUB2 bootloader configurationGroup -
Verify the UEFI Boot Loader grub.cfg Group Ownership
The file <code>/boot/efi/EFI/redhat/grub.cfg</code> should be group-owned by the <code>root</code> group to prevent destruction or modification of the file. To properly set the group owner of <cod...Rule Medium Severity -
Verify /boot/efi/EFI/redhat/user.cfg Group Ownership
The file <code>/boot/efi/EFI/redhat/user.cfg</code> should be group-owned by the <code>root</code> group to prevent reading or modification of the file. To properly set the group owner of <code>/b...Rule Medium Severity -
Verify the UEFI Boot Loader grub.cfg User Ownership
The file <code>/boot/efi/EFI/redhat/grub.cfg</code> should be owned by the <code>root</code> user to prevent destruction or modification of the file. To properly set the owner of <code>/boot/efi/E...Rule Medium Severity -
Verify /boot/efi/EFI/redhat/user.cfg User Ownership
The file <code>/boot/efi/EFI/redhat/user.cfg</code> should be owned by the <code>root</code> user to prevent reading or modification of the file. To properly set the owner of <code>/boot/efi/EFI/r...Rule Medium Severity -
Verify the UEFI Boot Loader grub.cfg Permissions
File permissions for <code>/boot/efi/EFI/redhat/grub.cfg</code> should be set to 700. To properly set the permissions of <code>/boot/efi/EFI/redhat/grub.cfg</code>, run the command: <pre>$ sudo ch...Rule Medium Severity -
Verify /boot/efi/EFI/redhat/user.cfg Permissions
File permissions for <code>/boot/efi/EFI/redhat/user.cfg</code> should be set to 600. To properly set the permissions of <code>/boot/efi/EFI/redhat/user.cfg</code>, run the command: <pre>$ sudo ch...Rule Medium Severity -
Set the UEFI Boot Loader Admin Username to a Non-Default Value
The grub2 boot loader should have a superuser account and password protection enabled to protect boot-time settings. <br> <br> To maximize the protection, select a password-protected superu...Rule Medium Severity -
Kernel panic timeout
The time, in seconds, to wait until a reboot occurs. If the value is0the system never reboots. If the value is less than0the system reboots immediately.Value -
UEFI Boot Loader Is Not Installed On Removeable Media
The system must not allow removable media to be used as the boot loader. Remove alternate methods of booting the system from removable media. <code>usb0</code>, <code>cd</code>, <code>fd0</code>, e...Rule Medium Severity -
zIPL bootloader configuration
During the boot process, the bootloader is responsible for starting the execution of the kernel and passing options to it. The default Red Hat Enterprise Linux 8 boot loader for s390x systems is ca...Group -
Enable Auditing to Start Prior to the Audit Daemon in zIPL
To ensure all processes can be audited, even those which start prior to the audit daemon, check that all boot entries in <code>/boot/loader/entries/*.conf</code> have <code>audit=1</code> included ...Rule Medium Severity -
Extend Audit Backlog Limit for the Audit Daemon in zIPL
To improve the kernel capacity to queue all log events, even those which start prior to the audit daemon, check that all boot entries in <code>/boot/loader/entries/*.conf</code> have <code>audit_ba...Rule Medium Severity -
Ensure all zIPL boot entries are BLS compliant
Ensure that zIPL boot entries fully adheres to Boot Loader Specification (BLS) by checking that/etc/zipl.confdoesn't containimage =.Rule Medium Severity -
Ensure zIPL bootmap is up to date
Make sure that <code>/boot/bootmap</code> is up to date.<br> Every time a boot entry or zIPL configuration is changed <code>/boot/bootmap</code> needs to be updated to reflect the changes.<br> Run ...Rule Medium Severity -
Ensure SELinux Not Disabled in zIPL
To ensure SELinux is not disabled at boot time, check that no boot entry in/boot/loader/entries/*.confhasselinux=0included in its options.
Rule Medium Severity -
Enable page allocator poisoning in zIPL
To enable poisoning of free pages, check that all boot entries in <code>/boot/loader/entries/*.conf</code> have <code>page_poison=1</code> included in its options.<br> To ensure that new kernels an...Rule Medium Severity -
Enable SLUB/SLAB allocator poisoning in zIPL
To enable poisoning of SLUB/SLAB objects, check that all boot entries in <code>/boot/loader/entries/*.conf</code> have <code>slub_debug=P</code> included in its options.<br> To ensure that new kern...Rule Medium Severity -
Disable vsyscalls in zIPL
To disable use of virtual syscalls, check that all boot entries in <code>/boot/loader/entries/*.conf</code> have <code>vsyscall=none</code> included in its options.<br> To ensure that new kernels a...Rule Medium Severity -
Protect Random-Number Entropy Pool
The I/O operations of the Linux kernel block layer due to their inherently unpredictable execution times have been traditionally considered as a reliable source to contribute to random-number entro...Group -
Ensure Solid State Drives Do Not Contribute To Random-Number Entropy Pool
For each solid-state drive on the system, run:# echo 0 > /sys/block/DRIVE/queue/add_random
Rule Medium Severity -
Kernel Configuration
Contains rules that check the kernel configuration that was used to build it.Group -
Hash function for kernel module signing
The hash function to use when signing modules during kernel build process.Value -
Configure Logwatch on the Central Log Server
Is this system the central log server? If so, edit the file/etc/logwatch/conf/logwatch.confas shown below.Group -
Do not allow ACPI methods to be inserted/replaced at run time
This debug facility allows ACPI AML methods to be inserted and/or replaced without rebooting the system. This configuration is available from kernel 3.0. The configuration that was used to build k...Rule Low Severity -
Emulate Privileged Access Never (PAN)
Enabling this option prevents the kernel from accessing user-space memory directly by pointing TTBR0_EL1 to a reserved zeroed area and reserved ASID. The user access routines restore the valid TTBR...Rule Medium Severity -
Disable kernel support for MISC binaries
Enabling <code>CONFIG_BINFMT_MISC</code> makes it possible to plug wrapper-driven binary formats into the kernel. This is specially useful for programs that need an interpreter to run like Java, Py...Rule Medium Severity -
Enable support for BUG()
Disabling this option eliminates support for BUG and WARN, reducing the size of your kernel image and potentially quietly ignoring numerous fatal conditions. You should only consider disabling this...Rule Medium Severity -
Trigger a kernel BUG when data corruption is detected
This option makes the kernel BUG when it encounters data corruption in kernel memory structures when they get checked for validity. This configuration is available from kernel 4.10. The configurat...Rule Low Severity -
Disable compatibility with brk()
Enabling compatiliby with <code>brk()</code> allows legacy binaries to run (i.e. those linked against libc5). But this compatibility comes at the cost of not being able to randomize the heap placem...Rule Medium Severity -
Disable the 32-bit vDSO
Certain buggy versions of glibc (2.3.3) will crash if they are presented with a 32-bit vDSO that is not mapped at the address indicated in its segment table. Setting <code>CONFIG_COMPAT_VDSO</code>...Rule Low Severity -
Enable checks on credential management
Enable this to turn on some debug checking for credential management. The additional code keeps track of the number of pointers from task_structs to any given cred struct, and checks to see that th...Rule Low Severity -
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 write to these files. The configuration that was use...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>/boot/config-*</code>. To check the configurat...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 unregister themselves from notifier chains. The config...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 configuration that was used to build kernel is availab...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 build kernel is available at <code>/boot/config-*</cod...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 check the configuration value for <code>CONFIG_DEVKMEM...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 configuration is available from kernel 4.13, but may be availa...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 rejecting memory ranges that are larger than the ...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, falling back to non-whitelisted hardened usercopy ...Rule High Severity
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