Guide to the Secure Configuration of Red Hat Enterprise Linux CoreOS 4
Rules, Groups, and Values defined within the XCCDF Benchmark
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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_hash" use="legacy"></xccdf-1.2:sub> as the hash func...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 allow the kernel modules to be signed with a key of...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 available at <code>/boot/config-*</code>. To check th...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 configuration is available from kernel 4.6. The configu...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 but the zeroing at free means that it is no longe...Rule Medium 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 used to build kernel is available at <code>/boot/co...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 timeout value greater than 0, the system will wait the ...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>. To check the configuration value for <code>CON...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 the virtual address where the kernel image is map...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 from kernel 4.8, but may be available if backported b...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 compiler with -mindirect-branch=thunk-extern supp...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 or other transports made available to the process ...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 filtering polices. The configuration that was used ...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 available at <code>/boot/config-*</code>. To check th...Rule Medium Severity -
Disable mutable hooks
Ensure kernel structures associated with LSMs are always mapped as read-only after system boot. The configuration that was used to build kernel is available at <code>/boot/config-*</code>. To ...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 discretionary access controls. The module will limit the use o...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 build kernel is available at <code>/boot/config-*</cod...Rule Medium Severity -
Enable TCP/IP syncookie support
Normal TCP/IP networking is open to an attack known as SYN flooding. It is denial-of-service attack that prevents legitimate remote users from being able to connect to your computer during an ongoi...Rule Medium Severity -
Unmap kernel when running in userspace (aka KAISER)
Speculation attacks against some high-performance processors can be used to bypass MMU permission checks and leak kernel data to userspace. This can be defended against by unmapping the kernel when...Rule Medium Severity -
Disable x86 vsyscall emulation
Disabling it is roughly equivalent to booting with vsyscall=none, except that it will also disable the helpful warning if a program tries to use a vsyscall. With this option set to N, offending pro...Rule Low Severity -
Ensure rsyslog is Installed
Rsyslog is installed by default. Thersyslogpackage can be installed with the following command:$ sudo dnf install rsyslog
Rule Medium Severity -
Ensure Rsyslog Authenticates Off-Loaded Audit Records
Rsyslogd is a system utility providing support for message logging. Support for both internet and UNIX domain sockets enables this utility to support both local and remote logging. Couple this uti...Rule Medium Severity -
Ensure Rsyslog Encrypts Off-Loaded Audit Records
Rsyslogd is a system utility providing support for message logging. Support for both internet and UNIX domain sockets enables this utility to support both local and remote logging. Couple this uti...Rule Medium Severity -
Ensure Rsyslog Encrypts Off-Loaded Audit Records
Rsyslogd is a system utility providing support for message logging. Support for both internet and UNIX domain sockets enables this utility to support both local and remote logging. Couple this uti...Rule Medium Severity -
Enable logrotate Timer
Thelogrotatetimer can be enabled with the following command:$ sudo systemctl enable logrotate.timer
Rule Medium Severity -
Ensure System Log Files Have Correct Permissions
The file permissions for all log files written by <code>rsyslog</code> should be set to 640, or more restrictive. These log files are determined by the second part of each Rule line in <code>/etc/r...Rule Medium Severity -
systemd-journald
systemd-journald is a system service that collects and stores logging data. It creates and maintains structured, indexed journals based on logging information that is received from a variety of sou...Group -
Verify Group Who Owns the system journal
' To properly set the group owner of/var/log/journal/.*/system.journal, run the command:$ sudo chgrp systemd-journal /var/log/journal/.*/system.journal
'Rule Medium Severity -
Verify Owner on the system journal
' To properly set the owner of/var/log/journal/.*/system.journal, run the command:$ sudo chown root /var/log/journal/.*/system.journal
'Rule Medium Severity -
Verify Permissions on the system journal
To properly set the permissions of/var/log/journal/.*/system.journal, run the command:$ sudo chmod 0640 /var/log/journal/.*/system.journal
Rule Medium Severity -
Ensure Logrotate Runs Periodically
The <code>logrotate</code> utility allows for the automatic rotation of log files. The frequency of rotation is specified in <code>/etc/logrotate.conf</code>, which triggers a cron task or a timer...Rule Medium Severity -
Enable rsyslog to Accept Messages via TCP, if Acting As Log Server
The <code>rsyslog</code> daemon should not accept remote messages unless the system acts as a log server. If the system needs to act as a central log server, add the following lines to <code>/etc/r...Rule Unknown Severity -
Enable rsyslog to Accept Messages via UDP, if Acting As Log Server
The <code>rsyslog</code> daemon should not accept remote messages unless the system acts as a log server. If the system needs to act as a central log server, add the following lines to <code>/etc/r...Rule Unknown Severity -
Remote Log Server
Specify an URI or IP address of a remote host where the log messages will be sent and stored.Value -
Ensure Logs Sent To Remote Host
To configure rsyslog to send logs to a remote log server, open <code>/etc/rsyslog.conf</code> and read and understand the last section of the file, which describes the multiple directives necessary...Rule Medium Severity -
Network Configuration and Firewalls
Most systems must be connected to a network of some sort, and this brings with it the substantial risk of network attack. This section discusses the security impact of decisions about networking wh...Group -
firewalld
The dynamic firewall daemon <code>firewalld</code> provides a dynamically managed firewall with support for network “zones” to assign a level of trust to a network and its associated connections an...Group -
Inspect and Activate Default firewalld Rules
Firewalls can be used to separate networks into different zones based on the level of trust the user has decided to place on the devices and traffic within that network. <code>NetworkManager</code>...Group -
IPSec Support
Support for Internet Protocol Security (IPsec) is provided with Libreswan.Group -
Install libreswan Package
The libreswan package provides an implementation of IPsec and IKE, which permits the creation of secure tunnels over untrusted networks. The <code>libreswan</code> package can be installed with the...Rule Medium Severity -
iptables and ip6tables
A host-based firewall called <code>netfilter</code> is included as part of the Linux kernel distributed with the system. It is activated by default. This firewall is controlled by the program <code...Group -
Verify ip6tables Enabled if Using IPv6
The <code>ip6tables</code> service can be enabled with the following manifest: <pre> --- apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfig metadata: labels: machineconfigu...Rule Medium Severity -
Verify iptables Enabled
The <code>iptables</code> service can be enabled with the following manifest: <pre> --- apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfig metadata: labels: machineconfigur...Rule Medium Severity -
Set Default ip6tables Policy for Incoming Packets
To set the default policy to DROP (instead of ACCEPT) for the built-in INPUT chain which processes incoming packets, add or correct the following line in <code>/etc/sysconfig/ip6tables</code>: <pre...Rule Medium Severity -
Disable IPv6 Networking Support Automatic Loading
To prevent the IPv6 kernel module (<code>ipv6</code>) from binding to the IPv6 networking stack, add the following line to <code>/etc/modprobe.d/disabled.conf</code> (or another file in <code>/etc/...Rule Medium Severity -
Set Default iptables Policy for Incoming Packets
To set the default policy to DROP (instead of ACCEPT) for the built-in INPUT chain which processes incoming packets, add or correct the following line in <code>/etc/sysconfig/iptables</code>: <pre>...Rule Medium Severity -
Set Default iptables Policy for Forwarded Packets
To set the default policy to DROP (instead of ACCEPT) for the built-in FORWARD chain which processes packets that will be forwarded from one interface to another, add or correct the following line ...Rule Medium Severity -
IPv6
The system includes support for Internet Protocol version 6. A major and often-mentioned improvement over IPv4 is its enormous increase in the number of available addresses. Another important featu...Group -
Disable Support for IPv6 Unless Needed
Despite configuration that suggests support for IPv6 has been disabled, link-local IPv6 address auto-configuration occurs even when only an IPv4 address is assigned. The only way to effectively pre...Group -
Ensure IPv6 is disabled through kernel boot parameter
To disable IPv6 protocol support in the Linux kernel, add the argument <code>ipv6.disable=1</code> to the default GRUB2 command line for the Linux operating system. Configure the default Grub2 kern...Rule Low Severity
Node 2
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