Guide to the Secure Configuration of Oracle Linux 9
Rules, Groups, and Values defined within the XCCDF Benchmark
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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 -
Kernel GCC plugin configuration
Contains rules that check the configuration of GCC plugins used by the compilerGroup -
Ensure rsyslog-gnutls is installed
TLS protocol support for rsyslog is installed. Thersyslog-gnutls
package can be installed with the following command:$ sudo yum install rsyslog-gnutls
Rule Medium Severity -
Ensure rsyslog is Installed
Rsyslog is installed by default. Thersyslog
package can be installed with the following command:$ sudo yum install rsyslog
Rule Medium Severity -
Enable rsyslog Service
The <code>rsyslog</code> service provides syslog-style logging by default on Oracle Linux 9. The <code>rsyslog</code> service can be enabled with the following command: <pre>$ sudo systemctl enabl...Rule Medium Severity -
Ensure cron Is Logging To Rsyslog
Cron logging must be implemented to spot intrusions or trace cron job status. If <code>cron</code> is not logging to <code>rsyslog</code>, it can be implemented by adding the following to the <i>RU...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 Log Files Are Owned By Appropriate User
The owner of all log files written by <code>rsyslog</code> should be <code>root</code>. These log files are determined by the second part of each Rule line in <code>/etc/rsyslog.conf</code> and t...Rule Medium Severity -
Ensure remote access methods are monitored in Rsyslog
Logging of remote access methods must be implemented to help identify cyber attacks and ensure ongoing compliance with remote access policies are being audited and upheld. An examples of a remote a...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 -
Enable systemd-journald Service
The <code>systemd-journald</code> service is an essential component of systemd. The <code>systemd-journald</code> service can be enabled with the following command: <pre>$ sudo systemctl enable sy...Rule Medium Severity -
Ensure logrotate is Installed
logrotate is installed by default. Thelogrotate
package can be installed with the following command:$ sudo yum install logrotate
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 logrotate Timer
Thelogrotate
timer can be enabled with the following command:$ sudo systemctl enable logrotate.timer
Rule Medium Severity -
Configure rsyslogd to Accept Remote Messages If Acting as a Log Server
By default, <code>rsyslog</code> does not listen over the network for log messages. If needed, modules can be enabled to allow the rsyslog daemon to receive messages from other systems and for the ...Group -
Ensure syslog-ng is Installed
syslog-ng can be installed in replacement of rsyslog. Thesyslog-ng-core
package can be installed with the following command:$ sudo yum install syslog-ng-core
Rule Medium Severity -
Enable syslog-ng Service
The <code>syslog-ng</code> service (in replacement of rsyslog) provides syslog-style logging by default on Debian. The <code>syslog-ng</code> service can be enabled with the following command: <pr...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 -
Ensure rsyslog Does Not Accept Remote Messages Unless Acting As Log Server
The <code>rsyslog</code> daemon should not accept remote messages unless the system acts as a log server. To ensure that it is not listening on the network, ensure any of the following lines are <i...Rule Medium Severity -
Firewalld Must Employ a Deny-all, Allow-by-exception Policy for Allowing Connections to Other Systems
Oracle Linux 9 incorporates the "firewalld" daemon, which allows for many different configurations. One of these configurations is zones. Zones can be utilized to a deny-all, allow-by-exception app...Rule Medium Severity -
Remote Log Server
Specify an URI or IP address of a remote host where the log messages will be sent and stored.Value -
Configure TLS for rsyslog remote logging
Configure <code>rsyslog</code> to use Transport Layer Security (TLS) support for logging to remote server for the Forwarding Output Module in <code>/etc/rsyslog.conf</code> using action. You can us...Rule Medium Severity -
Configure CA certificate for rsyslog remote logging
Configure CA certificate for <code>rsyslog</code> logging to remote server using Transport Layer Security (TLS) using correct path for the <code>DefaultNetstreamDriverCAFile</code> global option in...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 -
Set Default firewalld Zone for Incoming Packets
To set the default zone to <code>drop</code> for the built-in default zone which processes incoming IPv4 and IPv6 packets, modify the following line in <code>/etc/firewalld/firewalld.conf</code> to...Rule Medium Severity -
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 -
Configure Firewalld to Use the Nftables Backend
Firewalld can be configured with many backends, such as nftables.Rule Medium Severity -
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 -
Verify firewalld Enabled
Thefirewalld
service can be enabled with the following command:$ sudo systemctl enable firewalld.service
Rule Medium Severity -
Strengthen the Default Ruleset
The default rules can be strengthened. The system scripts that activate the firewall rules expect them to be defined in configuration files under the <code>/etc/firewalld/services</code> and <code>...Group -
IPSec Support
Support for Internet Protocol Security (IPsec) is provided with Libreswan.Group -
Verify Any Configured IPSec Tunnel Connections
Libreswan provides an implementation of IPsec and IKE, which permits the creation of secure tunnels over untrusted networks. As such, IPsec can be used to circumvent certain network requirements su...Rule Medium Severity -
Inspect and Activate Default Rules
View the currently-enforced <code>iptables</code> rules by running the command: <pre>$ sudo iptables -nL --line-numbers</pre> The command is analogous for <code>ip6tables</code>. <br> <br> ...Group -
Verify ip6tables Enabled if Using IPv6
Theip6tables
service can be enabled with the following command:$ sudo systemctl enable ip6tables.service
Rule Medium Severity -
Verify iptables Enabled
Theiptables
service can be enabled with the following command:$ sudo systemctl enable iptables.service
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 Addressing on All IPv6 Interfaces
To disable support for (<code>ipv6</code>) addressing on all interface add the following line to <code>/etc/sysctl.d/ipv6.conf</code> (or another file in <code>/etc/sysctl.d</code>): <pre>net.ipv6....Rule Medium Severity -
net.ipv4.conf.default.rp_filter
Enables source route verificationValue -
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 -
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 -
Disable IPv6 Addressing on IPv6 Interfaces by Default
To disable support for (<code>ipv6</code>) addressing on interfaces by default add the following line to <code>/etc/sysctl.d/ipv6.conf</code> (or another file in <code>/etc/sysctl.d</code>): <pre>n...Rule Medium Severity -
Configure IPv6 Settings if Necessary
A major feature of IPv6 is the extent to which systems implementing it can automatically configure their networking devices using information from the network. From a security perspective, manually...Group
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