Guide to the Secure Configuration of Red Hat Enterprise Linux 9
Rules, Groups, and Values defined within the XCCDF Benchmark
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Set LogLevel to INFO
The INFO parameter specifices that record login and logout activity will be logged. <br> The default SSH configuration sets the log level to INFO. ...Rule Low Severity -
Set SSH Daemon LogLevel to VERBOSE
The <code>VERBOSE</code> parameter configures the SSH daemon to record login and logout activity. To specify the log level in SSH, add or correct t...Rule Medium Severity -
Set SSH authentication attempt limit
The <code>MaxAuthTries</code> parameter specifies the maximum number of authentication attempts permitted per connection. Once the number of failur...Rule Medium Severity -
Set SSH MaxSessions limit
The <code>MaxSessions</code> parameter specifies the maximum number of open sessions permitted from a given connection. To set MaxSessions edit <co...Rule Medium Severity -
Ensure SSH MaxStartups is configured
The MaxStartups parameter specifies the maximum number of concurrent unauthenticated connections to the SSH daemon. Additional connections will be ...Rule Medium Severity -
Distribute the SSH Server configuration to multiple files in a config directory.
Make sure to have the <code>Include /etc/ssh/sshd_config.d/*.conf</code> line in the <code>/etc/ssh/sshd_config</code> file. Ideally, don't have an...Rule Medium Severity -
Enable Use of Privilege Separation
When enabled, SSH will create an unprivileged child process that has the privilege of the authenticated user. To enable privilege separation in SSH...Rule Medium Severity -
SSH server uses strong entropy to seed
To set up SSH server to use entropy from a high-quality source, edit the <code>/etc/sysconfig/sshd</code> file. The <code>SSH_USE_STRONG_RNG</code>...Rule Low Severity -
Reboot Required
A system reboot is implicitly required after some actions in order to complete the reconfiguration of the system. In many cases, the changes will n...Group -
Prevent remote hosts from connecting to the proxy display
The SSH daemon should prevent remote hosts from connecting to the proxy display. <br> The default SSH configuration for <code>X11UseLocalhost</code...Rule Medium Severity -
Strengthen Firewall Configuration if Possible
If the SSH server is expected to only receive connections from the local network, then strengthen the default firewall rule for the SSH service to ...Group -
System Security Services Daemon
The System Security Services Daemon (SSSD) is a system daemon that provides access to different identity and authentication providers such as Red H...Group -
SSSD certificate_verification option
Value of the certificate_verification option in the SSSD config.Value -
SSSD memcache_timeout option
Value of the memcache_timeout option in the [nss] section of SSSD config /etc/sssd/sssd.conf.Value -
SSSD ssh_known_hosts_timeout option
Value of the ssh_known_hosts_timeout option in the [ssh] section of SSSD configuration file /etc/sssd/sssd.conf.Value -
Certificate status checking in SSSD
Multifactor solutions that require devices separate from information systems gaining access include, for example, hardware tokens providing time-ba...Rule Medium Severity -
Enable Certmap in SSSD
SSSD should be configured to verify the certificate of the user or group. To set this up ensure that section like <code>certmap/testing.test/rule_...Rule Medium Severity -
Enable Smartcards in SSSD
SSSD should be configured to authenticate access to the system using smart cards. To enable smart cards in SSSD, set <code>pam_cert_auth</code> to ...Rule Medium Severity -
SSSD Has a Correct Trust Anchor
SSSD must have acceptable trust anchor present.Rule Medium Severity -
Configure SSSD to Expire Offline Credentials
SSSD should be configured to expire offline credentials after 1 day. To configure SSSD to expire offline credentials, set <code>offline_credential...Rule Medium Severity -
System Security Services Daemon (SSSD) - LDAP
The System Security Services Daemon (SSSD) is a system daemon that provides access to different identity and authentication providers such as Red H...Group -
SSSD LDAP Backend Client CA Certificate Location
Path of a directory that contains Certificate Authority certificates.Value -
USBGuard daemon
The USBGuard daemon enforces the USB device authorization policy for all USB devices.Group -
Install usbguard Package
Theusbguardpackage can be installed with the following command:$ sudo dnf install usbguard
Rule Medium Severity -
Enable the USBGuard Service
The USBGuard service should be enabled. The <code>usbguard</code> service can be enabled with the following command: <pre>$ sudo systemctl enable ...Rule Medium Severity -
Log USBGuard daemon audit events using Linux Audit
To configure USBGuard daemon to log via Linux Audit (as opposed directly to a file), <code>AuditBackend</code> option in <code>/etc/usbguard/usbgua...Rule Low Severity -
Authorize Human Interface Devices in USBGuard daemon
To allow authorization of Human Interface Devices (keyboard, mouse) by USBGuard daemon, add the line <code>allow with-interface match-all { 03:*:* ...Rule Medium Severity -
Authorize Human Interface Devices and USB hubs in USBGuard daemon
To allow authorization of USB devices combining human interface device and hub capabilities by USBGuard daemon, add the line <code>allow with-inter...Rule Medium Severity -
Authorize USB hubs in USBGuard daemon
To allow authorization of USB hub devices by USBGuard daemon, add line <code>allow with-interface match-all { 09:00:* }</code> to <code>/etc/usbgua...Rule Medium Severity -
Generate USBGuard Policy
By default USBGuard when enabled prevents access to all USB devices and this lead to inaccessible system if they use USB mouse/keyboard. To prevent...Rule Medium Severity -
X Window System
The X Window System implementation included with the system is called X.org.Group -
Disable X Windows
Unless there is a mission-critical reason for the system to run a graphical user interface, ensure X is not set to start automatically at boot and ...Group -
Remove the X Windows Package Group
By removing the xorg-x11-server-common package, the system no longer has X Windows installed. If X Windows is not installed then the system cannot ...Rule Medium Severity -
Disable graphical user interface
By removing the following packages, the system no longer has X Windows installed. <code>xorg-x11-server-Xorg xorg-x11-server-common xorg-x11-serv...Rule Medium Severity -
Disable X Windows Startup By Setting Default Target
Systems that do not require a graphical user interface should only boot by default into <code>multi-user.target</code> mode. This prevents accident...Rule Medium Severity -
Introduction
The purpose of this guidance is to provide security configuration recommendations and baselines for the Red Hat Enterprise Linux 9 operating system...Group -
General Principles
The following general principles motivate much of the advice in this guide and should also influence any configuration decisions that are not expli...Group -
Encrypt Transmitted Data Whenever Possible
Data transmitted over a network, whether wired or wireless, is susceptible to passive monitoring. Whenever practical solutions for encrypting such ...Group -
Least Privilege
Grant the least privilege necessary for user accounts and software to perform tasks. For example, <code>sudo</code> can be implemented to limit aut...Group -
Minimize Software to Minimize Vulnerability
The simplest way to avoid vulnerabilities in software is to avoid installing that software. On Red Hat Enterprise Linux 9,the RPM Package Manager (...Group -
Run Different Network Services on Separate Systems
Whenever possible, a server should be dedicated to serving exactly one network service. This limits the number of other services that can be compro...Group -
Configure Security Tools to Improve System Robustness
Several tools exist which can be effectively used to improve a system's resistance to and detection of unknown attacks. These tools can improve rob...Group -
Root Shell Environment Assumed
Most of the actions listed in this document are written with the assumption that they will be executed by the root user running the <code>/bin/bash...Group -
Test in Non-Production Environment
This guidance should always be tested in a non-production environment before deployment. This test environment should simulate the setup in which t...Group -
Enable SSH Server firewalld Firewall Exception
If the SSH server is in use, inbound connections to SSH's port should be allowed to permit remote access through SSH. In more restrictive firewalld...Rule Medium Severity -
Ensure that /etc/cron.allow exists
The file/etc/cron.allowshould exist and should be used instead of/etc/cron.deny.Rule Medium Severity -
389 Directory Server
389 Directory Server is a popular open-source LDAP server for Linux.Group -
Uninstall 389-ds-base Package
The 389-ds-base RPM is not installed by default on a Red Hat Enterprise Linux 9 system. It is needed only by the 389-ds server, not by the clients ...Rule Low Severity -
The s-nail Package Is Installed
A mail server is required for sending emails. The <code>s-nail</code> package can be installed with the following command: <pre> $ sudo dnf install...Rule Medium Severity -
Network Time Protocol
The Network Time Protocol is used to manage the system clock over a network. Computer clocks are not very accurate, so time will drift unpredictabl...Group
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