Guide to the Secure Configuration of Oracle Linux 9
Rules, Groups, and Values defined within the XCCDF Benchmark
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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,...Rule Medium Severity -
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...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>De...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 th...Group -
Configure Multiple DNS Servers in /etc/resolv.conf
Determine whether the system is using local or DNS name resolution with the following command: <pre>$ sudo grep hosts /etc/nsswitch.conf hosts: fi...Rule Medium Severity -
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 lin...Rule Medium Severity -
Ensure System is Not Acting as a Network Sniffer
The system should not be acting as a network sniffer, which can capture all traffic on the network to which it is connected. Run the following to d...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 tr...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 traffi...Group -
Install firewalld Package
Thefirewalld
package can be installed with the following command:$ sudo yum install firewalld
Rule Medium Severity -
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 t...Group -
Configure the Firewalld Ports
Configure the <code>firewalld</code> ports to allow approved services to have access to the system. To configure <code>firewalld</code> to open por...Rule Medium Severity -
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>...Rule Medium Severity -
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 ...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...Group -
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 analog...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 l...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 f...Rule Medium Severity -
net.ipv4.conf.default.rp_filter
Enables source route verificationValue -
Strengthen the Default Ruleset
The default rules can be strengthened. The system scripts that activate the firewall rules expect them to be defined in the configuration files <co...Group -
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 l...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 interf...Rule Medium Severity -
Restrict ICMP Message Types
In <code>/etc/sysconfig/iptables</code>, the accepted ICMP messages types can be restricted. To accept only ICMP echo reply, destination unreachabl...Group -
Log and Drop Packets with Suspicious Source Addresses
Packets with non-routable source addresses should be rejected, as they may indicate spoofing. Because the modified policy will reject non-matching ...Group -
IPv6
The system includes support for Internet Protocol version 6. A major and often-mentioned improvement over IPv4 is its enormous increase in the numb...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 ad...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/di...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 a...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 ...Group -
IPV6_AUTOCONF
Toggle global IPv6 auto-configuration (only, if global forwarding is disabled)Value -
net.ipv6.conf.all.accept_ra_defrtr
Accept default router in router advertisements?Value -
net.ipv6.conf.all.accept_ra_pinfo
Accept prefix information in router advertisements?Value -
net.ipv6.conf.all.accept_ra_rtr_pref
Accept router preference in router advertisements?Value -
net.ipv6.conf.all.accept_ra
Accept all router advertisements?Value -
net.ipv6.conf.all.accept_redirects
Toggle ICMP Redirect AcceptanceValue -
net.ipv6.conf.all.accept_source_route
Trackers could be using source-routed packets to generate traffic that seems to be intra-net, but actually was created outside and has been redirec...Value -
net.ipv6.conf.all.autoconf
Enable auto configuration on IPv6 interfacesValue -
net.ipv6.conf.all.forwarding
Toggle IPv6 ForwardingValue -
net.ipv6.conf.all.max_addresses
Maximum number of autoconfigured IPv6 addressesValue -
net.ipv6.conf.all.router_solicitations
Accept all router solicitations?Value -
net.ipv6.conf.default.accept_ra_defrtr
Accept default router in router advertisements?Value -
net.ipv6.conf.default.accept_ra_pinfo
Accept prefix information in router advertisements?Value -
net.ipv6.conf.default.accept_ra_rtr_pref
Accept router preference in router advertisements?Value -
net.ipv6.conf.default.accept_ra
Accept default router advertisements by default?Value -
net.ipv6.conf.default.accept_redirects
Toggle ICMP Redirect Acceptance By DefaultValue
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