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V-281362

CAT II (Medium)

RHEL 10 must configure a DNS processing mode in Network Manager to avoid conflicts with other Domain Name Server (DNS) managers and to not leak DNS queries to untrusted networks.

Rule ID

SV-281362r1167236_rule

STIG

Red Hat Enterprise Linux 10 Security Technical Implementation Guide

Version

V1R1

CCIs

CCI-002385 CCI-001115

Discussion

To ensure that DNS resolver settings are respected, a DNS mode in Network Manager must be configured. The following are common DNS values in "NetworkManager.conf [main]": - default: NetworkManager will update "/etc/resolv.conf" to reflect the nameservers provided by currently active connections. - none: NetworkManager will not modify "/etc/resolv.conf". Used when DNS is managed manually or by another service. - systemd-resolved: Uses "systemd-resolved" to manage DNS. - dnsmasq: Enables the internal "dnsmasq" plugin. Satisfies: SRG-OS-000420-GPOS-00186, SRG-OS-000142-GPOS-00091

Check Content

Verify RHEL 10 has a DNS mode configured in Network Manager.

$ NetworkManager --print-config
[main]
dns=none

If the dns key under "main" does not exist or is set to "dnsmasq", this is a finding.

Note: If RHEL 10 is configured to use a DNS resolver other than Network Manager, the configuration must be documented and approved by the information system security officer.

Fix Text

Configure RHEL 10 to use a DNS mode in Network Manager.

In "/etc/NetworkManager/NetworkManager.conf", add the following line in the "[main]" section:

dns = none

Where <dns processing mode> is default, none, or systemd-resolved.

Network Manager must be reloaded for the change to take effect:

$ sudo systemctl reload NetworkManager