The Photon operating system must disable systemd fallback Domain Name System (DNS).
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-256590 | PHTN-30-000245 | SV-256590r991589_rule | CCI-000366 | medium |
| Description | ||||
| Systemd contains an ability to set fallback DNS servers. This is used for DNS lookups in the event no system-level DNS servers are configured or other DNS servers are specified in the systemd "resolved.conf" file. If uncommented, this configuration contains Google DNS servers by default and could result in DNS leaking information unknowingly in the event DNS is absent or misconfigured at the system level. | ||||
| STIG | Date | |||
| VMware vSphere 7.0 vCenter Appliance Photon OS Security Technical Implementation Guide | 2024-12-16 | |||
Details
Check Text (C-256590r991589_chk)
At the command line, run the following command:
# resolvectl status | grep 'Fallback DNS'
If the output indicates that fallback DNS servers are configured, this is a finding.
Fix Text (F-60208r887443_fix)
Navigate to and open:
/etc/systemd/resolved.conf
Add or update the "FallbackDNS" entry to the following:
FallbackDNS=
Restart the systemd resolved service by running the following command:
# systemctl restart systemd-resolved
Note: If this option is not given, a compiled-in list of DNS servers is used instead, which is undesirable.