Vulnerability Discussion

To mitigate the risk of unauthorized access to sensitive information by entities that have been issued certificates by DOD-approved PKIs, all DOD systems (e.g., web servers and web portals) must be properly configured to incorporate access control methods that do not rely solely on the possession of a certificate for access.

Successful authentication must not automatically give an entity access to an asset or security boundary. Authorization procedures and controls must be implemented to ensure each authenticated entity also has a validated and current authorization. Authorization is the process of determining whether an entity, once authenticated, is permitted to access a specific asset. Information systems use access control policies and enforcement mechanisms to implement this requirement.

This requirement prevents attackers with physical access from trivially bypassing security on the machine and gaining root access. Such accesses are further prevented by configuring the bootloader password.

Check

Verify RHEL 10 requires authentication for single-user mode with the following command:

$ sudo grep systemd-sulogin /usr/lib/systemd/system/rescue.service
# ExecStart=-/usr/lib/systemd/systemd-sulogin-shell rescue

If the line is not returned from the default "systemd" file, use the following command to look for modifications to "rescue.service":

$ sudo grep systemd-sulogin /etc/systemd/system/rescue.service.d/*.conf
ExecStart=-/usr/lib/systemd/systemd-sulogin-shell rescue

If the line is not returned from either location, this is a finding.

Note: The configuration setting can be in either the default location or the drop-in file but not in both locations.

Fix

Configure RHEL 10 to require authentication for single-user mode.

Create a directory for supplementary configuration files:

$ sudo mkdir /etc/systemd/system/rescue.service.d/

Copy the original "rescue.service" file to the new directory with:

$ sudo cp /usr/lib/systemd/system/rescue.service /etc/systemd/system/rescue.service.d/rescue.service.conf

Open the new file:

$ sudo vi /etc/systemd/system/rescue.service.d/rescue.service.conf

Add or modify the following line in the new file:

ExecStart=-/usr/lib/systemd/systemd-sulogin-shell rescue

Comment out or remove the "ExecStart" and "ExecStartPre" lines in "/usr/lib/systemd/system/rescue.service" as they can only exist in one location.

Apply changes to unit files without rebooting the system:

$ sudo systemctl daemon-reload