1.4.3 Ensure authentication required for single user mode - rescue.service

Information

Single user mode (rescue mode) is used for recovery when the system detects an issue during boot or by manual selection from the bootloader.

Note: The systemctl option --fail is synonymous with --job-mode=fail. Using either is acceptable.

Rationale:

Requiring authentication in single user mode (rescue mode) prevents an unauthorized user from rebooting the system into single user to gain root privileges without credentials.

Solution

Edit /usr/lib/systemd/system/rescue.service and /usr/lib/systemd/system/emergency.service and set ExecStart to use /sbin/sulogin or /usr/sbin/sulogin:

ExecStart=-/bin/sh -c '/sbin/sulogin; /usr/bin/systemctl --fail --no-block default'

See Also

https://workbench.cisecurity.org/files/3490