Disable Network Router Discovery Daemon (rdisc)

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Description

The rdisc service implements the client side of the ICMP Internet Router Discovery Protocol (IRDP), which allows discovery of routers on the local subnet. If a router is discovered then the local routing table is updated with a corresponding default route. By default this daemon is disabled.

The rdisc service can be disabled with the following command:

$ sudo systemctl disable rdisc.service

Rationale

General-purpose systems typically have their network and routing information configured statically by a system administrator. Workstations or some special-purpose systems often use DHCP (instead of IRDP) to retrieve dynamic network configuration information.

Remediation

Shell script

The following script can be run on the host to remediate the issue.

#!/bin/bash

SYSTEMCTL_EXEC='/usr/bin/systemctl'
"$SYSTEMCTL_EXEC" stop 'rdisc.service'
"$SYSTEMCTL_EXEC" disable 'rdisc.service'
# Disable socket activation if we have a unit file for it
"$SYSTEMCTL_EXEC" list-unit-files | grep -q '^rdisc.socket\>' && "$SYSTEMCTL_EXEC" disable 'rdisc.socket'
# The service may not be running because it has been started and failed,
# so let's reset the state so OVAL checks pass.
# Service should be 'inactive', not 'failed' after reboot though.
"$SYSTEMCTL_EXEC" reset-failed 'rdisc.service'

Ansible playbook

The following playbook can be run with Ansible to remediate the issue.

- name: Disable service rdisc
  service:
    name: "{{item}}"
    enabled: "no"
    state: "stopped"
  register: service_result
  failed_when: "service_result is failed and ('Could not find the requested service' not in service_result.msg)"
  with_items:
    - rdisc
  tags:
    - service_rdisc_disabled
    - unknown_severity
    - disable_strategy
    - low_complexity
    - low_disruption
    - NIST-800-53-AC-17(8)
    - NIST-800-53-AC-4
    - NIST-800-53-CM-7


- name: Disable socket of service rdisc if applicable
  service:
    name: "{{item}}"
    enabled: "no"
    state: "stopped"
  register: socket_result
  failed_when: "socket_result is failed and ('Could not find the requested service' not in socket_result.msg)"
  with_items:
    - rdisc.socket
  tags:
    - service_rdisc_disabled
    - unknown_severity
    - disable_strategy
    - low_complexity
    - low_disruption
    - NIST-800-53-AC-17(8)
    - NIST-800-53-AC-4
    - NIST-800-53-CM-7