Disable snmpd Service

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Description

The snmpd service can be disabled with the following command:

$ sudo systemctl mask --now snmpd.service

Rationale

Running SNMP software provides a network-based avenue of attack, and should be disabled if not needed.

Remediation

Shell script

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

#!/bin/bash

# Remediation is applicable only in certain platforms
if ( ( dpkg-query --show --showformat='${db:Status-Status}' 'snmp' 2>/dev/null | grep -q '^installed$' && dpkg-query --show --showformat='${db:Status-Status}' 'linux-base' 2>/dev/null | grep -q '^installed$' ) ); then

SYSTEMCTL_EXEC='/usr/bin/systemctl'
if [[ $("$SYSTEMCTL_EXEC" is-system-running) != "offline" ]]; then
  "$SYSTEMCTL_EXEC" stop 'snmpd.service'
fi
"$SYSTEMCTL_EXEC" disable 'snmpd.service'
"$SYSTEMCTL_EXEC" mask 'snmpd.service'
# Disable socket activation if we have a unit file for it
if "$SYSTEMCTL_EXEC" -q list-unit-files snmpd.socket; then
    if [[ $("$SYSTEMCTL_EXEC" is-system-running) != "offline" ]]; then
      "$SYSTEMCTL_EXEC" stop 'snmpd.socket'
    fi
    "$SYSTEMCTL_EXEC" mask 'snmpd.socket'
fi
# 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 'snmpd.service' || true

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Ansible playbook

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

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - disable_strategy
  - low_complexity
  - low_disruption
  - low_severity
  - no_reboot_needed
  - service_snmpd_disabled

- name: Disable snmpd Service - Disable service snmpd
  block:

  - name: Disable snmpd Service - Collect systemd Services Present in the System
    ansible.builtin.command: systemctl -q list-unit-files --type service
    register: service_exists
    changed_when: false
    failed_when: service_exists.rc not in [0, 1]
    check_mode: false

  - name: Disable snmpd Service - Ensure snmpd.service is Masked
    ansible.builtin.systemd:
      name: snmpd.service
      state: stopped
      enabled: false
      masked: true
    when: service_exists.stdout_lines is search("snmpd.service", multiline=True)

  - name: Unit Socket Exists - snmpd.socket
    ansible.builtin.command: systemctl -q list-unit-files snmpd.socket
    register: socket_file_exists
    changed_when: false
    failed_when: socket_file_exists.rc not in [0, 1]
    check_mode: false

  - name: Disable snmpd Service - Disable Socket snmpd
    ansible.builtin.systemd:
      name: snmpd.socket
      enabled: false
      state: stopped
      masked: true
    when: socket_file_exists.stdout_lines is search("snmpd.socket", multiline=True)
  tags:
  - disable_strategy
  - low_complexity
  - low_disruption
  - low_severity
  - no_reboot_needed
  - service_snmpd_disabled
  - special_service_block
  when: ( "snmp" in ansible_facts.packages and "linux-base" in ansible_facts.packages
    )