Disable SSH Server If Possible

An XCCDF Rule

Description

The SSH server service, sshd, is commonly needed. However, if it can be disabled, do so. This is unusual, as SSH is a common method for encrypted and authenticated remote access.

ID: xccdf_org.ssgproject.content_rule_service_sshd_disabled
Severity: High
References: CM-3(6) IA-2(4)

SRG-APP-000141-CTR-000315 SRG-APP-000185-CTR-000490
Updated: about 1 year ago


[customizations.services]
disabled = ["sshd"]

- name: Block Disable service sshd
  block:

  - name: Disable service sshd
    block:
    - name: Disable service sshd
      systemd:
        name: sshd.service
        enabled: 'no'
        state: stopped
        masked: 'yes'
    rescue:

    - name: Intentionally ignored previous 'Disable service sshd' failure, service
        was already disabled
      meta: noop
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-53-CM-3(6)
  - NIST-800-53-IA-2(4)
  - disable_strategy
  - high_severity
  - low_complexity
  - low_disruption
  - no_reboot_needed
  - service_sshd_disabled

- name: Unit Socket Exists - sshd.socket
  command: systemctl -q list-unit-files sshd.socket
  register: socket_file_exists
  changed_when: false
  failed_when: socket_file_exists.rc not in [0, 1]
  check_mode: false
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-53-CM-3(6)
  - NIST-800-53-IA-2(4)
  - disable_strategy
  - high_severity
  - low_complexity
  - low_disruption
  - no_reboot_needed
  - service_sshd_disabled

- name: Disable socket sshd
  systemd:
    name: sshd.socket
    enabled: 'no'
    state: stopped
    masked: 'yes'
  when:
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - socket_file_exists.stdout_lines is search("sshd.socket",multiline=True)
  tags:
  - NIST-800-53-CM-3(6)
  - NIST-800-53-IA-2(4)
  - disable_strategy
  - high_severity
  - low_complexity
  - low_disruption
  - no_reboot_needed
  - service_sshd_disabled

include disable_sshd

class disable_sshd {
  service {'sshd':
    enable => false,
    ensure => 'stopped',  }
}

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

SYSTEMCTL_EXEC='/usr/bin/systemctl'
"$SYSTEMCTL_EXEC" stop 'sshd.service'
"$SYSTEMCTL_EXEC" disable 'sshd.service'"$SYSTEMCTL_EXEC" mask 'sshd.service'
# Disable socket activation if we have a unit file for it
if "$SYSTEMCTL_EXEC" -q list-unit-files sshd.socket; then
    "$SYSTEMCTL_EXEC" stop 'sshd.socket'
    "$SYSTEMCTL_EXEC" mask 'sshd.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 'sshd.service' || true

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

Disable SSH Server If Possible

Description

Remediation - OS Build Blueprint

Remediation - Ansible

Remediation - Puppet

Remediation - Shell Script