Configure SSH to use System Crypto Policy

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Description

Crypto Policies provide a centralized control over crypto algorithms usage of many packages. SSH is supported by crypto policy, but the SSH configuration may be set up to ignore it. To check that Crypto Policies settings are configured correctly, ensure that the CRYPTO_POLICY variable is either commented or not set at all in the /etc/sysconfig/sshd.

Rationale

Overriding the system crypto policy makes the behavior of the SSH service violate expectations, and makes system configuration more fragmented.

Remediation

Shell script

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

#!/bin/bash

SSH_CONF="/etc/sysconfig/sshd"

sed -i "/^\s*CRYPTO_POLICY.*$/Id" $SSH_CONF

Ansible playbook

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

- name: Configure SSH to use System Crypto Policy
  lineinfile:
    dest: /etc/sysconfig/sshd
    state: absent
    regexp: ^(?i)\s*CRYPTO_POLICY.*$
  tags:
  - CCE-80939-2
  - DISA-STIG-RHEL-08-010287
  - NIST-800-53-AC-17(2)
  - NIST-800-53-AC-17(a)
  - NIST-800-53-CM-6(a)
  - NIST-800-53-MA-4(6)
  - NIST-800-53-SC-13
  - PCI-DSS-Req-2.2
  - PCI-DSSv4-2.2.7
  - configure_ssh_crypto_policy
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required