Introduction

This ansible role applies v1.0.0 of the CIS Amazon Linux 2 Benchmark. The benchmark document is no longer directly available for download, but can be obtained with e-mail registration from CIS

This role was developed and tested against Amazon Linux 2 (2.0.20190313). It has been tested against Amazon Linux 2 (2.0.20190313) with equal success. Most extensive testing has been done using Ansible 2.6, but any version from 2.5 should work.

Why Would I Use This Role?

If you are attempting to obtain compliance against an industry-accepted security standard, like PCI DSS, APRA or ISO 27001, then you need to demonstrate that you have applied documented hardening standards against all systems within scope of assessment.

If you are running Amazon Linux, then this role attempts to provide one piece of the solution to the compliance puzzle.

Here Be Dragons!

If you are considering applying this role to any servers, you should have a basic familiarity with the CIS Benchmark (or other similar benchmarks) and an appreciation for the impact that it may have on a system.

Please take the time to familarise yourself with the standard and with the configurable default values, and exclude any items before applying to a system.

An examples of items that should be immediately considered for exclusion (or at least, for modification of the related default values) include:

• 3.3.2 and 3.3.3, which by default effectively limit access to the host (including via ssh) to localhost only.

Amazon Linux 2 and SE Linux

By default SElinux is disabled via grub in amazon linux.

The tasks in Section 1.6 of this role will enable SELinux. Alternatively, it can be manually enabled by following these steps:

edit /boot/grub/menu.lst Modifiy selinux=0 to selinux=1 touch /etc/selinux/config

Also install the following package to allow the ansible SElinux module to function on the host. yum install libselinux-python

A reboot will be neccessary for the changes to take effect.

Example Playbook

An example playbook which uses this role is as follows:

---

- hosts: localhost
  connection: local
  gather_facts: true
  become: yes

  roles:
    - ansible-cis-amazon-linux-2

A more advanced example, which includes modifications to the default values used, as well as the exclusion of some items in the benchmark which are considered unnecessary for a fictional environment, is as follows:

---

- hosts: localhost
  connection: local
  gather_facts: true
  become: yes

  vars:
    cis_level_1_exclusions:
      - 5.4.4
      - 3.4.2
      - 3.4.3
      - 6.2.13   
    cis_pass_max_days: 45
    cis_umask_default: 027
 
  roles:
    - { role: ansible-cis-amazon-linux-2,
        in_vm: true,
        cis_hosts_allowed_ip_range: '10.',
        cis_umask_default: "027",
        full_upgrade: true,
        cis_enable_rsyslog: true,
        cis_level_1_exclusions: [ 3.5.1.1, 5.3.4 ],
        cis_level_2_exclusions: [ ]
      }

either one of in_vm or in_vagrant must be set (to any value) according to your target/testing environment. Note that the use of become: yes is required as 99% of tasks require privileged access to execute.

Role Variables

See defaults/main.yml for variables which can be overriden according to preference.

Options

Tags (and combinations thereof) can be used to run a particular level of the CIS standard, a section, or an individual recommendation. For example:

• Run only Level 1 tasks

ansible-playbook playbook.yml -t level-1

• Run only Section 3 tasks

ansible-playbook playbook.yml -t section-3

• Run tasks 1.3.1 and 2.1.10 only

ansible-playbook playbook.yml -t 1.3.1,2.1.10

• Run scored tasks only

ansible-playbook playbook.yml -t scored

Limitations

At present, only the Level 1 items of the benchmark are implemented. Level 2 items will be added as time permits.

The following checks have not been implemented:

• 3.4.*. Firewall rulesets are environment specific.
• 3.5.*. Firewall rulesets are environment specific.
• 4.2.1.2. The determination of what should be logged and the destination of messages is environment specific.
• 4.2.2.2. The determination of what should be logged and the destination of messages is environment specific.
• 4.2.2.3. Inline editing of syslog-ng configuration file is considered too imprecise and is best solved by a supplied configuration file which addresses this and other related requirements.
• 4.2.2.4. Inline editing of syslog-ng configuration file is considered too imprecise and is best solved by a supplied configuration file which addresses this and other related requirements.
• 4.2.2.5. Inline editing of syslog-ng configuration file is considered too imprecise and is best solved by a supplied configuration file which addresses this and other related requirements.
• 4.3. The configuration of logrotate is site-specific.
• 5.3.2. Multi-line editing of pam configuration files is considered too imprecise and dangerous, and is best solved by a supplied configuration file which addresses this and other related requirements.
• 5.3.3. Multi-line editing of pam configuration files is considered too imprecise and dangerous, and is best solved by a supplied configuration file which addresses this and other related requirements.
• 5.5. Not implemented, because of potential impact to su -, and due to not knowing which consoles are in physically secure locations within AWS/site premises.

Compatibility

This role should be compatible with version 2.6.15 of Ansible. It should work with any point release within Ansible 2.6 major release, and there's a high likelihood of it working fine under Ansible 2.5, 2.7.

Vagrant version 2.2.4 was used during the development & testing of Amazon Linux 2 revision of the role.

Testing

A Vagrantfile is included in the misc/ directory role. If desired, this file and the playbook can be copied two levels up from the role directory, resulting in this directory structure:

├── Vagrantfile
├── ansible-role-cis-amazon-linux.yml
└── roles
    └── ansible-role-cis-amazon-linux

Then, to (re)run against a clean state of Amazon Linux 2 image: vagrant destroy -f && vagrant up

You can log into the test VM via SSH by issuing vagrant ssh.

Alternatively, the following testing processes are applied by the original developer of this role, and is untested with this version of the role made for Amazon Linux 2.

• The syntax of the role is checked. See make syntax.
• ansible-review is run against the role and any warnings which are deemed appropriate are remediated. See make review.
• The role is applied against a docker container using both ansible v2.1.3 and ansible v2.2. see make test.

The following tests have been flagged but are not yet implemented:

• Test application of the role against the Vagrant mvbcoding/awslinux image, using the ansible provisioner.

License

BSD.

Author Information

The original role for Amazon Linux 1 was developed by Anth Courtney. Amazon Linux 2 CIS Benchmark v1.0.0 compliance and enhancements throughout the role were implemented by Alp Ozcan

All feedback, issues and PRs are encouraged and appreciated.

Credits

Vagrant box used for testing was authored by gbailey