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dev-sec / ansible-ssh-hardening

This Ansible role provides numerous security-related ssh configurations, providing all-round base protection.
http://dev-sec.io/
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ansible hardening playbook protection role ssh ssh-agent ssh-configuration ssh-hardening ssh-server

readme

ssh-hardening (Ansible Role)

Attention: This role has been migrated to our hardening-collection:

Please open any issues and pull requests there!

Requirements

Role Variables

Configuring settings not listed in role-variables

If you want to configure ssh options that are not listed above, you can use ssh_custom_options (for /etc/ssh/ssh_config) or sshd_custom_options (for /etc/ssh/sshd_config) to set them. These options will be set on the beginning of the file so you can override options further down in the file.

Example playbook:

- hosts: localhost
  roles:
    - dev-sec.ssh-hardening
  vars:
    ssh_custom_options:
      - "Include /etc/ssh/ssh_config.d/*"
    sshd_custom_options:
      - "AcceptEnv LANG"

Changing the default port and idempotency

This role uses the default port 22 or the port configured in the inventory to connect to the server. If the default ssh port is changed via ssh_server_ports, once the ssh server is restarted, it will still try to connect using the previous port. In order to run this role again on the same server the inventory will have to be updated to use the new ssh port.

If idempotency is important, please consider using role ssh-hardening-fallback, which is a wrapper around this role that falls back to port 22 if the configured port is unreachable.

Example Playbook

- hosts: localhost
  roles:
    - dev-sec.ssh-hardening

Local Testing

The preferred way of locally testing the role is to use Docker. You will have to install Docker on your system. See Get started for a Docker package suitable to for your system.

You can also use vagrant and Virtualbox or VMWare to run tests locally. You will have to install Virtualbox and Vagrant on your system. See Vagrant Downloads for a vagrant package suitable for your system. For all our tests we use test-kitchen. If you are not familiar with test-kitchen please have a look at their guide.

Next install test-kitchen:

# Install dependencies
gem install bundler
bundle install

Testing with Docker

# fast test on one machine
bundle exec kitchen test ssh-ubuntu1804-ansible-latest

# test on all machines
bundle exec kitchen test

# for development
bundle exec kitchen create ssh-ubuntu1804-ansible-latest
bundle exec kitchen converge ssh-ubuntu1804-ansible-latest
bundle exec kitchen verify ssh-ubuntu1804-ansible-latest

# cleanup
bundle exec kitchen destroy ssh-ubuntu1804-ansible-latest

Testing with Virtualbox

# fast test on one machine
KITCHEN_YAML=".kitchen.vagrant.yml" bundle exec kitchen test ssh-ubuntu-1804

# test on all machines
KITCHEN_YAML=".kitchen.vagrant.yml" bundle exec kitchen test

# for development
KITCHEN_YAML=".kitchen.vagrant.yml" bundle exec kitchen create ssh-ubuntu-1804
KITCHEN_YAML=".kitchen.vagrant.yml" bundle exec kitchen converge ssh-ubuntu-1804

For more information see test-kitchen

FAQ / Pitfalls

I can't log into my account. I have registered the client key, but it still doesn't let me it.

If you have exhausted all typical issues (firewall, network, key missing, wrong key, account disabled etc.), it may be that your account is locked. The quickest way to find out is to look at the password hash for your user:

sudo grep myuser /etc/shadow

If the hash includes an !, your account is locked:

myuser:!:16280:7:60:7:::

The proper way to solve this is to unlock the account (passwd -u myuser). If the user doesn't have a password, you should can unlock it via:

usermod -p "*" myuser

Alternatively, if you intend to use PAM, you enabled it via ssh_use_pam: true. PAM will allow locked users to get in with keys.

Why doesn't my application connect via SSH anymore?

Always look into log files first and if possible look at the negotiation between client and server that is completed when connecting.

We have seen some issues in applications (based on python and ruby) that are due to their use of an outdated crypto set. This collides with this hardening module, which reduced the list of ciphers, message authentication codes (MACs) and key exchange (KEX) algorithms to a more secure selection.

After using the role Ansibles template/copy/file module does not work anymore!

This role by default deactivates SFTP. Ansible uses by default SFTP to transfer files to the remote hosts. You have to set scp_if_ssh = True in your ansible.cfg. This way Ansible uses SCP to copy files. Alternatively you can enable SFTP again by setting sftp_enabled to true.

Cannot restart sshd-service due to lack of privileges

If you get the following error when running handler "restart sshd"

Unable to restart service ssh: Failed to restart ssh.service: Access denied

or

failure 1 running systemctl show for 'ssh': Failed to connect to bus: No such file or directory

either run the playbook as root (without become: yes at the playbook level), or add become: yes to the handler.

This is a bug with Ansible: see here and here for more information.

Contributing

See contributor guideline.

License and Author

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.