Obtaining SSL certificates using Nginx and Ansible

For Ubuntu 18

Using Ansible and Nginx to programmatically obtain Let's Encrypt SSL certificates on Ubuntu 18.

There is a TLDR version and a Tutorial section after it.

The GitHub repository for this post resides here.

TLDR;

Prerequisites

  1. Provision a new machine from whichever provider you use (AWS, GCP, etc)

  2. Setup your A / CNAME records to point to the public ip address of your newly created virtual machine.

Steps

  1. Ensure that you have hardened the machine for security.

  2. Install Nginx on your new instance

  3. Install Python simplejson that will be used later with Let's Encrypt tools

  4. Install Let's Encrypt binaries via apt

  5. Setup Nginx config to allow Let's Encrypt to access your machine via HTTP

  6. Obtain SSL certification using Let's Encrpyt binaries

  7. Add cron job to automatically renew SSL certificates, and reload Nginx when it does so

  8. Have a great day and feel better about yourself

Configure hosts file

  1. Change the ip address to your own

  2. Set the value of ansible_ssh_private_key_file to point to the .pem file you obtained from AWS

Secure your server

Variables

  • hashed_deploy_user_password

  • login_ssh_public_key_filename

  • has_deployment_keys

  • has_ssh_config

To run playbook

$ ansible-playbook -i hosts secure_server.yml

Install Nginx

To run playbook

$ ansible-playbook -i hosts install_nginx.yml

Provision SSL certificates

Variables

  • letsencrypt_email: your email address where domain related emails will be sent

  • main_domain_name

  • all_domain_names: additional domain names that will be added to your certificate. Useful if you want the same certificate for example.com and www.example.com and use Nginx to redirect from www.example.com to example.com

  • deploy_sample_html: if you need a sample HTML page to be made available immediately after provisioning (for testing whether everything worked out)

$ ansible-playbook -i hosts provision_ssl_certificates.yml

Tutorial

Clone this repository into your local machine. Follow along once you have.

Note, you can fork this repository. Check the .gitignore file for a list of files that will be ignored by default. No file under files/keys will be committed.

1. Setup your hosts file / inventory

The hosts file / inventory is the Ansible way of keeping track of IP addresses of your servers. In this repository the file is named hosts. Square brackets [] are used to create groups of servers that you can then refer to by name inside Ansible playbooks.

Edit the hosts file to match the contents below. Replace the ip address with the public ip address of your newly created machine.

54.169.120.36

[webservers]
54.169.120.36

2. Apply security rules to newly created instance

  1. Create a new SSH key pair that you will use to login to machine once it is secured. For this example, it has been named testingordinarysystems (private key) and testingordinarysystems.pub (public key). Add these files to files/keys.

  2. Generate a password hash of the password you wish to use for sudo in the new machine. You can run mkpasswd --method=SHA-512 --stdin in your local console for the same.

  3. Set the appropriate values for variables login_ssh_public_key_filename (= testingordinarysystems.pub in this example) and hashed_deploy_user_passwordin secure_server.yml

  4. Leave the variables has_deployment_keys and has_ssh_config with false for now.

Now, run the secure_server playbook using the command below.

$ ansible-playbook -i hosts secure_server.yml

You should see a message like this

The authenticity of host '54.169.120.36 (54.169.120.36)' can't be established.
ECDSA key fingerprint is SHA256:......
Are you sure you want to continue connecting (yes/no)?

Answer yes. This will add the public key of the server to your known_hosts file. This is a one time operation. Future runs will not prompt you again.

At this point, in a few seconds, the rest of the process should fail miserably. The point being to get a bit more familiar with the possible errors that you may encounter down the line.

The error should be something along the lines of

fatal: [54.169.120.36]: UNREACHABLE! => {"changed": false, "msg": "Failed to connect to the host via ssh: Warning: Permanently added '54.169.120.36' (ECDSA) to the list of known hosts.\r\nReceived disconnect from 54.169.120.36 port 22:2: Too many authentication failures\r\nDisconnected from 54.169.120.36 port 22", "unreachable": true}

This is Ansible telling you that it needs additional information to be able to connect to you newly created machine.

Note: there's more to this error. If you're interested check out this superuser answer

On AWS, when you launch a new instance, it will prompt you to either create a new key pair for accessing your instance or choose from an existing one. If you're creating a new key pair, download the private key file (ends in .pem), save the file to files/keys. In this example, the file is named testing.pem.

Within your hosts file, make the following changes. Make sure you get the file names right.

54.169.120.36 ansible_user=ubuntu ansible_ssh_private_key_file=./files/keys/testing.pem ansible_ssh_common_args='-o IdentitiesOnly=yes'

[webservers]
54.169.120.36 ansible_user=ubuntu ansible_ssh_private_key_file=./files/keys/testing.pem ansible_ssh_common_args='-o IdentitiesOnly=yes'

Run the playbook again.

$ ansible-playbook -i hosts secure_server.yml

A new error should greet you.

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@         WARNING: UNPROTECTED PRIVATE KEY FILE!          @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
Permissions 0664 for 'testing.pem' are too open.
It is required that your private key files are NOT accessible by others.
This private key will be ignored.
Load key "testing.pem": bad permissions

Fix it by changing the file permissions on your downloaded pem file. The filename of your key will be different ofcourse.

$ chmod 400 ./files/keys/testing.pem

Run the playbook again.

$ ansible-playbook -i hosts secure_server.yml

You should see an output with a list of actions that the playbook has peformed on your machine.

PLAY [webservers] ****************************************************************************************************

TASK [secure_server : Update and upgrade apt packages] ***************************************************************
 [WARNING]: The value True (type bool) in a string field was converted to 'True' (type string). If this does not look
like what you expect, quote the entire value to ensure it does not change.

 [WARNING]: Could not find aptitude. Using apt-get instead

changed: [54.169.120.36]

TASK [secure_server : Ensure deploy user present] ********************************************************************
changed: [54.169.120.36]

TASK [secure_server : Set authorized key taken from file] ************************************************************
changed: [54.169.120.36]

TASK [secure_server : Set permissions on /home/deploy/.ssh/authorized_keys] ******************************************
changed: [54.169.120.36]

TASK [secure_server : include_tasks] *********************************************************************************
skipping: [54.169.120.36]

TASK [secure_server : include_tasks] *********************************************************************************
skipping: [54.169.120.36]

TASK [secure_server : Disable admin group in sudoers] ****************************************************************
changed: [54.169.120.36]

TASK [secure_server : Disable sudo group in sudoers] *****************************************************************
changed: [54.169.120.36]

TASK [secure_server : Add deploy to sudoers] *************************************************************************
changed: [54.169.120.36]

TASK [secure_server : Disable root login via password] ***************************************************************
changed: [54.169.120.36]

TASK [secure_server : Disable PasswordAuthentication] ****************************************************************
ok: [54.169.120.36]

TASK [secure_server : Install unattended-upgrades package] ***********************************************************
ok: [54.169.120.36]

TASK [secure_server : Enable periodic updates] ***********************************************************************
changed: [54.169.120.36]

TASK [secure_server : Enable ufw access for OpenSSH] *****************************************************************
changed: [54.169.120.36]

TASK [secure_server : Enable ufw] ************************************************************************************
changed: [54.169.120.36]

TASK [secure_server : Unconditionally reboot the machine after applying the updates] *********************************
changed: [54.169.120.36]

PLAY RECAP ***********************************************************************************************************
54.169.120.36              : ok=14   changed=12   unreachable=0    failed=0    skipped=2    rescued=0    ignored=0

The playbook has been successfully executed. Your server has some basic security in place now. You can now login to your machine using this command

$ ssh [email protected] -i ./files/keys/testingordinarysystems

It is definitely cumbersome to have to point to a particular ssh key everytime you want to login to your server. To make it easier, add the lines below to your ssh config file. If it doesn't exist, make one using the command below.

$ touch ~/.ssh/config

Add these lines to the file using your editor of choice. Replace the ip address with the ip address of your machine. Replace the IdentityFile with the absolute path to your ssh private key (the one without .pub at the end).

Host 54.169.120.36
 PreferredAuthentications publickey
 IdentityFile /home/ordinarysystems/Documents/github/ansible-letsencrypt-nginx/files/keys/testingordinarysystems
 IdentitiesOnly yes

You can now login to your machine using the command

$ ssh [email protected]

(Optional) Adding deployment keys to your machine

If this machine is going to be used to pull private repositories from GitHub/GitLab, etc, you can pre-setup the deployment keys necessary for the same.

Create a new SSH key pair, and add the public key to your list of authorized keys on GitHub/GitLab (out of scope for this tutorial). Name them deploy and deploy.pub. Place these files under files/keys.

Modify the file files/keys/ssh_config. Replace the Host and HostName parameters to values appropriate for your git provider. The example file assumes you use GitLab.

Set the parameters has_deployment_keys and has_ssh_config to true in secure_server.yml

Run the playbook again. Note, all the commands in the play are idempotent. This means you can run them any number of times, and the output will remain unchanged if nothing needs to be changed.

$ ansible-playbook -i hosts secure_server.yml

You should see output similar to the one below

PLAY [webservers] ****************************************************************************************************

TASK [secure_server : Update and upgrade apt packages] ***************************************************************
 [WARNING]: The value True (type bool) in a string field was converted to 'True' (type string). If this does not look
like what you expect, quote the entire value to ensure it does not change.

 [WARNING]: Could not find aptitude. Using apt-get instead

ok: [54.169.120.36]

TASK [secure_server : Ensure deploy user present] ********************************************************************
ok: [54.169.120.36]

TASK [secure_server : Set authorized key taken from file] ************************************************************
ok: [54.169.120.36]

TASK [secure_server : Set permissions on /home/deploy/.ssh/authorized_keys] ******************************************
ok: [54.169.120.36]

TASK [secure_server : include_tasks] *********************************************************************************
included: /home/ordinarysystems/Documents/github/ansible-letsencrypt-nginx/roles/secure_server/tasks/copy_deployment_keys.yml for 54.169.120.36

TASK [secure_server : Copy deployment private key] *******************************************************************
changed: [54.169.120.36]

TASK [secure_server : Copy deployment public key] ********************************************************************
changed: [54.169.120.36]

TASK [secure_server : include_tasks] *********************************************************************************
included: /home/ordinarysystems/Documents/github/ansible-letsencrypt-nginx/roles/secure_server/tasks/copy_ssh_config.yml for 54.169.120.36

TASK [secure_server : Copy ssh config file] **************************************************************************
changed: [54.169.120.36]

TASK [secure_server : Disable admin group in sudoers] ****************************************************************
ok: [54.169.120.36]

TASK [secure_server : Disable sudo group in sudoers] *****************************************************************
ok: [54.169.120.36]

TASK [secure_server : Add deploy to sudoers] *************************************************************************
ok: [54.169.120.36]

TASK [secure_server : Disable root login via password] ***************************************************************
ok: [54.169.120.36]

TASK [secure_server : Disable PasswordAuthentication] ****************************************************************
ok: [54.169.120.36]

TASK [secure_server : Install unattended-upgrades package] ***********************************************************
ok: [54.169.120.36]

TASK [secure_server : Enable periodic updates] ***********************************************************************
ok: [54.169.120.36]

TASK [secure_server : Enable ufw access for OpenSSH] *****************************************************************
ok: [54.169.120.36]

TASK [secure_server : Enable ufw] ************************************************************************************
ok: [54.169.120.36]

TASK [secure_server : Unconditionally reboot the machine after applying the updates] *********************************
changed: [54.169.120.36]

PLAY RECAP ***********************************************************************************************************
54.169.120.36              : ok=19   changed=4    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

You should now be able to pull your git repositories to this machine.

4. Install Nginx

To keep matters simpler for this tutorial, the Nginx Ansible role lives in it's own file, install_nginx.yml.

Run the command below to execute the play.

$ ansible-playbook -i hosts install_nginx.yml

You should see output like so

PLAY [webservers] **************************************************************

TASK [nginx : Add Nginx Repository] ********************************************
changed: [54.169.120.36]

TASK [nginx : Install Nginx] ***************************************************
changed: [54.169.120.36]

TASK [nginx : Enable ufw access for Nginx Full] ********************************
changed: [54.169.120.36]

RUNNING HANDLER [nginx : Start Nginx] ******************************************
ok: [54.169.120.36]

PLAY RECAP *********************************************************************
54.169.120.36              : ok=5    changed=4    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

You can verify this by logging into your machine and running the commands below

$ ssh [email protected]
$ sudo service nginx status

● nginx.service - A high performance web server and a reverse proxy server
   Loaded: loaded (/lib/systemd/system/nginx.service; enabled; vendor preset: enabled)
   Active: active (running) since Tue 2019-10-22 05:44:16 UTC; 4min 4s ago
     Docs: man:nginx(8)
 Main PID: 4443 (nginx)
    Tasks: 2 (limit: 1152)
   CGroup: /system.slice/nginx.service
           ├─4443 nginx: master process /usr/sbin/nginx -g daemon on; master_process on;
           └─4445 nginx: worker process

Oct 22 05:44:16 ip-172-31-17-175 systemd[1]: Starting A high performance web server and a reverse proxy server...
Oct 22 05:44:16 ip-172-31-17-175 systemd[1]: Started A high performance web server and a reverse proxy server.

If by some chance you've lost your sudo password for the deploy user, check the Common errors section at the bottom for instructions on how to change it.

5. Provision new SSL certificates for your machine

Finally! In the file provision_ssl_certificates.yml, set appropriate values for the variables

  1. letsencrypt_email (your email address where important communication will be sent regarding your domain)

  2. main_domain_name (example.com or whatever your domain name is)

  3. all_domain_names (example.com, www.example.com, ..., all of these domains will then be issued a single ssl certificate)

Run the command below to start

$ ansible-playbook -i hosts provision_ssl_certificates.yml

Everything will go along smoothly, for a while, and then, BAM! If you've followed along exactly, you should hit an error of this sorts.

fatal: [54.169.120.36]: FAILED! => {"changed": true, "cmd": "letsencrypt certonly -n --webroot -w /var/www/letsencrypt -m [email protected] --agree-tos -d test1.ordinary.systems -d www.test1.ordinary.systems", "delta": "0:00:13.765920", "end": "2019-10-22 06:54:01.466099", "msg": "non-zero return code", "rc": 1, "start": "2019-10-22 06:53:47.700179", "stderr": "Saving debug log to /var/log/letsencrypt/letsencrypt.log\nPlugins selected: Authenticator webroot, Installer None\nObtaining a new certificate\nPerforming the following challenges:\nhttp-01 challenge for test1.ordinary.systems\nhttp-01 challenge for www.test1.ordinary.systems\nUsing the webroot path /var/www/letsencrypt for all unmatched domains.\nWaiting for verification...\nCleaning up challenges\nFailed authorization procedure. www.test1.ordinary.systems (http-01): urn:acme:error:connection :: The server could not connect to the client to verify the domain :: Fetching http://www.test1.ordinary.systems/.well-known/acme-challenge/...: Timeout during connect (likely firewall problem)", "stderr_lines": ["Saving debug log to /var/log/letsencrypt/letsencrypt.log", "Plugins selected: Authenticator webroot, Installer None", "Obtaining a new certificate", "Performing the following challenges:", "http-01 challenge for test1.ordinary.systems", "http-01 challenge for www.test1.ordinary.systems", "Using the webroot path /var/www/letsencrypt for all unmatched domains.", "Waiting for verification...", "Cleaning up challenges", "Failed authorization procedure. www.test1.ordinary.systems (http-01): urn:acme:error:connection :: The server could not connect to the client to verify the domain :: Fetching http://www.test1.ordinary.systems/.well-known/acme-challenge/...: Timeout during connect (likely firewall problem)"], "stdout": "IMPORTANT NOTES:\n - The following errors were reported by the server:\n\n   Domain: www.test1.ordinary.systems\n   Type:   connection\n   Detail: Fetching\n   http://www.test1.ordinary.systems/.well-known/acme-challenge/...:\n   Timeout during connect (likely firewall problem)\n\n   To fix these errors, please make sure that your domain name was\n   entered correctly and the DNS A/AAAA record(s) for that domain\n   contain(s) the right IP address. Additionally, please check that\n   your computer has a publicly routable IP address and that no\n   firewalls are preventing the server from communicating with the\n   client. If you're using the webroot plugin, you should also verify\n   that you are serving files from the webroot path you provided.\n - Your account credentials have been saved in your Certbot\n   configuration directory at /etc/letsencrypt. You should make a\n   secure backup of this folder now. This configuration directory will\n   also contain certificates and private keys obtained by Certbot so\n   making regular backups of this folder is ideal.", "stdout_lines": ["IMPORTANT NOTES:", " - The following errors were reported by the server:", "", "   Domain: www.test1.ordinary.systems", "   Type:   connection", "   Detail: Fetching", "   http://www.test1.ordinary.systems/.well-known/acme-challenge/...:", "   Timeout during connect (likely firewall problem)", "", "   To fix these errors, please make sure that your domain name was", "   entered correctly and the DNS A/AAAA record(s) for that domain", "   contain(s) the right IP address. Additionally, please check that", "   your computer has a publicly routable IP address and that no", "   firewalls are preventing the server from communicating with the", "   client. If you're using the webroot plugin, you should also verify", "   that you are serving files from the webroot path you provided.", " - Your account credentials have been saved in your Certbot", "   configuration directory at /etc/letsencrypt. You should make a", "   secure backup of this folder now. This configuration directory will", "   also contain certificates and private keys obtained by Certbot so", "   making regular backups of this folder is ideal."]}

The important line in this mess is firewalls are preventing the server from communicating. But we've already told our firewall to allow communication to ports 80 and 443earlier on. What we haven't done yet, is to configure the AWS security group of our machine to allow incoming communication on these same ports.

The security group's inbound rules should read like so

Type    Protocol    Port Range      Source
HTTP    TCP         80              0.0.0.0/0
HTTPS   TCP         443             0.0.0.0/0
SSH     TCP         22              0.0.0.0/0

Once you've made the edits, run the playbook again

$ ansible-playbook -i hosts provision_ssl_certificates.yml

This time, everything works. You should see output like so

PLAY [webservers] **********************************************************************************************

TASK [Gathering Facts] *****************************************************************************************
ok: [54.169.120.36]

TASK [letsencrypt : Install Python simplejson] *****************************************************************
 [WARNING]: Could not find aptitude. Using apt-get instead

ok: [54.169.120.36]

TASK [letsencrypt : install letsencrypt] ***********************************************************************
ok: [54.169.120.36]

TASK [letsencrypt : create letsencrypt directory] **************************************************************
ok: [54.169.120.36]

TASK [letsencrypt : Remove default nginx config] ***************************************************************
ok: [54.169.120.36]

TASK [letsencrypt : Install system nginx config] ***************************************************************
ok: [54.169.120.36]

TASK [letsencrypt : Install nginx site for letsencrypt requests] ***********************************************
ok: [54.169.120.36]

TASK [letsencrypt : Reload nginx to activate letsencrypt site] *************************************************
changed: [54.169.120.36]

TASK [letsencrypt : Create letsencrypt certificate] ************************************************************
changed: [54.169.120.36]

TASK [letsencrypt : Generate dhparams] *************************************************************************
ok: [54.169.120.36]

TASK [letsencrypt : Add empty data directory for domain static files] ******************************************
changed: [54.169.120.36]

TASK [letsencrypt : Install nginx site for test1.ordinary.systems] *********************************************
changed: [54.169.120.36]

TASK [letsencrypt : Reload nginx to activate specified site] ***************************************************
changed: [54.169.120.36]

TASK [letsencrypt : Add letsencrypt cronjob for cert renewal] **************************************************
changed: [54.169.120.36]

PLAY RECAP *****************************************************************************************************
54.169.120.36              : ok=14   changed=6    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

If you chose to deploy the sample html page that comes along with this playbook (by setting deploy_sample_html: true in provision_ssl_certificates.yml), you can immediately visit https://<your_main_domain_name> and be greeted by some amazing CSS work by Lynn Fisher.

Quick note: static files for your domain have been configured to be served from the folder /var/www/{{ main_domain_name }} on your machine.

And that's it. By now you should feel comfortable with experimenting with Ansible. You hit errors, you fixed them. And then continued along as if nothing happened. You ran playbooks multiple times. You copied files to remove servers. You did a whole lot of cool stuff. Congratulations on being amazing :)

Quick Links

What Is DNS? | How DNS Works

For a primer on what A / CNAME records actually are and do, I highly recommend going through What Is DNS? | How DNS Works by Cloudflare.

Nginx

If you're new to Nginx, checkout the beginner's guide. You are not required to go through them as all the necessary configuration files required for this process are provided in this repository. It is ,however, highly recommended that you have a basic familiarity with the tools that you use.

Python simplejson

simplejson is a simple, fast, complete, correct and extensible JSON http://json.org encoder and decoder for Python 2.5+ and Python 3.3+.

Let's Encrypt

Let’s Encrypt is a free, automated, and open certificate authority (CA), run for the public’s benefit. It is a service provided by the Internet Security Research Group (ISRG).

Setting up Ansible inside a virtual environment

Common errors

Too many authentication failures for username

Backslashes in ansible <code>regex_replace</code>

Reset password for the deploy user

Login to your machine using the .pem file you obtained from AWS. And then type in the commands after.

$ ssh [email protected] -i ./files/keys/testingordinarysystems
$ sudo passwd deploy
...enter your new password
...exit and login using your deploy user
$ ssh [email protected]
...sudo password is now what entered above

Soumyajit Pathak picture

Another great article. These are perfect reference materials.

Thanks again. Appreciate the Github repo for source code reference.