How To Secure HAProxy with Let's Encrypt on CentOS 7
How To Secure HAProxy with Let's Encrypt on CentOS 7
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How To Secure HAProxy with Let's Encrypt on CentOS 7

PostedJanuary 26, 2016 16.9k views Let's Encrypt Security Load Balancing CentOS


Let's Encrypt is a new Certificate Authority (CA) that provides an easy way to obtain and install free TLS/SSL certificates, thereby enabling encrypted HTTPS on web servers. It simplifies the process by providing a software client, letsencrypt, that attempts to automate most (if not all) of the required steps. Currently, as Let's Encrypt is still in open beta, the entire process of obtaining and installing a certificate is fully automated only on Apache web servers. However, Let's Encrypt can be used to easily obtain a free SSL certificate, which can be installed manually, regardless of your choice of web server software.

In this tutorial, we will show you how to use Let's Encrypt to obtain a free SSL certificate and use it with HAProxy on CentOS 7. We will also show you how to automatically renew your SSL certificate.

HAProxy with Let's Encrypt TLS/SSL Certificate and Auto-renewal


Before following this tutorial, you'll need a few things.

You should have an CentOS 7 server with a non-root user who has sudo privileges. You can learn how to set up such a user account by following steps 1-3 in our initial server setup for CentOS 7 tutorial.

You must own or control the registered domain name that you wish to use the certificate with. If you do not already have a registered domain name, you may register one with one of the many domain name registrars out there (e.g. Namecheap, GoDaddy, etc.).

If you haven't already, be sure to create an A Record that points your domain to the public IP address of your server. This is required because of how Let's Encrypt validates that you own the domain it is issuing a certificate for. For example, if you want to obtain a certificate for, that domain must resolve to your server for the validation process to work. Our setup will use and as the domain names, so both DNS records are required.

Once you have all of the prerequisites out of the way, let's move on to installing the Let's Encrypt client software.

Step 1 — Install Let's Encrypt Client

The first step to using Let's Encrypt to obtain an SSL certificate is to install the letsencrypt software on your server. Currently, the best way to install Let's Encrypt is to simply clone it from the official GitHub repository. In the future, it will likely be available via a package manager.

Install Git and Bc

Let's install Git now, so we can clone the Let's Encrypt repository.

Install the git and bc packages with yum:

  • sudo yum install git bc

With git and bc installed, we can easily download letsencrypt by cloning the repository from GitHub.

Clone Let's Encrypt

We can now clone the Let’s Encrypt repository in /opt with this command:

  • sudo git clone /opt/letsencrypt

You should now have a copy of the letsencrypt repository in the /opt/letsencrypt directory.

Step 2 — Obtain a Certificate

Let's Encrypt provides a variety of ways to obtain SSL certificates, through various plugins. Unlike the Apache plugin, which is covered in a different tutorial, most of the plugins will only help you with obtaining a certificate which you must manually configure your web server to use. Plugins that only obtain certificates, and don't install them, are referred to as "authenticators" because they are used to authenticate whether a server should be issued a certificate.

We'll show you how to use the Standalone plugin to obtain an SSL certificate.

Verify Port 80 is Open

The Standalone plugin provides a very simple way to obtain SSL certificates. It works by temporarily running a small web server, on port 80, on your server, to which the Let's Encrypt CA can connect and validate your server's identity before issuing a certificate. As such, this method requires that port 80 is not in use. That is, be sure to stop your normal web server, if it's using port 80 (i.e. http), before attempting to use this plugin.

For example, if you're using HAProxy, you can stop it by running this command:

  • sudo systemctl stop haproxy

If you're not sure if port 80 is in use, you can run this command:

netstat -na | grep ':80.*LISTEN'

If there is no output when you run this command, you can use the Standalone plugin.

Run Let's Encrypt

Before using Let's Encrypt, change to the letsencrypt directory:

  • cd /opt/letsencrypt

Now use the Standalone plugin by running this command:

  • ./letsencrypt-auto certonly --standalone

Note: The Let's Encrypt software requires superuser privileges, so you will be required to enter your password if you haven't used sudo recently.

After letsencrypt initializes, you will be prompted for some information. This exact prompts may vary depending on if you've used Let's Encrypt before, but we'll step you through the first time.

At the prompt, enter an email address that will be used for notices and lost key recovery:

Email prompt

Then you must agree to the Let's Encrypt Subscribe Agreement. Select Agree:

Let's Encrypt Subscriber's Agreement

Then enter your domain name(s). Note that if you want a single cert to work with multiple domain names (e.g. and, be sure to include all of them:

Domain name prompt

If everything was successful, you should see an output message that looks something like this:

IMPORTANT NOTES: - If you lose your account credentials, you can recover through e-mails sent to - Congratulations! Your certificate and chain have been saved at /etc/letsencrypt/live/ Your cert will expire on 2016-03-15. To obtain a new version of the certificate in the future, simply run Let's Encrypt again. - Your account credentials have been saved in your Let's Encrypt 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 Let's Encrypt so making regular backups of this folder is ideal. - If like Let's Encrypt, please consider supporting our work by: Donating to ISRG / Let's Encrypt: Donating to EFF:

You will want to note the path and expiration date of your certificate, which was highlighted in the example output.

Note: If your domain is routing through a DNS service like CloudFlare, you will need to temporarily disable it until you have obtained the certificate.

Certificate Files

After obtaining the cert, you will have the following PEM-encoded files:

  • cert.pem: Your domain's certificate
  • chain.pem: The Let's Encrypt chain certificate
  • fullchain.pem: cert.pem and chain.pem combined
  • privkey.pem: Your certificate's private key

It's important that you are aware of the location of the certificate files that were just created, so you can use them in your web server configuration. The files themselves are placed in a subdirectory in /etc/letsencrypt/archive. However, Let's Encrypt creates symbolic links to the most recent certificate files in the /etc/letsencrypt/live/your_domain_name directory.

You can check that the files exist by running this command (substituting in your domain name):

  • sudo ls /etc/letsencrypt/live/your_domain_name

The output should be the four previously mentioned certificate files.

Combine Fullchain.pem and Privkey.pem

When configuring HAProxy to perform SSL termination, so it will encrypt traffic between itself and the end user, you must combine fullchain.pem and privkey.pem into a single file.

First, create the directory where the combined file will be placed, /etc/haproxy/certs:

  • sudo mkdir -p /etc/haproxy/certs

Next, create the combined file with this cat command (substitute the highlighted with your domain name):

  • DOMAIN='' sudo -E bash -c 'cat /etc/letsencrypt/live/$DOMAIN/fullchain.pem /etc/letsencrypt/live/$DOMAIN/privkey.pem > /etc/haproxy/certs/$DOMAIN.pem'

Secure access to the combined file, which contains the private key, with this command:

  • sudo chmod -R go-rwx /etc/haproxy/certs

Now we're ready to use the SSL cert and private key with HAProxy.

Step 3 — Install HAProxy

This step covers the installation of HAProxy. If it's already installed on your server, skip this step.

Install HAProxy with yum:

  • sudo yum install haproxy

HAProxy is now installed but needs to be configured.

Step 4 — Configure HAProxy

This section will show you how to configure basic HAProxy with SSL setup. It also covers how to configure HAProxy to allow us to auto-renew our Let's Encrypt certificate.

Open haproxy.cfg in a text editor:

  • sudo vi /etc/haproxy/haproxy.cfg

Keep this file open as we edit it in the next several sections.

Global Section

Add this line to the global section to configure the maximum size of temporary DHE keys that are generated:

haproxy.cfg — 1 of 5
   tune.ssl.default-dh-param 2048

Frontend Sections

Now we're ready to define our frontend sections.

Note: The default HAProxy configuration includes a frontend and several backends. Feel free to delete them as we will not be using them.

The first thing we want to add is a frontend to handle incoming HTTP connections, and send them to a default backend (which we'll define later). At the end of the file, let's add a frontend called www-http. Be sure to replace haproxy_public_IP with the public IP address of your HAProxy server:

haproxy.cfg — 2 of 5
frontend www-http
   bind haproxy_www_public_IP:80
   reqadd X-Forwarded-Proto:\ http
   default_backend www-backend

Next, we will add a frontend to handle incoming HTTPS connections. At the end of the file, add a frontend called www-https. Be sure to replace haproxy_www_public_IP with the public IP of your HAProxy server. Also, you will need to replace with your domain name (which should correspond to the certificate file you created earlier):

haproxy.cfg — 3 of 5
frontend www-https
   bind haproxy_www_public_IP:443 ssl crt /etc/haproxy/certs/
   reqadd X-Forwarded-Proto:\ https
   acl letsencrypt-acl path_beg /.well-known/acme-challenge/
   use_backend letsencrypt-backend if letsencrypt-acl
   default_backend www-backend

This frontend uses an ACL (letsencrypt-acl) to send Let's Encrypt validation requests (for /.well-known/acme-challenge) to the letsencrypt-backend backend, which will enable us to renew the certificate without stopping the HAProxy service. All other requests will be forwarded to the www-backend, which is the backend that will serve our web application or site.

Backend Sections

After you are finished configuring the frontends, add the www-backend backend by adding the following lines. Be sure to replace the highlighted words with the respective private IP addresses of your web servers (adjust the number of server lines to match how many backend servers you have):

haproxy.cfg — 4 of 5
backend www-backend
   redirect scheme https if !{ ssl_fc }
   server www-1 www_1_private_IP:80 check
   server www-2 www_2_private_IP:80 check

Any traffic that this backend receives will be balanced across its server entries, over HTTP (port 80).

Lastly, add the letsencrypt-backend backend, by adding these lines

haproxy.cfg — 5 of 5
backend letsencrypt-backend
   server letsencrypt

This backend, which only handles Let's Encrypt ACME challenges that are used for certificate requests and renewals, sends traffic to the localhost on port 54321. We'll use this port instead of 80 and 443 when we renew our Let's Encrypt SSL certificate.

Now we're ready to start HAProxy:

  • sudo systemctl start haproxy

Note: If you're having trouble with the haproxy.cfg configuration file, check out this GitHub Gist for an example.

The Let's Encrypt TLS/SSL certificate is now in place, and we're ready to set up the auto-renewal script. At this point, you should test that the TLS/SSL certificate works by visiting your domain in a web browser.

Step 5 — Set Up Auto Renewal

Let’s Encrypt certificates are valid for 90 days, but it’s recommended that you renew the certificates every 60 days to allow a margin of error. At the time of this writing, automatic renewal is still not available as a feature of the client itself, but you can manually renew your certificates by running the Let’s Encrypt client again.

A practical way to ensure your certificates won’t get outdated is to create a cron job that will automatically handle the renewal process for you. In order to avoid the interactive, menu-driven process that we used earlier, we will use different parameters when calling the Let’s Encrypt client in the cron job.

We will use the Standalone plugin used earlier, but configure it to use port 54321 so it doesn't conflict with HAProxy (which is listening on port 80 and 443). To do so, we'll use this command (substituting in your domain name for both highlighted domains):

  • cd /opt/letsencrypt
  • ./letsencrypt-auto certonly --agree-tos --renew-by-default --standalone-supported-challenges http-01 --http-01-port 54321 -d -d

Once that succeeds, you will need to create a new combined certificate file (replace with your domain name):

  • DOMAIN='' sudo -E bash -c 'cat /etc/letsencrypt/live/$DOMAIN/fullchain.pem /etc/letsencrypt/live/$DOMAIN/privkey.pem > /etc/haproxy/certs/$DOMAIN.pem'

Then reload HAProxy to start using the new certificate:

  • sudo service haproxy reload

Now that we know the commands that we need to renew our certificate, we can automate this process using scripts and a cron job.

Create a Let's Encrypt Configuration File

Before moving on, let's simplify our renewal process by creating a Let's Encrypt configuration file at /usr/local/etc/le-renew-haproxy.ini.

  • sudo cp /opt/letsencrypt/examples/cli.ini /usr/local/etc/le-renew-haproxy.ini

Now open the file for editing;

  • sudo nano /usr/local/etc/le-renew-haproxy.ini

Next, uncomment the email and domains lines, and update them with your own information. The file (with comments removed) should look something like this: — 1 of 2
rsa-key-size = 4096

email =

domains =,

Next, uncomment the standalone-supported-challenges line, and replace its value with http-01. This tells Let's Encrypt to use It should look like this (with the changed value highlighted red): — 2 of 2
standalone-supported-challenges = http-01

Now, instead of specifying the domain names in the command, we can use the Let's Encrypt configuration file to fill in the blanks. Assuming your configuration file is correct, this command can be used to renew your certificate:

cd /opt/letsencrypt
./letsencrypt-auto certonly --renew-by-default --config /usr/local/etc/le-renew-haproxy.ini --http-01-port 54321

Note: If you're having trouble with the le-renew-haproxy.ini configuration file, check out this GitHub Gist for an example.

Now let's create a script that we can use to renew our certificate.

Create a Renewal Script

To automate the renewal process, we will use a shell script that will verify the certificate expiration date for the provided domain and request a renewal when the expiration is less than 30 days away. This script will be scheduled to run once a week. This way, even if a cron job fails, there’s a 30-day window to try again every week.

First, download the script and make it executable. Feel free to review the contents of the script before downloading it.

  • sudo curl -L -o /usr/local/sbin/le-renew-haproxy
  • sudo chmod +x /usr/local/sbin/le-renew-haproxy

The le-renew-haproxy script takes as argument the domain name whose certificate you want to check for renewal. When the renewal is not yet necessary, it will simply output how many days are left until the given certificate expiration.

Note: The script will not run if the /usr/local/etc/le-renew-haproxy.ini file does not exist. Also, be sure that the first domain that is specified in the configuration file is the same as the first domain you specified when you originally created the certificate.

If you run the script now, you will be able to see how many days are left for this certificate to expire:

  • sudo /usr/local/sbin/le-renew-haproxy
Checking expiration date for The certificate is up to date, no need for renewal (89 days left).

Next, we will edit the crontab to create a new job that will run this command every week. To edit the crontab for the root user, run:

  • sudo crontab -e

Include the following content, all in one line:

crontab entry
30 2 * * 1 /usr/local/sbin/le-renew-haproxy >> /var/log/le-renewal.log

Save and exit. This will create a new cron job that will execute the le-renew-haproxy command every Monday at 2:30 am. The output produced by the command will be piped to a log file located at /var/log/le-renewal.log.


That's it! HAProxy is now using a free Let's Encrypt TLS/SSL certificate to securely serve HTTPS traffic.


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