Five Steps to Secure Varnish with Hitch and Let's Encrypt

Update (June 2017)

Some of the content in this post is outdated. We recommend that you read up on our Let's Encrypt with Hitch and Varnish tutorial instead.

Introduction

"Let’s Encrypt is a new Certificate Authority: It’s free, automated, and open". Using Let's Encrypt, anyone with ownership of a domain name can acquire a TLS certificate for their own personal use.

There are a number of client-tools available to support this process, and the project also supplies an official version. However this guide is based on the very user friendly Acmetool instead, as it simplifies the process and is available for a number of TLS proxies, including Hitch.

This tutorial will give you instructions for both Ubuntu 16.04 Xenial (soon to be released) and CentOS7. At the conclusion, you will have a fully working TLS setup with automatic certificate renewal.

Prerequisites

Before starting this tutorial you will need a couple of things.

Firstly you need a working Linux host, either set up with Ubuntu Xenial or CentOS7.

You will need root privileges throughout this tutorial, so either have access to the root user or sudo privileges (the step-by-step guide assumes sudo usage).

You must own or control a registered domain name that you wish to use the certificate with. If you do not yet own a domain name, please take a moment to acquire one from one of the many available registrars. (See Icann.org for an exhaustive list.)

When you are in control of a domain name, create an A-record with the name of the domain that points to the public IP-address of the host you are setting up. The following guide assumes that this A-record is set up and working, as the way the certificates are acquired relies on this for validation of domain name ownership.

In this guide we will use example.com as the domain name, and we will have set up both example.com and www.example.com to point to our hosts public IP-address.

Once you have the prerequisites in order, proceed to the actual software setup.

Step 1 - Install Hitch and Varnish

This step ensures the Hitch and Varnish packages are installed.

Ubuntu Xenial

Update the package metadata and install the required packages:

sudo apt-get update
sudo apt-get install hitch varnish


CentOS7 / Red Hat EL7

Install the required packages. In order to get Varnish 4.1 with added support for the PROXY protocol, we add the official Varnish repository first.

sudo yum install epel-release
sudo rpm --nosignature -i https://repo.varnish-cache.org/redhat/varnish-4.1.el7.rpm
sudo yum install hitch varnish


Step 2 - Configure Varnish

We want Varnish to forward all challenge requests to Acmetool, and we are going to create a request matching rule in VCL that will ensure this forwarding happens.

The idea is to add this rule in a separate VCL file to not interfere with the main Varnish VCL.

Again open your favorite editor and create /etc/varnish/acmetool.vcl with the following contents:

# Forward challenge-requests to acmetool, which will listen to port 402
# when issuing lets encrypt requests

backend acmetool {
   .host = "127.0.0.1";
   .port = "402";
}

sub vcl_recv {

    if (req.url ~ "^/.well-known/acme-challenge/") {
        set req.backend_hint = acmetool;

return(pass);

    }
}

Then we need to include this in our main VCL. Open the file /etc/varnish/default.vcl and add the VCL below your backend definitions:

include "/etc/varnish/acmetool.vcl";

As we will be using Hitch to forward requests, we want Varnish to listen to an additional port (6086) using the PROXY protocol support that was added in Varnish 4.1. (If for some reason you do not want to run Varnish 4.1, you can skip this step, and simply change the port used for Varnish in the hitch config to 6081.)

On Ubuntu Xenial, open the file /lib/systemd/system/varnish.service add -a '[::1]:6086,PROXY' to the ExecStart line. You then need to update systemd by running:

sudo systemctl daemon-reload

In CentOS7 the same option is added by editing /etc/varnish/varnish.params and ensure the DAEMON_OPTS setting includes the following: DAEMON_OPTS="-a '[::1]:6086,PROXY'"

Restart Varnish so that it will listen to the new ports, and use the correct forwarding rule for the challenge requests.

sudo service varnish restart

Step 3 - Install Acmetool

We will now install the Acmetool binaries using the available APT PPA for Ubuntu, and the copr repository for CentOS7.

Ubuntu Xenial

Acmetool is published in a PPA, so we will add this and then install the package:

sudo add-apt-repository ppa:hlandau/rhea
sudo apt-get update
sudo apt-get install acmetool


CentOS7 / Red Hat EL7

Acmetool is available in a copr repository. We will get the repository file and then install the package:

sudo wget --quiet -O /etc/yum.repos.d/hlandau-acmetool-epel-7.repo 'https://copr.fedorainfracloud.org/coprs/hlandau/acmetool/repo/epel-7/hlandau-acmetool-epel-7.repo'
sudo yum install acmetool


Step 4 - Acquire the certificate

Now we will use Acmetool to acquire a certificate.

Now we have everything in place and we run the Acmetool quickstart process. It should detect that we are using Hitch and automatically set up a hook that will generate Hitch-compatible certificate-packages from certificate requests.

sudo acmetool quickstart

Answer the prompts like this to enable live certificates authenticated through challenge requests proxied through Varnish.

------------------------- Select ACME Server -----------------------
1) Let's Encrypt (Live) - I want live certificates

----------------- Select Challenge Conveyance Method ---------------
2) PROXY - I'll proxy challenge requests to an HTTP server


Review and (hopefully) accept the letsencrypt.org Terms of Service, and enter your email address.

-------------------- Install HAProxy/Hitch hooks? ------------------
Yes) Do you want to install the HAProxy/Hitch notification hook?

-------------------- Install auto-renewal cronjob? -----------------
Yes) Would you like to install a cronjob to renew certificates automatically? This is recommended.


Before we continue to requesting our certificate we need to generate a Diffie-Hellman group file (aka dhparams), used for perfect forward secrecy.

sudo openssl dhparam -out /var/lib/acme/conf/dhparams 2048

Now we can finally get our certificate:

sudo acmetool want example.com

Step 5 - Configure Hitch

Now we should have our own valid certificate, and we can use it to set up Hitch. As previously mentioned we configured Varnish to listen to an additional port (6086) where it will accept requests using the PROXY protocol.

Use your favorite editor to create the file /etc/hitch/hitch.conf and copy the following contents into it, note the required user/group settings on CentOS/RHEL.

## Basic hitch config for use with Varnish and Acmetool

# Listening
frontend = "[*]:443"
ciphers  = "EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:AES256+EDH"

# Send traffic to the Varnish backend using the PROXY protocol
backend        = "[::1]:6086"
write-proxy-v2 = on

# If you run Varnish 4.0 use this instead
#backend        = "[::1]:6081"
#write-proxy-v2 = off

# List of PEM files, each with key, certificates and dhparams
pem-file = "/var/lib/acme/live/example.com/haproxy"

# Set uid/gid after binding a socket
# Uncomment these on CentOS/RHEL
#user = "hitch"
#group = "hitch"

Start Hitch with the new configuration:

sudo service hitch start

Conclusion

You now have a fully configured TLS-capable stack, and accessing your server via https:// should present the site with a valid certificate issued by Let's Encrypt.

Now you can continue on to configuring Varnish to suit your use.

Watch the TSL/SSL webinar

 

Photo (c) 2013 Punk Toad used under Creative Commons license.

04/02/16 19:00 by Denis Brækhus

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