The concept of a “Proxy” is often hugely misunderstood by people who know a little about these things, which results in a large amount of confusion for others who know less than those who know a little. It doesn’t help as the term “Proxy” is often used interchangeably with Reverse Proxy. While they have similar names, they serve completely different purposes. We’ll do another blog post soon on what a Reverse Proxy is. But before we do that, let’s take a look at a basic Network Firewall Proxy. What is it and why is it used?
Basic Network Physical Hardware Setup
Ok, so this is a hugely simplified diagram to illustrate the point. Let’s look at the physical hardware involved. It helps to get the point across about what a proxy is and most importantly how traffic is routed from A to Z when using these types of technologies.
You type the website into your web browser on your computer and that is how the traffic is ends up at the web server where the website lives. Some of underlying routing between the Public Internet and the Web Server have been omitted for simplicity in this diagram as we are focusing on the Network Firewall Proxy at the moment.
Physical Network Setup with Proxy Used
Now when we compare the above basic setup with the setup when you are using a Proxy, also known as a Proxy Server (generally something you manage) or Proxy Service (generally something you pay as a subscription fee for someone else to manage and you just plug into), you can see how there is just one additional step involved in the routing of how the network traffic gets from your computer to where it needs to get to on the internet.
That really is the only difference when you are using a Network Firewall Proxy VS not using one. As I mentioned at the start, don’t get this concept confused with things such as a Reverse Proxy which is completely different. Fundamentally, a Reverse Proxy does a similar ‘thing’, i.e. going via a middle man, but the architecture is significantly different and the tools used are significantly different. So despite their similar names, treat them as completely different things.
How to Configure a Network Firewall Proxy on your Hardware Firewall
Well as the section heading kind of suggests, you do this on your hardware firewall. To help you visualise this, let’s look at a hardware based pfSense firewall device which is capable of configuring a Network Firewall Proxy, here is what that looks like in the settings;
The above image shows you how you can easily configure a Proxy within your pfSense Firewall so that you can achieve this middle man setup as outlined in an earlier diagram. This Proxy could be one that you host yourself or one that is an external Software-as-a-Service SaaS Cloud Proxy that you subscribe to. Either way, pfSense gives you the options you need.
Why Use a Network Firewall Proxy?
You may be asking yourself right now why we even bother to use a Network Firewall Proxy. Well, you tend to find that it is fairly common practice in large enterprises as they like to monitor the network traffic to see what people are doing on the network. The physical hardware firewall just isn’t capable of doing the job easily as this is purely at the hardware level which is very low level and hence low levels of user functionality.
To put it into context, while modern websites are often updated multiple times per day, you’ll tend to find the software on a physical firewall is updated once every few years, and even still this is really just to patch any critical security vulnerabilities that have been discovered, not to improve the user experience of people using this device. Hence why Software-as-a-Service SaaS Proxy Services have become so popular.
Generally in the enterprise world, Proxys are used as one type security mechanism to protect both users and the corporate network from attack. While there are positives to this there can be drawbacks too. For example, let’s say you are accessing a trusted source such as Microsoft Office 365 online platform, https://www.office.com, why on earth would you run that through a Proxy service as you know full well that this is a trusted source. Let’s be honest, if Microsoft has a security incident that relates to how users are accessing their cloud services, we’re all f****d, and using a Proxy or not using a Proxy is going to be the least of all our issues. So we have to be sensible about how we use Proxy services.
This extra leg in the network journey adds latency (aka. It’s slower) for users. Slowness results in lack of productivity and lack of profitability as a business. Which is where the next topic comes into play around a Proxy Bypass.
Proxy Bypass
Here is where things get a little more nuanced. The name Proxy Bypass does exactly that, it allows you to configure things which are required to run through your Proxy, and things that should not run through your Proxy. There are many valid reasons why you need to implement Proxy Bypass to filter some parts of your internet traffic to go through the Proxy and others to not go through the Proxy.
You’ll find that some Proxy services (internal or external) are quite frankly a bit rubbish and don’t perform properly. Take for example any modern technology that does SSL validation at the client side, some Proxy services actively strip out SSL certificates in-transit and replace them with their own on different legs of the journey. Naturally with modern technology, they can detect this interference, so when the final Request-Response comes back to the client machine, it distrusts the response and bins it off – and rightfully so. This can cause a lot of problems for software developers who are utilising modern development technologies to pull in packages and dependencies from remote sources as part of their systems using things such as Maven, Gradle, NPM, Git and more.
Corporate networks acting as a Man-in-the-Middle Attack is not great. While, yes, there are corporate security controls that need to be adhered to, but at the same time, this means that when SSL is being decrypted on-route, that things such as passwords and credit card details can be read in plain text if one were to wish to do so. This is a very fine line between corporate security and employee/user privacy.
Summary
Hopefully that is a good summary of what a Network Firewall Proxy is and now you know not to confuse it with a Reverse Proxy. There are many different types of Proxys out there, from large enterprise class systems to self-hosted open source systems too.
Michael Cropper