No security without an architecture

Your diagrams don’t need to be perfect. But they do need to be there.

I attended a virtual demo this week. It didn’t work, but none of us was stressed by that: it was an internal demo, and these things happen. Luckily, the members of the team presenting the demo had lots of information about what it would have shown us, and a particularly good architectural diagram to discuss. We’ve all been in the place where the demo doesn’t work, and all felt for the colleague who was presenting the slidedeck, and on whose screen a message popped up a few slides in, saying “Demo NO GO!” from one of her team members.

After apologies, she asked if we wanted to bail completely, or to discuss the information they had to hand. We opted for the latter – after all, most demos which aren’t foregrounding user experience components don’t show much beyond terminal windows that most of us could fake up in half an hour or so anyway. She answered a couple of questions, and then I piped up with one about security.

This article could have been about the failures in security in a project which was showing an early demo: another example of security being left till late (often too late) in the process, at which point it’s difficult and expensive to integrate. However, it’s not. It clear that thought had been given to specific aspects of security, both on the network (in transit) and in storage (at rest), and though there was probably room for improvement (and when isn’t there?), a team member messaged me more documentation during the call which allowed me to understand of the choices the team had made.

What this article is about is the fact that we were able to have a discussion at all. The slidedeck included an architecture diagram showing all of the main components, with arrows showing the direction of data flows. It was clear, colour-coded to show the provenance of the different components, which were sourced from external projects, which from internal, and which were new to this demo. The people on the call – all technical – were able to see at a glance what was going on, and the team lead, who was providing the description, had a clear explanation for the various flows. Her team members chipped in to answer specific questions or to provide more detail on particular points. This is how technical discussions should work, and there was one thing in particular which pleased me (beyond the fact that the project had thought about security at all!): that there was an architectural diagram to discuss.

There are not enough security experts in the world to go around, which means that not every project will have the opportunity to get every stage of their design pored over by a member of the security community. But when it’s time to share, a diagram is invaluable. I hate to think about the number of times I’ve been asked to look at project in order to give my thoughts about security aspects, only to find that all that’s available is a mix of code and component documentation, with no explanation of how it all fits together and, worse, no architecture diagram.

When you’re building a project, you and your team are often so into the nuts and bolts that you know how it all fits together, and can hold it in your head, or describe the key points to a colleague. The problem comes when someone needs to ask questions of a different type, or review the architecture and design from a different slant. A picture – an architectural diagram – is a great way to educate external parties (or new members of the project) in what’s going on at a technical level. It also has a number of extra benefits:

  • it forces you to think about whether everything can be described in this way;
  • it forces you to consider levels of abstraction, and what should be shown at what levels;
  • it can reveal assumptions about dependencies that weren’t previously clear;
  • it is helpful to show data flows between the various components
  • it allows for simpler conversations with people whose first language is not that of your main documentation.

To be clear, this isn’t just a security problem – the same can go for other non-functional requirements such as high-availability, data consistency, performance or resilience – but I’m a security guy, and this is how I experience the issue. I’m also aware that I have a very visual mind, and this is how I like to get my head around something new, but even for those who aren’t visually inclined, a diagram at least offers the opportunity to orient yourself and work out where you need to dive deeper into code or execution. I also believe that it’s next to impossible for anybody to consider all the security implications (or any of the higher-order emergent characteristics and qualities) of a system of any significant complexity without architectural diagrams. And that includes the people who designed the system, because no system exists on its own (or there’s no point to it), so you can’t hold all of those pieces in your head of any length of time.

I’ve written before about the book Building Evolutionary Architectures, which does a great job in helping projects think about managing requirements which can morph or change their priority, and which, unsurprisingly, makes much use of architectural diagrams. Enarx, a project with which I’m closely involved, has always had lots of diagrams, and I’m aware that there’s an overhead involved here, both in updating diagrams as designs change and in considering which abstractions to provide for different consumers of our documentation, but I truly believe that it’s worth it. Whenever we introduce new people to the project or give a demo, we ensure that we include at least one diagram – often more – and when we get questions at the end of a presentation, they are almost always preceded with a phrase such as, “could you please go back to the diagram on slide x?”.

I nearly published this article without adding another point: this is part of being “open”. I’m a strong open source advocate, but source code isn’t enough to make a successful project, or even, I would add, to be a truly open source project: your documentation should not just be available to everybody, but accessible to everyone. If you want to get people involved, then providing a way in is vital. But beyond that, I think we have a responsibility (and opportunity!) towards diversity within open source. Providing diagrams helps address four types of diversity (at least!):

  • people whose first language is not the same as that of your main documentation (noted above);
  • people who have problems reading lots of text (e.g. those with dyslexia);
  • people who think more visually than textually (like me!);
  • people who want to understand your project from different points of view (e.g. security, management, legal).

If you’ve ever visited a project on github (for instance), with the intention of understanding how it fits into a larger system, you’ll recognise the sigh of relief you experience when you find a diagram or two on (or easily reached from) the initial landing page.

And so I urge you to create diagrams, both for your benefit, and also for anyone who’s going to be looking at your project in the future. They will appreciate it (and so should you). Your diagrams don’t need to be perfect. But they do need to be there.

Author: Mike Bursell

Long-time Open Source and Linux bod, distributed systems security, etc.. Now employed by Red Hat. マイク・バーゼル: オープンソースとLinuxに長く従事。他にも分散セキュリティシステムなども手がける。現在Red Hatのチーフセキュリティアーキテクト

One thought on “No security without an architecture”

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s