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Security risks as Drupal matures

An article from ComputerMinds - Building with Drupal in the UK since 2005.
12th Dec 2018

Nathan Page

Developer

After reading this from Ars Technica, which describes how a developer offered to 'help' the maintainer of an NPM module - and then slowly introduced malicious code to it - I can't help but wonder if the Drupal community is vulnerable to the exact same issue. Let's discuss!

Please, don't touch my package

NPM modules have been hacked at before, and it's not pretty when it happens. Because of the way we use packages, it's a lot easier for nasty code to get sucked in to a LOT of applications before anyone notices. Attacks on the code 'supply chain', therefore, have tended to be high-profile and high-damage.

NPM is used as a source for a huge number of code projects, many of which use other bits of code from other NPM packages. Even moderate applications for PC, mobile or web can have hundreds or thousands of NPM packages pulled in. It's common for packages to depend on other packages, which depend on other packages, which need other packages, which require... you get the picture? There are so many fragments, layers and extra bits that NPM is used for, that the developers of the applications don't necessarily know all the packages that are being pulled in to their application. It's so easy to just type "npm require somefancypackageineed" without thinking and without vetting. NPM will just go and get everything for you, and you don't need to care.

That's how it should be, right? We should be able to just add code and know that it's safe, right? In a perfect world, that would be fine. But in reality there's an increasingly large amount of trust being given when you add a package to your application, and developers don't realise it. It's events like this that are making people aware again that they are including code in their projects that they either do not scrutinise or do not know exists.

Drupal's moment will come

Fortunately, Drupal is a little different to NPM. Whilst modules are often dependent on other modules, we tend to have a lot less layers going on. It's much easier to know what modules and dependencies you're adding in when you include a new module. But that doesn't mean we're immune.

This particular incident came about when a tired, busy module maintainer was approached and offered help. It's a classic social engineering hack.

"Sure, I'll help you! [mwahaha]"

What struck me was that Drupal probably has hundreds of module maintainers in similar circumstances. Put yourself in those shoes, for a moment:
- You maintain an old Drupal 7 module
- It has a few thousand sites using it still
- You're busy, don't have time for it anymore

If somebody offered to sort it all out for you, what would you say? I'm pretty sure most would be ecstatic! Hurrah! But how would you vet your new favourite person in the whole world, before making them a co-maintainer and giving them the keys to the kingdom?

Alternatively, what of this:
- There is an old module, officially unmaintained
- It still has users
- The maintainer cannot be contacted

Drupal has a system for allowing people to be made maintainers of modules, when the original maintainer cannot be contacted. How are these people vetted? I'm sure there's some sort of check, but what if it's not enough?

In particular, I want to point out that as Drupal 7 ages, there will be more and more old, unmaintained and unloved modules still used by thousands of sites. If we forget them and fail to offer them sufficient protection, they will become vulnerable to attacks just like this. Drupal's moment will come.

This is an open source issue

It would be rather very easy to run away screaming right now, having decided that open source technologies sound too dangerous. So I'll put in some positive notes!

That Drupal should be increasingly exposed to the possibility of social engineering and malevolent maintainers is no new issue. There are millions of open source projects out there, all exposed to exactly these issues. As the internet grows and matures and ages, these issues will become more and more common; how many projects out there have tired and busy maintainers?!

For now, though, it must be said that the open source communities of the world have done what few thought possible. We have millions of projects and developers around the world successfully holding onto their trusty foundations, Drupal included. Many governments, enterprises and organisations have embraced the open source way of working on the premise that although there is risk in working differently, there is great merit in the reward. To this day, open source projects continue to thrive and to challenge the closed-source world. It is the scrutiny and the care of the open source community that keeps it clear and safe. As long as we continue to support and love and use our open source communities and contributions, they will stay in good repair and good stead.

If you were thinking of building a Drupal site and are suddenly now questioning that decision, then a read of Drupal's security statement is probably worthwhile.

Know your cattle by name

The key mitigation for this risk, it should be said, is for developers to know what code is in their application. It's our job to care and so it's our job to be paranoid. But it's not always easy. How many times have you installed a module without checking every line of code? How many times have you updated a module without checking the diff in Git? It's not always practicable to scan thousands and thousands of lines of code, just in case - and you'd hope that it's not necessary - but that doesn't mean it's not a good idea.

Using Composer with Drupal 8 makes installing new modules as easy as using NPM, and exposes the same problems to some extent. Add in a build pipeline, and it's very easy to never even see a single line of the new code that you've added to your project. Am I poking a paranoia nerve, yet? ;)

For further fun, think back to other attacks in the last year where sources for external JS dependencies were poisoned, resulting in compromised sites that didn't have a single shred of compromised code committed - it was all in the browser. How's THAT for scary!

In short, you are at risk if:
- You install a module without checking every line of code
- You update a module without checking every line of code / the diff
- You use a DEV release of a module
- You use composer
- Your application pulls in external dependencies

These actions, these ways of working all create dark corners in which evil code can lie undetected.

The light shall save you

Fortunately, it can easily be argued that Drupal Core is pretty safe from these sorts of issues. Phew. Thanks to the wide community of people contributing and keeping keen eyes on watch, Core code can be considered as well-protected. Under constant scrutiny, there's little that can go wrong. The light keeps the dark corners away.

Contrib land, however, is a little different. The most popular modules not only have maintainers (well done, guys!), but many supporting developers and regular release cycles and even official 'Security Coverage' status. We have brought light and trust to the contrib world, and that's a really important thing.

But what does 'Security Coverage' really provide? Can it fail? What happens if there is a malicious maintainer? I wonder.

When the light goes out

Many modules are starting to see the sun set. As dust gathers on old Drupal 7 modules and abandoned D8 alpha modules, the dark corners will start to appear. 'Security Coverage' status will eventually be dropped, or simply forgotten about, and issue lists will pile up. Away from the safety of strong community, keen eyes and dedicated maintainers, what used to be the pride of the Drupal community will one day become a relic. We must take care to keep pride in our heritage, and not allow it to become a source of danger.

Should a Drupal module maintainer be caught out by a trickster and have their work hacked, what would actually happen? Well, for most old D7 modules we'd probably see a few thousand sites pull in the code without looking, and it would likely take some time for the vulnerability to be noticed, let alone fixed.

Fortunately, most developers need a good reason to upgrade modules, so they won't just pull in a new malicious release straight away. But there's always a way, right? What if the hacker nicely bundled all those issues in the queue into a nice release? Or simply committed some new work to the DEV branch to see who would pull it in? There are loads of old modules still running on dev without an official release. How many of us have used them without pinning to a specific commit?

Vigilance is my middle name!

I have tried to ask a lot of questions, rather than simply doom-mongering. There's not an obvious resolution to all of these questions, and that's OK. Many may argue that, since Drupal has never had an issue like this before, we must already have sufficient measures in place to prevent such a thing happening - and I disagree. As the toolkit used by the world's hackers gets ever larger and ever more complex, we cannot afford to be lax in our perspective on security. We must be vigilant!

Module maintainers, remain vigilant. Ask good questions of new co-maintainers. Check their history. See what they've contributed. Find out who they really are.

Developers, remain vigilant. Know your cattle. Be familiar with what goes in and out of your code. Know where it comes from. Know who wrote it.

Drupalers, ask questions. How can we help module maintainers make good decisions? How can we support good developers and keep out the bad?

Some security tips!
- Always know what code you're adding to your project and whether you choose to trust it
- Drupal projects not covered by the Security Team should be carefully reviewed before use
- Know what changes are being made when performing module updates and upgrades
- If using a DEV version of a module in combination with a build process, always pin to a specific git commit (rather than HEAD), so that you don't pull in new code unknowingly