Programming Terrors Never End
I wanted to talk a bit about this tweet I saw the other day. The images are from an article called “Researcher hacks over 35 tech firms in novel supply chain attack”.
I haven’t really heard much about supply chain attacks before this, so lets start with a quick intro.
Supply Chain Attacks!
You could just go read the Wikipedia article, but I’ll try summarize.
When software is built, it is usually built with a bunch of dependencies. Instead of writing everything from the ground-up every time, developers use shared libraries.
Say you’re writing a website that needs to parse some input. Maybe you’re validating postal codes. Or phone numbers. Maybe you just need to check if a number is odd. But rather than writing that code yourself, you go looking for a package. Someone else must have run into this problem before, right? And if they were nice, they took their code, bundled it up and put it where other folks can grab it to include in their projects.
You could write and maintain your own library of stuff, of course.
But what if you don’t know how to turn the math behind the AES algorithm into code? Or you don’t know how to convert a PNG image to a JPEG, or a WAV to an MP3, or one of the other thousands of file conversions you might have to care about.
Or maybe you need to interface with the API for some company so you can send mail, find the coordinates for an address, use an AI to tag an image, or one of the hundreds of thousands of APIs out there that can be super useful.
For all of these things and more, there are packages out there to make your job easier. Or maybe you just don’t have the time! Maybe you need a captcha on your website right now and you don’t have the time to implement one yourself. Plus, using packages maintained by other people means that you aren’t the only person using it, which means you get stuff like:
- bug fixes!
- new features!
Without having to do anything! Which is pretty awesome.
Cool. So, Supply Chain Attacks?
So in order to use those packages you need two things ( well, three ):
- a place for information about those packages to live
- a way to define what packages you want to use in your code1
- a tool that can use the file that defines what packages to go and grab those packages for you and put them where your code can use them
Pretty much every language these days has something that fulfills these roles. NodeJS has NPM. Ruby has Gems. PHP has Composer. Python has PyPi. C# has Nuget. Java has…. Maven? Go has modules2.
For this supply chain attack the researcher discovered, there’s one more piece we need:
Companies like being able to use packages for code they write themselves, but maybe that code isn’t something they want to (or are ready to) open source. Maybe it contains too much secret sauce, or it’s just not ready for the public to use, or it’s just so specialized there’s no point in making it public.
So pretty much all of the packages managers have some way to say “hey, this module is private and can be found at X”. Or maybe you use a proxy that contains the private packages, and will go reach out to the public service when it doesn’t have the package ( and might cache it if it’s nice ).
But that’s where the problem ( and the attack ) comes in.
The part of the code that would check if a package existed would either:
- default to the public repo first
- default to the highest version, regardless of public or private
So this means that if I wrote some code that relied on the
private package and someone then created a
secret-api-module public package,
then when my package manager went to grab packages it’d grab the unsafe public
version instead of the private version.
You might think that grabbing packages doesn’t happen very often – maybe only when I first install a package to use, right?
See, a lot of companies use build servers that take care of building code3 so that they can get notified if a new feature breaks old tests, or as part of the deployment process. And to save space ( especially if a company has lots of projects on the go ) these build servers don’t keep old builds OR old package downloads around. Every time a build happens they download all the dependencies fresh. At the very least, part of deploying new code to production happens on a build machine so that you know that the code in production isn’t tainted with weird libraries or stuff from a developers machine.
Yeah, it’s not great. And that’s where the name “supply chain” comes from – because you’re not attacking the code in production via some bug, you’re literally attacking the supply chain that takes place before the code even goes to production.
What’s new about this variation is that previously attackers would have to create packages based on misspellings ( “goggle-map-api” instead of “google-map-api”, for example ) or giving bad info directly to a developer4. Now all that’s required is guessing what names a company might use for private packages.
This Is Why Programming Sucks
And this is what I actually wanted to write a post on. Being a programmer kind of sucks some days.
It means eventually coming to terms with the fact that you could write code to the best of your ability, using all the best practices like tests and feature flags and whatever else – and still have your code taken hostage.
You kind of just have to live with the fact that your code sits on a mountain of other peoples code. For example, thinking about some stuff I’ve got running in production right now, all of this stuff has to be secure and reasonably bug free:
- the packages used directly by the code
- any of the tools used during the build or deploy process
- any of the Docker images or their dependencies
- any OS packages installed during the docker image build package
- the OS of the docker image
- the Kubernetes software
- the OS & packages on the GCP Compute Engine nodes Kubernetes runs on
- the various layers between those nodes and the public internet ( the Google Cloud stack )
- everything between Google Cloud and a users phone
- everything on a user’s phone
And that’s the simple list. And there are probably at least a handful of unknown ( or known and simply unpatched ) vulnerabilities in that stack of things that could be used to take control of my stuff running in production and make it dance a merry jig.
And yeah, sure, you could write everything yourself and maybe just depend on the standard library. But even then you can get screwed; there are many, many, many stories of some critical part of the standard library being hilariously broken ( or just broken under specific circumstances ).
Or if you’re like me, you’re too lazy or not smart enough to write everything you need yourself. So you have to rely on packages, and just hope that everything is secure enough so that if someone pokes at your code in production it looks too hard to be worth it.
And honestly, that’s probably the best you can hope for. There’s plenty of unpatched old Wordpress installs just waiting to become part of a botnet, so unless you’re Google or Netflix5 then you’re probably not worth the effort of actually doing an in-depth attack.
Most companies aren’t multi-billion dollar companies that are worth the time and effort of sophisticated6 attacks. When you hear about some small-to-medium business being hacked, the actual cause is probably one of the following:
- someone used a bad password
- someone plugged in a USB key that had malware on it
- someone got phished
- some code with an unknown or unpatched vulnerability was exploited
- someone was incredibly stupid and left a laptop with critical information where it could get taken with very little effort
Basically, either low-effort hacks that can be easily automated and then thrown out into a botnet that will just run the attack against every computer connected to the internet – or social engineering.
And our job as programmers is to just try our best, apply patches to security holes in a timely manner, and pray we’re not sitting on a mountain of unknown vulnerabilities ( or that we’ve got really understanding bosses ).
Hopefully you also get to define what version you want too ↩︎
Which (I think) side-step the supply chain attack we’re talking about here. ↩︎
Maybe just when a PR happens, or maybe on every commit, or maybe just every hour – point is that pulling packages can happen any time. ↩︎
Basically telling someone on a forum or in a chat that “this package will totally solve your issues” ↩︎
This post was authored by Sean Patrick Hagen on 2021-04-01 12:59:46 -0700 PDT
Wanna see the commit? Go here: ffb9da281eb1912cd106032af43071c8d850a91e