Supply-Chain Attack against the Electron Development Platform
Electron is a cross-platform development system for many popular communications apps, including Skype, Slack, and WhatsApp. Security vulnerabilities in the update system allows someone to silently inject malicious code into applications. From a news article:
At the BSides LV security conference on Tuesday, Pavel Tsakalidis demonstrated a tool he created called BEEMKA, a Python-based tool that allows someone to unpack Electron ASAR archive files and inject new code into Electron’s JavaScript libraries and built-in Chrome browser extensions. The vulnerability is not part of the applications themselves but of the underlying Electron framework—and that vulnerability allows malicious activities to be hidden within processes that appear to be benign. Tsakalidis said that he had contacted Electron about the vulnerability but that he had gotten no response—and the vulnerability remains.
While making these changes required administrator access on Linux and MacOS, it only requires local access on Windows. Those modifications can create new event-based “features” that can access the file system, activate a Web cam, and exfiltrate information from systems using the functionality of trusted applications—including user credentials and sensitive data. In his demonstration, Tsakalidis showed a backdoored version of Microsoft Visual Studio Code that sent the contents of every code tab opened to a remote website.
Basically, the Electron ASAR files aren’t signed or encrypted, so modifying them is easy.
Note that this attack requires local access to the computer, which means that an attacker that could do this could do much more damaging things as well. But once an app has been modified, it can be distributed to other users. It’s not a big deal attack, but it’s a vulnerability that should be closed.
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enkio • August 8, 2019 1:48 PM
But once an app has been modified, it can be distributed to other users. It’s not a big deal attack, but it’s a vulnerability that should be closed.
There’s been a lot of pushback from Electron devs about that claim. It doesn’t appear in the write-up and may have been an offhand remark during the talk. Assuming publishers are signing the full installer/bundle as they should be doing, you can’t modify ASAR files and re-distribute with a valid signature.
It’s still worth reporting on though, considering how trivial it is to add that code and how stealthy it can be running in the apps context.