XZ backdoor in a nutshell

https://lemmy.zip/post/12859629

XZ backdoor in a nutshell - Lemmy.zip

I have heard multiple times from different sources that building from git source instead of using tarballs invalidates this exploit, but I do not understand how. Is anyone able to explain that?

If malicious code is in the source, and therefore in the tarball, what’s the difference?

I don’t understand the actual mechanics of it, but it my understanding is that it’s essentially like what happened with Volkswagon and their diesel emissions testing scheme where it had a way to know it was being emissions tested and so it adapted to that.

The malicious actor had a mechanism that exempted the malicious code when built from source, presumably because it would be more likely to be noticed when building/examining the source.

The malicious code wasn’t in the source code people typically read (the GitHub repo) but was in the code people typically build for official releases (the tarball). It was also hidden in files that are supposed to be used for testing, which get run as part of the official building process.