Hacker News Reader

Comment by jmb99 | Hacker News Reader

In this case, there is more than enough information given to make an exploit trivial for anyone actually investigating the issue. I don’t see a reason to distribute PoC exploit code here, it’s fairly clear what the problem is as well as at least one possible RCE implementation.

View on HN

A well-written article should still have spelled out what armchairhacker did. The article spent many paragraphs working through what seemed to me like a very obvious chain of reasoning that didn't need so much hand-holding, and then left me completely bewildered at the end with the last step. And even with the explanation, I'm still not sure why writing the files to a different path allows the hook to be written. (Surely Git knows that it's still in the middle of a recursive clone operation and that it therefore shouldn't accept any hooks?)

There are hundreds of files on your system that if you could write to them would cause a RCE. For example, `AUTOEXEC.BAT`. While the intermediate step (how do you go from writing a filename without an ^M to writing to an arbitrary file on the target OS?) is also somewhat surprising (and maybe points at some potential deeper fixes within git or potential TOCTOU bugs?), ultimately it's the exact same as several other vulnerabilities in this class from the same author (see the 2024 case-sensitivity bug they linked), so I forgive them for glossing over it.

Git probably doesn't allow the submodule path to be .git but does allow .git\r which would then actually be written to .git due to the broken escaping.

Git does "know" that – but it doesn't know it's writing a hook.

I think what they're saying is it shouldn't execute any hooks during a first clone operation.

The exploit being trivial also removes any reason not to show a complete PoC.

There is no security impact for most people anyway as the next step after a git clone is usually to run some kind of build command which executes arbitrary code from the repo.

Reply on news.ycombinator.com