I found this! I posted a semi-click-bait-ey tweet about it here [0], I think it’s important for people know how easy these bugs are to find now. It’s becoming borderline irresponsible not to audit your internet-facing code with modern AI tools.

[0] https://x.com/just1cz/status/2118009777922228361

Looks like you also found a similarly critical apt bug in 2019: https://lists.debian.org/debian-security-announce/2019/msg00...

Do you think there might be even more still lurking out there?

I do. I think that security-critical but overly complex software like this should be rewritten and certain aspects of it formally verified, since such things are now practical.

Nice work! A similar vulnerability in 2019 also found by you included the recommendation to update with:

  apt -o Acquire::http::AllowRedirect=false update
  apt -o Acquire::http::AllowRedirect=false upgrade

Since this also involves redirects, would that protect users while updating apt for this one also?

That sounds right to me, but FYI the APT maintainers themselves are recommending Acquire::Retries=0 as the mitigation since some mirrors might actually have redirects.

Speaking of which… if any of y’all work on security at OpenAI I have some questions for you about Daybreak! Please email me

But how do I update apt if apt is untrustable until fixed ? Good ol' .deb scp'd in dpkg'd.

dupe (2h ago): https://news.ycombinator.com/item?id=50364814

I feel like they should release manual update instructions since the update mechanism is vulnerable. Although I see my systems already updated via unattended upgrades.

edit: On lobste.rs I see a recommendation for `apt download`: https://lobste.rs/s/h7bvma/man_middle_arbitrary_code_executi...

How would an attacker inject a redirect into an apt package download?

MITM on the network, I guess like DNS takeover or the like.

So you pass through the upstream headers but then simulate a failure/resume and supply different contents for the resumed download.

So apt doesn't verify signatures on what is actually downloaded?

> Improper file handling when resuming an HTTP download allows a man-in-the-middle attacker to replace a package after verification

from the OP

APT can use HTTPS, but often doesn't, making a MITM attack easier (also the idea for a long time has been signatures are enough, and/or TLS certs used to be a lot harder to get, but at this point you should really be using both).

Https doesn't help with this if the MitM is the apt mirror you are using.

One reason http is still used is because you need an independent signature anyway since it is common to use mirrors that don't have the same level of trust as the debian maintainers

Still doesn't make sense to me. So package A is downloaded, signature verified, then package B is downloaded, but somehow the package A file is replaced? Is it something like that?

The somehow is package B has the same filename as package A.

Discussion here: https://news.ycombinator.com/item?id=50364814

I'm pretty sure apt is written in C++. Am I remembering wrong?

parts of apt are being redone in rust, but anyway this seems to be a logic bug (in c++ code)