For those of you not familiar, apt-cacher-ultra is fairly new (~9 months old), and it can reduce your exposure to this. It uses a completely different mechanism for verifying signatures, and does validate signatures, so if your apt clients grab the packages from the cache, it shouldn't be open to this bug.
The next version is going to include TLS and ACME support for the client->cache connection.
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.
Do you think there might be even more still lurking out there?
And what is your take on HTTPS for apt? I assume the MitM scenario for this and the previous bug could have been avoided by the use of HTTPS by default?
HTTPS would have mitigated this particular bug but it feels like rearranging deck chairs on the titanic to fight over that right now. We need to audit everything with powerful AI like, yesterday.
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.
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.
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.
> 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 next version is going to include TLS and ACME support for the client->cache connection.
https://github.com/linsomniac/apt-cacher-ultra
[0] https://x.com/just1cz/status/2118009777922228361
Do you think there might be even more still lurking out there?
And what is your take on HTTPS for apt? I assume the MitM scenario for this and the previous bug could have been avoided by the use of HTTPS by default?
edit: On lobste.rs I see a recommendation for `apt download`: https://lobste.rs/s/h7bvma/man_middle_arbitrary_code_executi...
So you pass through the upstream headers but then simulate a failure/resume and supply different contents for the resumed download.
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).
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