How the xz backdoor highlights a major flaw in Nix | Shade's Blog
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Background On Friday, March 29th, 2024, a historical and sophisticated security vulnerability (CVE-2024-3094) was discovered in the XZ Utils package and liblzma api in version 5.6.0 and 5.6.1. While this vulnerability mostly affects Debian and RedHat distributions, there was some interesting discussion regarding xz and Nix. How did this affect Nix and NixOS? The truth is not a whole lot in reality. I saw conflicting reports, but supposedly, the tarballs of xz that Nix downloads were not infected.

The main issue is the handling of security updates within the Nixpkgs ecosystem, which relies on Nix’s CI system, Hydra, to test and build packages. Due to the extensive number of packages in the Nixpkgs repository, the process can be slow, causing delays in the release of updates. As an example, the updated xz 5.4.6 package took nearly 5 days to become available in the unstable branch!

Fundamentally, there needs to be a change in how security fixes are handled in Hydra. As stated in the article, Nix was lucky to be unaffected, but multiple days to push out a security patch of this severity is concerning, even if there was no reason for concern.

  • 0xtero@beehaw.org
    324·
    9 months ago

    Kinda tired of the constant flow of endless “analysis” of xz at this point.
    There’s no real good solution to “upstream gets owned by evil nation state maintainer” - especially when they run it in multi-year op.

    It simply doesn’t matter what downstream does if the upstream build systems get owned without anyone noticing. We’re fucked.

    Debian’s build chroots were running Sid - so they stopped it all. They analyzed and there was some work done with reproducible builds (which is a good idea for distro maintainers). Pushing out security updates when you don’t trust your build system is silly. Yeah, fast security updates are nice, but it took multiple days to reverse the exploit, this wasn’t easy.

    Bottom line, don’t run bleeding edge distros in prod.

    We got very lucky with xz. We might not be as lucky with the next one (or the ones in the past).

    • PotatoesFall@discuss.tchncs.de
      12·
      9 months ago

      I think the post was more about pointing out how long it takes to put out a security patch. Security patches can also occur on stable.

      • 0xtero@beehaw.org
        2·
        9 months ago

        Yeah, I can get that. The xv situation probably wasn’t the best of examples though?

    • biribiri11@lemmy.ml
      5·
      9 months ago

      We might not be as lucky with the next one (or the ones in the past).

      Or the ones in the present, for what that’s worth

      • 0xtero@beehaw.org
        5·
        9 months ago

        I’m not sure why you think I didn’t? Sorry if it was unclear.

        From the blog:

        This incident has really made me wonder if running the unstable branch is a great idea or not.

        My comment:

        Bottom line, don’t run bleeding edge distros in prod.

        Hope this clarified my opinion! Have a good day!

    • nomad@infosec.pub
      1·
      9 months ago

      Bottom line, don’t run bleeding edge distros in prod.

      This. My company’s servers are all Debian stable. Not even sweating the issue.