Thread

1. kpcyrd · 1790876562 · focus · HN ↗

   This article is full of mistakes and misleading claims:

   1) It's claiming SHA1 insecurity is theoretical, while SHAttered from 2017 was specifically a pratical proof of concept. The only reason Git wasn't affected, is because they didn't bother bruteforcing a git-blob prefix.

   2) It's claiming collision attacks don't matter, only second-preimage attacks do. This is incorrect, collision attacks are enough for code-smuggling problems, when two repositories are on the same git commit (verified by the full commit hash), yet contain different code in their git checkout.

   3) The Linus quote "The real security is in distribution" is arguing that "git's content-addressed system should not be used to address content". It's arguing that, in case of curl|sh, you shouldn't use a sha256sum-gate to pin the content to something you've reviewed, you should instead ensure curl is fetching from an https server.

   1. kazinator · 1790879117 · focus · HN ↗

      The problem of a SH1 collision happening by coincidence is vanishingly low and theoretical.

      Nothing else matters.

      Git hashes are not supposed to be a security mechanism. If your basis for trusting that you have the right checkout is the git hash, in a situation where you have legitimate concern about untrusted parties manipulating remote repositories, then you're simply wrong.

      1. someonebaggy · 1790914315 · focus · HN ↗

         You could pull a malicious colliding PR and reject it. Then you pull the other half of the collision without realising it is, and it's something good and you merge it. But your CI server already saw the malicious one and thinks it's the same, so builds the malicious code

Unofficial Hacker News client; not affiliated with Y Combinator.